ABOUT PHYSIO VIBE

Spasticity is defined as an uncontrolled tightening of muscles caused by altered neurological function due to damage to the brain or spinal cord. More than 70% of patients with CP experience spasticity. Muscle stiffness, spasms and overactive reflexes are all associated with spasticity. The resultant discomfort and pain have a negative impact on mobility and independence. Medical treatments that address spasticity include oral medication (i.e. Baclofen) or in severe cases, may involve the implantation of a surgical pump. While WBV is not proposed as an alternative to these interventions, it should be considered as a potential method of reducing spasticity to enhance function. Studies have been conducted to determine the efficacy of WBV as a potential treatment for reducing spasticity and findings have been encouraging. One study examined the immediate effect on calf muscle spasticity in individuals with spastic CP following a single 20 minute session of WBV administered in two minute bouts at 20 Hz. Subjects maintained a semi-squat position on the platform with the knees at 30 degrees of flexion. Results indicated a reduction in spasticity which lasted for several hours after the treatment. This has important implications for inclusion of WBV as part of a rehabilitation program in that administering vibration treatment prior to conventional therapy may create a longer window of opportunity for motor learning during therapy sessions. When spasticity is decreased, muscle tone and length are more normalized, allowing for greater ease of movement. This change may also facilitate improved carryover during therapy sessions to promote longer lasting results.

Findings from another study suggested that spasticity may be reduced by a vibration stimulus. In this study, 44 children with CP affecting one or both sides of the body participated in a WBV program. WBV was delivered in a single session for a 1 minute bout between 16 and 25 Hz. After treatment, a 5% to 12% decrease in reflex activity was noted, which is correlated with a decrease in spasticity.

Passive muscle stretching is a standard treatment performed by both physical and occupational therapists to manage spasticity. While short-term effects of stretching are beneficial, this treatment is not able to target the root cause of the issue. One study investigated the effects of a WBV program combined with a passive stretching program in children and adolescents with spastic diplegic CP (CP involving both sides of the body with leg and arm involvement, although legs are more typically affected). The WBV treatment was administered for 10 minutes at 20 Hz, five times a week for 6 weeks, following 30 minutes of passive stretching, whereas the control group subjects only received passive stretching. Researchers concluded that the combination of both treatments had a more pronounced effect on reducing spasticity than passive stretching alone. These effects were noted immediately after the first treatment and were maintained after 6 weeks of treatment. 

Another study which included children with spastic diplegia and quadriplegia involved a single 20 minute WBV session at a frequency of 20 Hz, with the subject standing on the platform in a partial squat position (knees flexed to 30 degrees). The results showed that the spasticity of the leg muscles decreased after the WBV treatment.

In another randomized control trial, researchers implemented three series of WBV in 3 minute bouts to children (ages 8 to 12) at a frequency of 12 to 18 Hz. There were three different standing positions that the subjects assumed with the feet at different widths apart, allowing for adjustments to the amplitude at 2 mm, 4 mm and 6 mm. The results of this study showed that there was a significant decrease in the spasticity of the knee extensors of the stronger leg in the group that received WBV vs. no change in the control group.6

These findings echoed the results of an earlier study which was conducted with adult subjects. Adult participants between the ages of 21 and 41 were randomized into a WBV group and a resistance training group. The WBV group received treatment 3 times a week for 8 weeks in 6 minute bouts at 25 to 40 Hz, with the exact frequency selected by the subject based on their Borg rating of 7 which is ‘very strong’ (the Borg is a standard scale which measures perceived exertion during activity or exercise). The results of this study also showed decreased spasticity of the knee extensors in the WBV group.7

Muscle activation occurs through nerve stimulation which causes a muscular contraction. In order for strength to increase, muscles must be able to contract effectively. There are various factors which influence how well a muscle is able to contract, including muscle length (which may also be influenced by position), joint position and overall posture. WBV has been studied as a potential intervention to activate muscles and improve strength in individuals with CP. Since many people with CP rely on a wheelchair as their primary means of mobility, weakness associated with muscle disuse is a significant concern. Weakness perpetuates the problem of limited mobility, muscle and joint contractures, and is also associated with a decline in bone health. Even individuals who are able to stand and walk on a limited basis must still contend with the negative effects of muscle weakness. A recent study examined the effect of a WBV program on muscle activation in 44 children with unilateral or bilateral spastic CP who were able to stand with support. WBV was delivered in a one minute bout of 16 to 25 Hz under three different protocols, one of which examined maximal voluntary muscle activation of the lower leg muscles. Results based on EMG (electromyography) signals showed that there was an increase in maximum voluntary muscle activation of these muscles, suggestive of improved neuromuscular control.

Another study involved a 3 month WBV program in which vibration was administered 9 minutes per day, 5 days a week. Thirty children (ages 8 to 12) with spastic diplegia who were able to walk without an assistive device participated in the study. Results supported WBV as a potential intervention to improve muscle strength as all subjects who received WBV demonstrated a significantly greater increase in knee extensor strength compared with those who performed the same exercises without vibration.

