Grasping a better understanding of the intrinsic dynamics of rhythmical and discrete prehension

In this study, the authors examined the influence of the intrinsic dynamics of discrete and rhythmical prehension. Six adults underwent a scaling procedure in which the movement time was systematically increased so that it corresponded with 6 frequencies: 0.5, 0.75, 1.0, 1.25, 1.5, and 1.75 Hz. In posttests, participants moved at their own preferred pace. No differences were found in the relative time to final hand closure (T[rfc]) between the rhythmical and discrete conditions. The variability of T[rfc] was shown to be less at the preferred step of scaling than during the posttest. With the scaling technique, one can guide participants into more stable movement patterns than they can achieve when the metronome is not present, because, when the metronome is present, their movements become anchored to the external pacing cue. Those findings provide support for the use of a scaling technique to identify the influence of the intrinsic dynamics during rhythmical and discrete movements.     

Observational modeling effects for movement dynamics and movement outcome measures across differing task constraints: a meta-analysis

The authors conducted a meta-analysis of the observational modeling literature to quantify overall between-participants treatment effects obtained when movement behaviors are acquired. Effects were obtained and reported separately for movement dynamics (MD) and movement outcome (MO) measures. The overall mean observational modeling treatment effects (delta(u)Bi) were 0.77 and 0.17, respectively, for MD and MO measures. The effects reflected a significant advantage of observational modeling over practice-only control conditions. Most important, the magnitude of the obtained effects was far stronger for MD than for MO measures, confirming a distinctive response to observational modeling during motor learning. The advantage for MD measures over observational modeling measures was replicated for different types of tasks. Observational modeling was particularly beneficial for serial tasks (delta(u)Bi = 1.62 and 0.61, respectively, for MD and MO). There were slightly reduced effects for continuous tasks (delta(u)Bi = 1.01 and 0.51, respectively, for MD and MO) and smaller to medium-sized effects for discrete tasks (delta(u)Bi = 0.56 and 0.10, respectively, for MD and MO). The authors discuss those findings with reference to the visual perception perspective on observational modeling, i.e., that demonstrations primarily convey relative motions required to approximate modeled movement behaviors.     

Variation in coordination of a discrete multiarticular action as a function of skill level

The authors investigated coordination modes that emerged as a function of the interaction between skill level and task constraints in a multiarticular kicking action. Five skilled, 5 intermediate, and 5 novice participants attempted to satisfy specific height and accuracy constraints in kicking a ball over a barrier. Skilled and intermediate groups demonstrated a functional coordination mode involving less joint involvement at the proximal joints and greater joint involvement at distal joints, mimicking a chip-like action in soccer. Conversely, the novice group tended to produce larger ranges of motion throughout the kicking limb in a driving-like kicking action. Key differences were also found for task outcome scores, joint angle-angle relations, and ball-trajectory plots between the skilled and intermediate groups and the novice group. Findings from this study demonstrated that joint involvement during this discrete multiarticular action is a function of skill level and task constraints rather than a consequence of a global freezing-freeing strategy suggested in some previous research. The authors also highlight the merit of using a model of the acquisition of coordination in examining how coordination modes for multiarticular actions differ as a function of skill.     

Perceptions of sugar mommy practices in South Africa

The study sought to explore sugar mommy practices regarding their occurrence, acceptability as well as perceived reasons why older women and younger men enter into sugar mommy relationships. An exploratory qualitative study involving 135 participants from 11 diverse focus groups in terms of age, gender (females=27%) and geotype throughout the nine South African provinces was conducted. Data on the participants’ views, opinions and experiences of sugar mommy practices were collected using focus group interviews. The data were thematically analyzed. The study found that sugar mommy practices were prevalent in South Africa. The perceived reasons for acceptability were: love, survival, and correctness. Perceived reasons why older women have sexual relationships with younger men included: sexual fulfilment, domination, reduction of stress, physical attraction, procreation, lack of self-control, youthful feeling, migrancy, difficulty in finding partners of compatible age and young men being seen as not demanding. Perceived reasons why younger men have sexual relationships with older women included: material gain, reduction of stress, being enticed, rejection by women of compatible age, peer influence and belief that older women are purer. Given the increase in sugar mommy practices, which may have significant implications for the prevalence of HIV/AIDS, it is necessary to understand the underlying perceptions of these practices, in order to develop culturally relevant and socially acceptable intervention programmes.     

