Some comments in another thread about how limited TOW has a negative effect on progression and maintainence of skill made me think that a thread on other activities that contribute to sailing skills might be useful.
General fitness and strength is obviously an asset, esp for females or guys with poor upper body strength etc, so general weight training is going to help
If you look at an expert or pro level slalom sailor, you see a lot of movement of the legs, but the upper body and rig is nearly motionless, and very stable.
Developing that independence between upper and lower body is really key to maintaining balance on a small board or sinker esp in lulls or during tacking/gybing manouvers.
I have had a lot of fun using unstable surface training to help with this. I have a couple of small inflatable biconvex gym ball type thingies, about 30 cm in diameter and 20cm or so high. Just standing on them is exercise. Standing on one foot is harder again, then progressing to doing squats and one leg squats. You find your legs can jiggle and shake quite a lot, while your upper body needs to stay quiet.
A progression on that is to use a large gym ball and learn to first kneel on it, then progress to standing upright on it.
Now, I have to say, that is not easy, and it's wise to have a soft surface with lots of jump-off space when first attempting, but if you manage it, standing on any size windsurfer will never pose a problem ever again.
Any other suggestions for cross training in the quiet months most of us are currently enduring ?