Carrying Asymmetric Loads While Walking on a Treadmill Interferes with Lower Limb Coordination

The purpose of this study was to investigate the effect of different load carriage modes on coordinative patterns in the lower extremities during walking. Twenty-five university students walked on a treadmill at their preferred pace under three different load conditions: symmetric load (5% of body mass in messenger bags on each shoulder hanging vertically and against the hips), asymmetric load 1 (10% of body mass in a messenger bag on one shoulder hanging vertically against the ipsilateral hip), and asymmetric load 2 (10% of body mass in a messenger bag on one shoulder with the bag draped across the trunk to the contralateral hip). Altered thigh-shank and shank-foot couplings were found for the loaded side during the stance of gait when comparing the asymmetric 1 and 2 to the symmetric load. In addition, thigh-thigh coupling was changed during gait when comparing the asymmetric load 2 and symmetric load. However, we did not find any significant differences in intralimb and interlimb couplings between the two different asymmetric load conditions. The results suggest potential benefits when carrying symmetrical loads in order to decrease abnormal limb coordination in daily activities. Thus, it may be advisable to distribute load more symmetrically to avoid abnormal gait.

Pitching shoulder passive flexibility: torque-angle analysis for external rotation and internal rotation

In this study, a custom device was developed to analyse the pitching shoulder's external rotation (ER) and internal rotation (IR) passive flexibility. We analysed three novel measures: the resistance onset angle (ROA = angle where the shoulder begins stretching), rotational stiffness, and torque at the end range of motion (ROM). The purpose was to conduct a bilateral analysis to determine if there are significant differences between the throwing and non-throwing shoulder. Participants were 30 upper level pitchers (13 division I, 17 minor league). During testing, pitchers laid supine on a treatment table and the arm was secured to a rotational wheel with the shoulder abducted 90° and elbow flexed 90°. Dependent t-tests revealed significant (p < 0.01) and relatively extreme bilateral differences for all three variables. The throwing shoulder had: increased ER ROA (9°), decreased IR ROA (5.3°), increased ER stiffness (17%), increased IR stiffness (34%), increased ER torque (21%), and increased IR torque (30%). Secondary correlation analysis was completed to determine if the torque-angle variables were good predictors of the end ROM. Stiffness correlations were weak for ER (r = 0.35, p = 0.048) and IR (r = 0.42, p = 0.017) but ROA correlations were strong for ER (r = 0.85, p < 0.001) and IR (r = 0.86, p < 0.001).

Developing reliable measures of the passive torque-angle relationship for shoulder internal and external rotation: Implications for overhead athletics

OBJECTIVES

1) Thoroughly assess shoulder flexibility by establishing the passive torque-angle relationship for internal and external rotation with the arm in an overhead athletics position (abducted 90°) and 2) test the reliability of four passive torque-angle measures.

DESIGN

Reliability study.

SETTING

Data were collected in a university biomechanics laboratory.

PARTICIPANTS

Bilateral shoulder flexibility of 15 male college students (20.7 ± 1.1 y) was evaluated twice in two sessions over 7-10 days.

MAIN OUTCOME MEASURES

For both ER and IR, reliability was assessed bilaterally (intra-session, inter-session, and inter-tester) for the traditional range of motion measure and three novel kinetic measures: torque at end ROM, resistance onset angle, rotational stiffness. This resulted in 48 total assessments.

RESULTS

Thirty-four assessments had good to excellent reliability (ICC ≥ 0.8), 10 had fair reliability (0.7 ≤ ICC < 0.8), and 4 had poor reliability (ICC< 0.7). Three of the four flexibility measures had a good overall ICC score: ROM (0.83), torque at end ROM (0.84), and resistance onset angle (0.81). The fourth, stiffness, had a fair overall reliability score (0.74).

CONCLUSIONS

The passive torque-angle measures should be assimilated into clinical and research settings to determine the relevance to injury, rehabilitation, and performance.

The effect of wheelchair propulsion style on changes in time spent in extreme wrist orientations after a bout of fatiguing propulsion

This study compared how wheelchair propulsion styles affect changes in percentage of time spent in extreme wrist orientations, which have been associated with median nerve injury, after a fatiguing bout of propulsion. Twenty novice, non-disabled adult males learned arcing (ARC) and semicircular (SEMI) propulsion styles and utilised each to perform a wheelchair fatigue protocol. ARC and SEMI did not significantly differ in terms of changes after the fatigue protocol in percentage of time spent in extreme flexion/extension or radial/ulnar deviation at the push phase beginning or end. A pattern was observed, although not significant, of greater increases in percentage of time spent in extreme wrist extension and ulnar deviation during the push phase beginning and ulnar deviation during the push phase end while utilising SEMI relative to ARC. This study evinces that individual differences are greater than observed changes in extreme wrist orientations for both propulsion styles. Practitioner Summary: How wheelchair propulsion styles change with fatigue in terms of extreme wrist orientations was examined. This study evinces that individual differences are greater than observed changes in extreme wrist orientations for both propulsion styles and point towards the need for future research on individual differences utilising propulsion styles.

