Fatigue effects of marathon running on neuromuscular performance

The influence of an individual marathon race was investigated among 7 subjects who performed 2 types of unilateral isometric strength tests before and after the race. The tests included maximal isometric voluntary actions (MVA) of the knee extensor muscles and isometric endurance of 60% of pre-marathon MVA. The results showed dramatic reductions of the maximal isometric torque (26 ± 14%) and endurance time (39 ± 9%). Maximal integrated electromyographic activity (IEMG) of the vastus medialis muscle decreased by 36 ± 26% and that of the vastus lateralis muscle by 42 ± 25%. In the submaximal endurance test, the post-marathon isometric knee extension started at a higher level of IEMG and lower mean power frequency (MPF) for 6 of 7 subjects. These data suggest that the repeated stretch-shortening cycles during the marathon race affected the force production by reducing neural input to the muscles and deteriorating the efficiency of the contractile mechanism.