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fourteen - Biomechanical constraints to stair negotiation
- Edited by Alan Walker, The University of Sheffield
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- Book:
- The New Dynamics of Ageing
- Published by:
- Bristol University Press
- Published online:
- 09 April 2022
- Print publication:
- 28 February 2018, pp 277-304
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Summary
Introduction
The majority of falls in old age occur during stair descent (Svanstrom, 1974; Tinetti et al, 1988; Startzell et al, 2000; Hamel and Cavanagh, 2004). The physical injuries arising from such falls are of obvious concern, but of equal importance is the fear of falling, and loss of confidence and mobility. Therefore, it is imperative to establish effective measures to reduce the risk of stair falls and accidents, in order to maintain independence and quality of life in old age.
Stair ascent is challenging, and becomes increasingly difficult as people get older. However, paradoxically, it is during stair descent where problems are more common. This is because stepping down is a very complex task, for which the downward movement of the body has to be controlled and balance maintained each time the foot contacts the step (McFadyen and Winter, 1988; Riener et al, 2002). Our ability to do this depends on many factors, including muscle strength, joint mobility, proprioception, vision and balance ability, all of which deteriorate with age (for example, Evans and Campbell, 1993; Grimston et al, 1993; Maki and McIlroy, 1996; Reeves et al, 2006).
Two critical design characteristics in a staircase that are related to these functional parameters are the step-rise, which is the height of each step, and the step-going, the depth of the step. It is possible that older individuals may be less able to generate the muscle forces required to support the body on the upper step or to control the motion when landing on the lower step. In fact, we have already documented that older people use more of their available muscle strength in their knee extensors and ankle plantarflexors to ascend and descend a staircase than younger people (Reeves et al, 2008, 2009). Previously, we examined stair negotiation of standard step dimensions (going: 280 mm, rise: 170 mm) with older adults. However, it is likely that age-related differences are amplified, with greater strength reserves required for more demanding stair-negotiating tasks (particularly higher step-rise) for the old. On the other hand, if the step-going is small (as is often the case in older homes), the ball of the foot of the lead leg will be placed towards the front edge of the step during descent, risking a slip.
DIFFERENCES IN HUMAN ANTAGONISTIC ANKLE DORSIFLEXOR COACTIVATION BETWEEN LEGS; CAN THEY EXPLAIN THE MOMENT DEFICIT IN THE WEAKER PLANTARFLEXOR LEG?
- CONSTANTINOS N. MAGANARIS, VASILIOS BALTZOPOULOS, ANTONY J. SARGEANT
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- Journal:
- Experimental Physiology / Volume 83 / Issue 6 / November 1998
- Published online by Cambridge University Press:
- 03 January 2001, pp. 843-855
- Print publication:
- November 1998
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The present study examined the hypothesis that the antagonistic ankle dorsiflexor coactivation level during maximum isometric voluntary plantarflexion (MVC) is a function of ankle angle. Six male subjects generated plantarflexion and dorsiflexion MVC trials at ankle angles of -15 deg (dorsiflexed direction), 0 deg (neutral position), +15 deg (plantarflexed direction) and +30 deg having the knee flexed at an angle of 90 deg. In all contractions surface EMG measurements were taken from tibialis anterior and soleus which were considered representative muscles of all dorsiflexors and plantarflexors, respectively. Antagonistic dorsiflexor coactivation was expressed as normalized EMG and moment. Calculations of the antagonistic dorsiflexor moment were based on the tibialis anterior EMG-dorsiflexor moment relationship from contractions at 50, 40, 30, 20 and 10 % of the dorsiflexion MVC moment. In both legs dorsiflexor coactivation level followed an open U-shaped pattern as a function of ankle angle. Differences of 9 and 14 % (P < 0·05) were found in the measured net plantarflexion MVC moment between legs at ankle angles of -15 and +30 deg, respectively. No difference (P > 0·05) was found in the calf circumference between legs. Differences were found in the antagonistic dorsiflexor coactivation between legs at ankle angles of -15 and +30 deg. In the weaker leg the antagonistic EMG measurements were higher by 100 and 45 % (P < 0·01) and the estimated antagonistic moments were higher by 70 and 43 % (P < 0·01) compared with the weaker leg at -15 and +30 deg, respectively. This finding was associated with a decreased range of motion (ROM) in the weaker leg (14 %, P < 0·01), such that no difference (P > 0·05) was found in dorsiflexor antagonistic coactivation between legs at end-range ankle angles. The findings of the study (i) have to be taken into consideration when estimating musculoskeletal loads in the lower extremity, (ii) imply that stretching training can result in a stronger plantarflexion at end-range ankle angles through inhibition of the dorsiflexors, and (iii) imply a neural drive inadequacy during a plantarflexion MVC at end-range angles.