Archive for the ‘Injury Prevention’ Category

Arthritis Foundation Recommendations for ACL Injury Prevention

The Arthritis Foundation has developed a series of working groups called the Osteoarthritis Action Alliance. These groups included experts from various areas related to arthritis, including sports medicine. One of the groups was tasked to develop a set of recommendations for ACL injury prevention as individuals with ACL injury are an increased risk of developing osteoarthritis.
The following link goes to one of the informational flyers that was developed by this working group. It outlines an evidence driven set of guidelines for developing an effective ACL injury prevention program. Also, there are links to current programs that can be accessed online without any associated cost. One of the programs was developed by the UNC Sports Medicine Research Laboratory. We are very excited to have been able to be a part of this process and provide this information for the public.

Arthritis Foundation Flyer on ACL Injury Prevention

A direct link to the PEAKc program is also provided

PEAKc Program


Myofascial Trigger Points in the Gluteus Medius and Quadratus Lumborum in those with Patellofemoral Pain


Roach S, Sorenson E, Headley B, San Juan JG.  Prevalence of myofascial trigger points in the hip in patellofemoral pain.  Archives of Physical Medicine and Rehabilitation 2012 Nov 2. pii: S0003-9993(12)01079-9. doi: 10.1016/j.apmr.2012.10.022. [Epub ahead of print]

What issue was addressed in the study, and why?

Dysfunction of the hip abductor and external rotator muscles is frequently associated with  patellofemoral pain (PFP).  Hip muscle dysfunction is believed to allow for greater hip adduction and internal rotation, thus contributing to medial knee displacement (knee valgus collapse) during functional tasks and ultimately increased patellofemoral contact pressure.  However, the underlying factors associated with hip muscle dysfunction are not clear.

The presence of myofascial trigger points (MTrPs) may contribute to hip muscle dysfunction; however, previous research has not investigated whether MTrPs are actually present in those with PFP.  Therefore, the purpose of this study was to determine the prevalence of of MTrPs in the gluteus medius and quadratus lumborum of individuals with and without PFP.  A secondary purpose was to determine the effects of a single bout of trigger point pressure release therapy on hip muscle strength.

Who were the participants in the study?

A total of 52 participants were enrolled in the study

  • Patellofemoral Pain (PFP) group (n=26): reported general anterior, anterior/medial knee or retropatellar pain for 1 month or longer associated with prolonged sitting, stair ascent/descent, sports, and/or running.
  • Control group (n=26): no previous history of PFP

What did the researchers do for this study?

The dominant leg of all participants was assessed for the following:

  • Peak isometric strength during hip abduction
  • Presence of MTrPs in the gluteus medius
    • 3 locations within the gluteus medius were assessed: 1) proximal to greater trochanter and inferior to iliac crest; 2) anterior to first location (previously described), deep to the iliac creast; 3) posterior to the tensor fascia latae
    • Presence of MTrPs in the quadratus lumborum
      • Assessed in a side lying position with palpation over the lateral third of the lumbar transverse processes

Criteria for identifying the presence of a trigger point included localized taut bands with tenderness, and the presence of a jump sign.

After the initial testing session, the PFP group participants were randomly assigned to a treatment group or sham-control group.  Those PFP group participants assigned to the treatment group received approximately 60-seconds of direct manual pressure over each identified MTrP.  Those in the sham-control group did not receive actual direct pressure over their identified MTrPs, but rather the investigator gently laid their hands over the lateral hip for 60-seconds.

What new information was learned from this study?

Prevalence of MTrPs and strength comparisons between PFP and Control subjects:

The prevalence of MTrP’s was significantly greater in the gluteus medius and quadratus lumborum muscles for the PFP compared to control subjects.  Also, peak isometric hip abduction strength was significantly less in the PFP compared to control subjects.

  • 97% of PFP subjects demonstrated gluteus medius MTrPs compared to only 23% of control subjects
  • 87% of PFP subjects demonstrated bilateral quadratus lumborum MTrPs compared to only 13% of control subjects
    • 93% of PFP subjects demonstrated contralateral side quadratus lumborum MTrPs

Trigger Point Release Therapy:

A single bout of trigger point release therapy did not influence peak isometric hip abduction strength in the PFP subjects.

What are the clinical applications of this study?

