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Varrecchia T, Chini G, Tarbouriech S, Navarro B, Cherubini A, Draicchio F, Ranavolo A. The assistance of BAZAR robot promotes improved upper limb motor coordination in workers performing an actual use-case manual material handling. ERGONOMICS 2023; 66:1950-1967. [PMID: 36688620 DOI: 10.1080/00140139.2023.2172213] [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: 09/19/2022] [Accepted: 01/14/2023] [Indexed: 06/17/2023]
Abstract
This study aims at evaluating upper limb muscle coordination and activation in workers performing an actual use-case manual material handling (MMH). The study relies on the comparison of the workers' muscular activity while they perform the task, with and without the help of a dual-arm cobot (BAZAR). Eleven participants performed the task and the flexors and extensors muscles of the shoulder, elbow, wrist, and trunk joints were recorded using bipolar electromyography. The results showed that, when the particular MMH was carried out with BAZAR, both upper limb and trunk muscular co-activation and activation were decreased. Therefore, technologies that enable human-robot collaboration (HRC), which share a workspace with employees, relieve employees of external loads and enhance the effectiveness and calibre of task completion. Additionally, these technologies improve the worker's coordination, lessen the physical effort required to interact with the robot, and have a favourable impact on his or her physiological motor strategy. Practitioner summary: Upper limb and trunk muscle co-activation and activation is reduced when a specific manual material handling was performed with a cobot than without it. By improving coordination, reducing physical effort, and changing motor strategy, cobots could be proposed as an ergonomic intervention to lower workers' biomechanical risk in industry.
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Affiliation(s)
- Tiwana Varrecchia
- Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Rome, Italy
| | - Giorgia Chini
- Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Rome, Italy
| | | | | | | | - Francesco Draicchio
- Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Rome, Italy
| | - Alberto Ranavolo
- Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, INAIL, Rome, Italy
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Renda E, Lamanuzzi S, Dal Maso F, Côté JN. The effects of hand dominance, fatigue, and sex on muscle activation during a repetitive overhead fatiguing task. Hum Mov Sci 2023; 92:103149. [PMID: 37741198 DOI: 10.1016/j.humov.2023.103149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 08/08/2023] [Accepted: 09/15/2023] [Indexed: 09/25/2023]
Abstract
Previous studies have shown that the dominant arm is generally stronger and more resistant to fatigue. However, whether there are side differences in shoulder muscle activation during a fatiguing upper limb task, and whether this varies according to sex, is unknown. Thirty right-handed adults (15 females) were recruited to complete two sessions of an overhead repetitive fatiguing task (shoulder flexion between 90 and 135° at 1 Hz), performed in two separate sessions with their dominant arm (DA) and non-dominant arm (NDA) until exhaustion. Electromyographic (EMG) data was collected from 11 shoulder muscles of the moving arm, and their activation amplitude (RMS) and activation variability (SD) were assessed. Results show that time to exhaustion was not affected by arm or by sex. There were some main arm effects on EMG activity amplitude, with higher activity on the DA's pectoralis major (p < 0.001), and on the NDA's middle (p = 0.009) and posterior deltoid (p = 0.001) and infraspinatus (p < 0.001). The pectoralis major was affected by arm and fatigue mostly in males. Their DA's pectoralis major activity amplitude was higher, and the amplitude variability was lower, compared to the NDA, with both parameters showing fatigue-dependent decreases at the NDA only (arm x sex x fatigue: RMS: p = 0.007; SD: p = 0.001). As for females, the DA variability of their lower trapezius was smaller, and that of their subscapularis was higher, compared to the NDA (sex x arm, p = 0.028, p = 0.05). There was also more EMG variability on the supraspinatus' dominant side, and on the posterior deltoid and infraspinatus ND side. Results show an overhead shoulder flexion task dependency on pectoralis major control in males, and on lower trapezius and shoulder girdle stabilizers in females, which could be related to both sex- and gender-based factors. This knowledge can help identify side-specific injury risk factors due to overhead work in males and females, and help determine the appropriateness of implementing sex-specific workplace protocols, including alternating arms as fatigue compensatory and recovery strategies.
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Affiliation(s)
- Erika Renda
- Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec H2W 1S4, Canada; Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, Quebec H7V 1R2, Canada.
| | - Samuel Lamanuzzi
- Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec H2W 1S4, Canada; Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, Quebec H7V 1R2, Canada
| | - Fabien Dal Maso
- School of Kinesiology and Physical Education, University of Montreal, Montreal, Quebec H3T 1J4, Canada
| | - Julie N Côté
- Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec H2W 1S4, Canada; Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, Quebec H7V 1R2, Canada
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Cherubini A, Navarro B, Passama R, Tarbouriech S, Elprama SA, Jacobs A, Niehaus S, Wischniewski S, Tönis FJ, Siahaya PL, Chini G, Varrecchia T, Ranavolo A. Interdisciplinary evaluation of a robot physically collaborating with workers. PLoS One 2023; 18:e0291410. [PMID: 37819889 PMCID: PMC10566690 DOI: 10.1371/journal.pone.0291410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 08/29/2023] [Indexed: 10/13/2023] Open
Abstract
Collaborative Robots-CoBots-are emerging as a promising technological aid for workers. To date, most CoBots merely share their workspace or collaborate without contact, with their human partners. We claim that robots would be much more beneficial if they physically collaborated with the worker, on high payload tasks. To move high payloads, while remaining safe, the robot should use two or more lightweight arms. In this work, we address the following question: to what extent can robots help workers in physical human-robot collaboration tasks? To find an answer, we have gathered an interdisciplinary group, spanning from an industrial end user to cognitive ergonomists, and including biomechanicians and roboticists. We drew inspiration from an industrial process realized repetitively by workers of the SME HANKAMP (Netherlands). Eleven participants replicated the process, without and with the help of a robot. During the task, we monitored the participants' biomechanical activity. After the task, the participants completed a survey with usability and acceptability measures; seven workers of the SME completed the same survey. The results of our research are the following. First, by applying-for the first time in collaborative robotics-Potvin's method, we show that the robot substantially reduces the participants' muscular effort. Second: we design and present an unprecedented method for measuring the robot reliability and reproducibility in collaborative scenarios. Third: by correlating the worker's effort with the power measured by the robot, we show that the two agents act in energetic synergy. Fourth: the participant's increasing level of experience with robots shifts his/her focus from the robot's overall functionality towards finer expectations. Last but not least: workers and participants are willing to work with the robot and think it is useful.
