June '24 - Arm and Shoulder Injury 3

Arm and shoulder injury prevention and rehabilitation part 3

The interesting thing is that the muscles involved in accelerating the arm are some of the bigger one, where muscles decelerating tend to be smaller ones or specific small areas of bigger muscles. Often in shurikenjutsu it's the smaller deceleration muscles or tendons that can end up sore.

Common ones are the forearm flexors (tennis elbow area), the brachialis (which sits under the bicep), bicep tendons down at the elbow end or up at the shoulder end, shoulder rotator cuff muscles, the front part of the deltoid and in extreme cases muscles in the back around the should blade like the rhomboid. The other unique on for shuriken throwing is the back of the wrist up into the very bottom of the forearm, being related to how the wrist is cocked.

Rotation of the elbow in towards the centre line of the body during the deceleration and follow through is often the cause of brachialis, bicep and front detoid pain. Over rotation of the forearm to turn the palm down and then out to the side (facing away from the thigh) will pull excessively on the forearm flexors. This combined with rolling the shoulder over can cause pain in the rhomboid. More about the throwing mechanics might be a good future post, but the hand should travel in an ellipse rather than a circle. Rotator cuff issues can result from over extended throwing path (too straight at the top of the ellipse), cut short with too much down force, excessive tension in the preparation phase, throwing too hard with just the arm instead of using power from the legs and torso, and others. The back of the wrist is injured from tension held there either in preparation (over zealous cocking of the wrist and hand), while holding the wrist in the cocked position during the throw, or at the end as the hand releases into a more natural position.

Overall excessive tension is always bad for your technique and for your body. Without it you can still cause excess strain on those smaller muscles and often fixing that only takes a small adjustment in your technique. Videoing yourself is educational in many ways and can help you identify what adjustments you might need to stop being sore after throwing.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9076771/#Sec8title

Not our aim for shurikenjutsu, but image credit to https://bonytobeastly.com/how-to-build-bigger-arms/  It's a great diagram of all the arm muscles I'm talking about without looking all medical.

Link back to Articles page