The Physiological Strain Index Modified for Trained Heat-Acclimatized Individuals in Outdoor Heat

in International Journal of Sports Physiology and Performance
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Purpose: To determine if the Physiological Strain Index (PSI), in original or modified form, can evaluate heat strain on a 0–10 scale, in trained and heat-acclimatized men undertaking a competitive half-marathon run in outdoor heat. Methods: Core (intestinal) temperature (TC) and heart rate (HR) were recorded continuously in 24 men (mean [SD] age = 26 [3] y, VO2peak = 59 [5] mL·kg·min−1). A total of 4 versions of the PSI were computed: original PSI with upper constraints of TC 39.5°C and HR 180 beats·min−1 (PSI39.5/180) and 3 modified versions of PSI with each having an age-predicted maximal HR constraint and graded TC constraints of 40.0°C (PSI40.0/PHRmax), 40.5°C (PSI40.5/PHRmax), and 41.0°C (PSI41.0/PHRmax). Results: In a warm (26.1–27.3°C) and humid (79–82%) environment, all runners finished the race asymptomatic in 107 (10) (91–137) min. Peak TC and HR were 39.7°C (0.5°C) (38.5–40.7°C) and 186 (6) (175–196) beats·min−1, respectively. In total, 63% exceeded TC 39.5°C, 71% exceeded HR 180 beats·min−1, and 50% exceeded both of the original PSI upper TC and HR constraints. The computed heat strain was significantly greater with PSI39.5/180 than all other methods (P < .003). PSI >10 was observed in 63% of runners with PSI39.5/180, 25% for PSI40.0/PHRmax, 8% for PSI40.5/PHRmax, and 0% for PSI41.0/PHRmax. Conclusions: The PSI was able to quantify heat strain on a 0–10 scale in trained and heat-acclimatized men undertaking a half-marathon race in outdoor heat, but only when the upper TC and HR constraints were modified to 41.0°C and age-predicted maximal HR, respectively.

Byrne is with the Faculty of Health and Human Sciences, Peninsula Allied Health Centre, School of Health Professions, University of Plymouth, Plymouth, United Kingdom. Lee is with Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Republic of Singapore.

Byrne (chris.byrne@plymouth.ac.uk) is corresponding author.
International Journal of Sports Physiology and Performance
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References
  • 1.

    Sawka MNLeon LRMontain SJSonna LA. Integrated physiological mechanisms of exercise performance, adaptation, and maladaptation to heat stress. Compr Physiol. 2011;1(4):18831928. PubMed ID: 23733692

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2.

    Moran DSShitzer APandolf KB. A physiological strain index to evaluate heat stress. Am J Physiol. 1998;275(1 pt 2):129134. PubMed ID: 9688970

    • Search Google Scholar
    • Export Citation
  • 3.

    Moran DS. Stress evaluation by the physiological strain index (PSI). J Basic Clin Physiol Pharmacol. 2000;11(4):403423. PubMed ID: 11248950 doi:10.1515/JBCPP.2000.11.4.403

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4.

    Moran DSKenney WLPierzga JMPandolf KB. Aging and assessment of physiological strain during exercise-heat stress. Am J Physiol Regul Integr Comp Physiol. 2002;282(4):R1063R1069. PubMed ID: 11893610 doi:10.1152/ajpregu.00364.2001

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5.

    Moran DSMontain SJPandolf KB. Evaluation of different levels of hydration using a new physiological strain index. Am J Physiol. 1998;275(3 pt 2):R854R860. PubMed ID: 9728084

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6.

    Byrne CLee JKChew SALim CLTan EY. Continuous thermoregulatory responses to mass-participation distance running in heat. Med Sci Sports Exerc. 2006;38(5):803810. PubMed ID: 16672830 doi:10.1249/01.mss.0000218134.74238.6a

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7.

    Ely BREly MRCheuvront SNKenefick RWDegroot DWMontain SJ. Evidence against a 40 degrees C core temperature threshold for fatigue in humans. J Appl Physiol. 2009;107(5):15191525. doi:10.1152/japplphysiol.00577.2009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8.

