What is variable resistance training? And should you be doing it?
Variable resistance training is when you progressively add or reduce the load throughout a lift. This is commonly done through the use of bands or chains.
To answer the second question, we’re going to look at a meta analysis by Soria-Gila et al., (2015) which is published in the Journal of Strength and Conditioning Research. The meta analysis reviewed 7 studies of long term VRT (over 7 weeks) of over 235 participants, trained and untrained. The back squat, bench press and the leg press were studied. For the purposes of this article we are going to look at the data provided for trained individuals and even more specifically, the back squat and the bench press.
For the bench press, there were 3 studies of trained individuals (Anderson et al., 2008; Ghigiarelli et al., 2009; and McCurdy et al., 2009b).
For the squat, they reviewed 2 studies showing trained individuals. (Anderson et al, 2008; Rhea et al., 2009)
As you can see in the tables and chart above, the average increase in KGs for the VRT group is quite a bit higher than the control group using straight weight, even if you take out the outlier of the McCurdy et al., (2009b) study with the 22.41kg increase.
What explains this large increase in strength as opposed to lifting with straight weight?
Concentric: When using bands, acceleration through the early stage of the lift is crucial to combat the elastic effect. The instability caused by the bands may induce an optimal stimulus for strength gains and increase neuromuscular demand and motor unit recruitment beyond that of a straight weight set. (McCurdy et al., 2008a); Heckman & Enoka 2012)
Eccentric: VRT increases eccentric loading, forcing the athlete to decelerate the bar, which causes more EMG activity in the muscles. (Cronin et al., 2003)
According to Anderson et al., (2008, as discussed by Soria-Gila et al., 2015) the results demonstrate significant 1RM improvements obtained in the bench press and squat. Participants showed no significant increase in muscle cross-sectional area at the end of training period, suggesting neuromuscular improvements (p. 3267). Anderson et al., (2008) also suggests greater muscle fibre recruitment and stimulation during each lift may bring about greater neuromuscular adaptations and/or type IIx fibre recruitment with VRT (p. 326).
Absolute load (kg) used in the studies for the meta-analysis are significantly lower than weights a powerlifter may train with. The absolute cost of energy associated with a greater barbell load (kg) may influence the effectiveness of implementing VRT in an athlete’s training. Results of this study show a greater increase in 1RM when utilizing VRT for 12 week periods as opposed to shorter training periods (Soria-Gila et al., 2015). No data was collected on time frames longer than 12 weeks.
VRT protocol for strength is suggested as 80% bar weight in conjunction with 15-20% band or chain tension for maximal loading. For improvements in barbell velocity (speed) Soria-Gila et al., (2015) prescribes 20-30% barbell weight in conjunction with 30-40% band or chains for a total load of 60%.
VRT training modality enables athletes to more rapidly and efficiently achieve adaptations in their functional capacity when compared to more traditional resistance training methods. (Soria-Gila et al., 2015 p. 3268). VRT could be used as a complement to traditional training to vary the athletic stimulus, leading to faster training-induced adaptations.
Anderson, C. E., Sforzo, G. A., & Sigg, J. A. (2008). The effects of combining elastic and free weight resistance on strength and power in athletes. The Journal of Strength & Conditioning Research, 22(2), 567-574.
Cronin, J., McNAIR, P. E. T. E. R., & Marshall, R. (2003). The effects of bungy weight training on muscle function and functional performance. Journal of sports sciences, 21(1), 59-71.
Ghigiarelli, J. J., Nagle, E. F., Gross, F. L., Robertson, R. J., Irrgang, J. J., & Myslinski, T. (2009). The effects of a 7-week heavy elastic band and weight chain program on upper-body strength and upper-body power in a sample of division 1-AA football players. The Journal of Strength & Conditioning Research, 23(3), 756-764.
Heckman, C. J., & Enoka, R. M. (2012). Motor unit. Comprehensive Physiology, 2629-2682.
McCurdy, K., Langford, G., Jenkerson, D., & Doscher, M. (2008a). The validity and reliability of the 1RM bench press using chain-loaded resistance. The Journal of Strength & Conditioning Research, 22(3), 678-683.
McCurdy, K., Langford, G., Ernest, J., Jenkerson, D., & Doscher, M. (2009b). Comparison of chain-and plate-loaded bench press training on strength, joint pain, and muscle soreness in Division II baseball players. The Journal of Strength & Conditioning Research, 23(1), 187-195.
Rhea, M. R., Kenn, J. G., & Dermody, B. M. (2009). Alterations in speed of squat movement and the use of accommodated resistance among college athletes training for power. The Journal of Strength & Conditioning Research, 23(9), 2645-2650.
Soria-Gila, M. A., Chirosa, I. J., Bautista, I. J., Baena, S., & Chirosa, L. J. (2015). Effects of variable resistance training on maximal strength: a meta-Analysis. The Journal of Strength & Conditioning Research, 29(11), 3260-3270.