The Forgotten Factors Contributing to Pathokinematics - Part II

In the first part of this blog series, we talked about the role of hydration on movement.  Today, we will take a look at environmental factors as well as nutritional factors.

Heat and Humidity

 

When exercising in extreme heat and humidity, the body requires a much greater intake of fluids to maintain health and wellness.  Without the required intake of fluids, athletes are particularly subject to heat related issues, including serious illness that can even require immediate medical treatment. 

 

Heat exhaustion is the most common type of heat illness and is caused by decreased blood volume due to dehydration. With heat exhaustion, an individual can experience:

 

• Dizziness
• Headaches
• Nausea
• Profuse sweating
• Cool or clammy skin
• A rapid or weak pulse
• A body temperature that is at or slightly above normal.

If you have these symptoms, you should try to cool down as quickly as possible.  Body cooling can occur through conduction, convection and evaporation.  Evaporation is the most critical defense the body has to overheating.  It occurs when the body’s sweat changes on its surface from a liquid to a gas, which then cools the skin.  The relative humidity in the air surrounding a person’s body is the most important factor in determining how effective evaporation is for cooling the body’s core temperature. 

According to the National Oceanic and Atmospheric Administration’s (NOAA) Heat Index Chart, temperatures and humidity levels in combination below 80 degrees and 40% respectively are of no concern.  However, at 88 degrees Fahrenheit and 40% humidity, the heat index is at 88 and caution is needed.  If the temperature stays at 88 degrees Fahrenheit and the relative humidity rises to 75%, conditions are dangerous.

 

This is important to athletes and others who are exposed to heat while required to also exert themselves because the body’s most important mechanism for cooling as mentioned is evaporation.  As the heat index rises, and the humidity levels rise, the air cannot absorb as much moisture off the skin and so evaporation slows or even stops, eliminating the body’s ability to cool itself in that way.  When conditions are extremely dangerous, or when an athlete overexerts him or herself and fails to hydrate and cool off properly during exercise or activity, heat stroke can occur.  The official definition of heat stroke is when the body’s core temperature exceeds 105 degrees Fahrenheit.  Heat stroke can result in death if not treated immediately.  Other heat related issues that athletes can encounter include sunburn and heat cramps, which are painful spasms in the legs and abdomen.

Nutrition

It is important to remember that nutrition has a significant impact on performance, recovery and body composition.  There are basically two types of food:  energy dense foods and nutrient dense foods.  Energy dense foods are higher in calories relative to the size or volume of the food.  These foods should be consumed with caution because it is easy to provide the body with too many calories at times when they may not be needed for energy production.  Foods in this category include raisins, cheese, whole milk, butter, French fries, burgers, sweets, energy bars and soft drinks.  Nutrient dense foods however are bulkier and take more time and energy to eat.  These include grapes, other whole fruit, whole and uncooked raw vegetables, and lean meats, fish or other proteins, such as beans and legumes.

Many athletes discount the role of nutrition in sports performance and staying strong and injury free.  So many people say they exercise so they can eat and drink whatever they like whenever they like.  Then they are confused when they feel tired, lethargic and don’t get the results they desire in the gym, on the field or on the road.  In addition to facilitating increased performance, nutrition also plays a role in staying injury free.   Nutritional needs vary by the type, volume, frequency and intensity of training.  If you are training more, nutritional needs are greater and it is even more important to pay attention to the type, quality and timing of fuel intake.   Overall, athletes should attempt to do the following to maintain a healthy body composition, maximize performance, and reduce the likelihood of injury and the fatigue that can lead to injury via pathokinematics:

1.  Remove as many processed foods as possible from the diet
2. Concentrate on getting enough whole fruits and vegetables and lean protein
3. Be careful with starches and sugars, emphasizing them in your diet primarily during and immediately after intense training.[ii]

Another consideration for athletes is the balance between carbohydrates, protein and fat.  Carbohydrates are necessary to replenish glycogen stores that are used up during intense exercise which is discussed further in a later section.  Therefore, carbohydrates should be consumed immediately (within the first 30 minutes) after long or intense workouts in order to replenish glycogen stores and refuel for the next workout.  Protein must be consumed in order to build muscle and other tissue in the body that is broken down during training.  Finally, fats are also required in a healthy balanced diet (despite some commonly held thought) to help maintain the immune system and enable the body to process protein and carbohydrates for use in cells.

