By Andrea Leonard
I have been a personal trainer and strength and conditioning specialist for 24 years, but first and foremost, I am a parent to a high school and collegiate athlete. My son and daughter have been playing basketball since they were very young and have endured a multitude of overuse injuries (because who listens to their mom right?). I have had the opportunity to watch many coaching styles from elementary, middle, and high school, as well as AAU, private coaching, and college basketball.
As a parent I find myself in a difficult position; if I make a “strong” suggestion to the coach or, prohibit my daughter from participating in the biomechanically incorrect and age/condition inappropriate strength training program, then my daughter will be benched. This is the politics of sports! I have therefore taken it upon myself to educate the team parents and work with the girls, off of the court, to improve their balance, flexibility, and biomechanics (things that are tragically overlooked by the coach).
I wanted to take this opportunity to share with other parents, and athletes, the proper periodization and training protocol for an athlete.
First of all, each season should begin with a comprehensive evaluation of muscle balance and range of motion for each athlete. Without knowing what their “foundation” is made of, how can a coach build a solid “house?” If muscles are not functioning properly, resulting in faulting movement patterns and biomechanics, there will be a much higher prevalence of injury. The same applies to personal trainers who take on a new client without conducting a thorough health history and fitness evaluation. Sadly, in my experience, I see this happen all too often.
The term ‘program design’ means that one is making use of a purposeful system or plan to achieve a specific goal. This allows for each individual athlete to create an individual path to achieve a specific sport-related goal; separate from the team as a whole. In order for this to be effective, there are a few key components that must be addressed: how and why must the physiological, physical, and performance adaptations of stabilization, strength, and power take place in a planned, progressive manner to establish the proper foundation for each subsequent adaptation?
An athlete’s training program should be designed to meet both short and long-term goals. The variables include: how long each phase will take, how often will it change, and what SPECIFIC exercises will be utilized at each phase. According to NASM, an athletes program should first be organized into an annual plan, and then broken down even further into a monthly plan. Each monthly plan will be broken into weekly plans. This form of training, periodization, allows for maximal levels of adaptation while minimizing the risk of injury.
The first phase of training should be focused on stabilization. Following a comprehensive postural and biomechanical assessment, corrective exercises should be prescribed to correct muscle imbalances, joint dysfunction, and neuromuscular deficits. This initial phase? will also help to re-condition the athlete (post-season) and improve kinetic chain structural integrity. It is this phase of training that will help prepare the athlete for the higher- intensity phases of training. If this phase is skipped over, the risk of injury is increased. Athletes must begin at a low-intensity -with the focus not being on how much weight they can lift, but on high repetitions that focus on core strength and joint stabilization. Coaches and trainers should be focused on proprioception and increasing neuromuscular efficiency. Exercises should focus on proprioceptive challenges by challenging the athletes balance and stability with modalities such as a foam roller, BOSU(R) Balance Trainer, Balance Discs, etc. This phase should last approximately four weeks. If the athlete has remained fairly conditioned in the off-season, they can gradually increase intensity and decrease repetitions; focusing on endurance and strength in the stabilizing muscles. This is a great time to re-introduce plyometric and SAQ routines. Over the course of four weeks, the beginner athlete should go from 1 set of 12 reps (core, balance, and resistance training- maintaining 60% intensity over the course of four weeks), to 3 sets of 20 reps, 1 set of 5 reps to 2 sets of 8 reps (plyometrics), and SAQ should progress from 3 sets of technique drills and 2 sets of speed of movement drills to 4 sets of each. The conditioned athlete may begin and end with slightly higher reps and sets. Athletes should be encouraged to begin and to finish each training session with appropriate foam rolling and static stretching exercises.
