Adjustments to gait were examined when positioning the foot within a narrow target at the end of an approach for two impact conditions, hard and soft. Participants (6 M, 6 F) ran toward a target of three lengths along a 10-m walkway consisting of two marker strips with alternating black and white 0.5-m markings. Five trials were conducted for each target length and impact task, with trials block randomized between the 6 participants of each gender. A 50Hz digital video camera panned and filmed each trial from an elevated position adjacent to the walkway. Video footage was digitized to deduce the gait characteristics. A linear speed/accuracy tradeoff between target length and approach time was found for both impact tasks (hard, r = 0.99, p < 0.01; soft, r = 0.96, p < 0.05). For the hard-impact task, visual control time increased linearly (r = 0.99, p < 0.05) when whole-body approach velocity decreased. Visual control time was unaffected by whole-body approach velocity in the soft-impact task. A constant tau-margin of 1.08 describes the onset of visual control when approaching a target while running, with the control of braking during visual control described by a tau-dot of –0.85. Further research is needed to examine the control of braking in different targeting tasks.
Elizabeth J. Bradshaw and W.A. Sparrow
Anne-Marie Brouwer, Eli Brenner, and Jeroen B.J. Smeets
Before an aspect of a movement that is predicted by a control theory can be considered as evidence for that theory, it should be clear that this aspect is not the result of some other property of the movement. We investigate whether this condition is met in studies that claim to provide evidence for the tau-coupling theory. This theory proposes that moving targets are intercepted at a specified goal zone by maintaining a constant ratio between the tau (time to closure) of the gap between the hand and the goal zone and the tau of the gap between the hand and the moving target. In line with the theory, previous research has found a linear relationship between these two decreasing taus during the last part of such a movement. To investigate whether this linear relationship was a side-effect of smooth successful movements, we modeled smooth ballistic hand movements that were independent of the target's movement but led to successful interception. We found that the resulting taus of decreasing gaps were also related linearly. We conclude that this relationship cannot be considered as evidence for the tau-coupling theory.
Joanne Smith, Madeleine Grealy, and Gert-Jan Pepping
We investigated a general theory accounting for the guidance of ongoing movements in an interceptive reaching task. The aim was to assess the premise of tau-coupling that the coupling constant k, the ratio of taus (τs) of motion gaps between hand and object, reflects the kinematics of the on-going movement. The spatial and temporal constraints of the interceptive action were manipulated in three task conditions. While the time dependent counterpart of k, K(t) exhibited task effects, k itself could not distinguish between task manipulations. K(t) showed large variability during the initial acceleration phase, small variability during the rest of the movement, and task dependent changes during the final deceleration phase of interception. The findings highlight the importance of clarifying what constitutes as t-coupling.
Greg Doncaster, John Iga, and Viswanath Unnithan
, when appropriately scaled. Similarly, it was hypothesized that less mature players would display superior VO 2 kinetics (faster taus ) than their more mature counterparts. Methods Participants and Anthropometry A total of 21 highly trained youth soccer players aged between 12 and 14 years volunteered
Stein G.P. Menting, Marco J. Konings, Marije T. Elferink-Gemser, and Florentina J. Hettinga
behavior of the skaters during the race, the relation between start/intermediate rankings and final rankings was analyzed using Kendall tau-b correlations. Positive correlations would indicate that relatively, a top/bottom-place skater in that particular lap was also ranked in top/bottom place at the end
Arthur H. Bossi, Ciaran O’Grady, Richard Ebreo, Louis Passfield, and James G. Hopker
were calculated as partial eta squared ( η p 2 ). The relationship between lap and overall rankings was determined by Kendall tau-b correlations. 26 A Friedman test was carried out to investigate whether ranking changes—in absolute values—would be different among laps. Finally, sex differences were
Uri Gottlieb and Shmuel Springer
calculated using Cohen d , with value >0.8 considered a large effect size. Kendall tau was used to assess associations between continuous variables. Correlation coefficients were considered weak (<.3), moderate (.3–.5), and strong (>.5). A significance level of P < .05 was set. IBM SPSS Statistics for
