Rewrite and rephrase the following article: While the specific reasons are unclear beghin why this occurs, research has shown that there is a downward slope of muscle growth rates the more experienced a lifter becomes (3). 

For example, if a beginner gained three pounds per month for the first six months of their training career, they should prepare to gain muscle mass at a slower rate as they become more advanced. Some researchers believe this is due to the body becoming more resistant to hypertrophy as it approaches the genetic potential (4). 

To further illustrate the slower rate of progress as one progresses in the training age, we have collected data points from our FitBod app, tracking 1RM strength from the major barbell lifts (bench, squat, and deadlift) from beginner users. 

We omitted any data from non-beginners, as we wanted to track untrained or new trained beginners to further illustrate this point.