Phase two is for developing strength. This will include strength endurance, hypertrophy (developing muscle size), maximal strength, and improving overall performance. Assuming muscle imbalances and faulty biomechanics were addressed and corrected in phase one, it is now time to train the core musculature under heavier loads and through more complete ranges of motion. This, in turn, will increase the load-bearing capabilities of muscles, tendons, ligaments, and joints. The volume of training can now be increased to include an increase in reps, sets, and intensity. Over the course of four weeks, the athlete should go from 2 sets of 12 reps (core and balance) to 3 sets of 8 reps, 2 sets of 12 reps to 3 sets of 6 reps (resistance training- progressing from 70-80% intensity over the course of four weeks), 2 sets of 8 reps to 3 sets of 10 reps (plyometrics), and SAQ should progress from 3 sets of technique drills and 3 sets of speed of movement drills to 4 sets of each. This is the time to incorporate superset techniques that focus on the initial “stable” exercise, immediately followed by a stabilization exercise with similar biomechanical motions. An example might be a traditional bench press on an exercise bench followed immediately by push-ups on a stability ball. Athletes should be encouraged to begin and to finish each training session with appropriate foam rolling and static stretching exercises. This phase should last approximately four weeks.
Phase three will focus on maximal muscle growth (hypertrophy) through high levels of volume with minimal rest periods. Over the course of four weeks, the athlete should go from 2 sets of 12 reps (core and balance) to 3 sets of 8 reps, 3 sets of 12 reps to 5 sets of 6 reps (resistance training- progressing from 75-85% intensity over the course of four weeks), 2 sets of 8 reps to 3 sets of 10 reps (plyometrics), and SAQ should progress from 3 sets of technique drills and 3 sets of speed of movement drills to 4 sets of each. Athletes should be encouraged to begin and to finish each training session with appropriate foam rolling and static stretching exercises. The goal of the coach or trainer should be to continue to increase intensity and volume throughout this four-week phase.
Phase four focuses on increasing the load placed upon the tissues of the body and improves recruitment of more motor units, rate of force production, and motor unit synchronization. This phase will also increase the benefits of power training in the next two phases. The goal of the coach or trainer is to focus on increasing maximal strength through increased intensity. Over the course of four weeks, the athlete should go from 2 sets of 12 reps to 3 sets of 8 reps (core and balance), 4 sets of 5 reps to 6 sets of 3 reps (resistance training- progressing from 85-95% intensity over the course of four weeks), 2 sets of 8 reps to 3 sets of 10 reps (plyometrics), and SAQ should progress from 3 sets of technique drills and 3 sets of speed of movement drills to 4 sets of each.
Phase five focuses on power and increasing the rate of force production (speed of muscle contraction). The athlete will utilize strength and stabilization adaptations acquired in the previous phases of training; only now with more realistic speeds/forces that their body will encounter in their sport. The coach or trainer must now encourage the athlete to train with heavier loads (85-100%) at low speeds and light loads (30-45%) at high speeds. This will be accomplished by super-setting a strength exercise with a power exercise for each body part. An example would be having the athlete perform a traditional barbell bench press followed immediately by a medicine ball chest pass. An example of the speed component would be performing squats as fast as possible with a low load. The combination of these two methods will produce high-powered outputs.
- The progression for phase five is a bit different in rhythm than the previous phases. Week one begins with 2 sets of 12 reps (core and balance), 3 sets of 5 reps for strength and 10 reps for power (resistance training – 85% strength and 5% power), 2 sets of 8 reps (plyometrics), and SAQ is 3 sets of technique drills and 3 sets of speed of movement drills.
- Week two begins with 2 sets of 12 reps (core and balance), 4 sets of 4 reps for strength and 10 reps for power (resistance training – 90% strength and 5% power), 3 sets of 8 reps (plyometrics), and SAQ is 4 sets of technique drills and 3 sets of speed of movement drills.
- Week three begins with 3 sets of 10 reps (core and balance), 4 sets of 4 reps for strength and 8 reps for power (resistance training – 90% strength and 8% power), 3 sets of 10 reps (plyometrics), and SAQ is 4 sets of technique drills and 4 sets of speed of movement drills.
- Week four begins with 3 sets of 8 reps (core and balance), 5 sets of 2-3 reps for strength and 8 reps for power (resistance training – 95% strength and 10% power), 3 sets of 10 reps (plyometrics), and SAQ is 3 sets of technique drills and 3 sets of speed of movement drills.
At the conclusion of the fourth week the athlete can either cycle back through phase one and two to give their body a rest.
