Anaerobic Threshold: Myths & Misconceptions

During the last nearly 50 years, the blood lactate curve and lactate thresholds (LTs) have become important in the diagnosis of endurance performance. However, there are many misconceptions which have lead to misunderstanding in the research literature. Lactate Threshold (LT) is the point at which body converts over from using the Aerobic energy system to the Anaerobic Glycolysis energy as the primary source of energy production. In sports involving running activities, it can also be defined as the fastest running speed at which blood lactate levels remain in a relative steady state.

Introduction

During the last nearly 50 years, the blood lactate curve and lactate thresholds have become important in the diagnosis of endurance performance. However, there are many misconceptions which has lead to misunderstanding in the research literature. Lactate Threshold (LT) is the point at which body converts over from using the Aerobic energy system to the Anaerobic Glycolysis energy as the primary source of energy production. In sports involving running activities, it can also be defined as the fastest running speed at which blood lactate levels remain in a relative steady state.

The terms “lactate threshold,” “anaerobic threshold,” “aerobic threshold,” “lactate turn point,” “onset of blood lactate accumulation (OBLA),” and “maximal lactate steady state (MLSS)” are used somewhat interchangeably, although precise definitions may be quite different. Originally, LT was defined as a fixed lactate reading at 4.0 mmol/L, but more recent research has shown that lactate levels at LT can vary as much as 6 mmol/L, between 2 and 8 mmol/L (Beneke, 2000). The lactate threshold is dependent on many factors relating to the production and clearance of lactate. This interaction is what governs the amount of lactate in the blood and ultimately the LT (Billat et al., 2003).

It is important to note that we are measuring blood lactate when defining LT, not muscle lactate. That means that LT is dependent not only on how much lactate a muscle produces but how much actually makes it into the blood stream. When lactate is produced it can either stay in the muscle, travel to adjacent muscle fibers, move into the interstitial space between muscles, or travel to the blood stream. How much travels to the blood is partially dependent on both the difference between lactate levels in the blood and muscle and on the lactate transporter activity. Lactate appearance in the blood also depends on exercise intensity and the amount and type of muscle mass activated. The greater the intensity means a greater reliance on Glycolysis without as much aerobic respiration taking place. Also, the more intense an effort, the greater amount of Fast Twitch fibers are recruited, which because of their characteristics are more likely to produce lactate.

LT2

Lactate Threshold & Role in Sport

The LT measurement is very valuable as it is one of the more sensitive indicators of fitness levels in sport. For example, if training is ineffective the LT will be reached at a relatively low running speed; whereas with more effective training LT will be achieved at a higher speed. This as you can imagine will significant consequences when relating back to the sport. Elite athletes reach the LT at a much higher running speed than sub-elites, which allows them to run faster for longer. The LT is, once again, a function of effective training and also genetics. Many scientific studies indicate that the LT is now one of the best predictors of distance running performance.

The LT is also very valuable relative to training and competition. Training at the threshold has been found to improve performance and the capacity of the aerobic system. Extensive interval training using tempo runs is a typical training modality to improve LT levels. The LT for most males is between 160 and 175 beats per minute, with females being slightly higher, at about 170 to 185 beats per minute. Of all the measurements obtained during testing, the speed and heart rate at which the lactate threshold is obtained are probably the most important to remember when planning training.

For comparison purpose, in competitive University and national level distance runners, the LT is reached at speeds of 6:00 to 5:00 pace per mile. A higher speed at the threshold is desirable. The threshold represents a point where the accumulation of metabolites (e.g. H+) detrimental to performance may begin; thus, a faster threshold speed indicates that the athlete may perform at this speed for a fairly long period of time (possibly up to a marathon) without experiencing undue fatigue. However, when speed or workload exceeds the threshold, the accumulation of by-products and depletion of muscle fuels can lead to more rapid fatigue and a slowing of pace.

The lactate threshold is perhaps the best and most sensitive indicator of distance running performance. An individual who reaches the threshold at a speed of 10 mph (16.1 km/hr) would most likely defeat an individual who reaches the threshold at any lower running speed. It is thus desirable to increase the speed at which the threshold is obtained; this can be accomplished by methods outlined below.

LT3

Training Methods to Improve Lactate Threshold

1) Training at speeds/heart rates near or at the threshold

Training at a given heart rate zone is probably the most effective method for monitoring training intensity relative to the threshold. This has been shown to improve training effectiveness as training near or at the threshold provides a very effective stimulus for improving factors associated with endurance performance.

For example, it was found that when highly-trained distance runners added a weekly 20 min run at the lactate threshold the speed at which the threshold was reached increased after 14 weeks of such training (Sjodin et al., Eur. J. Appl. Physiol. 49:45, 1982). This research also demonstrated that the addition of this single weekly run significantly improved many of the enzymes, which produce energy in muscle. Thus, steady-state training (i.e., longer distance, continuous runs) at the lactate threshold will improve the metabolic capacity of skeletal muscle even in well-trained athletes. It was also found that the addition of the 20 min run improved running economy. Thus, relatively long-duration runs (15-30 min) at the speed or heart rate of the LT should be considered when designing an effective endurance training program for long distance runners. This should be appropriately modified for games based players e.g. Soccer and Rugby player.

The “theory” behind these adaptations is that at a speed greater than the LT, by-products such as Hydrogen ions (H+) begin to accumulate in the muscle. The accumulation of these by-products then results in a slower running speed and/or shortens the length of the workout where a high speed is attained. By keeping training intensity at the LT, the muscle and cardiovascular system can be optimally stressed for a relatively long period of time. In other words, the LT appears to be the “green zone” of training intensity; going above this workload results in fatigue, while going below it does not adequately stress the systems involved. It is this “stress” on the cardiovascular and muscular systems, which provides the stimulus for positive adaptations to occur. Such adaptations then lead to enhanced performance in sport.

2) Interval work

Relatively high-intensity, short rest period interval work has also been found to improve the lactate threshold. Cycles of 3 minutes of work with 1-2 minutes of rest have been found to reduce lactate accumulation during exercise. As with VO2max, the principal is that skeletal muscle and the heart adapt when the level of exercise is close or above VO2max. Unfortunately, this is quite intense exercise, which cannot be maintained for a long period of time (5-15 minutes) due to the accumulation of by-products associated with Glycolysis. Lactate diffuses out of the skeletal muscle by allowing a “recovery” period of walking or slow running between intense work bouts. Intervals thus allow a high workload to be maintained over a longer time period which results in maximal adaptations. With shorter, intense intervals, the stress is even greater. The endurance athlete and coach should thus not shy away from the performance of relatively “sprint” type work with an active recovery between each bout. Such work has been found to increase the lactate threshold, which is a very sensitive and accurate indicator of performance potential in endurance events.

