Stress can significantly affect physical health and fitness levels by triggering physiological responses such as increased heart rate and elevated cortisol levels. Chronic stress can lead to muscle tension, fatigue, and a weakened immune system, making individuals more susceptible to illness. Additionally, stress may contribute to unhealthy habits, including poor dietary choices and inactivity, which can adversely impact fitness levels. Effectively managing stress through techniques such as exercise, mindfulness, and relaxation can improve overall health and fitness.