Local vibration therapy has been clinically proven to reduce pain as well as increase pain threshold in several applications and pain types, both chronic and acute. The main theory that the scientific community holds for this is the Gate Control Theory. This theory indicates that non-pain signals are able to override pain signals and cause the pathway “gate” to close, preventing the brain from further receiving the pain signals [8].
Gate Control Theory
Non-painful sensory signals, essentially touch or vibration signals, are received differently than pain, or nociceptive signals (though not all pain is nociceptive) [9]. These signals are received by different receptor types, which are then carried by different types of neuron cells. The touch and vibration signals are propagated by A-β nerve fibers, while pain signals are carried by A-δ and C nerve fibers [4][8].
The A-β nerve fibers are much larger and carry signals more quickly than the pain carrying fibers of A-δ and C [10][11][12]. The theory holds that when these two systems are activated, the vibration signal is received by the brain and inhibitory neurons are stimulated preventing the pain signals from continuing to the brain [8][13].
Analgesic Studies for Vibration Therapy
Local vibration therapy has been tested on many types of pain, both chronic and acute, and has been shown to reduce pain consistently and significantly. The analgesic effect occurs both during the vibration stimulus, as well as for a large period of time following [14][15].
Pain types positively affected by locally applied vibration include myofascial, musculoskeletal, chronic lower back pain, postoperative pain, as well as pain from both general anesthetic as well as local dental anesthetic injections [16][17][18][19][20].
One study on the lower back pain of nurses found that vibration therapy was able to reduce pain scores by almost 50% and had a significant improvement over general muscle relaxation techniques [16]. Vibration was applied only for 10 minutes in this case.
Another study of 366 patients suffering from acute or chronic musculoskeletal pain tested the effects of vibratory stimulation applied locally. Many patients had been unable to find relief through other methods. 69% of the patients – over 250 of the 366 – reported a reduction in pain during the vibration therapy. The researchers found that pressure improved the effectiveness of the vibration, and that 25 – 45 minutes of therapy achieved the maximal duration of pain relief. They also noted that the best location for the vibratory stimulation was the site of the pain [14].
In another study of 99 patients receiving oral local anesthetic injections, researchers applied vibration therapy during the procedure. The reported pain scores indicated that the application of vibration reduced pain by 55 – 67%, depending primarily on injection location [8].
Vibration Therapy vs TENS
TENS devices are electrical units which apply electrical impulses to the surface of the skin. These impulses are more powerful than the native signals of the body and overwhelm the nervous system and thereby reduce the capacity for pain signals to be transmitted to the spinal cord and brain. It is effective in producing an analgesic effect [21].
One study reviewed the effects of both vibration therapy and TENS. Results of this study indicate the pain reducing capacity of vibration therapy is equal to that of TENS devices. In 29 out of 48 patients in this study, the vibratory stimulation was also rated to be more effective than aspirin at reducing pain [19].
Another study of pain-alleviating methods for local anesthetic injections in children tested both TENS and vibration therapy as well as topical anesthetic agents. These pain reducing methods were applied to the patients prior to injection. It was found that the TENS device had the largest reduction in pain, with vibratory stimulation following closely behind. Both methods were more effective than either topical anesthetic [22].
Vibration Therapy vs Massage
Massage therapy goes back long before the modern world and has significant benefits including the reduction of pain.
One study of 105 women reviewed the effects of both massage and vibration therapy on postoperative pain. The massage group of patients received 45 minutes of massage, while vibration was applied for 20-minutes. The researchers found that no significant differences could be found between vibration therapy and massage [20].
Biochemical Roles
There are also a number of neurotransmitters and hormones released as a result of vibration therapy which may help play a role in the pain reduction or analgesic effects of vibration therapy. These include cortisol, testosterone, and oxytocin [4].
Cortisol is known as the stress hormone and is an important adaptive response but can cause issues when constantly or overly released, leading to anxiety and many forms of health problems. There is a strong two-way correlation between pain and stress, with pain being known to cause stress itself, while long term stress may further degrade pain and disability [23].
One study found that high frequency locally applied vibration therapy of 300 Hz was found to decrease cortisol levels [24]. Another study replicated these findings with lower frequency vibration of 35 – 40 Hz [25].
Oxytocin is another hormone which may have a significant influence on the way humans experience and perceive pain [26]. Oxytocin has shown to be successful in treating the pain of headaches when directly administered [27].
One study found that local vibration therapy was able to increase blood oxytocin levels by more than 18% [28].
Testosterone is thought to play a role in the control of pain within the body, with a number of studies supporting this [29]. One study took 26 healthy men and separated them into two groups of high and low testosterone levels, then took pain ratings after placing their fingers in hot water at 122°F. The low testosterone group showed significantly higher unpleasantness, anxiety and fear than the group with high testosterone [30].
Local vibration has been shown to significantly increase testosterone levels in the blood after application [31].
