Validity And Reliability Of Small Respiratory Chamber To Assess Exercise Energy Expenditure

Abstract

The recently created small respiratory chambers (FLEX rooms) permit a more affordable solution and faster response time than the larger traditional whole room respiratory chambers. Despite the potential for FLEX to employed to assess acute energy expenditure (EE), it has never been validated for submaximal exercise. PURPOSE: To perform concurrent validation and reliability analysis of indirect calorimetry of FLEX against metabolic carts (Cart) during submaximal cycling. METHODS: Ten healthy participants were included in this study (41.5±15.2 years; BMI=25.8±3.3 kg/m2). Energy expenditure was evaluated on FLEX and mixing chamber Cart, simultaneously. FLEX is an 11,000-liter room operated by a push-pull system and mass flow controllers. Participants performed two submaximal exercise bouts of 30-minutes the same day with a 30-minute resting period between bouts, each bout had a light and a moderate load; they repeated the same protocol after two days. Oxygen uptake (VO2) and CO2 production (VCO2) were derived with the same equation. EE, Net EE, gross efficiency (GE) and net efficiency (NetEF) were calculated for each load (L1 & L2). FLEX within and between-day reliability was calculated by the standard deviation of the differences in kcal/min and %. Repeated measures analysis was utilized to explore differences between Cart and FLEX. RESULTS: EE and NetEE were not significantly different between cart and FLEX technologies (EEL1, FLEX= 4.29 vs. Cart= 4.13 kcal/min, EEL2, FLEX= 6.2 vs. Cart=6.0 kcal/min, P>0.05 for both; NetEEL1, FLEX= 2.7 vs. Cart=2.7 kcal/min, EEL2, FLEX= 4.63 vs. Cart=4.57 kcal/min, P>0.05 for both). GE and NetEF were similar between both systems for all loads (GEL1, FLEX= 11.8% vs. Cart= 12.3%, GEL2, FLEX= 16.3% vs. Cart= 18.9%, P>0.05 for both; NetEFL1, FLEX= 18.8% vs. Cart=18.9%, NetEFL2, FLEX= 22.0% vs. Cart= 22.4%, P>0.05 for both). FLEX assessments of EE were highly reliable within-day (L1= 0.11 kcal/min (2.5%) and L2= 0.07 kcal/min (1.1%)) and between-days (L1= 0.10 kcal/min (2.4%) and L2= 0.14 kcal/min (2.2%)). CONCLUSION: FLEX is a valid and reliable technique to assess energy metabolism during exercise without the cumbersome mouthpiece or mask required by metabolic carts.