Cardio is good for your heart, your mental outlook and controlling your weight, but it can interfere with muscle growth if you're burning more calories that you're taking in. However, unless you have an unhealthy obsession with exercise, you should be able to stimulate muscle growth by tweaking your diet. Consult your doctor before starting an exercise program if you have a history of heart problems, or risk factors for heart disease.
When you burn more calories with cardio exercise than you take in, you're going to lose fat. Although you may be able to use strength training to preserve current muscle tissue as you lose weight, it'll be difficult to add muscle at the same time. The right amount of cardiovascular exercise for you depends on your strength and weight goals, as well as your fitness level. If you want to lose fat and gain muscle, you may need to prioritize your goals and work toward one at a time.
If you need to lose a few pounds to reach a healthy weight, performing cardio five or six days a week can help you create the calorie deficit you need to burn unwanted fat. However, if your primary focus is muscle growth, you need to manage your calorie intake and expenditure to give your body access to the energy it needs for building muscle tissue. Pushing your body's limits with cardio potentially interferes with muscle recovery, which is necessary for muscle growth. The key is finding the right balance of diet, aerobic exercise and strength training.
Giving up cardio, or drastically cutting back on aerobic activity, could rob you of important cardiovascular, health and fitness benefits. Instead, evaluate the type of cardio you do, as well as the frequency, and tweak your routine so that you reap the benefits of both aerobic exercise and weight training. If you usually work out at moderate intensity for 45 minutes several days a week, try cutting your time down to 30 minutes, and alternate your workouts between lower intensity walking sessions, and your current activities. Ideally, you should keep your cardio at the current level and increase your caloric intake as you shift your fitness focus to muscle growth.
If you're not losing weight on your current exercise regimen, it's not necessary to cut back on your cardio in order to promote muscle growth. Evaluate your strength training regimen to make sure you're maximizing your muscle gain potential. Three weekly weight workouts should be sufficient to promote muscle gain, as long as you're performing enough repetitions to fatigue your muscles, and giving yourself 24 to 48 hours of rest between strength sessions. Overtraining with strength workouts can also interfere with muscle growth.