From my experience working in the fitness industry, this has been a question that has been asked many times. How much cardio is enough? When it comes to exercise it all depends who you ask. There are recommendations from 30 minutes up to 90 minutes of moderate intensity activity, most days of the week. There are some signs that we need to look for that could help us determine if you are performing too much activity.

Exercise Induced Immunodepression:

This is described as immunological changes due to prolonged and intensive exertion (2). Athletes that were involved in regular strenuous activity were at a higher risk for upper respiratory tract (URT) infection (1,2). This also caused other skeletal muscle and other mechanisms to be affected. So what can athletes do to prevent immunodepression? The only supplement that was found to have a significant impact was a carbohydrate supplement (1,2). This was found to reduce inflammation and lower cortisol levels.

Behavioral Aspect of High Frequency Exercises:

Other than affecting the immune system, excessive exercise has been found to have an addiction component. As fitness professionals, we would not think that being addicted to exercise would be a bad thing. I would actually like to see more people find exercise as a pleasure rather than torture. So, when does exercise become addictive? In a recent study, participants expressed that they exercised to control mood and have an ideal body shape. These participants would exercise to “scratch the itch” (3). This is referred to performing an exercise because it has the properties of being pleasurable (3). It is not meant to accomplish a long term goal, but to provide pleasure to the participant immediately following the exercise session. This experience would be referred to as a “high” or a “buzz” (4). Exercise addiction can become dangerous affecting an individual’s thinking, behavior patterns, establishing a craving for exercise, causing internal conflicts, conflicts with other people, and causing people to experienced withdrawal symptoms (4).

Overtraining Syndrome and Injury:

As expressed before, prolonged and intensive exertion can cause the immune system to become weak. Aside from that, excessive training can cause Overtraining Syndrome (OTS). OTS is better known as burnout and commonly occurs in athletes that train excessively often causing a reduction in progress, even after extended rest periods (5). Early forms of OTS can be described as muscle and joint soreness/pain, muscle weakness, and acute and chronic inflammation. This can lead to mild to severe injury and loss of muscle function (5). Here are some precautions one must take to help prevent or treat OTS:

1. organize your workouts
2. keep your workouts new and fresh
3. individualize the intensity to each individual or athlete
4. maintain optimal nutrition, sleep, and rest

References:

1. Nieman, D. (2008). Immunonutrition support for athletes. Nutrition Reviews, 66(6), 310-320.
2. Moreira, A., Kekkonen, R., Delgado, L., Fonseca, J., Korpela, R., & Haahtela, T. (2007). Nutritional modulation of exercise-induced immunodepression in athletes: a systematic review and meta-analysis. European Journal of Clinical Nutrition, 61(4), 443-460.
3. Cox, R., & Orford, J. (2004). A qualitative study of the meaning of exercise for people who could be labeled as ‘addicted’ to exercise -can ‘addiction’ be applied to high frequency exercising?. Addiction Research & Theory, 12(2), 167-188.
4. Terry, A., Szabo, A., & Griffiths, M. (2004). The exercise addiction inventory: a new brief screening tool. Addiction Research & Theory, 12(5), 489-499.
5. Smith, L. (2004). TISSUE TRAUMA: THE UNDERLYING CAUSE OF OVERTRAINING SYNDROME?. Journal of Strength & Conditioning Research (Allen Press Publishing Services Inc.), 18(1), 185-193.
6. Meeusen, R., Duclos, M., Gleeson, M., Rietjens, G., Steinacker, J., & Urhausen, A. (2006). Prevention, diagnosis and treatment of the Overtraining Syndrome. European Journal of Sport Science, 6(1), 1-14.

Article Provided by Rene’ Moreno- B.S., NASM- CPT, PES