Only progressively-heavy resistance with weight can build meaningful muscle strength with efficiency.
Cardio intervals, and other mostly-aerobic exercises like calisthenics and sports, can build or maintain useful endurance and athleticism, but not much strength.
(Athleticism and endurance are more important to me in life than strength and power. However, I had lost strength and muscle over time and, anyway, I think the Fitness Triad works in a synergistic way.)
- How much muscle mass can be gained in a month of heavy resistance work 2-3 times/week? At the very most, one lb for the ordinary person. Maybe dedicated gym rats can beat that, but not you and me. That would be 10 lbs. of red meat gain in a year, which is not likely or even possible for ordinary people like you and me. Maybe for body-builders who are able to lift very heavy.
Unless you are overweight or fat already, each lb. of muscle mass comes with about one lb. of fat+water. Not belly fat, but fat somewhere. That's the way it works. Because of my body build, I aim for wiry strength and not bulk. My physical structure can't and won't bulk and that is fine with me. As I have reported, though, my superb trainer wants to see some more red meat on me so I am trying to follow his dietary orders to eat more food.
- Recovery: Pushing and pulling heavy weights requires 4-5 day recovery for ordinary people. That's why I keep it simple and do weights with each muscle group just once a week. Cardio and Calisthenics do not need recovery days under ordinary circumstances.
- A proper diet is required for muscle recovery. I am working on that.
- Importance of high-weight and low reps: For large muscle groups - ie back, chest, and legs - pretty much everybody recommends approx 4-5 sets of 3-8 reps, working up towards about 80% of your one-rep max weight. In short, if you can do 10 of a large-muscle group, you need to increase the weight. Basically, high reps (more than 10) of these big movements (bench press, barbell squat, deadlift, pull-ups, leg press, military press, rows, inclined press) at lower weights are probably counterproductive and should be avoided.
- Does that low-rep plan apply to smaller muscles or isolated muscles? Not so much. When it comes to things like curls, tricep exercises, calf lifts, straight-arm pushes, skull crushers, leg curls, pull-downs, and the like, it seems fine to burn it out or do drop sets sometimes.
- Skeletal muscle diminishes with age. It is called muscle atrophy and is a normal part of aging. Unused cells die. That is termed apoptosis, like leaves falling from a tree. Atrophy of age is normal, that is, unless the muscle is put to stressful work. With work, muscle can be maintained or rebuilt to some degree at any age.
- How quickly does muscle lose strength without stress? The strength in a muscle begins to diminish after a month unless it is adequately and regularly stressed. Not used, but stressed. The human body, in its wisdom, sees no need to maintain something for no reason. That's the "use it or lose it" aspect. Similarly, heart muscle needs to be stressed regularly to stay tough.
Please discuss. We seem to have plenty of fitness-oriented readers of all ages and genders sexes.