Vibration exercise devices such as Power Plate and Soloflex are among the latest fitness technologies to promise maximum results with a minimum amount of time and effort.
Simply standing, sitting or lying on one of these vibrating machines for a few minutes a day, say the manufacturers, can increase muscle strength, flexibility and bone mass,as well as improve cellulite and speed up metabolism.
But are these 'miracle machines' merely a gimmick, or could vibration really be a valuable fitness tool?
The American Council on Exercise says it's too early to either endorse or denounce these devices. However, there's a growing body of evidence that this minimal-effort form of exercise may live up to the hype.
In both athletes and untrained people, whole-body vibration training (WBVT) can indeed increase muscle strength, power and flexibility with as little as four minutes a day, three times a week, for two to four months (Am J Phys Med Rehabil, 2006; 85: 956-62; Med Sci Sports Exerc, 2002; 34: 1523-8).
Comparative studies of WBVT and traditional resistance training have found similar gains in strength and, in some cases, more gain in explosive power (Med Sci Sports Exerc, 2003; 35: 1033-41; J Am Geriatr Soc, 2004; 52: 901-8).
The explanation, according to the current theory, is that WBVT stim-ulates the body's natural stretch reflex (contraction), activated when a muscle is under a static stretch or quickly stretched. WBVT continually stimulates this reflex until the vibra-tion stops. According to the makers of Power Plate, each vibration causes the body to reflexively relax and contract 25-50 times per second. Moreover, the activation of one muscle reflex is thought to affect the adjacent muscles, too.
In other words, all the user needs to do is assume various positions on the platform to target different muscle groups.
However, while it boosts flexibility and muscle strength, people looking for a quick-fix weight-loss solution may be disappointed. A 24-week study in Belgium found that WBVT did not reduce weight, total body fat or subcutaneous fat in untrained women. However, it did significantly increase fat-free mass (2.2 per cent), the part of the body that is not fat, so the women may have gained muscle instead (Int J Sports Med, 2004; 25: 1-5).
Nevertheless, the greatest benefit of WBVT may lie in its potential to increase bone mass. Postmenopausal women who engaged in WBVT three times a week for six months achieved significant increases in bone mineral density (BMD) of the hip, as well as improved strength and balance. It appears that vibration training may help to reduce falls and bone frac-tures in older women (J Bone Miner
Res, 2004; 19: 352-9).
WBVT also prevented bone loss in the spine and femur in postmeno-pausal women, whereas those using a placebo device lost 1.6 per cent and 2.13 per cent of spine and femur BMD, respectively (J Bone Miner Res, 2004; 19: 343-51).
WBVT is also promising in a num-ber of other age-related conditions (see box below).
Is vibration training safe?
Despite the potential benefits of WBVT, there are negative effects of vibration on the body. Research from the workplace shows that prolonged exposure to vibration-from drills or chainsaws, for example-can damage the peripheral nerves, blood vessels, joints, and visual/sensory percep-tion. In animals subjected to high levels of vibration, there have been reports of lung damage, gastrointes-tinal bleeding and even fatal heart haemorrhage (J Strength Cond Res, 2005; 19: 459-66).
However, these reactions depend on the frequency, magnitude, dura-tion and type of vibration, and the evidence so far suggests that the current WBVT technology, when performed in short bouts a few times a week, is unlikely to cause harm.
Indeed, a recent review reported that "it is possible to confirm that the procedure seems safe when subjects stand on vibrating plates for a relatively short time with knees semiflexed to limit transmission of vibrations to the head" (Br J Sports Med, 2005; 39: 585-9).
Other potential uses of WBVT
- Diabetes. Whole-body vibration training (WBVT) enhanced glycaemic control in type 2 diabetics (Int J Med Sci, 2007; 4: 159-63)
- Stroke. WBVT improved postural control in stroke patients (Am J Phys
Med Rehabil, 2004; 83: 867-73)
- Parkinson's disease. Parkinson's patients undergoing WBVT saw significant improvements in tremor and rigidity (NeuroRehabilitation, 2006; 21: 29-36)
- Sarcopenia (age-related loss of skeletal muscle mass, strength and function). WBVT was as effective as a traditional fitness programme
in increasing muscle strength and mass in men over the age of 60
(J Gerontol A Biol Sci Med Sci, 2007; 62: 630-5).