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Bohman K, El-Mobader S, Jakobsson L. Effects of restraint parameters using PIPER 6y in reclined seating during frontal impact. TRAFFIC INJURY PREVENTION 2022; 23:S123-S129. [PMID: 36214799 DOI: 10.1080/15389588.2022.2125304] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 09/05/2022] [Accepted: 09/13/2022] [Indexed: 06/16/2023]
Abstract
OBJECTIVE This study explores possible challenges for child occupants in reclined seating positions, applying current protection systems. Using PIPER 6 y in frontal impacts, the aim was to investigate the effect of restraint parameters in reclined seating positions, in addition to an upright position, varying booster design, shoulder belt outlet, and pretensioner activation. METHOD Eighteen full frontal impacts were simulated using the PIPER 6 y human body model restrained on a booster in a front passenger seat. The type of booster, pretensioner activation and shoulder belt outlet were varied with the vehicle seat in 'upright position' (25°) and 'reclined position' (40°). Three booster principles were used: booster seat (BoosterA), booster cushion (BoosterB) and representing properties of a vehicle built-in booster cushion (BoosterC). The two shoulder belt outlets include 'nominal D-ring' and 'rearward D-ring´. RESULTS Overall, activation of the pretensioner reduced the overall body displacement as well as the head and neck response in both seating positions. Submarining occurred only in the case of BoosterB in 'reclined position' without pretensioner. Some differences were observed for the lap belt interaction with pelvis in the non-submarining simulations. Greater pelvis displacement was observed in 'reclined position' as compared to 'upright position'. In both seating positions, greatest pelvis displacement was observed for BoosterB, due to relatively more forward initial lap belt position. While both provided favorable initial lap belt to pelvis contact, BoosterC offered more efficient lap belt restraint than BoosterA, since the lap belt remained lower on the pelvis and the vertical movement of the pelvis was more limited compared to BoosterA. When in 'reclined position', the 'rearward D-ring' position enabled earlier coupling of the torso due to initial shoulder belt to shoulder contact, resulting in lower head and neck responses as well as shorter head displacement compared to 'nominal D-ring'. CONCLUSIONS Submarining can be addressed in reclined seating positions using current booster design in combination with a seatbelt pretensioner. Lap belt routing was influenced by booster design and reclined seating, affecting the overall kinematics and responses of the PIPER 6 y. This study highlights the importance of including the whole context of child occupant protection when investigating reclined seating, such as the interaction and compatibility of booster, vehicle seat and seatbelt.
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Knighton TW, Chalmers PN, Sulkar HJ, Aliaj K, Tashjian RZ, Henninger HB. Anatomic total shoulder glenoid component inclination affects glenohumeral kinetics during abduction: a cadaveric study. J Shoulder Elbow Surg 2022; 31:2023-2033. [PMID: 35550434 PMCID: PMC9481675 DOI: 10.1016/j.jse.2022.03.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/23/2022] [Accepted: 03/27/2022] [Indexed: 02/01/2023]
Abstract
BACKGROUND Although typically favorable in outcome, anatomic total shoulder arthroplasty (aTSA) can require long-term revision. The most common cause for revision is glenoid loosening, which may result from eccentric cyclic forces and joint translations. "Rocking" of the glenoid component may be exacerbated by the joint geometry, such as glenoid inclination and version. Restoration of premorbid glenoid inclination may be preferable, although laboratory and computational models indicate that both superior inclination and inferior inclination have benefits. This discrepancy may arise because previous studies were limited by a lack of physiological conditions to test inclination. Therefore, a cadaveric shoulder simulator with 3-dimensional human motion was used to study joint contact and muscle forces with isolated changes in glenoid inclination. METHODS Eight human cadaveric shoulders were tested before and after aTSA. Scapular-plane abduction kinematics from human subjects were used to drive a cadaveric shoulder simulator with 3-dimensional scapulothoracic and glenohumeral motion. Glenoid inclination was varied from -10° to +20°, whereas compressive, superior-inferior shear, and anterior-posterior shear forces were collected with a 6-df load cell during motion. Outputs also included muscle forces of the deltoid and rotator cuff. Data were evaluated with statistical parametric mapping repeated-measures analysis of variance and t tests. RESULTS Inferior glenoid inclination (-10°) reduced both compressive and superior-inferior shear forces vs. neutral 0° inclination by up to 40%, and even more when compared with superior inclination (P < .001). Superior inclinations (+10° and +20°) tended to increase deltoid and rotator cuff forces vs. neutral 0° inclination or inferior inclination, on the order of 20%-40% (P ≤ .045). All force metrics except anterior-posterior shear were lowest for inferior inclination. Most aTSA muscle forces for neutral 0° inclination were not significantly different from native shoulders and decreased 45% and 15% in the posterior deltoid and supraspinatus, respectively (P ≤ .003). Joint translations were similar to prior reports in aTSA patients and did not differ between any inclinations or compared with native shoulders. Joint reaction forces were similar to those observed in human subjects with instrumented aTSA implants, providing confidence in the relative magnitude of our results. CONCLUSIONS Inferior inclination reduces overall forces in the shoulder. Superior inclinations increase the muscle effort required for the shoulder to achieve similar motion, thus increasing the forces exerted on the glenoid component. These results suggest that a preference toward aTSA glenoid components in inferior inclination may reduce the likelihood of glenoid loosening by reducing excessive muscle and joint contact forces.
