i am 45 yrs old. i workout a lot but still have a big left hamstring problem. i can stretch the right leg to about a 100 degree angle [lying on my back, pulling my leg towards my chest]. my left leg i can only stretch to about a 45 to 60 degree angle. so basically it is real tight. i also get a lot pain when i kayak. is there something i can try to loosen it up.

You need to dedicate yourself to stretching the impacted leg, 3 sets of 20-30 seconds, twice a day. Make sure when you perform the stretch you are grabbing your leg at the calf and keeping your leg as straight as possible at the knee. It can also help to apply heat for 10-15 minutes to the affected leg before stretching.

If you don't start to see improvement over the course of a couple weeks, you might actually have injured your hammy, and might want to see a doc about it.