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Aim: The purpose of the present study was to evaluate the associations between body composition and functional movement patterns in athletes of different sports. Methods: A cross-sectional study was conducted on 85 voluntary athletes (age 25.9 ± 5 years), representatives of 5 professional Italian teams: 30 volleyball players, 25 soccer players and 30 rugby players. Whole-body impedance measurements and Bioelectric Impedance Vectorial Analysis (BIVA) were performed in order to assess body composition in the athletes. Functional Movement Screen (FMS) was used to assess the presence of dysfunctional and asymmetrical movements. For a more detailed analysis, FMS was separated into three parts: FMSmove, FMSflex and FMSstability. Results: Total FMS score was significantly negatively correlated with percentage of fat mass (%F) and body mass index (BMI). A one-way analysis of variance showed significant differences in body composition and functional movement patterns measures in the three groups. A Tukey post hoc analysis revealed that rugby players have higher %F and body cellular mass (BCM) values than the other groups; moreover, they showed lower scores in FMSflex. The highest scores in FMSflex were obtained by the volleyball players. Conclusions: The main finding of this study was the significant association between higher %F and BMI with poorer functional movement in athletes. Furthermore, with respect to the sport played, rugby players showed significant differences in body composition and movement patterns compared to soccer and volleyball players. In general, reaching an optimal body composition is essential to improving the quality of movement, in order to achieve high performance. However, a large body mass in rugby players could be advantageous in some phases of the match. Reference 1. Fuller JT, Chalmers S, Debenedictis TA et al. (2017) High prevalence of dysfunctional, asymmetrical, and painful movement in elite junior Australian Football players assessed using the Functional Movement Screen. J Sci Med Sport. 20:134–138.

Aim: Investigation of the combined occurrence and characteristics of saccades and microsaccades during free-viewing sport task, with the intention to explore gaze behaviour that would optimize information gathering for action outcome prediction. Methods: Gaze behaviour of expert and novice table tennis players was recorder during a task in which subjects were instructed to predict the ball future direction after the opponent’s throw. Response accuracy, reaction time, fixations, microsaccades and saccades were recorded to estimate the relationship between gazing strategy and success in the task. Analysis of the sequence of saccades/fixations and microsaccade dynamics (during fixations) allowed to study allocation of overt or covert attention in successful predictions. Results: Compared to novices, experts showed more correct responses (70% vs. 64%) with shorter reaction time (411.88±94.62 vs. 468.56±123.22 ms). Experts fixated more times and for longer periods, with more saccades and microsaccades, on hand-racket during forehand and on trunk during backhand drive technique. Furthermore, experts showed a narrower frequency distribution of microsaccade orientations when fixating on hand-racket and trunk areas, meaning that the attention was focused on those small locations. Conclusions: Microsaccades and saccades can be related to the salience of interest areas during performance. Athletes who play ball games are repeatedly exposed to motion stimuli during their training, improving their perception of moving objects. The link between visuomotor performance and covert attention shifts could have a potential impact upon sports, as for example assessments of visual performance that can help to predict people who have elite potential. On these premises, one can suggest that vision training offers a mean to improve performance. References: 1. Piras A, Raffi M, Lanzoni IM, Persiani M, & Squatrito S. (2015) Microsaccades and prediction of a motor act outcome in a dynamic sport situation. Invest Ophthalmol Vis Sci Title, 56(8), 4520–4530. 2. Piras A, Lanzoni IM, Raffi M, Persiani M, & Squatrito S. (2016). The within-task criterion to determine successful and unsuccessful table tennis players. Int J Sports Sci Coach, 11(4).