I have broken down the periodization of training without getting into specific exercises; these will be based on the individuals’ initial assessment, fitness level, and sports-related goals. Regardless of sport, it is essential for the athlete and their parents to understand the most common athletic injuries and how they can be prevented. We can’t rely on the coaches or trainers to do this. I have seen many injuries occur because the coaches did not apply these principles in their training. If your athlete is involved in a sport that requires cutting and jumping, they will be at increased risk for injuries due to overtraining, poor neuromuscular control, arthrokinetic dysfunction, and/or improper biomechanics. PLEASE hear me when I say that this is critical information for you as parents. I can’t emphasize this enough! If you are not familiar with the sport your child is playing, if you have no real understanding of anatomy and biomechanics, and if you can’t tell if your child’s coach knows what they are doing or not, PLEASE hire a personal trainer, corrective exercise specialist, or an athletic trainer to teach your child the essentials of injury prevention. This will be the best money you ever spend for the future of your child’s athletic career and well into their adult life. This can only be done by a professional who can conduct a comprehensive postural and biomechanical assessment to determine a corrective exercise strategy.
Populations that are at a higher risk for these injuries include over ground runners, females, and those with a higher body mass index (BMI).
Jumping and running with poor form (biomechanics), overuse, poorly fitted shoes, and eccentric loading are all risk factors for Achilles tendonitis. In addition, cold weather, previous injury, age and male gender may further increase the risk.
Plantar fasciitis is a common cause of heel pain and can be incredibly painful and debilitating to the athlete. Most people report pain in the heel region upon getting out of bed in the morning or after sitting for prolonged periods. Typically it is caused by overuse that includes sudden increases in running, walking, or standing. It may be aggravated by training and force an athlete to take time off to allow the inflammation to go down. Risk factors include having less than 0 degrees of dorsiflexion, BMI greater than 30, a job that requires standing, and increased foot pronation/flat feet.
Stress fractures occur most commonly on the 2nd and 5th metatarsal (long bones of the foot). These injuries usually occur due to repeated loading of the foot through increases in walking and running, sudden increases in intensity or duration of an activity, decreases in the amount of time usually allowed for rest and recovery, changes in one’s training surface, changes in shoes, and inadequate nutrition. Achilles tendon contracture, low bone mass, and length differences between the 1st and 2ndmetatarsals may further increase the risk. Wearing the right type of shoes for the activity, and replacing them on a regular basis as they wear, are extremely important in preventing an injury to the foot.
All of the aforementioned foot injuries can be prevented with proper stretching. It is critical that the athlete maintain full range of motion in order to prevent injury. Stretches can and should be done for the Achilles tendon and the plantar fascia while strengthening exercises should be done for the calf, anterior tibialis, and toe flexors.
Ankle Sprains are reported to be the most common sports-related injury and the reason for most athletes’ time lost during the season. The rate of ankle injury in high school athletes is roughly one per every 17 participants per season (4) and college athletes suffer over 11,000 ankle sprains per year (5).
- Alateral ankle sprain is the most common type of sprain (1). It is estimated that approximately 47-73% of individuals who suffer an initial ankle sprain will re-sprain their ankle again (6, 7). Ankle trauma and ankle sprains are also associated with developing osteoarthritis with approximately 70% of ankle arthritis being attributed to trauma (8, 9). The most common risk factor for a lateral ankle sprain is a history of a prior sprain (10, 11). Athletes who had previously sprained their ankle were five times more likely to suffer an ankle injury (3). Other risk factors include shoes with air cells in the heels and lack of stretching prior to a game (10). High school basketball players with “poorer balance” experienced almost 7 times as many ankle sprains as those with superior balance (12).
- A medial ankle sprain is often caused by forceful and rapid eversion of the foot (13) that may be combined with external rotation and plantar flexion. They are not nearly as common as lateral ankle sprains. When injury does occur in this area, it may be more severe and involve fractures to bony structures. There are no listed risk factors for medial ankle sprains.
