A few weeks ago I was doing some standing pummeling; both my partner and I were fighting to get underhook positions in the clinch (some things you can do from an underhook). On my way to class I’d thought up a new way to get the underhook and now I wanted to try it out on someone in the flesh. As we were tussling back and forth I tried my new technique and felt a slight ‘pop’ in my shoulder followed by some sharp pain.
At first I was confused, since we weren’t going particularly hard and my opponent hadn’t cranked me or used a dirty trick. As I rubbed my sore shoulder I figured out what had happened: my new method for inserting the underhook involved turning my body to the left and reaching my right arm out to the right. My arm was cocked out to the side of my body like a hitchhiker on the side of the highway, instead of being in front of my body (like holding a mirror up to my face). This sideways arm position took my shoulder close to the limits of its flexibility where it needed only a very small amount of clockwise rotation to get tweaked.
I then realized that I should have known all this already from my whitewater canoeing and kayaking days. Informed paddlers are usually quite conscious to keep their arms inside the so-called paddler’s box, which Bruce Lessels defines as “…an imaginary box in front of your chest. The sides of the box are the planes that hold your arms. The front of the box if your fingertips. The back of the box is your chest, and the box moves as your rotate your torso left or right.”
Paddlers use this concept because it helps keep their strokes efficient, and also because it helps keep their shoulders safe from being dislocated, which is unfortunately a fairly common in the whitewater paddling community (see the fifth point).
If you are a grappler you won’t always be able to keep your arms in this imaginary box. Arm and body positions in grappling are a lot more variable than in kayaking, and also there are people actively trying to force your arm into a compromised position. You should be aware, however, that your arms are strongest, and your shoulders the safest, when your arms are in this imaginary box, and try to keep your arms within the box whenever you can. Think of the common shoulder locks like americanas, Kimuras and omo platas – they all rely on forcing the arm out to the side of the body, out of the relative safety of the box.
Should your arms drift from the box (or be forced from the box) and your shoulder get injured, paddlers also have a lot of good information on shoulder rehabilitation (see this previous tip for more info). My shoulder feels 100% again, so I don’t have to use this information this time, but it’s nice to know that it’s there if I need it.