Don’t Jump To Conclusions: Comparison Of The Knee Extensor Moment Across Plyometric Tasks And Running

INTRODUCTION: The knee extensor moment plays a key role in attenuating high levels of force during dynamic tasks such as running and jumping. While returning to running is a key goal for many athletes, there is no consensus on how to appropriately prepare for the knee extensor demands of running. Plyometric exercises such as double leg countermovement jumps (DL-CMJ) and single leg countermovement jumps (SL-CMJ) are thought to be key progressions of load prior to initiating running. However, this idea has gone unexplored, leaving clinicians to guess how to appropriately progress patients to running after a knee injury. PURPOSE: To compare the differences in the knee extensor moment during SL-CMJ and DL-CMJ to running. METHODS: 39 participants (24.1 ± 7.0 years, 26F, Tegner: 5.9 ± 1.4) performed an instrumented data collection running (3.0 m\s). They also performed 4 trials of DL-CMJ followed by SL-CMJ. Peak knee extensor moment during stance was determined from customized computer code. One-way repeated measures ANOVA was performed to compare means of peak knee extensor moment across tasks. Tukey’s post hoc test for multiple comparisons compared significant differences among groups. RESULTS: We found a significant main effect for mean peak knee extensor moment across tasks (F(2,38) = 29.19, p < 0.001). Post hoc pairwise comparisons showed DL-CMJ had lower peak knee extensor moment than running (1.00 ± 0.28 Nm/kg vs 1.29 ± 0.19 Nm/kg, p < 0.001). There was no difference in peak knee extensor moment between SL-CMJ and running (1.28 ± 0.31 Nm/kg vs. 1.29 ± 0.19 Nm/kg, p = 0.990). CONCLUSION: Despite higher vertical jump height on double leg countermovement jumps, knee extensor demand is significantly lower when compared to running. Practitioners should consider progressing to single leg countermovement jumps to adequately prepare athletes for the knee extensor demand of running. While this analysis focused on peak demands, future work should also consider cumulative load of running when developing a plyometric program.