The Effect of Propulsion Style on Wrist Movement Variability During the Push Phase After a Bout of Fatiguing Propulsion

BACKGROUND

Wheelchair propulsion has been linked to overuse injuries regardless of propulsion style. Many aspects of the arcing (ARC) and semicircular (SEMI) propulsion styles have been compared, but differences in intracycle movement variability, which have been linked to overuse injuries, have not been examined.

OBJECTIVE

To explore how ARC and SEMI affect changes in intracycle wrist movement variability after a fatiguing bout of propulsion.

DESIGN

Repeated measures crossover design.

SETTING

Wheelchair rollers and wheelchair fatigue course in a research laboratory.

PARTICIPANTS

Twenty healthy, nondisabled adult men without previous wheelchair experience.

INTERVENTIONS

Participants learned ARC and SEMI and used each to perform a wheelchair fatigue protocol.

MAIN OUTCOME MEASUREMENTS

Thirty seconds of propulsion on rollers were recorded by motion-capture cameras before and after a fatigue protocol for each propulsion style on 2 testing days. Angular wrist orientations (flexion/extension and radial/ulnar deviation) and linear wrist trajectories (mediolateral direction) were computed, and intracycle movement variability was calculated as standard deviations of the detrended and filtered values during the push phase beginning and end. Paired samples t tests were used to compare ARC and SEMI based on the percent changes from pre- to postfatigue protocol.

RESULTS

Both propulsion styles resulted in increased intracycle wrist movement variability postfatigue, but observed increases did not significantly differ between ARC and SEMI.

CONCLUSIONS

This study evinces that intersubject variability exceeded average changes in intracycle wrist movement variability for both propulsion styles. Neither propulsion style resulting in a greater change in intracycle movement variability may suggest that no single propulsion style is ideal for everyone. The large intersubject variability may indicate that the propulsion style resulting in the smallest increase in intracycle movement variability after a fatiguing bout of propulsion may differ for each person and may help explain why wheelchair users self-select to use different propulsion styles.

Adaptation Strategies of Individuals With Anterior Cruciate Ligament Reconstruction

Background:

Despite the strong implications for rehabilitation design, the capability of individuals with anterior cruciate ligament reconstruction (ACLR) to adapt and store novel gait patterns have not been well studied.

Purpose:

To investigate how reconstructive surgery may affect the ability to adapt and store novel gait patterns in persons with ACLR while walking on a split-belt treadmill.

Study Design:

Controlled laboratory study.

Methods:

Gait adaptation was compared between 20 participants with ACLR and 20 healthy controls during split-belt treadmill walking. Gait adaptation was assessed in slow- and fast-adapting parameters by (1) the magnitude of symmetry during late adaptation and (2) the amount of the asymmetry during de-adaptation.

Results:

Healthy individuals adapted a new walking pattern and stored the new walking pattern equally in both the dominant and nondominant limbs. Conversely, individuals with ACLR displayed impairments in both slow-adapting and fast-adapting derived gait adaptation and significant differences in behavior between the reconstructed and uninjured limb.

Conclusion:

While surgical reconstruction and physical therapy are aimed at improving mechanical stability to the knee, the study data suggest that fundamental features of motor control remain altered. After ACLR, participants display an altered ability to learn and store functional gait patterns.

Repetitive finger movement performance differs among Parkinson's disease, Progressive Supranuclear Palsy, and spinocerebellar ataxia

Background

Differentiating movement disorders is critical for appropriate treatment, prognosis, and for clinical trials. In clinical trials this is especially important as effects can be diluted by inclusion of inappropriately diagnosed participants. In early disease duration phases, disorders often have overlapping clinical features, such as impairments in repetitive finger movement, making diagnosis challenging. The purpose of this pilot study was to examine and compare repetitive finger movement performance in participants diagnosed with idiopathic Parkinson’s disease, Progressive Supranuclear Palsy, and spinocerebellar ataxias.

Methods

Participants completed an unconstrained index finger flexion/extension movement (i.e. finger tap) in time with an incremental acoustic tone. Measures of movement rate, movement amplitude, and coefficient of variation were compared among groups.

Results

Significant differences between groups were revealed for movement rate at faster tone rates. Participants with Parkinson’s disease tended to tap faster than the tone rate while participants with Progressive Supranuclear Palsy and spinocerebellar ataxia tended to tap slower. No significant differences were revealed for movement amplitude, but participants with spinocerebellar ataxia demonstrated greater variance in amplitude than participants with Parkinson’s disease.

Conclusion

Quantitative analysis of repetitive finger movement performance at faster rates may be helpful to differentiate Parkinson’s Disease, Progressive Supranuclear Palsy and spinocerebellar ataxia.

