Peter E. Pidcoe

Changes in landing biomechanics during a fatiguing landing activity

The objective of this study was to investigate the effects of LE fatigue on ground impact force, LE kinematics, and LE kinetics during landing. Ground reaction force (GRF), kinematic, and electromyogram (EMG) data were collected from 12 male subjects during a fatiguing landing activity (FLA). This activity allowed not only the biomechanical differences between unfatigued and fatigued landings to be determined, but also the time history of multiple biomechanical variables as fatigue progressed. EMG mean frequency analysis using data collected immediately before and after the FLA indicated that subjects experienced fatigue of the quadriceps muscles. Results indicated a decrease in ground impact force and an increase in maximum joint flexion during landing with fatigue. Joint impulse values were consistent with a distal to proximal redistribution of extensor moment production. Potential reasons for this redistribution are discussed. A trend reversal in hip and ankle impulse during the activity suggest a change in landing strategy as fatigue progressed. The data also suggest that the measured changes in landing biomechanics may have been influenced by other factors, in addition to fatigue, such as a neuromuscular protective mechanism to decrease impact force magnitude.

Repeatability of the modified Oxford foot model during gait in healthy adults

BACKGROUND The Oxford foot model (OFM) is a multi-segment model for calculating hindfoot and forefoot motion. Limited information is available regarding the repeatability and error of this model in adults. Therefore the purpose of this study was to assess the intra-tester reliability of OFM hindfoot and forefoot gait kinematics in adults at initial contact (IC) and toe-off (TO). METHODS Seventeen healthy adults (age=25.1±4.8 years, height=1.75±0.10m, weight=74.0±12.4kg) were tested on a single visit, during which 1 examiner recorded 2 sessions. For each session, 10 walking trials were recorded using a 12-camera motion analysis system (Vicon, Oxford, UK). Markers were removed and re-applied between sessions. Dynamic hindfoot and forefoot angles were calculated both with and without referencing to neutral stance (assuming neutral stance angles are zero in all planes). Using the 10 trial average, intraclass correlation coefficients (ICC(2,k)) and standard errors of the measurement were calculated for each reference condition, anatomical plane, and joint (hindfoot, forefoot). RESULTS Referencing to neutral stance resulted in good reliability (ICC≥0.83) and small error (≤2.45°) for hindfoot and forefoot angle in all planes. Without referencing to neutral stance, sagittal and transverse plane reliability were also good (ICC≥0.90) and error small (≤3.14°); however, frontal plane reliability was poor (ICC≤0.77), with large error (≥4.86°). DISCUSSION Our results show that overall the OFM is reliable during adult gait. Reliability for adults is higher than previously reported in children. Referencing joint angles to neutral stance decreased error by up to 2° from previous reports.

Clinical Examination Results in Individuals With Functional Ankle Instability and Ankle-Sprain Copers

CONTEXT Why some individuals with ankle sprains develop functional ankle instability and others do not (ie, copers) is unknown. Current understanding of the clinical profile of copers is limited. OBJECTIVE To contrast individuals with functional ankle instability (FAI), copers, and uninjured individuals on both self-reported variables and clinical examination findings. DESIGN Cross-sectional study. SETTING Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANTS Participants consisted of 23 individuals with a history of 1 or more ankle sprains and at least 2 episodes of giving way in the past year (FAI: Cumberland Ankle Instability Tool [CAIT] score = 20.52 ± 2.94, episodes of giving way = 5.8 ± 8.4 per month), 23 individuals with a history of a single ankle sprain and no subsequent episodes of instability (copers: CAIT score = 27.74 ± 1.69), and 23 individuals with no history of ankle sprain and no instability (uninjured: CAIT score = 28.78 ± 1.78). INTERVENTION(S) Self-reported disability was recorded using the CAIT and Foot and Ankle Ability Measure for Activities of Daily Living and for Sports. On clinical examination, ligamentous laxity and tenderness, range of motion (ROM), and pain at end ROM were recorded. MAIN OUTCOME MEASURE(S) Questionnaire scores for the CAIT, Foot and Ankle Ability Measure for Activities of Daily Living and for Sports, ankle inversion and anterior drawer laxity scores, pain with palpation of the lateral ligaments, ankle ROM, and pain at end ROM. RESULTS Individuals with FAI had greater self-reported disability for all measures (P < .05). On clinical examination, individuals with FAI were more likely to have greater talar tilt laxity, pain with inversion, and limited sagittal-plane ROM than copers (P < .05). CONCLUSIONS Differences in both self-reported disability and clinical examination variables distinguished individuals with FAI from copers at least 1 year after injury. Whether the deficits could be detected immediately postinjury to prospectively identify potential copers is unknown.