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Jorgensen MJ, Hakansson NA, Desai J. Influence of different passive shoulder exoskeletons on shoulder and torso muscle activation during simulated horizontal and vertical aircraft squeeze riveting tasks. APPLIED ERGONOMICS 2022; 104:103822. [PMID: 35689869 DOI: 10.1016/j.apergo.2022.103822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 04/22/2022] [Accepted: 06/01/2022] [Indexed: 06/15/2023]
Abstract
Aircraft manufacturing involves riveting utilizing squeeze riveting tools at heights from below elbow to overhead levels. This study assessed utilization of passive shoulder exoskeletons on shoulder and torso muscle activation during simulated squeeze riveting. Horizontal and vertical riveting tasks using squeeze riveting tools were performed by 16 aircraft workers wearing three different shoulder exoskeletons and a no-exoskeleton condition capturing electromyographic signals from shoulder and torso muscles. Exoskeletons reduced normalized EMG for the left anterior deltoid at both heights (6.6% and 15.7%), the right anterior deltoid (8.3%) and the right and left medial deltoid (9.3% and 8.9%) at the upper height for horizontal squeeze riveting. Exoskeletons reduced normalized EMG for the right and left anterior deltoids (7.0%-10.6%) and medial deltoids (1.3%-7.1%) within the upper zones during vertical squeeze riveting. Participants felt exoskeletons would be beneficial for squeeze riveting, however no preference was found among the exoskeletons used.
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Mukai H, Umehara J, Yagi M, Yanase K, Itsuda H, Ichihashi N. Effective stretching position for the posterior deltoid muscle evaluated by shear wave elastography. J Shoulder Elbow Surg 2022; 31:1658-1665. [PMID: 35245666 DOI: 10.1016/j.jse.2022.01.143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 01/19/2022] [Accepted: 01/23/2022] [Indexed: 02/01/2023]
Abstract
BACKGROUND Deteriorated extensibility of the posterior deltoid muscle is one of the factors of posterior shoulder tightness, and improvement in its extensibility is needed. However, no study has investigated which shoulder positions effectively stretch the posterior deltoid muscle in vivo. The aim of this study was to verify the effective stretching position of the posterior deltoid muscle in vivo by shear wave elastography. METHODS Fifteen healthy men participated in this study. The shear modulus of the posterior deltoid was measured at resting and 13 stretching positions: 60°, 90°, and 120° shoulder flexion; maximum shoulder flexion, horizontal adductions at 60°, 90°, and 120° shoulder flexion; internal rotations at 60°, 90°, and 120° shoulder flexion; and combinations of horizontal adduction with internal rotation at 60°, 90°, and 120° shoulder flexion. The shear moduli of each stretching position were compared to those of the rest. Then, among the stretching positions for which the shear modulus was significantly different from the rest, the shear moduli were compared using a three-way analysis of variance with repeated measures of the 3 factors-flexion, horizontal adduction, and internal rotation. RESULTS The shear moduli in all stretching positions were significantly higher than those of the rest, except for maximum shoulder flexion. The three-way analysis of variance with repeated measures revealed significant main effects in flexion and horizontal adduction. Comparing the flexion angles, the shear modulus was significantly higher at 90° than that at 60° and 120°. The shear modulus with horizontal adduction was significantly higher than that without horizontal adduction. Moreover, a significant two-way interaction was found only at flexion and horizontal adduction. The shear modulus with horizontal adduction was significantly higher at all angles than that without horizontal adduction at each flexion angle. Comparing the flexion angles with horizontal adduction, the shear modulus was significantly higher at 90° than that at 60° and 120°. No significant three-way interactions were found. CONCLUSION Shoulder flexion and horizontal adduction affected the extensibility of the posterior deltoid muscle, whereas the effect of shoulder internal rotation was limited. More precisely, maximal horizontal adduction at 90° shoulder flexion was the most effective stretching position for the posterior deltoid muscle.
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Goubault E, Martinez R, Assila N, Monga-Dubreuil É, Dowling-Medley J, Dal Maso F, Begon M. Effect of Expertise on Shoulder and Upper Limb Kinematics, Electromyography, and Estimated Muscle Forces During a Lifting Task. HUMAN FACTORS 2022; 64:800-819. [PMID: 33236930 DOI: 10.1177/0018720820965021] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
OBJECTIVE To highlight the working strategies used by expert manual handlers compared with novice manual handlers, based on recordings of shoulder and upper limb kinematics, electromyography (EMG), and estimated muscle forces during a lifting task. BACKGROUND Novice workers involved in assembly, manual handling, and personal assistance tasks are at a higher risk of upper limb musculoskeletal disorders (MSDs). However, few studies have investigated the effect of expertise on upper limb exposure during workplace tasks. METHOD Sixteen experts in manual handling and sixteen novices were equipped with 10 electromyographic electrodes to record shoulder muscle activity during a manual handling task consisting of lifting a box (8 or 12 kg), instrumented with three six-axis force sensors, from hip to eye level. Three-dimensional trunk and upper limb kinematics, hand-to-box contact forces, and EMG were recorded. Then, joint contributions, activation levels, and muscle forces were calculated and compared between groups. RESULTS Sternoclavicular-acromioclavicular joint contributions were higher in experts at the beginning of the movement, and in novices at the end, whereas the opposite was observed for the glenohumeral joint. EMG activation levels were 37% higher for novices but predicted muscle forces were higher in experts. CONCLUSION This study highlights significant differences between experts and novices in shoulder kinematics, EMG, and muscle forces; hence, providing effective work guidelines to ensure the development of a safe handling strategy is important. APPLICATION Shoulder kinematics, EMG, and muscle forces could be used as ergonomic tools to identify inappropriate techniques that could increase the prevalence of shoulder injuries.
