The exercise that Blad here is demonstrating is called 'wood chop'. It's very similar to the golf swing…The key points to make with this is bending at the knees, the hips while at the same time maintaining good posture…What we're trying to do here is develop core stability. So we're making sure he keeps his navel facing forward the whole time…Just like a golf swing when he comes to the top of the motion, he's going to have that back arm bent slightly.But at the same time he tries to keep his arms as far away from his torso as possible…The main muscles we're trying to target here, the transverse abdominus, the internal and external obliques…After we get through doing one side, then the other side from high to low—simply drop this down—that way we're working the same muscle groups but at a different angle…The next thing we're going to do is from right to left—directly across—working the same-type muscles but in a different plane of motion…Once he completes this set from both sides—drop it down to a lower angle. Now he's moving from a range of motion from low to high…Making sure that we train all the muscles on different planes of motion…The way that we progress this exercise is add a few more repetitions. We can also narrow the stance—and eventually increase the weight.The main reason for doing this exercise is not necessarily for sports enhancement, this more along the lines of injury prevention.