triceps pain doing lat pulls

[browncmp]

I dont understand how my triceps can hurt doing lat pulls. I sit at the machine, and granted Im short so I have to stand to pull the bar down, the lock my legs in... But, the first reps I feel this pinching sensation in my tri's. Why? It only happens during the pulling phase of the exercise. Once I get the bar to my chest, no more pain. It happens at lower weights, high weights I dont seem to feel it. Any thoughts?

[Leenad]

If you push down past your chest you'll feel it in your tris... Otherwise you shouldn't.

[browncmp]

But its not when the bar is at my chest, its when my arms are extended and I begin the rep. Its that first effort that causes the pinch, once I pull the bar down beyond halfway the pinch stops.