Most exercisers train 5-6 days weekly at moderate intensity. Fewer harder sessions (3-4 per week, with maximum effort) produce better outcomes — and allow recovery that actually drives adaptation.
What harder means
Last rep is genuinely difficult. Weight progressing weekly. Lifts feel like work, not movement. Recovery needed between sessions (delayed soreness, fatigue).
Train 3-4 hard days. Take 3-4 rest days (active rest is fine — walking, mobility). Most adults plateau because they train too often, not too little.