Archive

Archive for the ‘Movement Dysfunction’ Category

Resources for Real Time Movement Assessment

The importance of assessing movement quality has been discussed in several PEAKc posts over the past year.  Some movement assessment systems involve video analysis (e.g. Landing Error Scoring System) while others can be performed in real-time.  The majority of clinicians may not have the time or resources for video analysis, so to facilitate real-time assessments of movement quality I have uploaded PDF’s of two different real-time movement assessment systems.

Advertisements
Categories: Movement Dysfunction

Use of Visual and Verbal Feedback to Improve Lower Extremity Biomechanics, Pain and Function

Reference:

Willy RW, Scholz JP, Davis IS.  Mirror gait retraining for the treatment of patellofemoral pain in female runnersClin Biomech (Bristol, Avon). 2012 Dec;27(10):1045-51. doi: 10.1016/j.clinbiomech.2012.07.011.

http://www.ncbi.nlm.nih.gov/pubmed/22917625

What issue was addressed in the study, and why?

Increased contralateral pelvic drop, hip adduction and hip internal rotation are commonly described movement dysfunctions in those with patellofemoral pain (PFP) during functional tasks.  Weakness of the gluteal muscles, which help to stabilize the aforementioned motions, is also observed in those with PFP. However, previous research indicates that isolated hip muscle strengthening is not an effective method for altering lower extremity movement patterns.  Thus, alternative interventions appear to be necessary to ultimately improve these dysfunctional movement patterns.

Real-time feedback using motion analysis has been shown to be an effective means to alter lower extremity movement patterns during running.  In this previous research individual’s lower extremity biomechanics were monitored using an optical motion analysis system while subject’s received real-time feedback on their movement patterns.  A limitation of this research is that it is not clinically feasible to incorporate optical motion analysis equipment for real-time feedback in clinical settings.  Visual feedback using a mirror is a clinically feasible mechanism to provide real-time feedback on lower extremity movement patterns.  However, research has not investigated the effects of visual feedback provided by a mirror on lower extremity biomechanics during running.  Therefore, the purpose of this study was to examine the effects of a 2-week mirror gait retraining intervention on lower extremity biomechanics during running.  In addition, this study investigated whether the effects of mirror gait retraining were transferred to other functional tasks (single leg squatting and stair descent) and retained (1-month and 3 month retention periods).

Who were the participants in the study?

Ten females completed the study and met the following criteria: self-rated patellar pain of at least a 3 out of 10 scale during running, symptoms must be present during running and at least one other activity (squatting, jumping, kneeling, prolonged sitting, stair descent).  Individuals with patellofemoral instability or other knee related pathologies or history of lower extremity surgery were excluded from the study.

What did the researchers do for this study?

Lower extremity biomechanics were quantified using a motion analysis system during 3 tasks: running, single leg squat, and stair descent.  Lower extremity function was quantified using the Lower Extremity Functional Scale.  Pain was quantified using a visual analog scale.  These measures were take at 4 time periods: pre-training, immediately post-training, 1-month post-training, and 3-months post-training.

Participants who demonstrated abnormal hip motion (greater than 20-deg of peak hip adduction) during running were asked to participate in the mirror gait retraining intervention.  Those who met the criteria participated in a 2-week mirror gait retraining intervention where individuals trained 4 days each week (8 total training session).  The mirror gait retraining intervention was conducted as follows:

  • Subjects ran on a treadmill while observing themselves in a full length mirror in front of them (visual feedback).
  • During running the subjects received the following verbal cues: “Run with your knees apart with your kneecaps pointing straight ahead” and “Squeeze your buttocks”
  • No other concurrent interventions (e.g. stretching, strengthening, etc) were performed
  • During the first week of training the amount of visual and verbal feedback was increased each session.
  • During the second week of training the amount of visual and verbal feedback were steadily decreased across each session.  This was performed to shift the individual’s dependence from external cues (verbal and mirror feedback) to internal cues and reinforce motor learning of the new movement patterns.  During the sessions when subjects received less feedback they would receive intermittent feedback during the training session.
  • The duration of each training session was gradually increased from 15 to 30 minutes over the 2-weeks.
  • The participants were instructed to not run outside of their training sessions during the 2-week intervention period.

