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INTRODUCTION: Effects on strength performance and muscle activation in the contralateral limb have been observed after training with the ipsilateral limb (IL). Cross fatigue effects in the contralateral limb (CL) can occur at intervals of up to 48 h after a training session performed with the ipsilateral limb. The objective of this study was to verify the effect of a training session in the ipsilateral limb, on the strength and activation of the muscles in the contralateral limb also submitted to the training protocol. METHODS: 10 untrained men (mean ± SD: age = 23.7 ± 4.9 years) performed unilateral knee extension with both limbs in equated protocols, in two conditions with different intervals between limbs - 20 min and 24 h. RESULTS: There were no differences in the comparison of the force produced between the pre x post interventions with the CL limb, as well as in the activation of the quadriceps during its performance. These results were similar for the two different intervals between the protocols. CONCLUSION: It was concluded that when the CL member performs the protocol after the IL, the responses in the CL depend mainly on the requirement imposed on the protocol performed by this member, without influence of the training protocol performed previously with the IL member.

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Multiple exercises included in strength training involve greater activation of the quadriceps compared to hamstring muscles, which may lead to knee joint imbalances. The aim of this study was to examine the ratio of surface electromyography (sEMG) activity hamstring and quadriceps muscle groups (hamstring-to-quadriceps activation ratio; H:Q EMG), as well as lateral to medial hamstring activation ratio (LH:MH) in parallel squat, Romanian deadlift, hip thrust, lying leg curl and seated knee extension. The H:Q EMG was greater during lying leg curl compared to other exercises during both the concentric and eccentric phase, however the Romanian deadlift and hip thrust also resulted in relatively high H:Q EMG. Pairwise comparisons revealed that LH:MH was greater in the parallel squat compared to the Romanian deadlift and hip thrust in the concentric phase, and compared to the Romanian deadlift and hip thrust during the eccentric phase. Our data suggests that the lying leg curl promotes the greatest hamstring activation and H:Q EMG, amongst the exercises investigated, while also providing relatively homogenous LH:MH. The lying leg curl should be considered as a primary exercise in rehabilitation and training programmes, aiming to proportionally activate LH:MH and increase H:Q EMG, which may improve knee muscle balance.

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Previous studies of jumping in frogs have found power outputs in excess of what is possible from direct application of muscle power and concluded that jumping requires the storage and release of elastic strain energy. Of course, the muscles must produce the work required and their power output should be consistent with known muscle properties if the total duration of muscle activity is known. Using the Cuban tree frog, Osteopilus septentrionalis, I measured jumping performance from kinematics and used EMG measurements of three major jumping muscles to determine the duration of muscle activity. Using the total mass of all the hindlimb muscles, muscle mass-specific work output up to 60 J kg-1 was recorded. Distributed over the duration of the jump, both average and peak muscle mass-specific power output increased approximately linearly with the work done, reaching values of over 750 and 2000 W kg-1, respectively. However, the muscles were activated before the jump started. Both preactivation duration and EMG amplitude increased with increasing amounts of work performed. Assuming the muscles could produce work from EMG onset until toe-off, the average muscle mass-specific power over this longer interval also increased with work done, but only up to a work output of 36 J kg-1. The mean power above this value of work was 281 W kg-1, which is approximately 65% of the estimated maximum isotonic power. Several reasons are put forward for suggesting this power output, although within the known properties of the muscles, is nevertheless an impressive achievement.

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PURPOSE: Caffeine improves cycling time trial (TT) performance; however, it is unknown whether caffeine is ergogenic when competing against other riders. The aim of this study was to investigate whether caffeine improves performance during a 4-km cycling TT when riding against a virtual opponent, and whether it is associated with increased muscle activation and at the expense of greater end-exercise central and peripheral fatigue. METHODS: Using a randomized, crossover, and double-blind design, eleven well-trained cyclists completed a 4-km cycling TT alone without supplementation (CON), or against a virtual opponent after ingestion of placebo (OP-PLA) or caffeine (5 mg.kg-1, OP-CAF). Central and peripheral fatigue were quantified via the pre- to post-exercise decrease in voluntary activation and potentiated twitch force, respectively. Muscle activation was continually measured during the trial via electromyography activity. RESULTS: Compared to CON, OP-PLA improved 4-km cycling TT performance (P = 0.018), and OP-CAF further improved performance when compared to OP-PLA (P = 0.050). Muscle activation was higher in OP-PLA and OP-CAF than in CON throughout the trial (P = 0.003). The pre- to post-exercise reductions in voluntary activation and potentiated twitch force were, however, similar between experimental conditions (P > 0.05). Compared to CON, OP-PLA increased the rating of perceived exertion during the first 2 km, but caffeine blunted this increase with no difference between the OP-CAF and CON conditions. CONCLUSIONS: Caffeine is ergogenic when riding against a virtual opponent, but this is not due to greater muscle activation or at the expense of greater end-exercise central or peripheral fatigue.

