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1.
J Sports Sci ; 38(8): 863-872, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32138604

RESUMO

We aimed to evaluate the changes in double poling (DP) kinematics due to a long-distance cross-country skiing race in athletes with different performance levels. A total of 100 cross-country skiers, belonging to 10 different performance groups, were filmed on flat terrain 7 and 55 km after the start line, during a 58-km classical race. Cycle velocity, frequency and length decreased from the best to the lower-ranked group, while duty cycle increased (all P <.001). Between track sections, cycle velocity and length decreased, duty cycles increased (all P <.001) while frequency was unaltered (P =.782). Group*section interactions resulted for cycle velocity (P =.005). Considering all the participants together, % change in cycle velocity between sections correlated with % change in length and duty cycle (all P <.001). Thus i) skiers in better groups showed longer and more frequent cycles as well as shorter duty cycles than skiers in slower groups; ii) throughout the race all the groups maintained the same cycle frequency while decreasing cycle velocity and length; iii) better groups showed a lower reduction in cycle velocity. Individually, a low reduction in cycle velocity during the race related to the capacity to maintain long cycles and short duty cycles.


Assuntos
Destreza Motora/fisiologia , Resistência Física/fisiologia , Esqui/fisiologia , Fenômenos Biomecânicos , Feminino , Humanos , Masculino , Fadiga Muscular/fisiologia , Estudos de Tempo e Movimento
2.
J Sports Sci Med ; 19(1): 130-137, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32132836

RESUMO

Different shoes and strike patterns produce different biomechanical characteristics that can affect injury risk. Running shoes are mainly designed as lightweight, minimal, or traditional cushioned types. Previous research on different shoes utilized shoes of not only different mass but also different shoe structures. However, it is unclear whether biomechanical changes during running in different shoe types with differing mass are the result of the structural design or the mass of the shoe. Thus, the purpose of this study was to investigate the effect of shoes of different mass on running gait biomechanics. Twenty male runners participated in this study. The experimental shoe masses used in this study were 175, 255, 335 and 415 g. The peak vertical ground reaction force increased with shoe mass (p < 0.05), but the strike index, ankle plantarflexion at initial contact, peak moment of the ankle during the stance phase, and initial contact angles of the lower extremity joints did not change. During the pre-activation phase, the integrated EMG data showed that the tibialis anterior muscle was the most activated with the 175 g and 415 g shoes (p < 0.05). During the push-off phase, the semitendinosus, lateral gastrocnemius and soleus muscles displayed higher activation with the heavier shoes (p < 0.05). The center of pressure also moves forward; resulting in mid foot striking. The lightest shoes might increase gastrocnemius muscle fatigue during the braking phase. The heaviest shoes could cause semitendinosus and triceps surae muscle fatigue during the push-off phase. Therefore, runners should consider their lower extremity joints, muscle adaptation and cushioning to remain in their preferred movement path.


Assuntos
Pé/fisiologia , Corrida/fisiologia , Sapatos , Tornozelo/fisiologia , Traumatismos em Atletas/prevenção & controle , Fenômenos Biomecânicos/fisiologia , Eletromiografia , Desenho de Equipamento , Análise da Marcha , Humanos , Masculino , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Pressão , Corrida/lesões , Adulto Jovem
3.
J Sports Sci Med ; 19(1): 204-212, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32132844

RESUMO

Limited research has paralleled concomitant changes in external training load (eTL) and countermovement jump (CMJ) performance. Therefore, this investigation characterized eTL and CMJ performance changes across preseason training in Division 1 male collegiate basketball athletes, while examining the influence of position (Guard vs. Forward/Center) and scholarship status (Scholarship = S vs. Walk-on = WO). During 22 practices, eTL was monitored in 14 male athletes, with weekly CMJs performed to quantify neuromuscular performance (Jump Height [JH], Flight Time:Contraction Time [FT:CT], Reactive Strength Index Modified [RSIMod ]). PlayerLoad per minute was significantly higher during W1 and W2 (5.4 ± 1.3au and 5.3 ± 1.2au, respectively; p < 0.05) compared to subsequent weeks, but no additional differences in eTL parameters across time were observed. Scholarship athletes displayed greater PlayerLoad (S = 777.1 ± 35.6, WO = 530.1 ± 56.20; Inertial Movement Analysis (IMA) IMA_High (S = 70.9 ± 15.2, WO = 41.3 ± 15.2); IMA_Medium (S = 159.9 ± 30.7, WO = 92.7 ± 30.6); and IMA_Low (S = 700.6 ± 105.1, WO = 405 ± 105.0;) (p < 0.05), with no observed differences in eTL by position. Moderate decreases in FT:CT and RSIMod paralleled increased eTL. Significant increases in practice intensity (W1 and W2) did not impact CMJ performance, suggesting athletes could cope with the prescribed training loads. However, moderate perturbations in FT:CT and RSIMod paralleled the weeks with intensified training. Cumulatively, scholarship status appears to influence eTL while player position does not.


