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Riley C. Sheehan and Jinger S. Gottschall

Falls are the leading cause of injury for all age groups. However, adults over 65 are at a higher risk, with one-third falling each year. Transitioning between level and hill surfaces poses a greater fall risk than walking on either surface alone. Previous studies found that young adults adopted a cautious gait pattern to mitigate this risk. As older adults typically employ a cautious pattern during level walking, we investigated how they modify their gait pattern to safely transition between surfaces. Twenty adults over the age of 65 transitioned onto and off of a 15° ramp while we recorded kinematics and muscle activity. During the level-to-downhill and uphill-to-level transitions, participants took slower, shorter steps indicative of an exaggerated cautious gait pattern. The older adults also exhibited greater muscle activity during the transitions, which may be due to muscle weakness requiring compensatory strategies to meet the greater demands of the task. However, the slower, shorter steps when transitioning from uphill to level suggest that these compensations may not always be adequate. Thus, it is important to consider the relationship between physical abilities and task demands in evaluating walking terrains that may be excessively difficult or dangerous for older adults.

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Riley C. Sheehan and Jinger S. Gottschall

Individuals must constantly modify their gait patterns to safely transition between different surfaces. The goal of the current study was to determine if gait changes could be detected two steps from a transition, and whether these changes scaled with the angle of the hill. We hypothesized that during the anticipation of uphill walking and the aftereffect of downhill walking, the magnitude of kinetic and electromyography changes would be greatest at steep hill angles and fewer steps from the transition. We collected force and electromy-ography data as participants walked on the level ground before an uphill ramp and after a downhill ramp. As hypothesized, there were significant main effects for both the number of steps and angle of the hill for the first vertical GRF peak, as well as lateral gastrocnemius and vastus lateralis activity. Overall, our results indicate that when transitioning to and from hills, anticipation and aftereffect responses occur at least two steps from the transition and are scaled to the angle of the hill.

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Jinger S. Gottschall, Dmitri Y. Okorokov, Noriaki Okita and Keith A. Stern

Healthy young adults transition between level and hill surfaces of various angles while walking at fluctuating speeds. These surface transitions have the potential to decrease dynamic balance in both the anterior-posterior and medial-lateral directions. Hence, the purpose of the current study was to analyze modifications in temporal-spatial parameters during hill walking transitions. We hypothesized that in comparison with level walking, the transition strides would indicate the adoption of a distinct gait strategy with a greater base of support. Thirty-four participants completed level and hill trials on a walkway with a 15-degree portable ramp apparatus. We collected data during 4 transition strides between level and ramp surfaces. In support of our hypothesis, compared with level walking, the base of support was 20% greater during 3 out of the 4 transition strides. In short, our results illustrate that healthy young adults did adopt a distinct gait strategy different from both level and hill walking during transitions strides.

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Graham E. Caldwell

The effects of relative tendon/fiber proportion and tendon elasticity on the force output of the Hill muscle model (a contractile component [CC] in series with an elastic element [SEC]) were examined through computer simulation. Three versions of the Hill model were constructed. Model 1 examined the effect of relative tendon/fiber proportion on CC kinematics and kinetics during an isometric twitch, while Model 2 compared the effect of changes in tendon compliance. These models revealed force profile differences related to alterations in CC velocity, although the reasons underlying the variation in CC kinematics were different. The relative tendon/fiber proportion and tendon compliance differences were examined in combination in Model 3. Test simulations revealed response differences among the three model versions, and therefore verified Alexander and Ker's (1990) contention that the morphology of muscle is related to design criteria. It is suggested that the implementation of generalized muscle models to represent specific units of the musculoskeletal system should be done carefully and that the implementation process itself warrants further study.

