No doubt, kayaking is a complete upper body workout. Stretching the upper body before and after kayaking helps keep the body flexible with recovery time minimal. Here is a stretch for kayaking.
Kneel down on all fours (hands and knees). Stretch your arms out and forward--in front. Slowly lower your chest to the floor. Breathing out, stretch the shoulders completely. Press the arms to the floor and gradually arch your back. Make sure you hold this stretch 15 - 30 seconds.