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Toner J, Rickards J, Seaman K, Kuruganti U. Alteration in HDEMG Spatial Parameters of Trunk Muscle Due to Handle Design during Pushing. SENSORS (BASEL, SWITZERLAND) 2021; 21:6646. [PMID: 34640966 PMCID: PMC8512797 DOI: 10.3390/s21196646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/30/2021] [Accepted: 10/01/2021] [Indexed: 11/20/2022]
Abstract
Previous research identifies that pushing and pulling is responsible for approximately 9-18% of all low back injuries. Additionally, the handle design of a cart being pushed can dramatically alter a worker's capacity to push (≅9.5%). Surprisingly little research has examined muscle activation of the low back and its role in muscle function. Therefore, the purpose of this study was to examine the effects of handle design combination of pushing a platform truck cart on trunk muscle activity. Twenty participants (10 males and 10 females, mean age = 24.3 ± 4.3 years) pushed 475 lbs using six different handle combinations involving handle orientation (vertical/horizontal/semi-pronated) and handle height (hip/shoulder). Multichannel high-density EMG (HDsEMG) was recorded for left and right rectus abdominis, erector spinae, and external obliques. Pushing at hip height with a horizontal handle orientation design (HH) resulted in significantly less (p < 0.05) muscle activity compared to the majority of other handle designs, as well as a significantly higher entropy than the shoulder handle height involving either the semi-pronated (p = 0.023) or vertical handle orientation (p = 0.028). The current research suggests that the combination of a hip height and horizontal orientation handle design may require increased muscle demand of the trunk and alter the overall muscle heterogeneity and pattern of the muscle activity.
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Affiliation(s)
- Jacqueline Toner
- Andrew and Marjorie McCain Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, NB E3B5A3, Canada;
| | - Jeremy Rickards
- Faculty of Forestry and Environmental Management, University of New Brunswick, Fredericton, NB E3B5A3, Canada;
- Faculty of Kinesiology, University of New Brunswick, Fredericton, NB E3B5A3, Canada;
| | - Kenneth Seaman
- Faculty of Kinesiology, University of New Brunswick, Fredericton, NB E3B5A3, Canada;
| | - Usha Kuruganti
- Andrew and Marjorie McCain Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, NB E3B5A3, Canada;
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Horwath O, Envall H, Röja J, Emanuelsson EB, Sanz G, Ekblom B, Apró W, Moberg M. Variability in vastus lateralis fiber type distribution, fiber size, and myonuclear content along and between the legs. J Appl Physiol (1985) 2021; 131:158-173. [PMID: 34013752 DOI: 10.1152/japplphysiol.00053.2021] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human skeletal muscle characteristics such as fiber type composition, fiber size, and myonuclear content are widely studied in clinical and sports-related contexts. Being aware of the methodological and biological variability of the characteristics is a critical aspect in study design and outcome interpretation, but comprehensive data on the variability of morphological features in human skeletal muscle are currently limited. Accordingly, in the present study, m. vastus lateralis biopsies (10 per subject) from young and healthy individuals, collected in a systematic manner, were analyzed for various characteristics using immunohistochemistry (n = 7) and SDS-PAGE (n = 25). None of the analyzed parameters, fiber type % (FT%), type I and II fiber cross-sectional area (fCSA), percentage fiber type area (fCSA%), myosin heavy chain composition (MyHC%), type IIX content, myonuclear content, or myonuclear domain, varied in a systematic manner longitudinally along the muscle or between the two legs. The average within-subject coefficient of variation for FT%, fCSA, fCSA%, and MyHC% ranged between 13% and 18% but was only 5% for fiber-specific myonuclear content, which reduced the variability for myonuclear domain size to 11%-12%. Pure type IIX fibers and type IIX MyHC were randomly distributed and present in <24% of the analyzed samples, with the average content being 0.1% and 1.1%, respectively. In conclusion, leg or longitudinal orientation does not seem to be an important aspect to consider when investigating human vastus lateralis characteristics. However, single muscle biopsies should preferably not be used when studying fiber type- and fiber size-related aspects, given the notable sample-to-sample variability.NEW & NOTEWORTHY This study provides a comprehensive analysis of the variability of key human skeletal muscle fiber characteristics in multiple sites along and between the m. vastus lateralis of healthy and active individuals. We found a notable but nonsystematic variability in fiber type and size, whereas myonuclear content was distinctively less variable, and the prevalence of type IIX fibers was random and very low. These data are important to consider when designing and interpreting studies including m. vastus lateralis biopsies.
