Is there an optimal whole-body vibration exposure ‘dosage’ for performance improvement?

International Journal of Exercise Science 7(3) : 169-178, 2014. Whole-body vibration exposure has been shown to improve performance in vertical jumping and knee extensions. Some studies have addressed the question of dose optimality, but are inconclusive and inappropriately designed. Our purpose was to more thoroughly seek an optimum combination of duration, amplitude and frequency of exposure to side-alternating whole-body vibration. We used experimental designs constructed for response surface fitting and optimisation, using both blocked and unblocked second order central composite designs with 12 participants. Immediately after each exposure a discomfort index was recorded, then peak and average torque, peak and average jump height, together with peak and average jump power were recorded over three trials both pre- and post-exposure at each treatment combination. ANOVA revealed that all performance measures improved after vibration exposure. However, no successful response surface fits could be achieved for any of the performance measures, except weakly for average jump height and average jump power for a single subject. Conversely, the discomfort index increased linearly with both vibration amplitude and frequency, more steeply as exposure duration increased. We conclude that although vibration exposure has a significant positive effect on performance, its effect is so variable both between and within individuals that no real optimum can be discerned; and that high amplitudes, frequencies and durations lead to excessive discomfort

Acute whole-body vibration elicits post-activation potentiation

Whole-body vibration (WBV) leads to a rapid increase in intra-muscular temperature and enhances muscle power. The power-enhancing eVects by WBV can, at least in part, be explained by intra-muscular temperature. However, this does not exclude possible neural eVects of WBV occurring at the spinal level. The aim of this study was to examine if muscle twitch and patellar reXex properties were simultaneously potentiated from an acute bout of WBV in a static squat position. Six male and six female athletes performed three interventions for 5 min, static squat with WBV (WBV+, 26 Hz), static squat without WBV (WBV¡) and stationary cycling (CYCL, 70 W). Transcutaneous muscle stimulation consisting of a single 200 s pulse and three patellar tendon taps were administered prior to and then 90 s, 5, 10 min post-intervention. Ninety-seconds after WBV+ muscle twitch peak force (PF) and rate of force development (RFD) were signiWcantly higher (P < 0.01) compared to WBV¡ and CYCL. However the patellar tendon reXex was not potentiated. An acute continuous bout of WBV caused a post-activation potentiation (PAP) of muscle twitch potentiation (TP) compared to WBV¡ and CYCL indicating that a greater myogenic response was evident compared to a neural-mediated eVect of a reXex potentiation (RP)

THE POTENTIAL NEURAL MECHANISMS OF ACUTE INDIRECT VIBRATION

There is strong evidence to suggest that acute indirect vibration acts on muscle to enhance force, power, flexibility, balance and proprioception suggesting neural enhancement. Nevertheless, the neural mechanism(s) of vibration and its potentiating effect have received little attention. One proposal suggests that spinal reflexes enhance muscle contraction through a reflex activity known as tonic vibration stretch reflex (TVR), which increases muscle activation. However, TVR is based on direct, brief, and high frequency vibration (>100 Hz) which differs to indirect vibration, which is applied to the whole body or body parts at lower vibration frequency (5-45 Hz). Likewise, muscle tuning and neuromuscular aspects are other candidate mechanisms used to explain the vibration phenomenon. But there is much debate in terms of identifying which neural mechanism(s) are responsible for acute vibration; due to a number of studies using various vibration testing protocols. These protocols include: different methods of application, vibration variables, training duration, exercise types and a range of population groups. Therefore, the neural mechanism of acute vibration remain equivocal, but spinal reflexes, muscle tuning and neuromuscular aspects are all viable factors that may contribute in different ways to increasing muscular performance. Additional research is encouraged to determine which neural mechanism(s) and their contributions are responsible for acute vibration. Testing variables and vibration applications need to be standardised before reaching a consensus on which neural mechanism(s) occur during and post-vibratio

