How Fast Do You Really Lose Fitness?

We’ve all heard it and I’m sure some of us believe it whole heartedly but do you really lose fitness soon after stopping exercise? How fast does it happen? A day, a week, a month or longer. I’m writing this part before digging into the literature so It’s probably a good time to talk about my first thoughts on the subject. I haven’t really taken a real break from fitness for a long time. The month of December 2 years ago and for about 4 years 10 years ago while I was in grad school. I personally don’t find a big difference in what I can do after a 2 week break but… I do notice things make me sore the next day. After a month long break I think you start to notice changes. That said getting into running after years long breaks seems easier the second time for sure. Even though I don’t give up exercise completely after a training cycle I do end up cutting way, way back. After being in the best shape of my life and then cutting back to two or three times a week I start to notice changes in the way my body looks and the way I feel in about a month. But let’s find out together if science backs those feeling up?

There are a number of physical indictors of fitness and we’ll get into all of those. My prediction is that some start to fall off quickly while others take months. We’ll mostly be looking at two things here how fast is a drop detectable and especially when is that drop significant. So sidebar but not really, what does significant mean? We’re using it in the scientific (specifically statistical) sense here. So it doesn’t mean significant like that’s a really big deal the way we’re used to saying it. Significant in studies means that there is a measurable difference between 2 groups that is not likely due to chance alone. In other words there is a 95% plus chance there really is a difference between the two groups. In this case it will be between participants on day 0, or when they are still actively exercising and at some time point in the future when they re not. So it might be a tiny, itty bitty difference but saying it’s significant just means we’re pretty damn sure there is in fact a difference. So similar means we couldn’t detect a difference that was likely due to anything other than chance. Also we’re going to limit our look to human subjects and leave the mice and rats to someone else. Ok phew got that cleared up. So how fast do you really loose fitness after you stop exercising?

Maximal Oxygen Uptake (VO2 Max)

Men who ran 16 km daily for 2 weeks stopped exercising for 10 days and were measured 2 days out and 10 days out and followed a prescribed diet. For simplicity’s sake let’s call this study 1. In those runners there was no change in maximal oxygen uptake during exercise. (1) Similarly another study found a 9% decrease after 14 days of no running (3) and back to pertaining levels after about 4 weeks (8). VO2 Max returned completely to pre-training levels after 6 months. (6) VO2 Max is often regarded as a great measure of your overall level of cardiac and pulmonary (lung) fitness. So this one does drop off rather quickly which might explain why a first workout feels harder after a break. After a 2 week break you’re oxygen utilization is down about 10% which I’m thinking is probably somewhere around barely perceptible. After a month of inactivity your VO2 Max levels are almost back to normal but it’s encouraging that even after a month on the couch you are not starting from scratch. This measure was one of the fastest to drop off after training.

Blood Plasma Volume

Exercise is know to cause an increase on the overall volume of your blood. This makes your circulatory system work more efficiently and is an indicator of cardiovascular health.

Those same men above from study showed a 5% blood volume decrease after 2 days after stopping running but at 2 days out but at 10 days there were no additional changes detected. (1) After a month researches saw a 10% decease in blood volume and a similar change in heart stroke volume. (9). While there is a very fast decrease in blood plasma volume (a 5% decrease in 2 days) after a month that level only goes down about 10%. My takeaway from these research is that this is something I really don’t need to worry about. That initial increase is very short lived at 2 days but even a month out changes are not very big. So if you’ve had a months long break from exercise all is not lost and you’re still protected from your workouts months ago in this regard.

Body Weight

Body weight is pretty self explanatory right? Sometimes people, perhaps people who have used exercise to lose a significant amount of weight might start to stress about re-gaining if they stop exercising. People who lift to build muscle might worry about the opposite.

Take heart and take a chill pill, not really, you have at least a couple of weeks before you need to worry about any changes in weight due to detraining. Study 1 showed a 1 kg decrease in body weight after training cessation but no further changes were detected at 10 days and their % body fat did not change at all. (1) Not a huge change so it’s not that surprising that an other study found no changes after 14 days (3).

