Plank with support of knees

Create a stable line through the head, trunk and pelvis and keep abdominal tension for the prescribed time. Breathe normally without letting the lower back sag. Keep the same range from repetition to repetition instead of speeding up as you fatigue. Breathe continuously and end the set before technique starts to break down.

Choose a resistance that lets you preserve technique from start to finish. You should feel most of the work in abdominals, glutes and hip flexors and lower back; if you feel sharp pain, joint pinching or a clear loss of control, reduce the load or range and stop if symptoms persist.