Of course, vitamins and minerals are also needed for a well functioning body.  Most micronutrients are found in a well balanced, varied diet where foods are consumed in as close to their natural state as possible.  If your athlete is not getting a well balanced diet for some reason, sometimes a multivitamin is beneficial, though it should be remembered that vitamins and minerals taken in pill form are never as readily used by the body as those found in a natural diet of healthy, lean, whole and unprocessed foods.

Vitamins and minerals that are especially important for athletes and a few of the ways they impact performance are listed here:

 Vitamin A – Improves immune function; promotes skeletal growth; important for vision

Sources:  Beef liver, green, orange and yellow vegetables

Vitamin B1 – (Thiamin) helps convert starches and sugar into energy, promotes a strong heart muscle, prevents fatigue

Sources:  whole wheat, dried yeast, oatmeal, peanuts, port, bran, enriched rice, sunflower seeds, soybean sprouts

Vitamin B6 – Aids metabolism of protein, carbohydrates and fats, aids in keeping chemical balance between blood and tissue, builds hemoglobin

Sources:  brewer’s yeast, wheat bran, wheat germ, organ meats, beef, avocados, bananas, milk and eggs

Vitamin B2 (Riboflavin) – aids in releasing energy to body cells, enables use of fats, proteins and sugars

Sources:  Dairy, liver, kidney, yeast, leafy greens, fish, eggs

Vitamin B12 – Promotes use of protein, fats and carbohydrates, helps in formation of red blood cells, helps nervous system

Sources:  Liver, beef, pork, eggs, dairy, shellfish

Vitamin C – Required to absorb iron, some proteins and folic acid, prevents oxidation of other vitamins, aids in metabolism of amino acids and calcium, strengthens blood vessels and maintains bone density, promotes stamina, aids in healing

Sources:  citrus fruits, berries, green and leafy vegetables, tomatoes, cauliflower, potatoes (white and sweet)

Vitamin D – helps strengthen bones and helps protect the body against osteoporosis and cancer; maintains nervous system and heart action; modulates neuromuscular function, reduces inflammation

Sources:   sunlight on human skin, fish, some fortified foods, light-exposed mushrooms

Vitamin E – protects the body’s store of vitamin A, tissues and fat from destructive oxidation; aids blood flow to the heart, regulates protein and calcium metabolism

Sources:  Soybeans, vegetable oils, broccoli, Brussels sprouts, leafy greens, whole wheat, wheat germ, whole grain cereals, eggs.

Calcium—helps promote weight loss, build muscle tissue and strengthens bones; helps protect the body against osteoporosis

Sources:  Dairy, soybeans, sunflower seeds, legumes, sardines

Magnesium – aids in converting blood sugar into energy, helps regulate body temperature, promotes absorption and metabolism of other minerals, and activates enzymes for metabolism of carbohydrates and amino acids

Sources:  nuts, figs, seeds, dark green vegetables, wheat bran, avocados, bananas

Iron – present in all cells, one of the parts of hemoglobin which carries oxygen to the tissues by blood circulation

Sources:  liver, meat, raw clams, oysters, oatmeal, nuts, beans, wheat germ

Iodine – helps burn fat, aids in absorption of carbohydrates from the small intestine, regulates energy production

Sources:  kelp, seafood, vegetables

Copper – facilitates iron absorption, promotes protein metabolism

Sources:  shrimp, beef liver, whole wheat, prunes, nuts, raw oysters

Zinc – aids in metabolism of carbohydrates

Sources:  eggs, cheese, beef, pork, wheat germ, brewer’s yeast, pumpkin seeds, popcorn

Niacin – used with other vitamins to convert carbohydrates into energy

Sources:  liver, lean meat, whole wheat, brewer’s yeast, wheat germ, fish, eggs, roasted peanuts, poultry, sesame seeds, nuts.

Fiber  - lowers risk of diabetes and heart disease, lowers blood cholesterol, maintains healthy digestive system, helps control blood sugar, aids in weight loss

Sources:  fruits such as apples and citrus fruits, vegetables such as peas, beans, carrots, whole grains, wheat bran, legumes, nuts, oats, barley[iii]

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

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[i] NOAA, National Weather Service Office of Climate, Water, and Weather Services; “Heat:  A Major Killer,” 1325 East West Highway, Silver Spring, MD 20910 web site http://www.nws.noaa.gov/om/heat/index.shtml;

 

[ii] Going Long:  Training for Ironman Distance Triathlons, Joe Friel and Gordon Byrn, The Ultrafit Training Series, Velo Press, 2003, pages 10, 187.