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The bench press is performed in parapowerlifting with the back, shoulders, buttocks, legs and heels extended over the bench, and the use of straps to secure the athlete to the bench is optional. Thus, the study evaluated muscle activation, surface electromyography (sEMG), maximum velocity (MaxV) and mean propulsive velocity (MPV), and power in paralympic powerlifting athletes under conditions tied or untied to the bench. Fifteen experienced Paralympic powerlifting male athletes (22.27 ± 10.30 years, 78.5 ± 21.6 kg) took part in the research. The sEMG measurement was performed in the sternal portion of the pectoralis major (PMES), anterior deltoid (AD), long head of the triceps brachii (TRI) and clavicular portion of the pectoralis major (PMCL). The MaxV, MPV and power were evaluated using an encoder. Loads of 40%, 60%, 80% and 100% 1RM were analyzed under untied and tied conditions. No differences were found in muscle activation between the tied and untied conditions; however, sEMG showed differences in the untied condition between AD and TRI (F (3112) = 4.484; p = 0.005) in the 100% 1RM load, between PMCL and AD (F (3112) = 3.743; p = 0.013) in 60% 1RM load and in the tied condition, between the PMES and the AD (F (3112) = 4.067; p = 0.009). There were differences in MaxV (F (3112) = 213.3; p < 0.001), and MPV (F (3112) = 248.2; p < 0.001), between all loads in the tied and untied condition. In power, the load of 100% 1RM differed from all other relative loads (F (3112) = 36.54; p < 0.001) in both conditions. The tied condition seems to favor muscle activation, sEMG, and velocity over the untied condition.

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BACKGROUND: The shoulder joint is the most commonly injured joint in CrossFit practitioners, because of the high intensity and loads associated with this sport. Despite the large number of clinical cases, there is a shortage of studies that investigate influence of biomechanical aspects of upper limbs' injuries on CrossFit practitioners. This study hypothesized that there would be a difference in function, strength, and muscle activation between Crossfit practitioners with and without shoulder pain. METHODS: We divided 79 Crossfit practitioners into two groups according to whether they reported pain (n = 29) or no pain (n = 50) in the shoulder during Crossfit training. Muscle function, strength, and activation were assessed using the Disability Arm, Shoulder and Hand function questionnaire, Upper Quarter Y Balance Test and Closed Kinetic Chain Upper Extremity Stability Test shoulder tests, isometric muscle strength assessment by manual dynamometry and muscle activation by surface electromyography and pain report. RESULTS: The function based on questionnaire was associated with pain (p = 0.004). We observed a statistically significant difference between the two groups only in the surface electromyography activity of the lower trapezius, and in the variables of shoulder pain and function (p = 0.038). CONCLUSION: Crossfit practitioners with shoulder pain occurring during training showed good function and stability of the shoulder joint, but there was a reduction in the activation of stabilizing muscles, especially the lower trapezius. Trial registration Registro Brasileiro de Ensaios Clinico (Brasilian National Registry) with the ID: RBR-2gycyv.

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The ankle plantar flexor muscles act synergistically to control quiet and dynamic body balance. Previous research has shown that the medial (MG) and lateral (LG) gastrocnemii, and soleus (SOL) are differentially activated as a function of motor task requirements. In the present investigation, we evaluated modulation of the plantar flexors' activation from feet orientation on the ground in an upright stance and the ensuing reactive response to a perturbation. A single group of young participants (n = 24) was evaluated in a task requiring initial stabilization of body balance against a backward pulling load (5% or 10% of body weight) attached to their trunk, and then the balance was suddenly perturbed, releasing the load. Four feet orientations were compared: parallel (0°), outward orientation at 15° and 30°, and the preferred orientation (M = 10.5°). Results revealed a higher activation magnitude of SOL compared to MG-LG when sustaining quiet balance against the 10% load. In the generation of reactive responses, MG was characterized by earlier, steeper, and proportionally higher activation than LG-SOL. Feet orientation at 30° led to higher muscular activation than the other orientations, while the activation relationship across muscles was unaffected by feet orientation. Our results support the conclusion of task-specific differential modulation of the plantar flexor muscles for balance control.

