The beginner usually exerts too much pressure on the pedals, and has to correct the falling tendency of the machine. this is very hard work, and stiff arms and shoulders and blistered hands may be often thus accounted for; they are the result of badly balanced pedaling.

which is the best paraphrase of the instructions?

beginning riders don’t know what they’re doing and cause the bike to fall over. pedaling incorrectly results in bad balance, blisters, and stiffness.
beginning riders tend to press too hard on the pedals, which can then cause the bike to fall over. pedaling with poor balance is not only hard work, but it can also result in blisters and stiffness.
pedaling incorrectly causes many problems, such as bad balance. beginning riders should practice pedaling so they don’t cause the bike to fall over and get blisters and stiffness.
pedaling incorrectly causes the bike to fall over. beginning riders can get blisters and stiffness and should try to have better balance.