Aim: The self-motion perception produced by optic flow fields is part of the sensorimotor integration process finalized to the postural control. Depending on the stimulated portion of the retina, the corticocortical signals are differently processed. The aim was to investigate if retinal impairments modify the activity of postural muscles. Methods: We evaluated the electromyographic (EMG) activity of the tibialis anterior and soleus in 34 volunteers. Thirteen people at early stage of retinopathy were included in the ‘‘retinopathy group’’ (average age 62), eight people with a laser treatment on the peripheral retina were included in the ‘‘laser group’’ (average age 62) and thirteen healthy subjects formed the ‘‘control group’’ (average age 59). The EMG activity was recorded while the subjects viewed radial optic flow stimuli presented in the foveal, peripheral and full visual field. A repeated measures ANOVA was performed on the normalized EMG of each muscle, with side (right–left) as within-factor and group and stimuli as between-factors. Results: The EMG analysis of the tibialis showed a significant effect for group (p = 0.012) and an interaction effect side by group (p = 0.06). The EMG analysis of the soleus showed a significant effect for group (p\0.001) and an interaction effect side by group (p\0.001). Further, the retinopathy group showed the highest values of muscles activation, while the laser group presented the lowest. The retinopathy and the laser groups activated predominantly muscles of the same side, left and right respectively. The control group activated left tibialis and right soleus. Conclusion: Results showed that the retinal functionality influences the activity of postural leg muscles. We hypothesize that in presence of retinal damage the postural control system may induce a co-contraction of leg muscles in order to maintain stability. Results seem to indicate that an impairment of the peripheral retina reduces the muscles activity. References 1. Peterka, R. J. (2002). Sensorimotor integration in human postural control. Journal of neurophysiology, 88(3), 1097–1118 2. Raffi, M., Piras, A., Persiani, M., & Squatrito, S. (2014). Importance of optic flow for postural stability of male and female young adults. European journal of applied physiology, 114(1), 71–83. 3. Raffi, M., & Siegel, R. M. (2004). Multiple cortical representations of optic flow processing. In Optic flow and beyond (pp. 3–22). Springer Netherlands.

Optic flow is crucial for the maintenance of quiet stance in the upright position. However, little is known about the correlation between stimulus type and postural response. Aim of this study was to investigate the optic flow effect on the distribution of the prevalent direction of postural sway. Stabilometric data were recorded in 24 right-handed young volunteers who stood with each foot on a Kirstel force platform, facing a wide screen. Optic flow stimuli were full screen expansion and contraction, while random dot motion was used as control. For each stimulus we computed the maximum variance of sway direction (the prevalent oscillation direction) and the mean vector. The vector of the prevalent direction of postural sway was 127.7° in expansion, 223.7° in contraction and 211.4° for random stimulus. All stimuli showed a uniform distribution at the Rayleigh test, but we did not find a correlation between the stimuli, meaning that each stimulus evokes a proper postural sway. Contrary to males, females showed a prevalent forward sway during contraction. A possible explanation for this might be that a different muscular activation could cause a different posture during the stimulus presentation. It is possible that the activation of either plantaflexors or plantaextensors during the trial caused a continuous oscillation in anteroposterior direction. That would require the generation of a stronger vertical force to keep postural stability and to avoid backward fall.

While retinal optic flow (OF) is considered a major cue for self-motion and postural stability, it is still debated the relative importance of central vs peripheral vision in visuo-postural responses. Psychophysical studies, by assessing the body sway in response to OF stimuli give more importance to visual periphery as source of compensatory postural responses, while the central vision would play an accessory role. Aim of this study was to verify the different influence of central vs peripheral optic flow stimulation on the activation of lower limb postural muscles: bilateral tibialis anterior and gastrocnemius medialis. Surface EMG was recorded in 24 male and female participants while radial (expansion and contraction) OF stimuli were presented either in a central or peripheral region of a wide screen. The activity of the right tibialis anterior was the most affected by OF stimuli. We found an interaction of sex by muscle in favour of male subjects (78%). The majority of the subjects had a greater postural response for either central or peripheral stimulation, meaning that the influence of visual field region on visuo-postural balance may be subject-specific, probably depending on other stimulus parameters