MTrPs are more prevalent in the gluteus medius and quadratus lumborum muscles of those with PFP compared to healthy, control subjects.  The presence of MTrPs is also associated with decreased peak isometric hip abduction strength in PFP compared to healthy, control subjects.  These findings suggest that presence of MTrPs in the gluteus medius and quadratus lumborum muscles may be a factor to consider in the prevention and rehabilitation of PFP.  It is possible that MTrPs need be effectively treated to ultimately restore normal gluteus medius and quadratus lumborum function in those with PFP or at risk for PFP.

Unfortunately, a single bout of trigger point release therapy was not sufficient to restore peak isometric hip abduction strength in those with PFP.  It is not clear if the presence of MTrPs was reduced following the single bout of trigger point release therapy as this was not reported by the authors.  The authors indicate that “it was expected that the MTrP compression discomfort would significantly decrease” with the intervention; however, this did not appear to be verified.  Thus, future research is needed to determine if a single bout of trigger point release therapy that effectively eliminates the presence of MTrPs is sufficient to restore muscle strength.

What are the limitations of the study, and what areas should be considered for future research?

It is not clear if the investigators were blinded to the group membership (PFP or control) of the study participants.  If tester blinding was not performed then this may introduce bias into the MTrP prevalence results.

An isolated, single bout of trigger point release therapy may not be sufficient to restore normal muscle function.  Rather a systematic and integrated approach utilizing techniques for muscle inhibition, lengthening, and activation may be required to restore normal muscle function in those with MTrPs.  Future research is needed to examine this approach to restoring normal muscle function in those with MTrPs.

Increasing muscle flexibility through eccentric training – a systematic literature review


O’Sullivan K, McAuliffe S, DeBurca N.  The effects of eccentric training on lower limb flexibility: a systematic review.  British Journal of Sports Medicine 46(12):838-45, 2012.  doi: 10.1136/bjsports-2011-090835

What issue was addressed in the study, and why?

Lower extremity muscle flexibility is often reduced in those suffering from lower extremity musculoskeletal injury.  Static stretching is a commonly used exercise to improve muscle flexibility; however, several research studies indicate that static stretching is not effective at reducing future injury risk, post-exercise muscle soreness, or improving performance.  Thus, isolated static stretching is effective in improving flexibility; however, this does not appear to translate to reduced injury risk.

Animal based research demonstrates that eccentric training results in new sarcomeres to be created and aligned in series (sarcomerogenesis), thus facilitating greater muscle length and flexibility.  In addition, eccentric training has been shown to increase muscle force and alter the muscle’s length-tension curve by allowing peak torque to be produced at longer muscle lengths.  Due to these combined benefits (improved flexibility, peak force production, and ability to produce peak torque at longer muscle lengths), eccentric training has been proposed as an alternative method to improve muscle flexibility.  However, it is not clear if there is sufficient research from human subjects to support eccentric training as an effective method for improving lower extremity muscle flexibility.

Who were the participants in the study?

A systematic literature review was performed using the following search terms:

  • eccentric
  • strength OR training
  • flexib* OR range of motion OR fascicle

Only randomized clinical trials which compared eccentric training on measures of lower extremity muscle flexibility to either no intervention, or a different intervention, were selected for inclusion in this systematic literature.  A total of 530 potential relevant articles were retrieved.  A total of 6 articles ultimately met the inclusion criteria and were included in this review.

What did the researchers do for this study?

Two independent research assessed the methodologic quality of each included study using the PEDro scale.  Individual study quality was classified as “high” (PEDro = greater than 6 out of 10), “fair” (PEDro = between 4-5 out of 10),  or “poor” (PEDro = less than 4 out of 10) based on the study’s PEDro score.

The following lower extremity muscle groups were investigated in those studies included in the systematic literature review:

  • quadriceps (2 studies)
  • calf (2 studies)
  • hamstrings (2 studies)

Two different measures of muscle flexibility were measured in those studies included in the systematic literature review:

  • range of motion (goniometric assessment of joint motion)
  • fascicle length (diagnostic ultrasound assessment of muscle fascicle length)

What new information was learned from this study?

All 6 studies were rated as “high” quality based on their PEDro scores.  All of these studies revealed consistent evidence that eccentric training increases range of motion, or fascicle length, or both across all of the muscle groups studied.