Assuntos
Desempenho Atlético/fisiologia , Basquetebol/fisiologia , Destreza Motora/fisiologia , Condicionamento Físico Humano/fisiologia , Bolsas de Estudo , Humanos , Masculino , Fadiga Muscular/fisiologia , Condicionamento Físico Humano/métodos , Estudos Prospectivos , Adulto Jovem
4.
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
5.
Am J Physiol Regul Integr Comp Physiol ; 318(5): R981-R996, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32186893

RESUMO

Selenoprotein S (Seps1) can be protective against oxidative, endoplasmic reticulum (ER), and inflammatory stress. Seps1 global knockout mice are less active, possess compromised fast muscle ex vivo strength, and, depending on context, heightened inflammation. Oxidative, ER, and inflammatory stress modulates contractile function; hence, our aim was to investigate the effects of Seps1 gene dose on exercise performance. Seps1-/- knockout, Seps1-/+ heterozygous, and wild-type mice were randomized to 3 days of incremental, high-intensity treadmill running or a sedentary control group. On day 4, the in situ contractile function of fast tibialis anterior (TA) muscles was determined. Seps1 reduction or deletion compromised exercise capacity, decreasing distance run. TA strength was also reduced. In sedentary Seps1-/- knockout mice, TA fatigability was greater than wild-type mice, and this was ameliorated with exercise. Whereas, in Seps1+/- heterozygous mice, exercise compromised TA endurance. These impairments in exercise capacity and TA contractile function were not associated with increased inflammation or a dysregulated redox state. Seps1 is highly expressed in muscle fibers and blood vessels. Interestingly, Nos1 and Vegfa mRNA transcripts were decreased in TA muscles from Seps1-/- knockout and Seps1-/+ heterozygous mice. Impaired exercise performance with Seps1 reduction or deletion cannot be attributed to heightened cellular stress, but it may potentially be mediated, in part, by the effects of Seps1 on the microvasculature.


Assuntos
Citocinas/sangue , Estresse do Retículo Endoplasmático , Tolerância ao Exercício , Mediadores da Inflamação/sangue , Contração Isométrica , Proteínas de Membrana/deficiência , Músculo Esquelético/irrigação sanguínea , Músculo Esquelético/metabolismo , Estresse Oxidativo , Condicionamento Físico Animal , Selenoproteínas/deficiência , Animais , Citocinas/genética , Estresse do Retículo Endoplasmático/genética , Regulação da Expressão Gênica , Masculino , Proteínas de Membrana/genética , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microcirculação , Fadiga Muscular , Fibras Musculares de Contração Rápida/metabolismo , Fibras Musculares de Contração Rápida/patologia , Força Muscular , Músculo Esquelético/patologia , Oxirredução , Estresse Oxidativo/genética , Corrida , Selenoproteínas/genética , Fatores de Tempo
6.
J Sports Sci ; 38(9): 961-969, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32138596

RESUMO

This study examined the effects of lower-body compression garments on perceived recovery and subsequent performance in basketball athletes. In a parallel-group design, 30 recreational, male basketball athletes were randomly allocated to either a control (CON, n = 15, loose-fitting clothing) or experimental group (COMP, n = 15, compression garments) for 15 h following fatigue-inducing, basketball-specific exercise in the evening (1600-1800 h). Perceptual measures of fatigue and muscle soreness, as well as physical performance tests (sprints, jumps and agility), were performed pre-exercise, post-exercise, and post-recovery (15 h following exercise). Subjective and objective measures of sleep were recorded following the exercise trial. There were non-significant (p > 0.05), unclear-trivial differences between groups for all performance measures. Perceived post-recovery fatigue (d = -1.27, large) and muscle soreness (d = -1.61, large) were significantly lower in COMP compared to CON (p < 0.05). COMP exhibited better perceived sleep quality (d = 0.42, small, p = 0.18) than CON, with an unclear difference in sleep duration between groups (p > 0.05). Wearing lower-body compression garments overnight improved perceived fatigue and muscle soreness, but had negligible effects on subsequent physical performance in basketball athletes. Future research should focus on longer periods of compression wear following fatiguing exercise.


