Equivalent weight: Application of the assessment method on real task conducted by railway workers wearing a back support exoskeleton.

Commonly used risk indexes, such as the NIOSH Lifting Index, do not capture the effect of exoskeletons. This makes it difficult for Health and Safety professionals to rigorously assess the benefit of such devices. The community requires a simple method to assess the effectiveness of back-support exoskeleton's (BSE) in possibly reducing ergonomic risk. The method introduced in this work is termed "Equivalent Weight" (EqW) and it proposes an interpretation of the effect built on the benefit delivered through reduced activation of the erector spinae (ES). This manifests itself as an apparent reduction of the lifted load perceived by the wearer. This work presents a pilot study where a practical application of the EqW method is used to assess the ergonomic risk in manual material handling (MMH) when using a back support exoskeleton (StreamEXO). The results are assessed by combining observational measurements from on-site testing with five different workers and quantitative measures of the muscle activity reduction achieved during laboratory evaluation with ten workers. These results will show that when lifting, lowering, and carrying a 19 kg load the StreamEXO can reduce risk by up to two levels (from "high" to "low") in the target sub-tasks. The Lifting index (LI) was reduced up to 64% when examining specific sub-tasks and the worker's movement conduction.

Biomechanical assessment of two back-support exoskeletons in symmetric and asymmetric repetitive lifting with moderate postural demands.

Two passive back-support exoskeleton (BSE) designs were assessed in terms of muscular activity, energy expenditure, joint kinematics, and subjective responses. Eighteen participants (gender-balanced) completed repetitive lifting tasks in nine different conditions, involving symmetric and asymmetric postures and using two BSEs (along with no BSE as a control condition). Wearing both BSEs significantly reduced peak levels of trunk extensor muscle activity (by ~9-20%) and reduced energy expenditure (by ~8-14%). Such reductions, though, were more pronounced in the symmetric conditions and differed between the two BSEs tested. Participants reported lower perceived exertion using either BSE yet raised concerns regarding localized discomfort. Minimal changes in lifting behaviors were evident when using either BSE, and use of both BSEs led to generally positive usability ratings. While these results are promising regarding the occupational use of BSEs, future work is recommended to consider inter-individual differences to accommodate diverse user needs and preferences.

Assessment of posterior shoulder muscle stiffness related to posterior shoulder tightness in college baseball players using shear wave elastography.

BACKGROUND: Limitations of shoulder range of motion (ROM) have been reported to be at high risk for shoulder disorders in baseball players. In this study, we assessed posterior shoulder muscle stiffness using shear wave elastography in baseball players with and without posterior shoulder tightness. MATERIALS AND METHODS: In total, 21 college baseball players volunteered to participate in this study. Passive ROMs for shoulder abduction and horizontal adduction were measured using a goniometer. Subsequently, we divided all participants into 2 groups based on the differences between bilateral shoulder ROMs: STIFF+ and STIFF- groups. Thickness and elasticity of the posterior and inferior shoulder muscles were assessed using ultrasound. RESULTS: Shoulder abduction ROM on the throwing side was 114.5° ± 5.3° and 131.3° ± 5.7° in the STIFF+ and STIFF- groups, respectively, which was significantly different between the 2 groups (P = .023). Horizontal adduction ROM on the throwing side was 96.6° ± 4.9° and 110.9° ± 4.8° in the STIFF+ and STIFF- groups, respectively, which was also significantly different between the 2 groups (P = .014). The elasticity of infraspinatus and lower trapezius in the STIFF+ group was significantly greater than that in the STIFF- group (P = .018 and .033, respectively). DISCUSSION: In this study, we found that the elasticity of infraspinatus and lower trapezius in stiff shoulders was significantly greater than that in nonstiff shoulders, which indicated that the infraspinatus and lower trapezius could be the key muscles in posterior shoulder tightness.

Quantitative assessment of erector spinae muscles in patients with Mycobacterium avium complex lung disease.

