Runners have very resilient legs, and this is because running works the hip flexors, quads, glutes, hamstrings and calf muscles, as well as activates and strengthens the core muscles. That doesn't always equal physical strength, and often their upper bodies are less developed. This can lead to an imbalance in a runner's body.
Crossfit is a full-body workout that uses functional movements performed at a high intensity to increase overall strength.
These functional movements are what you do throughout your day without giving much thought to it. They include things like squatting when you sit, and pulling and pushing movements like when you’re opening and closing the door.
Runners can benefit from the strength training that Crossfit offers, as it will help with your balance, coordination and endurance. It will also develop muscle, which will help support and strengthen the joints and tendons. This will lead to an increase in speed when you’re running, as well as a lower chance of becoming injured.