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Tuesday, June 6, 2023

Immediate Effect of Grade IV Inferior Hip Joint Mobilization on Hip Abductor Torque: A Pilot Study

Brent Brookbush

Brent Brookbush


Research Review: Inferior Hip Mobilizations Increase Gluteus Medius Strength

By Nicholas Rolnick PT, DPT, MS, CSCS

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

Original Citation: Makofsky, H, Panicker, S, Abbruzzese, J, Aridas, C, Camp, M, Drakes, J, Franco, C and Sileo R. (2007). Immediate effect of grade IV inferior hip mobilization on hip abductor torque: a pilot study. Journal of Manual and Manipulative Therapy, 15(2), 103-111. ARTICLE .

Why the Study is Relevant: Research has demonstrated that a variety of lower extremity impairments may be correlated with gluteus medius weakness/under-activity (1-13). Prior studies have shown strength increases following joint mobilizations and manipulations (14-18); however, it was unclear whether hip mobilizations would have the same effect on hip musculature. This 2007 study demonstrated that grade IV inferior hip mobilizations increased gluteus medius torque production in 15 healthy individuals. These findings suggest that joint mobilizations may aid in increasing gluteus medius strength, and that mobilizations should be performed prior to gluteus medius activation techniques .

Hip joint mobilizations can improve the effectiveness of gluteus medius activation techniques. - Image courtesy of Brentbrookbush.com

Study Summary

Study DesignDouble-blinded randomized controlled trial
Level of EvidenceIB Evidence from at least one randomized controlled trial
Subject CharacteristicsDemographics
  • Age: 20-65
  • Gender: N/A
  • Number of participants: 30
    • 15 in control group
    • 15 in experimental group

Inclusion Criteria:

  • 20-65
  • A subjective report of well-being

Exclusion Criteria:

  • Any physical condition that may influence the result of the intervention, including pain, muscle splinting, systemic disease and surgery
  • Low back pain within the past six weeks
  • History of hip, knee or ankle pathology
  • Osteoporosis
  • Hyper- or hypomobility at the hip joint
  • Participants were randomly placed into experimental (EXP) or control (CON) groups.
    • Participants and investigators were blinded to the participant's group assignments.

  • Pre-intervention hip abductor torque was obtained with each participant in right-side lying and the hip in end-range abduction (to test the left hip abductors).
    • Participants performed five isometric hip abduction contractions of 5-seconds each against the dynamometer with 10-second rest intervals between contractions.
    • The average of these values was used for analysis.

  • Grades of mobilizations were different in the CON and EXP groups
    • EXP group received grade IV inferior hip joint mobilizations, with the hip in 45° hip abduction.
    • CON group received grade I inferior hip joint mobilizations, with the hip in 45° hip abduction.

  • Two physical therapy students (trained by a board-certified orthopedic physical therapist) performed the same mobilization (either grade IV or grade I) on participants in each group.
    • Three repetitions of 1-minute mobilizations, with 30-second rest intervals between, were performed

  • Fifteen minutes post mobilization, hip abductor torque was measured using the protocol described above.
Data Collection and Analysis
  • Hip abductor torque was calculated using a Cybex Norm Dynamometer®
  • Average of five isometric contractions.
  • Minimum detectable change (MDC) and standard error of measurement (SEM) was calculated using data from a prior study obtained with the Cybex Norm Dynamometer®.
  • Statistical analysis was performed using a one-tailed independent t-test with significance set at p < 0.05.
Outcome Measures
  • Averaged absolute difference and percent difference between pre-mobilization and post-mobilization hip abductor torque production.

Average hip abductor torque change from pre- to post-mobilization (in foot-pounds, ft-lb)

  • EXP group increased from 13.07 ft.-lbs to 15.33 ft.-lbs post-mobilization. (17.35% increase) (p < 0.05)
  • CON group decreased from 10.87 ft.-lbs to 10.47 ft.-lbs post-mobilization. (-3.68% decrease) (p > 0.05).

MDC for true hip abductor torque changes were calculated to be 1.88 ft.-lbs.

Our ConclusionsThe findings demonstrate inferior hip joint mobilizations can increase gluteus medius torque production, similar to the strength increases noted in other body regions post joint mobilization/manipulation.
Researchers' Conclusions

Gluteus medius muscle activation improved for at least 15 minutes following grade IV inferior hip joint mobilizations. To improve muscle function, inferior hip joint mobilizations should be performed prior to strengthening the hip abductors.

