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1.
J Appl Physiol (1985) ; 133(2): 490-505, 2022 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-35796610

RESUMO

The purpose was to investigate whether postactivation potentiation (PAP) mitigates power (i.e., torque × angular velocity) loss during dynamic fatiguing contractions and subsequent recovery by enhancing either muscle torque or angular velocity in human plantar flexors. In 12 participants, electrically stimulated (1, 10, and 50 Hz) dynamic contractions were done during a voluntary isotonic fatiguing protocol until a 75% loss in voluntary peak power, and throughout 30 min of recovery. At the initial portion of fatigue (20% decrease), power responses of evoked low frequencies (1 and 10 Hz) were enhanced due to PAP (156% and 137%, respectively, P < 0.001), whereas voluntary maximal efforts were depressed due to fatiguing mechanisms. Following the fatiguing task, prolonged low-frequency force depression (PLFFD) was evident by reduced 10:50 Hz peak power ratios (21%-24%) from 3 min onward during the 30-min recovery (P < 0.005). Inducing PAP with maximal voluntary dynamic contractions during PLFFD enhanced the peak power responses of low frequencies (1 and 10 Hz) by 128%-160%, P < 0.01. This PAP response mitigated the effects of PLFFD as the 1:50 (P < 0.05) and 10:50 (P > 0.4) Hz peak power ratios were greater or not different from the prefatigue (baseline) values. In addition, PAP enhanced peak torque more than peak angular velocity during both baseline and fatigue measurements (P < 0.03). These results indicate that PAP can ameliorate PLFFD acutely when evaluated during concentric isotonic contractions and that peak torque is enhanced to a greater degree compared with peak angular velocity at baseline and in a fatigued state.NEW & NOTEWORTHY Postactivation potentiation (PAP) enhanced stimulated low frequencies (1 and 10 Hz) during muscle fatigue development when assessed with power (torque × angular velocity) in a voluntary isotonic fatiguing task. Following the task during 30 min of recovery, prolonged low-frequency force depression (PLFFD) was evident, and inducing PAP with brief maximal contractions during this state ameliorated the effects of PLFFD. PAP enhanced peak torque more than peak angular velocity during both baseline and fatiguing conditions.


Assuntos
Contração Isotônica , Fadiga Muscular , Animais , Estimulação Elétrica/métodos , Peixes , Humanos , Contração Isométrica/fisiologia , Contração Muscular/fisiologia , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Torque
2.
PLoS One ; 16(12): e0260866, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34855891

RESUMO

PURPOSE: This study aimed to compare the post-activation performance enhancement (PAPE) induced by isometric and isotonic exercise on vertical jump performance. METHODS: 18 healthy trained men (25.8±2.7 years; 78.4±8.2 kg; 175.7±6.1 cm; 25.4±1.8 BMI; 126.72±10.8 kg squat 1-RM) volunteered for this study. They randomly performed two different PAPE protocols: Isotonic squats (ISOTS), which consisted of 2 sets of 3 repetitions at 75% of one-maximum repetition (1-RM); and isometric squats (ISOMS), which consisted of 2 sets of 4 seconds of submaximal (75% of 1-RM) isometric contraction at 90°-knee flexion. Countermovement jump (CMJ) height was tested at baseline and 4 minutes after each conditioning set. RESULTS: CMJ height significantly increased after set 1 in both PAPE protocols (ISOMS: p <0.001; ES = 0.34; ISOTS: p <0.001; ES = 0.24), with respect to the baseline jump. However, after set 2 no significant changes in CMJ height were observed for any protocol (ISOMS: p = 0.162; ES = 0.11; ISOTS: p = 0.976; ES = 0.06). No significant differences (p>0.05) were found between both isometric and isotonic exercise conditions. CONCLUSIONS: Despite both protocols showed similar PAPE effects on CMJ height after set 1, none of the protocols demonstrated greater efficacy in increasing subsequent performance in healthy trained men.


Assuntos
Atletas/estatística & dados numéricos , Desempenho Atlético/estatística & dados numéricos , Exercício Físico , Contração Isométrica , Contração Isotônica , Força Muscular , Músculo Esquelético/fisiologia , Adulto , Estudos Cross-Over , Humanos , Masculino , Postura
3.
Biomolecules ; 11(10)2021 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-34680085

RESUMO

In disease states, mesothelial cells are exposed to variable osmotic conditions, with high osmotic stress exerted by peritoneal dialysis (PD) fluids. They contain unphysiologically high concentrations of glucose and result in major peritoneal membrane transformation and PD function loss. The effects of isotonic entry of urea and myo-inositol in hypertonic (380 mOsm/kg) medium on the cell volume of primary cultures of rat peritoneal mesothelial cells and rat kidney outer medullary collecting duct (OMCD) principal cells were studied. In hypertonic medium, rat peritoneal mesothelial cells activated a different mechanism of cell volume regulation in the presence of isotonic urea (100 mM) in comparison to rat kidney OMCD principal cells. In kidney OMCD cells inflow of urea into the shrunken cell results in restoration of cell volume. In the shrunken peritoneal mesothelial cells, isotonic urea inflow caused a small volume increase and activated regulatory volume decrease (RVD). Isotonic myo-inositol activated RVD in hypertonic medium in both cell types. Isotonic application of both osmolytes caused a sharp increase of intracellular calcium both in peritoneal mesothelial cells and in kidney OMCD principal cells. In conclusion, peritoneal mesothelial cells exhibit RVD mechanisms when challenged with myo-inositol and urea under hyperosmolar isotonic switch from mannitol through involvement of calcium-dependent control. Myo-inositol effects were identical with the ones in OMCD principal cells whereas urea effects in OMCD principal cells led to no RVD induction.


