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An intense, 20-minute workout may enhance long-term memory by as much as 10 per cent in healthy young adults, according to researchers behind a small new study from the Georgia Institute of Technology...
Making muscles grow does involve weight training -- to that I'll agree. But stay with me.
It also involves lifting weights at a particular intensity (that means how heavy the weights are), combined with a particular volume (that means just how many sets of a given exercise you do in each workout). Remove one of those two factors, and your muscles won't grow.