Anybody else experience the back of their legs/knees locking-up during chinups? I try to pull with an arch to my back, and pull my elbows to my sternum in a row-motion, when doing chinups. I keep my knees bent more than 90 degrees, and I often have to straighten my leg mid-chinup to ward-off a cramp behind my knees. I have never had leg cramps during any other back movements. The problem is exacerbated post-leg-day. Did I permanently miswire my MMC and my brain thinks my hammy is my lat? Curious if anyone else has had issues like this?
For reference sake: I am doing 3-4 sets of 8-12 chinups, on a lackadaisical schedule, while killing time at work.