Shake up clients' workouts with low-impact whole-body vibration training.
No pain, no gain? This popular adage may not ring true for whole-body vibration (WBV), a new training method that has been used widely in Europe. Whole-body vibration training has been shown to increase muscular strength, explosive power and anabolic hormone levels when performed for as little as 4 minutes three times a week (Bosco et al. 2000; Torvinen et al. 2002). It requires relatively little exertion compared with traditional forms of exercise; yet studies comparing this training method to traditional strength training have found similar gains in strength and, in some cases, more gains in explosive power (Delecluse, Roelants & Verschueren 2003; Roelants et al. 2004). Since whole-body vibration training is low impact, it may be a particularly good choice for older or obese clients who have trouble doing traditional weight-bearing exercise.
Whole-body vibration is a neuromuscular training method that uses a low- to moderate-vibration stimulus to improve muscular strength and power. During the most frequently used mode of whole-body vibration training, a client stands on a vibrating platform and performs unloaded exercises, such as squats or lunges, for durations ranging from multiple 1-minute sessions to continuous 30-minute sessions.
The whole-body vibration platform produces oscillating vibrations that are delivered to the entire body. The vibrations are set at a frequency and amplitude that will provide a desired stimulus. Frequency, measured in hertz (Hz), refers to the number of vibrations per second; at 25 Hz, the targeted muscles receive 25 cycles of vibration per second, which makes them contract and relax 25 times in the same period. Amplitude, measured in millimeters (mm), refers to the extent of the vertical displacement of the platform during vibration. Higher frequencies and amplitudes increase the intensity of the vibrations. When an individual stands on the platform, the lower body receives the greatest vibration stimulus; the vibration lessens as it moves up the body.
The current theory is that whole-body vibration stimulates the body’s natural stretch reflex and causes muscle contractions in much the same way that a doctor’s tapping below a patient’s patella with a reflex hammer elicits a knee-jerk response. The stretch reflex is controlled by stretch receptors called muscle spindles that are located in skeletal muscle. Muscle spindles are usually activated when a muscle is under a static stretch or is quickly stretched or overstretched, causing a reflex contraction of the muscle. With whole-body vibration, this reflex action is continually stimulated, so a muscle continues to contract and relax until the vibration stops. In addition, studies have reported that activation of one muscle spindle will cause a reflex contraction and relaxation in many adjacent muscles (Issurin & Tenenbaum 1999; Cardinale & Lim 2003).
Muscle spindles work by activating motor neurons (nerves) in the spinal cord; these neurons initiate movement by sending signals from the brain to the muscles. Voluntary activation of motor neurons is a limiting factor in muscular force production. The improvements in muscular force production with whole-body vibration are a direct result of increased motor neuron activation by muscle spindles, leading to increased motor unit recruitment and force production. Whole-body vibration stimulates fast-twitch (type 2) motor units, which are usually recruited during high-intensity, explosive movements or whenever slow-twitch (type 1) motor units are maximally recruited. As a result, long-term, exhaustive exposure to whole-body vibration can lead to muscular fatigue and muscle soreness.
The majority of studies suggest that whole-body vibration training is just as effective as resistance training in eliciting gains in muscular strength and power. In fact, some findings suggest that whole-body vibration training may be more effective than resistance training if the desired result is an increase in power, since whole-body vibration training stimulates those hard-to-recruit fast-twitch motor units.
In the only placebo-controlled study, Delecluse and colleagues (2003) reported significant increases in isometric, dynamic and explosive strength (power) in young, healthy females following 12 weeks of whole-body vibration training. Subjects were placed into three groups: (1) whole-body vibration, (2) resistance training (RES) and (3) placebo (PLA). The whole-body vibration group performed static and dynamic knee extension exercises (squats, deep squats, wide-stance squats, one-legged squats and lunges) on the vibration platform (frequency: 35–40 Hz; amplitude: 2.5–5 mm) three times a week. Over the 12-week period, overload was accomplished by increasing the duration of vibration from 3 minutes to 20 minutes per session, increasing the number of repetitions per exercise, shortening the rest periods or increasing the frequency and/or amplitude of the vibration. The PLA group performed the same exercises on the vibration platform; however, the platform was set at a negligible frequency and amplitude. The RES group performed a moderate resistance training program for knee extensors on a leg press and leg extension machine. Like the whole-body vibration program, the RES program was slowly progressive. Findings revealed that isometric and dynamic knee extensor strength increased significantly in both the whole-body vibration group (9% and 16%, respectively) and the RES group (7% and 14.4%, respectively). The PLA group did not show an increase in either isometric or dynamic strength. Additionally, explosive strength increased by 7.6% in the whole-body vibration group, the only group to show a significant increase. These findings suggest that whole-body vibration training may be just as effective as resistance training for gaining muscular strength and may be superior to resistance training for increasing muscular power.
