Foot Cooling Reduces Exercise-Induced Hyperthermia in Men with Spinal Cord Injury

Effects of two external cooling strategies on physiological and perceptual responses of athletes with tetraplegia during and after exercise in the heat

Athletes with tetraplegia may experience marked hyperthermia while exercising under environmental heat stress due to their limited ability to dissipate heat through evaporative means. This study investigated the effectiveness of two external cooling strategies (i.e., spraying water onto the body surface or using a cooling vest) on physiological and perceptual variables in tetraplegic athletes during and after an aerobic exercise session in a hot environment. Nine male wheelchair rugby players performed an incremental test to determine their maximum aerobic power output. After that, they were subjected to three experimental trials in a counter-balanced order: control (CON, no body cooling), cooling vest (CV), and water spraying (WS). During these trials, they performed 30 min of a submaximal exercise (at 65% of their maximum aerobic power) inside an environmental chamber set to maintain the dry-bulb temperature at 32 °C. The following variables were recorded at regular intervals during the exercise and for an additional 30 min following the exertion (i.e., post-exercise recovery) with the participants also exposed to 32 °C: body core temperature (TCORE), skin temperature (TSKIN), heart rate (HR), rating of perceived exertion (RPE), thermal comfort (TC), and thermal sensation (TS). While exercising in CON conditions, the tetraplegic athletes had the expected increases in TCORE, TSKIN, HR, RPE, and TC and TS scores. HR, TC, and TS decreased gradually toward pre-exercise values after the exercise, whereas TCORE and TSKIN remained stable at higher values. Using a cooling vest decreased the temperature measured only on the chest and reduced the scores of RPE, TC, and TS during and after exercise but did not influence the other physiological responses of the tetraplegic athletes. In contrast, spraying water onto the athletes' body surface attenuated the exercise-induced increase in TSKIN, led to lower HR values during recovery, and was also associated with better perception during and after exercise. We conclude that water spraying is more effective than the cooling vest in attenuating physiological strain induced by exercise-heat stress. However, although both external cooling strategies do not influence exercise hyperthermia, they improve the athletes' thermal perception and reduce perceived exertion.

Upper-Body versus Lower-Body Cooling in Individuals with Paraplegia during Arm-Crank Exercise in the Heat

PURPOSE

For wheelchair users with a spinal cord injury, the lower body may be a more convenient cooling site than the upper body. However, it remains unknown if leg cooling reduces thermal strain in these individuals. We compared the impact of upper-body versus lower-body cooling on physiological and perceptual outcomes during submaximal arm-crank exercise under heat stress in individuals with paraplegia.

METHODS

Twelve male participants with paraplegia (T4-L2, 50% complete lesion) performed a maximal exercise test in temperate conditions, and three heat stress tests (32°C, 40% relative humidity) in which they received upper-body cooling (COOL-UB), lower-body cooling (COOL-LB), or no cooling (CON) in a randomized counterbalanced order. Each heat stress test consisted of four exercise blocks of 15 min at 50% of peak power output, with 3 min of rest in between. Cooling was applied using water-perfused pads, with 14.8-m tubing in both COOL-UB and COOL-LB.

RESULTS

Gastrointestinal temperature was 0.2°C (95% confidence interval (CI), 0.1°C to 0.3°C) lower during exercise in COOL-UB versus CON (37.5°C ± 0.4°C vs 37.7°C ± 0.3°C, P = 0.009), with no difference between COOL-LB and CON ( P = 1.0). Heart rate was lower in both COOL-UB (-7 bpm; 95% CI, -11 to -3 bpm; P = 0.01) and COOL-LB (-5 bpm; 95% CI, -9 to -1 bpm; P = 0.049) compared with CON. The skin temperature reduction at the cooled skin sites was larger in COOL-LB (-10.8°C ± 1.1°C) than in COOL-UB (-6.7°C ± 1.4°C, P < 0.001), which limited the cooling capacity in COOL-LB. Thermal sensation of the cooled skin sites was improved and overall thermal discomfort was lower in COOL-UB ( P = 0.01 and P = 0.04) but not in COOL-LB ( P = 0.17 and P = 0.59) compared with CON.

CONCLUSIONS

Upper-body cooling more effectively reduced thermal strain than lower-body cooling in individuals with paraplegia, as it induced greater thermophysiological and perceptual benefits.

The Thermoregulatory and Thermal Responses of Individuals With a Spinal Cord Injury During Exercise, Acclimation and by Using Cooling Strategies-A Systematic Review

Background: In individuals with a spinal cord injury thermoregulatory mechanisms are fully or partially interrupted. This could lead to exercise-induced hyperthermia in temperate conditions which can be even more distinct in hot conditions. Hyperthermia has been suggested to impair physiological mechanisms in athletes, which could negatively influence physical performance and subjective well-being or cause mild to severe health issues.

Objective: The aim was to evaluate the literature on the thermoregulatory and thermal responses of individuals with a spinal cord injury during exercise in temperate and hot conditions taking the effects of cooling techniques and heat acclimation into account.

