Motor Variability and Equivalence

Another argument in the case against the term "muscle memory" are the concepts of motor variability and motor equivalence.  When we perform even the simplest tasks, such as reaching and pressing a button, we will never move in exactly the same pattern.  Why?  There is much variability in terms of which joints to use, how to use the joints, which muscles to use, what order to recruit the muscles in, and how much force to produce.  Although the movements will look similar, they will never be exactly the same.  The fact that we can move in a similar motion but use different patterns of joint actions and muscle activation is called motor equivalence.

If you look at some of the elite quarterbacks in the NFL, or elite pitchers in MLB, you will notice that they all have a similar throwing motion, but there are a lot of differences between them.  The pictures of Brett Favre and Peyton Manning above demonstrate this.  Also, if you watch a single quarterback make several throws over the course of a practice or game, you will notice some differences.  These differences are a good thing, because they allow us to adapt to changes in the environment.  But this variability also presents a challenge, and helps explain why elite level athletes often times fail.  If muscle memory truly existed, we would be able to repeat the same motion every single time without mistakes.  The human body would essentially function like a computer.  We know that this isn't the case.

Dislocated Rib and SC Joint Sprain

During Monday's night NFL game, Steelers quarterback Ben Roethlisberger was sacked and landed right on the posterior aspect of his right elbow.  The defender also landed directly on his left shoulder.  He suffered a sprain of the sternoclavicular (SC) joint of his throwing shoulder.  This is where the clavicle meets the sternum.  It was likely caused by his humerus being forced up into his clavicle when he landed on the ground.  This is not a very common injury, but it can be very painful, especially for a quarterback.  Anytime you move your humerus (upper arm), the clavicle will rotate as well, so this would cause pain at the SC joint.  This is the injury that essentially ended Brett Favre's iron man streak two years ago.

Roethlisberger also had another injury that is not very common, and that is a dislocated rib.  I haven't found an article that says exactly which rib is dislocated, but my guess would be it is one of the first 3 or 4 ribs, due to the mechanism of injury.  It is unclear if the dislocation occurred where the rib attaches to the thoracic vertebrae in the back, or where it attaches to the sternum in the front through hyaline cartilage (probably the anterior attachment to the sternum).  In any case, it is a very painful injury, and even simple activities are difficult, such as breathing, because the ribcage moves when we breathe.  There is some concern about him taking another hit before the injury heals and the rib puncturing an internal organ.  Due to the pain and likelihood of a serious injury, he will probably not play for several weeks. 

Update on Marcus Lattimore

Recent reports are that Marcus Lattimore had successful knee surgery last Friday.  The report mentions that several ligaments had to be repaired, although it doesn't specify if these repairs were reconstructions (I'm 100% sure the ACL was a reconstruction), or a suture.  However, he did not have any fractures to his femur, patella, or tibia, and at this time he will not need any additional surgery.  This is good news and should definitely increase his chances of making a return to the football field.

Comparing Marcus Lattimore's Knee Injury to Willis McGahee's Knee Injury

I wrote last week about the knee injury Marcus Lattimore sustained during a recent game against Tennessee.  It has been reported that he tore all four knee ligaments, which will require extensive reconstruction, surgery, and rehabilitation.  This injury is very similar to one sustained by Willis McGahee almost 10 years ago, so I thought I would compare the two.

The mechanism of injury for both injuries is eerily similar.  As you can see, both of them are hit on the anterior aspect of the knee by a defender, in a very similar fashion.  Lattimore was also hit from behind, which probably contributed to him tearing all four knee ligaments.  McGahee tore his ACL, PCL, and MCL with his injury.  McGahee had to have his entire ACL reconstructed because it essentially tore in the middle and there was no hope for repair.  But, his PCL and MCL tore near their insertion into the bone, so instead of having to reconstruct those ligaments with a different piece of tissue, doctors were able to suture the ends back into the bone.  This was a bit of encouraging news for McGahee considering he tore 3 of his primary knee ligaments.

It is not known the exact location of the tears in the ligaments of Lattimore's knee.  More than likely, his ACL will require a complete reconstruction.  The location of the tear in the other ligaments will determine if a suture can be performed, such as in McGahee's case, or if those ligaments will be reconstructed as well.  The more complete tears that Lattimore has, the longer and more difficult has rehabilitation will be.  But, Willis McGahee has provided a very good blueprint for Lattimore and his sports medicine team to follow.