Bicycling for Exercise Helps Maintain a Youthful Metabolic Cost of Walking in Older Adults

Abstract

Impaired walking performance is a key determinant of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost compared to young adults. Specifically, healthy older adults have been shown to have a 15-20% greater metabolic cost of walking compared to young adults. However, a recent study suggests that older adults who routinely run for exercise have a lower metabolic cost of walking compared to older adults who walk for exercise. Yet, it remains unclear if other aerobic exercises such as bicycling elicits similar improvements on walking metabolic cost among older adults. PURPOSE: To determine if regular bicycling exercise affects metabolic cost of walking in older adults. To our knowledge, there has been no research looking at metabolic cost of walking in older adults who bicycle for exercise. METHODS: 13 young adults (23±2 years), 16 “older walkers” (71±5 years) who walk ≥30 min, 3x/week, and 17 “older bicyclists” (68±3 years) who bicycle ≥30 min, 3x/week, walked on a level treadmill at four speeds (0.75, 1.25, 1.60, and 1.75 m/s). Using an open circuit expired gas analysis, we measured V[Combining Dot Above]O2 and V[Combining Dot Above]CO2 in the last 2 minutes of each 6 minute trial to determine metabolic cost (J/kg/s). We compared metabolic cost in the three groups. RESULTS: Across the range of walking speeds, older bicyclists had a 9-17% lower metabolic cost of walking compared to older walkers (3.24±0.14 vs. 3.80±0.16 J/kg/s, respectively; p=.006) and similar metabolic cost of walking compared to young adults (p=.973). CONCLUSIONS: Bicycling exercise mitigates the age-related deterioration of walking metabolic cost, whereas walking for exercise appears to have a minimal effect on improving metabolic cost of walking in older adults. We suspect the greater aerobic intensity of bicycling exercise may maintain muscle mitochondrial efficiency in aging and thus helps explain the lower metabolic cost of walking in older bicyclists versus older walkers. Supported by Humboldt State University RSCA Grant #AY 15/16.