Data sources: Two electronic databases, PubMed and Web of Science were searched. Studies were eligible if they observed the influence of exercise on various thermoregulatory parameters (e.g., core and skin temperature, sweat rate, thermal sensation) in individuals with a spinal cord injury.

Results: In total 32 articles were included of which 26 were of strong, 3 of moderate and 3 of weak quality. Individuals with a high lesion level, especially those with a tetraplegia, reached a higher core and skin temperature with a lower sweat rate. The use of cooling techniques before and during exercise can positively affect the burden of the impaired thermoregulatory system in all individuals with a spinal cord injury.

Conclusion: Due to the absence of normal thermoregulatory abilities, individuals with a high-level spinal cord injury need special attention when they are exercising in temperate and hot conditions to prevent them from potential heat related issues. The use of cooling techniques can reduce this risk.

Heat-related issues and practical applications for Paralympic athletes at Tokyo 2020

International sporting competitions, including the Paralympic Games, are increasingly being held in hot and/or humid environmental conditions. Thus, a greater emphasis is being placed on preparing athletes for the potentially challenging environmental conditions of the host cities, such as the upcoming Games in Tokyo in 2020. However, evidence-based practices are limited for the impairment groups that are eligible to compete in Paralympic sport. This review aims to provide an overview of heat-related issues for Paralympic athletes alongside current recommendations to reduce thermal strain and technological advancements in the lead up to the Tokyo 2020 Paralympic Games. When competing in challenging environmental conditions, a number of factors may contribute to an athlete's predisposition to heightened thermal strain. These include the characteristics of the sport itself (type, intensity, duration, modality, and environmental conditions), the complexity and severity of the impairment and classification of the athlete. For heat vulnerable Paralympic athletes, strategies such as the implementation of cooling methods and heat acclimation can be used to combat the increase in heat strain. At an organizational level, regulations and specific heat policies should be considered for several Paralympic sports. Both the utilization of individual strategies and specific heat health policies should be employed to ensure that Paralympics athletes' health and sporting performance are not negatively affected during the competition in the heat at the Tokyo 2020 Paralympic Games.

Autonomic Nervous System in Paralympic Athletes with Spinal Cord Injury

Individuals sustaining a spinal cord injury (SCI) frequently suffer from sensorimotor and autonomic impairment. Damage to the autonomic nervous system results in cardiovascular, respiratory, bladder, bowel, and sexual dysfunctions, as well as temperature dysregulation. These complications not only impede quality of life, but also affect athletic performance of individuals with SCI. This article summarizes existing evidence on how damage to the spinal cord affects the autonomic nervous system and impacts the performance in athletes with SCI. Also discussed are frequently used performance-enhancing strategies, with a special focus on their legal aspect and implication on the athletes' health.

QUAD fever: beware of non-infectious fever in high spinal cord injuries

A case of cervical spinal cord injury and quadriparesis with prolonged fever is being described. Initially, the patient received treatment for well-documented catheter-related bloodstream infection. High spiking fever returned and persisted with no obvious evidence of infection. The usual non-infectious causes too were carefully excluded. QUAD fever or fever due to spinal cord injury itself was considered. The pathogenetic basis of QUAD fever is unclear but could be attributed to autonomic dysfunction and temperature dysregulation. Awareness of this little known condition could help in avoiding unnecessary antimicrobial therapy and in more accurate prognostication. Unlike several previous reported cases that ended fatally, the present case ran a relatively benign course. The spectrum of presentations may therefore be broader than hitherto appreciated.

Implications of altered autonomic control on sports performance in athletes with spinal cord injury

It is well known that athletes with spinal cord injury (SCI) may experience altered autonomic physiology that impacts their exercise capacity and sports performance. This is particularly relevant given the ever-increasing number of individuals with SCI who are actively engaged in sports at all levels, from community-based adaptive sports to elite Paralympic competitions. As such, the purpose of this article is to review the present literature regarding the implications of altered autonomic control on the safety and performance of athletes with SCI. A particular emphasis will be placed on the autonomic aspects of cardiovascular and thermoregulatory control in the athlete population, as well as the implications of autonomic dysreflexia in enhancing sports performance. Further research is needed to understand the autonomic factors that influence athletes with SCI in order to ensure optimal and safe sports competition. Additionally, this information is crucially relevant to the coaches, sports administrators, and team medical staff who work closely with athletes with SCI.

Effects of cooling before and during simulated match play on thermoregulatory responses of athletes with tetraplegia

OBJECTIVES

Athletes with high level spinal cord injuries (tetraplegia) are under greater thermal strain during exercise than the able-bodied. The purpose of this study was to investigate the effectiveness of pre-cooling using an ice vest and the combination of pre-cooling and cooling during play using water sprays in athletes with tetraplegia.

DESIGN

Counter-balanced, cross-over design.

METHODS

Eight wheelchair rugby players with tetraplegia completed a 60min intermittent sprint protocol (ISP) on a wheelchair ergometer in 20.2°C±0.2°C and 33.0%±3.1% relative humidity. The ISP was conducted on three occasions; no cooling (NC), pre-cooling with an ice vest (P) and pre-cooling with an ice vest and water sprays between quarters (PW). Gastrointestinal (T_gi) temperature, mean skin temperature (T_sk) and perceptual responses were measured throughout.

