Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 43.382
Filtrar
1.
Nat Commun ; 11(1): 4356, 2020 08 31.
Artigo em Inglês | MEDLINE | ID: mdl-32868777

RESUMO

Complex motor commands for human locomotion are generated through the combination of motor modules representable as muscle synergies. Recent data have argued that muscle synergies are inborn or determined early in life, but development of the neuro-musculoskeletal system and acquisition of new skills may demand fine-tuning or reshaping of the early synergies. We seek to understand how locomotor synergies change during development and training by studying the synergies for running in preschoolers and diverse adults from sedentary subjects to elite marathoners, totaling 63 subjects assessed over 100 sessions. During development, synergies are fractionated into units with fewer muscles. As adults train to run, specific synergies coalesce to become merged synergies. Presences of specific synergy-merging patterns correlate with enhanced or reduced running efficiency. Fractionation and merging of muscle synergies may be a mechanism for modifying early motor modules (Nature) to accommodate the changing limb biomechanics and influences from sensorimotor training (Nurture).


Assuntos
Músculo Esquelético/fisiologia , Corrida/fisiologia , Adulto , Fenômenos Biomecânicos , Criança , Pré-Escolar , Eletromiografia , Feminino , Humanos , Locomoção , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/crescimento & desenvolvimento
2.
Geriatr Gerontol Int ; 20(10): 943-950, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32886830

RESUMO

AIM: To re-evaluate the suitability of calf circumference as a surrogate marker of low muscle mass measured by both bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA). We also examined the effects of obesity and age on low muscle mass screening using calf circumference. METHODS: In total, 1239 adults participated in this cross-sectional study. We measured the maximum calf circumference in a standing position and appendicular skeletal muscle mass (ASM) using BIA and DXA. We defined low muscle mass based on the Asian Working Group for Sarcopenia 2019 consensus. RESULTS: Calf circumference was positively correlated with BIA-measured ASM/height2 (men: r = 0.81, women: r = 0.73) and DXA-measured ASM/height2 (men: r = 0.78, women: r = 0.76). In the subgroup analyses by obesity and age, calf circumference was also positively correlated with ASM/height2 . The optimal calf circumference cut-offs for low muscle mass screening measured by BIA and DXA were 35 cm (sensitivity 91%, specificity 84%) and 36 cm (sensitivity 82%, specificity 80%) for men, and 33 cm (sensitivity 82%, specificity 84%) and 34 cm (sensitivity 85%, specificity 72%) for women, respectively. CONCLUSIONS: Calf circumference is positively correlated with BIA- and DXA-measured muscle mass regardless of obesity and age and is a simple and accurate surrogate marker of muscle mass for diagnosing sarcopenia. Geriatr Gerontol Int 2020; 20: 943-950.


Assuntos
Perna (Membro)/fisiologia , Músculo Esquelético/fisiologia , Sarcopenia/diagnóstico , Absorciometria de Fóton , Adulto , Idoso , Idoso de 80 Anos ou mais , Composição Corporal , Índice de Massa Corporal , Estudos Transversais , Impedância Elétrica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Obesidade/fisiopatologia , Sensibilidade e Especificidade
3.
PLoS One ; 15(8): e0237842, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866205

RESUMO

Isokinetic dynamometry is the gold standard for testing maximal strength in elite sport and rehabilitation settings. To be clinically useful, such tests should be valid and reliable. Despite some evidence regarding the relative test vs retest reliability of knee dynamometry, there is still a paucity of research regarding the absolute reliability parameters. The purpose of this study was to assess the absolute and relative intra-device reproducibility of isokinetic knee flexion and extension using the novel SMM iMoment dynamometer. A total of 19 participants (13 males and 6 females, aged 24 (2) years, height 178 (9) cm and weight 76 (11) kg) performed two identical knee isokinetic tests with at least a week of rest between measurements. Peak torque of knee extension and flexion were determined at 60°/s. Moderate (0.892) to excellent (0.988) relative reliability using the intraclass correlation coefficient (ICC) was obtained for peak knee torque. Absolute reliability assessed with a standard error of measurement (SEM %) was low, ranging from 2.54% to 6.93%, whereas the smallest real difference (SRD %) was moderate, ranging from 7.04% to 19.22%. Furthermore, there were no significant correlations between means and differences of two measurements, and Bland-Altman plots also showed no signs of heteroscedasticity. Our measurement protocol established the moderate to excellent reliability of the novel SMM iMoment isokinetic dynamometer. Therefore, this dynamometer can be applied in sport rehabilitation settings to measure maximal knee strength.


