Distribution of different fibre types in human skeletal muscles 2. A study of cross‐sections of whole m. vastus lateralis

Abstract

In order to determine the total number of fibres and the extent to which the relative occurrence of different fibre types varies within m. vastus lateralis, 15 micrometers thick cross-sections of whole muscles were prepared. The total number of type 1 and type 2 fibres was determined in every 48th square millimetre of the section, and the results thus obtained were analysed using a computer program allowing an assessment of bivariate data in the form of contour plots. The total number of fibres varied both in proximal to distal direction in the same muscle and between individuals. No obvious correlation existed between the mean fibre area and the muscle cross-sectional area. The proportion of type 1 fibres in the whole muscle varied between individuals (from 44% to 57%) with a mean value for all five of 52%. The distribution of different fibre types varied within the muscle, mainly as a function of depth, with a predominance to type 2 fibres at the surface and type 1 fibres in deeper regions of the muscle. Thus, the fibre type distribution in m. vastus lateralis is not random. This must be taken into consideration when data on fibre type composition are compared with functional variables.

Effect of stimulation intensity on assessment of voluntary activation

“…In addition, if motor axons are in a refractory state at the instant of stimulus application, this can suppress superimposed torque, particularly at higher values of MVT. 32 Furthermore, there is a nonrandom distribution of fiber types in the quadriceps, with relatively more type II fibers 33 and more larger motor units 34,35 in superficial layers. Percutaneous stimulation, with lower stimulation currents will not reach deep into the muscle tissue, 18 and, therefore, potentially more type II fibers may be activated with submaximal muscle compared with maximal nerve stimulation.…”

Muscle fibre type composition in infant and adult populations and relationships with obesity

“…This strongly suggests that the child/adult differences in Figure 1 are likely to be a very real phenomenon that extends to a range of skeletal muscles in humans. Lexell and his co-workers 33 have reported that the distribution of different ®bre types varies within a muscle, mainly as a function of depth, with a predominance of Type 2 ®bres at the surface and Type 1 ®bres in deeper regions of the muscle. Thus, the ®bre type distribution is not random and while every endeavour was taken during the collection of muscle biopsy samples to ensure consistency, this must be taken into consideration when data on ®bre type composition are compared with functional variables.…”

Pulmonary oxygen uptake and muscle deoxygenation kinetics during recovery in trained and untrained male adolescents

“…Furthermore, in the vastus lateralis a slight predominance of slow twitch fibres has been shown in the deeper regions of the muscle tissue (Lexell et al 1983). Therefore a greater penetrative depth of near-infrared light would likely favour faster microvascular oxygen pressure (McDonough et al 2004) and thus [HHb] kinetics (Ferreira et al 2005) during recovery and may explain some of the differences between groups.…”