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Tuesday, June 6, 2023

Core Stability Measures as Risk Factors for Lower Extremity Injury in Athletes

Brent Brookbush

Brent Brookbush


Research Review: Core Stability Measures as Risk Factors for Lower Extremity Injury in Athletes

By: William Chancey Sumner, PTA, MS, CES, CAFS, HMS, FRCms, c-PT

Edited by: Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Leetun, D., Ireland, M., Willson, J., Ballantyne, B., Davis, I. (2004). Core stability measures as risk factors for lower extremity injury in athletes. Medicine and Science in Sports and Exercise, 36(6), 926-934. ABSTRACT

Introduction: Lower extremity injuries may impact between 30% and 50% of athletes during a competitive season, leading to missed time in practice, games, or an entire season (1-2). Many lower extremity injuries are associated with impaired core stability; especially, in female athletes (3-8). This 2004 prospective study by American researchers on collegiate athletes, shows that impaired core stability (lumbo pelvic hip complex ), specifically hip external rotation weakness, may increase lower-extremity injury risk. Human movement professionals should assess and address the hip external rotator  strength of athletes to reduce the risk of back and lower extremity injuries during the season.

Study Summary

Study DesignProspective study
Level of EvidenceIII - Evidence from non-experimental descriptive studies, such as comparative studies, correlation studies and case-control studies
Participant CharacteristicsDemographics
  • Number of participants: 139
  • Gender: 60 male and 79 female
  • Female Participant Mean Age: 19.1 +/- 1.37 yr
  • Female Participant Mean Weight: 65.1 +/- 10.0kg
  • Male Participant Mean Age: 0 +/- 0.90 yr
  • Male Participant Mean Weight: 78.8 +/- 13.3kg

Inclusion Criteria:

  • Collegiate athlete
    • Track
    • Cross-country
    • Basketball

  • Currently pain-free within the lower-extremity
  • Medically cleared to participate in their respective sport
  • Undergoing preparticipation sports examination

Exclusion Criteria:

  • Pain present at time of initial examination
  • Illness/injury not related to sport participation

Four testing stations were setup and the testing sequence was randomized.

Two examiners tested all participants.

Participants performed a randomized sequence of core stability/strength test: including anterior, posterior, and lateral core muscles during the preparticipation sports examination.

  • Lateral core testing required participants to be in a McGill side-plank position until their hip touched the surface.
    • This position requires both feet to be on the ground and the top hand to grasp the contralateral shoulder.

  • Anterior core testing included two positions:
    • Year-one: Participants performed the straight-leg lowering test in supine position with knees straight, and hips flexed to 90-degrees. The legs were lowered to the table over a 10-second period, keeping the lumbar spine neutral.
    • Year two: Participants performed the McGill flexor endurance test, in a seated position with 60° of back extension, held for as long as possible.

  • Posterior core testing was carried out in prone position, with the lower-extremity secured to a table and the torso unsupported (Biering-Sorenson position).
    • Testing required participants to maintain a horizontal torso for as long as possible.

  • The mean and maximum of 3 trials were taken for hip abduction and hip external rotation isometric strength trials.
    • Hip abductor strength was measured with the participant in side-lying position with a force plate placed 5 centimeters proximal to the lateral knee joint line
    • Hip external rotation strength was measured with the participant in a seated position and the force plate 5 centimeters above the medial malleolus

Participants were observed over a two-year period for injuries to the back and lower extremities.

Data Collection and Analysis
  • Mean and maximum force measures were taken for hip abduction (gluteus medius) and hip external rotation via a hand-held dynamometer (Nicholas – Lafayette Instruments, Lafayette, IN) anchored to a table.
  • Anterior, lateral and posterior core testing was timed using a stopwatch
  • Head university athletic trainers recorded all back and lower extremity injuries that occurred during practice and/or games.
    • Injury was defined as an event that caused the participant to miss practice/game time or require treatment from medical professionals

  • ANOVA (analysis of variance) used for comparison of core stability measurements
  • Significance level set at 0.05 (p < 0.05)
  • Logistical regression was utilized for analysis of the relationship between injury and core stability testing results.

Core stability measures were compared between genders and athletes who reported injury and did not report injury using a two analysis of variance test (SPSS 11.5.1, Chicago, IL)

Outcome Measures Incidence of back and lower extremity injuries
ResultsMale college athletes
  • 13 of 60 (22%) participants reported back or lower extremity injuries
  • 71% of injuries were ankle/foot related
  • One injury was season-ending (foot fracture)

Female college athletes

  • 28 of 79 (35%) participants reported back or lower extremity injuries
  • 62% of injuries were ankle/foot related
  • One injury was season-ending (ACL)

Injured athletes had lower core stability measures than non-injured peers.

  • Flexor endurance test: injured = 199 seconds +/- 91; uninjured 217 seconds +/- 149
  • Significant differences in strength noted in hip abduction and hip external rotation
    • Hip abduction (% body weight): injured = 28.6 +/- 5.5; uninjured = 31.6 +/- 7.1
    • Hip external rotation (% body weight): injured = 17.9 +/- 4.4; uninjured = 20.6 +/- 4.2

  • Hip external rotation was found to be the only measure with strong correlation to risk of injury over an athletic season.
    • P = 0.002

Our ConclusionsThe findings of this study support the importance of core stability and reinforce the typical muscular dysfunctions described in the Brookbush Institute’s predictive model of Lumbo Pelvic Hip Complex Dysfunction (LPHCD) and Lower Extremity Dysfunction (LED). A decrease in hip external rotator strength had the strongest correlation to lower extremity injury during the season. This may imply this test could be used as a pre-season screening tool.
Researchers' Conclusions

Hip external rotation strength was found to be the strongest predictor of injury.  Injured collegiate athletes had significant weakness in hip abductionhip external rotation and core musculature.  These findings support the assessment and treatment of proximal stabilizers of the lower extremities, specifically the hip external rotators.

