How does speed affect intensity of exercise?

Answer 1

The word intensity as it applies to Prilepin's chart for determining the optimal weight for reps and sets, is one thing, but I will assume you are asking what is the effect on your central nervous system if you perform an exercise faster. If you train faster with an increased speed, you will become faster in that exercise. Training slow makes you slow. There are those who say that as long as you train to failure, you will be activating the fast twitch muscle fibers and so you do not have to train so fast but most strength athletes use some type of speed training.

It must be noted that for speed strength training to have any great effect on your athleticism, you should be fairly strong first. Lift heavy things first and then work on your speed. This seems to be the best protocol.

Answer 2

If you have a good posture alignment, you have a forward lean which possibly has an effect on speed. Also if you run fast, you tend to lean forward. A good posture is very important, since a bad posture increases the risks of injury, when you run.