Organisms have evolved to survive rigorous environments and are not prepared to thrive in a world of caloric excess and sedentary behavior. A realization that physical exercise (or lack of it) plays a pivotal role in both the pathogenesis and therapy of type 2 diabetes mellitus (t2DM) has led to the provocative concept of therapeutic exercise mimetics. A decade ago, we attempted to simulate the beneficial effects of exercise by treating t2DM patients with 3 weeks of daily hyperthermia, induced by hot tub immersion. The short-term intervention had remarkable success, with a 1 % drop in HbA1, a trend toward weight loss, and improvement in diabetic neuropathic symptoms.

We tested the hypothesis that attention, memory, and executive function are impaired to a greater extent in passively heat-stressed older adults than in passively heatstressed younger adults. In a randomized, crossover design, 15 older (age: 69 Ϯ 5 yr) and 14 younger (age: 30 Ϯ 4 yr) healthy subjects underwent passive heat stress and time control trials. Cognitive tests (outcomes: accuracy and reaction time) from the CANTAB battery evaluated attention [rapid visual processing (RVP), choice reaction time (CRT)], memory [spatial span (SSP), pattern recognition memory (PRM)], and executive function [one touch stockings of Cambridge (OTS)]. Testing was undertaken on two occasions during each trial, at baseline and after internal temperature had increased by 1.0 Ϯ 0.2°C or after a time control period. For tests that measured attention, reaction time during RVP and CRT was slower (P Յ 0.01) in the older group. During heat stress, RVP reaction time improved (P Ͻ 0.01) in both groups. Heat stress had no effect (P Ն 0.09) on RVP or CRT accuracy in either group. For tests that measured memory, accuracy on SSP and PRM was lower (P Ͻ 0.01) in the older group, but there was no effect of heat stress (P Ն 0.14). For tests that measured executive function, overall, accuracy on OTS was lower, and reaction time was slower in the older group (P Յ 0.05). Reaction time generally improved during heat stress, but there was no effect of heat stress on accuracy in either group. These data indicate that moderate increases in body temperature during passive heat stress do not differentially compromise cognitive function in younger and older adults. cognitive function; aging; hyperthermia; thermal comfort ADULTS OVER THE AGE OF ϳ65 YR are at an increased risk of illness, injury, hospitalization, and death during heat waves (23, 29, 33-36, 63, 64). Age-related impairments in physiological responses to heat stress undoubtedly contribute to this increased risk (32). Heat-stressed older adults have attenuated increases in skin blood flow (30, 31) and sweating (26, 27), as well as impaired cardiovascular adjustments (42, 43). However, both physiological and psychological states influence health and safety (52, 53). Thus, a variety of factors may mediate the deleterious outcomes observed in the older population during heat waves.Healthy aging is associated with a general cognitive decline (49). Aspects of memory (4, 10, 12), attention (1, 12, 40), executive functioning (12,58,60), and processing speed (59) are typically [but not always (37, 48)] impaired with advancing age. This chronological cognitive decline may contribute to the risk of deleterious outcomes during heat waves in older adults by, for instance, leading to poor decision-making. Interestingly, perhaps because of the deleterious impact of heat stress on cerebral blood flow (46, 61) and/or disruptions in cerebral functional connectivity (66), many cognitive processes are impaired in heat-stressed younger adults [e.g., aspects of attention (19, 22, 65), memory (6, 19, 28, 41, 54), an...

Although the benefits of rehabilitative exercise training on strength and cardiorespiratory capacity are maintained at almost 4 years postburn, they are not restored fully to the levels of healthy children. Although the underlying mechanism of this phenomenon remains elusive, these findings suggest that future development of continuous exercise rehabilitation interventions after discharge may further narrow the gap in relation to healthy adolescents.

Objective Prolonged hospitalization due to burn injury results in physical inactivity and muscle weakness. However, how these changes are distributed among body parts is unknown. The aim of this study was to evaluate the degree of body composition changes in different anatomical regions during intensive care unit hospitalization (ICUh). Design Retrospective chart review. Setting Children’s burn hospital. Patients Twenty-four severely burned children admitted to our institution between 2000 and 2015. Interventions All patients underwent a dual-energy x-ray absorptiometry (DEXA) within 2 weeks after injury and 2 weeks before discharge to determine body composition changes. No subject underwent anabolic intervention. We analyzed changes of bone mineral content, bone mineral density, total fat mass, total mass, and total lean mass of the entire body and specifically analyzed the changes between the upper and lower limbs. Measurements and Main Results In the 24 patients, age was 10±5 years, total body surface area burned was 59±17%, time between DEXAs was 34±21 days, and length of stay was 39±24 days. We found a significant (p<0.001) average loss of 3% of lean mass in the whole body; this loss was significantly greater (p<0.001) in the upper extremities (17%) than in the lower extremities (7%). We also observed a remodeling of the fat compartments, with a significant whole-body increase in fat mass (p<0.001) that was greater in the truncal region (p<0.0001) and in the lower limbs (p<0.05). Conclusions ICUh is associated with greater lean mass loss in the upper limbs of burned children. Mobilization programs should include early mobilization of upper limbs to restore upper extremity function.

