It’s a coordinated effort of lots of reps, progression, with growth-signals (namely food) to pack on size. Most women who are afraid to “get big” are actually training for size by performing lengthy exercise efforts (like walking) and lifting light weights. If they trained super heavy for few reps with eating in check, they would get SMALLER.
Watch and learn (video here: https://www.instagram.com/p/B-zNqbxD-ue/). The first guy has a pretty average gym-goer build. He’s squatting 675lbs with a pause and no belt. He performs cleans with 500 and deadlifts 750. With a long sleeve shirt on, he doesn’t even look like he lifts. Legs are below average for an athlete. The second guy is in the middle of a circuit with light-to-moderate weight for lots of reps. It’s obvious he works out.
People think training like the first guy is what produces size, so they end up training like the second guy, lots of light reps, lengthy exercise sessions, sweaty, hungry all the time, and incapable of getting smaller. Ironically, avoiding heavy resistance keeps people bigger.
I realize that digging into exercise science and known physiology/biology is too much for most people, so I won’t bother with discussing fiber types, load-volume, tempos, TUT. But suffice it to say you aren’t going to just gain a bunch of size by getting strong. Don’t be an idiot. It doesn’t work that way. It CANNOT work that way. And you MUST become stronger to have any hope at improving health and fitness prospects.