Fitness Testing in Persons with Cerebral Palsy
In 1992 and 1993, Bhambhani and coworkers tested the validity and reliability of maximal aerobic power (VO2) during wheelchair ergometry (WE) and bicycle ergometry (BE) in six wheelchair athletes with cerebral palsy. Although there was no significant difference in aerobic power between WE and BE, the researchers found that there were large intra-individual differences. Higher VO2s were obtained on the WE test in subjects who used a wheelchair as their primary mode of ambulation, while the one subject who did not require any aids to ambulate, performed better on the BE.
In a later study, Bhambhani and coworkers evaluated the anaerobic threshold in 11 adult males with spastic cerebral palsy. They concluded that AT was not valid and reliable in this population, which could have been related to the type of test used (discontinuous), or the rate of lactate diffusion into the blood as a result of variations in muscle spasticity during the test. The investigators also found that only 5 of the 11 subjects were able to complete a bicycle ergometer test, while all 11 subjects were able to complete the wheelchair ergometer test. This was due to the high level of spasticity in the legs, which prevented adequate hip flexion necessary for pedaling the bicycle ergometer. This is slightly conflicting with Bhambhani's previous study in which he found that the bicycle ergometer was a better testing mode for the one subject who was able to ambulate. However, this subject may have had less spasticity in the legs thus permitting him or her to perform the cycling motion.
Holland and coworkers examined the test-retest reliability of the anaerobic threshold (called the ventilatory threshold [VT] in this paper) and maximal aerobic power in nine adults with cerebral palsy. They concluded that the VT was not an appropriate cardiorespiratory fitness parameter to measure in adults with cerebral palsy, but that VO2 max can be reliably measured in this population.
When testing subjects with cerebral palsy on VO2, it is important to find a modality that allows the person to achieve a maximal performance. For some, this may be the wheelchair ergometer, while for others who have less spasticity in the legs, a better test will be achieved with the bicycle ergometer. The more muscle groups that can be applied during testing, the greater likelihood of a higher and more accurate performance score.
Measuring Anaerobic Power
Tirosh, Bar-Or and Rosenbaum conducted one of the largest studies to date on the anaerobic power of children with cerebral palsy. Sixty-six children aged 5 to 18 years participated in the study. Thirty-eight of the subjects had cerebral palsy, 27 with spasticity, 10 with athetosis, and one with athetosis and ataxia; 28 children had other types of neuromuscular diseases (i.e., Duchenne's). The investigators measured power using the classic Wingate Anaerobic Test. They concluded that the test is highly reliable and reproducible for children with a neuromuscular disease.
Parker, Carriere, Hebestreit, and Bar-Or conducted a follow-up study and evaluated the anaerobic endurance and peak muscle power of 49 children with spastic cerebral palsy, ages 6 to 14 years. Nineteen subjects had quadriplegia, 16 had diplegia, and 14 had hemiplegia. They once again used the Wingate test to measure anaerobic power. The investigators found that the peak anaerobic power and muscle endurance of the upper and lower limbs in children with spastic cerebral palsy was, in their own words, distinctly subnormal.
In 1996, van de Berg-Emons et al., studied the reliability of tests to determine peak aerobic power, anaerobic power and isokinetic muscle strength in 12 Dutch children with spastic cerebral palsy. A secondary purpose was to compare their results to 39 nondisabled children matched on age and sex. Aerobic power was tested with a Monark bicycle ergometer; anaerobic power was measured using the standard Wingate test; and isokinetic muscle strength of the knee extensors and flexors was measured with the Cybex II isokinetic dynamometer. The investigators found that children with cerebral palsy can attain reliable measures on aerobic power, anaerobic power, and muscle strength, but that the higher intra-individual differences seen in the children with cerebral palsy suggest that the tests are "less suitable for children with cerebral palsy than in their healthy peers." Peak aerobic power, muscle strength and anaerobic power were found to be lower compared to the non-disabled children.
The Dutch investigators concluded that peak aerobic power, anaerobic power and isokinetic muscle strength in children with cerebral palsy were below average compared to children without disabilities of the same age and sex. Only three of 12 children (25%) had performance scores that fell within the "normal range" for their age and sex. The investigators noted that possible explanations could be "agonist/antagonist co-contraction, low muscle mass (especially of the fast-twitch fibers), the presence of contractures, detraining, and attention deficits." In any event, it is clear from this research that more emphasis must be placed on improving these fitness parameters in persons with cerebral palsy.
In 1997, van de Woude, et al., reported on anaerobic testing of 67 elite wheelchair athletes, including six athletes with cerebral palsy. The researchers concluded that anaerobic capacity can be reliably measured with a 30-second sprint test in wheelchair athletes, but in athletes with cerebral palsy there was wide diversity in performance that may be related to their level of function. Because of the many different disabilities used in their study, it is difficult to generalize the findings to any one group.