A muscle temperature compensation technique for EMG fatigue measures

PURPOSE The use of electromyogram-based fatigue measurements during high-intensity, dynamic activities is confounded by the accompanying increase in muscle temperature. The purpose of this communication was to demonstrate the use of a muscle temperature compensation technique for electromyogram (EMG) fatigue measurements. METHODS Subjects were six healthy men (mean age 30.8 +/- 5.6 yr) with no recent history of lower extremity injury. In part 1 of this study, the relationship between muscle temperature and EMG mean power frequency was determined for the vastus lateralis muscle (VL). The VL was heated with diathermy to a temperature of approximately 39 degrees C. Isometric EMG data were collected during the performance of a nonfatiguing protocol as the muscle cooled (39-34 degrees C). In part 2 of this study, the subjects rode a lower-extremity ergometer at workloads of 25%, 50%, and 75% of their VO2max. Isometric EMG and intramuscular temperature data were collected from the VL during intermittent interruptions of the activity. The relationship between muscle temperature and EMG mean power frequency established in part 1 was used with the measured change in muscle temperature to correct for the effect of temperature on the EMG mean power frequency. RESULTS The results from part 1 revealed a linear relationship between EMG mean power frequency and muscle temperature (N = 5, mean slope = 2.82 +/- 0.27 Hz. degrees C-1, R2 = 0.88 +/- 0.02). The mean slope was used as a muscle temperature compensation factor that quantified the influence of muscle temperature on EMG mean power frequency. For part 2, representative data from a single subject are presented to demonstrate the use of the muscle temperature compensation technique. CONCLUSION A muscle temperature compensation technique for EMG mean power frequency analysis has been demonstrated. This technique corrects for the detrimental influence of muscle temperature changes on EMG fatigue measurements, thereby improving the efficacy of EMG fatigue measurements during high-intensity, dynamic activities that result in muscle temperature increases.

Immediate changes in pressure pain sensitivity after thoracic spinal manipulative therapy in patients with subacromial impingement syndrome: A randomized controlled study

BACKGROUND Thoracic SMT can improve symptoms in patients with subacromial impingement syndrome. However, at this time the mechanisms of SMT are not well established. It is possible that changes in pain sensitivity may occur following SMT. OBJECTIVES To assess the immediate pain response in patients with shoulder pain following thoracic spinal manipulative therapy (SMT) using pressure pain threshold (PPT), and to assess the relationship of change in pain sensitivity to patient-rated outcomes of pain and function following treatment. DESIGN Randomized Controlled Study. METHODS Subjects with unilateral subacromial impingement syndrome (n = 45) were randomly assigned to receive treatment with thoracic SMT or sham thoracic SMT. PPT was measured at the painful shoulder (deltoid) and unaffected regions (contralateral deltoid and bilateral lower trapezius areas) immediately pre- and post-treatment. Patient-rated outcomes were pain (numeric pain rating scale - NPRS), function (Pennsylvania Shoulder Score - Penn), and global rating of change (GROC). RESULTS There were no significant differences between groups in pre-to post-treatment changes in PPT (p ≥ 0.583) nor were there significant changes in PPT within either group (p ≥ 0.372) following treatment. NPRS, Penn and GROC improved across both groups (p < 0.001), but there were no differences between the groups (p ≥ 0.574). CONCLUSION There were no differences in pressure pain sensitivity between participants receiving thoracic SMT versus sham thoracic SMT. Both groups had improved patient-rated pain and function within 24-48 h of treatment, but there was no difference in outcomes between the groups.

