It is important to warm up muscles before any form of exercise. In winter particularly, if you have not cycled or run down to the Club, do make sure that you do some form of warming-up exercise (e.g. a jog up to Thames Valley Skiff Club, or a light session on an ergo upstairs), before getting on the water. Keep your muscles warm with an extra layer until you are properlyy warm in the boat.
It is particularly important to warm up your hands, which may otherwise be cold for the whole outing. With your arms straight by your side, put your hands out to the side, penguin-style, and raise and lower your shoulders sharply to pump blood into your hands. Or windmill with your arms, as fast as you can. If your hands are cold during the outing, you can “taxi-driver” in the boat: slap both hands across your chest and round behind you.
It is also good to some some mild stretching before getting into the boat: most people have their preferred stretching routines, which may be combined with some warming-up. During the winter, most members will have a chance to attend land-training sessions, which include some stronger stretches which will help to lengthen muscles and improve your flexibility.
These land training sessions also include a range of core strengthening exercises, which are very effective not only for improving your posture in the boat, but also for reducing the risk of injury, particularly to the lower back.