Scaling of skeletal muscle shortening velocity in mammals representing a 100,000-fold difference in body size

Abstract

To fully understand the effect of scaling on skeletal muscle shortening velocity (V (0)), it is important to know which phenotypic characteristics drive the changes between species. The purpose of the current investigation was to compare the effects of body mass and femur length, as an estimate of total limb length, on V (0) in species that cover a 100,000-fold range of body masses. Using the slack test procedure, V (0) was determined for fibers expressing types I and IIa myosin heavy chain (MyHC) isoforms in the mouse, rat, dog, human, horse, and rhinoceros under identical experimental conditions. A significant scaling effect on V (0) was detected when compared to body mass (type I fibers, r=0.95, p<0.01; type IIa fibers, r=0.83, p<0.05). However, the horse's V (0) for both fiber types was faster than the human's, despite having a 5-fold greater body mass than the human. When V (0) was scaled vs limb length, the strength of the relationships improved in fibers expressing both types I and IIa MyHC (r=0.98, p<0.001, and r=0.89, p<0.05, respectively) and scaled with the expected relationship, with the species with the shorter femur, the horse, having the faster V (0). A similar effect can be seen with stride frequency scaling more closely with limb length than body mass. These results suggest that limb length, not body mass, is a more relevant factor driving the scaling effect on skeletal muscle shortening velocity.

Larger lacertid lizard species produce higher than expected iliotibialis muscle power output; the evolution of muscle contractile mechanics with body size in lacertid lizards

“…The between-species changes in mechanical properties with body size observed in the current study are different to what might be expected from previous literature comparing scaling relationships across species from widely different groups of animals (Seow and Ford, 1991;Rome et al, 1990;Medler, 2002;Pellegrino et al, 2003;Marx et al, 2006) or between individuals within a species. In general, the previous literature indicates that larger individuals have skeletal muscle mechanical properties indicative of slower fibre type.…”

“…A previous study found that the maximal shortening velocity of single muscle fibres decreased with increased body mass (M b ), from rat to rabbit to horse, scaling M b −0.18 in slow fibres and M b −0.07 in fast glycolytic fibres (Rome et al, 1990). Various scaling exponents have been found in other more recent studies comparing single fibres of the same fibre type between various mammalian species (Seow and Ford, 1991;Widrick et al, 1997;Pellegrino et al, 2003;Marx et al, 2006), with much of the variation in slope thought to be due to the species included in the study (Marx et al, 2006). A comprehensive review of published data demonstrated that maximal shortening velocity decreased with increased body mass, scaling across species M b −0.25 , whereas maximal isometric stress showed no significant relationship with body mass (Medler, 2002).…”

Distribution Pattern of Muscle Fiber Types in the Perivertebral Musculature of Two Different Sized Species of Mice

“…Differences in muscle size between large and small animals are mainly accounted by differences in the number and length of the fibers (Goldspink, 1977;Perry et al, 1988), whereas muscle fiber size has been shown to be independent from body size and rather depends on other physiological parameters, such as volume to surface ratio of the fibers (e.g., Burke, 1981;Armstrong and Phelps, 1984;Marx et al, 2006;Kinsey et al, 2007).…”

“…This means, oxidative enzymes are less active and glycolytic enzymes are more active in smaller mammals. A smaller maximum velocity during unloaded shortening of muscle fibers expressing a given MHC was shown for larger mammals by Marx et al (2006). Furthermore, fast fibers of larger mammals showed a higher molecular weight of the myosin light chain isoform 1 (MLC1F) associated with structural changes leading to a higher affinity to the actin molecules, and thus, a lower ATPase activity and slower cross-bridge kinetics (Bicer and Reiser, 2007).…”

(How) do animals know how much they weigh?

“…slow, intermediate or fast) tends to correlate with animal size; the relative abundance of fast fibers decreases (i.e. showing a transition from MyHC IIB to MyHC IIX/A to MyHC I) as body mass increases (Pellegrino et al, 2003;Marx et al, 2006;Schiaffino and Reggiani, 2011). Another example in this area is work by Coughlin and colleagues (Coughlin et al, 2001;Campion et al, 2012) on several species of centrarchid fish.…”