Mixed-Nerve Silent Period Characteristics During Muscle Output Regulation in Healthy Athletes: Preliminary Findings and Comparison with a Single Postoperative Case
Shinichi Daikuya, Yumi OkayamaBackground/Purpose
Sports injury induces peripheral and central neurophysiological alterations that influence motor control and recovery. The mixed-nerve silent period (SP), a transient suppression of voluntary muscle activity after electrical stimulation, reflects multilevel neural inhibitory mechanisms involving spinal and cortical pathways. This study aimed to elucidate central nervous system (CNS) excitability during muscle output regulation and explore neurophysiological characteristics in healthy athletes and contrast with findings from an athlete with delayed return to play.
Study type
Case report with observational reference data
Methods
Fourteen female university basketball players participated; The thirteen participants are healthy individuals, able to play without any problems, and one was three months post-meniscal repair who was unable to run since her surgery. All participants were instructed to maintain 25% maximal voluntary isometric contraction of knee extensors for 60 s without visual feedback while seated on the seat of the isokinetic muscle strength measurement device. During the task, SP was recorded from the ipsilateral opponens pollicis muscle. SP was compared between dominant and nondominant leg conditions among healthy participants and contrasted with the postoperative case. Differences between limbs were analyzed using paired t-tests, and the postoperative case was compared with healthy athletes using a Crawford–Howell modified t-test (p < 0.05).
Results
The SPs in healthy athletes were 106.3 ± 7.5 and 103.2 ± 6.5 ms for the dominant and nondominant sides, with no significant difference between sides. In the postoperative case, the injured (dominant) side exhibited prolonged SP (123.7 ms), deviating by >2 SD from healthy values, whereas the noninjured side remained within the normal range.
Conclusion
Prolonged SP may reflect enhanced cortical or brainstem inhibition associated with neuromuscular control impairment. SP assessment may serve as a neurophysiological indicator for evaluating central recovery and readiness to return to sport following injury.
However, larger prospective studies are needed to confirm its clinical utility.
Level of Evidence
4