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Tuesday, June 6, 2023

Hip Extensor Strength, Trunk Posture, and Use of Knee Extensor Muscles During Running

Brent Brookbush

Brent Brookbush


Hip-Extensor Strength, Trunk Posture, and Use of the Knee-Extensor Muscles During Running

By Alex Howard PT, DPT, CSCS

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

Original Citation: Teng, H. and Powers, C. (2016) Hip Extensor Strength, Trunk Posture, and Use of the Knee-Extensor Muscles During Running. Journal of Athletic Training, 51(8), 000-000. ARTICLE

Why is this relevant?:

Running is a common form of exercise performed by a wide range of individuals from the novice to professional athlete. The impact of lower extremity strength, trunk posture, and work output of the knee and hip extensors may highlight relationships development of certain lower extremity injuries, specifically at the knee.

Picture of Marathon Runners
Caption: Picture of Marathon Runners

Marathon Runners - By No machine-readable author provided. Melburnian assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1420320

Study Summary

Study Design Cohort study
Level of Evidence Level III: Evidence from non-experimental descriptive studies, such as comparative studies, correlation studies, and case-control studies
Subject Demographics

Characteristics: 40 recreational runners

    • Gender: Male 20, Female 20
    • Age(yrs): Male: 27.1 (+ 7.0), Female: 26.2 (+ 5.8)
    • Weight(kg): Male: 71.1 (+ 18.2), Female: 60.6 (+ 6.6)
    • Height(m): Male: 1.74 (+ 0.69), Female: 1.65 (+ 0.74)
    • Running distance/week (km): Male: 22.1 (+ 10.5), Female: 22.7 (+ 10.9)
    • Participants wore a tank top, shorts and personal running shoes

Inclusion Criteria:

  • Run at least 8.05 km per week
  • Natural heel strikers

Exclusion Criteria

  • Lower extremity or low back pain at time of study
  • History of lower extremity or low back surgery
  • Lower extremity or low back pathology that resulted in pain or discomfort during running in past 6 months
Outcome Measures
  • Reference maximal voluntary contraction for hip extension obtained from dominant leg in prone position
  • 21 reflective anatomical markers placed on bony landmarks to define standing calibration and joint axes. All tracing markers removed except on iliac crest, L5-S1 junction and acrominoclavicular joint. Data collection defined this as the trunk segment
  • Subjects ran at a speed of 3.4 meters/second (7.6 mph) on a 14 meter runway
  • Five successful running trials obtained
  • Successful running trial = foot of dominant leg landed within border of force plate and running speed + 5% of target velocity
  • Total work of the knee and hip extensors were obtained from absolute values calculated from energy absorption and generation during stance time of the running trials
  • A positive correlation between hip extensor strength and trunk flexion angle (forward lean) was observed ( r = 0.55)
  • A positive correlation between between hip extensor strength and hip extensor work was observed (r = 0.46)
  • An inverse correlation between hip extensor strength and knee extensor work was observed (r = -0.39)
  • After adjusting for sex, hip extensor strength remained correlated with trunk flexion angle, hip extensor work and knee extensor work
ConclusionsThis study provides evidence  that hip extensor strength may have an affect on sagittal plane trunk posture and hip and knee extensor work during running.  That is a decrease in hip extensor strength, may result in more upright posture and an increase knee extensor work.
Conclusions of the ResearchersHip extensor strength correlated with trunk posture and hip and knee extensor work during running.  Hip extensor strength explained 30.%% of variance in sagittal plane trunk posture, 21.2% of hip extensor work and a 15.2% variance in knee extensor work. Individuals with weaker hip extensors demonstrated less hip extensor work and more knee extensor work during running.

Dr. Brookbush performing a Manual Muscle Test for Gluteus Maximus on a patient.
Caption: Dr. Brookbush performing a Manual Muscle Test for Gluteus Maximus on a patient.

Dr. Brookbush performing a Manual Muscle Test for Gluteus Maximus on a patient.

Review & Commentary:

The authors of this study examined the relationship between hip extensor strength, trunk posture, knee extensor and hip extensor work during running.

The study design had several strengths. In an attempt to isolate variables, only heel strike runners were used, and all runners were asked to run at the same speed. Changes in velocity and the addition of increased plantar flexion will affect trunk, hip and knee angle, which would have confounded the results of this study. Further, kinematic data was acquired using 3D motion capture technology and standardized equations for torque, moment velocity, etc.. Last, only experienced and relatively conditioned runners were used in this study, decreasing the likelihood that training affect, a lack of sufficient experience, or conditioning contributed to the studies findings.

There were limitations to this study that should be discussed before application to practice. First, the maximal voluntary contraction for hip extensor strength was measured isometrically, where as a dynamic hip extensor measurement of strength may be more relevant to running tasks and have a stronger correlation with trunk posture and muscle activity. Further, it may have been interesting to include EMG data on relative gluteus maximus activity during running, to determine the relationship between maximum voluntary hip extension torque, gluteus maximus activity, running and trunk posture. Although appropriate for the study design, readers should note that the authors used pain-free runners. Caution should be used when considering these findings, relative to symptomatic clients/patients, as pain has been shown to alter muscle activity and lower extremity biomechanics. Again, appropriate for the study design but limiting transferability, this study used natural heel-strike runners wearing their own personal foot wear. This study may not be representative of mid-foot/forefoot runners, or those wearing specialized footwear.

Why is this study important?

The findings of this study suggest that decreased hip extensor strength, results in more upright running posture and increased reliance on knee extensor strength. An over-reliance on the knee extensors may result in an increase in stress/workload across the tibia-femoral and patella-femoral joints, leading to knee injury/pain. This may suggest that both an increase in hip extensor strength and a slight forward lean are attributes that runners should work toward attaining, especially in those with a history of knee pain and injury.

How does it affect practice?

Adding specific exercises for hip extensor strength to a runner's program may improve biomechanics. Although further research is needed, this may be especially true for those with chronic knee pain who exhibit an upright running posture, and or assessed gluteus maximus and gluteus medius weakness.

How does it relate to Brookbush Institute Content?

If a client presents with knee pain while running and decreased gluteus maximus strength, it is important to recognize the compensation pattern adopted and not become fixated on movement impairment/dysfunction specific to the knee joint . The relationships demonstrated in this study (trunk, hip and knee) are similar to those discussed in the Brookbush Institute predictive model of Lower Leg Dysfunction (LLD) , and the Overhead Squat Assessment sign "excessive forward lean ". An integrated, comprehensive strategy should be developed to establish a new motor pattern. This may include (but is not limited to) plantar flexor and hip flexor release and lengthening techniques, as well as lower extremity mobilization techniques and gluteus maximus activation exercises

The videos below demonstrate testing and activation for the Gluteus Maximus (primary hip extensor):

Gluteus Maximus Manual Muscle Testing (for an active population)

Gluteus Maximus Isolated Activation

Quick Glute Activation Circuit

Gluteus Maximus Reactive Activation

© 2016 Brent Brookbush

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