Effects of Volitional Spine Stabilization and Lower-Extremity Fatigue on the Knee and Ankle During Landing Performance in a Population With Recurrent Low Back Pain.

INTRODUCTION: Recurrent lower back pain (rLBP) and neuromuscular fatigue are independently thought to increase the risk of lower extremity (LE) injury. Volitional preemptive abdominal contraction (VPAC) is thought to improve lumbar spine and pelvis control in individuals with rLBP. The effects of VPAC on fatigued landing performance in individuals with rLBP are unknown. OBJECTIVES: To determine the effects of VPAC and LE fatigue on landing performance in a rLBP population. DESIGN: Cross-sectional pretest-posttest cohort control design. SETTING: A clinical biomechanics laboratory. SUBJECTS: 32 rLBP (age 21.2 ± 2.7 y) but without current symptoms and 33 healthy (age 20.9 ± 2.3 y) subjects. INTERVENTION(S): (i) Volitional preemptive abdominal contraction using abdominal bracing and (ii) fatigue using submaximal free-weight squat protocol with 15% body weight until task failure was achieved. MAIN OUTCOME MEASURE(S): Knee and ankle angles, moments, electromyographic measurements from semitendinosus and vastus medialis muscles, and ground reaction force (GRF) were collected during 0.30 m drop-jump landings. RESULTS: The VPAC resulted in significantly earlier muscle onsets across all muscles with and without fatigue in both groups (mean ± SD, 0.063 ± 0.016 s earlier; P ≤ .001). Fatigue significantly delayed semitendinosus muscle onsets (0.033 ± 0.024 s later; P ≤ .001), decreased GRF (P ≤ .001), and altered landing kinematics in a variety of ways. The rLBP group exhibited delayed semitendinosus and vastus medialis muscle onsets (0.031 ± 0.028 s later; P ≤ .001) and 1.8° less knee flexion at initial contact (P ≤ .008). CONCLUSION: The VPAC decreases some of the detrimental effects of fatigue on landing biomechanics and thus may reduce LE injury risk in a rLBP population.

A systematic review of orthopaedic manual therapy randomized clinical trials quality.

Study Design: Systematic review and meta-analysis. Objectives: To conduct a systematic review and meta-analysis of randomized clinical trials (RCTs) in the orthopaedic manual therapy (OMT) literature from January 2010 to June 2014 in order to determine if the CONSORT checklist and Cochrane Risk of Bias (RoB) assessment tools: (1) are reliable; (2) have improved the reporting and decreased the risk of bias in RCTs in the OMT literature; (3) differ based on journal impact factor (JIF); and (4) scores are associated with each other. Background: The CONSORT statement is used to improve the accuracy of reporting within RCTs. The Cochrane RoB tool was designed to assess the risk of bias within RCTs. To date, no evaluation of the quality of reporting and risk of bias in OMT RCTs has been published. Methods: Relevant RCTs were identified by a literature review from January 2010 to June 2014. The identified RCTs were assessed by two individual reviewers utilizing the 2010 CONSORT checklist and the RoB tool. Agreement and a mean composite total score for each tool were attained in order to determine if the CONSORT and RoB tools were reliable and varied by year and impact factor. Results: A total of 72 RCTs in the OMT literature were identified. A number of categories within the CONSORT and RoB tools demonstrated prevalence-adjusted bias-adjusted kappa (PABAK) scores of less than 0.20 and from 0.20 to 0.40. The total CONSORT and RoB scores were correlated to each other (r = 0.73; 95% CI 0.60 to 0.82; p < 0.0001). There were no statistically significant differences in CONSORT or RoB scores by year. There was a statistically significant correlation between both CONSORT scores and JIF (r = 0.64, 95% CI 0.47 to 0.76; p < 0.0001), and between RoB scores and JIF (r = 0.42, 95% confidence interval 0.21-0.60; p < 0.001). There was not a statistically significant correlation between JIF and year of publication. Conclusion: Our findings suggest that the CONSORT and RoB have a number of items that are unclear and unreliable, and that the quality of reporting in OMT trials has not improved in recent years. Improvements in reporting are necessary to allow advances in OMT practice. Level of Evidence: 1A.

