Exercise throughout 6° head-down tilt bed rest preserves thermoregulatory responses

Manabu Shibasaki, Thad E. Wilson, Jian Cui, Benjamin D. Levine, Craig G. Crandall

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Spaceflight and its bed rest analog [6° head-down tilt (HDT)] decrease plasma and blood volume and aerobic capacity. These responses may be associated with impaired thermoregulatory responses observed during exercise and passive heating after HDT exposure. This project tested the hypothesis that dynamic exercise during 13 days of HDT bed rest preserves thermoregulatory responses. Throughout HDT bed rest, 10 subjects exercised for 90 min/day (75% of pre-HDT maximum heart rate; supine). Before and after HDT bed rest, each subject exercised in the supine position at the same workload in a 28°C room. The internal temperature (Tcore) threshold for the onset of sweating and cutaneous vasodilation, as well as the slope of the relationship between the elevation in Tcore relative to the elevation in sweat rate (SR) and cutaneous vascular conductance (CVC; normalized to local heating maximum), were quantified pre- and post-HDT. Tcore thresholds for the onset of cutaneous vasodilation on the chest and forearm (chest: 36.79 ± 0.12 to 36.94 ± 0.13°C, P = 0.28; forearm: 36.76 ± 0.12 to 36.91 ± 0.11°C, P = 0.16) and slope of the elevation in CVC relative to Tcore (chest: 77.9 ± 14.2 to 80.6 ± 17.2%max/°C; P = 0.75; forearm: 76.3 ± 11.8 to 67.5 ± 14.3%max/°C, P = 0.39) were preserved post-HDT. Moreover, the Tcore threshold for the onset of SR (36.66 ± 0.12 to 36.74 ± 0.10°C; P = 0.36) and the slope of the relationship between the elevation in SR and the elevation in Tcore (1.23 ± 0.19 to 1.01 ± 0.14 mg·cm -2·min-1·°C-1; P = 0.16) were also maintained. Finally, after HDT bed rest, peak oxygen uptake and plasma and blood volumes were not different relative to pre-HDT bed rest values. These data suggest that dynamic exercise during this short period of HDT bed rest preserves thermoregulatory responses.

Original languageEnglish (US)
Pages (from-to)1817-1823
Number of pages7
JournalJournal of Applied Physiology
Volume95
Issue number5
StatePublished - Nov 2003

Fingerprint

Head-Down Tilt
Bed Rest
Sweat
Forearm
Thorax
Plasma Volume
Vasodilation
Heating
Skin
Space Flight
Sweating
Supine Position
Workload
Blood Vessels

Keywords

  • Skin blood flow
  • Sweating
  • Temperature regulation

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Exercise throughout 6° head-down tilt bed rest preserves thermoregulatory responses. / Shibasaki, Manabu; Wilson, Thad E.; Cui, Jian; Levine, Benjamin D.; Crandall, Craig G.

In: Journal of Applied Physiology, Vol. 95, No. 5, 11.2003, p. 1817-1823.

Research output: Contribution to journalArticle

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abstract = "Spaceflight and its bed rest analog [6° head-down tilt (HDT)] decrease plasma and blood volume and aerobic capacity. These responses may be associated with impaired thermoregulatory responses observed during exercise and passive heating after HDT exposure. This project tested the hypothesis that dynamic exercise during 13 days of HDT bed rest preserves thermoregulatory responses. Throughout HDT bed rest, 10 subjects exercised for 90 min/day (75{\%} of pre-HDT maximum heart rate; supine). Before and after HDT bed rest, each subject exercised in the supine position at the same workload in a 28°C room. The internal temperature (Tcore) threshold for the onset of sweating and cutaneous vasodilation, as well as the slope of the relationship between the elevation in Tcore relative to the elevation in sweat rate (SR) and cutaneous vascular conductance (CVC; normalized to local heating maximum), were quantified pre- and post-HDT. Tcore thresholds for the onset of cutaneous vasodilation on the chest and forearm (chest: 36.79 ± 0.12 to 36.94 ± 0.13°C, P = 0.28; forearm: 36.76 ± 0.12 to 36.91 ± 0.11°C, P = 0.16) and slope of the elevation in CVC relative to Tcore (chest: 77.9 ± 14.2 to 80.6 ± 17.2{\%}max/°C; P = 0.75; forearm: 76.3 ± 11.8 to 67.5 ± 14.3{\%}max/°C, P = 0.39) were preserved post-HDT. Moreover, the Tcore threshold for the onset of SR (36.66 ± 0.12 to 36.74 ± 0.10°C; P = 0.36) and the slope of the relationship between the elevation in SR and the elevation in Tcore (1.23 ± 0.19 to 1.01 ± 0.14 mg·cm -2·min-1·°C-1; P = 0.16) were also maintained. Finally, after HDT bed rest, peak oxygen uptake and plasma and blood volumes were not different relative to pre-HDT bed rest values. These data suggest that dynamic exercise during this short period of HDT bed rest preserves thermoregulatory responses.",
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