Core

A very important aspect of running is having a strong core. The core consist of the abdominal muscles, back, and pelvis. A strong core increases protection for your back, controls movement, and gives you a more stable center of gravity. For running purposes, a strong core makes it easier to move forward with strength and power. It also keeps you strong and upright when you start braking down during a hard workout or race.

The good thing about the core, is it's cheap to strengthen. You do not need a health club membership or fancy home gym equipment, just yourself and a comfortable place to sit/lay down. Although core work is not going to hurt your wallet, it's going to make you sore! So, be careful, take your time, and build into it.

Core Strength Ideas
Core Conditioning For Runners
Core Examples