Flexibility and achilles tendon: a brief review / Flexibilidade e tendão de aquiles: uma breve revisão

Performing flexibility training in an exercise program is important to improve range of motion (ROM). Tendons have a profound impact on the general function of the musculoskeletal system, influence the limitation of ROM, and its structure and mechanical properties can benefit from stretching protocols. The systematic use of lower limbs in locomotion caused the Achilles tendon to become the largest and strongest tendon in the human body. Therefore, understanding the best prescription and frequency of flexibility exercise leads to changes in tendon properties is essential for an appropriate and effective exercise routine. Thus, the aim of this review was to organize and discuss publications about the implications of triceps surae stretching in ROM, as well as its influence on tendon properties. Acute studies show that continuous stretching times between five and 10 minutes cause decreased tendon stiffness, which is not seen in fractionated stretching times less than five minutes. Chronic studies, in turn, also don't present significant results in stiffness with fractionated times and studies with continuous times were not found. Thus, it is not possible to know if a continuous stretching time (longer than one minute) or a total time longer than five minutes but fractionated, can influence the tendon stiffness. (AU)

A realização de treino de flexibilidade como rotina em um programa de exercícios é importante para melhorar amplitude de movimento (ADM). Os tendões têm um impacto profundo na função geral do sistema musculoesquelético, influenciam na limitação da ADM, e sua estrutura e propriedades mecânicas podem se beneficiar de protocolos de alongamento. O uso sistemático dos membros inferiores na locomoção fez com que o tendão de Aquiles se tornasse o maior e mais forte tendão do corpo humano. Portanto, entender qual a melhor prescrição e frequência de exercício de flexibilidade para que ocasione alterações nas propriedades tendíneas é essencial para uma rotina de exercícios adequada e eficaz. Sendo assim, o objetivo dessa revisão de literatura foi organizar e discutir publicações sobre as implicações do alongamento do tríceps sural na ADM, bem como sua influência nas propriedades tendíneas. Estudos agudos mostram que tempos contínuos entre cinco e 10 minutos de alongamento estático causam diminuição da rigidez tendínea, o que não é visto em tempos intervalados inferiores a cinco minutos. Os estudos crônicos, por sua vez, também não apresentam resultados significativos na rigidez com protocolos de alongamento intervalados e estudos com protocolos contínuos não foram encontrados. Dessa forma, não é possível saber se um tempo contínuo de alongamento (superior a um minuto) ou um tempo superior a cinco minutos, intervalado, podem influenciar na rigidez tendínea. (AU)

Triceps surae muscle-tendon unit mechanical property changes during 10 minutes of streching.

OBJECTIVE: To verify the effect of 10-min static stretching on the triceps surae mechanical properties. DESIGN: Quasi-experimental one-group pre test-post test study compared the time points of before, after, and minute by minute of one session of triceps surae passive static stretching. METHODS: 15 participants performed a 10-min plantar flexor passive static stretching on the isokinetic dynamometer. We evaluated passive torque and myotendinous junction (MTJ) displacement before, minute by minute, and after the intervention. In contrast, we evaluated the range of motion (ROM), passive torque, MTJ displacement, and hysteresis before and after the intervention. Paired t-test compared pre and post-intervention time points. Passive torque and MTJ displacement in the minute-by-minute evaluations were compared by repeated measures one-way ANOVA with a Bonferroni post-hoc test. RESULTS: ROM increased (effect size d = 0.56) and passive torque and muscle-tendon unit stiffness decreased (effect size d = 0.65 and d = 0.73, respectively) post-stretching. There was a reduction only in passive torque in the minute-by-minute evaluation, mainly at minutes five and seven. CONCLUSIONS: passive torque decreased over a 10-min static stretching session of the ankle plantar flexors, followed by a ROM increase and muscle-tendon unit, a stiffness decrease.

Moderate intensity cycling is better than running on recovery of eccentric exercise-induced muscle damage.