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Tao D, Yang K, Zhang T, Qu X. Typing with mobile devices: A comparison of upper limb and shoulder muscle activities, typing performance and perceived workload under varied body postures, typing styles and device types. APPLIED ERGONOMICS 2022; 102:103760. [PMID: 35395580 DOI: 10.1016/j.apergo.2022.103760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Revised: 03/13/2022] [Accepted: 03/29/2022] [Indexed: 06/14/2023]
Abstract
This study aimed to examine the effects of body posture, typing style and device type on upper limb and shoulder muscle activities, typing performance and perceived workload while typing with mobile devices. Participants were asked to type with two mobile devices (i.e., a tablet and a smartphone) under three postures and in two typing styles. Muscle activity was recorded for four upper limb and shoulder muscles on both sides with surface electromyography. Results showed that body posture and typing style yielded significant effects on tying performance, perceived workload, and muscle activities in the forearm, upper arm and shoulder. Typing with a tablet was more accurate and had greater muscle activities in the upper arm and forearm on both sides than typing with a smartphone. The findings may be useful in developing evidence-based guidelines for the wise use of mobile devices and for the prevention of risks for musculoskeletal disorders.
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Miyasaka J, Arai R, Yoshioka Y, Matsumura A, Hasegawa S, Kuriyama S, Nakamura S, Ichihashi N, Matsuda S. Electromyographic Analysis of a Selective Exercise for the Serratus Anterior Muscle Among Patients With Frozen Shoulder and Subacromial Impingement Syndrome. Am J Phys Med Rehabil 2022; 101:540-544. [PMID: 34347628 DOI: 10.1097/phm.0000000000001860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Patients with shoulder disorders show altered periscapular muscle activity (e.g., decreased serratus anterior and increased upper trapezius activities). We herein devised a novel method for strengthening serratus anterior without excessive upper trapezius activation, named squeezing ball exercise in which patients squeezed a ball between both elbows with maximum voluntary isometric contraction in the horizontal adduction direction with the arms elevated at a 45-degree angle. The present study aimed to investigate whether the squeezing ball exercise could produce high muscle activity in the serratus anterior in patients with frozen shoulder and subacromial impingement syndrome before the rehabilitation intervention. DESIGN This is a proof-of-concept study. Serratus anterior and upper trapezius activities during squeezing ball exercise were evaluated using electromyography in 16 patients with frozen shoulders and subacromial impingement syndrome. Electromyography signals were normalized using maximal voluntary isometric contraction, and the muscle balance ratios (upper trapezius/serratus anterior) were calculated. RESULTS The average serratus anterior and upper trapezius activity was 69.9% ± 30.8% and 10.2% ± 6.3% maximal voluntary isometric contraction during the squeezing ball exercise, respectively, whereas the upper trapezius-serratus anterior ratio of the affected side was 0.15 ± 0.07. CONCLUSIONS The high serratus anterior activation and low upper trapezius-serratus anterior ratio during squeezing ball exercise could be attributed to the limb position where shortened serratus anterior exerts itself without painful subacromial impingement. Squeezing ball exercise could be a novel rehabilitation tool for patients with frozen shoulders and subacromial impingement syndrome.
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Chung YC, Chen CY, Chang CM, Lin YL, Liao KK, Lin HC, Chen WY, Yang YR, Shih YF. Altered corticospinal excitability of scapular muscles in individuals with shoulder impingement syndrome. PLoS One 2022; 17:e0268533. [PMID: 35576229 PMCID: PMC9109916 DOI: 10.1371/journal.pone.0268533] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 05/02/2022] [Indexed: 11/19/2022] Open
Abstract
The purpose of this study is to assess and compare corticospinal excitability in the upper and lower trapezius and serratus anterior muscles in participants with and without shoulder impingement syndrome (SIS). Fourteen participants with SIS, and 14 without SIS were recruited through convenient sampling in this study. Transcranial magnetic stimulation assessment of the scapular muscles was performed while the participants were holding their arm at 90 degrees scaption. The motor-evoked potential (MEP), active motor threshold (AMT), latency of MEP, cortical silent period (CSP), activated area and center of gravity (COG) of cortical mapping were compared between groups using the Mann-Whitney U tests. The SIS group demonstrated following significances, higher AMTs of the lower trapezius (SIS: 0.60 ± 0.06; Comparison: 0.54 ± 0.07, p = 0.028) and the serratus anterior (SIS: 0.59 ± 0.04; Comparison: 0.54 ± 0.06, p = 0.022), longer CSP of the lower trapezius (SIS: 62.23 ± 22.87 ms; Comparison: 45.22 ± 14.64 ms, p = 0.019), and posteriorly shifted COG in the upper trapezius (SIS: 1.88 ± 1.06; Comparison: 2.76 ± 1.55, p = 0.048) and the serratus anterior (SIS: 2.13 ± 1.02; Comparison: 3.12 ± 1.88, p = 0.043), than the control group. In conclusion, participants with SIS demonstrated different organization of the corticospinal system, including decreased excitability, increased inhibition, and shift in motor representation of the scapular muscles.
