Only Two Weeks of Physical Inactivity Induces Insulin Resistance and Impairs Glycemic Control in Older Adults

Abstract

Periods of physical inactivity are known to result in deleterious consequences for skeletal muscle mass, strength, and insulin sensitivity. We propose that even transient periods of reduced activity likely have a greater impact in older individuals who often fail to fully recover. We aimed to examine the impact of two weeks of step reduction (SR), as a model of physical inactivity akin to that occurring during illness, on indices of glycemic control and muscle strength in thirteen healthy older adults (7 men, 6 women, 68 ± 3yr [all data mean±SD]). Participants underwent 7 d of monitored normal activity (pre‐SR) immediately before reducing their daily step‐count from 7379 ± 3809 to 967 ± 79 steps.d−1 for 14 d (SR), and then returning to their habitual step count for a period of 14 d (post‐SR). The HOMA‐IR and MATSUDA models of insulin resistance, and insulin sensitivity as well as glucose and insulin area under the curve GAUC and IAUC in response to an oral glucose tolerance test were assessed pre‐SR, SR, and post‐SR. Peak isometric maximal voluntary contraction (ISO‐MVCpeak), peak rate of torque development (RTDpeak) number of sit‐to‐stand cycles in 30 s, and total distance walked in 6 min were also assessed at these time points. HOMA‐IR increased from pre‐SR to SR (2.8 ± 0.3 to 3.6 ± 0.6, p<0.05) and MATSUDA decreased (3.7 ± 0.5 to 3.0 ± 0.1, p < 0.05), neither recovered at post‐SR. GAUC was not significantly different between pre‐SR (435 ± 121) and SR (467 ± 136) but was marginally lower at post‐SR (386 ± 140, p=0.05). IAUC increased from pre‐SR to SR (3796 ± 579 to 4329 ± 833, p<0.05) and, was still elevated at post‐SR (4051 ± 768, p<0.05). There was no change from pre‐SR to SR in either ISO‐MVCpeak (146 ± 34 to 148 ± 41 N.m, p>0.05), RTDpeak (2142 ± 1527 to 1956 ± 894 N.m.s−1, p>0.05), sit‐to‐stand cycles in 30 s (17 ± 5 to 16 ± 5, p>0.05) or total distance walked in 6 min (561 ± 108 to 563 ± 110 m, p>0.05). These data indicate that two weeks of SR negatively impacts indices of glycemic control in older adults that are not fully recovered after 14 d of return to habitual step count. However, indices of muscle function remained unaltered.Support or Funding InformationSupported by the Canadian Diabetes Association