Clinical Autonomic Research

, Volume 21, Issue 6, pp 381–387 | Cite as

Muscle sympathetic responses during orthostasis in heat-stressed individuals

  • Jian Cui
  • Manabu Shibasaki
  • David A. Low
  • David M. Keller
  • Scott L. Davis
  • Craig G. Crandall
Research Article



Whole-body heat stress compromises the control of blood pressure during an orthostatic challenge, although the extent to which this occurs can vary greatly between individuals. The mechanism(s) responsible for these varying responses remain unclear. This study tested the hypothesis that the individuals who are best able to tolerate an orthostatic challenge while heat stressed are the ones with the largest increase in sympathetic activity during orthostasis, indexed from recordings of muscle sympathetic nerve activity (MSNA).


MSNA, arterial blood pressure, and heart rate were recorded from 11 healthy volunteers throughout passive whole-body heating and during 15 min of 60° head-up tilt (HUT) or until the onset of pre-syncopal symptoms.


Whole-body heating significantly increased core temperature (~0.9°C), supine heart rate and MSNA. Eight of 11 subjects developed pre-syncopal symptoms resulting in early termination of HUT. The HUT tolerance time was positively correlated (R = 0.82, P = 0.01) with the increase in MSNA by HUT.


These data suggest that the individuals with the largest increase in MSNA during upright tilt have the greatest capacity to withstand the orthostatic challenge while heat stressed.


