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This investigation examined several parameters of agonist- and antagonist-muscle activity and movement time in young and old males during rapid, forearm flexion and extension tasks. Maximal isometric strength of the forearm flexors and extensors and limb-volume measurements were also procured. The subject sample included sixteen males in each of the following groups: 1) thirty to forty year olds, 2) fifty to sixty year olds, and 3) sixty-one to seventy year olds. The averaged, electromyographic patterns (AEMG) of the biceps brachii and triceps brachii muscles were recorded during unloaded and loaded trials of forearm flexion and extension to a predetermined target. Sixteen temporal and ten quantitative parameters were examined. Significant differences between age groups were observed for only the quantitative-parameter accuracy. The conclusions were that an individual's agonist- and antagonist-muscle-activity parameters are maintained into the seventh decade. Flexion and extension strengths decrease progressively with age. Analysis of the limb-volume measures revealed that the oldest group had the greatest amount of fat in each of the segments evaluated.
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Circular mantle muscle of squids and cuttlefishes consists of distinct zones of aerobic and anaerobic muscle fibers that are thought to have functional roles analogous to red and white muscle in fishes. To test predictions of the functional role of the circular muscle zones during swimming, electromyograms (EMGs) in conjunction with video footage were recorded from brief squid Lolliguncula brevis (5.0-6.8 cm dorsal mantle length, 10.9-18.3 g) swimming in a flume at speeds of 3-27 cm s(-1). In one set of experiments, in which EMGs were recorded from electrodes intersecting both the central anaerobic and peripheral aerobic circular mantle muscles, electrical activity was detected during each mantle contraction at all swimming speeds, and the amplitude and frequency of responses increased with speed. In another set of experiments, in which EMGs were recorded from electrodes placed in the central anaerobic circular muscle fibers alone, electrical activity was not detected during mantle contraction until speeds of about 15 cm s(-1), when EMG activity was sporadic. At speeds greater than 15 cm s(-1), the frequency of central circular muscle activity subsequently increased with swimming speed until maximum speeds of 21-27 cm s(-1), when muscular activity coincided with the majority of mantle contractions. These results indicate that peripheral aerobic circular muscle is used for low, intermediate, and probably high speeds, whereas central anaerobic circular muscle is recruited at intermediate speeds and used progressively more with speed for powerful, unsteady jetting. This is significant because it suggests that there is specialization and efficient use of locomotive muscle in squids.
OBJECTIVE: To determine the correlation between insulin concentrations and myoelectrical activity of the abomasum in cows with a left displaced abomasum (LDA). ANIMALS: 14 dairy cows with an LDA at the onset of lactation. PROCEDURE: During surgical correction of an LDA, 3 pairs of electrodes were placed in the smooth muscle of the gastrointestinal tract (abomasal body, pars pylorica, and duodenum) of each cow. Electromyographic recordings were obtained once per day for 7 days. Samples were collected and tested to determine concentrations of insulin, glucagon, cortisol, glucose, beta-hydroxybutyrate, and nonesterified fatty acids. RESULTS: All 14 cattle had high glucose and insulin concentrations at the time of admission, independent of ketosis. Concentrations of glucose and insulin decreased slowly after surgical treatment and were associated with a progressive increase in abomasoduodenal myoelectric activity. The 14 cows were allocated into 2 groups (suspected insulin-resistant cattle, n = 7; suspected non-insulin-resistant cattle, 7) on the basis of persistent hyperinsulinemia during the postoperative period. Seven days after surgery, the abomasoduodenal myoelectric patterns were still significantly lower for the insulin-resistant cows, compared with patterns for the non-insulin-resistant cows. CONCLUSIONS AND CLINICAL RELEVANCE: Insulin resistance appears to be common in cows with an LDA. Analysis of results of this study reveals that abomasal atony in cows with an LDA depends on persistence of high serum concentrations of insulin. Results of this study could provide an explanation for a pathogenetic factor of LDAs and the frequent relapses of cattle affected by this condition.
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College students of either androgynous or sex-typed orientation were randomly assigned to either an insoluble concept-formation task or a solvable one. Posttreatment scores were compared for measures of dysphoric mood (Multiple Affect Adjective List), electromyographic responses (corrugator and zygomatic), and discrete facial responses (Facial Action Coding System). In Study 1, 18 androgynous women were compared to 16 feminine women; in Study 2, 16 androgynous men were compared to 16 masculine men. The insoluble task was associated with more corrugator activity (frowning) than the solvable task in both studies. Feminine women displayed more corrugator responses across both tasks than androgynous women. However, masculine men did not differ from androgynous men in over-all corrugator response activity. Androgynous women smiled more than feminine women on the facial action coding measure. Men subjected to the insoluble task reported significantly more anxiety, depression, and hostility. Masculine men scored higher on anxiety during the insoluble task than androgynous men, while the latter scored somewhat higher on anxiety in the other condition.
Peripheral finger temperature, frontalis and upper trapezius EMG, and self-report of arousal were assessed for four subjects during abdominal and thoracic breathing in a single-subject reversal design. Two subjects displayed significant differences between abdominal and thoracic breathing conditions; one for frontalis EMG, trapezius EMG, and self-report of arousal and one for trapezius EMG. Two subjects showed no significant effects. All subjects reached performance criteria during training sessions. Abdominal breathing performance during reversals was 100% and 92% of sampled breath cycles for the two subjects who showed significant change, and 65% and 42% for the two subjects who showed none. Methodological issues for measurement of breathing patterns and peripheral skin temperature are discussed.
EMG recordings, typically obtained in biofeedback training sessions, tend to underestimate actual muscle activity in overweight and female pain patients. If unadjusted, these measures will likely result in erroneous diagnostic conclusions.
20 subjects' palatability reports and facial electromyographic (EMG) activities at the zygomaticus major, corrugator supercilli, and levator labii (superioris/alaeque nasi) regions were recorded while they were tasting water or pickle juice. The results showed that subjects reported significantly higher ratings of palatability to water than to pickle juice. The EMG activities at the levator labii region generated significantly higher power than those at the corrugator supercilli region while tasting water. The EMG activities at the levator labii region generated significantly higher power than those at the corrugator supercilli region and those at the zygomaticus major region while tasting pickle juice. It was concluded that the facial EMG activity at the levator labii region was the most sensitive indicator of palatability.
STUDY DESIGN: Prospective single-group repeated-measures design. OBJECTIVE: To use electromyographic (EMG) analysis during muscle testing to determine if there is a difference in function of the upper and lower parts of the serratus anterior (SA) muscle. BACKGROUND: The SA muscle is a very important scapular protractor and upward rotator. Authors have anatomically described the muscle as being divided into 2 or 3 parts, and have suggested that the upper part is more suited for protraction and the lower part for upward rotation of the scapula. METHODS AND MEASURES: Surface electrodes recorded EMG activity of the upper and lower parts of the SA muscle during 9 different muscle tests in 29 healthy subjects. RESULTS: Three muscle tests demonstrated significantly greater (P<.05) EMG activity in the lower part of the SA as compared to the upper part. There was no significant difference in the EMG activity of the upper and lower parts of the SA when the other 6 muscle tests were analyzed. CONCLUSION: When upward rotation was the primary position of the scapula during the muscle tests, the lower part of the SA was activated to a greater degree than the upper part. Muscle tests with maximum scapular protraction with varying degrees of upward rotation produced EMG activity with no significant difference when comparing the upper and lower parts of the SA. This information may be helpful for clinicians when muscle testing and developing exercise programs for the SA muscle.
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