In a similar study, Roelants et al. (2004) reported a significant increase in fat-free mass and strength with whole-body vibration. This study compared the effects of 24 weeks of resistance training and whole-body vibration (frequency: 35–40 Hz; amplitude: 2.5–5 mm) on body composition and knee extensor strength in untrained young women. Although there were no significant changes in body weight or percent body fat in either group, the whole-body vibration group significantly increased fat-free mass (by 2.2%). A significant increase in knee extensor strength was also reported in both groups.
In another study, conducted by Roelants, Delecluse and Verschueren (2004), 24 weeks of whole-body vibration training performed three times a week increased dynamic knee extensor strength in postmenopausal women by 15%. This strength increase was similar to the increase reported in the resistance-trained group. Speed of movement of the knee extensors was significantly increased only in the whole-body vibration group, further supporting the concept that whole-body vibration may be superior to resistance training for increasing power, as a large determinant of muscular power is speed of movement.
Torvinen and colleagues (2002) also reported significant results. In this study, young, healthy males and females performed 4 minutes of unloaded exercises on a vibration platform three to five times per week for 4 months (frequency: 25–40 Hz; amplitude: 2 mm). During each 4-minute vibration exposure, vibration frequency was increased progressively in 1-minute intervals. Vertical jump height increased 8.5% and knee extensor strength increased 2.5% in the whole-body vibration group. No improvements were reported in the control group. The authors concluded that performing unloaded exercises on a vibration platform for only 4 minutes per day can increase muscular strength and power in healthy individuals.
Whole-body vibration has also been reported to produce immediate effects on anabolic hormone levels and muscular power. Bosco and colleagues (2000) noted a significant increase in blood concentrations of testosterone and growth hormone following 10 one-minute sessions of whole-body vibration training (frequency: 26 Hz; amplitude: 4 mm) in healthy men. Whole-body vibration training also elicited a decrease in the blood concentration of cortisol, the body’s stress hormone, suggesting that whole-body vibration does not produce a general stress reaction, a response that is common for high-intensity exercise.
In another study, Issurin & Tenenbaum (1999) reported significant increases in maximal power following vibration stimulus during bilateral biceps curls in elite and amateur athletes. Each subject performed two separate series of three sets of bilateral biceps exercises. In the second set of one series, a vibration stimulus was delivered to the subjects by means of vibrating cables (frequency: 44 Hz; amplitude: 3 mm). Both elite and amateur athletes showed improvement—10.4% and 7.9% respectively—in maximal power following vibration exposure.
The above findings indicate that Whole-body vibration can elicit immediate improvements in muscle function and hormone production. However, the lasting effect of these acute responses has yet to be tested.
Osteoporosis, a condition characterized by the progressive loss of bone tissue, is one of the most common complications of aging. After menopause, bone mineral density (BMD) can decline at a rate as high as 3% per year in some women (Rubin et al. 2004). A handful of research studies have reported positive effects of whole-body vibration training on BMD in postmeno-pausal women. In a 24-week study (Verschueren et al. 2004), hip BMD showed a significant increase of 0.93% in postmenopausal women who participated in whole-body vibration three times a week. In a 12-month study (Rubin et al. 2004), whole-body vibration training effectively prevented bone loss in the spine and femur in postmenopausal women, whereas the placebo group lost 1.6% and 2.13% of spine and femur BMD, respectively. Although no studies to date have compared the bone benefits of whole-body vibration training to those of resistance training, current studies reveal that whole-body vibration may be an effective intervention for the prevention of osteoporosis.
Whole-body vibration is a fast, effective alternative to resistance training that enhances muscular strength and power in both sedentary and athletic populations. The low-impact nature of the exercise and the relatively low exertion required make whole-body vibration an attractive exercise mode when working with obese and elderly clients. Additionally, it can be a good cross-training option for athletes wishing to minimize the amount of repetitive joint loading on their bodies.