Assuntos
Contração Isotônica/genética , Rim/metabolismo , Diálise Peritoneal , Peritônio/metabolismo , Animais , Tamanho Celular/efeitos dos fármacos , Células Cultivadas , Meios de Cultura/farmacologia , Soluções para Diálise/análise , Epitélio/química , Epitélio/metabolismo , Humanos , Inositol/química , Inositol/farmacologia , Concentração Osmolar , Pressão Osmótica/efeitos dos fármacos , Peritônio/efeitos dos fármacos , Peritônio/patologia , Cultura Primária de Células , Ratos
4.
Nutr Health ; 27(1): 123-128, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32580620

RESUMO

BACKGROUND: Obesity is defined as a chronic disease, and is known as a public health problem in developed and developing countries. Several studies have shown the effects of anti-obesity of α-lactalbumin. AIM: This study was designed to investigate the effect of alpha-lipoic acid supplementation and electrical isotonic contraction on anthropometric parameters, body composition and angiogenesis factor, sirtunin-1 and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α) in obese people under a weight loss regime. METHODS: Obese people who meet the inclusion criteria are included. Participants are randomly divided into four groups (alpha-lipoic (1200 mg) +weight loss regime group; Faradic (three 1 hour sessions) + weight loss regime group; alpha-lipoic (1200 mg) + Faradic (three 1 hour sessions) + weight loss regime group; control group (1200 mg placebo) for 2 months. At the beginning and the end of the study, demographic information, dietary intake, anthropometric parameters, body composition and serum levels of the angiogenesis factor (sirtunin-1, PGC1α and nitric oxide) are measured. CONCLUSION: Recent studies reported the anti-obesity effects of alpha-lipoic acid. This study is novel, since a similar study has not yet been carried out. This study evaluates the effect of 600 mg of alpha-lipoic acid supplementation or having three sessions of 1 hour per week electrical isotonic contraction induced by Faradic for 2 months alone or in combination in obese people that are undergoing a weight loss regime. TRIAL REGISTRATION: Iran Clinical Trials Registry, ID: IRCT20131117015424N2. Registered 2018-04-02.


Assuntos
Composição Corporal/efeitos dos fármacos , Suplementos Nutricionais , Contração Isotônica/efeitos dos fármacos , Obesidade/dietoterapia , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Sirtuína 1/metabolismo , Ácido Tióctico/farmacologia , Programas de Redução de Peso , Adolescente , Adulto , Indutores da Angiogênese/metabolismo , Feminino , Humanos , Irã (Geográfico) , Masculino , Pessoa de Meia-Idade , Ensaios Clínicos Controlados Aleatórios como Assunto , Ácido Tióctico/administração & dosagem , Redução de Peso , Adulto Jovem
5.
Gut ; 70(6): 1078-1087, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33020209

RESUMO

OBJECTIVE: The enteric nervous system (ENS) plays a key role in controlling the gut-brain axis under normal and pathological conditions, such as type 2 diabetes. The discovery of intestinal actors, such as enterosynes, able to modulate the ENS-induced duodenal contraction is considered an innovative approach. Among all the intestinal factors, the understanding of the role of gut microbes in controlling glycaemia is still developed. We studied whether the modulation of gut microbiota by prebiotics could permit the identification of novel enterosynes. DESIGN: We measured the effects of prebiotics on the production of bioactive lipids in the intestine and tested the identified lipid on ENS-induced contraction and glucose metabolism. Then, we studied the signalling pathways involved and compared the results obtained in mice to human. RESULTS: We found that modulating the gut microbiota with prebiotics modifies the actions of enteric neurons, thereby controlling duodenal contraction and subsequently attenuating hyperglycaemia in diabetic mice. We discovered that the signalling pathway involved in these effects depends on the synthesis of a bioactive lipid 12-hydroxyeicosatetraenoic acid (12-HETE) and the presence of mu-opioid receptors (MOR) on enteric neurons. Using pharmacological approaches, we demonstrated the key role of the MOR receptors and proliferator-activated receptor γ for the effects of 12-HETE. These findings are supported by human data showing a decreased expression of the proenkephalin and MOR messanger RNAs in the duodenum of patients with diabetic. CONCLUSIONS: Using a prebiotic approach, we identified enkephalin and 12-HETE as new enterosynes with potential real beneficial and safety impact in diabetic human.


Assuntos
Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico/biossíntese , Glicemia/metabolismo , Diabetes Mellitus Tipo 2/fisiopatologia , Duodeno/fisiologia , Sistema Nervoso Entérico/fisiologia , Prebióticos , Receptores Opioides mu/metabolismo , Ácido 12-Hidroxi-5,8,10,14-Eicosatetraenoico/farmacologia , Adulto , Idoso , Animais , Diabetes Mellitus Experimental/fisiopatologia , Duodeno/inervação , Encefalinas/genética , Encefalinas/metabolismo , Sistema Nervoso Entérico/efeitos dos fármacos , Microbioma Gastrointestinal , Teste de Tolerância a Glucose , Humanos , Contração Isotônica/efeitos dos fármacos , Masculino , Camundongos , Pessoa de Meia-Idade , Músculo Liso/fisiologia , Neurônios/fisiologia , Óxido Nítrico Sintase Tipo I/genética , Óxido Nítrico Sintase Tipo I/metabolismo , Oligossacarídeos/farmacologia , PPAR gama/metabolismo , Precursores de Proteínas/genética , Precursores de Proteínas/metabolismo , RNA Mensageiro/metabolismo , Receptores Opioides mu/genética , Transdução de Sinais
6.
Cochrane Database Syst Rev ; 11: CD013449, 2020 11 03.
Artigo em Inglês | MEDLINE | ID: mdl-33141943

