The aim of this study was to assess postural response efficiency to a self-initiated perturbation using an original method based on the inverted pendulum model. Eight young subjects were asked to perform bilateral arm raising and lowering at 3 different speeds while standing on a force plate. The time necessary to recover a steady state following the movement was computed by analyzing the time evolution of the coefficient of determination between the center of pressure and center of mass difference variable (COP-COM) and the horizontal acceleration of the COM. Results show a spatial reorganization (hip strategy) of the segments following the perturbation and a strong influence of the linear relationship to the arm velocity. However, the conditions of arm velocity did not have any effect on the time response of the postural control, suggesting that this parameter would be an invariant characteristic of the movement. These results support the existence of an internal representation of the inertial constraints related to the movement execution.
Nicolas Termoz, Luc Martin, and François Prince
Brian J. Diefenbach, Anthony S. Kulas, Christopher J. Curran, and Patrick M. Rider
flexor muscle was influenced by changes in torque level at the medial elbow. (D) The length of the UCL was influenced by changes in torque level at the medial elbow. All properties were measured at 3 different torque conditions (neutral, passive valgus, and self-initiated varus). UCL indicates ulnar
Nabil Ilmane and Jacques LaRue
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. Results showed that the delays between the onsets of the postural and focal activities were significantly different between RC and both the SI and the AC conditions. Movement time, time to peaks (negative and positive), are shorter in the RC, intermediate in the AC, and longer in the SI condition. Variability was significantly larger in AC in comparison with RC and SI. These results support the existence of different control modes triggered by the temporal pressure; they demonstrate that these control modes can be generalized to complex intentional movements such as the throwing skill and to an anticipation-coincidence situation.
Kevin Patton and Melissa Parker
extrinsic motivating factors in pursuing a professional role change and the selection of a D-PETE program. Three factors stimulated participants to enter D-PETE: prompted by others, self-initiated, and a forced choice. While presented as distinct themes, the self-initiated factors represent altruistic
Ang Chen and Xinlan Liu
The expectancy-value theory postulates that motivation relies on individuals’ beliefs of success, perceived Attainment, Intrinsic Interest, and Utility values and Cost. This study examined Chinese college students’ expectancy-value motivation in relation to physical education and self-initiated physical activity.
A random sample of 368 Chinese university students responded to questionnaires on perceived expectancy beliefs, perceived values, and cost in terms of their experiences in mandatory physical education programs and in self-initiated after-school physical activity. They reported their choice decisions for continuing physical education. Data were analyzed using descriptive statistics, χ 2, logistic and linear regressions.
The physical education curriculum was perceived as a major cost to motivation. Motivated by the Intrinsic Interest and Utility value, most students chose to continue to take physical education. Self-initiated after-school physical activity was motivated by the Attainment value only. No association was found between self-initiated physical activity and Liking or Disliking of physical education.
Motivation for physical education and for self-initiated physical activity derived from different perceived values. The Attainment value motivates the students for self-initiated physical activity, whereas Intrinsic Interest and Utility values motivate them to choose to continue physical education.
Swati Shenoy and Alexander S. Aruin
The objective of this study was to determine if a forward-tilted seat and the resultant semi-kneeling body position associated with sitting on the Balans Multi Chair (BMC) affect postural control in sitting. Nine healthy subjects were seated on either the BMC or a regular (REG) chair with their arms extended. They were instructed to induce self-initiated body perturbations in four different directions by exerting brief pulses of force against a stationary frame positioned in front of them. Electromyographic (EMG) activities of trunk and leg muscles were recorded before and during the perturbations. The results show that sitting on both types of chairs was associated with anticipatory activation of trunk and upper leg muscles. In contrast, anticipatory activation of distal muscles was observed while sitting only on the REG chair and was absent while sitting on the BMC. The outcome of the study suggests that although the forward-tilting seat and semi-kneeling body position might help in preserving a normal lordosis, it is not associated with anticipatory activation of lower leg muscles, which might reduce the ability of an individual to counteract self-initiated body perturbations. These findings stress the important role of chair designs in the control of sitting posture.
Etem Curuk, Yunju Lee, and Alexander S. Aruin
, & Aruin, 2002 ). A significant decrease in the magnitude of the APAs on the affected side in persons with unilateral stroke has been reported during the performance of self-initiated perturbations, such as releasing a load from an extended arm ( Slijper et al., 2002 ). It was also described that the
Yubing Wang and Ang Chen
models that specifically focus on how PE can influence students’ out-of-school PA. The two models are the situational-to-self-initiated motivation model ( Chen & Hancock, 2006 ) and the transcontextual model ( Hagger & Chatzisarantis, 2016 ). The former model postulates how knowledge learning in PE
Tippawan Kaewmanee and Alexander S. Aruin
the base of support in predictable and stable states, such as sitting and quiet stance. Dynamic postural control is defined as the ability to maintain body stability during self-initiated or external perturbations. To maintain dynamic control during perturbations, the central nervous system (CNS
Ben D. Kern, Kim C. Graber, Amelia Mays Woods, and Tom Templin
approach ( Priestley, Biesta, & Robinson, 2015 ; Cothran, 2001 ), whereby teachers self-initiate change. For physical educators, the inadequacy of PD is confounded by the fact that most in-service PD is not specific to their needs, and they receive comparatively fewer PD opportunities than their classroom