A reliable notebook for taking notes, annotating equations, doing practice problems, and keeping track of course materials is a must. I love these Black n' Red notebooks. Personally I use this large full sized hard-bound version, but they have them available in small and medium sizes as well as spiral-bound instead.
A bonus these notebooks have is a "Useful Information" page right at the front. For Biomechanics there is Speed conversions between MPH and KPH as well as Metric to SI conversions for Lengths, Area, Volume, and Weight. Definitely a useful resources to have handy as you are tackling tough problems in this course.
It also has a nice bookmark ribbon to keep track of where you left off which I very much enjoy. The hard-bound cover also makes it great for taking notes or writing in odd positions like on your lap, the bus, or while in a lab and moving around.