Abstract
Resistance training with low loads in combination with blood flow restriction (BFR) facilitates increases in muscle size and strength comparable with high-intensity exercise. We investigated the effects of BFR on single motor unit discharge behavior throughout a sustained low-intensity isometric contraction. Ten healthy individuals attended two experimental sessions: one with, the other without, BFR. Motor unit discharge rates from the tibialis anterior (TA) were recorded with intramuscular fine-wire electrodes throughout the duration of a sustained fatigue task. Three 5-s dorsiflexion maximal voluntary contractions (MVC) were performed before and after the fatigue task. Each participant held a target force of 20% MVC until endurance limit. A significant decrease in motor unit discharge rate was observed in both the non-BFR condition (from 13.13 ± 0.87 Hz to 11.95 ± 0.43 Hz, P = 0.03) and the BFR condition (from 12.95 ± 0.71 Hz to 10.9 ± 0.75 Hz, P = 0.03). BFR resulted in significantly shorter endurance time and time-to-minimum discharge rates and greater end-stage motor unit variability. Thus, low-load BFR causes an immediate steep decline in motor unit discharge rate that is greater than during contractions performed without BFR. This shortened neuromuscular response of time-to-minimum discharge rate likely contributes to the rapid rate of neuromuscular fatigue observed during BFR.
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The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
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TWL, KS, MT and LG conceptualized the study design. KS and MST collected and assembled the data. TWL and MST completed analysis and interpretation of data. TWL drafted the manuscript. All authors have critically reviewed, revised, and approved the manuscript. All authors have approved the study and manuscript, warrant that it is factual, have agreed to its submission, and have the right to publish.
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Lowe, T.W., Tenan, M.S., Shah, K. et al. Low-load blood flow restriction reduces time-to-minimum single motor unit discharge rate. Exp Brain Res 241, 2795–2805 (2023). https://doi.org/10.1007/s00221-023-06720-8
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DOI: https://doi.org/10.1007/s00221-023-06720-8