In a study conducted with children (ages 8 to 12), a 12 week WBV program was implemented in three series of 3 minute bouts at a maximum of 18 Hz. Results showed that the group who received WBV demonstrated a significant increase in knee extension strength vs. no significant changes in the control group.

There was an interesting study which employed WBV to train trunk muscles of children with spastic diplegia and hemiplegia, GMFCS levels ranging from I to III. The goal of this study was directed at improving abdominal muscle strength and posture. Children with CP not only exhibit weakness of the limbs, but also of the trunk muscles, which results in lack of pelvic stability. This issue contributes to difficulty with movement and affects posture and balance. With the use of two-dimensional postural analysis, ultrasound imaging and a strength assessment noting the number of sit ups performed in one minute, it was noted that the WBV program produced favorable results. The subjects were able to perform an increased number of sit ups, demonstrated an increased resting thickness of all four abdominal muscles and exhibited postural changes which were maintained four weeks after the WBV treatment was completed. All of these findings are a reflection of improved strength, which has a positive impact on all aspects of function.

The ability to walk is one of the cornerstones of independent function. Individuals with CP may possess this ability at varying levels as some may be able to walk without an assistive device while others may require a walking aide. Multiple studies have been done to determine the effect of WBV programs on walking ability. Results have supported WBV as a safe and effective treatment to improve various aspects of gait. When evaluating gait, standard measures of improvement include changes in speed and step qualities. One study looked at the effects of a short term WBV program on walking parameters in addition to a conventional PT program compared to a PT program alone. Subjects included children ages 7 to 13, GMFCS level I, II or III, who were able to walk independently or with an assistive device. The subjects participated in a WBV program twice a week for a 3 week period. Vibration was delivered intermittently in 3 minute bouts with 3 minute rest breaks over a 20 minute period, at 20 to 24 Hz. The outcome measures illustrated improvements in gait speed, step length and step width when compared with conventional PT alone.

An investigational study with three women (ages 22-30) with spastic quadriplegia examined the influence of vibration on their quality of gait. WBV was administered three days a week for 4 weeks, in two 1 minute bouts at 20 Hz. It was noted that there was a significant increase in the range of motion at both knees after the first treatment as well as a significant increase in hip flexion mobility after the sixth treatment. The findings reinforced the hypothesis that low frequency, low amplitude vibration produces subtle mechanical impulses received by skin receptors which affected changes in the nerve impulses, which in turn reinforce neural control.

In an investigational study with eight subjects with CP, the effect of WBV on gait was examined. This study included adults, ages 20 to 51, with spastic diplegic or hemiplegic CP, who were mobile for short distances without an assistive device (CP5-8 in CP-IRSA Functional Classification System). Gait analysis was done after a 5 minute WBV program was completed, which was implemented in a series of five 1 minute bouts with 1 minute rest breaks in between. In this program, the individual frequency (I-frequency) that was ideal for each individual was determined prior to treatment, with the average being around 38 Hz. After treatment, participants demonstrated increased stride length and a more normalized walking pattern with an apparent increase in muscle length as noted by increased joint angles at the knee and ankle. In addition, there was a significant increase in dynamic ankle range of motion, possibly due to relaxation of the calf muscles.

An additional study looked at the combined effects of WBV with conventional PT vs. PT alone on gait. Participants included thirty children (15 males, 15 females, average age 9 to 10) randomized into two groups. The experimental group received WBV 3 times a week for 8 weeks in addition to a conventional PT program which involved a 30 minute session consisting of gentle massage, stretching and balance training. Those who received the combined treatment exhibited greater improvements in their walking qualities and other impairments as compared to the group who received PT alone. Gait speed improved by 0.11 meters/second, which was considered significant. 

There have also been case studies which support the various therapeutic effects of WBV. While the results of case studies cannot necessarily be directly applied to the overall study population, they are useful in highlighting the potential for positive outcomes and directing the focus of future research. One such study was done with an 8 year old boy with spastic diplegia who was categorized as GMFCS III. He was able to walk with crutches however mainly used a wheelchair. He received PT twice a week for 5 weeks in addition to a WBV program. The WBV treatment was administered in five to six 1 minute bouts delivered at 30 Hz. At the conclusion of the program, the child exhibited improved walking ability, noted by completion of the 5 meter walk test in a shorter duration with a decreased number of steps. These results are suggestive of improvements in strength, flexibility and balance, all of which positively affected his walking ability.

A small pilot study was conducted with pre-adolescent children ages 6 to 12, GMFCS levels II, III and IV, to assess various outcomes of WBV. The treatment involved the addition of a 6 month WBV program 5 days a week to an existing school based PT regimen. Subjects received WBV beginning at 12 Hz and increased to 18 Hz, for a total of 9 minutes (administered in three minute bouts with 3 minute rest breaks in between). Data showed a change of 0.18 m/s in the 10 meter walk test speed which reflected a 38% improvement, vs. no change in the control group.

