Why i ask is,between my cycling days.I do leg exercises given to me by the Hospital in 2003,after having two Arthroscopies on my left knee.I have found them helpful.But during today's ride my thighs felt heavy,and it was not a good ride,despite it being a perfect day.I have noticed this before.They are simple exercises,rising on the toes ten times.Bending each knee ten times and finally both knees at the same time.So does anyone do leg exercises.That are designed to help with the cycling.Just to say i do two or three of these exercise daily.So that is just 30 of each bending.