Ana Queralt

The effects of an auditory startle on obstacle avoidance during walking

Movement execution is speeded up when a startle auditory stimulus is applied with an imperative signal in a simple reaction time task experiment, a phenomenon described as StartReact. The effect has been recently observed in a step adjustment task requiring fast selection of specific movements in a choice reaction time task. Therefore, we hypothesized that inducing a StartReact effect may be beneficial in obstacle avoidance under time pressure, when subjects have to perform fast gait adjustments. Twelve healthy young adults walked on a treadmill and obstacles were released in specific moments of the step cycle. On average the EMG onset latency in the biceps femoris shortened by 20% while amplitude increased by 50%, in trials in which an auditory startle accompanied obstacle avoidance. The presentation of a startle increased the probability of using a long step strategy, enlarged stride length modifications and resulted in higher success rates, to avoid the obstacle. We also examined the effects of the startle in a condition in which the obstacle was not present in comparison to a condition in which the obstacle was visibly present but it did not fall. In the latter condition, the obstacle avoidance reaction occurred with a similar latency but smaller amplitude as in trials in which the obstacle was actually released. Our results suggest that the motor programmes used for obstacle avoidance are probably stored at subcortical structures. The release of these motor programmes by a startling auditory stimulus may combine intersensory facilitation and the StartReact effect.

A startle speeds up the execution of externally guided saccades

The control of eye movements depends in part on subcortical motor centres. Gaze is often directed towards salient visual stimuli of our environment with no conscious voluntary commands. To further understand to what extent preprogrammed eye movements can be triggered subcortically, we carried out a study in normal volunteers to examine the effects of a startling auditory stimulus (SAS) on externally guided saccades. A peripheral visual cue was presented in the horizontal plane at a site distant 15° from the fixation point, and subjects were instructed to make a saccade to it. SAS was presented together with the peripheral visual cue in 20% of trials. To force rapid visual fixation at the end of the saccade, targets were loaded with a second cue, a small arrow pointing towards the right or the left (or a neutral sign), not distinguishable with peripheral vision. Subjects were requested to perform a flexion/extension wrist movement, according to the direction of the arrow (or not to move if the second cue was the neutral sign). SAS presented together with the visual target caused a significant shortening of the latency of saccadic movements. The wrist movements performed as a response to the second cue had similar reaction times regardless of whether the trial contained a SAS or not. Our results show that voluntary saccades to peripheral targets are speeded up by activation of the startle circuit, and that this effect does not cause a significant disturbance in the execution of simple in-target cues. These results suggest that subcortical structures play a main role in preparation of externally guided saccades.

Leisure-Time Physical Activity and Psychological Well-Being in University Students:

An analysis of psychological well-being (self-esteem and subjective vitality) of 639 Spanish university students was performed, while accounting for the amount of leisure-time physical activity. The Spanish versions of the Rosenberg Self-Esteem Scale and Subjective Vitality Scale were employed. Participants were divided into four groups (Low, Moderate, High, and Very high) depending on estimation of energy expenditure in leisure-time physical activity. Men and women having higher physical activity rated higher mean subjective vitality; however, differences in self-esteem were observed only in men, specifically between Very high and the other physical activity groups.

Bicycling to university: evaluation of a bicycle-sharing program in Spain

This study examined the change in behavioral stages (e.g. contemplation, action and maintenance) of cycling to university before and after the implementation of a new public bicycle share program (PBSP) and promotion of its use. The study also determined the change in the prevalence, correlates of PBSP use and potential role in the promotion of healthy weight. An 8-month follow-up cross-sectional study (September 2010-April 2011) was carried out among undergraduate students during the first season of implementation of the PBSP in Valencia, Spain. The sample was 173 students (68.2% female) with a mean age of 21.3 years (SD 3.06) who attended a PBSP promotional session. The data were collected by questionnaire. Results indicated a significant increase of 14.6% in the action/maintenance stage of change and showed that 19% of the participants were PBSP users 8 months later. The behavioral stage did not change when students always had access to car/motorbike, lived further than 5 km from the university and had no bicycle stations within 250 m from home. Those most likely to start using PBSP were students who were in the contemplation stage, perceived fewer environmental and safety barriers to active commuting and had one or more stations within 250 m of home. PBSP users expended ∼257 metabolic equivalent·minutes/week bicycling to university, and there was a small reduction in BMI. Findings suggest that PBSPs can be considered as useful promoters of cycling behavior and may contribute to weight control in university students.

Speeding up gait initiation and gait-pattern with a startling stimulus

Human gait involves a repetitive leg motor pattern that emerges after gait initiation. While the automatic maintenance of the gait-pattern may be under the control of subcortical motor centres, gait initiation requires the voluntary launching of a different motor program. In this study, we sought to examine how the two motor programmes respond to an experimental manipulation of the timing of gait initiation. Subjects were instructed to start walking as soon as possible at the perception of an imperative signal (IS) that, in some interspersed trials was accompanied by a startling auditory stimulus (SAS). This method is known to shorten the latency for execution of the motor task under preparation. We reasoned that, if the two motor programmes were launched together, the gait-pattern sequence would respond to SAS in the same way as gait initiation. We recorded the gait phases and the electromyographic (EMG) activity of four muscles from the leg that initiates gait. In trials with SAS, latency of all gait initiation-related events showed a significant shortening and the bursts of EMG activity had higher amplitude and shorter duration than in trials without SAS. The events related to gait-pattern were also advanced but otherwise unchanged. The fact that all the effects of SAS were limited to gait initiation suggests that startle selectively can affect the neural structures involved in gait initiation. Additionally, the proportional advancement of the gait-pattern sequence to the end of gait initiation supports the view that gait initiation may actually trigger the inputs necessary for generating the gait-pattern sequence.

