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

Age-related differences concerning cardiorespiratory responses and myocardial function during exercise have not been extensively investigated in healthy populations.

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).

Oxygen uptake (VO₂), ventilation minute (V _E), heart rate (HR), stroke volume (SV), cardiac output (Q), O₂ pulse (O₂p), preejection period (PEP), and left ventricular ejection time (LVET) were assessed during cycle incremental exercise.

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 (∼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 O₂p (-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.

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.