Lateral hop to single leg sagittal plane hop to balance.
Caption: Lateral hop to single leg sagittal plane hop to balance.

Lateral hop to single leg sagittal plane hop to balance.

How this study contributes to the body of research:

Inhibited core stability and hip strength are associated with increased injury risk of the lower-extremity; including, ankle sprains and anterior cruciate ligament sprains (1-9). This study investigated the rate of injury of male and female collegiate athletes for two years after a preparticipation evaluation including core muscle endurance and hip strength testing. This study adds to a relatively small number of prospective studies demonstrating a correlation between movement impairment and the risk of future injury. Further, this study includes males and females and multiple outcomes measures, demonstrating that both sexes may have increased risk of injury when external rotator strength is not sufficient. This last point, may also imply that risk of injury is more highly correlated with certain impairments. Future research should include collegiate athletes from other sports and additional tests/outcome measures to aid in determining additional impairments that may contribute to the risk of injury.

How the Findings Apply to Practice:

The findings of this study demonstrate correlations between core muscle endurance, insufficient hip strength and injury in collegiate athletes. Of the factors tested, insufficient hip external rotator strength had the strongest relationship. Human movement professionals may assist in injury prevention by assessing core muscle endurance and hip strength prior to the season. If limited by time or resources, the findings of this study suggest that hip external rotator strength would likely be the best screening tool. Human movement professionals should have a repertoire of exercises and techniques to address any identified deficits .

This study had many methodological strengths, including:

  1. This was a prospective study with a two-year follow-up; prospective studies are relatively rare and desperately needed to aid in determining causation and sequence of events.
  2. The sequence of the four strength measurements were randomized for all participants, reducing the impact fatigue may have on the aggregated outcome data for any one test.
  3. Each university had a full-time staff of certified athletic trainers, improving compliance of reporting injury rates and aiding in the reliability of the findings.

Weaknesses and limitations that should be noted prior to clinical integration of the findings include:

  1. Researchers changed how anterior core measurements were taken after the first year, reducing the reliability and validity of this measurement. This should be addressed in future studies.
  2. Hip strength measurements were in units of force as a percentage of body weight, but height and limb length were not considered. Future research should consider height, limb length and relative torque in addition to force and body mass.
  3. The two examiners were not tested for intratester reliability prior to data collection.

How the study relates to Brookbush Institute Content?

This study demonstrates an assumption made in the Brookbush Institute’s (BI) predictive models of Lower Extremity Dysfunction (LED) and Lumbo Pelvic Hip Complex Dysfunction (LPHCD) , that is, that dysfunction, injury and pain are often the result of impaired movement and compensation patterns. Although this assumption was made with knowledge of research studies like this, further research is needed to continue determining which signs, symptoms and patterns can be reliably assessed, and which have the highest correlation with future injury. Further, the BI recommends activation exercises for hip and core musculature, and this should be followed by integrated exercises targeting the anterior oblique subsystem (AOS) and posterior oblique subsystem (POS).

The following videos illustrate common assessment techniques for the LED and LPHCD , as well as interventions commonly used to facilitate hip external rotator activation.

Overhead Squat Assessment: Sign Clusters - Lumbo Pelvic Hip Complex Dysfunction

Overhead Squat Assessment: Sign Clusters - Lower Extremity Dysfunction

Gluteus Medius Isolated Activation

Side Plank - Core Stability


  1. Messina, D., Farney, W., DeLee, J. (1999). The incidence of injury in Texas high school basketball: a prospective study among male and female athletes. American Journal of Sports Medicine, 27, 294-299
  2. Meeuwisse, W., Sellmer, R., Hagel, B. (2003). Rates and risk of injury during intercollegiate basketball. American Journal of Sports Medicine, 31, 379-385
  3. De Blaiser, C., Roosen, P., Willems, T., Danneels, L., Bossche, L., De Ridder, R. (2018). Is core stability a risk factor for lower extremity injuries in an athletic population? A systematic review. Physical Therapy Sport, 30, 48-56
  4. Araujo, S., Cohen, D., Hayes, L. (2015). Six weeks of core stability training improves landing kinetics among female capoeira athletes: a pilot study. Journal of Human Kinetics, 45, 27-37
  5. Brown, T., Palmieri-Smith, R., McLean, S. (2014). Comparative adaptations of lower limbbiomechanics during unilateral and bilateral landings after different neuromuscular-based ACL injury prevention protocols. Journal of Strength and Conditioning Research, 28(10), 2859-2871
  6. Jamison, S., McNally, M., Schmitt, L., Chaudhari, A. (2013). The effects of core muscle activation on dynamic trunk position and knee abduction moments: implications for ACL injury. Journal of Biomechanics, 46(13), 2236-2241
  7. Hewett, T. Myer, G., Ford, K. (2005). Reducing knee and anterior cruciate ligament injuries among female athletes: a systematic review of neuromuscular training interventions. Journal of Knee Surgery, 18(1), 82-88
  8. Nadler, S., Malanga, G., DePrince, M., Stitik, T., Feinberg, J. (2000). The relationship between lower extremity injury, low back pain, hip muscle strength in male and female collegiate athletes. Clinical Journal of Sport Medicine, 10(2), 89-97
  9. Zazulak, B. T., Hewett, T. E., Reeves, N. P., Goldberg, B., and Cholewicki, J. (2007). Deficits in neuromuscular control of the trunk predict knee injury risk. The American Journal of Sports Medicine35(7), 1123-1130

© 2018 Brent Brookbush

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