Day 20 is the lunge circuit at 12: 12 calf raises, 12 lunges and 12 side-to-side lunges, 2 minutes rest, 3, 4 or 5 sets by level. It returns every second week, and each visit adds two reps to every exercise.
The forward lunge and the side-to-side lunge cover two directions of leg strength, and both have a running job. Forward lunges load one leg at a time through a deep knee and hip bend - the closest bodyweight exercise to the position your front leg finds in mid-stride. Side-to-side lunges strengthen the hips and inner thighs that control how the knee tracks, which matters more and more as runs get longer and form gets tired. Calf raises open the circuit as always. At 12 reps, the lunge work is 6 per leg on each exercise, per set.
Forward lunges: step long enough for a vertical front shin, lower the back knee to just above the floor, drive up through the front heel, alternate legs. Side-to-side: sit deep over the bent leg with the other leg straight and both feet flat, then shift across without rising in between; 12 total across both sides. Calf raises full range, slow down.
Two lunges, two directions, two more reps - the hips get stronger in every plane you run in.
Make it Harder: Hold the bottom of each side-to-side lunge for a 2-count before shifting to the other side.
Make it Easier: Reduce both lunge exercises to 8 reps and keep the calf raises at 12.