What new information was learned from this study?

Running Biomechanics:

The following variables were significantly improved immediately following the intervention: peak hip adduction angle, peak thigh adduction angle, peak hip abduction moment, and contralateral pelvic drop.  However, there was no change in hip internal rotation.  After 1-month the following variables remained unchanged from post-test (suggesting successful retention of movement patterns): contralateral pelvic drop, peak thigh adduction moment, and peak hip abduction moment.  Thus, changes in peak hip adduction angle were not retained after 1-month of not performing the intervention.  After 3-months the following variables remained unchanged from post-test (suggesting successful retention of movement patterns): contralateral pelvic drop and peak thigh adduction angle.  Thus, changes in peak thigh adduction angle were not retained after 3-months of not performing the intervention.

Single Leg Squat Biomechanics:

The following variables were significantly improved immediately following the intervention (suggesting successful transfer of the new motor patterns during running to other functional tasks): peak hip adduction angle, peak thigh adduction angle, and peak hip abduction moment.  After 1-month the following variables remained unchanged from post-test: peak hip adduction angle, peak thigh adduction angle, and peak hip abduction moment.  After 3-months the following variables remained unchanged from post-test: peak hip adduction angle and peak thigh adduction angle.  Thus, changes in peak hip and thigh adduction were retained after 1 and 3-months of no training.  However, changes in peak hip abduction were retained after 1-month of no training, but not after 3-months of no training.

Stair Descent Biomechanics

Only peak hip adduction angle was significantly improved immediately following the intervention.  Thus, changes in peak hip adduction angle were transferred from running to stair descent; however, none of the other variables that were changed during running were transferred to stair descent.

Pain and Lower Extremity Function

Both pain and lower extremity function were significantly improved immediately after the intervention.  These improvements were retained at both the 1-month and 3-month follow periods.

What are the clinical applications of this study?

The findings indicate that the 2-week mirror gait re-training program was able to successfully improve hip biomechanics during running.  Also, many of these changes were successfully transferred to other functional tasks (single leg squat and stair descent).  Several of these changes were retained in all tasks.  In general, these findings suggest that the 2-week mirror gait re-training program used in this study was able to facilitate learning a new movement pattern (successful transfer and retention of new movement patterns).

In addition to improved movement patterns, pain and lower extremity function were also improved.  These findings suggest that improvements in pain and function may be associated with lower extremity movement pattern modifications.

Use of verbal feedback in combination with mirror gait retraining may be an important adjunct to a comprehensive and integrated intervention strategy to improve lower extremity biomechanics in those with PFP and altered hip biomechanics.

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

There was no control group utilized in this study.  Thus, it is not clear if changes in lower extremity biomechanics, pain, and lower extremity function were due to the intervention.  However, these findings provide initial evidence to suggest that the intervention utilized in this study may have clinical merit and warrants further investigation.

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

Reference:

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]

http://www.ncbi.nlm.nih.gov/pubmed/23127304

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.

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

Reference:

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]

http://www.ncbi.nlm.nih.gov/pubmed/23261019

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.

http://www.ncbi.nlm.nih.gov/pubmed/23068590

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:

http://www.ncbi.nlm.nih.gov/pubmed/18586134

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

Reference:

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.

Dynamic Core Strength Influences Upper and Lower Extremity Power

Shinkle J, Nesser TW, Demchak TJ, McMannus DM.  Effects of Core Strength on the Measure of Power in the Extremities. Journal of Strength and Conditioning Research 26(2):373-379, 2012.

