Effect of hand postures and object properties on forearm muscle activities using surface electromyography

Area of Science:

• Biomechanics
• Human Factors Engineering
• Neuroscience

Background:

• Understanding forearm muscle activation is crucial for preventing injuries and optimizing tasks involving object manipulation.
• Previous research has explored muscle activity during grasping, but the combined effects of hand posture and object properties require further investigation.

Purpose of the Study:

• To quantify the influence of various hand postures and object characteristics on forearm muscle activity.
• To determine the contribution of nine specific forearm muscles during object lifting tasks using surface electromyography (sEMG).

Main Methods:

• Ten male university students performed object lifting tasks.
• Objects varied in size (2-8 cm) and weight (400-1800 g), with cylindrical and rectangular shapes.
• Surface electromyography recorded activity from nine forearm muscles during standardized lifting and holding postures.

Main Results:

• Hand posture and object weight significantly affected forearm muscle activity.
• Object size also influenced muscle activation, whereas object shape did not show a significant effect.
• Pinching grips with the largest (8 cm) and heaviest (1800 g) objects elicited the greatest muscle activity, especially in the extensor pollicis longus and flexor pollicis longus.

Conclusions:

• Forearm muscle activation patterns are highly sensitive to hand-object interactions.
• Specific muscle groups, like the extensor and flexor pollicis longus, are key contributors during forceful grips.
• This study provides foundational data for understanding muscle function in relation to ergonomic design and occupational safety.