Training a muscle group TWO times per week and FOUR times per week has a similar effect on muscle growth and strength when weekly training volume is identical.

(Hamarsland et al., 2022)

There are three key variables we can manipulate in strength program design to optimize the results; Intensity (Load), Volume, and frequency. And there are many different ways you can use these variables in programming.

Hamarsland et al., 2022, a randomized controlled trial compared the effects of volume-equated training frequency on muscle mass and strength gains.

Twenty-one moderately participants were assigned into one of two groups.

1.    Low-frequency group – 2 times per week

2.    High-frequency group – 4 times per week

Training Intensity and total sets per muscle group per week were identical.

Both groups improved 1RM for the barbell back squat, hack squat, barbell bench press, and machine chest press, with no differences between groups. Similarly, total lean mass, lean leg mass, lean trunk mass, lean arm mass, and vastus lateralis thickness improved in both groups, with no differences between groups.

Reference:

Hamarsland H, Moen H, Skaar OJ, Jorang PW, Rødahl HS and Rønnestad BR (2022) Equal-Volume Strength Training With Different Training Frequencies Induces Similar Muscle Hypertrophy and Strength Improvement in Trained Participants.