Resting Heart Rate

After 10 days stopping exercise no changes in resting heart rate were detected in runners. (1) Resting heart rate is often looked at as an indicator of overall fitness especially as an indicator of heart health. There really isn’t a change in this very fast at all. Ten days after stopping exercise athletes show no difference in their resting heart rates so stop stressing about your Apple watch data while binging on Netflix. Or is that just me?

Blood Pressure

Lots of people turn to exercise as a means of naturally lowering their blood pressure. It works wonders for that but there’s no immediate cause for concern if you take a little break because 10 days after stopping intense daily exercise no changes in blood pressure are detectable. (1)

Peak Exercise Heart Rate

After 10 days of detraining researchers found that athletes had a 5% increase in peak exercise heart rate corresponding to about 9 bpm. (1) Once again not a huge change getting on to two weeks of inactivity. Interestingly this is probably attributable to the slight decrease around the same time in VO2 Max and stroke volume. If you are pushing a little less blood around with a little less oxygen in it your heart needs to beat a little bit faster to move oxygen out to those busy muscles. Isn’t science cool?

Metabolism Source during exercise

Endurance athletes in particular train to make changes to the fuel source they use during prolonged periods of exertion. Long runs anyone? As their level of condition goes up the amount of fat they use for energy also rises. But how quickly does that superhero skill go away? Within 10 days after stopping training there are changes in carbohydrate metabolism during exercise. A well trained athlete uses more fat than carbs than someone who is untrained and this largely returns to normal after a month (8). After 6 months carbohydrate metabolism completely returns to normal (6). This one surprised me a little bit. Changes in fat metabolism during exercise return to normal for the most part within a month showing that consistency in training really is key for endurance athletes.

Changes in your Muscles

A lot of athletes will be concerned about muscle loss when they’re not training. Taken together research suggests that this is in fact a concern but it’s not totally a use it or lose it situation. A few months out, about 5, your muscles have in fact returned to their per-training state but three months out you’re still realizing some of those gains. Take heart though after two whole months of inactivity your still rocking about 90% of that improvement from your training period. A meta-analysis (a review of studies) showed that over enough time maximal strength, force and power do go down over time but from this study we’re not sure how fast. It does however say (shocker) the longer you stop the greater the effect. (4) After 5 months it had returned to normal (6). Another study looked at the capillaries surrounding each muscle fiber 8 weeks after cyclists stopped after an initial training period of 8 weeks. Eight weeks of training caused participants to increase the number and area of capillaries around each muscle fiber by 20 – 30%. Eight weeks after stopping capillaries deceased between 5 – 10% depending on the measurement meaning training effects had  largely persisted (7). When changes in lactic acid threshold were examined after detraining similar results were obtained in cyclists. After three months of inactivity the lactic acid threshold of muscles was greatly reduced but remained above those of control subjects (10). For me this research explains a lot about why it’s never as hard to get back into something as it was to start in the first place. It also tells me a lot of people need to chill about brief periods away from exercise. If it takes 2 months to loose 10% of your muscular improvement ya’ll need to relax if it’s been less than a week or two!

Changes in Hormones

After stopping exercise for 2 weeks researchers found a change in how athletes use glucose in runners and lifters suggesting a slight decrease in insulin sensitivity. However there were no changes in the level of cholesterol in the blood after stopping training (3). Since your hormones are what is supposed to be somewhat sensitive to little short term changes in your body this is encouraging news. Think about what hormones are responsible for in a woman’s body each and every month!

Blood Flow in Your Brain

Runners who stopped for 10 days did show reduced blood flow to 8 regions of the brain in master athletes. (2) This research is really interesting to me. I find that my improvements in mood and even the level of thinking I can do are so immediate after and during a workout. The researchers in this study did a lot of musing about the potential protective effects of exercise in the aging brain. This get’s to be Really interesting when taken together with the findings in the next section.

Mental Health

A meta review of studies showed that across 19 different studies stopping exercise made depressive symptoms worse, same goes for anxiety. Studies followed participants for up to 42 days and the longer people stopped the worse these symptoms got. (5) When I start to think about changes in blood flow in the brain it’s not a big leap to start thinking about a possible mechanism for declines in mental health after stopping exercise. Almost any long term dedicated exerciser will tell you that it’s just as much about their mental health as their physical health at this point. It also starts to make sense why people can start to feel addicted to exercise when you consider how fast the mood boosting effects start to decline.

