Unloading Reaction

We have been discussing in neural control the role of reflexes in the control of voluntary movement.  Yesterday we discussed a hypothesis that believes that reflexes play a very minor role in movement, and the central, voluntary commands sent from the brain control almost all aspects of voluntary movement.  There is a pretty cool reflex known as the unloading reaction that disproves this theory.

Imagine that you are holding a dumbbell in your right hand, and you are attempting to keep your elbow flexed (bent) at about 90 degrees.  You are instructed to continuously try and contract the elbow flexors (think biceps brachii, brachialis) in order to maintain this position, and you are instructed to continue to try and activate the muscles no matter what happens.  As you are holding the dumbbell, it is quickly removed from your hand.  What happens to the activity of the elbow flexors?

When the dumbbell is removed from your hand, there is a period of almost complete silence (no activity) in the elbow flexors.  Why does this occur even when you are trying to activate the elbow flexors?  When the dumbbell is in your hand, it activates the muscle spindles in the biceps (the dumbbell is trying to lengthen the biceps, which activates the muscle spindles), which causes a reflexive contraction of the biceps.  When the dumbbell is removed from your hand, muscle spindles are no longer activated, so there is no reflexive contraction of the elbow flexors.  This demonstrates that reflexes play more than a minor role in the control of voluntary movement.

Disturbing, but not surprising news

A recent report in the Chronicle of Higher Education talks about the difficulty that many athletic trainers face in dealing with injuries, particularly concussions, because they either report directly to the head coach or feel pressure from the coaching staff to return an athlete to play before he is ready.  I'm not going to comment extensively on this, but you can read another opinion here, and this link contains a good animation of the problem.  For full disclosure, I worked for one of the athletic trainers quoted in the first article when I was at Auburn.  There is definitely a clear conflict of interest between an athletic trainer and a head coach, especially in the ultra competitive world of NCAA football.  Most coaches have the best interest of the athletes in mind, but during the middle of a game, they cannot objectively decide if a player is able to return to a game, nor  are they trained to make this decision.  A head coach should also not evaluate the the skills of a medical professional.  Except for a few high schools games I covered, I never had to make the ultimate decision about rather or not a player can return to a game (that responsibility ultimately should rest with the team physician), but I can attest that the times I had to tell an assistant coach that one of their position players could not return to a game was not enjoyable.  Hopefully this report will open some eyes and lead to positive changes. 

New rules are going to lead to more injuries?

I blogged last week about the new rules in the NFL and NCAA that are targeted at preventing football players from hitting their opponent in the head or leading with their head when making a tackle.  The purpose of these rules is to cut down on the number of head and neck injuries.  I've heard some commentary recently on ESPN from former players saying that these rules will cause an increase in the number of knee injuries.  They think because defenders cannot tackle offensive players by hitting them in the head, they will now target their knees, because they don't have any other option.  Now, I didn't play football, or coach football, but it seems to me like there are a lot of other options besides hitting a player in the knees or the head.  I know when I was working as an athletic trainer with the football teams at Southern Miss and Auburn the players were not taught to tackle by hitting in the head or knees.  They were taught to hit a player in the chest or middle of the body and then wrap them up.  I think there are other options for tackling besides the head and the knees.  It may take some adjustments, but I don't think these new rules should cause a huge spike in the number of knee injuries.

Tackling

If you are a football fan, then you know that the start of football season is less than two weeks away.  One of the hot button issues this off season has been tackling, specifically as it relates to hitting another player in the head or a tackler using his head to hit another player with.  The National Athletic Trainers Association (NATA) released a position statement last week urging officials to consistently penalize players that lead with the crown of their head.  The full statement can be seen here.  I've heard a lot of coaches, analysts, and former players complaining about the new rules and the fact that the NCAA and NFL officials will call more penalties on these types of hits.  While it will change the way some players tackle, the benefits of these new rules far outweigh the risk of a player potentially missing a tackle because he cannot lead with his head.  I will outline the theory behind these new rules below.

