Epidemiology of training injuries in amateur taekwondo athletes: a retrospective cohort study

The objectives of this study were to estimate the incidence and describe the pattern and severity of training injuries in taekwondo, and to compare pattern and severity of training injuries with competition injuries. One hundred and fifty-two active Australian amateur taekwondo athletes, aged 12 years or over, completed an online survey comprising questions on training exposure and injury history over the preceding 12 months. The main outcome measures were: overall injury incidence rate per athlete-year; training injury incidence rate per athlete-year, per 1000 athlete-training-sessions, and per 1000 athlete-hours of training; injury severity; and injury proportions by anatomical region and by type of injury. Injury incidence rates were calculated with 95% confidence intervals using standard methods, while injury proportions were compared using Fisher''s exact test. The vast majority (81.5%) of taekwondo injuries in an average athlete-year occurred during training. The training injury incidence rate was estimated to be 1.6 (95% CI: 1.4, 1.9) per athlete-year, 11.8 (95% CI: 10.4, 13.4) per 1000 athlete-training-sessions, and 7.0 (95% CI: 6.1, 7.9) per 1000 athlete-hours of training. Among athletes with five or fewer injuries, the severity and injury pattern of training injuries were, by and large, the same as for competition injuries. Approximately sixty percent (60.3%) of training injuries required treatment by a health professional. Considering the burden of training injuries exceeds that of competition injuries, taekwondo governing bodies and stakeholders are encouraged to devote more efforts towards the identification of risk factors for, and prevention of, training injuries in the sport of taekwondo.     

Urinary myoglobin quantification by high-performance liquid chromatography: An alternative measurement for exercise-induced muscle damage

This study investigated a means of quantifying urinary myoglobin using a novel reverse-phase high-performance liquid chromatography (RP–HPLC) method that is an alternative measure of exercise-induced muscle damage. It also investigated the effect of storage and alkalization on urinary myoglobin stability issues. An RP–HPLC method was validated by precision and repeatability experiments. Myoglobin stability was determined through spiked urine samples stored at various temperatures over an 8-week period using alkalization and dilution in a pH 7.0 buffer. The method was validated with urine collected from mixed martial arts fighters during a competition and training session. The method produced linearity from 5 to 1000 μg/ml (R² = 0.997), intra- and inter-assay coefficients of variation from 0.32 to 2.94%, and a lower detection limit of 0.2 μg/ml in the final dilution and 2 μg/ml in the original urine sample. Recovery ranged from 96.4 to 102.5%, myoglobin remained stable at 4 °C when diluted in a pH 7.0 buffer after 20 h, and a significant increase (P < 0.01) and an identifiable peak were observed following a mixed martial arts contest and training session. Storage length and conditions had significant effects (P < 0.05) on stability. The method's simplicity and noninvasive nature means it can be used as an alternative muscle damage assay following exercise and trauma.     

Spatial EMG potential distribution pattern of vastus lateralis muscle during isometric knee extension in young and elderly men

The aim of the present study was to compare spatial electromyographic (EMG) potential distribution during force production between elderly and young individuals using multi-channel surface EMG (SEMG). Thirteen elderly (72-79 years) and 13 young (21-27 years) healthy male volunteers performed ramp submaximal contraction during isometric knee extension from 0% to 65% of maximal voluntary contraction. During contraction, multi-channel EMG was recorded from the vastus lateralis muscle. To evaluate alteration in heterogeneity and pattern in spatial EMG potential distribution, coefficient of variation (CoV), modified entropy and correlation coefficients with initial torque level were calculated from multi-channel SEMG at 5% force increment. Increase in CoV and decrease in modified entropy of RMS with increase of exerted torque were significantly smaller in elderly group (p < 0.05) and correlation coefficients with initial torque level were significantly higher in elderly group than in young group at moderate torque levels (p < 0.05). These data suggest that the increase of heterogeneity and the change in the activation pattern are smaller in elderly individuals than in young individuals. We speculated that multi-channel SEMG pattern in elderly individual reflects neuromuscular activation strategy regulated predominantly by clustering of similar type of muscle fibers in aged muscle.     

A preliminary study of modification of gait in real-time using surface electromyography

Modification of abnormal gait was attempted in real-time using a surface electromyography-based protocol to teach recruitment of the anterior tibialis at the correct time in the gait cycle. Two children diagnosed with cerebral palsy were able to learn volitional control of the anterior tibialis as demonstrated by improved clearance of the toe on the swing phase of the gait and newly learned ability to recruit and relax the anterior tibialis. The children were able to walk with the new gait pattern and reproduce the old one at will. Implications for future research in this area are discussed.     