RESUMO

BACKGROUND: Obstructive sleep apnoea (OSA) is a syndrome characterised by episodes of apnoea (complete cessation of breathing) or hypopnoea (insufficient breathing) during sleep. Classical symptoms of the disease - such as snoring, unsatisfactory rest and daytime sleepiness - are experienced mainly by men; women report more unspecific symptoms such as low energy or fatigue, tiredness, initial insomnia and morning headaches. OSA is associated with an increased risk of occupational injuries, metabolic diseases, cardiovascular diseases, mortality, and being involved in traffic accidents. Continuous positive airway pressure (CPAP) - delivered by a machine which uses a hose and mask or nosepiece to deliver constant and steady air pressure- is considered the first treatment option for most people with OSA. However, adherence to treatment is often suboptimal. Myofunctional therapy could be an alternative for many patients. Myofunctional therapy consists of combinations of oropharyngeal exercises - i.e. mouth and throat exercises. These combinations typically include both isotonic and isometric exercises involving several muscles and areas of the mouth, pharynx and upper respiratory tract, to work on functions such as speaking, breathing, blowing, sucking, chewing and swallowing. OBJECTIVES: To evaluate the benefits and harms of myofunctional therapy (oropharyngeal exercises) for the treatment of obstructive sleep apnoea. SEARCH METHODS: We identified randomised controlled trials (RCTs) from the Cochrane Airways Trials Register (date of last search 1 May 2020). We found other trials at web-based clinical trials registers. SELECTION CRITERIA: We included RCTs that recruited adults and children with a diagnosis of OSA. DATA COLLECTION AND ANALYSIS: We used standard methodological procedures expected by Cochrane. We assessed our confidence in the evidence by using GRADE recommendations. Primary outcomes were daytime sleepiness, morbidity and mortality. MAIN RESULTS: We found nine studies eligible for inclusion in this review and nine ongoing studies. The nine included RCTs analysed a total of 347 participants, 69 of them women and 13 children. The adults' mean ages ranged from 46 to 51, daytime sleepiness scores from eight to 14, and severity of the condition from mild to severe OSA. The studies' duration ranged from two to four months. None of the studies assessed accidents, cardiovascular diseases or mortality outcomes. We sought data about adverse events, but none of the included studies reported these. In adults, compared to sham therapy, myofunctional therapy: probably reduces daytime sleepiness (Epworth Sleepiness Scale (ESS), MD (mean difference) -4.52 points, 95% Confidence Interval (CI) -6.67 to -2.36; two studies, 82 participants; moderate-certainty evidence); may increase sleep quality (MD -3.90 points, 95% CI -6.31 to -1.49; one study, 31 participants; low-certainty evidence); may result in a large reduction in Apnoea-Hypopnoea Index (AHI, MD -13.20 points, 95% CI -18.48 to -7.93; two studies, 82 participants; low-certainty evidence); may have little to no effect in reduction of snoring frequency but the evidence is very uncertain (Standardised Mean Difference (SMD) -0.53 points, 95% CI -1.03 to -0.03; two studies, 67 participants; very low-certainty evidence); and probably reduces subjective snoring intensity slightly (MD -1.9 points, 95% CI -3.69 to -0.11 one study, 51 participants; moderate-certainty evidence). Compared to waiting list, myofunctional therapy may: reduce daytime sleepiness (ESS, change from baseline MD -3.00 points, 95% CI -5.47 to -0.53; one study, 25 participants; low-certainty evidence); result in little to no difference in sleep quality (MD -0.70 points, 95% CI -2.01 to 0.61; one study, 25 participants; low-certainty evidence); and reduce AHI (MD -6.20 points, 95% CI -11.94 to -0.46; one study, 25 participants; low-certainty evidence). Compared to CPAP, myofunctional therapy may result in little to no difference in daytime sleepiness (MD 0.30 points, 95% CI -1.65 to 2.25; one study, 54 participants; low-certainty evidence); and may increase AHI (MD 9.60 points, 95% CI 2.46 to 16.74; one study, 54 participants; low-certainty evidence). Compared to CPAP plus myofunctional therapy, myofunctional therapy alone may result in little to no difference in daytime sleepiness (MD 0.20 points, 95% CI -2.56 to 2.96; one study, 49 participants; low-certainty evidence) and may increase AHI (MD 10.50 points, 95% CI 3.43 to 17.57; one study, 49 participants; low-certainty evidence). Compared to respiratory exercises plus nasal dilator strip, myofunctional therapy may result in little to no difference in daytime sleepiness (MD 0.20 points, 95% CI -2.46 to 2.86; one study, 58 participants; low-certainty evidence); probably increases sleep quality slightly (-1.94 points, 95% CI -3.17 to -0.72; two studies, 97 participants; moderate-certainty evidence); and may result in little to no difference in AHI (MD -3.80 points, 95% CI -9.05 to 1.45; one study, 58 participants; low-certainty evidence). Compared to standard medical treatment, myofunctional therapy may reduce daytime sleepiness (MD -6.40 points, 95% CI -9.82 to -2.98; one study, 26 participants; low-certainty evidence) and may increase sleep quality (MD -3.10 points, 95% CI -5.12 to -1.08; one study, 26 participants; low-certainty evidence). In children, compared to nasal washing alone, myofunctional therapy and nasal washing may result in little to no difference in AHI (MD 3.00, 95% CI -0.26 to 6.26; one study, 13 participants; low-certainty evidence). AUTHORS' CONCLUSIONS: Compared to sham therapy, myofunctional therapy probably reduces daytime sleepiness and may increase sleep quality in the short term. The certainty of the evidence for all comparisons ranges from moderate to very low, mainly due to lack of blinding of the assessors of subjective outcomes, incomplete outcome data and imprecision. More studies are needed. In future studies, outcome assessors should be blinded. New trials should recruit more participants, including more women and children, and have longer treatment and follow-up periods.


Assuntos
Terapia Miofuncional/métodos , Apneia Obstrutiva do Sono/terapia , Apneia/terapia , Criança , Pressão Positiva Contínua nas Vias Aéreas , Distúrbios do Sono por Sonolência Excessiva/terapia , Exercício Físico , Feminino , Humanos , Contração Isotônica , Masculino , Pessoa de Meia-Idade , Orofaringe/fisiologia , Ensaios Clínicos Controlados Aleatórios como Assunto , Ronco/terapia , Irrigação Terapêutica , Listas de Espera
7.
J Sport Rehabil ; 30(3): 512-515, 2020 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-33049706