William B. Haug, Eric J. Drinkwater, Lachlan J. Mitchell, and Dale W. Chapman
Initial short-track speed-skating 14-m start performance has substantial influence on 500-m race outcome at the international level, yet the relationship has not been systematically quantified. The purpose of this investigation was to examine the relationship between rank position entering first corner (RPEFC) and race outcome and to understand how this relationship changes with competition round and absolute race intensity. Data were compiled from 2011–2014 World Cup seasons and 2010 and 2014 Olympic Winter Games. Association between RPEFC and race outcome was determined through Kendall tau-rank correlations. A visual comparison was made of how the relationship changes with relative competition level (race tau correlations were sorted by competition round) and with race intensity (race tau correlations were sorted by within-event winning time). A very large relationship between RPEFC and race outcome was observed (correlations for cohort, τ = .60; men, τ = .53; women, τ = .67). When examined by competition round (quarter- to A-finals), no substantial change in relationship was observed (men, τ = .57–.46; women, τ = .73–.53). However, when the start–performance relationship was considered by within-event winning time, the relationship strength increased with decreasing time (men, τ = .61 to .46; women, τ = .76 to .57; fastest to 7th- and 8th-fastest combined, respectively). These results establish and quantify RPEFC as an important aspect of elite short-track 500-m race outcome. RPEFC as an indicator of race outcome becomes increasingly important with absolute race intensity, suggesting that RPEFC capability is a discriminating factor for competitors of similar top speed and speed endurance.
James H. Rimmer, David Braddock, and Glenn Fujiura
A body mass index (BMI) greater than 27 has been cited as a risk factor for heart disease and diabetes mellitus resulting from excess weight. The purpose of this study was to determine the association between BMI (>27) and two other obesity indices–height-weight and percent body fat–as well as to investigate the relationship between BMI and three blood lipid parameters–total cholesterol, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) in 329 adults with mental retardation (MR). Males were significantly taller and heavier than females, but females had a significantly higher BMI. Kendall’s Tau-C revealed a significant association between BMI and each of the following: height-weight, percent body fat, LDL-C, and HDL-C. However, there were a significant number of false negatives and false positives on each of the criteria. The congruence between at-risk BMI and two other obesity parameters (height-weight and percent body fat) in a population of adults with MR is not strong. Professionals should employ the BMI along with skinfold measures to assess a person’s at-risk status for excess weight.
A. Mark Williams, Joan Vickers, and Sergio Rodrigues
Processing efficiency theory predicts that anxiety reduces the processing capacity of working memory and has detrimental effects on performance. When tasks place little demand on working memory, the negative effects of anxiety can be avoided by increasing effort. Although performance efficiency decreases, there is no change in performance effectiveness. When tasks impose a heavy demand on working memory, however, anxiety leads to decrements in efficiency and effectiveness. These presumptions were tested using a modified table tennis task that placed low (LWM) and high (HWM) demands on working memory. Cognitive anxiety was manipulated through a competitive ranking structure and prize money. Participants’ accuracy in hitting concentric circle targets in predetermined sequences was taken as a measure of performance effectiveness, while probe reaction time (PRT), perceived mental effort (RSME), visual search data, and arm kinematics were recorded as measures of efficiency. Anxiety had a negative effect on performance effectiveness in both LWM and HWM tasks. There was an increase in frequency of gaze and in PRT and RSME values in both tasks under high vs. low anxiety conditions, implying decrements in performance efficiency. However, participants spent more time tracking the ball in the HWM task and employed a shorter tau margin when anxious. Although anxiety impaired performance effectiveness and efficiency, decrements in efficiency were more pronounced in the HWM task than in the LWM task, providing support for processing efficiency theory.