Impulsively starting to exercise, overdoing it and neglecting to rest can expose you to the adverse effects of exercise. In addition to being more likely to suffer injuries, exercising too much can leave you feeling weak, tired and dehydrated. According to Washington and Lee University, over-exercising can also trigger heart problems, osteoporosis and arthritis as well as problems conceiving and loss of the menstrual cycle in women. In general, it's expert-recommended to do at least 150 minutes of moderate cardio per week and include strength training on two days.