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Lee Herrington

Context:

A valgus position of the knee on functional loading tasks has been reported to be associated with patellofemoral-joint pain. Training programs to reduce knee valgus have been shown to be effective but take time. It would appear logical to use a brace or strap to help control this knee motion to reduce symptoms.

Objective:

To assess the impact of the SERF strap on knee valgus and patellofemoral-joint pain.

Design:

Repeated measures.

Setting:

University human performance laboratory.

Participants:

12 women with patellofemoral pain (mean age 24 ± 3.2 y).

Intervention:

Application of SERF strap.

Main Outcome Measures:

Knee-valgus angle on single-leg squat and step landing and visual analog scale pain score.

Results:

The application of the SERF brace significantly reduced the pain (P < .04) and knee valgus (P < .034) during both tasks.

Conclusion:

The SERF brace brings about a significant reduction in pain during functional tasks. Although the brace brought about a significant reduction in knee valgus, this failed to exceed the smallest-detectable-difference value, so the difference is likely to be related to measurement error. The mechanism as to why this the reduction in pain occurs therefore remains unclear, as this study in line with many others failed to demonstrate meaningful changes in kinematics that could provide an obvious explanation.

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Lee Herrington

Context:

Hamstring muscle length is commonly measured because of its perceived relationship to injury of both the hamstrings themselves and the pelvis and lumbar spine. The popliteal (knee-extension) angle measured from the starting position hip and knee at 90° is a commonly used indirect measure of hamstring muscle length. When this measure has been undertaken in the literature previously, little attention was paid to the position of the pelvis, which may significantly influence measurements taken.

Design:

Repeated-measures.

Setting:

University human performance laboratory.

Participants:

60 healthy physically active males (mean age 20.1 ± 1.8 y, range 18–24 y).

Intervention:

The 2 extremes of pelvic position (anterior and posterior).

Main Outcome Measure:

Popliteal angle (with maximal knee extension) was measured in 2 positions, 1 of full anterior and 1 of full posterior pelvic tilt.

Results:

The mean difference in popliteal angle between anterior to posterior pelvic positions was 13.4° ± 9° (range 0–26°); this was statistically significant (P = .0001).

Conclusion:

The findings of the study indicate that pelvic position has a significant effect on popliteal angle and therefore should be taken into account when measuring hamstring muscle length.

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Lee Herrington

Context:

Authors have investigated knee joint-position sense (JPS) in non-weight-bearing open kinetic chain (OKC) manner, but few have investigated JPS during closed kinetic chain (CKC) weight-bearing activities or the relationship between these two.

Objective:

To investigate the relationship between knee JPS during OKC and CKC maneuvers.

Design:

2-group (men and women) repeated-measures.

Setting:

Biomechanics laboratory.

Participants:

80 asymptomatic subjects.

Interventions:

None.

Main Outcome Measure:

Absolute error score of knee JPS during 2 conditions, a CKC squat or OKC knee-flexion maneuver.

Results:

Statistical analysis by 2-way ANOVA showed sex not to have a significant effect on error score (P = .475), but statistically significant differences between error scores occurred during the 2 tests (P = .0001), the CKC test producing lower error scores (group mean absolute error score OKC [5.6° ± 4.3°] and CKC [2.8° ± 2.4°]), with the absence of a correlation between scores of each test (r = .1).

Conclusion:

Testing JPS in a CKC scenario would seem appropriate—the ability is greatest (least errors), and conversely any deficits might be most obvious.

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Lee Herrington

Context:

A number of acute and overuse knee pathologies share a mechanism involving a poor dynamic alignment of the limb creating increased stress in the tissues. Inappropriate execution of a correct strategy during landing has been suggested to involve insufficient activity of the hip abductor and external rotator muscles. Limited data describing the relationships between hip-abductor muscle fatigue and hip/knee joint mechanics exists.

Objective:

To investigate the effect of fatigue of the hip abductor muscles on knee valgus angle.

Design:

Repeated measures.

Participants:

30 asymptomatic subjects: 15 female (age 20.4 ± 1.4, range 18–26 years; height 1.66 m, range 1.60–1.76 m; weight 63.9 kg, range 58–68 kg) and 15 male subjects (age 22 ± 3.2, range 18–28 years; height 1.84 m, range 1.65–1.90 m; weight 82.1 kg, range 69–93 kg).

Main outcome Measures:

Knee valgus (frontal plane projection) angle was assessed during a step landing task before and following a fatiguing protocol of the hip abductor muscles involving repeated 10 s maximal isometric contractions of the hip abductor muscles, until strength was recorded as 50% of preintervention score.

