To improve your grip, try the following:
New Year. New Me. Update: Week 17
Gareth Johnson
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A solid “do anywhere” hand strength exercise is to flex your fingers and thumb back as far as they will go, then clasp your hand into a tight fist squeezing as hard as you can. Then repeat as quickly as you can, flex out, clench in. Rotating your hand(s) clockwise and counterclockwise as you do that exercise will engage every muscle in your hand and forearm.

If you try it, you’ll likely be astonished at how quickly your forearms and hands fatigue.