Effects of physical activity on strength and skeletal muscle fat infiltration in older adults: a randomized controlled trial

Abstract

Considerable evidence suggests that the loss of strength and muscle mass appear to be inevitable consequences of aging. Moreover, aging is associated with an increase in body fat. This study examined whether increased physical activity could prevent or reverse the losses of strength and skeletal muscle mass as well as the gain in fat in older adults. Eleven men and 31 women completed a randomized trial consisting of either a physical activity (PA; n = 22) or successful aging health educational control (SA; n = 20) group. Isokinetic knee extensor strength and computed tomography-derived midthigh skeletal muscle and adipose tissue cross-sectional areas (CSA) were assessed at baseline and at 12 mo following randomization. Total body weight and muscle CSA decreased in both groups, but these losses were not different between groups. Strength adjusted for muscle mass decreased (-20.1 +/- 9.3%, P < 0.05) in SA. The loss of strength was completely prevented in PA (+2.5 +/- 8.3%). In addition, there was a significant increase (18.4 +/- 6.0%) in muscle fat infiltration in SA, but this gain was nearly completely prevented in PA (2.3 +/- 5.7%). In conclusion, regular physical activity prevents both the age-associated loss of muscle strength and increase in muscle fat infiltration in older adults with moderate functional limitations.

Fig. 1.

Changes in midthigh skeletal muscle cross-sectional area (CSA) in the physical activity and control groups. Both groups lost muscle (within-group change: *P < 0.05), although this loss was not statistically different between the 2 groups.

Fig. 2.

Changes in midthigh intermuscular adipose tissue (IMAT) in the physical activity and control groups. IMAT increased in the control group (within-group change: *P < 0.05, adjusting for multiple comparisons) but not in the physical activity group (†P < 0.05 for between-group change).

Fig. 3.

No statistically significant change in subcutaneous thigh adipose tissue (STAT) in either control or physical activity groups.

Fig. 4.

Changes in knee extensor strength in the physical activity and control groups. The control group lost muscle (within-group change: *P < 0.05, adjusting for multiple comparisons). This effect was not observed in the physical activity group, although the between-group change did not reach significance (†P = 0.06).

Fig. 5.

Changes in specific torque (knee extensor peak torque/quadriceps area) in the physical activity and control groups. Specific torque was reduced in the control group (within-group change: *P < 0.05, adjusting for multiple comparisons). This effect was not observed in the physical activity group, with a between-group difference in the change in specific torque (†P < 0.05).