Results:

Males showed no significant change in knee valgus angle at initial ground contact (p = .9 ES 0.1) or in maximum knee valgus (p = .64 ES 0.5) following the fatiguing. Females showed a significant increase in maximum knee valgus angle following the fatiguing (p = .0018 ES 1.0), though the knee valgus angle at initial contact was not changed (p = .12 ES 0.67). They also demonstrated a significant increase in the change in knee valgus angle between initial contact and maximum following the fatiguing (p = .0004 ES 0.88).

Conclusion:

Females appear more susceptible to the effects of hip muscle fatigue, leading to a detrimental change in landing kinematics which may then predispose them to knee injury.

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Nicola Relph and Lee Herrington

Context: Clinicians require portable, valid, and cost-effective methods to monitor knee joint-position-sense (JPS) ability. Objective: To examine the criterion-related validity of image-capture JPS measures against an isokinetic-dynamometer (IKD) procedure. Design: Random crossover design providing a comparison of knee JPS measures from image capture and IKD procedures. Participants: 10 healthy participants, 5 female, age 28.0 ± 13.29 y, mass 60.3 ± 9.02 kg, height 1.65 ± 0.07 m, and 5 male, 29.6 ± 10.74 y, mass 73.6 ± 5.86 kg, height 1.75 ± 0.07 m. Main Outcome Measures: The dependent variables were absolute error scores (AES) provided by 2 knee directions (flexion and extension). The independent variables were the method (image capture and IKD). Results: There was no significant difference between clinical and IKD AED into knee-extension data (P = .263, r = 0.55). There was a significant difference between clinical and IKD AES into knee-flexion data (P = .016, r =.70). Conclusions: Analysis of photographic images to assess JPS measurements using knee flexion is valid against IKD techniques. However, photo-analysis measurements provided a lower error score using knee-extension data and thus may provide an optimal environment to produce maximal knee JPS acuity. Therefore, clinicians do not need expensive equipment to collect representative JPS ability.

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Nicola Relph and Lee Herrington

Context: Knee joint-position sense (JPS) plays a critical role in controlled and stable joint movement. Poor ability to sense position of the knee can therefore increase risk of injury. There is no agreed consensus on JPS measurement techniques and a lack of reliability statistics on methods. Objective: To identify the most reliable knee JPS measurement technique using image capture. Design: Interexaminer, intraexaminer, and test-retest reliability of knee JPS measurements. Setting: Biomechanics laboratory. Participants: 10 asymptomatic participants. Interventions: None. Main Outcome Measures: Relative and absolute error scores of knee JPS in 3 conditions (sitting, prone, active) through 3 ranges of movement (10-30°, 30-60°, 60-90°), into 2 directions (flexion and extension) using both legs (dominant and nondominant) collected during 15 trials and repeated 7 d after the first data collection. Results: Statistical analysis by intraclass correlations revealed excellent interexaminer reliability between researchers (.98) and intraexaminer reliability within 1 researcher (.96). Test-retest reliability was highest in the sitting condition from a starting angle of 0°, target angle through 60-90° of flexion, using the dominant leg and absolute-error-score variables (ICC = .92). However, it was noted smallest detectable differences were a high percentage of mean values for all measures. Conclusions: The most reliable JPS measurement for asymptomatic participants has been identified. Practitioners should use this protocol when collecting JPS data during prescreening sessions. However, generalizability of findings to a class/group of clients exhibiting knee pathologies should be done with caution.

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Lee Herrington and Stephen Pearson

Context:

One factor believed to affect Patella tracking is an alteration in the timing of the contraction of the muscular stabilizers of the patella. The muscles responsible for this are Vastus Medialis Oblique (VMO) and Vastus Laterialis (VL). A number of authors believe that asynchronous recruitment of the VMO muscle occurs in patella mal-tracking, with the VL muscle firing first and VMO firing first with normal tracking. This has lead to a variety of exercise interventions to reverse the situation with varying success. The discrepancy between the majority of the available research findings and the clinical hypothesis of VMO action or facilitation of this action may in part be due to methodological variability between studies, especially lack of control of the exercise variables of angular velocity and relative load.

Objective:

To assess the effect of different quadriceps exercises on VMO and VL EMG recruitment timing, while controlling load and velocity of contraction.

Design:

Repeated measures.

Setting:

Biomechanics laboratory.

Main Outcome Measures:

Differences in time of onset of muscle activity between VMO and VL.

Results:

No significant difference existed between gender (P = 0.78). Analysis factorial ANOVA (muscle, contraction type and exercise type) showed the main effects of muscle (P = 0.15) and type of contraction (P = 0.79) did not have a significant effect, the nature of exercise (OKC or CKC) had a significant effect (P < 0.001). The interaction of muscle and exercise type (P = 0.34) also had a nonsignificant effect.

Conclusions:

Onset timing does not differ significantly between VMO and VL during a variety of exercise tasks.

