Extended visuomotor experience with inverted movements can overcome the inversion effect in biological motion perception.

Studies have demonstrated that perceiving human and animal movements as point-light displays is effortless. However, simply inverting the display can significantly impair this ability. Compared to non-dancers and typical dancers, vertical dancers have the unique experience of observing and performing movements upside down as being suspended in the air. We studied whether this unique visuomotor experience makes them better at perceiving the inverted movements. We presented ten pairs of dance movements as point-light displays. Each pair included a version performed on the ground whereas the other was in the air. We inverted the display in half of the trials and asked vertical dancers, typical dancers, and non-dancers about whether the display was inverted. We found that only vertical dancers, who have extended visual and motor experience with the configural and dynamic information of the movements, could identify the inversion of movements performed in the air. Neither typical dancers nor non-dancers, who have no motor experience with performing the inverted movements, could detect the inversion. Our findings suggest that motor experience plays a more critical role in enabling the observers to use dynamic information for identifying artificial inversion in biological motion.

The effects of mid-flight whole-body and trunk rotation on landing mechanics: implications for anterior cruciate ligament injuries.

The purpose was to quantify the effects of mid-flight whole-body and trunk rotation on knee mechanics in a double-leg landing. Eighteen male and 20 female participants completed a jump-landing-jump task in five conditions: no rotation, testing leg ipsilateral or contralateral (WBRC) to the whole-body rotation direction, and testing leg ipsilateral (TRI) or contralateral to the trunk rotation direction. The WBRC and TRI conditions demonstrated decreased knee flexion and increased knee abduction angles at initial contact (2.6 > Cohen's dz > 0.3) and increased peak vertical ground reaction forces and knee adduction moments during the 100 ms after landing (1.7 > Cohen's dz > 0.3). The TRI condition also showed the greatest knee internal rotation angles at initial contact and peak knee abduction and internal rotation angles and peak knee extension moments during the 100 ms after landing (2.0 > Cohen's dz > 0.5). Whole-body rotation increased contralateral knee loading because of its primary role in decelerating medial-lateral velocities. Trunk rotation resulted in the greatest knee loading for the ipsilateral knee due to weight shifting and mechanical coupling between the trunk and lower extremities. These findings may help understand altered trunk motion in anterior cruciate ligament injuries.

Mid-flight lateral trunk bending increased ipsilateral leg loading during landing: a center of mass analysis.

Increased lateral trunk bending to the injured side has been observed when ACL injuries occur. The purpose was to quantify the effect of mid-flight lateral trunk bending on center of mass (COM) positions and subsequent landing mechanics during a jump-landing task. Forty-one recreational athletes performed a jump-landing task with or without mid-flight lateral trunk bending. When the left and right trunk bending conditions were compared with the no trunk bending condition, participants moved the COM of the upper body to the bending direction, while the COM of the pelvis, ipsilateral leg, and contralateral leg moved away from the bending direction relative to the whole body COM. Participants demonstrated increased peak vertical ground reaction forces (VGRF) and knee valgus and internal rotation angles at peak VGRF for the ipsilateral leg, but decreased peak VGRF and knee internal rotation angles at peak VGRF and increased knee varus angles at peak VGRF for the contralateral leg. Mid-flight lateral trunk resulted in an asymmetric landing pattern associated with increased ACL loading for the ipsilateral leg. The findings may help to understand altered trunk motion during ACL injury events and the discrepancy in ACL injuries related to limb dominance in badminton and volleyball.

The Effect of Footwear on Free Moments During a Rotational Movement in Country Swing Dance.

