Many runners often worry that pausing training for rest will decrease fitness or affect preparation for upcoming races. However, expert reports by Professor William O. Roberts at the University of Minnesota (USA) indicate that muscle development and endurance enhancement occur precisely during the body's rest period after exercise.

This is when the body synthesizes protein to repair damaged muscle fibers, making muscle tissue stronger and better able to handle loads in subsequent training sessions. Therefore, runners need to flexibly adjust the number of rest days each week, depending on their skill level and race distance.

Adequate rest is essential to recover damaged muscle fibers and replenish energy. *Magnific*.

For amateur runners or beginners (5km-10km distances), two to three full rest days each week are essential for the musculoskeletal system to adapt to continuous impact stress. Meanwhile, for professional runners preparing for half marathon (21km) or full marathon (42km) distances, coaching experts recommend maintaining one to two rest days, flexibly combining passive rest and active recovery to allow the body to accumulate sufficient energy and ensure peak performance in subsequent running sessions.

Passive recovery is a state where the body rests, engaging in almost no physical activity, such as sleeping, lying down, or soaking feet in warm water. This method optimizes the body's glycogen synthesis and allows the central nervous system to rest after high-intensity workouts. However, because the body remains largely inactive, this method can reduce blood flow to damaged muscle fibers, leading to decreased circulation and slower recovery.

Therefore, runners should combine this with active recovery by performing low-intensity exercises for about 20-30 minutes, such as leisurely walking, gentle cycling, short-distance swimming, or yoga. These activities help maintain a moderate heart rate, increase blood flow carrying oxygen and nutrients to muscle cells, and reduce muscle stiffness after exercise.

A proper rest regimen is needed to replenish glycogen reserves for subsequent running sessions. *Magnific*.

Finally, runners also need to actively monitor physiological indicators that reflect the body's fatigue. According to sports medicine experts, the two most recognizable warning signs of overtraining are resting heart rate (RHR) and sleep quality.

When the body has not fully recovered, the heart rate measured in the morning right after waking up is often 5 to 10 beats per minute higher than the average, accompanied by restlessness, difficulty sleeping, or waking up multiple times during the night. These are signs for runners to proactively reduce training and take an additional one to two rest days, to protect the body from the risk of serious injury.

Duc Anh