title: Age-related maintenance of eccentric strength: a study of temperature dependence.
abstract: With adult aging, eccentric strength is maintained better than isometric strength leading to a higher ratio of eccentric/isometric force production (ECC/ISO) in older than younger adults. The purpose was to investigate the ECC/ISO during electrical activation of the adductor pollicis during lengthening (20-320° s(-1)) contractions in 24 young (n = 12, ∼24 years) and old (n = 12, ∼72 years) males across muscle temperatures (cold ∼19 °C; normal ∼30 °C; warm ∼35 °C). For isometric force, the old were 20-30 % weaker in the normal and cold conditions (P < 0.05) with no difference for the warm condition compared to young (P > 0.05). Half-relaxation time (HRT) did not differ across age for the normal and warm temperatures (P > 0.05), but it slowed significantly for old in the cold condition compared with young (∼15 %; P < 0.05), as well, there was a 20 and 40 % increase in muscle stiffness for the young and old, respectively. ECC/ISO was 50-60 % greater for the cold condition than the normal and warm conditions. There was no age difference in ECC/ISO across ages for the normal and warm conditions (P > 0.05), but for the cold, the old exhibited a 20-35 % higher ECC/ISO than did the young for velocities above 60° s(-1) (P < 0.05). A contributing factor to the elevated ECC/ISO is an increased proportion of weakly compared to strongly bound crossbridges. These findings highlight the relationship (r = 0.70) between intrinsic muscle contractile speed (HRT) and eccentric strength in old age.
authors.affiliation: Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON, Canada. gapower@uoguelph.ca.|Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Calgary, AB, Canada. gapower@uoguelph.ca.
authors.forename: Geoffrey A
authors.initials: GA
authors.lastname: Power
authors.affiliation: Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Calgary, AB, Canada.
authors.forename: Nordan
authors.initials: N
authors.lastname: Flaaten
authors.affiliation: Department of Human Physiology, University of Oregon, Eugene, OR, USA.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Dalton
authors.affiliation: Faculty of Kinesiology, Human Performance Laboratory, University of Calgary, Calgary, AB, Canada.
authors.forename: Walter
authors.initials: W
authors.lastname: Herzog
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D026741:Physical Therapy Modalities; D012016:Reference Values; D055948:Sarcopenia / Q000503:physiopathology / Q000534:rehabilitation; D013696:Temperature; D019415:Torque; D055815:Young Adult
keywords: Lengthening; Muscle; Residual force enhancement; Sarcopenia; Stiffness; Weakness