Functional changes of human quadriceps muscle injured by eccentric exercise

The present study evaluated functional changes of quadriceps muscle after injury induced by eccentric exercise. Maximal isometric torque of quadriceps and the surface electromyography (root mean square, RMS, and median frequency, MDF) of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles were examined before, immediately after and during the first 7 days after injury. Serum creatine kinase (CK) levels and magnetic resonance imaging (MRI) were used to identify muscle injury. The subject was used as her own control and percent refers to pre-injury data. Experiments were carried out with a sedentary 23-year-old female. Injury was induced by 4 bouts of 15 maximal isokinetic eccentric contractions (angular velocity of 5º/s; range of motion from 40º to 110º of knee flexion). The isometric torque of the quadriceps (knee at 90º flexion) decreased 52% immediately after eccentric exercise and recovered on the 5th day. The highest reduction of RMS occurred on the 2nd day after injury in both VL (63%) and VMO (66%) and only VL recovered to the pre-injury level on the 7th day. Immediately after injury, the MDF decreased by 5 and 3% (VMO and VL, respectively) and recovered one day later. Serum CK levels increased by 109% on the 2nd day and were still increased by 32% on the 7th day. MRI showed large areas of injury especially in the deep region of quadriceps. In conclusion, eccentric exercise decreased the isometric torque and electromyographic signals of quadriceps muscle, which were recovered in one week, despite the muscle regeneration signals.

Spectral analysis of the electromyograph of the erector spinae muscle before and after a dynamic manual load-lifting test

The aim of the present study was to assess the spectral behavior of the erector spinae muscle during isometric contractions performed before and after a dynamic manual load-lifting test carried out by the trunk in order to determine the capacity of muscle to perform this task. Nine healthy female students participated in the experiment. Their average age, height, and body mass (± SD) were 20 ± 1 years, 1.6 ± 0.03 m, and 53 ± 4 kg, respectively. The development of muscle fatigue was assessed by spectral analysis (median frequency) and root mean square with time. The test consisted of repeated bending movements from the trunk, starting from a 45º angle of flexion, with the application of approximately 15, 25 and 50% of maximum individual load, to the stand up position. The protocol used proved to be more reliable with loads exceeding 50% of the maximum for the identification of muscle fatigue by electromyography as a function of time. Most of the volunteers showed an increase in root mean square versus time on both the right (N = 7) and the left (N = 6) side, indicating a tendency to become fatigued. With respect to the changes in median frequency of the electromyographic signal, the loads used in this study had no significant effect on either the right or the left side of the erector spinae muscle at this frequency, suggesting that a higher amount and percentage of loads would produce more substantial results in the study of isotonic contractions.

Hepatitis C virus infection, cryoglobulinemia, and peripheral neuropathy: a case report

Hepatitis C virus (HCV) is essentially hepatotropic but its manifestations can extend beyond the liver. It can be associated with autoimmune diseases, such as mixed cryoglobulinemia, membranoproliferative glomerulonephritis, autoimmune thyroiditis, and lymphoproliferative disorders. The mechanisms that trigger these manifestations are not completely understood. We describe a 48-year-old man with chronic HCV infection (circulating HCV RNA and moderate hepatitis as indicated by liver biopsy), cryoglobulinemia, and sensory and motor peripheral neuropathy. The diagnosis of multineuropathy was confirmed by clinical examination and electromyographic tests. A nerve biopsy revealed an inflammatory infiltrate in the perineurial space and signs of demyelination and axonal degeneration. The patient had no improvement of neurological symptoms with the use of analgesics and neuro-modulators. He was then treated with interferon-alpha (3 million units subcutaneously, 3 times per week) and ribavirin (500 mg orally, twice a day) for 48 weeks. Six months after the end of therapy, the patient had sustained viral response (negative HCV RNA) and remission of neurological symptoms, but cryoglobulins remained positive. A review of the literature on the pathogenesis and treatment of neurological manifestations associated with HCV infection is presented. This report underscores the need for a thorough evaluation of HCV-infected patients because of the possibility of extrahepatic manifestations. Antiviral treatment with interferon and ribavirin can be effective and should be considered in patients with neurological complications associated with HCV infection.