- A high ankle sprain, known as a syndesmotic sprain, is typically caused by external foot rotation, talar eversion in the ankle mortise, and excessive dorsiflexion. This injury is most often associated with sports that involve planting and cutting, or those that require the athlete to wear rigid boots. Skiing, ice hockey, football, soccer, rugby, wrestling, and lacrosse are the sports with the highest risk of a high ankle sprain (6, 14). An athlete with flat feet may be more likely to be in a position of external ankle rotation when their foot is planted, this increasing the risk of a high ankle sprain (14).
Ankle sprain prevention and rehabilitation programs have proven effective at decreasing the incidence of ankle sprain in physically active individuals and improving ankle function (15). The most successful programs have combined proprioceptive and balance training on a daily basis. These exercises need not be sports-specific to accomplish the goal of ankle stability. It is essential to restore, or maintain, full range of motion at the ankle joint by incorporating? strengthening exercises that utilize resistance bands, weights, or body weight during functional activities (hopping, lateral movements, and cutting maneuvers). Over the course of several weeks programs may increase the number of repetitions, speed, and direction.
Lower extremity injuries account for 50% of injuries in college (16) and high school athletes (17). Two of the most common diagnoses are patellofemoral pain and ACL sprains and tears. In sports where both men and women compete, the injury rate was higher in women (18). For those that suffer an ACL injury requiring surgical intervention, their rehabilitation process may last anywhere from 6-36 months with only 75% being able to return to their previous activity levels (19). Those with acute ACL injury are seven times more likely to develop osteoarthritis in that knee (20) of the athletes with patellofemoral syndrome, 91% reported continued knee pain for 4-18 years after the initial presentation and 36% of those patients needed to restrict their physical activity (21).
One of the most common causes of patellofemoral syndrome and ACL injury is abnormal tracking of the patella (knee cap), that puts undo stress on the patellar cartilage. Abnormal tracking may be the result of lower extremity malalignment, altered muscle activation surrounding the knee musculature, decreased strength of the hip musculature, or any combination. Malalignment of the patella is commonly associated with an excessive Q-angle in a woman. This excessive Q-angle is believed to facilitate excessive lateral tracking of the patella, which may lead to the development of patellofemoral syndrome (22). Abnormal transverse and frontal plane motions of the femur can also alter patellofemoral mechanics and lead to patellofemoral syndrome. Weakness of the hip external rotators and abductors may allow the femur to move into excessive hip adduction and internal rotation, further increasing the lateral contact pressure of the patella on the femur (22). Additionally, decreased quadriceps flexibility, shortened reflex time of the VMO, reduction in vertical jump performance, increased medial-patellar mobility, tibial bowing, and increased quadriceps strength may be contributing factors to patellofemoral syndrome.
ACL injuries are 70-75% non-contact in nature and occur mostly when the body is undergoing rapid deceleration (20, 23, 25). The three most common causes of ACL injury are planting and cutting (29%), straight knee landing (28%), and one-step landing with a hyperextended knee (26%) (26). Having knock-knees, excessive leg rotation, and decreased knee flexion are common leg movements associated with ACL injuries (24, 27). When an athlete has knock-knees, their femurs are internally rotated at the hip joint. This creates extreme loading across the ACL and may cause a spontaneous rupture of the ligament. It is during this combined loading state that researchers have described the ACL to be at the greatest risk of injury (28, 29).
Patellofemoral exercise programs typically involve strengthening of the hip and surrounding knee musculature in order to decrease internal rotation, adduction, and knock-knees during functional activities. It is also essential to perform exercises to strengthen the quadriceps. Weight-bearing exercises are often recommended in the rehabilitation of athletes with patellofemoral syndrome because they are more functional than nonweight-bearing exercises due to the multi-joint movement requirements and more functional pattern of muscle recruitment.
Both proprioceptive and balance training exercises are used in the prevention of ACL injuries. Proprioceptive exercises improve balance and coordination by having the athlete perform various exercises standing on one leg, standing on an unstable surface, and standing on one leg while performing various tasks involving the upper body. Plyometric training is designed to improve the athlete’s agility, dynamic stability, and technique. Usually this will include jumping, landing, and cutting maneuvers performed in different directions and at varying intensity levels. The best way to determine a specific plan of action is through a comprehensive movement assessment of the athlete using the overhead and single-leg squat tests. Exercises may then be prescribed to correct faulty movement patterns.