Self-administered superior to inferior hip joint mobilization with hip flexion -Image courtesy of Brentbrookbush.com

Review & Commentary

To our knowledge, this study was the first to investigate the immediate effects of hip joint mobilization on gluteus medius  muscle strength in asymptomatic individuals. The findings add to a growing body of research demonstrating the impact of joint mobilization/manipulations on proximal muscle strength.

The study had many methodological strengths, including:

  • The double-blinded randomized controlled design minimized observer bias.
  • The mobilization that was performed is a treatment technique commonly used in clinical practice - increasing the applicability of the study.
  • The findings filled a gap in research. Prior research has demonstrated a relationship between join mobilization/manipulation and proximal muscles strength; however, it was unknown whether hip joint mobilizations would improve gluteus medius muscle strength, specifically.

Weaknesses that should be noted prior to clinical integration include:

  • The minimum detectable change for dynamometry strength values was based on a prior study that investigated by different researchers investigating test-retest reliability of the trunk muscles. The reliability of the dynamometer for hip abduction strength measurements may be different than the values reported.
  • Reliability of joint mobilization technique was not determined.
  • Future studies should include electromyography to help differentiate between muscle strength and muscle activation levels following joint mobilizations.
  • The participants were asymptomatic. It is unknown whether individuals with pain would respond differently.

How This Study is Important:

This study adds to a growing body of research that suggests joint mobilizations have an immediate effect on proximal muscle strength and activity (14-18).

The study also highlights differences in muscle activity following various grades of manual mobilization. Grade IV mobilizations are typically performed to improve range of motion, whereas Grade I mobilizations are used for pain management. The findings suggest that these techniques produce different outcomes in muscle strength. More research is needed to determine if differences exist between Grade II and Grade III mobilizations.

Arthrogenic muscle inhibition (AMI) is thought to be the mechanism responsible for the strength increases observed in this study and others (14-18). AMI was previously thought to occur only in injured individuals, but a growing body of research suggests that this mechanism also occurs in asymptomatic individuals, as well (19). Mechanoreceptors in the affected joint are thought to send inhibitory signals to the spinal cord to protect the joint, inhibiting voluntary activity in the muscles crossing that joint (19). More research is needed to determine the prevalence of AMI in healthy populations and the implications for rehabilitation and performance.

How the Findings Apply to Practice:

The effect joint mobilizations have on proximal muscle strength supports consideration of the human movement system as a holistic system; that is, the muscular system and joint system cannot be considered separate. Human movement professionals should consider incorporating hip joint mobilizations in a program designed to improve gluteus medius  strength.

How does it relate to Brookbush Institute Content?

The Brookbush Institute (BI) has recommended that joint mobilizations be performed prior to activation techniques . This order was based on the premise that joint mobilizations would increase range of motion and reduce obstruction from joint stiffness. The findings of this study (and others, 14-18) suggest that neuromuscular factors may contribute to an increase of force production post mobilization as well.

The findings of this study also support the interventions proposed in the BI's predictive models of Lower Extremity Dysfunction (LED) and Lumbo Pelvic Hip Complex Dysfunction (LPHCD) . In these models the hip is described as having a propensity toward excessive superior and anterior glide, and the gluteus medius  is classified as long/under-active. The findings of this study suggest mobilizing the hip joint inferiorly prior to beginning gluteus medius activation techniques . It should be noted that the BI also recommends release techniques prior to mobilization, for example, release of the gluteus minimus and tensor fasciae latae .

Human movement professionals should add hip joint mobilizations to a programs designed to improve gluteus medius  strength. While the self-administered mobilization recommended by the BI do not resemble the one performed in this study, both may facilitate relative inferior glide of the femur, suggesting that similar outcomes may result from both techniques. Human movement professionals whose scope includes joint mobilizations (DO’s, DPTs, DCs, ATCs) may practice manual mobilization techniques. Manual joint mobilization and manipulation techniques videos are coming soon!

Self-administered Hip Joint Mobilization (Lateral Distraction)

Self-administered Anterior to Posterior Hip Joint Mobilization with Flexion


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