1,720,991 research outputs found
Visual Strategies Underpinning the Spatiotemporal Demands During Visuomotor Tasks in Predicting Ball Direction
Full text linkWe investigated gaze behavior of expert goalkeepers during the prediction of penalty kicks in different spatiotemporal constraints: penalties taken from 11 and 6 m. From 11 m, goalkeepers were more successful in predicting ball direction, with longer movement time initiation and a visual strategy with more fixations and greater saccade rates than penalties from 6 m, where they exhibited fewer fixations with higher microsaccade rates. As long as the opponent’s distance is large and time pressure low, gaze can be frequently shifted between the kicker’s body and the ball, due to the low cost of saccades. Conversely, when the objects are close, there is increased reliance on foveal and parafoveal information. In conclusion, when the spatiotemporal constraint is less severe, goalkeepers adopt a visual strategy with more fixations and small saccades. When the spatiotemporal
constraint is more severe, they rely on peripheral vision to monitor kickers’ movements through the use of microsaccades
Keep Your Eye on the Ball; the Impact of an Anticipatory Fixation During Successful and Unsuccessful Soccer Penalty Kicks
Full text linkThe success of a sporting task requiring an object to be kicked or hit toward a target (e.g., kicking a ball into a goal) is impacted by the length of the Quiet Eye (QE). Limitations in the ocular motor system mean that after impact, these fast moving objects are not tracked using smooth pursuit eye movements. Rather, anticipatory fixations are used to re-fixate ahead of the moving object.Using a soccer penalty kick, the current study investigated whether striking a stationary object to generate high ball velocity results in an anticipatory fixation prior to ball contact and if this occurs at detriment to the QE period and task success.Facing a goalkeeper, 12 participants produced a successful (scored) and unsuccessful (saved) penalty whilst wearing a mobile eye tracker.QE was longer in the successful compared to unsuccessful penalty (p = 0.036) and was due to QE offset ending later in the successful compared to unsuccessful penalty (p = 0.008). An anticipatory fixation occurred later (p = 0.025) and was shorter (p = 0.005) in successful compared to unsuccessful penalties. The football was kicked wider (more accurately) within the goal during the successful compared to unsuccessful penalty (p < 0.001). Results highlight the importance of the QE period in successfully executing a soccer penalty kick. Unsuccessful penalties were associated with shorter QE length and earlier QE offset, which was due to initiating an anticipatory fixation in prediction of tracking the fast moving football, resulting in kicking the ball more centrally in the goal, making it easier for the goalkeeper to save
Understanding the underlying mechanisms of Quiet Eye: The role of microsaccades, small saccades and pupil-size before final movement initiation in a soccer penalty kick
Full text linkExperts keep a steady final fixation at a specific location just before final movement initiation, the so-called “quiet eye” (QE). However, the eyes are rarely “quiet”, and small eye movements occur during visual fixation. The current research investigated the subtle eye movements and underlying mechanisms immediately prior to and during QE. The gaze behaviour of 8 intermediate-level goalkeepers was recorded as they moved (either left or right) in an attempt to predict the future direction of the ball during a soccer penalty kick. Goalkeepers were more likely to predict the direction of the penalty, which was coupled with delaying movement initiation. The temporal sequence of microsaccade rates dropped ∼1000 ms before goalkeepers’ final movement initiation. Saccade rates increased, reaching a peak ∼500 ms before final movement initiation, concomitant with microsaccades reduction. Microsaccades predicted the goalkeepers’ direction, oriented to the right when goalkeepers moved to the right, and conversely to the left when they moved to the left. Microsaccades may be modulated by attention and appear functionally related to saccadic intrusions. Pupil-size increased proportionally with the lead up to the instance of the penalty being kicked, reaching a plateau at final movement initiation. In conclusion, microsaccades and small saccades could improve the perception of the soccer penalty kick, helping athletes during the period that precedes the critical movement initiation, shifting from covert to overt attention for identifying the useful cues necessary to guide the action
The Effect of Central Visual Impairment on Manual Prehension When Tasked with Transporting-to-Place an Object Accurately to a New Location
No full textPurpose.: To investigate whether differences exist between visually impaired and normal vision participants when completing a visually guided manual prehension task of transporting-to-place an object accurately to a new location.
Methods.: Participants with central visual impairment (n = 17) and normal vision (n = 10) were tasked with reaching-to-grasp an object and then transporting-to-place it accurately to a different (predefined) location. Analysis assessed movements of the object transport phase and error in object placement. Correlation analysis assessed the association between the movements and mean loss in the central 5°, 10°, and 20° of participant's integrated binocular visual field (VF), visual acuity (VA), and contrast sensitivity (CS).
