title: Dexterous manipulation is poorer at older ages and is dissociated from decline of hand strength.
abstract: BACKGROUND
  The ability to dynamically control fingertip force vector magnitude and direction is critical for dexterous manipulation. We quantified the dynamic control of fingertip forces to examine how dexterous manipulation declines with age.
  
  
  METHODS
  The strength-dexterity (SD) test measures fingertip forces during compression of a slender spring prone to instability and buckling. The greatest sustained compression (designed to be under 3 N), and force dynamics therein, have been shown to be simple and quick measures of dynamic dexterous manipulation ability. We measured pinch strength and strength-dexterity test in a cross-sectional population of 98 people from 18 to 89 years of age.
  
  
  RESULTS
  Dexterous manipulation ability is poorer at older ages, beginning in middle age (p < .001), with greater decline past 65 years of age. Fingertip force dynamics during spring compression and stabilization show a deterioration of neuromuscular control with age. Importantly, this novel detection of decline in dynamic manipulation ability is not correlated with, and thus cannot be entirely explained by, the known decline in pinch strength. We also measured standardized tests of dexterity in participants older than 45, and discuss how the strength-dexterity test uniquely captures features of sensorimotor capabilities for dexterous manipulation in this adult population.
  
  
  CONCLUSIONS
  Starting in middle age, changes in the functional interactions among sensory, motor, and neural capabilities result in measurably poorer dynamic dexterous manipulation. This deterioration of neuromuscular control motivates and enables future studies to understand the physiological bases for this functional decline so critical to activities of daily living and quality of life.
authors.affiliation: Division of Biokinesiology and Physical Therapy and.
authors.forename: Sudarshan
authors.initials: S
authors.lastname: Dayanidhi
authors.affiliation: Division of Biokinesiology and Physical Therapy and Department of Biomedical Engineering, The University of Southern California, Los Angeles, California. valero@usc.edu.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Valero-Cuevas
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D005385:Fingers / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009048:Motor Skills / Q000502:physiology*
keywords: Aging; Dexterous manipulation; Dynamical analysis.; Middle age; Pinch strength