    Mohr MNybo LGrantham JRacinais S. Physiological responses and physical performance during football in the heat. PLoS ONE. 2012;7(6):e39202. PubMed ID: 22723963 doi:10.1371/journal.pone.0039202

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9.

    Racinais SPeriard JDKarlsen ANybo L. Effect of heat and heat acclimatization on cycling time trial performance and pacing. Med Sci Sports Exerc. 2015;47(3):601606. PubMed ID: 24977692 doi:10.1249/MSS.0000000000000428

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10.

    Lucia AHoyos JSantalla AEarnest CChicharro JL. Tour de France versus Vuelta a Espana: which is harder? Med Sci Sports Exerc. 2003;35(5):872878. PubMed ID: 12750600

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11.

    Veltmeijer MTEijsvogels TMThijssen DHHopman MT. Incidence and predictors of exertional hyperthermia after a 15-km road race in cool environmental conditions. J Sci Med Sport. 2015;18(3):333337. PubMed ID: 24930073 doi:10.1016/j.jsams.2014.04.007

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12.

    DeMartini JKMartschinske JLCasa DJet al. Physical demands of National Collegiate Athletic Association Division I football players during preseason training in the heat. J Strength Cond Res. 2011;25(11):29352943. PubMed ID: 21904245 doi:10.1519/JSC.0b013e318231a643

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13.

    Aughey RJGoodman CAMcKenna MJ. Greater chance of high core temperatures with modified pacing strategy during team sport in the heat. J Sci Med Sport. 2014;17(1):113118. PubMed ID: 23689104 doi:10.1016/j.jsams.2013.02.013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14.

    Periard JDRacinais SKnez WLHerrera CPChristian RJGirard O. Thermal, physiological and perceptual strain mediate alterations in match-play tennis under heat stress. Br J Sports Med. 2014;48(suppl 1):i32i38.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15.

    Jay OBain ARDeren TMSacheli MCramer MN. Large differences in peak oxygen uptake do not independently alter changes in core temperature and sweating during exercise. Am J Physiol Regul Integr Comp Physiol. 2011;301(3):R832R841. PubMed ID: 21697517 doi:10.1152/ajpregu.00257.2011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16.

    Cramer MNJay O. Explained variance in the thermoregulatory responses to exercise: the independent roles of biophysical and fitness/fatness-related factors. J Appl Physiol.2015;119(9):982989. doi:10.1152/japplphysiol.00281.2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17.

    Selkirk GAMcLellan TM. Influence of aerobic fitness and body fatness on tolerance to uncompensable heat stress. J Appl Physiol. 2001;91(5):20552063. doi:10.1152/jappl.2001.91.5.2055

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18.

    Selkirk GAMcLellan TMWright HERhind SG. Mild endotoxemia, NF-kappaB translocation, and cytokine increase during exertional heat stress in trained and untrained individuals. Am J Physiol Regul Integr Comp Physiol. 2008;295(2):R611R623. PubMed ID: 18565834 doi:10.1152/ajpregu.00917.2007

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19.

    Tanaka HMonahan KDSeals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153156. PubMed ID: 11153730 doi:10.1016/S0735-1097(00)01054-8

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20.

    Nes BMJanszky IWisloff UStoylen AKarlsen T. Age-predicted maximal heart rate in healthy subjects: the HUNT fitness study. Scand J Med Sci Sports. 2013;23(6):697704. PubMed ID: 22376273 doi:10.1111/j.1600-0838.2012.01445.x

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21.

    Esteve-Lanao JLucia AdeKoning JJFoster C. How do humans control physiological strain during strenuous endurance exercise? PLoS ONE. 2008;3(8):e2943. PubMed ID: 18698405 doi:10.1371/journal.pone.0002943

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22.

    Hornery DJFarrow DMujika IYoung W. An integrated physiological and performance profile of professional tennis. Br J Sports Med. 2007;41(8):531536; discussion 536. PubMed ID: 17472999 doi:10.1136/bjsm.2006.031351

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23.

