The influence of stimulation frequency on force‐velocity characteristics of in situ rat medial gastrocnemius muscle

Abstract

SUMMARYForce (and power)-velocity characteristics were determined at different stimulation frequencies in in situ rat muscle with nerve stimulation at 36 'C. In isometric contractions (duration, 150 ms), maximal force is generated at -120 Hz. In contrast, in the high velocity (250 mm s-1) shortening contractions, frequencies of -400 Hz were needed to obtain maximal dynamic force, while 120 Hz elicited only -26 % of the maximum. At the highest velocity measured, power production was significantly different (P < 0.05) among frequencies of 80, 120, 200 and 400 Hz, suggesting that maximal shortening velocity should be assessed using very high stimulation frequencies. However, the results further indicate that lower frequencies may be adequate in exercise studies that investigate fatigue and changes in power output during series of repetitive contractions.

General – Muscle Contraction

“…At 80 Hz a preceding D200 or T400 not only showed an increase in peak power but also a shift t o the right in power-velocity relation. Similar observations were obtained previously when the stimulation frequency was increased (De Haan, 1998), which suggests a similar mechanism (e.g. enhanced Ca 2 + release/sensitivity).…”

Changes in characteristics of rat skeletal muscle after experimental allergic encephalomyelitis

“…A high firing frequency is needed to fully activate muscle fibers in isometric conditions, but even higher frequencies are necessary for maximal dynamic contractions (maximal power output). 8 However, in daily activities, skeletal muscles are activated submaximally with relatively low frequencies. The advantage of the slowing of relaxation is that muscle force may be relatively high at relatively low frequencies of stimulation (Fig.…”

“…9 Experimental allergic encephalomyelitis (EAE) is an experimental inflammatory demyelinating dis-ease of the central nervous system, and serves as an animal model to study demyelinating diseases of the central nervous system in general, and MS in particular. 24,25 In the induction phase (days [1][2][3][4][5][6][7][8][9][10], animals are immunized with myelin components to induce an anti-myelin immune response. 22,25 In particular, the effector phase of EAE (days 10 -18), during which local inflammatory responses cause the actual tissue damage, is relevant for studying the damaging events in MS.…”

Altered contractile properties of the quadriceps muscle in people with spinal cord injury following functional electrical stimulated cycle training

“…42 It should however be noted that higher stimulation frequencies are needed to generate maximal rate of force rise than to produce maximal tetanic tension. 28,43 Therefore, stimulation frequencies in excess of 100 Hz may have been required to obtain the maximal rate of force development. However, the use of higher stimulation frequencies may increase the risk for damage to the weak paralysed muscles and tendons, and we therefore decided not to use stimulation frequencies above 100 Hz.…”