BACKGROUND AND OBJECTIVE: No reports exist regarding skeletal muscle involvement in patients with Mycobacterium avium complex lung disease (MAC-LD). The cross-sectional area of the erector spinae muscles (ESMCSA) reflects physical activity and can be assessed by computed tomography (CT). We investigated the relationship between ESMCSA and physiological parameters and prognosis in MAC-LD patients. MATERIAL AND METHODS: In this prospective observational study, the ESMCSA was measured on single-slice axial CT images. MAC-LD patients and sex- and age-matched controls (non-MAC-LD participants) were evaluated. We evaluated the relationship between the ESMCSA and physiological parameters and prognosis. RESULTS: A total of 260 patients (209 female; median age, 69 years; 190 with nodular/bronchiectatic disease; 74 with cavitary lesions) were enrolled. The ESMCSA was not different between MAC-LD patients and controls. In MAC-LD patients, the ESMCSA was significantly associated with age, body mass index (BMI), pulmonary function, CT severity, and health-related quality of life (HRQL). Multivariate Cox proportional hazards analyses revealed that an ESMCSA < -1 standard derivation (hazards ratio [HR], 2.76; P = 0.047) was significantly associated with all-cause mortality, along with BMI < 18.5 kg/m2 (HR, 3.67; P = 0.02) and presence of cavitary lesions (HR, 5.84; P = 0.001). However, the ESMCSA was not significantly associated with all-cause mortality when current treatment status, % predicted functional vital capacity, and forced expiratory volume in 1 s were added to the analyses. CONCLUSIONS: Although the prognostic impact was limited, ESMCSA was significantly associated with HRQL and prognostic physiological parameters, such as BMI and pulmonary function.

Assessment of an active industrial exoskeleton to aid dynamic lifting and lowering manual handling tasks.

The aim of this study was to evaluate the effect of an industrial exoskeleton on muscle activity, perceived musculoskeletal effort, measured and perceived contact pressure at the trunk, thighs and shoulders, and subjective usability for simple sagittal plane lifting and lowering conditions. Twelve male participants lifted and lowered a box of 7.5 kg and 15 kg, respectively, from mid-shin height to waist height, five times, both with and without the exoskeleton. The device significantly reduced muscle activity of the Erector Spinae (12%-15%) and Biceps Femoris (5%). Ratings of perceived musculoskeletal effort in the trunk region were significantly less with the device (9.5%-11.4%). The measured contact pressure was highest on the trunk (91.7 kPa-93.8 kPa) and least on shoulders (47.6 kPa-51.7 kPa), whereas pressure was perceived highest on the thighs (35-44% of Max LPP). Six of the users rated the device usability as acceptable. The exoskeleton reduced musculoskeletal loading on the lower back and assisted with hip extensor torque during lifting and lowering. Contact pressures fell below the Pain Pressure Threshold. Perceived pressure was not exceptionally high, but sufficiently high to cause discomfort if used for long durations.

IN SEARCH FOR REAL-TIME NONINVASIVE ASSESSMENT OF MUSCLE FATIGUE DURING EXERTION: CAN DISPERSION OF HIGH-RESOLUTION MUSCLE ELECTRIC ACTIVITY DATA PROVIDE NEW INSIGHTS?

- Paralumbar muscle performance and fatigue were evaluated by measuring electromagnetic activity during entire body vibration (EBV) in 44 healthy subjects. Physical fitness of subjects was estimated on a 5-degree scale. Electric activity was recorded in 200 seconds with 1 kHz sampling on the Biopac Student Lab during EBV. Data were used to produce time series for two vectors of the phase space and spatial axis: X (left-right), Y (up-down) and Z (ventral-dorsal). Time series were evaluated by calculating fractal dimension by the R/S algorithm. Movement of the electric field along the Y-axis showed changes (up-down) extracted in the first and second quarter of the measurement (p=0.02 and p=0.03, respectively). These changes were not specific for gender but showed dependence on subject age and fitness. The fractal dimension values by the R/S algorithm were larger in female subjects. Results suggested the electric field changes during EBV in the up-down direction to contain information on muscular performance and fatigue, not dependent on gender, but on the age and degree of overall physical fitness.

Evaluating abdominal core muscle fatigue: Assessment of the validity and reliability of the prone bridging test.

