Comparison of the Electromyographic Activity of the Trunk and Rectus Femoris Muscles During Traditional Crunch and Exercise Using the 5-Minute Shaper Device.

Silva, FHO, Arantes, FJ, Gregorio, FC, Santos, FRA, Fidale, TM, Bérzin, F, Bigaton, DR, and Lizardo, FB. Comparison of the electromyographic activity of the trunk and rectus femoris muscles during traditional crunch and exercise using the 5-minute Shaper device. J Strength Cond Res 34(1): 1-10, 2020-Different training devices are available to trigger greater activation of the abdominal muscles compared with that achieved during traditional abdominal exercises. This study aimed to compare the electromyographic (EMG) activity of the upper and lower rectus abdominis, external oblique abdominis, erector spinae, and rectus femoris (RF) muscles during traditional crunch and exercise using the 5-minute Shaper device. A convenience sample of 15 healthy men (mean ± SD; age: 23.65 ± 4.49 years, body fat percentage: 14.26 ± 3.56%) was selected. All men regularly participated in physical activity. Electromyographic data were collected for 5 repetitions of each abdominal exercise (traditional crunch and exercise using the 5-minute Shaper device at beginner, intermediate, advanced, and extreme levels) in a randomized and counterbalanced manner. Data were collected using simple differential surface electrodes and analyzed using repeated-measures analysis of variance (p < 0.05). Electromyographic signals were quantified using a root-mean-square analysis and normalized using the maximum voluntary isometric contraction. Traditional crunch produced greater or similar EMG activity in the abdominal muscles and minimized RF activity compared to the 5-minute Shaper device, hence, traditional crunch is preferred for training, especially for individuals with weak abdominal musculature and lower back problems. Therefore, the use of the 5-minute Shaper device may be questioned when it is intended to intensify the activity of the abdominal muscles; however, this apparatus may be used if greater variations in training are desired, depending on individual preferences.

Fatigue analysis in the masseters and temporalis muscles in patients with temporomandibular disorder during short period of mastication.

The purpose of this experiment was to look for signals of muscle fatigue in volunteers with Temporomandibular Disorders (TMD) during short period of mastication. Twenty female volunteers selected by Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) participated, 10 with myogenic TMD (experimental) and 10 clinically normal (control). The Masseter and Temporalis muscles were evaluated electromyographically with active differential surface electrodes. The masticatory activity was recorded for 15 seconds and the signals were normalized by 4 seconds of teeth clenching. Three complete masticatory cycles were taken to calculating the median frequency (MF) and electromyographic amplitude (RMS). The data were submitted to statistics analysis and non-parametric tests. The results showed that RMS and median frequency did not change during the mastication period analyzed, indicating the absence of muscle fatigue, for the Masseter and Temporalis muscles in both groups (p> 0.05). These results confirm the absence of signals of muscle fatigue in masticatory muscles during short period of mastication even in individuals with TMD, possibly due to increased of blood flow, consequence of dynamic muscle contraction and the individual characteristics of muscle fiber composition and recruitment.

Fatigue analysis in the masseters and temporalis muscles in patients with temporomandibular disorder during short period of mastication

The purpose of this experiment was to look for signals of muscle fatigue in volunteers with Temporomandibular Disorders (TMD) during short period of mastication. Twenty female volunteers selected by Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) participated, 10 with myogenic TMD (experimental) and 10 clinically normal (control). The Masseter and Temporalis muscles were evaluated electromyographically with active differential surface electrodes. The masticatory activity was recorded for 15 seconds and the signals were normalized by 4 seconds of teeth clenching. Three complete masticatory cycles were taken to calculating the median frequency (MF) and electromyographic amplitude (RMS). The data were submitted to statistics analysis and non-parametric tests. The results showed that RMS and median frequency did not change during the mastication period analyzed, indicating the absence of muscle fatigue, for the Masseter and Temporalis muscles in both groups (p>0.05). These results confirm the absence of signals of muscle fatigue in masticatory muscles during short period of mastication even in individuals with TMD, possibly due to increased of blood flow, consequence of dynamic muscle contraction and the individual characteristics of muscle fiber composition and recruitment.

A proposta deste experimento foi procurar sinais de fadiga muscular em voluntarios com disfuncao temporomandibular (DTM) durante curto periodo de mastigacao. Vinte voluntarios do sexo feminino foram selecionados pelo Criterio de Diagnostico de Pesquisa para desordem tempomandibular, 10 com DTM miogenica (experimental) e 10 clinicamente normais (controle). Os musculos Masseter e Temporal foram avaliados eletromiograficamente com eletrodos diferenciais de superficie ativos. A atividade mastigatoria foi registrada por 15 segundos e os sinais foram normalizados por 4 segundos de apertamento dental. A frequencia mediana (FM) e da amplitude eletrmoigrafica (RMS) dos sinais eletromiograficos foram obtidos em 3 diferentes intervalos de tempo. Os valores da FM e RMS foram submetidos a analise estatistica descritiva e a testes nao parametricos. Os resultados demonstraram que o RMS e a FM nao mudaram durante o periodo de mastigacao, indicando ausencia de fatiga muscular para o musculo Masseter e Temporal, em ambos os grupos (p>0.05). Estes resultados confirmam a ausencia de sinais de fatiga muscular durante curto periodo de mastigacao, mesmo em individuos com DTM, possivelmente devido ao aumento do fluxo sanguineo em consequencia da dinamica de contracao muscular e das caracteristicas individuais da composicao das fibras musculares e do recrutamento.