An apparatus to measure in vivo biomechanical behavior of dorsi- and plantarflexors of mouse ankle

Abstract

We developed an apparatus to quantify the biomechanical behavior of the dorsi- and plantarflexor muscles of the ankle of an anesthetized mouse. When the dorsi- or plantarflexor muscle group is activated by electrical stimulation of either the peroneal or tibial nerve, the apparatus measures the moment developed about the ankle during isometric, isovelocity shortening, or isovelocity lengthening contractions. Displacements may be performed over the full 105 degrees range of ankle motion with an angular resolution of 0.09 degrees. Bidirectional isovelocity ramps in ankle angle up to 1,100 degrees/s are possible and are equivalent to maximum velocities of 2.3 fiber lengths/s (Lf/s) for the fibers in tibialis anterior muscle and 11.9 Lf/s for those in gastrocnemius muscle. During single contractions of the dorsi- and plantarflexor muscle groups at 37 degrees C and with both knee and ankle joint at 90 degrees neutral position, the isometric tetanic force developed was 1.4 and 3.3 N, power output at 2.2 Lf/s was 3.1 and 5.9 mW, and power absorption at 0.5 Lf/s was 4.9 and 9.0 mW, respectively. These values are in reasonable agreement with data from the same muscle groups tested in situ. We conclude that the apparatus provides valid measurements of force and power of the dorsi- and plantarflexor muscle groups.

Isometric and concentric performance of electrically stimulated ankle plantar flexor muscles in intact rat

“…In our study, the peak isometric force of plantar flexor muscles was 19·2 N (at an ankle position of 1·17 rad) and 8% lower than the optimum force of isolated plantar flexor muscles in situ (21·0 ± 0·8 N) of female rats of equivalent weight measured by attaching the tendon to a force transducer (Dodd et al 1995). Similar findings were reported for mice using a dynamometer; the isometric force of plantar flexor muscles in intact mice was lower (11%) than the isometric force measured in situ (Ashton-Miller et al 1992). It is concluded that the force output of plantar flexor muscles working in situ in intact rats can be accurately measured by recording the force under the sole of the foot.…”

Properties of single motor units in medial gastrocnemius muscles of adult and old rats.

“…The value of 207 kN m-2 for the specific F. of MGN muscles in adult rats is slightly lower than the value for most hindlimb muscles of rats (Eddinger, Moss & Cassens, 1985), or mice (Brooks & Faulkner, 1988). The lower value for specific F. results from the large angle of pennation for MGN muscle (Brooks & Faulkner, 1988;Ashton-Miller, He, Kadhiresan, McCubbrey & Faulkner, 1992) and the large aponeurosis (Holewijn, Plantinga, Woittiez & Huijing, 1984). After correcting for the 21 deg angle of pennation (Spector, Gardiner, Zernicke, Roy & Edgerton, 1980), and for the mass of the aponeurosis, the specific Fo increases to a value of 233 kN m-2, a value similar to that obtained for most hindlimb muscles of rodents (Brooks & Faulkner, 1988).…”

Functional deficits and insulin-like growth factor-I gene expression following tourniquet-induced injury of skeletal muscle in young and old rats

“…A nerve cuff constructed of Coonar wire, Silastic tubing, and Silastic cement was placed around the tibial nerve using a method described by Walters et al (69). An in vivo model similar to that designed by Ashton-Miller et al (6) was used to measure the force generated by the triceps surae muscle group (gastrocnemius, soleus, and plantaris). The knee of the anesthetized rat was secured at the tibial condyles by a modified clamp apparatus, while the foot was strapped to a foot pedal connected to a servomotor (Aurora model 310) to allow measurement of the force produced by plantar flexion.…”