Local vibration therapy is known to induce relaxation, seen through both hormonal changes as well as electrical measurements of the muscles and heart (EMG & ECG). Vibration therapy is often compared with massage, and we have reviewed studies which directly evaluate the effectiveness of both [20][43].
Vibrational therapy has shown to be just as effective as massage for both pain [20] and muscle recovery [43], requiring less than half the time of massage for each. Researchers have cited vibration therapy as a useful alternative to the more expensive traditional massage [1].
Another study again involving both massage and local vibration concluded that both massage and vibration therapy reduced anxiety and stress in all participants [49].
Heart Rate Variability (HRV)
Local vibration has been shown to improve heart rate variability (HRV) in individuals leading to a relaxation and stress-reducing response [3][50]. One study of 12 people reported that 11 of 12 of the participants reported feeling relaxed or rested after the vibration session, and that parasympathetic activity was increased [50].
Heart rate variability is a measure of electrical signals from the heart and is often used in research relating to stress and relaxation [51][52][53]. It can help to understand the health of the autonomic nervous system, the automated system which controls everything we are not consciously aware of such as digestion, heart rate, blood pressure, and much more. Parasympathetic activity in HRV is associated with relaxation and meditation and is seen to increase during yoga as well as mindfulness practices [51][52].
Electromyography (EMG)
Another measure of relaxation is the electromyogram or EMG. It is another type of biofeedback measurement which can help researchers understand what is happening within the body and mind.
EMG is the direct electrical measurements of small current signals in muscle correlated with the activity of the muscle. Our muscles release small electrical signals in their normal operation which are picked up and recorded on an EMG [54].
EMG is sometimes used to help treat or measure anxiety levels in patients [55][56]. High anxiety levels are generally correlated with higher baseline EMG activity as this would indicate muscle tension from stress [57].
One study measured the effect of local vibrations on participants on EMG recordings and found that EMG results indicated significant effect on reduced muscle tension, with participants reporting a consistent feeling of reduced tension [58]. Another study showed similar results, and concluded that vibration therapy could be an effective aid in relaxation [59].
Oxytocin
A study comparing foot massage by hand (traditional massage) to foot massage by machine (vibration therapy) found that in both cases blood oxytocin levels increased, though traditional massage saw a greater increase [28].
Vibrations are perceived as a tactile sensation and picked up by what is known as A-β nerve fibers, which pick up easily detectable touch signals [4][8]. Massage operates slightly differently, activating A-β nerve fibers as well as CT fibers which are more sensitive. Both nerve types are considered to play a role in oxytocin release, however CT nerve fibers have a significantly larger role [60].
Oxytocin is heavily linked to social interactions and stress regulation in humans [61] and is essential in creating the bond between a mother and her child after birth [62]. This hormone is linked with stress, dopamine, and even the body’s opioid receptors (think of endorphins) [62][63][64].
One study in rats found oxytocin to lead to sedation, a decrease in blood pressure, slower pain responses, and a decrease in corticosterone levels which is the primary “stress hormone” in rats (vs cortisol in humans) [63].
Another study in humans found high oxytocin levels to be associated with low norepinephrine levels, blood pressure and heart rate [65]. High levels of norepinephrine can be correlated to high central nervous system activity, stress, and anxiety.
Cortisol
Another hormone found to be impacted by local vibration therapy is cortisol. Cortisol levels are practically synonymous with the more subjective feeling of stress, and the terms are often used interchangeably in the field of research. Cortisol levels, and stress, are considered to have an impact on mental illness, personality, life expectancy, pain, and more.
Researchers have found that local vibrations are able to reduce cortisol levels, thereby indicating reduced stress and increased relaxation [24][25].