RESULTS

At the end of pre-cooling, the change in T_gi was not significantly different between conditions (P>0.05) but the change in T_sk was significantly greater in P and PW compared to NC (P<0.001). The change in T_gi over the ISP was significantly lower in PW and P compared to NC (P<0.05), whilst the change in T_sk was lower in PW compared to P and NC (P<0.05). Cooling had no effect on performance or perceptual responses (P>0.05).

CONCLUSIONS

Water spraying between quarters combined with pre-cooling using an ice vest lowers thermal strain to a greater degree than pre-cooling only in athletes with tetraplegia, but has no effect on simulated wheelchair rugby performance or perceptual responses.

Physiological and perceptual effects of precooling in wheelchair basketball athletes

OBJECTIVE

To investigate the physiological and perceptual effects of three precooling strategies during pre-exercise rest in athletes with a spinal cord injury (SCI).

DESIGN

Randomized, counterbalanced. Participants were precooled, then rested for 60 minutes (22.7 ± 0.2°C, 64.2 ± 2.6%RH).

SETTING

National Wheelchair Basketball Training Centre, Australia.

PARTICIPANTS

Sixteen wheelchair basketball athletes with a SCI.

INTERVENTIONS

Participants were precooled through; 1) 10 minutes of 15.8°C cold water immersion (CWI), 2) ingestion of 6.8 g/kg^-1 of slushie (S) from sports drink; 3) ingestion of 6.8 g/kg^-1 of slushie with application of iced towels to the legs, torso and back/arms (ST); or 4) ingestion of 6.8 g/kg^-1 of room temperature (22.3°C) sports drink (CON).

OUTCOME MEASURES

Core temperature (T_gi), skin temperature (T_sk), heart rate (HR), and thermal and gastrointestinal comfort.

RESULTS

Following CWI, a significant reduction in T_gi was observed compared to CON, with a greatest reduction of 1.58°C occurring 40 minutes post-cooling (95% CI [1.07, 2.10]). A significant reduction in T_gi following ST compared to CON was also observed at 20 minutes (0.56°C; [0.03, 1.09]) and 30 minutes (0.56°C; [0.04, 1.09]) post-cooling. Additionally, a significant interaction between impairment level and time was observed for T_gi and HR, demonstrating athletes with a higher level of impairment experienced a greater reduction in HR and significant decrease in rate of decline in T_gi, compared to lesser impaired athletes.

CONCLUSION

CWI and ST can effectively lower body temperature in athletes with a SCI, and may assist in tolerating warm conditions.

Effects of Cooling During Exercise on Thermoregulatory Responses of Men With Paraplegia

BACKGROUND

People with spinal cord injury (SCI) have an altered afferent input to the thermoregulatory center, resulting in a reduced efferent response (vasomotor control and sweating capacity) below the level of the lesion. Consequently, core body temperature rises more rapidly during exercise in individuals with SCI compared with people who are able-bodied. Cooling strategies may reduce the thermophysiological strain in SCI.

OBJECTIVE

The aim of this study was to examine the effects of a cooling vest on the core body temperature response of people with a thoracic SCI during submaximal exercise.

METHODS

Ten men (mean age=44 years, SD=11) with a thoracic lesion (T4-T5 or below) participated in this randomized crossover study. Participants performed two 45-minute exercise bouts at 50% maximal workload (ambient temperature 25°C), with participants randomized to a group wearing a cooling vest or a group wearing no vest (separate days). Core body temperature and skin temperature were continuously measured, and thermal sensation was assessed every 3 minutes.

RESULTS

Exercise resulted in an increased core body temperature, skin temperature, and thermal sensation, whereas cooling did not affect core body temperature. The cooling vest effectively decreased skin temperature, increased the core-to-trunk skin temperature gradient, and tended to lower thermal sensation compared with the control condition.

LIMITATIONS

The lack of differences in core body temperature among conditions may be a result of the relative moderate ambient temperature in which the exercise was performed.

CONCLUSIONS

Despite effectively lowering skin temperature and increasing the core-to-trunk skin temperature gradient, there was no impact of the cooling vest on the exercise-induced increase in core body temperature in men with low thoracic SCI.

Exercise and sports science Australia (ESSA) position statement on exercise and spinal cord injury

Traumatic spinal cord injury (SCI) may result in tetraplegia (motor and/or sensory nervous system impairment of the arms, trunk and legs) or paraplegia (motor and/or sensory impairment of the trunk and/or legs only). The adverse effects of SCI on health, fitness and functioning are frequently compounded by profoundly sedentary behaviour. People with paraplegia (PP) and tetraplegia (TP) have reduced exercise capacity due to paralysis/paresis and reduced exercising stroke volume. TP often further reduces exercise capacity due to lower maximum heart-rate and respiratory function. There is strong, consistent evidence that exercise can improve cardiorespiratory fitness and muscular strength in people with SCI. There is emerging evidence for a range of other exercise benefits, including reduced risk of cardio-metabolic disease, depression and shoulder pain, as well as improved respiratory function, quality-of-life and functional independence. Exercise recommendations for people with SCI are: ≥30min of moderate aerobic exercise on ≥5d/week or ≥20min of vigorous aerobic ≥3d/week; strength training on ≥2d/week, including scapula stabilisers and posterior shoulder girdle; and ≥2d/week flexibility training, including shoulder internal and external rotators. These recommendations may be aspirational for profoundly inactive clients and stratification into "beginning", "intermediate" and "advanced" will assist application of the recommendations in clinical practice. Flexibility exercise is recommended to preserve upper limb function but may not prevent contracture. For people with TP, Rating of Perceived Exertion may provide a more valid indication of exercise intensity than heart rate. The safety and effectiveness of exercise interventions can be enhanced by initial screening for autonomic dysreflexia, orthostatic hypotension, exercise-induced hypotension, thermoregulatory dysfunction, pressure sores, spasticity and pain.

