Effect of exercise intensity on exercise and post exercise energy expenditure in moderately obese women

Abstract

Walking and/or jogging has become a popular activity especially for moderate obese women who aim to maintain acceptable body fat levels. The question whether it is more beneficial to walk/jog at a moderate pace for a longer duration or at a fast pace for a shorter duration is often asked. Research literature fails to answer this question conclusively. The aim of this study was to determine if exercise and post exercise energy expenditure are affected by the intensity of exercise during a set distance of 4km walking and/or jogging. Subjects for this study were 12 moderately obese females with mean fat percentage of 31.7±6.3% and mean age of 38.2±4.6 years. For the low intensity protocol (LI) continuous indirect calorimetry, using the Cortex Metamax portable system, was performed for a 30 minute pre-exercise period of sedentary sitting, for a 4km walk/jog on a motorised treadmill at 57% of maximum heart rate, as well as for 4 hours post exercise. The high intensity protocol (HI) consisted of continuous indirect calorimetry for a 30-minute pre-exercise period of sedentary sitting, for a 4km walk/jog on a motorised treadmill at the highest voluntary pace of the subject, as well as for 4 hours post exercise. A minimum period of one week separated the HI and LI evaluations. Oxygen consumption and substrate utilisation during and 4 hours following LI and HI were analysed. The main findings were: 1) oxygen consumption (lO2) was significantly higher (p<0.05) during HI (54.5±9.8) than during LI (44.1±16.7); 2) post exercise oxygen consumption (lO2) did not differ significantly (p>0.05) between HI (79.9±13.2) and LI (82.4±15.2); 3) total (exercise plus 4-hour recovery) oxygen consumption (lO2) did not differ significantly (p>0.05) between HI (134.4±16.1) and LI (126.5±28.3); 4) post exercise fat utilisation (gm) was slightly lower after HI (18±18.7) than after LI (22.2±13.7), but the difference was not significant (p>0.05); 5) post exercise carbohydrate utilisation (gm) was slightly higher after HI (53.7±19.9) than after LI (46.5±21.0), but the difference was not significant (p>0.05); 6) total carbohydrate utilisation (gm) was significantly (p<0.05) higher with HI (100.7±33.7) than LI (73.8±30.2); and 7) total fat utilisation (gm) was lower with HI (26.1±17.1) than with LI (33.1±22.8), but it was not significant (p>0.05). This study did not find any significant advantage for mildly obese females to walk/jog for 4km at a very high intensity compared to a moderate intensity, in order to increase energy expenditure as well as enhance the oxidation of fat and thereby accelerate fat loss.


(S. African J. for Research in Sport, Physical Ed. and Recreation: 2001 23 (1): 1-8)