Effects of Swimming with Added Respiratory Dead Space on Cardiorespiratory Fitness and Lipid Metabolism

摘要

The aim of this study was to investigate the circulatory, respiratory, and metabolic effects of induced hypercapnia via added respiratory dead space (ARDS) during moderate-intensity swimming in recreational swimmers. A mixed-sex sample of 22 individuals was divided into homogeneous experimental (E) and control (C) groups controlled for maximal oxygen uptake (VO_(2)max). The intervention involved 50 min of front crawl swimming performed at 60% VO_(2)max twice weekly for 6 consecutive weeks. ARDS was induced via tube breathing (1000 ml) in group E. An incremental exercise test was administered pre- and post-intervention to assess cardiorespiratory fitness (CRF) by measuring VO_(2)max, carbon dioxide volume, respiratory minute ventilation, respiratory exchange ratio (RER), and heart rate at 50, 100, 150, 200 W and at maximal workload. Body mass index (BMI), fat mass (FM), and fat-free mass (FFM) were also measured. The mean difference in glycerol concentration (ΔGLY) was assessed after the first and last swimming session. No significant between-group differences were observed at post-intervention. No within-group differences were observed at post-intervention except for RER which increased in group E at maximal workload. A 6-week swimming intervention with ARDS did not enhance CRF. The RER increase in group E is not indicative of a substrate shift towards increased lipid utilization. No change in ΔGLY is evident of a lack of enhanced triglyceride hydrolyzation that was also confirmed by similar pre- and post-intervention BMI, FM, and FMM.Key points The study compared the effects of a 6-week swimming intervention with and without added respiratory dead space (ARDS).Swimming with ARDS did not improve cardiorespiratory fitness measures (VO_(2), VCO_(2), VE, HR) obtained in an incremental exercise test.Post-intervention RER increased after the ARDS swimming intervention, but this change does not suggest a substrate shift towards increased lipid utilization during exercise as evidenced by a lack of change in post-exercise glycerol concentration.No changes were observed in BMI, FM, and FFM.