Thermophysiological responses induced by a body heat removal system with Peltier devices in a hot environment

Individuals with spinal cord injuries often experience thermoregulation disorders as well as sensory and motor disabilities. In order to prevent such individuals from becoming hyperthermic, we developed a body heat removal system (BHRS) with thermoelectric devices. Our BHRS comprises four Peltier devices mounted on a wheelchair backrest and continuously transfers body heat through the contacting interface to the external environment. Here, we characterized thermophysiological responses induced by this novel contact-type cooling system. A cooling experiment in a hot environment with five able-bodied subjects demonstrated that sweating and systolic blood pressure in the back-cooling (BC) trial were significantly suppressed compared with those in no-cooling (NC) trial, while no difference was found in oral and skin temperatures. A correlation was observed between chest skin temperature and blood flow in the NC trial; this was not observed in the BC trial. These results suggest that BHRS modulates normal thermoregulatory responses, including sweating and vascular dilation and has the capability to partly replace these functions.

Cooling athletes with a spinal cord injury

Cooling strategies that help prevent a reduction in exercise capacity whilst exercising in the heat have received considerable research interest over the past 3 decades, especially in the lead up to a relatively hot Olympic and Paralympic Games. Progressing into the next Olympic/Paralympic cycle, the host, Rio de Janeiro, could again present an environmental challenge for competing athletes. Despite the interest and vast array of research into cooling strategies for the able-bodied athlete, less is known regarding the application of these cooling strategies in the thermoregulatory impaired spinal cord injured (SCI) athletic population. Individuals with a spinal cord injury (SCI) have a reduced afferent input to the thermoregulatory centre and a loss of both sweating capacity and vasomotor control below the level of the spinal cord lesion. The magnitude of this thermoregulatory impairment is proportional to the level of the lesion. For instance, individuals with high-level lesions (tetraplegia) are at a greater risk of heat illness than individuals with lower-level lesions (paraplegia) at a given exercise intensity. Therefore, cooling strategies may be highly beneficial in this population group, even in moderate ambient conditions (~21 °C). This review was undertaken to examine the scientific literature that addresses the application of cooling strategies in individuals with an SCI. Each method is discussed in regards to the practical issues associated with the method and the potential underlying mechanism. For instance, site-specific cooling would be more suitable for an athlete with an SCI than whole body water immersion, due to the practical difficulties of administering this method in this population group. From the studies reviewed, wearing an ice vest during intermittent sprint exercise has been shown to decrease thermal strain and improve performance. These garments have also been shown to be effective during exercise in the able-bodied. Drawing on additional findings from the able-bodied literature, the combination of methods used prior to and during exercise and/or during rest periods/half-time may increase the effectiveness of a strategy. However, due to the paucity of research involving athletes with an SCI, it is difficult to establish an optimal cooling strategy. Future studies are needed to ensure that research outcomes can be translated into meaningful performance enhancements by investigating cooling strategies under the constraints of actual competition. Cooling strategies that meet the demands of intermittent wheelchair sports need to be identified, with particular attention to the logistics of the sport.

The role of autonomic function on sport performance in athletes with spinal cord injury

Devastating paralysis, autonomic dysfunction, and abnormal cardiovascular control present significant hemodynamic challenges to individuals with spinal cord injury (SCI), especially during exercise. In general, resting arterial pressure after SCI is lower than with able-bodied individuals and is commonly associated with persistent orthostatic intolerance along with transient episodes of life-threatening hypertension, known as "autonomic dysreflexia." During exercise, the loss of central and reflexive cardiovascular control attenuates maximal heart rate and impairs blood pressure regulation and blood redistribution, which ultimately reduces venous return, stroke volume, and cardiac output. Thermoregulation also is severely compromised in high-lesion SCI, a problem that is compounded when competing in hot and humid conditions. There is some evidence that enhancing venous return via lower body positive pressure or abdominal binding improves exercise performance, as do cooling strategies. Athletes with SCI also have been documented to self-induce autonomic dysreflexia before competition with a view of increasing blood pressure and improving their performance, a technique known as "boosting." For health safety reasons, boosting is officially banned by the International Paralympics Committee. This article addresses the complex issue of how the autonomic nervous system affects sports performance in athletes with SCI, with a specific focus on the potential debilitating effects of deranged cardiovascular control.