 

[iii]

The Forgotten Factors Contributing to Pathokinematics

The focus of this blog series is on movement and the impact that movement has on performance and injury.  The following is a brief overview of several important factors that can contribute to pathokinematic movement in addition to those cited in the previous series related to differences between males and females.  Several of them are related to nutrition as you will see, which has significant impact on the ability of the athlete to move properly and sustain proper mechanics over time.  In sports medicine, nutrition is one area too often ignored.   

All of these factors influence energy conservation, endurance, speed and power in the athlete.  As we know, when energy levels are low, endurance, speed and power suffer.  Over time, as fatigue continues to set in, an athlete may be subject to an even greater likelihood of poor biomechanics, even if they are not present under well rested conditions.  In other words, even in cases where pathokinematics don’t normally exist in a given athlete, they can be caused by inattention to these issues.  And for those athletes who demonstrate certain lower extremity pathokinematics all the time, inattention to these factors can and does exacerbate them in many cases, especially in situations that require increased endurance, speed, power or strength.

Hydration

Water intake or hydration is a simple aspect of nutrition that has a huge impact on athletic  The   Aside from performance, though, it is critical to remember that water is essential to the human body, and without it we wouldn’t survive to compete in athletic activities.  Estimates are that a human can survive 8-14 days without water, depending on the rate of sweat, urine and tears leaving the body.  Water composes more than half of the human body, and is required for every single body function.  Water helps to:
correlation between hydration and endurance and speed during athletic performance is clearly shown in the research.
performance.

• Transport nutrients
• Dispel waste
• Regulate the body’s temperature
• Aid digestion
• Ensure healthy function of vital organs

Guyton's Textbook of Medical Physiology states that "the total amount of water in a man of average weight (70 kilograms) is approximately 40 liters, averaging 57 percent of his total body weight.”[i]   Specifically, lean muscle tissue contains about 99% water by weight, blood contains almost 70% water, body fat contains 10% water and bone has 22% water.  The human body is about 60% water in adult males and 55% in adult females.[ii]  Knowing that the human body is composed of so much water, the importance of hydration becomes even more apparent, yet it is rarely addressed in sports performance related literature or when treating athletes with injuries. 

The human body is constantly undergoing a complex set of chemical reactions. These chemical reactions are highly dependent on blood pH.  There is some disagreement among researchers about what constitutes a healthy pH in humans, but most agree it ranges from 6.1 to 7.5.  A healthy blood and body pH is essential in order to allow chemical reactions in the body to take place.  The rate limiting step, in most chemical reactions in the human body, is dependent on enzymes.  Enzymes are activated and deactivated by pH levels.  If pH levels are higher or lower than “optimal” then chemical reactions are slowed.  Water is essential to maintain a proper pH balance and therefore is essential for facilitating these reactions at the proper rate.  When water (H20) is introduced into the body, one of the hydrogen molecules cleaves off, leaving H + HO.  This free hydrogen ion aids in making the body’s pH more neutral.  This allows chemical reactions to take place more readily.   Therefore, proper hydration is believed to have the following critical effects in humans: 

1.     Improves muscle repair –  by creating a chemical environment more conducive to protein synthesis and repair of muscular tissue torn down during training

2.     Improves the efficiency of chemical reactions for both aerobic and anaerobic metabolism

3.     Improves viscosity of the blood –

a.     Allows improved oxygen and nutrient transport to muscle tissue

b.     Decreases stress on the heart by increasing stroke volume

4.     Improves elasticity of muscle and ligament tissues – which improves tolerance to the high force demands of athletic activity.

According to research published in the American Journal of Epidemiology in 2002, nearly 50% of the American population is considered clinically dehydrated.[iii]  Dehydration occurs when the amount of body fluid lost is greater than the amount of fluid that is replaced. In this state, the body is unable to cool itself, causing a lack of energy, muscle fatigue, cramps, heat exhaustion or possibly heat stroke.  Appendix J depicts a urine color chart that can be used to assess hydration levels as well as a chart from the Centers for Disease Control and Prevention outlining signs of dehydration.

