Doublet potentiation in the triceps surae is limited by series compliance and dynamic fascicle behavior

Mayfield, Dean L, Lichtwark, Glen A., Cronin, Neil J, Avela, Janne and Cresswell, Andrew G. (2015) Doublet potentiation in the triceps surae is limited by series compliance and dynamic fascicle behavior. Journal of Applied Physiology, 119 7: 807-816. doi:10.1152/japplphysiol.00403.2015

Author Mayfield, Dean L
Lichtwark, Glen A.
Cronin, Neil J
Avela, Janne
Cresswell, Andrew G.
Title Doublet potentiation in the triceps surae is limited by series compliance and dynamic fascicle behavior
Journal name Journal of Applied Physiology   Check publisher's open access policy
ISSN 8750-7587
Publication date 2015
Year available 2015
Sub-type Article (original research)
DOI 10.1152/japplphysiol.00403.2015
Open Access Status Not yet assessed
Volume 119
Issue 7
Start page 807
End page 816
Total pages 10
Place of publication Bethesda, United States
Publisher American Physiological Society
Collection year 2016
Language eng
Abstract Activation of skeletal muscle twice in quick succession results in nonlinear force summation (i.e. doublet potentiation). The force contributed by a second activation is typically of augmented amplitude, longer in duration and generated at a greater rate. The purpose of this study was to examine force summation in a muscle attached to a compliant tendon, where considerable internal shortening occurs during a fixed-end contraction. The triceps surae of 21 (Experiment 1) and nine (Experiment 2) young adults were maximally activated with doublet stimulation of different interstimulus intervals (ISIs) (5-100 ms) at several muscle lengths. Ultrasound images acquired from lateral gastrocnemius and soleus muscles allowed quantification of dynamic fascicle behavior. Force summation was muscle length-dependent. Force augmentation was limited to a short muscle length. Lateral gastrocnemius and soleus fascicles underwent large amounts of active shortening and achieved high velocities in response to doublet stimulation, dynamics unfavorable for force production. Summation amplitude and the sensitivity of summation to ISI were dramatically depressed in the triceps surae after comparison to muscles with less fixed-end compliance. We propose that the internal shortening permitted by high series compliance limited force augmentation by offsetting and/or interfering with activation and cross-bridge processes driving augmentation. High series compliance may also reduce the sensitivity of the summated response to ISI, an assertion supported by predictions from a Hill-type muscle model. These muscles may exhibit greater force augmentation during more accustomed stretch-shorten tasks (i.e. hopping), where the compliance of the Achilles tendon actually enables near-isometric fascicle behaviour.
Keyword Muscle mechanics
Muscle force
Force summation
Muscle-tendon interaction
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
School of Human Movement and Nutrition Sciences Publications
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Created: Tue, 18 Aug 2015, 15:56:50 EST by Sandrine Ducrot on behalf of School of Human Movement and Nutrition Sciences