THE ASSOCIATION BETWEEN TRUNK, HIP, AND KNEE FUNCTION AND

PERFORMANCE DURING A SINGLE-LEG SQUAT TEST Lori Bolgla, Eric Booth, Kaitlyn K. Browning, & Brianne Lapierre

Department of Physical Therapy, Georgia Regents University, Augusta, GA

BACKGROUND

PURPOSE/HYPOTHESES

METHODS

Upon arrival, subjects performed three plank exercises to assess anterior, lateral, and posterior core endurance.

RESULTS

CONCLUSIONS

The purpose of this study was to compare 1) trunk endurance, 2)

hip and knee strength, and 3) trunk, hip, and knee neuromuscular

activity in individuals who demonstrate good or poor SLS

performance.

Hypotheses: 1) Subjects with “poor” SLS performance will exhibit

decreased trunk endurance and decreased hip and knee strength.

2) Subjects with “poor” or “good” SLS performance will generate

different trunk, hip, and knee EMG activity during the SLS.

The knee is the most commonly injured lower extremity joint,

particularly among active individuals.

Core stability may influence the occurrence of certain knee

pathologies, such as anterior cruciate ligament injury,

patellofemoral pain, and iliotibial band syndrome.

Core stability has both active and passive components. Passive

components include bony and ligamentous structures, while active

components include the trunk, hip, and knee musculature.

The single-leg squat (SLS) is a common functional screening tool

used to examine gross lower extremity (LE) strength and

kinematics during dynamic movement.

To date, researchers have not simultaneously compared trunk, hip,

and knee strength and EMG activity during a SLS between

individuals who demonstrate “good” or “poor” SLS performance. .

Early identification of the active core impairments that influence

SLS performance can provide a means for targeted knee injury

prevention programs and knee rehabilitation protocols.

All subjects, regardless of SLS performance, demonstrated similar

core endurance, strength, and EMG activity during the SLS.

Higher level motor control, not strength, may contribute more to an

individual’s ability to correctly perform a SLS.

Activity specific motor control training may be needed to alter

underlying hip and knee pathomechanics.

Future studies should focus on developing protocols that integrate

motor control principles for knee injury prevention and rehabilitation

programs.

SINGLE-LEG SQUAT

REFERENCES

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Hip Extension Hip Abduction Knee Extension

Pe

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%)

Strength

Poor

Good

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Anterior Core Lateral Core Posterior Core

Ave

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e T

ime

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Core Endurance

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Good

Poor Performance

Knee-Medial-To-Foot

Good Performance

Knee-Over-Foot

SUBJECTS Ageberg, E., Bennell, K. L., Hunt, M. A., Simic, M., Roos, E. M., & Creaby, M. W.

(2010). Validity and inter-rater reliability of medio-lateral knee motion observed during a

single-leg limb mini squat. BMC Musculoskeletal Disorders, 11(265), 1-8.

DiMattia, M. A., Livengood, A. L., Uhl, T. L., Mattacola, C. G., & Malone, T. R. (2005).

What are the validity of the single-leg squat test and its relationship to hip-abduction

strength? Journal of Sport Rehabilitation, 14, 108-123.

Powers, C. M. (2010). The influence of abnormal hip mechanics on knee injury: a

biomechanical perspective. Journal of Orthopaedic & Sports Physical Therapy, 40(2),

42-51.

Willy, R.D., Davis, I.S. (2011). The effect of the hip-strengthening program on

mechanics during running and during a single-leg squat. Journal of Orthopaedic and

Sports Physical Therapy, 41(9), 625-632.

29 recreationally-active healthy adults (11 men, 18 women)

Age = 24.31 ± 1.51 y, Height = 174.03 ± 9.69 cm, Mass = 68.57 ±

10.97 kg

Exclusion Criteria: problems with balance, exercise restrictions, any

significant lower extremity or spinal injury or surgery

* P: poor performance;

G: good performance

† Expressed as 100%

of maximum voluntary

isometric contraction

^ Level of significance

at p = 0.05

EMG Data

Anterior Plank

Strength data was recorded for the gluteus maximus, gluteus medius, and rectus femoris using hand-held dynamometry.

Surface EMG electrodes were applied to the rectus abdominis,

abdominal obliques, lumbar extensors, gluteus maximus, gluteus medius, and rectus femoris to collect EMG activity during the SLS.

Subjects performed 5 repetitions of the SLS. An overall score of

good was received if the subject maintained knee-over-foot position ≥ 3 times.

Data was analyzed using independent t-tests to identify

between-group (good or poor performance) differences.

Lateral Plank Posterior Plank