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Juul-Kristensen B, Bech C, Liaghat B, Cools AM, Olsen HB, Søgaard K, Larsen CM. Assessment of shoulder rotation strength, muscle co-activation and shoulder pain in tetraplegic wheelchair athletes - A methodological study. J Spinal Cord Med 2022; 45:410-419. [PMID: 32808885 PMCID: PMC9135435 DOI: 10.1080/10790268.2020.1803659] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Objective: To develop a feasible protocol for testing maximum shoulder rotation strength in tetraplegic wheelchair athletes, and investigate concurrent validity of maximum isometric handheld dynamometer (HHD) towards maximum isokinetic dynamometer (ID) strength measurements; secondly, to study shoulder muscle activation during maximum shoulder rotation measurements, and the association between shoulder strength and shoulder pain.Design: Descriptive methodological.Setting: Danish Wheelchair Rugby (WCR) association for WCR tetraplegic athletes from local WCR-clubs.Participants: Twelve adult tetraplegics.Interventions: N/A.Outcome measures: Wheelchair User's Shoulder Pain Index (WUSPI) and Visual Analog Scale (VAS) measured shoulder pain, isometric HHD and ID (60°/s) measured maximum internal (IR) and external (ER) shoulder rotation strength. Surface Electromyography normalized to maximum EMG measured muscle activity (mm Infraspinatus and Latissimus Dorsi) during maximum shoulder rotation strength.Results: Concurrent validity of isometric HHD towards ID showed Concordance Correlation Coefficients of left and right arms 0.90 and 0.86 (IR), and 0.89 and 0.91 (ER), with no difference in muscle activity between isometric HHD and ID, but larger co-activation during ER. There was no association between shoulder strength and pain, except for significantly weak negative associations between ID and pain during ER for left and right arms (P = 0.03; P = 0.04).Conclusion: Standardized feasible protocol for tetraplegic wheelchair athletes for measuring maximum shoulder rotation strength was established. Isometric HHD is comparable with ID on normalized peak torques and muscle activity, but with larger co-activation. Strength was not clearly associated with shoulder pain.
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Pinho JP, Forner-Cordero A. Shoulder muscle activity and perceived comfort of industry workers using a commercial upper limb exoskeleton for simulated tasks. APPLIED ERGONOMICS 2022; 101:103718. [PMID: 35202960 DOI: 10.1016/j.apergo.2022.103718] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 02/10/2022] [Accepted: 02/11/2022] [Indexed: 06/14/2023]
Abstract
We compared the effects of using a commercial exoskeleton on shoulder muscle activity, task completion time, perceived effort and comfort while performing four tasks in different shoulder positions. Fourteen automotive industry workers performed four simulated tasks with shoulder at A≈0°, B ≈ 45°, C ≈ 90° and D ≈ 115° flexion. The electromyographic activity of the Medial Deltoid (MD) and the Anterior Deltoid (AD) decreased when wearing the exoskeleton. The effect sizes (ES) were, for MD: ES = 0, ES = -0.2, ES = -0.6, ES = -0.3; and for AD: ES = 0.3, ES = -0.6, ES = -0.8, ES = -0.6; for tasks A, B, C and D, respectively. We also found increased Anterior Deltoid/Triceps Brachii co-contraction, a typical joint stabilization mechanism. Wearing the exoskeleton increased the completion time of task B and reduced the perceived effort of tasks A and C, improving overall comfort. These findings are useful to organize the logistics of the workstations that use upper limb exoskeletons to improve the effectiveness of this equipment.
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Garosi E, Mazloumi A, Jafari AH, Keihani A, Shamsipour M, Kordi R, Kazemi Z. Design and ergonomic assessment of a passive head/neck supporting exoskeleton for overhead work use. APPLIED ERGONOMICS 2022; 101:103699. [PMID: 35114511 DOI: 10.1016/j.apergo.2022.103699] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 01/22/2022] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
Overhead work is an important risk factor associated with musculoskeletal disorders of the neck and shoulder region. This study aimed to propose and evaluate a passive head/neck supporting exoskeleton (HNSE) as a potential ergonomic intervention for overhead work applications. Fourteen male participants were asked to perform a simulated overhead task of fastening/unfastening nut in 4 randomized sessions, characterized by two variables: neck extension angle (40% and 80% of neck maximum range of motion) and exoskeleton condition (wearing and not wearing the HNSE). Using the HNSE, significantly alleviated perceived discomfort in the neck (p-value = 0.009), right shoulder (p-value = 0.05) and left shoulder (p-value = 0.02) and reduced electromyographic activity of the right (p-value = 0.005) and left (p-value = 0.01) sternocleidomastoid muscles. However, utilizing the exoskeleton caused a remarkable increase in right (p-value = 0.04) and left (p-value = 0.05) trapezius electromyographic activities. Performance was not significantly affected by the HNSE. Although the HNSE had promising effects with respect to discomfort and muscular activity in the static overhead task, future work is still needed to investigate its effect on performance and to provide support for the generalizability of study results.
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Ohashi S, Shionoya A, Harada K, Nagamori M, Uchiyama H. Posture Estimation Using Surface Electromyography during Wheelchair Hand-Rim Operations. SENSORS (BASEL, SWITZERLAND) 2022; 22:3296. [PMID: 35590986 PMCID: PMC9101678 DOI: 10.3390/s22093296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 04/18/2022] [Accepted: 04/22/2022] [Indexed: 06/15/2023]
Abstract
This study examined competitive wheelchairs that facilitate sports participation. They can be moved straight ahead using only one arm. Our designed and developed competitive wheel-chairs have a dual hand-rim system. Their two hand-rims, attached to a drive wheel on one side, can be operated simultaneously for straight-ahead movement. Specifically, based on integrated electromyography (iEMG) data calculated from surface electromyography (sEMG), we examined the wheelchair loading characteristics, posture estimation, and effects on body posture during one-arm propulsion movement. The first experiment yielded insights into arm and shoulder-joint muscle activation from iEMG results obtained for two-hand propulsion and dual hand-rim system propulsion. Results suggest that muscle activation of one arm can produce equal propulsive force to that produced by two arms. The second experiment estimated the movement posture from iEMG during one-arm wheelchair propulsion. The external oblique abdominis is particularly important for one-arm wheelchair propulsion. The iEMG posture estimation validity was verified based on changes in the user body axis and seat pressure distribution. In conclusion, as confirmed by iEMG, which is useful to estimate posture during movement, one-arm wheelchair use requires different muscle activation sites and posture than when using two arms.
