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Jos J. de Koning and Dionne A. Noordhof

know that it is not that simple. Is the winner really the best athlete? Did the training intervention give a performance benefit, and which performance-determining variable was improved? There is a lot of uncertainty in our day-to-day practice, while the world around us is asking for unambiguous

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Franklin Camargo-Junior, Marko Ackermann, Jefferson F. Loss and Isabel C.N. Sacco

The aim of this study was to investigate the effect of errors in the location of the center of pressure (5 and 10 mm) on lower limb joint moment uncertainties at different gait velocities (1.0, 1.5, and 2.0 m/s). Our hypotheses were that the absolute joint moment uncertainties would be gradually reduced from distal to proximal joints and from higher to lower velocities. Joint moments of five healthy young adults were calculated by inverse dynamics using the bottom-up approach, depending on which estimate the uncertainty propagated. Results indicated that there is a linear relationship between errors in center of pressure and joint moment uncertainties. The absolute moment peak uncertainties expressed on the anatomic reference frames decreased from distal to proximal joints, confirming our first hypothesis, except for the abduction moments. There was an increase in moment uncertainty (up to 0.04 N m/kg for the 10 mm error in the center of pressure) from the lower to higher gait velocity, confirming our second hypothesis, although, once again, not for hip or knee abduction. Finally, depending on the plane of movement and the joint, relative uncertainties experienced variation (between 5 and 31%), and the knee joint moments were the most affected.

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William P. Berg and Michael R. Hughes

Muscle activation was measured using EMG in 28 males (n = 28) while participants caught visually identical balls of known and unknown weights (50, 1.32, 2.18, and 2.99 kg) under variable (1–10s) and constant (3s) foreperiods. EMG integrals were computed for three time intervals before the catch (anticipatory), and one after (compensatory). Load uncertainty caused the CNS to use an anticipatory strategy characterized by preparation to catch balls of an unknown weight by utilizing about 92% of the muscle activation used to catch the heaviest possible ball under the known weight condition. The CNS appeared to scale anticipatory muscle activation to afford an opportunity to catch a ball of an unknown weight between .50 and 2.99 kg. The constant 3s foreperiod, which permitted temporal anticipation, did not influence the anticipatory neuromotor strategy adopted by the CNS to cope with load uncertainty. Load uncertainty also altered compensatory neuromotor control in catching.

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Daniel Cury Ribeiro and Jefferson Fagundes Loss

Link segment models are usually used to calculate proximal net reaction forces (PRF), as well as, proximal net moments (PNM). The correlation between electromyographic data and PNM is usually used to verify the model’s results. Nevertheless, this method permits only a qualitative verification of the obtained results. To assess model’s results in a quantitative perspective, another approach is needed. The aim of the current study was to assess the propagation of uncertainty on a link segment model results and identify the main sources of error on the quantification of PRF and PNM. One male performed five repetitions of different upper limb movements. An inverse dynamics approach associate with 3D link segment model was used to quantify PRF and PNM. The results of the model were evaluated by the use of Kleine and McClintock’s equation. The propagation of uncertainty for PRF reached, on average, 0.27 and for PNM, 0.97. The main cause of propagation of uncertainty was associated to the second time derivative calculations. Consequently, it is possible to suggest that the reduction of small distortions of center of mass acceleration will diminish the proximal net moment and proximal reaction force uncertainty values.

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Paul R. Surburg

The effects of uncertainty of occurrence and uncertainty of time—use of catch-trials and preparatory intervals—in simple reaction time (RT) trials were investigated with nonhandicapped and mentally retarded subjects. The results showed that: (a) Catch-trials impaired the performance of this task, (b) catch-trials did not differentiate among groups of subjects, and (c) preparatory intervals differently affected RT latencies of nonhandicapped and mentally retarded subjects. Interpretation of findings suggests that the use of catch-trials induced preparation decrements and that preparation decrements may explain in part the poorer RT performance of retarded subjects.

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Joshua M. Thomas and Timothy R. Derrick

The purpose of this research was to determine the effects of step uncertainty on shock attenuation and knee/subtalar synchrony. Uncertainty was manipulated by decreasing the intensity of light and introducing bumps to the running surface. Twelve experienced distance runners ran at their chosen pace on a treadmill with two surfaces (smooth and irregular) and three light intensities (light, medium, dark). Knee angle, subtalar angle, leg impacts, and head impacts were recorded at 1,000 Hz. Heart rate was also monitored. Injury potential was assessed by evaluating the impacts and asynchronous activity between the knee and subtalar joint. Stride length was not influenced by either source of uncertainty. Heart rate increased with the intensity of light on the smooth running surface but decreased with the intensity of light on the irregular surface. The knee was more flexed at heel contact during the irregular surface conditions but was not affected by the intensity of light. This decreased the effective mass of the impact and allowed greater peak leg accelerations and greater impact attenuation during irregular surface running. There was a decrease in the rearfoot angle at contact on the irregular surface that approached significance (p = 0.056). Knee/subtalar asynchrony increased with the intensity of light on the smooth surface but decreased on the irregular surface. It appears that participants used the knee joint to adapt to the irregular surface and thus accommodate changes in the terrain. The subtalar joint may have become more stable during irregular surface running to minimize the chance of inversion sprains. The effects of intensity of light were small and generally mediated the irregular surface effects. Overall, these adaptations likely reduced the potential for injury during irregular surface running but may have been detrimental to performance.

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Gary Robinson and Mark Freeston

A growing body of research has provided evidence for intolerance of uncertainty (IU)—a dispositional characteristic resulting from negative beliefs about uncertainty and its implications—as a possible transdiagnostic maintaining factor across a range of anxiety disorders. No studies have yet examined IU in performance anxiety in sport. The purpose of the present investigation, therefore, was to investigate the relationship between IU and performance anxiety in sport. Participants included 160 university athletes (51% female) who completed measures of IU, performance anxiety, and robustness of sport confidence. Regression analyses revealed that the inhibitory dimension of IU and robustness of sport confidence were significant predictors of performance anxiety. A simple mediation model was also tested and suggested indirect and direct effects of inhibitory IU on performance anxiety symptoms through robustness of sport confidence. Implications of these findings for researchers and practitioners and directions for future research are discussed.

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Chun-Hao Wang and Kuo-Cheng Tu

“backswing” from the forehand position was adopted for left and right spatial cues. According to discussions with one national team coach and some top-level badminton players, the backswing involves a higher level of directional uncertainty due to the fact that a professional player usually modifies the

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Masakazu Matsuoka, Hiroshi Kunimura and Koichi Hiraoka

inhibiting unnecessary responses, but uncertainty of the upcoming event disinhibits the response. This disinhibition occurs with prediction of the future event (prediction of the time or direction of the support surface translation), because inhibition of the unnecessary response is reasonable for efficient

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Leilani A. Madrigal, Vincenzo Roma, Todd Caze, Arthur Maerlender and Debra Hope

, brief fear of negative evaluation, intolerance of uncertainty, and negative affect) and unrelated constructs (i.e., positive affect, self-confidence). Method Participants Participants were randomly assigned to one of two groups for factor analytic studies: an exploratory factor analysis group ( n  = 271