Introduction Several researches have been aimed at studying the balance control looking at the variation of the center of pressure (COP) trajectory induced by variation of the visual field (Collins & De Luca, 1995; Accornero, 1997). Indeed, presence of a visual stimulus produce less sway speed than the dark (Lee & Lishman, 1975). However, little is known about the modulation of optic flow stimuli on the body sway. Aim of this study was to verify how the direction of optic flow can affect the COP parameters like speed, trace length, equivalent area and equivalent radius. Methods Stabilometric data were recorded in 24 healthy right-handed volunteers (12 M and 12 F, mean age 24.5±2.9) who standed on two Kirstel force platforms. Experiments were performed in the dark. Stimuli were presented on a wide screen, placed 115 cm from the subjects’ eyes, covering 135 x 107° of visual field. Stimuli were two full screen optic flow, expansion and contraction, and random dots motion as control stimulus. Postural responses data were acquired by the SMART BTS® at 1000 Hz (BTS® Bioengineering Inc.). Data acquisition included 5 trials per stimulus for about 30-s each. Results We performed a repeated measure ANOVA on the 24 subjects for each COP parameter. Speed: we found significant differences across the optic flow stimuli (p=0.042) and significant interaction between stimulus and sex (p=0.009). Trace length: results showed significant interaction between stimulus and sex (p=0.001). Equivalent area: we found significant interaction between stimulus and sex (p

A feedback control based on the visual perception self-motion contributes to postural stability, however little is known about the visual modulation of postural muscles. Aim of this study was to investigate the effect of optic flow direction on the muscle activation and to verify the correlation between visual stimuli, muscle activity and body sway. We used surface electromyography (EMG) and stabilometry on 24 right-handed young adults. Center of pressure (COP) and EMG data were acquired at once. We analyzed the bilateral activation of tibialis anterior and gastrocnemius medialis during full field expansion or contraction optic flow stimulation. A stimulus made of dots moving in random directions was used as control. The activity of the tibialis anterior and gastrocnemius medialis resulted well correlated to the antero-posterior COP displacement. We analyzed the highest EMG amplitude values to evaluate if optic flow differently modulated the muscle responses. The stimulus effect was significant in 23 subjects (96%). In the tibialis anterior we found a laterality effect in males (p

Introduction The direction of optic flow stimuli is an important cue for heading perception (Gibson, 1954). Several studies addressed the influence of visual stimuli on upright position, because vision provides the necessary information about the surrounding environment (Peterka & Benolken, 1995). However, little is known about the optic flow modulation on postural muscles. Aim of this study was to verify if the optic flow direction evokes different postural responses. We analyzed the bilateral muscular activation of two leg muscles, tibialis anterior and gastrocnemius medialis, during full field optic flow stimulation. Methods sEMG were recorded in 24 healthy right-handed volunteers (12 M and 12 F, mean age 24.5±2.9). Experiments were performed in the dark. Stimuli were presented on a wide screen, placed 115 cm from the subjects’ eyes, covering 135 x 107° of visual field. Stimuli were two full screen optic flow, expansion and contraction, and random dots motion as control stimulus. sEMG data were acquired by a 16 channels Pocket EMG (BTS® Bioengineering Inc.). Data acquisition included 5 trials per stimulus for about 30-s each. Results The muscle was considered significantly activated when its signal was greater than the baseline mean + 3SD (Hodges & Bui, 1996). Results showed that the great majority of the subjects had a different modulation on muscles activity depending on the type of optic flow stimulus. The right tibialis anterior was the most activated muscle. We also analyzed the highest amplitude values to evaluate if optic flow differently modulated the amplitude of the muscle responses. Results showed a significant effect (p

The posterior parietal cortex is involved in multimodal integration of sensory inputs for creating a stable internal representation of the extrapersonal space. Such representation is used by the neural network as basis to plan and generate motor outputs. Studies performed in our laboratory showed that neurons in area PEc in the parietal cortex, are activated by optic flow stimuli with a tuning for the focus of expansion (FOE) position in space, suggesting a role of this area in heading perception. To assess if heading is encoded in eye- or head-centered coordinates in area PEc, we recorded the extracellular activity of single neurons in two monkeys (M. fascicularis) trained in a reaction time task. To verify whether PEc neurons are able to integrate multimodal signals, such as those related to optic flow selectivity with extraretinal inputs, we varied the spatial position of FOE and target. We tested the retinotopic organization of FOE neuronal selectivity and then we compared the responses to the optic flow stimulus at same retinal FOE offset and different eye position. We also varied the head position in space along the horizontal axis. We show results on eye/head position modulation of neuronal optic flow responses in PEc cells, suggesting that area PEc combines optic flow input with extraretinal signals related to eye and/or head position. These results allow to hypothesise a role of this area in guiding locomotion by computing the transformation from eye-centered to head-centered coordinates.

