Strength can be maintained without training up to 3-4 weeks, but is gradually lost thereafter (strictly speaking, you can temporarily lose strength before this, but it comes back so quickly during retraining that it doesn’t matter)
Muscles start to atrophy after 2-3 weeks, though gains usually come back quickly, at least in beginners.
Endurance performance decreases by 4 to 25% after 3-4 weeks.
VO2 max declines by 6 to 20% in highly trained athletes at around 4 weeks of detraining.
Beginners can maintain endurance performance for at least 2 weeks without training, though recent VO2max gains can be reversed after 4 weeks.
Muscle, strength, endurance, and fat gains/losses vary from person to person (genetic inter-individual variability)
You look smaller during the first weeks of detraining because muscle glycogen stores shrink, not because you lose mass (though, the muscles literally become smaller because glycogen binds water). Good news: the effect is temporary since glycogen stores quickly expand when you resume training.
Flexibility is reduced after 4 weeks of detraining by ~7-30%
Bed rest/immobilization speeds up muscle atrophy
To maintain strength during 4+ weeks of detraining, train at least once per week (for beginners). Trained lifters could maintain strength gains with eccentric training.
To maintain hypertrophy during 4+ weeks of detraining, train at least once per week (for beginners). There’s not much long-term data for trained lifters, but eccentric training could help.
To maintain endurance during 4+ weeks of detraining, you can lower training volume by 60 to 90%, training frequency by no more than 20-30% in athletes but beginners can reduce it by 50 to 70%. Training intensity should be the same.
If injured, use alternative training forms such as strength training (which can maintain some endurance performance) or underwater running.
It’s easier to regain strength and muscle mass once it’s lost because of muscle memory (myonuclei and neural adaptations).
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