The purpose of this investigation was to characterize the effects of marathon training on single muscle fiber contractile function in a group of recreational runners. Muscle biopsies were obtained from the gastrocnemius muscle of seven individuals (22 ± 1 yr, 177 ± 3 cm, and 68 ± 2 kg) before, after 13 wk of run training, and after 3 wk of taper. Slow-twitch myosin heavy chain [(MHC) I] and fast-twitch (MHC IIa) muscle fibers were analyzed for size, strength (Po), speed ( Vo), and power. The run training program led to the successful completion of a marathon (range 3 h 56 min to 5 h 35 min). Oxygen uptake during submaximal running and citrate synthase activity were improved ( P < 0.05) with the training program. Muscle fiber size declined ( P < 0.05) by ∼20% in both fiber types after training. Po was maintained in both fiber types with training and increased ( P < 0.05) by 18% in the MHC IIa fibers after taper. This resulted in >60% increase ( P < 0.05) in force per cross-sectional area in both fiber types. Fiber Vo increased ( P < 0.05) by 28% in MHC I fibers with training and was unchanged in MHC IIa fibers. Peak power increased ( P < 0.05) in MHC I and IIa fibers after training with a further increase ( P < 0.05) in MHC IIa fiber power after taper. These data show that marathon training decreased slow-twitch and fast-twitch muscle fiber size but that it maintained or improved the functional profile of these fibers. A taper period before the marathon further improved the functional profile of the muscle, which was targeted to the fast-twitch muscle fibers.

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The purpose of this study was to determine the physiological and performance effects of two frequencies and volumes of long slow distance (LSD) training in novice male and female marathoners. Subjects (N = 51) were healthy college students who had not previously run a marathon. They were matched on peak oxygen consumption (VO2peak) into a 6 d.wk-1 (G6) or a 4 d.wk-1 (G4) training group. Both groups trained at 60% to 75% of the heart rate reserve for 15 weeks but G4 trained with 20% less total volume. All groups responded similarly to the training by decreasing percent body fat and maximum heart rate and by increasing fat free mass and VO2peak. All groups significantly decreased the oxygen (O2) cost, lactate level, and heart rate at a submaximal running speed. Within the same gender, performance in the marathon was not different between groups. It was concluded that both training programs prepared subjects equally well to run a marathon.

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