[show abstract][hide abstract] ABSTRACT: INTRODUCTION
Whole-body vibration (WBV) training is an emerging treatment with potential benefits for muscle and bone health (Cardinale and Rittweger, 2006; Prisby et al., 2008). There are several WBV devices and the differences are not easily quantifiable. The development of legislation designed to minimise occupational exposure to WBV has led to the formation of standards to quantify vibration ‘dose’ incorporating the human response at different frequencies (Mansfield, 2005). Currently the settings on the WBV platforms do not reflect vibration ‘dose’. In addition the settings on the machines tend to be arbitrary (e.g. ‘low’, ‘high’, etc.), making it difficult to compare with safety standards. This experiment takes a multidisciplinary approach to translate knowledge and rigor in quantifying vibration exposure in an occupational context to characterise the vibration experienced by users of WBV training platforms.
This experiment numerically describes the vibration delivered by six devices according to the methods outlined in the Physical Agents (Vibration) Directive [PA(V)D; 2002]. Quantifying vibration ‘dose’ provides a metric to compare vibration between devices and settings, as well as an opportunity to compare the vibration delivered with current occupational safety standards.
Acceleration was measured using surface mounted piezoresistive triaxial accelerometers (S2-10G-MF, NEXGEN Ergonomics, Biometrics Ltd) and collected on portable data logging equipment (P3X8 V2.11, DataLOG, Biometrics Ltd). The data were analysed using software within LabVIEW (National Instruments Corporation) according to ISO 2631-1 (1997). Comparisons were made between devices, the range of user modifiable settings available on each device and the manufacturers’ descriptions of these settings.
All of the devices produced sinusoidal vibration in the vertical axis. The Galileo with a tilting action was the only device which delivered noteworthy vibration in more than one axis. Combinations of displacement and frequency resulted in an extensive range in magnitude of vibration in the vertical axis [1.05–112.53 r.m.s. (unweighted) m/s2; 0.23–22.64 r.m.s. (weighted) m/s2 (see Figure 1)]. The devices that had adjustable frequency were engineered to provide a range of frequencies at fixed displacements. As a result, according to simple laws of physics, the highest magnitudes of vibration were also at the highest frequencies [see Figure 1(a)]. Applying frequency weighting, however, reduced the magnitude the most at the highest frequencies, flattening this trend [see Figure 1(b)].
Figure 1: Vertical axis vibration magnitude (a) unweighted, (b) weighted, versus measured frequency for each device at each displacement setting.
This characteristic was such that vibration ‘dose’ was similar for different frequencies at each displacement setting for all the devices except the Galileo which delivers lower frequency vibration [see Figure 1(b)].
In all cases the manufacturers’ descriptions of the user modifiable settings related in a logical way to the vertical displacement measured (e.g. ‘high’ was greater than ‘low’). However these descriptions were not comparable between platforms (e.g. ‘high’ on one device was equivalent to ‘low’ on another).
The Juvent provided the lowest vibration ‘dose’ and would not exceed daily exposure action or limit values even if experienced continuously for 24hours. The highest ‘dose’ measured was on the Galileo at the highest displacement, however the guidance for ISO 2631-1 was based on research from seated individuals and not a tilting action in standing.
The marked differences in vibration magnitude between platforms emphasise the need to describe WBV training protocols in precise terms and to use caution in choosing protocols.
At each fixed displacement for the Medical ProFitVIBE, Next Generation Power Plate and VibroGym vibration ‘dose’ is similar regardless of the frequency such that the only setting change which makes any real difference to vibration ‘dose’ is displacement (i.e. ’low’ or ‘high’). PA(V)D provides a standardised way to quantify vibration ‘dose’ however more research is required to investigate the human response to different actions of vibration in a standing posture.
European Council. Directive 2002/44/EC of the European Parliament and Of The Council on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (Vibration) (sixteenth individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC. Official Journal of the European Communities. 2002;No L 177:13-9.
Cardinale M and Rittweger J. Vibration exercise makes your muscles and bones stronger: fact or fiction? Journal of the British Menopause Society. 2006;12(1):12-8.
International Organization for Standardization. Mechanical vibration and shock - Evaluation of human exposure to whole-body vibration - Part 1 general requirements. ISO 2631-1. Geneva:International Organization for Standardization; 1997.
Mansfield NJ, Human response to vibration. London: CRC Press LLC; 2005.
Prisby RD, Lafage-Proust MH, Malaval L, Belli A, Vico L. Effects of whole body vibration on the skeleton and other organ systems in man and animal models: What we know and what we need to know. Ageing Research Reviews. 2008;7(4):319-29.
[For figure please see uploaded resource]
Medicine and Science in Sports and Exercise - MED SCI SPORT EXERCISE. 01/2009; 41.
[show abstract][hide abstract] ABSTRACT: This study investigated the effect of a single session of resistance exercise on postprandial lipaemia. Eleven healthy normolipidaemic men with a mean age of 23 (standard error = 1.4) years performed two trials at least 1 week apart in a counterbalanced randomized design. In each trial, participants consumed a test meal (1.2 g fat, 1.1 g carbohydrate, 0.2 g protein and 68 kJ x kg(-1) body mass) between 08.00 and 09.00 h following a 12 h fast. The afternoon before one trial, the participants performed an 88 min bout of resistance exercise. Before the other trial, the participants were inactive (control trial). Resistance exercise was performed using free weights and included four sets of 10 repetitions of each of 11 exercises. Sets were performed at 80% of 10-repetition maximum with a 2 min work and rest interval. Venous blood samples were obtained in the fasted state and at intervals for 6 h postprandially. Fasting plasma triacylglycerol (TAG) concentration did not differ significantly between control (1.03 +/- 0.13 mmol x l(-1)) and exercise (0.94 +/- 0.09 mmol x l(-1)) trials (mean +/- standard error). Similarly, the 6 h total area under the plasma TAG concentration versus time curve did not differ significantly between the control (9.84 +/- 1.40 mmol l(-1) x 6 h(-1)) and exercise (9.38 +/- 1.12 mmol x l(-1) x 6 h(-1)) trials. These findings suggest that a single session of resistance exercise does not reduce postprandial lipaemia.
