Day 6 is a circuit again, 3, 5 or 7 sets by level with 2 minutes rest, and it splits its attention between your legs and the back of your shoulders. The top row is 5 lunges on the left, 10 calf raises and 5 lunges on the right. The bottom row moves to the floor face down: 5 W-extensions, 10 reverse angels and 5 W-extensions. The lunge count is one of the few on the program that is stated per side, so it really is 5 with the left leg leading and then 5 with the right.
The lunges are forward lunges, hands on hips, stepping out and lowering the back knee toward the floor before pushing back to standing. Running is single-leg work, and the lunge is the closest thing to a stride done slowly enough to feel. The calf raises between the two sides keep the lower legs in the conversation on every circuit day. The floor row is all posture: in W-extensions you lie on your front with your arms bent into a W, lift your chest slightly and extend the arms out straight ahead before pulling them back; in reverse angels the arms sweep straight from your hips to overhead and back, hovering off the floor the whole way. Both wake up the muscles between your shoulder blades that keep your arms swinging freely when you run.
Lunge with a long enough step that your front shin stays roughly vertical, and keep your torso upright rather than leaning forward. On calf raises, pause a moment at the top. For the prone work, keep your gaze at the floor, lift the arms from the shoulder blades rather than by arching your lower back, and keep your hands off the floor between reps so the rear shoulders never switch off.
Legs in front, shoulders behind - the parts that carry a run and the parts that steer it.
Make it Harder: Add a 5-count hold at full extension on the last reverse angel of every set, arms straight and hovering.
Make it Easier: Shorten the lunge step and cut the reverse angels to 6 per set.
