Effect of stride length on symptoms of exercise-induced muscle damage during a repeated bout of downhill running

The purpose of this study was to assess the effects of changes in stride le ngth on the symptoms of exercise-induced muscle damage (EMID) during a repe ated bout of downhill running in a group of 18 men and women, Muscle tender ness, plasma creatine kinase activity (CK) and maximal voluntary isometric force were measured before and after two downhill runs, with each run separ ated by 5 weeks. The first downhill run was at the preferred stride frequen cy (PSF). Participants were then randomly allocated to one of three sex-bal anced groups with equal numbers of men and women: overstride (-8% PSF), und erstride (+8% PSF) and normal stride frequency for the second downhill run. Stride length had no effect (P>0.05) on muscle tenderness, CK or iso-metri c peak force. Increases in muscle tenderness (P<0.001) and CK were lower (P <0.05) following the second downhill run, although there was no difference in the pattern and extent of the strength decrement between the two runs, T here mere also no differences (P>0.05) in muscle tenderness, CK or the rela tive strength loss between the men and the women. Results suggest that the symptoms of EIMD are unaffected by gender and small alterations to the norm al stride pattern during constant velocity downhill running. The observatio n that muscle tenderness and CK were reduced following a repeated bout of s imilar eccentric exercise is consistent with the phenomenon known as the 'r epeated bout effect' of muscle damage.