Changing exercises and body positions are needed to maximize muscle growth; it is important to change exercises frequently, but not too often. There needs to be some consistency in your workouts. If you change your workout from day to day, this can be counterproductive.
HOW OFTEN SHOULD YOU CHANGE YOUR WORKOUT ROUTINE FOR MUSCLE GROWTH SUMMARY
- Changing your workout routine too often may result in less favorable muscle growth.
- Consistently using an exercise will result in better strength gains than frequently changing exercises.
- Changing the exercise angle can increase muscle growth in various muscle regions.
4/22: CHANGING YOUR WORKOUT CAN LEAD TO BETTER MUSCLE GROWTH
A systematic review of the literature examined the effects of training variation and muscle growth. An overall positive effect for different exercises was found for strength and muscle mass.
However, they addressed that changing exercises too frequently can hurt muscle growth, potentially because of difficulty in achieving progressive overload.
Changing an exercise too frequently can cause excess muscle damage because there is no adaptation process with more prolonged fatigue. Moderate exercise variation was suggested to be better for increasing muscle mass, whereas excessively changing exercise can be detrimental to muscle growth.
They suggested that exercise variation has an inverted U-shaped curve, with moderate changes being beneficial and excess being detrimental.  In sum, if you are a bodybuilder looking for maximal hypertrophy, it is best to use a variety of exercises to stimulate different muscle regions. In contrast, a strength athlete will need less variation.
5/25 USE A VARIETY OF EXERCISES TO STIMULATE OPTIMAL MUSCLE GROWTH
If you want to optimally stimulate muscle growth, it’s best to use a variety of exercises. When a muscle increases in size, it does not increase throughout the entire region; individual parts (i.e., regional hypertrophy) are stimulated, and some grow more than others. Researchers had subjects train with an equal volume and intensity but performed two different exercises.
One group performed smith machine squats, and the other did leg extensions. Researchers used ultrasound and measured muscle growth in the legs in various muscle regions (25% and 50% of the femur length). The subjects followed a high protein diet of 2 g/kg/bw throughout the 5-week resistance training protocol.
The squat increased the vastus lateralis more, whereas the leg extension increased the rectus femoris to a greater extent. See the chart below. If you want to develop optimal leg muscle growth, the study suggests using a variety of exercises to stimulate muscle growth. (15)