Adaptation in motor strategies for postural control associated with sensory reweighting.

The purpose of this study was to identify and differentiate the motor strategies associated with sensory reweighting adapted during specific sensory integration tasks by healthy young adults. Thirty-six subjects (age range: 21-33 years) performed standing computerized dynamic posturography balance tasks across progressively increasing amplitudes of visual (VIS), somatosensory (SOM) and both (VIS+SOM) systems perturbation conditions. Adaptation in the motor strategy was measured as changes in electromyographic (EMG) activities and joint angles. The contribution of the perturbed sensory input in maintaining postural stability was calculated to determine the sensory reweighting. A multivariate design was used to model a linear combination of motor adaptation variables that discriminates specific sensory integration tasks. Results showed a significant progressive decrease in postural sway per unit amplitude of sensory perturbation in each condition, indicating dynamic sensory reweighting. Linear discriminant function analysis indicated that the adaptation in motor strategy during the VIS condition was associated with increased activity of EMG and joint angles in the upper body compared to the lower body. Conversely, during the SOM and VIS+SOM conditions, the adaptation in motor strategy was associated with decreased activity of EMG and joint angles in the lower body compared to the upper body. Therefore, the adaptation in motor strategies associated with sensory reweighting were different for different sensory integration tasks.

Exploration of arm weight effects on hemiparetic stroke participants' gait performance.

BACKGROUND: This study explores the potential benefits of an arm weight intervention for improving gait performance in stroke survivors. Consistent with an interlimb neural coupling mechanism, the investigators hypothesized that arm weight would improve gait performance. METHODS: Nine stroke and nine healthy participants (1 female; age: 58.0 ± 6.8 years) participated. Participants walked over-ground at their preferred speed in four conditions: no weight (C1), non-hemiparetic (healthy: dominant) side weights (C2), hemiparetic (non-dominant) side weights (C3), and bilateral weights (C4). Statistical analyses included repeated analysis of variance (ANOVA) and paired t-test planned comparisons to explore the effects of added weight on gait speed, step width, step length, cadence, and arm swing amplitude. Single-subject analyses used randomization tests to delineate further the weight's effect on gait speed. FINDINGS: The stroke group walked significantly faster with arm weight (p = 0.048), exhibiting large ANOVA (η2p = 0.28) and C1 vs. C4 planned comparison (p = 0.021; dD = 0.95) effect sizes. Four of nine stroke participants significantly increased gait speed in at least one condition, and seven of nine exhibited large effect size increases (d = 0.85-4.71). The stroke group's hemiparetic-side step length and cadence significantly (p = 0.008) increased in C4 compared to C1, exhibiting large effect size increases (rb = 0.96). Four of nine healthy participants significantly increased gait speed in at least one condition, with five of nine exhibiting large effect size increases (d = 0.80-6.63). INTERPRETATION: This study's exploratory results demonstrate arm weight's potential for improving higher-functioning stroke survivors' gait performance. Arm weight addition merits further investigation as a possible rehabilitation intervention in the stroke population.

Is the quality of systematic reviews influenced by prospective registration: a methods review of systematic musculoskeletal physical therapy reviews.