Breathing pattern, thoracoabdominal motion and muscular activity during three breathing exercises

The objective of the present study was to evaluate breathing pattern, thoracoabdominal motion and muscular activity during three breathing exercises: diaphragmatic breathing (DB), flow-oriented (Triflo II) incentive spirometry and volume-oriented (Voldyne) incentive spirometry. Seventeen healthy subjects (12 females, 5 males) aged 23 ± 5 years (mean ± SD) were studied. Calibrated respiratory inductive plethysmography was used to measure the following variables during rest (baseline) and breathing exercises: tidal volume (Vt), respiratory frequency (f), rib cage contribution to Vt (RC/Vt), inspiratory duty cycle (Ti/Ttot), and phase angle (PhAng). Sternocleidomastoid muscle activity was assessed by surface electromyography. Statistical analysis was performed by ANOVA and Tukey or Friedman and Wilcoxon tests, with the level of significance set at P < 0.05. Comparisons between baseline and breathing exercise periods showed a significant increase of Vt and PhAng during all exercises, a significant decrease of f during DB and Voldyne, a significant increase of Ti/Ttot during Voldyne, and no significant difference in RC/Vt. Comparisons among exercises revealed higher f and sternocleidomastoid activity during Triflo II (P < 0.05) with respect to DB and Voldyne, without a significant difference in Vt, Ti/Ttot, PhAng, or RC/Vt. Exercises changed the breathing pattern and increased PhAng, a variable of thoracoabdominal asynchrony, compared to baseline. The only difference between DB and Voldyne was a significant increase of Ti/Ttot compared to baseline. Triflo II was associated with higher f values and electromyographic activity of the sternocleidomastoid. In conclusion, DB and Voldyne showed similar results while Triflo II showed disadvantages compared to the other breathing exercises.

Comparison of the Polar S810i monitor and the ECG for the analysis of heart rate variability in the time and frequency domains

The aim of the present study was to compare heart rate variability (HRV) at rest and during exercise using a temporal series obtained with the Polar S810i monitor and a signal from a LYNX® signal conditioner (BIO EMG 1000 model) with a channel configured for the acquisition of ECG signals. Fifteen healthy subjects aged 20.9 ± 1.4 years were analyzed. The subjects remained at rest for 20 min and performed exercise for another 20 min with the workload selected to achieve 60% of submaximal heart rate. RR series were obtained for each individual with a Polar S810i instrument and with an ECG analyzed with a biological signal conditioner. The HRV indices (rMSSD, pNN50, LFnu, HFnu, and LF/HF) were calculated after signal processing and analysis. The unpaired Student t-test and intraclass correlation coefficient were used for data analysis. No statistically significant differences were observed when comparing the values analyzed by means of the two devices for HRV at rest and during exercise. The intraclass correlation coefficient demonstrated satisfactory correlation between the values obtained by the devices at rest (pNN50 = 0.994; rMSSD = 0.995; LFnu = 0.978; HFnu = 0.978; LF/HF = 0.982) and during exercise (pNN50 = 0.869; rMSSD = 0.929; LFnu = 0.973; HFnu = 0.973; LF/HF = 0.942). The calculation of HRV values by means of temporal series obtained from the Polar S810i instrument appears to be as reliable as those obtained by processing the ECG signal captured with a signal conditioner.

Sleep pattern and learning in knockdown mice with reduced cholinergic neurotransmission