Wheelchair ergonomic hand drive mechanism use improves wrist mechanics associated with carpal tunnel syndrome

Among conventional manual wheelchair (CMW) users, 49% to 63% experience carpal tunnel syndrome (CTS) that is likely induced by large forces transmitted through the wrist and extreme wrist orientations. The ergonomic hand drive mechanism (EHDM) tested in this study has been shown to utilize a more neutral wrist orientation. This study evaluates the use of an EHDM in terms of wrist orientations that may predispose individuals to CTS. Eleven adult full-time CMW users with spinal cord injury participated. Motion data were captured as participants propelled across a flat surface, completing five trials in a CMW and five trials in the same CMW fitted with the EHDM. Average angular wrist orientations were compared between the two propulsion styles. Use of the EHDM resulted in reduced wrist extension and ulnar deviation. The shift to more neutral wrist orientations observed with EHDM use may reduce median nerve compression.

Validation of a cardiorespiratory fitness assessment for firefighters

Currently, a submaximal protocol is used to measure cardiorespiratory fitness in firefighters by estimating their true aerobic capacity (V[Combining Dot Above]O2max); however, this submaximal test has not been cross-validated among firefighters. Thirty firefighters (85% male, 15% female), completed the submaximal protocol and the maximal (Bruce) treadmill protocol on separate occasions. Pearson's correlation analyses between the submaximal and Bruce protocol revealed a significant moderate positive correlation (r = 0.635, p = 0.005). The range of mean V[Combining Dot Above]O2max values and SDs produced from the submaximal and maximal protocols varied greatly (35.4-50.9 vs. 28.6-58.4 ml·kg·min, and SD of 3.91 vs. 7.22, respectively). The submaximal V[Combining Dot Above]O2 test underestimated the true V[Combining Dot Above]O2max in the majority of firefighters (72.4%) and overestimated the true V[Combining Dot Above]O2max in the remainder of firefighters. Participants with a higher body fat percentage were more likely (p = 0.0157) to have an overestimated true V[Combining Dot Above]O2max than those with a lower-body fat percentage. Our results indicate the current submaximal V[Combining Dot Above]O2 test used to measure cardiorespiratory fitness in firefighters is an improvement over previous protocols. However, our findings also show that the accuracy of this submaximal test for predicting the true V[Combining Dot Above]O2max in firefighters is questionable, and may not identify firefighters who possess substandard cardiorespiratory fitness, particularly in those with a higher percentage of body fat. Thus, the results of this study indicate that improvements to the current Fire Service Joint Management, Wellness & Fitness Initiative (WFI) V[Combining Dot Above]O2 assessment is still needed to accurately reflect the true V[Combining Dot Above]O2max of individual firefighters.

Persons with reconstructed ACL exhibit altered knee mechanics during high-speed maneuvers

Anterior cruciate ligament (ACL) injury is a sports trauma that causes long-term disability. The function of the knee during dynamic activities can be severely limited even after successful surgical reconstruction. This study examined the effects of approach velocity during side-step cutting on knee joint mechanics in persons with reconstructed ACL (ACLR). 22 participants (11 with unilateral ACLR, 11 matched-controls) participated. Knee joint mechanics were tested in 3 approach conditions: counter-movement, one-step, and running. Dependent variables, including peak knee flexion, extension, valgus, varus, internal rotation, external rotation angles and corresponding peak joint moments, were assessed during the stance phase of cutting. Two 2×3 ("group" by "approach condition") mixed MANOVA tests were used to examine the effects of ACLR and approach velocity on knee mechanics. ACLR participants exhibited higher knee internal rotator moment (0.22 vs. 0.13 Nm/kg, p=0.003). Inter-group comparisons revealed that the ACLR participants exhibited significantly higher abductor and internal rotator moments only in the running condition (1.86 vs. 1.16 Nm/kg, p=0.018; 0.28 vs. 0.17 Nm/kg, p=0.010, respectively). Our findings suggested that patients with ACLR may be at increased risk of re-injury when participating in high-demand physical activities. Task demand should be considered when prescribing progressive therapeutic interventions to ACLR patients.

Comparison of metabolic cost, performance, and efficiency of propulsion using an ergonomic hand drive mechanism and a conventional manual wheelchair

OBJECTIVE

To compare the metabolic cost (oxygen uptake per unit time [V˙o2 consumption], heart rate, and number of pushes), performance (velocity and distance traveled), and efficiency (oxygen uptake per distance traveled [Vo2 efficiency]) of propulsion using a novel ergonomic hand drive mechanism (EHDM) and a conventional manual wheelchair (CMW).

DESIGN

Repeated-measures crossover design.

SETTING

Semicircular track.

PARTICIPANTS

Adult full-time manual wheelchair users with spinal cord injuries (N=12; mean age ± SD, 38.8±12.4y; mean body mass ± SD, 73.7±13.3kg; mean height ± SD, 173.6±11.1cm) who were medically and functionally stable and at least 6 months postinjury.

INTERVENTION

Participants propelled themselves for 3.5 minutes at a self-selected pace in a CMW and in the same chair fitted with the EHDM.