INTRODUCTION: It is unknown if verified prospective registration of systematic reviews (SRs) and the randomized clinical trials (RCTs) that they use affect an SR's methodological quality on A MeaSurement Tool to Assess Systematic Reviews 2 (AMSTAR 2). METHODS: Data originated from interventional SRs published in International Society of Physiotherapy Journals Editors (ISPJE) member journals, indexed in MEDLINE, between 1 January 2018 and 18 August 2021. Blinded reviewers identified the SRs and extracted the data for the variables of interest for the SRs and the RCTs. RESULTS: Two of 14 ISPJE member journals required prospective SR registration. Twenty SRs were identified, and 169 unique, retrievable RCTs were included within those SRs. One (5.0%) of the 20 SRs and 15 of the 169 (8.9%) RCTs were prospectively registered and published consistent with this intent. Nineteen (95.0%) of the 20 identified SRs was categorized as 'critically low' on the AMSTAR 2. DISCUSSION: SRs and the RCTs identified within them were infrequently prospectively registered, prospectively verifiable, or prospectively verified based on the established research record. CONCLUSIONS: Ensuring that SRs and RCTs have fidelity with the research record from conception to publication may help rule out low-value interventions, decrease variability in physical therapy practice, and solidify evidence-based physical therapy practice.

Do Prospective Intent and Established Metrics Correlate with Journal Impact Factor in Musculoskeletal Physical Therapy Trials?: A Secondary Analysis of A Methodological Review.

OBJECTIVES: To determine if there are any statistically significant associations between: 1) randomized clinical trials (RCTs) investigating physical therapy musculoskeletal interventions, 2) journal impact factor (JIF), 3) frequency of RCT citation, 4) whether prospective intent was identifiable, and 5) the Physiotherapy Evidence Database (PEDro) scores. METHODS: MEDLINE indexed RCTs addressing musculoskeletal interventions published between January 2016 and July 2020 in physical therapy journals were included. Two blinded reviewers identified the RCTs and extracted the variables of interest. RESULTS: With a familywise alpha adjustment, there was no statistically significant correlation between JIF and number of citations (rho = 0.187; p = 0.0280). Statistically significant weak positive correlations were identified between the JIF and prospectively registered RCTs (rho = 0.240; p = 0.0046), JIF and PEDro scores (rho = 0.250; p = 0.0031), and PEDro scores and prospectively registered RCTs (rho = 0.335; p < 0.0001). CONCLUSION: The findings of this study suggest that JIF and PEDro scores may not be accurate measures of RCT quality. Failing to ensure that published RCTs followed their prospective intent and using bibliometrics that fail to accurately measure what they propose appears to create untrustworthy preprocessed resources for practicing physical therapists during the evidence-based practice process. LEVEL OF EVIDENCE: 1a.

Association of disturbances in the thoracic outlet in subjects with carpal tunnel syndrome: a case-control study.

INTRODUCTION: A limited amount of research has investigated the potential relationship between carpal tunnel syndrome (CTS) and thoracic outlet dysfunction. PURPOSE OF THE STUDY: To compare the prevalence of positive clinical tests suggestive of disputed neurogenic thoracic outlet syndrome (TOS) in subjects with CTS (CTS+) with that of subjects without CTS (control). STUDY DESIGN: Case-control study. METHODS: Subjects with electrodiagnostically confirmed CTS (CTS+) were recruited consecutively and matched by age (±2 years) and gender with asymptomatic (control) subjects. Subjects underwent clinical testing for neurogenic TOS using two provocative tests: modified Cyriax release test and elevated arm stress test (EAST). Subjects were tested for the presence of an elevated first rib using cervical rotation lateral flexion (CRLF) test. RESULTS: A total of 32 investigational subjects and 32 matched control subjects was included in each group (mean age: 43.5+5.9 years). A significantly greater number of CTS+ subjects presented with positive provocative testing for TOS (modified Cyriax release test p=0.005; EAST approached significance p=0.027) and for the presence of an elevated first rib (CRLF test p=0.003) as compared with controls. The likelihood of neck pain, shoulder pain, or an elevated first rib was 16 times greater in the CTS+ group as compared with that in the control group. CONCLUSIONS: A greater number of subjects with CTS presented with proximal dysfunctions suggestive of TOS and history of neck and shoulder pain. Evaluation of proximal structures involved with thoracic outlet dysfunction in persons with CTS has clinical merit. LEVEL OF EVIDENCE: Level III-b.