Assuntos
Desempenho Atlético/fisiologia , Basquetebol/fisiologia , Fadiga/prevenção & controle , Mialgia/prevenção & controle , Meias de Compressão , Adulto , Basquetebol/psicologia , Humanos , Masculino , Fadiga Muscular/fisiologia , Mialgia/fisiopatologia , Percepção , Sono/fisiologia , Adulto Jovem
7.
Int J Sports Med ; 41(6): 360-364, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32059241

RESUMO

Vitamin D has been shown to benefit a diverse range of health functions including muscle function. The aim of the present study was to identify serum 25(OH)D3 levels in a sample of adolescent dancers and compare them to muscle function and injury incidence. We incorporated a cross-sectional design to study 49 pre-professional male and female dancers (17±4.44 yrs, 52.1±6.72 kg, 1.63±0.07 m) in full-time training in Bazil. Serum 25[OH]D3 was analyzed by Enzyme-linked Immunosorbent Assay; quadriceps and hamstring peak torque and muscle fatigue were measured by isokinetic dynamometer at 60 and 300° s-1. Injury type and location in the previous 6-months were determined by self-report questionnaire. Participants were categorized into 2 groups: normal or insufficient/deficient (>or<30 ng/ml 25[OH]D3). Results indicated the normal serum 25[OH]D3 group had significantly lower fatigue rates than the insufficient/deficient group (p<0.05) but not for the other muscle function parameters. Fifty-seven percent of participants reported at least 1 injury. The most common were sprains (33%) and tendinopathies (19%). Injured dancers had significantly lower peak torque at 60°/s. The link between serum 25[OH]D3 and reduced muscle fatigue resistance has not been shown before, though the underlying mechanisms aren't apparent and the link between muscular strength and injury has been previously evidenced.


Assuntos
Calcifediol/sangue , Dança/lesões , Dança/fisiologia , Músculo Esquelético/fisiologia , Adolescente , Estudos Transversais , Feminino , Humanos , Masculino , Fadiga Muscular/fisiologia , Força Muscular/fisiologia , Entorses e Distensões/diagnóstico , Tendinopatia/diagnóstico , Adulto Jovem
8.
Phys Ther ; 100(3): 438-446, 2020 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-32043129

RESUMO

BACKGROUND: Survivors of breast cancer commonly report functional limitations, including cancer-related fatigue (CRF) and decreased aerobic capacity. One key gap is addressing the 3 energy systems (aerobic, anaerobic lactic, and alactic), requiring assessment to establish a baseline exercise intensity and duration. OBJECTIVE: This study examined the feasibility of energy system-based assessment, also providing descriptive values for assessment performance in this population. DESIGN: This was a cross-sectional study. METHODS: Seventy-two posttreatment survivors of breast cancer were recruited. Following a baseline musculoskeletal assessment, women attempted 3 energy system assessments: submaximal aerobic (multistage treadmill), anaerobic alactic (30-second sit-to-stand [30-STS]), and anaerobic lactic (adapted burpees). Heart rate (HR) and rating of perceived exertion (RPE) were recorded. Secondary outcomes included body composition, CRF, and upper- and lower-limb functionality. RESULTS: Seventy of 72 participants performed the 30-STS and 30 completed the adapted burpees task. HR and RPE specific to each task were correlated, reflecting increased intensity. Women reported low-moderate levels of CRF scores (3% [2.1]) and moderate-high functionality levels (upper-limb: 65.8% [23.3]; lower-limb: 63.7% [34.7]). LIMITATIONS: All survivors of breast cancer had relatively low levels of CRF and moderate functioning. Additionally, on average, participants were classified as "overweight" based on BMI. CONCLUSION: This study is the first to our knowledge to demonstrate feasibility of energy system assessment in survivors of breast cancer. Using a combination of HR and RPE, as well as baseline assessment of each energy system, clinicians may improve ability to prescribe personalized exercise and give patients greater ability to self-monitor intensity and progress.


