Strength training can be manipulated through volume and intensity to achieve different goals. The most common goals/phases of strength training are endurance/ anatomical adaptation, hypertrophy, strength, and power.

 Exercises done in the endurance/ anatomical adaptation phase use:

• a moderate amount of sets (3-4),
• a large amount of reps (>15)
• and a low weight (<60% of 1 Rep Max).

The goal of this phase is to get familiar with the exercise and to establish proper form. This phase is almost always the first phase in a strength training program.

The Hypertrophy phase will generally use:

• a large amount of sets (3-5),
• a large amount of reps (8-15) however, the intensity is increased generally hovering around 60% - 80% of 1 Rep Max.

The goal of this phase is to build muscle. Muscle mass is increased by placing more load on the muscle for a longer duration resulting in more microfiber tears. The micro tears are then repaired resulting in a larger muscle fiber.

The Strength phase will use:

• a large amount of sets (4-6),
• a low amount of reps (1-6),
• and a very high intensity (85% - 100% of 1 Rep Max).

The strength phase is used to improve the brain-to-muscle connections so that the muscle can exert more force. Essentially this phase teaches the brain and new muscle that was built from the hypertrophy phase to now be more efficient resulting in a stronger contraction.

The power phase is typically the last phase of a strength program. The power phase will use:

• a moderate to large amount of sets (2-6),
• a low amount of reps (1-6),
• and a moderate intensity (70%-85% of 1 Rep Max).

The power phase works similar to the strength phase where it is trying to improve the brain-to-muscle connection. The difference now is the element of speed is added to the equation. By lowering the overall intensity, speed can be introduced resulting in a quicker and more powerful movement. 

Through a combination of each phase, you can build a well rounded program that will help you maintain your muscle mass. Each phase should be given 2-4 days/week and 2-6 weeks to be built on with a recovery week in between each phase. Exercise selection will depend on what you have available, but a heavier emphasis should be put on large, multi-joint movements (ex: squat, deadlift, etc.).

Exercise machines can be a good place to start in the weightroom. Machines allow you to better isolate a certain muscle group, however the element of stability is removed due to the machine only being able to move in one directional plane. Machines are also easy to use so you don’t need as much experience in the weightroom to use them.

Free weights allow you to work multiple muscle groups at once while also improving stability of the joint. Free weights do require a little more experience to be able to identify proper form. Due to free weights' ability to incorporate stability training, more emphasis should be given to it. If you know you are very weak in a particular muscle group or are just starting in the weightroom then machines would be good to incorporate too. 

The maintenance of muscle mass can be difficult given the factors working against you. By incorporating strength training to your current training you can reduce, and to a degree, reverse the impact that age has on muscle mass. Being able to, or seeking out someone who can develop a strength program that transitions you through each phase will set you up for success. Finally, ensuring you are taking in as much energy if not more than you are using will also put you on the right track to maintaining muscle mass. Maintaining muscle may be tricky, but it’s not impossible.