Drop punt kicking induces eccentric knee flexor weakness associated with reductions in hamstring electromyographic activity

Abstract Objectives To examine the effect of 100 drop punt kicks on isokinetic knee flexor strength and surface electromyographic activity of bicep femoris and medial hamstrings. Design Randomized control study. Methods Thirty-six recreational footballers were randomly assigned to kicking or control groups. Dynamometry was conducted immediately before and after the kicking or 10 min of sitting (control). Results Eccentric strength declined more in the kicking than the control group ( p d  = 1.60), with greater reductions in eccentric than concentric strength after kicking ( p  = 0.001; d  = 0.92). No significant between group differences in concentric strength change were observed ( p  = 0.089; d  = 0.60). The decline in normalized eccentric hamstring surface electromyographic activity (bicep femoris and medial hamstrings combined) was greater in the kicking than the control group ( p d  = 1.78), while changes in concentric hamstring surface electromyographic activity did not differ between groups ( p  = 0.863; d  = 0.04). Post-kicking reductions in surface electromyographic activity were greater in eccentric than concentric actions for both bicep femoris ( p  = 0.008; d  = 0.77) and medial hamstrings ( p d  = 1.11). In contrast, the control group exhibited smaller reductions in eccentric than concentric hamstring surface electromyographic activity for bicep femoris ( p  = 0.026; d  = 0.64) and medial hamstrings ( p  = 0.032; d  = 0.53). Reductions in bicep femoris surface electromyographic activity were correlated with eccentric strength decline ( R  = 0.645; p  = 0.007). Conclusions Reductions in knee flexor strength and hamstring surface electromyographic activity are largely limited to eccentric contractions and this should be considered when planning training loads in Australian Football.