Footwear in dance has been studied for support and cushioning, but little research has been conducted on free moments, which may result from high frictional coefficients. Conversely, insufficient friction between shoes and floors may increase the risk of falls and compromise dance performance. The purpose of this study was to examine the effect of different types of footwear with different coefficients of friction on peak and average free moments during a rotational movement in country swing dance. Fifteen country swing dancers completed a rotational movement under four footwear conditions: barefoot, rubber-bottom boots, leather-bottom boots, and running shoes. The peak and average free moments applied to the left and right legs were measured using two force plates. Coefficients of static friction between different shoes and force plate surfaces were quantified and found to be greater for the rubber-bottom boots and running shoes than the leather-bottom boots. For the left (push off) leg, free moments were greater for the running shoe and rubber-bottom boot conditions compared to the barefoot and leather-bottom boot conditions. For the right (rotating) leg, free moments were greatest for the running shoe condition, second greatest for the barefoot and rubber-bottom boot conditions, and least for the leather-bottom boot condition. The leatherbottom boots may decrease twisting loads resulting from free moments. Coefficients of friction and free moments should be considered for future longitudinal studies to investigate potential cause-effect relationships among footwear, potential for injury, and dance performance.

Lower-Extremity Kinematics Differed Between a Controlled Drop-Jump and Volleyball-Takeoffs.

Previous studies utilizing jump-landing biomechanics to predict anterior cruciate ligament injuries have shown inconsistent findings. The purpose of this study was to quantify the differences and correlations in jump-landing kinematics between a drop-jump, a controlled volleyball-takeoff, and a simulated-game volleyball-takeoff. Seventeen female volleyball players performed these 3 tasks on a volleyball court, while 3-dimensional kinematic data were collected by 3 calibrated camcorders. Participants demonstrated significantly increased jump height, shorter stance time, increased time differences in initial contact between 2 feet, increased knee and hip flexion at initial contact and decreased peak knee and hip flexion for both left and right legs, and decreased knee-ankle distance ratio at the lowest height of midhip for the 2 volleyball-takeoffs compared with the drop-jump (P < .05, Cohen's dz ≥ 0.8). Significant correlations were observed for all variables between the 2 volleyball-takeoffs (P < .05, ρ ≥ .6) but were not observed for most variables between the drop-jump and 2 volleyball-takeoffs. Controlled drop-jump kinematics may not represent jump-landing kinematics exhibited during volleyball competition. Jump-landing mechanics during sports-specific tasks may better represent those exhibited during sports competition and their associated risk of anterior cruciate ligament injury compared with the drop-jump.

Effects of timing of signal indicating jump directions on knee biomechanics in jump-landing-jump tasks.

A variety of the available time to react (ATR) has been utilised to study knee biomechanics during reactive jump-landing tasks. The purpose was to quantify knee kinematics and kinetics during a jump-land-jump task of three possible directions as the ATR was reduced. Thirty-four recreational athletes performed 45 trials of a jump-land-jump task, during which the direction of the second jump (lateral, medial or vertical) was indicated before they initiated the first jump, the instant they initiated the first jump, 300 ms before landing, 150 ms before landing or at the instant of landing. Knee joint angles and moments close to the instant of landing were significantly different when the ATR was equal to or more than 300 ms before landing, but became similar when the ATR was 150 ms or 0 ms before landing. As the ATR was decreased, knee moments decreased for the medial jump direction, but increased for the lateral jump direction. When the ATR is shorter than an individual's reaction time, the movement pattern cannot be pre-planned before landing. Knee biomechanics are dependent on the timing of the signal and the subsequent jump direction. Precise control of timing and screening athletes with low ATR are suggested.

Tattoos of the Head, Neck and Hands.

Tattooing is ancient and gaining popularity in present day society. While many tattoos are decorative body art, certain tattoos of the head, neck and hands may provide helpful insights into, among other traits, the personality, beliefs or orientation of an individual.

Relationship Between Force Production During Isometric Squats and Knee Flexion Angles During Landing.