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Affiliation(s)
- Oscar Horwath
- Department of Physiology, Nutrition and Biomechanics, Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Helena Envall
- Department of Physiology, Nutrition and Biomechanics, Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Julia Röja
- Department of Physiology, Nutrition and Biomechanics, Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Eric B Emanuelsson
- Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
| | - Gema Sanz
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden.,Gnomics, Murcia, Spain
| | - Björn Ekblom
- Department of Physiology, Nutrition and Biomechanics, Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - William Apró
- Department of Physiology, Nutrition and Biomechanics, Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden.,Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden
| | - Marcus Moberg
- Department of Physiology, Nutrition and Biomechanics, Åstrand Laboratory, Swedish School of Sport and Health Sciences, Stockholm, Sweden.,Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
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Pradhan A, Malagon G, Lagacy R, Chester V, Kuruganti U. Effect of age and sex on strength and spatial electromyography during knee extension. J Physiol Anthropol 2020; 39:11. [PMID: 32293538 PMCID: PMC7161225 DOI: 10.1186/s40101-020-00219-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 03/13/2020] [Indexed: 11/10/2022] Open
Abstract
Background Multichannel surface electromyography (EMG) is a method to examine properties of motor unit (MU) activity using multiple electrodes arranged on a two-dimensional grid. This technique can be used to examine alterations in EMG activity distribution due to contraction intensity as well as due to physiological differences such as age or sex. Therefore, the purpose of this study was to compare strength and high-density surface EMG (HDsEMG) features during isometric and isokinetic knee extensions between older and younger men and women. Methods Twenty younger (ages 19–25 years) and twenty older (ages 64–78) men and women performed submaximal and maximal isometric (at a joint angle of 90°) and isokinetic knee extensions, while HDsEMG was recorded from the vastus lateralis. Spatial distribution was estimated using the root mean square (RMS), and 2-dimensional (2D) maps were developed to examine spatial features. Coefficient of variation (CV) and modified entropy were used to examine alterations in muscle heterogeneity and pattern. Peak torque and HDsEMG parameters were compared across age and gender. Results Younger males and females produced significantly higher mean torque than the older group (p < 0.001) for all contractions. Both age- and sex-related significant differences (p < 0.05) were found for EMG spatial features suggesting neuromuscular differences. Modified entropy was significantly higher and CV was lower for young females compared to young males (p < 0.05) across both isometric and isokinetic contractions. Conclusions We found that isometric and isokinetic knee extension strength, spatial distribution, and intensity differ as a function of age and sex during knee extensions. While there were no differences detected in entropy between age groups, there were sex-related differences in the younger age category. The lack of age-related differences in entropy was surprising given the known effects of aging on muscle fiber composition. However, it is often reported that muscle coactivation increases with age and this work was limited to the study of one muscle of the knee extensors (vastus lateralis) which should be addressed in future work. The findings suggest while both age and sex affect muscle activation, sex had a greater effect on heterogeneity. The results obtained will help to develop improved rehabilitation programs for aging men and women.
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Affiliation(s)
- Ashirbad Pradhan
- Andrew and Marjorie McCain Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
| | - Gemma Malagon
- Andrew and Marjorie McCain Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada.,Tecnologico de Monterrey, Monterrey, Mexico
| | - Rebecca Lagacy
- Andrew and Marjorie McCain Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
| | - Victoria Chester
- Andrew and Marjorie McCain Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada
| | - Usha Kuruganti
- Andrew and Marjorie McCain Human Performance Laboratory, Faculty of Kinesiology, University of New Brunswick, Fredericton, NB, E3B 5A3, Canada.
