As we saw in the last post, the group of people who put together the exercise programs originally, had only one thing in mind - health. It would make sense to think that a program with this in mind would have to be safe. You won't be doing any exercise is you are injured... Compare this to a lot of the "exercise programs" out there now - Crossfit, P90X, Interval Training etc. - they all have a high risk of injury. They are more like playing a sport. Sports are fun, but they are not - in my humble opinion - exercise.
So what is exercise? It's work. It's work with a very satisfying result at the end. It's kind of like digging a big hole in order to plant a fruit tree. It's hard work digging the whole (especially when you think it's deep enough, put the tree in and realize you have an other 2 feet to dig!) but when you do get the tree in, you feel great, and your reward is watching it flower in the spring and bare fruit. Exercise is like that. It's hard, but you get a reward for that hard work.
So this is one of the reasons we go slow. To make it harder. It's not really to make it harder, but more about making the movement more efficient. The slower you move a weight, the less momentum and speed help to make it easier.
Imagine you are holding 40 pounds in your hands and then you slowly lift it up above your head arms out stretched. You could say that the weight is above your head, and you put it there. Now imagine putting the weight above your head, but this time giving it a little swing and tossing it up above your head and then catching it. Both times, the weight was above your head. Both times you used your muscles and joints to lever it up there. The second time however, you can't really say you were holding it up above your head. It was in mid flight. If you actually try that, you'll see that trowing it up is a lot easier than slowly bringing it up there. The reason is speed. As soon as you add speed to movement, you create momentum, and this momentum helps the weight move forward - think about when you hit the breaks in a car and the things that aren't attached keep moving forward. Even light objects are hard to stop when they have that momentum, so when you are creating that momentum, it's helping you move the weight. You don't want that when you are doing exercise. What you want is to create a prolonged stress (positive stress) on the muscles until they reach a point where they can't move any more. This is called "failure", and it simply means that your muscles are temporarily unable to continue contracting. They have used up all of the energy they had stored, and must wait now to restock that energy. At this point in your exercise ie. moving your 45 pound weight slowly, you are done your set (movement) and will now rest until you feel ready to do an other different movement.
So now you understand why you need to move the weight slowly in order to create more resistance, or make the exercise more efficient and harder. Remember, exercise is supposed to be a little like hard work. Only that it's a lot safer, and the we're building your body, something well worth the investment for the return.
Next up... why moving the weight slowly is safer (besides the obvious).