Relationships between the magnitude of representational momentum and the spatial and temporal anticipatory judgments of opponent’s kicks in taekwondo

For successful actions in a fast, dynamic environment such as sports, a quick successful anticipation of a forthcoming environmental state is essential. However, the perceptual mechanisms involved in successful anticipation are not fully understood. This study examined the relationships between the magnitude of representational momentum (RM) as a forward displacement of the memory representation of the final position of a moving object (which implies that observers perceptually “see” a near future forthcoming dynamic environmental state) and the temporal and spatial anticipatory judgments of the opponent’s high or middle kicks in taekwondo. Twenty-seven participants (university taekwondo club members and non-members) observed video clips of taekwondo kicks that vanished at one of 10 frame positions prior to the kick impact and performed three tasks consecutively: anticipatory coincidence timing (CT) with the arrival of kick impact, judgment of the kick type (high and middle kicks) by forced choice, and judgment of the vanishing frame position (measuring RM). Our results showed significant group effects for the number of correct kick-type judgments and the judgment threshold for kick-type choice (kick-typeJT), which was estimated in terms of individual psychometric function curves. A significant correlation was found between the magnitude of RM (estimated at kick-typeJT) and kick-typeJT, but not between the CT errors (estimated at kick-typeJT) and kick-typeJT. This indicates that the magnitude of RM may play an influential role in quick kick-type judgments, but not in coincidence timing while observing an opponent’s kick motion. These findings suggest that subjective anticipatory perception or judgment of the future spatial state is vital to anticipatory actions under severe time constraints

Data_Sheet_1_Relationships between the magnitude of representational momentum and the spatial and temporal anticipatory judgments of opponent’s kicks in taekwondo.docx

For successful actions in a fast, dynamic environment such as sports, a quick successful anticipation of a forthcoming environmental state is essential. However, the perceptual mechanisms involved in successful anticipation are not fully understood. This study examined the relationships between the magnitude of representational momentum (RM) as a forward displacement of the memory representation of the final position of a moving object (which implies that observers perceptually “see” a near future forthcoming dynamic environmental state) and the temporal and spatial anticipatory judgments of the opponent’s high or middle kicks in taekwondo. Twenty-seven participants (university taekwondo club members and non-members) observed video clips of taekwondo kicks that vanished at one of 10 frame positions prior to the kick impact and performed three tasks consecutively: anticipatory coincidence timing (CT) with the arrival of kick impact, judgment of the kick type (high and middle kicks) by forced choice, and judgment of the vanishing frame position (measuring RM). Our results showed significant group effects for the number of correct kick-type judgments and the judgment threshold for kick-type choice (kick-typeJT), which was estimated in terms of individual psychometric function curves. A significant correlation was found between the magnitude of RM (estimated at kick-typeJT) and kick-typeJT, but not between the CT errors (estimated at kick-typeJT) and kick-typeJT. This indicates that the magnitude of RM may play an influential role in quick kick-type judgments, but not in coincidence timing while observing an opponent’s kick motion. These findings suggest that subjective anticipatory perception or judgment of the future spatial state is vital to anticipatory actions under severe time constraints.</p

Safety and efficacy of microwave endometrial ablation for patients with previous uterine surgery: a pilot study

MEA (microwave endometrial ablation) is a treatment that can control hypermenorrhea. With the increase in the number of caesarean sections and myomectomies, an increasing number of patients with MEA have undergone previous incision of the uterine myometrium. Uterine perforation is major complication. Here we compared the incidence of complications and recurrence between groups with or without previous uterine surgery. 35 patients who underwent MEA were enrolled in the study. We assessed the thickness of uterine myometrium by MRI and transvaginal ultrasonography (TV-US). 12 patients (34%) had previous uterine surgery; Among 12 patients with previous uterine surgery, 6 (50%) showed thinning of the myometrium. No patient showed any complications. There was no difference in recurrence rate between two groups (1/12 = 8% and 2/23 = 8%, respectively). MEA can be performed safely and effectively even for patients with previous uterine surgery.IMPACT STATEMENT What is already known on this subject? MEA (microwave endometrial ablation) is a treatment that can control hypermenorrhea.A few serious complications have been reported, including uterine perforation and intestinal injury. There have been no collective reports on women with a history of uterine surgery, and the decision to perform MEA and the detailed procedures have not been clarified. What do the results of this study add? No patient who received MEA showed any complication regardless of previous uterine surgery. There was no difference in recurrence rate of hypermenorrhea between groups with and without previous uterine surgery. MEA could be performed safely and effectively in patients with previous uterine surgery preoperative imaging and intraoperative ultrasounds What are the implications of these findings for clinical practice and/or further research? Curently, with the increase in the number of caesarean sections and myomectomies, the increasing number of patients with MEA have undergone previous incision of the uterine myometrium and this causes thinning of the myometrium. MEA can be safely performed without losing any therapeutic effect, even in patients with a history of uterine surgery, by using MRI and TV-US as preoperative evaluations

Enhancement of force generated by individual myosin heads in skinned rabbit psoas muscle fibers at low ionic strength.

Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca(2+)-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have examined the effect of low ionic strength on the mechanical properties and the contraction characteristics of skinned rabbit psoas muscle fibers in both relaxed and maximally Ca(2+)-activated states. By progressively decreasing KCl concentration from 125 mM to 0 mM (corresponding to a decrease in ionic strength μ from 170 mM to 50 mM), relaxed fibers showed changes in mechanical response to sinusoidal length changes and ramp stretches, which are consistent with the idea of actin-myosin linkage formation at low ionic strength. In maximally Ca(2+)-activated fibers, on the other hand, the maximum isometric force increased about twofold by reducing KCl concentration from 125 to 0 mM. Unexpectedly, determination of the force-velocity curves indicated that, the maximum unloaded shortening velocity Vmax, remained unchanged at low ionic strength. This finding indicates that the actin-myosin linkages, which has been detected in relaxed fibers at low ionic strength, are broken quickly on Ca(2+) activation, so that the linkages in relaxed fibers no longer provide any internal resistance against fiber shortening. The force-velocity curves, obtained at various levels of steady Ca(2+)-activated isometric force, were found to be identical if they are normalized with respect to the maximum isometric force. The MgATPase activity of muscle fibers during isometric force generation was found not to change appreciably at low ionic strength despite the two-fold increase in Ca(2+)-activated isometric force. These results can be explained in terms of enhancement of force generated by individual myosin heads, but not by any changes in kinetic properties of cyclic actin-myosin interaction

Definite differences between in vitro actin-myosin sliding and muscle contraction as revealed using antibodies to myosin head.

Muscle contraction results from attachment-detachment cycles between myosin heads extending from myosin filaments and actin filaments. It is generally believed that a myosin head first attaches to actin, undergoes conformational changes to produce force and motion in muscle, and then detaches from actin. Despite extensive studies, the molecular mechanism of myosin head conformational changes still remains to be a matter for debate and speculation. The myosin head consists of catalytic (CAD), converter (CVD) and lever arm (LD) domains. To give information about the role of these domains in the myosin head performance, we have examined the effect of three site-directed antibodies to the myosin head on in vitro ATP-dependent actin-myosin sliding and Ca2+-activated contraction of muscle fibers. Antibody 1, attaching to junctional peptide between 50K and 20K heavy chain segments in the CAD, exhibited appreciable effects neither on in vitro actin-myosin sliding nor muscle fiber contraction. Since antibody 1 covers actin-binding sites of the CAD, one interpretation of this result is that rigor actin-myosin linkage is absent or at most a transient intermediate in physiological actin-myosin cycling. Antibody 2, attaching to reactive lysine residue in the CVD, showed a marked inhibitory effect on in vitro actin-myosin sliding without changing actin-activated myosin head (S1) ATPase activity, while it showed no appreciable effect on muscle contraction. Antibody 3, attaching to two peptides of regulatory light chains in the LD, had no significant effect on in vitro actin-myosin sliding, while it reduced force development in muscle fibers without changing MgATPase activity. The above definite differences in the effect of antibodies 2 and 3 between in vitro actin-myosin sliding and muscle contraction can be explained by difference in experimental conditions; in the former, myosin heads are randomly oriented on a glass surface, while in the latter myosin heads are regularly arranged within filament-lattice structures

Dependence of relaxed muscle fiber stiffness on ionic strength.

<p>Stiffness values of relaxed muscle fibers were obtained by applying sinusoidal length changes (peak-to-peak amplitude, 0.5% of Lo; frequency, 2 kHz), and the values relative to the value at 125 mM KCl are plotted against KCl concentration of experimental solution. Vertical bars represent S.E.M. (n = 5). The stiffness measurements were made in a random sequence.</p

Simultaneous recordings of MgATPase activity and isometric force in maximally Ca²⁺-activated muscle fibers.

<p>MgATPase activity (upper traces) and isometric force (lower traces) obtained from one and the same fiber at 125 mM KCl (A) and at 0 mM KCl (B). Note that the slope of MgATPase records does not differ markedly between the two records, despite the twofold increase of isometric force.</p