Comparison of metabolic substrates between exercise and cold exposure in skaters

To test the effect of a cold condition on metabolic substrate and possible development of muscle injuries, short track skaters (n=9) and inline skaters (n=10) took rest and submaximal cycled (65% V(.)O2max) in cold (ambient temperature: 5+/-1 degrees C, relative humidity: 41+/-8%) and warm conditions (ambient temperature: 21+/-1 degrees C, relative humidity: 35+/-5%), for 60 min, each. Blood glucose (BG), triglyceride (TG), free fatty acid (FFA), and total cholesterol (TC) were determined to investigate the effect on energy metabolism. To estimate possible muscle injury in the cold condition, creatine kinase (CK), lactate dehydrogenase (LDH), and myoglobin (Mb) were also measured. TG and FFA levels were increased during exercise in the cold condition, but were unaffected by the difference of skaters. Of the myocellular enzymes, CK was significantly higher during the transition from submaximal exercise to recovery phase in a short track skater compared with inline skater group, indicating a higher physical strain. Additionally, the level of Mb in the inline skater group significantly elevated during recovery phase in the cold compared with in the warm condition. It is concluded that exercise caused stress that was dependent on the ambient temperature. Therefore, exercise in the cold condition altered the circulating level of energy substrate and increased muscle injuries.