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SUMMARY: Anatomical studies describe the vastus medialis (VM) as being subdivided into two morphologically distinct components, the vastus medialis obliquus (VMO) and the vastus medialis longus (VML). However, there are discrepancies regarding the functional differentiation of these components. The aim of this study was to compare the levels of activation of the VMO and the VML by high density surface electromyography. Twelve healthy young women (age: 21.4 ± 2.0 years; weight: 58.1 ± 7.5 kg; height: 1.6 ± 0.1 m), performed an open kinetic chain knee exercise during which the EMG activity of the VMO and the VML was recorded with two- dimensional matrices of 32 surface electrodes. The exercises were performed with three levels of resistance (5, 10 and 15 % of the body weight (BW)), considering three phases: concentric, isometric and excentric. In the isometric phase the VMO had greater activation than the VML with the three levels of resistance (p<0.05). In the excentric phase, the VMO also showed greater activation than the VML with the 10 and 15 % BW resistance levels, while in the concentric phase, the VMO showed greater activity than the VML with only the 15 % BW resistance. The results indicated significant differences in the activation level of the two components of the VM. This bears importance in the development of exercises intended to achieve a greater or more selective activation of the VMO. In the sample subjected to evaluation, the EMG recordings describe a greater activation of the VMO in comparison to the VML, which is more important in the isometric and excentric phases of the flexion/extension of the knee in an open kinetic chain. These findings suggest a functional compartmentalization of the VM.

RESUMEN: Los estudios anatómicos describen que el músculo vasto medial (VM) se subdivide en dos componentes morfológicamente distintos, el vasto medial obliquus (VMO) y el vasto medial largo (VML). Sin embargo, existen discrepancias con respecto a la diferenciación funcional de estos componentes. El objetivo de este estudio fue comparar los niveles de activación del VMO y el VML mediante electromiografía de superficie de alta densidad. Doce mujeres jóvenes sanas (edad: 21,4 ± 2,0 años; peso: 58,1 ± 7,5 kg; altura: 1,6 ± 0,1 m), realizaron un ejercicio de rodilla de cadena cinética abierta durante el cual se registró la actividad EMG de la VMO y la VML con dos matrices dimensionales de 32 electrodos de superficie. Los ejercicios se realizaron con tres niveles de resistencia (5, 10 y 15% del peso corporal (PC)), considerando tres fases: concéntrica, isométrica y excéntrica. En la fase isométrica el VMO tuvo mayor activación que el VML con los tres niveles de resistencia (p <0,05). En la fase excéntrica, el VMO también mostró mayor activación que el VML con los niveles de resistencia de 10 y 15% BW, mientras que en la fase concéntrica, el VMO mostró mayor actividad que el VML con solo el 15 % de resistencia al BW. Los resultados indicaron diferencias significativas en el nivel de activación de los dos componentes de la VM. Esto tiene importancia en el desarrollo de ejercicios destinados a lograr una activación mayor o más selectiva del VMO. En la muestra sometida a evaluación, los registros EMG describen una mayor activación del VMO en comparación con el VML, que es más importante en las fases isométrica y excéntrica de la flexión / extensión de la rodilla en cadena cinética abierta. Estos hallazgos sugieren una compartimentación funcional de la VM.

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The present article aims to compare electromyographic (EMG) activity of the knee extensors during traditional resistance training (TRT) and no load resistance training with or without visual feedback (NL-VF and NL-NF). Sixteen healthy men (age: 25.2 ± 3.6) volunteered to participate in the study. Participants visited the laboratory on three occasions involving: (1) a 10 repetition maximum test (10 RM test), (2) familiarization and (3) performance of knee extensions using TRT, NL-VF and NL-NF in a random order, with 10 min of rest between them. TRT involved the performance of a set to momentary muscle failure using the 10 RM load. NL-NF involved the performance of 10 repetitions with no external load, but with the intention to maximally contract the muscles during the whole set. NL-VF involved the same procedure as NL-NF, but a monitor was positioned in front of the participants to provide visual feedback on the EMG activity. Peak and mean EMG activity were evaluated on the vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF). Results: there were no significant differences in VM and VL peak EMG activity among different situations. There was a significant difference for peak EMG activity for RF, where TRT resulted in higher values than NL-VF and NL-NF (p < 0.05). Higher values of mean EMG activity were found for VM, VL and RF during TRT in comparison with both NL-VF and NL-NF. Conclusions: resistance training with no external load produced high levels of peak muscle activation, independent of visual feedback, but mean activation was higher during TRT. These results suggest that training with no external load might be used as a strategy for stimulating the knee extensors when there is limited access to specialized equipment. Although the clinical applications of no load resistance training are promising, it is important to perform long-term studies to test if these acute results will reflect in muscle morphological and functional changes.