Assuntos
Joelho/fisiologia , Dinamômetro de Força Muscular , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Músculo Esquelético/fisiologia , Amplitude de Movimento Articular , Reprodutibilidade dos Testes , Torque , Adulto Jovem
4.
PLoS One ; 15(8): e0236731, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866151

RESUMO

Ankle proprioception is crucial for balance and relies upon accurate input from calf muscle spindles. Spindle input, in turn, depends upon the physiological and mechanical properties of surrounding muscle tissue. Altering these properties could affect ankle proprioception, with potential consequences for balance. Here we determine the effects of prior muscle cooling, stretch and contraction upon performance of a contralateral ankle joint matching task. Participants stood passively leaning against a board oriented 22° rearward from vertical. Their right ankle was rotated to a randomised position between ± 6° plantar/dorsiflexion. The task was to align the left ankle to the same position, without vision. In the first experiment, immediately prior to each testing session, participants either produced a strong calf muscle contraction in a fully plantarflexed (tiptoe) posture or underwent 15° dorsiflexion stretch. Contraction had no effect on task performance, whereas stretch produced a significant bias in ankle placement of 0.89 ± 0.6°, indicating that participants perceived their foot to be more plantarflexed compared to a control condition. In the second experiment, the right lower leg was cooled in iced water (≤ 5°C) for 10 minutes. Cooling increased joint matching error by ~0.4°, through a combination of increased bias and variability. These results confirm that conditioning the triceps surae muscles can alter perception of ankle joint position. Since body movement during quiet stance is in the order of 1°, the magnitude of these changes are relevant for balance.


Assuntos
Tornozelo/fisiologia , Músculo Esquelético/fisiologia , Propriocepção , Adulto , Retroalimentação Fisiológica , Feminino , Humanos , Masculino , Contração Muscular , Temperatura Cutânea , Adulto Jovem
5.
Nat Commun ; 11(1): 4643, 2020 09 16.
Artigo em Inglês | MEDLINE | ID: mdl-32938935

RESUMO

Time-restricted feeding (TRF) improves metabolism independent of dietary macronutrient composition or energy restriction. To elucidate mechanisms underpinning the effects of short-term TRF, we investigated skeletal muscle and serum metabolic and transcriptomic profiles from 11 men with overweight/obesity after TRF (8 h day-1) and extended feeding (EXF, 15 h day-1) in a randomised cross-over design (trial registration: ACTRN12617000165381). Here we show that muscle core clock gene expression was similar after both interventions. TRF increases the amplitude of oscillating muscle transcripts, but not muscle or serum metabolites. In muscle, TRF induces rhythmicity of several amino acid transporter genes and metabolites. In serum, lipids are the largest class of periodic metabolites, while the majority of phase-shifted metabolites are amino acid related. In conclusion, short-term TRF in overweight men affects the rhythmicity of serum and muscle metabolites and regulates the rhythmicity of genes controlling amino acid transport, without perturbing core clock gene expression.


Assuntos
Aminoácidos/sangue , Ritmo Circadiano/genética , Jejum , Lipídeos/sangue , Músculo Esquelético/metabolismo , Adulto , Relógios Circadianos/genética , Estudos Cross-Over , Expressão Gênica , Humanos , Metabolismo dos Lipídeos , Masculino , Músculo Esquelético/fisiologia , Sobrepeso/dietoterapia , Sobrepeso/metabolismo
6.
Int Heart J ; 61(5): 913-921, 2020 Sep 29.
Artigo em Inglês | MEDLINE | ID: mdl-32921668

RESUMO

Previous study has identified marked differences in patient characteristics and causes of inappropriate shock (IAS) between Japan and the Western societies in terms of subcutaneous implantable cardioverter-defibrillator (S-ICD). However, evidence of IAS in Asian populations including Japan has been limited to one observational study.Thus, we conducted a single-center registry study that tracks the postoperative course of 61 consecutive patients who received S-ICD from February 2016 to January 2020. Our findings showed that IAS occurred in 9.8% of the study population (6/61), which is comparable to the previously reported incidence. Remarkably, T-wave oversensing did not result in an IAS (0/6). Instead, myopotential oversensing was determined to have caused the most IAS events (4/6), while atrial fibrillation ranked second (2/6). A provocation maneuver (e.g., abdominal clench, push-ups, lifting a heavy item) reproduced myopotential noise disguised as R-waves, which should potentially trigger an IAS if uninterrupted. R-wave amplitude of the IAS group appeared relatively low compared to that of the non-IAS group although this finding was not tested significant. Furthermore, no temporal changes were noted in R-wave amplitude between the time of implantation and IAS events, suggesting that it is neither constantly low nor acutely dropped R-wave amplitude but a relatively high noise level that drives IAS. All the myopotential-IAS patients were found to be male. Right-sided lead implantation was associated with a higher incidence of IAS.This study highlights the fact that IAS continues to occur due to myopotential noise oversensing instead of T-wave oversensing. To minimize the risk of IAS, it is desirable to search and secure high R-wave voltage.