RESUMO

Clinical Scenario: Patellar tendinopathy is a common musculoskeletal disorder affecting the lower-extremities and a difficult condition to manage for athletes that are in season. To facilitate improvement in function and to decrease pain, initial treatment for patellar tendinopathy is typically conservative. Traditional interventions may include eccentric training, cryotherapy, patellar counterforce straps, oral anti-inflammatories, injectable agents, phonophoresis, iontophoresis, orthotics, therapeutic ultrasound, and extracorporeal shockwave. In addition, recent literature suggests that implementing isometric and isotonic contractions may be effective in reducing patellar tendon pain. Focused Clinical Question: How effective are isometric contractions compared with isotonic contractions in reducing pain for in-season athletes with patellar tendinopathy? Summary of Key Findings: Implementation of isometric and isotonic exercises statistically reduced pain levels in the short term of 4 weeks for in-season athletes; however, isometric contractions provided statistically greater pain relief immediately for up to 45 minutes postintervention compared with isotonic contractions. Clinical Bottom Line: Current evidence supports the use of isometric and isotonic contractions to reduce pain for in-season athletes with patellar tendinopathy. Based on the reviewed literature, clinicians should consider utilizing heavy loaded isometrics or progressive heavy loaded isotonic exercises, which showed reduction in pain levels immediately after intervention and at 4-week follow-up for both intervention groups. Isometric contractions appear to provide greater pain relief immediately after intervention. Strength of Recommendation: There is Grade B evidence from 2 level 2 randomized controlled trials and 1 level 3 randomized crossover study supporting the use of isometric and isotonic contractions to reduce patellar tendon pain for in-season athletes.


Assuntos
Traumatismos em Atletas/terapia , Terapia por Exercício/métodos , Contração Isométrica , Contração Isotônica , Manejo da Dor/métodos , Ligamento Patelar/lesões , Tendinopatia/terapia , Humanos
8.
Annu Int Conf IEEE Eng Med Biol Soc ; 2020: 2311-2314, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-33018470

RESUMO

Models of muscle contraction are typically based on a measured force-velocity relation embodied as Hill's contractile element [1]. Adopting a particular force-velocity relation dictates the muscle's mechanical properties. Dynamic crossbridge based models, such as Huxley's [2], typically focus on ultrastructural mechanics. This study adapts a dynamic lumped model of cardiac muscle contraction [3] for description of mouse soleus skeletal muscle. This compact, dynamic model exhibits the main features of skeletal muscle contraction with few assumptions. The main differences between cardiac and skeletal muscle dynamics are described. This approach gives one equation and set of parameters capable of modeling isometric and isotonic contractions, skeletal muscle's force-length relation, variations in contractility, and the force-velocity relation. This new constitutive equation may be useful for modeling striated muscle as part of larger biomechanical models.


Assuntos
Músculo Esquelético , Contração Miocárdica , Animais , Coração , Contração Isotônica , Camundongos
9.
ABCS health sci ; 45: [1-4], 02 jun 2020. tab, graf
Artigo em Inglês | LILACS | ID: biblio-1097543

RESUMO

INTRODUCTION: For post-surgical rehabilitation of the anterior cruciate ligament, the medialis and the lateralis vastus need to be worked on for good recovery. There is the discussion about the isometric and isotonic exercises to be used in the rehabilitation phase, and their results diverge in the literature. OBJECTIVE: This study aims to compare the activation of the medialis and the lateralis vastus in isometric and isotonic exercises. METHODS: Eleven subjects (seven men and four women) physically active and experienced in resistance training participated in the study. Anamnesis, anthropometric assessment, 10 Repetition maximum (RM) load test, maximum voluntary isometric contraction test and squat test were performed. RESULTS: For the vastus lateralis of the right leg, the electromyographic activity was significantly higher in the maximal isometric voluntary contraction compared to the dynamic squatting (p<0.05). The same was observed for the left leg (p<0.05). CONCLUSION: Recruitment of the medial and the lateral vastus in isometric exercises is higher in relation to isotonic exercises.


INTRODUÇÃO: Para a reabilitação pós-cirúrgica do ligamento cruzado anterior, os vastos medial e lateral precisam ser trabalhados visando uma boa recuperação. Discute-se a respeito dos exercícios isométricos e isotônicos a serem utilizados na fase de reabilitação, tendo seus resultados divergentes na literatura. OBJETIVO: Assim, o objetivo do presente estudo é comparar a ativação dos vastos medial e lateral em exercícios isométricos e isotônicos. MÉTODOS: Participaram deste estudo 11 sujeitos (sete homens e quatro mulheres), fisicamente ativos e com experiência em musculação. Foi realizada a anamnese, a avaliação antropométrica, o teste de carga de 10 repetições máximas (RM), o teste de contração voluntária isométrica máxima e o teste de agachamento. RESULTADOS: No vasto lateral da coxa direita, a atividade eletromiográfica foi significativamente maior na contração voluntária isométrica máxima em relação ao agachamento dinâmico (p<0,05). O mesmo foi observado na coxa esquerda (p<0,05). CONCLUSÃO: O recrutamento dos vastos medial e lateral em exercícios isométricos é maior em relação a exercícios isotônicos.


Assuntos
Humanos , Masculino , Feminino , Lactente , Músculo Quadríceps , Lesões do Ligamento Cruzado Anterior/reabilitação , Contração Isométrica , Contração Isotônica , Eletromiografia
10.
Medicina (Kaunas) ; 56(4)2020 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-32326179

RESUMO

Background and objectives: Obese people have many foot-related disorders and plantar fasciitis (PF) is the most common disorder among them. However, research on the role of therapeutic exercises in PF is lacking and there is no evidence to suggest its benefits. As such, a further insight into therapeutic exercises is needed within this group. This case study investigated the effect of three-dimensional (3D) ankle exercises using a combined isotonic (CI) technique on function and balance in an obese subject with PF. Material and methods: The subject in this study was a 28-year-old obese woman who was diagnosed with PF by an orthopedic surgeon. A 3D ankle exercise program was commenced three times a week for 15 min over 4 weeks. The evaluations were conducted at five intervals: pre-test, and at 1, 2, 3 and 4 weeks from the initiation of the intervention. The tests were conducted in the following order: the patient-specific functional scale test (PSFS), an ultrasound of the plantar fascia, the heel pressure and balance test, the pressure pain threshold (PPT), and the 4-way ankle strength test. Results: The mean score of the PSFS test reduced by 70.55% after 4 weeks of the intervention. The thickness of the plantar fascia and heel pressure measured during single-leg standing decreased by 6.67% and 10.37%, respectively, after 4 weeks of the intervention. The anteroposterior and medial-lateral balance ability showed improvements of 8.29% and 8.61%, respectively, after 4 weeks of the intervention. The PPT improved by 38.01% after 4 weeks of the intervention. In the 4-way ankle strength test, dorsiflexion, plantar flexion, inversion, and eversion increased by 14.46%, 9.63%, 4.3% and 13.25%, respectively, after 4 weeks of the intervention. Conclusion: 3D ankle exercises utilizing the CI technique were shown to be effective in improving foot function, pressure pain, and muscle strength in dorsiflexion and inversion in an obese patient with PF.