In order to avoid dehydration and the potential dangers associated with it, the following guidelines should be adhered to:

• Drink fluids before feeling thirsty and before, during and after exercise or prolonged heat exposure;
• Water is the best fluid for everyone and the recommended amount is 0.5 to 1.0 ounces per pound of body weight per day.  Fluids can also come from fruits, juices, soups and vegetables, but these fluids should not be relied upon to replace pure water;
• When exercising with high intensity for more than 45 minutes, sports drinks can replenish lost electrolytes;
• It’s a good idea to keep a water bottle, hands-free system or similar portable container on hand and drink from it throughout the day and especially when exercising;  
• Check the color of urine to see if fluid intake is adequate. Clear or light-colored urine indicates proper hydration;
• Avoid caffeine, some energy drinks and alcohol.  Some energy drinks have high amounts of caffeine which acts as a diuretic and accelerate water loss;
• Take frequent breaks from strenuous, sweat producing activities to hydrate adequately so that the body has time to cool and recover.

The Gatorade Institute has shown that as little as 1% dehydration can result in a 10% decrease in performance in elite athletes[iv].  Although all the mechanisms are not completely understood, it is obvious that hydration can and does play a critical role in performance, endurance, and power.  That being said, there is some variation in recommendations for water consumption, and requirements are highly dependent on activity, environmental conditions and individual needs.  Current recommendations in the literature range from .5 to 1.0 oz/pound of body weight.  When considering your own water needs, it is typically best to measure your current intake and gradually work your way up to a recommended range, while paying close attention to what “feels” best for you.  Again, see Appendix J for a urine color to assess hydration levels and a chart outlining physical signs of dehydration.

Dr. Nessler is a practicing physical therapist with over 18 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

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[i] Guyton’s Textbook of Medical Physiology

 

[ii] Guyton’s Textbook of Medical Physiology

 

[iii] American Journal of Epidemiology in 2002

 

[iv] Walsh, R; Noakes, T; Hawley, J; Dennis, S. Impaired High-Intensity Cycling Performance Time at Low Levels of Dehydration, Int J Sports Med 1994; 15(7): 392-398

 

Factors That Contribute to Pathokinematics - Part IV

Last week we looked at the role of biomechanics and neuromuscular function.  This week we will wrap up this series by looking at the role of hormones and core/hip strength. 

Hormones:

There has been a lot of evidence on the effects of gender specific hormones (i.e. estrogen and progesterone) on joint laxity and ligament strength.  Since the type and amount of circulating hormones are gender specific, studies have focused on the effects of “female” hormones on joint and ligament integrity.  It is speculated that the release of these hormones affects the laxity of the joint and possibly the strength of the ACL.  However, in spite of this assumption, currently there is little consensus in the medical community on the relationship between the female menstrual cycle and ACL injury.[i]

Core (Including the Hip) Strength:

The “core” has been a term that has emerged in the research and fitness literature over the last ten years that is currently used to describe anything that includes the abdomen.  Yet, despite the prevalence of this definition’s use and over use, it has not been well defined or well understood.  Many authors have attempted to define it but there has not been full consensus in the research of what defines or composes the core. 

In the fitness industry, the core is typically thought of as the abdominal muscles and the lower back, as stated above.  However, in the medical research community, the core typically refers to the trunk and hip musculature including but not limited to: abdominals (upper abdominals, obliques and transverse abdominus), back extensors (multifidus, erector spinae and quadratus laborum), hip musculature (gluteus medius, gluteus maximus and tensor fascia lata), and external rotators of the hip and lower extremity musculature (quadriceps/hamstrings/sartorius/gracilis).  For our purposes, the term “core” will be used to define all of the musculature from the chest to the knees. 

The reason we include this region is there are over 30 muscles that have some form of influence on the lumbar spine and pelvis and which greatly influence the way that force is absorbed and transmitted through this region to the extremities.  It is our belief that the muscles that influence the position of the spine and pelvis have a direct influence on the strength and control of the legs and hips.  Hip muscles, in particular the gluteus medius and hip external rotators, are also key muscles that work to prevent collapsing of the leg in toward the mid-line in full weight bearing situations and thereby prevent a resultant knee valgus (a component of pathokinematics).  The research seems to support this supposition. 

