Everyone performing resistance training, always seems to be searching for the 'best parameters'. Volume, intensity, and frequency. We fear training too little and training too much. Somewhere in the blurred gray middle is the optimal dose. It can be very confusing, especially with 3 major parameters to adjust. Further, life's circumstances (stress, sleep, daily activity, etc.) can all change, which alters our recovery ability. What is optimal one week, or even one day, might be too much or too little the next.
Different training methodologies solve, or attempt to solve this by nailing down as many of the variables as possible. This leaves less parameters to worry about. If you only have one adjustable variable, it makes life much simpler. For example,
When the term "hardgainer" first came out, many people were over-joyed to find they weren't the only ones who were beating their heads against the wall, making small to zero progress. Then the label became a dirty word. Everyone who claimed to be a 'hardgainer' was lazy, copping the easy way out, making excuses. I'm sure there are people who really are "hardgainers" and people who really are lazy and use the term to justify not working hard. Just as their are people faking injuries to receive disability checks, as well as people who really are disabled and deserve the support. Calling all people on disability lazy is blatently wrong, just as calling all hardgainers "lazy" is the same. Everyone has a sum of all things in their life, that determines their ability to gain as well as their final level. Genetics, stress, mental outlook, age, nutrition, injuries, etc. etc. Just because one person finds that by increasing their volume, and/or frequency, and basically working much harder, that they gain better, does not mean this will work for everyone. Some, usually with robust recovery abilities, find that working harder always produces better gains. They tend to scoff at those who lose progress when increasing their training. They would need to walk a mile in a true hardgainer's shoes to appreciate what many of us go through. I myself, can feel the effects of overwork even the next day. An almost hung over feeling, usually accompanied by a headache, achiness, and other mild flu like symptoms. Some of us are much more fragile then they realize. So, depending on what you can handle, and what your doing, less or more might be the answer. And then, less or more of which variable?
First, we can look to other successes to see which options even possibly work. Let's take one at a time.
One can indeed increase the weight on the bar, without gaining mass. Beginners do this from actual neural learning and advanced trainees from coordination increases a.k.a. skill. But what you cannot do is get bigger without getting stronger. If the muscles are growing, they are adding myofibrils in parallel which automatically increase the strength of the muscle, (proportionally to the cross sectional area of the fibrils). Further, if you are increasing your strength, you are at least on the right track. If a program change slows your strength gains, you have made an error in that change. There is no program that will slow strength gains at the same time it increases mass gains. How you perform your exercises, your form, rep range, TUL, etc. is what affects the stimulation, not how many times you repeat it, or how often you repeat it.
So how do we know what we should do? First, everyone must do some experimenting. See how 'you' respond to different variables. Your mind, your body, all of you. Do you enjoy it? If you do not enjoy your training, you will not put the effort forth, or stick to the program to even reap the benefits, no matter how well it 'could' work. What one needs to do, is pick a sane approach and perform that routine properly. Keep an eye on progress, how you feel, etc. Then, adjust one of the three main parameters as needed. Re-check results. Did it help? Did it hinder? No change even? From knowing the huge variety of methods used for success, instead of feeling confused, we should feel free. It's ok to train twice a week, it's ok to train once every 10 days. What ever works best IS best. The take home message is this: If anyone says you 'have to' do this or that to succeed, think if it's really true. Has everyone who ever succeeded, I mean EVERYONE, done this? If not, it's false information and should be disreguarded.
You may not be able to train at maximum levels. Train at YOUR optimum, set your program up so it works during all periods of your life. Don't be afraid to adjust as needed. Complete changes can ruin progress but adjustments that help you continue to progress are good. In fact, very rigid programs are one of the main reasons for so many failures with training. A rigid program dictates that no matter how you feel, or what your progress is like, you must stick to it. It becomes more imporant to perform it, than to make progress. We train for results, not to serve a program.