Assuntos
Terapia por Exercício/métodos , Fasciíte Plantar/terapia , Obesidade/complicações , Adulto , Tornozelo/fisiopatologia , Fasciíte Plantar/complicações , Feminino , Humanos , Contração Isotônica/fisiologia , Amplitude de Movimento Articular
11.
Rev. esp. patol. torac ; 31(4): 240-248, dic. 2019. ilus, graf, tab
Artigo em Espanhol | IBECS | ID: ibc-187184

RESUMO

Objetivo: el objetivo del estudio fue evaluar la función muscular periférica de pacientes con EPOC moderadasevera, mediante la medición de la fuerza muscular isométrica e isotónica del cuádriceps y la masa muscular mediante ecografía. Método: fueron incluidos pacientes con EPOC moderada-severa estables, remitidos a Rehabilitación Respiratoria. En la extremidad dominante, se midió la fuerza isométrica (dinamómetro hidráulico), test 1RM y se realizó una ecografía para obtener el área transversal y dimensiones de diversas secciones musculares. Resultados: participaron 34 pacientes con EPOC estable: GOLD 2 (n = 11), GOLD 3 (n = 12) y GOLD 4 (n = 11) Los GOLD 4 tenían un IMC P50 (P25 - P75) 25,3 (22,5 - 28,8), significativamente menor que los GOLD 3: 32,0 (27,5 - 34,0); p = 0,025. Se evidenció debilidad del cuádriceps (1RM/peso <0,60 1RM/IMC <120%), de forma global: 0,33 (0,22 - 0,41) y 93% (61 - 112) respectivamente, y en cada grupo, sin diferencias significativas entre ellos. Tampoco hubo diferencias significativas entre los grupos en las mediciones de ecografía muscular. La fuerza isotónica (1RM) se correlacionó con el grosor del cuádriceps QT (r = 0,529; p = 0,003) y el grosor del músculo vasto intermedio Q1(r = 0,514; p = 0,004) La fuerza isométrica se correlacionó con el QT (0,621; p <0,001), Q1 (0,441; p = 0,009) y el área transversal AQ (r = 0,587; p <0,001) Para cada grupo, el QT y la fuerza isométrica se correlacionaron significativamente. Conclusión: en nuestra serie de pacientes se demuestra la existencia de debilidad muscular del cuádriceps, independientemente del grado de severidad de la enfermedad y en estrecha relación con la masa muscular de dicho músculo. Palabras clave: disfunción muscular, fuerza isotónica, 1RM, fuerza isométrica, ecografía muscular


Objective: The objective of this study was to evaluate peripheral muscle function in patients with moderate-severe COPD by measuring isometric and isotonic muscular strength of the quadriceps and muscle mass through ultrasound. Method: This study included stable patients with moderate-severe COPD who were referred to pulmonary rehabilitation. In the dominant extremity, isometric strength (hydraulic dynamometer) and the 1RM test were measured and an ultrasound was done to determine the transversal area and dimensions of different sections of muscle. Results: 34 stable patients with COPD participated: GOLD 2 (n = 11), GOLD 3 (n = 12) and GOLD 4 (n = 11). GOLD 4 patients had a BMI P50 (P25 - P75) 25.3 (22.5 - 28.8), which was significantly lower than GOLD 3 patients: 32.0 (27.5 - 34.0); p = 0.025. Weakness in the quadriceps was observed (1 RM/weight <0.60; 1 RM/BMI <120%) overall: 0.33 (0.22 - 0.41) and 93% (61 - 112), respectively, and in each group, without significant differences between groups. There were also no significant differences between groups for ultrasound muscle measurements. Isotonic strength (1 RM) correlated to quadricep thickness QT (r = 0.529; p = 0.003) and vastus intermedius muscle thickness Q1(r = 0.514; p = 0.004). Isometric strength correlated to QT (0.621; p <0.001), Q1 (0.441; p = 0.009) and transversal area AQ (r = 0.587; p <0.001). QT and isometric strength were significantly correlated in each group. Conclusion: In our study, patients showed muscular weakness in the quadriceps, regardless of the degree of disease severity and this weakness was closely related to the mass of said muscle


Assuntos
Humanos , Músculo Quadríceps/fisiologia , Doença Pulmonar Obstrutiva Crônica/diagnóstico , Força Muscular/fisiologia , Músculo Quadríceps/diagnóstico por imagem , Músculo Quadríceps/patologia , Ultrassonografia , Contração Isotônica/fisiologia , Contração Isométrica/fisiologia , Espirometria , Análise de Variância , Debilidade Muscular/diagnóstico por imagem
12.
Int J Mol Sci ; 20(12)2019 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-31238505

RESUMO

The relation between the force (load) and the velocity of shortening (V) in contracting skeletal muscle is part of a rectangular hyperbola: (P + a) V = b(Po - P); where Po is the maximum isometric force and a and b are constants. The force-velocity (P-V) relation suggests that muscle can regulate its energy output depending on the load imposed on it (Hill, 1938). After the establishment of the sliding filament mechanism (H.E. Huxley and Hanson, 1954), the P-V relation has been regarded to reflect the cyclic interaction between myosin heads in myosin filaments and the corresponding myosin-binding sites in actin filaments, coupled with ATP hydrolysis (A.F. Huxley, 1957). In single skeletal muscle fibers, however, the P-V relation deviates from the hyperbola at the high force region, indicating complicated characteristics of the cyclic actin-myosin interaction. To correlate the P-V relation with kinetics of actin-myosin interaction, skinned muscle fibers have been developed, in which the surface membrane is removed to control chemical and ionic conditions around the 3D lattice of actin and myosin filaments. This article also deals with experimental methods with which the structural instability of skinned fibers can be overcome by applying parabolic decreases in fiber length.


