Habitual elbow joint use time is associated with pain adaptation but not strength performance in young adults: a cross-sectional multithreshold classification study

This study investigated the differences between weekly elbow joint use time, pain level, and isokinetic moment in young adults using multiple exposure classification strategies. A total of 67 participants were categorized using three grouping approaches: median-based (<6 hr vs. ≥6 hr/wk), quartile-based (<6, 6-8, 8-10, and >10 hr/wk), and threshold-based (<10 hr vs. ≥10 hr/wk). Elbow joint pain was assessed using a visual analog scale and isokinetic moment was assessed using an isokinetic dynamometer at angular velocities of 60°/sec, 120°/sec, and 180°/sec for both flexion and extension. Across all classification approaches, nondominant elbow pain was consistently lower in higher-use groups (P<0.05), whereas dominant-side pain did not differ significantly. Most isokinetic moments were also comparable between groups; however, dominant flexor peak torque at 120°/sec was slightly lower in the ≥10 hr/wk group (P=0.049). These findings suggest that weekly elbow joint use time is more strongly associated with pain-related neuromuscular adaptation than with measurable strength performance in young adults. Multithreshold classification approaches may provide a more comprehensive framework for evaluating exposure-related upper-extremity functional characteristics.