Your muscles work best at the mid-range of any normal motion. This comes due to the best overlap for the possible contraction sites. At the endpoints of any motion, the sites that allow connections overcrowd or are too far apart. This means that although you may feel stronger or weaker at the endpoints because of your leverage, these positions always allow less tension. This would mean you do not need a great range of motion, especially as the endpoints of some exercises may harm your joints.
You also make tension by working hard with heavy weights. Heavy is relative. Training heavy means that the last reps feel difficult. A variety of rep ranges can build muscle and strength. Work hard to add weight within your range. As low as a single rep and as high as thirty reps can both work well. During the set though, you must eventually attempt to move the weight as fast as possible, even if the weight moves slowly. The intention to move the weight quickly activates the fast-twitch muscle fibers. It must feel heavy at the end of the set because this slows down the movement. Motions done too fast allow less tension, such as when sprinting. Some sites have too little time to form.
Tension, or the squeeze you feel when muscles contract, is the main growth factor to get stronger and more muscular. Studies show that if you create enough tension, for even a few seconds, that you can grow. So we know that by slowing down through heavy weight and by focusing on the mid-range that we can best develop it. Does this alone matter though? Perhaps not, according to some research and real-world evidence.
Secondary growth factors may influence strength and size greatly as well. The stress from anaerobic processes, such as when feeling the burn, may matter. The damage from mechanical stress that leads to micro-trauma and soreness may play a role as well. Mechanical stress comes from tension through a large range of motion. This causes inflammation that may lead to better growth by affecting your growth hormone and other factors. Stretching that occurs with a fuller range of motion beyond just the middle portion with the greatest tension may lead to more tearing. This may lead to more blood flow that supplies nutrients and remove fatigue by-products. The pump that occurs as you do plenty of reps may even aid this as well.
If these factors really count, you would want to avoid my style of training. I believe that only a single set of almost any good rep range done to positive failure works. Trainees may have a personal preference, but it does not matter much in my opinion. You just need to get stronger.
To address secondary growth factors, you would want more volume. Bodybuilders do many exercises and sets, lots of stretching, and get the pump and soreness from each workout. Those trying to do this efficiently may do a single heavy set. They then follow this up with a set of higher reps. Some call this a reverse pyramid. They try to include both going heavy and a little work that builds up some lactic acid for all major muscles. Maybe you could even do one set of at least moderate reps, a few low rep sets, or much more. You would try to add some more work without overdoing it so you can still recover. You would also strive for as full a range of motion as possible. This would help with the other factors beyond tension.
I have always found that strength mirrors size gains for an individual. Someone with better leverages, such as an Olympic weightlifter or powerlifter, may build less muscle per unit of strength. Muscle endurance, such as when dealing with lactic acid, seems unrelated to me. The other factors, such as tearing and hormone release, come sufficiently as side effects from focusing on tension. If the buildup of lactic acid perhaps fails to stimulate growth but may potentiate the recovery from the damage of heavy weights, then perhaps it does have value. In this case, I would argue that intervals satisfies these criteria. A series of brutal sprints with short rests will generate lactic acid, even though I use these for other reasons. I may have accidentally hit the sweet spot. I also feel this prevents overtraining. Either way, you address what heavy sets miss with intervals: getting your heart rate up and perhaps these secondary growth factors as well.
You have to experiment to figure these things out. I found I could skip thinking about secondary growth factors to progress. Tension reigns as king. Perhaps you will find differently. One thing I can assure you. Keep the same weights, year after year, and expect to look exactly the same. This will happen regardless of how much volume you do for the sake of secondary growth factors. In any case, I would argue if they do influence size and strength, you will find that intervals address them enough. You could perform these intervals after lifting, as I recommend anyway.
Following my methods may indirectly support secondary growth factors. You need to choose if you need more volume with lifting to address them further. As always, aim for efficiency. Never forget the importance of progress with heavy weights. I would argue this is all that you require.
Self-education is, I firmly believe, the only kind of education there is.
– Isaac Asimov