Knowledge about the lactate threshold can also help in designing workloads/heart rates for various types of training. See general recommendations (Coen et al., Int. J. Sports Med., 12:519-524, 1991). Implementation of these guidelines may help prevent overtraining and staleness and also provide a maximal stimulus to the muscle and cardiorespiratory systems for development. Keep in mind that these recommendations are based upon treadmill data under room conditions; different environmental conditions (i.e., heat) and terrain (hills) can alter the relationship and significance of findings.

1) Overdistance runs and “easy” or recovery days should be performed at 80 to 90% of the lactate threshold

2) Intensive, continuous distance runs (15-30 min duration) can be performed at approximately 100% of the lactate threshold, as discussed above. No more than one of these workouts should be performed per week

3) Longer interval work (i.e., 800-1000 m repeats) should be performed at approximately 110-120% of the lactate threshold

4) For shorter, intense interval work the lactate threshold is usually not considered. Keep in mind that such work, although commonly considered “anaerobic” can maximally stimulate the aerobic systems if adequate sets are performed with rest between the sets

This discussion has emphasized the importance of the lactate threshold to the endurance athlete. A key question for the coach/athlete is how to monitor if the threshold is changing over the course of a month or years over training. Unfortunately, measuring the lactate threshold can only be effectively performed in a laboratory setting. New research needs to look at methods of estimating the lactate threshold without having to use the laboratory setting. These will significantly advance the practical application side from a coaching perspective as well as allowing the coach to make more informed decisions in terms of program design and intervention strategies.

This article was written by EPI CEO Karl Gilligan

Written by Karl Gilligan

Founder & CEO 

Elite Performance Institute (EPI)

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Lactic Acid: Friend or Foe?

For decades the main culprit of fatigue and the thorn in the side of many athletes was a foe called lactic acid. It has been called a waste product of anaerobic metabolism and has been believed to be responsible for the uncomfortable “burn” of intense exercise and directly responsible for the metabolic acidosis of exercise, leading to decreased muscle contractility and ultimately cessation of exercise. Unfortunately, for decades we have been misguided. We now know, lactic acid, or more correctly termed lactate, is correlated with fatigue but not a causative factor. This doesn’t mean that our training plans were all wrong or that we need to drastically alter how we improve our player’s fitness levels. It just means we have been misguided in what we were trying to improve and the implications of our training methods.

Introduction

For decades the main culprit of fatigue and the thorn in the side of many athletes was a foe called lactic acid. It has been called a waste product of anaerobic metabolism and has been believed to be responsible for the uncomfortable “burn” of intense exercise and directly responsible for the metabolic acidosis of exercise, leading to decreased muscle contractility and ultimately cessation of exercise. Unfortunately, for decades we have been misguided. We now know, lactic acid, or more correctly termed lactate, is correlated with fatigue but not a causative factor. This doesn’t mean that our training plans were all wrong or that we need to drastically alter how we improve our player’s fitness levels. It just means we have been misguided in what we were trying to improve and the implications of our training methods.

As we now know lactate is correlated with fatigue, so that as fatigue increases so does lactate levels increase. So if lactate is not the culprit, then who is? As fatigue increases so too does the build-up of accompanying byproducts such Hydrogen ions (H+) resulting in a direct linear relationship between it and lactate levels. One of the keys to performance in many sports is to delay the build up these accompanying products. If the rate of those products accumulation can be decreased, fatigue can be delayed. So while lactate is not the culprit, it corresponds with the build up of by-products that can cause fatigue. Strength & Conditioning coaches commonly use sessions to enhance lactate tolerance or the lactate threshold. While the traditional method of intensive intervals for lactate tolerance and extensive intervals using tempo runs for lactate threshold is very effective, knowing the underlying mechanisms of these components will help coaches design better sessions to enhance those variables.

400m

 

Lactic Acid Versus Lactate: An Important Differentiation

Despite the ubiquitous use of the term “lactic acid” in both scientific and lay fitness and sports medicine communities, the actual presence of meaningful quantities of lactic acid in the human body has been called into question. It is true that the glycolytic production of lactate is associated with hydrogen ion (Hþ) production, as represented in the following summary equations (Robergs et al., 2004):

Glucose → 2 lactate + 2 H+

Glycogen → 2 lactate + 1 H+

However, as detailed in the 2004 review of the biochemistry of exercise-induced metabolic acidosis by Robergs, Ghiasvand, and Parker, these summary equations do not imply that lactate is the source of H+, but rather that the proton release of glycolysis is likely associated with the non-mitochondrial hydrolysis of adenosine triphosphate (ATP). Although other explanations for H+ formation have been proposed, most investigators now agree that lactic acid is not produced in muscle (Lindinger et al, 2005). Although the construct of “lactic acidosis” appears intuitive and continues to be propagated in physiology texts and Strength & Conditioning education, no convincing evidence exists in support of this theory. Regardless of whether this stance represents as “sloppy nomenclature” as suggested by Lindinger et al (2005) or a true inherent misunderstanding of lactate’s production, it undoubtedly leads to confusion among many Strength & Conditioning coaches. For this reason, we will only use the term lactate.

glycolysis-pqthway

By-Product Build Up

In games based sports like Soccer and Rugby or Track & Field events like 400m and 800m, there is a significant anaerobic demand. Due to this anaerobic demand, certain by-products will accumulate in the body. For example, if the sprints are short but repeated in a game of Soccer, creatine levels will build up due to the demand on the ATP-CP for energy supply (ATP production). However, if the sprints become longer with the ball in play for longer periods and less time to recover, H+ levels will increase due to the greater demand on the Anaerobic Glycolysis system for energy supply.

Previous studies have demonstrated that an increase in H+, which is a proton that dissociates from lactate and would decrease the pH, may impair muscle contractility (Mainwood & Renaud, 1985). While the previously accepted notion that lactate played a direct role in fatigue, essentially acting as a “poison” to the muscles, has been disproved, it does not discount the entire acidosis concept of fatigue (Noakes, 2007). While lactate itself may not cause fatigue, it corresponds with other products in the body which may have contribute to fatigue, thus lactate can still be used in studies as a marker of fatigue. For instance, an increase in circulating blood lactate corresponds well with a decrease in pH and increase in H+. An increase in H+ has been shown to reduce the shortening speed of a muscle fiber, while a reduction in pH impairs Ca2++ re-uptake in the Sarcoplasmic Reticulum and may inhibit phosphofructokinase (PFK) (Hargreaves & Spriett, 2006; Brooks et al. 2004). In addition, a decrease in pH could stimulate pain receptors (Brooks et al., 2004). All of these actions could potentially cause fatigue.

The ability of the muscle to buffer the H+ could potentially delay fatigue. As mentioned above, a rise in H+ concentration causes many processes that could potentially lead to fatigue. Training has been shown to increase buffering capacity in both recreational and well trained athletes (Laursen & Jenkins, 2002). Furthermore, in one study, the buffering capacity of 6 elite cyclists was found to be significantly related to their performance in a 40km time trial (Weston et al., 1996). This demonstrates the importance of dealing with by-products and buffering capacity when it comes to performance. Due to the impact of acidosis on energy production and performance, much of the coaching and scientific literature focuses on delaying this process. Of particular interest is the concept of the lactate threshold, which will be discussed in our next follow up article.