Journal of Sports Sciences 04/2005; 23(3):251-60. · 2.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this research is to explore the use of whole-body vibration platforms commercially available in the health and sports sector. Experiments were conducted using two platforms providing a sinusoidal stimuli, one with a vertical (Platform 1) and one with a tilting action (Platform 2). A range of platform settings from 5 to 50 Hz were used. Comparison of these settings with the actual movement was made using a tri axial accelerometer mounted on the platforms to obtain the power spectrum density and magnitude of vibration (m/s² r.m.s.) weighted and unweighted. The participants stood on each of the platforms with a bent knee (angle of 130 ◦ ) for 30 seconds on each of 4 settings in a randomised order. Following each stimuli the participants were asked to rate the intensity of the experience using a numeric category ratio (CR100). The range of frequencies and magnitudes measured were approximately 5 to 39 Hz and 1 to 60 m/s² r.m.s. There was a positive correlation between mean subjective rating of intensity and magnitude of vibration. Subjective ratings of intensity per magnitude of vibration were greatest at 5 Hz and an increase in 1 m/s² r.m.s.weighted was equivalent to approximately 8 units on the CR100 scale. At comparable magnitude and frequency there was no significant difference in subjective response between the platforms. No correlation between age or Body Mass Index (BMI) and subjective rating of intensity were observed.
[show abstract][hide abstract] ABSTRACT: A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University. The personal and social consequences of poor mobility and injuries sustained during falls in older people are a major public health concern. As the proportion of older people in the UK rises, this public health issue will become increasingly relevant. Whole-body vibration (WBV) training has the potential to improve postural stability, muscular power and bone health and hence potentially reduce loss of mobility and risk of falls and fractures. It is thus timely to evaluate potential benefits in older people and given the potential detrimental effects of vibration, it is also important to evaluate any risks in this population. To date the efficacy of WBV training has not been established in community dwelling frail older people and appropriate standards or the best WBV training protocol have not been established for any segment of the population. The vibration ‘dose’ of seven WBV training devices was determined according to statutory guidelines designed to minimise occupational vibration exposure. There was an extensive range of vibration available on these devices (frequency weighted r.m.s. acceleration in the vertical axis between 0.23 m/s2 to 22.64 m/s2). Two devices were selected, one with a tilting and one with a vertical motion to evaluate the human response to WBV training. Short periods (8 x 30s) of WBV training at magnitudes of 1.68 to 59.85 m/s² r.m.s. acceleration (1.66 to 12.11 m/s² frequency weighted), between 5 and 39 Hz, though intense, was acceptable for healthy men and women between 22 and 83 years of age. Increasing magnitude resulted in increasing perception of intensity however 5 Hz produced the greatest perception of intensity per magnitude of vibration. Frequency weighted acceleration was a useful predictor of subjective intensity of WBV training for tilting and vertical WBV training. Using the conclusions drawn from the previous two studies appropriate WBV training protocols were selected for a randomised controlled intervention study in a clinical setting. 104 patients referred to Nottingham University Hospitals NHS Trust for a falls prevention programme were invited to take part, 61 of whom were eligible and agreed to participate. The participants aged between 64 and 95 years old were randomly allocated to Control, Tilting or Vertical WBV training groups. In addition to usual care, which included an exercise programme designed to reduce the risk of falls, all participants stood in a half squat position for up to 6 x 1 min bouts 3 times a week for 12 weeks on a tilting (Galileo; 29.8 Hz, 36.0 m/s2 r.m.s), vertical (Next Generation Power Plate; 28.4 Hz, 15.3 m/s2 r.m.s) or stationary (low frequency noise during bouts as a placebo) WBV training platform. 12 weeks of tilting or vertical WBV training was well tolerated and no serious adverse affects were reported in this population of frail older people. There were no additional symptoms or shifts in tactile sensitivity of the feet, compared with standing on a stationary platform. In comparison to the Control group improvements in leg power, jump height and bone metabolism profile (increased P1NP) were observed in the combined tilting and vertical WBV training groups. There were no between group differences in measures of functional mobility and balance [Timed Up and Go (TUG) time, chair stand test, four stage balance test, functional reach, Four Square Step Test (FSST) time, postural sway], fear of falling (FES), ability to carry out activities of daily living (NEADL), physical activity (PASE) or general health and well being (SF 36). This study was unique in showing that the addition of WBV training to an existing falls prevention programme had a beneficial effect on measures of lower leg power and bone formation. Despite this the addition of WBV training did not add any additional benefit to the current falls prevention programme in functional measures previously associated with an increased risk of falling in older people. In the same population of frail older people a single session of WBV training (combined Tilting and Vertical WBV training groups) elicited an acute increase in muscular performance (knee extensor power and jump height), and no difference in static balance compared with standing on a stationary device (Control group). Having found that the addition of either tilting or vertical WBV training improves aspects of musculoskeletal health in frail older people undertaking a falls prevention programme further research including fall and fracture incidence, bone density and structure and rate of force development may be beneficial. Due to the enormous range of vibration delivered and since not all devices delivered vibration indicated by the settings it is recommended that future studies report not only platform settings but measured frequencies, magnitudes (unweighted and weighted), direction and waveforms.