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Will a 2-Week Vacation Ruin All Your Gym Progress?

It’s probably happened to you. You’ve finally gotten into a steady routine at the gym, showing up like clockwork every evening at 5:25 p.m. It’s taken you about a month, but your squats have been feeling great, you’ve managed to go a whole week without getting sore, and you swear your shoulders are looking more toned.


But your vacation is coming up, and you’ll be going to France for two weeks. Naturally, you’re thrilled to go because it’s been a lifelong dream to see the Eiffel Tower and the Louvre. But if you’re being completely honest about it, it’s stressful knowing you’ll be away from the gym for that long.

Not only are you worried that you’ll gain 10 pounds from all the croissants you plan to eat, but you’re afraid of losing a month’s worth of fitness. You know all those gains won’t stick around while you’re off galavanting in Europe, and that you’ll have to start all over when you get back.

Maybe you’re thinking you should just skip the gym tonight. After all, why are you working so hard for something you’re about to lose?

Before you get hasty and banish your gym sneakers to the darke

How Long Does It Take to Lose Strength?

You already know it takes a while to get stronger. You’ve also probably heard that if you don’t use those muscles, you lose them. But how quickly does that happen?

In 2016, a group of researchers was curious about how long it would take to gain strength, as well as how long it would last. So they designed a study to test it out. If they could show that even short-term training helped build strength, it would allow physical therapists and other rehab professionals to develop simpler and cheaper programs to help their patients recover from injury.

The researchers recruited 19 healthy men who were minimally active and didn’t have a regular gym routine. They divided them into two groups: a control group that didn’t exercise at all throughout the study, and an experimental group that participated in a resistance-training program.

What’s cool about the exercise program is that it wasn’t your typical eight-week cycle consisting of a variety of total-body exercises. No, the training program lasted only three days, and it consisted of only one exercise that worked only one limb. That’s right — the experimental group did only leg extension exercises with their dominant leg for three days.

After completing all three days of training, the participants came back to the lab three times for follow-up tests: 48 hours, one week, and two weeks after the final training session. All three assessments indicated that three days of training was enough to elicit strength increases from the participants. The strength of the trained leg, on average, was about 22% greater than it was during the pre-training assessment.

Yet that’s not even the most impressive statistic. All three post-training assessments showed about a 16% strength improvement in the untrained limb. Even the leg that wasn’t trained got stronger.

What’s more, these effects didn’t disappear instantly. The post-training assessments showed that even after the participants went back to their minimally-active lifestyles, their strength gains stuck around for two weeks.

How Does This Happen?

A lot happened in this study, and it might be challenging to comprehend. How did three days of training have such a noticeable impact on strength? How did those gains not vanish within one day of inactivity? And, for Pete’s sake, how did the untrained limb get stronger too?

It seems the brain might be responsible for all three of these effects. Let’s break them down.

1. Short-Term Strength Increases

When you first started working out, you probably noticed that you got a little better each time you stepped foot in the gym. Personal records came quickly, and improvements in strength and endurance were frequent and sometimes astonishing.

The initial improvements you saw were mostly due to neural adaptations. That means it’s not so much your muscles getting bigger (although that happens); it’s more your brain’s ability to activate the muscles you have. This effect is called neuromuscular efficiency.

That’s likely what happened to the participants in this study. It’s not that they suddenly developed more muscle fibers — it’s that their brain responded eagerly to the training and learned to activate the right muscles in just three days.

2. Detraining

Losing part or all of your strength after you stop working out is a principle called “detraining.” You can blame your brain for the bulk of this effect — at least at first. It likely happens because your neural drive — that is, the sum of all the brain signals going to your muscles — gets weaker. This decreases motor unit activation (which is your brain’s ability to stimulate the appropriate muscles) and prevents you from being able to bench press as much as you used to.

Some studies suggest that elite athletes experience detraining more quickly than recreational exercisers (or novices), but this doesn’t seem to be a hard-and-fast rule. A study done on both rugby and American football athletes showed that they maintained their strength levels for three weeks after pausing their resistance-training program. However, they did continue to practice their sports during this hiatus, which may have helped preserve their gains.

Even though it’s possible to retain strength for weeks without training, that doesn’t mean athletes are wasting their time by working out so frequently. Other research has illustrated that lack of exercise can cause rapid, significant declines in power output, even if strength is still unaffected — so it’s crucial that athletes stay in the gym.

3. Contralateral Strength Gains

Now, what about the leg that didn’t work for its strength? How can it just mooch off of the other limb?

You may notice that the researchers in this study had participants train their dominant leg. That wasn’t just an arbitrary choice.

In motor control theory, there is a concept called bilateral transfer, which means that learning a single-handed task is easier if you’ve already learned it on the opposite hand. While this effect happens in both directions, it’s generally accepted that the result is more pronounced if you train the dominant side first. That’s why the researchers had participants use only their preferred leg.

How do strength gains transfer to the untrained leg? There are a few different theories, but again, you can thank your brain! One theory is that you have a motor schema (a representation in your memory) of how to perform the movement, which is accessible by both limbs. Another is that the motor neurons activated during exercise also trigger the neurons that go to the same muscles on your body’s other side.

What This Means for You

Yes, the study exploring the effects of three days of strength training was intended to help clinicians write smarter rehab programs. But you don’t have to be injured to take advantage of this information.

Everything you just read means it’s okay to go on vacation and leave the gym at home. Especially if you’re active (walking along the beach, exploring Tokyo on foot, climbing the Swiss Alps), you won’t have to start over from scratch when you come back. Even though you may feel out of shape when you return, it’ll only take a couple of sessions to get your brain back online. Then you can pick back up where you left off.

This also means that it’s never too late — or too overwhelming — to start exercising. Your body can benefit from doing just one exercise for three days, which means you don’t need the fitness level of an elite athlete to see some meaningful improvements in your health.

So, lace up your shoes and get on your way! Your brain will be very excited.