A good fit body will help avoid early season injuries that will take 4-6 weeks on the average to heal when they happen. Avoid those injuries by doing some exercises to strengthen the muscles in your lower back, shoulders and wrists. For your lower back, start by concentrating on your lower abdomen muscles . Fit in this area takes the majority of the strain off the lower back. The good ole common sit-up is a great place to start.
Crunches work well too.
For your shoulders and wrists , concentrate on the areas around the rotator cuffs and the top of the wrist. Wrist curls with those light weights work wonders. If you have a stationary bike or can ride a bike during the winter, this is great for your legs . With all these areas and exercises, consult a fitness consultant at a local gym and your doctor. You aren't trying to become Mr. or Ms. World body builder, just add some strength.