Deprivation of socio-sensory interactions during early life impairs brain function in adulthood. In previous investigations we showed that early isolation severely affects neuron development in several structures of the hippocampal region, including the entorhinal cortex. In the present study we investigated the effects of early isolation on signal processing along the entorhinal cortex-dentate-CA3-CA1 system, a major memory circuit of the hippocampal region. Male and female guinea-pigs were assigned at 6-7 days of age to either a social or an isolated environment. At 90-100 days of age the animals were anesthetized and field potentials were recorded from the entorhinal cortex-dentate-CA3-CA1 circuit, driven by dorsal psalterium commissural volleys. Analysis of the input-output function in the different structures showed that in isolated males there was a small reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in layer II of the entorhinal cortex. No changes occurred in isolated females. In isolated males and females there was a reduction in the input-output function of the population excitatory postsynaptic potential and population spike evoked in the dentate gyrus, CA3 and CA1, but this effect was larger in males. In isolated males, but not in females, the population spike/population excitatory postsynaptic potential ratio was reduced in all investigated structures, indicating that in males the size of the discharged neuron population was reduced more than due to the decreased input. Results show that isolation reduces the synaptic function in the whole entorhinal cortex-dentate gyrus-CA3-CA1 system. While the entorhinal cortex was moderately impaired, the dentate-hippocampal system was more severely affected. The impairment in the signal transfer along the entorhinal cortex-dentate gyrus-CA3-CA1 system was heavier in males, confirming the larger susceptibility of this sex to early experience. This work provides evidence that malfunctioning of a major hippocampal network may underlie the learning deficits induced by impoverished surroundings during early life.

Background Diabetic retinopathy is a principal cause of visual damage and blindness, in which laser treatment offers proven therapy. The progressive degeneration of the retina, secondary to diabetes, is believed to cause postural instability although this is not well documented. The aim of this research was to assess how optic flow stimuli contribute to the control of stance in people with impaired retinal functions. Research question Does the different retinal functionality correspond to different specific patterns of movements and muscles recruitment? Methods Postural mechanisms and motor strategies were measured by testing subjects in quiet stance on a force platform with surface electromyography under different optic flow stimulations. Root mean square values of the center of pressure time-varying signals and normalized EMG values were used to evaluate the postural sway. Results People with diabetic retinopathy, and to a greater extent laser group, were more unstable than healthy subjects. The greater amplitude of the body sway observed in the retinopathy group, and especially in the laser group, could be an expression of the difficulty for this population in processing this kind of visual information. Significance The increase in muscle activity indicates that there are musculoskeletal and postural changes in the lower limb musculature with increasing severity of diabetic retinopathy. An impaired retinal function might negatively affect postural control in a way that is dependent on the severity of retinal damage.

Optic flow is a perceptual cue processed for self-motion control. The aim of this study was to investigate whether postural control is modulated by the speed of radial optic flow stimuli. The experiments were performed on 20 healthy volunteers using stabilometry and surface electromyography (EMG). The subjects were instructed to fixate a central fixation point while radial optic flow stimuli were presented full field, in the foveal and in the peripheral visual field at different dots speed (8, 11, 14, 17 and 20°/s). Fixation in the dark was used as control stimulus. The EMG analysis showed that male and female subjects reacted to the stimuli with different muscle activity (main effects for gender, muscle and laterality: p < 0.001). The analysis of the center of pressure (COP) parameters showed that optic flow stimuli had a different effect on the left and right limbs of males and females (main effects of laterality: p < 0.015; interaction effects of gender and laterality: p < 0.016). The low speed of optic flow stimuli (8 and 11°/s) evoked non-uniform directions of oscillations especially in peripheral stimulation in all subjects, meaning that optic flow simulating slow self-motion stabilizes body sway.