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Affiliation(s)
| | | | | | | | | | - An Jacobs
- IMEC-SMIT-Vrije Universiteit Brussel, Brussels, Belgium
| | - Susanne Niehaus
- Federal Institute of Occupational Safety and Health, Dortmund, Germany
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Hu Z, Zhang Y, Dong T, Dong M, Kim S, Kim Y. Gender Differences in Neuromuscular Control during the Preparation Phase of Single-Leg Landing Task in Badminton. J Clin Med 2023; 12:jcm12093296. [PMID: 37176736 PMCID: PMC10179252 DOI: 10.3390/jcm12093296] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 05/01/2023] [Accepted: 05/04/2023] [Indexed: 05/15/2023] Open
Abstract
BACKGROUND Studies on the biomechanical mechanisms of an anterior cruciate ligament (ACL) injury have been extensively studied, but studies on the neuromuscular control-related risk factors for an ACL injury in specific maneuvers have not been reported for badminton players. STUDY DESIGN Controlled laboratory study. METHODS Sixteen badminton players (8 male, 8 female) performed a single-leg badminton ball landing task, and lower limb muscle activity, kinematic data, and ground reaction force were measured during this procedure using marker-based movement analysis, force plates, and electromyography (EMG). Gender differences in the lower limb kinematic data, mean values of normalized lower limb muscle activation (MVC%), and co-contraction values during the landing preparation phase (100 ms before initial contact) were analyzed using MANOVA. RESULTS In the badminton landing task, the knee valgus angle was greater in females than in males (6.27 ± 2.75 vs. 1.72 ± 3.20) in the pre-landing preparation position. Compared to male badminton players, females exhibited greater gluteus maximus (44.92 ± 18.00 vs. 20.34 ± 11.64), rectus femoris (41.56 ± 9.84 vs. 26.14 ± 10.46), and medial gastrocnemius (37.39 ± 17.31 vs. 19.11 ± 11.17) lateral gastrocnemius (36.86 ± 17.82 vs. 13.59 ± 2.71) muscle activity (MVC%). CONCLUSION Female badminton players exhibit neuromuscular control strategies that may be inadequate for ACL protection and may be a potential risk factor for a high incidence of ACL injury In the future, when devising injury prevention plans for female badminton players, optimizing neuromuscular control during the pre-landing phase can be targeted.
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Affiliation(s)
- Zhe Hu
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Yanan Zhang
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Tengfei Dong
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Maolin Dong
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Sukwon Kim
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Youngsuk Kim
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
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Hu Z, Kim Y, Zhang Y, Zhang Y, Li J, Tang X, Sohn J, Kim S. Correlation of Lower Limb Muscle Activity with Knee Joint Kinematics and Kinetics during Badminton Landing Tasks. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph192416587. [PMID: 36554467 PMCID: PMC9778979 DOI: 10.3390/ijerph192416587] [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] [Received: 10/26/2022] [Revised: 11/30/2022] [Accepted: 12/06/2022] [Indexed: 05/27/2023]
Abstract
A study on a single-leg landing task after an overhead stroke in badminton suggests that poor knee biomechanical indicators may be a risk factor for anterior cruciate ligament (ACL) injury. A preventive program targeting neuromuscular control strategies is said to alter the biomechanics of the knee joint and have a beneficial effect on reducing ACL injury. However, the relationship between muscle activity around the knee joint and knee biomechanical risk factors in the badminton landing task is unclear. The purpose of this study was to investigate the relationship between this movement pattern of muscle activity and knee kinematics and kinetics. This experiment analyzed knee muscle activity and biomechanical information in a sample of 34 badminton players (17 male, 17 female) during a badminton landing task. We assessed the relationship between the rectus femoris (RF), medial hamstring (MHAM), lateral hamstring (LHAM), medial gastrocnemius (MGAS), lateral gastrocnemius (LGAS), medial and lateral hamstring to quadriceps co-contraction ratio (MH/Q and LH/Q) with the knee flexion angle, valgus angle, extension moment, valgus moment, and proximal tibial anterior shear force. A moderate negative correlation was found between the peak knee flexion angle and electromyography (EMG) activity in LGAS (r = 0.47, p = 0.0046, R2 = 0.23, 95% CI: 0.16 to 0.70). Peak proximal tibial shear force showed strong and positive correlations with RF EMG activity (r = 0.52, p = 0.0016, R2 = 0.27, 95% CI: 0.22 to 0.73) and strong and negative correlations with MH/Q (r = 0.50, p = 0.0023, R2 = 0.25, 95% CI: 0.20 to 0.72). The knee extension moment showed moderate and positive correlations with RF EMG activity (r = 0.48, p = 0.0042, R2 = 0.23, 95% CI: 0.17 to 0.70) and strong and negative correlations with MH/Q (r = 0.57, p = 0.0004, R2 = 0.33, 95% CI: 0.29 to 0.76). The peak knee valgus moment showed strong and positive correlations with LH/Q (r = 0.55, p = 0.0007, R2 = 0.31, 95% CI: 0.26 to 0.75). Our findings suggest that there is a correlation between lower extremity muscle activity and knee kinematics and kinetics during the single-leg landing task in badminton; therefore, lower extremity muscle activity should be considered when developing rehabilitation or injury prevention programs.