As you can see in the picture above, the tackler on the right of the screen is making contact with the offensive player with his head down, or in a flexed position.  This results in axial loading of the cervical spine.  When the head is in a natural, upright position, there a slight forward curvature of the cervical spine.  When the neck is flexed and the head is down, this removes the natural curve from the cervical spine, and easily allows

the force to be transmitted from the head down the cervical vertebrae.  In the picture directly above, you can see how the spine is loaded, and as the amount of force increases, the amount of deformation to the cervical spine also increases.  This can ultimately result in a fracture and/or dislocation of the cervical vertebrae that causes paralysis.  The only tackling technique that results in axial loading to the cervical spine is one in which the head is down and contact is made to the crown of the head.  While it is still possible to sustain a neck injury when tackling with the head up, the chances of sustaining a life threatening/altering injury are greatly decreased.  This article contains more information on tackling techniques and the dangers/risks associated with head down tackling.  While I am sure this issue will remain a controversial topic, the best way to prevent catastrophic head/neck injuries is to prevent players from tackling with the head down.

Tim Hudson's Injury

If you are a baseball fan, then you have probably heard and seen about the injury to Braves' pitcher Tim Hudson last week.  While covering 1st base, Eric Young Jr. inadvertently stepped on Hudson's right leg just above the ankle on the lateral side.  Early reports where that Hudson fractured his ankle.  This is a very vague description, as there are several bones in the ankle.  After undergoing surgery, it was revealed the Hudson fractured his fibula and tore his deltoid ligament.

The fibula is the bone located on the lateral side of the lower leg.  It runs from just below the knee down to the ankle, and forms the lateral portion of the ankle.  The very distal (bottom) end of the fibula is called the lateral malleolus.  Looking at the picture of the injury, Hudson fractured his fibula just above the lateral malleolus.  Since the fibula is thinner than the tibia and doesn't play as large a role in weight bearing, the recovery can be easier (still difficult) than a fractured tiba (the medial shin bone that bears about 90% of our weight when standing).  Hudson also tore his deltoid ligament, which is the thick ligament on the medial side of the ankle.  It is actually a collection of four ligaments shaped like a triangle (deltoid).  It helps prevent the ankle from excessive eversion (when the bottom of the foot moves away from the midline, such as in the picture above).

Although Hudson is 38 years old, he has a pretty good chance of pitching again.  His rehab from the injury will probably take 3-6 months, and he should be ready to go by spring training.  Hopefully he can make a full recovery.

Platelet-Rich Plasma Injections

During the last blog post, I mentioned that one of the treatments Bryce Harper received for his injured knee was platelet-rich plasma injections.  This has become a popular treatment among athletes these days.  It is typically used during the inflammatory phase of the healing process to help accelerate recovery.  It involves taking a sample of blood from the same patient, separating out the platelet rich plasma, and then injecting the plasma into the injured tissue, such as a tendon or a ligament.  The patient must avoid exercise for a few days before starting or re-starting the rehabilitation program.  There are animal studies that have shown it is effective, and many athletes have claimed it has helped them improve.  It will likely become an even more popular treatment choice in the future.

What's wrong with Bryce Harper's Knee?

I apologize for the delay between blog posts.  Things were very hectic at the end of the spring semester and the beginning of the summer.  If you are a baseball fan, then you know Bryce Harper, the young star outfielder for the Washington Nationals, injured his knee over a month ago when he collided with the outfield wall.  Haper missed a few games, played in a few, and then recently went on the disabled list.  So, what injury did Harper sustain?

Harper was diagnosed with bursitiis, which was confirmed today by Dr. Andrews.  Bursitis is inflammation of a bursa.  A bursa is a fluid filled sac that is found near many of our joints, such as the knee, ankle, elbow, and shoulder.  In the picture above, you can see that there are four bursa around the knee.  It is likely that Harper injured his prepatellar bursa when he ran into the wall.  The prepatellar bursa is located directly above the patella.  It is very superficial and easily injured during collisions.  When a bursa sac is irritated, it can cause a lot of swelling and inflammation around a joint.  This can make movements of the knee painful and difficult.  It generally does not cause swelling within the joint, because the bursa is located outside the joint.  The best course of treatment for bursitis is rest and anti-inflammatory medication.  However, this option is not often chosen during the middle of a competitive season.  Because Harper's knee was not responding, they had to place him on the disabled list.  I will discuss the treatment he received for this injury from Dr. Andrews in the next blog post.