Assuntos
Contração Muscular/fisiologia , Fibras Musculares Esqueléticas/fisiologia , Músculo Esquelético/fisiologia , Animais , Humanos , Contração Isotônica , Cinética , Modelos Biológicos , Fibras Musculares Esqueléticas/ultraestrutura , Proteínas Musculares/química , Proteínas Musculares/metabolismo , Força Muscular , Músculo Esquelético/ultraestrutura , Fenômenos Fisiológicos Musculoesqueléticos , Miosinas/química , Miosinas/metabolismo , Relação Estrutura-Atividade
13.
Rev. andal. med. deporte ; 12(2): 93-98, jun. 2019. ilus, tab
Artigo em Português | IBECS | ID: ibc-184505

RESUMO

Objetivo: Comparar respostas hemodinâmicas e autonômicas cardíacas após sessões agudas de exercício resistido dinâmico e isométrico. Método: Após familiarização às sessões experimentais e teste de uma repetição máxima, 12 homens (idade: 49.0±6.4 anos) sem o uso de medicamentos e experiência em exercício resistido foram randomizados de forma cruzada à duas sessões experimentais de exercício resistido dinâmico e isométrico compostos por um circuito de seis exercícios alternados por segmento corporal e à uma intensidade de 60% de uma repetição máxima. Aos momentos de repouso e recuperação foram mensuradas a pressão arterial sistólica e diastólica e registrado os intervalos R-R com posterior cálculo de índices da variabilidade da frequência cardíaca. Resultados: Não foram observadas diferenças estatisticamente significantes nas respostas pressóricas entre as sessões experimentais. O duplo produto se recuperou para valores basais aos 25min da recuperação em ambas as sessões. A frequência cardíaca permaneceu mais elevada durante momentos da recuperação na sessão dinâmico, ao passo que a sessão isométrica recuperou menos batimentos cardíacos para essa mesma variável. Adicionalmente, o balanço simpato-vagal permaneceu elevado e indicadores parassimpáticos diminuídos, em relação ao repouso, após sessão isométrica. Conclusão: Não ocorreram diferenças nas respostas hemodinâmicas entre as sessões de exercício resistido. Por outro lado, demonstrou-se diferentes recuperações para a frequência cardíaca e variáveis autonômicas após as sessões experimentais


Objetivo: Comparar respuestas hemodinámicas y autonómicas cardíacas después de sesiones agudas de ejercicio resistido dinámico y isométrico. Método: Después de familiarización en las sesiones experimentales y prueba de una repetición máxima, 12 hombres (edad: 49.0±6.4 años) sin el uso de medicamentos y experiencia en ejercicio resistido fueron randomizados de forma cruzada a dos sesiones experimentales de ejercicio resistido dinámico y isométricos compuestos por un circuito de seis ejercicios alternados por segmento corporal con una intensidad del 60% de una repetición máxima. Durante los momentos de reposo y recuperación se midieron la presión arterial sistólica y diastólica y se registraron los intervalos R-R con posterior cálculo de índices de la variabilidad de la frecuencia cardíaca. Resultados: No se observaron diferencias estadísticamente significativas en las respuestas de presión arterial entre las sesiones experimentales. El doble producto se recuperó a valores basales a los 25min de la recuperación en ambas sesiones. La frecuencia cardiaca permaneció más elevada durante momentos de recuperación en la sesión dinámica, mientras que la sesión isométrica recuperó menos latidos cardíacos para esa misma variable. Todavía, el balance simpático-vagal permaneció elevado e indicadores parasimpáticos disminuidos, en relación al reposo, después de la sesión isométrica. Conclusión: No ocurrieron diferencias en las respuestas hemodinámicas entre las sesiones de ejercicio. Sin embargo, se demostró diferentes recuperaciones entre las variables autonómicas después de las sesiones experimentales


Objective: To compare hemodynamic and cardiac autonomic responses after acute sessions of dynamic and isometric resistance exercise. Methods: After familiarization with the experimental sessions and maximal repetition test, 12 men (age: 49.0±6.4 years) without medication and experience in resistance exercise were cross-randomized in two experimental sessions of dynamic and isometric resistance exercise composed by a circuit with six alternating exercises per body segment and at intensities of 60% of a one maximum repetition. At rest and recovery moments, systolic and diastolic blood pressure were measured and R-R intervals were recorded with subsequent calculation of heart rate variability indexes. Results: No statistically significant differences were observed in blood pressure responses between experimental sessions. The rate pressure product recovered to baseline at 25min of recovery in both sessions. The heart rate remained higher during moments of recovery in the dynamic session, while the isometric session recovered fewer heart beats for that same variable. In addition, the sympatho-vagal balance remained high and the parasympathetic indicators decreased in relation to rest after the isometric session. Conclusion: There were no differences in hemodynamic response between resistance exercise sessions. Otherwise, different recoveries between the autonomic variables after the experimental sessions were demonstrated


Assuntos
Humanos , Masculino , Adulto , Pessoa de Meia-Idade , Treinamento de Força/métodos , Resistência Física/fisiologia , Exercício Físico/fisiologia , Hemodinâmica/fisiologia , Monitorização Hemodinâmica/métodos , Testes de Função Cardíaca/estatística & dados numéricos , Teste de Esforço/métodos , Frequência Cardíaca/fisiologia , Contração Isométrica/fisiologia , Contração Isotônica/fisiologia , Tolerância ao Exercício/fisiologia , Monitores de Aptidão Física
14.
Amino Acids ; 51(1): 27-37, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29905904

RESUMO

ß-Alanine (BA) supplementation may be ergogenic during high-intensity exercise, primarily due to the buffering of hydrogen cations, although the effects of beta-alanine supplementation on strength endurance are equivocal. The aim of the study was to determine the effects of 4 weeks of beta-alanine supplementation on skeletal muscle endurance using a battery of performance tests. This study employed a parallel group, repeated measures, randomised, double-blinded and placebo-controlled design. Twenty recreationally strength-trained healthy males completed tests of isotonic strength endurance (repeated bench and leg press), along with tests of isometric and isokinetic endurance conducted using an isokinetic dynamometer. Tests were performed before and after a 4 week intervention, comprising an intake of 6.4 g day-1 of BA (n = 9) or placebo (maltodextrin, n = 11). Time-to-exhaustion during the isometric endurance test improved by ~ 17% in the BA group (p < 0.01), while PL remained unchanged. No significant within-group differences (p > 0.1) were shown for any of the performance variables in the isokinetic test (peak torque, fatigue index, total work) nor for the total number of repetitions performed in the isotonic endurance tests (leg or bench press). Four weeks of BA supplementation (6.4 g day-1) improved isometric, but not isokinetic or isotonic endurance performance.


