title: Muscle filament spacing and short-term heavy-resistance exercise in humans.
abstract: 1. Six weeks of a dynamic heavy-resistance training of the quadriceps muscle in healthy young men resulted in a continuous increase in muscle strength, in an increase in muscle cross-sectional area (significant only in the second half of the training period) and in an increase in radiological density of the muscle tissue of 3.1% (2P less than 0.001) in the first three weeks and 1.6% (2P less than 0.01) in the second three weeks. 2. The linear distance between myosin filaments (38.7 +/- 0.3 nm before, 38.7 +/- 0.4 nm after training; mean +/- S.E.M.) as well as the ratio of actin to myosin filaments (3.94 +/- 0.03 before, 3.86 +/- 0.06 after training) did not change with training. 3. These results refute the concept that the increases in muscle strength or radiological density during short-term heavy-resistance training are caused by changes in myofilament spacing.
authors.affiliation: Department of Anatomy, University of Bern, Switzerland.
authors.forename: H
authors.initials: H
authors.lastname: Claassen
authors.forename: C
authors.initials: C
authors.lastname: Gerber
authors.forename: H
authors.initials: H
authors.lastname: Hoppeler
authors.forename: J M
authors.initials: JM
authors.lastname: Lüthi
authors.forename: P
authors.initials: P
authors.lastname: Vock
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D015444:Exercise; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D009132:Muscles / Q000000981:diagnostic imaging / Q000502:physiology* / Q000648:ultrastructure; D009218:Myosins / Q000032:analysis; D011859:Radiography; D012518:Sarcomeres / Q000648:ultrastructure; D013997:Time Factors
chemical_list: D009218:Myosins