References:

  1. Robergs RA, Ghiasvand F, Parker D. Biochemistry of exercise- induced metabolic acidosis. Am J Physiol Regul Integr Comp Physiol 2004;287:R502-R516.
  2. Lindinger MI, Kowalchuk JM, Heigenhauser GJ. Applying physico- chemical principles to skeletal muscle acid-base status. Am J Physiol Regul Integr Comp Physiol 2005;289:R891-R894; author reply R904-R910.
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Strength & Conditioning Philosophy

A Strength & Conditioning philosophy is something which defines a S&C Coach. It encompasses many layers some of which can include; how you think in regards sports performance, your system of training as well as your coaching style. As we get more experienced as coaches, our philosophy can change and evolve however big rocks stay the same so we should never loose sight of the fundamentals. At EPI we strongly recommend young S&C Coaches should write down their Strength & Conditioning philosophy, in doing so they can think more clearly about how they look at sports performance and what they can do to facilitate this process.

EPI Strength & Conditioning Philosophy

The overall goal of a strength & conditioning program is to develop athletic performance whilst making the athlete/team more robust to injury. At Elite Performance Institute (EPI) we rely on three key pillars, these include:

  1. Movement quality
  2. Principles of training
  3. System of training

Movement Quality

One of the primary goals of an S&C Coach is to enable their athletes to express force more efficiently for their sport. We can do this using both general and specific methods in our exercise selection choices. Force development can be achieved in the weights room and on the track/pitch/court depending on the sport. In order to express force efficiently and effectively, we must first determine if the athlete has the appropriate range around the joint(s) to perform some key exercises we want to use in the S&C program. Secondly, we should determine how competent they are at expressing different types of force and at different speeds. Finally, we must determine if the athlete has adequate movement skill development to perform the exercises we would like to use e.g. Olympic lifts.

Movement screens are a great way of determining fundamental movement competency in terms of mobility, stability and motor control. They can also be used as a way of determining who may be at risk of a non-contact injury due to a poor score. At EPI, we use the Movement Compensation Screen (MCS) along with our ROM tests to determine if an athlete has the appropriate movement competency for some of the key exercises we want to use in the weights room e.g. Squats, Deadlifts, Olympic lifts, etc.

As S&C coaches, we need a baseline determination of where our athletes lie in terms of their force expression. Depending on their sport, chronological age, training age and level in sport (amateur/professional) some of these tests would not be used. However, at the elite level we can assess our athletes with the following:

  • Max Strength (3RM testing Back Squat/Bench Press)
  • *Strength-Speed (1RM Squat Clean/55% Loaded Squat Jump)
  • *Speed-Strength (3RM Hang Clean/30% Loaded Squat Jump)
  • Reactive Strength 1 (CMJ/Drop CMJ/Squat Jump)
  • Reactive Strength 2 (Depth Jump/5 Single Leg Hop Test)

*Linear transducer device (Tendo Fitrodyne/GymAware) should be used during these tests to determine power output. For competent lifters 1RM and 3RM can be used for the Squat Clean and Hang Clean exercises respectively. For athletes unable to Olympic lift, loaded squat jumps at 55% and 30% of their 1RM Back Squat can be used.

Determining if an athlete has the appropriate movement skills to perform all the key exercises you would like to use in the S&C program is quite straight forward. A lot of this comes down to experience, an experienced coach can quickly make out the good movers and bad movers within the group from session to session. If conducting baseline fitness testing, an experienced coach will quickly see who can move well or not when conducting the tests. A more effective way to quantify movement quality in bilateral, unilateral and jump landing positions is to use the Movement Compensation Screen (MCS) during pre-season testing/screening.

Redeveloped Ravenhill Stadium, Belfast 2/4/2014 General view of the gym area Mandatory Credit ©INPHO/Presseye/Darren Kidd

Principles of Training

There are many principles of training which an S&C Coach must consider when organising the training process. At Elite Performance Institute (EPI), we believe the principle of “adaptation” is critically important however there are others which are central to the training process. See below this extended list:

  1. Adaptation
  2. Overload
  3. Specificity
  4. Reversibility
  5. Recovery
  6. Variation

Adaptation

As S&C coaches, every session we perform we are looking for a training adaptation to be elicited from the work performed. Whether it is strength, power, speed, ESD or recovery session, we want to elicit the appropriate response. Adaptations to the demands of training occur gradually, so coaches need to be patient when looking for significant improvements. Efforts to accelerate the process may lead to injury, illness, or “overtraining”. Many adaptive changes reverse when training ceases. Conversely, an indadequate training load will not provide an adequate stimulus, and a compensatory response will not occur.

supercomp

Overload

Training loads must be increased gradually in a systematic approach to allow the body to adapt and to avoid injury. Varying the type, volume, and intensity of the training load allows the athlete an opportunity to recover, and to over-compensate. Loading must continue to increase incrementally as adaptation occurs, otherwise the training effect will plateau and further improvement will not occur. Manipulation of training overload and recovery must be delivered using a balanced and structured approach, failure to do so can result in poor performance and/or injury.

overload

Specificity

Energy system development (ESD), muscle fiber types, and neuro-muscular responses adapt specifically to the type of training to which they are subjected. For example, strength endurance has no transfer of training effect to speed performance. Conversely, endurance training activates aerobic pathways, with little effect on speed or strength adaptations. Even so, a well-rounded training programme should contain a variety of elements (aerobic, anaerobic, speed, strength, flexibility), and involve all of the major muscle groups in order to prevent imbalances and avoid injuries. It is the role of the S&C Coach to create balance in the training process for the athlete/sport they are working in, with primary emphasis on identifying the key fitness components which will facilitate sports performance.

Reversibility

A regular training stimulus is required in order for adaptation to occur and to be maintained. Without suitable, repeated bouts of training, fitness levels remain low or regress to their pre-training levels. For this reason, the training process is typically broken down into training phases/blocks whereby specific fitness components are developed over a 3-4 week period.

Recovery & Variation

Muscle groups adapt to a specific training stimulus in about three weeks and then plateau. Variations in training and periods of recovery are needed to continue progressive loading, without the risks of injury and/or overtraining. Training sessions should alternate between heavy, light, and moderate in order to permit recovery. The content of training programmes must also vary in order to prevent boredom and “staleness”.

System of Training

A system of training acts like a road map for a S&C Coach when working in sport and needs to be in the forefront of the coaches mind. A system of training should define their the coaching style, thinking process and methodology they want to use to develop the athletic qualities needed for the sport and to facilitate injury prevention. Systems of training can vary from coach to coach, however, without any system it is questionable whether the coach has full comprehension of the training process and methodology they use to enhance sports performance. At Elite Performance Institute (EPI), we have an eight step approach we use as part of our system of training.