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Affiliation(s)
- Zhe Hu
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Youngsuk Kim
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Yanan Zhang
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Yuxi Zhang
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Jiaying Li
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Xuan Tang
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Jeehoon Sohn
- Department of Physical Education, Jeonju University, Jeonju 55069, Republic of Korea
| | - Sukwon Kim
- Department of Physical Education, Jeonbuk National University, Jeonju 54896, Republic of Korea
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Shankar S, Naveenkumar R, Nithyaprakash R, Narmatha S, Sai RR, Nandhakumar M. Impact of digital boards on hand and neck muscle activity during online teaching process. EDUCATION AND INFORMATION TECHNOLOGIES 2022; 27:5627-5640. [PMID: 35035258 PMCID: PMC8747848 DOI: 10.1007/s10639-021-10854-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
Academicians across the globe due to Covid 19 shifted to online teaching as a mainstream method by replacing the chalk and talk method. The main objective of this study is to find the impact of different sizes of digital boards used for online teaching on muscle activity and muscle fatigue, and then results are compared with conventional writing. Initially, a questionnaire survey is conducted among 100 college professors about the issue they faced while using online teaching methods. Experimental analysis are then conducted using electromyography sensor (sEMG) among ten college professors and their muscle activity on the dominant hand and neck while writing on two commercially available digital boards namely Type 1 (small writing area) and Type 2 (large writing area). Four muscles namely Flexor carpi radialis, Extensor carpi radialis, Biceps brachii, and Sternocleidomastoid (SCM) are chosen for the study. The results are then compared with muscle activity while writing on conventional A4 sheets. Normalized root mean square (RMS) is used to assess the muscle activity and the trend line of MPF value is utilized to assess the muscle fatigue. The results show that SCM muscle has more muscle activation compared to other selected muscles followed by flexor carpi radialis. Subjective analysis is carried out using the Borg scale, which has reported that Type 2 digital board having larger working area was preferred by the participants as it reduces muscle fatigue.
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Affiliation(s)
- S. Shankar
- Department of Mechatronics Engineering, Kongu Engineering College, Erode, Tamil Nadu 638060 India
| | - R. Naveenkumar
- Department of Mechanical Engineering, Kongu Engineering College, Erode, Tamil Nadu 638060 India
| | - R. Nithyaprakash
- Department of Mechatronics Engineering, Kongu Engineering College, Erode, Tamil Nadu 638060 India
| | - S. Narmatha
- Department of Mechatronics Engineering, Kongu Engineering College, Erode, Tamil Nadu 638060 India
| | - R. Rithic Sai
- Department of Mechatronics Engineering, Kongu Engineering College, Erode, Tamil Nadu 638060 India
| | - M. Nandhakumar
- Department of Mechatronics Engineering, Kongu Engineering College, Erode, Tamil Nadu 638060 India
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7
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Colamarino E, de Seta V, Masciullo M, Cincotti F, Mattia D, Pichiorri F, Toppi J. Corticomuscular and Intermuscular Coupling in Simple Hand Movements to Enable a Hybrid Brain-Computer Interface. Int J Neural Syst 2021; 31:2150052. [PMID: 34590990 DOI: 10.1142/s0129065721500520] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Hybrid Brain-Computer Interfaces (BCIs) for upper limb rehabilitation after stroke should enable the reinforcement of "more normal" brain and muscular activity. Here, we propose the combination of corticomuscular coherence (CMC) and intermuscular coherence (IMC) as control features for a novel hybrid BCI for rehabilitation purposes. Multiple electroencephalographic (EEG) signals and surface electromyography (EMG) from 5 muscles per side were collected in 20 healthy participants performing finger extension (Ext) and grasping (Grasp) with both dominant and non-dominant hand. Grand average of CMC and IMC patterns showed a bilateral sensorimotor area as well as multiple muscles involvement. CMC and IMC values were used as features to classify each task versus rest and Ext versus Grasp. We demonstrated that a combination of CMC and IMC features allows for classification of both movements versus rest with better performance (Area Under the receiver operating characteristic Curve, AUC) for the Ext movement (0.97) with respect to Grasp (0.88). Classification of Ext versus Grasp also showed high performances (0.99). All in all, these preliminary findings indicate that the combination of CMC and IMC could provide for a comprehensive framework for simple hand movements to eventually be employed in a hybrid BCI system for post-stroke rehabilitation.