MAIN OUTCOME MEASURES

Velocity, distance traveled, number of pushes, V˙o2 consumption, Vo2 efficiency, and heart rate were compared by wheelchair condition for the last 30 seconds of each trial using paired t tests (α=.01).

RESULTS

The CMW condition resulted in more distance traveled (33.6±10.8m vs 22.4±7.8m; P=.001), greater velocity (1.12±0.4m/s vs .75±.30m/s; P=.001), and better Vo2 efficiency (.10±.03mL·kg(-1)·m(-1) vs .15±.03mL·kg(-1)·m(-1); P<.001) than the EHDM condition, respectively. No significant differences were found between the 2 conditions for number of pushes (27.5±5.7 vs 25.7±5.4; P=.366), V˙o2 consumption (6.43±1.9mL·kg(-1)·min(-1) vs 6.19±1.7mL·kg(-1)·min(-1); P=.573), or heart rate (100.5±14.5 beats per minute vs 97.4±20.2 beats per minute; P=.42).

CONCLUSIONS

The results demonstrate that metabolic costs did not differ significantly; however, performance and efficiency were sacrificed with the EHDM. Modifications to the EHDM (eg, addition of gearing) could rectify the performance and efficiency decrements while maintaining similar metabolic costs. Although not an ideal technology, the EHDM can be considered as an alternative mode of mobility by wheelchair users and rehabilitation specialists.

Perceptions of wellness and burnout among certified athletic trainers: sex differences

CONTEXT

Athletic trainers are exposed to various stressors, increasing the potential for burnout and decreasing perceived wellness. Burnout and decreased perceived wellness can result from many factors: years of experience, hours per week worked, or decreased levels of physical activity. Another factor that accounts for a portion of the variance is sex differences.

OBJECTIVE

To determine the differences in burnout, physical activity, and perceived wellness scores relating to sex in District 9 of the National Athletic Trainers' Association (NATA).

DESIGN

Cross-sectional study.

SETTING

Web-based questionnaire.

PATIENTS OR OTHER PARTICIPANTS

Athletic trainers who were included in the e-mail directory of NATA District 9 (men = 232, women = 158).

INTERVENTION(S)

A 19-item questionnaire for burnout, a 36-item questionnaire for perceived wellness, and a 16-item activity questionnaire for physical activity and demographics.

MAIN OUTCOME MEASURE(S)

The variables included demographics (hours per week worked, years of experience, sex), Copenhagen Burnout Inventory (CBI; scores range from 0-100, and higher scores represent a higher level of burnout), Perceived Wellness Survey (PWS; scores range from 1-36, and scores close to 29 are considered healthy), and Baecke Physical Activity Questionnaire (BPAQ; scores range from 1-15, and higher scores represent more physical activity).

RESULTS

Of the 1560 members contacted, 390 responded (response rate = 25%), and 59.5% (n = 232) were male. The mean scores were 38.73 ± 16.9 for men and 46.2 ± 17.1 for women for the CBI, 16.68 ± 2.76 for men and 16.41 ± 2.81 for women for the PWS, and 8.42 ± 1.32 for men and 8.77 ± 1.36 for women for the BPAQ. Men and women worked an average of 55.60 ± 26.03 and 47.86 ± 20.57 hours per week, respectively, and had a mean experience of 14.79 ± 9.86 and 8.92 ± 6.51 years, respectively. Women reported a higher level of burnout (t388 = -4.255, P = .001) and greater levels of physical activity (t388 = -2.52, P = .01) than men. Men reported working more hours (t388 = 3.131, P = .002) and having more years of experience (t388 = 6.568, P = .001) than women. Perceived wellness was not different between sexes (t388 = 0.958, P = .34).

CONCLUSIONS

Our results suggest that women experienced moderate to high burnout and men experienced moderate burnout. Interestingly, men reported lower levels of burnout but worked more hours than women. Future researchers should focus on why women experience higher levels of burnout but work fewer hours. These findings may lead to educational interventions that might reduce burnout and increase professional longevity and quality of work.

Age and Parkinson's disease related kinematic alterations during multi-directional gait initiation

Previous literature suggests that older adults and persons with Parkinson's disease (PWP) exhibit impaired performance during gait initiation (GI) and turning while walking. While researchers have identified specific impairments during GI and turning separately in these populations, little is known about when these two tasks occur concurrently. Our objective was to determine how multi-directional GI kinematics are affected by aging and Parkinson's disease. Kinematic data were collected on 12 healthy young adults (HYA), 11 healthy older adults (HOA) and 11 PWP during GI in four conditions: forward, medial 45°, lateral 45°, and lateral 90°. Spatiotemporal characteristics and segmental angles were analyzed using separate 3 (group)×4 (condition) mixed ANOVA. Combined across all the conditions, HOA took a smaller (P=0.009) and slower (P=0.023) first step, and slower second step (P=0.021) compared to HYA. PWP took a slower first step (P=0.009), and longer time to initiate the second step (P=0.017) compared to HOA. Also, PWP had greater head rotation at the start of GI during the medial 45° condition (P=0.043) and reduced overall segmental rotation before toe-off of the second step during the lateral 45° condition (P=0.035), and at heel-strike of first step (P=0.031) and before toe-off of second step during lateral 90° condition (P=0.035). For HOA, their general slowness of movement could be attributed to aging effects. For PWP, rigidity and bradykinesia could impair activities of daily living like multi-directional GI and may be associated with an increased risk of falls.

