Characterizing median nerve deformation and recovery processes in response to repeated isometric wrist torque exertions.

BACKGROUND: This study examined median nerve deformation during isometric wrist torque and characterized time-dependent recovery following load release. METHODS: Twenty-five healthy adults performed isometric wrist torque exertions at 50% maximal voluntary torque in four torque-grip experimental conditions (flexion with gripping, FG; extension with gripping, EG; flexion without gripping, FN; and extension without gripping, EN). Each torque-grip condition was repeated in 10 consecutive trials. For each trial, ultrasound images were acquired prior to torque production (baseline), at 50% maximal voluntary torque maintenance, and 0.25, 0.5, 1.0, and 2.0 s after torque release. Median nerve cross-sectional area (MNCSA) was measured to quantify deformation and recovery processes as a function of torque direction, gripping, time, and repetition. RESULTS: For all torque-grip conditions, MNCSA decreased during torque maintenance compared to baseline (p < 0.001), indicating acute cross-sectional deformation consistent with compression. No significant differences were found between flexion and extension, or between gripping and non-gripping, during torque maintenance. After torque release, MNCSA recovered progressively but remained below baseline at 2.0 s. Repetition did not alter the overall recovery pattern, though a small difference appeared at 1.0 s in the EN condition between initial and post-repeated trials. A post-repetitive difference between FN and EN was also observed at 1.0 s. CONCLUSION: Isometric wrist torque produces an immediate reduction in MNCSA, followed by a gradual rather than instantaneous recovery. While the effect of repeated gripping was small, minor deviations after repetition may indicate early cumulative mechanical loading. Dynamic and recovery-based assessments may provide additional insight for detecting early nerve compression risk.