Thermoregulatory resposes during exercise in a hot climate in children with spastic cerebral palsy

Compared to healthy children, those with spastic cerebral palsy (CP) require more energy and produce more metabolic heat during activities such as walking. To determine whether this affects their thermoregulatory ability during exercise in the heat, children with spastic diplegic CP (n = 4; age = 9.3–11.1 y) and pair-matched healthy controls (CON) visited the lab twice. During Visit I (thermoneutral environment) they arm cranked at 40 rpm for 3×10 min. Heart rate (HR) was measured continuously. This session allowed the determination of a moderate exercise intensity for the CP group (HR 120–130 bpm) that would be maintained for 3 bouts in the subsequent visit. Each CON performed as per their matched CP, at the same W·kg−1 body mass (0.57 W·kg−1 ± .19, M ± SD). During Visit II (hot climate: 35°C; 50% relative humidity) subjects exercised as in Visit I. Body mass, rectal (Tr) and skin (Tsk) temperatures were measured periodically. Sweating rate (SR) was determined from net body mass changes corrected for urine output, drink intake and respiratory water loss. Differences between CP and CON in Visit II were determined using a paired t-test (α = 0.05). While the energy required to crank, estimated by oxygen uptake (ml·kg−1·min−1) in the last 3 min of each bout, was not different between the groups (CP = 12.6 ± 2.9; CON = 12.2 ± 3.7), CP HR was greater than in CON by 8.5% (exercise; P = 0.02) and 12.1% (rest; P = 0.01). Tr increased in CP by 0.08 °C ± 0.08, but decreased in CON by 0.05 °C ± 0.08 (P = 0.0001). Tsk increases were 33% less in CP (P = 0.0001) than in CON. Though there was no difference in SR, 3 of 4 CP had a higher (20.8%) SR. We suggest that children with CP, even when the exercise mode does not induce greater metabolic heat, may experience greater physiologic strain due to decreased ability to lose heat through conduction and convection, compared to healthy children. These patients might also have a greater reliance on evaporative heat loss through sweating.