Assuntos
Limiar Anaeróbio/fisiologia , Neoplasias da Mama/fisiopatologia , Sobreviventes de Câncer , Exercício Físico/fisiologia , Desempenho Físico Funcional , Adulto , Idoso , Composição Corporal , Neoplasias da Mama/terapia , Estudos Transversais , Teste de Esforço/métodos , Tolerância ao Exercício , Extremidades/fisiopatologia , Estudos de Viabilidade , Feminino , Frequência Cardíaca , Humanos , Pessoa de Meia-Idade , Fadiga Muscular/fisiologia , Esforço Físico , Postura Sentada , Posição Ortostática
9.
J Sports Sci ; 38(5): 568-575, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32019482

RESUMO

This study aimed to assess the effect of playing surface (Natural [NT] and Artificial [AT] Turf) on the fatigue response to a soccer-specific exercise protocol (SSEP). Eighteen male soccer players completed the SSEP on NT and AT with pre-, post-, and 48 h post-assessments of eccentric knee flexor (eccKF) and concentric knee extensor peak torque (PT), peak countermovement (CMJ) and squat jump (SJ) height, and Nordic hamstring break angle. No significant main effects for surface or any surface and time interactions were observed for any of the outcome measures, except for eccKF PT recorded at 3.14 rad·s-1, which was significantly lower 48 h post-trial in the AT condition (AT = 146.3 ± 20.4 Nm; NT = 158.8 ± 24.7 Nm). Main effects for time were observed between pre- and post-trial measures for eccKF PT at all angular velocities, Nordic break angle, CMJ and SJ height. Nordic break angle, and both CMJ and SJ height were significantly impaired 48 h post-trial when compared to pre-trial. The findings of the current study suggest surface dependent changes in eccKF PT which may have implications for recovery and subsequent performance after competition on AT.


Assuntos
Planejamento Ambiental , Exercício Físico/fisiologia , Articulação do Joelho/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Futebol/fisiologia , Adulto , Desempenho Atlético/fisiologia , Estudos Cross-Over , Músculos Isquiossurais/fisiologia , Humanos , Masculino , Fenômenos Fisiológicos Musculoesqueléticos , Desempenho Físico Funcional , Amplitude de Movimento Articular , Futebol/lesões , Torque , Adulto Jovem
10.
J Sports Sci ; 38(6): 644-651, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32009514

RESUMO

The purpose of this study was to investigate the neuromuscular and perceptual fatigue responses of elite rugby players during the inaugural Under-18 (U18) Six Nations Festival. One hundred and thirty-three male players from five national squads (73 forwards, 60 backs) were examined during the competition. Each national squad was involved in three matches separated by 96 h each. Over the competition, players completed a daily questionnaire to monitor perceived well-being (WB) and performed daily countermovement jumps (CMJ) to assess neuromuscular function (NMF). Reductions in WB were substantial 24 h after the first and second match in forwards (d=0.77±0.21, p<0.0001; d=0.84±0.22, p< 0.001) and backs (d=0.89±0.22, p <0.0001; d=0.58±0.23, p<0.0001) but reached complete recovery in time for the subsequent match. Reductions in CMJ height were substantial 24 h after the first and second match for forwards (d=0.31±0.15, p=0.001; d=0.25±0.17, p=0.0205) and backs (d=0.40±0.17, p=0.0001; d=0.28±0.17, p=0.0062) and recovered at 48 h after match-play. Average WB and CMJ height attained complete recovery within matchday cycles in the investigated international competition. The findings of this study can be useful for practitioners and governing bodies involved with fixture scheduling and training prescription during competitive periods.


Assuntos
Comportamento Competitivo/fisiologia , Fadiga/fisiopatologia , Futebol Americano/fisiologia , Fadiga Muscular/fisiologia , Adolescente , Humanos , Estudos Longitudinais , Extremidade Inferior/fisiologia , Masculino , Percepção/fisiologia , Esforço Físico/fisiologia , Estudos Prospectivos , Fatores de Tempo
11.
PLoS One ; 15(1): e0227675, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32004350

RESUMO

Mixed Martial Arts (MMA) is a multielement combat sport where fighters need to quickly react to an opponent's movements under fatigued conditions. Research indicates that fast reaction time is important in many sports, but the effect of fatigue has shown negative, null, or even positive influences on reaction time. However, few studies have been conducted in a controlled setting, especially using MMA figthers, whose matches are frequently resolved in a split-second. Therefore, this study investigated whether acute neuromuscular fatigue affects reaction and movement times, and their consistency in MMA fighters (N = 45). Before and after an upper-body Wingate test, a simple visual reaction time task was completed. Results showed a significant negative effect of fatigue on the reaction times and their consistency, with longer reactions (1.5% change) and lower consistency (14.7% change) after the Wingate test. Further, greater amounts of fatigue during the Wingate test seemed to negatively affect the consistency of post-Wingate movement time. Due to cumulative fatigue and the dynamic nature of MMA, our data indicate that not only the decrements in aerobic and anaerobic power likely affect a fighter's performance, but their reaction time and motor time may also be compromised during a fight.