Assuntos
Desfibriladores Implantáveis , Cardioversão Elétrica/estatística & dados numéricos , Músculo Esquelético/fisiologia , Taquicardia Ventricular/diagnóstico , Fibrilação Ventricular/diagnóstico , Adolescente , Adulto , Idoso , Criança , Erros de Diagnóstico , Falha de Equipamento , Feminino , Humanos , Japão , Masculino , Pessoa de Meia-Idade , Taquicardia Ventricular/terapia , Fibrilação Ventricular/terapia , Adulto Jovem
7.
Sports Biomech ; 19(6): 723-737, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32942954

RESUMO

The aim of this study was to understand if and how surface-induced vibrations and road bike damping affect short-term neuromuscular performance in cycling. Thirty cyclists (mass 75.9 ± 8.9 kg, height 1.82 ± 0.05 m, Vo2max 63.0 ± 6.8 ml/min/kg) performed steady-state and maximum effort tests with and without vibration exposure (front dropout: 44 Hz, 4.1 mm; rear dropout: 38 Hz, 3.5 mm) on a damped and a nondamped bike. Transmitted accelerations to the musculoskeletal system, activation of lower extremity muscles (gast. med., soleus, vast. med., rec. fem.) and upper body muscles (erec. spinae, deltoideus, tric. brachii), oxygen uptake, heart rate and crank power output were measured. The main findings indicate a transmission of vibration to the whole body, but since no major propulsive muscles increase their activation with vibration, the systemic energy demand increases only marginally with vibration. Damping reduces vibrations at the upper body, which indicates an increase in comfort, but has no effect on the vibration transfer to the lower extremities. Therefore, road bike damping does not affect neuromuscular response of the propulsive muscle groups and energy demand. Consequently, short-term power output does not increase with damping.


Assuntos
Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Meio Ambiente , Músculo Esquelético/fisiologia , Vibração , Aceleração , Fenômenos Biomecânicos , Estudos Transversais , Frequência Cardíaca/fisiologia , Humanos , Extremidade Inferior/fisiologia , Masculino , Músculo Esquelético/inervação , Consumo de Oxigênio/fisiologia , Tronco/fisiologia , Extremidade Superior/fisiologia
8.
Ideggyogy Sz ; 73(7-08): 249-252, 2020 Jul 30.
Artigo em Húngaro | MEDLINE | ID: mdl-32750241

RESUMO

Objective - Conflicting theoretical models exist regarding the mechanism related to the ability of the Jendrassik maneuver to reinforce reflex parameters. Our objective was to investigate if vigorous handgrip would induce changes in recurrent inhibition of soleus motoneurons. Method - Soleus H reflex was evoked by stimulating the tibial nerve at rest and during bilateral vigorous handgrip, alternating single (H1) and paired stimulation (H2). At paired stimulation we used interstimulus intervals of 10, 15, 20 and 25 ms and supramaximal test stimulus. H1- and H2-wave amplitudes were expressed as percentage of maximal M-wave amplitude. Conditioned H2 wave maximal (H2max) and minimal (H2) amplitudes evoked at rest and expressed as a percentage of the unconditioned H1max amplitude were compared with the corresponding values obtained during handgrip by means of paired Student test and Bonferroni correction. Subjects - At the study participated 28 healthy volunteers. Results - The H1max/Mmax × 100 values obtained during handgrip (37.5±10.1) were significantly higher than those obtained at rest (27.1±7.4). The H2max/H1max × 100-va-lues obtained at paired stimulation were significantly higher during handgrip than at rest, while no significant diffe-rence was found between the H2/H1max × 100-values obtained during handgrip and at rest respectively. Discussion - The H2max/H1max is determined by both the excitability of the motoneurons and the recurrent inhibition elicited by the conditioning stimulus, while H2/H1max indicates only the level of recurrent inhibition. According to our results the Renshaw cells retain their inhibitory effect on the soleus alpha motoneurons during remote muscle contraction. Conclusion - Soleus H reflex enhancement during Jendrassik maneuver is not due to decrease of recurrent inhibition.


