What maintains energy supply at peak aerobic exercise in trained and untrained older men?
Level 4 - case-series / case-control
Cross-sectional comparative physiological study
PubMed 17622751 · doi:10.1159/000104898
What was done
Fifteen trained older men (mean age 59.3 ± 1.1 years) and 15 untrained older men (mean age 60.1 ± 1.1 years) underwent maximal cardiopulmonary exercise testing on a bicycle ergometer. Hemodynamic and oxygen utilization variables were measured at rest and peak exercise using echocardiography, gas exchange analysis, and blood oxygen content assessments.
What was found
At rest, trained men had significantly (p < 0.05) higher end-diastolic volume (108.1 ± 5.8 vs. 100.7 ± 6.2 ml) and stroke volume (68.1 ± 4.3 vs. 57.3 ± 6.5 ml), and lower resting heart rate (68.7 ± 9.3 vs. 81.3 ± 8.2 beats/min) and mean arterial pressure (90.6 ± 6.9 vs. 95.4 ± 7.2 mm Hg). At peak exercise, trained men achieved significantly higher (p < 0.05) end-diastolic volume (156.1 ± 8.2 vs. 134.1 ± 7.6 ml), stroke volume (123.0 ± 7.9 vs. 96.0 ± 4.8 ml), cardiac output (20.2 ± 1.5 vs. 15.0 ± 1.3 L/min), and peak oxygen uptake (42.1 ± 2.1 vs. 31.1 ± 2.4 ml/kg/min). Diastolic blood pressure (70.3 ± 5.6 vs. 77.5 ± 4.2 mm Hg) and total peripheral resistance [4.3 ± 0.8 vs. 5.9 ± 1.41 (dyn·s·cm⁻⁵)·10⁻¹] were significantly lower in trained men.
Why it matters
This study shows that preserved aerobic capacity in trained older adults is predominantly driven by central cardiovascular function (stroke volume and cardiac output) rather than major differences in intrinsic mitochondrial adaptation.
Limits
The study is limited by a small sample size (n = 30) and a cross-sectional observational design that cannot determine causality or rule out self-selection bias. The cohort was restricted to men around 60 years of age, limiting generalizability to women and older age groups.
Cited by
- supports Maximal cardiac output in untrained and moderately trained individuals is around 15 to 20 liters per minute.