The OP apparently is rather unique in his proclivity to cramp. Many of us can ride many miles and/hours and never cramp or need to stretch. Since he is so unique, general practices, or non-practices, don’t seem to apply to him. I would think trial and error as well as a gentle conditioning program might tell him what he needs to know.
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Road 🚴🏾♂️ & Mountain 🚵🏾♂️