Assuntos
Antebraço/fisiologia , Reflexo H , Força da Mão , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Eletromiografia , Reflexo H/fisiologia , Humanos , Músculos/inervação , Nervo Tibial/fisiologia
9.
PLoS One ; 15(8): e0231996, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32857774

RESUMO

Lower-limb wearable robotic devices can improve clinical gait and reduce energetic demand in healthy populations. To help enable real-world use, we sought to examine how assistance should be applied in variable gait conditions and suggest an approach derived from knowledge of human locomotion mechanics to establish a 'roadmap' for wearable robot design. We characterized the changes in joint mechanics during walking and running across a range of incline/decline grades and then provide an analysis that informs the development of lower-limb exoskeletons capable of operating across a range of mechanical demands. We hypothesized that the distribution of limb-joint positive mechanical power would shift to the hip for incline walking and running and that the distribution of limb-joint negative mechanical power would shift to the knee for decline walking and running. Eight subjects (6M,2F) completed five walking (1.25 m s-1) trials at -8.53°, -5.71°, 0°, 5.71°, and 8.53° grade and five running (2.25 m s-1) trials at -5.71°, -2.86°, 0°, 2.86°, and 5.71° grade on a treadmill. We calculated time-varying joint moment and power output for the ankle, knee, and hip. For each gait, we examined how individual limb-joints contributed to total limb positive, negative and net power across grades. For both walking and running, changes in grade caused a redistribution of joint mechanical power generation and absorption. From level to incline walking, the ankle's contribution to limb positive power decreased from 44% on the level to 28% at 8.53° uphill grade (p < 0.0001) while the hip's contribution increased from 27% to 52% (p < 0.0001). In running, regardless of the surface gradient, the ankle was consistently the dominant source of lower-limb positive mechanical power (47-55%). In the context of our results, we outline three distinct use-modes that could be emphasized in future lower-limb exoskeleton designs 1) Energy injection: adding positive work into the gait cycle, 2) Energy extraction: removing negative work from the gait cycle, and 3) Energy transfer: extracting energy in one gait phase and then injecting it in another phase (i.e., regenerative braking).


Assuntos
Análise da Marcha/métodos , Marcha/fisiologia , Robótica/instrumentação , Adulto , Tornozelo/fisiologia , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos , Exoesqueleto Energizado/tendências , Feminino , Quadril/fisiologia , Articulação do Quadril/fisiologia , Humanos , Joelho/fisiologia , Articulação do Joelho/fisiologia , Locomoção , Extremidade Inferior/fisiologia , Masculino , Músculo Esquelético/fisiologia , Corrida/fisiologia , Caminhada/fisiologia
10.
Nutrients ; 12(8)2020 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-32785021

RESUMO

Old age is associated with lower physical activity levels, suboptimal protein intake, and desensitization to anabolic stimuli, predisposing for age-related muscle loss (sarcopenia). Although resistance exercise (RE) and protein supplementation partially protect against sarcopenia under controlled conditions, the efficacy of home-based, unsupervised RE (HBRE) and multi-ingredient supplementation (MIS) is largely unknown. In this randomized, placebo-controlled and double-blind trial, we examined the effects of HBRE/MIS on muscle mass, strength, and function in free-living, older men. Thirty-two sedentary men underwent twelve weeks of home-based resistance band training (3 d/week), in combination with daily intake of a novel five-nutrient supplement ('Muscle5'; M5, n = 16, 77.4 ± 2.8 y) containing whey, micellar casein, creatine, vitamin D, and omega-3 fatty acids, or an isocaloric/isonitrogenous placebo (PLA; n = 16, 74.4 ± 1.3 y), containing collagen and sunflower oil. Appendicular and total lean mass (ASM; +3%, TLM; +2%), lean mass to fat ratios (ASM/% body fat; +6%, TLM/% body fat; +5%), maximal strength (grip; +8%, leg press; +17%), and function (5-Times Sit-to-Stand time; -9%) were significantly improved in the M5 group following HBRE/MIS therapy (pre vs. post tests; p < 0.05). Fast-twitch muscle fiber cross-sectional areas of the quadriceps muscle were also significantly increased in the M5 group post intervention (Type IIa; +30.9%, Type IIx, +28.5%, p < 0.05). Sub-group analysis indicated even greater gains in total lean mass in sarcopenic individuals following HBRE/MIS therapy (TLM; +1.65 kg/+3.4%, p < 0.05). We conclude that the Muscle5 supplement is a safe, well-tolerated, and effective complement to low-intensity, home-based resistance exercise and improves lean mass, strength, and overall muscle quality in old age.


