Burn Injury Does Not Exacerbate Heat Strain during Exercise while Wearing Body Armor

Comparative analysis of high-intensity interval training and traditional rehabilitation programs for accelerated recovery from musculoskeletal injuries

BACKGROUND

Musculoskeletal injuries, such as strains, are prevalent across all age groups and have a substantial impact on daily functioning and quality of life.

OBJECTIVE

To examine the effectiveness of high-intensity interval training (HIIT) with traditional rehabilitation programs on pain, range of motion (ROM), muscular strength, and functional changes in promoting accelerated recovery from musculoskeletal injuries.

METHODS

A total of 80 participants (54 males, 26 females; mean age 35.6 years) with various musculoskeletal injuries were randomly assigned to either the HIIT group (n= 40) or the traditional rehabilitation group (n= 40). The HIIT group underwent a six-week supervised program, with three sessions per week. The traditional rehabilitation group followed a similar six-week program emphasizing low to moderate intensity exercises and traditional rehabilitation techniques. Outcome measures, including pain levels, ROM, muscular strength, and functional outcomes, were assessed pre- and post-intervention.

RESULTS

Significant improvements were observed in both the HIIT and traditional rehabilitation groups. However, the HIIT group demonstrated superior outcomes. Participants in the HIIT group experienced a greater reduction in pain levels compared to the traditional rehabilitation group (mean visual analog scale (VAS) score decrease of 5.2 vs. 3.8, respectively, p< 0.05). Functional outcomes significantly favored the HIIT group, with participants achieving faster completion times in the Timed Up and Go test (mean reduction of 2.1 seconds vs. 1.5 seconds, respectively, p< 0.01) and longer distances in the Single Leg Hop test (mean increase of 32 cm vs. 25 cm, respectively, p< 0.05).

CONCLUSION

HIIT showed superior effectiveness over traditional rehabilitation in accelerating recovery from musculoskeletal injuries, with greater pain reduction and improved functional outcomes. Incorporating HIIT into rehabilitation protocols may offer an efficient approach for expedited recovery and enhanced functional capacity.

Edward F. Adolph Distinguished Lecture. It's more than skin deep: thermoregulatory and cardiovascular consequences of severe burn injuries in humans

Each year, within the United States, tens of thousands of individuals are hospitalized for burn-related injuries. The treatment of deep burns often involves skin grafts to accelerate healing and reduce the risk of infection. The grafting procedure results in a physical disruption between the injured and subsequently debrided host site and the skin graft placed on top of that site. Both neural and vascular connections must occur between the host site and the graft for neural modulation of skin blood flow to take place. Furthermore, evaporative cooling from such burn injured areas is effectively absent, leading to greatly impaired thermoregulatory responses in individuals with large portions of their body surface area burned. Hospitalization following a burn injury can last weeks to months, with cardiovascular and metabolic consequences of such injuries having the potential to adversely affect the burn survivor for years postdischarge. With that background, the objectives of this article are to discuss 1) our current understanding of the physiology and associated consequences of skin grafting, 2) the effects of skin grafts on efferent thermoregulatory responses and the associated consequences pertaining to whole body thermoregulation, 3) approaches that may reduce the risk of excessive hyperthermia in burn survivors, 4) the long-term cardiovascular consequences of burn injuries, and 5) the extent to which burn survivors can "normalize" otherwise compromised cardiovascular responses. Our primary objective is to guide the reader toward an understanding that severe burn injuries result in significant physiological consequences that can persist for years after the injury.

Thermoregulatory Responses with Size-matched Simulated Torso or Limb Skin Grafts

Skin grafting following a burn injury attenuates/abolishes sweat production within grafted areas. It is presently unknown whether the thermoregulatory consequences of skin grafting depend on anatomical location.

PURPOSE

To test the hypothesis that a simulated burn injury on the torso will be no more or less detrimental to core temperature control than on the limbs during uncompensable exercise-heat stress.

METHODS

Nine non-burned individuals (7 males, 2 females) completed the protocol. On separate occasions, burn injuries of identical surface area (0.45 ± 0.08 m2 or 24.4% ± 4.4% of total body surface area) were simulated on the torso or the arms/legs using an absorbent, vapor-impermeable material that impedes sweat evaporation in those regions. Participants performed 60 min of treadmill walking at 5.3 km·h-1 and a 4.1% ± 0.8% grade, targeting 6 W·kg-1 of metabolic heat production in 40.1°C ± 0.2°C and 19.6% ± 0.6% relative humidity conditions. Rectal temperature, heart rate, and perceptual responses were measured.

RESULTS

Rectal temperature increased to a similar extent with simulated injuries on the torso and limbs (condition-by-time interaction: P = 0.86), with a final rectal temperature 0.9 ± 0.3°C above baseline in both conditions. No differences in heart rate, perceived exertion, or thermal sensation were observed between conditions (condition-by-time interactions: P ≥ 0.50).

CONCLUSION

During uncompensable exercise-heat stress, sized-matched simulated burn injuries on the torso or limbs evoke comparable core temperature, heart rate, and perceptual responses, suggesting that the risk of exertional heat illness in such environmental conditions is independent of injury location.

Interaction of Exercise Intensity and Simulated Burn Injury Size on Thermoregulation

PURPOSE

This study aimed to test the hypothesis that the elevation in internal body temperature during exercise in a hot environment is influenced by the combination of exercise intensity and BSA burned.

METHODS

Ten healthy participants (8 males, 2 females; 32 ± 9 yr; 75.3 ± 11.7 kg) completed eight exercise trials on a cycle ergometer, each with different combinations of metabolic heat productions (low, 4 W·kg-1; moderate, 6 W·kg-1) and simulated BSA burn in a hot environmental chamber (39.9°C ± 0.3°C, 20.1% ± 1.5% RH). Burns were simulated by covering 0%, 20%, 40%, or 60% of participants' BSA with a highly absorbent, vapor-impermeable material. Gastrointestinal temperature (TGI) was recorded, with the primary analysis being the increase in TGI after 60 min of exercise.

RESULTS

We identified an interaction effect for the increase in TGI (P < 0.01), suggesting TGI was influenced by both intensity and simulated burn BSA. Regardless of the percentage BSA burn simulated, the increase in TGI was similar across low-intensity trials (0.70°C ± 0.26°C, P > 0.11 for all). However, during moderate-intensity exercise, the increase in TGI was greater for the 60% (1.78°C ± 0.38°C, P < 0.01) and 40% BSA coverage trials (1.33°C ± 0.44°C, P = 0.04), relative to 0% (0.82°C ± 0.36°C). There were no differences in TGI responses between 0% and 20% trials.

CONCLUSION

These data suggest that exercise intensity influences the relationship between burn injury size and thermoregulatory responses in a hot environment.