Aging is associated with a decline in daily energy expenditure that is disproportionately greater than the decline in daily energy intake. Collectively, these events can create a “positive” energy balance, secondary gains in central and total body fat, and a subsequently higher risk of morbidity and mortality. Participation in regular physical activity is a logical strategy to attenuate the decline in energy expenditure with aging, as physical activity can comprise between 10–50% of an older person’s daily energy expenditure. Understanding the influence of regular physical activity on energy expenditure with advancing age is clinically relevant, particularly since estimates predict that nearly 25% of the population will be ≥ 65 years of age by the year 2030. This brief review will focus on the current state of aging, energy expenditure, and physical activity literature. Topics to be addressed include: (a) measurement of physical activity in older adults; (b) aging and physical inactivity; and (c) influence of regular aerobic exercise on resting metabolic rate (RMR), thermic effect of food (TEF), and non-exercising physical activity.
Raymond D. Starling
Kevin J. Cole, David L. Costill, Raymond D. Starling, Bret H. Goodpaster, Scott W. Trappe and William J. Fink
The purpose of this investigation was to determine the effect of caffeine ingestion on work output at various levels of perceived exertion during 30 min of isokinetie variable-resistance cycling exercise. Ten subjects completed six trials 1 hr after consuming either 6 mg · kg−1 caffeine (3 trials) or a placebo (3 trials). During each trial the subjects cycled at what they perceived to be a rating of 9 on the Borg rating of perceived exertion scale for the first 10 min, a rating of 12 for the next 10 min, and a rating of 15 for the final 10 min. Total work performed during the caffeine trials averaged 277.8 ± 26.1 kJ, whereas the mean total work during the placebo trials was 246.7 ± 21.5 kJ (p < .05). Blood glycerol and free fatty acid levels increased over time to a significantly greater degree in the caffeine trials than in the placebo trials (p < .05). However, there were no significant differences between conditions in respiratory exchange ratio. These data suggest that caffeine may play an ergogenic role in exercise performance by altering both neural perception of effort and substrate availability.