This paper explores the physiological and performance-related effects of endurance cycling under contrasting environmental conditions, specifically comparing hot (34°C) and cold (10°C) settings. Environmental temperature is a critical factor influencing athletic performance, as it affects thermoregulatory mechanisms, cardiovascular function, and muscular efficiency. High ambient temperatures can lead to increased core body temperature, accelerated sweating and dehydration, and elevated cardiovascular strain, all of which may impair power output and endurance capacity. In contrast, cold environments challenge the body in different ways, such as inducing peripheral vasoconstriction, altering muscle contractility, and affecting neuromuscular coordination. Drawing upon empirical studies, this research examines key performance parameters, including power output, which reflects the cyclist’s ability to generate force over time; muscle activation patterns, which indicate neuromuscular engagement and fatigue resistance; body temperature regulation, which shows the body’s capacity to maintain homeostasis; and perceived fatigue, which provides a subjective measure of exertion and psychological strain. By comparing these variables across hot and cold conditions, the study aims to elucidate the distinct physiological and psychological responses that environmental extremes elicit in endurance athletes. The findings from this investigation are expected to provide practical insights for training, competition preparation, and recovery strategies, enabling athletes and coaches to optimize performance while minimizing the risks associated with thermal stress. Understanding how heat and cold impact endurance cycling not only informs sport-specific interventions but also contributes to broader knowledge of human adaptation to extreme environmental conditions.