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?
It has been suggested that the biceps and legs can tollerate a lot of volume but benefit even from little volume.
Forearm musculature has not been tested, but judging from strongmen and arm wrestlers, incredibly high volume for forearms seems to work just fine.
Do not make the mistake to hold the gripper, it's good for building static strength. But for muscle growth you want to do both the eccentric and the concentric movement squize it and the open instead of holding it squized continuously. That's why grip competitors often have puny and skinny forearms even though they hold records. Static strength might be useful but it doesn't contribute much to muscle growth.
I would start by doing 1 set of as many reps as possible on each hand, and progress from there. If it gets too easy (doubt) add another set after a week.