1. you need to stretch hard and long enough to induce DOMS (physiological change)
2. it takes at least 2 weeks to reap noticeable benefits.
3. you need to continue stretching every other day to maintain flexibility, otherwise the muscles slowly revert to the original elasticity.
4. it drills the importance of routine and pushing through pain.
5. thigh is more complex than the calf, you must pay attention to 3 areas: hamstring, quad, and adductors.
i highly recommend stretching in advance especially if you are pushing the "safe" limits (8cm femur 5cm tibia) for your lengthening phase.
https://journals.physiology.org/doi/abs/10.1152/jappl.1993.75.3.1263
Quote Muscle length increased 60% (12 days), 34% (16 days), 59% (20 days), 50% (24 days), and 51% (28 days). Mean fiber area increased 111% (12 days), 142% (16 days), 75% (20 days), 90% (24 days), and 39% (28 days). Fiber number, which was measured histologically, increased significantly by 82% only in the 28 days of stretch group.
https://journals.physiology.org/doi/abs/10.1152/ajpcell.1991.260.3.C400
QuoteThe weight was removed after 30 days of stretch, and terminal experiments were conducted 0, 30, 60, or 90 days thereafter. Average slow beta-fiber area increased by 53.4 +/- 17.5% (SE) after 30 days of stretch, but it was not different from control area by 30 days poststretch removal.