Other  and Takeaways

After reading about this for a few hours every night for a week never mind a thesis or a review paper a whole large journal issue of review articles could be written about this. Given more time (about 4 years) I could have produced some crazy graphs. But throughout all the articles I read I found that in general the better trained you are before stopping exercise the less the effects are of stopping. In other words the better shape you were in the slower you lose fitness when you stop. The same rang true for older athletes meaning that older athletes lost more fitness faster after stopping than younger ones. (4) For the most part this research taken together is very encouraging! If you’ve been away from it for 10 days to a week there are only a few nominal changes in your overall level of fitness. Your VO2 max is down about 10%, the blood flow in your brain is a bit lower but your muscles, cholesterol levels, and overall level of heath are largely unchanged.

A month or more off you’re still largely in the shape you were before. You’ll probably find it more exhausting since your maximal oxygen levels are down and your endurance wasn’t where is was before but your muscles are still most of what they were before so it shouldn’t be too hard to get back there. Has it been many months since your last workout well all hope is not lost some of that good work you did in your last training cycle means you’re not starting completely from scratch.

I was also struck by how old some of this research is dating back to the 1980’s. It turns out we’ve known for a very long time, my whole lifetime in fact that a few days and a week off from training is literally no big deal. This made me wonder about people posting, lecturing and musing about loosing fitness so fast. The cynic in me wonders if that’s not partly due to certain players in the fitness industry creating a sense of urgency to keep you constantly spending? The optimist/realist side of me thinks it’s more about what’s going on in your head both literally and figuratively. Personally I feel not as great when I take a break from what I used to be doing. Working a major training plan for a half or triathlon makes me feel pretty damn good about myself! I feel powerful, other than being tiered my mood is great and I feel so purposeful. Others probably feel the same way. In the off season (aka winter) I’m usually managing two maybe three workouts a week and no where near the time spent. Given those rapid changes in blood flow is it any wonder I (and likely others) feel very different about where we are fitness wise?

So the next time you’re freaking out, or someone is prompting you to freak out about losing fitness soooo fast think about all of this. Good established science says that a week off is literally nothing and two weeks pretty much almost nothing. Sure you might notice some big changes in how you feel but rest assured your still just as fit as you were for all intensive purposes. If you’ve taken a 2 month break you’re certainly not back to square one, it probably won’t hurt as bad as you’re expecting getting back. If it’s been half a year well yeah you’ve lost a great deal but it’s still going to be easier now than had you never started in the first place!

Does this research surprise you or even shock you? Or are you like me thinking that makes a lot of sense with your own personal experiences? Why do you think the idea that we start to lose a lot of fitness in a few days still persists?

Read what I read

1. Cullinane et al., 1986. Cardiac size and VO2max do not decrease after short-term exercise cessation. Medicine and science in sports and exercise. 
2. Alfini et al., 2016. Hippocampal and Cerebral Blood Flow after Exercise Cessation in Master Athletes. Frontiers in Aging and Neuroscience.
3. Hortobagyi et al., 1993. Effects of exercise cessation on lipids and lipoproteins in distance runners and power athletes. European journal of applied physiology.
4. Bosquet et al., 2013. Effect of training cessation on muscular performance: A meta‐analysis. Scandinavian journal of medicine and science in sports.
5. Weinstein et al., 2017. Mental health consequences of exercise withdrawal: A systematic review. General hospital psychiatry.
6. Fournier et al. 1982. Skeletal muscle adaptation in adolescent boys: sprint and endurance training and detraining. The journal of medicine and science in sport exercise.
7. Klausen et al., 1981. Adaptive changes in work capacity, skeletal muscle capillarization and enzyme levels during training and detraining. Acta Physiologica.
8. Mujika and Sabino. 2001. Cardiorespiratory and metabolic characteristics of detraining in humans. Medicine and science in sports medicine.
9. Coyle et al., 1986. Effects of detraining on cardiovascular responses to exercise: role of blood volume. Journal of applied physiology.
10. Chi et al., 1983. Effects of detraining on enzymes of energy metabolism in individual human muscle fibers. American journal of cell physiology.