Discriminating between copers and people with chronic ankle instability

CONTEXT

Differences in various outcome measures have been identified between people who have sprained their ankles but have no residual symptoms (copers) and people with chronic ankle instability (CAI). However, the diagnostic utility of the reported outcome measures has rarely been determined. Identifying outcome measures capable of predicting who is less likely to develop CAI could improve rehabilitation protocols and increase the efficiency of these measures.

OBJECTIVE

To determine the diagnostic utility and cutoff scores of perceptual, mechanical, and sensorimotor outcome measures between copers and people with CAI by using receiver operating characteristic curves.

DESIGN

Case-control study.

SETTING

Sports medicine research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty-four copers (12 men, 12 women; age = 20.8 ± 1.5 years, height = 173 ± 11 cm, mass = 78 ± 27 kg) and 24 people with CAI (12 men, 12 women; age = 21.7 ± 2.8 years, height = 175 ± 13 cm, mass = 71 ± 13 kg) participated.

INTERVENTION(S)

Self-reported disability questionnaires, radiographic images, and a single-legged hop stabilization test.

MAIN OUTCOME MEASURE(S)

Perceptual outcomes included scores on the Foot and Ankle Disability Index (FADI), FADI-Sport, and a self-report questionnaire of ankle function. Mechanically, talar position was quantified by measuring the distance from the anterior tibia to the anterior talus in the sagittal plane. Sensorimotor outcomes were the dynamic postural stability index and directional indices, which were calculated during a single-legged hop stabilization task.

RESULTS

Perceptual outcomes demonstrated diagnostic accuracy (range, 0.79-0.91), with 95% confidence intervals ranging from 0.65 to 1.00. Sensorimotor outcomes also were able to discriminate between copers and people with CAI but with less accuracy (range, 0.69-0.70), with 95% confidence intervals ranging from 0.37 to 0.86. The mechanical outcome demonstrated poor diagnostic accuracy (0.52).

CONCLUSIONS

The greatest diagnostic utility scores were achieved by the self-assessed disability questionnaires, which indicated that perceptual outcomes had the greatest ability to accurately predict people who became copers after their initial injuries. However, the diversity of outcome measures that discriminated between copers and people with CAI indicated that the causal mechanism of CAI is probably multifactorial.

17β-Hydroxyestra-4,9,11-trien-3-one (Trenbolone) preserves bone mineral density in skeletally mature orchiectomized rats without prostate enlargement

Testosterone enanthate (TE) administration attenuates bone loss in orchiectomized (ORX) rats. However, testosterone administration may increase risk for prostate/lower urinary tract related adverse events and polycythemia in humans. Trenbolone enanthate (TREN) is a synthetic testosterone analogue that preserves bone mineral density (BMD) and results in less prostate enlargement than testosterone in young ORX rodents. The purpose of this experiment was to determine if intramuscular TREN administration attenuates bone loss and maintains bone strength, without increasing prostate mass or hemoglobin concentrations in skeletally mature ORX rodents. Forty, 10 month old male F344/Brown Norway rats were randomized into SHAM, ORX, ORX+TE (7.0mg/week), and ORX+TREN (1.0mg/week) groups. Following surgery, animals recovered for 1 week and then received weekly: vehicle, TE, or TREN intramuscularly for 5 weeks. ORX reduced total and trabecular (t) BMD at the distal femoral metaphysis compared with SHAMs, while both TREN and TE completely prevented these reductions. TREN treatment also increased femoral neck strength by 28% compared with ORX animals (p<0.05), while TE did not alter femoral neck strength. In addition, TE nearly doubled prostate mass, compared with SHAMs (p<0.05). Conversely, TREN induced a non-significant 20% reduction in prostate mass compared with SHAMs, ultimately producing a prostate mass that was 64% below that found in ORX+TE animals (p<0.01). Hemoglobin concentrations and levator ani/bulbocavernosus (LABC) muscle mass were elevated in ORX+TE and ORX+TREN animals to a similar degree above both SHAM and ORX conditions (p<0.01). In skeletally mature rodents, both high-dose TE and low-dose TREN completely prevented the ORX-induced loss of tBMD at the distal femoral metaphysis and increased LABC mass. TREN also augmented femoral neck strength and maintained prostate mass at SHAM levels. These findings indicate that TREN may be an advantageous agent for future clinical trials evaluating agents capable of preventing bone loss resulting from androgen deficiency.

