Prolonged Vibration of the Biceps Brachii Tendon Reduces Time to Failure When Maintaining Arm Position With a Submaximal Load

Abstract

Prolonged vibration of the biceps brachii tendon reduces time to failure when maintaining arm position with a submaximal load. J Neurophysiol 95: 1185-1193, 2006. First published November 9, 2005 doi:10.1152/jn.00807.2005. Vibration reduces the amplitudes of the tendon jerk response and the Hoffmann and stretch reflexes in the muscle exposed to the vibration, yet does not alter the time to task failure when the task involves exerting a submaximal force against a rigid restraint. Because the amplitude of the stretch reflex is greater when a limb acts against a compliant load than a rigid restraint, the purpose was to determine the influence of prolonged tendon vibration on the time to failure when maintaining limb position with the elbow flexor muscles. Twenty-five healthy men performed the fatiguing contraction by maintaining elbow angle at 1.57 rad until failure while supporting a load equal to 20% of maximal voluntary contraction (MVC) force. The fatiguing contraction was performed on 3 separate days with different levels of vibration applied to the biceps brachii tendon: no vibration, subthreshold for a tonic vibration reflex (TVR), and suprathreshold for a TVR. MVC force before the fatiguing contraction was similar across the three sessions (mean of 3 sessions: 313 Ϯ 54 N, P ϭ 0.83). Despite a similar decline in MVC force after the fatiguing contraction across conditions (-18.0 Ϯ 8.0%, P Ͼ 0.05), the time to task failure was 3.7 Ϯ 1.4 min for the suprathreshold TVR condition, 4.3 Ϯ 2.1 min for the subthreshold TVR condition, and 5.0 Ϯ 2.2 min for the no-vibration condition (P Ͻ 0 0.001). The average EMG of the elbow flexor muscles was similar (P ϭ 0.22) during the fatiguing contractions. However, the fluctuations in limb acceleration at task onset were greater for the suprathreshold TVR condition (P Ͻ 0.01), but were not different between the subthreshold TVR and no-vibration conditions (P Ն 0.22). Furthermore, the difference in the SD of limb acceleration between the no-vibration and vibration conditions was correlated with the difference in time to failure for the no-vibration and subthreshold TVR conditions (P ϭ 0.03; r 2 ϭ 0.22), but not for the no-vibration and suprathreshold TVR conditions (P ϭ 0.90; r 2 ϭ 0.001). These findings indicate that prolonged vibration reduced the time to failure of a sustained contraction when subjects maintained limb position, suggesting that peripheral inputs to the motor neuron pool play a significant role in sustaining a contraction during tasks that require active control of limb position.

Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions

“…The greater variability exhibited by the left-handed subjects may be a consequence of the fatiguing contractions engaging extensive cortical networks (Korotkov et al 2005;Liu et al 2003;Post et al 2009) that involve previously reported cortical asymmetries in left-handed individuals (van den Berg et al 2011). Although the current study does not provide insight on the underlying mechanisms, one functional consequence of the greater variability exhibited by left-handed participants is that interventions capable of prolonging endurance time for these types of fatiguing contractions (Barry et al 2008;Mottram et al 2006;Riley et al 2008;Semmler et al 2000;Yue et al 1997) would more consistently transfer changes in performance across tasks in right-handed than in left-handed persons.…”

Unraveling the neurophysiology of muscle fatigue

“…Our current hypothesis is that stretch responsiveness is increased during position control by enhanced gamma motor neuron activity (Ludvig et al, 2007;Mottram et al, 2006;Shemmell et al, 2009), but that the more rapid depression of spinal excitability during the position task involves greater modulation of Ia afferent feedback by presynaptic inhibition (Fig. 10).…”

The acute effects of local muscle vibration frequency on peak torque, rate of torque development, and EMG activity

“…For example, Couto et al (2013), found that maximal voluntary contraction of the quadriceps improved after 4 weeks of 8 Hz and 26 Hz LMV. However, other studies indicate that LMV causes a reduction in force output (Kouzaki et al, 2000;Mottram et al, 2006), and this could be related to the parameters of stimulation. Also, the neurophysiological influences may differ between LMV and WBV, as WBV stimulates multiple receptors throughout the lower extremity (Pollock et al, 2011) and influence motor unit firing frequency and synchronization, muscle tuning, intramuscular coordination, and central motor command (Cochrane, 2011).…”