Lower Extremity Stiffness in Collegiate Distance Runners Pre- and Post-Competition

Abstract

During running, the lower extremities are compared to a spring due to their ability to store and release energy. Recent evidence suggests a relationship between increased lower extremity stiffness and enhanced athletic performance, specifically in distance running. Current literature lacks information on the influence of fatigue on leg stiffness across multiple days in response to competition. PURPOSE: To determine how leg stiffness in runners was influenced in the 24- and 48-hour period following a cross country race. METHODS Twenty-two collegiate cross-country runners (13 M, 9 F, 19.5 ± 1.4 yo) were recruited and participated. Leg stiffness was assessed 24h before a race and 24h and 48h post-race. Participants performed three static jumps (SJ) and three countermovement jumps (CMJ) on two force plates (AMTI Optima OPT464508; Watertown, MA; 1000 Hz). During each jump, participants held a dowel across the shoulders to prevent arm swing. Participants then performed a hop test (HT) where they completed 10-s of straight leg maximal hopping in sync with a metronome (2.2Hz). Leg stiffness was calculated, in agreement with previously reported methods, from the vertical ground reaction force of the 5th-7th hop of the HT. Repeated measures ANOVA and post-hoc analysis were used to assess significance (p ≤ 0.05). RESULTS: A significant main effect was found for SJ height, CMJ height and leg stiffness. Leg stiffness was significantly reduced 24h post-race (pre-race 36.84 ± 4.96 kN · m-1, 24h post 33.11 ± 8.05 kN · m-1, p = 0.05) and then increased significantly from 24h post-race to 48h post-race (36.84 ± 6.88 kN · m-1,p = 0.015). No significant differences were found in post-hoc analysis for CMJ height (pre-race 30.81 ± 5.79 cm, 24h post-race 29.89 ± 6.06 cm, 48h post-race 31.44 ± 6.47 cm, p > 0.05) and eccentric utilization ratio (pre-race 1.24 ± 0.10, 24h post-race 1.20 ± 0.10, 48h post-race 1.22 ± 0.10, p > 0.05). SJ height increased significantly from 24h to 48h post-race (24h post-race 25.99 ± 5.65 cm, 48h post-race 27.19 ± 5.63 cm, p > 0.05). CONCLUSION: Following a cross country race leg stiffness significantly declined in a group of collegiate runners 24 hours post-race but returned to baseline 48 hours post-race. Sport scientists and coaches may be able to monitor leg stiffness as a metric to properly prescribe training regiments.