The ability to transmit force and coordinate neuromuscular recruitment between the hips, core, and upper torso is vital for athletic performance as well as heavy strength training. The side windmill plank is one of the few exercises that requires the upper torso, core, and hip muscles to work together synergistically in one controlled high-tension isometric.
Start with both feet stacked. Once you nail the form with this basic position, try incorporating hip abduction by lifting the top leg while keeping both feet perfectly parallel to each other.
This plank variation quickly exposes and addresses energy leaks that may exist between various segments of the body, like the hips and core.