Assuntos
Composição Corporal , Suplementos Nutricionais , Força Muscular , Músculo Esquelético/fisiologia , Treinamento de Resistência , Sarcopenia/terapia , Idoso , Anabolizantes/uso terapêutico , Compartimentos de Líquidos Corporais , Caseínas/uso terapêutico , Terapia Combinada , Creatina/uso terapêutico , Método Duplo-Cego , Exercício Físico , Ácidos Graxos Ômega-3/uso terapêutico , Humanos , Masculino , Fibras Musculares de Contração Rápida , Proteínas Musculares , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Músculo Quadríceps , Sarcopenia/fisiopatologia , Autocuidado , Vitamina D/uso terapêutico , Vitaminas , Proteínas do Soro do Leite/uso terapêutico
11.
Proc Biol Sci ; 287(1933): 20200431, 2020 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-32811308

RESUMO

Ground contact duration and stride frequency each affect muscle metabolism and help scientists link walking and running biomechanics to metabolic energy expenditure. While these parameters are often used independently, the product of ground contact duration and stride frequency (i.e. duty factor) may affect muscle contractile mechanics. Here, we sought to separate the metabolic influence of the duration of active force production, cycle frequency and duty factor. Human participants produced cyclic contractions using their soleus (which has a relatively homogeneous fibre type composition) at prescribed cycle-average ankle moments on a fixed dynamometer. Participants produced these ankle moments over short, medium and long durations while maintaining a constant cycle frequency. Overall, decreased duty factor did not affect cycle-average fascicle force (p ≥ 0.252) but did increase net metabolic power (p ≤ 0.022). Mechanistically, smaller duty factors increased maximum muscle-tendon force (p < 0.001), further stretching in-series tendons and shifting soleus fascicles to shorter lengths and faster velocities, thereby increasing soleus total active muscle volume (p < 0.001). Participant soleus total active muscle volume well-explained net metabolic power (r = 0.845; p < 0.001). Therefore, cyclically producing the same cycle-average muscle-tendon force using a decreased duty factor increases metabolic energy expenditure by eliciting less economical muscle contractile mechanics.


Assuntos
Metabolismo Energético/fisiologia , Músculo Esquelético/fisiologia , Tendões/fisiologia , Adulto , Tornozelo/fisiologia , Feminino , Marcha/fisiologia , Humanos , Masculino , Contração Muscular/fisiologia , Corrida/fisiologia , Caminhada/fisiologia
12.
PLoS One ; 15(8): e0236781, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32776961

RESUMO

It has been reported that Bach1-deficient mice show reduced tissue injuries in diverse disease models due to increased expression of heme oxygenase-1 (HO-1)that possesses an antioxidant function. In contrast, we found that Bach1 deficiency in mice exacerbated skeletal muscle injury induced by cardiotoxin. Inhibition of Bach1 expression in C2C12 myoblast cells using RNA interference resulted in reduced proliferation, myotube formation, and myogenin expression compared with control cells. While the expression of HO-1 was increased by Bach1 silencing in C2C12 cells, the reduced myotube formation was not rescued by HO-1 inhibition. Up-regulations of Smad2, Smad3 and FoxO1, known inhibitors of muscle cell differentiation, were observed in Bach1-deficient mice and Bach1-silenced C2C12 cells. Therefore, Bach1 may promote regeneration of muscle by increasing proliferation and differentiation of myoblasts.


Assuntos
Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Diferenciação Celular , Músculo Esquelético/fisiologia , Mioblastos/citologia , Regeneração , Proteínas Smad/metabolismo , Animais , Fatores de Transcrição de Zíper de Leucina Básica/deficiência , Fatores de Transcrição de Zíper de Leucina Básica/genética , Linhagem Celular , Técnicas de Silenciamento de Genes , Inativação Gênica , Camundongos , Músculo Esquelético/citologia , Transcriptoma/genética
13.
PLoS One ; 15(8): e0236497, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785230

RESUMO

When human movement is assisted or controlled with a muscle actuator, such as electrical muscle stimulation, a critical issue is the integration of such induced movement with the person's motion intention and how this movement then affects their motor control. Towards achieving optimal integration and reducing feelings of artificiality and enforcement, we explored perceptual simultaneity through electrical muscle stimulation, which involved changing the interval between intentional and induced movements. We report on two experiments in which we evaluated the ranges between detection and stimulus for perceptual simultaneity achievable with an electromyography-triggered electrical muscle stimulation system. We found that the peak range was approximately 80-160 ms, with the timing of perceptual simultaneity shifting according to different adaptation states. Our results indicate that perceptual simultaneity is controllable using this adaptation strategy.


