Modulation of corticospinal excitability and short intracortical inhibition during submaximal force outputs of the biceps brachii in chronic resistance trained and non-resistance trained individuals

Most of studies investigating neural mechanisms during isometric voluntary contractions have focused mainly on the corticospinal tract. Little is known about the modulation of the intracortical inhibitory and facilitatory circuits during different levels of muscle activation. Also, studies using a transcranial magnetic stimulation (TMS) to examine neural adaptations have shown that excitability of the corticospinal tract is modulated following chronic resistance training. But, the effects of a long period of resistance training on the modulation of intracortical interactions has not examined yet. The current study was designed to assess corticospinal excitability and short intracortical inhibition (SICI) modulation using two different TMS protocols during different target forces. Using these techniques, we sought to determine whether a central nervous system excitability and SICI system changes as a function of contraction intensity, as well as determine whether these probable changes were similar in chronic resistance trained (RT) and non-RT subjects

Pennation Angle and Fascicle Length of Human Skeletal Muscles to Predict the Strength of an Individual Muscle Using Real-Time Ultrasonography: A Review of Literature

Introduction: Muscle fascicle length and pennation angle are two muscle structural parameters which can be non-invasively measured using methods like ultrasonography. The aim of the present literature review was to introduce fascicle length and pennation angle for the estimation of the force of an individual skeletal muscle using ultrasonography. Methods and Materials: The data for the current review study was obtained from Pubmed, Science Direct, Scopous, Google Scholar, Sprinter Link Database, and other authoritative references available on the Internet and in libraries between the years 1995-2015. A total number of 113 articles were obtained. In sum, 45 articles were collected and reviewed. Keywords such as muscle, fascicle, length, angle, force, and ultrasonography were searched to fulfill the purpose of the study. Results: Detailed information on the pennation angle and fascicle length is essential to predict the force of an individual muscle. It has been suggested that changes in muscle fascicle angle and length correlated variably with the muscles force production. Conclusions: Real-time ultrasonography has been introduced as a valuable measurement tool for estimation of the force individual muscle via measuring the muscle architecture parameters, such as pennation angle and fascicle length. However, factors like physiological, anatomical, and biomechanical properties have to be considered when predicting the force of an individual skeletal muscle.Key words: Muscle, Fascicle, Length, Pennation angle, Force, Ultrasonograph

Reliability of the Thickness Measurement and Histogram of Elbow Flexors by Ultrasonography in Patients with Fascioscapulohumoral Dystrophy and Healthy Subjects

Introduction: Ultrasonography is a non-invasive and available technique used to assess normal and pathological tissue in people with neuromuscular diseases. The aim of this study was to determine relative and absolute reliability of ultrasonography in evaluation of thickness and histogram of elbow flexor muscles in patients with facioscapulohumeral muscular dystrophy (FSHD and healthy subjects. Materials and Methods: The present study was carried out on an experimental group of six patients with FSHD and a control group comprising 6 healthy individuals. The thickness and histogram of elbow flexors were evaluated while subjects were in sitting position with knees bent, arms at 90 degrees abduction, elbows at 90 degrees flexion and forearms in neutral position. The probe was placed on the anterior surface of arm at 2/3 distance between the lateral tip of acromion and the lateral epicondyle of the humerus. Standard deviation of echogenicity based on histogram curve was also used to estimate the echogenic uniformity of muscle tissue (STDE), subsequently two parameters including L-mean and STDE were recorded. The intra-class correlation coefficient (ICC), standard error measurement (SEM) and minimal detectable changes (MDC) tests were applied to measure relative and absolute reliability and to estimate the measurement errors. Results: The values of the reliability of muscle thickness measurement were ICC=0.95, SEM=2.14 and MDC=5.94 and ICC=0.95, SEM=1.34 and MDC=3.72 in the experimental group and the control group respectively. Additionally, for L-mean measurements it appeared to be ICC=0.89, SEM=1.75 and MDC=4.86 among patients and ICC=0.66, SEM=1.04 and MDC=2.89 in healthy subjects. Finally, the reliability of STDE measurement was revealed to be ICC=0.98, SEM=0.18 and MDC=0.51 and (ICC=0.75, SEM=0.63 and MDC=1.74) among the participants of the experimental and the control groups. Conclusion: The results of this study showed that ultrasonography method used in this study had a high level of accuracy to measure the thickness and histogram of elbow flexors in both healthy subjects and patients with FSHD. The method can be recommended to compare or determine the effectiveness of different treatment methods in patients with FSHD.Key words: Elbow Flexors, Fascioscapulohumoral Dystrophy Histogram, Reliability; Thickness, Ultrasonograph