  1. Create a needs analysis
  2. Identify key fitness components
  3. Perform a movement screen
  4. Perform fitness testing
  5. Profile your athlete(s)
  6. Create S&C program
  7. Enhance force-velocity curve
  8. Enhance energy system development (ESD)

Written by Karl Gilligan

Founder & CEO 

Elite Performance Institute (EPI)

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Max Velocity Sprint Mechanics

Sprinting is a complex skill orientated task that places a high neuromuscular demand on any athlete  and requires high levels of coordinated movement and appropriate sequencing of muscle activations to perform at peak levels. As coaches, we should be aware that acceleration and max velocity sprinting are interlinked but also independently performed movements. This article will review maximal velocity sprint mechanics with particular focus on the primary factors affecting performance, and the characteristics required to optimise max velocity sprinting mechanics. 

Table of Contents

  1. Introduction
  2. Stride Length vs Stride Rate
  3. Force Production & Sprinting Speed
  4. Minimize Braking Forces
  5. Conclusion
  6. References

Introduction

Before going in to an in-depth discussion of sprinting mechanics, let’s first examine some fundamental concepts of sprinting performance. Historically, speed performance has always been based around two key variables: stride length and stride rate. Coaching systems around speed performance were made more simple with primary focus being placed on enhancing both of these characteristics. However, more experienced coaches knew that it was not as simple as it seemed because the two variables are actually interdependent in a loosely inverse relationship. The reason being as one variable increases the other often decreases. Research from Weyand et al. (2000) began to change the sprint coaching landscape. Dr Weyand and colleagues ground braking research paper “Faster top running speeds are achieved with greater ground forces not more rapid leg movements” published in the Journal of Applied Physiology altered coaches philosophy on speed development and created a shift away from stride length and stride rate being the primary determinants of speed performance.

Stride Length vs Stride Frequency

The fastest sprinters tend to have stride lengths and stride frequencies as great as 2.5-2.6m and 5 steps per second respectively (Mann, 2005). Interestingly, the source of these outstanding characteristics is actually a single attribute. It was Weyand and colleagues (2000) research paper which demonstrated that force applied at ground contact is the most important determinant of running speed. This same research indicated that the speed at which an athlete moves their legs through the air is of little importance, essentially negating the impact of stride frequency as a key variable.

The benefit of greater force application into the ground is two-fold. First, greater force application will increase stride length. In addition, greater force applied to the ground will cause a greater displacement of the athlete’s body during mid swing phase causing greater stride length. The second benefit of increased force application is not so obvious and is often misunderstood. This benefit is that of increased stride frequency. Therein lies the question, how can increased stride frequency be caused by increased force application to the ground? Let’s try to simplify things to explain further. Stride frequency is comprised of two components: ground contact time and flight time. Research on elite sprinters indicates that the best sprinters spend less time on the ground (Mann, 1986; 2005; Mann & Herman, 1985). This is because the forces they produce are so great that they enter a period of flight more rapidly than weaker and slower sprinters. As a result, despite not moving their limbs significantly faster through the air (Weyand et al., 2000), faster and more skilled sprinters tend to have greater stride frequency because they reduce the amount of time they spend on the ground.  As a result of an accumulation of research from Mann and Weyand, we now know that stride length and stride rate are related to max velocity speed performance but are not the primary causative factors associated with performance.

speed

Force Application & Sprinting Speed

If you ask all the successful sprint coaches and biomechanists such as Charlie Francis, Tom Tellez, Loren Seagrave, Ralph Mann and Peter Weyand, they will all contend that force production and application is critically important for sprinting performance. Essentially an athlete must increase the force they apply to the ground and do so over increasingly shorter periods of time. Just as important as the magnitude of force application however, is the direction of that force application. For instance, during acceleration athletes attempt to apply large horizontal forces to facilitate braking inertia and maximising speed off the mark. This results in a large forward lean (45°-60° subject to sprinting on track or pitch).

During max velocity sprinting, athletes should attempt to minimise braking forces and increase vertical propulsive forces. Vertical propulsive forces are important because once momentum has been maximally developed during the acceleration period, the body will tend to keep moving forward at the same speed as long as the internal and external forces acting on the body are balanced. With more vertical force generation, more time will be spent in the air which will allow the athlete to reposition their limbs more effectively for the next ground contact.

With these fundamental concepts in mind, what can coaches do to maximise max velocity sprint performance? From my perspective and all the tutors at Elite Performance Institute (EPI), we focus on three primary areas:

  1. Develop the force-velocity curve
  2. Focus on direction of force application
  3. Optimise sprinting mechanics

We assess all aspects of the the athlete’s FV curve to identify any limitations. For max velocity sprinting, these can include speed-strength and fast stretch shortening cycle (SSC) qualities. We then prioritise vertical force production exercises for both the FV curve development as well as speed mechanics.

Minimise Braking Forces

Another key objective of efficient sprinting is minimizing braking forces that the athlete encounters at ground contact. Braking forces refer to those forces which act in the opposite direction of the desired movement. Carl Lewis was often thought to be getting faster as they ran past 60m, he simply decelerated less than his competitors. In comparison to this, one of his competitors Desai Williams (one of Charlie Francis athletes), would accelerate exceptionally well but would traditionally decelerate very poorly in the final 30-40m of a race. A prime example of this was in the 1988 Seoul Olympics when he was second to Ben Johnson for the first forty meters, but only finished 7th by the end of the race (Ray Stewart tore his hamstring early in race and hobbled over the finish line in 8th).

The primary cause of excessive braking forces is making ground contact too far in front of the athlete’s center of mass (an athlete’s center of mass is roughly located in the vicinity of their hips). Why one athlete applies more braking forces at maximal velocity than another is difficult to say and is often multi-factorial than one simple isolated reason. Ideally, an athlete should minimise the horizontal distance between their center of mass and the point of ground contact. In simple terms, they need to strike the ground directly under their hips and not out in front of their body. Why do they do it? Often it is an veiled attempt to attain further maximal velocity rather than accepting they have reached their maximal speed and switch their focus to maintaining it with appropriate speed mechanics. Another reason is because they attempt to increase their force production in an effort to increase their stride length with the hope of increased velocity. Regardless of the reason, unfolding the tibia and stretching the leg out in front of the body with each step in an attempt to increase stride length will only increase horizontal braking forces, increase ground contact time and slow the athlete down.

Just watch Usain Bolt in the video below and how well he strikes under his COM during stance phase.

