I have been suffering from a loss of strength in my left thigh muscle for the last 18months now. There is no pain and I am an active fit person. I am 42 yr old male. It started when I would play tennis and it would be fine for the first 30 minutes but then my left leg started to feel like it was losing strength. My left foot would start to drag as I had to concentrate to lift my leg up as the leg felt weak. By the end of the game I was totally struggling to walk properly and felt paranoid that I had to over exaggerate my walking. The left leg was weak and shaking. Once I rest for 30 minutes its fine and back to normal. I have got by with it but it is starting to impact on my normal everyday life as the weakness comes a lot sooner now. Just walking around the shops and I can start to feel the weakness in my left leg. Just cutting the grass today was a struggle. the left leg is significantly weaker than the right one and sometimes when the leg is bent it sometimes feels like I am going to fall over. I have no pain anywhere on my body. I had an episode in 2007 for about 3 months where I lost strength in my left leg for about 10 seconds when I was running and then it would be fine. This just corrected itself after 3 months and went away I am considering getting some steroids to help improve my muscle strength.