Should low-quality evidence dominate high-level evidence? A systematic review and meta-analysis of systematic reviews of musculoskeletal physical therapy interventions.

OBJECTIVES: To determine the: 1) quality of articles cited in systematic reviews (SRs); 2) methodological quality of the SRs; and 3) impact of quality on level 1A evidence. METHODS: SRs related to musculoskeletal physical therapy interventions were identified. The methodological quality of the SRs and articles cited by the SRs were assessed by two blinded reviewers. Data analysis was performed by a third blinded researcher. Additional comparisons were made based on the Journal Impact Factor, spin, financial bias, and conflict of interest. RESULTS: Twenty-four SRs were identified; 21/24 SRs had 'critically low' quality on the AMSTAR 2. Thirty-four percent of included studies were 'low quality,' and 58% of SRs included studies that had unreported external validity. One-half of the SRs represented 'spin,' and one-third of the SRs generated conclusions based on low-quality clinical trials. DISCUSSION: The 'critically low' SRs methodological quality was exacerbated by low-quality research inclusion. Most SRs failed to follow best practices, including prospective registration and integration of professional librarians in the search process. Based on the high proportion of SRs that include low-quality trials and overall low methodological quality, further discussion regarding practice recommendations on level vs. quality of evidence is warranted. LEVEL OF EVIDENCE: 1a.

The Unknown Prevalence of Postrandomization Bias in 15 Physical Therapy Journals: A Methods Review.

OBJECTIVES: To determine the prevalence of prospective clinical trial registration and postrandomization bias in published musculoskeletal physical therapy randomized clinical trials (RCTs). DESIGN: A methods review. LITERATURE SEARCH: Articles indexed in MEDLINE and published between January 2016 and July 2020 were included. STUDY SELECTION CRITERIA: Two independent blinded reviewers identified the RCTs using Covidence. We included RCTs related to musculoskeletal interventions that were published in International Society of Physiotherapy Journal Editors member journals. DATA SYNTHESIS: Data were extracted independently for the variables of interest from the identified RCTs by 2 blinded reviewers. The data were presented descriptively or in frequency tables. RESULTS: One hundred thirty-eight RCTs were identified. One third of RCTs were consistent with their prospectively registered intent (49/138); consistency with prospectively registered intent could not be determined for two thirds (89/138) of the RCTs. Four RCTs (8%)reported inconsistent results with the primary aims and 7 (14%) with the outcomes from the prospective clinical trial registry, despite high methodological quality (Physiotherapy Evidence Database [PEDro] scale score). Differences between prospectively registered and non-prospectively registered RCTs for PEDro scale scores had a medium effect size (r = 0.30). Two of 15 journals followed their clinical trial registration policy 100% of the time; in 1 journal, the published RCTs were consistent with the clinical trial registration. CONCLUSION: Postrandomization bias in musculoskeletal physical therapy RCTs could not be ruled out, due to the lack of prospective clinical trial registration and detailed data analysis plans. J Orthop Sports Phys Ther 2021;51(11):542-550. Epub 21 Sep 2021. doi:10.2519/jospt.2021.10491.

Immediate Improvements in Patellofemoral Pain Are Associated With Sagittal Plane Movement Training to Improve Use of Gluteus Maximus Muscle During Single Limb Landing.