6-15% of athletes experience low back pain each year resulting in decreased training level, conditioning, and performance. The symptoms of generalized low back pain typically take 4-6 weeks to resolve and can account for a significant amount of time loss during a competitive season. Athletes who suffer one low back injury are significantly more likely to suffer another and may be predisposed to future osteoarthritis and long-term disability.
Disc injury occurs when the outer fibrous structure of the disc fails, allowing the internal contents of the disc top to extrude and irritate the nerves by the spinal cord. This is generally thought to occur from a combination of motion and compressive loading. Disc pressure increases with lumbar flexion and decreases in lordosis. A combination of flexion and lateral bending has been demonstrated to increase the strain placed on the discs (30, 31). Strengthening the multifidus and transverse abdominis may help to minimize low back pain. Maintenance of proper lordoctic posture is associated with increased muscle activation in the lower spine (32).
If sacroiliac joint stability is not maintained, loads can’t be transferred efficiently between the trunk and the legs, which may result in abnormal loading of the tissues at the SI joint along with the development of pain. Strengthening the transverse abdominis and internal oblique may help to minimize shearing loads across the SI joint and help to maintain stability. Teaching the athlete to execute a proper “drawing-in maneuver” during performance should increase the stability of the SI joint and allow for the most efficient transfer of forces between the trunk and the legs.
Studies have shown that the most effective exercise programs for decreasing back and improving function include abdominal and core exercises as well as stretching and strengthening exercises (33). A comprehensive program will help to improve neuromuscular control and flexibility while creating equilibrium between tight/overactive muscles and weak/inhibited muscles. This may be achieved following a comprehensive individual analysis of both posture and biomechanics by a trained professional. Once identified, altered movement patterns can be corrected through proper exercise prescription, minimizing, or eliminating existing back pain and preventing future episodes.
Shoulder pain affects 21% of the general population (34, 35) with 40% lasting for at least a year (36). Shoulder impingement is the most common diagnosis accounting for 40-65% of reported shoulder pain (37), whereas traumatic shoulder dislocations account for 15-25% of shoulder pain (38-39) 70% of which will experience recurrent shoulder instability within 2 years (40, 41). Shoulder pain may be the result of degenerative changes to the shoulder’s structures as well as altered shoulder mechanics. Ongoing degenerative changes may affect the rotator cuff by weakening the tendons through overhead movements, increased loads above shoulder height, forward head and rounded shoulder posture, and altered scapular muscle activity (41-45). These factors may overload the shoulder muscles and lead to shoulder pain and dysfunction. Choosing appropriate strength training exercises, designed for the athlete’s specific- sport, can be essential in preventing these issues. All too many times I’ve witnessed people raising weight unnecessarily above shoulder height, knowing that they are setting themselves up for future degeneration and injury.
Rotator cuff injuries such as tendonitis, sprains, and ruptures account for approximately 75-80% of shoulder injuries. These injuries affect the shoulder’s ability to facilitate function of the upper extremity in performing tasks that involve reaching forward or overhead. This not only affects sports performance, but activities of daily living.
Shoulder impingement is the compression of the structures that run beneath the coracoacromial arch due to a decrease in the subacromial space. The impinged muscles are usually supraspinatus and infraspinatus tendons, subacromial bursa, and the long head of the biceps tendon. Repetitive overhead motions that are required in many sports can lead to inflammation and irritation and, in turn, cause muscular inefficiency of the rotator cuff muscles. Bony deformities of the acromion, rotator cuff weakness, shoulder instability, and abnormal movement of the shoulder joint may all be contributing factors.
Shoulder instability may occur due to injury associated with improper mechanics and poor conditioning. The most common is anterior instability that results from an abducted and externally rotated arm during a fall or similar incident. The resulting damage to the anterior/inferior glenohumeral ligament, and often the glenoid labrum, leads to significant disability with overhead activities that will usually warrant surgical correction (15, 46). The athlete may use self-myofascial release techniques to increase extensibility of overactive muscles followed by static stretching exercises that are held for 30-45 seconds. The underactive muscles of the scapulae should be strengthened through appropriate strength training exercises that emphasize scapular stability and maintenance of scapular retraction and depression.
