Many runners notice the same pattern every year. Winter miles often feel different. You may take longer to warm up, sweat later, and hold a steady effort with less strain. That experience has fueled a familiar belief: cold weather somehow makes running easier, or even boosts performance.

But the explanation isn’t grit, motivation, or mental toughness.

A 2016 study published in Temperature shows that cold environments change how the body regulates heat during exercise, and that shift helps explain why running in the cold often feels different. 

Rather than improving muscles or endurance directly, colder conditions alter how quickly heat builds up once you start moving, and that difference matters for sustained effort.

Understanding what this study actually found helps separate winter running myths from the underlying biology. It also explains why cold-weather miles often feel different long before fatigue sets in. 

Why Endurance Has Limits

The study begins with a simple yet critical premise: overheating is one of the main factors limiting sustained physical activity. During running, muscles convert energy into movement very inefficiently. More than 80% of that energy is released as heat rather than mechanical work.

As exercise continues, this heat accumulates. If the body cannot manage it, core temperature rises toward thresholds that trigger protective responses—slowing pace, increasing discomfort, and eventually forcing fatigue.

Endurance, in this context, is largely a balancing act between heat produced and heat dissipated.

How Your Body Handles Heat During Exercise

At rest, the body maintains a stable core temperature through thermoregulatory metabolism. In cold conditions, the baseline heat production is higher to offset greater heat loss to the environment.

When exercise begins, things change. Muscle contractions sharply increase heat production. In when running on a hot summer day, your body relies heavily on increasing skin blood flow and sweating to remove excess heat. However, these strategies compete with blood flow to working muscles and are delayed until the core temperature rises significantly.

This delay is key. It means the body often tolerates rising temperature until it approaches a fatigue threshold.

What Changes When You Run in the Cold 

In the study, researchers examined how ambient temperature alters this process by measuring body temperature dynamics in rats running at multiple speeds under different environmental conditions.

The researchers found something counterintuitive. Cold environments do not reduce the heat generated by exercising muscles. Muscle heat production increased with running speed regardless of temperature.

What changed was heat production in the body’s core, unrelated to exercise, what the authors refer to as “thermoregulatory thermogenesis,” or the heat your body creates to maintain temperature.

As soon as exercise started, the body dialed back its normal background heat production, and this effect was even greater in colder environments, occurring before core temperature began to increase.

Here’s What the Study Found

In short, the study found that it’s easier for the body to balance heat produced and heat dissipated in cooler environments. 

The early suppression of thermoregulatory heat production produced a distinctive effect: a brief hypothermic phase at the start of exercise in cooler environments. Core temperature dropped slightly or rose more slowly before eventually increasing to typical exercise levels due to muscle-generated heat.

As the ambient temperature is decreased, this suppression becomes larger and lasts longer. In the coolest conditions tested, the reduction in core heat production nearly matched the heat coming from muscles, keeping core temperature below baseline for much of the run.

Importantly, this response happened before body temperature increased. That means it was not a reaction to overheating. It was a compensatory adjustment triggered by the onset of physical activity itself.

The authors conclude that exercising in cold environments suppresses thermoregulatory thermogenesis, partially offsetting exercise-generated heat and slowing the rise in core temperature. 

Why Cold Runs Feel Different & How to Use That to Your Advantage

Cold runs feel different because the body manages heat differently from the moment exercise begins. In cooler conditions, non-exercise heat production is suppressed early, slowing the rise in core temperature and delaying thermal strain.

For runners, the practical takeaway is simple: cool conditions often allow steady efforts to feel more sustainable. It’s an enhanced environment where holding pace, controlling effort, and building consistency becomes easier—not because you’re fitter, but because heat buildup within is working against you less. This makes cold weather an ideal time for steady aerobic runs rather than aggressive pace chasing. 

Using that to your advantage means treating cold runs as an opportunity for controlled, steady work. Settle into effort rather than forcing pace, avoid overdressing early, and recognize that discomfort at the start doesn’t mean the run will feel harder overall.

Cold weather doesn’t guarantee better performance. But understanding how it changes heat stress gives you a clearer signal for pacing, effort, and consistency—so winter training feels intentional instead of guesswork.