Leading Fitness Gym Center in Udaipur Healthline Fitness Studio http://healthlineudaipur.com/ While aerobic exercise is a great thing to do for your overall health, fitness, and wellbeing, there are some pretty good reasons not to let your training sessions creep over the 1-hour mark too Cardio sessions which run to over an hour are likely to make you more stressed, less able to build muscle effectively, and can negatively affect your testosterone levels. When training, it's important to keep in mind the level of intensity you stick to during long cardio sessions.