FIBER-TYPE AND CITRATE SYNTHASE ACTIVITY IN THE HUMAN GASTROCNEMIUS AND VASTUS LATERALIS WITH AGING

The purpose of this study was to determine whether enzymatic and histo chemical characteristics of human skeletal muscle are altered with agi ng. Tissues from the vastus lateralis (VL) and gastrocnemius were anal yzed for citrate synthase (CS) activity and fiber type in 55 sedentary men (age range 18-80 yr). In this population, CS activity in the gast rocnemius was negatively related to age (r = -0.32, P < 0.05); there w as no relationship in the VL. Treadmill-determined maximal oxygen cons umption was positively related (r = 0.40, P < 0.05) to CS in the gastr ocnemius but not in the VL. CS activity in the gastrocnemius was 24% l ower in the oldest (greater than or equal to 60 yr, n = 10) vs. the yo ungest (less than or equal to 30 yr; n = 12) men; there was no change in CS activity in the VL with aging. No changes in fiber type were evi dent with age in either muscle. These data suggest a reduction in oxid ative enzyme activity in human skeletal muscle with the aging process; this relationship may be muscle-group specific.