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MUSC Health Blog

Keyword: sports-medicine

By Ethan Konoza, ATC
Athletic Trainer
MUSC Health Sports Medicine

Flexibility in relation to the human body can be defined as the range of motion (ROM) of a joint that is largely affected by the muscles, tendons, and bones around the joint (Borges, Medeiros, Minotto, Lima, 2017). There are several methods to increase ones flexibility and ROM. Proprioceptive neuromuscular facilitation (PNF) in particular is a stretching technique that has been shown to effectively increase ROM and flexibility (Hindle, Whitcomb, Briggs, Hong, 2012). PNF stretching can be performed to increase passive range of motion (PROM) and active range of motion (AROM). Two of the most common methods discussed in the current literature of PNF stretching include a contract relax (CR) method and a contract relax antagonist contract (CRAC) method. The CR method is performed by lengthening the muscle targeted for stretch and holding it in lengthened position while maximal isometric contracting of the same target muscle is being performed for a set amount of time. This is then followed by relaxation of the target muscle while being passively stretched. (Hindle et al., 2012; Maharjan, Mallikarjunaiah, 2015; Muscolino, 2017). The CRAC method of PNF stretching is performed similarly to CR but with an antagonist contraction instead of passive stretching following relaxation of the targeted muscle. There are four theories as to why PNF stretching is effective in increasing ROM. These include autogenic inhibition, reciprocal inhibition, stress relaxation, and the gate control theory (Hindle et al., 2012; Maharjan, Mallikarjunaiah, 2015).

Muscle spindles and Golgi tendon organs (GTO) are two types of muscle proprioceptors that are protective in nature but also play an important role in how these proposed mechanisms work to increase ROM during PNF stretching. Muscle spindles are located within the belly of a muscle and senses stretch or lengthening of a muscle (Powers & Howley, 2018; Muscolino, 2017). When a muscle becomes stretched (lengthened) to a point the muscle spindle too is stretched. The stretching of the muscle spindle causes an impulse and an afferent neuron is sent to the central nervous system (CNS) through the spinal cord. The CNS receives and interprets this information. If a muscle is lengthened too far the CNS will send an efferent neuron to cause a reflex contraction called a myotatic reflex to contract (shortening of the muscle) to prevent any more lengthening to that muscle to prevent damage or tearing. (Powers & Howley, 2018; Muscolino, 2017). The GTO is another type of muscle proprioceptor that is located near the musculotendinous junction and is attached to muscle fibers. The GTO detects changes in tension within a muscle. When a muscle contracts (shortens) increased tension is placed upon the GTO (Hindle et al., 2012; Powers & Howley, 2018; Maharjan, Mallikarjunaiah, 2015; Muscolino, 2017). The shortening of the muscle causes the GTO to become stretched and in turn creates an impulse that sends an afferent neuron to the CNS by way of the spinal cord. The CNS then interprets this information sent by the GTO detecting a pulling force on a tendon. This pulling force can damage and injure the tendon. This ultimately causes another impulse to be sent to relax the muscle so that no more tension is place upon the tendon (Powers & Howley, 2018; Muscolino, 2017) This is termed the GTO reflex or inverse myotatic reflex as it has the opposite or inverse effect of the myotatic reflex created by the muscle spindle.

It is important to note that both muscle proprioceptors discussed are protective in their design. Due to this protective element, the GTO’s inhibitory type reflex in particular can be utilized in increasing the amount of stretch that can be placed upon a muscle. Isometric contraction of the target muscle causes tension to be placed upon the muscle and its tendon, which in turn activates the GTO reflex. The GTO reflex causes relaxation of the targeted muscle due to its protective nature. This relaxation of the muscle by way of the GTO reflex prevents excessive tension or stretching on the tendon to avoid tearing or damage. This relaxation of the muscle allows for further stretch to be placed upon the targeted muscle and in turn allows for increases in ROM and ultimately flexibility seen from PNF stretching.

While by design the GTO acts as a protective measure by sending an inhibitory reflex to the target muscle, we are essentially using this reflex as means of enhancing the effectiveness of the stretch. That is getting the muscle to relax so that we can further stretch the muscle. By adding tension to the GTO by asking our athletes to isometrically contract during PNF stretching we are triggering their bodies into sending this inverse myotatic reflex to inhibit any further contraction of that targeted muscle. This inhibitory reflex is what allows us to stretch the targeted muscle further. Stretching the soft tissue is just one area of the mobility and ROM puzzle. Optimizing mobility leads to proper execution of functional movements, which in turn reduces the likelihood of injury and ultimately improves performance.