OBJECTIVE: The authors sought to examine the immediate effects of movement training aimed at improving use of gluteus maximus (GMAX) in the sagittal plane on hip internal rotation and self-reported patellofemoral pain (PFP) during single-limb landing. METHODS: Seventeen females with PFP participated. Lower extremity kinematics and kinetics, GMAX activation, and self-reported PFP were obtained before and after a single-session movement training program aimed at increasing the use of GMAX. Dependent variables of interest included self-reported PFP, average GMAX activation, average hip extensor moment, and peak hip internal rotation. Post-training changes were evaluated using paired t tests and Wilcoxon signed rank tests. RESULTS: Following movement training, self-reported PFP decreased significantly (mean [standard deviation]) (3.9 [1.1] vs 0.8 [1.3] on a 0-10 scale). Additionally, significant increases were observed for the average hip extensor moment (0.6 [0.3] vs 1.8 [0.4] Nm/kg) and average GMAX activation (41.0% [18.3] vs 51.6% [25.7] maximum voluntary isometric contraction), whereas peak hip internal rotation decreased significantly (8.5 degrees [5.8] vs 6.0 degrees [5.3]). CONCLUSION: Movement training aimed at improving the use of GMAX in the sagittal plane resulted in clinically relevant changes in self-reported pain, GMAX activation, and hip kinetics and kinematics. Improving the use of GMAX during movement merits consideration when designing rehabilitation programs for females with PFP. IMPACT: The current study highlights the clinical utility of movement training for persons with PFP and provides a biomechanical rationale for its use as a potential intervention in this population.

Effects of tai chi exercise on posturography, gait, physical function and quality of life in postmenopausal women with osteopaenia: a randomized clinical study.

OBJECTIVE: to evaluate the effects of tai chi exercise on risk factors for falls in postmenopausal women with osteopaenia through measurements of balance, gait, physical function and quality of life. DESIGN: a randomized, controlled, single-blinded, 24-week trial with stratification by age and bone mass. SETTING: general community. PARTICIPANTS: Sixty-one independently living elderly females aged 65 years and older with low bone mass. INTERVENTIONS: subjects were recruited and randomly assigned to 24 weeks of tai chi (60 minutes/session, three sessions/week, n = 30) or a control group (n = 31). OUTCOME MEASURES: computerized dynamic posturography, gait, 'timed up and go', five-chair sit-to-stand and quality of life assessed at baseline, 12 and 24 weeks. RESULTS: after 24 weeks, subjects in the tai chi group demonstrated an increase in stride width (P = 0.05) and improvement in general health (P = 0.008), vitality (P = 0.02) and bodily pain (P = 0.03) compared with those in the control group. There was no significant difference in balance parameters, 'timed up and go', five-chair sit-to-stand and other domains of quality of life. CONCLUSION: tai chi exercise may reduce risk factors for falls by increasing the stride width, and may improve quality of life in terms of general health, vitality and bodily pain in postmenopausal women with osteopaenia.

The effect of stretching on muscle responses and postural sway responses during computerized dynamic posturography in women and men.

OBJECTIVE: To evaluate the effect of stretching on the parameters of postural sway and on the kinematic variables associated with balance control in women and men. DESIGN: Mixed repeated measures design with 2 levels. SETTING: Research laboratory. PARTICIPANTS: Fifteen women and fifteen men (mean age 23.4+/-2.2). INTERVENTION: Two separate sessions of (1) lower extremity stretching and (2) no-stretching, immediately prior to balance testing with simultaneous surface electromyographic (EMG) recordings of muscle responses. MAIN OUTCOME MEASURES: EMG latencies and average amplitudes for 4 lower extremity muscles for the preferred stance limb during computerized dynamic posturography (CDP) tests, specifically the Postural Evoked Response Test, Adaptation Test, Motor Control Test, Sensory Organization Test, and Unilateral Stance Test. RESULTS: Analyses of variance indicated no significant main effect for stretching and 2 significant main effects for gender for the Motor Control Test (P=.021) and latency of tibialis anterior (P=.009). Analyses of covariance with covariants of height and active knee extension revealed no significant main effect of stretching or of gender on muscles responses or CDP performance. CONCLUSIONS: In both women and men, lower extremity stretching did not significantly affect muscle responses or performance during CDP.

Kinematic Validation of Postural Sway Measured by Biodex Biosway (Force Plate) and SWAY Balance (Accelerometer) Technology.