Rehabilitative Ultrasound Imaging to Study the Gastrocnemius Muscles Morphology in Patients with Genu Varum and Valgum Deformities

Introduction: Genu varum and genu valgum deformities are highly prevalent in Iran. These deformities bring about changes in the structure and function of muscles around the knees. The aim of the present investigation was to study the structure of medial and lateral gastrocnemius muscles in patients with primary genu varum and genu valgum deformities and individuals with normal knee alignment, using rehabilitative ultrasound imaging. Method and Materials: : A Honda 2100 (Honda Co., Japan) real time ultrasound scanner was used in the current the study. The dominant legs of 18 women, 6 with genu varum (mean age: 22.00±1.78 years), 6 with genu valgum (mean age: 21.67±1.03 years), and 6 with normal alignment (mean age: 21.83±1.72 years) were examined. The morphological parameters like muscle thickness, pennation angle and fascicle length of medial and lateral gastrocnemius muscle were compared among groups. Results: In participants with genu varum, the medial gastrocnemius was thinner, closer and shorter in terms of muscle thickness, pennation angle, and fascicle lengths when compared to the lateral gastrocnemius (P<0.05). However, in participants with genu valgum, it was the other way around (P<0.05). In participants with normal alignment, there was no statistically significant difference between the medial and lateral gastrocnemius muscle structures. Conclusions: The rehabilitative ultrasound imaging is highly recommended for studying the structure of gastrocnemius muscle. The structural differences between medial and lateral gastrocnemius muscles may be due to the long term neuromuscular adaptation to knee joint alignment in both genu varum and genu valgum deformities.Key words: Genu, Valgum, Varum, Rehabilitative, Ultrasound, Imagin

Neuromuscular Mechanisms Underlying Changes in Force Production during an Attentional Focus Task

We examined the effects of attentional focus cues on maximal voluntary force output of the elbow flexors and the underlying physiological mechanisms. Eleven males participated in two randomized experimental sessions. In each session, four randomized blocks of three maximal voluntary contractions (MVC) were performed. The blocks consisted of two externally and two internally attentional focus cued blocks. In one of the sessions, corticospinal excitability (CSE) was measured. During the stimulation session transcranial magnetic, transmastoid and Erb’s point stimulations were used to induce motor evoked potentials (MEPs), cervicomedullary MEP (CMEPs) and maximal muscle action potential (Mmax), respectively in the biceps brachii. Across both sessions forces were lower (p = 0.024) under the internal (282.4 ± 60.3 N) compared to the external condition (310.7 ± 11.3 N). Muscle co-activation was greater (p = 0.016) under the internal (26.3 ± 11.5%) compared with the external condition (21.5 ± 9.4%). There was no change in CSE. Across both sessions, force measurements were lower (p = 0.033) during the stimulation (279.0 ± 47.1 N) compared with the no-stimulation session (314.1 ± 57.5 N). In conclusion, external focus increased force, likely due to reduced co-activation. Stimulating the corticospinal pathway may confound attentional focus. The stimulations may distract participants from the cues and/or disrupt areas of the cortex responsible for attention and focus

An Ultrasonographic Investigation of Craniocervical Extensor Muscles in Patients with Chronic Non-specific Neck Pain

Introduction: The purpose of the present study was to measure the thickness and the strength of craniocervical extensor muscles in men with chronic non-specific neck pain and healthy controls. Materials and Methods: Fifteen men with chronic non-specific neck pain (CNNP) and 15 healthy controls were participated in this study. The thicknesses of the craniocervical extensor muscles (rectus capitis posterior major(RCPM)) and oblique capitis superior (OCS) in addition to the strength of upper cervical extensor muscles were measured at resting position and during maximal voluntary isometric contraction (MVIC) of craniocervical extensor muscles using ultrasonography device and a dynamometer which was designed for the purpose of study. Results: The thicknesses of RCPM and OCS muscles were significantly smaller in the patients group than the healthy controls at resting position and during maximal isometric contraction (P<0.001). There was a significant reduced MVIC in patients with CNNP when compared to controls (P=0.008). Conclusion: The reduced craniocervical extensor muscles strength and thickness in patients with CNNP may be due to pain and reflex inhibition which is originating from cervical neuromusculoskeletal structures. Craniocervical muscles assessments may be needed while evaluating patients with CNNP.Keywords: Craniocervical, Muscle, Neck, Pain, Strength, Thickness, Ultrasonograph