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Adriana M. Degani, Alessander Danna-Dos-Santos and Mark L. Latash

We tested the hypothesis that a sequence of mechanical events occurs preceding a step that scales in time and magnitude as a whole in a task-specific manner, and is a reflection of a “motor program.” Young subjects made a step under three speed instructions and four tasks: stepping straight ahead, down a stair, up a stair, and over an obstacle. Larger center-of-pressure (COP) and force adjustments in the anteriorposterior direction and smaller COP and force adjustments in the mediolateral direction were seen during stepping forward and down a stair, as compared with the tasks of stepping up a stair and over an obstacle. These differences were accentuated during stepping under the simple reaction time instruction. These results speak against the hypothesis of a single motor program that would underlie postural preparation to stepping. They are more compatible with the reference configuration hypothesis of whole-body actions.

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Eric Yiou and Manh-Cuong Do

This study examined how the central nervous system organizes mediolateral (ML) “anticipatory postural adjustments” (APAs) for stepping initiation (SI) to take into account the postural perturbation induced by voluntary lateral arm raising. Subjects purposely stepped in isolation (“isolated stepping”) or in combination with lateral raising of dominant arm (“motor sequence”). SI was carried out with the leg ipsilateral or controlateral to raising arm. Results showed that APA amplitude increased from “ipsilateral isolated stepping” to “ipsilateral sequence”, but did not change in conditions involving controlateral leg; ML instability increased from “ipsilateral isolated stepping” to “ipsilateral sequence”, but decreased from “controlateral isolated stepping” to “controlateral sequence”. These changes were exacerbated when inertia was added at the hand during raising. These results suggest that APAs for SI are globally scaled as a function of the biomechanical consequences of forthcoming arm movement on ML postural stability.

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Satoshi Hamai, Ken Okazaki, Satoru Ikebe, Koji Murakami, Hidehiko Higaki, Hiroyuki Nakahara, Takeshi Shimoto, Hideki Mizu-uchi, Yukio Akasaki and Yukihide Iwamoto

The purpose of this study was to investigate in vivo kinematics in healthy and osteoarthritic (OA) knees during stepping using image-matching techniques. Six healthy volunteers and 14 patients with a medial OA knee before undergoing total knee arthroplasty performed stepping under periodic anteroposterior radiograph images. We analyzed the three-dimensional kinematic parameters of knee joints using radiograph images and CT-derived digitally reconstructed radiographs. The average extension/flexion angle ranged 6°/53° and 16°/44° in healthy and OA knees, with significant difference in extension (P = .02). The average varus angle was –2° and 6° in healthy and OA knees, with a significant difference (P = .03). OA knees showed 1.7° of significantly larger varus thrust (P = .04) and 4.2 mm of significantly smaller posterior femoral rollback (P = .04) compared with healthy knees. Coronal limb alignment in OA knees significantly correlated with varus thrust (R 2 = .36, P = .02) and medial shift of the femur (R 2 = .34, P = .03). Both normal and OA knees showed no transverse plane instability, including anteroposterior, mediolateral directions, or axial rotation. In conclusion, OA knees demonstrated different kinematics during stepping from normal knees: less knee extension, larger varus thrust, less posterior translation, and larger medial shift.

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Jonathan D. Connor, Robert G. Crowther and Wade H. Sinclair

Evasive maneuvers, such as the side- or split-step, are common occurrences in all playing levels of rugby league (RL). These maneuvers are employed to either evade defenders or increase the difficulty of a defender making a tackle ( Gabbett, 2012 ), with previous research focused on the

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Hiroaki Hobara, Sakiko Saito, Satoru Hashizume, Hiroyuki Sakata and Yoshiyuki Kobayashi

The average velocity of a 100-m sprint is the product of the average step frequency and average step length. Although both parameters are inversely correlated, an increase in 1 factor will result in an improvement in sprint velocity, provided the other factor does not undergo a proportionately

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Emily E. Gerstle, Kristian O’Connor, Kevin G. Keenan and Stephen C. Cobb

population, one-third of all falls on steps occur on the first or last step. 2 Further, in a study following older adults and the circumstances of their falls, 49% of outdoor falls resulting in injury occurred on the sidewalk, street, or a curb. 3 The prevalence of ankle sprains caused by falls

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Clare B. Johnson, Shannon L. Mihalko and Karl M. Newell

The study reported had three purposes, namely, to analyze the effect of aging (cohort groups 20–29, 60–69, 70–79, and 80–89 years of age), step length, and self-efficacy on the time to reacquire stability after the execution of a step. The analysis of force-platform data showed that the time to reacquire a stable posture after taking a step increased with increments of age. Correlation analysis showed that older adults were less confident in their ability to complete daily activities without falling or losing balance and that participants with lower levels of balance-related efficacy required a longer time to reacquire stability. These findings provide evidence that aging imposes temporal limitations in the regaining of postural stability that are related to individuals’ perceptions of balance and falls efficacy.

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Catrine Tudor-Locke and Elroy J. Aguiar

Ambulation (stepping) is an essential component of many activities of daily living (e.g., household chores, active transport), with walking being the most commonly reported physical activity choice across the globe ( Hulteen et al., 2017 ). As such, step counting has become a standard measurement

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Timothy A. Hanke, Bruce Kay, Michael Turvey and David Tiberio

Virtually all naturally occurring human voluntary movements, whether discrete or rhythmic in nature, act in collaboration with and upon a background of ongoing, dynamic postural stabilization. A step is integral for intentional actions such as the initiation and ongoing execution of walking, as

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Catrine Tudor-Locke, John M. Schuna Jr, Damon L. Swift, Amber T. Dragg, Allison B. Davis, Corby K. Martin, William D. Johnson and Timothy S. Church

meeting public health recommendations for physical activity. 13 By contrast, traditional Amish women average approximately 14,000 steps per day 14 and are considered “highly active.” 15 Systematic reviews of step-counting programs that have employed a step goal, 16 specifically a 10,000 steps per day