Borges, M. O., Medeiros, D. M., Minotto, B. B., Lima, C. S. (2017). Comparison between static stretching and proprioceptive neuromuscular facilitation on hamstring flexibility: systematic review and meta-analysis. European Journal of Physiotherapy, 20. 12-19.

Hindle, K., Whitcomb, T., Briggs, W., & Hong, J. (2012). Proprioceptive Neuromuscular Facilitation (PNF): Its Mechanisms and Effects on Range of Motion and Muscular Function. Journal of Human Kinetics, 31: 105-113.

Maharjan, J., Mallikarjunaiah, H. S. (2015). Proprioceptive neuromuscular facilitation stretching versus static stretching on sprinting performance among collegiate sprinters. International Journal of Physiotherapy, 2, 619-626.

Muscolino, J. E. (2017). Kinesiology: The Skeletal System and Muscle Function. MO, St. Louis. Elsevier

Powers, S. K., & Howley, E. T. (2018). Exercise physiology: Theory and application to fitness and performance. New York, NY: McGraw-Hill Education.

By Kathleen Choate, ATC, CSCS, CEAS
Athletic Trainer
MUSC Health Sports Medicine

Most of us have seen it or felt it. We see an athlete go down on the field with an injury during a game. The athletic trainer runs out, lifts the leg, pushes the toes back, and starts massaging the calf. This athlete is likely a victim of exercise associated muscle cramps (EAMC) and can cost players valuable playing time. Many players swear by treatments to prevent it such as bananas, pickle juice, Pedialyte, or sports drinks. For some they work, for others they don’t. My goal is to help you learn what strategies are most likely to effectively prevent and treat EAMC.

Causes and Prevention

The currently accepted theory for EAMC is called the “altered neuromuscular control theory.”1  In a nutshell, this theory means that the muscles cramp up because of muscle fatigue.

The strategies for preventing EAMC that have been backed by scientific evidence include the following:
• Training for competition by addressing neuromuscular endurance and muscle imbalances. Plyometrics could be helpful in this area.1
• Tapering workouts in the days leading up to competition.1
• Warm-up prior to exercise. I always recommend a dynamic warm-up.1
• Rest breaks during or in between competitions.1
• Start the competition in a controlled effort.1

While hydration and electrolytes are not currently accepted ways of preventing EAMC, they could help prevent a variety of heat related illnesses. For that reason, you should still plan to hydrate with water or sports drinks prior, during, and after physical activities.


The strategies for treating EAMC that have been backed by scientific evidence includes stretching and ice.1  Please don't force the stretch since being too aggressive can cause a strain in the muscle. While ice is effective and a less painful treatment, I’ve noticed that this method usually takes the longest to relieve the cramp.

While still an unproven hypothesis, I personally believe massage or use of a foam roller or stick roller on the affected muscle are also extremely effective. Brace yourself for the pain, because this is also the most painful treatment.

In extreme cases where the cramps do not resolve, especially if multiple body parts are involved, they may have to be treated by a physician in the Emergency Room. If you have muscle cramps frequently, and nothing you’ve tried seems to prevent them, discuss this with your physician to identify any other potential causes and treatments.


Edouard, P. (2014). Exercise associated muscle cramps: Discussion on causes, prevention and treatment. Science & Sports, 29(6), 299-305. doi:10.1016/j.scispo.2014.06.004

By Marty Travis, MS, ATC
Athletic Trainer
MUSC Health Sports Medicine

It’s fall football season. As usual, coaches, players, and parents are asking about prophylactic knee braces as soon as the first knee injury occurs. There is just no clear answer. Some studies have shown some decrease of MCL injuries on teams using the braces, while other studies have actually shown an increase of MCL injuries when braces are used. Still other studies have shown no significant changes on teams using the braces.

I used to be an advocate of braces early in my career during the 1980s and 1990s, not because of research studies but because the late, great Dr. Bob McDavid was one of my early mentors. He had one of the first patents for prophylactic lateral knee braces/guards. He also had patented many other types of sports medicine equipment. The college football teams that I covered all provided McDavid knee guards to defensive and offensive linemen. The teams had fairly low rate of MCL injuries to the linemen, but this was just a casual observation. I did not conduct any official research studies.

