I am like jackb in that I do not stretch before a ride
I have always felt that the best exercise for exercise- -Is exercise. Doing a long ride- then I take it steady at first and ease myself into the ride. If on the ride my back aches- then I stretch it while still riding- Calf muscles get tight then out of the saddle and on the low pedal- put my weight on that foot and lower the heel- So many exercises that I can do while riding to ease a problem.
The only exception is if Power is required very early in the ride. I do one offroad ride that within 100 yards there is a stiff climb in which my HR will max out- and it cannot be taken slowly unless you walk it. I just go for a couple of miles to get the HR up before I attempt that hill. I do not like pushing a heavy bike up a steep hill.
But after a ride- I will find the muscles that are causing a problem. That is where I will do exercises to get mobility back into the body before I collapse into a heap- not to get up for a long while.
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How long was I in the army? Five foot seven.
Spike Milligan