Lifelong Endurance Exercise as a Countermeasure Against Age-Related \(\dot{V}{\text{O}}_{{ 2 {\text{max}}}}\)V˙O2max Decline: Physiological Overview and Insights from Masters Athletes

It has been well established that arterial stiffness, manifest as an increase in arterial pulse wave velocity or late systolic amplification of the carotid artery pressure pulse, increases with age. However, the populations studied in prior investigations were not rigorously screened to exclude clinical hypertension, occult coronary disease, or diabetes. Furthermore, it is unknown whether exercise capacity or chronic physical endurance training affects the age-associated increase in arterial stiffness. Carotid arterial pressure pulse augmentation index (AGI), using applanation tonometry, and aortic pulse wave velocity (APWV) were measured in 146 male and female volunteers 21 to 96 years old from the Baltimore Longitudinal Study of Aging, who were rigorously screened to exclude clinical and occult cardiovascular disease. Aerobic capacity was determined in all individuals by measurement of maximal oxygen consumption (VO2max) during treadmill exercise. In this healthy, largely sedentary cohort, the arterial stiffness indexes AGI and APWV increased approximately fivefold and twofold, respectively, across the age span in both men and women, despite only a 14% increase in systolic blood pressure (SBP). These age-associated increases in AGI and APWV were of a similar magnitude to those in prior studies of less rigorously screened populations. Both AGI and APWV varied inversely with VO2max, and this relationship, at least for AGI, was independent of age. In endurance trained male athletes, 54 to 75 years old (VO2max = 44 +/- 3 mL.kg-1.min-1), the arterial stiffness indexes were significantly reduced relative to their sedentary age peers (AGI, 36% lower; APWV, 26% lower) despite similar blood pressures. Even in normotensive, rigorously screened volunteers in whom SBP increased an average of only 14% between ages 20 and 90 years, major age-associated increases of arterial stiffness occur. Higher physical conditioning status, indexed by VO2max, was associated with reduced arterial stiffness, both within this predominantly sedentary population and in endurance trained older men relative to their less active age peers. These findings suggest that interventions to improve aerobic capacity may mitigate the stiffening of the arterial tree that accompanies normative aging.

This study determined the decline in oxidative capacity per volume of human vastus lateralis muscle between nine adult (mean age 38.8 years) and 40 elderly (mean age 68.8 years) human subjects (age range 25-80 years). We based our oxidative capacity estimates on the kinetics of changes in creatine phosphate content ([PCr]) during recovery from exercise as measured by (31)P magnetic resonance (MR) spectroscopy. A matched muscle biopsy sample permitted determination of mitochondrial volume density and the contribution of the loss of mitochondrial content to the decline in oxidative capacity with age. The maximal oxidative phosphorylation rate or oxidative capacity was estimated from the PCr recovery rate constant (k(PCr)) and the [PCr] in accordance with a simple electrical circuit model of mitochondrial respiratory control. Oxidative capacity was 50 % lower in the elderly vs. the adult group (0.61 +/- 0.04 vs. 1.16 +/- 0.147 mM ATP s(-1)). Mitochondrial volume density was significantly lower in elderly compared with adult muscle (2.9 +/- 0.15 vs. 3.6 +/- 0.11 %). In addition, the oxidative capacity per mitochondrial volume (0.22 +/- 0.042 vs. 0.32 +/- 0.015 mM ATP (s %)(-1)) was reduced in elderly vs. adult subjects. This study showed that elderly subjects had nearly 50 % lower oxidative capacity per volume of muscle than adult subjects. The cellular basis of this drop was a reduction in mitochondrial content, as well as a lower oxidative capacity of the mitochondria with age.

This study assesses the association between cardiorespiratory fitness and long-term mortality in adults undergoing exercise treadmill testing.