Sympathetic nervous system Heat stress disorders Tilt-table test Syncope 


  1. 1.
    Allen J, Crossley R (1972) Effect of controlled elevation in body temperature on human tolerance to 1Gz acceleration. J Appl Physiol 33:418–420Google Scholar
  2. 2.
    Convertino VA, Ludwig DA, Cooke WH (2004) Stroke volume and sympathetic responses to lower-body negative pressure reveal new insight into circulatory shock in humans. Auton Neurosci 111:127–134PubMedCrossRefGoogle Scholar
  3. 3.
    Cooke WH, Rickards CA, Ryan KL, Kuusela TA, Convertino VA (2009) Muscle sympathetic nerve activity during intense lower body negative pressure to presyncope in humans. J Physiol 587:4987–4999PubMedCrossRefGoogle Scholar
  4. 4.
    Crandall CG, Etzel RA, Farr DB (1999) Cardiopulmonary baroreceptor control of muscle sympathetic nerve activity in heat-stressed humans. Am J Physiol 277:H2348–H2352PubMedGoogle Scholar
  5. 5.
    Cui J, Blaha C, Moradkhan R, Gray KS, Sinoway LI (2006) Muscle sympathetic nerve activity responses to dynamic passive muscle stretch in humans. J Physiol 576:625–634PubMedCrossRefGoogle Scholar
  6. 6.
    Cui J, Shibasaki M, Low DA, Keller DM, Davis SL, Crandall CG (2010) Heat stress attenuates the increase in arterial blood pressure during the cold pressor test. J Appl Physiol 109(5):1354–1359PubMedCrossRefGoogle Scholar
  7. 7.
    Cui J, Wilson TE, Crandall CG (2002) Baroreflex modulation of sympathetic nerve activity to muscle in heat-stressed humans. Am J Physiol Regul Integr Comp Physiol 282:R252–R258PubMedGoogle Scholar
  8. 8.
    Cui J, Wilson TE, Crandall CG (2002) Phenylephrine-induced elevations in arterial blood pressure are attenuated in heat-stressed humans. Am J Physiol Regul Integr Comp Physiol 283:R1221–R1226PubMedGoogle Scholar
  9. 9.
    Cui J, Wilson TE, Crandall CG (2004) Muscle sympathetic nerve activity during lower body negative pressure is accentuated in heat-stressed humans. J Appl Physiol 96:2103–2108PubMedCrossRefGoogle Scholar
  10. 10.
    Cui J, Zhang R, Wilson TE, Crandall CG (2004) Spectral analysis of muscle sympathetic nerve activity in heat-stressed humans. Am J Physiol Heart Circ Physiol 286:H1101–H1106PubMedCrossRefGoogle Scholar
  11. 11.
    Fu Q, Witkowski S, Levine BD (2004) Vasoconstrictor reserve and sympathetic neural control of orthostasis. Circulation 110:2931–2937PubMedCrossRefGoogle Scholar
  12. 12.
    Halliwill JR (2000) Segregated signal averaging of sympathetic baroreflex responses in humans. J Appl Physiol 88:767–773PubMedGoogle Scholar
  13. 13.
    Hayoz D, Noll G, Passino C, Weber R, Wenzel R, Bernardi L (1996) Progressive withdrawal of muscle nerve sympathetic activity preceding vaso-vagal syncope during lower-body negative pressure. Clin Sci (Lond) 91(Suppl):50–51Google Scholar
  14. 14.
    Iwase S, Mano T, Saito M (1987) Effects of graded head-up tilting on muscle sympathetic activities in man. Physiologist 30:S62–S63PubMedGoogle Scholar
  15. 15.
    Keller DM, Cui J, Davis SL, Low DA, Crandall CG (2006) Heat stress enhances arterial baroreflex control of muscle sympathetic nerve activity via increased sensitivity of burst gating, not burst area, in humans. J Physiol 573:445–451PubMedCrossRefGoogle Scholar
  16. 16.
    Keller DM, Low DA, Wingo JE, Brothers RM, Hastings J, Davis SL, Crandall CG (2009) Acute volume expansion preserves orthostatic tolerance during whole-body heat stress in humans. J Physiol 587:1131–1139PubMedCrossRefGoogle Scholar
  17. 17.
    Keller DM, Sander M, Stallknecht B, Crandall CG (2010) alpha-Adrenergic vasoconstrictor responsiveness is preserved in the heated human leg. J Physiol 588:3799–3808PubMedCrossRefGoogle Scholar
  18. 18.
    Kregel KC, Gisolfi CV (1990) Circulatory responses to vasoconstrictor agents during passive heating in the rat. J Appl Physiol 68:1220–1227PubMedGoogle Scholar
  19. 19.
    Levine BD, Pawelczyk JA, Ertl AC, Cox JF, Zuckerman JH, Diedrich A, Biaggioni I, Ray CA, Smith ML, Iwase S, Saito M, Sugiyama Y, Mano T, Zhang R, Iwasaki K, Lane LD, Buckey JC Jr, Cooke WH, Baisch FJ, Eckberg DL, Blomqvist CG (2002) Human muscle sympathetic neural and haemodynamic responses to tilt following spaceflight. J Physiol 538:331–340PubMedCrossRefGoogle Scholar
  20. 20.
    Lind A, Leithead C, McNicol G (1968) Cardiovascular changes during syncope induced by tilting men in the heat. J Appl Physiol 25:268–276PubMedGoogle Scholar
  21. 21.
    Mano T, Iwase S (2003) Sympathetic nerve activity in hypotension and orthostatic intolerance. Acta Physiol Scand 177:359–365PubMedCrossRefGoogle Scholar
  22. 22.
    Massett MP, Lewis SJ, Kregel KC (1998) Effect of heating on the hemodynamic responses to vasoactive agents. Am J Physiol 275:R844–R853PubMedGoogle Scholar
  23. 23.
    Massett MP, Lewis SJ, Stauss HM, Kregel KC (2000) Vascular reactivity and baroreflex function during hyperthermia in conscious rats. Am J Physiol Regul Integr Comp Physiol 279:R1282–R1289PubMedGoogle Scholar
  24. 24.
    Niimi Y, Matsukawa T, Sugiyama Y, Shamsuzzaman AS, Ito H, Sobue G, Mano T (1997) Effect of heat stress on muscle sympathetic nerve activity in humans. J Auton Nerv Syst 63:61–67PubMedCrossRefGoogle Scholar
  25. 25.
    Oberg B, Thoren P (1972) Increased activity in left ventricular receptors during hemorrhage or occlusion of caval veins in the cat. A possible cause of the vaso-vagal reaction. Acta Physiol Scand 85:164–173PubMedCrossRefGoogle Scholar
  26. 26.
    Smith ML, Ellenbogen KA, Eckberg DL (1992) Sympathoinhibition and hypotension in carotid sinus hypersensitivity. Clin Auton Res 2:389–392PubMedCrossRefGoogle Scholar
  27. 27.
    Taylor WF, Johnson JM, Kosiba WA, Kwan CM (1989) Cutaneous vascular responses to isometric handgrip exercise. J Appl Physiol 66:1586–1592PubMedGoogle Scholar
  28. 28.
    Vaddadi G, Esler MD, Dawood T, Lambert E (2010) Persistence of muscle sympathetic nerve activity during vasovagal syncope. Eur Heart J 31:2027–2033PubMedGoogle Scholar
  29. 29.
    Vallbo AB, Hagbarth KE, Torebjork HE, Wallin BG (1979) Somatosensory, proprioceptive, and sympathetic activity in human peripheral nerves. Physiol Rev 59:919–957PubMedGoogle Scholar
  30. 30.
    Victor RG, Leimbach WN Jr (1987) Effects of lower body negative pressure on sympathetic discharge to leg muscles in humans. J Appl Physiol 63:2558–2562PubMedGoogle Scholar
  31. 31.
    Wallin BG, Sundlof G (1982) Sympathetic outflow to muscles during vasovagal syncope. J Auton Nerv Syst 6:287–291PubMedCrossRefGoogle Scholar
  32. 32.
    Wilson TE, Cui J, Crandall CG (2002) Effect of whole-body and local heating on cutaneous vasoconstrictor responses in humans. Auton Neurosci 97:122–128PubMedCrossRefGoogle Scholar
  33. 33.
    Wilson TE, Cui J, Zhang R, Witkowski S, Crandall CG (2002) Skin cooling maintains cerebral blood flow velocity and orthostatic tolerance during tilting in heated humans. J Appl Physiol 93:85–91PubMedGoogle Scholar
  34. 34.
    Yamazaki F, Yamauchi K, Tsutsui Y, Endo Y, Sagawa S, Shiraki K (2003) Whole body heating reduces the baroreflex response of sympathetic nerve activity during Valsalva straining. Auton Neurosci 103:93–99PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Jian Cui
    • 1
    • 2
  • Manabu Shibasaki
    • 1
  • David A. Low
    • 1
  • David M. Keller
    • 1
    • 3
  • Scott L. Davis
    • 1
    • 3
  • Craig G. Crandall
    • 1
    • 3
  1. 1.Institute for Exercise and Environmental MedicineTexas Health Presbyterian Hospital DallasDallasUSA
  2. 2.Penn State Heart and Vascular InstitutePenn State College of MedicineHersheyUSA
  3. 3.University of Texas Southwestern Medical CenterDallasUSA

Personalised recommendations