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Metabolic stress is a primary mechanism of muscle hypertrophy and is associated with microvascular oxygenation and muscle activation. Considering that drop-set (DS) and crescent pyramid (CP) resistance training systems are recommended to modulate these mechanisms related to muscle hypertrophy, we aimed to investigate if these resistance training systems produce a different microvascular oxygenation status and muscle activation from those observed in traditional resistance training (TRAD). Twelve volunteers had their legs randomized in an intra-subject cross-over design in TRAD (3 sets of 10 repetitions at 75% 1-RM), DS (3 sets of ∼50-75% 1-RM) and CP (3 sets of 6-10 repetitions at 75-85% 1-RM). Vastus medialis microvascular oxygenation and muscle activation were respectively assessed by non-invasive near-infrared spectroscopy and surface electromyography techniques during the resistance training sessions in the leg-extension exercise. Total hemoglobin area under the curve (AUC) (TRAD: -1653.5 ± 2866.5; DS: -3069.2 ± 3429.4; CP: -1196.6 ± 2675.3) and tissue oxygen saturation (TRAD: 19283.1 ± 6698.0; DS: 23995.5 ± 15604.9; CP: 16109.1 ± 8553.1) increased without differences between protocols (p>0.05). Greater decreases in oxygenated hemoglobin AUC and hemoglobin differentiated AUC were respectively found for DS (-4036.8 ± 2698.1; -5004.4 ± 2722.9) compared with TRAD (-1951.8 ± 1720.0; -2250.3 ± 1305.7) and CP (-1814.4 ± 2634.3; 2432.2 ± 2891.4) (p<0.03). Higher increases of hemoglobin deoxygenated AUC were found for DS (1426.7 ± 1320.7) compared with TRAD (316.0 ± 1164.9) only (p=0.04). No differences were demonstrated in electromyographic amplitudes between TRAD (69.0 ± 34.4), DS (61.3 ± 26.7) and CP (60.9 ± 38.8) (p>0.05). Despite DS produced lower microvascular oxygenation levels compared with TRAD and CP, all protocols produced similar muscle activation levels.

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INTRODUÇÃO: Recentes evidências têm demonstrado resultados bastante promissores para o uso de estratégias não invasivas de neuromodulação na melhora de habilidades físicas ou esportivas. A estimulação elétrica periférica (EEP) e a estimulação transcraniana por corrente contínua (ETCC) são técnicas não invasivas e não farmacológicas bastante utilizadas para modular a excitabilidade neuronal de áreas cortico-motoras e estimular a recuperação funcional. No entanto, poucos estudos têm investigado o efeito dessas técnicas na melhora do desempenho muscular. OBJETIVO: Investigar o efeito da estimulação elétrica periférica sensorial (EEPs) seguida de estimulação elétrica periférica motora (EEPm) ou estimulação transcraniana por corrente contínua (ETCC) na força isométrica máxima dos extensores do joelho em indivíduos saudáveis. MÉTODO: 20 universitários saudáveis foram distribuídos aleatoriamente em dois blocos distintos de 10 participantes cada: Bloco n°1 EEPs real + EEPm real ou EEPs simulada + EEPm real e bloco n°2 EEPs real + ETCC real ou EEPs simulada + ETCC real em uma única sessão. A contração voluntária isométrica máxima (CVIM) dos extensores do joelho foi avaliada por meio da dinamometria manual antes, durante e 10 min pós-estimulação. RESULTADOS: A CVIM dos extensores do joelho aumentou significativamente 10 minutos pós-ETCC isolada (diferença média = 0,23 N/Kg; IC 95% = 0,01 a 0,44 N/Kg; p = 0,04). A ETCC isolada também apresentou maior proporção cumulativa de respondedores seguido de EEPs+ETCC. CONCLUSÃO: A estimulação transcraniana por corrente contínua induz a aumentos significativos na CVIM em indivíduos saudáveis. No entanto, a aplicação prévia de estimulação elétrica periférica sensorial não impulsiona os efeitos da estimulação elétrica periférica motora ou cerebral na CVIM.

