Non linear relationships between anthropometric and motor-endurance variables.

Nonlinear regressions are rare in anthropology. In this paper we have tried to identify the significance and the character of the linear and non-linear relations between some anthropometric measures and the motor-endurance status. All subjects (300 moderately physically active males, mean aged 24 +/- 3.4 years) were measured for body weight, body height, body mass index, push-ups, sit ups, standing high jump, 50 meters swimming, and 1500 meters running. Linear (general model: y = a+bx) and nonlinear regression (general model: y = a+bx+cx2) was calculated simultaneously. According to the presented results the non-linear-square relation between variables can be expected: a) if there is evident cause why two absolutely different sub-groups of subjects should reach equal results in the criterion, b) if a non-linear-square basis for the established relationship can be found. In conclusion, simple linear and non linear regression procedures are to be used for the identification of linear and nonlinear predictors in nonlinear multiple regressions.