I have a fairly long commute to work (1-hr each way) and want to be as productive as possible during. Some days I listen to music, but most days I either listen to NPR, informative podcasts, or non-fiction audiobooks. I have really enjoyed the increased productivity there, because I am learning a lot while driving, but I recently decided that since I drive automatic, I have a free hand I could work out with, to increase productivity even further (the drive is extremely easy with little traffic and few turns). Thus, I decided to purchase a handgrip strengthener to utilize while on my commute. My question is, for the purpose of increasing forearm size, how should I be using it? Should I put it at lower weight and do it for the whole commute? Should I put it at higher weight and do sets/reps? How many sets/reps? Should I be squeezing, holding (for how long?), and then letting go? Or just rapidly squeezing and relaxing?