The influence of reduced daily ambulation on glycemic control, body composition and physical function in older adults

Abstract

Short-term physical inactivity in older adults has been shown to cause muscular atrophy and impaired glycemic control, however, the ability to recover remains unknown. We aimed to determine the impact of step-reduction (SR) on older adults and if they could recover simply by returning to habitual activity. Ten older adults (6 men, 4 women, 69 ± 3 yr) completed 7d of normal baseline activity (BL), subsequently underwent SR by 86 ± 9% (8568 ± 3741 to 973 ± 76 steps/d; p<0.001) for 14d and then returned to 8383 ± 4513 steps/d for 14d (RC). During an oral glucose tolerance test (OGTT), SR resulted in elevated plasma glucose concentration ([G]) area under the curve (AUC; 325 ± 126 to 375 ± 137, p = 0.13), maximum [G] (10.2 ± 2.4 to 11.9 ± 1.7 mM, p = 0.027) and 2-hr [G] (7.9 ± 1.3 to 9.1 ± 1.1 mM, p = 0.085), while all [G] indices returned to BL after RC. However, Matsuda insulin sensitivity index was reduced (3.5 ± 0.3 to 2.7 ± 0.7, p < 0.001) and homeostatic model assessment of insulin resistance was elevated (2.8 ± 0.3 to 3.6 ± 0.7, p = 0.02) with SR, remaining different than BL after RC (p < 0.005). During free-living conditions, 3-hr post-prandial [G] (PPG) AUC and peak PPG increased following SR (p > 0.05), returning to BL with RC. Body composition and physical function remained unchanged with SR. These results show that periods of physical inactivity, characterized by reduced daily stepping, do not present detectable changes in body composition or physical function yet result in reduced glycemic control in older adults. While elevations in blood [G] are abolished with 14d of normal physical activity, our findings suggest that the SR-associated reductions in insulin sensitivity are not normalized as quickly.