Physical Activity Level is Associated with the O2 Cost of Walking in Cerebral Palsy

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Abstract
To determine, in children and adolescents with cerebral palsy (CP), the relationship between physical activity level (PAL) and i) oxygen cost of walking, and ii) peak V̇O2. In 11 subjects (10.6–16.3 yr) with mild CP, PAL, the ratio of total energy expenditure to resting energy expenditure, was determined from 3 d of heart rate (HR) monitoring (field), with individual HR-V̇O2 calibrations done in the lab. The oxygen cost of walking was measured during three 3-min walks on a treadmill at 60, 75, and 90% of each subject’s fastest treadmill walking speed (FWS). Subjects also performed a maximal treadmill exercise test. Alpha was set at 0.05. One subject was an outlier and eliminated from all simple linear regression analyses. For the remaining 10 subjects, PAL (1.37 ± 0.18) was related (r = −0.70 to −0.84) to net V̇O2 at 60 and 75% FWS (13.1 ± 4.1 and 16.2 ± 4.2 mL·kg−1·min−1), net V̇O2·m−1, averaged across the three speeds (0.32 ± 0.23 mL·kg−1·m−1), and percent peak V̇O2 at all three speeds (54.5 ± 21.5, 63.5 ± 20.9, and 75.5 ± 15.1%). PAL was not significantly related to net V̇O2 at 90% FWS (20.8 ± 5.3 mL·kg−1·min−1) or to peak V̇O2 (34.0 ± 9.2 mL·kg−1·min−1). For this population, those with low PAL may also have a high oxygen cost of walking. These individuals’ PAL was not related to their peak V̇O2. Further research is required to determine whether interventions that decrease the oxygen cost of walking also affect PAL and whether changes in PAL affect the oxygen cost of walking.