A fundamental property of muscle, which has been known for many years (see Hill, 1950, in the Bibliography), is that if you make a muscle contract so as to get maximum force out of it, then it only contracts very slowly. On the other hand, if you make it contract as quickly as possible, then you don't get much force.
The physical property which relates force and velocity is power (which is force mulitplied by velocity). If you make a muscle contract at a force and speed which maximises power, then it only contracts with a force of about one-third of the maximum that it is capable of producing.
[Science stuff: energy and power]
Think of climbing a flight of stairs. If you are carrying a heavy backpack, you stagger up slowly, gasping for breath at every step. If you are not carrrying anything, you bound lightly up, two steps at a time (maybe).
When you are carrying a heavy load your muscles have to contract with a lot of force in order to lift the load, and so they contract slowly. When you are not carrying much, then your muscles do not have to produce so much force, and so they can contract more quickly.
The amount of energy you produce carrying a given load is the same whether you climb the stairs quickly or slowly. What differs if you climb the stairs at different speeds with the same load is the power output - i.e. the rate at which you produce energy. As we have just seen, you simply cannot climb the stairs quickly if you are carrying a heavy load - your power output is too low.
HOWEVER, we have already noted that a good jump requires a high force, and a high velocity of movement, and it is perfectly obvious that grasshoppers can jump well. So somehow they must be able to overcome this fundamental muscle limitation. How do they do that?