How Fast Do You Lose Fitness?

In this episode. find out how fast you lose muscular and cardiovascular fitness if you stop training.

Ben Greenfield
4-minute read
Episode #284

In “How Fast Do You Get Out of Shape? you learn about a study, which observed that conditioned athletes who had been training regularly for at least a year and then suddenly stopped lost half of the aerobic conditioning after 3 months, as well as research that shows that beginner exercisers who have worked out for about 2 months experience a complete loss of all aerobic conditioning after 2 months of not working out.

But lately, new research was highlighted in an article from Outside Magazine, in which a sports physiologist named Iñigo Mujika explained you should never, ever stop training for more than two weeks if you can help it.

In the article, Mujika explains how when you first start working out, you get strong very quickly with just a few sessions, because your muscles aren’t very big. These gains happen primarily due to neuromuscular adaptations, not musculoskeletal adaptation. Basically, this means that before your muscles even start to get bigger or thicker, your brain gets better at communicating with your muscles, and recruiting more of those muscles.

In the meantime, when it comes to endurance training, (defined as at least 30 minutes per day, five days a week of increasing your heart rate to at least 60 percent of its max), you experience primarily an increase your plasma and blood volume, which is why, a few weeks into an endurance training program, your heart rate won’t spike as high as it did when you first started training, and you also get better at shedding off body heat via sweating, and better at utilizing fatty acids as a fuel.

Mujika explains that if you keep up your strength training, you'll gain muscle mass and strength and if you keep up your endurance training, then after six months of endurance training, it’s possible to increase blood volume by as much as 27 percent

So what’s the catch? All of these benefits quickly disappear when you stop training, and Mujika says: “When you stop training, almost immediately, we think three days, you lose plasma volume and blood volume in general…your heart rate for a given intensity increases.” 

After approximately 10-14 days, your maximum oxygen utilization drops at a rate of about 0.5% a day. After two weeks off, your brain’s ability to recruit muscle drops by 1-5% drop. After three to four weeks off, your muscles begin to atrophy, your fatty acid utilization drops and you become more sensitive to fluctuations in blood sugar.

In the end, Mujika says that you can roughly expect it to take twice as long to get back into shape as the time you’ve spent being inactive, meaning if you take two weeks off, it could take 4 weeks to build back up to your previous fitness. But if you’re already fit with a good training history, that time can definitely be shortened.

So what are my quick and dirty tips to consistently train, day in-day-out , week after week, all year long?


All content here is for informational purposes only. This content does not replace the professional judgment of your own health provider. Please consult a licensed health professional for all individual questions and issues.

About the Author

Ben Greenfield

Ben Greenfield received bachelor’s and master’s degrees from University of Idaho in sports science and exercise physiology; personal training and strength and conditioning certifications from the National Strength and Conditioning Association (NSCA); a sports nutrition certification from the International Society of Sports Nutrition (ISSN), an advanced bicycle fitting certification from Serotta. He has over 11 years’ experience in coaching professional, collegiate, and recreational athletes from all sports, and as helped hundreds of clients achieve weight loss and fitness success.