Impaired cholinergic neurotransmission can affect memory formation and influence sleep-wake cycles (SWC). In the present study, we describe the SWC in mice with a deficient vesicular acetylcholine transporter (VAChT) system, previously characterized as presenting reduced acetylcholine release and cognitive and behavioral dysfunctions. Continuous, chronic ECoG and EMG recordings were used to evaluate the SWC pattern during light and dark phases in VAChT knockdown heterozygous (VAChT-KDHET, n=7) and wild-type (WT, n=7) mice. SWC were evaluated for sleep efficiency, total amount and mean duration of slow-wave, intermediate and paradoxical sleep, as well as the number of awakenings from sleep. After recording SWC, contextual fear-conditioning tests were used as an acetylcholine-dependent learning paradigm. The results showed that sleep efficiency in VAChT-KDHET animals was similar to that of WT mice, but that the SWC was more fragmented. Fragmentation was characterized by an increase in the number of awakenings, mainly during intermediate sleep. VAChT-KDHET animals performed poorly in the contextual fear-conditioning paradigm (mean freezing time: 34.4±3.1 and 44.5±3.3 s for WT and VAChT-KDHET animals, respectively), which was followed by a 45% reduction in the number of paradoxical sleep episodes after the training session. Taken together, the results show that reduced cholinergic transmission led to sleep fragmentation and learning impairment. We discuss the results on the basis of cholinergic plasticity and its relevance to sleep homeostasis. We suggest that VAChT-KDHET mice could be a useful model to test cholinergic drugs used to treat sleep dysfunction in neurodegenerative disorders.

Late-onset spinal motor neuronopathy- a new neuromuscular disease

The aim of this study was to clarify the clinical phenotype of late-onset spinal motor neuronopathy (LOSMoN), an adult-onset autosomal dominant lower motor neuron disorder identified first in two families in Eastern Finland, in order to clarify its genetic background. Motor neuron disorders (MNDs) are characterized by dysfunction and premature death of motor neurons in the brain and spinal cord. MNDs can manifest at any age of the human lifespan, ranging from pre- or neonatal forms such as spinal muscular atrophy type I (SMA I) to those preferentially affecting the older age groups exemplified by sporadic amyotrophic lateral sclerosis (ALS). With a combination of genetic linkage analysis and genome sequencing using DNA from a total of 55 affected members of 17 families and a whole genome scan, we were able to show that LOSMoN is caused by the c.197G>T p.G66V mutation in the gene CHCHD10. This study showed that LOSMoN has very characteristic features that help to differentiate it from other more malignant forms of motor neuron disease, such as ALS, which was erroneously diagnosed in many patients in our cohort. Lack of fibrillations in the first dorsal interosseus muscle on EMG and extensive grouping of non-atrophic type IIA/2A fibers on muscle biopsy were shown to be common findings in LOSMoN, but rare or absent in ALS patients. The results of this study will help clinicians recognize the characteristic phenotype of LOSMoN disease and thus improve their diagnostic accuracy, and will also allow physicians to provide adequate genetic counseling for patients.

The surface electromyography-force relationship during isometric dorsiflexion in males and females

This study evaluated sex-related differences in the tibialis anterior (TA) surface electromyography (EMG) to force relationship. One-hundred participants (50 males and 50 females) performed three isometric contractions at 20, 40, 60, 80, and 100% of maximal voluntary contraction (MVC) in an apparatus designed to isolate the action of the dorsiflexors. The surface EMG signal was amplified (lOOOx), band-pass filtered (10-500Hz), and sampled at 2048 Hz. The load cell signal was low-passed filtered at 100 Hz and sampled at the same rate. Males were stronger than females {P <0.05). However, there was no significant difference in root-mean-square (RMS) values between sexes {P <0.05). Both sexes exhibited a quadratic increase in RMS across force levels (P <0.05). The mean power frequency (MNF) for males was greater than for females {P <0.05). Males and females exhibited a linear increase in both frequency measures up to 80% of MVC (P <0.05). Between 80 and 100% MVC, the frequency values for the females plateaued while males showed a decrease {P <0.05). The magnitude of the difference in MNF between males and females was consistent with sex-specific TA physiology. In general, the pattern of means for RMS and MNF between males and females revealed no sex-related differences in the surface EMG/force relationship. We therefore conclude that there are no sex-related differences in the gradation of muscle force.

