Hemispheric synchronization patterns linked with shooting performance in archers.

Sustainable attention, effective visual-spatial perception, and motor control skills are considered highly important for achieving superior athletic performance. The aim of the current study was to investigate hemispheric synchronization patterns of brain electrical activation related to successful and unsuccessful shots of archers using electroencephalography (EEG). This study involved 16 elite archers, each shooting 36 arrows. The 10 shots closest to the target's center were successful, while the 10 farthest shots were unsuccessful. The transformed EEG data, obtained through surface Laplacian filtering, were divided into 5 sub-bands (theta, alpha1, alpha2, beta1, beta2) by calculating the alpha peak frequencies. The synchronization values of the electrode pairs were calculated using the Phase Locking Value (PLV) method. To compare the EEG data for successful and unsuccessful shots in all frequency bands, the linear mixed models were fitted. Perceived fatigue levels were quantified using a visual analog scale (VAS). Spearman's correlation analysis was conducted to examine the relationship between fatigue and shooting performance. The results showed significantly higher coupling strength for C3-O1, C4-O2, O1-O2, F3-F4, C4-T8, T7-O2, F4-C4, C3-O2 and F4-T8 pairs during successful shooting. Moreover, the coupling strengths for F3-O2, F4-T7, C3-C4, C3-T8, T7-T8, C4-O1, F3-T8, and F4-O2 were significantly higher in unsuccessful shooting. The current findings revealed differences in the synchronization patterns associated with shooting performance. It is observed that visual-motor performance is correlated with an increase in cortical synchronization values during successful shots. These findings have the potential to serve as a theoretical reference that contributes to superior performance.

Comparison of EMG activity in shank muscles between individuals with and without chronic ankle instability when running on a treadmill.

Changes in movement capabilities after an injury to the ankle may impose adaptations in the peripheral and central nervous system. The purpose of our study was to compare the electromyogram (EMG) profile of ankle stabilizer muscles and stride-time variation during treadmill running in individuals with and without chronic ankle instability (CAI). Recreationally active individuals with (n = 12) and without (n = 15) CAI ran on a treadmill at two speeds. EMG activity of four shank muscles as well as tibial acceleration data were recorded during the running trials. EMG amplitude, timing of EMG peaks, and variation in stride-time were analyzed from 30 consecutive stride cycles. EMG data were time-normalized to stride duration and amplitude was normalized relative to the appropriate maximal voluntary contraction (MVC) task. Individuals with CAI had similar EMG amplitudes and peak timing, but an altered order of peak EMG activity in ankle stabilizer muscles, a significantly greater EMG amplitude for PL with an increase in speed, and a greater stride-time variability during treadmill running compared with individuals who had no history of ankle sprains. The results of our study indicate that individuals with CAI exhibit altered activation strategies for ankle stabilizer muscles when running on a treadmill.

Comparison of EMG Activity in Leg Muscles between Overground and Treadmill Running.

INTRODUCTION: Treadmills have been widely used for training and performance testing during which the treadmill grade is usually set to 0%-2% grade. The purpose of our study was to compare the level of activation of lower body muscles when running at two speeds in an overground condition and on a treadmill at 0%, 1%, and 2% grades. METHODS: We recorded EMG data of eight lower body muscles from 13 recreationally active individuals during overground and treadmill running at 2.92 and 4.58 m·s -1 . Maximal voluntary contraction (MVC) tests were performed (3 × 6 s) to identify maximal torque and EMG values. The stride cycles, from one foot strike to the next, were identified using a pair of triaxial accelerometers. A two-way repeated-measures ANOVA was used to examine the differences in EMG activity across running conditions and speeds. Cohen's d effect size was calculated to indicate the difference between the overground and the treadmill running conditions. RESULTS: The effect sizes were moderate to negligible for differences between the EMG integral values for overground running and the three treadmill grades. The coefficient of variation for stride time during overground running was significantly larger than that of the treadmill running at 4.58 m·s -1 . CONCLUSIONS: The results showed that the overall EMG profiles of the thigh and shank muscles were similar for the overground and treadmill conditions, but the similarity was greatest for thigh muscles when running on the treadmill at 1% grade and for shank muscles at 2% grade. The variability in stride time was greater during overground running than when running on a treadmill and was associated with elevated EMG activity of some muscles.

The new wireless EEG device Mentalab Explore is a valid and reliable system for the measurement of resting state EEG spectral features.

Technological advancements in neuroscience have provided many conveniences to scientists, researchers, and consumers. The emerging electroencephalography (EEG) devices are good examples 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 h, 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 test-retest reliability analysis. Power spectral density (PSD) was calculated using Welch method. The PSD (eyes closed p < 0.0001; eyes open p = 0.01-0.0001), alpha peak frequency (p < 0.0001), and alpha suppression (p = 0.002-0.0001) from the two EEG devices as well as the test-retest results from the Mentalab device were significantly correlated. 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 eyes-closed condition. The two measurements completed ∼24 h apart using the Mentalab system were similar for all the variables. We showed that the consumer-grade Mentalab Explore with gel electrodes is a reliable and valid EEG recording device for rsEEG spectral features.