Oxygen consumption, oxygen cost, heart rate, and perceived effort during split-belt treadmill walking in young healthy adults

During split-belt treadmill walking the speed of the treadmill under one limb is faster than the belt under the contralateral limb. This unique intervention has shown evidence of acutely improving gait impairments in individuals with neurologic impairment such as stroke and Parkinson's disease. However, oxygen use, heart rate and perceived effort associated with split-belt treadmill walking are unknown and may limit the utility of this locomotor intervention. To better understand the intensity of this new intervention, this study was undertaken to examine the oxygen consumption, oxygen cost, heart rate, and rating of perceived exertion associated with split-belt treadmill walking in young healthy adults. Fifteen participants completed three sessions of treadmill walking: slow speed with belts tied, fast speed with belts tied, and split-belt walking with one leg walking at the fast speed and one leg walking at the slow speed. Oxygen consumption, heart rate, and rating of perceived exertion were collected during each walking condition and oxygen cost was calculated. Results revealed that oxygen consumption, heart rate, and perceived effort associated with split-belt walking were higher than slow treadmill walking, but only oxygen consumption was significantly lower during both split-belt walking than fast treadmill walking. Oxygen cost associated with slow treadmill walking was significantly higher than fast treadmill walking. These findings have implications for using split-belt treadmill walking as a rehabilitation tool as the cost associated with split-belt treadmill walking may not be higher or potentially more detrimental than that associated with previously used treadmill training rehabilitation strategies.

Simple change in initial standing position enhances the initiation of gait

PURPOSE

Older adults and individuals with Parkinson's disease exhibit impaired gait initiation performance with less effective anticipatory postural adjustments (APA) and less dynamic stepping characteristics. These observations may reflect impaired interactions between the postural and locomotor components of this task. The purpose of this study was to evaluate the effectiveness of altering the stance position of the initial swing limb on improving APA characteristics and stepping performance.

METHODS

Three groups (healthy young adults, individuals with Parkinson's disease, and age-matched older adults) of 12 participants initiated gait from three initial stance conditions: normal, backward displaced swing limb, and forward displaced swing limb. Ground reaction forces and whole body kinematics were recorded to characterize the APA and step parameters.

RESULTS

Initiating gait from the back condition produced more forceful weight shifting (P < 0.001), greater propulsive forces (P < 0.001), and faster center-of-mass velocities throughout the stepping phases (P < 0.05).

CONCLUSIONS

Translating the swing limb 0.5-ft-length backward seems to enhance the interaction between posture and locomotion, which may have therapeutic potential for improving gait initiation performance.

Pain-related fear and catastrophizing predict pain intensity and disability independently using an induced muscle injury model

Timing of assessment of psychological construct is controversial and results differ based on the model of pain induction. Previous studies have not used an exercise-induced injury model to investigate timing of psychological assessment. Exercise-induced injury models may be appropriate for these investigations because they approximate clinical pain conditions better than other experimental stimuli. In this study we examined the changes of psychological constructs over time and determined whether timing of assessment affected the construct's association with reports of pain intensity and disability. One-hundred twenty-six healthy volunteers completed the Fear of Pain Questionnaire (FPQ-III), Pain Catastrophizing Scale (PCS), and Tampa Scale of Kinesiophobia (TSK) prior to inducing muscle injury to the shoulder. The PCS and TSK were measured again 48 and 96 hours postinjury induction. Pain intensity and disability were collected at 48 and 96 hours and served as dependent variables in separate regression models. Results indicated that the FPQ-III had the strongest prediction of pain intensity from baseline to 96 hours. After baseline the PCS and TSK were stronger predictors of pain intensity and disability, respectively. These data provide support for the use of psychological constructs in predicting outcomes from shoulder pain. However, they deviate from the current theoretical model indicating that fear of pain is a consequence of injury and instead suggests that fear of pain before injury may influence reports of pain intensity.

PERSPECTIVE

The current study provides evidence that fear of pain can be assessed prior to injury. Furthermore, it supports that after injury pain catastrophizing and kinesiophobia are independently associated with pain and disability. Overall these data suggest that timing of psychological assessment may be an important consideration in clinical environments.

The influence of sex, age and BMI on the degeneration of the lumbar spine

Previous research on lumbar spine osteophyte formation has focused on patterned development and the relation of age and sex to degeneration within the vertebral bodies. The inclusion of osteophytes originating on the laminae and body mass index (BMI) may result in a more complete evaluation. This study investigates lumbar osteophyte development on the laminae and vertebral bodies to determine whether osteophyte development: (i) is related bilaterally, at different lumbar levels, and superior and inferior margins; (ii) on the laminae and vertebral bodies are reciprocally dependent responses; (iii) is correlated with sex, age and/or BMI. Seventy-six individuals (39 females, 37 males) were randomly selected from a modern skeletal collection (Bass Donated Collection). Osteophyte development was scored in eight regions on each vertebra at all five lumbar levels. A factor analysis considered all 40 scoring regions and Pearson's correlation analyses assessed the relatedness of age and BMI with the consequent factors. The factor analysis separated the variables into two similar factors for males and females defined as: (i) superior and inferior vertebral body scores and (ii) superior laminar scores at higher lumbar levels. The factor analysis also determined a third factor for females defined as: (iii) inferior laminar scores at lower lumbar levels. The severity of vertebral body osteophytes increased with age for both sexes. Additionally for females, as BMI increased, osteophyte severity increased for both the superior laminar margins higher in the column and the vertebral bodies. Dissimilarities between the factors in males and females and the correlation of BMI to osteophyte severity exclusively in females provide evidence for different biomechanical processes influencing osteophyte development.