OBJECTIVE: To compare the effects of moderate intensity running and cycling on markers of exercise-induced muscle damage in men. STUDY DESIGN: Randomized controlled trial. SETTING: Laboratory. PARTICIPANTS: Thirty volunteers were randomized in three groups [running (RG; n = 10), cycling (CG; n = 10) and control (CON; n = 10)] and were evaluated at baseline, post 24, 48 and 72 h of knee extensors' muscle damage protocol. CON performed passive recovery, while RG and CG performed active recovery immediately after the protocol, as well as 24 h and 48 h afterwards. MAIN OUTCOMES: (i) maximal voluntary isometric contraction (MVIC); (ii) delayed-onset muscle soreness (DOMS); (iii) plasma creatine kinase (CK) and lactate dehydrogenase (LDH) levels. RESULTS: No group-by-time interaction was found in any outcome evaluated (p > 0.05). All groups presented decreases in MVIC and increases in DOMS (p < 0.001), without differences in CK and LDH. Compared with CON, exercise groups presented likely beneficial effects for LDH, while only CG had a likely beneficial effect for DOMS. Lastly, CG presented likely/very likely beneficial effects for MVIC and DOMS compared to RG. CONCLUSION: Although the null hypothesis analysis did not find differences, the magnitude-based inference analysis suggested that moderate intensity cycling have likely beneficial effects on knee extensor muscle recovery after eccentric exercise protocol.

Proprioceptive Training on Dynamic Neuromuscular Control in Fencers: A Clinical Trial.

CONTEXT: Fencing is a sport of agility, with a higher incidence of lower-limb injuries, of which the ankle sprain is the most prevalent. Injury prevention is very important to improve performance and decrease the withdrawal time of athletes. Proprioceptive training programs can be added to the training of athletes, since, in addition to easy application and low cost, proprioception has the function of stabilizing the ankle joint to prevent injuries. OBJECTIVE: To verify the influence of a 12-week proprioceptive training program on dynamic neuromuscular control in fencing athletes. DESIGN: The study was a clinical trial, and the athletes were allocated, for convenience, in the intervention group or in the control group. SETTING: The study was developed in 4 stages (preintervention, intervention, postintervention, and follow-up of 3). The neuromuscular control during the star excursion balance test was evaluated. PARTICIPANTS: The participants were 19 fencing athletes (intervention group: 10, and control group: 9), aged 14-35 years, from a multisport club. INTERVENTIONS: The athletes performed the proprioceptive training during 12 weeks, 3 times a week, with a duration of 30 minutes. MAIN OUTCOME MEASURES: Dynamic neuromuscular control. RESULTS: The data and SE were considered for statistical analysis, submitted to the generalized estimates equations test with Bonferroni post hoc. The level of significance was .05. The distance reached in the star excursion balance test increased significantly in all 8 directions evaluated in the 2 legs of the intervention group. CONCLUSIONS: The proprioceptive training program was able to improve dynamic neuromuscular control in fencing athletes.

Effects of proprioceptive training on the incidence of ankle sprain in athletes: systematic review and meta-analysis.

OBJECTIVE:: To investigate how dynamic neuromuscular control, postural sway, joint position sense, and incidence of ankle sprain are influenced by balance training in athletes compared with the control group in randomized clinical trials. DATA SOURCES:: The search strategy included MEDLINE, Physical Therapy Evidence Database, Cochrane Central Register of Controlled Trials, and Latin American and Caribbean Center on Health Sciences Information. Randomized controlled trials (RCTs) were published by June of 2018. METHODS:: RCTs that evaluate the effectiveness of proprioception in these outcomes: dynamic neuromuscular control, postural sway, joint position, and the incidence of ankle sprains in athletes aged between 18 and 35 years. Two reviewers independently screened the searched records, extracted the data, and assessed risk of bias. The treatment effect sizes were pooled in a meta-analysis using the RevMan 5.2 software. Internal validity was assessed through topics suggested by Cochrane Collaborations. RESULTS:: Of the 12 articles included ( n = 1817), eight were in the meta-analysis ( n = 1722). The balance training reduced the incidence of ankle sprains in 38% compared with the control group ( RR: 0.62; 95% CI: 0.43-0.90). In relation to the dynamic neuromuscular control, the training showed increase in the distance of reach in the anterior (0.62 cm, 95% CI: 0.13-1.11), posterolateral (4.22 cm, 95% CI: 1.76-6.68), and posteromedial (3.65 cm, 95% CI: 1.03-6.26) through the Star Excursion Balance test. Furthermore, training seems to improve postural sway and joint position sense. CONCLUSION:: Balance training reduces the incidence of ankle sprains and increases dynamic neuromuscular control, postural sway, and the joint position sense in athletes.

