Observing changes in motoneuron characteristics following distorted sensorimotor input via blood flow restriction

Disruption of the blood supply to a limb in conjunction with active movement boosts muscle growth, aids in rehabilitation, and allows controlled exploration of the sensorimotor system. Yet, the underlying neuromechanical changes have not been observed in great detail. This study aims to report the acute neuromuscular effects of temporary blood flow restriction (BFR) through behavioral changes at the level of motor units (MUs) using high-density surface electromyography on the abductor digiti minimi muscle during 20 trapezoidal and sinusoidal isometric force tracking tasks (5 pre-BFR, 5 during BFR, and 10 post-BFR). Unsurprisingly, during BFR, reported discomfort levels increased significantly (ρ < 0.001) regardless of the task (+239% trapezoidal, +228% sinusoidal). However, BFR had very little impact on task tracking performance, though the reconstructed force derived from the underlying neural drive (smoothed cumulative spike train of MUs) deviated substantially during BFR (-40% in trapezoidal, -47% in sinusoidal). Regardless of the condition, the numbers of extracted MUs were consistent (20-26 in trapezoidal, 23-29 in sinusoidal). Interestingly, the interspike interval (ISI) of these units increased by 28% in trapezoidal and 24% in sinusoidal tasks during BFR, with ISI steadily returning to original values post-BFR. These results indicate that acute BFR transiently alters the active MU pool, and MU firing behavior, yet only slightly affects the resulting task performance. However, pre-BFR motor function is gradually restored after BFR release. These findings provide insights into the resulting effects of acute BFR administration and the complex response it elicits from the sensorimotor system.NEW & NOTEWORTHY To improve our understanding of how acute blood flow restriction (BFR) intervention affects neuromechanical function and motor unit characteristics, we applied high-density surface electromyography on the abductor digiti minimi muscle during isometric trapezoidal and sinusoidal precision force tracking tasks. Although BFR increased discomfort, it minimally affected force tracking performance; however, it did alter the underlying motor unit behavior. These findings further enhance our understanding of the neural mechanisms underlying BFR.