Contractile properties of rat, rhesus monkey, and human type I muscle fibers

Abstract

It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

How important are skeletal muscle mechanics in setting limits on jumping performance?

“…A few studies have isolated single fibres of specific fibre types, from the same muscle, in a large body mass range of mammalian species, to subsequently determine scaling relationships within the study. Similar scaling exponents to those reported by Medler for maximum shortening velocity have been found for type I muscle fibres [(M b -0.11 (Widrick et al, 1997) and M b -0.13 (Seow and Ford, 1991)]. However, these mammalian muscle scaling exponents have been determined using force-velocity studies (isotonic) that rely on curve-fitting techniques to estimate maximal shortening velocity (Marsh and Bennett, 1986), which they are prone to underestimate (Claflin and Faulkner, 1985;Widrick et al, 1997;James et al, 1998).…”

“…Similar scaling exponents to those reported by Medler for maximum shortening velocity have been found for type I muscle fibres [(M b -0.11 (Widrick et al, 1997) and M b -0.13 (Seow and Ford, 1991)]. However, these mammalian muscle scaling exponents have been determined using force-velocity studies (isotonic) that rely on curve-fitting techniques to estimate maximal shortening velocity (Marsh and Bennett, 1986), which they are prone to underestimate (Claflin and Faulkner, 1985;Widrick et al, 1997;James et al, 1998). Studies using the slack test, which directly measures unloaded shortening velocity, have demonstrated larger scaling exponents (-0.18 to -0.21) in slow fibres than have been found using force-velocity studies (Table·1).…”

“…Studies using the slack test, which directly measures unloaded shortening velocity, have demonstrated larger scaling exponents (-0.18 to -0.21) in slow fibres than have been found using force-velocity studies (Table·1). Widrick and coworkers (Widrick et al, 1997) further confirmed the scaling relationship of type I fibres found by Rome and coworkers (Rome et al, 1990) despite using a few different mammalian species. Data of Toniolo and coworkers (Toniolo et al, 2005) suggests that the fastest muscle fibres, which are of greater importance in maximal activities such as escape responses, have very similar maximum unloaded shortening velocity in each species over a large body size range.…”

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

“…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).…”

Sarcopenia and its implications for the elderly

“…A handful of studies of the contractile properties and biochemical composition of human single muscle ®ber have been published (Fitts et al, 1989;Larsson & Moss, 1993;Harridge et al, 1995;Lankford et al, 1995;Larsson et al, 1995Larsson et al, , 1996Larsson & Frontera, 1997;Widrick et al, 1996Widrick et al, , 1997Galler et al, 1997). However, as noted above, the cellular mechanisms underlying muscle weakness and atrophy in aging humans have not been elucidated.…”