Relationship between 5-minute walk distance and peak aerobic power in youth with cerebral palsy

Relationship between 5-minute walk distance and peak aerobic power in youth with cerebral palsy
DW MORGAN PHD 1, EA HOLBROOK MS 2, SL STEVENS MS 2, KB EMISON BS 2, J HUTCHENS 2, EE ARGO 4, GA MENCIO 3, DL DAMIANO 5
1 Center for Physical Activity and Health in Youth, Middle Tennessee State University, Mur freeboro, TN;
2 Health and Human Performance, Middle Tennessee State University, Murfreesboro, TN;
3 Orthopaedics and Rehabilitation, Vanderbilt University Medical Center, Nashville, TN;
4 Rehabilitation Services, Vanderbilt University Medical Center, Nashville, TN;
5Functional and Applied Biomechanics Section, NIH Clinical Center, Bethesda, MD, USA

Background/Objectives: Peak aerobic power (peak V02) reflects an individual’s ability to maximally transport and consume oxygen and is a key parameter influencing physiological stress experienced during sustained ambulation in children with motor disorders. Because the measurement of peak V02 requires specialized protocols and equipment and can be cumbersome for patients, it is often impractical in clinical settings. Hence, there is a need to validate the effectiveness of functional locomotors tasks which can accurately reflect aerobic fitness levels in children with disabilities. Against this backdrop, the purpose of this study was to quantify the relationship between distance covered in a 5-minute over ground walk and peak V02 in youth with cerebral palsy (CP).
Design: Validation study
Participants and Setting: A volunteer sample of 18 children with CP (11 males, 7 females, Gross Motor Function Classification System Levels I and II; mean age= 10.7 ± 2.8 years) was tested in a university setting.
Materials/Methods: Following initial accommodation to treadmill walking and two subsequent treadmill walking sessions performed at sub maximal intensities, each child walked for 5 minutes around a marked gymnasium floor. Prior to testing, participants were instructed to cover as much distance as possible during the allotted time period. A calibrated measuring wheel was used to determine the total distance traversed during the walking test. Within a week after completing the over ground walk, peak V02 was measured using a grade-incremented protocol. Walking speed, established initially on the basis of V02 and heart rate responses obtained in previous sub maximal trials, was adjusted during the first minutes of testing, if necessary, to elicit an appropriate exercise intensity for each child. Treadmill grade was raised 2.5% every 2 minutes until volitional exhaustion ensued. During the latter stages of the test, 1-minute samples of expired air were collected in meteorological balloons and analyzed to obtain serial measures of V02.
Results: Results indicated that mean values for 5-minute walk distance and peak V02 were 392 ± 73 m and 29.9 ± 6.4 ml/kg/min, respectively. Pearson product-moment correlation analysis also revealed a significant (r=0.60; P<0.01) positive association between walking distance and peak V02.
Conclusion/Significance: Findings from out study demonstrate that a moderately strong relationship exists between 5-minute walk distance and peak V02 in children with cerebral palsy who are independently mobile. These data suggest that a simple test of walking endurance can be used as an indirect measure of cardio respiratory fitness and may potentially reflect training-related improvements in endurance capability in youth with CP.

 
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