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Influence of biceps brachii tendon mechanical properties on elbow flexor force steadiness in young and old males
Author(s) -
Smart R. R.,
Baudry S.,
Fedorov A.,
Kuzyk S. L.,
Jakobi J. M.
Publication year - 2018
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/sms.13024
Subject(s) - isometric exercise , tendon , medicine , achilles tendon , biceps , elbow , forearm , biomechanics , strain (injury) , anatomy , physical therapy
Elbow flexor force steadiness ( FS ) depends on strength and decreases with age. Achilles tendon mechanics effect standing balance and isometric plantarflexion FS . This study investigated the influence of distal biceps brachii ( BB ) tendon mechanics and elbow flexor strength on age‐related decline in FS . Nine young (23 ± 2 years) and nine old (77 ± 5 years) males performed submaximal isometric elbow flexion tasks at low (2.5%, 5%, 10% maximal voluntary contraction ( MVC )) and high (20%, 40%, 60%, 80% MVC ) forces in a neutral forearm position. Distal BB tendon elongation and cross‐sectional area ( CSA ) were recorded on ultrasound to calculate mechanics of strain, stress, and stiffness. Coefficient of variation ( CV ) of force was used to assess relationship of FS to tendon mechanics and strength. Young were 22% stronger and 41% steadier than old ( P < .05). Tendon stiffness (170.1 ± 132.9 N/mm; 113.0 ± 55.1 N/mm) did not differ with age ( P > .05). Young had 40% less strain compared to old at 5% MVC , but 42% greater strain at 60% and 80% MVC ( P ≤ .05). Stress was ~18% greater in young at 10%, 20%, and 80% MVC ( P ≤ .05). At low forces, CV of force was predicted by stress ( r 2 = 0.56) in young, and stress and MVC ( r 2 = 0.641) in old. At high forces for both age groups, CV of force was predicted by MVC and stress ( r 2 = 0.39‐0.43). Stress and strain is greater in young compared with old males. Because strength influences tendon mechanics and is also associated with FS , absolute strength is a large and modifiable contributor to age‐related decline in FS .