First and foremost, many people lack the mobility and movement control to execute heavy loaded barbell movements safely. They would be better served focusing on exercises that establish proper movement patterns, build core stability, and stress the joints and muscles in ways that build them up instead of tear them down.

The basic movement patterns that train your lower half—squatting, hinging, lunging—produce the greatest metabolic response. Most importantly, having a strong lower half is the best way to protect your body from the most common pain points: low back pain and knee pain.

the obsessive focus on splitting up all the muscles of the upper body, dedicating an entire training day to each, while neglecting the biggest muscles in the body: the legs. It makes absolutely no sense to train the lower half of your body only once per week while giving all the smaller muscles so much detailed attention.

Another problem with bodybuilding programming is

most bodybuilding routines blatantly neglect all exercise that doesn’t have the pure purpose of building muscle mass. Mobility work, core stabilization training, endurance exercise, and joint-building movements all get left by the wayside.

One problem with this approach is that your muscles don’t work in isolation. Each primary muscle has an entire cast of stabilizing muscles that surround it. If these smaller stabilizing muscles are neglected, muscle imbalances occur that quickly create movement faults, mobility restrictions, and joint irritation.

The workouts consist of set after set of mass-focused movements, usually in the form of isolation exercises and machines to target the muscle of the day.

Research from the American Journal of Medicine shows that aging adults can gain nearly 2.5 pounds of lean muscle and increase their overall strength by 25% to 30% with just four to five months of consistent training.

Another study from the Canadian Journal of Applied Physiology found that the primary driver of age-related muscle loss (sarcopenia) was not age itself but reduced neuromuscular activity.