There were a wide variety of eccentric training protocols used across the 6 studies.  A summary of the eccentric training protocols used is listed below:

  • Duration of eccentric training: 6 to 10 weeks
  • Repetitions: 6 to 10 repetitions
  • Sets: 1 to 6 sets
  • Duration of eccentric contraction: 3 to 6 seconds
  • Training load: 50 to 100% of eccentric 1 RM

Based on these findings, eccentric training is an effective means of improving lower extremity muscle flexibility, assessed by either joint range of motion or muscle fascicle length.  This finding is consistent across the different muscle groups assessed and eccentric training protocols utilized across the 6 studies included in this systematic literature review.

What are the clinical applications of this study?

The magnitude of change in muscle flexibility when performing eccentric training appears to be similar to the improvement seen when performing static stretching.  Thus, eccentric training does not appear to be more effective than static stretching.  However, given the added benefits of eccentric training (increased peak torque, ability to generate peak torque at longer muscle lengths) it may be considered a viable supplement to other forms of flexibility training.

The training duration required to achieve increased muscle flexibility following eccentric training is not clear.  The shortest duration training period was 6-weeks in the included studies.  However, animal research has shown that sarcomerogenesis begins to occur after 10 days of eccentric training.  It is also unclear how long flexibility gains are maintained after ceasing eccentric training.  Future research is needed to better investigate these aspects of eccentric training on muscle flexibility.

What are the limitations of the study, and what areas should be considered for future research?

All of the included studies utilized healthy, uninjured participants.  Thus, these findings cannot be generalized to individuals who suffer from a musculoskeletal injury.  It is known that eccentric training can facilitate increased post-exercise soreness, thus eccentric training may not be an appropriate modality for improving flexibility in those with musculoskeletal injury.

At this point in time there are no specific parameters that can be recommended for improving muscle flexibility using eccentric training.  Future research is needed to investigate the optimal training parameters (duration, repetitions, sets, eccentric contraction time, training load, frequency, etc) for improving muscle flexibility.

Categories: Injury Prevention

Decreased Gluteus Maximus Activation Following Hip Joint Effusion – Presence of Arthrogenic Muscle Inhibition?


Freeman S, Mascia A, McGill S.  Arthrogenic neuromusculature inhibition: A foundational investigation of existence in the hip joint.  Clinical Biomechanics 2012 Dec 20. pii: S0268-0033(12)00271-9. doi: 10.1016/j.clinbiomech.2012.11.014. [Epub ahead of print]

What issue was addressed in the study, and why?

Arthrogenic muscle inhibition (AMI) is a reflexive inhibition of musculature surrounding a joint due to pain and/or joint effusion.  AMI results in reduced voluntary muscle activation and ultimately decreases in muscle force output.  AMI has been repeatedly shown to occur in the quadriceps muscles following knee joint injury or effusion.  It is possible that other joints and muscles may also experience AMI, similar to the knee joint and quadriceps muscles.

The gluteus maximus is theorized to be weakened and inhibited in those with lower extremity injury.   However, the neurophysiologic mechanism for this is not yet understood.  It is possible that the gluteus maximus may experience AMI in the presence of hip joint injury or effusion; however, this has not been previously investigated.  Therefore, the purpose of this study was to examine the effects of simulated hip joint effusion on voluntary gluteus maximus muscle activation.  It was theorized that the presence of hip joint effusion would cause facilitate AMI of the gluteus maximus, thereby result in decreased voluntary gluteus maximus muscle activation.

Who were the participants in the study?

A control (9 healthy participants) and intervention (12 participants who complained of hip pain and dysfunction and demonstrated findings of hip labral pathology during physical examination) group of participants were utilized in the study.

What did the researchers do for this study?

Surface EMG electrodes were attached to the gluteus maximus muscle of all subjects to measure the activation amplitude during 4 different exercises: 1) supine pelvic bridge, 2) prone hip extension, 3) active straight leg raise, 4) active hip abduction.

Both intervention and control groups were tested pre-intervention and post-intervention.  The intervention group subjects had a sterile saline solution injected into their pathologic hip joint until the point of near full capsular distension.  The control group subjects rested between test sessions and did not receive an injection.

What new information was learned from this study?

