Article | June 2017

Are you too Tired to Run?

Prevent Central Nervous System Fatigue: Give Your Brain the Rest It Needs

Written by Antonio Williams, M.S., NASM, P.E.S
Case Management Specialist, Health Educator

Do you find that despite regular exercise, you can’t get past that same frustrating point of fatigue? Sleep may be the culprit.

Several factors can affect how you perform in your workouts.

  • Diet: What you eat and when you eat it
  • Environment: Temperature, training altitude and humidity
  • Strength and skills: Your capacity and coordination in relation to a particular type of workout
  • Central nervous system: How long your brain can continue to send signals to your muscles telling them to contract during a workout

Fatigue is the inability to maintain output or force during continuous muscle contractions. At the beginning of your workout, you are full of energy. While you work out, your brain sends signals to your muscles. But, like any other organ or muscle in your body, your brain tires. When this happens, it begins to send signals to your muscles more slowly. Eating well and hydrating regularly help extend your brain's ability to send signals to your muscles more quickly.

Sooner or later, no matter how well you fuel your brain, fatigue will set in. You’ll feel yourself moving differently than when you first began your workout. This is when most injuries occur, late in the workout, late in the game, late in the race. Listen to your body and quit while you're ahead.

Sufficient sleep is critical to the optimal function of the central nervous system making it essential for any training program. Without enough rest, your brain may not be able to send signals as quickly or for as long as you need to reach your full potential.

While diet, environmental conditions, strength and coordination may be more obvious factors that affect the success of your fitness routine don't let central nervous system fatigue sabotage your workouts. Prioritize sleep to reap the maximum benefits of your fitness efforts.

Man asleep on couch


Jones, J, NASM Study Guide Chapter 2 – Basic Exercise Science, May 18, 2013,

Gerdon, R, Why Endurance Athletes Should Re-think Fatigue, Bicycle Lab,

Griffin, R, Can Sleep Improve Your Athletic Performance, WebMD, August 13, 2014,

This is general health information and not medical advice or services. You should consult your doctor for medical advice or services, including seeking advice before undertaking a new diet or exercise program.