RELATIONSHIP BETWEEN PHYSICAL ACTIVITY, BODY FAT, AND PHYSICAL FITNESS IN A SAMPLE OF YOUNG ADULT FEMALES

Abstract

Body fat levels (BF) are dependent of the caloric balance between intake and the energy expenditure. The caloric expenditure is highly dependent of habitual physical activity levels (PA), which positively influences the physical fitness (PF) levels and health. Behind this, the BF is, in many cases, negatively associated with PF. PURPOSE: to identify the relationship between PA and PF, to identify the PA effects in BF and in the PF, and to identify the BF effect in the PF of young adult females. METHODS: The sample comprises 78 young adult females (21,05 years of age). The PF was evaluated through the following items: step test for the estimation of VO2 (ml.kg−1.min−1), sit-up (SU), sit and reach (SR), push-up (PU), and cardiac pulse at rest (CP). The BF indicator was the sum of subcutaneous adipose tissue (including skin) measured by B-mode ultrasonography, using a real-time linear electronic scanner, with a 7.5 MHz scanning head (Ecocamera Aloca SSD-500), at 5 sites: triceps, sub scapula, suprailiac, abdominal, and thigh. The PA was assessed through a questionnaire (Baecke et. al, 1982). This questionnaire allows the computation of 3 indexes: index of PA in work, index of PA in sport participation, and index of PA in leisure time except sport. The canonical correlation (Rc) between the PA (independent set) and PF (dependent set) was calculated to establish the relationship between PA and PF. The sample was divided in 3 groups according to the PA levels (low, medium and high), and the MANOVA and ANOVA was used to identify the effects of PA on PF and BF levels respectively. The same methodology with MANOVA was used to identify the effects of BF in PF. RESULTS: As we expected the results of canonical correlation indicate a significant and positive association between the PA and PF (Rc = 0.59; c2 (15) = 43.73; p < 0.001). The canonical coefficient for PF items are low, only the results for SU and VO2 exceed the criterion of 0.30 (0.67 and 0.43 respectively), indicating that this two items are the most important PF items contributors to the overall relationship between the PA and PF, and therefore the ones that are most influenced by the PA levels. The results of MANOVA indicate a significant difference between the PA groups (Λ = 0.761; F (10, 142) = 2,082, p = 0.03) and between the BF groups (Λ = 0.748; F (10, 142) = 2223, p = 0.02) in PF. In the PA groups the difference occur in SU between the medium and high PA groups, and in VO2 between the low and high PA groups. In the BF groups the difference occurs only in SU between low and high BF groups. The ANOVA results indicate a significant difference between PA groups in BF, the difference occur only between the medium and high PA groups. CONCLUSION: As expected the PA and PF are positively associated. The PA has a positive effect in the PF levels and in the low levels of body fat. The BF has a negative effect on PF.