I think it's the same for any skill when you are trying to fine tune it. I certainly feel like I'm working harder when I'm working on my form. Paying attention to sensory inputs that you would normally ignore means concentration and leads to tension. Once you've had the practice you can relax and let your training take over.
As a prallel, I am training as a ski instructor and that is a sport that is totally about form. When we are demonstrating a simple beginner exercise in front of a coach I get a lot of tension and get way more tired than I would just bombing a slalom run.
I'd back off the speed even more until I was sure of my form.
According to some of the literature available, shin splints are a result of twisting caused by running with your feet turned out. By concentrating on running with my feet in line, I seem to have been able to stop getting shin splints.