Mixed
Under volume-equated conditions, performing resistance training 4 times per week produces greater upper-body maximal strength gains than 2 times per week, while both frequencies yield similar improvements in muscle size (hypertrophy) and power.
If you can only train twice a week, focus on full-body workouts to build muscle size and power; you will get strong enough for most goals. If you have the time and want to maximize upper-body strength (like bench press), split that same total amount of work across four sessions. Do not increase your total volume when adding days; just spread it out.
four sessions of resistance training per week produced greater gains in muscular strength for the upper body measures (i.e, 1RM bench press and arm curl) when compared to two sessions per week under volume-equated conditions... RT with a frequency of at least 2 days per week is adequate to enhance muscle size
Why this rating
Randomized controlled trial with volume equating, though sample size is small (n=35) and participants are young recreationally trained men.
Source
Peer Review #1 of "Effects of different resistance training frequencies on body composition and muscular performance adaptations in men (v0.1)"
Hamid Arazi et al. · 2021
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