Bogdanis, Tsoukos, Kaloheri, Terzis, Veligekas, & Brown (2017), compared unilateral and bilateral plyometric training on jumping performance and strength. The study consisted of 15 education students (age range: 18.2-25.8 years, 8 male, 7 female). They were randomly assigned to either a unilateral (n=7) or bilateral (n=8) training group. The study design was a repeated measures and baseline testing measured maximal isometric force and RFD, 1RM leg extension and curl, and countermovement and drop jump performance. Two familiarization sessions took place to reduce performance benefits derived from testing experience. Countermovement jump height was calculated using a force plate, which is a highly reliable method. The ICC of countermovement jumps was 0.99 (p<0.01). Drop jump height was calculated by the same method. The subjects dropped from a height of 30 cm, with either one or both legs, and then immediately jumped. Along with jump height, reactive strength index (a measure of explosiveness) was found by multiplying height x inverse of ground contact time. ICC for the drop jump were 0.95 for height, 0.96 for contact time, and 0.99 for the reactive strength index. Isometric strength and RFD were measured using a force plate mounted onto a rigid leg press with an approximate knee angle of 101 degrees. Subjects were instructed to push as fast and hard as possible for 4 seconds. RFD was recorded at 0-50, 100, 200, and 300 ms. ICC for RFD of single leg movements ranged from 0.873-0.98 and for bilateral from 0.951 to 0.990. The training intervention consisted of 2 sessions per week for 6 weeks (12 sessions) on non-consecutive days. Each group performed the same number of jumps and exercises with the only difference being the exercises being performed either unilateral or bilaterally. Rest was 1 minute between sets and 3 minutes between exercises. Statistically analysis revealed significant improvements for both groups in the countermovement jump. The unilateral group improved by 11.0±5.5% (p<0.001, d=0.59) and the bilateral group by 12.1±7.2% (p<0.001, d=1.01). Additionally, only the unilateral group significantly improved in unilateral countermovement jump performance (19.0±7.1%, p<0.001, d=1.17). No significant findings were noted for the drop jump and both group improved similarly (5% for bilateral and 9% for unilateral). For the reactive strength index, post-hoc testing revealed improvements in the unilateral group only (1.01±0.22 to 1.25±0.25 m•s-1, p=0.001, d=1.03). Isometric testing was significantly improved in both groups for bilateral testing. However, the unilateral group demonstrated significantly greater single leg strength (2-fold, d=1.22). For rate of force development, a 2-way ANOVA showed RFD50 was unchanged for the bilateral measurements. RFD100 was increased similarly between groups (d=0.66 for bilateral and d=1.05 for unilateral). The sum of left and right legs for RFD50 and RFD100 was improved only in the U group (d=0.77 and d=1.0, respectively. No interactions were found for RFD200 or RFD300. Leg strength was also increased similarly in both groups and the average strength increase for extension 1 RM being 30.8±14.7% (p<0.001, d=0.92) and for leg curl 1 RM being 22.2±14.1% (p=0.001, d=0.51). In summary, this study provides evidence that unilateral training provides performance benefits for both unilateral and bilateral tasks while bilateral training only improves bilateral performance. An additional and novel finding was the RFD improvements in the unilateral group only at early time periods.
Bogdanis, G. C., Tsoukos, A., Kaloheri, O., Terzis, G., Veligekas, P., & Brown, L. E. (2017). Comparison between Unilateral and Bilateral Plyometric Training on Single and Double Leg Jumping Performance and Strength. Journal of Strength and Conditioning Research, 1. doi:10.1519/jsc.0000000000001962
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