Assuntos
Artes Marciais/fisiologia , Fadiga Muscular/fisiologia , Tempo de Reação/fisiologia , Adolescente , Adulto , Limiar Anaeróbio/fisiologia , República Tcheca , Humanos , Masculino , Adulto Jovem
12.
Muscle Nerve ; 61(3): 416-424, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31893464

RESUMO

INTRODUCTION: The conditional nebulin knockout mouse is a new model mimicking nemaline myopathy, a rare disease characterized by muscle weakness and rods within muscle fibers. We investigated the impact of nebulin (NEB) deficiency on muscle function in vivo. METHODS: Conditional nebulin knockout mice and control littermates were studied at 10 to 12 months. Muscle function (force and fatigue) and anatomy (muscles volume and fat content) were measured in vivo. Myosin heavy chain (MHC) composition and nebulin (NEB) protein expression were assessed by protein electrophoresis. RESULTS: Conditional nebulin knockout mice displayed a lower NEB level (-90%) leading to a 40% and 45% reduction in specific maximal force production and muscles volume, respectively. Nebulin deficiency was also associated with higher resistance to fatigue and increased MHC I content. DISCUSSION: Adult nebulin-deficient mice displayed severe muscle atrophy and weakness in vivo related to a low NEB content but an improved fatigue resistance due to a slower contractile phenotype.


Assuntos
Proteínas Musculares/genética , Músculo Esquelético/fisiopatologia , Miopatias da Nemalina/fisiopatologia , Animais , Modelos Animais de Doenças , Feminino , Membro Posterior , Camundongos Knockout , Contração Muscular , Fadiga Muscular , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Miopatias da Nemalina/genética , Miopatias da Nemalina/patologia , Cadeias Pesadas de Miosina/metabolismo
13.
Int J Sports Physiol Perform ; 15(5): 663-670, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32000138

RESUMO

PURPOSE: To investigate the factors associated with underperformance and the subsequent changes in training characteristics and supportive actions when returning to the world's best cross-country skier. METHODS: The participant is the most decorated winter Olympian, with 8 Olympic gold medals, 18 World Championship titles, and 114 World Cup victories. Training data were categorized by training form (endurance, strength, and speed); intensity (low, moderate, and high); and mode (running, cycling, and skiing/roller skiing). In addition, test data were retrospectively analyzed, and interviews were performed with the participant and her support team. RESULTS: After the competitive season, the participant had 8 weeks without systematic training and an evaluation process aiming to detect the factors contributing to underperformance. Here physiological, technical, and psychological challenges were detected. As a consequence, the participant included less high-intensity training (1.2 vs 2.1 sessions/wk, P = .011); more moderate-intensity training (0.9 vs 0.4 sessions/wk, P = .016); and more low-intensity training (6.9 vs 5.9 sessions/wk, P = .036) during the general preparation phase but with similar total endurance training load as previous season. In addition, more strength training (1.6 vs 1.1 h/wk, P = .036) and new ski-specific strength exercises were included. Finally, the athlete's autonomy when planning and adjusting training was increased, nontraining stressors were reduced, more frequent testing was included, systematic mental training was initiated, her nutritional strategy was adjusted, and her asthma treatment was optimized. CONCLUSIONS: Overall, the current case study could be used as a framework for the holistic approach to treating an overtraining condition and for generation of new hypothesis in this exiting area.