Changes in Physical Activity Domains During the Transition Out of High School: Psychosocial and Environmental Correlates.

BACKGROUND This study examined changes in multiple physical activity domains during the transition out of high school and psychosocial and environmental determinants of these changes. METHODS A 1-year prospective study was designed. The baseline sample was composed of 244 last-year high school students (58.6% female) from Valencia, Spain. Follow-up rate was 46%. Physical activity and potential determinants were measured by the Global Physical Activity Questionnaire and other evaluated scales in 2 waves. RESULTS Total physical activity and active commuting (AC) decreased, respectively, by 21% and 36%, only in males. At time 1, access to car/motorbike (inverse), planning/psychosocial barriers (inverse), street connectivity (positive) and parental education (inverse) were significantly associated with AC (P < .05). Prospectively, the increase in distance to school/workplace was associated with AC decrease among males (P < .001). In both genders, there was a decrease in leisure-time physical activity (LTPA; -35% in males, -43% in females). At time 1, self-efficacy and social support were positive correlates of LTPA (P < .05). Social support decreases were associated with reductions in LTPA for males (P < .05). CONCLUSIONS Several psychosocial and environmental correlates of physical activity change were identified, and these are promising targets for interventions.

Preparedness for landing after a self-initiated fall

A startling auditory stimulus (SAS) causes a faster execution of voluntary actions when applied together with the imperative signal in reaction time tasks (the StartReact effect). However, speeding up reaction time may not be the best strategy in all tasks. After a self-initiated fall, the program for landing has to be time-locked to foot contact to avoid damage, and therefore advanced execution of the program would not be convenient. We examined the effects of SAS on the landing motor program in 8 healthy subjects that were requested to let themselves fall from platforms either 50 or 80 cm high at the perception of a visual imperative signal and land on specific targets. In trials at random, SAS was applied either together with the imperative signal (SAS(IS)) or at an appropriate prelanding time (SAS(PL)). As expected, the latency of takeoff was significantly shortened in SAS(IS) trials. On the contrary, the timing of foot contact was not significantly different for SAS(PL) compared with control trials. No changes were observed in the size of the electromyograph bursts in the two experimental conditions with respect to the control condition. Our results indicate that the landing program after a self-initiated fall may in part be organized at the time of takeoff and involve precise information on timing of muscle activation. Once launched, the program is protected against interferences by external inputs.

The Impact of Mandatory Helmet-Use Legislation on the Frequency of Cycling to School and Helmet Use Among Adolescents.

BACKGROUND This paper analyzes changes in the frequency of cycling to school and helmet wearing after the introduction of a mandatory helmet law, and attempts to identify factors associated with the acceptance of helmet use. METHODS A mixed-method study was designed with a 7-month follow-up period (April 2014 to November 2014). The initial sample included 262 students (aged 12 to 16 years) from Valencia, Spain. The data were collected by questionnaire and 2 focus-group interviews were conducted. RESULTS No significant changes in cycling-to- school behavior were found during the study period. Cycle helmet use improved, especially among boys, those who used their own bike, and among adolescents who lived within 2 km of school (P < .05 in all cases). The most common reasons given for not using a helmet were social factors. Peer-group pressure had a negative influence on helmet use among adolescents. Participants also indicated that helmet use is inconvenient, in particular among students who used the public bicycle-sharing program. CONCLUSION The implementation of the helmet-use law did not have a negative impact on the frequency of cycling to school. Our findings provide an empirical basis for designing educational interventions and programs to increase helmet use among adolescents.

Barreras percibidas en el desplazamiento activo al centro educativo: fiabilidad y validez de una escala

OBJECTIVE To examine the reliability and validity of a scale to measure perceived barriers to active commuting to school among Spanish young people. METHOD The validity of the scale was assessed in a sample of 465 adolescents (14-18 years) using a confirmatory factor analysis and studying its association with self-reported active commuting to school. The reliability of the instrument was evaluated in a sub-sample that completed the scale twice separated by a one-week interval. RESULTS The results showed that the barriers scale had satisfactory fit indices, and two factors were determined. The first included environment- and safety-related items (α=0.72), while the other concerned planning and psychosocial items (α=0.64). Active commuting to school showed significant correlations with the total score of the barriers scale (rho=-0.27; p <0.001), with the environmental/safety barriers (rho=-0.22; p <0.001), as well as with the planning/psychosocial barriers (rho=-0.29; p <0.001). Test-retest ICCs for the barriers ranged from 0.68 to 0.77. CONCLUSION The developed scale has acceptable validity and good reliability to assess barriers to active commuting to school among Spanish young people.

Intra and intersession repeatability and reliability of the S-Plate® pressure platform

AIM The aim of this study was to assess the repeatability and reliability of the S-Plate® pressure platform in a group of healthy subjects. MATERIAL AND METHODS Forty subjects, free from physical conditions that would affect normal gait, walked along a five-meter corridor while data were recorded from the pressure platform. A total of 10 steps (five each side) were obtained as well as five static trials; the same measurements were repeated one week later. Peak and mean plantar pressures and contact area were recorded for both dynamic and static trials. Additionally, weight supported on each limb was documented during static trials. To assess intrasession and intersession repeatability and reliability, the intraclass correlation coefficients (ICCs) and coefficient of variation (CoV) were calculated. RESULTS Taking the ICC values into account, every static and dynamic variable analysed showed moderate to excellent reliability and the CoV values were all below 12%. CONCLUSION Measurements of either static or dynamic plantar pressure variables with the S-Plate® pressure platform show good repeatability and reliability, and so it is useful for comparing steps within and between sessions.