China
Africa
Explore chapters and articles related to this topic
Second Stage Of Labor
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
The Valsalva maneuver is ordinarily associated with relaxation of the levator ani muscle, which expands around the presenting fetus; but in some women Valsalva produces levator ani muscle contraction, which is referred to as levator ani muscle coactivation. This has been demonstrated by transperineal ultrasound. In one prospective study, transperineal ultrasound in the second stage of labor was used to measure levator ani muscle coactivation in a group of nulliparous women undergoing labor induction to assess labor outcomes and duration. Women with levator ani muscle coactivation had significantly longer active second-stage duration (about 32 minutes). There was no significant difference between women who underwent operative delivery when compared with the SVD group in the prevalence of levator ani muscle coactivation [18]. In summary, women with levator ani coactivation have a longer second stage but no difference in SVD rate.
Rowing and Sculling Mechanics
Published in Christopher L. Vaughan, Biomechanics of Sport, 2020
Antonio Dal Monte, Andrzej Komor
Based on these studies, the initial optimum position as well as the optimum muscle coactivation was easily found in a few interactive steps, and an improvement of approximately 5% of the performance index was found with respect to a real motion pattern of studied power (IPreal = 487, IPopt = 507).
Development of Neuromuscular Coordination with Implications in Motor Control
Published in Mark De Ste Croix, Thomas Korff, Paediatric Biomechanics and Motor Control, 2013
Eleftherios Kellis, Vassilia Hatzitaki
Muscle activation is regulated by neural mechanisms of central and peripheral origin. With regard to peripheral neural mechanisms, it is known that in the typical adult, a sudden change in muscle stretch causes firing of Ia afferent fibres, which are excitatory on the agonist alpha motoneuron by way of a monosynaptic connection in the spinal cord and inhibitory on the antagonist alpha motoneuron through an inhibitory interneuron in the spinal cord (Myklebust et al. 1986). It is not known whether this chain of events occurs similarly in the developing child; in most cases, we assume that reflexes of this type hold true for children as well. The simultaneous facilitation of the agonist muscle and inhibition of the antagonist muscle is called reciprocal inhibition. From a mechanical point of view, the presence of high muscle coactivation from muscles that act in opposite directions (antagonistic muscles) around a joint will determine the moment of force exerted around the joint and, in turn, the characteristics of joint movement. The higher the coactivation of the agonists and antagonists, the less the resultant joint moment (Kellis 2003). Consequently, changes in muscle coactivation provide useful information regarding neuromuscular development in children, which is also essential for joint stability (see Chapter 11).
A potential upper motor neuron measure of bulbar involvement in amyotrophic lateral sclerosis using jaw muscle coherence
Published in Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration, 2021
Functional muscle coupling allows for synergistic muscle coactivations, which simplifies the motor control task to facilitate the generation of fast movement (5,33). This is supported by our findings which associated the disrupted muscle coupling, as indicated by decreased intermuscular coherence, with increased jaw acceleration time and reduced speaking rate. Among different functionally related muscle pairs, the coherence for the masseter–digastric pair showed the strongest correlation with speech performance, suggesting that disrupted functional coupling between jaw antagonists may underlie the slowness of speech—a well-established bulbar sign in ALS (12,14,15,17,19). This finding is in line with the mechanical role of jaw antagonists in stabilizing the temporomandibular joint and increasing jaw frequency response (34).
How Has Electromyography Been Used to Assess Reaching in Infants? A Systematic Review
Published in Journal of Motor Behavior, 2021
Mariana Vieira da Fonseca, Ana Letícia de Souza Oliveira, Roberta de Matos Figueiredo, Rosana Tannús Freitas Lima, Aline Martins de Toledo
According to the results previously described, it can be surmised that electromyography was useful for broadening the understanding of aspects involved in a complex activity such as reaching. Although studies address similar analyses of muscle dynamics (degree of activation, muscle fiber recruitment, muscle coactivation, among others), their interpretations go beyond simply recording muscle activity in infants during reaching. The use of electromyography provided a better understanding of the dynamics between upper limb muscles, from the beginning of reaching acquisition to the early months of practice of this skill. In addition, EMG findings was helpful to elucidate the contribution of primary motor muscle (i.e., biceps brachii) and its role in improving the performance of reaching. Finally, EMG contributed to understanding the influence of posture on muscle coactivation, demonstrating an advantage of the sitting position compared with the supine position, when the therapeutic goal is to improve biceps-triceps coactivation.
Functional Behavior Assessment of the Unintentional Discharge of Firearms in Law Enforcement
Published in Journal of Organizational Behavior Management, 2018
Table 2 displays percentage of total UDs and percentage of total injuries, respectively, for each subcategory of six antecedent classes. In some cases, reports contained evidence of more than one antecedent class and subcategory. Data for within-class percentages were as follows: Routine firearm tasks (n = 162) included clearing (34.0% and 20.6%), function checks (24.1% and 11.8%), holstering/unholstering (17.9% and 38.2%), storing/moving (14.2% and 14.7%), and conducting maintenance (9.9% and 14.7%). Muscle coactivation (n = 74) included a loss of balance (28.4% and 28.6%), use of the other hand (20.3% and 42.9%), a loss of grip (20.3% and 19.0%), the use of another finger (18.9% and 4.8%), use of a leg (10.8% and 0.0%), and use of other arm (1.4% and 4.8%). Unfamiliar firearm tasks (n = 37) included those involving unfamiliar firearms (43.2% and 66.7%), hand transfers (27.0% and 0.0%), holsters/belts (13.5% and 33.3%), arm/hand crossovers (10.8% and 0.0%), and changes in equipment location (5.4% and 0.0%). Contact with objects (n = 16) included inanimate objects (53.8% and 50%), officer’s apparel (30.8% and 30%), and animate objects (15.4% and 20%). Startle stimuli (n = 6) were visual (50.0% and 100%), auditory (33.3% and 0.0%), and somesthetic (16.7% and 0.0%) in nature. Vestibular-induced startle stimuli were not reported. Medical conditions (n = 1) involved one instance of a seizure. Twitch/tremor was not reported.