Let me be clear; I am not a doctor or a fitness expert. This post is just to let you know what I do to get in shape for kayaking. If you paddle correctly, then you mostly use your core muscles, not your arms. Flexibility is also key for kayaking, so my best recommendation is to do yoga. It increases your flexibility and strengthens your core. You don’t have to join a class; you can just get a DVD and workout at home. Target actually has a very good selection of yoga equipment and DVDs.
I am a big believer in cross training. Walk, hike, bike, ski, snowshoe, or do anything that improves your overall fitness level.
Because I live in the Northeast, I also like to have a good repertoire of indoor activities for winter. I actually enjoy work out videos. My favorites are Great Body Guaranteed and 10 Minute Trainer (both from Beachbody.com). I also like Billy Blank’s Tae Bo DVDs, but these are not for the faint of heart.
Basically, what it comes down to is general fitness level and flexibility. So just get moving and get stretching.