The adaptations in muscle architecture following whole body vibration training.

OBJECTIVE: This study aims to investigate the effect of 8-week whole-body vibration (WBV) added to conventional training on muscular architecture, dynamic muscle strength and physical performance compared to controls in young basketball players. METHODS: Sixteen young basketball players between the ages of 14-16 years were randomly assigned to whole body vibration group (VG) or control group (CG). Both groups were trained with a conventional program. Pennation angle (PeA), fascicle length and muscle thickness of Rectus Femoris (RF) and Vastus lateralis were measured by ultrasonography. Isokinetic dynamic muscle testing at 180 °/s and 60°/s, squat jump (SJ) and flexibility were evaluated before and after 8 weeks of training programs. Primary outcome measure was the fascicle length. RESULTS: Fascicle length of RF, SJ height and flexibility increased significantly within VG compared to pretraining (p<0.05). SJ height increased in VG compared to CG significantly following training (p<0.05). PeA, fascicle length, muscle thicknesses, strength and flexibility did not differ between groups. CONCLUSION: Eight weeks of WBV training improved fascicle length of RF, SJ height, and flexibility compared to pre-training. Addition of WBV to conventional training did not cause improvement in muscle architecture, strength and flexibility compared to conventional training alone.

A Systematic Review and Meta-Analysis on the Longitudinal Effects of Unilateral Knee Extension Exercise on Muscle Strength.

The aim of the study was to investigate the time-dependent increase in the knee extensors' isometric strength as a response to voluntary, unilateral, isometric knee extension exercise (UIKEE). To do so, a systematic review was carried out to obtain data for a Bayesian longitudinal model-based meta-analysis (BLMBMA). For the systematic review, PubMed, Web of Science, SCOPUS, Chochrane Library were used as databases. The systematic review included only studies that reported on healthy, young individuals performing UIKEE. Studies utilizing a bilateral training protocol were excluded as the focus of this review lied on unilateral training. Out of the 3,870 studies, which were reviewed, 20 studies fulfilled the selected inclusion criteria. These 20 studies were included in the BLMBMA to investigate the time-dependent effects of UIKEE. If compared to the baseline strength of the trained limb, these data reveal that UKIEE can increase the isometric strength by up to 46%. A meta-analysis based on the last time-point of each available study was employed to support further investigations into UIKEE-induced strength increase. A sensitivity analysis showed that intensity of training (%MVC), fraction of male subjects and the average age of the subject had no significant influence on the strength gain. Convergence of BLMBMA revealed that the peak strength increase is reached after ~4 weeks of UIKEE training.

Developmental differences of kinematic and muscular activation patterns in instep soccer kick.

Kinematic and neuromuscular activity differences amongst soccer players in different age groups were examined in this study. Thirty male soccer players evenly divided into three age groups (Group 1: age 12-13; Group 2: age 14-15; Group 3: age 16-17) were asked to perform instep kicks towards a target 11 m away. Their anthropometrics, instep kick kinematics, resultant ball velocities, both legs isokinetic strength, and electromyography (EMG) during kicking were compared amongst the three age groups. There were significant differences in height, body mass, body mass index, ball velocities, and isokinetic strength values amongst three age groups. Also, kicking kinematics including angular and linear velocities of hip, knee, ankle, and toe were significantly different (p < 0.05) amongst groups in several kicking phases. Furthermore, the activities of m. rectus femoris, m. vastus medialis, m. biceps femoris were significantly different amongst groups (p < 0.05). The ball velocities and leg strength parameters increased with age, neuromuscular activations, and kinematic parameters differed especially in leg-coking and forward swing phase of instep soccer kick. It should be concluded that an increase of resultant ball velocity of the instep kick is closely associated with chronical age, the development of leg muscle strength, and the neuromuscular activity of the kicking leg.

Effect of gender on the quadriceps-to-hamstrings coactivation ratio during different exercises.

