Cardiorespiratory Coordination in Hypercapnic Test Before and After High-Altitude Expedition

Area of Science:

• Physiology
• Human Adaptation
• Exercise Science

Background:

• Cardiovascular and respiratory systems coordinate for human adaptation.
• Hypoxia and training alter cardiorespiratory coordination (CRC).
• The delayed effect of high-altitude (HA) acclimatization on CRC is not well understood.

Purpose of the Study:

• To compare CRC in mountaineers before and after a HA expedition using acute hypercapnia.
• To investigate the delayed effects of HA acclimatization on CRC.

Main Methods:

• Nine trained male mountaineers were studied at sea level before and after a 20-day HA expedition (4,000-7,000 m).
• Cardiorespiratory coordination was assessed during baseline, hypercapnic rebreathing, and recovery states using principal component (PC) analysis.
• Exercise addiction scores were correlated with PC analysis results.

Main Results:

• Post-HA, a higher proportion of mountaineers showed one dominant PC (9/9) compared to Pre-HA (5/9), indicating improved CRC.
• The variance explained by PC1 increased significantly Post-HA (75.6%) versus Pre-HA (65.6%).
• Heart rate loading onto PC1 increased Post-HA, and CRC was strongly correlated with exercise addiction scores (r=0.9, P=0.001).

Conclusions:

• Acute hypercapnic challenge reveals enhanced cardiorespiratory coordination in mountaineers following high-altitude exposure.
• The observed increase in CRC after HA acclimatization is significantly associated with exercise addiction.