Warrior I
How to do it
From standing, step the left foot straight back and turn it in about forty-five degrees, planting the whole foot with the heel down. Bend the right knee until it stacks over the right ankle, working toward the thigh coming parallel with the floor. Draw the left hip forward so both hip points face the front of the mat — the back hip will resist this, and squaring it is most of the work. Let the tailbone drop, knit the front ribs in, and reach both arms overhead alongside the ears. Hold or flow on, then switch sides.
Why it's good for runners
The planted heel is what makes this different from a high lunge, and it's what makes it valuable. With the back foot flat and the hips squared, the stretch runs in one long line from the front of the back hip down through the calf and Achilles — the hip flexor that shortens on every stride and the calf complex that absorbs every landing, lengthened together under bodyweight. Squaring the hips is what gets it there: let the back hip drift open and the line goes slack. It's also the shape that asks most of your ankle, which is the joint that decides whether you roll through a footstrike or fall off the front of it.
Common mistakes
Don't let the back heel lift — that's a high lunge, a good pose in its own right but not this one, and it takes the calf out of the equation. Don't let the back hip swing open toward the side of the mat; that's Warrior II, and it empties the hip flexor stretch. And don't arch the low back to get the arms higher — drop the tailbone first and reach only as far as that allows. If the heel won't stay down or the hips won't square, the stance is too long: step in.