Exercise, substrate utilization and energy requirements in the elderly.

We consider the impact of endurance and resistance exercise on energy expenditure and substrate utilization in the elderly. We present data to show that endurance exercise increases resting metabolic rate in elderly men and women and these changes appear to be sympathetically mediated. Preliminary data also shows that vigorous endurance exercise causes a compensatory decline in energy expenditure during the non-exercising portion of the day, suggesting that this type of exercise prescription may actually be counter-productive to promoting fat loss. Several studies using resistance training interventions in older individuals suggests that this exercise mode also increases resting metabolic rate and basal sympathetic nervous system activity. The impact of age and endurance exercise on fat mobilization and oxidation are briefly considered. The major findings are that whole body fat oxidation decreased with advancing age and this decrease was primarily related to the age-associated decrease in fat-free mass. Furthermore, endurance training altered basal utilization patterns in the elderly by shifting disposal of fatty acids from nonoxidative to oxidative pathways and that increases in fat oxidation were related to the increase in norepinephrine appearance rate. Exercise interventions that preserve fat-free mass and/or enhance aerobic capacity may increase or maintain fat oxidation and possibly blunt the tendency towards increasing adiposity in older individuals.