Acute effect of different time periods of passive static stretching on the hamstring flexibility.

BACKGROUND: Several factors are associated with the presence of chronic low back pain; one of them is the flexibility of the hamstring muscles that influences the posture of the pelvic spine. OBJECTIVE: Investigate the influence of two different time periods of passive static stretching on the flexibility of the hamstring. METHODS: Forty-six physiotherapy students were divided into two groups performing stretching exercises: 30 s and 60 s duration. The collections consisted of: (1) pre-test: evaluation of the flexibility of the hip and knee, using a manual goniometer by means of the following tests: Straight Leg Raise Test (SLR), Passive Hip Flexion Test (PHFT) and Modified Knee Extension Test (MKET), (2) intervention: stretching with different runtimes, (3) post-test: reappraisal of flexibility, conducted immediately after the intervention. RESULTS: Significant difference was observed intra groups, group that did stretching exercises lasting 30 seconds (G30) (SLR p = 0.000. PHFT p = 0.003 and MKET p = 0.000) and group that did stretching exercises lasting 60 seconds (G60) (SLR p = 0.000. PHFT p = 0.001 and MKET p = 0.002). Comparing the groups, no significant difference was found (SLR p = 0.307; PHFT p = 0.904; MKET p = 0.132). CONCLUSION: Thus it can be inferred that 30 seconds are sufficient for increased flexibility of young women. Therefore the time-treatment sessions can be optimized. Only the acute effect of stretching was observed; further investigation of the long-term effect is required.

Nível de ativação muscular do vasto medial em diferentes exercícios fisioterapêuticos / Activation level of vastus medialis muscle in different rehabilitation exercises

A Síndrome da Dor Femoropatelar (SDFP) tem como uma das causas a lateralização excessiva da patela, que ocorre frequentemente pelo enfraquecimento do músculo Vasto Medial (VM). Dessa forma, na prevenção e reabilitação da SDFP, o fortalecimento de VM é imprescindível. Objetivo: Comparar o nível de ativação do VM em quatro diferentes exercícios utilizados na prevenção e na reabilitação da SDFP compreendendo isometria de extensão de joelhos a 30° e 60° e isometria no agachamento a 60° associado ou não a adução de quadril. Métodos: A amostra foi de 14 sujeitos saudáveis sedentários, com idade entre 20 e 40 anos. O sinal EMG do músculo VM foi coletado durante Contração Isométrica Voluntária Máxima (CIVM) com duração de cinco segundos para cada exercício. Do sinal EMG captado foi recortado um período de três segundos e a partir disso foram obtidos os valores Root Mean Square (RMS) para cada exercício. Resultados: Demonstram que houve ativação do VM significativamente maior nos exercícios de extensão quando comparados com os exercícios de agachamento. Porém, não houve diferença significativa entre os dois exercícios de extensão, assim como entre os exercícios de agachamento. Conclusão: Os melhores exercícios para maximizar a ativação do VM são os exercícios isométricos de extensão do joelho, independente do ângulo avaliado, pois apresentam maior nível de ativação do VM, imprescindível para a prevenção e reabilitação da SDFP

