Bar holds are a basic isometric exercise to improve grip strength by increasing muscular endurance in the forearms.
Stand with your feet shoulder-width apart next to a barbell on two weight plates. Grab the bar with an overhand grip, hands positioned slightly wider than your shoulders.
Lift the bar off the plates and grip it as tightly as possible with your chest up and your shoulders down and back. Stand as tall as you can and hold the bar next to your thighs. Pause and hold, then return to start.
Squeeze your abs and glutes as you hold the bar and breath normally.