Intramuscular adipose tissue and central activation in older adults

Introduction: Intramuscular adipose tissue (IMAT) is a potential contributor to declining force production and may be related to impaired central activation; therefore, the purpose of this report is to describe IMAT composition and its association with central activation in older adults. The central activation ratio (CAR) of the knee extensors was assessed using a superimposition technique in 15 older adults (29 legs) along with the cross-sectional area of IMAT and lean tissue. Results: IMAT and CAR are inversely related in older adults (r = -0.51, P = 0.005), and many subjects with high IMAT have deficits in central activation, whereas those with low IMAT have normal central activation. Conclusions: These novel findings may assist in unraveling why muscle force production and lean tissue cross-sectional area are not strongly linked, as the ability to centrally activate muscle appears to be unrelated to lean muscle area and may be dependent in part on IMAT levels. Muscle Nerve 46:813816, 2012