Strategies to identify changes in SEMG due to muscle fatigue during cycling.

Detection, quantification and analysis of muscle fatigue are crucial in occupational/rehabilitation and sporting settings. Sports organizations such as the Australian Institute of Sports (AIS) currently monitor fatigue by a battery of tests including invasive techniques that require taking blood samples and/or muscle biopsies, the latter of which is highly invasive, painful, time consuming and expensive. SEMG is non-invasive monitoring of muscle activation and is an indication of localized muscle fatigue based on the observed shift of the power spectral density of the SEMG. But the success of SEMG based techniques is currently limited to isometric contraction and is not acceptable to the human movement community. This paper proposes and tests the use of spectral analysis of narrow windows of SEMG near the peak of a cyclic activity to identify the onset of muscle fatigue during cyclic activities. The results demonstrate a highly significant relationship of reduction of the median frequency with the onset of muscle fatigue. The paper also reports the validation of the SEMG study using biochemical analysis of muscle biopsy and blood tests and further verified using power output of the cycle and speed of pedalling.

EEG coherence changes between right and left motor cortical areas during voluntary muscular contraction.

It is known that movements of the right side of the body are controlled by the left motor cortex of the brain. The aim of this study is to evaluate the contribution of right motor cortex of the brain in the central motor control of right-sided muscle contraction. EEG/EEG coherence analysis has been used to determine the functional coupling between the right and left motor cortical areas in twenty normal volunteers, during maximum voluntary contraction (MVC) and 50% MVC of right Adductor Pollicis muscle (APM). It shows that the maximum mean coherence values were: 0.751 during MVC at 10 and 12 Hz, and 0.274 during 50% of MVC at 22 Hz. The minimum mean coherence values were: 0.716 during MVC at 48 and 50 Hz, and 0.242 during 50% MVC at 34 Hz. The high coherence values obtained during MVC, and to a lesser extent during 50% of MVC, could be attributed to the need of recruitment of both motor cortical areas during the decision phase of central motor control of voluntary muscular contraction. The "will" to perform maximum voluntary contraction could be a major factor, which contribute to the higher coherence values obtained during MVC than these associated with 50% of MVC.

Electroacupuncture for tension-type headache on distal acupoints only: a randomized, controlled, crossover trial.

OBJECTIVE: To investigate the efficacy of electroacupuncture, applied to distal acupoints only, for tension-type headache. BACKGROUND: Electroacupuncture is commonly used for tension-type headache, but when applied to distal acupoints only, evidence of its efficacy is lacking. DESIGN: A randomized, single-blinded, sham-controlled, crossover clinical trial. Methods.-The trial had 5 stages: baseline (2 weeks), phases I and II (each 4 weeks), washout period (2 weeks), and follow-up (3 months after phase II). Forty patients were randomly assigned to either group A or group B. Group A received real electroacupuncture during phase I, then sham electroacupuncture in phase II. Group B received the treatments in reverse order. Outcome measures were headache frequency and duration, pain intensity using a visual analog scale, mechanical pain threshold, headache disability, and sickness impact. Data were analyzed by univariate 2-way analysis of variance. RESULTS: Thirty-seven patients completed the trial. There were no significant differences between the 2 groups at baseline. At the end of phase I, group A, but not group B, demonstrated significant improvement in mean (standard error of the mean [SEM]) headache frequency (3.0 per month [0.3] versus 12.0 per month [1.7]), duration (13.3 hours [3.5] versus 32.0 hours [6.2]), pain intensity (32.8 mm [4.1] versus 47.5 mm [2.7]), pain threshold (right side, 2.9 kg/second [0.1] versus 0.9 kg/second [0.1]; left side, 2.4 kg/second [0.1] versus 1.1 kg/second [0.1]), headache disability score (6.0 [1.0] versus 16.3 [1.6]), and sickness impact score (288.7 [48.0] versus 687.1 [77.2]). For each parameter, significant differences also were demonstrated for both groups between baseline and phase II, and baseline and follow-up. There were no significant differences between the groups at the end of follow-up (P >.05). CONCLUSION: Electroacupuncture to distal points alone is effective for short-term symptomatic relief of tension-type headache.

Relationship of magnitude of electromyogram of the lumbar muscles to static posture.

