Acute effects of quadriceps muscle versus tendon prolonged local vibration on force production capacities and central nervous system excitability

Purpose The present study aimed to directly compare the effects of 30 min muscle (VIB muscle ) vs. tendon (VIB tendon ) local vibration (LV) to the quadriceps on maximal voluntary isometric contraction (MVIC) and rate of torque development (RTD) as well as on central nervous system excitability (i.e. motoneuron and cortical excitability). Methods Before (PRE) and immediately after (POST) LV applied to the quadriceps muscle or its tendon, we investigated MVIC and RTD (STUDY #1; n = 20) or vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) electromyography responses to thoracic electrical stimulation (TMEPs; motoneuron excitability) and transcranial magnetic stimulation (MEPs; corticospinal excitability) (STUDY #2; n = 17). MEP/TMEP ratios were further calculated to quantify changes in cortical excitability. Results MVIC decreased at POST ( P = 0.017) without any difference between VIB tendon and VIB muscle , while RTD decreased for VIB tendon ( P = 0.013) but not VIB muscle . TMEP amplitudes were significantly decreased for all muscles ( P = 0.014, P < 0.001 and P = 0.004 for VL, VM and RF, respectively) for both LV sites. While no changes were observed for MEP amplitude, MEP/TMEP ratios increased at POST for VM and RF muscles ( P = 0.009 and P = 0.013, respectively) for both VIB tendon and VIB muscle . Conclusion The present results suggest that prolonged muscle and tendon LV are similarly effective in modulating central nervous system excitability and decreasing maximal force. Yet, altered explosive performance after tendon but not muscle LV suggests greater neural alterations when tendons are vibrated.