Functional mobility is a general term used to describe various aspects of daily function. This may encompass standing, walking, changing positions (transfers, such as rising from a chair, or changing positions in bed) and activities of daily living including those involving self-care. Individuals with CP exhibit various levels of functional mobility, which may range from total independence to total assistance for all activities. WBV has been identified as a potential treatment for individuals with CP as a part of a rehabilitation program to improve functional mobility. The Gross Motor Function Measure is an 88 item assessment specifically designed to evaluate the changes in mobility of children with CP. In the same investigational study referenced above, the 8 year old boy who completed the WBV program demonstrated more than a 7% increase in his Gross Motor Function Measure scores for dimension C (crawling and kneeling) and dimension D (walking). 

Another study highlighted the positive effects of WBV on mobility based on improvement in the 6 minute walk test (6MWT) and chair rise test results. Both tests have been standardized in older adults, however are also used in other populations, including CP, to assess functional mobility. The 6MWT is a measure of how far an individual is able walk at a comfortable pace on a hard level surface in 6 minutes. The chair rise test utilized in this study measured the amount of time it took the individual to rise to stand from a sitting position three consecutive times. While both tests are measures of functional mobility, the six minute walk test provides insight regarding a person’s functional leg strength, endurance and lung function while the chair rise highlights functional leg strength and balance. In this clinical trial, forty children categorized as GMFCS II or III (mild to moderate CP) completed a 20 week WBV program. Sessions were administered for a total of 9 minutes (implemented in 3 minute bouts with rest breaks), beginning at 12 Hz and increased to 20 Hz at the 4 week mark. The 6 minute walk test scores improved an average of 11% for GMFCS II subjects and an average of 35% for GMFCS III subjects. The individuals also demonstrated improvements in their chair rise test scores as noted by reduced time to transfer from sit to stand. 

The results of a previous study conducted with a smaller group of children with spastic diplegia and quadriplegia also demonstrated improvement in functional mobility parameters. All subjects received a single session of WBV as well as a control period without WBV. Treatment was administered for 20 minutes at 20 Hz in a partial squat position (knees flexed to 30 degrees). Changes in both the 6MWT score was significant for the WBV group compared to the control group. This improvement was also highly correlated with a change in the TUG score, which is a test that measures the time it takes for a subject to rise from a standard chair, walk 10 feet (3 meters) away from and back to the chair, then return to a sitting position. A higher score indicates a longer time to the complete the test, which is correlated with a higher falls risk. The results of this study support WBV as a potentially effective treatment to improve functional mobility.

A meta-analysis of six studies was done to evaluate the outcome of WBV training on different aspects of function. The Gross Motor Function Measure examines various dimensions of function, including Dimension E, which includes walking, running and jumping. The analysis noted that one study showed significant improvement in Dimension E in the WBV group vs. the control group.

Maintaining bone health is critical in the prevention of fractures, especially considering the increased risk of fractures in individuals with CP. Osteoporosis is common in this population due to reduced or lack of weight-bearing activity, especially for those who are wheelchair bound. This increased risk associated with the negative side effects of a forced sedentary lifestyle include reduced bone mineral density (BMD) and reduced muscle mass, which predispose an individual to osteoporotic changes and increase the potential for fractures. With this in mind, it is important to consider targeted interventions directed at improving bone health. WBV has been studied as a potential treatment to improve bone structure, more specifically bone density, in patients with CP. Forty subjects with mild to moderate CP participated in a study which involved a 20 week WBV program. The protocol involved a 9 minute training session administered in 3 minute bouts with 3 minute rest breaks, 4 times a week. Vibration was initially administered at 12 Hz and was increased to a maximum of 20 Hz at the 4 week mark. It was noted that all forty patients who participated in this clinical trial demonstrated an increase in lean muscle mass of the total body, trunk and legs. The results also showed an increase in bone mass and BMD for the total body, the lumbar spine and the legs, which was confirmed with diagnostic testing (DXA: Dual-energy x-ray absorptiometry, a standard test to measure bone mineral density). The improvements in muscle mass, bone mass and BMD are encouraging as they have implications for the prevention and/or treatment of osteoporosis. 

Another study looked at the effect of a 6 month WBV program combined with physical therapy in children with spastic diplegia compared to a control group who received physical therapy only. The WBV treatment was administered 10 minutes a day, five days a week at 25 Hz. Bone density measured by DXA for the total body, femoral neck (an area of the thigh bone particularly susceptible to fracture) and the lumbar spine, was assessed before and after treatment. The researchers concluded that the addition of WBV to the PT program produced more significant changes in bone density than PT alone. One theory is that WBV may increase or at least maintain bone mass by stimulating bone remodeling through increased fluid circulation and activation of osteoblasts (cells that form bone) while reducing the activity of osteoclasts (cells that break down bone).

A prospective study conducted with children with CP ages 6 to 12 examined the effect of high frequency, low magnitude vibration on bone and muscle. WBV was delivered for 10 minutes a day for a 6 month period, followed by a 6 month period of standing without WBV. The main difference that was appreciated was an increase in the cortical bone area and structure during the vibration period (cortical refers to the dense outer shell of most bones, also known as compact bone). Findings suggest that these improvements may be correlated with decreased risk of fracture of the long bones. Researchers also hypothesized that WBV may have a more pronounced effect on less functional children, acknowledging that larger studies should be done to include more involved subjects. 

In summary, WBV is considered a safe, effective and well tolerated modality for individuals with CP.