The ability to develop high levels of muscular strength and power is considered to be a critical component in many, if not most, sports. Because of this, new training methods are constantly being sought in an attempt to improve strength and power development. One such method is variable resistance training (VRT). This research aims to determine the effect of VRT on back squat one repetition (1RM) strength, vertical jump height and 30m sprint time.
Twenty male high school athletes (mean age 17.5 ± 0.7 years) were pair matched based on 1RM scores (predicted from 4RM). Subjects completed a five-week within-group standardised training programme, with the control group completing fixed load back squats and the experimental group completing variable resistance back squats (with the use of elastic bands). Pre- and post-training vertical jump height, predicted 1RM squat strength and 10m, 20m and 30m sprint speeds were measured.
The VRT group had greater increases in strength and vertical jump than the fixed load training group, with a moderate difference in pre- to post-training predicted 1RM (mean; ± 90% confidence limit; 7.0; ±6.1%) and a small difference in the within-group changes in vertical jump height (4.6; ± 5.4%) from pre- to post-training. VRT also produced a small difference (4.8; ±5.3%) in pre- to mid-training 1RM changes. All other changes were trivial or unclear.
Eleven male semi-elite athletes (mean age 19.9 ± 2.0 years) also participated in this research as a case study. Findings in this case study supported the effectiveness of VRT over fixed load training in improving back squat predicted 1RM strength, but not vertical jump height or 30m sprint time. However, no findings in the semi-elite case study were statistically clear due to a lack of statistical power. Further research is required into the effects of this training technique on mature athletes.
This study also aimed to determine the level of regression that occurs in resistance afforded by elastic resistance bands as a result of repeated use. In order to ascertain the reliability of training loads used throughout the study, the resistance of each band was also measured at the mid-point and completion of the training study. This determined the rate of degradation that occurred to variable resistance elastic bands with use. Due to minor changes in the amount of variable resistance afforded by the bands after use, loading protocols were modified at the midpoint of training to reflect these changes.
This study has found that variable resistance training is an effective training tool in improving 1RM back squat strength and vertical jump height in mature high-school athletes. Preliminary research into the effect of VRT on semi-elite athletes also points to greater improvements in lower limb strength and vertical jump height when compared to fixed load training, although these findings are subject to further research. These results suggest that VRT is a useful training technique in lower body strength and power development in the vertical plane of movement. As such, VRT may be implemented with confidence into training programmes desiring to improve lower limb strength and vertical jump height.