Muscle loss is a really complex process. Simply put, it is an ongoing tug-of-war, between muscle protein synthesis and muscle protein breakdown, where the muscle protein breakdown side starts to win gradually.

How quickly that tug-of-war turns in favour of muscle loss, first depends on just how little you’re doing physically.

Scientific evidence tells us that, if you don’t do any physical activity at all, you can lose a lot of muscle really fast. A 2016 study from Dirk’s and colleagues found that:

“Complete bed rest caused significant muscle loss, in just one week.”

However, this study may not be relevant to many of you, since these subjects weren’t regularly training in the first place. Also, unless you’re seriously injured or hospitalised, chances are you won’t be restricted to a bed for 7 days. Even if you’re not training at all, chances are most of you will still be getting out of bed and doing some sort of everyday activity.

And, as it turns out, just walking around is actually quite a lot better at preventing muscle loss, than lying in bed all day, even if you aren’t actually training.

This was evidenced in a recent study from Hawaiian colleagues, where they took 20 subjects, with at least one year of training experience and had them stop training altogether for two weeks, but still carried out their regular daily activities.

So, with no complete bed rest this time, there was no significant drop-off in muscle mass, after two weeks of not training.

3 WEEKS BREAK

However, after two or three weeks of no training, most people are going to start noticing some muscle shrinkage. This is the same time frame, that muscle researchers Fisher and Steele cited in their review of evidence-based recommendations for hypertrophy, quoting:

“Up to three weeks is the maximum time frame you can take a break, without fear of atrophy”.

On the other hand, some experts claim that this isn’t actually true. They believe that, muscle loss is mostly just a loss of glycogen and water stores, inside the muscle and not actual contractile tissue loss.

This theory would explain why the rebounds we see after short breaks are so quick. If it’s just water and glycogen loss, those fuel stores should refill very quickly, as soon as you start training again.

2 MONTHS BREAK

Thus, not training for up to three weeks doesn’t seem to be too bad, as long as you are moving around. But, what about training breaks that last longer than this? What if you’re forced to skip you Calisthenics workouts, for about two months?

Well, based on studies, it seems that you could expect to lose up to half of your gains, if you take two months off. In a 2006 study, they put subjects on an eight-week training program and then have them abruptly stopped training, for another eight weeks. So about two months on, followed by two months off.

During the first two months they saw a 10% increase in muscle size, but during the two months of no training, they saw those gains cut in half.

So, even after two months of no training, they still kept about half the muscle they had built in eight weeks, by just continuing everyday activities. That is fairly encouraging, especially if you consider that most people should be able to do a little more than simply get out of bed.

Now, keep in mind these subjects were essentially newbies, so they trained for two months and then took two months off. Most people with more training experience, might see less relative loss in that same time frame.

HOW TO AVOID MUSCLE LOSS

So, can you figure out how much muscle much is in stake, each time you take a break? The answer is really complex…

However, there are three main factors that determine, the amount of muscle you will, actually, lose.

1. Apply some tension to the muscle

As we’ve seen, complete bed rest is a lot worse than just walking and doing everyday activities, because those simple movements will, mechanically, activate most muscles to some extent.

That itself will, also, be quite worse than doing simple bodyweight workouts, which is probably a bit worse than doing advanced Calisthenics training.

On a 2011 study, Bickel and colleagues found that:

“Even reducing training volume all the way down to 1/9 of what you were doing before, was enough to maintain muscle mass on average for 32 weeks.”

This is quite encouraging, as it states that even low volume workouts should be enough to keep most of your muscle hanging around, for at least six or seven months.

2. Eat enough protein

Muscle mass is built when the net protein balance is positive (+) : muscle protein synthesis exceeds muscle protein breakdown.

In general, it is recommended that 10-35% of your daily energy intake comes from protein. So, 1.2-1.7 grams of protein per kilogram (or 0.5-0.8 grams per pound) of body weight per day is a good range for dieting trainees.

3. eat at maintenance calories

How much muscle you lose depends on your diet and, especially, your total caloric intake.

A new paper, published last year from Alan Aragon and Brad Schoenfeld, noted that:

“A sustained energy deficit compromises muscular potential, by inhibiting muscle protein synthesis and molecular anabolic signalling, whereas being in a caloric surplus provides the ideal milieu for promoting muscle growth.”

While this research is focused on maximising muscle growth, this same advice still holds on minimising muscle loss. This is because, muscle loss is ultimately driven by muscle protein synthesis losing the tug-of-war.

Consequently, you want to avoid being in a caloric deficit and at least, eat at maintenance or in a slight caloric surplus, if your main goal is to avoid muscle loss.

AGE

Another thing a lot of people worry about is age.

Based on the mountain of research, exploring age-related muscle loss, it would seem reasonable to assume that, muscle loss from not training increases as you get older.

However this isn’t actually all that clear. According to a 2016 review in the Journal of Frailty and Aging, it appears that:

“Periods of muscle disuse result in muscle losses of a similar magnitude, compared to the young.”

Nevertheless, these authors still highlight the importance of muscle mass maintenance from metabolic health, in aging.

With that being said, the Bickle paper from earlier did find that, the 1/9 training volume protocol was only enough to maintain muscle mass in the younger group and not in the older group. This could imply that, older individuals need amore volume to keep their gains sticking around.

Conclusively, for anyone under 60, just hitting simple bodyweight workouts, once or twice per week, should be enough to keep the muscle you’ve built hanging around.

muscle memory

Even in the unlikely event of, you deciding to do absolutely nothing for the next two months or two years, worry not. It’s a lot easier to rebuild lost muscle, than it is to build new muscle from scratch.

A famous pioneering study from 2010 showed that:

“Muscle nuclei that were formed during training, stuck around basically forever.”

The original theory was that, as soon as you start training again, those nuclei can start pumping out new muscle proteins and you rebuild all your lost muscle.

Even though, this was the prevailing theory up until about the middle of last year, this research was performed on rodents. And as it turns out, a new study from Snijders and colleagues, conducted on humans this time, found something different:

“Myonuclear content increased significantly with training, but returned to baseline after 1 year of not training.”

So maybe they don’t stick around forever after all…

This has led many experts in the field to wonder if epigenetic changes are, actually, playing the main role in muscle memory.

Conclusively, while the actual mechanism is currently up for debate, the existence of muscle memory itself is not. Whether owing to nuclear tension or epigenetic modifications, muscle memory is real and it will help you build back any muscle that you lost, a lot faster than it took you to build it in the first place.