Effect of a cooling vest on core temperature in athletes with and without spinal cord injury

BACKGROUND

It is well accepted that persons with spinal cord injury (SCI) have impaired ability to regulate core temperature due to impaired vasomotor and sudomotor activity below their level of injury. Impaired heat dissipation puts SCI athletes at great risk of exercise-induced hyperthermia (EIH) (>37.8°C). There is minimal evidence for efficacy of any specific cooling method in SCI athletes in a thermoneutral sport-specific setting.

OBJECTIVE

To evaluate the extent of EIH in persons with and without SCI and subsequently examine the effect of a cooling vest to attenuate rise in core body temperature (Tc).

METHODS

SCI (n = 17) and able-bodied (AB; n = 19) athletes participated in a 60-minute intermittent sprinting exercise in a thermoneutral (21.1°C-23.9°C) environment. Participants were separated according to their level of injury: tetraplegia defined as above T1 (TP; n = 6), high paraplegia defined as T5 through T1 (HP; n = 5), low paraplegia defined as T6 and below (LP; n = 6), and AB (n = 19). Tc was recorded at 15-minute intervals using an ingestible thermometer pill. This protocol was completed with a cooling vest (V) and without a cooling vest (NV).

RESULTS

All SCI and most AB athletes experienced EIH. After 60 minutes, Tc of TP athletes was significantly increased compared to HP (P = .03) and AB athletes (P = .007). There was no significant effect of the vest on Tc over time for any group.

CONCLUSIONS

TP athletes have the highest risk of exercise-induced hyperthermia. The cooling vest does not significantly attenuate rise in Tc in SCI or AB athletes.

Disordered cardiovascular control after spinal cord injury

Damage to the spinal cord disrupts autonomic pathways, perturbing cardiovascular homeostasis. Cardiovascular dysfunction increases with higher levels of injury and greater severity. Disordered blood pressure control after spinal cord injury (SCI) has significant ramifications as cord-injured people have an increased risk of developing heart disease and stroke; cardiovascular dysfunction is currently a leading cause of death among those with SCI. Despite the clinical significance of abnormal cardiovascular control following SCI, this problem has been generally neglected by both the clinical and research community. Both autonomic dysreflexia and orthostatic hypotension are known to prevent and delay rehabilitation, and significantly impair the overall quality of life after SCI. Starting with neurogenic shock immediately after a higher SCI, ensuing cardiovascular dysfunctions include orthostatic hypotension, autonomic dysreflexia and cardiac arrhythmias. Disordered temperature regulation accompanies these autonomic dysfunctions. This chapter reviews the human and animal studies that have furthered our understanding of the pathophysiology and mechanisms of orthostatic hypotension, autonomic dysreflexia and cardiac arrhythmias. The cardiovascular dysfunction that occurs during sexual function and exercise is elaborated. New awareness of cardiovascular dysfunction after SCI has led to progress toward inclusion of this important autonomic problem in the overall assessment of the neurological condition of cord-injured people.

Cardiovascular determinants of exercise capacity in the Paralympic athlete with spinal cord injury

This report briefly summarizes the cardiovascular factors that influence exercise physiology and, eventually, sports performance of athletes with a spinal cord injury (SCI). The consequences of an SCI are numerous and concern voluntary muscle function, deep and superficial sensitivity, and autonomic function to a degree determined by the level and completeness of the spinal lesion. Athletes with SCI perform with their upper body, which limits their maximal exercise capacity and puts them at a disadvantage compared with leg exercise in terms of mechanical efficiency and physiological adaptations to exercise. Studies generally find that maximal oxygen consumption and mechanical power output are inversely related to spinal lesion level. Athletes with cervical or dorsal lesions down to Th6 have limited maximal heart rates owing to a lack of sympathetic drive to the heart. Blood redistribution from body areas lacking autonomic control is impaired, thus reducing venous return and limiting cardiac stroke volume during exercise. Thermoregulatory function is affected through a lack of afferent neural feedback and limited efferent vasomotor and sudomotor control below the lesion. Strategies to support venous return and to promote body cooling potentially improve physiological responses and athletic performance, especially in individuals with high lesion levels. The latter are subject to autonomic dysreflexia, a generalized sympathetic vasoconstriction below the lesion resulting from nociceptive stimulations in insensate body regions. Acute episodes induce high blood pressure, may enhance exercise performance and must be treated as a clinical emergency. Deliberate triggering of this reflex is prohibited by the International Paralympic Committee.

Hemorrhagic shock and encephalopathy syndrome in a quadriplegic child: an argument for the triggering role of impaired thermoregulatory response

STUDY DESIGN

A case presentation of hemorrhagic shock and encephalopathy syndrome (HSES).

OBJECTIVE

To describe an unusual complication of uncontrolled fever in a tetraplegic child and to discuss possible pathophysiological mechanisms in these circumstances.

SUMMARY OF BACKGROUND DATA

HSES is a rare and dramatic disorder of unknown origin occurring mainly in infants and young children. Clinical features of HSES associate hyperpyrexia, acute diarrhea, circulatory collapse, coma, convulsions, and multiple organ failure (MOF). Altered physiologic thermoregulatory response in infants exposed to abruptly increased core temperature or altered thermal environment, and links with heat stroke, have been mentioned in previous publications.

