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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
Acidic Smell After Cardio Exercise Photo Credit: lzf/iStock/GettyImages

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 the 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 running or cycling, 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 needs.

Read more: How Does the Food We Eat Actually Give Us Energy?

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 study published in 2005 in The Journal of Physiology, 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 alleviate 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.

Getting the Most From Your Workout

Dehydration is another factor in the ammonia smell. Dehydration makes your sweat more concentrated, which can increase the odor. Make sure your urine is straw colored, not dark yellow or brown.

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.

Read more: 3 Energy Systems in the Body

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