BACKGROUND: The Biodex Biosway® Balance System and SWAY Balance® Mobile smartphone application (SBMA) are portable instruments that assess balance function with force plate and accelerometer technology, respectively. The validity of these indirect clinical measures of postural sway merits investigation. PURPOSE: The purpose of this study was to investigate the concurrent validity of standing postural sway measurements by using the portable Biosway and SBMA systems with kinematic measurements of the whole body Center of Mass (COM) derived from a gold-standard reference, a motion capture system. STUDY DESIGN: Cross-sectional; repeated measures. METHODS: Forty healthy young adults (21 female, 19 male) participated in this study. Participants performed 10 standing balance tasks that included combinations of standing on one or two legs, with eyes open or closed, on a firm surface or foam surface and voluntary rhythmic sway. Postural sway was measured simultaneously from SBMA, Biosway, and the motion capture system. The linear relationships between the measurements were analyzed. RESULTS: Significant correlations were found between Biosway and COM velocity for both progressively challenging single and double leg stances (τ b = 0.3 to 0.5, p < 0.01 to <0.0001). SBMA scores and COM velocity were significantly correlated only for single leg stances (τ b = -0.5 to -0.6, p < 0.0001). SBMA scores had near-maximal values with zero to near-zero variance in double leg stances, indicating a ceiling effect. CONCLUSION: The force plate-based Biodex Biosway is valid for assessing standing postural sway for a wide range of test conditions and challenges to standing balance, whereas an accelerometer-based SWAY Balance smartphone application is valid for assessing postural sway in progressively challenging single leg stance but is not sensitive enough to detect lower-magnitude postural sway changes in progressively challenging double leg stances.

Low reproducibility of randomized clinical trials methodology related to sampling: a systematic methodological review.

Objectives: The reporting of sampling methods in Randomized Clinical Trials (RCTs) allows for research quality assessment, determination of sampling bias, and assures the presence of details necessary for reproducibility in future trials. The purpose of this study was to: (1) determine if sampling methodology was reproducible in RCTs related to musculoskeletal physical therapy (MSKPT) interventions to treat non-specific low back pain (NSLBP) and (2) establish if there was a relationship between sample reproducibility and established measures of research quality.Methods: Data were collected through a systematic review by a professional librarian. The identified RCTs were assessed for methodological quality by two blinded individual reviewers. Data analysis was performed by a third, blinded researcher; additional comparisons were made based on Journal Impact Factor and PEDro score.Results: Ninety-nine published peer-reviewed RCTs were identified that met inclusion criteria. Only 29% of the articles were judged to be reproducible based on the reported sampling methodology. There were meaningful correlations between two out of ten of the sampling reporting criteria and the judgement made if the sample was reported in significant detail to allow for replication. There was no relationship between sampling reporting criteria, Journal Impact Factors (JIFs), and Physiotherapy Evidence Database (PEDro) scores.Discussion: The reporting of sampling methodology needs to be considered to ensure reproducibility and avoid sampling bias. Despite the proliferation of measures of research quality, the overall reporting quality of RCTs continues to be inadequate to allow widespread reproducibility of trials.Level of Evidence: 1a.

Effect of sex hormones on neuromuscular control patterns during landing.

The purpose of the study was to investigate the effects of sex hormones across menstrual cycle phases on lower extremity neuromuscular control patterns during the landing phase of a drop jump. A repeated-measures design was utilized to examine sex hormone effects in 26 recreationally active eumenorrheic women. Varus/valgus knee angle and EMG activity from six lower extremity muscles were recorded during three drop jumps from a 50 cm platform in each phase of the menstrual cycle. Blood assays verified sex hormone levels and cycle phase. The semitendinosus muscle exhibited onset delays (p0.006) relative to ground contact during the luteal phase, and demonstrated a significant (p0.05) difference between early and late follicular phases. Muscle timing differences between the gluteus maximus and semitendinosus were decreased (p0.05) in the luteal compared to early follicular phases. These results suggest a different co-contractive behavior between the gluteus maximus and semitendinosus, signifying a shift in neuromuscular control patterns. It appears that female recreational athletes utilize a different neuromuscular control pattern for performing a drop jump sequence when estrogen levels are high (luteal phase) compared to when they are low (early follicular phase).

