What happens if you stop aerobic exercising?

A client of mine who spent up to 5 days per week on the treadmill doing intervals of walking and jogging for an hour fell off the wagon recently. Although she continued her 2 day per week strength training routine, she felt run down and even her strength training endurance was impacted. When she finally got back on the treadmill after several weeks she was only able to walk at a reduced speed for 40 minutes.

Although you may not always want to do your cardio exercise, it’s easier to continue some sort of routine and level of intensity rather than trying to start back up, and that is not just in your head.

First, it will help you to know what happens over time when you do aerobic exercise consistently. Overall your body becomes more efficient. Your muscles increase their endurance capacity; you are able to use less carbohydrate stores as energy and burn more fat. Aerobic training increases the stroke volume of the heart or the output of oxygenated blood returning to the working muscles and the muscles become more efficient at extracting oxygen from the blood.

If you stop doing aerobic exercise, within the first 12 days stroke volume is reduced by 7%. Already, in less than two weeks you have lost almost 10% of endurance level you had achieved. A study by the ACSM (American College of Sports Medicine) concluded that lack of aerobic exercise for nearly three months, cost the subjects nearly 15% of their stroke volume and therefore their endurance. The same study showed that endurance levels could be maintained by less frequent or shorter duration cardio exercise but could not be maintained by decreased intensity in exercise.

Bottom line: It’s easier mentally and physically to continue to do some sort of cardio frequently than it is to try to start up your routine again. Also, if you are not in the mood, it is better to spend any amount of time, at your usual level of intensity, whenever you can, than to just do some cardio at a much lower level of intensity. For example, if you normally jog 30 minutes 5 times a week at an intensity level of 6, you can maintain your endurance level if you continue 3 times a week for 20 minutes at a level of 6 than if you started to walk 4 times a week for 30 minutes at an intensity level of 4.