All individuals are capable of gaining muscle mass through repeated resistance training over time, and true nonresponse to resistance training is not consistent across different training periods, suggesting that failure to gain muscle during one training phase is not attributable to genetic limitations.

Study: Higher resistance training volume offsets muscle hypertrophy non-responsiveness in older individuals.

Some people don’t grow muscles with light workouts, but this study shows they can still grow muscle if they do more reps or sets—so it’s not their genes holding them back, just that the first workout plan wasn’t enough.

Study: Repeated Resistance Training Reveals the Reproducibility of Muscle Strength and Size Responses Within Individuals

The study shows that people who don’t gain muscle in one training period often do in another, so not responding isn’t permanent or due to genetics.

Study: Skeletal muscle mass, strength, and physical performance gains are similar between healthy postmenopausal women and postmenopausal breast cancer survivors after 12 weeks of resistance exercise training

The study found that both healthy women and breast cancer survivors gained muscle from weight training, showing that most people can build muscle with exercise, even if they’ve had health challenges.

Study: Muscle Mass and Strength Gains Following Resistance Exercise Training in Older Adults 65-75 Years and Older Adults Above 85 Years.

The study shows that even people over 85 years old can build muscle and get stronger with regular strength training, just like younger seniors. This supports the idea that almost everyone can gain muscle with effort, regardless of age or assumed limitations.