What happens when you quit exercising, or 'detrain'?

March 16, 2016 4:56 PM

I have been a daily exerciser (30-90 minutes on average, mixed cardio/strength/yoga) for a decade. I'm currently recovering from a month-long exercise rut/detraining - in other words, very little exercise due to a number of issues I'm already working to overcome - and am now curious: other than the infamous muscle loss and fat gain, what other major physiological changes start to take place after a few weeks without regular exercise?

I'll be honest. Exercise is all about having habits in place, but sometimes it's just really motivating to know what I'm losing.

For example, how the sudden lack of exercise is likely already causing my blood pressure to steadily rise over time, in addition to my blood sugar levels.

I want to be terrified by the facts. Facts > anecdata, and citations are always appreciated, but I'm still open to anecdata because hey, who doesn't love a good scary story?

Note that I, of course, already feel a lot of the adverse effects of going without regular exercise, but having said adverse effects "spelled out" for me is what seems to be helping me get back into a routine. I have a hard time sitting on my derrière knowing that it's not only growing in size, but becoming less efficient.

posted by nightrecordings to Health & Fitness (12 answers total)

Anecdatum: when I don't exercise, I get depressed. Exercise tends to improve mood, energy, and motivation. If you're focused on the physical changes, you might not have noticed this.
posted by mysterious_stranger at 5:04 PM on March 16, 2016 [2 favorites]

Response by poster: Clarification and then no more thread-sitting: I should have been more specific, my apologies. By physiological I'm including the nervous system/brain, so changes in mood/energy/motivation count. I have certainly noticed those changes in addition to other more physical changes.
posted by nightrecordings at 5:08 PM on March 16, 2016

Casual googling reveals that the more fit you are, the longer it takes the body to fully experience the full effects of detraining. According to the U of Berkeley:

When you stop exercising, many physiological changes take place. You begin to lose the cardiovascular (aerobic) gains you made—notably your heart’s ability to pump blood more efficiently, your muscles’ improved capacity to process oxygen, and your body’s enhanced ability to use carbs for fuel. Training-induced improvements in blood pressure, blood cholesterol, and blood sugar levels start to disappear. And when you stop strength training, you slowly lose the gains you made in muscle fiber size and other neuromuscular training adaptations.

Even two weeks of detraining can lead to a significant decline in cardio fitness, according to the American College of Sports Medicine. Not exercising for two to eight months leads to loss of virtually all fitness gains. In general, the loss of aerobic capacity occurs more rapidly than declines in muscle strength.

Apparently, if you detrain completely for a significant period of time, it will take just as long to return to your previous level of fitness as it took to get there in the first place.
posted by xyzzy at 5:18 PM on March 16, 2016 [1 favorite]

You can watch the changes in your resting heart rate in real time -- take your pulse the old fashioned way, or there are lots of apps for your smart phone that will do it for you. My RHR on waking rose about 10 bpm within a month of needing to leave the gym due to injury.
posted by telegraph at 5:39 PM on March 16, 2016

I am going to completely not answer your question:

What Happened When I Stopped Exercising
I ran cross country and track in high school and college. After that I ran several Ragnar Relays, a few half marathons, and ran a marathon in Boston-qualfying time. My general pace for a daily run was 7:30 to 8:00. At 25 I stopped running but continued biking to work. Then at 28 I stopped biking to work. From 28 to 30 - the time I did not exercise - I lost 20 lbs without trying, my blood pressure remained low, and my cholesterol rose negligibly. Once or twice in that time I went for a ~3 mile run at a 9:00 pace.

Now That I Have Started Exercising Again
I started exercising regularly again about three weeks ago. In that time a fair amount has changed for me.
1. I eat 3 meals a day instead of 0-2ish, I am conscious about what nutrients I am eating and making sure that my meals won't interfere with my workout.
2. I am sleeping more and going to bed earlier because I am tired, but I am also more alert and awake during the day.
3. My productivity at work compared to a month ago is night and day: being interrupted in the middle of a task won't derail my day; I am finishing everything I start, wrapping up my day that same day instead of the next morning; I have much more impulse control, like I am able to think before I do things like reviewing documents before I call the person to talk about the documents. And yet, I'm leaving work earlier because I need to get home to fit in my workout.
4. I am doing more chores more often. I work out at home, and when I'm cooling off I will wash some dishes or sweep or whatever. I just feel more inclined to practice self-care, and keeping my home in order becomes a part of that.

To make a dorky analogy: if my good habits and practices are bricks, working out is the mortar that holds them together. I have no idea why but I know that now that I'm working out it is worlds easier to keep my defects at bay.
posted by good lorneing at 7:47 PM on March 16, 2016 [4 favorites]

One proposed mechanism for how exercise positively affects mood involves tryptophan transport into the brain. Tryptophan is a precursor to serotonin, and it has to compete with branched chain amino acids in the serum for transport across the blood-brain barrier. Prolonged rigorous execise creates a favorable ratio of tryptophan/BCAAs in the blood, resulting in a higher rate of tryptophan transport, and ultimately serotonin, in the brain.
posted by gimli at 9:31 PM on March 16, 2016 [1 favorite]

Even two weeks of detraining can lead to a significant decline in cardio fitness, according to the American College of Sports Medicine. Not exercising for two to eight months leads to loss of virtually all fitness gains.

My RHR on waking rose about 10 bpm within a month of needing to leave the gym due to injury.

This has to be the most demotivating thing regarding working out that I have ever read. Literally my kneejerk reaction was, "jesus christ why bother then" (Upon further thought, I know there's lots of good reasons. But that was the first thing that popped into my head, and I still feel like it makes it awfully Sisyphean.)
posted by gloriouslyincandescent at 11:55 PM on March 16, 2016 [3 favorites]

gloriouslyincandescent, it strikes me as exactly opposite. If you could get and maintain the benefits of exercise without doing it frequently and regularly, then what a fucking waste of time it would be for all those poor sods who hit the gym every day!

Also, for what it's worth (opposite to OP's request), while my aerobic fitness seemed to fade rapidly, my strength was shockingly persistent. All told I was out of the weight room for about 18 months, and when I came back it only took six months before I was as strong as I was before the whole unpleasant incident. Muscles remember, even when it seems like they're gone.
posted by telegraph at 5:18 AM on March 17, 2016

Related to detraining, but a way to prevent some loss of detraining is to consider strength as the capacity of both the 1) muscle fibers, and 2) the brains ability to signal the muscles. Googling will show a number of studys that will show that "thinking" of doing the muscle exercises (just motor visualization, not isometric exercise) can still help keep the strong signaling from the brain even if the muscle's will atrophy to the same degree. Total strength loss as defined by ability to do an exercise to failur will have the group doing "thinking" exercises showing less loss than the control immobilized groups doing nothing.

quick link example: http://jn.physiology.org/content/112/12/3219.
posted by nobeagle at 7:23 AM on March 17, 2016 [2 favorites]

io9 addressed this issue in a well-researched article a few months ago.
posted by Fuego at 7:45 PM on March 18, 2016

I don't sleep as well.
posted by jessca84 at 11:05 PM on March 18, 2016

Less frequent bowel movements, which I find really unpleasant
posted by bluedora at 1:56 AM on March 19, 2016 [1 favorite]