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Conclusion

Max velocity sprinting performance is maximized when the largest possible forces are applied to the ground in appropriate directions over very short periods of time. From a coaching perspective, an athlete should optimise their force production through appropriate strength training and speed mechanics training. In addition, they should look to minimise braking forces and increase vertical propulsive forces. On Elite Performance Institute (EPI) National Certificate in Strength & Conditioning (NCSC) course, we assess our athletes using our Speed Mechanics Assessment which involves assessing frontside and backside mechanics. The goal of the athlete is to minimise poor backside mechanics and enhance frontside mechanics. Finally outside of these technical points, FV curve needs to be developed with accessory work on gluteal and hamstring strength along with enhancing tendon stiffness to facilitate greater utilisation of stored elastic energy during ground contact.

References

  1. Mann, R. (1986). The biomechanical analysis of sprinters. Track Technique, 3000-3003.
  2. Mann, R. (2005). The Mechanics of Sprinting. CompuSport: Primm, NV.
  3. Mann, R. and Herman, J. (1985) Kinematic analysis of Olympic sprint performance: men’s 200 meters. International Journal of Sport Biomechanics, 1, 151-162.
  4. Mann, R.A., and Hagy, J. (1980). Biomechanics of walking, running, and sprinting. American Journal of Sports Medicine, 8(5), 345-350.
  5. Weyand, P., Sternlight, D., Bellizzi, M. and Wright, S. (2000). Faster top running speeds are achieved with greater ground forces not more rapid leg movements. Journal of Applied Physiology, 89, 1991-2000.

Written by Karl Gilligan

Founder & CEO 

Elite Performance Institute (EPI)

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Plyometric Training & Stretch Shortening Cycle (SSC)

This article reviews the research relating to Plyometric Training and the Stretch Shortening Cycle (SSC). The article is intended to provide Strength & Conditioning Coaches with an oveview of the the SSC, best coaching strategies, testing and monitoring of the SSC, specificity of exercise selection along with other important training concepts related to this method of training. 

Table of Contents

  1. Introduction
  2. Classification of SSC
  3. SSC Performance Tests & Monitoring
  4. Plyometric Training Coaching Model
  5. Practical Application & Conclusion
  6. References

Introduction

Early research on human muscles by Komi and Bosco (1978), and Komi (1984; 1986) demonstrated that concentric muscle work was increased when preceded by active stretch (eccentric action). This phenomenon is known as the stretch-shortening cycle (SSC) and has been extensively studied over the last number of decades. The SSC is a natural type of muscle function in which muscle   is stretched (eccentric phase) immediately before being contracted (concentric phase). Two mechanisms are the basis of both, voluntary and involuntary motor processes involved in the stretch-shortening cycle. The first mechanism (the neuromuscular model) is based on the so-called stretch reflex, which is also called the muscle spindle reflex or myotatic reflex, and on the Golgi tendon organ reflex (GTO reflex; Radliffe and Farentinos, 1999). The second mechanism of the stretchshortening cycle (the mechanical model) involves the use of the elastic energy of the muscle-tendon complex. Examples of SSC actions include natural movements seen in every day life such as walking or running or in sport such as sprinting, changing direction or wind-up movements such as throwing a ball. Although we will all have greater heights to which our SSC potential can reach (mainly due to genetic make up), the SSC is a trainable quality which can be developed by the Strength & Conditioning Coach to facilitate sports performance.

Classification of SSC

Schmidtbleicher (1992) has suggested that the SSC can be classified into two types, these include:

  • Fast SSC
  • Slow SSC

The fast SSC is characterized by short contraction times (<0.25s) with small angular displacements and can be observed in exercises such as depth jumping or hopping exercises. The slow SSC involves longer contraction times (0.25-0.50s), larger angular displacements and can be observed in exercises such as countermovement jumps or box jumps. The contraction times during both slow and fast exercises are typically determined through the use of electronic jump mats or force plates, and serve as an important variable when looking to develop the SSC.

ssc

Testing & Monitoring of the SSC

Slow SSC Tests:

  • Countermovement Jump (CMJ)
  • Standing Long Jump (SLJ)

Fast SSC Test:

  • Reactive Strength Index (RSI)

CMJ Test

The CMJ is the typically the preferred choice of concentric power measurement from the Strength & Conditioning Coach, given it uses an electronic jump mat and there is a greater volume of research to validate it’s usage. Jump height on the mat is measured and recorded in cm of height eg 35cm.  To perform the test, hands are placed on the hips, and stay there throughout the test. The athlete squats down and then immediately jumps vertically as high as possible, landing back on the mat on both feet at the same time. The take-off must be from both feet, with no initial steps or shuffling and they must land on the balls of their feet not their heels. They must also not pause at the base of the squat. The best result of at least three attempts is recorded – athletes get a fourth and final jump if improvements are being made on each of their three previous jumps.

counter_movement_jump

SLJ Test

The SLJ is a very useful alternative to the CMJ for coaches who do not posess an electronic jump mat. The athlete stands behind a line marked on the ground with feet slightly apart. A two foot take-off and landing is used, with swinging of the arms and bending of the knees to provide forward drive. The subject attempts to jump as far as possible, landing on both feet without falling backwards. The best result of at least three attempts is recorded – athletes get a fourth and final jump if improvements are being made on each of their three previous jumps.

slj-test

Reactive Strength Index (RSI) Test

Reactive strength is a representation of the fast SSC potential. It assesses an athletes’ ability to change quickly from an eccentric to a concentric contraction and their ability to develop maximal forces in minimal ground contact time. Typically RSI has been measured using drop jumps from a box onto an electronic jump mat. RSI is a ratio between ground contact time and height jumped,  as a result both these variables need to be considered in conjunction with the overall RSI score. The electronic mat measures ground contact time in the drop jump directly and calculates jump height based on the athlete’s “flight time”. See the RSI equation below:

rsi

Plyometric Training & Coaching Model

Plyometic exercises can be classified into slow and fast stretch-shortening cycle exercises (see above). In addtion to this, they can be further broken down into jumps, hops and bounds (see below). At Elite Performance Institute (EPI), we look to initially improve movement quality first by coaching the “fundamental” jumps before then progressing onto what we call “performance” jumps, hops & bounds. We want our athletes to establish correct movement and co-ordination of the fundamental jump exercises (CMJ, SJ, tuck jump and wall jump & reach) before progressing athletes onto more demanding plyometric exercises.

Jump = two legged take off followed by two legged land

Hop = single leg take off followed same single leg land

Bound = single leg take off followed by opposite single leg land

Practical Applications & Conclusion

Before Strength & Conditioning Coaches begin to prescribe plyometric exercises to their athletes, it is recommended they conduct some SSC profiling using CMJ/SLJ and RSI tests. In doing so they will have a greater understanding of their athletes SSC needs. Once profiled, they should then consider the force-velocity (FV) curve with regards their Strength & Conditioning program and whether they want to only focus solely on reactive strength adaptations or include reactive strength development with explosive or max strength training as part of a concurrent training program.

fv-curve_001

EPI recommends athletes who have limited SSC training begin with slow SSC exercises before progressing onto higher intensity SSC exercises. In addition, whether they are developing slow of fast SSC exercises it is also recommded the S&C Coach applies an appropriate “coaching model” to his athletes training. This will faciliate their co-ordination development as well as reducing the risk of injury.