Microsaccades are linked with extraretinal mechanisms that significantly alter spatial perception before the onset of eye movements. We sought to investigate whether microsaccadic activity is modulated by the speed of radial optic flow stimuli. Experiments were performed in the dark on 19 subjects who stood in front of a screen covering 135 × 107° of the visual field. Subjects were instructed to fixate on a central fixation point while optic flow stimuli were presented in full field, in the foveal, and in the peripheral visual field at different dot speeds (8, 11, 14, 17, and 20°/s). Fixation in the dark was used as a control stimulus. For almost all tested speeds, the stimulation of the peripheral retina evoked the highest microsaccade rate. We also found combined effects of optic flow speed and the stimulated retinal region (foveal, peripheral, and full field) for microsaccade latency. These results show that optic flow speed modulates microsaccadic activity when presented in specific retinal portions, suggesting that eye movement generation is strictly dependent on the stimulated retinal regions.

Purpose: PEMF stimulation results in a higher O2 muscle supply during exercise through increased O2 release and uptake. Given the importance of oxygen uptake in sport activity, especially in aerobic disciplines such as cycling, we sought to investigate the influence of PEMF on muscle activity when subjects cycled at an intensity between low and severe. Methods: Twenty semi-professional cyclists performed a constant-load exercise with randomized active (ON) or inactive (OFF) PEMF stimulation. Each subject started the recording session with 1 min of cycling without load (warm-up), followed by an instantaneous increase in power, as the individualized workload (constant-load physical effort). PEMF loops were applied on the vastus medialis and biceps femoris of the right leg. We recorded the electromyographic activity from each muscle and measured blood lactate prior the exercise and during the constant-load physical effort. Results: PEMF stimulation caused a significant increase in muscle activity in the warm-up condition when subjects cycled without load (p < 0.001). The blood lactate concentration was higher during PEMF stimulation (p < 0.001), a possible consequence of PEMF’s influence on glycolytic metabolism. Conclusion: PEMF stimulation augmented the activity and the metabolism of muscular fibers during the execution of physical exercise. PEMF stimulation could be used to raise the amplitude of muscular responses to physical activity, especially during low-intensity exercise.

The aim of the present investigation was to assess the effect of long-term recreational swimming training on the cardiac autonomic responses in the healthy population. 70 habitual recreational swimmers (48.6±14.3 yrs.) and 60 sedentary adults (51.5±10.4 yrs.) were recruited. Arterial blood pressure was recorded with participants in supine position for 10 min, and the last 5 min were used to assess heart rate variability, baroreflex sensitivity, and hemodynamic analysis. The analysis of the questionnaire showed that the swimmers had practiced swimming for a mean of 14 years and 207 min/week. No difference was detected for body mass index between groups. Heart rate variability showed significant differences between groups both in the time and frequency domain analysis. We also found significant differences for baroreflex sensitivity. At rest, cardiac output and stroke volume were higher, whereas, heart rate, mean arterial pressure and total peripheral resistances were lower in the swimmers than in the sedentary subjects. Since heart rate variability measures are independent predictors of mortality, the present findings suggest that habitual recreational swimming may be protective against sudden cardiovascular events and, more in general, have a positive impact on cardiovascular health.

Optic flow is a crucial signal in maintaining postural stability. We sought to investigate whether the activity of postural muscles and body sway was modulated by eye position during the view of radial optic flow stimuli. We manipulated the spatial distribution of dot speed and the fixation point position to simulate specific heading directions combined with different gaze positions. The experiments were performed using stabilometry and surface electromyography (EMG) on 24 right-handed young, healthy volunteers. Center of pressure (COP) signals were analyzed considering antero-posterior and medio-lateral oscillation, COP speed, COP area, and the prevalent direction of oscillation of body sway. We found a significant main effect of body side in all COP parameters, with the right body side showing greater oscillations. The different combinations of optic flow and eye position evoked a non-uniform direction of oscillations in females. The EMG analysis showed a significant main effect for muscle and body side. The results showed that the eye position modulated body sway without changing the activity of principal leg postural muscles, suggesting that the extraretinal input regarding the eye position is a crucial signal that needs to be integrated with perceptual optic flow processing in order to control body sway.

