Effects of endurance training on muscle fibre ATP‐ase activity, capillary supply and mitochondrial content in man.

Abstract

SUMMARYSeven young females were subjected to 24 weeks of intensive endurance training. Adaptive changes in myofibrillary ATP-ase activity, capillary supply and mitochondrial content were investigated with light-and electron microscopy in needle biopsies from the quadriceps femoris.1. The average value for the maximal oxygen uptake increased from 45-7 to 57-2 (ml. kg-1 min-') (25.2 %, P < 0-005).2. The average number of capillaries per muscle fibre increased from 1P39 to 1-79 (28.8 %, P < 0-005). Since no significant change in fibre area was found, this suggests that a considerable number of new capillaries have been formed during the training period.3. An increased capillary supply of all fibre types was found, being greatest for type I and smallest for type IIB.4. The relative amount of type I fibres before and after the training period was 57-9 and 56*5 % respectively (n.s.), for type IIA fibres 26-4 and 31 5 % (P < 0.005), for type JIB fibres 9-2 and 3.4 % (P < 0.005) and for type IIC fibres 0 4 and 2.2 % (P < 0.005). Thus, in the type II group, significant changes in subtypes take place during the endurance training. The data suggest that type IIAB may represent a transitional state between type IIA and IIB. 5. Correlation of capillary supply, myofibrillar ATP-ase activity and mitochondrial content (determined semiquantitatively) of individual muscle fibres indicates that the capillary supply to a given fibre is more closely related to its mitochondrial content than to the fibre type as determined on the basis of myofibrillar ATP-ase activity.

Selective long-term electrical stimulation of fast glycolytic fibres increases capillary supply but not oxidative enzyme activity in rat skeletal muscles

“…Factors other than hypoxia, such as increases in capillary perfusion andÏor shear stress, are therefore likely to act as important promoters of capillary growth in stimulated muscles (Hudlick a et al 1992). The importance of mechanical factors in directing the specificity of the angiogenic response to increased muscle activity is supported by the data of Ingjer (1979). He found an increased capillary supply in muscles of endurance-trained athletes in the vicinity of fast oxidative fibres, but not around fast glycolytic fibres which are not involved in movements during this type of exercise.…”

Alterations of skeletal muscle in chronic heart failure.

“…Similarly, the capillary length density has been shown to decrease with immobilization,41 whereas the capillary supply is substantially increased in accordance with the oxidative capacity of skeletal muscle during exercise training. 49,52 It is conceivable, therefore, that the same mechanisms control mitochondrial content and capillary supply of skeletal muscle. 49 Recently, the concept has been put forward that a generalized myopathy may occur in some patients with dilated cardiomyopathy, based on qualitative ultrastructural data in a limited number of patients and divergent morphological abnormalities of upper arm skeletal muscle.…”

“…49,52 It is conceivable, therefore, that the same mechanisms control mitochondrial content and capillary supply of skeletal muscle. 49 Recently, the concept has been put forward that a generalized myopathy may occur in some patients with dilated cardiomyopathy, based on qualitative ultrastructural data in a limited number of patients and divergent morphological abnormalities of upper arm skeletal muscle. 53 Although the present investigation focused on the quantitative assessment of mitochondria in weight-bearing muscles (and did not reveal abnormalities noted by these investigators), we cannot exclude the possibility that generalized myogenic process affects both cardiac and skeletal muscle in a subset of patients with dilated cardiomyopathy, a clinical entity with various and very different etiologies.…”

Testing Metabolic Theories

“…The metabolic rate of small species following endurance training should therefore be relatively Body mass (kg) Post-training relative capillary density Figure 6: Relationship between post-endurance-training capillary density, expressed relative to capillary density of untrained individuals, and body mass. Data are from published studies, including a range of training durations, methods, and intensities (Hermansen and Wachtlova 1971;Andersen and Henriksson 1977;Ingjer 1979;Adolfsson et al 1981;Klausen et al 1981;Hoppeler et al 1984Hoppeler et al , 1985Essén-Gustavsson et al 1989;Bigard et al 1991;Rivero et al 1995;McCall et al 1996;Serrano et al 2000;Amaral et al 2001;Waters et al 2004;Chinsomboon et al 2009;Geng et al 2010). …”