Walking economy in male adults with Down syndrome

Abstract

The purpose of this study was to investigate walking economy in response to steady-state locomotion in adult males with Down syndrome (DS) and in healthy controls. Twelve participants with DS (34.5 +/- 7.0 years) and 11 non-disabled controls (34.3 +/- 8.7 years) performed submaximal (0% grade, 2.5 km h(-1) for 8 min) and maximal treadmill tests with metabolic and heart-rate measurements. For submaximal walking, submaximal oxygen uptake (VO(2)) (9.1 vs. 9.5 mL kg(-1) min(-1)), net VO(2) (5.9 vs. 5.4 mL kg(-1) min(-1)) were not different between the groups (P > 0.05). However, oxygen-pulse (6.6 vs. 8.6 mL/beat) was lower and relative work intensity (44.6 vs. 19.9% of max) was higher in individuals with DS compared to controls (P < 0.05). Findings indicate similar walking economy between groups. Nevertheless, participants with DS exercised at lower submaximal oxygen-pulse and higher percentage of VO(2peak). Therefore, despite similar walking economy, participants with DS have lower cardiorespiratory function than controls for a given steady-state treadmill speed.

Walking Economy of Adults with Down Syndrome

“…As previously reported [15] , individuals with DS exhibited similar walking economy as controls during horizontal locomotion at their preferred walking speed. We also found that, they responded with higher delta VO 2 to a given delta speed, suggesting that, under these conditions, they are less efficient walkers than controls.…”

“…Additionally, as reported by Smith et al [21] , with suffi cient practice, they become more effi cient without modifying stiff ness and angular impulse as much as non-disabled controls. In support of this, Mendonca et al [15] showed that adults with DS have similar walking economy as controls during a slow speed treadmill task, after 24 familiarization sessions. Our results agree and further extend those fi ndings, as we obtained no between-group diff erences in walking economy during locomotion at our slowest treadmill speed, and four practice sessions were suffi cient for proper adaptation of adults with DS to this specifi c motor task.…”

“…Accordingly, adults with DS prefer walking velocities of approximately 2.5 km . h − 1 [22] and present similar walking economy as nondisabled controls at this specifi c treadmill workload [15] . On the other hand, for adults without disabilities, the work done at each step to lift the center of mass of the body equals the work done to increase its foreward speed at 4 km .…”

“…h − 1 and held constant at three diff erent treadmill grades (0, 2.5 and 5 % ), for 5 min each. The submaximal treadmill speeds were selected on the basis of the results reported by Smith and Ulrich [22] , Mendonca et al [15] and Cavagna et al [5] . Accordingly, adults with DS prefer walking velocities of approximately 2.5 km .…”

“…As a consequence, individuals with DS are likely to have higher metabolic cost at a given walking speed [2] . Only one study has previously compared walking economy of adults with DS with that of non-disabled controls [15] . There were no group diff erences in submaximal VO 2 during a single low speed walking task on a treadmill fl at surface, after a long period of familiarization.…”