The aims of this study were to research the amplitude and median frequency characteristics of selected abdominal, back, and hip muscles of healthy subjects during a prone bridging endurance test, based on surface electromyography (sEMG), (a) to determine if the prone bridging test is a valid field test to measure abdominal muscle fatigue, and (b) to evaluate if the current method of administrating the prone bridging test is reliable. Thirty healthy subjects participated in this experiment. The sEMG activity of seven abdominal, back, and hip muscles was bilaterally measured. Normalized median frequencies were computed from the EMG power spectra. The prone bridging tests were repeated on separate days to evaluate inter and intratester reliability. Significant differences in normalized median frequency slope (NMFslope ) values between several abdominal, back, and hip muscles could be demonstrated. Moderate-to-high correlation coefficients were shown between NMFslope values and endurance time. Multiple backward linear regression revealed that the test endurance time could only be significantly predicted by the NMFslope of the rectus abdominis. Statistical analysis showed excellent reliability (ICC=0.87-0.89). The findings of this study support the validity and reliability of the prone bridging test for evaluating abdominal muscle fatigue.

Role of the Middle Lumbar Fascia on Spinal Mechanics: A Human Biomechanical Assessment.

STUDY DESIGN: Biomechanical experiment. OBJECTIVE: The aims of the present study were to test the effect of fascial tension on lumbar segmental axial rotation and lateral flexion and the effect of the angle of fascial attachment. SUMMARY OF BACKGROUND DATA: Tension in the middle layer of lumbar fascia has been demonstrated to affect mechanical properties of lumbar segmental flexion and extension in the neutral zone. The effect of tension on segmental axial rotation and lateral flexion has, however, not been investigated. METHODS: Seven unembalmed lumbar spines were divided into segments and mounted for testing. A 6 degree-of-freedom robotic testing facility was used to displace the segments in each anatomical plane (flexion-extension, lateral bending, and axial rotation) with force and moment data recorded by a load cell positioned beneath the test specimen. Tests were performed with and without a 20 N fascia load and the subsequent forces and moments were compared. In addition, forces and moments were compared when the specimens were held in a set position and the fascia loading angle was varied. RESULTS: A fascial tension of 20 N had no measurable effect on the forces or moments measured when the specimens were displaced in any plane of motion (P > 0.05). When 20 N of fascial load were applied to motion segments in a set position small segmental forces and moments were measured. Changing the angle of the fascial load did not significantly alter these measurements. CONCLUSION: Application of a 20 N fascial load did not produce a measureable effect on the mechanics of a motion segment, even though it did produce small measurable forces and moments on the segments when in a fixed position. Results from the present study are inconsistent with previous studies, suggesting that further investigation using multiple testing protocols and different loading conditions is required to determine the effects of fascial loading on spinal segment behavior. LEVEL OF EVIDENCE: N/A.

Isometric abdominal wall muscle strength assessment in individuals with incisional hernia: a prospective reliability study.

PURPOSE: To determine the reliability of measurements obtained by the Good Strength dynamometer, determining isometric abdominal wall and back muscle strength in patients with ventral incisional hernia (VIH) and healthy volunteers with an intact abdominal wall. METHODS: Ten patients with VIH and ten healthy volunteers with an intact abdominal wall were each examined twice with a 1 week interval. Examination included the assessment of truncal flexion and extension as measured with the Good Strength dynamometer, the completion of the International Physical Activity Questionnaire (IPAQ) and the self-assessment of truncal strength on a visual analogue scale (SATS). The test-retest reliability of truncal flexion and extension was assessed by interclass correlation coefficient (ICC), and Bland and Altman graphs. Finally, correlations between truncal strength, and IPAQ and SATS were examined. RESULTS: Truncal flexion and extension showed excellent test-retest reliability for both patients with VIH (ICC 0.91 and 0.99) and healthy controls (ICC 0.97 and 0.96). Bland and Altman plots showed that no systematic bias was present for neither truncal flexion nor extension when assessing reliability. For patients with VIH, no significant correlations between objective measures of truncal strength and IPAQ or SATS were found. For healthy controls, both truncal flexion (τ 0.58, p = 0.025) and extension (τ 0.58, p = 0.025) correlated significantly with SATS, while no other significant correlation between truncal strength measures and IPAQ was found. CONCLUSIONS: The Good Strength dynamometer provided a reliable, low-cost measure of truncal flexion and extension in patients with VIH.