Plank

Purpose: To improve the core strength, form, and endurance. This exercise also reinforces the use of the pelvic tilt in functional exercises. 

Instructions:  Start on your forearms and knees or on your stomach and forearms , engage your core muscles, and lift up so you're supported only by your forearms and toes. Look a little bit ahead of you on the ground, pelvic tilt, squeeze your glutes, quads, and hamstrings to hold this pose for 30 seconds at first, gradually increasing the time when you progress this exercise.

Common Errors:  Sticking your butt come too high in the air - your body should be a straight line from the shoulders to the heels. Drop your butt and pelvic tilt. If this is difficult, try it first on your knees - assume the plan position shown in the video, then drop down onto your knees without losing your core engagement. Hold the position here.