Current Research

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Summary: Participants completed biweekly bench press or pull-up exercises for multiple successive weeks. Palm cooling was applied for 3 minutes between sets. Over 3 weeks of bench press training, palm cooling increased work volume by 40% vs. 13% without cooling. Over 6 weeks of pull-up training, palm cooling increased work volume by 144% in pull-up experienced subjects vs. 5% without cooling and by 80% in pull-up naïve subjects vs. 20% without cooling.

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Summary: This study was designed to determine if cooling of the palm under slight negative pressure increased the duration of activity under a constant workload.  8 subjects were asked to walk on a treadmill moving at 5.46 km/h, at a 9% incline, at an ambient temperature of 40°C.  Each subject was tested with and without cooling with slight negative pressure.  Body temperature was measured using an esophageal probe. The test was terminated when subjects achieved 90% of predicted maximum output.  Body temperature rise was slowed in individuals with both palm cooling and negative pressure.  Heart rate rose in direct correlation to body temperature.  Individuals with both cooling and negative pressure extended their period of activity by remaining on the treadmill 25% longer.  An indication that endurance can be enhanced through cooling during exercise.

Unpublished
Summary: An initial experiment had a subject doing 10 sets of pull ups to muscle failure with 3 min rests. The purpose was to raise body temperature to test the parameters for extracting heat from the hand. One day, after completing 10 sets and cooling at the conclusion of the workout, the subject went back to the bar and did the same number of pull-ups as in the first set --- the muscle fatigue was gone. Upon discovering this, over the next 6 weeks (with 2 sessions/week) the subject cooled after the 10th set. Over that 6-week study the subject went from a total of 100 pull ups to 180 pull ups. For the next 6 weeks the subject cooled after every other set during the 3 min rest (except for control days). The subject improved from 180 pull ups to 616 pull ups. The most significant gains were seen on cooling days, not control days. Gains were maintained throughout the study period, providing lasting performance benefits.

Unpublished
Summary: A tight end for the San Francisco 49ers performed triceps dips in his regular exercise routine. He was able to do 40 in his first set with decreasing numbers in 4 subsequent sets ending in muscle fatigue (103 total dips). On a subsequent trial day, he was cooled between sets and his numbers for 5 sets were considerably higher (135 total dips) and he was able to do 4 additional sets (63 additional dips). He continued to use cooling during his 2x/week workouts and in 4 weeks he was doing 310 dips in a session.

Unpublished
Summary: A tight end for the Oakland Raiders chose to do workouts that were 6 sets of 225 lb bench presses. He started at a baseline of 51 reps. After 3 weeks with cooling between sets, his reps increased to 60 (improvement of 17.6%). During a 4-week control period with no cooling, he maintained his gains but did not improve further. Then during another 2-week period using cooling between set, his reps increased to 67 per session (a total improvement of 31.4%).

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Summary: Test individuals were subjected to treadmill exercises (5.6 km/h, 9–16% slope, and 25–45 min duration) in a 106.7°F room while wearing insulating pants and jackets to induce heat stress. Post exercise, the individuals put on additional insulating gear and rested in the hot environment for 60 additional minutes. The core temperatures of the group that used palm cooling recovered body temperature at a rate that was double those with no cooling. In addition, using multiple devices to cool feet, palms and face recovered body temperature at a rate that was four times those with no cooling.

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Summary: The effects of PPE outerwear and palm cooling on heat storage were assessed.  Subjects wore an outer-layer PPE ensemble that simulated the outerwear worn by healthcare professionals in infectious disease settings (impermeable protective coveralls with hood and foot coverings, a polypropylene balaclava worn under the PPE hood, and plastic bags secured with surgical tape).  Subjects engaged in fixed load treadmill exercise in room temperature or rested in a 113°F room. The use of PPE outerwear increased the rate of core temperature rise by five-fold during vigorous exercise. Palm cooling attenuated the rate of core temperature rise by 30–60% during rest and light, moderate, and vigorous exercise while wearing PPE outerwear.‍

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Summary: The effects of cooling different body areas after heat stress while wearing MOPP (Mission Oriented Protective Posture) military garments was studied. Subjects wore workout gear under MOPP to perform strenuous walking on a treadmill that raised their body temperature to 39.2°C. Subjects then applied additional insulation and rested in the hot room for 30 additional minutes. During this time subjects either: 1. Rested, 2. Applied cold packs to traditional cooling areas: bilateral neck, armpit, and groin, or 3. Applied cold packs to glabrous skin: bilateral cheeks, palms and foot soles. Cold packs were replaced as needed. Glabrous skin cooling rates were nearly double that of traditional area cooling rates.

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Summary: 16 subjects were studied as they recovered from general anesthesia. Each subject was mildly hypothermic as a result of the anesthetic procedure, with their average body temperature at 34.6°C. 10 subjects were rewarmed using a thermal pad with the application of sub atmospheric pressure to the limb; 6 subjects were treated only using a thermal pad. Body temperature was monitored until the subjects had returned to a temperature of 36°C. For
subjects receiving both heat and sub atmospheric pressure recovery occurred in 8 minutes while the heat only group took 59 minutes.

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Summary: This study shows that when mammals emerge from anesthesia at a normal body temperature, they wake up more quickly and do not tremor. Twelve rats were studied. Each subject was anesthetized three separate times on different days with differing thermal treatments. The rats were either: 1. Allowed to become hypothermic during anesthesia (32–34°C), 2. Kept warm (37–39°C) throughout anesthesia, or 3. Allowed to become hypothermic during anesthesia (32–34°C) but then rewarmed (37–39°C) prior to ending anesthesia. When the rats emerged from anesthesia hypothermic, they had tremors until they reached normal body temperature. All rats who emerged from anesthesia at 37–39°C had no tremors and also regained their motor function more quickly. ‍

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Summary: Ten ambulatory Multiple Sclerosis patients completed one or more randomized paired trials of walking on a treadmill at a variety of inclines, some with palm cooling during their walk and some without. Those participants with palm cooling during exercise were able to exercise for 35% longer than those without cooling.

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Summary: A review of previous studies showing that vacuum-enhanced heat exchange via the glabrous skin is a disruptive technology for several reasons. It forces re-formulation of the models of human thermoregulation that are used to design thermal protective gear. It offers an effective means of treating heat and cold stress. It provides an insight into controversies about the effects of temperature on human athletic performance.  It offers a means of enhancing strength and work volume training responses that are more effective than performance-enhancing supplements such as anabolic steroids. Authors conclude that there are many potential applications of vacuum-enhanced cooling of the glabrous skin in medicine, occupational health and safety, and sport.

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Summary: This is a review article that discusses much of the early information on thermoregulation in mammals.  It provides experimental evidence that the palms can be reliably used as a countercurrent heat exchange site for both controlled warming and cooling of the body during exercise or under extreme environmental conditions.  It includes thermal images of black bear showing temperature gradients with the highest temperatures seen in the soles of the feet and the muzzle and snout.  A comparison shows similar heat distribution in a person during a run, with the hottest areas being the face and hands.  It shows the results of an exercise period in a warm room that demonstrates that cooling one palm delays the onset of exhaustion during the exercise period and increases the rate of recovery after exercise. ‍