Muscle mass peaks in the late twenties and begins to decline slowly in the thirties, more noticeably in the forties, and accelerates thereafter. This is not primarily about testosterone. It is largely about the interaction of activity levels, protein intake, and the muscle's declining response to a given training stimulus, a phenomenon researchers call anabolic resistance.
The practical news is that trained men in their forties, fifties, and sixties can still build meaningful muscle. The methods do not change dramatically, but the margins for error narrow.
What actually changes
Several things shift with age, and they matter for how you should train and eat:
- Type II muscle fibers, the fast-twitch fibers responsible for power and much of muscle mass, atrophy faster than type I fibers
- Recovery slows, so the same volume that was tolerable at 25 can produce cumulative fatigue at 45
- Tendons and joint tissues adapt more slowly than muscle, which raises injury risk when volume ramps quickly
- The anabolic response to a given dose of protein or a given training set is blunted, meaning you often need slightly more of each stimulus to get the same result
- Sleep quality often declines, and sleep is where recovery happens
What does not change much is the fundamental principle. Progressive overload, adequate protein, and consistent training still drive hypertrophy. The changes are mostly in dose, recovery, and injury management.
Protein, in practical terms
The older recommendation of 0.8 grams per kilogram per day is a minimum to prevent deficiency, not an optimum for building or maintaining muscle. Research on older adults consistently supports higher intakes, typically in the range of 1.2 to 1.6 grams per kilogram per day for men who are training, and possibly more in periods of aggressive muscle-building or dieting.
Just as important as the total is the distribution:
- Aim for three to four protein-containing meals per day
- Each meal should provide roughly 30 to 40 grams of quality protein, enough to maximize the per-meal muscle protein synthesis response
- Include a protein source near training, though the specific timing matters less than total daily intake
Leucine, an amino acid particularly important for triggering muscle protein synthesis, is more concentrated in animal proteins and dairy. Plant-based eaters can still build muscle but generally need higher total protein and thoughtful combinations.
Training that works after 40
The research is consistent: heavy resistance training remains the most effective single intervention for maintaining muscle and strength as you age. The specifics that matter most:
- Compound movements, some pattern of squat, hinge, push, pull, and carry, remain the base
- Load matters more than variety. Two to four sets per exercise, in the 5 to 15 rep range, close to failure, drives most hypertrophy
- Frequency of two to three sessions per muscle group per week outperforms once-weekly training for most people
- Warm up more than you did at 25, and treat mobility work as part of the training, not optional
- Program deloads, planned weeks of reduced volume, every four to eight weeks
Cardio is not the enemy of muscle. Two to three sessions per week of aerobic work, mixed intensity, improves recovery capacity and cardiovascular health without meaningfully interfering with strength gains for most people.
The single most preventable derailment in a training program past 40 is the injury from doing too much too soon. Progress in ten-percent increments, not fifty.
Recovery, sleep, and the boring parts
Sleep is where most of the tissue repair happens. Consistently getting under six hours reduces muscle protein synthesis, raises cortisol, and impairs training performance. Address sleep before adding supplements.
Alcohol interferes with recovery meaningfully at higher doses, and its cumulative effect on body composition after 40 is not subtle. This is not a call for abstinence, but the tradeoff is worth naming.
Supplements worth considering
Most supplement categories are noise. A few have consistent evidence:
- Creatine monohydrate, three to five grams daily, is the most-studied performance supplement and helps preserve muscle and cognition as you age
- Whey or a comparable protein powder as a convenient way to hit daily targets
- Vitamin D if you are deficient, which many men are
Testosterone therapy is not a shortcut to muscle for men with normal levels, and it carries real tradeoffs discussed elsewhere.
The bottom line
Building muscle after 40 requires more attention to recovery, protein, and injury prevention than it did at 25, but the fundamentals still work. Lift heavy things, eat enough protein, sleep, and stay consistent. The men who look and function well at 60 are almost always the ones who kept doing this quietly for decades.