    Wingo JEGanio MSCureton KJ. Cardiovascular drift during heat stress: implications for exercise prescription. Exerc Sport Sci Rev. 2012;40(2):8894. PubMed ID: 22410803 doi:10.1097/JES.0b013e31824c43af

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24.

    Tikuisis PMcLellan TMSelkirk G. Perceptual versus physiological heat strain during exercise-heat stress. Med Sci Sports Exerc. 2002;34(9):14541461. PubMed ID: 12218738 doi:10.1097/00005768-200209000-00009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 25.

    Lee JKNio AQLim CLTeo EYByrne C. Thermoregulation, pacing and fluid balance during mass participation distance running in a warm and humid environment. Eur J Appl Physiol. 2010;109(5):887898. PubMed ID: 20237797 doi:10.1007/s00421-010-1405-y

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 26.

    Byrne CLim CL. The ingestible telemetric body core temperature sensor: a review of validity and exercise applications. Br J Sports Med. 2007;41(3):126133. PubMed ID: 17178778 doi:10.1136/bjsm.2006.026344

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27.

    Brotherhood JR. Heat stress—a challenge for sports science in Australia. J Sci Med Sport. 2008;11(1):12. PubMed ID: 18078785 doi:10.1016/j.jsams.2007.10.014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 28.

    Achten JJeukendrup AE. Heart rate monitoring: applications and limitations. Sports Med. 2003;33(7):517538. PubMed ID: 12762827 doi:10.2165/00007256-200333070-00004

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 29.

    Schlader ZJRaman AMorton RHStannard SRMundel T. Exercise modality modulates body temperature regulation during exercise in uncompensable heat stress. Eur J Appl Physiol. 2011;111(5):757766. PubMed ID: 20978782 doi:10.1007/s00421-010-1692-3

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30.

    Selley EAKolbe TVan Zyl CGNoakes TDLambert MI. Running intensity as determined by heart rate is the same in fast and slow runners in both the 10- and 21-km races. J Sports Sci. 1995;13(5):405410. PubMed ID: 8558627 doi:10.1080/02640419508732256

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 31.

    Robinson S. Temperature regulation in exercise. Pediatrics. 1963;32(suppl):691702.

  • 32.

    Pugh LGCorbett JLJohnson RH. Rectal temperatures, weight losses, and sweat rates in marathon running. J Appl Physiol. 1967;23(3):347352. PubMed ID: 6047956 doi:10.1152/jappl.1967.23.3.347

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 33.

    Wyndham CHStrydom NB. The danger of an inadequate water intake during marathon running. S Afr Med J. 1969;43(29):893896. PubMed ID: 5821601

  • 34.

    Maron MBWagner JAHorvath SM. Thermoregulatory responses during competitive marathon running. J Appl Physiol. 1977;42(6):909914. PubMed ID: 881391 doi:10.1152/jappl.1977.42.6.909

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 35.

    Maughan RJLeiper JBThompson J. Rectal temperature after marathon running. Br J Sports Med. 1985;19(4):192195. PubMed ID: 4092138 doi:10.1136/bjsm.19.4.192

  • 36.

    Noakes TDMyburgh KHdu Plessis Jet al. Metabolic rate, not percent dehydration, predicts rectal temperature in marathon runners. Med Sci Sports Exerc. 1991;23(4):443449. PubMed ID: 2056902 doi:10.1249/00005768-199104000-00009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 37.

    Armstrong LEPumerantz ACFiala KAet al. Human hydration indices: acute and longitudinal reference values. Int J Sport Nutr Exerc Metab. 2010;20(2):145153. PubMed ID: 20479488 doi:10.1123/ijsnem.20.2.145

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 38.

    Cheuvront SNKenefick RWMontain SJSawka MN. Mechanisms of aerobic performance impairment with heat stress and dehydration. J Appl Physiol. 2010;109(6):19891995. doi:10.1152/japplphysiol.00367.2010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
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