Changes in Total Hemoglobin Mass and Its Relationship With Conditioning Indices During Altitude Training at 1700 m

Increased total hemoglobin (Hb) mass is a physiological adaptation to altitude training; however, considerable individual differences have been observed in this response. This study aimed to determine the relationship between changes in total Hb mass (Hbmass) and conditioning indices during altitude training at an elevation of 1700 m.

Sixteen male long-distance runners participated in an altitude training camp at 1700 m for 9 to 23 days. The Hbmass was determined using a carbon monoxide rebreathing method. Daily conditioning indices, including arterial oxygen saturation (SpO2), heart rate (HR), SpO2/HR ratio, subjective ratings of fatigue, sleep depth, training intensity, sleep duration, and daily running distance, were measured or recorded each morning.

Hbmass increased by 1.4% (1.9%) on average, with individual changes ranging from -2.1% to 4.6% (-18 to 35 g). A significant positive correlation was observed between ΔHbmass and duration of stay at altitude (r = .695, P = .003). In the multiple regression analysis, duration of stay (B = .235, P = .001) and the SpO2/HR ratio (B = -4.462, P = .001) were identified as significant predictors of Hbmass change (R2 = .819).

These findings suggest that increases in Hbmass may occur even at an altitude of 1700 m when sufficient exposure duration is ensured. Furthermore, the SpO2/HR ratio may serve as a practical indicator reflecting individual physiological responses during altitude training.