Correlated changes in the firing rate of human motor units during voluntary contraction

1996 ◽  
Vol 111 (3) ◽  
Author(s):  
KemalSitki T�rker ◽  
Annie Schmied ◽  
HongBing Cheng
Keyword(s):  
Firing Rate ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Human Motor ◽  
Human Motor Units

Properties of human motor units after prolonged activity at a constant firing rate

2003 ◽  
Vol 154 (4) ◽  
pp. 479-487 ◽  
Author(s):  
K. V. B. Johnson ◽  
S. C. Edwards ◽  
C. Van Tongeren ◽  
P. Bawa
Keyword(s):  
Firing Rate ◽  
Motor Units ◽  
Human Motor ◽  
Human Motor Units

scholarly journals Effects of joint immobilization on firing rate modulation of human motor units

2001 ◽  
Vol 530 (3) ◽  
pp. 507-519 ◽  
Author(s):  
Kazuhiko Seki ◽  
Yuko Taniguchi ◽  
Mitsuo Narusawa
Keyword(s):  
Firing Rate ◽  
Motor Units ◽  
Rate Modulation ◽  
Human Motor ◽  
Human Motor Units

Firing rate trajectories of human motor units during activity-dependent muscle potentiation

2021 ◽  
Author(s):  
Alexander M. Zero ◽  
Eric A. Kirk ◽  
Charles L. Rice
Keyword(s):  
Contractile Function ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Persistent Inward Currents ◽  
Motor Unit Firing ◽  
Inward Currents ◽  
Post Tetanic Potentiation ◽  
Human Motor ◽  
Activity Dependent ◽  
Human Motor Units

During activity-dependent potentiation (ADP) motor unit firing rates (MUFRs) are lower, however, the mechanism for this response is not known. During increasing torque isometric contractions at low contraction intensities, MUFR trajectories initially accelerate and saturate demonstrating a non-linear response due to the activation of persistent inward currents (PICs) at the motoneuron. The purpose was to assess whether PICs are a factor in the reduction of MUFRs during ADP. To assess this, MUFR trajectories were fit with competing functions of linear regression and a rising exponential (i.e., acceleration and saturation). Using fine-wire electrodes, discrete MU potential trains were recorded in the tibialis anterior during slowly increasing dorsiflexion contractions to 10% of maximal voluntary contraction following both voluntary (post-activation potentiation; PAP) and evoked (post-tetanic potentiation; PTP) contractions. In 8 participants, 25 MUs were recorded across both ADP conditions and compared to the control with no ADP effect. During PAP and PTP, the average MUFRs were 16.4% and 9.2% lower (both P≤ 0.001), respectively. More MUFR trajectories were better fit to the rising exponential during control (16/25) compared to PAP (4/25, P<0.001) and PTP (8/25, P=0.03). The MU samples that had a rising exponential MUFR trajectory during PAP and PTP displayed an ~11% lower initial acceleration compared to control (P<0.05). Thus, synaptic amplification and MUFR saturation due to PIC properties are attenuated during ADP regardless of the type of conditioning contraction. This response may contribute to lower MUFRs and likely occurred because synaptic input is reduced when contractile function is enhanced.

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