METHODS

We report a case of HSES occurring in a 6-year-old girl with post-traumatic C4 quadriplegia. She eventually experienced hyperpyrexia, deep shock, watery diarrhea, and severe MOF developed rapidly. Despite rapidly resolving MOF, severe brain lesions consistent with HSES were observed and resulted in permanent neurologic impairment.

RESULTS

Negative bacterial and viral screening eliminated a septic origin. In this child, impaired thermoregulatory response to acute hyperpyrexia resulting from complete quadriplegia could be the necessary condition for the development of HSES in the presence of acute hyperpyrexia of unknown origin.

CONCLUSION

Quadriplegic patients, especially young children, could be considered at increased risk of developing severe MOF and acute central nervous system impairment consistent with HSES, when exposed to heat stress and should be treated promptly.

Heat loss through the glabrous skin surfaces of heavily insulated, heat-stressed individuals

Insulation reduces heat exchange between a body and the environment. Glabrous (nonhairy) skin surfaces (palms of the hands, soles of the feet, face, and ears) constitute a small percentage of total body surface area but contain specialized vascular structures that facilitate heat loss. We have previously reported that cooling the glabrous skin surfaces is effective in alleviating heat stress and that the application of local subatmospheric pressure enhances the effect. In this paper, we compare the effects of cooling multiple glabrous skin surfaces with and without vacuum on thermal recovery in heavily insulated heat-stressed individuals. Esophageal temperatures (T(es)) and heart rates were monitored throughout the trials. Water loss was determined from pre- and post-trial nude weights. Treadmill exercise (5.6 km/h, 9-16% slope, and 25-45 min duration) in a hot environment (41.5 degrees C, 20-30% relative humidity) while wearing insulating pants and jackets was used to induce heat stress (T(es)>or=39 degrees C). For postexercise recovery, the subjects donned additional insulation (a balaclava, winter gloves, and impermeable boot covers) and rested in the hot environment for 60 min. Postexercise cooling treatments included control (no cooling) or the application of a 10 degrees C closed water circulating system to (a) the hand(s) with or without application of a local subatmospheric pressure, (b) the face, (c) the feet, or (d) multiple glabrous skin regions. Following exercise induction of heat stress in heavily insulated subjects, the rate of recovery of T(es) was 0.4+/-0.2 degrees C/h(n=12), but with application of cooling to one hand, the rate was 0.8+/-0.3 degrees C/h(n=12), and with one hand cooling with subatmospheric pressure, the rate was 1.0+/-0.2 degrees C/h(n=12). Cooling alone yielded two responses, one resembling that of cooling with subatmospheric pressure (n=8) and one resembling that of no cooling (n=4). The effect of treating multiple surfaces was additive (no cooling, DeltaT(es)=-0.4+/-0.2 degrees C; one hand, -0.9+/-0.3 degrees C; face, -1.0+/-0.3 degrees C; two hands, -1.3+/-0.1 degrees C; two feet, -1.3+/-0.3 degrees C; and face, feet, and hands, -1.6+/-0.2 degrees C). Cooling treatments had a similar effect on water loss and final resting heart rate. In heat-stressed resting subjects, cooling the glabrous skin regions was effective in lowering T(es). Under this protocol, the application of local subatmospheric pressure did not significantly increase heat transfer per se but, presumably, increased the likelihood of an effect.

A new hand-cooling device to enhance firefighter heat strain recovery

This study tested a new portable cooling device for fire fighting recovery. Participants (N = 8) walked and did arm curls (time-weighted VO(2): 1.6 L x min(-1) on a treadmill for 40 min in a heated chamber (wet bulb globe temperature: 33.7 degrees C; relative humidity: 40-45%) while wearing firefighter turn-out gear and self-contained breathing apparatus (SCBA). Immediately on finishing exercise, participants recovered for 40 min with either a hand-cooling device or seated passive recovery at an ambient temperature of 22 degrees C, 35% RH in a repeated-measures counterbalanced design. The cooling device had little impact on recovery during the first 30 min; however, compared with passive cooling, the cooling device resulted in significantly lower rectal temperature (T(re)) during the last 10 min. Relative to starting T(re) of the recovery period, Delta T(re) at 35 min had fallen 0.51 +/- 0.19 degrees C (passive) and 0.76 +/- 0.30 degrees C (active) (p = 0.03); and at 40 min Delta T(re) had fallen 0.63 +/- 0.17 degrees C (passive) and 0.88 +/- 0.31 degrees C (active) (p = 0.03). Cooling capacity of the device calculated from Delta T(re) over the whole recovery period averaged about 144% of passive. Reductions in heat storage enhance worker safety and performance in hot environments.