Assuntos
Suplementos Nutricionais , Contração Isométrica/efeitos dos fármacos , Contração Isotônica/efeitos dos fármacos , Substâncias para Melhoria do Desempenho/administração & dosagem , Resistência Física/efeitos dos fármacos , beta-Alanina/administração & dosagem , Adulto , Exercício Físico , Humanos , Masculino , Dinamômetro de Força Muscular , Músculo Esquelético/metabolismo , Substâncias para Melhoria do Desempenho/farmacologia , Adulto Jovem , beta-Alanina/farmacologia
15.
Ann Biomed Eng ; 47(2): 590-600, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30386951

RESUMO

In this combined in vivo and computational modeling study, we tested the central hypothesis that ankle joint rotation and triceps surae muscle loading have independent and combinatory effects on the calcaneal (i.e., Achilles) tendon moment arm (CTma) that are not fully captured in contemporary musculoskeletal models of human movement. We used motion capture guided ultrasound imaging to estimate instantaneous variations in the CTma during a series of isometric and isotonic contractions compared to predictions from scaled, lower extremity computational models. As hypothesized, we found that muscle loading: (i) independently increased the CTma by up to 8% and (ii) attenuated the effects of ankle joint rotation, the latter likely through changes in tendon slack and tendon curvature. Neglecting the effects of triceps surae muscle loading in lower extremity models led to an underestimation of the CTma, on average, particularly in plantarflexion when those effects were most prominent. We also found little agreement between in vivo estimates and model predictions on an individual subject by subject basis, alluding to unaccounted for variation in anatomical morphology and thus fundamental limitations in model scaling. Together, these findings contribute to improving our understanding of the physiology of ankle moment and power generation and novel opportunities for model development.


Assuntos
Tendão do Calcâneo , Articulação do Tornozelo , Diagnóstico por Imagem , Modelos Biológicos , Movimento/fisiologia , Músculo Esquelético , Rotação , Tendão do Calcâneo/diagnóstico por imagem , Tendão do Calcâneo/fisiologia , Adulto , Articulação do Tornozelo/diagnóstico por imagem , Articulação do Tornozelo/fisiologia , Feminino , Humanos , Contração Isométrica/fisiologia , Contração Isotônica/fisiologia , Masculino , Músculo Esquelético/diagnóstico por imagem , Músculo Esquelético/fisiologia , Suporte de Carga/fisiologia
16.
Gen Physiol Biophys ; 37(4): 363-374, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29956669

RESUMO

One of commonly used approaches of biophysical modeling of muscle contractile apparatus is spatially explicit discrete lattice models in Monte Carlo simulation. Such models allow to reproduce structural features and actin-myosin interaction in the muscle contractile system more accurately. Limitation of such models is their low computational efficiency and stochasticity under certain circumstances. This work introduces deterministic approximation of stochastic model that considers a pair of rigid contractile filaments interaction. Approximation background is discreetness of spacing between cross-bridges and binding sites. Due to this property cross-bridges can be divided into discrete groups with the same strain, and considered statistically using the set of ordinary differential equations. Deterministic model is more computationally efficient, operates with average values. Within the given approach isotonic contraction was simulated. A comparison with Monte Carlo simulation demonstrates that approximation reproduces results for stochastic model with large number of cross-bridges. Also within the deterministic model a mechanism and essential conditions for oscillations appearance in isotonic transient response, relations of their parameters with geometrical ones of filaments lattice were examined, theoretical and experimental results were compared. The proposed approach can also be applied to approximation of continuous Huxley-based models solutions. Advantage over existing numerical methods is their greater numerical stability.


Assuntos
Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Modelos Biológicos , Miosinas/metabolismo , Fenômenos Biomecânicos , Contração Isotônica , Movimento , Ligação Proteica , Processos Estocásticos
17.
Musculoskelet Sci Pract ; 37: 17-19, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29958120

RESUMO

BACKGROUND: Early quadriceps muscle strength assessment after a total knee arthroplasty (TKA) provides timely information on progress, but little is known about the pain profile and predictive validity associated with common clinical muscle strength tests. This study aimed to, in patients with a recent TKA, examine the associations of isometric and isotonic quadriceps strength with gait speed, accounting for knee pain experienced during testing. METHODS: A sample of 76 patients (mean age 68 years; 46 women) with a recent TKA (median, 1.5 months) participated. Quadriceps strength was measured on both limbs using a knee extension machine. Isotonic strength was assessed with a one-repetition maximum test. Isometric strength was measured at 40° and 70° of knee flexion using a custom-built load cell. To allow for valid comparisons between the tests, quadriceps strength symmetry ratios were calculated. Knee pain during testing was measured using an 11-point pain scale. Fast gait speed was measured using the 10-m walk test. RESULTS: Compared with isotonic test, quadriceps strength ratio was higher for the 40° flexion isometric test (P = 0.01), and this difference may be explained by the lower knee pain intensity elicited during the isometric tests (P's < 0.001). All strength measures were closely associated with fast gait speed after adjustment for knee pain and covariates (P's < 0.001). CONCLUSIONS: Early in the post-TKA period, isometric and isotonic strength tests may be used to assess quadriceps strength but these tests are not interchangeable. Isometric quadriceps testing may be preferable to isotonic testing as it was associated with lower knee pain intensity.