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Watanabe K, Kouzaki M, Ogawa M, Akima H, Moritani T. Relationships between muscle strength and multi-channel surface EMG parameters in eighty-eight elderly. Eur Rev Aging Phys Act 2018; 15:3. [PMID: 29682086 PMCID: PMC5894231 DOI: 10.1186/s11556-018-0192-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 04/02/2018] [Indexed: 11/10/2022] Open
Abstract
Background Since age-related muscle strength loss cannot be explained solely by muscle atrophy, other determinants would also contribute to muscle strength in elderly. The present study aimed to clarify contribution of neuromuscular activation pattern to muscle strength in elderly group. From 88 elderlies (age: 61~ 83 years), multi-channel surface electromyography (EMG) of the vastus lateralis muscle was recorded with two-dimensional 64 electrodes during isometric submaximal ramp-up knee extension to assess neuromuscular activation pattern. Correlation analysis and stepwise regression analysis were performed between muscle strength and the parameters for signal amplitude and spatial distribution pattern, i.e., root mean square (RMS), correlation coefficient, and modified entropy of multi-channel surface EMG. Results There was a significant correlation between muscle strength and RMS (r = 0.361, p = 0.001) in the elderly. Muscle thickness (r = 0.519, p < 0.001), RMS (r = 0.288, p = 0.001), and normalized RMS (r = 0.177, p = 0.047) were selected as major determinants of muscle strength in stepwise regression analysis (r = 0.664 in the selected model). Conclusion These results suggest that inter-individual difference in muscle strength in elderly can be partly explained by surface EMG amplitude. We concluded that neuromuscular activation pattern is also major determinants of muscle strength on elderly in addition to indicator of muscle volume.
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Affiliation(s)
- Kohei Watanabe
- 1Laboratory of Neuromuscular Biomechanics, School of International Liberal Studies, Chukyo University, Yagotohonmachi, Showa-ku, Nagoya, 466-8666 Japan
| | - Motoki Kouzaki
- 2Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
| | - Madoka Ogawa
- 3Graduate School of Education and Human Development, Nagoya University, Nagoya, Japan.,4Japan Society for the Promotion of Science, Tokyo, Japan
| | - Hiroshi Akima
- 3Graduate School of Education and Human Development, Nagoya University, Nagoya, Japan.,5Research Center of Health, Physical Fitness & Sports, Nagoya University, Japan raduate School of Education and Human Development, Nagoya University, Nagoya, Japan
| | - Toshio Moritani
- 6Faculty of Sociology, Kyoto Sangyo University, Kyoto, Japan.,7School of Health and Sports Sciences, Chukyo University, Nagoya, Japan
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Dirks ML, Wall BT, van Loon LJC. Interventional strategies to combat muscle disuse atrophy in humans: focus on neuromuscular electrical stimulation and dietary protein. J Appl Physiol (1985) 2017; 125:850-861. [PMID: 28970205 DOI: 10.1152/japplphysiol.00985.2016] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Numerous situations, such as the recovery from illness or rehabilitation after injury, necessitate a period of muscle disuse in otherwise healthy individuals. Even a few days of immobilization or bed rest can lead to substantial loss of skeletal muscle tissue and compromise metabolic health. The decline in muscle mass is attributed largely to a decline in postabsorptive and postprandial muscle protein synthesis rates. Reintroduction of some level of muscle contraction by the application of neuromuscular electrical stimulation (NMES) can augment both postabsorptive and postprandial muscle protein synthesis rates and, as such, prevent or attenuate muscle loss during short-term disuse in various clinical populations. Whereas maintenance of habitual dietary protein consumption is a prerequisite for muscle mass maintenance, supplementing dietary protein above habitual intake levels does not prevent muscle loss during disuse in otherwise healthy humans. Combining the anabolic properties of physical activity (or surrogates) with appropriate nutritional support likely further increases the capacity to preserve skeletal muscle mass during a period of disuse. Therefore, effective interventional strategies to prevent or alleviate muscle disuse atrophy should include both exercise (mimetics) and appropriate nutritional support.
