Answer: Need for acclimatization, efforts in breathing, and/or reduced oxygen levels.
Explanation:
Need for Acclimatization: The body requires time to adjust to high altitude, and without proper acclimatization, athletes might experience altitude sickness symptoms like headaches, nausea, and fatigue.
Effort in Breathing: Athletes must breathe more frequently and deeply to get enough oxygen, leading to faster fatigue. This increased respiratory effort requires additional energy, which can deplete their overall energy reserves more quickly. Additionally, the strain on the respiratory muscles can cause discomfort and reduce efficiency in their movements, further contributing to a decrease in performance.
Lower Oxygen Levels: The reduced oxygen pressure at high altitudes means there is less oxygen available for the muscles, decreasing aerobic capacity and endurance. This can lead to a slower delivery of oxygen to the bloodstream, affecting the body's ability to sustain prolonged physical activity.