Excessive lateralization, which often occurs by the weakening of Vastus Medialis (VM) muscle of the patella, is one of the causes of Patellofemoral Pain Syndrome (PFPS) For prevention and rehabilitation of PFPS, the VM strength is essential. Objective: The aim of the study was to compare the VM activation level in four different exercises used in the prevention and rehabilitation of PFPS that are isometric knee extension at 30° and 60° and isometric squat at 60° with or without hip adduction. Methods: A sample of 14 sedentary healthy subjects, aged between 20 and 40 years was included. The EMG signal of VM muscle was collected during Maximal Voluntary Isometric Contraction with duration of five seconds for each exercise. From the captured EMG signal, a period of three seconds was cut and thereafter the Root Mean Square value for each exercise was obtained. Results: The results showed that there was significantly greater activation in VM extension exercises compared to squat exercises. However, there was no significant difference between the two extension exercises, as well as between squat exercises. Conclusion: It can be concluded that the best exercises to maximize the activation of the VM are the isometric knee extension, regardless of the rated angle, since they have greater VM activation level, essential for the prevention and rehabilitation of PFPS

Avaliação do déficit bilateral em contrações isométricas dos extensores de joelhos / Evaluation of bilateral deficit in isometric contractions of the knee extensors

O treinamento de força tem sido referido como uma importante ferramenta para o incremento e a manutenção da saúde. Os exercícios que compõem um programa de treino podem ser executados em condição unilateral ou bilateral. Alguns estudos têm apresentado valores mais reduzidos de produção de força e sinal eletromiográfico em condições bilaterais do que o somatório desses valores em condições unilaterais. Essa diferença na produção de força, bem como no sinal eletromiográfico é denominada déficit bilateral. O objetivo do presente estudo foi avaliar a produção de força e a atividade eletromiográfica dos músculos reto da coxa e vasto lateral no exercício de extensão isométrica de joelhos, nas condições unilateral e bilateral. A amostra foi constituída de 10 indivíduos do sexo masculino, com idades entre 18 e 30 anos, não praticantes de treinamento de força. Foram registrados os valores de força e atividade elétrica com a utilização de uma célula de carga e eletrodos de superfície, respectivamente, no teste isométrico de extensão de joelhos (120º). Os resultados apontaram valores maiores (p<0,05) para a produção de força e sinal eletromiográfico na condição unilateral do exercício, reportando um déficit bilateral tanto na força como na atividade eletromiográfica. Estes resultados sugerem que o treino unilateral promove maior estímulo muscular, constituindo-se como uma importante estratégia a ser utilizada na prescrição dos exercícios de força.

Strength training has been reported as an important tool for enhancing and maintaining health. Resistance exercises can be executed unilaterally or bilaterally. Some studies have reported lower strength and electromyography (EMG) signal values in bilateral conditions than the sum of these values in unilateral conditions. This difference in strength and EMG is called the bilateral deficit. The aim of this study was to evaluate the strength and EMG activity of the rectus femoris and vastus lateralis during unilateral and bilateral isometric knee extension. The sample consisted of 10 non-resistance trained males aged 18 to 30 years. Strength and EMG were recorded through use of a load cell and surface electrodes, respectively. A 120º knee extension was used for the isometric knee extension test. The results showed significantly higher values for strength and EMG signal (p <0.05) in unilateral conditions, as well as bilateral deficit in both strength and EMG signal. These results suggest that unilateral training promotes greater muscle stimulation, and can thus represent an important strategy to be used in the prescription of strength training exercises.

