FRI0491-HPR Qualitative differences in the muscle activities in the forearm flexor and extensor muscles in healthy men and women in different ages

Background Balance between flexor and extensor muscle activity is essential for optimal function. This has been demonstrated previously for the lower extremity, trunk and shoulder function, but information on the relationship in hand function is lacking. Objectives The purpose of this study was to evaluate whether there are qualitative differences in finger extension force, grip force, force duration, force balance and the muscle activities in the forearm flexor and extensor muscles in healthy men and women in different ages. Methods Healthy controls (men, n=65, women, n=40) were included. Primary outcome was muscle activity measured with S-EMG and finger flexion- and finger extension force in Newton (N). The maximal force from the first trial was used as reference value (maximal voluntary isometric contraction, MVIC). The S-EMG activity of the m. extensor digitorum communis (EDC) and the m. flexor carpi radialis (FCR) were measured on the dominant hand when performing seven clinically often used hand exercises. Hand function was also evaluated with the self-reported questioner Quick DASH and VAS pain and VAS stiffness. Results The force balance between finger extension and flexion force was statistically significant for both men (r=0.51, p=0.000) and women (r=0.78, p=0.000). The finger extension force was not influenced by age, but flexion force was significantly correlated to age. The coefficient of determination showed that age and gender can explain 45-55% of differences in the force measurements. Muscle activity from hand exercises was significant related to gender for EDC and muscle activity in FCR showed significantly relation to age. Only 3 of the 7 hand exercise were adjustable for both men and women unrelatedly to age. Concerning the muscle activation in EDC and FCR in daily activities, the age and gender explain 31% respectively 19% of the differences. Conclusions This study shows that there are differences between men and women’s hand force capacity and that gender and age can explain 45-55% of the differences. Furthermore this study shows that the EDC muscle is related to gender and FCR is related to age. In a longer perspective this information is useful for designing optimal training program for adjusted for gender and age. References Greig M, Wells R. A systematic exploration of distal arm muscle activity and perceived exertion while applying external forces and moments. Ergonomics. [Research Support, Non-U.S. Gov’t]. 2008 Aug;51(8):1238-57. Nordenskiold U, Grimby G. Assessments of disability in women with rheumatoid arthritis in relation to grip force and pain. Disabil Rehabil. 1997 Jan;19(1):13-9. Kapandji I. The physiology of the joints - annotated diagrams of the mechanics of the human joints. Edingburgh London, Melborne and New York: Churchill Livingstone; 1982. Brorsson S, Nilsdotter A, Sollerman C, Baerveldt AJ, Hilliges M. A new force measurement device for evaluating finger extension function in the healthy and rheumatoid arthritic hand. Technol Health Care. 2008;16(4):283-92. Disclosure of Interest None Declared