3D movement and muscle activity patterns in a violin bowing task

Objective: Overuse injuries in violinists are a problem that has been primarily analyzed through the use of questionnaires. Simultaneous 3D motion analysis and EMG to measure muscle activity has been suggested as a quantitative technique to explore this problem by identifying movement patterns and muscular demands which may predispose violinists to overuse injuries. This multi-disciplinary analysis technique has, so far, had limited use in the music world. The purpose of this study was to use it to characterize the demands of a violin bowing task. Subjects: Twelve injury-free violinists volunteered for the study. The subjects were assigned to a novice or expert group based on playing experience, as determined by questionnaire. Design and Settings: Muscle activity and movement patterns were assessed while violinists played five bowing cycles (one bowing cycle = one down-bow + one up-bow) on each string (G, D, A, E), at a pulse of 4 beats per bow and 100 beats per minute. Measurements: An upper extremity model created using coordinate data from markers placed on the right acromion process, lateral epicondyle of the humerus and ulnar styloid was used to determine minimum and maximum joint angles, ranges of motion (ROM) and angular velocities at the shoulder and elbow of the bowing arm. Muscle activity in right anterior deltoid, biceps brachii and triceps brachii was assessed during maximal voluntary contractions (MVC) and during the playing task. Data were analysed for significant differences across the strings and between experience groups. Results: Elbow flexion/extension ROM was similar across strings for both groups. Shoulder flexion/extension ROM increaslarger for the experts. Angular velocity changes mirrored changes in ROM. Deltoid was the most active of the muscles assessed (20% MVC) and displayed a pattern of constant activation to maintain shoulder abduction. Biceps and triceps were less active (4 - 12% MVC) and showed a more periodic 'on and off pattern. Novices' muscle activity was higher in all cases. Experts' muscle activity showed a consistent pattern across strings, whereas the novices were more irregular. The agonist-antagonist roles of biceps and triceps during the bowing motion were clearly defined in the expert group, but not as apparent in the novice group. Conclusions: Bowing movement appears to be controlled by the shoulder rather than the elbow as shoulder ROM changed across strings while elbow ROM remained the same. Shoulder injuries are probably due to repetition as the muscle activity required for the movement is small. Experts require a smaller amount of muscle activity to perform the movement, possibly due to more efficient muscle activation patterns as a result of practice. This quantitative multidisciplinary approach to analysing violinists' movements can contribute to fuller understanding of both playing demands and injury mechanisms .

A comparison of electrophysiological changes during the sleep onset period of psychophysiological insomniacs, psychiatric insomniacs and normal sleepers

The EEG of the sleep onset period of psychophysiological insomniacs, psychiatric insomniacs and controls was compared using power spectral analysis (FFT). Eighteen drug-free subjects were equally divided into three groups according to their responses in the Brock Sleep and Insomnia Questionnaire, the Minnesota Multiphasic Personality Inventory and the Sleep Disorders Questionnaire. Group 1 consisted of psychophysiological insomniacs, group 2 included insomniacs with an indication of psychiatric disturbances, and group 3 was a control group. EEG, EOG and EMG were recorded for two consecutive nights. Power spectral analysis (FFT) of EEG at C4 from the sleep onset period (defined as lights out to the first five minutes of stage 2) was performed on all standard frequency bands, delta: .5-4 Hz; theta: 4-8 Hz; alpha: 8-12 Hz; sigma: 12-15 Hz beta: 15-25 Hz. Psychophysiological insomniacs had less alpha during wakefulness than the other two groups and did not show the dramatic drop in alpha across the sleep onset period, which characterizes normal sleep. They also had less delta, especially during stage 2 on night 2. They also showed less delta in the last quartile of the chronological analysis of the sleep onset period. Psychiatric insomniacs showed lower relative beta power values overall while psychophysiological insomniacs showed higher relative beta power values during wakefulness. This microanalysis 11 confirms that the sleep onset period is generally similar for psychiatric insomniacs and normal sleepers. This may be due to the sample of psychiatric insomniacs being heterogeneous or may reflect a sleep onset system that is essentially intact. Psychophysiological insomniacs have higher cortical arousal during the sleep onset period than do the psychiatric insomniacs and the controls. Clear differences in the sleep onset period of psychophysiological insomniacs exist. The dramatic changes in power values in these two groups are not seen in the psychophysiological insomniacs, which may make the discrimination between wakefulness and sleep more difficult.