This work reports research that investigated the relationship of the strength of contraction of different muscles of the lumbar back to maintain static posture. The paper reports the study of surface electromyogram of the muscles and uses scattering and neural networks on the strength of the EMG measured using root mean square (RMS). The signal is studied before and after the removal of electrocardiogram (ECG) artifact from the signal using a modified independent component analysis technique. The three dimensional scattering plots do not show any observable trends while the neural networks before the removal of ECG does not converge while after removal of ECG the neural network shows a high level of accuracy. The results demonstrate that there is a complex relation between the four EMG and posture and this relationship is revealed only after of ECG from EMG.

Electrocardiogram removal from electromyogram of the muscles.

Surface electromyogram (SEMG) of the lumbar back muscles is being used for determining posture disorders for people suffering from low back pain. But SEMG of the back has a strong electrocardiogram (ECG) artefact. Research was conducted to determine the difference in the SEMG before and after the removal of ECG artefact from the SEMG recording using gating, subtraction and multi-step independent component analysis (MICA). The paper reports results of experiments conducted on eleven subjects over two days. The results show that removal of ECG artefact from the raw signal can substantially alter the RMS of the signal demonstrating the need for careful filtering of the signal for analysis. The paper also reports of the success of MICA for removing the ECG artefact.

The frequency of positive common spinal clinical examination findings in a sample of premenstrual syndrome sufferers.

OBJECTIVE: As part of a randomized clinical trial to determine the efficacy of chiropractic therapy on premenstrual syndrome (PMS), subjects were evaluated for initial underlying spinal dysfunction. SUBJECTS: Fifty-four subjects with diagnosed PMS (using a Moos PMS questionnaire plus daily symptom monitoring) and 30 subjects with no diagnosable PMS were recruited by newspaper advertising and referrals. DESIGN: All subjects underwent a full history and physical and chiropractic examination carried out by 1 of 2 fully qualified and registered chiropractors, each with a minimum of 10 years experience. The results of the assessment for the PMS group were compared with those of the non-PMS group. SETTING: RMIT teaching clinics. DATA ANALYSIS: The data collected were entered into a spread sheet and contingency tables were created. The data were analyzed by use of chi-squared tests, with the statistical significance being set at P < .05. RESULTS: The PMS group had a higher percentage of positive responses for each of 12 measured spinal dysfunction indexes except for range of motion of the low back. The indexes where the increase was statistically significant (P < .05) were cervical, thoracic, and low back tenderness, low back orthopedic testing, low back muscle weakness, and the neck disability index. An average of 5.4 of the 12 indexes were positive for the PMS group compared with 3.0 for the non-PMS group. CONCLUSIONS: A relatively high incidence of spinal dysfunction exists in PMS sufferers compared with a comparable group of non-PMS sufferers. This is suggestive that spinal dysfunction could be a causative factor in PMS and that chiropractic manipulative therapy may offer an alternative therapeutic approach for PMS sufferers.

A randomized, placebo-controlled clinical trial on the efficacy of chiropractic therapy on premenstrual syndrome.

OBJECTIVE: To evaluate the efficacy of chiropractic therapy on the treatment of symptoms associated with premenstrual syndrome. DESIGN: A prospective, randomized, placebo-controlled, crossover clinical trial. SETTING: Multicenter private clinics. SUBJECTS: Twenty-five subjects with diagnosed premenstrual syndrome (with a Moos premenstrual syndrome questionnaire plus daily symptom monitoring). INTERVENTION: After randomization, 16 of the subjects received high-velocity, low-amplitude spinal manipulation plus soft tissue therapy 2 to 3 times in the week before menses for at least 3 cycles. The remaining 9 subjects received a placebo treatment with a spring-loaded adjusting instrument wound down for minimum force. After a 1-cycle washout, the 2 groups changed over. OUTCOME MEASURE: Daily rating of symptom level, comparing total scores for premenstrual week with baseline for treatment and placebo phases. DATA ANALYSIS: The data were analyzed with paired Student t tests and Wilcoxon signed rank tests, with the statistical significance set at P < .05. RESULTS: There was a significant decrease in scores after treatment compared with baseline scores (P = .00001) and a statistically significant decrease in scores for the treatment phase compared with the placebo (P = .006). For group 1 (n = 16), there was a significant decrease in scores after treatment compared with baseline scores (P = .0001) and a statistically significant decrease in scores for the treatment phase compared with the placebo (P = .041). For group 2 (n = 9), there was a significant decrease in scores during treatment compared with the baseline (P = .01); however, there was no difference at the P = .05 level between treatment and placebo scores. CONCLUSIONS: Within the limitations of the study, the results support the hypothesis that the symptoms associated with PMS can generally be reduced by chiropractic treatment consisting of adjustments and soft-tissue therapy. However, the role of a placebo effect needs further elucidation, given that the group receiving the placebo first, although improving over the baseline, showed no further improvement when they had actual treatment.

