Effects of in vivo-like activation frequency on the length-dependent force generation of skeletal muscle fibre bundles

Abstract

It is known that a range of firing frequencies can be observed during in vivo muscle activity, yet information is lacking as to how different in vivo-like frequencies may affect force generation of skeletal muscle. This study examined the effects of constant (CSF, constant within one contraction) and decreasing stimulation frequencies (DSF) on mean sarcomere length-force characteristics of rat gastrocnemius medialis fibre bundles. The CSF resulted in an optimal mean sarcomere length (lso) of 2.30 (SEM 0.02), 2.46 (SEM 0.03), 2.76 (SEM 0.03) and more than 2.99 (SEM 0.07) lm, for 100, 50, 30 and 15 Hz, respectively. Compared to 100-Hz stimulation, both lso and the ascending limb of the relationship significantly shifted to higher lengths with lower frequencies. No shift was encountered for the initial part of the descending limb. The DSF reduced the frequency-induced shift to higher mean lengths [lso 2.33 (SEM 0.02), 2.52 (SEM 0.08) and more than 2.92 (SEM 0.10) microm, respectively, for 50, 30 and 15 Hz]. No effect of activation time on length-force characteristics was observed. It was concluded from these studies that the frequency and history of stimulation is a major determinant of the length-force characteristics of muscle fibre bundles, and should be taken into account when analysing animal and human locomotion. The previously observed frequency-induced shift in whole muscle length-force relationship resides mainly at the level of fibre bundles.

Muscle performance during frog jumping: influence of elasticity on muscle operating lengths

“…One other concern in translating force-length behaviour measured in vitro to in vivo function is a potential effect of stimulation frequency. Several studies have shown that a muscle's force-length curve shifts toward longer lengths at lower stimulation frequencies (Rack & Westbury 1969;Roszek et al 1994;Zuurbier et al 1998;Brown et al 1999). Brown and colleagues (1999) found that a threefold drop in stimulation frequency (from 120 to 40 pps) resulted in a shift of approximately 10 per cent L o .…”

Progressive surgical dissection for tendon transposition affects length‐force characteristics of rat flexor carpi ulnaris muscle

“…To this point, isometric muscular length-force characteristics have been studied using isolated preparations of: (1) single isolated muscle fiber [3], (2) isolated fascicles [27], or (3) isolated whole muscle in situ [26]. Therefore, the possible role of the surrounding connective tissue in force transmission has largely been neglected.…”

Myofascial Force Transmission via Extramuscular Pathways Occurs between Antagonistic Muscles

“…As a consequence, for more than a century, isometric length-force characteristics have been the subject of extensive research. Such experimental work involved whole muscle isolated except for its blood supply [Rack and Westbury, 1969;Bobbert et al, 1990;Gareis et al, 1992], isolated small muscle fascicles [Street, 1983;Zuurbier et al, 1995;Willems and Purslow, 1997;Zuurbier et al, 1998] and single muscle fibres [Ramsey and Street, 1940;Gordon et al, 1966;ter Keurs et al, 1978;Julian and Morgan, 1981;Willems and Purslow, 1997]. Even work on force transmission from muscle fibres focussed on muscles that are mechanically isolated from its surroundings.…”

“…Even work on force transmission from muscle fibres focussed on muscles that are mechanically isolated from its surroundings. This was studied within either non-spanning fibred muscle [Loeb et al, 1987;Purslow and Duance, 1990;Eldred et al, 1993;Purslow and Trotter, 1994;Roy et al, 1995;Trotter et al, 1995;Brown et al, 1998;Purslow, 2002] or within muscles consisting of fibres that span the distance between its proximal and distal aponeurosis [Huijing et al, 1998]. …”