# Low-Intensity Whole-Body Vibration: A Useful Adjuvant in Managing Obesity? A Pilot Study
## 4 Discussion  
The rationale of the present investigation was to study the effects of WBV exposure within the existing safety limits defined by the ISO-2631 for the Italian occupational standards. To the best of our knowledge, previous studies have investigated only high-intensity WBV associated with dynamic exercise and no randomized controlled trials at different WBV exposures are present in the literature. Our preliminary results showed that low-intensity WBV does not appear effective in improving strength or function in subjects with obesity. Upper and lower limb strength and functional tests (sit-to-stand and stand-to-sit, 6 MWT) did not show significant improvements in the two groups undergoing WBV and in the two groups exercising in semisquat without vibration. Previous studies with WBV at higher intensities (2.28 g to over 5 g) showed an increase in strength in different populations [6; 9; 22; 29] and an improvement in walking capacity [30]. Only two studies with WBV at lower intensities (0.3-0.4 g) for 3 months showed improvements in the chair-stand test [12] and maximal isometric knee extensors torque and performance as measured by a counter movement jump [9]. Several factors may account for such different results. Firstly, in our program, the patients did not perform any dynamic exercise. Secondly, although the g-force output generated by our vibration platform was of similarly low intensity, the duration of our protocol was only 3 weeks. During the training period we did not modulate variables such as: intensity, volume, exercise selected, rest intervals between sets and frequency, as usually performed in a progressive resistance training program. We opted for a steady low intensity WBV because our aim was to observe whether low intensity vibration certainly falling within the safety recommended limits could affect the musculoskeletal responses of neuromuscular spindles, tendon organs of Golgi and mechanoreceptors or elicit metabolic responses. However, a program duration of 3 weeks may represent too short a period of time to observe muscular adaptation. Furthermore, the strength tests carried out were not specific enough for the proposed exercise, with the patients being tested for lower limb strength in a sitting and not in a standing position, as during training. Additionally, during weight loss the level of protein intake is essential to preserve fat free mass and muscle strength. It is possible that the low-calorie diet with a protein intake of 1-1.3 g protein/kg ideal body weight may have compromised the fat free mass of patients. When combined with exercise program, a hypoenergetic diet with an elevated daily intake of protein (2-3 \(\times\) RDA) can promote overall improvements in body composition [31]. Several metabolic variables usually included in the definition of metabolic syndrome improved. Systolic and diastolic arterial blood pressure, cholesterol, LDL, and glucose levels decreased significantly, independent of the study group allocation. This result underlines the beneficial effect of physical activity on metabolic variables [32; 33]. The lack of a significant difference between the experimental and control group indicates an insufficient training stimulus from the vibration platform. Based on our results, a specific effect of the WBV platform on metabolic improvements cannot be identified. This is in contrast with what has been reported in a long-term WBV protocol on metabolic components [26]. The different results could depend on a different duration of the study protocol, vibration platform intensity, and modality of the exercise, which was isometric in our study and dynamic in the other. In contrast with the pioneering observations published by [PERSON] [24], we did not find any difference in either testosterone or GH levels between groups after the training period, possibly due to the severe degree of obesity of our patients, which blunted the training-induced response of these anabolic hormones [28].