regarding google & muscle fiber size increases do primarily to sprint & plyometric type training:
Muscle Power and Fiber Characteristics Following 8 Weeks of Plyometric Training
JEFFREY A. POTTEIGER, ROBERT H. LOCKWOOD, MARK D. HAUB, BRETT A. DOLEZAL, KHALID S. ALMUZAINI, JAN M. SCHROEDER, and CAROLE J. ZEBASDepartment of Health, Sport, and Exercise Sciences, University of Kansas, Lawrence, Kansas 66045.
ABSTRACT We examined changes in muscle power output and fiber characteristics following a 3 d·wk?~H~R1, 8-week plyometric and aerobic exercise program. Male subjects (n = 19) were randomly assigned to either group 1 (plyometric training) or group 2 (plyometric training and aerobic exercise). The plyometric training consisted of vertical jumping, bounding, and depth jumping.
Aerobic exercise (at 70% maximum heart rate) was performed for 20 minutes immediately following the plyometric workouts. Muscle biopsy specimens were collected from the musculus vastus lateralis before and after training. Type I and type II fibers were identified and cross-sectional areas calculated. Peak muscle power output, measured using a countermovement vertical jump, significantly increased from pretraining to posttraining for group 1 (2.8%) and group 2 (2.5%).
***Each group demonstrated a significant increase in fiber area from pretraining to posttraining for type I (group 1, 4.4%; group 2, 6.1%) and type II (group 1, 7.8%; group 2, 6.8%) fibers, but there were no differences between the groups. Following plyometric training, there is an increased power output that may in part be related to muscle fiber size.
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EFFECTS OF SPRINT AND PLYOMETRIC TRAININGON MORPHOLOGICAL CHARACTERISTICS INPHYSICALLY ACTIVE MEN
Goran Markovic?~A, Igor Jukic?~A, Dragan Milanovic?~A and Dus?~Lan Metikos?~LFaculty of Kinesiology, University of Zagreb, Zagreb, CroatiaOriginal scientific paperUDC 796.091.2:572.7-055.1
Abstract:The purpose of this study was to compare the effects of sprint and plyometric training on morphologicalcharacteristics of physically active men. One hundred and fifty one physical education students (18-24 s arrof age) were allocated into one of three groups: the plyometric group (PG; n = 50), the sprint group (SG; n = 50), and the control group (CG; n = 51). Both experimental groups participated in a training programme3 times a week for 10 weeks.
SG performed maximal sprints for distances between 10 and 50 meters, whilethe training programme in PG consisted of hurdle jumps and drop jumps. Anthropometric measurementwas performed in the week before and the week after the experiment. There were no significant differences (P > 0.05) in magnitude of changes in any of the analysed anthropometric variables between the groups.
However, a significant decrease (P < 0.0167) in the percentage of body fat (6.1%) was found in SG. We alsofound a significant decrease (P < 0.0167) in body mass (1%), fat-free mass (0.4%) and body mass index (0.9%) for the SG, but the magnitude of these changes was rather low.
***We conclude that the short-term explosivetraining programmes in which muscles operate in the fast stretch-shortening cycle conditions (i.e., ng,intiijumping) have a limited potential to induce morphological changes in physically active men.
study 1 vs study 2, fight!