Delayed and disorganized muscle activation as a potential injury mechanism in men's basketball jump shots

Background: Effective neuromuscular coordination during the basketball jump shot is essential for optimizing performance and reducing injury risk. Inconsistent temporal sequencing of muscle activation may compromise upper-limb joint stability, increasing susceptibility to injury. Although shooting mechanics have been widely studied, the effects of skill level and shooting distance on upper-limb muscle activation timing remain unclear. Methods: Twenty male participants (10 skilled, 10 unskilled) performed open jump shots from 5.0 m and 6.8 m. Surface electromyography recorded activity of four upper-limb muscles: anterior deltoid (AD), biceps brachii (BB), triceps brachii (TB), and flexor carpi radialis (FCR). Root mean square (RMS) signals were filtered and normalized. Muscle activation onset was defined as five consecutive data points exceeding 20% of peak RMS amplitude. Temporal activation patterns were analyzed to examine neuromuscular control strategies and potential shoulder injury risk. Results: In both groups and at both distances, muscle activation was mainly concentrated in the mid-to-late movement and release phases. Increasing shooting distance delayed the overall activation onset. Skilled players demonstrated earlier activation of key muscles (AD, TB), faster activation rise, earlier peak timing, and generally higher peak amplitudes (AD, BB, TB). In contrast, unskilled players showed earlier but more dispersed activation patterns and relied more on wrist flexor (FCR) activation during long-distance shots. Notably, unskilled players exhibited earlier BB activation at both distances, suggesting a higher risk of subacromial impingement. Conclusions: Skilled players exhibit more efficient and protective neuromuscular activation strategies, whereas unskilled players’ earlier BB activation may increase shoulder injury risk during jump shooting.