Assuntos
Eletromiografia , Córtex Motor/fisiologia , Movimento/fisiologia , Músculo Esquelético/fisiologia , Adulto , Estimulação Elétrica , Mãos/fisiologia , Humanos , Masculino , Córtex Motor/diagnóstico por imagem , Músculo Esquelético/diagnóstico por imagem , Visão Ocular/fisiologia , Adulto Jovem
14.
PLoS One ; 15(8): e0238036, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853244

RESUMO

The aging process affects the entire human body, including the stomatognathic system, and can trigger not only occlusal but also postural imbalances involving other muscular chains. Hippotherapy has been used to promote cervical, postural, and balance control in individuals with diverse impairments. The present study used electromyography to evaluate the masseter and temporal muscles in an elderly population pre- and post-hippotherapy. Participants included 17 individuals, mean age 66,5±7 years. Electromyographic recording of the bilateral masseter and temporal muscles was performed during the postural resting condition and activities that involved the active participation of these muscles in different conditions. The practitioner performed no other type of activity or exercise during the intervention because the objective is to evaluate the effect of the three-dimensional movement provided by the horse. Raw electromyographic data were tabulated using commercially available software (IBM® SPSS® Statistics 234.0) and subjected to statistical analysis, in which p ≤ 0.05 was considered to be statistically significant. Post-hippotherapy, there was lower electromyographic activity for the masseter and temporalis muscles in all the static mandibular tasks, with significant effect for time for the right temporal muscle (p = 0.038), the left temporal muscle (p = 0.028) and in the all dynamic mandibular tasks for the left temporal muscle (p = 0.025) and the left masseter muscle (p = 0.027). Hippotherapy promotes a reduction in the myoelectric activity of the masticatory muscles of elderly individuals.


Assuntos
Eletromiografia , Terapia Assistida por Cavalos , Músculo Esquelético/fisiologia , Idoso , Feminino , Humanos , Masculino , Mastigação/fisiologia , Pessoa de Meia-Idade
15.
PLoS One ; 15(8): e0237887, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32817652

RESUMO

The effects of High-Intensity Functional Training (HIFT) on body composition and the relationship of the latter with performance are not well defined. In this work we investigated, by means of Dual-energy X-ray Absorptiometry, the relative proportions of fat-, lean soft tissue-, and mineral mass in CrossFit® (CF, a popular mode of HIFT) participants (n = 24; age, 28.2 ± 3.39 y; BMI, 25.3 ± 2.04 kg/m2) with at least 1 year of CF training experience and weekly amount of training > 10 h/w (n = 13; Higher Training, HT) or < 10 h/w (n = 11; Lower Training, LT) as well as age- matched and BMI-matched physically active controls (CHT, CLT). Performance was assessed in the "Fran" workout. Data were analyzed by one-way or repeated measures ANOVA where needed. Association between variables was assessed with the Pearson's correlation coefficient r. Partial correlation was used where needed. Results showed that HT performed better than LT in the "Fran" (P < 0.001) and they had higher whole-body bone mineral density (P = 0.026) and higher lean soft mass (P = 0.002), and borderline lower percent fat mass (P = 0.050). The main difference between CF participants (HT, LT) and their respective controls (CHT, CLT) was a lower adiposity in the former. In CF participants, performance positively correlated with appendicular lean soft tissue mass (P = 0.030). It can be concluded that, in CF participants, a higher amount of weekly training improves most notably lean body mass and increases performance in association with increased skeletal muscle mass. CF participation is especially effective in reducing fat mass vs. age- and BMI-matched physically active controls.