Assuntos
Artroplastia do Joelho/reabilitação , Exercício Físico/fisiologia , Contração Isotônica/fisiologia , Força Muscular/fisiologia , Osteoartrite do Joelho/cirurgia , Músculo Quadríceps/fisiologia , Amplitude de Movimento Articular/fisiologia , Idoso , Feminino , Humanos , Pessoa de Meia-Idade , Medição da Dor , Recuperação de Função Fisiológica/fisiologia
18.
J Appl Physiol (1985) ; 125(3): 706-714, 2018 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-29856265

RESUMO

Fatiguing contractions change the force-velocity relationship, but assessment of this relationship in fatigue has usually been obtained after isometric contractions. We studied fatigue caused by isometric or isotonic contractions, by assessment of the force-velocity relationship while the contractions maintaining fatigue were continued. This approach allowed determination of the force-velocity relationship during a steady condition of fatigue. We used the in situ rat medial gastrocnemius muscle, a physiologically relevant preparation. Intermittent (1/s) stimulation at 170 Hz for 100 ms resulted in decreased isometric force to ~35% of initial or decreased peak velocity of shortening in dynamic contractions to ~45% of initial. Dynamic contractions resulted in a transient initial increase in velocity, followed by a rapid decline until a reasonably steady level was maintained. Data were fit to the classic Hill equation for determination of the force-velocity relationship. Isometric and dynamic contractions resulted in similar decreases in maximal isometric force and peak power. Only Vmax was different between the types of contraction ( P < 0.005) with greater decrease in Vmax during isotonic contractions to 171.7 ± 7.3 mm/s than during isometric contractions to 208.8 mm/s. Curvature indicated by a/Po (constants from fit to Hill equation) changed from 0.45 ± 0.04 to 0.71 ± 0.11 during isometric contractions and from 0.51 ± 0.04 to 0.85 ± 0.18 during isotonic contractions. Recovery was incomplete 45 min after stopping the intermittent contractions. At this time, recovery of low-frequency isometric force was substantially less after isometric contractions, implicating force during intermittent contractions as a determining factor with this measure of fatigue. NEW & NOTEWORTHY The force-velocity relationship was captured while fatigue was maintained at a constant level during isometric and dynamic contractions. The curvature of the force-velocity relationship was less curved during fatigue than prefatigued, but within 45 min this recovered. Low-frequency fatigue persisted with greater depression of low-frequency force after isometric contractions, possibly because of higher force contractions during intermittent contractions.


Assuntos
Contração Isométrica/fisiologia , Contração Isotônica/fisiologia , Fadiga Muscular/fisiologia , Animais , Estimulação Elétrica , Feminino , Cinética , Músculo Esquelético/fisiologia , Ratos , Ratos Sprague-Dawley
19.
J Bodyw Mov Ther ; 22(2): 430-437, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29861246

RESUMO

INTRODUCTION: Several studies have been developed to determine which type of muscular action (isometric, isotonic and isokinetic) elicits more gains in functional strength and muscle mass. The comparisons between training outcomes are inconclusive due to lack of exercise standardization. OBJECTIVE: To compare muscle strength, mass, and functional performance in response to isometric, isotonic, and isokinetic contractions, when training loads (volume and intensity) are equated. METHOD: Data were derived from a university community-recruited sample (n = 31 men). INTERVENTIONS: Untrained men were assigned to isotonic (IT), isometric (IM), or isokinetic (IK) group, and trained their dominant quadriceps muscle 3 sessions/week for 8 weeks with a dynamometer. Muscle strength was assessed using Cybex 6000 dynamometer; the triple-hop-distance test was used to assess functional performance, and dual energy x-ray absorptiometry to assess lean muscle mass. RESULTS: After training, muscle lean muscle mass increased in isometric (+3.1%, p < 0.01) and isotonic groups (+3.9%, p < 0.01); only the isokinetic group showed a significant improvement in the triple-hop-distance test (4.84%, p < 0.01). CONCLUSION: Clinicians should consider isometric training as an alternative for isotonic training to gain muscle mass, and isokinetic training to improve functional performance of daily activities and/or sports.


Assuntos
Contração Muscular/fisiologia , Força Muscular/fisiologia , Treinamento de Força/métodos , Adolescente , Adulto , Índice de Massa Corporal , Humanos , Contração Isométrica/fisiologia , Contração Isotônica/fisiologia , Masculino , Músculo Esquelético/fisiologia , Adulto Jovem
20.
PLoS One ; 13(5): e0196838, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29723252

RESUMO

Isotonic testing and measures of rapid power production are emerging as functionally relevant test methods for detection of muscle aging. Our objective was to assess reliability of rapid velocity and power measures in older adults using the isotonic mode of an isokinetic dynamometer. Sixty-three participants (aged 65 to 82 years) underwent a test-retest protocol with one week time interval. Isotonic knee extension tests were performed at four different loads: 0%, 25%, 50% and 75% of maximal isometric strength. Peak velocity (pV) and power (pP) were determined as the highest values of the velocity and power curve. Rate of velocity (RVD) and power development (RPD) were calculated as the linear slopes of the velocity- and power-time curve. Relative and absolute measures of test-retest reliability were analyzed using intraclass correlation coefficients (ICC), standard error of measurement (SEM) and Bland-Altman analyses. Overall, reliability was high for pV, pP, RVD and RPD at 0%, 25% and 50% load (ICC: .85 - .98, SEM: 3% - 10%). A trend for increased reliability at lower loads seemed apparent. The tests at 75% load led to range of motion failure and should be avoided. In addition, results demonstrated that caution is advised when interpreting early phase results (first 50ms). To conclude, our results support the use of the isotonic mode of an isokinetic dynamometer for testing rapid power and velocity characteristics in older adults, which is of high clinical relevance given that these muscle characteristics are emerging as the primary outcomes for preventive and rehabilitative interventions in aging research.


Assuntos
Envelhecimento/fisiologia , Contração Isotônica , Joelho/fisiologia , Dinamômetro de Força Muscular , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Contração Isométrica , Masculino , Força Muscular , Reprodutibilidade dos Testes , Fatores de Tempo , Suporte de Carga
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