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Affiliation(s)
- Marlou L Dirks
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht , The Netherlands
| | - Benjamin T Wall
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht , The Netherlands
| | - Luc J C van Loon
- NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Maastricht , The Netherlands
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Moore CW, Beveridge TS, Rice CL. Fiber type composition of the palmaris brevis muscle: implications for palmar function. J Anat 2017. [PMID: 28620932 DOI: 10.1111/joa.12652] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The palmaris brevis (PB) is a small muscle of variant morphology located on the ulnar aspect of the palm, superficial to the hypothenar eminence. Functionally, the PB has been proposed to protect the neurovasculature of the ulnar canal from compressive forces during repetitive or intermittent trauma associated with grasping. Although PB function has been inferred from cadaveric observations, it is unknown whether it has the contractile capacity and fatigue-resistance necessary to withstand these functional demands. Insight into the functional specialization of the PB can be provided through investigating the proportions of type I and type II muscle fibers by staining for myosin heavy chain (MHC) isoforms using immunohistochemical methods. Therefore, the purpose of this study was to quantify the proportion of type I and type II muscle fibers to provide insight into the role of the PB in palmar function based on its gross histological structure. Sixteen PB specimens were harvested from the hands (eight right, eight left) of eight formalin-embalmed cadavers (mean age: 75 ± 14 years; three males, five females). PB muscle composition was determined by labeling serial cross-sections with MHC type I and type II monoclonal antibodies. The results indicate that the PB is primarily composed of type I muscle fibers (72.2 ± 13.7%), with no significant differences between left and right hands. Given the predominance of type I muscle fibers, our findings indicate the PB may be fatigue-resistant and thus, capable of contracting for prolonged durations. This supports cadaveric observations indicating that the PB functions to protect the ulnar neurovasculature of the palm by providing a muscular barrier in addition to serving as a functional anchor to the hypothenar fat pad when objects are firmly compressed into the palm.
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Affiliation(s)
- Colin W Moore
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON, Canada
| | - Tyler S Beveridge
- Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
| | - Charles L Rice
- School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON, Canada.,Department of Anatomy & Cell Biology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, ON, Canada
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Zhang M, Gould M. Segmental Distribution of Myosin Heavy Chain Isoforms Within Single Muscle Fibers. Anat Rec (Hoboken) 2017; 300:1636-1642. [DOI: 10.1002/ar.23578] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Accepted: 10/06/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Ming Zhang
- Anatomy Department; University of Otago; Dunedin 9054 New Zealand
| | - Maree Gould
- Anatomy Department; University of Otago; Dunedin 9054 New Zealand
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Watanabe K, Holobar A, Kouzaki M, Ogawa M, Akima H, Moritani T. Age-related changes in motor unit firing pattern of vastus lateralis muscle during low-moderate contraction. AGE (DORDRECHT, NETHERLANDS) 2016; 38:48. [PMID: 27084115 PMCID: PMC5005913 DOI: 10.1007/s11357-016-9915-0] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 04/11/2016] [Indexed: 05/19/2023]
Abstract
Age-related changes in motor unit activation properties remain unclear for locomotor muscles such as quadriceps muscles, although these muscles are preferentially atrophied with aging and play important roles in daily living movements. The present study investigated and compared detailed motor unit firing characteristics for the vastus lateralis muscle during isometric contraction at low to moderate force levels in the elderly and young. Fourteen healthy elderly men and 15 healthy young men performed isometric ramp-up contraction to 70 % of the maximal voluntary contractions (MVC) during knee extension. Multichannel surface electromyograms were recorded from the vastus lateralis muscle using a two-dimensional grid of 64 electrodes and decomposed with the convolution kernel compensation technique to extract individual motor units. Motor unit firing rates in the young were significantly higher (~+29.7 %) than in the elderly (p < 0.05). There were significant differences in firing rates among motor units with different recruitment thresholds at each force level in the young (p < 0.05) but not in the elderly (p > 0.05). Firing rates at 60 % of the MVC force level for the motor units recruited at <20 % of MVC were significantly correlated with MVC force in the elderly (r = 0.885, p < 0.0001) but not in the young (r = 0.127, p > 0.05). These results suggest that the motor unit firing rate in the vastus lateralis muscle is affected by aging and muscle strength in the elderly and/or age-related strength loss is related to motor unit firing/recruitment properties.
