This video shows you how to do standing forward fold in a yoga class if your hamstring/calves/lower back are tight. The second half of the video is technique
Standing Forward Fold (Uttanasana): Instructions, Tips & Benefits
7 Yoga Poses for Tight Hamstrings
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To Bend or Not to Bend (the Knees in a Forward Fold*) - Jules Mitchell Yoga
Eccentric Hamstring Training: Fire Up Your Forward Fold - Yoga Medicine
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Wide-Legged Standing Forward Bend: How to Practice Prasarita Padottanasana
Tight Hamstrings? Here's Why & The 3 Best Poses For A Deep Yoga Hamstring Stretch
How to do Wide-legged Standing Forward Fold
Standing Forward Bend: How to Practice Uttanasana