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Revista Brasileira de Medicina do Esporte
On-line version ISSN 1806-9940
SAAD, Paulo César Bálade; GUIMARAES, Alcides; DAL PAI, Vitalino and KROLL, Lúcio Benedicto. Histologic and histochemical analysis of fibers of rectus of abdomen and paraesternal intercostal muscles of Wistar rats after swimming exercise. Rev Bras Med Esporte [online]. 2002, vol.8, n.4, pp.144-150. ISSN 1806-9940. http://dx.doi.org/10.1590/S1517-86922002000400003.
The objective of the present study was to evaluate the influence of swimming exercise on metabolic and contractile abilities of rectus of abdomen and the paraesternal intercostal muscle fibers. Adult Wistar rats were initially submitted to an adaptation period and then divided into control and exercise groups. Exercised animals were submitted to swimming for 15, 30, 45, and 60 days, 1 hr/day, 5days/week. At the end of each period, the animals were killed. Small segments of the above muscles were frozen in N-hexane at -70ºC, pre-cooled with liquid nitrogen for two minutes. Histological transverse sections (7 µm) were obtained in a cryostat microtome at -20ºC. Some serial sections were stained with HE. Subsequent sections were reacted for NADH-TR to evaluate the oxidizing capacity, and for m-ATPase, after acid and alkaline pre-incubations mediums. Under microscopic examination, the frequencies of fiber types were sampled. Muscle fibers revealed to be grouped in different fascicles, presenting polygonal outlines, with different diameters. Three kind of fibers were detected: SO (slow oxidative), FOG (fast oxidative glycolytic) and FG (fast glycolytic), presenting a mosaic pattern distribution. The analysis of the results demonstrated that after 60 days of exercise, the abdominal muscles showed a significant increase in the frequency of SO fibers. After 15 days, a significant decrease in frequency of intermediate FOG fibers and an increase of FG fibers. The paraesternal intercostal muscles revealed a significant increase in the percentage of SO fibers in the 60 day-exercised animals, a percentage increase of FOG fibers in the animals of 45 and 60 days, and a percentage decrease of FG fibers in those of 30, 45 and 60 days. So, due to hydrostatic pressure in swimming exercise, the degree of work was greater in the inspiration muscles. This increase was parallel with the increase of aerobic adaptation of fibers and fatigue resistance.
Keywords : Respiratory muscles; Swimming exercise; Muscle fiber types.