How Quickly Do You Lose Fitness When You Stop Training?

Picture of Singapore Stan Chart marathon by RunSociety from Flickr

Well, many of you've just done your last race of the season. Yes, after the Standard Chartered Singapore Marathon 2016 this morning it's off season time at last.

Now it's time to take some much needed rest, both physically and mentally and not worry about training for a while.

The most common question and worst fear among my patients who run (or race triathlons) is how quickly do they go out of shape if they stop running (or training).

Ever wondered how long before detraining kicks in? Well, just as you don't become a fast runner overnight, you don't lose your fitness that quickly too. Nothing goes up in a straight line, there'll be some peaks and valleys. Likewise you don't lose your fitness overnight too.

Okay, first the good news. Research on detraining or how quickly you go out of shape shows that those who are less well-trained have less to lose. This make sense considering the elite athletes have further to fall.

Elite athletes can lose up to half of their aerobic fitness within the first 12-21 days of not training. They can then lose half of their remaining fitness in the next 12-21 days and so on. The bad news, those who've trained for a few months have a slower decline, but lost all fitness within 4 weeks.

Most studies suggest that an elite athlete's VO2 max levels drop 7 percent if they stop training for 12-21 days. They can lose another 9 percent from days 21-84.

One major reason for the quick fitness decline is the loss of blood volume. In the first 12-21 days that you stop training, you can lose up to 500 milliliters of blood. It's a simple supply and demand situation. When you stop training, you take away the demand.

The body loses the ability to bring oxygen to the muscles and you also have less fluid available for sweating (which cools the body).

The good news is with retraining, you can regain blood volume in a week although it takes a while for your red blood cells to grow again.

Other than blood volume, your mitochondria cell density, lactate threshold and your ability to oxidize fat stores all deteriorate.

Researchers have found it difficult however to measure time to regain your fitness. A common suggestion is that for every week lost, it takes two weeks to regain that previous level. The reason for this all those functional capabilities mentioned above.

When I was still racing, I used to take two weeks off at the end of the season. Yes, two weeks of no swimming, running, cycling and weight training. This allowed me to recuperate both physically, recharge mentally and also to spend time with my family, loved ones and friends. And when its time to train again, I'd be raring to go.

Do bear in mind that not all systems in your body detrain or retrain equally. Do consider your age. Runners in their 20's can resume training as though they never took time off. Older runners will take longer. 

Strength gains (from weight training) are not lost as quickly as aerobic (or cardiovascular fitness) and it usually takes 4 weeks before you start to lose peak muscle strength and maybe that will be another article later on.

So congrats and well done to those of you who ran this morning and make sure you take that well deserved time off.

References

Coyle EF, Hemmert MK et al (1986). Effects Of Detraining On Cardiovascular Responses To Exercise: Role Of Blood Volume. JAP. 60(1): 95-99.

Joyner MJ and Coyle EF (2008). Endurance Exercise Performances: The Physiology Of Champions. J Physiol. 586(1): 35-44. DOI: 10.1113/j.physiol.2007.143834.