For optimal muscle growth, research suggests that 3-5 exercises per major muscle group is a good starting point. This allows for sufficient time to complete each set and rep range, without overwhelming the muscles. However, it's also important to consider the volume and intensity of your workout routine. Increasing the number of exercises by 1-2 can lead to greater muscle growth, but be cautious not to overdo it. For example, instead of doing 3 sets of 12 reps for each exercise, you could try 3 sets of 8 reps with 1-2 additional exercises that target different muscle fibers.
It's also worth noting that muscle growth is highly dependent on rest and recovery time. Adequate sleep, nutrition, and supplementation can play a significant role in muscle hypertrophy. Don't skimp on sleep, aim for 7-9 hours of rest per night to allow your muscles to recover and rebuild.
A well-balanced workout routine should include a mix of compound exercises like squats, deadlifts, and bench press, as well as isolation exercises that target specific muscle groups. This will help ensure that you're working all the major muscle groups and allowing for proper recovery time between sets.