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Dupuis F, Sole G, Mercier C, Roy JS. Impact of fatigue at the shoulder on the contralateral upper limb kinematics and performance. PLoS One 2022; 17:e0266370. [PMID: 35363812 PMCID: PMC8975159 DOI: 10.1371/journal.pone.0266370] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 03/18/2022] [Indexed: 12/03/2022] Open
Abstract
Background Altered movement patterns have been proposed as an etiological factor for the development of musculoskeletal pain. Fatigue influences upper limb kinematics and movement performance which could extend to the contralateral limb and potentially increasing risk of injury. The aim of this study was to investigate the impact of fatigue at the dominant arm on the contralateral upper limb movement. Methods Forty participants were randomly assigned to one of two groups: Control or Fatigue Group. All participants completed a reaching task at the baseline and post-experimental phase, during which they reached four targets with their non-dominant arm in a virtual reality environment. Following the baseline phase, the Fatigue Group completed a shoulder fatigue protocol with their dominant arm only, while the Control Group took a 10-minute break. Thereafter, the reaching task was repeated. Upper limb and trunk kinematics (joint angles and excursions), spatiotemporal (speed and accuracy) and surface electromyographic (sEMG) activity (sEMG signal mean epoch amplitude and median frequency of the EMG power spectrum) were collected. Two-way repeated-measures ANOVA were performed to determine the effects of Time, Group and of the interaction between these factors. Results There was a significant Time x Group interaction for sternoclavicular elevation range of motion (p = 0.040), movement speed (p = 0.043) and accuracy (p = 0.033). The Fatigue group showed higher contralateral sternoclavicular elevation and increased movement error while experiencing fatigue in the dominant arm. Moreover, the Control group increased their speed during the Post-experimental phase compared to baseline (p = 0.043), while the Fatigue group did not show any speed improvement. There was no EMG sign of fatigue in any of the muscles evaluated. Conclusion This study showed that fatigue at the dominant shoulder impacts movement at the contralateral upper limb. Such changes may be a risk factor for the development of shoulder pain in both the fatigued and non-fatigued limbs.
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Lavallée-Bourget MH, Campeau-Lecours A, Tittley J, Bielmann M, Bouyer LJ, Roy JS. The use of a three-dimensional dynamic arm support prevents the development of muscle fatigue during repetitive manual tasks in healthy individuals. PLoS One 2022; 17:e0266390. [PMID: 35363820 PMCID: PMC8975113 DOI: 10.1371/journal.pone.0266390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 03/20/2022] [Indexed: 11/19/2022] Open
Abstract
Work-related upper extremity disorders are costly to society due to resulting medical costs, presenteeism and absenteeism. Although their aetiology is likely multifactorial, physical workplace factors are known to play an important role in their development. Promising options for preventing work-related upper extremity disorders include assistive technologies such as dynamic arm supports designed to follow the movement of the arm while compensating for its weight. The objective of this study was to assess the effects of a dynamic arm support on perceived exertion, muscle activity and movement patterns of the upper limb during repetitive manual tasks in healthy individuals. Thirty healthy right-handed individuals were allocated either a static or a dynamic task to perform with and without a dynamic arm support. During the task, surface electromyographic activity (anterior and middle deltoid, upper trapezius) and upper limb kinematics (elbow, shoulder, sternoclavicular) were measured using surface EMG and inertial sensors. Results showed that the dynamic arm support significantly reduced perceived exertion during the tasks and limited the development of muscular fatigue of the anterior and middle deltoid as demonstrated by EMG signal mean epoch amplitudes and median frequency of the EMG power spectrum. The dynamic arm support also prevented a decrease in shoulder elevation and an increase in total shoulder joint excursion during static and dynamic task, respectively. These results denote the potential benefits of dynamic arm supports in work environments. Further studies should focus on their efficacy, acceptability and implementability in work settings.
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De Bock S, Rossini M, Lefeber D, Rodriguez-Guerrero C, Geeroms J, Meeusen R, De Pauw K. An Occupational Shoulder Exoskeleton Reduces Muscle Activity and Fatigue During Overhead Work. IEEE Trans Biomed Eng 2022; 69:3008-3020. [PMID: 35290183 DOI: 10.1109/tbme.2022.3159094] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Objective. This paper assesses the effect of a passive shoulder exoskeleton prototype, Exo4Work, on muscle activity, muscle fatigue and subjective experience during simulated occupational overhead and non-overhead work. Methods. Twenty-two healthy males performed six simulated industrial tasks with and without Exo4Work exoskeleton in a randomized counterbalanced cross-over design. During these tasks electromyography, heart rate, metabolic cost, subjective parameters and performance parameters were acquired. The effect of the exoskeleton and the body side on these parameters was investigated. Results. Anterior deltoid activity and fatigue reduced up to 16% and 41%, respectively, during isometric overhead work, and minimized hindrance of the device during non-overhead tasks. Wearing the exoskeleton increased feelings of frustration and increased discomfort in the areas where the exoskeleton and the body interfaced. The assistive effect of the exoskeleton was less prominent during dynamic tasks. Conclusion. This exoskeleton may reduce muscle activity and delay development of muscle fatigue in an overhead working scenario. For dynamic applications, the exoskeleton's assistive profile, which mimics the gravitational torque of the arm, is potentially sub-optimal. Significance. This evaluation paper is the first to report reduced muscle fatigue and activity when working with an occupational shoulder exoskeleton providing one third of the gravitational torque of the arm during overhead work. These results stress the potential of occupational shoulder exoskeletons in overhead working situations and may direct towards longitudinal field experiments. Additionally, this experiment may stimulate future work to further investigate the effect of different assistive profiles.
