Sweat smells like ammonia
I seem especially troubled by the heat this year, and my sweat volume is far greater and it smells overwhelmingly of ammonia. On the way home from a ride the car reeks like I've spilled an entire bottle of ammonia. This is all new this summer. No changes in diet or training. Would you have any ideas on the cause of this? By the way, my power seems way down. Thanks.

James Bailey

Pam Hinton replies

James,

Well, your sweat smells like ammonia because it contains ammonia. Why the sudden change in odor? If your training and diet haven't changed, I don't have any idea. You may be wondering how ammonia gets into sweat. I can answer that question. Ammonia is produced in skeletal muscle during prolonged exercise, enters the blood stream, and is secreted by the sweat glands.

Ammonia is generated in skeletal muscle as a byproduct of adenosine triphosphate (ATP) breakdown into adenosine monophosphate (AMP) and inorganic phosphate. During high-intensity exercise, the rate of ATP consumption exceeds ATP production and AMP begins to accumulate in the cell. Ammonia is released from the excess AMP by the enzyme, AMP deaminase. During prolonged, exhaustive exercise, skeletal muscle generates ammonia from oxidation of branch chain amino acids (BCAAs) to make ATP. In the process, the amino group is removed from the BCAA, producing ammonia.

Elevated ammonia within the skeletal muscle and blood negatively affect performance. Neuromuscular function is impaired by ammonia, leading to local muscle fatigue. Ammonia can cross the blood-brain barrier. So it accumulates in the brain when blood levels are high. The brain's capacity to get rid of ammonia is adequate for short-term maximal exercise, but it is overwhelmed during prolonged, exhaustive exercise. Abnormally high levels of ammonia in the brain can disrupt normal neurotransmitter function.

Ammonia depletes the excitatory neurotransmitters, glutamate and its precursor, gamma-amino butyrate, leading to central fatigue. Training and diet affect the production of ammonia during exercise. Endurance training decreases the amount of ammonia produced in skeletal muscle, thereby lowering blood and sweat ammonia concentrations. Depletion of muscle glycogen following a low carbohydrate diet increases the blood ammonia response to exercise due to increased use of BCAAs for energy. Carbohydrate consumption during prolonged, submaximal exercise reduces muscle ammonia production from BCAA degradation.

Since your training and diet haven't changed, it's a bit of a mystery why your sweat has gone ammonia on you. Your best solution seems to be a change of clothes for the car ride home.