Biomechanics: Striking Injury Prevention Rehabilitation Strategies

Understanding Concussions for MMA

Concussions are mild traumatic brain injuries that result from acceleration of the head that creates shearing forces on the brain. While an obvious sign of a concussion is being knocked unconscious one does not have to get KOed or hit in the head for a concussion to occur; indirect blows to other areas in the body can cause an impulse that may impact the brain.

Signs and symptoms of concussions include (Neidecker 2018):
1. Somatic:
Headache, vomiting, nausea, light / noise sensitivity and vision problems.
2. Cognitive:
Fogginess, difficulty concentrating, memory issues, slow to react / respond.
3. Behavioral:
Labile mood, irritability.
4. Physical signs:
Loss of consciousness, confusion, slurred/slow speech, sluggish, change in movement.
5. Balance:
Dizziness, difficulty walking and stumbling.

Physiology of a concussion
Trauma to the brain leads to an alteration of regular brain function. This dysfunction occurs at the metabolic level: cell membrane disruption and axon stretching. This leads to an abnormal release of neurotransmitters, which then causes the body to attempt to restore homeostasis by increasing the pumping of the sodium / potassium. The depletion of energy stores in the brain make regular brain activities require more energy.

There are two phases of a concussion: Excitatory and spreading depression.
Excitatory phase: The initial phase includes many typical concussion symptoms: loss of consciousness, headache, concussion, brain fog, daze, fatigue, slurred spree has, nausea, dizziness and vomiting. This phase should resolve within 7-10 days for 80% of people who suffer concussions.

Spreading depression phase: Drop in brain chemical production. N-Acetylaspartate (NAA) is considered a neuron-specific metabolite and its reduction a marker of neuronal loss (Signoretti 2001). In the second phase the brain is still vulnerable to injury even against mild impacts. Additional impact can result in a more severe brain injury. How long does this second phase last? Most people would assume once symptoms have ceased they are ready for a return to training, however brain chemicals may not normalize until day 30 (Vagnozzi 2010).

Concussions: Linear vs. Rotational forces:
The type of force and location of head impact may increase the likelihood of a concussion. Studies show that strikes aimed to the side of the head may be more effective than strikes aimed at the front. “Higher linear and angular accelerations produced longer periods of unconsciousness (more than 3 times) on the side than at any of the other locations. (Hodgson 1983)”. “Model predictions have shown that the laterally impacted brain experiences a larger skull deformation, a higher intracranial pressure, and a higher shear deformation as compared to a brain impacted from the frontal direction. (Zhang 2004)”. Based on the anatomical design of the brain, brain tissue deforms easier to shear forces and rotational accelerations have a higher potential to cause shear-induced tissue damage. “Shear deformation caused by rotational acceleration is the predominant mechanism of injury in concussion ( Meaney 2010)”.

Incidence of concussions in MMA
A recent retrospective study (Curran-Sills 2018) examined the incidence of concussions in MMA over a 5 year period. Of the 343 bouts (amateur/professional) observed there were 162 injuries, 101 of those injuries were reported concussions!

That is 14.7 concussions per 100 AE (athlete exposure). Each bout was categorized as 2 AE. Based on the statistic the author theorized that an MMA athlete may experience 4.4 concussions in a 10 year period. Comparison: Hockey (27.6), Football (2.2), Rugby (0.8). This data is in regard to competition only. The rigors of training for a fight, including hard sparring, are not included. In the early days of the sports there were camps that had notoriously tough sparring. Recently there has been a trend among camps to reduce the amount of hard sparring done in fight camp.

When is it safe to return to training?
Symptoms may last for only 5 days but the metabolic energy crisis in the brain may last for up to 30 days. Even when you think you are fine your brain is still vulnerable.

Recommended guideline on when to return to competition. (Zurich consensus, McCrory et al 2013)
1. Symptoms resolution.
2. Neurological assessment return to baseline.
• Cranial nerve normal.
• Balance normal.
• Vestibular ocular reflex (VOR) normal. 
3. Neuro-cognitive assessment return to baseline.
4. Graduated physical exertion.

Return to fighting protocol (Nalepa et al 2017)
A fighter should start phase 1 after a week from initial concussion. A fighter can progress to the next step after 24 hours if there are no concussion symptoms. If symptoms increase than the fighter must regress one step. A fighter should not progress to phase 3 if there are any lingering concussion symptoms. Fighters should get cleared by a medical professional trained in concussion management before returning to training / competition. As a martial artist I understand wanting to return to training as soon as possible but without adequate recovery it is possible for symptoms to become chronic and linger.

Phase 1. Return to general fitness

Step 1 Light aerobic activity: Gradually escalating of heart rate via exertion (<70% max HR). Stationary bike or elliptical. •Step 2 Moderate aerobic activity: Greater escalating of heart rate (>70% max HR). Jogging, swimming.
Step 3 Sport-specific / resistance training: Begin resistance training and sport specific movements.

Phase 2. Return to non-contact fighting activities

Step 1 Bag/ mitt work with movement: This challenges the vestibular and visual system while performing sport-specific movements.
Step 2 Shadow boxing / drills: Re-introduces the fighter to sport environment and challenge dynamic balance with footwork.
Step 3 One-sided sparring and grappling: Sparring without concern for contact. This allows the fighter to work on reacting off the opponent without the risk of impact.

Phase 3. Return to contact / sparring fighting activities

Step 1 Short sparring: Short duration and long rest between rounds.
Step 2 Longer sparring: Longer duration and shorter rest between rounds.
Step 3 Regular sparring: Normal parameters for intensity and volume of training.

Concussion awareness in the mixed martial arts community needs to improve to allow for adequate recovery for the athletes. In my opinion baseline concussion testing should be mandatory for each state. At the moment California is the only state in the US that requires a neurocognitive component to be granted a professional MMA license.  

References:
1. Curran-Sills, G., & Albedin, T. (2018). Risk factors associated with injury and concussion in sanctioned amateur and professional mixed martial arts bouts in Calgary, Alberta. BMJ open sport & exercise medicine, 4(1). e000348.
2. Hodgson, V. R., Thomas, L. M., & Khalil, T. B. (1983). The role of impact location in reversible cerebral concussion (No. 831618). SAE Technical Paper.
3. McCrory, P., Meeuwisse, W. H., Aubry, M., Cantu, B., Dvořák, J., Echemendia, R. J., … & Sills, A. (2013). Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012. Br J Sports Med, 47(5), 250-258.
4. Meaney, D. F., & Smith, D. H. (2011). Biomechanics of concussion. Clinics in sports medicine, 30(1), 19-31.
5. Neidecker, J., Sethi, N. K., Taylor, R., Monsell, R., Muzzi, D., Spizler, B., … & Reyes, P. (2018). Concussion management in combat sports: consensus statement from the Association of Ringside Physicians. Br J Sports Med, bjsports-2017.
6. Nalepa B, Alexander A, Schodrof S, et al. Fighting to keep a sport safe: toward a structured and sport-specific return to play protocol. Phys Sportsmed 2017;45:1–6.
7. Signoretti S, et al. N-Acetylaspartate reduction as a measure of injury severity and mitochondrial dysfunction following diffuse traumatic brain injury. J Neurotrauma. 2001.
8. Vagnozzi R, et al. Assessment of metabolic brain damage and recovery following mild traumatic brain injury: a multicentre, proton magnetic resonance spectroscopic study in concussed patients. Brain. 2010.
9. Zhang, L., Yang, K. H., & King, A. I. (2004). A proposed injury threshold for mild traumatic brain injury. Transactions-American Society of Mechanical Engineers Journal of Biomechanical Engineering, 126(2), 226-236.

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