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Tse DHT, Kwok WY, So BCL. Investigation of Underwater Shoulder Muscle Activity during Manikin-Carrying in Young Elite Lifesaving Athletes. SENSORS (BASEL, SWITZERLAND) 2022; 22:s22062143. [PMID: 35336316 PMCID: PMC8948697 DOI: 10.3390/s22062143] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 02/17/2022] [Accepted: 03/08/2022] [Indexed: 05/17/2023]
Abstract
Manikin carrying is a lifesaving sports technique, in which athletes stroke with one arm and carry a manikin of 60 kg with the other arm as they swim. Stabilizing the manikin exerts great demand on the shoulder muscles of the carrying arm; thus, this study aimed to investigate the muscle activation of the carrying shoulder and the possible factors associated with it. This was a cross-sectional study, in which 20 young elite lifesaving athletes were recruited from the Hong Kong Lifesaving Society. The muscle activity of the posterior deltoid (PD), teres major (TM), and middle trapezius (MT) were recorded with wireless surface electromyography (sEMG) during the performance of 25-m manikin carrying in a swimming pool. The 25-m manikin-carrying was divided into and analyzed in 3 phases: initial, middle, and end phase. The initial phase was defined as the period from the athlete's first swimming stroke to the end of the third stroke; the middle phase was defined as the period between the initial and the end phase; and the end phase was defined as the period from the last third stroke to the last stroke at the 25-m finishing line. The first web space and grip strength were measured. The speed and number of inhalations were calculated. PD showed muscle activity of 55.73% of maximal voluntary isometric contraction (MVIC) in the initial phase and 40.21% MVIC in middle phase. TM showed a muscle activity of 65.26% MVIC in the initial phase and 64.35% MVIC in the middle phase. MT showed 84.54% MVIC in the initial phase and 68.54% MVIC in the middle phase. Young elite athletes showed significant use of PD, TM, and MT during manikin-carrying. The muscle activity levels correlated with the first web space, grip strength, speed, and number of inhalations of the athletes.
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Stefanou T, Guiraud D, Fattal C, Azevedo-Coste C, Fonseca L. Frequency-Domain sEMG Classification Using a Single Sensor. SENSORS (BASEL, SWITZERLAND) 2022; 22:s22051939. [PMID: 35271086 PMCID: PMC8914710 DOI: 10.3390/s22051939] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/21/2022] [Accepted: 02/24/2022] [Indexed: 06/02/2023]
Abstract
Working towards the development of robust motion recognition systems for assistive technology control, the widespread approach has been to use a plethora of, often times, multi-modal sensors. In this paper, we develop single-sensor motion recognition systems. Utilising the peripheral nature of surface electromyography (sEMG) data acquisition, we optimise the information extracted from sEMG sensors. This allows the reduction in sEMG sensors or provision of contingencies in a system with redundancies. In particular, we process the sEMG readings captured at the trapezius descendens and platysma muscles. We demonstrate that sEMG readings captured at one muscle contain distinct information on movements or contractions of other agonists. We used the trapezius and platysma muscle sEMG data captured in able-bodied participants and participants with tetraplegia to classify shoulder movements and platysma contractions using white-box supervised learning algorithms. Using the trapezius sensor, shoulder raise is classified with an accuracy of 99%. Implementing subject-specific multi-class classification, shoulder raise, shoulder forward and shoulder backward are classified with a 94% accuracy amongst object raise and shoulder raise-and-hold data in able bodied adults. A three-way classification of the platysma sensor data captured with participants with tetraplegia achieves a 95% accuracy on platysma contraction and shoulder raise detection.
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Baeyens JP, Flix Díez L, Serrien B, Goossens M, Veekmans K, Baeyens R, Daems W, Cattrysse E, Hohenauer E, Clijsen R. Effects of Rehearsal Time and Repertoire Speed on Upper Trapezius Activity in Conservatory Piano Students. MEDICAL PROBLEMS OF PERFORMING ARTISTS 2022; 37:1-12. [PMID: 35234800 DOI: 10.21091/mppa.2022.1001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 11/27/2021] [Indexed: 06/14/2023]
Abstract
BACKGROUND Repetitive piano play may overload neck and shoulder muscles and tendons, leading to playing-related musculoskeletal disorders (PRMDs). METHODS In this pilot study (EMG data of the extensor carpi radialis have been published separately), surface electromyography (sEMG) activity of the upper trapezius (UT) was captured in 10 conservatory piano students while playing a fast and a slow music score selected from the individual's repertoire, each 3 minutes long. Measurements were made at baseline and again after 2 hrs and 4 hrs of rehearsal time of the piano études. The amplitude of the sEMG signal was processed by a smoothing algorithm, and the frequency component with a non-orthogonal wavelets procedure. Amplitude of the sEMG was expressed in percent of maximal voluntary contraction (%MVC) at baseline, and the frequency component using median frequency based on the frequency band powers. Statistical analysis encompassed repeated measures ANOVAs for the amplitude and frequency components of the sEMG signal (set at 5%). The students also rated the intensity of rehearsals using a visual analog scale (VAS). RESULTS The median values for the %MVC presented a global mean for the left trapezius of 5.86 (CI90% 4.71, 6.97) and 5.83 for the right trapezius (CI90% 4.64, 7.05). The rehearsals at moderate intensity increased the amplitude of %MVC of the upper trapezius by around 50% and decreased the median frequency. CONCLUSIONS Playing faster presented higher magnitudes of activity of the upper trapezius. The decrease in the median frequency in response to long rehearsals may be a sign of muscle fatigue.
