Hand strain when off road I tried fat biking this week, I've done hardly any off road or MTB cycling before and was very nervous.

I found keeping my hands over the brakes in case I had to stop suddenly strained my hands between thumb and first finger, especially as the ground was very rocky.

Is this just something your body gets used to or are there techniques I can improve here?
Along with checking position on the bike it's worth checking to see whether the reach can be adjusted on your brakes in case you're over-stretching your hand. Check the angle too - stand behind the bike and reach the bar, extend your fingers straight forward following the line of your arm and adjust the lever to meet under your finger(s).