Expertise effects on decision-making in sport are constrained by requisite response behaviours – A meta-analysis

ObjectivesA quantitative review of the effects of requisite responses and methods of stimulus presentation for assessing decision-making expertise in sport was undertaken.DesignAn electronic literature search was conducted in the online databases: SPORTDiscus with Full Text and ISI Web Knowledge All Databases. Articles for analysis were selected according to prior defined criteria.MethodsWe considered 111 effect sizes in studies involving 882 expert and non-expert participants. Effect sizes were calculated for six common protocols for measures responses: verbalized knowledge, eye movement measures, decision time, response accuracy, movement accuracy, and movement time. Two moderator variables were also considered to assess effects of research protocols on the dependent variables: “the requisite response” and “stimulus presentation”. A random effect model was used to calculate effect sizes.ResultsAnalysis of moderator variables suggested that expertise effects were more apparent for “requisite responses” when participants were required to actually perform sporting actions and for “stimulus presentation” under in situ task constraints than for other conditions.ConclusionsFuture empirical work on expertise and decision-making needs to consider task representativeness in considering requisite responses of participants in simulating performance environment conditions. Use of representative task constraints with performers required to perform sport actions in in situ conditions appeared the most functional empirical protocols to enhance validity of data.     

Interpersonal distance regulates functional grouping tendencies of agents in team sports

The authors examined whether, similar to collective agent behaviors in complex, biological systems (e.g., schools of fish and colonies of ants), performers in team sports displayed functional coordination tendencies, based on local interaction rules during performance. To investigate this issue, they used videogrammetry and digitizing procedures to observe interpersonal interactions in common 4 versus 2 + 2 subphases of the team sport of rugby union, involving 16 participants aged between 16 and 17 years of age. They observed pattern-forming dynamics in attacking subunits (n = 4 players) attempting to penetrate 2 defensive lines (n = 2 players in each). Data showed that within each attacking subunit, the 4 players displayed emergent functional grouping tendencies that differed between the 2 defensive lines. Results confirmed that grouping tendencies in attacking subunits of team games are sensitive to different task constraints, such as relative positioning to nearest defenders. It was concluded that running correlations were particularly useful for measuring the level of interpersonal coordination in functional grouping tendencies within attacking subunits.     

Approximate entropy normalized measures for analyzing social neurobiological systems

When considering time series data of variables describing agent interactions in social neurobiological systems, measures of regularity can provide a global understanding of such system behaviors. Approximate entropy (ApEn) was introduced as a nonlinear measure to assess the complexity of a system behavior by quantifying the regularity of the generated time series. However, ApEn is not reliable when assessing and comparing the regularity of data series with short or inconsistent lengths, which often occur in studies of social neurobiological systems, particularly in dyadic human movement systems. Here, the authors present two normalized, nonmodified measures of regularity derived from the original ApEn, which are less dependent on time series length. The validity of the suggested measures was tested in well-established series (random and sine) prior to their empirical application, describing the dyadic behavior of athletes in team games. The authors consider one of the ApEn normalized measures to generate the 95th percentile envelopes that can be used to test whether a particular social neurobiological system is highly complex (i.e., generates highly unpredictable time series). Results demonstrated that suggested measures may be considered as valid instruments for measuring and comparing complexity in systems that produce time series with inconsistent lengths.     

Informational constraints shape emergent functional behaviours during performance of interceptive actions in team sports

Objectives

This study aimed to explain how defenders intercept the trajectory of a passing ball by understanding how they coupled their actions to critical information sources in a competitive performance setting in team sports.

Design

Time series data on movement displacements of fifteen senior male futsal performers were recorded and digitized during nine competitive futsal games.

Method

Performance was recorded by a digital camera and digitized with TACTO software. The spatial-temporal dynamics of performers during ten intercepted and ten non-intercepted passes were compared. Time to ball interception was calculated by the difference between the time of each defender to an interception point in ball trajectory and the time of the ball’s arrival at the same interception point. Initial distances between defenders and ball and velocity data of defenders and ball over time were also recorded.

Results

Time to ball interception revealed positive values when passes were not intercepted, and negative to zero values when passes were intercepted. At the moment of pass initiation defenders’ distances to the ball constrained their possibilities for successful interception. Analysis of defenders’ adaptations to the environment revealed that continuous changes in the defenders’ velocities constrained their success of the interception.

Conclusions

Intercepted passes seemed to be influenced by the continuous regulation of a defender’s velocity relative to the ball’s trajectory. Time to ball interception is a variable that captured the emergent functional behaviours of players attempting to intercept the trajectory of a pass in the team sport of futsal.