Foto del docente

Alessandro Piras

Junior assistant professor (fixed-term)

Department of Biomedical and Neuromotor Sciences

Academic discipline: M-EDF/01 Physical Training Sciences and Methodology

Research

Keywords: fixations saccade eye-hand coordination eye movements autonomic nervous system heart rate variability

Research Interests

  1. Cognition, Gaze and Motor Behaviour

    My main research aim is to contribute to the understanding of how the visual system controls and modulates the motor behaviour. The relationship between perception and action is crucial for understanding the motor activity. The main interest is on the perceptual processes and their influence on cognitive and motor activities, which play a critical role in sport performances. Given that athletes must process a large number of sensory information in order to analyze each specific action, at the perceptual level, they differ from normal people for the ability to track items that move at faster speed. I focused my study to eye movements in standardized sport situations, creating spatial and temporal interactions between eye and body movements. I try to simulate sports situations as close as possible to the match, or using specific movies (Piras et al. 2010) or in a real sports situations (real-world tasks) where professional athletes should respond in a short time interval (Piras and Vickers 2011, Piras et. al 2014). In the first paper, we studied the differences in fixations and saccadic eye movements between expert volleyball players and novice subjects using an eye tracking system (EyeLink II, head mounted video-based eye tracker). Participants had to watch a volleyball filmed sequence in which a setter receives a ball tossed from the coach and sets it forward or backward (position 2 and 4 of a volleyball field). Then, the number and duration of fixations to specific interest areas (IAs) were counted. In addition, the sequences of saccades from each IA to the others were analyzed. Results showed that expert players performed fewer fixations of longer duration and spent more time looking first at the initial pass trajectory and then at the setter’s hands, disregarding the ball trajectory. In the second study, when I spent my rotation at the Neuro-Motor Psychology Lab, Faculty of Kinesiology in Calgary, I investigated, in a real-world task, gaze behaviour of male goalkeepers, at intermediate skill level, attempting to stop penalty kicks executed with the instep and inside foot. A mobile eye tracker (lightweight tracker that could be used with and without eyeglasses, for experiments that involve tracking the eyes while the subject moves and speaks during experiments in real-world contexts), and an external camera were used to collect the gaze and motor behaviours of the goalkeepers, as well as the penalty takers’ motor behaviours and flight of the ball. An analysis of the final fixations on the ball and visual pivot (area between kicking leg, non-kicking leg and ball) confirmed that if the final fixation was too long on the ball then goals occurred, while a longer duration fixation on the visual pivot was a characteristic of saves. Furthermore, gaze behaviour of expert and novice judo fighters was investigated while they were doing a real sport-specific task. Using EyeLink II eye trackers (with Scene Camera option, capable for real world based eye tracker), athletes were tested while they performed a first grip either in attack or defence condition against one of the authors (E.P., an Olympic level athlete) who behaved in a manner similar to a simulated training situation. Each trial began when a referee said “Hajime” and finished when one of the athletes grasped the lapel or the sleeve of the opponent and the referee said “Matte”. The variables analyzed in my study concern the spatial and temporal interactions between eye-hand and eye-foot coordination differences in the number and duration of fixations and saccades between elite athletes and beginners. The number and duration of fixations in particular interest areas, the sequence of saccadic eye movements, allowed us to reconstruct the visual search strategy of each subject.

  2. Electromyography and stabilometry

    In the past two years, I participated in a study aimed at investigating the effect of optic flow stimuli on the muscular activation. The research program consists on evaluating how optic flow influences the postural stability because, in a moving visual environment, postural control requires the dynamic matching of vision with the postural control system. We focused on two aspects: the dimension of the stimulated visual field and the gender differences. To achieve this goal, we used two techniques: surface electromyography and stabilometry on 24 right-handed young adults (12 males and 12 females). We recorded the bilateral activation of tibialis anterior, gastrocnemius medialis, biceps femoris and vastus medialis while the subjects viewed optic flow stimuli presented full field, in the peripheral and foveal visual field. Results showed different postural alignments in males and females (Raffi et al. 2013). Visual stimuli always evoke an excitatory input on postural muscles, but the stimulus structure produces different postural effects. Peripheral optic flow stimuli stabilize postural sway, while random and foveal optic flow provoke larger sway variability similar to those evoked in the absence of visual stimulation. Results of this study also underline the peculiar role of each foot during the optic flow visual stimulation (Persiani et al. 2015).

  3. Heart Rate Variability and Baroreflex sensitivity

The portion of the nervous system that controls the visceral functions of the body is the autonomous nervous system (ANS). The autonomic adjustments are not usually accessible to conscience; for that reason, this system is frequently called involuntary or neurovegetative motor system. This system tonically and reflexely influences different physiological variables among which blood pressure, peripheral resistance, and heart rate. Heart rate variability (HRV) and baroreflex sensitivity (BRS) are risk factors for cardiovascular mortality and vulnerability to life-threatening arrhythmias after acute myocardial infarction. Recent studies also suggest that low HRV is associated with occurrence of adverse cardiac events in a random population of middle-aged subjects. Endurance trained athletes generally have resting bradycardia, and it has been suggested to be mediated by training induced increase in vagal outflow. Aerobic training was found to substantially increase both HRV and BRS in untrained subjects, and it was suggested that endurance training increases vagal activity that may have an antifibrillatory effect during ischemia. However, my key points are to know how intensively, how often, and for how long one must exercise to obtain favorable changes in HRV and BRS, in both trained and untrained subjects. In our laboratory we have evaluated the effects of peripheral heart action (PHA) training in comparison to high intensity interval training (HIIT) on changes in autonomic regulation and physical fitness. The PHA method was specifically designed to keep blood circulating throughout the whole body during the entire workout, with few exercises (five–six) performed at low-intensity that stress the upper and lower body musculature, with the intention of alternating one exercise for the upper torso and one for the lower extremities with active pauses (no rest period) between exercises. Our results showed that PHA resistance exercise promoted cardiovascular adaptations, with a decrease in the power spectral component of vascular sympathetic activity and an increase in the vagal modulation. Low-frequency oscillation estimated from systolic blood pressure variability seems to be a suitable index of the sympathetic modulation of vasomotor activity. This investigation also want to emphasize the beneficial effects of this particular resistance exercise training, considering also that the increase in muscular strength is inversely associated with all-cause mortality and the prevalence of metabolic syndrome, independent of cardiorespiratory fitness levels (Piras et al. 2015).