Essentials: Increase Strength & Endurance with Cooling Protocols | Dr. Craig Heller

What happens when you get cold

Stepping into a cold shower or an ice bath produces an immediate sympathetic response: a strong sensory shock and a surge of adrenaline. That jolt can make you feel alert, but feeling better does not automatically mean your physiological state is improved for performance. Cold exposure triggers vasoconstriction in peripheral circulation, which can actually reduce your capacity to lose heat if applied to the wrong areas. In full immersion, however, the large surface area exposed to cold overwhelms local vasoconstriction and you still lose heat overall. A key distinction Dr. Heller emphasizes is between whole-body immersion and localized cooling: the physical dynamics and perceptual effects differ, and so do the outcomes for exercise and safety.

How heat limits performance: the role of local muscle temperature

Dr. Heller highlights that heat is a rapid and important limiter of muscular performance. During intense anaerobic work, metabolic heat production in active muscles can rise dramatically — far faster than blood flow can remove it. Because blood is the primary route for heat to leave a muscle, the muscle can overheat even though core temperature may not have risen equivalently. A temperature-sensitive enzyme that helps deliver fuel to mitochondria becomes impaired at roughly 39–39.5°C, quickly shutting down the muscle's ability to continue producing force. This enzymatic shutdown is a fast mechanism underlying failure during repeated sets, particularly in large compound movements where big muscles generate large amounts of heat. Surface cooling such as cold towels or fans is a poor way to cool internal muscle blood because skin and fascia are good insulators; the most effective route for cooling active muscle is by cooling the blood returning to the heart.

Heat-loss portals: palms, soles, and upper face

Mammals evolved specialized low-resistance vascular shunts beneath hairless skin areas to enable efficient heat transfer. In humans these include the palms, soles, and the upper face. These glabrous regions contain arterial-to-venous shunts that can move large volumes of blood with low resistance, making them powerful avenues for dumping heat into the environment or for delivering cooled blood centrally. Because these areas can rapidly exchange heat with the environment without the insulating effect of hair, targeted cooling here influences systemic temperature more effectively than cooling hairy skin or applying cold packs to the torso. Dr. Heller explains that gripping handlebars tightly or wearing gloves and thick socks impedes heat loss through these portals and can reduce performance; loosening the grip or exposing palms and soles allows better cooling during effort.

Thermostat and perception: warnings about misdirection

The brain's thermoregulatory center, the preoptic anterior hypothalamus, integrates skin and core temperature signals to govern responses like sweating and blood flow. Local cooling of the skin or neck can send deceptive input to this thermostat, making a person feel cooler even as core temperature continues to rise. Cooling the neck or head will feel refreshing and can protect the brain by cooling venous blood, but it can also mask dangerous systemic overheating and create a false sense of readiness to continue intense exertion. Dr. Heller warns that in progressing heat illness people may paradoxically vasoconstrict and stop sweating, and heart rate rises markedly; motivated athletes can override subjective discomfort and push into life-threatening heat stroke. Recognizing symptoms of severe heat stress — high heart rate, sudden exhaustion, and loss of sweating — is essential.

Practical cooling protocols for improved endurance and strength

Dr. Heller describes experimental and applied protocols that leverage glabrous-skin cooling to increase work capacity. In the lab and in applied settings, cooling the palms, soles, and upper face produces pronounced benefits for both aerobic endurance and repeated anaerobic output. One consistent laboratory protocol involves 3-minute cooling intervals between sets, which harnesses the fastest portion of the heat-loss curve and fits typical rest periods. Importantly, the stimulus should be cool rather than ice-cold; excessive cold triggers reflex vasoconstriction in the very portals you want open and reduces heat loss. Short, moderate cooling of the palms prevents vasoconstriction while extracting heat from core circulation via the venous return.

Demonstrations and results

Dr. Heller recounts powerful demonstrations of these principles. In one early example, NFL athlete Greg Clark performed a standard dip routine, then returned for sessions where his palms were cooled during three-minute rest intervals. The immediate outcome was markedly higher repetitions across sets and an ability to add sets well beyond prior limits. Over several weeks of twice-weekly sessions with palm cooling, the athlete's total dip volume rose dramatically, ultimately reaching 300 dips per session. In other experiments, walking uphill on a treadmill in extreme heat saw endurance roughly double with continuous targeted cooling. These performance gains translate into real training adaptations: increased work volume produces typical strength and endurance improvements that persist even when cooling is not used later.

Crude methods, technology, and field comparisons

For people experimenting outside a lab, cold packages such as frozen peas or berries passed between hands can be helpful if used carefully. The critical on-the-ground test is the feel of the palm to another person: a warm-feeling palm after cooling suggests vasoconstriction and an ineffective or counterproductive stimulus; a palm that still feels warm to the holder means blood flow remains and cooling is working. Boundary layers limit the effectiveness of simple contact with a frozen pack unless movement or convective flow is provided. Dr. Heller contrasts this with field rescue protocols that traditionally recommend putting cold packs in the armpits or groin; his team found that cooling palms, soles, and face can double the rate of core cooling versus those standard locations. To translate lab advances to practical tools, Dr. Heller helped develop a palm-cooling device marketed by Arteria; the product, Coolmitt (coolmitt.com), is being trialed by professional and military teams and designed to deliver moderate, controlled cooling to glabrous skin during rest intervals.

Safety and concluding notes

Targeted cooling offers a potent, evidence-based way to increase both endurance and repeated-strength performance by addressing heat accumulation, a primary limiter of work. The approach requires care: avoid ice-cold stimuli that induce vasoconstriction, be mindful that local cooling can alter perception of heat without reducing core temperature, and monitor for signs of heat illness. When applied properly, palm, sole, and face cooling extend time-to-exhaustion, increase repetition volume during strength training, and lead to durable training adaptations.