Neuromuscular adaptations in endurance-trained boys and men

Competitive sports participation in youth is becoming increasingly more common in the Western world. It is widely accepted that sports participation, specifically endurance training, is beneficial for physical, psychomotor, and social development of children. The research on the effect of endurance training in children has focused mainly on healthrelated benefits and physiological adaptations, particularly on maximal oxygen uptake. However, corresponding research on neuromuscular adaptations to endurance training and the latter's possible effects on muscle strength in youth is lacking. In children and adults, resistance training can enhance strength and mcrease muscle activation. However, data on the effect of endurance training on strength and neuromuscular adaptations are limited. While some evidence exists demonstrating increased muscle activation and possibly increased strength in endurance athletes compared with untrained adults, the neuromuscular adaptations to endurance training in children have not been examined. Thus, the purpose of this study was to examine maximal isometric torque and rate of torque development (RID), along with the pattern of muscle activation during elbow and knee flexion and extension in muscle-endurancetrained and untrained men and boys. Subjects included 65 males: untrained boys (n=18), endurance-trained boys (n=12), untrained men (n=20) and endurance-trained men (n=15). Maximal isometric torque and rate of torque development were measured using an isokinetic dynamometer (Biodex III), and neuromuscular activation was assessed using surface electromyography (SEMG). Muscle strength and activation were assessed in the dominant arm and leg, in a cross-balanced fashion during elbow and knee flexion and extension. The main variables included peak torque (T), RTD, rate of muscle activation (Q30), Electro-mechanical delay (EMD), time to peak RTD and co-activation index. Age differences in T, RTD, electro-mechanical delay (EMD) and rate of muscle activation (Q30) were consistently observed in the four contractions tested. Additionally, Q30, nonnalized for peak EMG amplitude, was consistently higher in the endurancetrained men compared with untrained men. Co-activation index was generally low in all contractions. For example, during maximal voluntary isometric knee extension, men were stronger, had higher RTD and Q30, whether absolute or nonnalized values were used. Moreover, boys exhibited longer EMD (64.8 ± 18.5 ms vs. 56.6 ± 15.3 ms, for boys and men respectively) and time to peak RTD (112.4 ± 33.4 ms vs. 100.8 ± 39.1 ms for boys and men, respectively). In addition, endurance-trained men had lower T compared with untrained men, yet they also exhibited significantly higher nonnalized Q30 (1.9 ± 1.2 vs. 1.1 ± 0.7 for endurance-trained men and untrained men, respectively). No training effect was apparent in the boys. In conclusion, the findings demonstrate muscle strength and activation to be lower in children compared with adults, regardless of training status. The higher Q30 of the endurance-trained men suggests neural adaptations, similar to those expected in response to resistance training. The lower peak torque may su9gest a higher relative involvement oftype I muscle fibres in the endurance-trained athletes. Future research is required to better understand the effect of growth and development on muscle strength and activation patterns during dynamic and sub-maximal isometric contractions. Furthennore, training intervention studies could reveal the effects of endurance training during different developmental stages, as well as in different muscle groups.

Active isolated stretching : an investigation of the mechanical mechanisms

The Active Isolated Stretching (AIS) technique proposes that by contracting a muscle (agonist) the opposite muscle (antagonist) will relax through reciprocal inhibition and lengthen without increasing muscle tension (Mattes, 2000). The clinical effectiveness of AIS has been reported but its mechanism of action has not been investigated at the tissue level. Proposed mechanisms for increased range of motion (ROM) include mechanical or neural changes, or an increased stretch tolerance. The purpose of the study was to investigate changes in mechanical properties, i.e. stiffness, of skeletal muscle in response to acute and long-term AIS stretching for the hamstring muscle group. Recreationally active university-aged students (female n=8, male n=2) classified as having tight hamstrings, by a knee extension test, volunteered for the study. All stretch procedures were performed on the right leg, with the left leg serving as a control. Each subject was assessed twice: at an initial session and after completing a 6-week AIS hamstring stretch training program. For both test sessions active knee extension (ROM) to a position of "light irritation", passive resisted torque and stiffness were determined before and after completion of the AIS technique (2x10 reps). Data were collected using a Biodex System 3 Pro (Biodex Medical Systems, NY, USA) isokinetic dynamometer. Surface electromyography (EMG) was used to monitor vastus lateralis (VL) and hamstring muscle activity during the stretching movements. Between test sessions, 2x10 reps of the AIS bent knee hamstring stretch were performed daily for 6-weeks.

