Perception of effort at low and moderate intensity exercise in survivors of childhood acute lymphoblastic leukaemia.

OBJECTIVE

The study examined the degree to which male and female survivors of acute lymphoblastic leukaemia (ALL) perceive effort at low and moderate intensity exercise in association with related physiological variables.

MATERIALS AND METHODS

Participants were 67 children. Thirty-five (14 boys and 21 girls) were long-time survivors of ALL and 32 (18 boys and 14 girls) were control subjects. The Children's Effort Rating Table (CERT) was used to measure whole-body perceived exertion at low and moderate intensity exercise. Peak oxygen uptake was measured using a motorized treadmill. CERT and physiological data were analysed using 2 x 2 mixed analyses of variance, appropriate t-tests and coefficients of correlation.

RESULTS

In absolute terms, boys treated for ALL found perception of effort to be more strenuous at both low (3.9 vs. 3.5 units) and moderate (6.1 vs. 5.3 units) intensity exercise than control subjects, although differences were not significant (p > 0.05); girls treated for ALL found perception of effort to be the same as controls at low intensity exercise (3.1 vs. 3.1 units) but slightly higher than controls at moderate intensity exercise (5.6 vs. 5.2 units); neither of these differences were significant (p > 0.05). When CERT values were adjusted for (.-)VO(2) peak (%) and heart rate (HR) peak (%) differences remained non-significant. There were no significant interactions (Intensity x Group) in males, but the interaction for (.-)VO(2) peak (%) was significant in females (p < 0.05). The main effect for Intensity (low and moderate) was significant for all variables in boys and girls (p < 0.0001). The main effect for Group (ALL and controls) identified significantly greater absolute (b.p.m.) and relative (%) HR values in ALL boys at low and moderate intensity exercise. In female ALL and control subjects the interaction (Intensity x Group) distinguished between (.-)VO(2) peak (%) at moderate intensity exercise and HR peak (%) at low and moderate intensity exercise. Coefficients of correlation between perceived effort and (.-)VO(2) peak (%) in boys and girls were low to high (0.28-0.76), and between absolute and relative HR were also low to high (0.33-0.73). There were low correlations between time 'off therapy' and perceived effort, (.-)VO(2) peak (%) and HR peak (%) (-0.003 to -0.49).

CONCLUSION

It was concluded that perception of effort in survivors of ALL at low and moderate intensity exercise was the same as that of control subjects. Correlations between perceived effort and physiological variables at moderate exercise were low to high, while those between perceived effort and time from treatment were generally weak.