Assuntos
Comportamento Competitivo/fisiologia , Condicionamento Físico Humano/métodos , Resistência Física/fisiologia , Esqui/fisiologia , Esqui/psicologia , Transtornos Traumáticos Cumulativos/prevenção & controle , Dieta , Feminino , Humanos , Fadiga Mental/fisiopatologia , Fadiga Muscular/fisiologia , Autonomia Pessoal , Condicionamento Físico Humano/fisiologia , Treinamento de Resistência , Estresse Psicológico/prevenção & controle , Fatores de Tempo
14.
J Electromyogr Kinesiol ; 50: 102384, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31918365

RESUMO

This study investigated the acute effect of active recovery (AR) following fatigue induced by 80 three-second maximal voluntary isometric plantar flexion contractions (MVICs) in 12 young men. AR consisted of a total of 180 voluntary isometric ramp contractions of the plantar flexors (0.75-s contraction/relaxation) targeting 10% of MVIC torque. MVIC torque, voluntary activation and root mean square values of electromyographic signals for the triceps surae normalized by each peak-to-peak amplitude of compound motor action potential were determined before, and immediately, 10, 20 and 30 min after the fatiguing task. Evoked torques were similarly assessed except for immediately after it. The AR and passive recovery were randomly performed on two days by each participant between 5 min and 10 min after the fatiguing task. For all the parameters other than MVIC torque, there was no significant difference between the conditions at any time point. MVIC torque decreased significantly immediately after the fatiguing task regardless of condition (P < 0.05), and the corresponding decrease in MVIC torque recovered 30 min after the fatiguing task only in AR (P < 0.05). These results suggest an acute positive effect of AR on recovery of neuromuscular function and/or contractile properties after fatigue.


Assuntos
Contração Isométrica , Fadiga Muscular , Músculo Esquelético/fisiologia , Adulto , Humanos , Masculino , Recuperação de Função Fisiológica , Torque
15.
J Electromyogr Kinesiol ; 50: 102385, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31935583

RESUMO

INTRODUCTION: We compared the recovery of muscle electrical properties after maximal voluntary contractions (MVCs) of 1 and 3 min duration by examining separately the first and second phases of the muscle compound action potential (M wave). METHODS: M waves were evoked by supramaximal single shocks to the femoral nerve throughout the 30-min recovery following 1-min and 3-min MVCs. The amplitude, duration, and area of the M-wave first and second phases, along with peak-to-peak amplitude and total area, were measured from the knee extensors. RESULTS: (1) The amplitude of the M-wave first phase increased to the same extent (and had the same time course of recovery) after the 1 and 3-min MVCs, whereas the amplitude of the second phase increased more markedly after the 1-min than after the 3-min MVC (P < 0.05). (2) The first phase remained enlarged for 2 min after exercise, whereas the augmentation of the second phase only lasted for 30 s. (3) After 30 min of recovery, the amplitude, area, and duration of both the first and second phases were decreased compared to control values (P < 0.05). CONCLUSIONS: The similar enlargement of the M-wave first phase after the 1 and 3-min MVCs suggests that the extracellular K+ concentration attained after these contractions was similar. The mechanisms responsible for the long-term decreases in M-wave amplitude and duration are unknown at present, but are likely due to a decrease in the amplitude of individual transmembrane potentials and an increase in conduction velocity.


Assuntos
Potencial Evocado Motor , Contração Isométrica , Fadiga Muscular , Músculo Esquelético/fisiologia , Adulto , Nervo Femoral/fisiologia , Humanos , Joelho/fisiologia , Articulação do Joelho/fisiologia , Masculino , Recuperação de Função Fisiológica
16.
Diabetes ; 69(4): 578-590, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31974138

RESUMO

A single bout of exercise enhances insulin action in the exercised muscle. However, not all human studies find that this translates into increased whole-body insulin action, suggesting that insulin action in rested muscle or other organs may be decreased by exercise. To investigate this, eight healthy men underwent a euglycemic-hyperinsulinemic clamp on 2 separate days: one day with prior one-legged knee-extensor exercise to local exhaustion (∼2.5 h) and another day without exercise. Whole-body glucose disposal was ∼18% lower on the exercise day as compared with the resting day due to decreased (∼37%) insulin-stimulated glucose uptake in the nonexercised muscle. Insulin signaling at the level of Akt2 was impaired in the nonexercised muscle on the exercise day, suggesting that decreased insulin action in nonexercised muscle may reduce GLUT4 translocation in response to insulin. Thus, the effect of a single bout of exercise on whole-body insulin action depends on the balance between local effects increasing and systemic effects decreasing insulin action. Physiologically, this mechanism may serve to direct glucose into the muscles in need of glycogen replenishment. For insulin-treated patients, this complex relationship may explain the difficulties in predicting the adequate insulin dose for maintaining glucose homeostasis following physical activity.


