BACKGROUND: The energy demands of movement may be characterised by the energy cost C, which indicates how much energy is needed to carry a body mass of 1 kg over a distance of 1 m. It is generally accepted that the lower C represents a lesser amount of mechanical work executed with the same efficiency. The purpose of this study was to assess the influence of body fat on energy cost of running in healthy non-trained females. METHODS: Energy cost of running (C) was determined on the treadmill in a group of healthy non-trained females (N=63, mean age=39.+/-10.2 years, body mass=64.6+/-5.5 kg, height= 166.2+/-5.7 cm, VO2max.kg(-1)=35.0+/-3.6 ml.kg(-1)min(-1)), differing significantly in the percentage of body fat (18.9-30.2%), assessed by the 10 skinfold measurements. RESULTS: Mean value of C was 3.97+/-0.07 J.kg(-1)m(-1). The lowest values of C were found in subjects with the lowest %BF (C ranged from 3.81 to 4.06 J.kg(-1).m(-1)). There is a significant positive correlation between C and %BF [C (J.kg(-1).m(-1))= 0.0185*%BF (%) + 3.5090; r=0.7805; p<0.001; r2=0.6091], C and body mass (BM) [C (J.kg(-1).m(-1)) = 0.0083*BM (kg) + 3.4384; r=0.6176; p<0.001; r2 = 0.3814], and C and free fat mass (FFM) [C (J.kg(-1).m(-1))=0.0087*FFM (kg) + 3.5543; r=0.3521; p<0.05; r2=0.1240]. There is a negative correlation between C and VO2max.kg(-1) [C (J.kg(-1).m(-1))=-0.0181* VO2max.kg(-1) (ml.kg(-1).min(-1)) +4.6071; r=-0.8810; p<0.0001; r2=0.7761], and VO2max.kg(-1) and %BF [VO2max.kg(-1) (ml.kg(-1).min(-1)) =-0.8401* %BF(%) + 54.1021; r=-0.7142; p<0.0001; r2=0.5101]. CONCLUSIONS: From the collected data for untrained females we may conclude: first, the higher the training state (VO2max.kg(-1)), the lower the energy cost of running. Second, the energy cost of running C increases with the increase in body mass, %BF and FFM. Third, the training state decreases (VO2max.kg(-1)) with the increase in %BF.

Research Laboratory Charles University Faculty of Physical Education and Sports Prague Czech Republic