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Acidic Smell After Cardio Exercise

author image Michelle Matte
Michelle Matte is an accomplished fitness professional who holds certifications in personal training, pilates, yoga, group exercise and senior fitness. She has developed curricula for personal trainers and group exercise instructors for an international education provider. In her spare time, Matte writes fiction and blogs.
Acidic Smell After Cardio Exercise
A woman is running outside. Photo Credit: m-imagephotography/iStock/Getty Images

One of the unpleasant side effects of vigorous exercise is body odor. When you sweat, bacteria on your skin naturally produce that familiar locker room aroma. But during prolonged exercise, you may notice an acid or ammonia odor that is different from your usual armpit fare. That smell is related to the breakdown of amino acids, and may indicate that you need to tweak your nutrition.

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Energy Pathways in Human Body

When you exercise, your body's first choice of fuel is carbohydrate, found in the form of glucose in the blood and glycogen in the muscles and liver. As glucose stores become depleted during long-duration, low intensity rhythmic activities, including walking or jogging, your body will gradually draw on fat stores for energy. But because fat is an oxidative fuel, your body cannot use it for prolonged high-intensity activities, and it will begin to break down protein from muscle to satisfy its energy demand.

Ammonia And Amino Acids

The onset of protein breakdown is often marked by an ammonia odor in the sweat and on the breath. Ammonia, whose chemical structure is NH3, is a metabolic byproduct of the stripping away of the nitrogen molecule from amino acids so the remaining carbon can be converted to glucose. The nitrogen then bonds with hydrogen to form ammonia, a component of urea, and eventually leaves the body via the urine, in sweat and in moisture expired on your breath.

Carbohydrate Intake And Performance

When amino acids are broken down during prolonged exercise, ammonia levels in the central nervous system and the brain increase significantly. In a 2004 study by Lars Nybo, et. al., elevated ammonia levels in the brain during exercise were found to have a correlation with the onset of fatigue, especially in untrained subjects. The researchers suggested that increased carbohydrate consumption would assuage cerebral ammonia accumulation and stave off fatigue during exercise. The implications of this study are significant for individuals wishing to perform at peak levels. Limiting carbohydrate intake can interfere with training and performance.

Importance of Hydration

Another factor contributing to high ammonia levels and resultant fatigue is inadequate hydration. Amino acid breakdown takes place in the liver, and the ammonia byproduct is normally eliminated through the urine. However, if fluid is inadequate to facilitate the flushing of ammonia, it will remain in the body longer and may end up in the central nervous system during exercise,

Getting Most From Workout

Many people skimp on carbohydrates for fear of gaining weight. However, ample carbohydrate consumption and hydration before your workout can enhance and prolong performance, netting you a greater caloric burn while sparing lean mass. Consuming more protein will not spare muscle, and will tax the kidneys. A diet containing an ample balance of complex carbohydrates will give you a leaner, more powerful physique in the long run.

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