Results.: Compared to normal vision participants, visually impaired participants took significantly longer to complete the movement and exhibited increased deceleration time, greater number of velocity corrections, and more errors in object placement (P < 0.05). Findings demonstrated that participants with central visual impairment were more cautious when executing the movement, which contributed to uncertainty regarding end-position location. A higher number of movement indices were correlated with loss in the central 5° compared to the 10° and 20° of the VF. VA and CS were significantly correlated with a number of movement variables.
Conclusions.: Despite the increased time taken by visually impaired participants to complete the task, they were still less accurate than normals when placing the object. Decrements in movement control were most associated with loss in the central 5° when compared to the central 10° and 20° of the VF, which was evidenced in the deceleration/“online” component of the movement
Effects of saddle angle on heavy intensity time trial cycling: Implications of the UCI rule 1.3.014
No full textThe UCI dictates that during sanctioned events, the saddle of the bicycle may be at angle of no more than 3° of forward rotation, so as to prevent performance advantages (Rule 1.3.014). This research investigates the effect on performance when rotating the saddle beyond the mandated angle during a laboratory 4km time trial (TT). Eleven competitive male cyclists (age 26±6 (mean±SD) yrs, height 179.2±6.7 cm, body mass 72.5±6.7 kg; V̇O2max 70.9±8.6 ml∙kg-1∙min-1) completed laboratory 4km TTs using saddle angles of 0°, 3° and 6°. Completion time and mean power were recorded, in addition to lower appendage kinematics, crank torque kinetics and cardiorespiratory responses. There were no significant changes in TT time, power output, cardiorespiratory variables or crank torque kinetics as a function of saddle angle (P>0.05). There were significant effects on minimum and maximum hip angle and the horizontal displacement of the greater trochanter (P<0.05). At 6° the maximum hip angle and forward displacement of the greater trochanter was greater compared to 0° and 3°. Minimum hip angle was greater at 6° than 3° (P<0.05). In conclusion, contravening UCI rule 1.3.014 by using a saddle angle beyond 3° does not result in performance advantages during a laboratory 4 km. However, tilting the saddle does appear to cause a forward displacement of the pelvis leading to an opening of the hip angle at the top and bottom of the pedal stroke
The effects of forward rotation of posture on heavy intensity cycling: Implications of UCI rule 1.3.013
No full textUCI rule 1.3.013 limits the forward displacement of the nose of the saddle to 5cm rearward of the centre of the bottom-bracket. This study tests the effects of contravening this rule on 4km laboratory time trials and highlights biomechanical and physiological responses that could be of interest to coaches and bike fitters. Ten competitive male cyclists age 26±2 (mean±SD) yrs, height 180±5 cm, body mass 71±6 kg; V̇ O2max 70.9±8.6 ml·kg-1·min-1) completed 4km time trials and heavy intensity bouts. Riding posture was rotated forward where the nose of the saddle was 0, 2, 4, and 6cm to the rear of the bottom bracket (P0, P2, P4 and P6). End time, power, cardiorespiratory responses, lower appendage kinematics and crank torque kinetics were measured. There was no significant effect of position on 4 km time trials completion time or power. During 4 km time trials and heavy intensity bouts, gas exchange variables and lower limb range of motion were unchanged (P>0.05). Trunk lean angle, cardiac output and stroke volume were greater at P6 than other positions (P0.05). Results indicate, contravening rule 1.3.013 does not bring about improvements to 4km laboratory TTs. The rearward shift in peak crank torque most likely occurs as a function of altered muscle activation. Haemodynamic variations are possibly related to changes in peripheral resistance at the most forward position. Further work is necessary to allude to probable improvements in aerodynamics
The effect of trial frames on adaptive gait
No full textPurpose:
Research investigating how vision affects adaptive gait typically tests participants whilst wearing their own spectacles or whilst wearing trial case lenses mounted in a trial frame. Trial frames are temporary frames allowing different lenses to be inserted, permitting different visual conditions to be simulated. Trial frames occlude part of the wearer's peripheral visual field. The current study investigated how use of trial frames affects adaptive gait.
Methods:
Fifteen participants (age 25 ± 5 years) with normal uncorrected vision negotiated a single floor based obstacle habitually (not wearing a trial frame) or wearing trial frames which occluded part of the lower visual field (half-eye) or circumferential peripheral visual field (full aperture). No lenses were used in the trial frames. Analysis assessed visual field occlusion and the kinematics of obstacle crossing.
Results:
Visual field was reduced wearing either trial frame. Compared to the habitual condition, participants wearing either type of trial frame lifted their foot significantly higher over the obstacle and increased the time taken to step over the obstacle; a result of uncertainty regarding the precise location (height) of the obstacle due to the occlusion of visual information from the inferior visual field. There were no differences in obstacle crossing between trial frame conditions.
Conclusions:
Wearing either full or half eye trial frames can in itself influence adaptive gait. Whilst consideration needs to be given to the visual correction that participants wear during gait research, the method of mounting these lenses also requires consideration
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
