Author(s)

Omorede E. Osayande^*, Eloghosa E. Ogbonmwan, Andrew C. Ugwu

Department of Physiology, University of Benin, Benin City, Nigeria.

Sweat is a hypotonic fluid excreted by sweat glands to cool the body. There are conflicting reports on whether or not body composition has an effect on thermoregulatory responses especially during exercise. This study was aimed at determining and comparing sweat rate and electrolyte composition in underweight (BMI < 18.5 kg/m²), normal weight (18.5 kg/m² > BMI < 25 kg/m²), overweight (25kg/m² < BMI < 30 kg/m²) and obese women (BMI > 30 kg/m²) during moderate exercise. Forty women (19 - 25 years) were used during this study after assessing their health status. They were stratified for BMI with each group having a total of ten women. It was ensured that all the women used in the study were euhydrated before commencing the research. Before sweat collection, the treadmill was calibrated according to the Bruce Treadmill Protocol. Sweat samples were obtained with a sweat suction apparatus from a 120 cm² circular area marked on the skin of the face and neck, after a 15 minute fast walk on a treadmill at an inclination of 15° and at a speed of 4.2 km/h at 27°C room temperature. The time at which sweating commenced in the subjects was recorded. Sweat rate (L/hour) was calculated using the formula: sweat rate (L/hr) = (pre-exercise body weight - Post-exercise body weight)/exercise duration. Each sweat sample was collected and analysed immediately. The results showed that obese women had a significantly (P < 0.05) higher sweat rate and underweight women had a significantly (P < 0.05) lower sweat rate than all the other groups. Furthermore, subjects with a high body surface area showed significantly higher sweat rates compared to subjects with lower body surface area. Sweat electrolyte composition did not change in all BMI groups. In conclusion, obese subjects are more likely to develop fluid imbalances than underweight and normal weight subjects during moderate exercise. Also, underweight women might be at a thermoregulatory disadvantage because of their reduced body fat and body surface area.

Sweat Rate, Sweat Electrolyte Composition, Thermoregulation, Body Mass Index, Moderate Exercise

Osayande, O. , Ogbonmwan, E. and Ugwu, A. (2016) Sweat Rate and Electrolyte Composition in Young Women of Varying Body Mass Indices during Moderate Exercise. Journal of Biosciences and Medicines, 4, 14-22. doi: 10.4236/jbm.2016.44003.