Cardiac function at treadmill exercise in various age groups

We compared the response to a modified Bruce treadmill exercise (EX) protocol lasting 7 min in 5 groups of male individuals free of clinical heart disease: I (age less than 35 years, N = 12), II (age 35-44 years, N = 10), III (age 45-54 years, N = 13), IV (age 55-64 years, N = 13) and V (age greater than 65, mean 70.35 +/- 4.67 years, N = 20). The following data were compared: (a) Heart rate (HR), systolic (SBP) and diastolic blood pressure (DBP); resting (R) and their % changes at pre-EX standing and at 3, 6, 7 min, immediately and 2 and 4 min after EX (where EX is a relatively low grade of exercise). (b) The R QS2/QT and PEP/LVET ratios and their % change immediately and 4 min after EX. Resting and peak SBP was higher in groups IV and V. The various groups responded in a similar way to EX. The only significant difference was that the older age group (V) showed on the whole an increase in DBP with EX while groups I-III showed a decrease and group IV no change. This finding may reflect a lesser diminution in vascular resistance with EX in old age. However, inotropic and chronotropic reserves appear similar to those of younger individuals.