To learn more about athletic training, injury prevention, and nutrition you can contact Andrea Leonard at 503-502-6776 or firstname.lastname@example.org.
www.elite-fitnesstraining.com | www.thecancerspecialist.com
Andrea Leonard is the Founder and President of the Cancer Exercise Training Institute. She is a certified as a corrective exercise specialist by The National Academy of Sports Medicine (NASM), as a personal trainer by The American College of Sports Medicine (ACSM), the National Academy of Sports Medicine (NASM), the American Council on Exercise (ACE), and as a Special Populations Expert by The Cooper Institute. She is also a continuing education provider for the National Academy of Sports Medicine and The American Council on Exercise.
- Hertel J. Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability.J Athl Train2002; 37:364-75.
- Kaminski TW, Hartsell HD. Factors contributing to chronic ankle instability: a strength perspective. J Athl Train2002; 37: 394-405
- McKay GD, Goldie PA, Payne WR et al. Ankle injuries in basketball; Injury rate and risk factors. Br J Sports Med2001; 35:103-08
- Garrick JG. The frequency of injury, mechanism of injury, and epidemiology of ankle sprains. AM J Sports Med1977; 5; 241-42.
- Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15 sports: summary and recommendations for injury prevention initiatives. J Athl Train2007; 42:311-9.
- Yeung MS, Chan KM, So CH et al. An epidemiological survey on ankle sprain.Br J Sports Med1994; 28: 112-16.
- Ekstrand J, Gillquist J. Soccer injuries and their mechanisms: a prospective study. Med SciExerc1983; 15; 267-70
- Saltzman CL, Salamon ML, Blanchard GM et al. Epidemiology of ankle arthritis: report of consecutive series of 639 patients from a tertiary orthopaediccente. Iowa Orthop J2005: 25:44-6.
- Valderrababo V, Hintermann B, Horisberger M et al. Ligamentous posttraumatic ankle osteoarthritis. Am J Sports Med2006;34:612-20
- McKay GD, Goldie PA, Payne WR et al. Ankle injuries in basketball: injury rate and risk factors. Br J Sports Med20012; 35: 103-08
- 11.Beynnon BD, Renstrom PA, Alosa DM. Predictive factors for lateral ankle sprains: a literature review. J Athl Train 2002; 37: 376-80
- 12.McGuine TA, Greene JJ, Best T et al. Balance as predictor of ankle injuries in high school basketball players. Clin J Sport Med2000; 10: 239-44.
- 13.Hoppenfeld S. Physical Examination of the Spine and the Extremities, 1sted. London: Prentice Hall; 1976.
- Williams GN, Jones MH, Amendola A. Syndesmotic ankle sprains in athletes. Am J Sports Med 2007; 35: 1197-207
- Hale SA, Hertel J, Olmsted-Kramer LC. The effect of a 4-week comprehensive rehabilitation program on postural control and lower extremity function in indivduals with chronic ankle instability. J Orthop Sports Phys Ther2007:37:303-11
- 16.Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15v sports: summary and recommendations for injury prevention initiatives. J Athl Train 2007;42:311-9
- Fernandez WG, Yard EE, Comstock RD. Epidemiology of lower extremity injuries among U.S. high school athletes.AcadEmerg Med.2007;14:641-45
- Agel J, Arendt E, Bershadsky B. Anterior cruciate ligamentrs injury in national collegiate athletic association basketball and soccer; a 13-year review. Am J sSports Med 2005;33:524-30
- Noyes FR<Mooar PA, Matthews DS et al. The symptomatic anterior cruciate-deficient knee. Part 1: the long-term functional disability in athletically active individuals. J Bone Joint Surg AM. 1983;65:154-62
- Wilder FV, Hall BJ, Barrett JPJ et al. History of acute knee injury and osteoarthritis of the knee: a prospective epidemiological assessment. The Clearwater Arthritis Study.Osteoarthritis Cartilage2002;10:611-6
- 21.Stahopulu E, Baildam E. Anterior knee pain: a long term follow-up. Rheumatology.2003;42:380-2
- Huberti HH, Hayes WC. Pattellofemoral contact pressures. The influence of Q angle and tendofemoral contact.J Bone Joint Surg1984;66A;715-24
- Arendt E, Dick R. Knee injury patterns among men and women in collegiate basketball and soccer. NCAA data and review of literature.Am J Sports Med1995;23:694-701
- Boden BP, Dean GS, Feagin JA et al. Mechanisms of anterior cruciate ligament injury. Orthopod2000;23:573-78
- Ireland ML, Wall C. Epidemiology and comparison of knew injuries in elite male and female United States basketball athletes. Med Sci Sports Exerc1990;22:S82
- Arendt E. Anterior cruciate ligament injuries in women. Sport Med Arthroscop Rev1997;5:149-55
- Ireland ML. Anterior cruciate ligament injury in female athletes: epidemiology. J Ath Train1999;34:150-54
- 28.Markolf K, Burchfield D, Shapiro M et al. Combined knee loading states that generate high anterior cruciate ligament forces.J Orthop Res1995;13:930-35.
