Exploring The Impact Of Load Carriage And Fatigue On Countermovement Jump Phases: A Pilot Study

Load carriage (LC) is an essential burden of tactical athletes (TA) to ensure operation success and safety. Prolonged LC results in localized fatigue (LF), which is associated with reduced occupational performance and increased injury risk. To mitigate these adverse effects it is important to understand the independent and additive effects of LC and LF on neuromuscular (NM) function. The countermovement jump (CMJ) assesses numerous NM metrics in one attempt. To assess changes related to LC an LF it is crucial to identify performance and injury-sensitive metrics. PURPOSE: To assess the independent and additive effects of LC and LF on the eccentric (EP), concentric (CP), and landing (LP) phase of the CMJ.METHODS: After a dynamic warm-up participants (n = 10, males = 9, age = 28.3 ± 6.8 yr, Ht = 174.4 ± 8.5 cm, mass = 78.1 ± 11.8 kg) completed 3 unloaded CMJ, 3 CMJ with a 20 kg vest, a Wingate test to induce LF, then completed 3 loaded CMJ. Each set of 3 CMJ had 15 seconds of rest between attempts. Repeated measures ANOVA with Bonferroni post hoc tests were utilized to compare the effect of non-fatigued unloaded (NFU), non-fatigued loaded (NFL), and fatigued loaded (FL) conditions on CMJ metrics. Peak force (PF), rate of force development (RFD), peak power (PP), and impulse (IMP) were computed relative to body mass. Alpha was set to <0.05. RESULTS: LC and LF reduced jump height in an additive manner with CMJ metrics from all 3 phases being altered (Table 1). There were main effects of condition on PF in all phases of the CMJ (NFU > NFL; NFU > FL), on RFD in the EP and LP (NFU > NFL; NFU > FL), and on PP in the CP and LP (NFU > NFL > FL). There was a main effect of condition on IMP in the CP CMJ phase only (NFU > NFL > FL). CONCLUSION: Changes in CP PP, CP IMP, and LP PP were most sensitive to LC and LF. The results support recent work suggesting changes in CP rapid strength may be a marker of LF. Future research should explore surrogate measures that are sensitive to both LC and LF that emulate TA movements to enhance ecological validity.