The intervention group demonstrated significantly decreased gluteus maximus activation during the supine pelvic bridge and prone hip extension exercises.  There were no such changes during the active straight leg raise and active hip abduction exercises for the intervention group.  No changes were observed in the control group between pre- and post-intervention measures of gluteus maximus activation.

Decreases in gluteus maximus activation of intervention group subjects was isolated to the side of the injection/joint effusion as there were no changes in contralateral gluteus maximus activation.  Thus, these findings indicate that voluntary activation of the gluteus maximus muscle is decreased following hip joint effusion.

What are the clinical applications of this study?

These findings extend previous research demonstrating the presence of AMI in the quadriceps muscle group following knee joint effusion and suggest a similar phenomenon occurs at the hip joint.  Decreased gluteus maximus activation following hip joint effusion may result reduced force output/strength, which may alter normal lower extremity biomechanics.  Interventions aimed to reduce AMI of the gluteus maximus following hip joint injury/effusion may be required to fully restore normal gluteal muscle function.  Research has not investigated specific interventions to combat AMI of the gluteus maximus; however, research investigating quadriceps AMI suggests that the following are important components and may be considered for treatment of gluteus maximus AMI:

  • Pain and effusion control (cryotherapy)
  • TENS (transcutaneous electrical stimulation) to stimulate spinal reflexive pathways
  • NMES (neuromuscular electrical stimulation) to stimulate inhibited muscles
  • TMS (transcranial magetic stimulation) to increase cortical motor excitability

What are the limitations of the study, and what areas should be considered for future research?

Only voluntary activation of the gluteus maximus was quantified.   Previous research investigating AMI of the quadriceps utilized electrical stimulation to examine the H-reflex, which is analogous to the spinal stretch reflex.  Thus, while AMI of the gluteus maximus appears to occur following hip joint effusion, the specific neural pathways by which AMI results cannot be determined through this study.  Future research examining the specific neural pathways and mechanisms for gluteus maximus AMI post joint effusion is needed to better establish effective therapeutic interventions.

Research is needed to identify targeted interventions to combat gluteus maximus AMI.  In addition, it is important that these interventions be part of an integrated rehabilitation strategy to restore neuromuscular control and movement efficiency once gluteus maximus activation deficits have been restored.

Neuromuscular characteristics associated with knee valgus collapse during an overhead squat

Padua DA, Bell DR, Clark MA.  Neuromuscular characteristics of individuals displaying excessive medial knee displacement.  Journal of Athletic Training 47(5):525-536, 2012.

What issue was addressed in the study, and why?

Knee valgus motion is frequently hypothesized as a risk factor for multiple lower extremity injuries.  An aim of many exercise programs is to correct for excessive knee valgus motion through a variety of mobility, stability, and strengthening techniques.  The successful correction of knee valgus motion requires an understanding of the underlying neuromuscular characteristics associated with it.  Multiple theories have been proposed to explain the muscle imbalances associated with knee valgus motion; however, there is little scientific evidence to support these theories.  Identifying differences in muscle activation patterns between those who do and do not display knee valgus collapse is an initial step to validating the muscle imbalances associated with this movement dysfunction.  Therefore, the purpose of this study was to compare hip and ankle muscle activation amplitude in those with and without visual presence of knee valgus motion (medial knee displacement) during an double leg (overhead) squat task.

Who were the participants in the study?

A total of 37 participants volunteered for this study and were separated into two groups based on the presence of medial knee displacement during an double leg squat task.  The control group (CON, n=19) did not demonstrate medial knee displacement.  The medial knee displacement group (MKD, n=18) were observed to have their patella move medial to their great toe during the double leg squat, but not once a 2-inch lift was positioned under their heels.  Individuals who displayed MKD during both no-heel lift and heel-lift conditions were excluded from the study.

This was done as there are different muscle imbalances believed to be associated with knee valgus motion during no-heel-lift and heel-lift conditions.  MKD that is displayed during the no-heel-lift condition, but not during the heel-lift condition is believed to be associated with ankle muscle imbalances.  MKD that is displayed during both no-heel-lift and heel-lift conditions is thought to represent a hip muscle imbalance.  Thus, this study focused on identifying the presence of ankle muscle imbalances given the inclusion criteria.

What did the researchers do for this study?