The effect of vibration exercise on aspects of muscle physiology and muscular performance : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy, Massey University, Palmerston North, New Zealand

It has been proposed that the increases in muscle force and power following acute vibration exercise are similar to that of several weeks of conventional resistance or explosive power training. Further, it has been purported that vibration exercise operates via a stretch-reflex response which elicits a small change in muscle length. However, despite its wide use there remain gaps of knowledge on aspects such as physiological effects, mechanism of action, clinical effects, and even details of regimens for particular therapeutic use. Therefore, the aim of this thesis was to investigate the acute effects of vibration exercise on muscle performance and to examine the physiological aspects of its use in the young and older people, and competitive athletes. This thesis reported that acute upper-body vibration enhanced concentric peak power, but it was not significantly greater than concentric (arm-cranking) exercise. When matched for metabolic rate, vibration exercise elevated muscle temperature more quickly than traditional forms of warm-up by cycling or passive heating, but there were no significant differences in the increase in muscle power between the interventions, which suggested that the interventions were temperature dependent. There was no apparent benefit in performing a shallow, fast tempo dynamic squat with vibration because muscle temperature, cardiovascular indices, and metabolic rate were increased by the same amount and rate without vibration. Further, the Jendrassik manoeuvre did not potentiate the metabolic rate in young or older adults when superimposed with vibration exercise and the patellar reflex was not enhanced after vibration exercise, but muscle twitch potentiation was evident. However, low frequency vibration exercise induced a small change in muscle length and increased muscle activation, suggesting that spinal reflexes were involved. In conclusion, vibration exercise with a static squat could be used as a warm-up modality after interval breaks, as it would incur a low metabolic cost and be time efficient. It appears that the increases in muscle performance from vibration exercise are not caused by a neurogenic potentiation because patellar tendon reflex showed no significant augmentation and muscle twitch properties were enhanced. Vibration exercise elicited a small increase in metabolic rate and cardiovascular indices. Given that a main objective of a balanced exercise programme is to increase aerobic capcity it would be unwise to completely substitute conventional aerobic exercise with vibration. However, when conventional aerobic exercise is not possible, for example, in aged, cardiovascular compromised persons, vibration exercise could be implemented at an early stage because it could provide a safe induction of a low level of cardiovascular strain. Vibration exercise has the potential to benefit sport, exercise, and health however, it should be used to compliment other modalities but it should never be used in preference or in isolation to other programmes

Differential effects of whole body vibration durations on knee extensor strength

The effectiveness and optimality of whole body vibration (WBV) duration on muscular strength is yet to be determined. Hence the aim of this study was to investigate the effects of three different durations of continuous WBV exposure on isometric right knee extensor strength measured pre and post exposure. The study involved 12 trained male subjects (age 23.7 ± 4.2 years, height 1.82 ± 0.06 m, weight 81.8 ± 15.5 kg). Pre and post knee extensor strength was measured using the Biodex™ System 3. Peak and mean torques were recorded over three maximal 2 s contractions with 10 s intervals. All subjects completed three interventions of WBV lasting 2, 4, or 6 min, in a balanced randomized order. Whole body vibration was performed on the Galileo™ machine set at 26 Hz with peak-to-peak amplitude of 4 mm. We found significant interaction (duration × pre-post) effects for both peak and mean torque. Two minutes of WBV provided a significantly different (p < 0.05) effect (peak torque +3.8%, mean torque +3.6%) compared to 4 min (-2.7% and -0.8%, respectively), and compared to 6 min (-6.0% and -5.2%, respectively), while 4 min produced significantly different results compared to 6 min for peak torque measurements only. Two minutes of WBV produced an improvement in isometric right knee extension strength compared to 4 and 6 min, both of which produced strength decreases. Nevertheless, the mechanisms and optimal dose-response character of vibration exposure remain unclear

Comparing muscle temperature during static and dynamic squatting with and without whole-body vibration

