Leg strength and stiffness as ability factors in 100 m sprint running

The purpose of this study was to determine the importance of leg strength and stiffness relative to i) 100 m sprint performance, ii) mean speed on the three phases of the 100 m race (30-60-100 m) and iii) the speed differences between these phases.Nineteen regional to national level male sprinters competed in a 100 m race. Video analysis was used to determine mean velocity parameters. Two subgroups were created since some of the runners decreased their velocity during the third phase (G1), whereas others maintained or accelerated it (G2). Leg strength (concentric half-squats - counter movement jump) and stiffness (hopping) were determined. Simple (r) and multiple regressions (R) were used.The mean performance over 100 m was 11.43 sec (10.72-12.87 sec). The concentric half-squats were related to 100 m (r=0.74, p0.001) and to the mean speed of each phase (R=0.75, p0.01). The counter movement jump was related to 100 m (r=0.57, p0.05) and was the predictor of the first phase (r=0.66, p0.01). The hopping test was the predictor of the two last phases (R=0.66, p0.05). Athletes who had the greatest leg stiffness (G1) produced the highest acceleration between the first and the second phases, and presented a deceleration between the second and the third ones.The concentric half-squats test was the best predictor in the 100 m sprint. Leg stiffness plays a major role in the second phase.