In a prospective study of 140 athletes during one season found that those who tore their ACLs had significantly weaker hip abductors and external rotators than those who remained healthy.[ii]  A study published in the Journal of Orthopedic and Sports Physical Therapy in 2007 showed that improvement in trunk stability had a direct effect on vertical take-off velocity as well.[iii]  These studies indicate the need for core strengthening to be a major component and consideration in any performance and injury prevention program, particularly for females.   Focus areas should include the lower abdominals, the transverse abdominus and the gluteus medius muscles.

To demonstrate the importance of core strength and its correlation to lower extremity muscle strength, let’s take a look at the effect that poor core strength has specifically on quadriceps strength.  The quadriceps consist of 4 muscles (rectus femoris, vastus lateralis, vastus medialis and vastus intermedius) and this group of muscles crosses both the hip joint and the knee joint.  It originates at the pelvis (anterior superior iliac spine) and attaches below the knee (tibial tuberosity).  Poor strength of the core allows the pelvis to rotate and fall forward each time the leg is extended in walking or running activities, and this causes excessive movement of the pelvis.  This movement is defined based on the plane of motion in which it occurs.  A trendelenburg pattern occurs when there is movement of the pelvis in one plane, the coronal plane.  A corkscrew pattern occurs when there is movement of the pelvis in three planes, the coronal, transverse and sagittal planes.   

These hip movements bring the origin of the quadriceps closer to the insertion point at the hip and thus shorten the length of the quadriceps.  Based on the information that we learned in Chapter 5 about length tension relationships, we know that this shortened position (even if only a millimeter’s difference) would prevent the quadriceps from producing as much force as they could if they were in their optimally extended position.  If the quadriceps are not able to produce optimal force, there would be a direct effect on power output, athletic performance and shock absorption at the knee.  The athletes with weaker quadriceps tend to have harder landings with jump stops and hence increased force to the patella femoral and tibial femoral joints.  This can add to increased risk for ligament and meniscal injuries at the knee.   Thus by this example, we can easily understand how decreased attention to hip and trunk strength training among both genders can result in poor control of the lower extremities leading to altered biomechanical patterns. 

This is just one example of how poor strength and endurance of the core affects performance and mechanics in the lower limb.  But, there are similar effects of increased stress and excessive movements in the lumbar spine, the sacroiliac joint, the hip, the knee, and the foot and ankle areas.  Knowing the vast influence the core muscles have on the entire kinetic chain, including and especially the lower limbs, it becomes evident why it must be included in any prevention and performance enhancement program for both sexes.

In conclusion, we have discussed pathokinematics and the positive effect that addressing poor movement patterns in the athlete has on performance and injury prevention.  We have closely examined several important differences between males and females that influence movement patterns.  We also know that performance and strength training positively impacts athletic performance as well.  This has been well documented in the literature, and subsequently has become a standard part of athletics at the junior high, high school and collegiate levels. 

In most settings however, the methodology and approach to performance and strength training has remained relatively unchanged in the last ten to fifteen years.  There continues to be little consideration of gender differences in the design and implementation of performance training programs.  Knowing some of the physiological differences between males and females aids us in modifying training routines to address these differences specifically and in the most effective and efficient ways.  As a result we are able to target weaknesses in the kinetic chain that can lead to injury and limit athletic performance for both genders. 

Next week we will continue this discussion by looking at the impact that cardiovascular system has.  We hope you enjoy and share the passion and our blog with your colleagues is the biggest compliment. #ACL #Prevention @PhysioCorp

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

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[i]  Griffin, L. Y., Agel, J., Albohm, M. J., Arendt, E. A., Dick, R. W., Garrett, W. E., Garrick, J. G., Hewett, T. E., Huston, L., Ireland, M. L., Johnson, R. J., Kibler, W. B., Lephart, S., Lewis, J. L., Lindenfeld, T. N., Mandelbaum, B. R., Marchak, P., Teitz, C. C., and Wojtys, E. M.: Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies. J. Am. Acad. Orthop. Surg. 8:141-150, 2000.

 

[ii] Leetun, D. T., Ireland, M. L., Willson, J. D., Ballantyne, B. T., and Davis, I. M.: Core stability measures as risk factors for lower extremity injury in athletes. Med. Sci. Sports Exerc. 36:926-934, 2004.

