Maximal Aerobic and Anaerobic Exercise Responses in Children with Cerebral Palsy

The objective of this study is to compare the maximal aerobic and anaerobic exercise responses of children with cerebral palsy (CP) by level of motor impairment and in comparison with those of typically developing children (TD). Seventy children with CP, with varying levels of motor impairment (Gross Motor Function Classification System (GMFCS) I-III), and 31 TD performed an incremental continuous maximal aerobic exercise test and a 20-s anaerobic Wingate test on a cycle ergometer. Peak oxygen uptake (V˙O2peak), anaerobic threshold (AT), peak ventilation (V˙Epeak), peak oxygen pulse (peak O2 pulse), peak ventilatory equivalent of oxygen (peak V˙E/V˙O2) and carbon dioxide (peak V˙E/V˙CO2), peak aerobic power output (POpeak), and mean anaerobic power (P20mean) were measured. Isometric leg muscle strength was determined as a secondary outcome. Analysis revealed a lower V˙O2peak for CP (I: 35.5 ± 1.2 (SE); II: 33.9 ± 1.6; III: 29.3 ± 2.5 mL·kg-1·min-1) compared with TD (41.0 ± 1.3, P < 0.001) and a similar effect for AT (I: 19.4 ± 0.9; II: 19.2 ± 1.2; III: 15.5 ± 1.9; TD: 24.1 ± 1.0 mL·kg-1·min-1, P < 0.001). V˙Epeak and peak O2 pulse were also lower, whereas peak V˙E/V˙CO2 was higher in CP compared with TD (P < 0.05) and peak V˙E/V˙O2 similar between groups. All these variables showed no differences for different motor impairment levels. POpeak was lower for CP (I: 2.4 ± 0.1; II: 1.8 ± 0.1; III: 1.4 ± 0.2 W·kg-1) versus TD (3.0 ± 0.1, P < 0.001), together with a lower P20mean in CP (I: 4.6 ± 0.2; II: 3.3 ± 0.2; III: 2.5 ± 0.4 W·kg-1) versus TD (6.4 ± 0.2, P < 0.001), and both decreased significantly with increasing motor impairment. Children with CP have decreased aerobic and anaerobic exercise responses, but decreases in respiratory and aerobic exercise responses were not as severe as predicted by motor impairment. Future research should reveal the role of inactivity on the exercise responses of children with CP and possibilities for improvement through training interventions.