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Affiliation(s)
- Emma Colamarino
- Department of Computer, Control and Management Engineering, Sapienza University of Rome, Via Ariosto 25, Rome 00185, Italy.,Fondazione Santa Lucia IRCCS, Via Ardeatina 306-354, Rome 00179, Italy
| | - Valeria de Seta
- Department of Computer, Control and Management Engineering, Sapienza University of Rome, Via Ariosto 25, Rome 00185, Italy.,Fondazione Santa Lucia IRCCS, Via Ardeatina 306-354, Rome 00179, Italy
| | | | - Febo Cincotti
- Department of Computer, Control and Management Engineering, Sapienza University of Rome, Via Ariosto 25, Rome 00185, Italy.,Fondazione Santa Lucia IRCCS, Via Ardeatina 306-354, Rome 00179, Italy
| | - Donatella Mattia
- Fondazione Santa Lucia IRCCS, Via Ardeatina 306-354, Rome 00179, Italy
| | | | - Jlenia Toppi
- Department of Computer, Control and Management Engineering, Sapienza University of Rome, Via Ariosto 25, Rome 00185, Italy.,Fondazione Santa Lucia IRCCS, Via Ardeatina 306-354, Rome 00179, Italy
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Radecka A, Knyszyńska A, Łuczak J, Lubkowska A. Adaptive changes in muscle activity after cryotherapy treatment: Potential mechanism for improvement the functional state in patients with multiple sclerosis. NeuroRehabilitation 2021; 48:119-131. [PMID: 33386821 DOI: 10.3233/nre-201535] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND The available literature lacks data about the influence of whole body cryotherapy (WBC) on muscle activity in patients with sclerosis multiplex (MS). OBJECTIVE Assessment of the influence of the 20 WBC series on the surface electromyography (sEMG) signal and the relationship between it and the functional state in patients with MS. METHODS The study group was 114 of MS patients (aged 45.24±11.88yr.,) which 74 of them received 20 of WBC. An assessment was made of: the hand grip (HGS), Timed 25-Foot Walk, Fatigue Severity Scale, sEMG signal from the dominant limb. RESULTS After a series of 20 WBC: in the rest electromyograms, an increase of extensor carpi radialis (ECR) and a decrease of flexor carpi radialis (FCR) amplitude were demonstrated (non-normalized signal ECR p = 0.0001); significant differences in sEMG rest signals between ECR and FCR have decreased; for voluntary contraction in both assessed antagonistic muscle amplitude was significantly decreased (p = 0.0005; p = 0.0316, p = 0.0185); an increase of HGS (p < 0.001); gait improvement (p = 0.001); decrease fatigue (p = 0.024). No significant changes were observed in the control group. CONCLUSIONS Series of 20 WBC improves the functional state and reduces fatigue in patients with MS, which may be due to adaptive changes in bioelectrical muscle activity.
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Affiliation(s)
- Aleksandra Radecka
- Department of Functional Diagnostics and Physical Medicine, Pomeranian Medical University in Szczecin, Szczecin, Poland
| | - Anna Knyszyńska
- Department of Functional Diagnostics and Physical Medicine, Pomeranian Medical University in Szczecin, Szczecin, Poland
| | - Joanna Łuczak
- College of Engineering and Health in Warsaw, Faculty of Health Sciences, Warsaw, Poland.,Department of Cardiological Rehabilitation, Central Clinical Hospital of the Ministry of Internal Affairs and Administration in Warsaw, Warsaw, Poland
| | - Anna Lubkowska
- Department of Functional Diagnostics and Physical Medicine, Pomeranian Medical University in Szczecin, Szczecin, Poland
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9
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Andrade DC, Manzo O, Beltrán AR, Álvarez C, Del Rio R, Toledo C, Moran J, Ramirez-Campillo R. Kinematic and Neuromuscular Measures of Intensity During Plyometric Jumps. J Strength Cond Res 2021; 34:3395-3402. [PMID: 28820857 DOI: 10.1519/jsc.0000000000002143] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Andrade, DC, Manzo, O, Beltrán, AR, Álvarez, C, Del Rio, R, Toledo, C, Moran, J, and Ramirez-Campillo, R. Kinematic and neuromuscular measures of intensity during plyometric jumps. J Strength Cond Res 34(12): 3395-3402, 2020-The aim of this study was to assess jumping performance and neuromuscular activity in lower limb muscles after drop jumps (DJs) from different drop heights (intensity) and during continuous jumping (fatigue), using markers such as reactive strength, jump height, mechanical power and surface electromyography (sEMG). The eccentric (EC) and concentric (CON) sEMG from the medial gastrocnemius (MG), biceps femoris (BF), and rectus (R) muscles were assessed during all tests. In a cross-sectional, randomized study, 11 volleyball players (age 24.4 ± 3.2 years) completed 20-90-cm (DJ20 to DJ90) DJs and a 60-second continuous jump test. A 1-way analysis of variance test was used for comparisons, with Sidak post hoc. The α level was <0.05. Reactive strength was greater for DJ40 compared with DJ90 (p ≤ 0.05; effect size (ES): 1.27). In addition, jump height was greater for DJ40 and DJ60 compared with DJ20 (p ≤ 0.05; ES: 1.26 and 1.27, respectively). No clear pattern of neuromuscular activity appeared during DJ20 to DJ90: some muscles showed greater, lower, or no change with increasing heights for both agonist and antagonist muscles, as well as for EC and CON activity. Mechanical power, but not reactive strength, was reduced in the 60-second jump test (p ≤ 0.05; ES: 3.46). No changes were observed in sEMG for any muscle during the EC phase nor for the R muscle during the CON phase of the 60-second jump test. However, for both MG and BF, CON sEMG was reduced during the 60-second jump test (p ≤ 0.05; ES: 5.10 and 4.61, respectively). In conclusion, jumping performance and neuromuscular markers are sensitive to DJ height (intensity), although not in a clear dose-response fashion. In addition, markers such as mechanical power and sEMG are, especially sensitive to the effects of continuous jumping (fatigue). Therefore, increasing the drop height during DJ does not ensure a greater training intensity and a combination of different drop heights may be required to elicit adaptations.
