Optimalisatie van vibratietraining protocollen voor verschillende populaties

Local vibration therapy to prevent and/or reverse sarcopenia, osteoporosis, and resulting falls and fractures: Optimized mechanical loading as a potential strategy to safely and efficiently address major public health problems Introduction: Osteoporosis (progressive loss of bone tissue) and sarcopenia (decline of lean muscle mass and muscle strength, characterized by muscle weakness) are becoming increasingly important public health problems in the elderly population. Both osteoporosis and sarcopenia contribute to an increased fall risk, an increased number of hip and vertebral fractures, and reduced mobility. Hip fracture has a high mortality and morbidity rate and of those who survive the operative intervention for an osteoporotic hip fracture, less than 50 % are restored to their pre fracture functional state. The present project is intended to search for efficient and feasible interventions to prevent or reverse bone and muscle loss.Most strategies to treat postmenopausal bone loss have been focusing on (antiresorptive) medication. More recently, the potential contribution of load-bearing, high-impact exercise to preserve bone density and prevent osteoporosis has received some attention. Regarding sarcopenia, numerous studies have demonstrated that resistance training or weight training is an effective countermeasure for age-related muscle loss. Limitations of traditional exercise programs to improve muscle mass and skeletal integrity include the lack of long-term compliance and the potential for injuries of the joints, ligaments, and tendons. It is therefore imperative to continue the search for more attractive, low-risk exercise programs with the goal of improving the outcome.Whole body vibration (WBV) training might be an alternative training method combining factors of both impact exercise and conventional resistance training. During WBV the subject stands on a platform that generates vertical sinusoidal vibrations. These mechanical stimuli are transmitted to the body where they stimulate the bone and also the primary endings of the muscle spindles. The latter activate, in turn, alpha-motor neurons resulting in muscle contractions, comparable to the tonic vibration reflex. In previous studies performed by our group, we found that whole body vibration training (frequency 30 40 Hz, peak acceleration 3 10 g) constitutes an efficient alternative for strength training, both in the young sedentary as well as in the elderly population. Additionally, we were able to show that 6 months vibration training in elderly females resulted in a net benefit of about 1.5 % in bone mineral density of the hip compared with controls. Finally, we showed that long-term vibration training results in an increase of quadriceps muscle mass. In line with our own research, a recent meta analysis has underscored the potential of vibration to increase muscle strength and the group of Rubin and co-workers found that mechanical accelerations at a specific frequency and amplitude were efficient at maintaining the bone density at the hip in postmenopausal women. In a more recent paper by the same group in young female subjects, this low-impact, high frequency vibration also resulted in increased muscle mass of the paraspinal muscles .Overall, these findings support the concept of vibration therapy as a potential combination therapy for elderly subjects at risk for osteoporosis and sarcopenia, which might help to reduce the number of falls and fractures. However, many questions regarding vibration as an intervention strategy remain to be answered, to optimize both its efficacy and safety. First, the degree by which variations in the vibration excitation signal alter the efficacy to provoke beneficial effects on muscle and bone is largely unknown. Second, possible risks associated with vibration training have not received much attention. Third, the application modalities of vibration therapy should be optimized to become applicable in a broader range of subjects while delivering stimuli in a more targeted fashion, to specific regions of interest.Whole body vibration in its present form (subjects standing on a vibrating platform) is inadequate for a large segment of the elderly population (e.g., subjects with osteoarthritis at the knee, wheelchair bound subjects, bedridden individuals, etc.). Additionally, the transmission of the vibration stimulus from the feet to the lumbar spine during WBV is probably insufficient to provoke adaptations at this level. Delivering the vibration stimuli locally (i.e., more targeted) at those regions most at risk for fractures (hip and spine) or most in need of muscle strengthening might be more effective. A preliminary study with local paraspinal muscle vibration was performed in our laboratory where fourteen subjects were randomized in a control group or a local vibration training group. Both groups received segmental stabilization training (60 Hz, 0, 5 mm) for 6 weeks. The results showed a significant increase in back muscle strength-endurance in the local vibration group compared to the control group. Aim: The aim of the study is to optimize the efficacy and safety of the vibration excitation pattern (amplitude, frequency) as well as to optimize the application methods whole and local body vibrations including: 1. optimization of the vibration signal characteristics during WBV with respect to muscular activation on one hand and effective and safe loading of specific bone regions of interest on the other hand; 2. optimization of the vibration signal characteristics and application positions for local vibration to have optimal transmission to skeletal sites of interest (hip, spine); 3. conduction of a randomized controlled trial to assess the effects of one year local vibration therapy applied at calf, thigh, hip and spine on muscle strength, muscle mass, bone density and structure, postural control and falls in a group of frail elderly residing in long-term care settings. Methods: Healthy (young and elderly) subjects free from contraindications to vibration training participate. To identify the excitation pattern and its relationship with the muscle activation, vibration transmission and muscular activity will be obtained. To measure the transmission of the vertical vibration of the platform to specific body parts tri-axial accelerometers will be used placed on several body points. Wireless bipolar surface EMG electrodes will record the EMG signal from several muscles. The active Krypton 3D system will be used to determine the body kinematics during WBV. To identify the excitation patterns and application positions that can be used in a local vibration paradigm a CT-based computer model finite element (FE) of a femur will be used. In the third phase vibrators will be positioned on supine lying subjects once per day, 5 times a week for one year. The training volume will be increased systematically over the training period by increasing the duration of one vibration bout and the number of vibration bouts. Conclusion: Local vibration might improve the muscle mass, muscle strength and different components of postural control, as well to increase the bone mineral density of elderly subjects, diminishing the risk of falls and fractures. It might be used to prevent osteoporosis and sarcopenia in elderly.status: publishe