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

ObjectivesTo examine the effect of 100 drop punt kicks on isokinetic knee flexor strength and surface electromyographic (sEMG) activity of bicep femoris (BF) and medial hamstrings (MH).DesignRandomised control study.MethodsThirty-six recreational footballers were randomly assigned to kicking or control groups. Dynamometry was conducted immediately before and after the kicking or 10 minutes of sitting (control).ResultsEccentric strength declined more in the kicking than the control group (p < 0.001; 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 sEMG (BF and MH combined) was greater in the kicking than the control group (p < 0.001; d =1.78), while changes in concentric hamstring sEMG did not differ between groups (p = 0.863; d = 0.04). Post-kicking reductions in sEMG were greater in eccentric than concentric actions for both BF (p = 0.008; d = 0.77) and MH (p < 0.001; d = 1.11). In contrast, the control group exhibited smaller reductions in eccentric than concentric hamstring sEMG for BF (p = 0.026; d = 0.64) and MH (p = 0.032; d = 0.53). Reductions in BF sEMG were correlated with eccentric strength decline (R = 0.645; p = 0.007).ConclusionsReductions in knee flexor strength and hamstring sEMG are largely limited to eccentric contractions and this should be considered when planning training loads in Australian Football.