Precision in isometric precision grip force is reduced in middle-aged adults.
ABSTRACT We investigated age related changes in the control of precision grip in 29 healthy adults spanning early adulthood to middle age (21-67 years). Subjects performed a visually guided, isometric precision grip ramp-and-hold force-tracking task. Target force levels were 3, 6, and 9 N. Precision and performance of force regulation was quantified. Larger errors were made during the ramp than during the hold phase. Age correlated positively with the amount of error at the lowest (3 N) force level in both phases. Force onsets were systematically earlier in middle-aged subjects and the average slope of the force during the ramp decreased with increasing age. The results show that precision during low grip force control decreases already during middle age and those subjects may modify their force generation strategies to compensate for early and subtle degenerative changes in the motor system before decline in grip strength is apparent.
SourceAvailable from: Jean-Jacques Temprado[Show abstract] [Hide abstract]
ABSTRACT: ABSTRACT The authors examined age-related differences in fine motor control during a bimanual coordination task. The task required the modulation of fingertip forces in the precision grip according to a visually presented sinusoidal antiphase pattern (force range 2-12 N; frequency 0.2 Hz). Thirty-four right-handed participants of three age groups (young, early middle-aged, and late middle-aged) practiced 30 trials of the task. Accuracy and variability of relative timing and relative forces at minima and maxima of the sine wave were analyzed for hand-hand and hand-stimulus couplings and compared between age groups. Analysis showed for relative timing and force weaker hand-hand than hand-stimulus coupling as well as lower accuracy and higher variability for minima as compared to maxima. Further, we analyzed practice effects by comparing the first and last trials and characterized the course of practice by detecting the transition of a steeper to a shallower acquisition slope for the different age groups. Late middle-aged participants demonstrated poorer performance than both other groups for all parameters. All groups improved performance to a similar amount. However, an age-related difference in acquisition strategy is visible. Late middle-aged participants seemed to have focused on improvement of force amplitude, whereas young and early middle-aged focused on timing.Journal of Motor Behavior 11/2014; 47(1). DOI:10.1080/00222895.2014.981499 · 1.41 Impact Factor
Annals of Physical and Rehabilitation Medicine 10/2012; 55:e114. DOI:10.1016/j.rehab.2012.07.300
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ABSTRACT: Background The present study aimed at characterizing the effects of increasing (relative) force level and aging on isometric force control. To achieve this objective and to infer changes in the underlying control mechanisms, measures of information transmission, as well as magnitude and time-frequency structure of behavioral variability were applied to force-time-series. Results Older adults were found to be weaker, more variable, and less efficient than young participants. As a function of force level, efficiency followed an inverted-U shape in both groups, suggesting a similar organization of the force control system. The time-frequency structure of force output fluctuations was only significantly affected by task conditions. Specifically, a narrower spectral distribution with more long-range correlations and an inverted-U pattern of complexity changes were observed with increasing force level. Although not significant older participants displayed on average a less complex behavior for low and intermediate force levels. The changes in force signal’s regularity presented a strong dependence on time-scales, which significantly interacted with age and condition. An inverted-U profile was only observed for the time-scale relevant to the sensorimotor control process. However, in both groups the peak was not aligned with the optimum of efficiency. Conclusion Our results support the view that behavioral variability, in terms of magnitude and structure, has a functional meaning and affords non-invasive markers of the adaptations of the sensorimotor control system to various constraints. The measures of efficiency and variability ought to be considered as complementary since they convey specific information on the organization of control processes. The reported weak age effect on variability and complexity measures suggests that the behavioral expression of the loss of complexity hypothesis is not as straightforward as conventionally admitted. However, group differences did not completely vanish, which suggests that age differences can be more or less apparent depending on task properties and whether difficulty is scaled in relative or absolute terms.BMC Neuroscience 02/2015; BMC Neuroscience(16:12). DOI:10.1186/s12868-015-0153-7 · 2.85 Impact Factor