Running for exercise mitigates age-related deterioration of walking economy

Abstract

Introduction: Impaired walking performance is a key predictor of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost (worse economy) compared to young adults. However, older adults who consistently run have been shown to retain a similar running economy as young runners. Unfortunately, those running studies did not measure the metabolic cost of walking. Thus, it is unclear if running exercise can prevent the deterioration of walking economy.

Purpose: To determine if and how regular walking vs. running exercise affects the economy of locomotion in older adults.

Methods: 15 older adults (69 ± 3 years) who walk ≥ 30 min, 3x/week for exercise, "walkers" and 15 older adults (69 ± 5 years) who run ≥ 30 min, 3x/week, "runners" walked on a force-instrumented treadmill at three speeds (0.75, 1.25, and 1.75 m/s). We determined walking economy using expired gas analysis and walking mechanics via ground reaction forces during the last 2 minutes of each 5 minute trial. We compared walking economy between the two groups and to non-aerobically trained young and older adults from a prior study.

Results: Older runners had a 7-10% better walking economy than older walkers over the range of speeds tested (p = .016) and had walking economy similar to young sedentary adults over a similar range of speeds (p = .237). We found no substantial biomechanical differences between older walkers and runners. In contrast to older runners, older walkers had similar walking economy as older sedentary adults (p = .461) and ∼ 26% worse walking economy than young adults (p<.0001).

Conclusion: Running mitigates the age-related deterioration of walking economy whereas walking for exercise appears to have minimal effect on the age-related deterioration in walking economy.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1. Mean (SE) gross metabolic power as a function of walking speed in older walkers (▴) and older runners (⧫) walkers (▴).

Lines represent least square regression for older walkers (y = 2.709x2–3.539x+4.523, r2 = 0.86) and older runners (y = 2.382x2–3.189x+4.233, r2 = 0.89). Symbols shown on vertical axis represent standing metabolic rate of both groups. Asterisks (*) indicate significant differences between older runners and walkers (p<0.05).

Figure 2. Mean (SE) gross metabolic cost of transport as a function of speed in older walkers (▴) and older runners (⧫).

Asterisks (*) indicate significant differences between older walkers and runners (p<.05>

Figure 3. Average individual leg vertical (A) and horizontal (B) ground reaction force for older walkers (dashed lines) and older runners (solid lines) at the intermediate walking speed of 1.25 m/s.

Figure 4. Gross metabolic power as a function of speed2 in older sedentary adults (•), older walkers (▴), older runners (⧫), and young sedentary adults (○).

Lines denote least square regression within each group (older sedentary: y = 1.46x+2.30, r2 = 0.91; older walkers: y = 1.31x+2.52, r2 = 0.86; older runners: y = 1.12x+2.42, r2 = 0.88; young sedentary: y = 1.01x+2.27, r2 = 0.87). Symbols on vertical axis represent standing metabolic rate of each group.