Here’s the key: the colder the stimulus (water immersion, shower, etc.), the shorter the time required for exposure to the cold. One study showed a significant and long-lasting increase in dopamine levels when people were in cold water (60°F) for about an hour up to their necks, with their heads above water.

Other studies confirm Stanford’s findings. For example, when researchers in Poland measured the skin temperature of 23 men immediately after intense exercise, they found that those who cooled down the fastest also showed the highest levels of cardiovascular fitness (Jastrzebska et al. 2022).

Dr. Thomas Seager began to understand metabolic health in 2001, when his 6-year-old son was diagnosed with diabetes. He spent more than twenty years meticulously recording diet, exercise and metabolism to monitor his son’s insulin levels.