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Affiliation(s)
- David Cristóbal Andrade
- Laboratory of Cardiorespiratory Control, Pontifical Catholic University of Chile, Santiago, Chile
| | - Oscar Manzo
- Education Department, Education Faculty, Universidad de Antofagasta, Antofagasta, Chile
| | - Ana Rosa Beltrán
- Education Department, Education Faculty, Universidad de Antofagasta, Antofagasta, Chile
| | - Cristian Álvarez
- Department of Physical Activity Sciences, Research Nucleus in Health, Physical Activity and Sport, Universidad de Los Lagos (University of Los Lagos), Osorno, Chile; and
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Pontifical Catholic University of Chile, Santiago, Chile
| | - Camilo Toledo
- Laboratory of Cardiorespiratory Control, Pontifical Catholic University of Chile, Santiago, Chile
| | - Jason Moran
- Center for Sports and Exercise Science, School of Biological Sciences, University of Essex, Colchester, United Kingdom
| | - Rodrigo Ramirez-Campillo
- Department of Physical Activity Sciences, Research Nucleus in Health, Physical Activity and Sport, Universidad de Los Lagos (University of Los Lagos), Osorno, Chile; and
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10
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Normalising surface EMG of ten upper-extremity muscles in handcycling: Manual resistance vs. sport-specific MVICs. J Electromyogr Kinesiol 2020; 51:102402. [PMID: 32092642 DOI: 10.1016/j.jelekin.2020.102402] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 01/28/2020] [Accepted: 02/07/2020] [Indexed: 11/20/2022] Open
Abstract
Muscular activity in terms of surface electromyography (sEMG) is usually normalised to maximal voluntary isometric contractions (MVICs). This study aims to compare two different MVIC-modes in handcycling and examine the effect of moving average window-size. Twelve able-bodied male competitive triathletes performed ten MVICs against manual resistance and four sport-specific trials against fixed cranks. sEMG of ten muscles [M. trapezius (TD); M. pectoralis major (PM); M. deltoideus, Pars clavicularis (DA); M. deltoideus, Pars spinalis (DP); M. biceps brachii (BB); M. triceps brachii (TB); forearm flexors (FC); forearm extensors (EC); M. latissimus dorsi (LD) and M. rectus abdominis (RA)] was recorded and filtered using moving average window-sizes of 150, 200, 250 and 300 ms. Sport-specific MVICs were higher compared to manual resistance for TB, DA, DP and LD, whereas FC, TD, BB and RA demonstrated lower values. PM and EC demonstrated no significant difference between MVIC-modes. Moving average window-size had no effect on MVIC outcomes. MVIC-mode should be taken into account when normalised sEMG data are illustrated in handcycling. Sport-specific MVICs seem to be suitable for some muscles (TB, DA, DP and LD), but should be augmented by MVICs against manual/mechanical resistance for FC, TD, BB and RA.
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Schäfer LU, Hayes M, Dekerle J. The magnitude of neuromuscular fatigue is not intensity dependent when cycling above critical power but relates to aerobic and anaerobic capacities. Exp Physiol 2018; 104:209-219. [PMID: 30468691 DOI: 10.1113/ep087273] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/22/2018] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Is the magnitude of neuromuscular fatigue dependent upon exercise intensity above critical power (CP) when W' (the curvature constant of the power-duration relationship) is depleted? What is the main finding and its importance? The magnitude of neuromuscular fatigue is the same after two bouts of supra-CP cycling (3 versus 12 min) when controlling for W' depletion but is larger for individuals of greater anaerobic capacity after the shorter bout and smaller for individuals of greater aerobic capacity after the longer exercise bout. These findings provide new insight into the mechanisms underpinning exercise above CP. ABSTRACT The aim of the present study was to test whether the development of neuromuscular fatigue within the severe-intensity domain could be linked to the depletion of the curvature constant (W') of the power-duration relationship. Twelve recreationally active men completed tests to determine peak oxygen consumption, critical power (CP) and W', followed by two randomly assigned constant-load supra-CP trials set to deplete W' fully in 3 (P-3) and 12 min (P-12). Pre- to postexercise changes in maximal voluntary contraction, potentiated quadriceps twitch force evoked by single (Qpot ) and paired high- (PS100) and low-frequency (PS10) stimulations and voluntary activation were determined. Cycling above CP reduced maximal voluntary contraction (P-3, -20 ± 10% versus P-12, -15 ± 7%), measures associated with peripheral fatigue (Qpot , -35 ± 13 versus -31 ± 14%; PS10, -38 ± 13 versus -37 ± 17%; PS100, -18 ± 9 versus -13 ± 8% for P-3 and P-12, respectively) and voluntary activation (P-3, -12 ± 3% versus P-12, -13 ± 3%; P < 0.05), with no significant difference between trials (P > 0.05). Changes in maximal voluntary contraction and evoked twitch forces were inversely correlated with CP and peak oxygen consumption after P-12, whereas W' was significantly correlated with changes in Qpot and PS10 after P-3 (P < 0.05). Therefore, the magnitude of neuromuscular fatigue does not depend on exercise intensity when W' is fully exhausted during severe-intensity exercise; nonetheless, exploration of inter-individual variations suggests that mechanisms underpinning exercise tolerance within this domain differ between short- and long-duration exercise.
