Adrenergic receptor genotype influence on midthigh intermuscular fat response to strength training in middle-aged and older adults

Abstract

Background. There is little information regarding the effects of strength training on intermuscular fat (IMF). This study examines changes in IMF in response to strength training in carriers of the adrenergic receptor (ADR) β2Glu27 polymorphism versus noncarriers and between carriers of ADRα2b Glu9 polymorphism versus noncarriers. Methods. Midthigh IMF and muscle area were measured by computed tomography (CT) before and after 10 weeks of single-leg strength training in healthy, sedentary middle-aged and older (50-83 years) men (n = 46) and women (n = 52) in both their trained and untrained (control) legs. Results. The strength training program resulted in a substantial increase in one-repetition maximum strength (p < .001) and muscle area (p < .001), but no significant changes in IMF in the whole group. However, IMF was significantly reduced with strength training in participants carrying ADRβ2 Glu27 (-2. 3 ± 1.0 cm2, p = .028), but no significant change was observed with ADRβ2 Glu27 noncarriers. The decrease in IMF in ADRα2b Glu9 carriers (-1.9 ± 1.0 cm 2, p = .066) was significantly different (-2.9 ± 1.5 cm 2, p = .043) from a nonsignificant increase in ADRα2b Glu 9 noncarriers. ADRβ2 Glu27 carriers who also carried ADRα2b Glu9 significantly lost IMF with strength training (-3.8 ± 1.5 cm2, p = .018). Conclusion. ADR genotype influences IMF response to strength training. Copyright 2007 by The Gerontological Society of America.