Thoracic Spine Manipulation in Individuals With Subacromial Impingement Syndrome Does Not Immediately Alter Thoracic Spine Kinematics, Thoracic Excursion, or Scapular Kinematics: A Randomized Controlled Trial

STUDY DESIGN Randomized controlled trial. OBJECTIVES To determine if thoracic spinal manipulative therapy (SMT) alters thoracic kinematics, thoracic excursion, and scapular kinematics compared to a sham SMT in individuals with subacromial impingement syndrome, and also to compare changes in patient-reported outcomes between treatment groups. BACKGROUND Prior studies indicate that thoracic SMT can improve pain and disability in individuals with subacromial impingment syndrome. However, the mechanisms underlying these benefits are not well understood. METHODS Participants with shoulder impingement symptoms (n = 52) were randomly assigned to receive a single session of thoracic SMT or sham SMT. Thoracic and scapular kinematics during active arm elevation and overall thoracic excursion were measured before and after the intervention. Patient-reported outcomes measured were pain (numeric pain-rating scale), function (Penn Shoulder Score), and global rating of change. RESULTS Following the intervention, there were no significant differences in changes between groups for thoracic kinematics or excursion, scapular kinematics, and patient-reported outcomes (P>.05). Both groups showed an increase in scapular internal rotation during arm raising (mean, 0.9°; 95% confidence interval [CI]: 0.3°, 1.6°; P = .003) and lowering (0.8°; 95% CI: 0.0°, 1.5°; P = .041), as well as improved pain reported on the numeric pain-rating scale (1.2 points; 95% CI: 0.3, 1.8; P<.001) and function on the Penn Shoulder Score (9.1 points; 95% CI: 6.5, 11.7; P<.001). CONCLUSION Thoracic spine extension and excursion did not change significantly following thoracic SMT. There were small but likely not clinically meaningful changes in scapular internal rotation in both groups. Patient-reported pain and function improved in both groups; however, there were no significant differences in the changes between the SMT and the sham SMT groups. Overall, patient-reported outcomes improved in both groups without meaningful changes to thoracic or scapular motion. LEVEL OF EVIDENCE Therapy, level 1b-.

Rehabilitation of an Elite Gymnast With a Type II Manubriosternal Dislocation

Background and Purpose This case report describes the rehabilitation of an elite, 15-year-old gymnast after a nonreduced type II manubriosternal dislocation. The rehabilitation took place in a gymnastics venue but was guided by a physician and a licensed physical therapist. Case Description The gymnast participated in a 13-week rehabilitation program for range of motion and strengthening that was based on a biomechanical hierarchy. Rehabilitation began at week 2 after injury for the lower extremities and at week 4 for the upper extremities. Outcomes By week 4, the patient began upper-extremity strengthening, and by week 6, the patient had no pain with palpation and tolerated light sternal loading. At week 9, a plain-film radiograph revealed a stable manubriosternal joint, and by week 13, the patient returned to gymnastics pain-free. Discussion This case report shows that, after a 13-week regimen of progressive and repetitive, cyclical tensile and compressive loading, the manubriosternal joint was stable, and the elite gymnast was able to return to the sport, successfully competing in a regional competition.

Individuals With Functional Ankle Instability, but not Copers, Have Increased Forefoot Inversion During Walking Gait

Altered gait kinematics in individuals with functional ankle instability (FAI) are thought to contribute to instability; however, research fi ndings are inconsistent. Findings may be clarifi ed with the use of a multisegment foot model and a coper group. Participants included 69 individuals: 23 with FAI, 23 controls, and 23 copers (individuals with a history of ankle sprain but no instability). Forefoot and hindfoot sagittal and frontal plane angles at initial contact (IC) were calculated during gait. For the forefoot and hindfoot, a multivariate analysis of variance tested group diff erences. For the forefoot in the frontal plane, there was a signifi cant group diff erence at IC. The FAI group had signifi cantly more inverted ankles than controls, but copers were not signifi cantly diff erent from the FAI or control groups. The lack of diff erence between the FAI and coper groups may indicate that increased inversion error in FAI does not explain symptoms of instability. [Athletic Training & Sports Health Care.

