JOKER47 said:
Ok. What would the benefit be in doing 3 reps with a weight you can do 10 reps with? Wouldn't even fatigue the muscle. (Speed work not being the goal.)
I do light weight at the end of a workout using high reps. That gives me a nice "pump", burn, and fatigues the muscle nicely. 3 reps wouldn't accomplish the same thing.
To use your analogy, I wouldn't walk a marathon that I could jog either. No benefit to my training as a runner.
oker
well remeber you do more than one set.
firstly you'll move every rep of each set faster, more force, every rep will have better form. I could easily do 10x3 with that sort of weight, and every rep would be pretty close to each other in force output and speed, plus look good form wise.
in your 10 rep set the last 4 reps will gradually get worse in form and slow way down and you'll be busting nuts to complete them - big CNS strain. First set you get 10, next set you may only get 7 reps with even worse form, then third set you may get 5 hard reps. Next set maybe 3-4 reps, and so on.
at the end of the session we both get the same amount of work
done, but I'll be in much better shape than you are, and I'll recover faster, and probbaly won't be as sore as you are

I'll get stronger faster and I'll gain as much mass as you are, but mine will be more functional.
Don't forget you attempt to maximally acclerate the weight. This would not be like walking, but doing 30m sprints

Sure you can do 100m sprints, but 30m ones work just as well, they work power better and you can do more of them in a session, which leads to "mass gains"