Starting to exercise isn't easy for anyone. It sure wasn't for me, even though I knew all too well how important exercise is for controlling my diabetes.

It's a particularly personal example of the universal problem called inertia, which Sir Isaac Newton told us about 321 years ago in the greatest single scientific work ever. Inertia means that a body at rest tends to remain at rest.

But that's only part of it, the down side. Inertia's up side is that a body in motion tends to remain in motion.

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