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Cornette P, Jaabar IL, Dupres V, Werthel JD, Berenbaum F, Houard X, Landoulsi J, Nourissat G. Impact of Collagen Crosslinking on Dislocated Human Shoulder Capsules-Effect on Structural and Mechanical Properties. Int J Mol Sci 2022; 23:ijms23042297. [PMID: 35216412 PMCID: PMC8877509 DOI: 10.3390/ijms23042297] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 02/14/2022] [Accepted: 02/15/2022] [Indexed: 02/04/2023] Open
Abstract
Classical treatments of shoulder instability are associated with recurrence. To determine whether the modification of the capsule properties may be an alternative procedure, the effect of crosslinking treatment on the structure and mechanical properties of diseased human shoulder capsules was investigated. Joint capsules harvested from patients during shoulder surgery (n = 5) were treated or not with UV and/or riboflavin (0.1%, 1.0% and 2.5%). The structure and the mechanical properties of the capsules were determined by atomic force microscopy. The effect of treatments on cell death was investigated. Collagen fibrils were well-aligned and adjacent to each other with a D-periodicity of 66.9 ± 3.2 nm and a diameter of 71.8 ± 15.4 nm in control untreated capsules. No effect of treatments was observed on the organization of the collagen fibrils nor on their intrinsic characteristics, including D-periodicity or their mean diameter. The treatments also did not induce cell death. In contrast, UV + 2.5% riboflavin induced capsule stiffness, as revealed by the increased Young's modulus values (p < 0.0001 for each patient). Our results showed that the crosslinking procedure changed the biomechanics of diseased capsules, while keeping their structural organisation unchanged at the single fibril level. The UV/riboflavin crosslinking procedure may be a promising way to preserve the functions of collagen-based tissues and tune their elasticity for clinically relevant treatments.
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Zhao J, Li Z. Recognition of Volleyball Player's Arm Motion Trajectory and Muscle Injury Mechanism Analysis Based upon Neural Network Model. JOURNAL OF HEALTHCARE ENGINEERING 2022; 2022:8114740. [PMID: 35222893 PMCID: PMC8872696 DOI: 10.1155/2022/8114740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/20/2022] [Accepted: 01/21/2022] [Indexed: 11/18/2022]
Abstract
At present, in sports training for volleyball, it still mainly depends on the personal experience of the coach. Training costs are high, and the quality is difficult to maintain stable. Even with the introduction of training assistance software, it is often necessary to manually enter complex data, and the research samples are mostly single individuals. Serving is one of the basic and important technical movements of volleyball, and its standardization is of great significance to the stable performance of the scene. This article proposes an analysis of the volleyball player's arm trajectory based on the background of human posture recognition and analysis, based on the neural network model. The changes in the angles of the shoulders, elbows, and wrist when serving the ball reflect the different trajectories of the arm. Experiments show that the height of the throwing arm from the ground accounts for 98% of the height. The horizontal angle of the throwing arm at the moment the ball leaves the hand is positively correlated with the throwing time and height, and the reasonable trajectory has an impact on the stability of the throwing ball. The closer the trajectory of the tossing arm is to the vertical, the more stable the tossing is.
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Silva ER, Maffulli N, Migliorini F, Santos GM, de Menezes FS, Okubo R. Function, strength, and muscle activation of the shoulder complex in Crossfit practitioners with and without pain: a cross-sectional observational study. J Orthop Surg Res 2022; 17:24. [PMID: 35033136 PMCID: PMC8760714 DOI: 10.1186/s13018-022-02915-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Accepted: 01/03/2022] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The shoulder joint is the most commonly injured joint in CrossFit practitioners, because of the high intensity and loads associated with this sport. Despite the large number of clinical cases, there is a shortage of studies that investigate influence of biomechanical aspects of upper limbs' injuries on CrossFit practitioners. This study hypothesized that there would be a difference in function, strength, and muscle activation between Crossfit practitioners with and without shoulder pain. METHODS We divided 79 Crossfit practitioners into two groups according to whether they reported pain (n = 29) or no pain (n = 50) in the shoulder during Crossfit training. Muscle function, strength, and activation were assessed using the Disability Arm, Shoulder and Hand function questionnaire, Upper Quarter Y Balance Test and Closed Kinetic Chain Upper Extremity Stability Test shoulder tests, isometric muscle strength assessment by manual dynamometry and muscle activation by surface electromyography and pain report. RESULTS The function based on questionnaire was associated with pain (p = 0.004). We observed a statistically significant difference between the two groups only in the surface electromyography activity of the lower trapezius, and in the variables of shoulder pain and function (p = 0.038). CONCLUSION Crossfit practitioners with shoulder pain occurring during training showed good function and stability of the shoulder joint, but there was a reduction in the activation of stabilizing muscles, especially the lower trapezius. Trial registration Registro Brasileiro de Ensaios Clinico (Brasilian National Registry) with the ID: RBR-2gycyv.
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Gunaydin OE, Ertekin E, Gunaydin G. Four weeks of exercise regimen for sedentary workers with rounded shoulder posture: a randomized controlled study. SAO PAULO MED J 2022; 141:e2022257. [PMID: 36102464 PMCID: PMC10065112 DOI: 10.1590/1516-3180.2022.0257.r1.06072022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Accepted: 07/06/2022] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Rounded shoulder (RS) posture causes neck and shoulder pathologies. Mechanical correction taping (MCT) is often incorporated into postural corrective therapies; however, its effects on muscle stiffness are unclear. OBJECTIVE We investigated the effect of MCT with different tape fabrics, along with exercise, on upper trapezius and pectoralis minor muscle stiffness and the posture of sedentary workers. DESIGN AND SETTING A randomized controlled study was performed at Aydın Adnan Menderes University, Aydın, Turkey. METHODS The study included 39 workers with RS posture. Two intervention groups (performance tape: PT and classic tape: CT) were taped twice a week and administered a home exercise program for 4 weeks. The control (C) group performed only home exercises. RS was measured using an acromion-testing table (AT), stiffness using shear wave elastography ultrasound, and shoulder angle (SA) using a smartphone application at baseline and 4 weeks. Time and group interactions were determined using 3 × 2 mixed analysis of variance. RESULTS Intragroup analyses revealed a significant main effect of time on AT distance (η2 = 0.445) and SA (η2 = 0.325) in the PT and C groups (P < 0.05) and left upper trapezius stiffness (η2 = 0.287) in the CT and C groups (P < 0.05). In the post hoc analyses, no difference was noted between the groups from baseline to 4 weeks (P > 0.05). CONCLUSION Scapular MCT added to postural exercises did not show any difference between the intervention groups and controls in terms of muscle stiffness and posture in sedentary workers.