Decreased knee flexion angles during landing are associated with increased anterior cruciate ligament loading. The underlying mechanisms associated with decreased self-selected knee flexion angles during landing are still unclear. The purpose of this study was to establish the relationship between the peak force production at various knee flexion angles (35, 55, 70, and 90°) during isometric squats and the actual knee flexion angles that occur during landing in both men and women. A total of 18 men and 18 women recreational/collegiate athletes performed 4 isometric squats at various knee flexion angles while vertical ground reaction forces were recorded. Participants also performed a jump-landing-jump task while lower extremity kinematics were collected. For women, significant correlations were found between the peak force production at 55 and 70° of knee flexion during isometric squats and the knee flexion angle at initial contact of landing. There were also significant correlations between the peak force production at 55, 70, and 90° of knee flexion during isometric squats and the peak knee flexion angle during landing. These correlations tended to be stronger during isometric squats at greater knee flexion compared with smaller knee flexion. No significant correlations were found for men. Posture-specific strength may play an important role in determining self-selected knee flexion angles during landing for women.

The effect of time-of-day on static and dynamic balance in recreational athletes.

The purpose of this study was to investigate the effect of time-of-day (morning vs. afternoon) on static and dynamic balance in recreational athletes. A total of 34 recreational athletes completed the single-leg stance test with or without eyes open, lower quarter Y-balance test, upper quarter Y-balance test, and single-leg landing balance test in a random order in the morning (7:00-10:00 am) and afternoon (3:00-6:00 pm) for two consecutive days. Compared with the morning, participants demonstrated decreased centre of pressure (COP) sway areas (p = 0.002; Cohen's d (d) = 0.28) and sway speeds (p = 0.002; d = 0.17) during the eyes-open single-leg stance test, increased stance time (p = 0.031; d = 0.16) and decreased COP sway areas (p = 0.029; d = 0.22) during the eyes-closed single-leg stance test, and increased reaching distances (p = 0.024; d = 0.10) during the upper quarter Y-balance test in the afternoon. The between-day effect (day 1 vs. day 2) was observed for several parameters. Time-of-day had a minimal effect on dynamic balance and a noticeable effect on static balance. Time-of-day may be considered as a factor in designing balance training programmes and intervention studies for recreational athletes.

Generation of vertical angular momentum in single, double, and triple-turn pirouette en dehors in ballet.

The purpose of this study was to investigate the vertical angular momentum generation strategies used by skilled ballet dancers in pirouette en dehors. Select kinematic parameters of the pirouette preparation (stance depth, vertical center-of-mass motion range, initial shoulder line position, shoulder line angular displacement, and maximum trunk twist angle) along with vertical angular momentum parameters during the turn (maximum momentums of the whole body and body parts, and duration and rate of generation) were obtained from nine skilled collegiate ballet dancers through a three-dimensional motion analysis and compared among three turn conditions (single, double, and triple). A one-way ('turn') multivariate analysis of variance of the kinematic parameters and angular momentum parameters of the whole body and a two-way analysis of variance ('turn' × 'body') of the maximum angular momentums of the body parts were conducted. Significant 'turn' effects were observed in the kinematic/angular momentum parameters (both the preparation and the turn) (p <  0.05). As the number of turns increased, skilled dancers generated larger vertical angular momentums by predominantly increasing the rate of momentum generation using rotation of the upper trunk and arms. The trail (closing) arm showed the largest contribution to whole-body angular momentum followed by the lead arm.

Effect of selected mouthwashes with and without toothbrushing on the surface hardness of a resin modified glass-ionomer and two compomers.