Volitional Preemptive Abdominal Contraction and Upper Extremity Muscle Latencies During D1 Flexion and Scaption Shoulder Exercises.

CONTEXT: The abdominal-bracing maneuver, a volitional preemptive abdominal contraction (VPAC) strategy, is commonly used during resisted shoulder exercises. How VPAC affects shoulder-muscle function during resisted shoulder exercise is unknown. OBJECTIVE: To identify the effects of VPAC on selected parascapular and glenohumeral muscles during specific shoulder exercises with or without resistance. DESIGN: Cross-sectional study. SETTING: Clinical biomechanics research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-two asymptomatic volunteers between 18 and 40 years of age. INTERVENTION(S): Participants performed arm elevation in scaption and D1 shoulder-flexion (D1F) patterns with and without resistance and VPAC. MAIN OUTCOME MEASURE(S): Electromyography was used to test the muscle-contraction amplitudes and onset timing of the anterior deltoid, posterior deltoid, upper trapezius, lower trapezius, and serratus anterior. Muscle-response amplitudes were quantified using root mean square electromyography. Shoulder-muscle relative-onset timing was quantified in reference to kinematic elbow-movement initiation. RESULTS: The VPAC increased serratus anterior amplitude during D1F ( P < .001) and scaption ( P < .001) and upper trapezius amplitude ( P < .001) in scaption. All muscle amplitudes increased with resistance. The VPAC decreased muscle-onset latencies for the anterior deltoid ( P < .001), posterior deltoid ( P = .008), upper trapezius ( P = .001), lower trapezius ( P = .006), and serratus anterior ( P = .001) during D1F. In addition, the VPAC decreased muscle-onset latencies for the anterior deltoid ( P < .001), posterior deltoid ( P = .007), upper trapezius ( P < .001), lower trapezius ( P < .001), and serratus anterior ( P < .001) during scaption. CONCLUSIONS: The VPAC affected only the parascapular muscles that had the greatest scapular-stabilizing roles during the specific open chain movement we tested. It decreased latencies in all muscles. These neuromuscular changes may enhance the stability of the shoulder during D1F and scaption exercises.

Changes in patellofemoral pain resulting from repetitive impact landings are associated with the magnitude and rate of patellofemoral joint loading.

BACKGROUND: Although a relationship between elevated patellofemoral forces and pain has been proposed, it is unknown which joint loading variable (magnitude, rate) is best associated with pain changes. The purpose of this study was to examine associations among patellofemoral joint loading variables and changes in patellofemoral pain across repeated single limb landings. METHODS: Thirty-one females (age: 23.5(2.8) year; height: 166.8(5.8) cm; mass: 59.6(8.1) kg) with PFP performed 5 landing trials from 0.25 m. The dependent variable was rate of change in pain obtained from self-reported pain scores following each trial. Independent variables included 5-trial averages of peak, time-integral, and average and maximum development rates of the patellofemoral joint reaction force obtained using a previously described model. Pearson correlation coefficients were calculated to evaluate individual associations between rate of change in pain and each independent variable (α = 0.05). Stepwise linear multiple regression (αenter = 0.05; αexit = 0.10) was used to identify the best predictor of rate of change in pain. FINDINGS: Subjects reported an average increase of 0.38 pain points with each landing trial. Although, rate of change in pain was positively correlated with peak force (r = 0.44, p = 0.01), and average (r = 0.41, p = 0.02) and maximum force development rates (r = 0.39, p = 0.03), only the peak force entered the predictive model explaining 19% of variance in rate of change in pain (r2 = 0.19, p = 0.01). INTERPRETATION: Peak patellofemoral joint reaction force was the best predictor of the rate of change in pain following repetitive singe limb landings. The current study supports the theory that patellofemoral joint loading contributes to changes in patellofemoral pain.

Effects of arm weight on gait performance in healthy subjects.