This article was written by EPI CEO Karl Gilligan

References

  1. Flanagan EP and Comyns TM. The use of contact  time and the reactive strength index to optimise fast stretch-shortening cycle training. Strength Cond J 30: 33–38, 2008.
  2. Komi PV, Bosco C. Utilization of stored elastic energy in leg extensor muscles by men and women. Med Sci Sport, 1978; 10: 261-265.
  3. Komi PV. Neural mechanisms in strength and power training. Conference Book of International Conference on Weightlifting and Strength Training, K. Hakkinen (ed.), Lahti, Finland, 1998; 11-16.
  4. Komi PV. Physiological and biomechanical correlates of muscle function: effects of muscle structure and stretch-shortening cycle on force and speed. Exer Sport Sci Rev, 1984; 12: 81-121.
  5. Komi PV. Stretch-shortening  cycle: a powerful model to study normal and fatigued muscle. J Biomech  33:1197–1206,  2000.
  6. McClymont D. The use  of the reactive strength  index as an indicator of plyometric training conditions. In: Reilly T, Cabri J, and Arau´ jo D, eds. Science and Football V: The Proceedings of the Fifth World Congress on Sports  Science and Football. Lisbon, Portugal, 11–15 April 2003.  New York:
    Routledge;  2008.  pp. 408–416.
  7. Schmidtbleicher D. Training for power events. In P.V Komi (Ed.),The Encyclopeadia of Sports Medicine. Vol 3: Strength and Power in sport (pp. 169-179), 1992. Oxford, UK: Blackwell.

Written by Karl Gilligan

Founder & CEO 

Elite Performance Institute (EPI)

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Movement Compensation Screen (MCS)

Movement screening is a critical part of preventing injury in athletic population groups. The Movement Compensation Screen (MCS) is a valid clinial assessment tool that can reliably assess players in real-time who may be at risk of injury. Coaches/trainers/healthcare practitioners can now use the screen to assess their athletes/players/clients movement competency in biliateral, unilateral and jump landing positions. From here, appropriate corrective exercises are then prescribed to improve their movement limitations.

Table of Contents

  1. Introduction
  2. What is the MCS?
  3. MCS Research Abstract
  4. MCS Scoring System
  5. MCS 1 – Overhead Squat (OHS) Scoresheet
  6. Future Research
  7. Conclusions
  8. References

Introduction

Functional screening tools are popular in sports-medicine settings and are commonly used to evaluate balance, movement dysfunctions, and muscle imbalances.1-4 The goal of some clinical functional screens is to provide a concise, cost-effective and easily implementable method to identify problems in the musculoskeletal system that may lead to athletic injury.3, 5-7  Such tools can provide an efficient method for clinicians to predict and identify individuals who may be at risk for injury. In addition, sports-medicine clinicians can use the results from the screens to develop  pre-habilitation programmes to reduce this injury risk.8

Several risk factors for injury have been reported, such as joint laxity, range of movement (ROM), strength and balance. However, the evidence is, at best, mixed as to whether these variables are indeed significant risk factors for injury occurrence. Joint laxity has been shown in several studies to be significant in both males and females,9-11 whereas other studies found no association.12-14  The same variability has been reported for a lack of joint ROM.9,15,16   With regard to muscle strength, two studies11,12 found an association between strength differences between antagonist muscles in the leg and thigh and injury, however, these findings were questioned by other reports.10,14,15   Finally, research regarding the association between balance and injury has also displayed conflicting evidence with some findings demostrating a positive relationship between balance and injury,5,17 and others11,14 showing no relationship. Collectively, all this work suggests that the design of an effective pre-season screening tool will require much more research to find and evaluate variables that may predispose an athlete to injury.

What is the MCS?

The Movement Compensation Screen (MCS) is a clinical assessment tool that has been developed to assess an individual’s closed kinetic chain flexibility, mobility and stability using sport-specific tasks. Subjects are tested on three tests using bilateral, unilateral and jump landing environments.

The tests include:

  1. MCS 1 – Overhead Squat (OHS)
  2. MCS 2 – Single Leg Squat (SLS)
  3. MCS 3 – Jump Landing Mechanics (JLM)

The three tests were chosen as they utilize the typical positions often seen in the sport-specific environments and are thought to provide the foundation of more complex athletic movements.
ohs-pic  sls-pic jlm-pic

 

 

 

 

 

MCS Research Abstract

The Movement Compensation Screen (MCS) is a valid and reliable clinical assessment tool for prediction of non-contact injuries

Karl D. Gilligan

ABSTRACT

Context: Movement screening is a critical part of preventing injury in athletic population groups. A valid clinial assessment tool that can reliably assess players in real-time who may be at risk of injury would be very useful for sports teams.

Objective: This study sought to determine if the MCS could predict lower extremity injury in elite soccer  and amateur gaelic football (GAA) players, and to examine the inter-rater reliability of the MCS.

Design: Retrospective study with pilot reliability study.

Setting: Clinical setting.

Participants: 53 male volunteers (23 elite soccer and 30 amateur GAA players).

Intervention: Data on inter-rater reliability of the MCS was first obtained on a team of six physiotherapists using three subjects. Scores on the MCS, comprised of three movement tests, were calculated before the start or their competitive seasons. A sports injury retrospective questionnaire was used at the end of the season to record injury data.

Main Outcome Measures: Intra-class correlation coefficient (ICC) was used to calculate interrater reliability of the MCS. A Mann Whitney U-test was performed to determine if a significant difference existed in MCS composite scores between injured and non-injured players. A receiver operator characteristic (ROC) curve analysis was used to determine a cut-off score for the MCS that maximized sensitivity and specificity.

Results: ICC for the combined group of raters was 0.992. A Mann Whitney U-test revealed a significant (P=3´10-6) difference between the mean scores of injured and non-injured groups. Subjects with an MCS composite score of ≥ 26 were significantly more likely to sustain an injury with a Cohen’s Kappa (k) of 0.621 indicating a substantial agreement.

Conclusions: Compensatory movement patterns can increase the risk of injury in male soccer and GAA players, and can be identified by using a MCS screening tool.

Key Words: Injury risk, male athlete, movement screening

MCS Scoring

mcs-1-2-scoring1

MCS 1 – Overhead Squat (OHS) Scoresheet

mcs-1-overhead-squat-scoresheet1
Future Research

To make results more generalizable, future studies incorporating a larger, more diverse range of athletes including female athletes from various sports are warranted in order to determine if the MCS can be used to predict injury in these sports as well as female population groups. Future research on the MCS could also be directed towards the performance aspect of Strength & Conditioning as opposed to the injury prediction side, specifically if poor performance on the MCS results in poor performance on performance testing results (eg linear speed, power, etc).