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Allan Munro, Lee Herrington and Paul Comfort

Context:

Injuries to the anterior cruciate ligament (ACL) and patellofemoral joint (PFJ) are a significant problem in female athletes. A number of screening tasks have been used in the literature to identify those at greatest risk of injury. To date, no study has examined the relationship in 2-dimensional (2D) knee valgus between common screening tasks to determine whether individuals exhibit similar movement patterns across tasks.

Objective:

To establish whether frontal-plane projection angle (FPPA) during the single-leg squat (SLS), single-leg land (SLL), and drop jump (DJ) are related.

Design:

Cross-sectional study.

Setting:

University laboratory.

Participants:

52 national-league female football players and 36 national-league female basketball players.

Main Outcome Measures:

2D FPPA during the SLS, SLL, and DJ screening tasks.

Results:

Significant correlations were found between tasks. FPPA in the SLS was significantly correlated with SLL (r = .52) and DJ (r = .30), whereas FPPA in the SLL was also significantly correlated to DJ (r = .33). FPPA was significantly greater in the SLS than in the SLL (P < .001) and DJ (P < .001) and in the SLL than in the DJ (P < .001).

Conclusion:

The results showed that 2D FPPA is correlated across the SLS, SLL, and DJ tasks. However, significantly greater FPPA values in the unilateral tasks suggest that the DJ may not identify risk of injury in sports where primary injury mechanisms are during unilateral loading tasks. Therefore, it is recommended that both unilateral and bilateral tasks be included when screening for ACL and PFJ injury risk.

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Allan Munro, Lee Herrington and Michael Carolan

Context:

Two-dimensional (2D) video analysis of frontal-plane dynamic knee valgus during common athletic screening tasks has been purported to identify individuals who may be at high risk of suffering knee injuries such as anterior cruciate ligament tear or patellofemoral pain syndrome. Although the validity of 2D video analysis has been studied, the associated reliability and measurement error have not.

Objective:

To assess the reliability and associated measurement error of a 2D video analysis of lower limb dynamic valgus.

Design:

Reliability study.

Participants:

20 recreationally active university students (10 women age 21.5 ± 2.3 y, height 170.1 ± 6.1 cm, weight 66.2 ± 10.2 kg, and 10 men age 22.6 ± 3.1 y, height 177.9 ± 6.0 cm, weight 75.8 ± 7.9 kg).

Main Outcome Measurement:

Within-day and between-days reliability and measurement-error values of 2D frontal-plane projection angle (FPPA) during common screening tasks.

Interventions:

Participants performed single-leg squat and drop jump and single-leg landings from a standard 28-cm step with standard 2D digital video camera assessment.

Results:

Women demonstrated significantly higher FPPA in all tests except the left single-leg squat. Within-day ICCs showed good reliability and ranged from .59 to .88, and between-days ICCs were good to excellent, ranging from .72 to .91. Standard error of measurement and smallest detectable difference values ranged from 2.72° to 3.01° and 7.54° to 8.93°, respectively.

Conclusions:

2D FPPA has previously been shown to be valid and has now also been shown to be a reliable measure of lower extremity dynamic knee valgus. Using the measurement error values presented along with previously published normative data, clinicians can now make informed judgments about individual performance and changes in performance resulting from interventions.

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Gemma N. Parry, Lee C. Herrington and Ian G. Horsley

Context: Muscular power output of the upper limb is a key aspect of athletic and sporting performance. Maximal power describes the ability to immediately produce power with maximal velocity at the point of release, impact, or takeoff, with research highlighting that the greater an athlete’s ability to produce maximal power, the greater the improvement in athletic performance. Despite the importance of upper-limb power for athletic performance, there is presently no gold-standard test for upper-limb force development performance. Objective: The aim of this study was to investigate the test–retest reliability of force plate–derived measures of the countermovement push-up in active males. Design: Test–retest design. Setting: Controlled laboratory. Participants: Physically active college athletes (age 24 [3] y, height 1.79 [0.08] m, body mass 81.7 [9.9] kg). Intervention: Subjects performed 3 repetitions of maximal effort countermovement push-up trials on Kistler force plates on 2 separate test occasions 7 days apart. Main Outcome Measures: Peak force, mean force, flight time, rate of force development, and impulse were analyzed from the force–time curve. Results: No significant differences between the 2 trial occasions were observed for any of the derived performance measures. Intraclass correlation coefficient and within-subject coefficient of variation calculations indicated performance measures to have moderate to very high reliability (intraclass correlation coefficient = .88–.98), coefficient of variation = 5.5%–14.1%). Smallest detectable difference for peak force (7.5%), mean force (8.6%), and rate of force development (11.2%) were small to moderate. Conclusion: Force platform–derived kinetic parameters of countermovement push-up are reliable measurements of power in college-level athletes.