CONTEXT: Coactivation ratio of quadriceps to hamstring muscles (Q:H) and medial to lateral knee muscles (M:L) contributes to the dynamic stability of the knee joint during movement patterns recommended during rehabilitation and important for daily function. OBJECTIVE: To compare the quadriceps-to-hamstring and medial-to-lateral knee muscles' coactivation ratios between men and women during the following closed kinetic chain exercises performed on a balance board: forward lunge, side lunge, single-leg stance, and single-leg squat. DESIGN: Cross-sectional. PARTICIPANTS: 20 healthy subjects (10 female and 10 male). MAIN OUTCOME MEASURES: Surface electromyography was used to measure the activation level of quadriceps (vastus lateralis and medialis) and hamstrings (biceps femoris and medial hamstrings) during forward- and side-lunge, single-leg-stance, and single-leg-squat exercises. Subjects were instructed during each exercise to move into the test position and to hold that position for 15 s. EMG was recorded during the 15-s isometric period where subjects tried to maintain a "set" position while the foot was on a balance board. Analysis of variance was used for statistical analysis. RESULTS: There was a significant exercise-by-gender interaction for Q:H ratio (F3,48 = 6.63, P = .001), but the exercise-by-gender interaction for M:L ratio was not significant (F3,48 = 1.67, P = .18). Women showed larger Q:H ratio in side-lunge exercises than men (P = .002). Both genders showed larger M:L and lower Q:H ratio in a single-leg-stance exercise than in the other exercises. CONCLUSIONS: The results indicate that the forward- and side-lunge and single-leg-squat exercises should not be recommended as exercise where a balanced coactivation between quadriceps and hamstring muscles is warranted. Single-leg-stance exercise could be used when seeking an exercise where the ratio is balanced for both women and men.

Activation of selected ankle muscles during exercises performed on rigid and compliant balance platforms.

STUDY DESIGN: Experimental laboratory study. OBJECTIVE: To compare how the design of 2 balance platforms affects ankle musculature activation for various weight-bearing exercises. BACKGROUND: Balance platforms are widely used in both training and rehabilitation, and a better understanding of how platform design and type of exercise modify the demands on the ankle musculature may be helpful in staging exercise progression. METHODS: Surface electromyography was used to measure the activation level of the fibularis longus, tibialis anterior, and medial gastrocnemius while performing 4 exercises on 2 different balance platforms (compliant and rigid). Twenty-four (12 females, 12 males) healthy, sedentary subjects participated in the study. Analysis of variance was used for statistical analysis. RESULTS: There was no significant interaction between balance platforms and exercises (P>.05), and the type of platform did not influence muscle activation for the 3 muscles monitored (P>.05). The highest activation level for the fibularis longus and medial gastrocnemius was obtained during single-leg stance, and for the tibialis anterior during the single-leg squat (P<.05). CONCLUSION: In this study, although the demands on the ankle musculature were similar for selected exercises performed on a compliant versus a rigid balance platform, muscle activation level varied based on the exercise.

Muscular activation patterns of the bow arm in recurve archery.

In archery shooting, the archer should hold the bow in place using only the pressure produced through drawing back the bowstring. Most coaches discourage the archer from gripping the bow as this is believed to produce a sideways deflecting torque on the bow and arrow during the release. The purpose of this study was to compare the bow hand forearm muscular activation patterns of elite archers with beginners to define the muscular contraction-relaxation strategies in the bow hand forearm muscles during archery shooting and investigate the effects of performance level on these strategies. Electromyographic activity of the M. flexor digitorum superficialis and the M. extensor digitorum of 10 elite and 10 beginner archers were recorded together with a pulse synchronized with the clicker snap. Raw electromyographic records as 1s before and after the clicker pulse were rectified, integrated, and normalized. The data was then averaged for successive shots of each subject and later for both groups of archers. The main difference between the elite and beginner archers was that the elite archers had a greater activation of the M. extensor digitorum, which indicates that they avoid gripping the bow-handle not only relaxing the flexor muscles, but also contracting the extensor muscle groups. This muscular contraction strategy secures the archer to not interfere with the forward movement of the bow, which is the forward acceleration of the bow caused by the pushing power of the bowstring.

Reliability and validity testing of an archery chronometer.

Keeping the arrow velocity constant during consecutive shots and responding to "clicker's fall "are considered to be an important feature of archery performance. A specially designed device called an archery chronometer was developed to measure the reaction time of an archer to clicker's fall, arrow velocity, and external factors that may affect arrow velocity. The purposes of this study were to test (1) the validity of Clicker Reaction Time (CRT) measurer, and (2) the reliability of CRT in accordance with the Flying Time (FT)/Average Speed (AS), temperature (TEMP), wind speed (WS) and wind direction (WD) measurements. 20 elite archers participated in this study. The Reaction Time (RT), which was derived from EMG values and CRT from the archery chronometer were correlated to test the validity of the CRT measurer. The test re-test method was applied to test the reliability of archery chronometer. CRT scores were related with RT scores (r = .787, p < 0.01). The archery chronometer was valid in terms of predicting reaction time. The device was found to be reliable in measuring CRT, AS, FT, WS, WD, and TEMP. It was concluded that archery chronometer could be used for technical evaluation and enhancing ones shooting technique in archery. Key PointsClicker Reaction Time could be used as a predictor of Reaction Time in archery.Archery Chronometer can be used for evaluating the archers' shooting technique and the bow-arrow interaction.Archery Chronometer can also be used as an indicator for ballistic flight of an arrow.Archery Chronometer can be used by the coaches and the archers to evaluate and enhance shooting technique in the natural settings of their training environment.