An ideal exercise program consists of many aspects to fitness, and cardio training is only one of them.
The ratio of how much strength training versus cardio you do will vary depending on your own goals, but to focus on just cardio regardless of what your goal is can come with some less-than-desirable results.
1. You start to lose muscle
Performing cardio only is not helpful for maintaining and building muscle.
With the loss of muscle tissue comes the risk of weight gain through less energy being used by the body (slower metabolism) and, unless strength training is included into the overall program, body composition will often reflect higher levels of body fat: yes, skinny fat is real!
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2. You may not lose fat
Cardio is effective at burning energy during the actual session, but past a certain point – once the body becomes familiar with the intensity – fat loss can slow down, even while you think you’re working hard.
3. Your bones and posture are affected
Strength training is essential for keeping our bones healthy, and without the presence of resistance training, bone density can be compromised.
Strength work is highly recommended for increasing bone density and strong tendons and ligaments. With stronger bones and muscles, your posture can improve and keep many niggles at bay.
4. You’ll be sore a lot of the time
Continual and repetitive movement can encourage persistent soreness and a higher risk of injury. If you keep recruiting the same muscle with the same action, your body gets tired and stressed.
5. You’ll be at risk of health issues
With a cardio-only approach to your exercise, your joints are more likely to suffer and begin to breakdown.
Elevated levels of cortisol (stress hormone) through excessive cardio can place a strain on the ability to lose body fat effectively. The release of hormones that regulate hunger can also become imbalanced.
6. Adaptation
Doing the same kind of exercise can lead to the body adapting to the activity somewhat and this can bring progress to a halt or plateau.
In order to experience shifts in improvements and moving towards your goals, moving away from doing the same thing over and over with a balanced approach to training styles.
7. Increased hunger
Lengthy cardio sessions can increase the appetite, and if this is not kept in check, weight gain can creep in.
People who do more cardio tend to eat more high-GI foods pre and post exercise, which can contribute to fat burning suppression and weight gain.
Rewarding hard cardio workouts with food is a common trap.