Chronic Omega-3 Fatty Acid Supplementation And Oxygen Uptake Kinetics During Heavy Exercise

Abstract

PURPOSE: To examine the effects 6 weeks of chronic omega-3 fatty acid (O3FA) supplementation (3 g EPA, 2 g DHA) on oxygen uptake and muscle extraction kinetics during constant load cycling in normoxic and normobaric hypoxic conditions. METHODS: 13 endurance trained cyclists were divided into two groups, O3FA (n = 6, VO2max = 60.2 ± 4.5 ml·kg-1·min-1), and placebo (n= 7, VO2max = 66.2 ± 4.1 ml·kg-1·min-1). Subjects completed an incremental exercise protocol to determine maximal oxygen consumption and maximal power output on a magnetically-braked cycle ergometer. In subsequent sessions, subjects completed three minutes of a constant load cycling test at 75% of normoxic peak power at simulated altitude (FIO2= 15.0%) and at sea-level (FIO2 = 20.9%), prior to 6 weeks of supplementation (baseline) with either O3FA or placebo. Following supplementation, subjects repeated the normoxic and hypoxic constant-load cycle exercise bouts. Breath-by-breath VO2 was measured continuously, and skeletal muscle deoxygenation (deoxygenated hemoglobin+myoglobin [HHb] via near-infrared spectroscopy [NIRS]) were measured. Kinetic time constant was calculated as time to 63% of primary component response (HHb-τ1 and VO2- τ1). RESULTS: Chronic O3FA supplementation improved the VO2 uptake response time (VO2- τ1 = 21.3 ± 6.4s post-supplementation; 31.6 ± 6.2s pre-supplementation; p < 0.05) during exercise in normoxia, with no changes in the placebo group pre- to post-supplementation. VO2 primary component amplitude was lower in the O3FA group (3.19 ± 0.60 L/min post-supplementation; 3.44 ± 0.60 L/min pre-supplementation; p < 0.05) in normoxia, following supplementation. There were no significant differences in any of the [HHb] parameters during normoxic exercise in either group. There were no significant differences in any of the [HHb] or VO2 parameters during hypoxic exercise between pre- and post-supplementation in either group. CONCULUSION: 6 weeks of O3FA supplementation is beneficial in improving oxygen uptake kinetics during heavy exercise in normoxic conditions, thus may lead to improvements in exercise tolerance to constant heavy load exercise. However, no improvements were seen in [HHb] or oxygen uptake kinetics in hypoxia following O3FA supplementation.