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Affiliation(s)
- Kohei Watanabe
- Laboratory of Neuromuscular Biomechanics, School of International Liberal Studies, Chukyo University, Yagotohonmachi, Showa-ku, Nagoya, 466-8666, Japan.
| | - Aleš Holobar
- Faculty of Electrical Engineering and Computer Science, University of Maribor, Maribor, Slovenia
| | - Motoki Kouzaki
- Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
| | - Madoka Ogawa
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Hiroshi Akima
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
- Graduate School of Education and Human Development, Nagoya University, Nagoya, Japan
| | - Toshio Moritani
- Laboratory of Applied Physiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
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Rudroff T, Kindred JH, Benson JM, Tracy BL, Kalliokoski KK. Greater glucose uptake heterogeneity in knee muscles of old compared to young men during isometric contractions detected by [(18)F]-FDG PET/CT. Front Physiol 2014; 5:198. [PMID: 24904432 PMCID: PMC4035600 DOI: 10.3389/fphys.2014.00198] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 05/09/2014] [Indexed: 11/16/2022] Open
Abstract
We used positron emission tomography/computed tomography (PET/CT) and [18F]-FDG to test the hypothesis that glucose uptake (GU) heterogeneity in skeletal muscles as a measure of heterogeneity in muscle activity is greater in old than young men when they perform isometric contractions. Six young (26 ± 6 years) and six old (77 ± 6 years) men performed two types of submaximal isometric contractions that required either force or position control. [18F]-FDG was injected during the task and PET/CT scans were performed immediately after the task. Within-muscle heterogeneity of knee muscles was determined by calculating the coefficient of variation (CV) of GU in PET image voxels within the muscles of interest. The average GU heterogeneity (mean ± SD) for knee extensors and flexors was greater for the old (35.3 ± 3.3%) than the young (28.6 ± 2.4%) (P = 0.006). Muscle volume of the knee extensors were greater for the young compared to the old men (1016 ± 163 vs. 598 ± 70 cm3, P = 0.004). In a multiple regression model, knee extensor muscle volume was a predictor (partial r = −0.87; P = 0.001) of GU heterogeneity for old men (R2 = 0.78; P < 0.001), and MVC force predicted GU heterogeneity for young men (partial r = −0.95, P < 0.001). The findings demonstrate that GU is more spatially variable for old than young men and especially so for old men who exhibit greater muscle atrophy.
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Affiliation(s)
- Thorsten Rudroff
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - John H Kindred
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - John-Michael Benson
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - Brian L Tracy
- Integrative Neurophysiology Laboratory, Department of Health and Exercise Science, Colorado State University Fort Collins, CO, USA
| | - Kari K Kalliokoski
- Turku PET Centre, University of Turku and Turku University Hospital Turku, Finland
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Watanabe K, Kouzaki M, Moritani T. Task-dependent spatial distribution of neural activation pattern in human rectus femoris muscle. J Electromyogr Kinesiol 2012; 22:251-8. [DOI: 10.1016/j.jelekin.2011.11.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 10/06/2011] [Accepted: 11/03/2011] [Indexed: 10/14/2022] Open
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Spatial EMG potential distribution pattern of vastus lateralis muscle during isometric knee extension in young and elderly men. J Electromyogr Kinesiol 2011; 22:74-9. [PMID: 21996320 DOI: 10.1016/j.jelekin.2011.09.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2011] [Revised: 09/20/2011] [Accepted: 09/20/2011] [Indexed: 11/20/2022] Open
Abstract
The aim of the present study was to compare spatial electromyographic (EMG) potential distribution during force production between elderly and young individuals using multi-channel surface EMG (SEMG). Thirteen elderly (72-79years) and 13 young (21-27years) healthy male volunteers performed ramp submaximal contraction during isometric knee extension from 0% to 65% of maximal voluntary contraction. During contraction, multi-channel EMG was recorded from the vastus lateralis muscle. To evaluate alteration in heterogeneity and pattern in spatial EMG potential distribution, coefficient of variation (CoV), modified entropy and correlation coefficients with initial torque level were calculated from multi-channel SEMG at 5% force increment. Increase in CoV and decrease in modified entropy of RMS with increase of exerted torque were significantly smaller in elderly group (p<0.05) and correlation coefficients with initial torque level were significantly higher in elderly group than in young group at moderate torque levels (p<0.05). These data suggest that the increase of heterogeneity and the change in the activation pattern are smaller in elderly individuals than in young individuals. We speculated that multi-channel SEMG pattern in elderly individual reflects neuromuscular activation strategy regulated predominantly by clustering of similar type of muscle fibers in aged muscle.
