The effect of carrying a portable respiratory gas analysis system on energy expenditure during running

Introduction: Improvements in respiratory gas analysis technology have made the availability of portable gas analysers widely available. Previous studies have shown that the majority of these systems are a valid and reliable method of determining respiratory responses during intense (Meyer et al., 2005) and light exercise (Ingle et al., 2007). Whilst these systems have been widely used, little is known of the impact on energy expenditure (EE) on individuals that are required to carry them during exercise bouts. Method: Eight male participants of mean (SD) age 25.0 (9.47) y, body mass 78.5 (8.39) kg, and height 1.83 (0.08) m, completed two randomly ordered incremental exercise bouts on a motorised treadmill. Following a period of four minutes of standing, participants were required to walk at 4km/h for four minutes. Thereafter the treadmill increased in speed every four minutes in order to induce a variety of exercise intensity demands (7, 10, 12, 14, km/h and maximal exercise). The experimental trial required participants to complete the exercise bout whilst wearing a portable (PT) respiratory gas analysis system (Metamax 3B, Cortex, Germany) in a harness on the chest. During the control trial (CT) the weight of the gas analyser was supported by a harness adjacent to the treadmill. Throughout each exercise trial respiratory gases, heart rate (HR) and rating of perceived exertion (RPE) were measured. Respiratory gases were used to calculate EE via indirect calorimetry (Frayn 1983). All data were analysed using a General Linear Model ANOVA with Repeated Measures, significance was accepted at p< 0.05. Results: During the exercise bouts, the rate of EE increased as the intensity of exercise increased (p<0.001). There was a significantly greater rate of EE during PT between the running speeds of 7 – 14 km/hr (p=0.048), but no significant differences were observed during standing, walking or at maximal exercise (p>0.05). Conversely there were no significant effects of wearing the gas analyser on VO2 max. (4.100.53, and 4.28 0.75 for the LC and PT trials respectively), HR or RPE (p>0.05). Conclusion: The use of portable gas analysis systems have no effect on the energy expended during standing or walking for short periods, but caution may need to be taken, particularly if exercise bouts are both submaximal and prolonged in nature