True or False: Lack of sleep and high stress levels can lead to muscle breakdown.

The statement is true because both lack of sleep and high stress levels significantly impact the body's physiology, contributing to muscle breakdown. Sleep is crucial for recovery and muscle repair; during sleep, the body produces growth hormone, which aids in muscle growth and recovery. Without adequate sleep, these processes can be disrupted, leading to a higher rate of muscle breakdown.

High stress levels can also lead to increased cortisol production, a hormone that, when elevated chronically, can break down muscle tissue. Cortisol mobilizes energy during stress but can also inhibit protein synthesis and stimulate muscle catabolism, contributing to muscle loss over time. This synergy between sleep deprivation and stress can exacerbate muscle breakdown, especially if an individual is engaged in physical activities or training.

Considering the other responses, stating that the lack of sleep and high stress levels do not contribute to muscle breakdown (false) overlooks well-established physiological mechanisms. Indicating a conditional relationship (sometimes) or limiting it to extreme cases minimizes the consistent negative effects of both factors on muscle health, which have been widely documented. Thus, the correct answer effectively captures the connections between these health issues and muscle breakdown.