The idea that you build muscle by “breaking it down” and then “building it up” during recovery may be a flawed one. Studies measuring muscle damage (Z-lines, strength after a workout, muscle soreness) show no relation to muscle gains. Adjusted markers of muscle growth (MPS) are the same regardless of muscle damage.
What IS noted is that muscle damage and muscle soreness is highest when you start a new workout routine, but decreases a lot after around 3 weeks of training. It is during these 3 weeks that you risk training “sub-optimally”. At the same time switching things up (periodization) has been shown to improve gains.
So do switch things up every 12 weeks or so, but start easy to give your body time to adapt.
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