Comparison of substrate metabolism and net mechanical efficiency during running on a treadmill in lean, obese and normal weight girls

Body composition is closely related to health and exercise performence. Therefore, the purpose of the present study was to compare the substrate metabolism and mechanical efficiency during running on a treadmill in lean, obese and normal-weight girls.

For this purpose, 9 lean girls (body fat 19.17 ± 3.56 percent), 9 obese girls (body fat 42.29 ± 4.42 percent) and 9 normal-weight girls (body fat 27.23 ± 3.58 percent) volunteered in the research project. The exercise plan was to run on a treadmill with an intensity of 75% of maximum heart rate for 30 minutes. The fat and carbohydrates oxidation, energy expenditure and mechanical efficiency of the subjects were measured with a gas analyzer system duing 30 minutes in the baseline and 30 minutes during activity. Then, the collected data were analyzed using multivariate variance analysis and LSD tests at the level of p < 0.05.

During the activity phase, the fat and carbohydrate oxidation and mechanical efficiency of the obese subjects were significantly higher as compare to lean and normal individuals (p=0.001, p=0.001, p=0.04 respectively). Moreover, absolute energy expenditure during the exercise at the obese subjects was significantly higher than lean subjects (p=0.02).

According to the results of the present study obese girls, compared to lean and normal weight ones, indicated higher substrate metabolism and net mechanical efficiency.