The 2012 NBA season has been unique in a variety of ways: shortened season due to the strike, jam-packed playing schedule on a weekly basis, and an abnormally-high number of injuries to major joints.
Many "experts" would have you believe that the shortened schedule had nothing to do with many of the high-profile injuries suffered recently, especially in the cases of ACL tears and ligament damage. However, I wasn't so sure that fatigue didn't play at least a minimal factor in these injuries. So, I decided to do a bit of light reading while on the shitter. Here is what I learned:
Injuries to the anterior cruciate ligament (ACL) are commonly seen as traumatic, spur-of-the-moment, high-impact injuries. As such, this type of injury doesn't necessarily need a level of fatigue in order to occur. However, it has been proven that fatigue does play a huge role in many instances of ACL tears.
Jeremy Lin, Ricky Rubio, Derrick Rose, Iman Schumpert, and now Baron Davis are the most notable NBA players to have suffered a knee joint or an ACL ligament injury in the last few months. It is also important to point out that in most of those cases, the injury occurred with little to no contact. Why did that happen?
According to McLean and Samorezov (2009), "Fatigue contributes directly to anterior cruciate ligament (ACL) injury via promotion of high risk biomechanics. The potential for central fatigue to dominate this process, however, remains unclear. With centrally mediated movement behaviors being trainable, establishing this link seems critical for improved injury prevention. We thus determined whether fatigue-induced landing biomechanics were governed by a centrally fatiguing mechanism." So what does all that mean?
Central fatigue - or Central Fatigue Theory - "involve mechanisms that cause more than the usual amount of the amino acid tryptophan to pass the blood-brain barrier, which stimulates an increase in the amount of serotonin (5-HT) that is produced. 5-HT is a neurotransmitter that causes people to feel relaxed and, if enough is produced, to feel sleepy. For the athlete, this could translate into muscular fatigue." In other words, mental fatigue can lead to muscle fatigue, which increases the risk of injury surrounding main joint systems in the body. Like the knee.
How does central fatigue occur? There are many theories, but the most widely-accepted has to do with improper nutrition for a prolonged period. Factors such as low blood sugar, high fat intake, and increased tryptophan consumption can lead to various nutritional complications in the body. In the case of high fat intake, for example, "fats will compete for a particular protein carrier in the blood leaving a higher proportion of free tryptophan that can cross the blood-brain barrier. This causes an increase in 5-HT production, which may lead to premature fatigue." While I have no way of knowing the nutritional habits of the players mentioned above, this may shine some light on where NBA training staffs may have failed in terms of injury prevention. The question is valid only because of the high number of similar injuries coupled with a hectic playing schedule (where proper nutrition may be sacrificed due to constant travel, for example). Again, I really have no way of knowing, but it would make sense.
Quite obviously muscle fatigue can lead to instability in the knee joint, especially if the hamstrings, calfs, and quads are fatigued. For NBA players who constantly need to cut - or change direction - quickly, this instability can lead to shearing forces applied to the joint, thus paving the way for a ligament tear. This may have been evident in the cases where players suffered non-contact injuries (Rose, Schumpert, Davis).
I firmly believe that the shortened season and increased workload contributed greatly to the types of knee injuries seen this season. To what extent, I am unsure; however based on the journals I read, it may have a greater impact than what many would like us to believe.
Source:
http://www.ncbi.nlm.nih.gov/pubmed/19568192
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