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Affiliation(s)
- Lisa U Schäfer
- Fatigue and Exercise Laboratory, School of Sport and Service Management, University of Brighton, Eastbourne, UK
| | - Mark Hayes
- Fatigue and Exercise Laboratory, School of Sport and Service Management, University of Brighton, Eastbourne, UK
| | - Jeanne Dekerle
- Fatigue and Exercise Laboratory, School of Sport and Service Management, University of Brighton, Eastbourne, UK
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12
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Singla D, Hussain ME, Bhati P, Moiz JA, Ahmad I, Verma S, Ali K. Reliability of Electromyographic Assessment of Biceps Brachii and Triceps Brachii in Cricketers. J Chiropr Med 2018; 17:151-159. [PMID: 30228806 DOI: 10.1016/j.jcm.2018.04.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 03/28/2018] [Accepted: 04/02/2018] [Indexed: 01/22/2023] Open
Abstract
Objective The purpose of this study is to determine the intraexaminer and interexaminer reliability of electromyographic assessment of biceps brachii (BB) and triceps brachii (TB) muscles in cricketers. Methods Sixteen healthy male cricketers (ages 14-35 years) recruited from Jamia Millia Islamia, New Delhi, India were tested on 2 occasions that were held 1 week apart. On the first occasion, only examiner 1 performed the testing; on the second occasion, examiner 1, examiner 2, and examiner 3 all performed testing. While testing for surface electromyography (sEMG) activity of BB and TB muscles, participants were asked to produce maximal voluntary isometric contraction (MVIC), which was to be held for 5 seconds against the resistance provided by an examiner. Participants performed 3 MVICs per muscle per examiner, with a rest interval of 3 minutes between consecutive contractions. Intraclass correlation coefficient, standard error of measurement, and minimum detectable change were calculated to determine the reliability of repeated sEMG measurements. Results Nonsignificant differences were observed for the 2 trials completed by examiner 1 (paired t test) and testing done by all 3 examiners (repeated measures analysis of variance) at P < .05 for both BB and TB. Intraclass correlation coefficient values ranged from .84 to .86 for BB and .89 to .98 for TB. Standard error of measurement (minimum detectable change) was .052 (.144) mV and .041 (.114) mV for BB intraexaminer and interexaminer reliability testing, respectively, and .018 (.051) mV and .043 (.119) mV for TB intraexaminer and interexaminer reliability testing. Ninety-five percent of the mean differences between almost all of the repeated measurements were found to lie within the agreement intervals estimated by Bland-Altman plots. Conclusion This preliminary study suggests that sEMG is a reliable tool with excellent intraexaminer and interexaminer reliability for assessing the activity of BB and TB muscles in male cricketers. These findings suggest that sEMG can be used to assess MVIC activity of these muscles in clinical settings, as well as in research area.
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Affiliation(s)
- Deepika Singla
- Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Jamia Nagar, Okhla, Delhi, India
| | - Mohammad Ejaz Hussain
- Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Jamia Nagar, Okhla, Delhi, India
| | - Pooja Bhati
- Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Jamia Nagar, Okhla, Delhi, India
| | - Jamal Ali Moiz
- Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Jamia Nagar, Okhla, Delhi, India
| | - Irshad Ahmad
- Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Jamia Nagar, Okhla, Delhi, India
| | - Shalini Verma
- Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Jamia Nagar, Okhla, Delhi, India
| | - Kamran Ali
- Centre for Physiotherapy and Rehabilitation Sciences, Jamia Millia Islamia, Jamia Nagar, Okhla, Delhi, India
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Granzow RF, Schall MC, Smidt MF, Chen H, Fethke NB, Huangfu R. Characterizing exposure to physical risk factors among reforestation hand planters in the Southeastern United States. APPLIED ERGONOMICS 2018; 66:1-8. [PMID: 28958420 DOI: 10.1016/j.apergo.2017.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 05/18/2017] [Accepted: 07/21/2017] [Indexed: 05/27/2023]
Abstract
Low back and neck/shoulder pain are commonly reported among reforestation hand planters. While some studies have documented the intensive cardiovascular demands of hand planting, limited information is available regarding exposures to physical risk factors associated with the development of musculoskeletal disorders (MSDs) among hand planters. This study used surface electromyography (EMG) and inertial measurement units (IMUs) to characterize the muscle activation patterns, upper arm and trunk postures, movement velocities, and physical activity (PA) of fourteen Southeastern reforestation hand planters over one work shift. Results indicated that hand planters are exposed to physical risk factors such as extreme trunk postures (32.5% of time spent in ≥45° trunk flexion) and high effort muscle exertions (e.g., mean root-mean-square right upper trapezius amplitude of 54.1% reference voluntary exertion) that may place them at increased risk for developing MSDs. The findings indicate a need for continued field-based research among hand planters to identify and/or develop maximally effective interventions.
