Whole body vibration training (WBVT) is a neuromuscular training method that has become very popular over the last decade, with numerous devices becoming available for use in exercise and physical therapy. It has also become increasing popular within the sporting environment (Cardinale and Wakeling, 2005).
The delivery of vibrations (30–50Hz) to the body stimulates many biological systems. This can lead to physiological changes including stimulation of skin receptors, muscle spindles, joint mechanoreceptors and changes in neurotransmitter, cerebral activity and hormone concentrations (Schuhfried et al., 2005). Vibration strongly affects the afferent discharge from fast adapting Meissner and Pacinian corpuscles, muscle spindles and Ib afferents from GTO are also responsive to muscle vibration (Rittweger, 2010). Pacinian corpuscles respond to high frequencies of vibration (80-450Hz), whereas Meissner corpuscles respond to low frequencies (10-80Hz) (Weerakkody et al., 2007).
WBVT has been shown to improve muscular strength, power and flexibility in athletes (Wyon et al. 2010; Wilcock et al., 2009; Cochrane and Stannard, 2005; Cardinale and Bosco, 2003). However the current literature available on the use of WBVT on proprioception, postural control and balance shows varying results. Most of the research found was conducted using special populations and older adults as their subjects, which showed mixed results (Rees et al., 2009; Trans et al., 2009; Aaboe et al., 2007; Bogaerts et al., 2007; Cheung et al., 2007; Wang and Shiang, 2007; Turbanski et al., 2005; Van Nes et al., 2004). Only two studies were found that used athletic populations (Moezy et al., 2008; Mahieu et al., 2006) and they showed contrasting results. Moezy et al. (2008) studied the effects of WBVT on knee proprioception and postural stability after ACL reconstruction on national and international level athletes. They reported significant improvements in proprioception and balance. Although a trial by Mahieu et al. (2006) on the effects of WBVT versus conventional resistance training on strength and postural control on competitive skiers found that neither, WBVT or conventional resistance training had an effect on postural control.
The fact that little research has been conducted on WBVT using athletic populations, should it be used so widely in sport and exercise?
A trial conducted last year looked at the effect of a single bout of WBVT on basketball players from the University of Central Lancashire using , The Vibrosphere® (Promedvi: Sweden) which is a unique device that combines balance and WBVT, which the manufacturers state can lead to a rapid improvement in proprioception and balance (Promedvi, 2011). Proprioception was measured using 3D biomechanical analysis of 5 single leg squats (SLS) where the participants were aiming to bend their knee to 30 degrees each time, pre the WBVT intervention and then immediately post and 5, 10 and 15 minutes post the intervention. Their proprioception was measured by how accurate they were to bend there knee to 30 degrees during the 5 SLS. The WBVT intervention had the participants stood on the Vibrosphere in a 30 degree half squat, using 1 minute of vibration : 1 minute rest, protocol for 10 minutes. The accuracy and stability of this movement was recorded using 3D motion analysis cameras and software.
Participiant on Vibrosphere
The results of this study suggest that WBVT using the Vibrosphere had a negative effect on proprioception as measured by knee joint position sense and velocity in basketball players. It showed reduced accuracy of the SLS movement post the WBVT when compared to before. It also showed participants to have increased medial movement post the WBVT intervention.
The results are clinically relevant due to some of the participants showing greater knee joint position sense (JPS) error in the Sagittal plane and increased medial movement velocity of the knee in the Coronal plane after the WBVT (Vibrosphere®) intervention.
The first figure shows a female participant performing a SLS pre the WBVT intervention. The second figure shows them immediately post the WBVT and you can see the increased medial movement and reduced proprioceptive accuracy (11.2 degree error).
As discussed earlier, the effect of WBVT on mechanoreceptors and joint stability (Rittweger, 2010; Jordan et al., 2005; Riemann and Lephart, 2002b; Thompson and Bellanger, 2002) could have lead to the increased JPS error and medial instability shown in the figure above. The increased medial movement (valgus stress) and reduced proprioceptive sense could lead to an increased risk of injury. Proprioception and balance has been shown to be responsible for a reduced injury rate with Panics et al. (2008) linking an increase in proprioceptive sense to improvements in JPS. They postulate that these measures may be responsible for a reduced incidence of injuries to the lower limbs and therefore reduced JPS could increase the risk of injury. Hewett et al. (2005) looked at female athletes who participated in high injury risk sports which included basketball, and assessed their neuromuscular control during a jump landing task. They found that increased dynamic valgus and high adduction stresses at the knee, increased the risk of ACL injury.
Which poses the question with the lack of research of WBVT using athletic populations and these results showing that it reduces proprioception, which could lead to an increased injury risk. Is it a safe training method to do prior to physical activity or sport?
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