The effectiveness of hand cooling at reducing exercise-induced hyperthermia and improving distance-race performance in wheelchair and able-bodied athletes

The purpose of this study was to examine the effectiveness of reducing core temperature in postexercise hyperthermic subjects and to assess if hand cooling (HC) improves subsequent timed distance performance. Following a detailed measurement check on the use of insulated auditory canal temperature (Tac), eight wheelchair (WA) athletes and seven male able-bodied (AB) athletes performed two testing sessions, comprising a 60-min exercise protocol and 10-min recovery period, followed by a performance trial (1 km and 3 km for WA and AB, respectively) at 30.8°C (SD 0.2) and 60.6% (SD 0.2) relative humidity. In a counterbalanced order, HC and a no-cooling condition was administered during the 10-min recovery period before the performance trial. Nonsignificant condition × time interactions for both WA ( F15,75 = 1.5, P = 0.14) and AB ( F15,90 = 1.2, P = 0.32) confirmed that the exercise-induced changes (Δ) in Tac were similar before each intervention. However, the exercise-induced increase was evidently greater in AB compared with WA (2.0 vs. 1.3°C change, respectively). HC produced ΔTac of −0.4°C (SD 0.4) and −1.2°C (SD 0.2) in comparison (WA and AB, respectively), and simple-effects analyses suggested that the reductions in Tac were noteworthy after 4 min of HC. HC had an impact on improving AB performances by −4.0 s (SD 11.5) ( P < 0.05) and WA by −20.5 s (SD 24.2) ( P > 0.05). In conclusion, extraction of heat through the hands was effective in lowering Tac in both groups and improving 3-km performance in the AB athletes and trends toward positive gains for the 1-km performance times of the WA group.

Cooling via one hand improves physical performance in heat-sensitive individuals with multiple sclerosis: a preliminary study

Background

Many individuals afflicted with multiple sclerosis (MS) experience a transient worsening of symptoms when body temperature increases due to ambient conditions or physical activity. Resulting symptom exacerbations can limit performance. We hypothesized that extraction of heat from the body through the subcutaneous retia venosa that underlie the palmar surfaces of the hands would reduce exercise-related heat stress and thereby increase the physical performance capacity of heat-sensitive individuals with MS.

Methods

Ten ambulatory MS patients completed one or more randomized paired trials of walking on a treadmill in a temperate environment with and without cooling. Stop criteria were symptom exacerbation and subjective fatigue. The cooling treatment entailed inserting one hand into a rigid chamber through an elastic sleeve that formed an airtight seal around the wrist. A small vacuum pump created a -40 mm Hg subatmospheric pressure enviinside the chamber where the palmar surface of the hand rested on a metal surface maintained at 18–22°C. During the treatment trials, the device was suspended from above the treadmill on a bungee cord so the subjects could comfortably keep a hand in the device without having to bear its weight while walking on the treadmill.

Results

When the trials were grouped by treatment only, cooling treatment increased exercise durations by 33% (43.6 ± 17.1 min with treatment vs. 32.8 ± 10.9 min. without treatment, mean ± SD, p < 5.0·10^-6, paired t-test, n = 26). When the average values were calculated for the subjects who performed multiple trials before the treatment group results were compared, cooling treatment increased exercise duration by 35% (42.8 ± 16.4 min with treatment vs. 31.7 ± 9.8 min. without treatment, mean ± SD, p < 0.003, paired t-test, n = 10).

Conclusion

These preliminary results suggest that utilization of the heat transfer capacity of the non-hairy skin surfaces can enable temperature-sensitive individuals with MS to extend participation in day-to-day physical activities despite thermally stressful conditions. However, systematic longitudinal studies in larger cohorts of MS patients with specific deficits and levels of disability conducted under a variety of test conditions are needed to confirm these preliminary findings.

Practical management: common medical problems in disabled athletes

Disabled athletes face many challenges during training and competition. As the number of disabled athletes grows, sports medicine professionals must become proficient in dealing with this population. A functional classification system is used to classify disabled athletes into 1 of 6 categories: wheelchair athletes, amputees, athletes with cerebral palsy, visual impairment, intellectual impairment, and les autres. Injury patterns have been identified for certain groups, with wheelchair athletes typically sustaining upper extremity injuries, blind athletes sustaining lower extremity injuries, and cerebral palsy athletes sustaining both. Common problems affecting wheelchair athletes include autonomic dysreflexia, difficulty with thermoregulation, pressure sores, neurogenic bladder, premature osteoporosis, peripheral nerve entrapment syndromes, and upper extremity injuries. Cerebral palsy athletes often have injuries involving the knee and foot due to problems with spasticity and foot deformities. Amputee athletes sustain injuries to the stump, spine, and intact limbs, while blind athletes suffer lower extremity injuries. Intellectually disabled athletes frequently have underlying ocular and visual defects, congenital cardiac anomalies, and atlantoaxial instability that predispose them to injuries. This article reviews key information pertinent to the care of these athletes.