OBJECTIVES: Physical properties of some restorative dental materials can change as a result of exposure to mouthwashes and toothbrushing. The purpose of this laboratory study was to investigate the possible effects of three commercially available mouthwashes on the surface hardness and weight of a resin modified glass-ionomer and two compomers when used with and without tooth brushing. METHODS: Specimens of the restorative materials in the study (Vitremer, Compoglass and Dyract) were prepared. Half of the specimens were only exposed to a mouthwash (Plax, Macleans, Listerine, Corsodyl or deionised water as control). The remaining specimens were exposed to one of the mouthwashes in conjunction with tooth brushing. The initial surface hardness and the surface hardness after 24 weeks were assessed using a Wallace hardness testing instrument. The specimens were assessed for possible weight changes between baseline and 24 weeks using a digital balance. RESULTS: Mouthwash only: The Wallace hardness values of Vitremer and Compoglass increased in all groups. For Vitremer the increase was significantly higher in Macleans group in comparison with the control, Listerine and Corsodyl groups (P<0.05). For Compoglass the increase in Plax and Macleans groups were significantly higher compared with the control group (P<0.05). Dyract specimens revealed an increase in Wallace hardness values in all test groups whilst the control group revealed a decrease (P<0.05 except for Plax). Mouthwash and toothbrushing. Wallace hardness for all materials increased. The difference was not significant between groups (P>0.05). Weighing the specimens of Vitremer revealed that after 24 weeks exposure to mouthwash and toothbrushing some groups had lost weight while an increase in weight was observed in others (P>0.05). For Compoglass and Dyract, all groups had lost weight after 24 weeks (P>0.05). SIGNIFICANCE: Exposure of the materials investigated in this study to the mouthwashes and toothbrushing had adverse effects on surface hardness. The adverse effects were more apparent when the mouthwashes were used alone.

Teaching "doctoring": a model curriculum for family medicine.

The authors present a model of an interdisciplinary, longitudinal (lifecycle), generalist "doctoring" course that spans the first 2 years of osteopathic medical education and training. This course is intended to run concurrently with a nongeneralist curriculum and to link this curriculum sequentially. The educational topics and objectives show a unique alignment with anatomy and osteopathic principles. The course encompasses (1) logical sequencing of curricular content; (2) a strong interconnection between the didactic and clinical practice experiences throughout the continuum of education and training; (3) additional exposure to clinical applications during the early and formative stages of medical education; and (4) additional coverage of specific clinical competency areas.

Effect of selected mouthwashes on the surface roughness of resin modified glass-ionomer restorative materials.

OBJECTIVES: It is known that the use of mouthwashes and toothbrushing can affect some restorative dental materials. The purpose of this laboratory study was to investigate the effect of four commercially available mouthwashes on the surface roughness of a number of resin modified glass-ionomer restorative materials when used with and without tooth brushing. METHODS: Specimens of the restorative materials in the study (Vitremer, Compoglass and Dyract) were prepared. Half of the specimens were only exposed to a mouthwash (Plax, Macleans, Listerine, Corsodyl or deionised water as control). The remaining specimens were exposed to one of the mouthwashes in conjunction with tooth brushing. The initial surface roughness and the subsequent changes in surface roughness were assessed by scanning electron microscopy (SEM) and profilometry. The assessment times were: baseline, 4, 12 and 24 weeks. RESULTS: Initial SEM observations of the surface morphology of the specimens revealed a rougher surface for Vitremer in comparison to the other two materials. Assessments at increasing time intervals showed that specimens exposed to a mouthwash only appeared to become rougher. The appearance of specimens exposed to mouthwash and brushing seemed to become even rougher with increasing time. The results of the profilometric assessment showed that at 24 weeks, specimens exposed to mouthwash only, had an overall increase in the surface roughness values for all three materials investigated. The differences between groups allocated to different mouthwashes were not however statistically significant (P>0.05). Exposure to mouthwash and toothbrushing over the same time period resulted in an increase in roughness values in all groups. The differences between mouthwash groups were not statistically significant at this stage (P>0.05). SIGNIFICANCE: Exposure of the materials investigated to the mouthwashes included in the study had adverse effects on surface roughness. The adverse effects were more pronounced with tooth brushing.

Two-centre evaluation of a resin composite/ self-etching restorative system: three-year findings.

