How much should your left arm participate?

[Delaware Golf]

Rich,

Could just be the effect of hanging on to the club a little too tightly through 300 hits.

Make a fist and tighten your grip to see the effect on the muscles of the forearm.

Swinging the club does not tighten those muscles but tightening your grip will.

After hitting 100 balls your muscles will fatigue let alone hitting 300 balls.