Previous studies have investigated how additional arm weights affect gait. Although light weights (0.45 kg) seemed to elicit performance improvements in Parkinsonian patients, it was not studied how light weights affect gait parameters in healthy individuals. It is important to understand normal responses in a healthy population so that clinical effects might be better understood. Therefore, the purpose of this study was to investigate the effects of arm weights on arm swing amplitude, gait performance, and muscle activity in healthy people. Twenty-two subjects walked overground at their preferred speed under different weight carriage conditions (C1: no weight; C2: unilateral arm weight; C3: bilateral arm weights; C4: waist weights). Gait speed increased in C2 (p = 0.018) and C4 (p = 0.013) when compared with C1(C1: 1.21 ±â€¯0.08; C2: 1.25 ±â€¯0.11; C3: 1.24 ±â€¯0.11; C4: 1.25 ±â€¯0.11 m/s) with an increase in cadence during C2 (p < 0.001), C3 (p = 0.008), and C4 (p < 0.001) (C1: 105.5 ±â€¯5.2; C2: 108.5 ±â€¯5.6; C3: 107.9 ±â€¯5.6; C4: 108.5 ±â€¯5.3 steps/min) and in tibialis anterior electromyographic activity on the unweighted side in C2 (p = 0.048) (C1: 21.05 ±â€¯4.59; C2: 25.10 ±â€¯6.10; C3: 23.93 ±â€¯4.75; C4: 24.33 ±â€¯6.32 µV). The results indicate that an additional sensory input with the application of the weights may result in an overcompensation with the whole body and facilitate faster walking speed when applied on one arm or around the waist. The locations of the weights and amount of the weights may elicit different responses. Various strategies of adding weights should be further investigated as a potential intervention to improve performance in individuals with various gait impairments. Although there is evidence for benefits of this intervention in Parkinsonian patients, further study is warranted in other patient populations, such as stroke patients, who might benefit from this intervention to improve gait performance.

Effects of Volitional Spine Stabilization and Lower Extremity Fatigue on Trunk Control During Landing in Individuals With Recurrent Low Back Pain.

STUDY DESIGN: Controlled laboratory study. BACKGROUND: Recurrent low back pain (LBP) and neuromuscular fatigue are independently thought to increase the risk of spine injury. Volitional preemptive abdominal contraction (VPAC) is thought to improve lumbar spine and pelvis control in individuals with recurrent LBP. The effects of VPAC on fatigued landing performance in individuals with recurrent LBP are unknown. OBJECTIVES: To determine the effects of VPAC and lower extremity fatigue on trunk control during landing in a population of individuals with recurrent LBP. METHODS: Thirty-two recurrent LBP (mean ± SD age, 21.2 ± 2.7 years) and 33 healthy (age, 20.9 ± 2.3 years) subjects performed 0.30-m drop-jump landings with and without VPAC and fatigue. Trunk, pelvis, and hip biomechanical and electromyographic variables were obtained using 3-D motion capture. Hypotheses were tested using analysis of variance. RESULTS: Volitional preemptive abdominal contraction resulted in significantly earlier muscle onsets across all muscles, with and without fatigue, in both groups (mean ± SD, 0.058 ± 0.019 seconds earlier; P≤.001) and altered lumbar lateral flexion (1.4° ± 14.8° greater right lateral flexion; P = .002). Fatigue significantly delayed muscle onsets (0.040 ± 0.014 seconds later; P≤.001) and altered pelvic obliquity (1.4° ± 11.0° greater; P≤.001) and trunk side flexion (2.0° ± 14.8° less; P≤.001). The recurrent LBP group exhibited delayed muscle onsets (0.039 ± 0.031 seconds later; P≤.004) and 4.2° less hip abduction at initial contact (P≤.008) in comparison to healthy controls. CONCLUSION: Volitional preemptive abdominal contraction decreases some of the detrimental effects of fatigue on landing biomechanics and thus may reduce spine injury risk in individuals with recurrent LBP.