Assuntos
Glicemia/metabolismo , Exercício Físico/fisiologia , Insulina/farmacologia , Fadiga Muscular/fisiologia , Músculo Esquelético/metabolismo , Adulto , Técnica Clamp de Glucose , Glicogênio Sintase/metabolismo , Humanos , Masculino , Músculo Esquelético/efeitos dos fármacos , Fosfatidilinositol 3-Quinases/metabolismo
17.
PLoS One ; 15(1): e0228089, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31999750

RESUMO

INTRODUCTION: Cognitive stress (CS) changes the peripheral attributes of a muscle, but its effect on multi-head muscles has not been investigated. The objective of the current research was to investigate the impact of CS on the three heads of the triceps brachii (TB) muscle. METHODS: Twenty-five young and healthy university students performed a triceps push-down exercise at 45% one repetition maximum (1RM) with and without CS until task failure, and the rate of fatigue (ROF), endurance time (ET) and number of repetitions (NR) for both exercises were analyzed. In addition, the first and last six repetitions of each exercise were considered non-fatiguing (NF) and fatiguing (Fa), respectively, and the root mean square (RMS), mean power frequency (MPF) and median frequency (MDF) for each exercise repetition were evaluated. RESULTS: The lateral and long head showed significant differences (P<0.05) in the ROF between the two exercises, and all the heads showed significant (P<0.05) differences in the RMS between the two exercises under NF conditions. Only the long head showed a significant difference (P<0.05) in the MPF and MDF between the two exercises. CS increases the ET (24.74%) and NR (27%) of the exercise. The three heads showed significant differences (P<0.05) in the RMS, MPF and MDF under all exercise conditions. CONCLUSION: A lower ROF was obtained with CS. In addition, the RMS was found to be better approximator of CS, whereas MPF and MDF were more resistant to the effect of CS. The results showed that the three heads worked independently under all conditions, and the non-synergist and synergist head pairs showed similar behavior under Fa conditions. The findings from this study provide additional insights regarding the functioning of each TB head.


Assuntos
Cognição , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiopatologia , Estresse Psicológico/fisiopatologia , Adulto , Análise de Variância , Eletromiografia , Exercício Físico , Humanos , Masculino , Resistência Física , Postura/fisiologia , Processamento de Sinais Assistido por Computador , Fatores de Tempo
18.
PLoS One ; 15(1): e0227214, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31910235

RESUMO

The aim of this study was to investigate the effects of fatigue induced by repeated sprint in the kicking accuracy and velocity in female soccer players. Eighteen Under-23 female soccer players from a Spanish professional club were subjected to a fatigue protocol based on a repeated-sprint ability (RSA) test. Measurements of the kicking velocity (maximal ball velocity) and accuracy (Loughborough Soccer Shooting Test) were taken before and after fatigue induction. Correlations between the change in the maximal ball velocity/accuracy and the heart rate (HR), the fatigue index (FI), the sprint decrement (Sdec) and the rating of perceived exertion (RPE) were made. There was a significant difference between maximal ball velocity under fatigue conditions with respect to non-fatigue conditions (p = 0.001; ES = 0.89). However, despite a lower kicking accuracy punctuation with fatigue, this was not statistically significant (p = 0.433; ES = 0.22). Significant correlations were found between the maximal kicking velocity and the FI (r = 0.632, p < 0.01) and the Sdec (r = -0.554, p < 0.05) and between the kicking accuracy and the RPE (r = -0.506, p < 0.05). In conclusion, there was a significant reduction in the maximal kicking velocity, but not in the kicking accuracy, under fatigued conditions. The RSA-related FI and Sdec were the best predictors of the maximal kicking velocity and the RPE for the kicking accuracy.


Assuntos
Atletas , Desempenho Atlético/fisiologia , Fadiga Muscular/fisiologia , Corrida/fisiologia , Futebol/fisiologia , Adolescente , Teste de Esforço , Feminino , Humanos , Espanha , Adulto Jovem
19.
J Neuroeng Rehabil ; 17(1): 8, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992323