Decreased static and dynamic postural control in children with autism spectrum disorders

The purpose of this study was to investigate postural control in children with Autism Spectrum Disorders (ASD) during static and dynamic postural challenges. We evaluated postural sway during quiet stance and the center of pressure (COP) shift mechanism during gait initiation for 13 children with ASD and 12 age-matched typically developing (TD) children. Children with ASD produced 438% greater normalized mediolateral sway (p<0.05) and 104% greater normalized anteroposterior sway (p<0.05) than TD children. Consequently, normalized sway area was also significantly greater (p<0.05) in the group with ASD. Similarly, the maximum separation between the COP and center of mass (COM) during quiet stance was 100% greater in the anteroposterior direction (p<0.05) and 146% greater in the resultant direction (p<0.05) for children with ASD. No significant difference was observed in the mediolateral direction, in spite of the 123% greater separation detected in children with ASD. During gait initiation, no group differences were detected in the posterior COP shift mechanism, suggesting the mechanism for generating forward momentum is intact. However, significantly smaller lateral COP shifts (p<0.05) were observed in children with ASD, suggesting instability or an alternative strategy for generating momentum in the mediolateral direction. These results help to clarify some discrepancies in the literature, suggesting an impaired or immature control of posture, even under the most basic conditions when no afferent or sensory information have been removed or modified. Additionally, these findings provide new insight into dynamic balance in children with ASD.

Lower trunk kinematics and muscle activity during different types of tennis serves

BACKGROUND

To better understand the underlying mechanisms involved in trunk motion during a tennis serve, this study aimed to examine the (1) relative motion of the middle and lower trunk and (2) lower trunk muscle activity during three different types of tennis serves - flat, topspin, and slice.

METHODS

Tennis serves performed by 11 advanced (AV) and 8 advanced intermediate (AI) male tennis players were videorecorded with markers placed on the back of the subject used to estimate the anatomical joint (AJ) angles between the middle and lower trunk for four trunk motions (extension, left lateral flexion, and left and right twisting). Surface electromyographic (EMG) techniques were used to monitor the left and right rectus abdominis (LRA and RRA), external oblique (LEO and REO), internal oblique (LIO and RIO), and erector spinae (LES and RES). The maximal AJ angles for different trunk motions during a serve and the average EMG levels for different muscles during different phases (ascending and descending windup, acceleration, and follow-through) of a tennis serve were evaluated.

RESULTS

The repeated measures Skill x Serve Type x Trunk Motion ANOVA for maximal AJ angle indicated no significant main effects for serve type or skill level. However, the AV group had significantly smaller extension (p = 0.018) and greater left lateral flexion (p = 0.038) angles than the AI group. The repeated measures Skill x Serve Type x Phase MANOVA revealed significant phase main effects in all muscles (p < 0.001) and the average EMG of the AV group for LRA was significantly higher than that of the AI group (p = 0.008). All muscles showed their highest EMG values during the acceleration phase. LRA and LEO muscles also exhibited high activations during the descending windup phase, and RES muscle was very active during the follow-through phase.

CONCLUSION

Subjects in the AI group may be more susceptible to back injury than the AV group because of the significantly greater trunk hyperextension, and relatively large lumbar spinal loads are expected during the acceleration phase because of the hyperextension posture and profound front-back and bilateral co-activations in lower trunk muscles.

Jump-landing direction influences dynamic postural stability scores

The purpose of this investigation was to determine dynamic postural stability differences among forward, diagonal, and lateral single leg-hop-stabilization protocols in healthy subjects. A one-within repeated measures design was used to determine the effects of jump direction on dynamic postural stability during landing. Subjects were required to perform a two-legged forward, diagonal, and lateral jump to a height equivalent to 50% of their maximum vertical leap, land on a single leg and balance for three seconds. Twenty-six subjects [10 males (22+/-3.9 years of age, 70.9+/-7.6kg, and 176.8+/-6.5cm) and 16 females (20.6+/-.5 years of age, 65.6+/-9.1kg, and 166.4+/-5.9cm)] volunteered to participate in this investigation. Dynamic postural stability indices for the anterior/posterior, medial/lateral, and vertical planes were collected during jump-landing trials of each direction. The results of the investigation show that medial/lateral and vertical dynamic postural stability were significantly affected by the direction of the jump. More specifically, lateral and diagonal jump-landings produce increased medial/lateral stability index (MLSI) scores and forward jump-landings produce increased vertical stability index (VSI) scores. The results suggest that in a healthy population, jump protocol direction will statistically affect dynamic postural stability in the frontal and vertical planes. These alterations could be exacerbated in individuals with lower extremity impairments and further research is warranted.