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Affiliation(s)
- Robert F Granzow
- Department of Industrial and Systems Engineering, Auburn University, 3301 Shelby Center for Engineering Technology, Auburn, AL 36849, USA.
| | - Mark C Schall
- Department of Industrial and Systems Engineering, Auburn University, 3301 Shelby Center for Engineering Technology, Auburn, AL 36849, USA.
| | - Mathew F Smidt
- School of Forestry and Wildlife Sciences, Auburn University, 3423 School of Forestry and Wildlife Sciences, Auburn, AL 36849, USA.
| | - Howard Chen
- Department of Occupational and Environmental Health, University of Iowa, UI Research Park #164 IREH, Iowa City, IA 52242, USA.
| | - Nathan B Fethke
- Department of Occupational and Environmental Health, University of Iowa, S347 CPHB, Iowa City, IA 52242, USA.
| | - Rong Huangfu
- Department of Industrial and Systems Engineering, Auburn University, 3301 Shelby Center for Engineering Technology, Auburn, AL 36849, USA.
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Balshaw TG, Fry A, Maden-Wilkinson TM, Kong PW, Folland JP. Reliability of quadriceps surface electromyography measurements is improved by two vs. single site recordings. Eur J Appl Physiol 2017; 117:1085-1094. [PMID: 28391392 PMCID: PMC5427161 DOI: 10.1007/s00421-017-3595-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 03/23/2017] [Indexed: 12/01/2022]
Abstract
Purpose The reliability of surface electromyography (sEMG) is typically modest even with rigorous methods, and therefore further improvements in sEMG reliability are desirable. This study compared the between-session reliability (both within participant absolute reliability and between-participant relative reliability) of sEMG amplitude from single vs. average of two distinct recording sites, for individual muscle (IM) and whole quadriceps (WQ) measures during voluntary and evoked contractions. Methods Healthy males (n = 20) performed unilateral isometric knee extension contractions: voluntary maximum and submaximum (60%), as well as evoked twitch contractions on two separate days. sEMG was recorded from two distinct sites on each superficial quadriceps muscle. Results Averaging two recording sites vs. using single site measures improved reliability for IM and WQ measurements during voluntary (16–26% reduction in within-participant coefficient of variation, CVW) and evoked contractions (40–56% reduction in CVW). Conclusions For sEMG measurements from large muscles, averaging the recording of two distinct sites is recommended as it improves within-participant reliability. This improved sensitivity has application to clinical and research measurement of sEMG amplitude.
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Affiliation(s)
- T G Balshaw
- School of Sport, Exercise, and Health Sciences, Loughborough University, Leicestershire, LE11 3TU, UK. .,Institute for Sports Research, Nanyang Technological University, Singapore, Singapore. .,Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, Loughborough University, Leicestershire, UK.
| | - A Fry
- School of Sport, Exercise, and Health Sciences, Loughborough University, Leicestershire, LE11 3TU, UK
| | - T M Maden-Wilkinson
- School of Sport, Exercise, and Health Sciences, Loughborough University, Leicestershire, LE11 3TU, UK.,Faculty of Health and Wellbeing, Collegiate Campus, Sheffield Hallam University, Sheffield, UK
| | - P W Kong
- Institute for Sports Research, Nanyang Technological University, Singapore, Singapore.,Physical Education and Sports Science Academic Group, National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | - J P Folland
- School of Sport, Exercise, and Health Sciences, Loughborough University, Leicestershire, LE11 3TU, UK.,Institute for Sports Research, Nanyang Technological University, Singapore, Singapore.,Arthritis Research UK Centre for Sport, Exercise and Osteoarthritis, Loughborough University, Leicestershire, UK
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McDonald AC, Sonne MWL, Keir PJ. Optimized maximum voluntary exertion protocol for normalizing shoulder muscle activity. Int Biomech 2017. [PMCID: PMC7857445 DOI: 10.1080/23335432.2017.1308835] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Affiliation(s)
- Alison C. McDonald
- Occupational Biomechanics Laboratory, Department of Kinesiology, Ivor Wynne Centre, McMaster University, Hamilton, Canada
| | - Michael W. L. Sonne
- Occupational Biomechanics Laboratory, Department of Kinesiology, Ivor Wynne Centre, McMaster University, Hamilton, Canada
| | - Peter J. Keir
- Occupational Biomechanics Laboratory, Department of Kinesiology, Ivor Wynne Centre, McMaster University, Hamilton, Canada
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Zacaron KAM, Dias JMD, Alencar MA, Almeida LLD, Alberto Mourão-Júnior C, Dias RC. Electromyographic normalization of vastus lateralis and biceps femoris co-contraction during gait of elderly females. FISIOTERAPIA EM MOVIMENTO 2016. [DOI: 10.1590/1980-5918.029.004.ao15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Abstract Introduction: Analyze muscle co-contraction using electromyographic signals, which are normalized to compare individuals, muscles and studies. Maximum voluntary isometric contraction (MVIC) and peak electrical activity (PEA) during movement are the most widely used forms of normalization. Objective: Compare inter-subject variability and investigate the association between the co-contraction indices of the vastus lateralis and biceps femoris during gait, normalized by MVIC and PEA. Methods: Thirty elderly women, aged 70.33 ± 3.69 years took part. Electrical muscle activity during MVIC and gait was recorded using a Biopac MP100 electromyograph. MVIC was performed in a Biodex isokinetic dynamometer. For normalization, the signals were divided by the Root Mean Square values of MVIC and PEA of gait. Results: The coefficient of variation of non-normalized data was 69.3%, and those normalized by PEA and MVIC were 30.4% and 48.9% respectively. Linear regression analysis resulted in a prediction model: PEA = 0.04 + 0.16 x MVIC. The goodness of fit of the regression model was statistically significant (p=0.02). The confidence interval (95% CI) for the intercept was between 0.02 and 0.29 and for MVIC between 0.03 and 0.06. Conclusions: The data normalized by PEA showed less variation than those normalized by MVIC. A 100% variation in data normalized by MVIC resulted in a 16% variation in data normalized by PEA, while variation in normalization by MVIC accounts for 17% of the variation in normalization by PEA and vice versa.