Surface EMG electrodes were used to record the activation amplitude from the medial gastrocnemius, lateral gastrocnemius, tibialis anterior, adductor magnus, gluteus medius, and gluteus maximus muscles.  An electromagnetic motion analysis system was used to quantify medial knee displacement motion.  All variables were measured during two different double leg squat tasks performed at a controlled movement velocity and squat depth.  Subjects performed the double leg squat task during both no-heel-lift and heel-lift (2-inch) conditions.  During all double leg squat trials the individuals were instructed to keep their heels on the floor and maintain their toes pointing straight ahead.

What new information was learned from this study?

There was no difference between the CON and MKD groups for gluteus medius and gluteus maximus activation amplitude during both the no-heel-lift and heel-lift double leg squat tasks.  However, the MKD group demonstrated 34% greater activation of the adductor magnus muscle compared to the CON group.

The MKD group demonstrated greater gastrocnemius (40% greater) and tibialis anterior (25% greater) muscle activation amplitude compared to the CON group during both double leg squat tasks.

What are the clinical applications of this study?

Presence of MKD that is corrected with heel-lifts is associated with increased gastrocnemius, tibialis anterior, and adductor magnus muscle activation amplitude.  However, there was no difference in gluteal muscle activation amplitude between MKD and CON participants.  Thus, there appears to be 2 neuromuscular strategies associated with knee valgus motion.  Increased gastrocnemius and tibialis anterior activation likely increases ankle joint stiffness, thus limits the available dorsiflexion range of motion during functional tasks, which is theorized to lead to compensatory knee valgus motion.  Increased adductor magnus activation can lead to an imbalance between the gluteals and adductor muscles, resulting in a net hip adduction moment during the squat task.  In fact, the MKD participants in the current study demonstrated 4 times greater adductor magnus activation compared to their gluteal muscles, which indicates a significant muscle imbalance between these muscle groups.  This would ultimately result in the visual presence of knee valgus motion as the femur moved medially during the squat task.

Interventions aimed at inhibiting and lengthening the gastrocnemius, tibialis anterior, and adductor magnus muscles may be necessary components of exercise interventions aimed at correcting knee valgus motion.

What are the limitations of the study, and what areas should be considered for future research?

All of the participants were healthy at the time of testing.  Thus, these findings are limited to healthy individuals and it is possible that different muscle activation patterns may exist in those who display knee valgus motion and are symptomatic.  Future research is needed to confirm the presence of ankle muscle imbalances (increased gastrocnemius and tibialis anterior activation) and synergistic dominance of the adductor magnus (increased adductor magnus activation) in those with MKD who are also symptomatic.

The findings from this study are part of a larger study whose findings were previously published in the following article:

ACL Injury Rates Reduced by 50-85% Following Implementation of a Preventive Training Program

Sadoghi P, Keudell von A, Vavken P.  Effect of Anterior Cruciate Ligament Injury Prevention Training Programs. The Journal of Bone and Joint Surgery 94: 1-8, 2012.

PMID: 22456856

RATIONALE & PURPOSE: Anterior cruciate ligament (ACL) rupture has been identified to be a significant encumbrance on today’s healthcare system, and represents a significant financial, emotional, and physical burden for the individual suffering the injury. The most common treatment for the injury is surgical repair, using a tissue graft to replace the damaged structure. Current literature suggests that even with surgical repair there are enduring consequences of injury, with a predisposition for osteoarthritis most commonly being identified as a long-term repercussion. Perhaps the most glaring aftereffect of ACL rupture is that of increased risk of ACL injury compared to those who have never sustained an ACL injury. Recent publications suggest that an individual who has previously sustained an ACL injury is up to 6 times at risk for suffering an ACL injury compared to an individual with no history of ACL rupture. It is thus prudent that effective injury prevention strategies be implemented to help reduce one’s risk of primary injury as well as re-injury.

