Differences in motor performance between children and adolescents in Mozambique and Portugal: impact of allometric scaling.

BACKGROUND: Children from developed and developing countries have different anthropometric characteristics which may affect their motor performance (MP). AIM: To use the allometric approach to model the relationship between body size and MP in youth from two countries differing in socio-economic status-Portugal and Mozambique. SUBJECTS AND METHODS: A total of 2946 subjects, 1280 Mozambicans (688 girls) and 1666 Portuguese (826 girls), aged 10-15 years were sampled. Height and weight were measured and the reciprocal ponderal index (RPI) was computed. MP included handgrip strength, 1-mile run/walk, curl-ups and standing long jump tests. A multiplicative allometric model was adopted to adjust for body size differences across countries. RESULTS: Differences in MP between Mozambican and Portuguese children exist, invariably favouring the latter. The allometric models used to adjust MP for differences in body size identified the optimal body shape to be either the RPI or even more linear, i.e. approximately (height/mass(0.25)). Having adjusted the MP variables for differences in body size, the differences between Mozambican and Portuguese children were invariably reduced and, in the case of grip strength, reversed. CONCLUSION: These results reinforce the notion that significant differences exist in MP across countries, even after adjusting for differences in body size.

Criterion-related validity and test-retest reliability of the 20m square shuttle test.

We assessed validity and reliability of the new 20m square shuttle run test (SST) for predicting maximal oxygen uptake (V O(2max)) and compared it with its predecessor, the 20m Multistage Shuttle Run Test (MST). In a repeated-measures randomised-block design, 74 healthy adult males performed the SST, the MST and a treadmill test (TT). To assess reliability, 40 of the total 74 volunteers were randomly-selected to perform the SST and MST twice. Unlike the SST (p>0.05), mean predicted V O(2max)(V predO(2max)) from the MST was significantly increased from that measured during the TT (p<0.05). The V predO(2max) from SST and MST correlated with TT V O(2max) at r=0.95 (p<0.001) and r=0.63 (p<0.001), respectively. Prediction error of SST was -0.3+/-3.3mlkg(-1)min(-1) with a coefficient of variation of +/-3.5%, while the equivalent values for MST were 4.2+/-7.3mlkg(-1)min(-1) and +/-7.4%. Mean test-retest V predO(2max) did not differ for both SST and MST (p>0.05), while the corresponding test-retest correlation coefficients were r=0.85 (p<0.001) and r=0.72 (p<0.001). Reliability errors in 95% limits of agreement were 0.3+/-4.8 and 0.6+/-6.8mlkg(-1)min(-1) while coefficients of variation were +/-5.2% and +/-6.8% for the SST and MST, respectively. It is concluded that SST is a more valid proxy than MST for predicting laboratory V O(2max) based on the current procedures, while both tests are sufficiently reliable in healthy male adults.