PURPOSE: This two-centre study evaluated the clinical performance of Class I and Class II restorations of the giomer material Beautifil, placed using Fluorobond, a self-etching adhesive system, to determine the suitability of the test system as an alternative for the restoration of posterior teeth. MATERIALS AND METHODS: A total of 108 restorations, comprising 72 Class II and 36 Class I restorations, was placed predominantly in molars (82%). Evaulations using modified USPHS/Ryge criteria were conducted at baseline and thereafter at 6 months and 1, 2, and 3 years. Die stone replicas of the restored teeth were examined retrospectively. RESULTS: A total of 5 restorations was found to fail during the study-- 3 in the first year and 2 during the third year of the study. Occlusal marginal adaptation was less than ideal at baseline in 11% of cases, primarily as a consequence of overcontouring, as observed in the die stone replicas. The combined percentage Alpha ratings at 3 years were: colour match, 98%; marginal adaptation (occlusal), 78%; marginal adaptation (proximal), 97%; anatomic form (occlusal), 99%; anatomic form (proximal), 95%; surface roughness (occlusal), 100%; surface roughness (proximal), 100%; marginal staining (occlusal), 90%; marginal staining (proximal) 81%; interfacial staining (occlusal), 99%; interfacial staining (proximal), 100%; contacts (occlusal), 95%; contacts (proximal), 93%; sensitivity, 100%; secondary caries, 100%; lustre of restoration, 100%. CONCLUSION: It is concluded that the 3-year performance of Fluorobond-bonded Beautifil for Class I and II restorations demonstrated some marginal changes, but most of the direct evaluation ratings were > 90% Alpha, with the performance observed being similar in the two centres.

Quality of removable partial dentures worn by the adult U.S. population.

STATEMENT OF PROBLEMS: Research-based assessments of the quality of removable partial dentures (RPDs), especially within a large patient population, are lacking. PURPOSE: This study evaluated the prevalence and quality of RPDs by use of the National Health and Nutrition Survey (NHANES III) data set. MATERIAL AND METHODS: Estimates of the health and nutritional status of the American population were obtained from the NHANES III data set (1988-1994). Calibrated dentists performed dental examinations on 17,884 adults. If the subject wore an RPD, its quality was assessed with 5 criteria: integrity, tooth wear, the presence of temporary reline material or adhesive, stability, and retention. In this study, the data on RPD defects were used to assess the prevalence of problems. The original population was divided into 4 subgroups: paired RPD data = subjects wearing both maxillary and mandibular RPDs (n = 600 prostheses, 300 maxillary and 300 mandibular); single RPD data = subjects with only one RPD (n = 1003 prostheses, 511 maxillary and 492 mandibular); maxillary versus mandibular RPD data = all subjects with all RPDs (n = 1603 prostheses, 811 maxillary and 792 mandibular); and pooled RPD data = all subjects with a single RPD plus subjects with 2 RPDs, counting only the RPD with the most defects (n = 1303 prostheses, 674 maxillary and 629 mandibular). The subjects were analyzed with descriptive statistics. The distribution of defects in the RPDs was examined for possible associations with chi(2) tests. The paired data for patients with both maxillary and mandibular RPDs were analyzed with Wilcoxon signed rank tests. The prevalence of RPDs as a function of patient age and the association between RPD defects and patient age were analyzed with chi(2) tests. The results were considered highly significant at P<.0001 and significant at P<.05. RESULTS: Of the 17,884 adults who underwent a dental examination, 1306 had RPDs. Three patients were excluded because their records were incomplete, leaving 1303 patients available for analysis. Most of the prostheses examined (65%) had at least 1 defect. Lack of stability was the most prevalent single defect. Distinctions in the type and prevalence of defects were observed between mandibular and maxillary RPDs. Mandibular RPDs had significantly more problems related to retention, whereas maxillary RPDs had significantly more problems related to the presence of reline material and to integrity defects. Tooth wear defects were significantly associated with patient age (P<.0001). Only one third of the RPDs were considered satisfactory according to NHANES III criteria. CONCLUSION: A review of the database used in this study indicated that, in spite of a decline in tooth loss, RPDs are still used in all age cohorts, including young adults. A large number of RPDs were found to have defects.