The effect of 10 days of heat acclimation on exercise performance in acute hypobaric hypoxia (4350 m)

White, Ailish C.; Salgado, Roy M.; Astorino, Todd A.; Loeppky, Jack A.; Schneider, Suzanne M.; McCormick, James J.; McLain, Trisha A.; Kravitz, Len; Mermier, Christine M.

doi:10.1080/23328940.2015.1072659

Cited by 22 publications

(40 citation statements)

References 40 publications

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“…Participants ranged from moderately active to trained. This sample size is consistent with previous work in this area that has identified differences in key cardiovascular and exercise performance indices in thermoneutral normoxic (Lorenzo et al., ) or hypoxic conditions (White et al., ). All participants were near‐sea‐level residents, non‐smokers, and had not been exposed to altitudes >1500 m or temperatures >30°C for >1 month before the start of the study.…”

Section: Methodssupporting

confidence: 90%

“…Few studies to date have investigated the potential of HA to improve exercise performance in acute hypoxia (Heled et al., ; Lee, Miller, James, & Thake, ; White et al., ). The first study to test this cross‐tolerance approach was conducted by Heled et al.…”

Section: Introductionmentioning

confidence: 99%

“…Subsequently, White et al. () examined whether 10 days of HA would improve exercise performance and maximal aerobic power (

{\dot{V}}_{O_{2} peak}

) during acute hypobaric hypoxia (4350 m) in trained men.

{\dot{V}}_{O_{2} peak}

remained unaffected by HA at 4350 or 1600 m, whereas there was a tendency for an improved 16 km time‐trial performance at 4350 m after HA.…”

Section: Introductionmentioning

confidence: 99%

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Heat acclimation does not affect maximal aerobic power in thermoneutral normoxic or hypoxic conditions

Sotiridis

Debevec

Ciuha

et al. 2019

Experimental Physiology

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New Findings What is the central question of this study?Controlled‐hyperthermia heat‐acclimation protocols induce an array of thermoregulatory and cardiovascular adaptations that facilitate exercise in hot conditions. We investigated whether this ergogenic potential can be transferred to thermoneutral normoxic or hypoxic exercise conditions. What is the main finding and its importance?We showed that heat acclimation did not affect maximal cardiac output or maximal aerobic power in thermoneutral normoxic or hypoxic conditions. Heat acclimation augmented the sweating response in thermoneutral normoxic conditions. The cross‐adaptation theory, according to which heat acclimation could facilitate hypoxic exercise capacity, is not supported by our data. Abstract Heat acclimation (HA) mitigates heat‐induced decrements in maximal aerobic power (V̇O2 peak ) and augments exercise thermoregulatory responses in the heat. Whether this beneficial effect of HA is observed in hypoxic or thermoneutral conditions remains unresolved. We explored the effects of HA on cardiorespiratory and thermoregulatory responses to exercise in normoxic, hypoxic and hot conditions. Twelve men [V̇O2 peak 54.7(standard deviation 5.7) ml kg−1 min−1] participated in a HA protocol consisting of 10 daily 90‐min controlled‐hyperthermia (target rectal temperature, Tre = 38.5°C) exercise sessions. Before and after HA, we determined V̇O2 peak in thermoneutral normoxic (NOR), thermoneutral hypoxic (fractional inspired O2 = 13.5%; HYP) and hot (35°C, 50% relative humidity; HE) conditions in a randomized and counterbalanced order. Preceding each maximal cycling test, a 30‐min steady‐state exercise bout at 40% of the NOR peak power output was used to evaluate thermoregulatory responses. Heat acclimation induced the expected adaptations in HE: reduced Tre and submaximal heart rate, enhanced sweating response and expanded plasma volume. However, HA did not affect V̇O2 peak or maximal cardiac output (P = 0.61). The peak power output was increased post‐HA in NOR (P < 0.001) and HE (P < 0.001) by 41 ± 21 and 26 ± 22 W, respectively, but not in HYP (P = 0.14). Gross mechanical efficiency was higher (P = 0.004), whereas resting Tre and sweating thresholds were lower (P < 0.01) post‐HA across environments. Nevertheless, the gain of the sweating response decreased (P = 0.05) in HYP. In conclusion, our data do not support a beneficial cross‐over effect of HA on V̇O2 peak in normoxic or hypoxic conditions.

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Section: Methodssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

“…Subsequently, White et al. () examined whether 10 days of HA would improve exercise performance and maximal aerobic power (

{\dot{V}}_{O_{2} peak}

) during acute hypobaric hypoxia (4350 m) in trained men.

