Technology for Adaptive Aging (2004) / Chapter Skim
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3 Movement Control in the Older Adult
3 Movement Control in the Older Adult
Pages 64-92
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From page 64... ...
The review begins with a discussion of processing speed defined by reaction time and presents differences between young and older adults on simple and complex tasks. The following topics include changes that occur in older adults related to the control of movement including: reduced movement speed, movement composition differences, increased variability, reduced force control, and coordination difficulties.
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From page 65... ...
Thus, those involved in enhancing the performance capabilities of these individuals need to have a good understanding of how the aging processes diminish motor performance. RESPONSE INITIATION Reaction time is defined as the time required to initiate a movement response following a visual, auditory, or other sensory signal and is thought to reflect the speed of transmission of the central nervous system (Stelmach and Goggin, 1988)
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From page 66... ...
Some researchers have sought to decompose reaction time into premotor and motor time. Premotor time is defined as the time from the presentation of the stimulus until the onset of muscle activity and is thought to reflect cognitive processes, whereas motor time is the time from muscle activation to the beginning of the movement and reflects efficiency of the motor system.
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From page 67... ...
Differences in movement times between young and older adults were amplified as task difficulty increased with an 80-ms time difference at the high ID compared with a 29-ms difference at the low ID. Task difficulty according to Fitts's law can be manipulated in two ways: by a change in either the target size or the distance between the start and the end of the movement.
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From page 68... ...
. In addition to longer deceleration phases, older adults produce movements with 30-70 percent lower peak velocity compared with young adults (Ketcham et al., 2002; Bellgrove, Phillips, Bradshaw, and Gallucci, 1998; Cooke et al., 1989; Goggin and Meeuwsen, 1992; Pratt et al., 1994)
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From page 69... ...
Acceleration profiles can be partitioned into movement substructures (primary and secondary submovements) for a more in-depth analysis.
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From page 70... ...
80 60 Traveled 40 Submovement Distance 20 Primary in 0 1 2 3 4 5 6 7 8 9 10 Blocks (10 Trials/Block) FIGURE 3-2 Percentage of distance traveled in the primary submovement for older and young adults in a point-to-point aiming task over 10 blocks of 10 trials.
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From page 71... ...
These data, along with other studies that have used kinematic and movement subparsing techniques, have shown that the initial phases of the movement are similar in young and older adults, with older adults producing movements with lower peak velocity outputs. Conversely, these methods have shown marked differences in the terminal phase of the movement, measured by the deceleration phase, proportion of the movement covered in the primary submovement, and the subsequent secondary submovements, suggesting that older adults need to make corrective adjustments to their movement as they approach the target.
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From page 72... ...
(1994) found that older adults showed higher variability in the distance traveled in the primary submovement that did not improve as much as young adults with extensive practice.
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From page 73... ...
Force Control and Regulation Force control is an elementary component of movement production because smooth and accurate movements require efficient modulation of force outputs. Changes in the regulation of force outputs lead to decrements in the initiation and control of movements.
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From page 74... ...
Changes in force regulation and control have large implications for most functional tasks -- for example, turning a door knob or picking up a glass of liquid. These changes may be a result of motor unit reorganization and muscle composition changes; see "Muscle Composition and Muscle Activation Patterns" below (Erim, Beg, Burke, and de Luca, 1999; Galganski et al., 1993; Hakkinen et al., 1996; Yue, Ranganathan, Siemionow, Liu, and Sahgal, 1999; Clamann, 1993; Davies and White, 1983; Milner-Brown et al., 1973)
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From page 75... ...
, or antiphase, where the two limbs move in the same absolute direction (homologous muscles activated at a 180-degree offset or opposite of each other)
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From page 76... ...
A reduced capability to detect the position of the limb has large implications for movement control, and therefore it is important to identify age differences in proprioception. Investigators test proprioceptive capabilities by having individuals reproduce joint positions or recognize joint displacements.
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From page 77... ...
. The existing motor units are reorganized to include more muscle fibers per innervation and subsequently change the way force outputs are achieved.
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From page 78... ...
Changes in joint characteristics, muscle composition, and activation characteristics as well as higher levels of disuse in older adults (Raab, Agre, McAdam, and Smith, 1988; Bassey, 1998) lead to overall decreases in flexibility in older adults (Shepard, Berridge, and Montelpare, 1990; Spirduso, 1995)
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From page 79... ...
studied postural control mechanisms during quiet stance over a 30-s period. They compared early and late sway stability and found that older adults were substantially more unstable than young adult controls in the first 200 ms of the trial when sensory feedback was not available; they became increasingly stable after 200 ms, similar to young adult controls, when sensory feedback had sufficient time to be processed and implemented into control (Collins et al., 1995)
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From page 80... ...
These decrements result in an increased risk for falls and greatly influence functional tasks of daily living. SKILL LEARNING The ability of older adults to learn new skills and relearn previously learned skills is an important area of motor behavior research.
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From page 81... ...
They also addressed whether specificity of skill or overall general fitness influenced reaction and movement time performance by testing an active group, subjects who were either runners or racquet sport players. Spirduso and Clifford also found that older active adults had faster reaction times and movement times than sedentary men of the same age regardless of whether they were runners or racquet sport players.
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From page 82... ...
. Strength training has been shown to have a specific impact on muscle composition and subsequent motor function.
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From page 83... ...
have demonstrated that balance training programs that include tasks that involve multiple processes increase the attentional demands associated with balance control and become more like real-world experiences in which a person must respond to multiple inputs. Tasks such as maintaining balance while performing rhythmic movements between limbs increase the postural response resources available to individuals and subsequently improve compensatory strategies (Tang and Woollacott, 1998)
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From page 84... ...
programming in aging: A kinematic analysis. Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 53(A3)
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From page 85... ...
Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 54(5)
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From page 86... ...
. Beneficial effect of proprio ceptive physical activities on balance control in elderly human subjects.
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From page 87... ...
Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 51(1)
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From page 88... ...
Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 54(6)
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From page 89... ...
. The contractile properties of human motor units during voluntary isometric contractions.
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From page 90... ...
. Quadriceps muscle strength, contractile properties, and motor unit firing rates in young and old men.
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From page 91... ...
Journals of Gerontology Series A: Biological Sciences & Medical Sciences, 52(4)
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From page 92... ...
. Effect of aging on the accuracy of visually guided saccadic eye movement.
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