How many rest days do I need?
Rest the muscle, not the week: train each muscle about twice a week with a day or two in between, which usually leaves two or three days off.
Lifting four days a week is not four days of work for your chest. What needs the day off is the muscle you hammered, not your whole body, which is why splits exist.
Two rules cover most people. Leave a day between hard sessions for the same muscle, and take a full day off when sleep is short, joints ache or your lifts drop two sessions in a row. Walking, easy cycling and stretching on those days are fine; they are not what you are recovering from.
Soreness is a bad signal here. It fades as your body adapts to the exercise, not as your training stops being hard.
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- Schoenfeld, B.J. et al. (2016). Effects of resistance training frequency on measures of muscle hypertrophy: a systematic review and meta-analysis. Sports Med 46(11). Training a muscle twice a week beat once a week; beyond twice the evidence thins.
- Ratamess, N.A. et al. (2009). American College of Sports Medicine position stand. Progression models in resistance training for healthy adults. Med Sci Sports Exerc 41(3). Novices: two to three sessions a week covering the whole body, with days between them.
- Damas, F. et al. (2018). The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis. Eur J Appl Physiol 118(3). Damage and the repair response fade as you get used to the training, so early soreness is a poor guide to how much rest you need.