Variable Resistance Training (VRT) – Bands & Chainsepicontrol
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
- Benefits of VRT
- Chain Resistance
- Band Resistance
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).
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).
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).
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).
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