INTRODUCTION: Recent evidence has shown very promising results for the use of noninvasive neuromodulation strategies in improving physical strength or sports skills. Peripheral electrical stimulation (PES) and transcranial direct current stimulation (tDCS) are non-invasive and non-pharmacological techniques widely used to modulate neuronal excitability of corticomotor areas and to induce functional improvements. However, few studies have investigated the effect of these techniques on improving muscle performance. OBJECTIVE: To investigate the effect of sensory peripheral electrical stimulation (PESs) followed by motor peripheral electrical stimulation (PESm) or transcranial direct current stimulation (tDCS) on the maximal isometric force production of the knee extensors in healthy individuals. METHODS: Twenty healthy university students were randomly assigned to two distinct blocks with 10 participants in each block: 1) block n°1 PESs + PESm or sham PESs + PESm, 2) block n°2 PESs + tDCS or sham PESs + tDCS (each in a single session). The maximum voluntary isometric contraction (MVIC) of the knee extensors was evaluated by manual dynamometry pre-, during and 10 min post-stimulation. RESULTS: MVIC of the knee extensors was significantly increased 10 min post-tDCS alone (mean difference = 0.23 N/kg, 95% CI = 0.01 to 0.44 N/kg, p = 0.04). Isolated tDCS also had a higher cumulative proportion of responders, followed by PESs + tDCS. CONCLUSIONS: Transcranial direct current stimulation induces a significant increase in MVIC in healthy subjects. However, prior application of peripheral electrical stimulation does not compound the effects of peripheral electrical motor or cerebral stimulation.

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BACKGROUND: One proposed mechanism of chronic low back pain might be paraspinal muscle impairment. Commonly, this impairment is treated with stabilization exercises. However, the effect size of stabilization exercises has been previously reported to be small. DESIGN: Randomized controlled trial. OBJECTIVE: To investigate the clinical benefit of using neuromuscular electrical stimulation as a supplement to stabilization exercises in patients with chronic low back pain. METHODS: Thirty participants with chronic low back pain were randomized into a stabilization exercise only group (n=15) or a stabilization exercise plus neuromuscular electrical stimulation group (n=15). The stabilization exercises included abdominal, side support, and quadruped exercises. The neuromuscular electrical stimulation was applied to the lumbar paraspinal muscles for 20min each session. Both groups received their respective interventions twice a week for 6 weeks. Participant eligibility for inclusion was age between 18 and 60 years, body mass index ≤34, chronic low back pain ≥3 months, Numeric Pain Rating Scale ≥3, Modified Oswestry Disability Questionnaire score ≥20 and ability to understand English. Outcome measurements were self-reported neuromuscular electrical stimulation tolerability scale, Modified Oswestry Disability Questionnaire, Numeric Pain Rating Scale, Fear-Avoidance Beliefs Questionnaire and paraspinal muscle strength. RESULTS: The neuromuscular electrical stimulation was reported to be tolerable. There were no significant between-group differences on any of the outcome measures (p>0.05). CONCLUSIONS: The application of neuromuscular electrical stimulation on the paraspinal muscles was reported to be tolerable. Supplementing stabilization exercises with neuromuscular electrical stimulation did not offer any additional clinical benefit for the chronic low back pain patients.

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Hippotherapy is a therapeutic method that uses the horse's movement to achieve functional results in practitioners with Down syndrome (DS), who present motor and neurophysiological changes that affect the musculoskeletal system. Evaluating the motor behavior related to the control and the improvement of muscle activation in practitioners with Down syndrome subjected to hippotherapy. 10 practitioners were divided into two groups: Down Group (DG) ­ practitioners with DS, and Healthy Group (HG) ­ practitioners with no physical impairment. The muscles gluteus medius, tensor fasciae latae, rectus femoris, vastus medialis, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius were evaluated by electromyography using gross RMS values, which correspond to muscle activation; the evaluations were performed on the 1st and 10th hippotherapy sessions (frequency: once a week), and after 2 months interval without treatment, they were performed on the 1st and 10th hippotherapy sessions (frequency: twice a week). It was noted that activation of the studied muscles increased with the passing of sessions, regardless the weekly frequency of attendance; however, the period without treatment resulted in reduction of this effect. Practitioners with DS presented satisfactory changes in muscle activation pattern, in learning and in motor behavior during hippotherapy sessions.