 

[iii] Butcher, PT, MSc, Scott J., Craven, PT, MSc, Bruce R., Chilibeck, PhD, Philip D., Spink, PhD, Kevin S., Grona, PT, MSc, Stacy Lovo, Sprigings, PhD, Eric J.:  The Effect of Trunk Stability Training on Vertical Takeoff Velocity.  Journal of Orthopaedic and Sports Physical Therapy; Volume 37, Number 5, May 2007.

 

Factors That Contribute to Pathokinematics - Part III

Last week we looked at the impact body composition and peak height have on pathokinematics.  This week we will look more in depth to the impact that the circulatory and cardiovascular system have on pathokinematics. 

Circulatory Differences:

Adult women have 6% fewer red blood cells per liter of blood than men.  Women also have a 10 to 15% lower hemoglobin concentration and hematocrit as compared to men.  As a result, female athletes transport less oxygen per liter of blood than males do.  This could explain why female athletes are more susceptible to fatigue which can lead to increased pathokinematics later in the game, and ultimately more injuries during sporting activities.  Cardiovascular conditioning and muscle endurance training (via supersets and other strategies which will be discussed in later chapters) become even more important for female athletes because of these circulatory differences.   It is also important to educate female athletes about anemia, sports-induced anemia and a potential increase in the need for iron intake via natural or supplemental sources as well, particularly when involved in sports with heavy endurance or intensity components.

Cardiorespiratory Capacity:

When looking at the cardiovascular system, there are numerous physiological differences between the genders which have an effect on performance and body mechanics.  One of the most significant differences is in the thoracic cage.  Women have a smaller thoracic cage than men which means lung volumes are relatively less for females versus males.  The total lung capacity (the amount of air in the lungs after maximal inspiration) is significantly less in women than men.  This means that women take in fewer milliliters of air with every breath (~4200 ml for women compared to ~6000 ml for men).  The vital capacity (the amount of air that can be forced out of the lungs following maximal inspiration) is also significantly less in women than in men.  This means that women use fewer milliliters of air with every breath (~3200 ml for women compared to ~4800 ml for men). 

Not only is there a difference in lung volumes but also in the size of the heart.  Because of smaller hearts, the volume of blood the heart is able to hold and move with each contraction (stroke volume) is smaller in females, resulting in lower cardiac output.  Less blood is pumped per beat and therefore, less oxygen is transported to the cells of the body.  As a result, women have a higher heart rate than men when at the same VO2 max (an excellent physiological indicator of cardiorespiratory endurance). 

Knowing that these physiological differences exist between males and females, it is extremely important to consider the aerobic demands of a given sport and to include training protocols that address those demands specifically.  This includes not only cardiovascular training, but incorporating training methods which tax muscular strength and endurance while concurrently elevating heart rate.

Biomechanics:

Studies focusing on biomechanical risk factors have identified gender related differences relative to the position of the hip, knee and ankle during performance of landing and cutting tasks.  It is thought that pathokinematics demonstrated by females place them at greater risk for anterior cruciate ligament (ACL) injury due in part to their potential to excessively load the ligament during landing and cutting tasks in particular.   Specifically, internal rotation of the hip and knee valgus (resulting from hip adduction) are thought to place increased stress on the ACL as mentioned before.  Studies have found that when comparing males and females, females demonstrate greater hip internal rotation[i] [ii] and knee valgus[iii] [iv] [v] when performing landing tasks. In addition, females have been found to demonstrate greater valgus torques at the knee during cutting[vi] [vii] and landing tasks,[viii] further increasing the potential for excessive loading of the ligament.  This indicates not only a need for proprioceptive training for the female athlete but also the need for implementing jump training and training in movements specific to the sport. 

Neuromuscular Function, Kinesthesia and Proprioception:

Often there is confusion in the literature about the concepts of neuromuscular function, kinesthesia and proprioception.  Proprioception is a specialized sense that includes information about the position of a joint in the human body and the sensation of movement of that joint, or kinesthesia.  This information is transmitted via the central nervous system and used in unconscious neuromuscular control.[ix]   Females have been found to have less positional body awareness regarding movement or kinesthesia than males.  There are many hypotheses under discussion about why this is true.  Some hypothesize that this is the result of less overall athletic experience in general, fewer types of athletic experiences or fewer exposures to certain types of athletic experiences.  Prior to the implementation of Title IX, female athletes would get involved in athletics at later ages than male athletes and therefore had less overall athletic exposure or training.  Others speculate that the differences may be due to a lack of proximal control, which is control of the body nearest to a given point of reference.  In other words, the hips and lower back (or the core) are proximal to the lower leg, and when there is less control in the core, there is an increase in the likelihood of injury in the proximate body parts, i.e., the knee and/or the foot and ankle. 

