Week 4: Push Ups
A great way to start developing upper body strength. Keep your back flat, abs tight, legs bent up at a 45 degree angle, arms shoulder-width apart. Be sure to get good depth when you go down, which will stretch you pectoral muscles. If you're strong enough, do the straight-legs version.
As always, make sure to keep plenty of water on hand so you stay hydrated, eat properly, get plenty of rest, and pay attention to your form.
