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Strength Increase after Whole Body Vibration Compared with Resistance training. Christophe Delecluse, Sabine Verschueren, Machteld Roelants Faculteit Lichamelijke Opvoeding en Kinesitherapie Katholieke Universiteit Leuven België
WBV-training: positive influence on muscle strength? • Lack of scientific support • Mechanism: vibration stimulus stimulation sensory receptors in muscle (presumably muscle spindles) activation alpha motor neurons Tonic vibration reflex leading to muscle contraction: stimulus for increase in strength?
Bosco et al. 1999 (Clin Physiol): volleyball players, increase in strength-speed, strength-power leg press Bosco et al. 2000 (Eur J Appl Physiol): team sports, 7% increase mechanical power knee-extensors (leg press), 3,8% increase jump height Torvinen et al. 2002 (Clin Physiol & Func Im): 3,2% increase isometric strength knee-extensors, 2,5% increase jump height Torvinen et al. 2002 (Int J Sports Med):no effects on isometric strength knee-extensors, jump height Studies acute effects WBV
Bosco et al. 1998 (Biol of Sport): physically active subjects, 10 days WBV-training, 6,1% increase in power, 12% increase jump height Runge et al. 2000 (J Musculoskel Neuron Interact): elderly subjects, 2 months WBV-training, 18% increase in ‘chair rising time’ Torvinen et al. 2002 (Med Sci Sports and Exc): untrained subjects, 4 months WBV-training, 8,5% increase jump height, 2,5% increase isometric strength knee-extensorsDe Ruiter et al. 2002 (Geneeskunde en Sport): physically active subjects,no improvement in isometric and explosive strength knee-extensors No unambiguous results: Differences in training schedules, group composition, physical condition No placebo group No comparison to regular resistance training Long term WBV studies
Purpose of this study • long term study: • Investigate effects on isometric strength knee-extensors of exercises performed on platforms with and without vibration (placebo) • Compare effects to resistance training of moderate intensity (10-20RM)
Method • 67 young ladies (21,4±1,8 jaar) • untrained • 4 groups (random) WBV group, N=18 Placebo group (PL), N=19 Resistance group (RES), N=18 Control group (CO), N=12 • 12 weeks, 3 x/week (36 sessions)
Vibration platform (Power Plate®) progressive increase in intensity and volume 35-40Hz / 2,5-5,0mm 2,28 - 5,05g Total vibration time per session: 3-20 min rest period: 60-5 sec Placebo platform - equal platform not resulting in increased muscle contraction - amplitude negligible - acceleration only 0,4g WBV group PL group Static and dynamic exercises for knee-extensors: squat, deep squat, one legged squat, lunge,...
EMG activity in the m. rectus femoris(high squat) VIBRATION 35 Hz
Resistance-training group • University fitness centre • 20 min warm up: bicycle, step, treadmill • Resistance training schedule with moderate intensity for knee-extensors (Kraemer 2002, ACSM) • leg press, leg extension (Technogym®): 2 sets 20 RM 15 RM 12 RM 10RM W1 W3 W6 W9 W12
Pre-post measuring • Iso-kinetic dynamometer (REV9000, Technogym®) • maximum voluntary isometric strength knee-extensors (angle in knee: 130°) • post-test: min. 72 hours after last training session
Results (1) ISO † pre * * 230 post 210 190 Knee-extensor moment (N.m) 170 150 130 110 KR WBV PL CO N=18 N=18 N=19 N=12 Group
Results (2) • Isometric strength • significant interaction effect (group x time) • F (3)=15,94; P<0.001 (ANOVA for repeated measurements) • significant increase (P<0.001) pre-post (contrast analysis): • in WBV group: 16,6 ± 10,8% • in RES group: 14,4% ± 5,3% • no significant difference (P>0.05) pre-post: • in PL group: 3,8 ± 11,4 % • in CO group: -7,3 ± 15,9%
Causes of strength gain • Hypothesis: strength gain after 12 weeks WBV mainly due to neural adaptations ~ resistance training (Enoka 1997, J Biomech) • extensive sensory stimulation: possible more efficient use of sensory information in production of strength • input of proprioceptors (Ia, IIa, Ib) is used in building up isometric strength (Gandevia 2001, Physiol Rev)
Conclusions (1) • The muscle contractions during WBV efficient stimulus for strength gain in knee extensors in untrained subjects • Torvinen et al. 2002: • only 3,7% increase in strength in knee-extensors after 2 months WBV-training placebo effect this study • this study: 16,6% Difference in training schedule: time, volume, intensity,… ‘full motor unit activation’ leads to fatigue in motor units = stimulus to strength gain (Sales 1987, Exerc Sport Sci Rev)
Conclusions (2) • 12 weeks WBV training with untrained ladies: • Strength gain in knee-extensors comparable to resistance training of moderate intensity (10-20RM) • effect not attributable to stance or exercises on platform but to increased muscle activity (EMG) during WBV • NO placebo-effect
Strength gain following 12 weeks of whole body vibration training • C. Delecluse, M. Roelants, S. Verschueren • Published in Medicine and Science in Sports and Exercise Vol.35, No.6, pp. 1033-1041, 2003