Plank: Build strength in those arms by putting yourself in Plank position. From Cat and Cow, put your feet straight back behind you. You should be in a push-up position—this is Plank! Stay here for a few seconds, making sure your feet, pelvis, and torso are all one straight line.
Cat and Cow: Come to all fours on your mat (hands and knees). First try Cat—arch your back towards the ceiling, looking into your navel. Now comes Cow, where you arch towards the floor this time, and bring your head up to look ahead of you. Do this as many times as feels right, timing your breath as you go.
Downward Dog: This is probably one yoga pose you've seen before if you've ever watched workout TV! From Plank position, simply push your hips to the sky.
Try to keep those hips up while pushing your feet back to the earth. If this is too rough for you, you can bend your knees a tad. Keep your shoulders as far from your ears as you can!
Pigeon: Great for stretching hamstrings and hip extensors! From Downward Dog, send one of your feet up to your hands. Lean forward for a lunge. Right now you should look like a track runner. Supporting yourself on strong arms and your back foot, place your forward leg on its side. Take the support away and let yourself down over that front leg. More advanced tip: Bring your back leg up by bending your knee - this is the goal to strive towards.
Chair: Take yourself out of pigeon by going to hands and knees (and repeating the routine over again from Cat and Cow to Downward Dog). Now step one foot forward, then the other. Keeping your legs bent, come up to standing but 'sit back' a little, as if you were about to sit in a seat. Stay here, and raise your arms to feel the energy coursing through those quad muscles!