The aim of this study was to investigate the influence of shallow dynamic squatting (DS) versus static squatting (SS) with or without concurrent side-to-side alternating whole-body vibration (WBV) on vastus lateralis temperature and cardiovascular stress as indicated by heart rate (HR). Ten participants (five men, five women) participated in four interventions [DS with WBV (DS+), DS without WBV (DS-), SS with WBV (SS+), SS without WBV (SS-)] 48 h apart, in a randomized order. The interventions were preceded by a approximately 20-min rest period, consisted of 10 mins with or without WBV (26 or 0 Hz) with SS (40 degrees of knee flexion) or DS (55 degrees of knee flexion, at a cadence of 50 bpm) where SS+ and DS- were metabolically matched. Muscle (T(m)), core (T(c)), skin temperature (T(sk)), HR and VO(2) were recorded during each intervention. For T(m), there was a time (P<0.01) and WBV (P<0.01) effect but no squat effect was evident, and there was time xWBV interaction effect (P<0.01). In all four interventions, the work load was too low to cause cardiovascular stress. Instead normal, moderate physiological effects of exercise on autonomic control were observed as indicated by HR; there were no significant increases in T(sk) or T(c). There appears to be no benefit in performing an unloaded, shallow DS+ at a tempo of 50 bpm as T(m,) HR, VO(2) are likely to be increased by the same amount and rate without WBV. However, combining SS with WBV could be advantageous to rapidly increasing soft tissue temperature prior to performing rehabilitation exercises when dynamic exercise cannot be performed

Take-Off Efficiency: Transformation of Mechanical Work Into Kinetic Energy During the Bosco Test

Purpose. The aim of the study is to present a new method for determining the efficiency of take-off during a 60-s Bosco repeated vertical jump test. Method. The study involved 15 physical education students (age: 21.5 ± 2.4 years; height: 1.81 ± 0.08 m; mass: 76 ± 9 kg). The data were collected with the use of a pedobarographical system (Pedar-x; Novel, Munich, Germany). The statistical analysis utilized a simple linear regression model. Results. Owing to possible fatigue, flight time and flight height decreased. The average flight height was 0.260 ± 0.063 m, and the average contact time equalled 0.54 ± 0.16 s. The average anaerobic power values calculated for the 60-s work period had the mean value of 21.9 ± 6.7 W · kgBW-1; there was a statistically significant (p < 0.05) decrease in anaerobic power during the 60-s Bosco test. Conclusions. The efficiency of mechanical work was highest at the beginning of the test, reaching values of up to 50%. The efficiency of mechanical work conversion into mechanical energy seems to be an appropriate determinant of rising fatigue during the 60-s Bosco jumping test

Preliminary Examination of the Biological and Industry Constraints on the Structure and Pattern of Thoroughbred Racing in New Zealand over Thirteen Seasons: 2005/06–2017/18

This study aimed to examine thirteen seasons of flat racing starts (n = 388,964) in the context of an ecological system and identify metrics that describe the inherent characteristics and constraints of the New Zealand Thoroughbred racing industry. During the thirteen years examined, there was a 2–3% per year reduction in the number of races, starts and number of horses. There was a significant shift in the racing population with a greater number of fillies (aged 2–4 years) having a race start, and subsequent longer racing careers due to the inclusion of one more racing preparation post 2008 (p &lt; 0.05). Additionally, there was an increasingly ageing population of racehorses. These changes resulted in more race starts in a career, but possibly because of biological constraints, there was no change in the number of race starts per season, starts per preparation, or days spelling between preparations (p &lt; 0.05). There was no change in the proportion of horses having just one race start (14% of new entrants), indicating that the screening for suitability for a racing career remained consistent. These data identify key industry parameters which provide a basis for future modelling of intervention strategies to improve economic performance and reduce horse injury. Consideration of the racing industry as a bio-economic or ecological model provides framework to test how the industry may respond to intervention strategies and signal where changes in system dynamics may alter existing risk factors for injury