Assuntos
Composição Corporal/fisiologia , Exercício Físico/fisiologia , Treinamento Intervalado de Alta Intensidade/métodos , Músculo Esquelético/fisiologia , Absorciometria de Fóton , Tecido Adiposo , Adiposidade/fisiologia , Adulto , Braço/fisiologia , Glicemia , Índice de Massa Corporal , Peso Corporal , Densidade Óssea , Capilares/fisiologia , Humanos , Masculino , Músculo Esquelético/anatomia & histologia , Adulto Jovem
16.
Life Sci ; 259: 118187, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32781061

RESUMO

AIMS: Voluntary exercise training has cardioprotective effects in humans, but the underlying mechanism is unknown. This research was done to estimate the effect of voluntary exercise training to attenuate middle-aged maturity-induced cardiac apoptosis. MATERIALS AND METHODS: The study was designed to divide 64 male mice randomly into four groups, consisting of a 9-month sedentary pre-middle-aged group (9M), 15-month sedentary middle-aged group (15M), and two exercise groups using a voluntary wheel running respectively (9M+EX, 15M+EX). After 3 months, the condition of cardiac apoptosis in different groups was measured by HE dying, TUNEL and DAPI staining, and Western Blot analysis. KEY FINDINGS: TUNEL-positive cells were increased in 15M group compared with 9M group, while decreased in 9M+EX and 15M+EX groups compared with their control groups respectively. Protein levels of AIF, Endo G, TNF-α, TNFR1, TRAF2, TRADD, Fas, FasL, FADD, activated caspase 8, 3, 9, Bax/Bcl2, Bak/BclxL, and tBid were decreased in 9M+EX and 15M+EX groups compared with their control groups respectively. The protein levels of pBad/Bad, 14-3-3, IGF1, IGFR1, pPI3K/PI3K, and pAKT/AKT were more activated in the 9M+EX and 15M+EX groups than those in their control groups respectively. Significant differences were found between 9M group and 15M group for the protein levels of TRAF2, FADD, Bax/Bcl2, tBid and pAKT/AKT. SIGNIFICANCE: Voluntary exercise training as an important lifestyle modification may prevent cardiac widely dispersed apoptosis and enhance cardiac survival at middle-aged maturity.


Assuntos
Envelhecimento/fisiologia , Apoptose/fisiologia , Coração/fisiologia , Condicionamento Físico Animal/fisiologia , Animais , Marcação In Situ das Extremidades Cortadas , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias Cardíacas/fisiologia , Músculo Esquelético/citologia , Músculo Esquelético/fisiologia , Corrida/fisiologia , Comportamento Sedentário
17.
Proc Natl Acad Sci U S A ; 117(33): 19866-19872, 2020 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-32753385

RESUMO

There is a growing interest in scientific literature on identifying how and to what extent interventions applied to a specific body region influence the responses and functions of other seemingly unrelated body regions. To investigate such a construct, it is necessary to have a global multivariate model that considers the interaction among several variables that are involved in a specific task and how a local and acute impairment affects the behavior of the output of such a model. We developed an artificial neural network (ANN)-based multivariate model by using parameters of motor skills obtained from kinematic, postural control, joint torque, and proprioception variables to assess the local fatigue effects of the abductor hip muscles on the functional profile during a single-leg drop landing and a squatting task. Findings suggest that hip abductor muscles' local fatigue produces a significant effect on a general functional profile, built on different control systems. We propose that expanded and global approaches, such as the one used in this study, have great applicability and have the potential to serve as a tool that guarantees ecological validity of future investigations.


Assuntos
Fadiga Muscular , Músculo Esquelético/fisiologia , Desempenho Físico Funcional , Feminino , Humanos , Destreza Motora , Redes Neurais de Computação , Equilíbrio Postural , Adulto Jovem
18.
Am J Physiol Regul Integr Comp Physiol ; 319(3): R323-R328, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32783690

RESUMO

Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate- and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e., attenuation of sympathetic vasoconstriction in the exercising muscles) is impaired in Black men compared with White men. Thirteen White and 14 Black healthy young men were studied. FBF (duplex Doppler ultrasound) and mean arterial pressure (MAP; Finometer) were measured at rest and during rhythmic handgrip exercise at 30% maximal voluntary contraction. FVC was calculated as FBF/MAP. Sympathetic activation was induced via lower body negative pressure (LBNP) at -20 Torr for 2 min at rest and from the 3rd to the 5th min of handgrip. Sympathetic vasoconstriction was assessed as percent reductions in FVC during LBNP. The groups presented similar resting FVC, FBF, and MAP. During LBNP at rest, reductions in FVC were not different between White (-35 ± 10%) and Black men (-32 ± 14%, P = 0.616), indicating similar reflex-induced sympathetic vasoconstriction. During handgrip exercise, there were minimal reductions in FVC with LBNP in either group (White: -1 ± 7%; Black: +1 ± 8%; P = 0.523), indicating functional sympatholysis in both groups. Thus, contrary to our hypothesis, our findings indicate a preserved functional sympatholysis in healthy young Black men compared with White men, suggesting that this mechanism does not appear to contribute to reduced exercise hyperemia during moderate-intensity rhythmic handgrip in this population.


Assuntos
Exercício Físico/fisiologia , Força da Mão/fisiologia , Consumo de Oxigênio/fisiologia , Vasoconstrição/fisiologia , Adulto , Humanos , Masculino , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Fluxo Sanguíneo Regional/fisiologia , Sistema Nervoso Simpático/fisiopatologia
19.
PLoS One ; 15(7): e0235156, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32667945

RESUMO

BACKGROUND: Single repetition, contraction-phase specific and total time-under-tension (TUT) are crucial mechano-biological descriptors associated with distinct morphological, molecular and metabolic muscular adaptations in response to exercise, rehabilitation and/or fighting sarcopenia. However, to date, no simple, reliable and valid method has been developed to measure these descriptors. OBJECTIVE: In this study we aimed to test whether accelerometer data obtained from a standard smartphone placed on the weight stack can be used to extract single repetition, contraction-phase specific and total TUT. METHODS: Twenty-two participants performed two sets of ten repetitions of their 60% one repetition maximum with a self-paced velocity on nine commonly used resistance exercise machines. Two identical smartphones were attached on the resistance exercise weight stacks and recorded all user-exerted accelerations. An algorithm extracted the number of repetitions, single repetition, contraction-phase specific and total TUT. All exercises were video-recorded. The TUT determined from the algorithmically-derived mechano-biological descriptors was compared with the video recordings that served as the gold standard. The agreement between the methods was examined using Limits of Agreement (LoA). The association was calculated using the Pearson correlation coefficients and interrater reliability was determined using the intraclass correlation coefficient (ICC 2.1). RESULTS: The error rate of the algorithmic detection of single repetitions derived from two smartphones accelerometers was 0.16%. Comparing algorithmically-derived, contraction-phase specific TUT against video, showed a high degree of correlation (r>0.93) for all exercise machines. Agreement between the two methods was high on all exercise machines as follows: LoA ranged from -0.3 to 0.3 seconds for single repetition TUT (0.1% of mean TUT), from -0.6 to 0.3 seconds for concentric contraction TUT (7.1% of mean TUT), from -0.3 to 0.5 seconds for eccentric contraction TUT (4.1% of mean TUT) and from -1.9 to 1.1 seconds for total TUT (0.5% of mean TUT). Interrater reliability for single repetition, contraction-phase specific TUT was high (ICC > 0.99). CONCLUSION: Data from smartphone accelerometer derived resistance exercise can be used to validly and reliably extract crucial mechano-biological descriptors. Moreover, the presented multi-analytical algorithmic approach enables researchers and clinicians to reliably and validly report missing mechano-biological descriptors.


Assuntos
Acelerometria/instrumentação , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Treinamento de Resistência , Smartphone , Adulto , Idoso , Feminino , Voluntários Saudáveis , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Levantamento de Peso/fisiologia , Adulto Jovem
20.
Nat Commun ; 11(1): 3722, 2020 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-32709902

RESUMO

Human movement occurs through contraction of the basic unit of the muscle cell, the sarcomere. Sarcomeres have long been considered to be arranged end-to-end in series along the length of the muscle into tube-like myofibrils with many individual, parallel myofibrils comprising the bulk of the muscle cell volume. Here, we demonstrate that striated muscle cells form a continuous myofibrillar matrix linked together by frequently branching sarcomeres. We find that all muscle cells contain highly connected myofibrillar networks though the frequency of sarcomere branching goes down from early to late postnatal development and is higher in slow-twitch than fast-twitch mature muscles. Moreover, we show that the myofibrillar matrix is united across the entire width of the muscle cell both at birth and in mature muscle. We propose that striated muscle force is generated by a singular, mesh-like myofibrillar network rather than many individual, parallel myofibrils.


Assuntos
Fenômenos Mecânicos , Músculo Esquelético/fisiologia , Miofibrilas/fisiologia , Sarcômeros/fisiologia , Animais , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia Eletrônica , Contração Muscular/fisiologia , Desenvolvimento Muscular , Músculo Esquelético/citologia , Miofibrilas/patologia , Sarcômeros/patologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA