9:15AM - from Osterville Fitness Center - 60mins easy - 45-55sec walk on the 10mins - right calf tightened up behind the knee...felt it a little at the end of yesterday...a little worse today...started to feel eerily similar to an injury I had last August. I feel the back extensions on the GHD machine are the culprit. When I had a similar problem a while back, I was doing a lot of the back extensions and I swore I wouldn't do them anymore...because they put a lot of pressure on the tendons and connective tissue behind the knee. Doh!!