Conclusion

Fundamental movement patterns such as those assessed by the MCS can be done so using sport specfic tests in the clinical setting. Early research on the Movement Compensation Screen (MCS) has shown that compensatory movement patterns can increase the likelihood of injury in Soccer and GAA players, and can be identified by using the MCS. The early retrospective descriptive study on the MCS demonstrated that players with a composite score of ≥26 had a greater chance of suffering a non-contact injury over the course of one competitive season.

From this initial research, the MCS shows potential to be an effective predictor of non-contact lower extremity injury in Soccer and GAA players. However, more research on the injury prediction capabilities of the MCS should be conducted before making a definitive conclusion.

This article was written by EPI CEO Karl Gilligan

References

  1. Riemann BL, Guskiewicz KM, Shields EW. Relationship between clinical and forceplate measures of postural stability. J Sport Rehabil. 1999;8:71–82.
  2. Hertel J, Miller S, Denegar CR. Intertester and intertester reliability during the Star Excursion Balance test. J Sport Rehabil. 2000;9:104-116.
  3. Kiesel K, Plisky PJ, Voight ML. Can serious injury in Professional Football be predicted by a preseason Functional Movement Sc North American Journal of Sports Physical Therapy. 2007;2(3):147-158.
  4. Padua DA, Marshall SW, Boling MC, Thigpen CA, Garrett WE, Beutler AI. The Landing Error Scoring System (LESS) is a valid and reliable clinical assess- ment tool of jump-landing biomechanics: The JUMP-ACL study. Am J Sports Med.2009; 37(10):1996–2002.
  5. McGuine TA, Greene JJ, Best T, Leverson G. Balance as a predictor of ankle injuries in high school basketball players. Clin J Sport Med. 2000;10(4):239–244.
  6. DiStefano LJ, Padua DA, DiStefano MJ, Marshall SW. The Landing Error Scoring System predicts non-contact injury in youth soccer Med Sci Sports Exerc. 2009;41(5):520–521.
  7. Cook , Burton L., Hoogenboom B. Pre-Participation Screening: The Use of Fundamental Movements as an Assessment of Function – Part 1. North American Journal of Sports Physical Therapy. 2006;1(2):62-72.
  8. Meir R., Diesel W., Archer E. Developing a pre-habilitation programme in a collision sport: A model developed within English premiership rugby union football. Strength Cond. 2007;29:50-62.
  9. Krivickas LS, Feinberg JH. Lower extremity injuries in college athletes: relation between ligamentous laxity and lower extremity muscle tightness. Archives of Physical Medicine & Rehabilitation. 1996;77(11):1139-1143.#
  10. Ostenberg A., Roos H. Injury risk factors in female European football. A prospective study of 123 players during one season. Scandinavian Journal of Medicine & Science in Sports. 2000;10(5):279-285.
  11. Soderman K., Alfredson H., Pietila T., Werner S. Risk factors for one leg injuries in female soccer players: a prospective investigation during one out-door season. Knee Surgery, Sports Traumatology, Arthroscopy. 2001;9(5):313-321.
  12. Baumhauer JF, Alosa DM, Renstrom PAFH, Trevino S, Beynnon B. A prospective study of ankle injury risk factors. The American Journal of Sports Medicine. 1995;23(5):564-570
  13. Hopper DM, Hopper JL, Elliott BC. Do selected kinanthropometric and performance variables predict injuries in female netball players? Journal of Sports Sciences. 1995;13(3):213-222.
  14. Beynnon BD, Renstrom PA, Alosa DM, Baumhauer JF, Vacek PM. Ankle ligament risk factors; a prospective study of college athletes. Journal of Orthopaedic Research. 2001;19(2):213-220.
  15. Milogrom C, Shlamkovitch N, Finestone A, Eldad A, Laor A, Danon YL et al. Risk factors for lateral ankle sprain: a prospective study among military recruits. Foot & Ankle. 1991;12(1):26-30.
  16. Arnason A, Gudmundsson A, Dahl HA, Johannsson E. Soccer injuries in Iceland. Scandinavian Journal of Medicine & Science in Sports. 1996;6(1):40-45.
  17. Tropp H, Ekstrand J, Gillquist J. Stabilometry in functional instability of the ankle and its value in predicting injury. Medicine & Science in Sports & Exercise. 1984;16(1):64-66.
  18. Chorba RS, Chorba DJ, Bouillon LE, Overmyer CA, Landis JA. Use of A Functional Movement Screening Tool to Determine Injury Risk in Female Collegiate Athlet North American Journal of Sports Physical Therapy. 2010;5(2):47-54.
  19. Minick KI, Kiesel KB, Burton L, Taylor A, Plisky P, Butler RJ. Interrater reliability of the functional movement sc Journal of strength and conditioning research / National Strength & Conditioning Association. 2010;24(2):479-486.
  20. Peate WF, Bates G, Lunda K, Francis S, Bellamy Core strength: a new model for injuryprediction and prevention. Journal of occupational medicine and toxicology (London, England). 2007;2:3.
  21. Burton SL. Performance and injury predictability during firefighter candidate training. Unpublished. 2006.
  22. Yard EE, Collins CL, Comstock RD. A comparison of high school sports injury surveillance data reporting by certified athletic trainers and coaches. Athl. Train. Nov-Dec 2009;44(6):645-652.
  23. Powell JW, Barber-Foss KD. Injury patterns in selected high school sports. A review of the 1995-1997 seasons. J Athl Train. Jul-Sept 1999;34(3):277-284.
  24. Shankar PR, Fields SK, Collins CL, Dick RW, Comstock RD. Epidemiology ofhigh school and collegiate football injuries in the United States, 2005-2006. Am J Sports Med. Aug 2007;35(8):1295-1303.
  25. Ristolainen L. Sports Injuries in Finnish Elite Cross-Country Skiers, Swimmers, Long-Distance Runners and Soccer Players. Scand J Med Sci Sports. 2011; 22(4).
  26. Landis JR, Koch GG. The measurement of observer agreement for categorical data. 1977;33(1):159-174.
  27. Knapik JJ, Bauman CL, Jones BH, Harris JM, Vaughan L. Preseason strength and flexibility imbalances associated with athletic injuries in femal collegiate athletes. Am J Sports Med. 1991;19(1):76-81.
  28. Hennessy L, Watson AWS. Flexibility and posture assessment in relation to hamstring injury. Br J Sp Med. 1993;27(4).

Written by Karl Gilligan

Founder & CEO 

Elite Performance Institute (EPI)

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Variable Resistance Training (VRT) – Bands & Chains

In recent years, it has become popular for S&C Coaches to utilise resistance training with the addition of bands and chains. In this article, we consider the advantages of manipulating an exercise to match the resistance provided with the force capabilities of the lifter, which generally change throughout the movement. We explain how bands and chains can be used to manipulate a variety of exercises that have the potential to enhance performance in sport. Finally whilst there are many similarities between the use of bands and chains for resistance training, there are key differences which will be discussed in more detail.

