The purpose of the study was to examine the relationship between muscle force generated during isometric contractions (i.e. at a constant muscle–tendon unit length) and the intermuscular (between adjacent muscles) pressure in synergistic muscles. Therefore, the pressure at the contact area of the gastrocnemius and plantaris muscle was measured synchronously to the force of the whole calf musculature in the rabbit species Oryctolagus cuniculus. Similar results were obtained when using a conductive pressure sensor, or a fibre-optic pressure transducer connected to a water-filled balloon. Both methods revealed a strong linear relationship between force and pressure in the ascending limb of the force-length relationship. The shape of the measured force–time and pressure–time traces was almost identical for each contraction (r=0.97). Intermuscular pressure ranged between 100 and 700 mbar (70,000 Pa) for forces up to 287 N. These pressures are similar to previous (intramuscular) recordings within skeletal muscles of different vertebrate species. Furthermore, our results suggest that the rise in intermuscular pressure during contraction may reduce the force production in muscle packages (compartments).
The authors declare no competing or financial interests.
L.R., K.L. and T.S. performed experiments; L.R. analysed data and prepared figures; L.R., T.S., R.B. and M.B. designed the study, interpreted results, and edited, revised and drafted the manuscript; all authors approved the final version of manuscript.
This work was funded by the Deutsche Forschungsgemeinschaft [German Research Foundation (DFG)] under grant SI 841/3-1, 2 and BO 3091/4-1, 2 to T.S. and M.B., respectively.
- Received November 27, 2015.
- Accepted May 16, 2016.
- © 2016. Published by The Company of Biologists Ltd