Muscle cooling modulates tissue oxidative and biochemical responses but not energy metabolism during exercise

• Published in: European journal of applied physiology Vol. 120; no. 8; pp. 1761 - 1775
• Main Authors: Gagnon, Dominique D., Hancock, Curtis, McCue, Alexus, Beckett-Brown, Nicholas, Gagnon, Jeffrey, Williams, Laura, Marsh, David, Munten, Stephanie
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2020; Springer Nature B.V
• Subjects: Adult; Biomedical and Life Sciences; Biomedicine; Body Temperature; Carbon Dioxide - blood; Cooling; Energy Metabolism; Exercise; Female; Gases; Heart Rate; Hormones - blood; Human Physiology; Humans; Hypothermia, Induced; Insulin; Lipid Metabolism; Male; Metabolism; Muscle, Skeletal - metabolism; Muscle, Skeletal - physiology; Musculoskeletal system; Occupational Medicine/Industrial Medicine; Original Article; Oxidation; Oxygen - blood; Oxygen Consumption; Oxygenation; Physical training; Skeletal muscle; Sports Medicine; NIRS; Temperature; Muscle; Exercise; Metabolism
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-020-04407-4

Purpose This study investigated whether muscle cooling and its associated effects on skeletal muscle oxidative responses, blood gases, and hormonal concentrations influenced energy metabolism during cycling. Methods Twelve healthy participants (Males: seven; Females: five) performed two steady-state exercise sessions at 70% of ventilatory threshold on a cycle ergometer. Participants completed one session with pre-exercise leg cooling until muscle temperature ( T m ) decreased by 6 °C (LCO), and a separate session without cooling (CON). They exercised until T m returned to baseline and for an additional 30 min. Cardiovascular, respiratory, metabolic, hemodynamic variables, and skeletal muscle tissue oxidative responses were assessed continuously. Venous blood samples were collected to assess blood gases, and hormones. Results Heart rate, stroke volume, and cardiac output all increased across time but were not different between conditions. V̇O 2 was greater in LCO when muscle temperature was restored until the end of exercise ( p  < 0.05). Cycling in the LCO condition induced lower oxygen availability, tissue oxygenation, blood pH, sO 2 %, and pO 2 ( p  < 0.05). Insulin concentrations were also higher in LCO vs. CON ( p  < 0.05). Importantly, stoichiometric equations from respiratory gases indicated no differences in fat and CHO oxidation between conditions. Conclusion The present study demonstrated that despite muscle cooling and the associated oxidative and biochemical changes, energy metabolism remained unaltered during cycling. Whether lower local and systemic oxygen availability is counteracted via a cold-induced activation of lipid metabolism pathways needs to be further investigated.