Anatomical differences in pelvic anatomy between males and females may contribute to increased weakness of the gluteus medius, lower abdominals and transverse abdominus, all of which contribute to neuromuscular control of the core as noted above.  According to Zazulack et. al. in studies published in 2006, there are significant gender differences in the neuromuscular control of the core which contribute to abnormal movement patterns at the hip and knee. [x]  In a study published in the American Journal of Sports Medicine in 2003, there was a significant gender difference in electromyographic activity of the proximal hip components with single leg squats (specifically the gluteus medius muscle).[xi]  When assessing proprioception, if there is a loss of this proximal hip stability, then the test outcomes are poor. 

Decreased kinesthesia or proprioception has been indicated as a direct causative factor in non-contact ALC injuries, as it affects an athletes’ ability to adapt to unexpected obstacles and safely control sudden changes in the direction of movement.  In a study published in The American Journal of Sports Medicine by Hewitt, et al in 2005, women were found to have significantly less neuromuscular control of the lower leg resulting in increased valgus loading on the ACL.[xii]   This lack of control can also lead to increased stress to the foot and ankle, hip and lower back.  A study from 1996 showed that proprioceptive training alone reduced the incidence of ACL injuries by 7 times, indicating that this type of training by itself can have a significant impact on performance and injury prevention.[xiii]   In a follow up study in the Journal of Knee Surgery in 2005, the authors found that even moderate proprioceptive training significantly reduced the risk for knee injury, exclusive of any other type of change in training protocols.[xiv]   Whether or not increased injury rates in females are the result of proximal hip weakness, decreased athletic exposure, or decreased kinesthesia or proprioception, including aggressive neuromuscular re-education should be an important part of any female athlete’s training protocol. 

Next week we will continue this discussion by looking at the impact that core and hip strength have.  We hope you enjoy and share the passion and our blog with your colleagues is the biggest compliment. #ACL #Prevention @PhysioCorp

Dr. Nessler is a practicing physical therapist with over 17 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment.  He is the developer of an athletic biomechanical analysis and author of a college textbook on this subject.  He serves as the National Director of Sports Medicine for Physiotherapy Associates, is a Safety Council Member for USA Cheer National Safety Council and associate editor of the International Journal of Athletic Therapy and Training. 

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[i] Chaudhari, A. M., Hearn, B. K., and Andriacchi, T. P.: Sport-Dependent Variations in Arm Position During Single-Limb Landing Influence Knee Loading: Implications for Anterior Cruciate Ligament Injury. American Journal of Sports Medicine. 33:824-830, 2005.

 

[ii] Lephart, S. M., Ferris, C. M., Riemann, B. L., Myers, J. B., and Fu, F. H.: Gender differences in strength and lower extremity kinematics during landing. Clin. Sports Med.162-169, 2002.

 

[iii] Chaudhari, A. M., Hearn, B. K., and Andriacchi, T. P.: Sport-Dependent Variations in Arm Position During Single-Limb Landing Influence Knee Loading: Implications for Anterior Cruciate Ligament Injury. American Journal of Sports Medicine. 33:824-830, 2005.

 

[iv] DeRosa, C; Porterfield, J.  Mechanical Low Back Pain: Perspectives in Functional Anatomy.  Saunders, 1995.

 

[v] McLean, S. G., Lipfert, S. W., and van den Bogert, A. J.: Effect of gender and defensive opponent on the biomechanics of sidestep cutting. Med. Sci. Sports Exerc. 36:1008-1016, 2004.

 

[vi] McLean, SG., Huang, X., and van den Bogert, A. J.: Association between lower extremity posture at contact and peak knee valgus moment during sidestepping: Implications for ACL injury. Clinical Biomechanics. 20:863-870, 2005.

 

[vii] Sigward SM and Powers CM: The Influence of gender on knee kinematics, kinetics, and muscle activation patterns during side-step cutting. Clin Biomech. 2005. In press.

 

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