Equoterapia é um método terapêutico que utiliza o movimento do cavalo para alcançar resultados funcionais, realizada em praticantes com síndrome de Down (SD), que apresentam alterações neurofisiológicas e motoras que afetam o sistema musculoesquelético. Avaliar o comportamento motor relacionado ao controle e melhora a ativação muscular em praticantes com SD submetidos ao tratamento equoterapêutico. Participaram dez praticantes divididos em dois grupos: grupo Down (GD) - praticantes com SD, e grupo Saudável (GS) - praticantes sem comprometimento físico. Os músculos glúteo médio, tensor da fáscia lata, reto femoral, vasto medial, vasto lateral, bíceps femoral, tibial anterior e gastrocnêmio foram avaliados por meio da eletromiografia, utilizando o valor de RMS bruto que corresponde à ativação muscular, e as avaliações foram realizadas na primeira e décima sessões de equoterapia (frequência: 01 vez por semana); e após intervalo de dois meses sem tratamento, foi realizada na primeira e décima sessões de equoterapia (frequência: 02 vezes por semana). Observou-se que a ativação muscular dos músculos estudados aumentou com o passar das sessões, independente da frequência semanal de atendimento; mas o período sem tratamento resultou em redução deste efeito. Os praticantes com SD apresentaram mudanças satisfatórias no padrão de ativação muscular, na aprendizagem e no comportamento motor no decorrer das sessões de equoterapia.

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We previously showed that a yin meridian of the upper limb decreased electromyographic activity (root mean square) and muscle strength ipsilateral and contralateral to the side of stimulation. Here, we tested the upper trapezius (UT) muscle response after stimulation of a yang meridian of the upper limb, the small intestine (SI). Thirty-eight healthy volunteers were randomized into the following groups: UT muscle (SI14), distant of the UT muscle (SI8), without stimulation (CG), and sham (R3). An acupuncturist certificated by the Brazilian Society of Physical Therapists and Acupuncturists performed the needle insertion. Each volunteer received only one stimulation to the right upper limb. The evaluation occurred before, 5 minutes after, and 20 minutes after needle withdrawal. The root mean square activity increased on the right side in the UT muscle for the SI8 and SI14 groups (F3,37 = 4.67; p < 0.025) at the 20-minute evaluation. The most vigorous response occurred on the contralateral side because the effects were maintained for 5 minutes after withdrawal (F3,37 = 4.52; p < 0.025). Both groups showed an increase in the UT muscle strength at the 20-minute evaluation (F3,37 = 3.41; p < 0.025). The CG and R3 groups did not show any changes. Our data indicate that SI a yang meridian increases the UT muscle response.

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Abstract: Introduction The biomechanical changes that arise after breast cancer increase the need for new rehabilitation programs. The aim of this study was to evaluate medium- and long-term effects of vibration therapy on pain intensity, range of motion, myoelectric activity, and muscle strength of post-surgical breast cancer women. Methods This controlled longitudinal clinical study was composed of 14 breast cancer women, who underwent vibration therapy treatment (VTG), and 14 healthy women, who constituted the control group (CG). The VTG performed ten 15-minutes sessions of vibration therapy on their affected upper limb. The volunteers were evaluated before and after treatment protocol, and three months later. Results We observed an attenuation of pain intensity after vibration therapy (p < 0.0001) and significant increase in range of motion during extension, abduction, and adduction movements of the horizontal shoulder. We noticed a trend in the reduction of compensatory movements, which activated the muscle contraction mechanism. The scapular dynamometer values for shoulder strength were significant. The VTG had less muscle strength than the CG in all situations: before treatment (p < 0.0001), after treatment (p = 0.0024), and 3 months later (p = 0.0008). The VTG increased muscle strength after treatment (p = 0.0005) and 3 months later (p = 0.0006). Conclusion Vibration therapy attenuated pain symptoms, improved shoulder movements, activated muscle contraction mechanism, and increased shoulder strength, which may be benefits of the conducted physical therapy.

