As we enter the New Year, many of us decide to set new targets in the form of resolutions. Following the festive period, diet culture puts a lot of pressure on us to “shed the holiday weight,” but this is unfair. You still deserve to eat well and fuel your body even if you went hard on the mince pies last month. If, however, you’re keen to move your body more in 2021, a new study published in the Journal of Applied Physiology has discovered an interesting link between exercise and temperature. The research, which looked at High-Intensity Interval Exercise (HIIE) in the cold, marks the first time the immediate and long-term effects of this type of exercise have been scientifically investigated.
Previous research has shown that HIIE (such as sprints) increases the rate of acute lipid oxidation both before and after exercise, meaning it uses up more fuel and continues to “burn fat” after we’ve stopped moving. Lipid oxidation rate is also increased when exercising in cold temperatures. The team on the research wanted to examine the effects of cold stress during HIIE on the metabolism of lipids, both during exercise and after. They asked 11 moderately fit overweight adults between 18 and 30 years of age to practice evening HIIE sessions in average (21°C/ 70°F) and cold (0°C/32°F) environments. The HIIE session involved 10 sets of 60-second frantic cycling (the kind you might do in this scenario) interspersed with 90-seconds of cycling at a leisurely pace, taking samples to assess lipid oxidation both before and immediately after the exercise. The following morning, they were treated to a high-fat breakfast after which indirect calorimetry was used to measure the participant’s metabolism. Blood samples were also collected to look at changes in the metabolites found in our blood.
The analyses revealed that during acute exercise (mad cycling) lipid oxidation increased by 113 percent in cold environments compared to warmer cycling arenas. While it might seem that a bleep test on an ice rink could be the way forward for maximum burning potential, lipid density, plasma insulin and triglyceride concentrations didn’t vary much between the warm and cold conditions. In fact, the researchers actually concluded that HIIE in the cold had less favorable outcomes for after-breakfast lipid and glycemic responses compared to those who had worked out in the warmer control.
“We observed that high-intensity interval exercise in a cold environment does change acute metabolism compared to a thermoneutral environment,” wrote the researchers in the study. “However, the addition of a cold stimulus was less favorable for postprandial metabolic responses the following day."
It's important to note this was a small study with just 11 participants, so it's hard to draw strong conclusions without further study into how temperature affects metabolism during exercise. It’s also important to remember, however, that exercising in the cold can only glean benefits if you don’t die of hypothermia. Something to stew on before you go running laps of a near-frozen lake.