Thermoregulation during Exercise in Individuals with Spinal Cord Injuries

The increased participation in wheelchair sports in conjunction with environmental challenges posed by the most recent Paralympic venues has stimulated interest into the study of thermoregulation of wheelchair users. This area is particularly pertinent for the spinal cord injured as there is a loss of vasomotor and sudomotor effectors below the level of spinal lesion. Studies within this area have examined a range of environmental conditions, exercise modes and subject populations. During exercise in cool conditions (15-25 degrees C), trained paraplegic individuals (thoracic or lumbar spinal lesions) appear to be at no greater risk of thermal injury than trained able-bodied individuals, although greater heat storage for a given metabolic rate is evident. In warm conditions (25-40 degrees C), trained subjects again demonstrate similar core temperature responses to the able-bodied for a given relative exercise load but elicit increased heat storage within the lower body and reduced whole-body sweat rates, increasing the risk of heat injury. The few studies examining a wide range of lesion levels have noted that, for paraplegic individuals where heat production is matched by available sweating capacity, excessive heat strain may be offset. Studies relating to tetraplegic subjects (cervical spinal lesions) are fewer in number but have consistently shown this population to elicit much faster rates of core and skin temperature increase and thermal imbalance in both cool and warm conditions than paraplegic individuals. These responses are due to the complete absence or severely reduced sweating capacity in tetraplegic subjects. During continuous exercise protocols, the main thermal stressor for tetraplegic subjects appears to be environmental heat gain, whereas during an intermittent-type exercise protocol it appears to be metabolic heat production. Fluid losses during exercise and heat retention during passive recovery from exercise are related to lesion level. Future research is recommended to focus on the specific role of absolute and relative metabolic rates, sweating responses, training status and more sport- and vocation-specific exercise protocols.

Effects of Heat Removal Through the Hand on Metabolism and Performance During Cycling Exercise in the Heat

Objective: This two-part study tested the hypotheses that the use of a new cooling device, purported to extract heat from the body core through the palm of the hand, would (a) attenuate core temperature rise during submaximal exercise in the heat, thereby suppressing exercise-associated metabolic changes, and (b) facilitate a higher sustained workload, thus shortening the completion time of a time-trial performance test. Methods: In Study 1, 8 male triathletes (age 27.9 ± 2.0 yrs, mass 77.2 ± 3.1 kg, [Formula: see text]Peak 59.0 ± 4.1 ml•min−1•kg−1) cycled for 1 hr at the same absolute workload (∼60% [Formula: see text]peak) in a heated room (31.9 ± 0.1 °C, 24 ±1% humidity) on two occasions counterbalanced for cooling (C) or noncooling (NC). In Study 2, 8 similar subjects (age 26.9 ± 2.0 yrs, mass 75.2 ± 3.7 kg, [Formula: see text]peak 54.1 ± 3.1 ml•min−1•kg−1) performed two 30-km cycling time-trial performance tests under the same conditions (CT NCT). Results: In Study 1, cooling attenuated the rise in tympanic temperature (TTY) (1.2 ± 0.2 vs. 1.8 ± 0.2 °C; p <  0.01) and lowered mean oxygen consumption ([Formula: see text] 2.4 ± 0.1 vs. 2.7 ± 0.1 L•min−1; p <  0.05) and blood lactate (1.7 ± 0.2 vs. 2.2 ± 0.2 mmol. L−1; p <  0.01) during exercise. There were no significant differences in respiratory exchange ratio (RER), blood glucose, heart rate (HR), face temperature (TF), or back temperature (TB) between NC and C. In Study 2, time to complete 30 km was 6 ± 1% less with cooling than without cooling (60.9 ± 2.0 vs. 64.9 ± 2.6 min; p <  0.01). During the last 20% of CT, subjects sustained a workload that was 14 ± 5% (p = 0.06) higher than NCT at the same TTY and HR. Conclusions: Heat extraction through the hand during cycle ergometer exercise in the heat can (a) lower TTY, lactate concentration, and [Formula: see text] during a submaximal set-workload test and (b) reduce the time it takes to complete a 30-km time-trial test. Key words: core temperature, hyperthermia, thermoregulation, hand-cooling

Effects of two cooling strategies on thermoregulatory responses of tetraplegic athletes during repeated intermittent exercise in the heat

Athletes with spinal cord injury (SCI), and in particular tetraplegia, have an increased risk of heat strain and consequently heat illness relative to able-bodied individuals. Strategies that reduce the heat strain during exercise in a hot environment may reduce the risk of heat illness. To test the hypotheses that precooling or cooling during intermittent sprint exercise in a heated environment would attenuate the rise in core temperature in tetraplegic athletes, eight male subjects with SCI (lesions C(5)-C(7); 2 incomplete lesions) undertook four heat stress trials (32.0 +/- 0.1 degrees C, 50 +/- 0.1% relative humidity). After assessment of baseline thermoregulatory responses at rest for 80 min, subjects performed three intermittent sprint protocols for 28 min. All trials were undertaken on an arm crank ergometer and involved a no-cooling control (Con), 20 min of precooling (Pre), or cooling during exercise (Dur). Trials were administered in a randomized order. After the intermittent sprint protocols, mean core temperature was higher during Con (37.3 +/- 0.3 degrees C) compared with Pre and Dur (36.5 +/- 0.6 degrees C and 37.0 +/- 0.5 degrees C, respectively; P < 0.01). Moreover, perceived exertion was lower during Pre (13 +/- 2; P < 0.01) and Dur (12 +/- 1; P < 0.01) compared with Con (14 +/- 2). These results suggest that both precooling and cooling during intermittent sprint exercise in the heat reduces thermal strain in tetraplegic athletes. The cooling strategies also appear to show reduced perceived exertion at equivalent time points, which may translate into improved functional capacity.