Reduced exercise ventilatory efficiency at moderate altitude

Cardiopulmonary Exercise Testing (CPET) is crucial for assessing the physiological response to physical exertion. This study focuses on the impact of acute exposure to moderate altitude (MA), 1500-3500 meters above sea level, on ventilatory, cardiovascular, and performance parameters. While research explores high altitude (HA) effects, limited information exists for MA. A cohort of seven healthy, untrained individuals underwent CPETs at sea level (SL) and MA (2325 m). Pulmonary function tests and maximal CPETs were conducted, and statistical analyses were performed to compare results at different altitudes. No statistically significant differences were observed in cardiovascular (heart rate, mean arterial pressure, oxygen pulse) and performance (watt max, VO2) parameters between SL and MA. However, a noteworthy reduction in ventilatory efficiency at MA, indicated by increased steepness in the VE/VCO2 slopes, was identified (+15% of VE/VCO2 s1, p-value < 0.01; +19% of VE/VCO2 s2, p-value 0.04), with a significant increase in VE peak (SL: 126 ± 41 L/min, MA: 145 ± 47 L/min, p-value 0.04). The observed reduction in ventilatory efficiency is commonly reported at HA but has not been previously described at MA. Unlike previous literature on trained individuals, untrained subjects in this study did not exhibit significant reductions in VO2 peak or power peak at MA. Ventilation, while increased at MA, did not represent a limiting factor in physical exercise. This study provides valuable insights into the physiological responses of untrained individuals to acute exposure to MA. These findings have implications for individuals exposed to moderate altitudes, expanding our understanding of altitude physiology beyond HA scenarios.