Prolonged infrapatellar tendon vibration does not influence quadriceps maximal or explosive isometric force production in man

Purpose: The influence of muscle/tendon vibration on maximal muscle performance is unclear. This study examined the effect of a prolonged tendon vibration stimulus on maximum voluntary contraction (MVC) and explosive voluntary contraction (EVC) performance. Methods: Eighteen young healthy males (nine strength trained and nine untrained) completed a series of isometric unilateral knee extensions (EVCs, electrically evoked octet responses, MVCs, ramp contractions) pre and post two separate 30-min intervention trials; infrapatellar tendon vibration (80 Hz), and quiet sitting (control). H _max and M _max were measured at the start and end of each series of contractions, both pre- and post-intervention (i.e., at four time points). Knee extensor force and both quadriceps and hamstrings EMG were measured throughout each series of contractions. Results: Vibration had no effect on either maximum force (ANOVA, trial × time interaction P = 0.92), explosive force (P ≥ 0.36), or the associated agonist EMG amplitude during these tasks (P ≥ 0.23). Octet responses were also unaffected by vibration (P ≥ 0.39). Conversely, post-intervention H _max/M _max was 60 % lower in the vibration trial vs. control, and remained 38 % lower at the end of the post-intervention measurements (t test, both P < 0.01). Individual H _max/M _max depression did not correlate to changes in either maximum or explosive force (Spearman's Rank, P ≥ 0.54), and training status had no influence on the effect of vibration. Conclusion: Prolonged infrapatellar tendon vibration depressed H-reflex amplitude, but did not affect either maximal or explosive isometric force production of the quadriceps.