The cortical representation of visual perception requires the integration of several-signal processing distributed across many cortical areas, but the neural substrates of such perception are largely unknown. The type of firing pattern exhibited by single neurons is an important indicator of dynamic circuitry within or across cortical areas. Neurons in area PEc are involved in the spatial mapping of the visual field; thus, we sought to analyze the firing pattern of activity of PEc optic flow neurons to shed some light on the cortical processing of visual signals. We quantified the firing activity of 152 optic flow neurons using a spline interpolation function, which allowed determining onset, end, and latency of each neuronal response. We found that many PEc neurons showed multiphasic activity, which is strictly related to the position of the eye and to the position of the focus of expansion (FOE) of the flow field. PEc neurons showed a multiphasic activity comprised of excitatory phases interspersed with inhibitory pauses. This phasic pattern seems to be a very efficient way to signal the spatial location of visual stimuli, given that the same neuron sends different firing patterns according to a specific combination of FOE/eye position.

Optic flow stimuli are crucial for the control of stance in the upright position. The visual control of posture has recently received a lot of interest from several researchers. One of the most intriguing aspects is the contribution of the different parts of the visual field in the control of stance. Here we reviewed the results of several studies performed with different methodologies that tried to determine the effect of optic flow on postural control, by analyzing the role of the central and peripheral visual fields. Although the results were controversial, the majority of these studies agreed to assign the most important role in postural control to the peripheral retina. However, these studies were performed using different approaches and different definitions of the central and peripheral visual fields. The choice of the exact portion of the retina to be stimulated is crucial given that the stimulation of the central and the peripheral parts of the retina leads to the activation of different geniculo-cortical pathways and results in different cortical processing of information.

This investigation examined the effect of partial-body cryostimulation (PBC) performed in the recovery time between a strength training and an interval running (IR) session. Nine rugby players (age, 23.7 ± 3.6 years; body mass index, 28.0 ± 2.6 kg·m−2) were randomly exposed to 2 different conditions: (i) PBC: 3 min at −160 °C, and (ii) passive recovery at 21 °C. We performed the bioelectrical impedance analysis (BIA) and recorded temperature and cardiac autonomic variables at 3 time points: at baseline, after strength training, and after 90 min of recovery. In addition, blood lactate concentration was measured 1 min before and 2.5 min after the IR. Heart rate (HR), energy cost, minute ventilation, oxygen uptake, and metabolic power were assessed during the IR. Homeostatic hydration status was affected by the execution of an intense strength training subsession. Then, after PBC, the BIA vector was restored close to normohydration status. Autonomic variables changed over time in both conditions, although the mean differences and effect sizes were greater in the PBC condition. During IR, HR was 3.5% lower after PBC, and the same result was observed for oxygen uptake (∼4.9% lower) and ventilation (∼6.5% lower). The energy cost measured after cryotherapy was ∼9.0% lower than after passive recovery. Cryotherapy enhances recovery after a single strength training session, and during subsequent IR, it shows a reduction in cardiorespiratory and metabolic parameters. PBC may be useful for those athletes who compete or train more than once in the same day, to improve recovery between successive training sessions or competitions.