PMID: 22228111

RATIONALE AND PURPOSE:  Core stability and strength are frequently described to be important factors for developing maximal power in the extremities.  Previous research has demonstrated that core stability / strength are important factors for endurance and injury prevention.  However, there is limited research to support the importance of core stability / strength on maximal power output in the extremities.  Previous research investigating the influence of core stability / strength on power output of the extremities is limited by only assessing core stability / strength using static assessments.  Thus, limiting our understanding of the importance of core stability / strength on power output.  The purpose of this study was two fold: 1) to develop a functional test of core musculature and 2) to determine the association between a function test of core musculature with the ability to transfer force from the lower to the upper extremities.

OVERVIEW OF RESEARCH METHODS: 25 NCAA Division football athletes participated as subjects in this study.  All subjects underwent a series of tests for core strength and athletic performance.  The core strength tests incorporated a series of different weighted medicine ball throws.  The athletic performance tests incorporated a series of commonly performed tests of power output.

Core Strength Tests (2 trials of each test were performed, the throw with the greatest distance was used for analysis):

  • Dynamic Medicine Ball Throws (Forward, Backward, Right, and Left): During the dynamic medicine ball throws the individual sat on a weight bench with their hips flexed to 90-deg. The trunk was free to move, thus the trunk and upper extremity were used to contribute to the throwing motion.
  • Static Medicine Ball Throws (Forward, Backward, Right, and Left): During the static medicine ball throws the individual sat on a weight bench with their hips flexed to 90-deg and their chest strapped to the back rest.  The trunk was not able to move, thus the upper extremity was the primary contributor to the throwing motion.
  • The medicine ball throw tests were designed to test upper extremity power generation with (dynamic tests) and without (static tests) the use of the core musculature to measure the effect of the core on throw distance.

Athletic Performance Tests:

  • Push Press Power: Performed with 50% of subject’s bodyweight.  A myotest accelerometer was attached to barbell and the participant performed 5 repetitions where average power was recorded.
  • Countermovement vertical jump
  • Proagility shuttle run
  • 40-yard sprint
  • One repetition maximum bench press
  • One repetition maximum squat

Correlational analyses were performed to assess the relationship between measures of core strength and athletic performance for the different variables.

KEY FINDINGS: The dynamic medicine ball throws (tests where core strength is evaluated) were significantly correlated with the following measures of athletic performance:

  • One repetition maximum squat (Dynamic Forward Throw)
  • One repetition bench press (Dynamic Forward Throw)
  • Countermovement vertical jump (Dynamic Throw to Left and Right)
  • Push Press (Dynamic Throw to Left and Right)
  • The Dynamic Throw Backward was not correlated with any measures of the performance variables.

CLINICAL IMPLICATIONS: The dynamic medicine ball throws allow the subjects to obtain a body position that enables them to use their core musculature to improve the distance of the throw.  The Dynamic Medicine Ball Throws (tests of core strength) were measured with some aspect of performance, except for the proagility shuttle run and the 40-yard sprint tests.  Thus, these results demonstrate the core strength is an important factor related to power output of the extremities.  However, core strength seems to be less important for measures of speed (40 yard sprint) and agility (proagility shuttle run).

Previous research has not seen such an association between measures of core strength with physical performance measures.  A likely explanation is that previous research has utilized more static assessment of core strength and endurance, such as a timed prone or side plank test.  While these static measures of core strength and endurance provide important information related to core stability and injury risk, they do not appear to be predictive of physical performance.  Thus, a more comprehensive battery of core strength tests may be needed to fully evaluate core function.  Static tests of core strength/endurance can be used to determine the role of the local stabilizing muscle’s ability to stabilize the spine.  Dynamic tests, such as the medicine ball throws, can be used to assess both the local and global muscles contributions to physical performance.

These findings are important as this is some of the first research to demonstrate the link between core strength and physical performance.  As such, core strength training is supported as a vital aspect for performance enhancement training.

%d bloggers like this: