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1.
J Sports Med Phys Fitness ; 60(8): 1057-1064, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32955831

RESUMO

BACKGROUND: Rock climbers are characterized by enhanced forearm fatigue resistance. This study compared the forearm isometric force of rock climbers (RC), strength-matched power lifters (PL) and aerobically trained (AT) athletes to determine the contribution of muscle oxygen desaturation during ischemia. METHODS: Aerobically trained athletes (N.=6, 23±1 years, 77±1 kg), power lifters (N.=7, 24±1 years, 80±3 kg) and rock climbers (N.=8, 25±2 years, 74±2 kg) took part in a controlled forearm ischemic occlusion (5 min) assessment using near infrared spectroscopy. In addition, three fatigue protocols were completed: protocol 1, sustained maximal voluntary contraction (MVC) until exhaustion; protocol 2, sustained 40% MVC for 3 mins duration; protocol 3, an intermittent 40% MVC (5-s contraction, 5-s recovery) for a duration of 3 mins. Forearm contractile fatigue was quantified as the reduction in MVC. RESULTS: MVC was equivalent between groups (P>0.05). Sustained MVC force (time to decline 50% MVC) was longer in the RC versus AT (AT: 35±5, PL: 46±6, RC: 54±4 s, P<0.05) and both AT and PL for sustained 40% MVC (AT: 56±9, RT: 62±8, RC: 87±7 s, P<0.05). Reduction in MVC was less in RC post intermittent 40% contractions (P<0.05). Oxygen desaturation half-time was longer in the RC versus AT (AT: 65±9, RT: 86±7, RC: 99±7 s, P<0.05) and this was associated with time to 50% MVC (P<0.05, r2=0.53) and time to 40% MVC task failure (P<0.05, r2=0.32). CONCLUSIONS: Rock climbers' enhanced isometric fatigue-resistance and ability to maintain MVC was associated with a lower oxygen consumption of the forearm flexors during the ischemic state. This suggests a training adaptation involving intracellular oxygen consumption.


Assuntos
Antebraço/fisiologia , Montanhismo/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Adaptação Fisiológica , Adulto , Dedos/fisiologia , Antebraço/irrigação sanguínea , Antebraço/diagnóstico por imagem , Humanos , Contração Isométrica/fisiologia , Masculino , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/diagnóstico por imagem , Consumo de Oxigênio , Condicionamento Físico Humano/fisiologia , Espectroscopia de Luz Próxima ao Infravermelho , Levantamento de Peso/fisiologia , Adulto Jovem
2.
J Sports Med Phys Fitness ; 60(8): 1148-1158, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32955841

RESUMO

BACKGROUND: There is paucity of data examining the effectiveness of long-term Hatha yoga-based (HY) programs focused on the health-related fitness (H-RF) of asymptomatic, sedentary women. The purpose of this study was to examine the effects of a 6-month HY-based training program on H-RF components in sedentary middle-aged women. METHODS: Eighty sedentary women were randomly assigned into either the HY group (HYG) (N.=42) or the control group (CG) (N.=38). The 6-month HYG program involved a progressive series of Vinyasa Flow poses performed 3 times/week for 60 minutes (40 minutes within the exercise zone of 60-75% HRmax). The CG participants did not undergo any physical training or education. Health-related fitness parameters included measures of pre- and post-training: body composition, muscular strength and maximal voluntary isometric torques of elbow flexors and knee extensors, cardio-respiratory fitness, lower back and hamstring flexibility and a static-dynamic balance. RESULTS: Two-way mixed design ANOVA revealed significant main effects for all the indicators of H-RF. Tukey post-hoc tests confirmed that the HYG demonstrated significant improvements in every variable tested. Examples of the benefits achieved include (all P<.001): an average loss of 1.03 kg and a 4.82% decrease in body fat, 14.6% and 13.1% gains in isometric strength of the knee extensors and elbow flexors respectively, an increase in relative VO2max of 6.1% (33.12±5.30 to 35.14±4.82 mL/kg/min), a 4-cm or 10.4% increase in their MSAR, and an average improved Balance Index of 5.6 mm/s. Reversely, the CG showed non-significant changes in H-RF variables (all P>0.05; percent range from -1.4% to 1.1%). CONCLUSIONS: By participating in a moderate-intensity 6-month HY-based training program, middle-aged women can significantly improve their HR-F status. The application of progressive target heart rate goals facilitated greater than expected improvements in cardio-respiratory fitness and improvements in body composition.


Assuntos
Aptidão Física/fisiologia , Comportamento Sedentário , Ioga , Adulto , Composição Corporal , Aptidão Cardiorrespiratória , Cotovelo/fisiologia , Feminino , Frequência Cardíaca , Humanos , Contração Isométrica/fisiologia , Joelho/fisiologia , Estudos Longitudinais , Pessoa de Meia-Idade , Força Muscular/fisiologia , Equilíbrio Postural/fisiologia , Torque
3.
J Electromyogr Kinesiol ; 53: 102439, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32563844

RESUMO

Muscle fibre conduction velocity (MFCV) is a basic physiological parameter biophysically related to the diameter of muscle fibres and properties of the sarcolemma. The aim of this study was to assess the intersession reproducibility of the relation between voluntary force and estimates of average muscle fibre conduction velocity (MFCV) from multichannel high-density surface electromyographic recordings (HDsEMG). Ten healthy men performed six linearly increasing isometric ankle dorsiflexions on two separate experimental sessions, 4 weeks apart. Each session involved the recordings of voluntary force during maximal isometric (MViF) and submaximal ramp contractions at 35-50-70% of MViF. Concurrently, the HDsEMG activity was detected from the tibialis anterior muscle and MFCV estimates were derived in 250-ms epochs. Absolute and relative reproducibility of MFCV initial value (intercept) and rate of change (regression slope) as a function of force were assessed by within-subject coefficient of correlation (CVw) and with intraclass correlation coefficient (ICC). MFCV was positively correlated with voluntary force (R2 = 0.75 ± 0.12) in all individuals and test conditions (P < 0.001). Average CVw for MFCV intercept and slope were of 2.6 ± 2.0% and 11.9 ± 3.2% and ICC values of 0.96 and 0.94, respectively. Overall, MFCV regression coefficients showed a high degree of intersession reproducibility in both absolute and relative terms. These results may have important practical implications in the tracking of training-induced neuromuscular changes and/or in the monitoring of the progress of neuromuscular disorders when a full sEMG signal decomposition is problematic or not possible.


Assuntos
Eletromiografia/métodos , Contração Isométrica/fisiologia , Fibras Musculares Esqueléticas/fisiologia , Condução Nervosa/fisiologia , Adulto , Humanos , Masculino , Músculo Esquelético/fisiologia , Reprodutibilidade dos Testes , Adulto Jovem
4.
J Electromyogr Kinesiol ; 53: 102438, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32569878

RESUMO

The general purpose of normalization of EMG amplitude is to enable comparisons between participants, muscles, measurement sessions or electrode positions. Normalization is necessary to reduce the impact of differences in physiological and anatomical characteristics of muscles and surrounding tissues. Normalization of the EMG amplitude provides information about the magnitude of muscle activation relative to a reference value. It is essential to select an appropriate method for normalization with specific reference to how the EMG signal will be interpreted, and to consider how the normalized EMG amplitude may change when interpreting it under specific conditions. This matrix, developed by the Consensus for Experimental Design in Electromyography (CEDE) project, presents six approaches to EMG normalization: (1) Maximal voluntary contraction (MVC) in same task/context as the task of interest, (2) Standardized isometric MVC (which is not necessarily matched to the contraction type in the task of interest), (3) Standardized submaximal task (isometric/dynamic) that can be task-specific, (4) Peak/mean EMG amplitude in task, (5) Non-normalized, and (6) Maximal M-wave. General considerations for normalization, features that should be reported, definitions, and "pros and cons" of each normalization approach are presented first. This information is followed by recommendations for specific experimental contexts, along with an explanation of the factors that determine the suitability of a method, and frequently asked questions. This matrix is intended to help researchers when selecting, reporting and interpreting EMG amplitude data.


Assuntos
Consenso , Técnica Delfos , Eletromiografia/métodos , Eletromiografia/normas , Músculo Esquelético/fisiologia , Projetos de Pesquisa/normas , Adulto , Eletrodos , Feminino , Humanos , Contração Isométrica/fisiologia , Masculino
5.
Rev. andal. med. deporte ; 13(2): 60-64, jun. 2020. ilus, tab, graf
Artigo em Português | IBECS | ID: ibc-194365

RESUMO

OBJETIVO: Analisar e comparar a atividade eletromiográfica (domínio temporal e espectral) dos músculos reto do abdome, oblíquo externo do abdome, oblíquo interno do abdome, eretor da espinha e multífido no exercício prancha ventral em superfície instável: bosu normal e invertido, durante 45 segundos de contração isométrica. MÉTODO: Quinze voluntários, adultos jovens, saudáveis e fisicamente ativos (21.73 ± 1.31 anos, estatura 177.10 ± 3.90 cm; 74.27 ± 5.38 kg, e 10.97 ± 1.60 % gordura corporal), sem histórico de lombalgia. O sinal eletromiográfica foi analisado no domínio temporal e espectral em três etapas distintas em cada exercício: Início (ETAPA A: 5 a 10 segundos), meio (ETAPA B: 20 a 25 segundos) e fim (ETAPA C: 40 a 45 segundos) e normalizado pela contração isométrica voluntária máxima. Utilizou eletrodos de superfície diferenciais simples com ganho de 20 vezes. No tratamento estatístico foi aplicado teste ANOVA two-way, com post hoc de Sidak (p < 0.05). RESULTADOS: Foi demonstrada similaridade na atividade eletromiográfica no domínio temporal de todos os músculos comparando bosu normal e invertido. Além disso, os resultados exibiram aumento da atividade eletromiográfica e redução da frequência mediana (slope negativo) durante as diferentes etapas em ambos os exercícios. CONCLUSÃO: Devido à similaridade de atividade eletromiográfica, a escolha da utilização da bosu normal ou invertido não se difere para indivíduos treinados, entretanto, a escolha do tempo de 45 segundos é uma estratégia interessante para aumentar a atividade eletromiográfica dos músculos do core e trabalhar a resistência à fadiga muscular, fatores imprescindíveis para prevenção de lombalgia


OBJETIVO: El objetivo de este estudio es analizar la relación entre la actividad electromiográfica de los músculos Reto del Abdomen, Oblicuo Externo, Oblicuo Interno, Eretor de la Espina y Multífido en el ejercicio tabla ventral en superficie inestable: bosu normal e invertido, durante 45 segundos de contracción isométrica. MÉTODO: Quince voluntarios, adultos jóvenes, sanos y físicamente activos (21.73 + 1.31 años, estatura 177.10 + 3.90 cm, 74.27 + 5.38 kg, y 10.97 + 1.60% Grasa Corporal), sin antecedentes de lumbalgia. La señal electromiográfica se analizó, en el dominio temporal y espectral, en tres etapas distintas en cada ejercicio: inicio (ETAPA A: 5 y 10 segundos), medio (ETAPA B: 20 y 25 segundos) y fin (ETAPA C: 40 y 45 segundos). Se utilizaron electrodos de superficie diferenciales simples con una ganancia de 20 veces, y la señal fue analizada en el dominio temporal y normalizada por la máxima contracción isométrica voluntaria. En el tratamiento estadístico se aplicó la prueba de Shapiro Wilk y ANOVA bidireccional, con post hoc de Sidak (p <0.05) para la señal electromiográfica de cada músculo. RESULTADOS: Hubo diferencias significativas entre las fases para todos los músculos, con énfasis en el recto del abdomen y oblicuo externo en las fases B y C e interacción significativa entre el ejercicio y la fase para todos los músculos. El bosu normal e invertido demostraron semejanza en la actividad electromiográfica para todos los músculos, pero en etapas diferentes (C y B / C, respectivamente). CONCLUSIÓN: Debido a la semejanza de actividad electromiográfica, la elección de la utilización de bosu normal e invertido es similar para individuos entrenados, sin embargo, la elección del tiempo de 45 segundos es una estrategia interesante para aumentar la actividad electrromiográfica de los músculos del core y trabajar la resistencia a la fatiga muscular, factores imprescindibles para la prevención de la lumbalgia


OBJECTIVE: To analyze and compare the electromyographic activity of the rectus abdominus, external oblique, internal oblique, erector spinae and multífido muscles in the bridge exercise with an unstable surface: normal and inverted bosu, for 45 seconds of isometric contraction. METHOD: Fifteen volunteers, young, healthy and physically active adults (21.73 ± 1.31 years, height 177.10 ± 3.90 cm, 74.27 ± 5.38 kg, and 10.97 ± 1.60% Body Fat), with no history of low back pain. The electromyographic signal was analyzed in three different steps in each exercise: start (STAGE A: 5 and 10 seconds), middle (STAGE B: 20 and 25 seconds) and end (STAGE C: 40 and 45 seconds). Simple differential surface electrodes with 20-fold gain were used and the signal was analyzed in the temporal domain and normalized by the maximum voluntary isometric contraction. In the statistical treatment, the Shapiro Wilk test and two-way ANOVA, with Sidak post hoc test (p <0.05) were applied to the electromyographic signal of each muscle. RESULTS: There were significant differences between phases for all muscles, with emphasis on rectus abdominus and external oblique in phases B and C and a significant interaction between exercise and phase for all muscles. normal and inverted bosu demonstrated similarity in electromyographic activity for all muscles, but at different stages (C and B / C, respectively). CONCLUSION: Due to the similarity of electromyographic activity, the choice of using normal or inverted bosu does not differ for trained individuals, however, choosing a 45-second time is an interesting strategy to increase the electromyographic activity of core muscles and to work resistance to muscle fatigue, essential factors for the prevention of low back pain


Assuntos
Humanos , Masculino , Adulto Jovem , Adulto , Contração Isométrica/fisiologia , Dor Lombar/prevenção & controle , Eletromiografia/métodos , Músculos Abdominais Oblíquos/fisiologia , Exercício Físico/fisiologia , Voluntários Saudáveis , Análise de Variância
6.
PLoS One ; 15(6): e0234401, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32584826

RESUMO

Previous studies suggest that marathon running induces lower extremity muscle damage. This study aimed to examine inter- and intramuscular differences in hamstring muscle damage after a marathon using transverse relaxation time (T2)-weighted magnetic resonance images (MRI). 20 healthy collegiate marathon runners (15 males) were recruited for this study. T2-MRI was performed before (PRE) and at 1 (D1), 3 (D3), and 8 days (D8) after marathon, and the T2 values of each hamstring muscle at the distal, middle, and proximal sites were calculated. Results indicated that no significant intermuscular differences in T2 changes were observed and that, regardless of muscle, the T2 values of the distal and middle sites increased significantly at D1 and D3 and recovered at D8, although those values of the proximal site remained constant. T2 significantly increased at distal and middle sites of the biceps femoris long head on D1 (p = 0.030 and p = 0.004, respectively) and D3 (p = 0.007 and p = 0.041, respectively), distal biceps femoris short head on D1 (p = 0.036), distal semitendinosus on D1 (p = 0.047) and D3 (p = 0.010), middle semitendinosus on D1 (p = 0.005), and distal and middle sites of the semimembranosus on D1 (p = 0.008 and p = 0.040, respectively) and D3 (p = 0.002 and p = 0.018, respectively). These results suggest that the distal and middle sites of the hamstring muscles are more susceptible to damage induced by running a full marathon. Conditioning that focuses on the distal and middle sites of the hamstring muscles may be more useful in improving recovery strategies after prolonged running.


Assuntos
Traumatismos em Atletas/diagnóstico por imagem , Traumatismos em Atletas/etiologia , Músculos Isquiossurais/diagnóstico por imagem , Músculos Isquiossurais/lesões , Corrida/fisiologia , Traumatismos em Atletas/fisiopatologia , Desempenho Atlético/fisiologia , Feminino , Músculos Isquiossurais/patologia , Humanos , Contração Isométrica/fisiologia , Japão , Imagem por Ressonância Magnética , Masculino , Fatores de Tempo , Torque , Adulto Jovem
7.
Sports Health ; 12(4): 395-400, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32525452

RESUMO

BACKGROUND: Little is known about the optimal exercise intensity and the effects of arm position on elastic resistance exercise. The purpose of this study was to investigate scapular muscle activity in different arm positions utilized during standing elastic resistance exercise. HYPOTHESIS: Lower trapezius (LT), serratus anterior (SA), and infraspinatus (IS) muscle activity will vary across arm positions above shoulder level. Also, oscillation resistance exercise will result in increased muscle activity compared with isometric contraction. STUDY DESIGN: Controlled laboratory study. LEVEL OF EVIDENCE: Level 4. METHODS: A total of 19 uninjured male collegiate baseball players volunteered to participate in this study. The electromyography (EMG) activity of the LT, upper trapezius (UT), middle deltoid (MD), SA, and IS muscles was determined using surface EMG in 3 arm positions: diagonal pattern 1 (D1), 120° of shoulder abduction (120), and 90° shoulder abduction with external rotation and elbow flexion (90/90) during both isometric contraction and oscillation resistance exercise. RESULTS: No difference in EMG activity of the LT muscle was found between the 120 and 90/90 position. However, the 120 position increased UT and MD muscle activity significantly more than those of the 90/90 position. The D1 arm position significantly increased SA muscle activity more than the 120 and 90/90 positions while the LT muscle activity was nearly silent. CONCLUSION: The standing 90/90 position effectively generated both LT and IS muscle EMG activity while minimizing both UT and MD muscle activity. CLINICAL RELEVANCE: The use of oscillation movements under elastic loading can create high muscle activation in the LT muscle without an adverse effect of the humeral head position and scapular rotation.


Assuntos
Braço/fisiologia , Treinamento de Resistência/métodos , Manguito Rotador/fisiologia , Músculos Superficiais do Dorso/fisiologia , Músculo Deltoide/fisiologia , Eletromiografia , Humanos , Contração Isométrica/fisiologia , Masculino , Escápula , Adulto Jovem
8.
Sci Rep ; 10(1): 7728, 2020 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-32382067

RESUMO

To assess if the alteration of neuromuscular properties of knee extensors muscles during heavy exercise co-vary with the SCV ([Formula: see text] slow component), eleven healthy male participants completed an incremental ramp test to exhaustion and five constant heavy intensity cycling bouts of 2, 6, 10, 20 and 30 minutes. Neuromuscular testing of the knee extensor muscles were completed before and after exercise. Results showed a significant decline in maximal voluntary contraction (MVC) torque only after 30 minutes of exercise (-17.01% ± 13.09%; p < 0.05) while single twitch (PT), 10 Hz (P10), and 100 Hz (P100) doublet peak torque amplitudes were reduced after 20 and 30 minutes (p < 0.05). Voluntary activation (VA) and M-wave were not affected by exercise, but significant correlation was found between the SCV and PT, MVC, VA, P10, P100, and P10/P100 ratio, respectively (p < 0.015). Therefore, because the development of the SCV occurred mainly between 2-10 minutes, during which neuromuscular properties were relatively stable, and because PT, P10 and P100 were significantly reduced only after 20-30 minutes of exercise while SCV is stable, a temporal relationship between them does not appear to exist. These results suggest that the development of fatigue due to alterations of neuromuscular properties is not an essential requirement to elicit the SCV.


Assuntos
Exercício Físico/fisiologia , Joelho/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/metabolismo , Oxigênio/metabolismo , Adulto , Eletromiografia , Humanos , Contração Isométrica/fisiologia , Articulação do Joelho/fisiologia , Masculino , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Torque , Adulto Jovem
9.
J Electromyogr Kinesiol ; 53: 102427, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32470865

RESUMO

Because of its superficial location, surface electrodes are commonly used to record lower trapezius activity. Recent evidence, however, would suggest that surface electromyography is not a valid to record activity from other superficially placed shoulder muscles. Therefore, the aim of this study was to determine the validity of using surface electrodes to record lower trapezius activity. Ten asymptomatic subjects performed ramped isometric (0-100% maximum load) and dynamic (70% maximum load) shoulder tasks. Intramuscular electrodes were inserted into lower trapezius and rhomboid major. Surface electrodes were placed over lower trapezius around the intramuscular electrodes. Differences in the recorded activity of lower trapezius between surface and intramuscular electrodes were tested using a 2 factor repeated measures analysis of variance with factors: test and electrode type. Similarity in the recorded activity patterns between the two electrodes was tested using Pearson's correlation coefficient (r). Results indicated that there was no difference in lower trapezius activity levels (p = 0.98) or activation patterns (r ≥ 0.74) recorded by the intramuscular and surface electrodes. The results of this study indicate that any potential crosstalk contamination in the surface electrode signal is having little influence on the recorded activity from lower trapezius and therefore, support the common practice of surface electromyography to investigate lower trapezius function.


Assuntos
Eletromiografia/métodos , Desempenho Psicomotor/fisiologia , Ombro/fisiologia , Músculos Superficiais do Dorso/fisiologia , Adulto , Eletrodos , Eletromiografia/instrumentação , Feminino , Humanos , Contração Isométrica/fisiologia , Masculino , Adulto Jovem
10.
Sports Health ; 12(4): 361-372, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32392094

RESUMO

BACKGROUND: The effect of preoperative hip strength on outcomes after hip arthroscopy for femoroacetabular impingement syndrome (FAIS) is unclear. The purpose of this study was to determine whether preoperative isometric hip strength is associated with outcome scores at 6 months as well as achieving the minimal clinically important difference (MCID) and patient acceptable symptomatic state (PASS) in patients undergoing hip arthroscopy for FAIS. HYPOTHESIS: Increased preoperative isometric strength will be correlated with short-term postoperative outcomes and will be predictive of achieving higher functional status. STUDY DESIGN: Case series. LEVEL OF EVIDENCE: Level 4. METHODS: Data from 92 consecutive patients undergoing primary hip arthroscopy for treatment of FAIS from March through August 2018 were analyzed. All patients included in the analysis had preoperative measures of isometric hip strength on both affected and unaffected limbs, as well as preoperative and 6-month patient-reported outcome (PRO) scores. Analysis was performed to determine correlations between normalized isometric hip strength measurements and PROs and whether strength measurements were predictive of achieving MCID or PASS. RESULTS: A total of 74 (80.4%) patients had 6-month PROs and were included in the final analysis. Hip extension strength on both sides was correlated with all postoperative PROs (all P > 0.05). Abduction strength on both sides was correlated with postoperative Hip Outcome Score-Activities of Daily Living subscale score, achieving MCID on at least 1 score threshold, and reaching the international Hip Outcome Tool-12 threshold score for achieving PASS (all P < 0.05). Regression analysis showed that extension strength on the affected side was the only strength measurement predictor of achieving PASS (1.043; P = 0.049). CONCLUSION: Preoperative isometric hip extension and abduction strength are correlated with 6-month postoperative PRO scores. Furthermore, hip extension strength is a predictor of achieving clinically meaningful outcomes. CLINICAL RELEVANCE: This study highlights the possible importance of preoperative optimization of hip function to maximize outcomes in patients undergoing hip arthroscopy for FAIS.


Assuntos
Artroscopia , Impacto Femoroacetabular/fisiopatologia , Impacto Femoroacetabular/cirurgia , Articulação do Quadril/fisiopatologia , Força Muscular/fisiologia , Período Pré-Operatório , Adulto , Artroscopia/reabilitação , Feminino , Humanos , Contração Isométrica/fisiologia , Masculino , Diferença Mínima Clinicamente Importante , Medidas de Resultados Relatados pelo Paciente , Análise de Regressão , Fatores Sexuais
11.
J Neuroeng Rehabil ; 17(1): 64, 2020 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-32410626

RESUMO

PURPOSE: The purpose of this study was to investigate transient bimanual effects on the force control capabilities of the paretic and non-paretic arms in individuals post stroke across submaximal and maximal force control tasks. METHODS: Fourteen chronic stroke patients (mean age = 63.8 ± 15.9; stroke duration = 38.7 ± 45.2 months) completed two isometric force control tasks: (a) submaximal control and (b) maximal sustained force production. Participants executed both tasks with their wrist and fingers extending across unimanual (paretic and non-paretic arms) and bimanual conditions. Mean force, force variability using coefficient of variation, force regularity using sample entropy were calculated for each condition. RESULTS: During the submaximal force control tasks (i.e., 5, 25, and 50% of maximum voluntary contraction), the asymmetrical mean force between the paretic and non-paretic arms decreased from unimanual to bimanual conditions. The asymmetry of force variability and regularity between the two arms while executing unimanual force control tended to decrease in the bimanual condition because of greater increases in the force variability and regularity for the non-paretic arm than those for the paretic arm. During the maximal sustained force production tasks (i.e., 100% of maximum voluntary contraction), the paretic arm increased maximal forces and decreased force variability in the bimanual condition, whereas the non-paretic arm reduced maximal forces and elevated force variability from unimanual to bimanual conditions. CONCLUSIONS: The current findings support a proposition that repetitive bimanual isometric training with higher execution intensity may facilitate progress toward stroke motor recovery.


Assuntos
Paresia/reabilitação , Recuperação de Função Fisiológica/fisiologia , Reabilitação do Acidente Vascular Cerebral/métodos , Acidente Vascular Cerebral/complicações , Idoso , Feminino , Lateralidade Funcional/fisiologia , Humanos , Contração Isométrica/fisiologia , Masculino , Pessoa de Meia-Idade , Paresia/etiologia , Paresia/fisiopatologia , Extremidade Superior/fisiopatologia
12.
Int J Sports Med ; 41(9): 596-602, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32396966

RESUMO

This study aimed at determining the effect of kinesio-taping (KT) on muscle performance and delayed onset muscle soreness (DOMS) after exercise induced muscle damaged. Sixty-six healthy men volunteered to participate (age:18-25 y/o), who performed 200 isokinetic lengthening contractions of the dominant quadriceps. Then subjects were randomized to either control (no treatment), sham (no tape tension), or KT (10% tape tension) groups. Muscle performance was assessed by peak torque and muscular work during maximal isometric and concentric isokinetic contractions. DOMS intensity was assessed using a visual analog scale. Measurements were taken pre-exercise (Pre), 48 h and 96 h post-exercise. Repeated measures ANOVA was used for comparisons within group, and ANCOVA for comparisons among groups. Muscle damage was confirmed in all participants by an increase in CK activity level (p<0.01). Decrease in isometric and isokinetic peak torque was detected at 48 h in the control and sham groups (p<0.01). Muscular work decreased in all groups at 48 h (p<0.01). No differences between groups were detected in muscular performance variables. Increase in DOMS intensity was determined in all groups at 48 h. Comparisons between groups showed lower DOMS intensity in the KT group at 48 h. KT decreased DOMS intensity perception after exercise-induced muscle damage; however, it did not impact muscular performance.


Assuntos
Desempenho Atlético/fisiologia , Fita Atlética , Mialgia/prevenção & controle , Músculo Quadríceps/fisiologia , Adolescente , Adulto , Creatina Quinase/sangue , Exercício Físico/fisiologia , Humanos , Contração Isométrica/fisiologia , Masculino , Contração Muscular/fisiologia , Percepção da Dor/fisiologia , Músculo Quadríceps/lesões , Músculo Quadríceps/metabolismo , Fatores de Tempo , Torque , Adulto Jovem
13.
Clin Interv Aging ; 15: 645-654, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32440107

RESUMO

Background/Objectives: Early detection of fall risk in persons older than 65 is of clinical relevance, but the diagnostic accuracy of currently used functional tests (eg short physical performance battery [SPPB] and timed up and go test [TUG]) to assess older persons' fall risks remains moderate. Recent literature highlights the importance of strong hip abductors to prevent falls. We thus aimed to assess the diagnostic accuracy of hip abductor strength measures to assess older persons' fall risks. Methods: Hip abductor maximum voluntary isometric strength (ABD MVIS), rate of force generation (ABD RFG), and the SPPB and TUG functional fall risk assessments were assessed in 60 persons aged over 65 years (82.0 ± 6.1 years). The diagnostic accuracy (area under the curve [AUC], sensitivity [sens], specificity [spec], positive predictive value [PPV], negative predictive value [NPV], and positive and negative likelihood ratios [LR+, LR-]) was evaluated at a clinically important 90% sensitivity level. Cut-off values for clinical use were calculated. Results: In our population, hip ABD MVIS (AUC 0.8, sens 90.6%, spec 57.1%, PPV 70.7%, NPV 84.2%, LR+ 2.1, LR- 0.2, and cut-off value ≤ 1.1 N/kg) and hip ABD RFG (AUC 0.8, sens 90.6%, spec 46.4%, PPV 65.9%, NPV 81.3%, LR+ 1.7, LR- 0.2, and cut-off ≤ 8.47 N/kg/s) show diagnostic accuracy comparable to other fall risk assessments (SPPB and TUG) and a high net sensitivity when used in a test battery. Conclusion: Hip ABD MVIS or RFG shows good diagnostic accuracy to differentiate between older fallers and nonfallers compared to the chosen external criterion history of falls. The high net sensitivity when hip ABD MVIS or RFG is combined with currently used fall risk assessments shows promise in contributing value to a test battery and should be investigated further in longitudinal studies.


Assuntos
Acidentes por Quedas/prevenção & controle , Articulação do Quadril/fisiologia , Modalidades de Fisioterapia/normas , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Contração Isométrica/fisiologia , Masculino , Assunção de Riscos , Sensibilidade e Especificidade
14.
Clin Exp Hypertens ; 42(7): 595-600, 2020 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-32249609

RESUMO

OBJECTIVE: Isometric resistance training may reduce resting blood pressure (BP); however, the magnitude of this effect varies among individual subjects and few studies attempted to predict it. This study aimed to investigate the potential hypotensive effects of isometric training and their association with cardiovascular reactivity to acute isometric exercise and muscle strength in young women. METHODS: In this randomized trial, twenty young women were randomly assigned to either the training (n = 10) or control (n = 10) group. Women from the training group performed unilateral isometric handgrip sessions for 8 weeks (4 × 2 min at 25% of maximal voluntary contraction [MVC]; 3 days/week). Cardiovascular reactivity to acute isometric exercise and MVC were measured at baseline. Resting BP was assessed during and after the intervention. RESULTS: Resting systolic BP significantly lowered only in the training group. The change in resting systolic BP following an 8-week intervention was significantly associated with the systolic BP and diastolic BP reactivity to the acute exercise at baseline during set 3 and 4 (P <.05). The handgrip MVC was associated with changes in systolic BP (r = 0.79, P =.007), diastolic BP (r = 0.68, P =.032), and mean arterial pressure (r = 0.79, P =.006). These results indicated that high cardiovascular reactivity and strength attenuate the hypotensive effects following isometric training in young women. CONCLUSIONS: The hypotensive effects following isometric training may be identified by BP reactivity to acute isometric exercise or handgrip strength in young women.


Assuntos
Pressão Sanguínea , Exercício Físico/fisiologia , Força da Mão/fisiologia , Contração Isométrica/fisiologia , Treinamento de Resistência , Adolescente , Feminino , Humanos , Descanso/fisiologia , Adulto Jovem
15.
J Sports Med Phys Fitness ; 60(7): 947-956, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32253892

RESUMO

BACKGROUND: We aimed to examine the associations of cardiorespiratory fitness (CRF), static strength and explosive strength with cognitive functions in young males. METHODS: Eighty-six young males (age 16-24 years) participated in the study and took part in a number of tests including: static strength (grip strength test), explosive strength (Sargent jump test), and CRF (via direct measure of maximal oxygen uptake [VO2max]). Static strength and explosive strength were scaled by allometrically modeled skeletal muscle mass (SMM) and height while VO2max was scaled by SMM and body mass (BM). Cognition was assessed by inhibitory control, simple and choice reaction time tasks using computerized Cambridge Neuropsychological Test Battery (CANTAB). Central processing time was measured by surface electromyography changes in isometric contraction response to an audio stimulus. RESULTS: VO2max scaled by BM (but not SMM), was associated with better central processing time and stop-signal reaction time (SSRT). Explosive strength was also associated with better central processing time independent of VO2max. However, static strength was not associated with cognition. CONCLUSIONS: The results suggest that explosive strength is a better predictor of central processing than static strength or VO2max in young males. Longitudinal studies are needed to examine whether explosive strength training in youth would improve central processing time.


Assuntos
Aptidão Cardiorrespiratória/fisiologia , Cognição/fisiologia , Força Muscular/fisiologia , Músculo Esquelético/fisiologia , Adolescente , Eletromiografia , Humanos , Contração Isométrica/fisiologia , Masculino , Testes Neuropsicológicos , Consumo de Oxigênio/fisiologia , Tempo de Reação , Treinamento de Resistência , Adulto Jovem
16.
J Sports Sci ; 38(14): 1615-1623, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32316854

RESUMO

Post-activation potentiation likely acutely improves power-based performance; however, few studies have demonstrated improved endurance performance. Forty collegiate female rowers performed isometric potentiating (ISO), dynamic potentiating (DYN) and control (CON) warm-up protocols on a rowing ergometer, followed by a three-minute all-out test to evaluate their total distance, peak power, mean power, critical power, anaerobic working capacity (W') and stroke rate. Fifteen-second splits were also analysed. ISO consisted of 5 × 5-second static muscle actions with the ergometer handle rendered immovable with a nylon strap, while DYN consisted of 2 × 10-second all-out rowing bouts, separated by a 2-minute rest interval. The participants were divided into high and low experience groups by median experience level (3.75 years) for statistical analysis. Significant differences (DYN > CON; p < 0.05) were found for distance (+5.6 m), mean power (+5.9 W) and W' (+1561.6 J) for more experienced rowers (n = 19) and no differences for less experienced rowers (n = 18). Mean power in DYN was significantly greater than CON and ISO in the 15-30, 30-45, 45-60 and 60-75 second intervals independent of experience level. These results suggest that DYN may benefit experienced female rowers and that these strategies might benefit a greater power output over shorter distances regardless of experience.


Assuntos
Resistência Física/fisiologia , Exercício de Aquecimento , Esportes Aquáticos/fisiologia , Estudos Cross-Over , Teste de Esforço , Feminino , Humanos , Contração Isométrica/fisiologia , Adulto Jovem
17.
Artigo em Inglês | MEDLINE | ID: mdl-32325707

RESUMO

BACKGROUND: This study examined the motor unit (MU) control strategies for non-fatiguing isometric elbow flexion tasks at 40% and 70% maximal voluntary isometric contraction. METHODS: Nineteen healthy individuals performed two submaximal tasks with similar torque levels: contracting against an immovable object (force task), and maintaining the elbow joint angle against an external load (position task). Surface electromyographic (EMG) signals were collected from the agonist and antagonist muscles. The signals from the agonist were decomposed into individual action potential trains. The linear regression analysis was used to examine the MU recruitment threshold (RT) versus mean firing rates (MFR), and RT versus derecruitment threshold (DT) relationships. RESULTS: Both agonist and antagonist muscles' EMG amplitudes did not differ between two tasks. The linear slopes of the MU RT versus MFR and RT versus DT relationships during the position task were more negative (p = 0.010) and more positive (p = 0.023), respectively, when compared to the force task. CONCLUSIONS: To produce a similar force output, the position task may rely less on the recruitment of relatively high-threshold MUs. Additionally, as the force output decreases, MUs tend to derecruit at a higher force level during the position task.


Assuntos
Potenciais de Ação/fisiologia , Eletromiografia , Contração Isométrica/fisiologia , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Recrutamento Neurofisiológico , Adulto , Braço/fisiologia , Articulação do Cotovelo/fisiologia , Eletromiografia/métodos , Humanos , Análise e Desempenho de Tarefas
18.
Phys Ther ; 100(6): 897-906, 2020 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-32157308

RESUMO

BACKGROUND: Functional outcomes with early rehabilitation in the acute care setting have improved; however, an improved understanding of muscle fatigue using surface electromyography (sEMG) is warranted to better guide patient-centered exercise prescription. OBJECTIVES: The objectives of this study were to assess the safety and feasibility of collecting sEMG at the acute care bedside and to determine differences in muscle fatigue during isometric and dynamic submaximal contractions among patients in the hospital, healthy younger participants, and healthy older participants. DESIGN: The study used an observational cohort design. METHODS: There were 37 participants. Median frequency (Fmed) of the myoelectric signal of the quadriceps femoris muscles and time to task failure (TTTF) were measured using sEMG during an isometric and dynamic fatiguing contraction. Primary analysis compared TTTF between groups for both types of contractions. Secondary analysis compared Fmed at initiation and termination of fatiguing contraction. RESULTS: High-quality sEMG measures were safe and feasible to collect at the acute care bedside with no adverse events. There was a statistically significant difference in TTTF between groups after isometric and dynamic contractions; hospitalized patients fatigued faster than healthy younger and healthy older participants after both contractions. With the exception of the vastus lateralis during a dynamic contraction in healthy younger and hospitalized patients, there was a statistically significant difference between Fmed at initiation and termination of contraction, indicating that subjects' muscles did truly fatigue. LIMITATIONS: A limitation of the study was the small sample size of patients who were hospitalized without matched controls. CONCLUSIONS: sEMG is a lab quantitative technique that was found to be safe and feasible to assess muscle fatigue in the acute care environment. The protocol yielded similar results to previously published literature for healthy younger and healthy older people. Further research is needed to better understand how to integrate sEMG findings into patient-centered exercise prescriptions.


Assuntos
Eletromiografia/métodos , Contração Isométrica/fisiologia , Fadiga Muscular/fisiologia , Músculo Quadríceps/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Coortes , Eletromiografia/efeitos adversos , Estudos de Viabilidade , Feminino , Voluntários Saudáveis , Hospitalização , Humanos , Masculino , Pessoa de Meia-Idade , Força Muscular , Testes Imediatos , Estatísticas não Paramétricas , Adulto Jovem
19.
J Sports Sci ; 38(9): 985-993, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32175825

RESUMO

The aim of this study was to investigate the physical determinants of weightlifting competition performance based on Isometric Mid-Thigh Pull (IMTP) and Countermovement Jump (CMJ) force-time variables, in a cross-sectional and longitudinal analysis. Ten British advanced international female weightlifters' competition results and neuromuscular assessment data collected as part of the British Weight Lifting World Class Programme were utilised for the purpose of this study. All data were averaged for two consecutive 1-year periods. The cross-sectional analysis utilised the second year of data, whereas the longitudinal analysis assessed the mean change between the two years. The cross-sectional analysis results reveal IMTP Net Isometric Peak Force (PF) and CMJ Peak Power (PP) predict 94.2%, 95.1% and 91.8% of the variance in Total, Snatch and Clean & Jerk competition performance, respectively (p = <0.5). The longitudinal analysis results revealed that ∆IMTP PF was the only predicting factor of longitudinal change in weightlifting competition performance predicting 41.5%, 41.7% and 42.5% of ∆Total, ∆Snatch and ∆Clean & Jerk, respectively (p = <0.5). The assessments and equations may be utilised by coaches or sports scientists to inform the prescription of training and help predict competition performance.


Assuntos
Desempenho Atlético/fisiologia , Comportamento Competitivo/fisiologia , Contração Isométrica/fisiologia , Músculo Esquelético/fisiologia , Levantamento de Peso/fisiologia , Adulto , Estudos Transversais , Teste de Esforço , Feminino , Humanos , Estudos Longitudinais , Músculo Esquelético/inervação , Exercício Pliométrico , Coxa da Perna , Adulto Jovem
20.
Phys Ther Sport ; 43: 127-133, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32146433

RESUMO

OBJECTIVES: To compare ankle, knee and hip isometric peak torque between young and middle-aged adults with CAI, copers and un-injured controls. DESIGN: Cross-sectional. SETTING: Research Laboratory. PARTICIPANTS: One hundred fifty-six young and middle-aged adults with or without CAI volunteered. MAIN OUTCOME MEASURES: A handheld dynamometer measured isometric dorsiflexion, plantarflexion, knee extension, hip extension and hip abduction peak force during a 5 s trial. Average peak torque was calculated and normalized to body mass. RESULTS: A significant Age by Injury interaction for dorsiflexion suggest middle-aged un-injured controls (p < 0.001) and copers (p < 0.001) had lower isometric peak torque compared to their young adult counterparts, but there were no differences between young and middle-aged adults with CAI (p > 0.05). Significant Injury main effects suggest the CAI group had decreased plantarflexion (p = 0.004) and hip extension (p = 0.010) strength compared to un-injured controls, but not copers (p > 0.05). Significant Age main effects for all primary outcome measures were observed, indicating peak torque decreased with age (p < 0.05). CONCLUSIONS: Regardless of age, isometric ankle and hip peak torque was lower in participants with CAI compared to un-injured controls, but not copers. These findings provide further evidence towards the impact of CAI in both young and middle-aged adults.


Assuntos
Adaptação Psicológica , Articulação do Tornozelo/fisiopatologia , Articulação do Quadril/fisiopatologia , Contração Isométrica/fisiologia , Instabilidade Articular/fisiopatologia , Adolescente , Adulto , Idoso , Doença Crônica , Estudos Transversais , Feminino , Humanos , Instabilidade Articular/psicologia , Masculino , Pessoa de Meia-Idade , Dinamômetro de Força Muscular , Adulto Jovem
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