Today I discuss the facts with coaches, parents, and players and let them develop their own feelings on braces. Skill players were always against using braces because they thought they slowed them down, but big linemen seem to lean toward using braces. A big factor in determining whether or not to use braces is financial. The cost can range from $50 for an off-the-shelf brace from a sporting goods shop to $900 for a custom-fitted brace.

Right now I am neutral about using the prophylactic braces for a healthy knee. I recommend parents and athletes read the position statement by the American Academy of Orthopaedic Surgeons on knee bracing to help them decide.

By Amberle Phillips, MA, ATC, SCAT
Athletic Trainer
MUSC Health Sports Medicine

Adequate amounts of sleep are vital for athletic performance and mental function. This is especially true for younger athletes. Sleep deprivation among college-aged athletes can be attributed to travel for sport, stress, balancing academics, athletics, and social life. The National Athletic Trainers’ Association recommends eight hours of sleep for individuals aged 17-22 years.

Sleep deprivation may impact mental health. The body’s ability to deal with stress and emotions depends on sleep to regulate proper functionality. Without sleep the mind is unable to process situations effectively and may cause emotional instability and inability to process stressful situations. Mood and depression are also affected by lack of sleep. Sleep deprivation may cause increased depression and other mood swings. The mind is not the only thing that is impacted by lack of sleep; the body’s cells are also affected.

During sleep is when the cells in the body grow, repair and rebuild helping injuries heal and preventing further injury from occurring. Cells need the rest that sleep provides to catch up on the days’ work that the body did. The cells will repair themselves and create new cells to assist in growth, and repair. The healing of cells that takes place during sleep is also the time when muscle cells and tissue can grow. Poor sleep and shortened sleep may also lead to weight gain and obesity. This is especially true in adolescents whom require more sleep than adults.

Here are a few tips and tricks that can be done to help fall asleep and to stay asleep:

  • Turn off all devices 1 hour prior to bedtime
  • Create a bedtime routine
  • Exercise daily
  • Meditation or total muscle relaxation techniques
  • Avoid caffeine late in the day
  • Stick to a schedule, even on the weekends

By Stephanie Davey, MEd, ATC, PES
Athletic Trainer
MUSC Health Sports Medicine

The middle of July means that high school football is just a couple of weeks away. In South Carolina, most of our high schools start around July 27th. If your son is planning to play football and go through preseason, there are a few things they need to focus on off the field in order to be safe and productive on the field.

Hopefully, your son has already been working on his conditioning. This will go a long way to him being able to acclimate to the South Carolina heat. South Carolina High School League mandates an acclimatization practice plans that all high schools must follow. If you have questions about that plan you can find it on the South Carolina High School League website

Hydration is always the first thing that comes to mind when we think of preseason football. Your son must be hydrated prior to reporting to practice each day. There is no way to catch up if they are already dehydrated when they arrive. Two ways to tell if they are hydrated is monitoring the color and volume of their urine and making sure they weigh in and out of practices. Their urine should be a light yellow color and high in volume before they go to bed each night. Secondly, they should be weighing in prior to practice and out after practice. They can do this at home or with their athletic trainer. For every pound that they lost during practice, they need to drink 20-24 oz of fluid. If they do not regain the weight they’ve lost during the previous practice, they may need to be held out of practice until they’ve rehydrated. To rehydrate, they should consume water and a sports drink. Soda and beverages with a high caffeine content should be avoided. Energy drinks should not be consumed at all.

The next thing to focus on is proper nutrition. The body is just like a car, the better fuel you put in it the better it performs. Your son needs quality food that is high in nutrition volume with a good balance of carbohydrates, proteins, and fats. Your son needs 40 – 50 kcals/kg of body weight. They should consume 4-8g/kg of carbohydrates and 2-3 g/kg of proteins.  Foods to focus on are lean meats, eggs, nut butters, protein shakes, pastas, and fruits and vegetables. Fruit and vegetables with a high water content can also help to hydrate. Your son needs to eat prior to practice, even if it is an early morning practice. It shouldn’t be a big heavy meal, but they need to have some source of energy before practice.

The last thing to focus on is sleep. The National Institute of Health recommends that high school athletes get an average of 9-10 hours of sleep each night.  Proper sleeping habits with allow your son’s body the time it needs to recover after each practice.  It allows him to stay focused and think clearly during practice. Better recovery and better focus leads to better performance.

Taking these steps will go a long way towards protecting your son during preseason football, ensuring that he has a fun, productive and safe football season.


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