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Cross Acclimation between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia.
Front Physiol 2016; 7:78FP

Abstract

BACKGROUND

The potential for cross acclimation between environmental stressors is not well understood. Thus, the aim of this investigation was to determine the effect of fixed-workload heat or hypoxic acclimation on cellular, physiological, and performance responses during post acclimation hypoxic exercise in humans.

METHOD

Twenty-one males (age 22 ± 5 years; stature 1.76 ± 0.07 m; mass 71.8 ± 7.9 kg; [Formula: see text]O2 peak 51 ± 7 mL(.)kg(-1.)min(-1)) completed a cycling hypoxic stress test (HST) and self-paced 16.1 km time trial (TT) before (HST1, TT1), and after (HST2, TT2) a series of 10 daily 60 min training sessions (50% N [Formula: see text]O2 peak) in control (CON, n = 7; 18°C, 35% RH), hypoxic (HYP, n = 7; fraction of inspired oxygen = 0.14, 18°C, 35% RH), or hot (HOT, n = 7; 40°C, 25% RH) conditions.

RESULTS

TT performance in hypoxia was improved following both acclimation treatments, HYP (-3:16 ± 3:10 min:s; p = 0.0006) and HOT (-2:02 ± 1:02 min:s; p = 0.005), but unchanged after CON (+0:31 ± 1:42 min:s). Resting monocyte heat shock protein 72 (mHSP72) increased prior to HST2 in HOT (62 ± 46%) and HYP (58 ± 52%), but was unchanged after CON (9 ± 46%), leading to an attenuated mHSP72 response to hypoxic exercise in HOT and HYP HST2 compared to HST1 (p < 0.01). Changes in extracellular hypoxia-inducible factor 1-α followed a similar pattern to those of mHSP72. Physiological strain index (PSI) was attenuated in HOT (HST1 = 4.12 ± 0.58, HST2 = 3.60 ± 0.42; p = 0.007) as a result of a reduced HR (HST1 = 140 ± 14 b.min(-1); HST2 131 ± 9 b.min(-1) p = 0.0006) and Trectal (HST1 = 37.55 ± 0.18°C; HST2 37.45 ± 0.14°C; p = 0.018) during exercise. Whereas PSI did not change in HYP (HST1 = 4.82 ± 0.64, HST2 4.83 ± 0.63).

CONCLUSION

Heat acclimation improved cellular and systemic physiological tolerance to steady state exercise in moderate hypoxia. Additionally we show, for the first time, that heat acclimation improved cycling time trial performance to a magnitude similar to that achieved by hypoxic acclimation.

Authors+Show Affiliations

Department for Health, University of BathBath, UK; Centre for Applied Biological and Exercise Sciences, Coventry UniversityCoventry, UK.Centre for Applied Biological and Exercise Sciences, Coventry University Coventry, UK.Centre for Applied Biological and Exercise Sciences, Coventry University Coventry, UK.Centre for Applied Biological and Exercise Sciences, Coventry University Coventry, UK.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

27014080

Citation

Lee, Ben J., et al. "Cross Acclimation Between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia." Frontiers in Physiology, vol. 7, 2016, p. 78.
Lee BJ, Miller A, James RS, et al. Cross Acclimation between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia. Front Physiol. 2016;7:78.
Lee, B. J., Miller, A., James, R. S., & Thake, C. D. (2016). Cross Acclimation between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia. Frontiers in Physiology, 7, p. 78. doi:10.3389/fphys.2016.00078.
Lee BJ, et al. Cross Acclimation Between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia. Front Physiol. 2016;7:78. PubMed PMID: 27014080.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Cross Acclimation between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia. AU - Lee,Ben J, AU - Miller,Amanda, AU - James,Rob S, AU - Thake,Charles D, Y1 - 2016/03/08/ PY - 2015/11/20/received PY - 2016/02/15/accepted PY - 2016/3/26/entrez PY - 2016/3/26/pubmed PY - 2016/3/26/medline KW - cross-acclimation KW - cycling KW - heat KW - heat shock proteins KW - hypoxia SP - 78 EP - 78 JF - Frontiers in physiology JO - Front Physiol VL - 7 N2 - BACKGROUND: The potential for cross acclimation between environmental stressors is not well understood. Thus, the aim of this investigation was to determine the effect of fixed-workload heat or hypoxic acclimation on cellular, physiological, and performance responses during post acclimation hypoxic exercise in humans. METHOD: Twenty-one males (age 22 ± 5 years; stature 1.76 ± 0.07 m; mass 71.8 ± 7.9 kg; [Formula: see text]O2 peak 51 ± 7 mL(.)kg(-1.)min(-1)) completed a cycling hypoxic stress test (HST) and self-paced 16.1 km time trial (TT) before (HST1, TT1), and after (HST2, TT2) a series of 10 daily 60 min training sessions (50% N [Formula: see text]O2 peak) in control (CON, n = 7; 18°C, 35% RH), hypoxic (HYP, n = 7; fraction of inspired oxygen = 0.14, 18°C, 35% RH), or hot (HOT, n = 7; 40°C, 25% RH) conditions. RESULTS: TT performance in hypoxia was improved following both acclimation treatments, HYP (-3:16 ± 3:10 min:s; p = 0.0006) and HOT (-2:02 ± 1:02 min:s; p = 0.005), but unchanged after CON (+0:31 ± 1:42 min:s). Resting monocyte heat shock protein 72 (mHSP72) increased prior to HST2 in HOT (62 ± 46%) and HYP (58 ± 52%), but was unchanged after CON (9 ± 46%), leading to an attenuated mHSP72 response to hypoxic exercise in HOT and HYP HST2 compared to HST1 (p < 0.01). Changes in extracellular hypoxia-inducible factor 1-α followed a similar pattern to those of mHSP72. Physiological strain index (PSI) was attenuated in HOT (HST1 = 4.12 ± 0.58, HST2 = 3.60 ± 0.42; p = 0.007) as a result of a reduced HR (HST1 = 140 ± 14 b.min(-1); HST2 131 ± 9 b.min(-1) p = 0.0006) and Trectal (HST1 = 37.55 ± 0.18°C; HST2 37.45 ± 0.14°C; p = 0.018) during exercise. Whereas PSI did not change in HYP (HST1 = 4.82 ± 0.64, HST2 4.83 ± 0.63). CONCLUSION: Heat acclimation improved cellular and systemic physiological tolerance to steady state exercise in moderate hypoxia. Additionally we show, for the first time, that heat acclimation improved cycling time trial performance to a magnitude similar to that achieved by hypoxic acclimation. SN - 1664-042X UR - https://www.unboundmedicine.com/medline/citation/27014080/Cross_Acclimation_between_Heat_and_Hypoxia:_Heat_Acclimation_Improves_Cellular_Tolerance_and_Exercise_Performance_in_Acute_Normobaric_Hypoxia_ L2 - https://doi.org/10.3389/fphys.2016.00078 DB - PRIME DP - Unbound Medicine ER -