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This study analyzed the electromyographic and strength responses of the flexor muscles of the wrist following stimulation of acupuncture points. A total of 52 participants were randomly divided into four groups: local (heart 3, HT3), distant (heart 4, HT4), control (bladder 60, BL60), and naïve control groups. To obtain the root mean square electromyographic activity, we placed surface electrodes over the wrist flexors. To obtain kilogram force (kgf) values, we attached a force transducer to the floor and to the hands of participants. Both values were recorded over three repetitions of maximal isometric wrist flexion contractions. Data were analyzed using one-way analyses of variance, followed by Dunnett's post-hoc tests. We found reductions in electromyographic activity contralateral to the stimulated point in the distant group 10 minutes after removal of the needles (F(3,48) = 3.25; p < 0.05). Regarding muscle strength, ipsilateral and contralateral stimulation in the distant group produced kgf levels prior to and 10 minute and 20 minutes after withdrawal of the acupuncture needle that were lower than that obtained prior to insertion of the needle (F(3,48) = 5.82; p < 0.05). Thus, stimulation of the acupuncture points distant from the wrist flexors reduced ipsilateral and contralateral muscle strength and decreased the root mean square values contralateral to the site of stimulation.

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Os métodos de treinamento de força são aplicados através da manipulação das variáveis metodológicas, que podem modificar as características do treinamento. Dessa forma, o objetivo do presente estudo foi investigar o efeito do método de séries pareadas de agonista-antagonista (PAA) versus o método tradicional (MT) sobre o volume total de treinamento (VTT) ou eficácia, a eficiência (VTT/tempo) e o sinal eletromiográfico (EMG). Participaram do estudo 10 sujeitos treinados (22,4 ± 0,9 anos, 173 ± 5 cm, 74,8 ± 7,8kg, 13,1 ± 2,3% gordura corporal). No MT foram realizadas 3 séries no exercício de supino vertical (SV) e, em seguida, 3 séries na remada aberta (RA). No PAA foram realizadas 3 séries pareadas entre o SV e RA. Foram adotados dois minutos de intervalo entre as séries em ambos os protocolos. Os sinais de EMG do latíssimo do dorso (LD), porção clavicular do peitoral maior (PMC), bíceps braquial (BB) e tríceps braquial cabeça longa (TBL) foram coletados durante a RA. Para as comparações entre os protocolos e séries aplicou-se a ANOVA two-way e post hoc de Bonferroni adotando-se p < 0,05. Verificou-se aumento significativo no VTT no PAA comparado ao MT. A atividade EMG dos músculos LD e BB foi significativamente maior no PAA em comparação ao MT. Em relação ao PMC e TBL, verificou-se redução significativa no PAA comparado ao MT. Logo, o PAA parece ser uma opção interessante em programas que visam aumento no VTT, bem como, economia de tempo (eficiência) sem comprometer o desempenho muscular.

The methods of resistance training are applied by the manipulation of methodological variables that might change training characteristics. Therefore, the purpose of this study was to investigate the effect of agonist-antagonist paired sets (APS) versus the traditional method (TM) on total training volume (TTV), efficiency (TTV/time), and electromyographic (EMG) activity. Ten trained male (22.4 ± 0.9 years, 173 ± 5.2cm, 74.8 ± 7.8 kg, 13.1 ± 2.3% body fat) participated in this study. In the MT, subjects performed 3 sets of bench press (BP) exercise and then 3 sets of wide grip seated row (SR). In the PAA, they performed 3 paired sets of BP and SR. Two-minutes of rest interval was adopted between sets in both protocols. EMG signal of the latissimus dorsi (LD), the clavicular portion of the pectoralis major (PMC), biceps brachii (BB) and triceps long head (TBL) were recorded during SR. For comparisons between protocols and sets the two-way ANOVA and Bonferroni post hoc tests were applied, adopting p < 0.05. There was significant increase in TTV for APS compared to TM. The EMG activities of the LD and BB muscles were significantly higher in APS compared to TM. Regarding the PMC and TBL, there was a significant reduction in APS compared to TM. Therefore, the APS may be an interesting alternative to resistance training programs that aim to increase VTT in a time efficient manner without compromising muscle performance.

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This study aimed to evaluate the motor response time and ability to develop joint torque at the knee and ankle in older women with and without a history of falls, in addition to investigating the effect of aging on these capacities. We assessed 18 young females, 21 older female fallers and 22 older female non-fallers. The peak torque, rate of torque development, rate of electromyography (EMG) rise, reaction time, premotor time and motor time were obtained through a dynamometric assessment and simultaneous electromyography. Surface EMGs of the rectus femoris (RF), vastus lateralis (VL), biceps femoris (BF), gastrocnemius lateralis (GL) and tibialis anterior (TA) muscles were recorded. Knee extension and flexion peak torques were lower in older fallers than in non-fallers. Knee extension and flexion and ankle plantarflexion and dorsiflexion peak torques were lower in both older groups than in the younger group. The rate of EMG rise of the BF and the motor time of the TA were lower and higher, respectively, in older fallers than in the younger adults. The time to reach peak torque in knee extension/flexion and ankle plantarflexion/dorsiflexion and the motor times of the RF, VL, BF and GL were higher in both older groups than in the younger groups. The motor time of the TA during ankle dorsiflexion and the knee extension peak torque were the major predictors of falls in older women, accounting for approximately 28% of the number of falls. Thus, these results further reveal the biomechanical parameters that affect the risk of falls and provide initial findings to support the prescription of exercises in fall prevention programs.