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Evolutionary psychologists need to distinguish between the evolutionary process, ancestral selection pressures, and psychological mechanisms. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025577] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Selfishness reexamined: No man is an island. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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How useful is a concept such as muscle partitioning? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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The physiological basis and implications of differential motor activation. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Selfish genes and ingroup altruism. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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A Comparative approach to muscle function. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x0002505x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Abstract
AbstractSocial dilemmas occur when the pursuit of self-interest by individuals in a group leads to less than optimal collective outcomes for everyone in the group. A critical assumption in the human sciences is that people's choices in such dilemmas are individualistic, selfish, and rational. Hence, cooperation in the support of group welfare will only occur if there are selfish incentives that convert the social dilemma into a nondilemma. In recent years, inclusive fitness theories have lent weight to such traditional views of rational selfishness on Darwinian grounds. To show that cooperation is based on selfish incentives, however, one must provide evidence that people do not cooperate without such incentives. In a series of experimental social dilemmas, subjects were instructed to make single, anonymous choices about whether or not to contribute money for a shared “bonus” that would be provided only if enough other people in the group also contributed their money. Noncontributors cited selfish reasons for their choices; contributors did not. If people are allowed to engage in discussion, they will contribute resources at high rates, frequently on irrational grounds, to promote group welfare. These findings are consistent with previous research on ingroup biasing effects that cannot be explained by “economic man” or “selfish gene” theories. An alternative explanation is that sociality was a primary factor shaping the evolution of Homo sapiens. The cognitive and affective mechanisms underlying such choices evolved under selection pressures on small groups for developing and maintaining group membership and for predicting and controlling the behavior of other group members. This sociality hypothesis organizes previously inexplicable and disparate phenomena in a Darwinian framework and makes novel predictions about human choice.
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Continuous and discrete models and measures of speech events. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Partitioning hypothesis in perspective. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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A multiple source, or, is a striped apple more striped than a striped orange? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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The use of mathematical models in perceptual theory. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Ecological and social factors in hominid evolution. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Central partitioning may be altered during high-frequency activation of the lamotoneuron connection. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Speech perception by ear, eye, hand, and mind. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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What is the organization, scope, and functional significance of partitioning? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Abstract
AbstractStudies have shown that in the mammalian neuromuscular system stretch reflexes are localized within individual muscles. Neuromuscular compartmentalization, the partitioning of sensory output from muscles, and the partitioning of segmental pathways to motor nuclei have also been demonstrated. This evidence indicates that individual motor nuclei and the muscles they innervate are not homogeneous functional units. An analysis of the functional significance of reflex localization and partitioning suggests that segmental control mechanisms are based on subdivisions of motor nuclei–muscle complexes. A partitioned organization of segmental control mechanisms could utilize (1) the potential functional diversity of muscle fiber types, (2) the variety of mechanical actions of individual muscles arising from their distributed origins and insertions, and (3) diverse architectural features such as intramuscular variations in pinnation and complex in-series and in-parallel arrangements of muscle fibers. The differentiated activity observed in some muscles during natural movements also calls for localized segmental control mechanisms. Partitioning may also play a role in mechanical interactions between contracting motor units and in increasing the stability of neuromuscular systems. The functional advantages of reflex localization and partitioning suggest they are probably common features of segmental systems, whose organization reflects the structure and function of their associated neuromuscular systems.
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Do we need two souls to explain cooperation? Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Acoustic reflex partitioning in the stapedius. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Reflex partitioning and differential control of human motor units. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x00025231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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On the regional distribution of muscle spindles. Behav Brain Sci 2010. [DOI: 10.1017/s0140525x0002522x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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