Pre- and post-impact muscle activation in the tennis volley: effects of ball speed, ball size and side of the body

AIM

To examine the pre- and post-impact activation of five upper extremity muscles in the tennis volley across conditions of ball speed, ball type and side of the body.

METHODS

A repeated measures design in a biomechanics laboratory setting was used. A total of 24 recreational tennis players (mean (SD) age 24 (5) years, height 176 (10) cm, mass 76 (13) kg) were recruited from a university. Participants performed tennis volleys under 18 ball conditions: three ball speeds (slow, medium and fast), with three ball types (two oversize and one regular size) each from two sides (forehand and backhand). Average normalised electromyographic levels of the flexor carpi radialis, extensor carpi radialis, triceps brachii, anterior/middle deltoid and posterior/middle deltoid of the hitting arm during pre- and post-impact phases (200 ms before and after ball-racquet impact, respectively) were assessed.

RESULTS

For the pre-impact phase, a significant muscle and side interaction (p<0.001) and significant main effects for speed (p = 0.002) and muscle (p<0.001) were observed. For the post-impact phase, significant interactions were observed for ball type and side (p = 0.002), ball speed and side (p = 0.011) and muscle and side (p = 0.001), as well significant main effects for muscle (p<0.001), speed (p = 0.035) and side (p<0.001).

CONCLUSION

Oversize tennis balls do not significantly increase upper extremity muscle activation compared to regular size balls during a tennis volley. The highest post-impact activation was observed in the ECR indicating a vigorous wrist stabilisation role that could irritate players with lateral epicondylalgia.

Failed jump landing trials: deficits in neuromuscular control

The purpose of this investigation was to compare neuromuscular control variables during successful and failed jump landings in multiple directions (sagittal, diagonal, and lateral). All data were collected during a single leg hop stabilization maneuver, which required subjects to stand 70 cm from the center of a force plate, jump off both legs, touch a designated marker placed at a height equivalent to 50% of their maximum vertical jump, and land on a single leg for all directions. Twenty-six subjects [10 males (22+/-3.9 years of age, 70.9+/-7.6 kg, and 176.8+/-0.5 cm) and 16 females (20.6+/-0.5 years of age, 65.6+/-9.1 kg, and 166.4+/-5.9 cm)] volunteered to participate in this investigation. Muscle activation times, average preparatory, and reactive electromyographic (EMG) amplitudes were calculated for the vastus medialis, semi-membranosis, lateral gastrocnemius, and tibialis anterior. EMG data revealed that successful jump landing trials had earlier activation times and higher preparatory and reactive EMG amplitudes. There was no difference for EMG activation times or amplitudes among directions. The results indicate neuromuscular control differences between successful and failed trials because of earlier muscle onset and greater amplitude. The results also suggest that in a healthy population, the direction of the jump protocol will not affect lower extremity EMG characteristics.

Dynamic Postural Stability Deficits in Subjects with Self-Reported Ankle Instability

PURPOSE

A limited understanding of how functional ankle instability (FAI) affects dynamic postural stability exists because of a lack of reliable and valid measures. Therefore, the purpose of this investigation was to determine whether a new reliable index for dynamic postural stability could differentiate between those with stable ankles and those with FAI.

METHODS

Data were collected on 108 subjects (54 subjects with stable ankles (STABLE group); 54 subjects with functionally unstable ankles (FAI group)). Subjects performed a single-leg-hop stabilization maneuver in which they stood 70 cm from the center of a force plate, jumped off both legs, touched a designated marker placed at a height equivalent to 50% of their maximum vertical leap, and landed on a single leg. The dynamic postural stability index and directional stability indices (medial/lateral, anterior/posterior, and vertical) were calculated. The raw and normalized (to energy dissipated) indices were compared between groups.

RESULTS

Significant differences were noted for the anterior/posterior stability index (FAI = 0.36 +/- 0.09, STABLE = 0.30 +/- 0.06). Similar results were seen for the vertical stability index (FAI = 0.73 +/- 0.17, STABLE = 0.61 +/- 0.13), the normalized dynamic postural stability index (FAI = 0.85 +/- 0.17, STABLE = 0.73 +/- 0.12), the normalized vertical stability index (FAI = 0.007 +/- 0.004, STABLE = 0.005 +/- 0.001), and the dynamic postural stability index (FAI = 0.008 +/- 0.003, STABLE = 0.006 +/- 0.001).

CONCLUSIONS

These results indicate that the dynamic postural stability index is a sensitive measure of dynamic postural stability and is capable of detecting differences between individuals with stable ankles and individuals with functionally unstable ankles.