Up to 80% of ACL injuries have been identified to be a result of a noncontact mechanism, indicating the injury was a result of an individual’s self-imposed motion. Understanding that human movement is modifiable, a substantial volume of research efforts have been aimed at identifying methods to promote safe and efficient movement strategies in individuals who may be exposed to events in which ACL rupture have been known to occur. High-risk circumstances have been identified as athletic activities demanding high-magnitude accelerations/decelerations and changes in direction. As a result, various ACL injury prevention programs have been deployed in the athletic population, and after scientific study have been determined to be individually effective in reducing ACL injury incidence. As such, studies investigating the effects of ACL injury prevention programs on ACL injury incidence are growing numerous. However, different studies present a broad range of prevention programming, thus making it difficult to determine the specific elements of programming that are most efficacious in reducing ACL injury rates. Furthermore, due to deployment of prevention efforts in different populations the general effect of programming has not been described. Thus the purpose of this systematic review study was to evaluate and describe the general effect of ACL injury prevention programming on decreasing injury incidence, and to identify if there is a programming protocol that is “best” in terms of reducing ACL injury incidence.

OVERVIEW OF RESEARCH METHODS: An initial search of online databases of peer-reviewed journals with the search terms “anterior cruciate ligament, knee, injury, prevention, and control” returned 909 results. The authors report including only studies that were described to be “prospective, controlled studies that directly compared ACL injury prevention programs to no treatment in human subjects,” resulting in a final evaluation of 8 studies. Data from the 8 studies was pooled to compare the risk of experiencing an ACL injury between those completing a prevention program and those not executing a prevention program. In addition to evaluating the overall effect of prevention programming on reducing ACL injury risk across the populations of the studies, the effect of programming for males and females was differentiated. An attempt to compare the effectiveness of different programs was unsuccessful due to the differing populations each study represented. However a qualitative analysis of elements common to programs proving to be effective in reducing injury rates was carried out.


  • ACL injury prevention programs effectively decrease ACL injury risk by 62% in male and female soccer, basketball, volleyball, and team handball athletes.
  • ACL injury prevention programs decrease ACL injury risk by 85% in male athletes.
  • ACL injury prevention programs decrease ACL injury risk by 52% in female athletes.
  • There was no specific program that was identified to be the “best” program in reducing ACL injury risk.
  • EffectiveACL injury prevention programs:
    • Include at least 10 minutes of exercises
    • Are executed at least 3 times per week
    • Focus on neuromuscular training

CLINICAL IMPLICATIONS: The results of this systematic literature review provides cogent evidence supporting the implementation of ACL injury prevention programming into clinical practice by sports medicine professionals. ACL injury prevention programming efforts that at a minimum include at least 10 minutes of exercises, conducted at least 3 times per week, focusing on neuromuscular decrease an individual’s risk of ACL injury. Individuals who are exposed to athletic activities representing high-risk exposures such as soccer, basketball, team handball, and volleyball, or any physical activity that incorporates high-magnitude accelerations/decelerations and changes in direction should execute ACL injury prevention programming.

Furthermore, it is understood that the sports medicine professional may not have the ability to individually reach each athlete who may experience exposure to high-risk events, thus it is imperative physicians, athletic trainers, and physical therapists be capable of educating athletes, coaches, parents, and administrators regarding the benefits and of ACL injury prevention programming. Additionally it is imperative sports medicine professionals be able to direct the above individuals to efficacious programming efforts. Currently many effective programming resources are available and are listed below.

Written by Barnett Frank, MA, ATC
Approved by Darin Padua, PhD, ATC

Changes in Movement Control are Influenced by Duration of Training – Implications for Rehabilitation and Injury Prevention


Padua DA, DiSefano LJ, Marshall SW, Beutler AI, de la Motte SJ, DiStefano MJ.  Retention of Movement Pattern Changes After a Lower Extremity Injury Prevention Program Is Affected by Program Duration.  American Journal of Sports Medicine 40(2):300-306, 2012

What issue was addressed in the study, and why?

Prevention of ACL and other knee injuries is an important issue for sports medicine professionals given the high cost and long term disability associated with these injuries.  Recent randomized controlled trial studies have shown that 15-minute injury prevention exercise program scan reduce the rate of ACL and knee injuries during sport.  However, injury rates return to their original levels once individuals cease performing the injury prevention exercise program.

The primary goals of injury prevention exercise programs are to improve neuromuscular control and overall movement quality.  Findings of elevated injury rates once stopping an injury prevention program suggest that changes in neuromuscular control and movement quality are not permanent; however, research has not investigated this topic.  Therefore, the purpose of this study was to determine if changes in movement quality/control are maintained once individuals had stopped performing an injury prevention program for 3 months.  This study also investigated the influence of program duration (3-month training program vs. 9-month training program) on people’s ability to maintain improvements in movement quality/control.