Effects of Visual Display on Joint Excursions Used to Play Virtual Dodgeball

Background Virtual reality (VR) interventions hold great potential for rehabilitation as commercial systems are becoming more affordable and can be easily applied to both clinical and home settings. Objective In this study, we sought to determine how differences in the VR display type can influence motor behavior, cognitive load, and participant engagement. Methods Movement patterns of 17 healthy young adults (8 female, 9 male) were examined during games of Virtual Dodgeball presented on a three-dimensional television (3DTV) and a head-mounted display (HMD). The participant’s avatar was presented from a third-person perspective on a 3DTV and from a first-person perspective on an HMD. Results Examination of motor behavior revealed significantly greater excursions of the knee (P=.003), hip (P<.001), spine (P<.001), shoulder (P=.001), and elbow (P=.026) during HMD versus 3DTV gameplay, resulting in significant differences in forward (P=.003) and downward (P<.001) displacement of the whole-body center of mass. Analyses of cognitive load and engagement revealed that relative to 3DTV, participants indicated that HMD gameplay resulted in greater satisfaction with overall performance and was less frustrating (P<.001). There were no significant differences noted for mental demand. Conclusions Differences in visual display type and participant perspective influence how participants perform in Virtual Dodgeball. Because VR use within rehabilitation settings is often designed to help restore movement following orthopedic or neurologic injury, these findings provide an important caveat regarding the need to consider the potential influence of presentation format and perspective on motor behavior.

Relationship Between Gluteus Medius Muscle Activity, Pelvic Motion, and Metabolic Energy in Running (P190)

PURPOSE: To investigate the relationship between gluteus medius muscle (GM) activity, pelvic motion, and changes in metabolic energy demands while running. METHODS: Five healthy, female subjects (mean age 22.8±2.2) were obtained from a sample of convenience. Subjects were recreational runners who ran ≥ 5 miles per week (mean 28.0 miles±15.2). Subjects were asked to run on a treadmill for 30 minutes at a self-selected speed (6.52 mph±0.2). Muscle Activity — Surface electromyography (sEMG) data was collected on the GM at a rate of 1000 Hz (MyoSystem 1200™, Noraxon). Kinematics — Three-dimensional data on pelvic position was sampled at a rate of 60 Hz using an electromagnetic kinematic tracking system (MotionMonitor™, Innovative Sports Training) with sensors (Polhemus Fastrak) secured over the posterior superior iliac spines. Metabolic Energy — Oxygen consumption (VO2) was obtained through ventilatory expired gas analysis (SensorMedics, Inc., Yorba Linda, CA) during rest, exercise and five minutes into recovery. The change in VO2 between 25–30 minutes (average value) was determined (δVO2) as was the time constant of VO2 recovery kinetics. MatLab v 7.1 was used for kinematics analyses. A Pearson’s Correlation was calculated using SPSS v 14.0; statistical significance was defined as p<0.05. RESULTS: Peak GM amplitude exhibited a positive trend with VO2 recovery kinetics (R2=0.807) and the rate of change in pelvic drop (R2=0.647). Pelvic drop and kinetics were significantly correlated (R2=0.942). However, δVO2 was not correlated with peak GM activity, pelvic drop, or kinetics. CONCLUSION: VO2 recovery kinetics were not influenced by δVO2, rather by biomechanical factors. Subjects with increased pelvic drop exhibited increased GM activity, and these two variables led to increased kinetics. These findings suggest that increased pelvic motion during running results in metabolic inefficiency, and could therefore adversely affect running performance.