Association Among Age, Muscle Size And Strength In Young Adults

Abstract

Purpose Muscular strength is a key determinant of an older person's ability to maintain an active and healthy lifestyle. A reduction in muscle mass and strength has been commonly attributed to aging, but less is known about the relationship in younger adults. Therefore the purpose of the study was to assess the association between age, muscle mass and strength. This data is part of a larger study examining functional Single Nucleotide Polymorphisms associated with human muscle size and strength. Methods 888 Subjects (24.3±5.7 yrs old, range: 17.7–40.6) completed a 12 wk progressive resistance training program of the elbow flexors and extensors of the nondominant arm. Subjects' isometric and dynamic elbow fiexor strength (1RM) were measured before and after the 12 wk training period. Isometric strength, peak force at 90± joint angle, was measured using a specially constructed, modified preacher bench and strain gauge (model 32628CTL Lafayette Instruments Company). Dynamic 1RM was measured using a preacher curl bench (Yukon International Inc.) and dumbbells (Powerblocks, Intellbell, Inc.). Cross-sectional area of upper arm muscle at the biceps midbelly was measured using magnetic resonance imaging (MRI) before and after training. Habitual dietary intake was maintained over the course of the study. Data were analyzed using SPSS version 11.0. Pearson correlation coefficients were calculated for baseline and post-training measurements. Results We found that age was significantly and positively correlated to baseline biceps size (r=0.1827, p<0.0001) and elbow flexor strength (r=0.1035, p=0.0034; r=0.1042, p=0.0026, isometric and 1RM respectively), but not triceps size nor whole arm size. Age was related to change in 1RM (r=−0.2276 p<0.0001; r=−0.2386 p<0.0001, absolute and percent respectively), but no other measure of change in muscle size or strength. Conclusion These data suggest that even in young adults age has a small, but significant postive effect on muscle size and strength whereas it plays a minor yet negative role in a young, healthy adult's ability to alter strength with resistance training. Supported by: NIH-IDS RO1 NS 40606-02