It Is Not Just Muscle Fatigue That Slows You Down During Exercise, Your Brain Gets Tired Too!

When an endurance athlete crosses the finish line of a race and collapses on the ground out of pure exhaustion, the majority of us assume that it is down to muscle fatigue and oxygen debt. However, the actual reason behind this display of fatigue may actually have more to do with our brains than our muscles!

We have known for quite some time that serotonin is released when we exercise, improving our mood and helping us to continue exercising. However, scientists have recently discovered that a surplus of serotonin actually triggers a braking mechanism in the brain known as central fatigue. In other words, serotonin is both the accelerator of exercise and the brake.

Central fatigue is a tiredness that affects the brain and nervous system as opposed to the muscles themselves. This slows us down to the point where we have to stop out of exhaustion, when without this mechanism our muscles could have continued for a much longer period of time. Scientists are researching ways of controlling serotonin levels in a bid to enhance endurance performance.


Cotel F, Exley R, Cragg SJ, Perrier J-F, Seratonin Spillover onto the Axon Initial Segment of Motoneurons Induces Central Fatigue by Inhibiting Action Potential Initiation, PNAS, 2013.

About the Author

Job Role Sports Nutritionist and Social Media Coordinator Qualifications Bsc Sport and Exercise Science Steph has a competitive athletic background which spans 19 years. As a child she performed with the English Youth Ballet and had performed on the West End stage by the age of 10. Her enthusiasm for sport and fitness continued to grow as she did, encouraging her to learn more about nutrition and training. She began using her knowledge and personal experience to help others when she began coaching at the age of 16. From here, she went on to study Sport and Exercise Science at the University of Essex during which time she also received the Most Promising Newcomer Award from her University to mark her outstanding contribution to sport. During her first year of study she was introduced to partner stunt acrobatics and artistic gymnastics. After one year of dedicating herself to a lifestyle revolving around her sport, she was training with the best team in the UK who are currently ranked fifth in the world. Steph has worked in both the private and public sector coaching children and adults from grassroot to elite level as well as providing them with cutting edge advice on how to reach their goals. Steph has received awards for her choreography and has competed nationally and internationally meaning that she can back up her scientific knowledge with a wealth of experience. As our resident Sports Nutritionist, Steph is here to provide the most current and evidence based fitness, health and nutrition information to help you reach your health and fitness goals.
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