Countermovement jump performance after metabolically, but not mechanically demanding exercise: limited sensitivity to prolonged low-frequency force depression.

Rationale: Previous studies indicate that countermovement jump (CMJ) parameters may reflect neuromuscular fatigue following exhaustive exercise. However, changes in CMJ performance in response to non-muscle damaging exercise, and its relation to prolonged low-frequency force depression (PLFFD) is yet unknown.

Purpose: This study aimed to evaluate the relationship between PLFFD and CMJ test parameters following exhaustive cycling exercise to task failure.

Methods: A sample of 11 recreationally active adults completed an incremental cycling protocol to task failure. CMJ performance, low-frequency (10 Hz) force, and maximal voluntary contraction (MVC) force output were assessed at baseline (pre-exercise), immediately after task failure (0 min), and at 8 min, 15 min, 60 min, 24 h, and 48 h post-task failure. PLFFD was assessed as the ratio of 10 Hz to MVC force.

Results: Compared to baseline, PLFFD was larger from 0 min (7.4%) to 60-min (6.7%, p < 0.002). In contrast, no substantial changes in CMJ parameters were observed, except for a reduced concentric impulse (ConImp) lasting 8 min post-exercise.

Conclusion: The results show that CMJ parameters remain unchanged following non-eccentrically loaded exhaustive exercise, while PLFFD is significantly higher for up to 60 min post-exercise. This raises questions about the utility of CMJ as a fatigue assessment tool in athletic populations. This suggests that CMJ testing may not effectively detect the presence of PLFFD following non-muscle damaging exercise and future research should explore alternative measures for monitoring neuromuscular fatigue in training contexts.