Lately I have been trying out some new excercises to train my legs.
One of which is the Lunge.
Now I noticed that when doing them without weight, I had no problem at all. But when I took about 10kg each hand (which should be easy since I'm not new to training legs) I had a very painful stretchy-like feeling in my hamstring.
I'm keeping my back straight and making sure that my knee doesn't come over my toes.
Is there any idea on what this might cause?
(Personal Trainer said that form wasn't causing the pain, I switched to different hamstring excercises)