- Arms S, Pope M, Johnson R et al. The biomechanics of anterior cruciate ligament rehabilitation and reconstruction.Am J Sports Med1984;12:8-18.
- Schmidt H, Kettler A, Heuer F et al. Intradiscal pressure, shear strain, and fiber strain in the intervertebral disc under combined loading.Spine 2007;32:748-55.
- 31.Shirazi-Adl A. Biomechanics of the lumbar spine in sagittal/lateral movements. Spine 1994;19:2407-14
- 32.Arjmand N, Shirazi-Adl A. Biomechanics of changes in lumbar posture in static lifting. Spine 2005;30:2637-48
- Hayden JA, van Tulder MW, Malmivaara A et al. Exercise therapy for treatment of non-specific low back pain. Cochrane Database Syst Rev2005;CD000335
- Bongers PM. The cost of shoulder pain at work.Br Med J 2001;322:64-65
- Urwin M, Symmons D, Allison T et al. Estimating the burden of musculoskeletal disorders in the community; the comparative prevalence of symptoms of different anatomical sites, and the relation to social deprivation. Ann Rheum Dis1998;57:649-55
- Van der Heijden G. Shoulder disorders; a state of the art review. Bailleres Best Pract Res ClinRheummatol1999;13:287-309
- van der Windt DA, Koes BW, Boeke AJ et al. Shoulder disorders in general practive; prognostic indicators of outcome. Br J Gen Pract 1996;46:519-23
- 38.Hovelius L. Incidence of shoulder dislocation in Swedish ice hockey players. Am J Sports Med 1978;6:373.
- Simonet WT, Melton III J, Cofield RH et al. Incidence of anterior shoulder dislocation in Olmsted County, Minnesota. ClinOrthop Related Res 1983;186:186-91
- 40.Buscayret F, Edwards TB, Szabo I et al. Glonohumeral arthritis in anterior instability before and after surgical intervention. Am J Sports Med2004;32:1165-72.
- Cameron ML, Kocher MS, Briggs KK et al. The prevalence of glenohumeral osteoarthritis in unstable shoulders.Am J Sports Med2003;31:53-55.
- Lukasiewicz AC, McClure P, Michener L et al. Comparison of 3-dimensional scapular position and orientation between subjects with and without shoulder impingement. J Orthop Sports Phys Ther1999;29:574-83; discussion 84-86.
- Ludewig PM, Cook TM. Alterations in shoulder kinematics and associated muscle activity in people with symptoms of shoulder impingement.Phys Ther2000;80:276-91.
- Thigpen CA, Padua DA, Karas SG. Comparison of scapular kinematics between individuals with and without multidirectional shoulder instability.J Athl Train2005;34(4):644-52.
- Thigpen CA, Padua DA, Xu N et al. Comparison of scapular muscle activity between individuals with and without multidirectional shoulder instability. J Orthop Sports Phys Ther2005;35:A4-PL18
- Warner JJ, Michel LJ, Arslanian LE et al. Patterns of flexibility, laxity, and strength in normal shoulders and shoulders with instability and impingement. Am J Sports Med1990;18:366-75