Anaerobic threshold in wheelchair athletes with cerebral palsy: validity and reliability.

This study examined the validity and reliability of the anaerobic threshold (AT) using blood lactate (ATLa) and respiratory gas exchange (ATg) criteria during cycle ergometry (CE) and wheelchair ergometry (WE) in athletes with spastic cerebral palsy (CP). Eleven subjects attempted a discontinuous incremental test protocol, two minutes work interspersed with one minute rest, twice each on the CE and WE. Only five out of the 11 subjects were able to complete the CE tests, whereas all the subjects were able to complete the WE test. Inadequate hip flexion due to muscle spasticity was the primary limiting factor during the CE tests. Although the maximal aerobic power using this protocol was reliable during WE (r = 0.89, p < .05), the validity and reliability of the AT identified by two independent evaluators using these two techniques was questionable. Evaluator 1 was able to identify ATLa and ATg in seven out of the 11 cases, whereas evaluator 2 was successful in five and seven cases, respectively. It is unclear from these results whether the poor validity and reliability of the AT was due to the discontinuous test protocol used, or whether it was due to inconsistencies in the rate of lactate diffusion from the muscle into the blood due to variations in muscle spasticity during the test.