Here’s another absurd belief that needs to be vanquished. 

Muscles exist to contract and produce force. Activity is the reason muscle exists. And strength training is activity designed to maximise the muscles capacity to get work done. 

Muscle does not just disappear the moment you stop training. Like a parked Porsche, muscle lays in limbo waiting for activity and a chance to work. The longer it remains idle, the more work it will take to get it started. 

After a while, the Porsche rusts away and can’t be used. But at no point does the Porsche become a Wagon-R. 

Takeaway

Here’s what happens when you stop training:

1. The muscle gradually goes away. Simply because, systematic activity or regular load bearing activity is the reason muscle exists in the first place. When the stimulus stops, the muscle slowly but surely starts to go away. 

2. Strength training is not the most energy intensive thing one can do. But it provides the best value for time spent in terms of improving joint health and optimal stimulus to retain muscle. When you stop training, you stop spending the 200-500 calories possibly spent on exercise. If you don’t reduce your food intake by a similar level, this amount contributes to an energy surplus that becomes body fat. 

In summary if you stop training especially after a productive stint packing on muscle and strength, the result is a double whammy, you spend fewer calories and you lose muscle too. 

Your body composition worsens as you lose muscle.

And surplus energy is stored as fat since there is no stimulus for muscle to be retained.