This is a great way to increase endurance in your lower body. Find a wall that gives you enough room to lean against with a floor where your feet have a good grip to. Start about 2 feet away from the wall facing away. Slowly lean back so that your back is flat along the wall. Slide your body down until your knees are at a 90-degree angle and hold there. Start off holding for 1 minute in the perfect 'chair-like' position. Increase your endurance by adding minutes each time you perform this exercise.
Tip: Be sure to keep your body low in the 90-degree angle. Your back should always be perfectly straight along the wall. To increase resistance, try holding dumbbells in each hand down by your side. Don't cheat by
putting your hands on your quads like Ryan is doing in the video below :)