Aldosterone dynamics during graded exercise at sea level and high altitude

Area of Science:

• Physiology
• Altitude Medicine
• Exercise Science

Background:

• Understanding hormonal regulation during exercise is crucial for athletes and individuals exposed to environmental stressors.
• High-altitude (HA) environments significantly impact physiological functions, including cardiorespiratory and endocrine systems.
• Acclimatization to HA involves complex adaptations in hormonal balance and metabolic responses.

Purpose of the Study:

• To investigate the hormonal responses to graded exercise in low-altitude residents at sea level (SL) and during acute and chronic exposure to 4,300 m.
• To examine the interplay between the renin-angiotensin-aldosterone system and cortisol during exercise under varying altitudes.
• To determine the effects of acclimatization on these hormonal responses.

Main Methods:

• Eight low-altitude residents underwent controlled exercise protocols (graded bicycle ergometry) at SL and after 1 (acute) and 11 (chronic) days at HA (4,300 m).
• Caloric, water, and electrolyte intake, as well as environmental conditions, were standardized.
• Blood samples were collected at rest and during light (40% VO2 max) and moderate (75% VO2 max) exercise to measure plasma hormone levels.

Main Results:

• Mean maximal oxygen uptake (VO2 max) was 27% lower at HA compared to SL.
• Resting plasma aldosterone, renin, and angiotensin II were significantly lower on day 1 at HA but normalized by day 11, indicating adaptation.
• Hormonal responses (renin, angiotensin II, aldosterone) increased with workload at both SL and HA, but were blunted acutely at HA.
• Cortisol levels remained stable across conditions and exercise intensities.

Conclusions:

• Aldosterone secretion during graded exercise is primarily regulated by the renin-angiotensin system at SL.
• Acute exposure to HA alters the responsiveness of the renin-angiotensin-aldosterone system during exercise.
• Chronic HA exposure leads to adaptation, with hormonal responses approaching SL levels, suggesting successful acclimatization.