Instrumentation methodology for recording and feeding-back surface electromyographic (SEMG) signals

The use of biofeedback devices has been plagued by the garbage in—garbage out problem since its inception. This paper reviews the basics of how to use biofeedback devices for surface electromyographic applications at each stage in the process from sensors to displays so meaningful information can be gathered and utilized.     

THE INFLUENCE OF KARATE PRACTICE LEVEL AND SEX ON PHYSIOLOGICAL AND PERCEPTUAL RESPONSES IN THREE MODERN KARATE TRAINING MODALITIES

Objective

The aim of the present study was to examine the influence of karate practice level (national vs international level) and sex (women vs men) on physiological and perceptual responses in three modern karate training modalities (tactical-technical (TT), technical-development (TD), and randori).

Method

The study included 18 karatekas participating in an eight-session training camp of four TT, two TD, and two randori. During each session, the percentage of maximal heart rate (HR), blood lactate concentration [La^-], and rating of perceived exertion (RPE) were assessed.

Results

The main results showed that the percentage of maximal HR was significantly higher in women than in men regardless of practice level or training modality (70.3 ± 4.1 vs 66.2 ± 6.3, respectively). Moreover, [La^-] and RPE were significantly lower in international-level karatekas compared with their national-level counterparts whatever the sex or training modality ([La^-] = 11.4 ± 2.6 vs 8.3 ± 2.4 mmol · L^-1 and RPE = 3.6 ± 1.2 vs 4.3 ± 1.5, respectively). Last, physiological and perceptual responses were significantly higher during randori in comparison with TT and TD for both sexes.

Conclusion

The combination of [La^-] and RPE thus seems to be a good indicator for discriminating between national- and international-level karatekas, and randori seems to be an effective means to reproduce official karate sparring.     

Regional neuromuscular regulation within human rectus femoris muscle during gait

The spatial distribution pattern of neuromuscular activation within the human rectus femoris (RF) muscle was investigated during gait by multi-channel surface electromyography (surface EMG). Eleven healthy men walked on a treadmill with three gait speeds (4, 5, and 6 km/h) and gradients (0°, 12.5°, and 25°). The spatial distribution of surface EMG was tested by central locus activation (CLA), which is calculated from 2-D multi-channel surface EMG with 46 surface electrodes. For all conditions, CLA was around the middle regions during the swing-to-stance transition and moved in a proximal direction during the stance phase and stance-to-swing transition (p<0.05). CLA during the stance-to-swing transition and early swing phase significantly moved to proximal site with increasing gait speed (p<0.05). During the early stance and swing phases, with increasing grade, CLA significantly moved distally (p<0.05). These results suggest that the RF muscle is regionally activated during a gait cycle and is non-uniformly regulated longitudinally.     

Use of Multiple-Site Performance-Contingent SEMG Reward Programming in Pediatric Rehabilitation: A Retrospective Review

We completed a retrospective review of the effectiveness of multi-site, performance-contingent reward programming on functional change in motor performance of 16 treatment resistant children. Patients were previously treated in physical or occupational therapy for head control, standing balance training, sitting and upper extremity use (brachial plexus injury). They then participated in a program that utilized multiple surface electromyography sites the use of which was rewarded with videos for performing the correct constellation of recruitment pattern (e.g., contracting some muscles while relaxing others). Onset of reward was calibrated for each patient and transfer of skill to outside the clinic was encouraged by linking a verbal cue to the correct motor plan. Fourteen of the 16 patients improved. The implications of the use of this technique in the treatment of motor dysfunction is discussed.     

SEMG evaluations: an overview

This article reviews the current techniques of surface electromyography (SEMG) assessment. Discussed are static, dynamic, and combination assessment techniques and the rational for their use.     

Volume conduction models for surface EMG; confrontation with measurements

Volume conduction models are used to describe and explain recorded motor unit potentials (MUPs). So far it has remained unclear which factors have to be taken into account in a volume conduction model. In the present study, five different models are confronted with measured MUP distributions over the skin surface above the m. biceps brachii generated by MUs at different depths and recorded by small surface electrodes. All model simulations include fibres of finite length. The models differ in the size of the volume conductor (finite/infinite), the number of different layers (1, 2 or 3) and the conductivities of these layers (representing muscle, subcutaneous fat and skin). All measured and simulated MUPs contain a mainly negative propagating wave followed by a positive wave simultaneously present at all electrode positions. The magnitude of the different MUP components relative to each other and as a function of motor unit (MU) and electrode position differ between the models studied and the measurements. All simulated MUPs changed faster with observation distance than the measured MUPs. The three-layer model, in which muscle tissue was surrounded by a subcutaneous fat layer and by a layer of skin resulted in MUPs closest to the measured MUPs.     