RESUMO

PURPOSE: Motivated by the goal of developing new methods to detect early signs of sarcopenia, we investigated if surface electromyographic (SEMG) data recorded during the performance of cyclic, submaximal back extensions are marked by age-specific differences in their time and frequency characteristics. Furthermore, day-to-day retest reliability of the EMG measures was examined. METHODS: A total of 86 healthy volunteers used a back dynamometer to perform a series of three maximal voluntary contractions (MVC) consisting of isometric back extensions, followed by an isometric back extension at 80% MVC, and finally 25 slow cyclic back extensions at 50% MVC. SEMG data was recorded bilaterally at L1, L2, and L5 from the iliocostalis lumborum, longissimus, and multifidus muscles, respectively. Tests were repeated two days and six weeks later. A linear mixed-effects model with fixed effects "age, sex, test number" and the random effect "person" was performed to investigate age-specific differences in both the initial value and the time-course (as defined by the slope of the regression line) of the root mean square (RMS-SEMG) values and instantaneous median frequency (IMDF-SEMG) values calculated separately for the shortening and lengthening phases of the exercise cycles. Generalizability Theory was used to examine reliability of the EMG measures. RESULTS: Back extensor strength was comparable in younger and older adults. The initial value of RMS-SEMG and IMDF-SEMG as well as the RMS-SEMG time-course did not significantly differ between the two age groups. Conversely, the IMDF-SEMG time-course showed more rapid changes in younger than in older individuals. Absolute and relative reliability of the SEMG time-frequency representations were comparable in older and younger individuals with good to excellent relative reliability but variable absolute reliability levels. CONCLUSIONS: The IMDF-SEMG time-course derived from submaximal, cyclic back extension exercises performed at moderate effort showed significant differences in younger vs. older adults even though back extension strength was found to be comparable in the two age groups. We conclude that the SEMG method proposed in this study has great potential to be used as a biomarker to detect early signs of sarcopenic back muscle function.


Assuntos
Envelhecimento/fisiologia , Músculos do Dorso/fisiologia , Diagnóstico Precoce , Eletromiografia/métodos , Sarcopenia/diagnóstico , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Exercício Físico/fisiologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Pessoa de Meia-Idade , Fadiga Muscular/fisiologia , Reprodutibilidade dos Testes , Adulto Jovem
20.
Sports Health ; 12(3): 296-303, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31994970

RESUMO

BACKGROUND: Because of the complex and multifaceted nature of running injuries, a multifactorial approach when investigating running injuries is required. HYPOTHESIS: Compared with uninjured runners, injured runners would exhibit different running biomechanics, display more fatigue changes, and would run a greater weekly running volume; more injured runners would also report having a previous injury. STUDY DESIGN: Prospective cohort study. LEVEL OF EVIDENCE: Level 4. METHODS: At commencement of the study, data were collected on demographics, anthropometrics, training history, previous injury history, and center-of-mass accelerations during a long-distance overground run. Participants completed weekly training diaries and were monitored for 1 year for an injury. RESULTS: A total of 76 runners completed the study, with 39 (22 male; 17 female) reporting an injury. Compared with male uninjured runners, male injured runners were heavier and ran a greater weekly distance. Male runners (injured and uninjured) exhibited increases in mediolateral center-of-mass accelerations during the run. Compared with female uninjured runners, female injured runners were heavier, ran with longer flight times and lower step frequencies, and more of them had reported an injury in the previous year and had increased speed training in the weeks prior to injury. Over 60% of male injured runners and over 50% of female injured runners had increased their weekly running distance by >30% between consecutive weeks at least once in the 4 weeks prior to injury. CONCLUSION: Factors that may be related to injury for male runners include being heavier, running a greater weekly distance, and exhibiting fatigue changes in mediolateral center-of-mass accelerations. Factors that may be related to injury for female runners include being heavier, having an injury in the previous year, running with longer flight times and lower step frequencies, and increasing speed training prior to injury. Increases in weekly running distance in 1 consecutive week (particularly >30%) needs to be monitored in training, and this along with the other factors found may have contributed to injury development. CLINICAL RELEVANCE: This study found that multiple factors are related to running injuries and that some factors are sex specific. The findings can aid in injury prevention and management.


Assuntos
Transtornos Traumáticos Cumulativos/fisiopatologia , Extremidade Inferior/lesões , Corrida/lesões , Aceleração , Adulto , Fenômenos Biomecânicos , Transtornos Traumáticos Cumulativos/etiologia , Transtornos Traumáticos Cumulativos/prevenção & controle , Feminino , Seguimentos , Marcha/fisiologia , Humanos , Extremidade Inferior/fisiopatologia , Masculino , Pessoa de Meia-Idade , Fadiga Muscular/fisiologia , Condicionamento Físico Humano , Postura/fisiologia , Estudos Prospectivos , Fatores de Risco , Corrida/fisiologia , Fatores Sexuais
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