Who were the participants in the study?

A total of 140 youth soccer athletes participated in this study.  Individuals who improved their movement quality/control over the course of the injury prevention program were included in the final analysis (84 total subjects).  Individuals were further subdivided into 2 groups based on the duration of their injury prevention program (3-month training period (short duration) = 33 subjects; 9-month training period (extended duration) = 51 subjects).

What did the researchers do for this study?

All participants performed an integrated exercise program that incorporated flexibility, balance, strength, and plyometric/agility exercises.  The exercise program was performed as a dynamic warm up in replace of the normal warm up routine.  The exercise program took 10-15 minutes to perform and was completed 3-4 times per week during the intervention period.  The Short-Duration group performed the exercises for 3-months.  The Extended-Duration group performed the exercises for 9-months.  Trained research assistants taught the athletes the exercise program and visited the athletes once a week to monitor compliance and correct exercise technique.  Participants were instructed to think about their movement and rely on specific cues when performing the exercises (keep toes pointing forward, keep knees over toes, land as soft as possible).

Prior to beginning the exercise program (Pre Test) the participants performed a jump-landing task (3-trials) that was recorded with a video camera.  The Landing Error Scoring System (LESS) was then used to grade the individual’s overall movement quality.  Participants repeated the jump-landing task after immediately completing the exercise program (Post Test) and again after 3-months of performing the exercise program (Retention Test).  The researchers then compared the Short-Duration and Extended-Duration groups LESS scores across the three time periods (Pre Test, Post Test, Retention Test).

What new information was learned from this study?

Both the Short Duration and Extended Duration groups improved their LESS scores from Pre Test to Post Test.  There was no difference in the amount of improvement in LESS scores between groups.  However, at the Retention Test the Short Duration group’s LESS scores returned to Pre Test levels and were worse than at Post Test.  This was not the case for the Extended Duration group as their Retention Test LESS scores remained the same as at Post Test and were still improved compared to Pre Test.  Thus, the Extended Duration group retained their improvements in movement quality / control while the Short Duration group did not.

This study demonstrates that the duration of training has a significant impact on the ability to maintain improvements (retention) in movement quality/control following an injury prevention program.  Extended Duration exercise programs appear to be an important component of successfully achieving retention of improvements in movement quality/control once ceasing to perform the program.

What are the clinical applications of this study?

Several important clinical applications come from this study.  First, we should not assume that improvements in movement quality/control are permanent once an individual has made initial changes in their movement patterns.  Individuals in the Short Duration group were able to improve their movement quality/control after 3 months of training, but after stopping the program they returned to their baseline levels.  This especially important when considering rehabilitation and corrective exercise programs as it is common to achieve changes in movement quality / control in less then 3 months and then the patient / client stops performing the program.  These findings suggest that individuals will only return to their original movement patterns if continued assessment and maintenance of the exercise program is maintained.

Second, longer duration exercise programs that are continued once individuals have initially improved their movement patterns may be required to elicit more permanent changes in one’s movement patterns.  Individuals in the Extended Duration group likely achieved improvements in movement quality/control after 3-months as did the Short Duration group.  However, the Extended Duration group continued to perform these exercises for an additional 6-months after achieving this improvement.  The additional performance of the exercises after making initial improvements may have allowed for these individuals to master the exercises and elicit more permanent improvements in their movement patterns.  These findings have direct implications to rehabilitation and corrective exercise programs.

These findings suggest that injury prevention training should be a continual process where athletes are repeatedly monitored and perform their exercise program even after making initial improvements.  By replacing the traditional warm up with these types of injury prevention programs we can achieve the same effects as traditional warm ups, but have the added benefit of improving movement quality.

What are the limitations of the study, and what areas should be considered for future research?

Several limitations should be considered.  First, the LESS is a clinical assessment of movement quality/control and is not the same as 3-D motion analysis; however, the LESS has been shown to have good validity and reliability relative to 3-D motion analysis.  Future research may consider using 3-D motion analysis to study retention following an injury prevention program.  Another possible limitation was the age group of study participants (11-17 years).  It is not clear if the duration of training has similar effects in younger or older populations.  Future research may consider investigating different age groups and also different retention time periods.

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