I've copied this in from my dull-as-ditchwater Ex_STAB Rehab thread. What's going on when the leg muscles get tired before I get out of breath? I've set out some thoughts below but I really don't know if this is right from a physiological point of view. I'd really appreciate some informed comment on this and I think there will be others in my position who would welcome it too. If you are giving an opinion from a professional point of view it would lend weight to your argument if you can indicate what your qualification is. It's a real puzzle to me so I appreciate your remarks.