Functional and electrophysiological analysis of wrist flexors and extensors: insights into muscle imbalances and activation patterns

Objectives. Muscle imbalances in wrist flexors and extensors contribute to the development of work-related upper limb disorders (WRULDs). Understanding the dynamic between force production and neuromuscular activation is essential for developing ergonomic and rehabilitation strategies. This study investigates the functional characteristics of wrist flexors and extensors and their role in WRULDs.
Materials and methods. The study included 23 participants (mean age: 24.7 ± 4.1 years), with 22 being right-handed. Dynamometry and electromyography (EMG) values were analyzed during rest and maximal effort for flexors and extensors of the right and left wrists. Functional ratios (flexor/extensor and rest/maximal effort) and spectrum frequency comparisons were evaluated. Data analysis was conducted using Jamovi.
Results. Flexors exhibited consistently higher force outputs than extensors, with significant differences across right and left wrists (p < 0.001). Mean dynamometry values for the right wrist flexors and extensors were 98.5 ± 19.4 N and 80.6 ± 22.2 N, while left wrist values were 98.3 ± 31.7 N and 83.7 ± 22.8 N. EMG analysis revealed higher resting activation in flexors, particularly in the left wrist (185 ± 34.8 Hz vs. 144 ± 33.1 Hz, p < 0.001). Maximal effort analysis showed extensors dominated activation (e.g., 158 ± 21.8 Hz vs. 122 ± 22.9 Hz in the right wrist, p < 0.001). Since most participants were right-handed, findings highlight how the non-dominant hand can also become overloaded in compensatory tasks.
Conclusions. The study identifies differences in force and activation patterns between flexors and extensors and between dominant and non-dominant wrists. Flexors exhibited chronic tension at rest, while extensors demonstrated greater fatigue resistance during maximal effort. These findings highlight the need for ergonomic interventions and WRULD prevention.