Impact of aging on aerobic capacity. At age 80, the total available energy for use is lower than that at age 70. Therefore, tasks such as walking comprise a greater proportion of the total aerobic capacity in older adults (67% versus 50%); the reserve (energy) available for completing additional activities is reduced.
Potential impact of high energy cost of walking on energy reserves. Higher energy cost of walking utilizes a greater proportion of the total energy capacity. The higher energy cost of walking reduces the reserve energy available to perform additional activities.