Análise da força isométrica máxima e do sinal de EMG em exercícios para os membros inferiores / Analysis of maximal isometric force and EMG signal in lower limb exercise

O objetivo deste estudo foi comparar a força isométrica máxima (FIM) e a atividade elétrica dos músculos vasto medial (VM), vasto lateral (VL), reto femoral (RF), glúteo máximo (GM) e bíceps femoral (BF) entre contrações isométricas voluntárias máximas (CIVM) executadas em diferentes posições articulares e identificar as mais adequadas para normalizar o sinal de eletromiografia (EMG) de cada um dos músculos referidos, quando estes são ativados em condições dinâmicas. A amostra foi constituída de 10 indivíduos do sexo masculino, com idades entre 20 e 30 anos, familiarizados com treinamento de força. Foram realizadas CIVMs em diferentes ângulos articulares para os grupos extensores e flexores do joelho (0°, 60°, 90°) e extensores (-30°, 0°, 60°) e flexores do quadril (90°, 120°). Sobre a FIM foram encontrados valores significativamente diferentes entre as posições em 60° para flexão de joelhos e para extensão de joelhos em 60° e 90° (p<0,01) e não houve diferenças significativas entre as posições na flexão e extensão do quadril (p>0,05). Em relação ao sinal EMG, foram encontrados valores significativamente diferentes entre os ângulos para a extensão de joelhos somente no RF em 90° (p<0,01). Para a flexão de joelhos, flexão e extensão de quadril não foram encontradas diferenças siginificativas entre os músculos nos diferentes ângulos avaliados (p>0,05). Estes resultados sugerem que a posição de 60° é a mais adequada para avaliação dos flexores e extensores do joelho e que todas posições testadas neste estudo apresentam-se como adequadas para a avaliação da flexão e extensão de quadril.

The aim of this study was to compare maximal isometric force (MIF) and the electrical activity of the vastus medialis, vastus lateralis, rectus femoris, gluteus maximus and biceps femoris long head muscles between maximal voluntary contractions (MVC) performed at different joint angles, and to identify the most suitable positions to normalize the electromyography (EMG) signals from each of these muscles when they are activated under dynamic conditions. Ten men ranging in age from 20 to 30 years, who were familiar with strength training exercise, were studied. MVC at different joint angles of the knee extensors and flexors (0°, 60°, 90°) and hip extensors (-30°, 0°, 60°) and flexors (90°, 120°) were tested. The MIF values differed significantly between the 60° knee flexion and 60° and 90° knee extension positions (p<0.01). The same was not observed for hip flexion or extension (p>0.05). Significantly higher EMG values were only observed for the rectus femoris muscle at 90° knee extension (p<0.01). No differences between muscles were found for knee flexion, hip flexion or hip extension at the joint angles tested (p>0.05). These results suggest that the 60° knee joint flexion position is the most suitable for assessment of knee extension and flexion MIF, and that all positions tested in this study are suitable for the assessment of hip flexion and extension.

Análise eletromiográfica do quadríceps durante a extensão do joelho em diferentes velocidades / Electromyographical analysis of the quadriceps during knee extension at different speeds

A síndrome de dor fêmuro-patelar (SDFP) é uma disfunção comum, geralmente causada por trações laterais excessivas da patela. Indivíduos com SDFP, usualmente apresentam inibição do vasto medial oblíquo (VMO), o qual é responsável pela tração medial patelar. O tratamento conservador envolve o reforço do quadríceps para promover melhor estabilidade e tração patelar. Muitos pesquisadores buscam o recrutamento seletivo do VMO, com o intuito de otimizar o tratamento. O objetivo deste estudo é investigar, através da eletromiografia, a interferência da velocidade angular e diferentes formas de fixação do tubo elástico na atividade quadricipital. Dez indivíduos do sexo masculino com ausência de lesão muscular ou articular participaram deste estudo. Indivíduos com ângulo Q fora do intervalo de 10-15° foram excluídos da pesquisa. O tubo elástico foi fixado paralelo e oblíquo em relação ao corpo do indivíduo. As extensões de joelho foram realizadas com velocidades angulares de 60 e 120°/seg. Nenhuma atividade seletiva do VMO foi encontrada. Comparando os níveis de atividade muscular, durante as duas velocidades angulares houve aumento no nível de atividade eletromiográfica em todas porções do quadríceps, apenas para a fixação do tubo elástico paralela. Os resultados sugerem uma atividade sinérgica entre o VMO e as outras porções do quadríceps.