Postural Preparation to Stepping: Coupled Center of Pressure Shifts in the Anterior-Posterior and Medio-Lateral Directions.

We explored changes in the postural preparation to stepping introduced by modifications of the initial coordinates of the center of pressure (COP). We hypothesized that the postural adjustments in the anterior-posterior direction would persist across all initial COP manipulations while the adjustments in the medio-lateral direction would be highly sensitive to the initial COP coordinate. Healthy subjects stood on a force plate, shifted the body weight to one of the initial conditions that spanned the range of COP coordinates in both directions, and initiated a single step or started to walk.

Global stress response during a social stress test: impact of alexithymia and its subfactors.

Objectives: Alexithymia is a personality trait characterized by difficulties in identifying, describing and communicating one's own emotions. Recent studies have associated specific effects of this trait and its subfactors with hypothalamo-pituitary-adrenal (HPA) axis markers during stress. The aim of this study was to analyze the association between alexithymia and its subfactors with HPA and sympatho-adrenal medullar (SAM) activity.

Influence of ankle loading on the relationship between temporal pressure and motor coordination during a whole-body paired task.

We investigated whether ankle loading modifies the relationship between temporal pressure and motor coordination during a whole-body paired task. Eight young healthy adults standing in an erect posture performed multiple series of simultaneous rapid leg flexions paired with ipsilateral index finger extensions. They repeated the task ten times in three load conditions: unloaded, loaded (where additional 5-kg inertia was attached to the ankles), and post-loaded (immediately following the loaded condition).

Age-related differences in motor coordination during simultaneous leg flexion and finger extension: influence of temporal pressure.

Although the effect of temporal pressure on spatio-temporal aspects of motor coordination and posture is well established in young adults, there is a clear lack of data on elderly subjects. This work examined the aging-related effects of temporal pressure on movement synchronization and dynamic stability. Sixteen young and eleven elderly subjects performed series of simultaneous rapid leg flexions in an erect posture paired with ipsilateral index-finger extensions, minimizing the difference between heel and finger movement onsets.

Lecturing to 200 students and its effects on cytokine concentration and salivary markers of adrenal activation.

Stress not only activates the SAM system and the hypothalamic-pituitary-adrenal axes, but also the immune system. The aims of this study are to assess the physiological variations in saliva (cytokines, cortisol and alpha-amylase) and perceived stress in professors when they had to lecture to 200 students. A total of eight unstimulated saliva samples were collected from nine professors: four on a working day that included the lecture and four controls on a working day without a lecture.

Postural and focal inhibition of voluntary movements prepared under various temporal constraints.

Large disturbances arising from the moving segments (focal movement) are commonly counteracted by anticipatory postural adjustments (APAs). The aim of this study was to investigate how APAs - focal movement coordination changes under temporal constraint. Ten subjects were instructed to perform an arm raising movement in the reactive (simple reaction time) and predictive (anticipation-coincidence) tasks.

Modulation of anticipatory postural adjustments in a complex task under different temporal constraints.

The aim of this experiment was to explore the behavioral effects of various temporal pressures on the anticipatory postural adjustments (APAs) in a complex task. Eighteen handball players performed a handball direct throw in three conditions of temporal pressure: (1) a reactive condition (RC), the throw was initiated as quickly as possible following a visual stimulus; (2) an anticipation-coincidence condition (AC), by synchronizing the impact of the ball with the passage of a visual mobile on a target; and (3) a self-initiated (SI) throw. The whole-body postural oscillation and the acceleration of the wrist were measured before and during the throwing action.

Influence of experience on postural control: effect of expertise in gymnastics.

The authors investigated how expertise in motor skills that require fine postural control, such as gymnastics, influences postural regulation. Gymnasts and nongymnasts performed a postural stabilization task after anterior-posterior destabilization while looking at a target in front of them. The authors recorded and analyzed the center of pressure and the ankle, knee, and hip displacements.

A new methodology providing evidence of two distinct processes in the production of hand/foot simultaneous responses.

To get simultaneous responses of the hand and the foot, it is mandatory to compensate for the longer peripheral motor conduction delay of the foot. According to the reactive-projective model [Paillard, J. (1948).

Effect of arousal on internal clock speed in real action and mental imagery.

The possible implication of an internal clock as a mechanism accounting for the temporal homology between actual and mental walking is studied. To observe this phenomenon, stressful sound stimuli were used to increase arousal, which is known to activate the internal clock. Seventeen participants performed three tasks: (1) a time production task, used as a reference task reflecting the internal clock speed; (2) an actual walking task; and (3) a mental walking task, all three in two sound conditions (no noise and noise).

Relation between sport and spatial imagery: comparison of three groups of participants.

The literature suggests that sport may be considered a spatial activity and that engaging in spatial activities increases the capacity of an individual to implement mental imagery. Moreover, mental rotation calls upon motor processes that are heavily involved in sporting activities. For these reasons, the authors hypothesized that athletes ought to perform mental rotation tasks better than nonathletes.

Effects of one night's sleep deprivation on anaerobic performance the following day.

The purpose of this study was to determine the effect of one night's sleep deprivation on anaerobic performance in the morning and afternoon of the following day. Thirteen healthy males were studied twice in a balanced, randomized design. The experiment consisted of two conditions 1 week apart.

Relation between sport activity and mental rotation: comparison of three groups of subjects.

The aim was to observe the relation between sport activity and performance on a mental image-transformation task. A classical mental rotation task using abstract stimuli was administered to three groups: (a) gymnasts who used mental and physical rotations in their practice, (b) athletes whose activities required very little motor rotation, and (c) nonathletes. Both sport groups performed similarly and obtained significantly shorter response times than those of the nonathletes.

Physical exercise and time of day: influences on spontaneous motor tempo.

To identify whether spontaneous motor rhythm is influenced by external or internal events and whether this rhythm fluctuates across the day in parallel with heart rate diurnal variations, we simultaneously recorded heart rate and spontaneous motor rate before and after a pedaling task performed five times a day by 10 healthy human subjects. Each subject performed a Spontaneous Motor Tempo, i.e.

Effects of regular training at the same time of day on diurnal fluctuations in muscular performance.

The aim of this study was to determine whether there is an effect of time of day on the adaptation to strength training at maximal effort. Fourteen participants took part in this experiment. Their peak anaerobic power (Wingate anaerobic test) and peak knee extension torque at six angular velocities (1.

Effects of apnea on motor and cardiac rhythms.

Usually, spontaneous rhythm of movements is studied through tasks involving an increase in heart rate (HR) such as physical exercises, locomotion or mental tasks. This experiment, instead, checks whether spontaneous rhythm is influenced by HR deceleration provoked by a voluntary apnea. The performances in a motor spontaneous tempo (MST) task performed for 3 min were compared to the same finger-tapping task performed in apnea.