A 30-year follow-up of the Dallas Bed rest and Training Study II. Effect of age on cardiovascular adaptation to exercise training

Background-Aerobic power declines with age. The degree to which this declin e is reversible remains unclear. In a 30-year longitudinal follow-up study, the cardiovascular adaptations to exercise training in 5 middle-aged men p reviously trained in 1966 were evaluated to assess the degree to which the age-associated decline in aerobic power is attributable to deconditioning a nd to gain insight into the specific mechanisms involved. Methods and Results-The cardiovascular response to acute submaximal and max imal exercise were assessed before and after a 6-month endurance training p rogram. On average, (V) over dot o(2max) increased 14% (2.9 versus 3.3 L/mi n), achieving the level observed at the baseline evaluations 30 years befor e. Likewise, (V) over dot o(2max) increased 16% when indexed to total body mass (31 versus 36 mL/kg per minute) or fat-free mass (44 versus 51 mL/kg f at-free mass per minute). Maximal heart rate declined (181 versus 171 beats /min) and maximal stroke volume increased ( 121 versus 129 mL) after traini ng, with no change in maximal cardiac output (21.4 versus 21.7 L/min); subm aximal heart rates also declined to a similar degree. Maximal AVDo(2) incre ased by 10% (13.8 versus 15.2 vol%) and accounted for the entire improvemen t 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 max imal (V) over dot o(2) attained after training 30 years earlier, despite a similar relative training load. The improved aerobic power after training w as primarily the result of peripheral adaptation, with no effective improve ment in maximal oxygen delivery.