Effect of muscle length on phasic stretch reflexes in humans and cats.

1. This is a report of the effects at different muscle lengths of the muscle's immediate history on the tendon jerk and Hoffman (H)-reflex in triceps surae of human subjects and cats. 2. In adult human subjects the size of the tendon jerk was measured as electromyogram (EMG) and torque in response to a tendon tap. Before each test tap the muscle was conditioned by a maximum voluntary contraction carried out with the foot either plantarflexed or dorsiflexed by 30 degrees from the test position. After a contraction with the foot dorsiflexed, the subsequent reflex response was smaller than after a contraction with the foot plantarflexed. 3. The same conditioning procedure was carried out with the H-reflex. The reflex was elicited by transcutaneous electrical stimulation of the tibial nerve in the popliteal fossa. Here the reflex after a contraction with the foot dorsiflexed was larger than after plantarflexion. In other words, the effects of conditioning were the opposite for the tendon jerk and H-reflex. 4. The effects of muscle conditioning were tested over a range of muscle lengths. As the test length was made progressively longer, that is, the foot more dorsiflexed, the difference in size of the tendon jerk following the two forms of conditioning became less, whereas for the H-reflex it remained the same. 5. These findings were confirmed in cats anesthetized with alpha-chloralose. The tendon jerk was elicited by a quick stretch applied to the triceps surae muscle group, and the H-reflex represented by the monosynaptic reflex recorded from the central, cut end of the ventral root in response to electrical stimulation of the triceps nerve. Muscle conditioning consisted of a 1-s period of stimulation at 20 pulses/s, at fusimotor strength, of the peripheral end of the cut ventral root at a muscle length 5 mm longer or shorter than the test length. In the cat, as in human subjects, the effect of conditioning on the tendon jerk reversed at long muscle lengths, whereas the monosynaptic reflex showed no reversal. 6. It had been proposed previously that the effects of conditioning on stretch reflexes could be explained by development of slack in the intrafusal fibers of muscle spindles after a contraction at a longer-than-test length. The presence of slack lowers the resting discharge of spindles and reduces the afferent response to a tendon tap.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of muscle history on the stretch reflex in cat and man.

1. This is a report of experiments on cat and man which demonstrate effects of a muscle's previous history of contraction and length changes on the size of the stretch reflex. 2. In adult human subjects the size of the tendon jerk was measured in ankle extensor muscles by tapping the Achilles tendon. Muscle conditioning consisted of a maximum voluntary contraction with the foot dorsiflexed or plantarflexed by 30 deg from the test position, after which the subject was asked to relax while the foot was held still for several seconds before being returned to the test position and a tendon tap given. After a contraction of the lengthened muscle the tendon jerk was smaller than after a contraction of the shortened muscle. 3. The experiment was then repeated, but instead of a tendon jerk an H (Hoffmann) reflex was elicited by transcutaneous electrical stimulation of the tibial nerve in the popliteal fossa. The reflex after a conditioning contraction of the lengthened muscle was larger than after a contraction of the shortened muscle. In other words muscle conditioning produced opposite effects on the tendon jerk and H reflex. 4. These findings were confirmed in cats anaesthetized with chloralose. After a conditioning contraction of triceps surae at a length 5 mm longer than the test length (hold-long) a quick tendon stretch produced a smaller reflex response than following a conditioning contraction with the muscle 5 mm shorter than the test length (hold-short). The reverse trend was seen with a reflex elicited by direct electrical stimulation of the muscle nerve, which stimulates the H reflex. 5. One consequence of a conditioning contraction is that it leads to an alteration of the level of resting discharge of muscle spindles. We propose that the larger tendon jerk after a contraction of the shortened muscle is the result of changes in stretch sensitivity of muscle spindles. The reverse effect on the H reflex we attribute to a rise in the level of resting discharge of muscle spindles, which, we propose, leads to reflex inhibition of motoneurones. 6. We support this conclusion with evidence from an experiment in which the size of the conditioning step was systematically altered. Even quite small hold-short conditioning steps led to depression of the H reflex in man and the monosynaptic reflex in cats. Recordings from single afferents showed that such small steps were also accompanied by a detectable rise in spindle resting discharge.(ABSTRACT TRUNCATED AT 400 WORDS)