Will I lose muscle if I take a week off from working out?

On Ep. 129, Nikkiey says significant muscle wasting generally doesn't start until about three weeks of inactivity, and even then the rate of loss is relatively low. On Ep. 366 she puts the window at two, three or four weeks of complete inactivity with no training stimulus at all. Either way, a single week sits well short of that line. She adds that most women come back from a lighter week feeling and performing better than before.

The reason your strength holds up is muscle memory and what Nikkiey calls neuromuscular adaptations, the connections between your brain and your muscles built through training. Those stay largely intact during short breaks. She describes feeling a little weak for the first couple of days back, then strong again within about a week. After two weeks off she noticed slightly less definition, but the muscle was still there, and she says the fear of losing progress is usually bigger than the actual change.

Where a break does cost you is when it stretches out. Nikkiey notes that two months off is a different story, and she points to the pattern of being off for weeks, back for two, then off for another month. On Ep. 274 she warns that the guilt spiral after time off can set you back faster than the time off itself, so let the break be a break and then pick back up.

And if the fear is about identity, on Ep. 251 Nikkiey shares that worrying her body would regress was the heaviest thought for her when she slowed down, and she came to see it as ego and conditioning. A week off doesn't undo years of work. Consistency over the long run is what builds results.