For the initial evaluations in 1966, 5 healthy 20-year-old male volunteers were assessed at baseline, spent 3 weeks at complete bed rest with no weight bearing allowed (similar to clinical treatment of acute myocardial infarction at the time), and then underwent 8 weeks of intensive endurance training. Cardiopulmonary function was evaluated by determining maximal oxygen uptake (VO2max) during stress testing to exhaustion, the gold standard measure of integrated cardiorespiratory capacity reflecting the capacity of the circulatory and respiratory systems to deliver oxygen to skeletal muscle during exercise, measured at baseline, after bed rest, and after endurance training, with results summarized in the Table.

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These same 5 volunteers were studied 30 years later (1996) at baseline and after endurance training, with no bed rest exposure evaluated, with results previously published summarized in the Table. Contrasted with the 27% decline in VO2max with bed rest in the 1966 study, baseline VO2max had declined by 12% over the 30-year interval. Thus, 3 weeks of bed rest at age 20 years reduced cardiovascular capacity more than 30 years of aging.

While complete bed rest is a quite extreme case of inactivity, I think this is quite indicative of how fast our bodies deteriorate when we don’t move enough during each day.

The study is not new, but I found about it recently and thought it was worth sharing.