Activation of shoulder muscles in healthy men and women under isometric conditions

Purpose: Due to the low osseous lead of the shoulder joint a large portion of the shoulder muscles, in addition to executing movements, deals with stabilising tasks. This requires a permanent readjustment of the intermuscular co-ordination of all involved muscles. The aim of the study was to verify the existence of gender dependent differences in intramuscular co-ordination patterns of shoulder muscles.

Method: Fifteen healthy men and nine healthy women, who executed 24 isometric exercises in sagittal, frontal and horizontal planes with a loading of 50% of their individual isometric maximum force, were investigated. In every plane, four angular positions were chosen and both opposite force directions were measured, respectively. SEMG was taken from 13 muscles of the shoulder and the upper arm. Due to inter-individual differences SEMG amplitudes were normalised. Results: Gender specific differences of functional intermuscular co-ordination patterns could be proven systematically. Women showed less activation of muscles acting in the main force direction. In addition, those muscles less necessary for the actual force production were more activated in women than in men.

Conclusions: Functionally comparable shoulder function showed a gender dependency in terms of functional intermuscular co-ordination.     

Respiratory Sinus Arrhythmia Versus Neck/Trapezius EMG and Incentive Inspirometry Biofeedback for Asthma: A Pilot Study

This pilot study compared biofeedback to increase respiratory sinus arrhythmia (RSA) with EMG and incentive inspirometry biofeedback in asthmatic adults. A three-group design (Waiting List Control n = 5, RSA biofeedback n = 6, and EMG biofeedback n = 6) was used. Six sessions of training were given in each of the biofeedback groups. In each of three testing sessions, five min. of respiratory resistance and EKG were obtained before and after a 20-min biofeedback session. Additional five-min epochs of data were collected at the beginning and end of the biofeedback period (or, in the control group, self-relaxation). Decreases in respiratory impedance occurred only in the RSA biofeedback group. Traub-Hering-Mayer (THM) waves (.03-.12 Hz) in heart period increased significantly in amplitude during RSA biofeedback. Subjects did not report significantly more relaxation during EMG or RSA biofeedback than during the control condition. However, decreases in pulmonary impedance, across groups, were associated with increases in relaxation. The results are consistent with Vaschillo's theory that RSA biofeedback exercises homeostatic autonomic reflex mechanisms through increasing the amplitude of cardiac oscillations. However, deep breathing during RSA biofeedback is a possible alternate explanation.     

The influence of taste on swallowing apnea, oral preparation time, and duration and amplitude of submental muscle contraction

Prior research has documented a modulating effect of taste on swallowing. We hypothesized that presentation of tastant stimuli would be a significant variable in swallowing-respiratory coordination, duration of oral bolus preparation, and submental muscle contraction. Twenty-three healthy females were presented with 1-cm(3) gelatin samples flavored with 4 tastants of increasing intensities. Visual analogue scale ratings of perceived intensity of each were used to identify relative equivalent concentrations across the 4 tastants. Data were then collected during ingestion of 5 trials of the 4 equivalent tastants using measurements of nasal airflow and submental surface electromyography (sEMG) to record biomechanical measures. Chi-square analysis failed to identify a statistically significant influence of taste on the phase location of swallowing apnea. Repeated measures analysis of variance demonstrated significant taste effects for oral preparation time, submental sEMG amplitude, and duration (P < 0.02). Sweet tastants were prepared for a shorter time when compared with bitter tastants. Swallow duration for sour, salty, and bitter tastants were longer than sweet and neutral tastants. Sour tastants resulted in the greatest amplitude of submental muscle contraction during swallowing. This study supports existing research that found that sour substances were swallowed with more effort when compared with other tastes.     

The Influence of Stress and Energy Level on Learning Muscle Relaxation During Gross-Motor Task Performance Using Electromyographic Feedback

The aim was to investigate the influence of mood on learning muscle relaxation. Self-reported mood (assessed by the Stress-Energy Checklist) at baseline was related to learning muscle relaxation induced by electromyographic feedback training during performance of a gross-motor task. Feedback training was provided either intermittently (Intermittent Feedback Task, IF, n=12) or continuously (Continuous Feedback Task, CF, n=9). Results reveal a negative correlation between the learning effect at short-term and energy dimension for the IF Task. It can be concluded that mood experienced prior to a learning task is relevant for the learning effect and this effect may be dependent on the schedule of feedback used.