title: Kinematics and muscle activation patterns during a maximal voluntary rate activity in healthy elderly and young adults.
abstract: BACKGROUND
  Maximal voluntary rate (MVR) performance tasks can provide important age-related information to the limiting factors associated with movement and the development of fatigue.
  
  
  OBJECTIVE
  To determine whether kinematic and muscle activation patterns during an MVR task differ between young and older adults.
  
  
  METHODS
  We continuously measured frequency, amplitude, peak velocity, index of co-contraction and median frequencies of the index finger flexors and extensors during a 20-s MVR task in 10 young and 10 older subjects.
  
  
  RESULTS
  Index finger amplitude and peak velocity in flexion and extension were significantly lower in the older group. During the MVR, amplitude was maintained in the old (1-4 s, 53.2° ± 2.8° vs. 15-19 s, 48.6° ± 3.2°, ns) but not in the younger group (1-4 s, 64.9° ± 4.9° vs. 15-19 s, 59.4° ± 3.3°; p = 0.001). Frequency declined in the young (1-4 s, 5.2 ± 0.24 Hz vs. 15-19 s, 4.4 ± 0.25 Hz; p = 0.001) and old (1-4 s, 4.6 ± 0.17 Hz vs. 15-19 s, 4.0 ± 0.15 Hz; p = 0.01). Similarly, peak flexion velocity of the young (1-4 s, 1.77 ± 0.07 × 103°/s vs. 15-19 s, 1.01 ± 0.07 × 103°/s, p = 0.01) and older groups (1-4 s, 1.04 ± 0.07 × 103°/s vs. 15-19 s, 0.78 ± 0.06 × 103°/s; p = 0.016) as well as peak extension velocity of the young (1-4 s, 1.01 ± 0.053 × 103°/s vs. 15-19 s, 0.78 ± 0.06 × 103°/s, p = 0.01) and older groups (1-4 s, 0.72 ± 0.04 × 103°/s vs. 15-19 s, 0.58 ± 0.05 × 103°/s, p = 0.012) significantly decreased throughout the MVR. Median frequency of the flexors and extensors were maintained and were not different between groups. Only the older group experienced an increase in the index of co-contraction.
  
  
  CONCLUSIONS
  The changes in kinematics over time are not a result of a decrease in pre-post test force or velocity, but rather central factors affecting movement coordination.
authors.affiliation: Department of Exercise Science, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.|McGill Vision Research Unit, Department of Ophthalmology, McGill University, Montreal, QC, H3A 1A1, Canada.
authors.forename: Eva
authors.initials: E
authors.lastname: Chadnova
authors.affiliation: Department of Exercise Science, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.|PERFORM Centre, Concordia University, Montreal, QC, Canada.|CRIR-Constance Lethbridge Rehabilitation Centre, Montreal, QC, Canada.
authors.forename: Nancy
authors.initials: N
authors.lastname: St-Onge
authors.affiliation: Department of Exercise Science, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada.|PERFORM Centre, Concordia University, Montreal, QC, Canada.|FRQS Groupe de Recherche en Neurobiologie Comportementale, Montreal, QC, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Courtemanche
authors.affiliation: Department of Exercise Science, Concordia University, 7141 Sherbrooke Street West, Montreal, QC, H4B 1R6, Canada. robert.kilgour@concordia.ca.|PERFORM Centre, Concordia University, Montreal, QC, Canada. robert.kilgour@concordia.ca.|McGill Nutrition and Performance Laboratory (MNUPAL), McGill University Health Centre, Montreal, QC, Canada. robert.kilgour@concordia.ca.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Kilgour
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D005221:Fatigue; D005260:Female; D005385:Fingers / Q000502:physiology; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular; D055815:Young Adult
keywords: Aging; Co-contraction; Fatigue; Kinematics; Maximal voluntary movement rate; Motor performance