Objective A maximal aerobic capacity below the 20th percentile is associated with an increased risk of all-cause mortality.1 Adult burn survivors have a lower aerobic capacity compared to non-burned adults when evaluated 38±23 days post-injury.2 However, it is unknown if burn survivors with well-healed skin grafts (i.e., multiple years post injury), also have low aerobic capacity. This project tested the hypothesis that aerobic fitness, as measured by maximal aerobic capacity (VO2max), is reduced in well-healed adult burn survivors when compared to normative values from non-burned individuals. Methods Twenty-five burn survivors (36 ± 12 years old; 13 females) with well-healed split thickness grafts (median: 16 years post-injury, range: 1 to 51 years) covering at least 17% of their body surface area (mean: 40±16%; range: 17 to 75%) performed a graded cycle ergometry exercise test to volitional fatigue. Expired gases and minute ventilation were measured via a metabolic cart for the determination of VO2max. Each subject’s VO2max was compared with sex- and age-matched normative values from population data published by the American College of Sports Medicine (ACSM), the American Heart Association (AHA), and recent epidemiological data.3 Results Subjects had a VO2max of 29.4 ± 10.1 ml O2/kg body mass/min (median: 27.5; range: 15.9 to 53.3). Using ACSM normative values, mean VO2max of the subjects was in the lower 24th percentile (median: 10th percentile). 88% of the subjects had a VO2max below AHA age-adjusted normative values. Similarly 20 of the 25 subjects had a VO2max in the lower 25% percentile of recent epidemiological data. Conclusions Relative to non-grafted subjects, 80–88% of the evaluated skin graft subjects had a very low aerobic capacity. Based upon these findings, adult burn survivors are disproportionally unfit relative to the general U.S. population, and this puts them at an increased risk of all-cause mortality.1

Currently, there are no clear guidelines for the implementation of rehabilitative exercise training (RET) in burned individuals. Therefore, we quantified the training logs for exercise intensity, frequency, and duration of 6 weeks of this program to develop a basic framework for outpatient RET in patients recovering from severe burns. Thirty-three children (11 female, [mean ± SD] 12 ± 3 years, 145 ± 18 cm, 40 ± 11 kg, 49 ± 31 BMI percentile) with severe burns (49 ± 15% total body surface area burned, with 35 ± 22% third-degree burns) completed our 6-week resistance and aerobic exercise training program. Cardiorespiratory fitness (peak VO2), strength, power, and lean body mass (LBM) were measured before and after RET. Outcome measures were analyzed as a relative percentage of values in age- and sex-matched nonburned children (11 female, 12 ± 3 years, 154 ± 20 cm, 49 ± 22 kg, 56 ± 25 BMI percentile). At discharge, burned children had lower LBM (77% of age-sex-matched nonburn values), peak torque (53%), power (62%), and cardiorespiratory fitness (56%). After 6 weeks of training, LBM increased by 5% (82% of nonburn values), peak torque by 18% (71%), power by 20% (81%), and cardiorespiratory fitness by 18% (74%; P < .0001 for all). Quantification of data in exercise training logs suggested that physical capacity can be improved by aerobic exercise training performed at five metabolic equivalents (>70% of peak VO2) at least 3 days/week and 150 minutes/week and by resistance training performed at volume loads (reps × sets × weight) of 131 kg for the upper body and 275 kg for the lower body for 2 days/week. We present for the first time the quantification of our RET and provide clear exercise prescription guidelines specific to children with severe burn injury.

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Grafted skin impairs heat dissipation, but it is unknown to what extent this impacts body temperature during exercise in the heat. PURPOSE We examined core body temperature responses during exercise in the heat in a group of individuals with a large range of grafts covering their body surface area (BSA; 0-75%). METHODS Forty-three individuals (19 females) were stratified into groups based upon BSA grafted: Control (0% grafted, n=9), 17-40% (n=19), and >40% (n=15). Subjects exercised at a fixed rate of metabolic heat production (339 ± 70 W; 4.3 ± 0.8 W/kg) in an environmental chamber set at 40°C, 30% RH for 90 min or until exhaustion (n=8). Whole-body sweat rate and core temperatures were measured. RESULTS Whole body sweat rates were similar between groups (Control: 14.7±3.4 ml/min, 17-40%: 12.6±4.0 ml/min, and >40%: 11.7±4.4 ml/min, P>0.05), but the increase in core temperature at the end of exercise in the >40% BSA grafted group (1.6±0.5°C) was greater than the 17-40% (1.2±0.3°C) and Control (0.9±0.2°C) groups (P<0.05). Absolute BSA of non-grafted skin (expressed in m2) was the strongest independent predictor of the core temperature increase (r2=0.41). When re-grouping all subjects, individuals with the lowest BSA of non-grafted skin (<1.0 m2) had greater increases in core temperature (1.6±0.5°C) than those with >1.5 m2 non-grafted skin (1.0±0.3°C, P<0.05). CONCLUSIONS These data imply that individuals with grafted skin have greater increases in core temperature when exercising in the heat and that the magnitude of this increase is best explained by the amount of non-grafted skin available for heat dissipation.