How many times a week should you train a muscle for more growth?

Short answer

The number of sessions itself had almost no effect on muscle growth. With the same weekly sets, training a muscle 1 time or 2-4 times a week grew it about the same. What drove growth was the number of sets.

How many times a week should you train a muscle for more growth?
'More often = more growth' — does this formula hold?
Chest on Monday, back on Tuesday: some say hitting each muscle only once a week holds you back, and that you need 2-3 sessions per muscle to grow more. We checked the research step by step.
At first, 2 times a week won
10 pooled studies favored it over 1 time a week
A 2016 analysis that pooled 10 studies found that training a muscle 2 times a week gave a higher growth score, 0.49, than 1 time a week (0.30). That is where the '2 times per muscle per week' rule spread from.
But once weekly sets were matched
The difference disappeared across 25 studies
A 2019 analysis of 25 studies found that when weekly sets were the same, training more or less often made no difference to muscle growth. The result held for upper and lower body alike. Only in studies that did not match sets did higher frequency come out slightly ahead.
Head-to-head trials agreed
16 sets in one session or split in two grew the same
When 20 people trained each muscle 1 time a week with 16 sets, or 2 times a week with 8 sets, for 8 weeks, arm and thigh muscle thickness changed no differently. When 21 people split the same sets into 2 or 4 sessions a week for 9 weeks, muscle gains were also the same.
Sets built the muscle, not sessions
Across 2,058 people: more sets, more muscle
A 2026 analysis that pooled 67 studies and 2,058 people found that muscles grew more as weekly sets rose (with smaller gains as sets climbed). Weekly frequency, by contrast, had a negligible effect on muscle size. Where frequency clearly mattered was strength.
So is splitting sessions pointless?
Splitting let people lift more total weight
When 18 people did the same leg sets either in 1 day or spread over 3 sessions for 6 weeks, the split group lifted 58% more total weight on squats and 76% more on leg press. Thigh thickness still grew the same. The payoff of splitting was lifting more weight with the same sets, not bigger muscles.
Bottom line: weekly sets come before frequency
Pick your sets, then split them however suits you
With the same sets, training a muscle 1 time or 2-4 times a week grew it about the same. With 16 sets a week, 16 in 1 day or 8 twice both work. If your last sets fall apart in a long session, splitting into 2-3 sessions works, and for strength, training more often had the edge.