|Dog paddle is a great drill!
In order to train consistently for swimming or any other sport, one needs to remain healthy. Deliberate, focussed practice must be implemented in all training sessions. That combined with consistency in your training will give you the best chance to progress.
Check out this video "Prevent swimmers shoulders...Injury prehab program" that the folks at Vasa Inc made back in 2010. Simple, effective, sport specific exercises that will keep your shoulders healthy and swimming through the winter months.
Make it a great week of training,