A 30-Year Follow-Up of the Dallas Bed Rest and Training Study

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Abstract
Background— Aerobic power declines with age. The degree to which this decline is reversible remains unclear. In a 30-year longitudinal follow-up study, the cardiovascular adaptations to exercise training in 5 middle-aged men previously trained in 1966 were evaluated to assess the degree to which the age-associated decline in aerobic power is attributable to deconditioning and to gain insight into the specific mechanisms involved. Methods and Results— The cardiovascular response to acute submaximal and maximal exercise were assessed before and after a 6-month endurance training program. On average, V̇o2max increased 14% (2.9 versus 3.3 L/min), achieving the level observed at the baseline evaluations 30 years before. Likewise, V̇o2max increased 16% when indexed to total body mass (31 versus 36 mL/kg per minute) or fat-free mass (44 versus 51 mL/kg fat-free mass per minute). Maximal heart rate declined (181 versus 171 beats/min) and maximal stroke volume increased (121 versus 129 mL) after training, with no change in maximal cardiac output (21.4 versus 21.7 L/min); submaximal heart rates also declined to a similar degree. Maximal AVDo2 increased by 10% (13.8 versus 15.2 vol%) and accounted for the entire improvement of aerobic power associated with training. Conclusions— One hundred percent of the age-related decline in aerobic power among these 5 middle-aged men occurring over 30 years was reversed by a 6-month endurance training program. However, no subject achieved the same maximal V̇o2 attained after training 30 years earlier, despite a similar relative training load. The improved aerobic power after training was primarily the result of peripheral adaptation, with no effective improvement in maximal oxygen delivery.