Context: Sports practice leads athletes to develop a specific body composition, coordination patterns, and basic motor skills based on the different tactical and physical needs. Objectives: To present and compare a wide range of functional movement patterns and body composition (BC) parameters of high-level male athletes playing different sports and to determine if there was a relationship between the parameters examined. Design: Cross-sectional study. Setting: Team facilities. Participants: A total of 30 volleyball, 25 soccer, and 30 rugby players (age = 25.9 [5.0] y and body mass index = 25.6 [4.1] kg/m2). Interventions: Functional movement patterns and anthropometric measurements were collected by a physician specifically trained. Main Outcome Measures: Body mass index, fat mass, fat-free mass, upper-arm muscle and fat area, calf muscle and fat area, thigh muscle and fat area, and functional movement screen (FMS) scores. In addition to considering the FMS total score, the authors separated the screen into 3 parts: FMSmove, FMSflex, and FMSstab. Results: The rugby players showed a higher number of asymmetrical and dysfunctional movements than the other athletes (P P P r = −.616; P r = −.519; P Conclusions: Functional movement patterns and BC differ in athletes according to the sport practiced. Furthermore, reaching an optimal BC is essential to achieve a satisfactory quality of movement.

The optic flow visual input directly influences the postural control. The aim of the present study was to examine the relationship between visually induced heading perception and postural stability, using optic flow stimulation. The dots were accelerated to simulate a heading direction to the left or to the right of the vertical midline. The participants were instructed to indicate the perceived optic flow direction by making a saccade to the simulated heading direction. We simultaneously acquired electromyographyc and center of pressure (COP) signals. We analysed the postural sway during three different epochs: (i) the first 500 ms after the stimulus onset, (ii) 500 ms before saccade onset, epoch in which the perception is achieved and, (iii) 500 ms after saccade onset. Participants exhibited a greater postural instability before the saccade, when the perception of heading was achieved, and the sway increased further after the saccade. These results indicate that the conscious representation of the self-motion affects the neural control of posture more than the mere visual motion, producing more instability when visual signals are contrasting with eye movements. It could be that part of these effects are due to the interactions between gaze shift and optic flow.

Running with the ball is a soccer-specific activity frequently used by players during match play and training drills. Nevertheless, the energy cost (EC) of on-grass running with the ball has not yet been determined. The purpose of this study was therefore to assess the EC of constant-speed running with the ball, and to compare it with the EC of normal running. Eight amateur soccer players performed two 6- min runs at 10 km/h on artificial turf, respectively with and without the ball. EC was measured with indirect calorimetry and, furthermore, estimated with a method based on players’ accelerations measured with a GPS receiver. The EC measured with indirect calorimetry was higher in running with the ball (4.60±0.42 J/kg/m) than in normal running (4.19±0.33 J/kg/m), with a very likely moderate difference between conditions. Instead, a likely small difference was observed between conditions for EC estimated from GPS data (4.87±0.07 vs. 4.83±0.08 J/kg/m). This study sheds light on the energy expenditure of playing soccer, providing relevant data about the EC of a typical soccer-specific activity. These findings may be a reference for coaches to precisely determine the training load in drills with the ball, such as soccer-specific circuits or small-sided games.

The present study shows the relationship between microsaccades and heading perception. Recent research demonstrates that microsaccades during fixation are necessary to overcome loss of vision due to continuous stimulation of the retinal receptors, even at the potential cost of a decrease in visual acuity. The goal of oculomotor fixational mechanisms might be not retinal stabilization, but controlled image motion adjusted to be optimal for visual processing. Thus, patterns of microsaccades may be exploited to help to understand the oculomotor system, aspects of visual perception, and the dynamics of visual attention. We presented an expansion optic flow in which the dot speed simulated a heading directed to the left or to the right of the subject, who had to signal the perceived heading by making a saccade toward the perceived direction. We recorded microsaccades during the optic flow stimulation to investigate their characteristics before and after the response. The time spent on heading perception was similar between right and left direction, and response latency was shorter during correct than incorrect responses. Furthermore, we observed that correct heading perception is associated with longer, larger and faster microsaccade characteristics. The time-course of microsaccade rate shows a modulation across the perception process similar to that seen for other local perception tasks, while the main direction is oriented toward the opposite side with respect to the perceived heading. Microsaccades enhance visual perception and, therefore, represent a fundamental motor process, with a specific effect for the build-up of global visual perception of space.