Comparison of wrist flexor and extensor muscle recruitment between adults with and without chronic wrist hypermobility.

BACKGROUND

Chronic wrist hypermobility (CWH), a common condition among young adults due to atraumatic carpal region laxity or benign joint hypermobility, is characterized by decreased strength and proprioception, often without pain. Wrist function depends on both dynamic and static stabilizers, which mediate neuromuscular reflex responses. CWH may alter normal wrist neuromuscular recruitment and cause inadequate dynamic stabilization at different functional forearm positions.

PURPOSE: This study aimed to determine electromyographic (EMG) wrist muscle recruitment differences between individuals with and without CWH during sustained gripping activity, and whether forearm position influences muscle recruitment differently between these two groups.

STUDY

DESIGN

Quasi-experimental cross-sectional.

METHODS

Forty-four wrists were screened for CWH. Twenty-five wrists were allocated to a CWH group, and 19 wrists were allocated to a healthy control (HC) group. A purposive sample of 15 CWH and 15 HC-matched wrists was analyzed. EMG of the extensor carpi radialis brevis/longus (ECRB/L), extensor carpi ulnaris (ECU), flexor carpi ulnaris (FCU), and flexor carpi radialis (FCR) muscles, and grip force were recorded (% average) during a 10-second sustained gripping task using a hand-held dynamometer integrated with EMG. Electrode placement was enhanced via diagnostic ultrasound. Testing position (supination, pronation, neutral) was randomized.

RESULTS

Groups had comparable demographics (64% females; 85% right-handedness). Midcarpal instability (100%) and benign joint hypermobility syndrome (44%) were the most prevalent etiologies. MANOVA determined significant (p < 0.05, ƞ2 0.04-0.15) group differences for ECU, ECRB/L, and FCU, favoring the HC group regardless of forearm position. CWH individuals had higher FCR activity and lower grip force. No EMG differences existed across forearm positions within or between groups.

CONCLUSIONS

CWH results in decreased dynamic stability from the ECU, FCU, and ECRB/L during gripping activity, regardless of forearm position. Increased FCR activity may serve as a compensatory mechanism for volar wrist stability. These findings may guide the prescription of muscle-specific stabilization exercises for individuals with CWH and midcarpal instability.