Reliability of muscle fiber conduction velocity in the tibialis anterior

This document could not have been completed without the hard work of a number of individuals. First and foremost, my supervisor, Dr. David Gabriel deserves the utmost recognition for the immense effort and time spent guiding the production of this document through the various stages of completion. Also, aiding in the data collection, technical support, and general thought processing were Lab Technician Greig Inglis and fellow members of the Electromyographic Kinesiology Laboratory Jon Howard, Sean Lenhardt, Lara Robbins, and Corrine Davies-Schinkel. The input of Drs. Ted Clancy, Phil Sullivan and external examiner Dr. Anita Christie, all members ofthe assessment committee, was incredibly important and vital to the completion of this work. Their expertise provided a strong source of knowledge and went to ensure that this project was completed at exemplary level. There were a number of other individuals who were an immense help in getting this project off the ground and completed. The donation of their time and efforts was very generous and much needed in order to fulfill the requirements needed for completion of this study. Finally, I cannot exclude the contributions of my family throughout this project especially that of my parents whose support never wavers.

Neuromotor Mechanisms Involved in the Recovery from Local Muscular Fatigue

The phenomenon of over-recovery consists of a participant’s maximal force levels returning to values above initial levels. The present study examined the presence and causes of over-recovery following local muscular fatigue. Fourteen males completed two fatigue protocols consisting of maximal isometric dorsiflexion contractions. Upon completion of the fatigue protocol participants’ force was monitored over a 15 minute recovery period. Dorsiflexion force and surface electromyography (sEMG) from the tibialis anterior and soleus were monitored concurrently. Following the two fatigue conditions (10 and 20% force decrement) force recovered to 100.5 and 99.5% of initial levels for each condition, respectively. Surface EMG root-mean-square amplitude and MPF exhibited changes consistent with a warm-up effect. It was concluded that over-recovery was not present in the tibialis anterior following a local muscular fatigue. However, the return in force to initial values, rather than a persistent decrement as normally observed, was mediated by the warm-up effect.

Do Neuro-Muscular Adaptations Occur in Endurance-Trained Boys and Men?

Most research on the effects of endurance training has focused on endurance training's health-related benefits and metabolic effects in both children and adults. The purpose of this study was to examine the neuromuscular effects of endurance training and to investigate whether they differ in children (9.0-12.9 years) and adults (18.4-35.6 years). Maximal isometric torque, rate of torque development (RTD), rate of muscle activation (Q30), electromechanical delay (EMD), and time to peak torque and peak RTD were determined by isokinetic dynamometry and surface electromyography (EMG) in elbow and knee flexion and extension. The subjects were 12 endurance-trained and 16 untrained boys, and 15 endurance-trained and 20 untrained men. The adults displayed consistently higher peak torque, RTD, and Q30, in both absolute and normalized values, whereas the boys had longer EMD (64.7+/-17.1 vs. 56.6+/-15.4 ms) and time to peak RTD (98.5+/-32.1 vs. 80.4+/-15.0 ms for boys and men, respectively). Q30, normalized for peak EMG amplitude, was the only observed training effect (1.95+/-1.16 vs. 1.10+/-0.67 ms for trained and untrained men, respectively). This effect could not be shown in the boys. The findings show normalized muscle strength and rate of activation to be lower in children compared with adults, regardless of training status. Because the observed higher Q30 values were not matched by corresponding higher performance measures in the trained men, the functional and discriminatory significance of Q30 remains unclear. Endurance training does not appear to affect muscle strength or rate of force development in either men or boys.