The relationship of the energetic cost of slow walking and peak energy expenditure to gait speed in mid-to-late life

Abstract

Objective: Peak energy expenditure is highly correlated with usual gait speed; however, it is unknown whether the energetic cost of walking is also an important contributor to usual gait speed when considered as a component of peak walking capacity.

Design: The energetic cost of 5 mins of slow treadmill walking (0.67 m/sec), peak overground walking energy expenditure, and usual gait speed over 6 m were assessed cross-sectionally in 405 adults aged 33 to 94 yrs in the Baltimore Longitudinal Study of Aging.

Results: Mean (SD) energy expenditures during slow and peak sustained walking were 8.9 (1.4) and 18.38 (4.8) ml kg(-1) min(-1), respectively. Overall, the energetic cost of slow walking as a percentage of peak walking energy expenditure was strongly associated with usual gait speed (P < 0.001); however in stratified analyses, this association was maintained only in those with peak walking capacity below 18.3 ml kg(-1) min(-1) (P = 0.04), the threshold associated with independent living.

Conclusions: In older persons with substantially reduced peak walking capacity, the energetic cost of walking is associated with gait speed, particularly when peak walking capacity nears the minimum level considered necessary for independent living. Thus, optimal habilitation in older frail persons may benefit from both improving fitness and reducing the energetic cost of walking.

Figures

Figure 1

Usual Gait Speed (m/s) & Age (yrs) A lowess fit curve displays the curvilinear relationship between usual gait speed (m/s) and age (yrs).

Figure 2a

Energetic Cost of Walking (ml/kg/min) & Age (yrs) A lowess fit line displays the linear relationship between the average energetic cost of slow walking (ml/kg/min) and age.

Figure 2b

Peak Walking Energy Expenditure (ml/kg/min) & Age (yrs) A lowess fit curve displays the relationship between average peak walking energy expenditure (ml/kg/min) and age.

Figure 3

Cost Ratio and Usual Gait Speed (m/s) A lowess fit line displays the relationship between the ratio of slow walking energy expenditure to peak energy expenditure and usual gait speed (m/s).

Figure 4

Compression of Energy Reserves and Age A linear fit graph displays the compression of energy availability (peak walking energy expenditure) and energy utilization for basic tasks (slow walking energy) and age.