{\dot{V}}_{O_{2} peak}

remained unaffected by HA at 4350 or 1600 m, whereas there was a tendency for an improved 16 km time‐trial performance at 4350 m after HA.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Heat acclimation does not affect maximal aerobic power in thermoneutral normoxic or hypoxic conditions

Sotiridis

Debevec

Ciuha

et al. 2019

Experimental Physiology

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“…In this study, where V E measurements during incremental exercise were made at 1,600 and 4,350 m in subjects acutely exposed to higher altitude without prior acclimatization (38), it was noted that V E STPD was lower at submaximal workloads at 4,350 m than at 1,600 m. This led us to explore and quantify this different response from that noted in earlier studies in acclimatized subjects where ventilatory acclimatization (36) had taken place. The purpose of this report was to determine whether this difference in V E STPD during exercise might be useful to estimate the magnitude and temporal progression of hypoxic ventilatory acclimatization.…”

Section: Introductionmentioning

confidence: 66%

“…Between 22 and 28 days later, these tests were repeated at 455 mmHg, and 4 and 6 days later at 633 mmHg. During the 25-day interval, the subjects underwent a 10-day heat acclimation protocol (38).…”

Section: Experimental Designmentioning

confidence: 99%

V_ESTPD as a measure of ventilatory acclimatization to hypobaric hypoxia

Loeppky

Sheard

Salgado

et al. 2016

Physiology International

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This study compared the ventilation response to an incremental ergometer exercise at two altitudes: 633 mmHg (resident altitude = 1,600 m) and following acute decompression to 455 mmHg (≈4,350 m altitude) in eight male cyclists and runners. At 455 mmHg, the V E STPD at RER <1.0 was significantly lower and the V E BTPS was higher because of higher breathing frequency; at VO 2 max, both V E STPD and V E BTPS were not significantly different. As percent of VO 2 max, the V E BTPS was nearly identical and V E STPD was 30% lower throughout the exercise at 455 mmHg. The lower V E STPD at lower pressure differs from two classical studies of acclimatized subjects (Silver Hut and OEII), where V E STPD at submaximal workloads was maintained or increased above that at sea level. The lower V E STPD at 455 mmHg in unacclimatized subjects at submaximal workloads results from acute respiratory alkalosis due to the initial fall in HbO 2 (≈0.17 pHa units), reduction in PACO 2 (≈5 mmHg) and higher PAO 2 throughout the exercise, which are partially pre-established during acclimatization. Regression equations from these studies predict V E STPD from VO 2 and P B in unacclimatized and acclimatized subjects. The attainment of ventilatory acclimatization to altitude can be estimated from the measured vs. predicted difference in V E STPD at low workloads after arrival at altitude.

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Cross-Adaptation: Heat and Cold Adaptation to Improve Physiological and Cellular Responses to Hypoxia

et al. 2017

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To prepare for extremes of heat, cold or low partial pressures of oxygen (O2), humans can undertake a period of acclimation or acclimatization to induce environment-specific adaptations, e.g. heat acclimation (HA), cold acclimation (CA), or altitude training. While these strategies are effective, they are not always feasible due to logistical impracticalities. Cross-adaptation is a term used to describe the phenomenon whereby alternative environmental interventions, e.g. HA or CA, may be a beneficial alternative to altitude interventions, providing physiological stress and inducing adaptations observable at altitude. HA can attenuate physiological strain at rest and during moderate-intensity exercise at altitude via adaptations allied to improved O2 delivery to metabolically active tissue, likely following increases in plasma volume and reductions in body temperature. CA appears to improve physiological responses to altitude by attenuating the autonomic response to altitude. While no cross-acclimation-derived exercise performance/capacity data have been measured following CA, post-HA improvements in performance underpinned by aerobic metabolism, and therefore dependent on O2 delivery at altitude, are likely. At a cellular level, heat shock protein responses to altitude are attenuated by prior HA, suggesting that an attenuation of the cellular stress response and therefore a reduced disruption to homeostasis at altitude has occurred. This process is known as cross-tolerance. The effects of CA on markers of cross-tolerance is an area requiring further investigation. Because much of the evidence relating to cross-adaptation to altitude has examined the benefits at moderate to high altitudes, future research examining responses at lower altitudes should be conducted, given that these environments are more frequently visited by athletes and workers. Mechanistic work to identify the specific physiological and cellular pathways responsible for cross-adaptation between heat and altitude, and between cold and altitude, is warranted, as is exploration of benefits across different populations and physical activity profiles.

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The effect of 10 days of heat acclimation on exercise performance in acute hypobaric hypoxia (4350 m)

Cited by 22 publications

References 40 publications

Heat acclimation does not affect maximal aerobic power in thermoneutral normoxic or hypoxic conditions

Heat acclimation does not affect maximal aerobic power in thermoneutral normoxic or hypoxic conditions

V_ESTPD as a measure of ventilatory acclimatization to hypobaric hypoxia

Cross-Adaptation: Heat and Cold Adaptation to Improve Physiological and Cellular Responses to Hypoxia

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The effect of 10 days of heat acclimation on exercise performance in acute hypobaric hypoxia (4350 m)

Cited by 22 publications

References 40 publications

Heat acclimation does not affect maximal aerobic power in thermoneutral normoxic or hypoxic conditions

Heat acclimation does not affect maximal aerobic power in thermoneutral normoxic or hypoxic conditions

VESTPD as a measure of ventilatory acclimatization to hypobaric hypoxia

Cross-Adaptation: Heat and Cold Adaptation to Improve Physiological and Cellular Responses to Hypoxia

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Product

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V_ESTPD as a measure of ventilatory acclimatization to hypobaric hypoxia