Background/Purpose: Adults with Down syndrome (DS) show higher net energetic cost (net EC) and higher net energetic cost per unit distance traveled (net ECtransport) than adults without DS during treadmill walking. They also prefer to walk faster than the speeds that minimize the net ECtransport. These findings may not apply to over-ground walking. This study therefore examined whether adults with DS have higher net EC and net ECtransport and whether they prefer to walk at speeds that minimize the net ECtransport during over-ground walking.
Method: Expired gases were collected from 11 adults with DS (28 ± 6 yrs; 6 women) and 15 adults without DS (27 ± 6 yrs; 7 women) while performing six over-ground walking trials, each lasting six minutes, at their preferred walking speed and at speeds of 0.5, 0.75, 1.0, 1.25, and 1.5 m/s. Net EC and net ECtransport were expressed in dimensionless terms to account for between-group differences in body dimensions. The energetically optimal walking speed and the minimal net ECtransport were determined from the net ECtransport to walking speed curve for each participant. Preferred walking speeds were expressed in m/s and as Froude numbers to account for the shorter legs of persons with DS. Differences in net EC and net ECtransport between groups were evaluated with 2 x 5 (group x speed) ANOVA. Between-group differences in preferred walking speed were analyzed with independent t-tests. Within-group differences between preferred and energetically optimal walking speeds and between the net ECtransport at preferred walking speed and the minimal net ECtransport were analyzed with paired t-tests.
Analysis/Results: Adults with DS showed higher net EC and net ECtransport than adults without DS across speeds (p<0.001). Preferred walking speed both in m/s and as a Froude number was slower in adults with DS than in adults without DS (p<0.05). The preferred walking speed of adults with and without DS was faster than their respective energetically optimal walking speed (p<0.05). Furthermore, the net ECtransport at preferred walking speed was higher than the minimal net ECtransport for each group (p<0.05).
Conclusions: Adults with DS have higher net EC and net ECtransport and prefer to walk over-ground slower than adults without DS. Adults with and without DS prefer to walk over-ground faster than their energetically optimal walking speeds. Therefore, adults with and without DS may not minimize the net ECtransport during over-ground walking.
Funded by Special Olympics Healthy Athletes Health Professions Student Grant