title: Velocity dependence of eccentric strength in young and old men: the need for speed!
abstract: Older adults better maintain eccentric strength relative to isometric strength, as indicated by a higher ratio of eccentric:isometric torque as compared with younger adults. The effect of increasing angular velocities (>200°/s) on the age-related maintenance of eccentric strength has not been tested and thus it is unknown whether the eccentric:isometric ratio is velocity dependent in old age. The purpose of this study was to investigate eccentric strength of the ankle dorsiflexors over a large range of lengthening angular velocities in young and older men. Isometric neuromuscular properties were assessed on a HUMAC NORM dynamometer. Nine young (∼24 years) and 9 older (∼76 years) healthy men performed maximal voluntary eccentric contractions at angular velocities of 15-360°/s. Despite near full voluntary activation (>95%), the older men were ∼30% weaker than the young men for isometric strength (P < 0.05). Across all lengthening velocities, older men had a greater eccentric:isometric ratio than young men (P < 0.05). Additionally, there was a velocity dependence of strength in both young and older men: eccentric strength increased as velocity increased up to 120°/s (P < 0.05) and plateaued thereafter. In young and older men, eccentric strength at 15°/s was ∼20% and ∼40% greater than isometric strength (P < 0.05), while at 360°/s eccentric strength was ∼50% and ∼90% greater, respectively (P < 0.05). These findings indicate that with increasing angular velocity, both young and older men have considerable increases in the eccentric:isometric ratio of torque production.
authors.affiliation: a Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Calgary, AB T2N 1N4, Canada.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Power
authors.affiliation: b Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada.
authors.forename: Demetri P
authors.initials: DP
authors.lastname: Makrakos
authors.affiliation: b Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Stevens
authors.affiliation: b Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada.|c Department of Anatomy and Cell Biology, The University of Western Ontario, London, ON N6A 3K7, Canada.
authors.forename: Charles L
authors.initials: CL
authors.lastname: Rice
authors.affiliation: b Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON N6G 2M3, Canada.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Vandervoort
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D000843:Ankle Joint / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D055815:Young Adult
keywords: EMG; aging; amélioration de la force résiduelle; elderly; faiblesse; lengthening; muscle; personnes âgées; raideur; residual force enhancement; stiffness; vieillissement; weakness; étirement