Table of Contents

  1. Introduction
  2. Benefits of VRT
  3. Chain Resistance
  4. Band Resistance
  5. Conclusion
  6. References

Introduction

There is a strong relation between strength, power and dynamic athletic performance (Baker & Nance, 1999; Kawamori & Haff, 2004; Tan, 1999). Therefore, the ability to develop high levels of muscular strength and power are critical components in many sporting activities (Kilduff et al., 2007). S&C Coaches are continuously looking for new training techniques in an attempt to improve strength and power adaptations in their athletes. One such method that has recently become popular is Variable Resistance Training (VRT) (Ghigiarelli et al., 2009; McCurdy, Langford, Jenkerson & Doscher., 2008).

VRT is a broad term used to describe loading techniques that provide changing loads throughout a movement and traditionally involves an increasing load during the concentric phase and decreasing load during the eccentric phase. The concept of VRT however is not a new one. As early as the 1940’s experimentation with counter balances and pulley systems was being used to produce progressive resistance exercise, whilst in the 1980’s pulley machines with changing radii were utilised as a type of variable resistance training (Keohane, 1986).

As well as using more traditional mechanisms, variable resistance can also be produced through the use of elastic bands. VRT of this nature has been used in rehabilitation to provide controlled stretch and strengthening and to increase range of motion after trauma (Patterson, Stegink, Hogan & Nassif, 2001; Wallace, Winchester & McGuigan, 2006). The addition of chains to fixed load has also been utilised as a mechanism for producing variable resistance and has received some attention in previous literature (Ghigiarelli et al., 2009; McCurdy, Langford, Ernest, Jenkersin & Doscher, 2009). Recently, variable resistance has been applied to strength and power training in an attempt to obtain improved training adaptations (Wallace et al., 2006).

chains

Benefits of Variable Resistance Training (VRT)

It has been theorised that VRT may be a more effective training stimulus than fixed load training, as fixed load training results in a period of deceleration once the inertia of a load is overcome early in the concentric phase of a movement (Keohane 1986). This deceleration occurs as a necessity to slow the momentum of a load to prevent it from being thrown. In contrast, many other sports specific training techniques such as jumping and ballistic movements produce a continuing increase in force throughout the concentric phase until the load is released (Ebben, Flanagan & Jensen, 2007; Welter & Bobbert, 2002). Variable resistance was designed to more closely reflect the length-tension relationship during a movement than traditional fixed load training (Kauhansen, Hakkinen, & Komi, 1989). The linear increase in load afforded by variable resistance bands is thought to closely match the increase in accumulated muscular force and increased torque about a joint throughout a concentric movement, and may allow for a greater period of activation (Mcmasters, Cronin, McGuigan, 2009; Wallace et al., 2006). Variable resistance is thought to provide an optimal load to be maintained throughout a greater range of motion and thus cause greater strength and power adaptations (Ebben & Jensen 2002; Faron, 1985; Ghigiarelli et al., 2009; Wallace et al., 2006).

It has been purported that training eccentrically at loads which exceed normal training thresholds allows for greater muscular adaptation to be developed (Higbie, Cureton, Warren & Prior, 1996). It has also been suggested that VRT may cause greater eccentric loading to occur by increasing the eccentric velocity and therefore the force needed to decelerate the load during this phase (Conlin, 2002; Cronin, McNair, & Marshall., 2003). Theoretically, there may be an additional advantage in using elastic tension which may not be relevant to the use of chains as a mechanism to provide variable resistance (Conlin, 2002; Cronin et al, 2003). However, in contrast to the purported benefits of VRT, it has also been suggested that variable resistance may be ineffective in producing strength adaptations, as reduced load at the end of an eccentric movement may not be an adequate stimulus to cause improvements in this range of movement (McCurdy et al., 2009).

Band Resistance

Elastic bands have become increasingly more popular as a performance enhancement tool and subsequently have been investigated systematically to better understand the mechanisms responsible for the performance adaptations that have been observed (Anderson et al., 2008; Argus et al., 2011). It has been demonstrated that elastic bands can challenge or assist the strength curve by providing variation in how a muscle complex is challenged over a range of motion (Cronin et al., 2003).

To understand why proponents of elastic bands favor this training modality, it is important to consider that the human strength curve is influenced by the torque (measure of how much a force acting on an object causes that object to rotate) about single joints using 2 or 3 dimensional co-ordinate systems (Frost et al., 2010). The human strength curve,  can be classified into 3 categories: ascending, descending, and bell shaped (see diagram below) (Kulig et al., 1984; McMaster et al., 2009).

Force curve

The shape of the curve is determined by the force angle relationship. An example of exercises influenced by a descending curve where maximum strength is required at the end of the concentric phase are upper body pulling exercises such as the bent over row, chin-ups, and bench pulls (Fleck, 2004). Single-joint movements such as bicep curls or leg extensions are examples of bell-shaped strength curve exercises where maximum strength occurs around the middle of the movement’s range of motion (Fleck, 2004). Finally, exercises such as a squatting, dead-lifting, and/or weightlifting movements are examples of an ascending strength curve (Fleck, 2004).

The fact that training with elastic bands aims to challenge the ascending strength curve by providing a variable load throughout a range of motion with the most resistance experienced at or near full muscular extension where athletes typically exhibit the highest force production capability is a primary reason why elastic bands in combination with constant resistance may be superior over constant resistance alone (Argus et al., 2011; Cronin et al., 2003). Elastic bands used as a resistive modality compliment the length-tension relationship by requiring a progressive recruitment in high-threshold motor units, thus, requiring the highest motor unit recruitment at the most mechanically advantageous position within that movement (Frost et al., 2010).

References

  1. Anderson CE, Sforzo GA, and Sigg JA. The effects of combining elastic and free weight resistance on strength and power in athletes. J Strength Cond Res 22: 567– 574, 2008.
  2. Argus CK, Gill ND, Keogh JW, Blazevich AJ, and Hopkins WG. Kinetic and training comparisons between assisted, resisted, and free countermovement jumps. J Strength Cond Res 25: 2219–2227, 2011.
  3. Cronin J, Mcnair P, and Marshall R. The effects of bungy weight training on muscle function and functional performance. J Sport Sci 21: 59–71, 2003.
  4. Fleck SJ. Designing Resistance Training Programs. Champaign, IL: Human Kinetics, 2004. pp: 31.
  5. Frost DM, Cronin J, and Newton RU. A biomechanical evaluation of resistance. Sports Med 40: 303–326, 2010.
  6. Kulig K, Andrews JG, and Hay JG. Human strength curves. Exerc Sport Sci Rev 12: 417–466, 1984.
  7. McMaster DT, Cronin J, and Mcguigan MR. Forms of variable resistance training. J Strength Cond Res 31: 50–64, 2009.
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