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Affiliation(s)
| | | | - Mariana Asmar Alencar
- Universidade Federal de Minas Gerais, Brazil; Universidade Fundação Mineira de Educação e Cultura, Brazil
| | | | | | - Rosângela Correa Dias
- Universidade Federal de Minas Gerais, Brazil; Universidade Federal de São Paulo, Brazil
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Królikowska A, Czamara A, Kentel M. Does Gracilis Tendon Harvest During ACL Reconstruction with a Hamstring Autograft Affect Torque of Muscles Responsible for Shin Rotation? Med Sci Monit 2015; 21:2084-93. [PMID: 26190033 PMCID: PMC4514330 DOI: 10.12659/msm.893930] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Background A growing body of evidence indicates that in patients after anterior cruciate ligament reconstruction (ACLR) with a combined semitendinosus and gracilis (STGR) graft there are large deficits in the internal rotation strength, which has led some authors to recommend harvest of only ST tendon whenever possible. The purpose of this study was to assess the isometric (IT) and peak torque (PT) of the muscles responsible for shin rotation in patients after ACLR with an ST or with an STGR graft. Material/Methods Twenty patients with an ST graft and 20 patients with a combined STGR graft underwent a 6-month postoperative rehabilitation program after ACLR. At the end of the rehabilitation program, the IT and PT of the muscles responsible for internal (IR) and external rotation (ER) of the shin were measured. The results were compared to the results of a control group. Additionally, to determine the reliability of the dynamometer for clinical research, a test-retest assessment was performed. Results There were no statistically significant differences between the 3 groups of participants. Nevertheless, in the STGR group there was a statistically significant difference between the IT of muscles internally rotating the shin in the involved knee and uninvolved knee at 25° of the internal shin rotation. Conclusions Comparison of IT and PT measurements performed after 24 weeks of postoperative rehabilitation generally showed no differences between patients after ACLR with the use of ST graft and patients who received a combination graft consisting of STGR. Nevertheless, there was an influence of GR harvest on internal shin rotation torque at a deep internal rotation angle.
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Affiliation(s)
| | - Andrzej Czamara
- Department of Physiotherapy, The College of Physiotherapy in Wrocław, Wrocław, Poland
| | - Maciej Kentel
- Department of Physiotherapy, The College of Physiotherapy in Wrocław, Wrocław, Poland
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Do surface electrode recordings validly represent latissimus dorsi activation patterns during shoulder tasks? J Electromyogr Kinesiol 2015; 25:8-13. [DOI: 10.1016/j.jelekin.2014.10.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 09/24/2014] [Accepted: 10/17/2014] [Indexed: 11/22/2022] Open
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Schall MC, Fethke NB, Chen H, Kitzmann AS. A Comparison of Examination Equipment Used During Common Clinical Ophthalmologic Tasks. ACTA ACUST UNITED AC 2014; 2:105-117. [PMID: 37180554 PMCID: PMC10174276 DOI: 10.1080/21577323.2014.964812] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Background Ophthalmologists report a high prevalence of work-related musculoskeletal symptoms, particularly of the neck and shoulders. Improving the design of equipment used in the clinical environment may reduce exposures to physical risk factors (e.g., sustained muscular exertions and non-neutral postures) associated with neck and shoulder pain among ophthalmologists. Purpose To compare estimates of neck and shoulder muscle activity and upper arm posture during use of conventional and alternative examination equipment common in clinical ophthalmologic practice. Methods Fifteen ophthalmologists performed one mock clinical examination using conventional equipment and one mock clinical examination using alternative equipment with the potential to reduce exposure to sustained muscular exertions and non-neutral upper arm postures. The alternative equipment included a slit-lamp biomicroscope with inclined viewing oculars, adjustable elbow supports, and a wider table-top with more room for supporting the arms in comparison to the conventional slit-lamp biomicroscope. A wireless binocular indirect ophthalmoscope was also evaluated that had a more even weight distribution than the conventional design. Measurements of upper trapezius and anterior deltoid muscle activity, upper arm posture, and perceived usability were used to compare the conventional and alternative equipment. Results In comparison to the conventional slit lamp biomicroscope, the alternative slit lamp biomicroscope led to (i) 12% to 13% reductions in upper trapezius muscle activity levels, (ii) a 9% reduction in left anterior deltoid muscle activity levels, and (iii) a 15% reduction in the percentage of work time spent with the left upper arm elevated in positions greater than 60°. In addition, participants rated the comfort and adjustability of both the alternative slit lamp biomicroscope and binocular indirect ophthalmoscope more favorably than the conventional equipment. Conclusions The results suggest that the alternative slit-lamp biomicroscope may help to reduce overall muscular demands and non-neutral postures of the neck and shoulder region among ophthalmologists.
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Affiliation(s)
- Mark C. Schall
- Department of Mechanical and Industrial Engineering, University of Iowa, 3131 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA 52242, USA
| | - Nathan B. Fethke
- Department of Occupational and Environmental Health, University of Iowa, Iowa City, Iowa, USA
| | - Howard Chen
- Department of Mechanical and Industrial Engineering, University of Iowa, 3131 Seamans Center for the Engineering Arts and Sciences, Iowa City, IA 52242, USA
| | - Anna S. Kitzmann
- Department of Ophthalmology and Visual Sciences, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA
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