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The aim was to investigate and compare the effects of proprioceptive neuromuscular facilitation (PNF) and static stretching (SS) on maximal voluntary contraction (MVC) and muscle activation in indoor soccer players. Thirty-three young adult men were divided into two groups: (i) sedentary and (ii) trained. Each group completed three different experimental trials: SS, PNF and no stretching (NS). The MVC of knee extension was evaluated before and immediately after each condition along with electromyography from the vastus lateralis (VL) and rectus femoris (RF) muscles of the dominant leg. PNF or SS techniques induced no decrease on MVC and muscle electromyographical activity in indoor soccer players (P>0·05). The electromyography of the RF and VL was lower after SS only in the sedentary group (P≤0·05). Short-duration PNF or SS has no effect on isometric MVC and muscle activity in indoor soccer players.

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Investigar os efeitos do alongamento muscular na resposta aguda neural tornou-se foco bastante atrativo de pesquisas atuais quando se considera que o desempenho da força está diretamente relacionado a alterações dos níveis de ativação muscular. Este estudo avaliou os efeitos de 10 a 40 segundos de alongamento estático na ativação muscular e no desempenho da força precedido ao teste de repetição máxima de sujeitos treinados. Foram avaliados 20 homens com idade média de 21,75 (± 3,49) randomizados em quatro grupos de acordo com os seguintes tempos de alongamento: TF10s, TF20s, TF30s, TF40s - TF corresponde a Treinamento de Força. Na etapa Controle (C) os sujeitos foram submetidos ao teste de repetição máxima no exercício de supino com halteres. Na etapa Experimental (E) foram submetidos ao alongamento estático com intensidade de 10 por cento de 1RM, seguidamente realizaram o teste de repetição máxima. Nas duas etapas foram realizadas as análises da ativação muscular com eletromiografia de superfície. Como procedimento estatístico utilizou-se ANOVA one way comparando características antropométricas e funcionais dos grupos, o teste t foi utilizado para amostras pareadas, comparando controle e experimental (p < 0,05). Resultados: Não foram encontradas diferenças estatisticamente significativas (p > 0,05); no desempenho da força e nos níveis de ativação agonista comparando os diferentes tempos de alongamento da etapa (E) ao experimento sem alongamento da etapa (C). Conclusão: O exercício de alongamento nos tempos e intensidades estudados parecem não exercer efeito agudo sobre os níveis de ativação a ponto de potencializar o desempenho da força em teste de repetições máxima. Desta forma, outras intensidades de alongamento podem ser investigadas buscando modular positivamente estes resultados.

The investigation of the effects of muscle stretching on the neural acute response has become a fairly attractive issue on current research when it is considered that strength performance is closely related to alterations on the levels of muscle activation. This study assessed the effects of 10 to 40 seconds of static stretching on the muscle activation as well as strength performance preceded by a repetition maximum test of trained subjects. 20 men, mean age of 21.75 (± 3.9), randomized in four groups according to the following stretching times: RT10s, RT20s, RT30s, RT40s - where RT corresponds to Resistance Training, were assessed. In the Control phase (C), the subjects were submitted to the repetition maximum test in the bench press with dumbbells exercise. In the Experimental Phase (E), they were submitted to static stretching with intensity of 10 percent of 1RM followed by the repetition maximum test. Muscle activation was assessed in the two phases with surface electromyography. One-way ANOVA was applied for statistical assessment, comparing anthropometric and functional characteristics of the groups, t test was used for paired samples, comparing control and experimental ones (p < 0.05). Results: Statistically significant differences have not been found (p > 0.05) in strength performance or levels of agonist activation when the different studied times and intensities in the (E) phase and the experiment with no stretching in the (C) phase were compared. Conclusion: Stretching exercise in the studied times and intensities does not seem to acutely affect the levels of activation in order to boost strength performance in a repetition maximum test. Therefore, different stretching intensities can be investigated with the aim to positively modulate these outcomes.

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