Thompson, K., Spriet, L.L. & Burr, J.F. (2018)
The aim of the current study was to determine whether performing RST with well-trained sprinters results in a potentiation effect, leading to improvements in subsequent maximal sprint performance over 0-20m. Varsity level sprinters (n=12), were randomized to either a RST or un-resisted sprint (URS) group. Each group performed 24 paired sprints, over 4 days, each separated by 1wk. Sprint protocols consisted of either 3x20m maximal RST or URS with a maximal sprint performed prior to (initial) and after (final) training protocols. Sprint times were compared using a 2(group) x 2(time) repeated measures ANOVA. No significant change was observed between initial (RST=3.37±0.18s, URS=3.45±0.14s) and final (RST=3.37±0.18s, URS=3.42±0.25s) sprints over 0-20 m in either the RST (Δ=-0.01s) or URS (Δ=+0.01s) group (p=0.62). This statistically demonstrates that there is no potentiating effect of RST on subsequent maximal sprint performance in well-trained sprinters, while highlighting the consistency with which they perform, and thus the small magnitude of change required in an individual athlete to effect meaningful change. As such, the larger between-subject variation may reduce the detection of meaningful changes when using null hypothesis testing. By expressing delta times (initial-final) against within-subject “typical error” and summing the number of participants whose time changed by more than the associated error, the RST group had a 17% frequency of positive responses amongst sprinters. In contrast, 0% of the URS group improved. Importantly; however, decrements in performance were observed in 13% and 4% of observations in RST and URS groups, respectively. Group mean changes do not support a potentiating effect of RST on 20m sprint time; however, analysis of individual response suggests that sprint time following RST is more frequently decreased than increased.