The tire pull and drag is a simple obstacle that uses a technique that is very similar to rowing, well more like rowing through barely wet cement. The best way to start describing it is along with photos.
1. You get to your tire and drag it until the rope is fully out stretched
2. Once the tire is there you walk back to the start and have yourself a nice seat behind the stake that the rope is tied to. The other position (seen below, guy without shirt on) is to stand in a leaning back manor so your weight is naturally moving in the direction you are pulling the tire. Then get two hands on the rope and pull it towards yourself. You can also incorporate your legs as you would while using a rowing machine to add power. You repeat this by leaning forward again grabbing further down on the rope and pulling until the tire reaches back where it started on the stake.
That’s all there is to it. Hit the rowing machine to strengthen up these muscles as well as your overall core and leg muscles.