Strength Increase after Whole Body Vibration Compared with

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? n n Lack of scientific support Mechanism: stimulus vibration stimulation sensory receptors in muscle (presumably muscle spindles) neurons contraction: activation alpha motor Tonic vibration reflex leading to muscle stimulus

Studies acute effects WBV 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 kneeextensors, jump height

Long term WBV studies Bosco et al. 1998 (Biol of Sport): physically active subjects, 10 days WBVtraining, 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-extensors De 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

Purpose of this study n 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 -20 RM)

Method 67 young ladies (21, 4± 1, 8 jaar) n untrained n 4 groups (random) WBV group, N=18 Placebo group (PL), N=19 Resistance group (RES), N=18 Control group (CO), N=12 n 12 weeks, 3 x/week (36 sessions) n

WBV group PL group Static and dynamic exercises for knee-extensors: squat, deep squat, one legged squat, lunge, . . . n Vibration platform (Power Plate®) n progressive increase in intensity and volume – – – 35 -40 Hz / 2, 5 -5, 0 mm 2, 28 - 5, 05 g Total vibration time per session: 3 -20 min – rest period: 60 -5 sec n Placebo platform - equal platform not resulting in increased muscle contraction - amplitude negligible - acceleration only 0, 4 g

EMG activity in the m. rectus femoris (high squat) VIBRATION 35 Hz

EMG activity in the m. gastrocnemius

Resistance-training group n n 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 W 1 15 RM W 3 12 RM W 6 10 RM W 9 W 12

Pre-post measuring n Iso-kinetic dynamometer (REV 9000, Technogym®) n maximum voluntary isometric strength knee-extensors (angle in knee: 130°) n post-test: min. 72 hours after last training session

Results (1) Knee-extensor moment (N. m) ISO † 230 * pre post * 210 190 170 150 130 110 KR N=18 WBV N=18 Group PL N=19 CO N=12

Results (2) n Isometric strength – significant interaction effect (group x time) n F (3)=15, 94; P<0. 001 (ANOVA for repeated measurements) – significant increase (P<0. 001) pre-post (contrast analysis): n in WBV group: 16, 6 ± 10, 8% n in RES group: 14, 4% ± 5, 3% – no significant difference (P>0. 05) pre-post: n in PL group: 3, 8 ± 11, 4 % n in CO group: -7, 3 ± 15, 9%

Causes of strength gain n 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 n input of proprioceptors (Ia, Ib) is used in building up isometric strength (Gandevia 2001, Physiol Rev)

Conclusions (1) n n 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 Difference in training schedule: time, volume, intensity, … – this study: 16, 6% ‘full motor unit activation’ leads to fatigue in motor units = stimulus to strength gain (Sales 1987, Exerc Sport Sci Rev)

Conclusions (2) n 12 weeks WBV training with untrained ladies: – Strength gain in knee-extensors comparable to resistance training of moderate intensity (10 -20 RM) – effect not attributable to stance or exercises on platform but to increased muscle activity (EMG) during WBV n NO placebo-effect

n Strength gain following 12 weeks of whole body vibration training – C. Delecluse, M. Roelants, S. Verschueren n Published in Medicine and Science in Sports and Exercise Vol. 35, No. 6, pp. 1033 -1041, 2003