Abdulkerim Darendeli

Groups of motor units receive common synaptic inputs from specialized networks of premotor neurons to produce movement. Here, we test whether common inputs received by motor units in the first dorsal interosseous are fixed or task‐dependent during submaximal isometric contractions. Discharge times of motor units were identified and tracked across a set of conditions. Factor analysis identified a single motor unit mode that captured most of the covariation in the discharge rates of motor units, presumably reflecting common synaptic inputs. This was supported by the high correlation values between motor unit pairs from the same participant. Next, displacement analysis on the discharge rates of motor units was computed to capture the magnitude of departures from a monotonic control structure expected from fixed common inputs. For the same force profile, activity of motor units was limited to a set of discharge rate–time trajectories across trials, suggesting a constrained pattern of premotor inputs to motor units. Importantly, changes in force profile and muscle length modulated synaptic inputs to motor units, as observed in the divergent rate–time trajectories of motor units and high displacement values. These findings highlight that common input is a key feature in the neural control of motor units and is subject to substantial modulation. The composition of inputs to motor units depends on the force profile and muscle length, and the system relies on reusing a common input structure when performing the same task.

Bu kitabın amacı hareket bilimlerini işleyen biyomedikal mühendislik, sinirbilimi, fizyoterapi, biyoloji, egzersiz ve spor alanlarında çalışan öğrenciler, eğitimciler ve bilim insanları için hareketin temelleri hakkında bir perspektif sunmak ve sıklıkla kullanılan elektromyografi tekniklerini açıklamaktır. Sıralanan bu alanlarda, özellikle de yakından takip ettiğim hareket ve spor bilimleri alanında, dilimizde yazılmış literatürde bariz eksiklikler olması ve son on yılda görülen beklenmedik hızdaki bilimsel ilerlemeler nedeniyle bu bilgilerin yayılması önemlidir. Bu kitapta ileri sürülen ifadelerin kritik olarak değerlendirilmesi ve yenilikçi yaklaşımların yolunu açması arzulanmaktadır. Hakem sürecinden geçmiş bilimsel yayınlarla kitapların oluşum süreçleri, ömürleri ve ele alınan konuyu işleme biçimleri oldukça farklıdır. Hareket bilimleri alanındaki ilerlemeler her iki tür kaynaktan da tutarlı olarak takip edilmelidir. Sekiz ana bölümden oluşan bu kitapta ilk olarak insan hareketinin açığa çıkması için son durak olan motor ünite ele alınmıştır. İlginçtir ki ilgili alanların lisans eğitiminde hareket genellikle kaslara atfedilirken, kaslara elektriksel kodlarla bilgi sağlayan kaynaklar göz ardı edilmektedir. Birinci bölümde ana hatlarıyla harekete giden yolda rol alan tüm anahtar birimler işlenmiştir. Elektromyografi yönteminin hareket ve spor bilimlerindeki uygulamalarına geçmeden önce, kitabın ikinci bölümünde ilgili terimler açıkça tanımlanmıştır. Elektromyografi yönteminde elektrot ve konum seçim stratejileri kitabın üçüncü bölümünde işlenmiştir. Elektromyografi yöntemini kullanacak araştırmacılar için, kitabın dördüncü bölümünde MATLAB ve R yazılımlarından örneklerle sinyal işleme aşamaları anlatılmış ve kendiniz de uygulayabilmeniz için her iki yazılım için de kodlar açık erişim olarak verilmiştir. Bunu takip eden sıradaki üç bölümde elektromyografi yöntemi, kullanım alanları, uygulama talimatları, güç ve sınırlılıkları, gerçekçi olarak ne tür bilgilerin çıkarılabileceği işlenmiştir. Kitabı sonlandırırken elektromyografi yönteminin geçmişi, bugünü ve geleceği ele alınmıştır.

The purpose of the study was to investigate the influence of contraction history on force steadiness and the associated EMG activity during submaximal isometric contractions performed with the dorsiflexor muscles. The key feature of the protocol was a triangular ramp contraction performed in the middle of a steady contraction at a lower target force. The target force during the ramp contraction was 20% MVC greater than that during the steady contraction. Thirty-seven healthy individuals (21 men and 16 women) performed the submaximal tasks with the ankle dorsiflexors. Electromyography (EMG) signals were recorded from tibialis anterior with a pair of surface electrodes. The coefficient of variation for force was significantly greater during the second steady contraction compared with the first one at each of the seven target forces (p < 0.015; d = 0.38–0.92). Although the average applied force during the steady contractions before and after the triangular contraction was the same (p = 0.563), the mean EMG amplitude for the steady contractions performed after the triangular contraction was significantly greater at each of the seven target forces (p < 0.0001; d = 0.44–0.68). Also, there were significant differences in mean EMG frequency between the steady contractions performed before and after the triangular contraction (p < 0.01; d = 0.13–0.82), except at 10 and 20% MVC force. The greater force fluctuations during a steady submaximal contraction after an intervening triangular contraction indicate a change in the discharge characteristics of the involved motor units.

Technological advancements in neuroscience have provided many conveniences to scientists, researchers, and consumers. The emerging electroencephalography (EEG) devices is a good example for it. The objective of this study was to investigate the validity and reliability of a new wireless EEG device Mentalab Explore for resting-state EEG (rsEEG) recordings in eyes open and eyes closed conditions. Twenty-three healthy subjects were recruited for the study. The subjects visited the laboratory on two occasions. On the first day, both devices were used to record rsEEG data, and after 24 hours, only the Mentalab Explore was used to record rsEEG for test-retest reliability analysis. We compared the alpha peak frequency, suppression, and mean power between the two devices. Intraclass correlation coefficient was calculated for testretest reliability analysis. There were no significant differences in alpha peak frequency or suppression between the clinical-grade and the new devices for O1 and O2 channels in eyesclosed condition. The two measurements completed ∼24 h apart using the Mentalab system were similar for all the variables. There were also significant correlations between the devices and test-retest measurements for alpha peak frequency, suppression, and power. We showed that the consumer-grade Mentalab Explore with gel electrodes is a reliable and valid EEG recording device for rsEEG spectral features.

Background and Study Aim. Sprint performance plays a major role in success of field-based team sports such as soccer. The aim of this study was to evaluate the relationship between sprinting performance and both lower and upper extremity explosive strength in young soccer players. Material and Methods. One hundred forty-seven soccer players (mean±SD; age 11.6±1.66 years, height 143.2±11.8 cm, body mass 37.1±10.2 kg and training experience 1.11±1.5 years) voluntarily participated in this study. The sprinting performance of each player was determined using their 5, 10, 20 and 30m single sprint times. The lower and upper extremity explosive strength were evaluated by standing long jump and medicine ball throwing tests respectively. Prior to the study, each of the players was given detailed information about the risks and injuries they could encounter during the study, and parental consent was obtained by their signatures on informed voluntary consent forms since the subjects were under the age of 18. Permission to conduct the study was obtained from Ankara University Medical Faculty’s Surgical and Medical Research Ethics Committee. Results. The results indicated a strong relationship between sprinting performance and horizontal jump performance (r=-.671 ̶ -.764; p=0.001) and also a large relationship between sprinting performance and upper extremity strength (r=-.633 ̶ -.703; p=0.001). The sprint performance (n=147) also significantly correlated with body weight (r=-.345 ̶ -.373; p=0.001) and height (r=-.445 ̶ -.505; p=0.001). Conclusions. The study results suggest that upper extremity strength is as important as the lower extremity strength for sprinting performance and that trainers should emphasize lower and upper extremity strength in training intended to improve sprinting performance.