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Claudia Meyer, Sophie Hill, Keith D. Hill and Briony Dow

and receipt of falls prevention knowledge relevant to their clients, in the local environmental context ( Meyer, Dow, Hill, Tinney, & Hill, 2016 ). A discussion tool can support both service providers (as KBs) and people with dementia and their caregivers to collaboratively prioritize and address

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Thomas Curran and Andrew P. Hill

for athletes. These outcomes include (among others) poorer coping, lower subjective well-being, and higher burnout (e.g.,  Gaudreau & Verner-Filion, 2012 ; Hill, Hall, Appleton, & Kozub, 2008 ; Hill, Hall, & Appleton, 2010 ). However, the effects of self-oriented perfectionism have emerged as more

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Rebecca Quinlan and Jessica A. Hill

30671906 4. Howatson G , McHugh MP , Hill JA , et al . Influence of tart cherry juice on indices of recovery following marathon running . Scand J Med Sci Sport . 2010 ; 20 : 843 – 852 . doi: 10.1111/j.1600-0838.2009.01005.x 5. Garcıa-Lafuente A , Guillamone E , Villares A , Rostagno

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Fabien Dal Maso, Mickaël Begon and Maxime Raison

One approach to increasing the confidence of muscle force estimation via musculoskeletal models is to minimize the root mean square error (RMSE) between joint torques estimated from electromyographic-driven musculoskeletal models and those computed using inverse dynamics. We propose a method that reduces RMSE by selecting subsets of combinations of maximal voluntary isometric contraction (MVIC) trials that minimize RMSE. Twelve participants performed 3 elbow MVIC in flexion and in extension. An upper-limb electromyographic-driven musculoskeletal model was created to optimize maximum muscle stress and estimate the maximal isometric force of the biceps brachii, brachialis, brachioradialis, and triceps brachii. Maximal isometric forces were computed from all possible combinations of flexion-extension trials. The combinations producing the smallest RMSE significantly reduced the normalized RMSE to 7.4% compared with the combination containing all trials (9.0%). Maximal isometric forces ranged between 114–806 N, 64–409 N, 236–1511 N, and 556–3434 N for the brachii, brachialis, brachioradialis, and triceps brachii, respectively. These large variations suggest that customization is required to reduce the difference between models and actual participants’ maximal isometric force. While the smallest previously reported RMSE was 10.3%, the proposed method reduced the RMSE to 7.4%, which may increase the confidence of muscle force estimation.

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Riley C. Sheehan and Jinger S. Gottschall

In a previous study, we found that participants modified how they transitioned onto and off of ramp configurations depending upon the incline. While the transition strategies were originally attributed to ramp angles, it is possible that the plateau influenced the strategies since the final surface height also differed. Ultimately, for the current study, we hypothesized that an individual’s transition strategies would have significant main effects for ramp angle, but not plateau height. Twelve healthy, young adults transitioned onto 3 distinct ramp configurations, a 2.4-m ramp angled at 12.5° ending at a plateau height of 53 cm, a 1.2-m ramp angled at 23.5° ending at a plateau height of 53 cm, and a 2.4-m ramp angled at 23.5° ending at a plateau height of 99.5 cm. Kinematics, kinetics, and muscle activity were measured during the stance phase before contacting the ramp. In support of our hypothesis, impact peak, active peak, and all of the muscle activity variables had a significant main effect for ramp angle, with greater vertical force peaks and muscle activity on steeper ramp transitions. These findings support our previous interpretation that individuals use estimations of ramp angle, not plateau height, to determine their transition strategies.

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Denise M. Hill, Sheldon Hanton, Nic Matthews and Scott Fleming

The study examined the effect of an evidence-based intervention on choking in golf. It is informed by the work of Hill, Hanton, Matthews and Fleming (2010a) that explored the experiences of elite golfers who either choked or excelled under pressure. The perceptions of elite golf coaches who worked with both ‘chokers’ and those who excelled, were also considered. It revealed that choking may be alleviated through the use of process goals, cognitive restructuring, imagery, simulated training and a pre/postshot routine. The present study incorporated each strategy into an intervention that was introduced to two professional golfers (aged 22) who choked under pressure regularly. Through an action research framework the impact of the intervention was evaluated over a ten month period via qualitative methods. The results indicated the intervention alleviated the participants’ choking episodes and so provides information that can be of use to practitioners working with golfers who choke.