Cardiorespiratory responses and myocardial function within incremental exercise in healthy unmedicated older vs. young men and women

Background Age-related differences concerning cardiorespiratory responses and myocardial function during exercise have not been extensively investigated in healthy populations. Aims To compare cardiorespiratory performance and myocardial function during maximal exercise in healthy/unmedicated men (older, n = 24, 63-75 years; young, n = 22, 19-25 years) and women (older, n = 18, age = 63-74 years; young, n = 23, 19-25 years). Methods Oxygen uptake (VO2), ventilation minute (V-E), heart rate (HR), stroke volume (SV), cardiac output (Q), O-2 pulse (O(2)p), preejection period (PEP), and left ventricular ejection time (LVET) were assessed during cycle incremental exercise. Results HR and SV remained equivalent between age groups until 75 and 50% peak workload, respectively. Q increased by 2.5 and 4.5 times in older and young groups, respectively. However, Q/VO2 ratio was always similar across age and sex groups (similar to 0.50). The energetic efficiency ratio (W/VO2) was also alike in older and young men, but slightly lower in women. At maximal exercise, cardiorespiratory responses were lower in older than young men and women: VO2 (-40 to 50%), V-E (-35 to 37%), HR (-23%), SV (-26 to 29%), Q (-43 to 45%), and O(2)p (-15 to 20%). Cardiac and SV indices were lower in older than young groups by approximately 42 and 25%, respectively. LVET was longer in the older individuals, while PEP was similar across age groups. Hence, PEP/LVET was lowered among older vs. young men and women. Conclusion Submaximal work capacity was preserved in healthy and unmedicated older individuals. Age-related lessening of maximal performance in both sexes was due to poor chronotropic and, particularly, inotropic properties of the heart.