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Sarshari E, Boulanaache Y, Terrier A, Farron A, Mullhaupt P, Pioletti D. A Matlab toolbox for scaled-generic modeling of shoulder and elbow. Sci Rep 2021; 11:20806. [PMID: 34675343 PMCID: PMC8531442 DOI: 10.1038/s41598-021-99856-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 09/28/2021] [Indexed: 11/12/2022] Open
Abstract
There still remains a barrier ahead of widespread clinical applications of upper extremity musculoskeletal models. This study is a step toward lifting this barrier for a shoulder musculoskeletal model by enhancing its realism and facilitating its applications. To this end, two main improvements are considered. First, the elbow and the muscle groups spanning the elbow are included in the model. Second, scaling routines are developed that scale model's bone segment inertial properties, skeletal morphologies, and muscles architectures according to a specific subject. The model is also presented as a Matlab toolbox with a graphical user interface to exempt its users from further programming. We evaluated effects of anthropometric parameters, including subject's gender, height, weight, glenoid inclination, and degenerations of rotator cuff muscles on the glenohumeral joint reaction force (JRF) predictions. An arm abduction motion in the scapula plane is simulated while each of the parameters is independently varied. The results indeed illustrate the effect of anthropometric parameters and provide JRF predictions with less than 13% difference compared to in vivo studies. The developed Matlab toolbox could be populated with pre/post operative patients of total shoulder arthroplasty to answer clinical questions regarding treatments of glenohumeral joint osteoarthritis.
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Hamano N, Shitara H, Tajika T, Ichinose T, Sasaki T, Kuboi T, Shimoyama D, Kamiyama M, Miyamoto R, Endo F, Nakase K, Kobayashi T, Yamamoto A, Takagishi K, Chikuda H. Relationship between upper limb injuries and hip range of motion and strength in high school baseball pitchers. J Orthop Surg (Hong Kong) 2021; 29:23094990211003347. [PMID: 33779394 DOI: 10.1177/23094990211003347] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We aimed to examine the relationship between hip range of motion (ROM) and abduction strength and throwing-related shoulder/elbow injuries in high school baseball pitchers. The study included 135 baseball pitchers. We asked them to fill out a questionnaire at the checkups, that included the dominant arm and the years of baseball experience. To avoid a confirmation bias, the examiners were blinded to the participants' hand dominance. All players underwent physical function measurements, such as height, weight, shoulder and hip strength, and shoulder and hip ROM. Shoulder and elbow injury was defined as shoulder and elbow pain that the patient had been aware of in the past 3 years. The results of injured and non-injured pitchers were compared. Eighty-five pitchers had experienced a shoulder or elbow injury in the past 3 years. The shoulder ROM and strength in the injured and non-injured groups did not differ to a statistically significant extent. The hip external rotation ROM on the dominant side, the hip abduction strength on the non-dominant side, and the hip abduction strength on the dominant side were significantly lower in the injured group than in the non-injured group. The results may contribute to reducing the incidence of these injuries.
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Dupuis F, Sole G, Wassinger C, Bielmann M, Bouyer LJ, Roy JS. Fatigue, induced via repetitive upper-limb motor tasks, influences trunk and shoulder kinematics during an upper limb reaching task in a virtual reality environment. PLoS One 2021; 16:e0249403. [PMID: 33831037 PMCID: PMC8031876 DOI: 10.1371/journal.pone.0249403] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Accepted: 03/17/2021] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Efficient shoulder movement depends on the ability of central nervous system to integrate sensory information and to create an appropriate motor command. Various daily encountered factors can potentially compromise the execution of the command, such as fatigue. This study explored how fatigue influences shoulder movements during upper limb reaching. METHODS Forty healthy participants were randomly assigned to one of two groups: Control or Fatigue Group. All participants completed an upper limb reaching task at baseline and post-experimental, during which they reached four targets located at 90° of shoulder abduction, 90° external rotation at 90° abduction, 120° scaption, and 120° flexion in a virtual reality environment. Following the baseline phase, the Fatigue Group completed a shoulder fatigue protocol, while Controls took a 10-minute break. Thereafter, the reaching task was repeated. Upper limb kinematic (joint angles and excursions) and spatiotemporal (speed and accuracy) data were collected during the reaching task. Electromyographic activity of the anterior and middle deltoids were also collected to characterize fatigue. Two-way repeated-measures ANOVA were performed to determine the effects of Time, Group and of the interaction between these factors. RESULTS The Fatigue group showed decreased mean median power frequency and increased electromyographic amplitudes of the anterior deltoid (p < 0.05) following the fatigue protocol. Less glenohumeral elevation, increased trunk flexion and rotation and sternoclavicular elevation were also observed in the Fatigue group (Group x Time interaction, p < 0.05). The Control group improved their movement speed and accuracy in post-experimental phase, while the Fatigue group showed a decrease of movement speed and no accuracy improvement (Group x Time interaction, p < 0.05). CONCLUSION In a fatigued state, changes in movement strategy were observed during the reaching task, including increased trunk and sternoclavicular movements and less glenohumeral movement. Performance was altered as shown by the lack of accuracy improvement over time and a decrease in movement speed in the Fatigue group.
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