Alain Belli

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

Previous investigations reported enhanced osseous parameters subsequent to administration of whole body vibration (WBV). While the efficacy of WBV continues to be explored, scientific inquiries should consider several key factors. Bone remodeling patterns differ according to age and hormonal status. Therefore, WBV protocols should be designed specifically for the subject population investigated. Further, administration of WBV to individuals at greatest risk for osteoporosis may elicit secondary physiological benefits (e.g., improved balance and mobility). Secondly, there is a paucity of data in the literature regarding the physiological modulation of WBV on other organ systems and tissues. Vibration-induced modulation of systemic hormones may provide a mechanism by which skeletal tissue is enhanced. Lastly, the most appropriate frequencies, durations, and amplitudes of vibration necessary for a beneficial response are unknown, and the type of vibratory signal (e.g., sinusoidal) is often not reported. This review summarizes the physiological responses of several organ systems in an attempt to link the global influence of WBV. Further, we report findings focused on subject populations that may benefit most from such a therapy (i.e., the elderly, postmenopausal women, etc.) in hopes of eliciting multidisciplinary scientific inquiries into this potentially therapeutic aid which presumably has global ramifications.

Characterization of the mechanical properties of backpacks and their influence on the energetics of walking

The objectives of the experiment were (i) to characterize the mechanical properties of backpacks and (ii) to study the influence of a flexible backpack on the energetics and kinematics of walking. Twelve subjects walked at different speeds on a treadmill with each of two backpacks loaded with 25% bodyweight, with either a rigid or a flexible link between the body attachment and the suspended loads. A single degree of freedom linear model of the link between the pack and the trunk was used to calculate the stiffness and damping coefficient of the two backpacks. The oxygen consumption (VO2) and the vertical acceleration of both the backpack and trunk were measured. The vertical excursion of the pack given by the model was significantly correlated with that actually measured (R=0.87, p<0.001). At 3.7 and 4.5 km h(-1) the flexible pack induced lower acceleration peaks (respectively -22% and -8%; p<0.05) and tended to reduce VO2 (p=0.055 at 4.5 km h(-1)) compared with the rigid one. At 5.2 and 6 km h(-1) both the accelerative forces and VO2 increased with the flexible pack (p<0.05) mainly because of the high vertical movement of the pack. It was concluded that a simple model can be used to predict the vertical excursion of the pack and that a flexible backpack can provide energetic benefits when its oscillations are nearly in phase with those of the trunk. However, any resonance effect can lead to a modified walking pattern and an increased metabolic cost.

Eight weeks of local vibration training increases dorsiflexor muscle cortical voluntary activation

The aim of this study was to evaluate the effects of an 8-wk local vibration training (LVT) program on functional and corticospinal properties of dorsiflexor muscles. Forty-four young subjects were allocated to a training (VIB, n = 22) or control (CON, n = 22) group. The VIB group performed twenty-four 1-h sessions (3 sessions/wk) of 100-Hz vibration applied to the right tibialis anterior. Both legs were tested in each group before training (PRE), after 4 (MID) and 8 (POST) wk of training, and 2 wk after training (POST2W). Maximal voluntary contraction (MVC) torque was assessed, and transcranial magnetic stimulation (TMS) was used to evaluate cortical voluntary activation (VATMS), motor evoked potential (MEP), cortical silent period (CSP), and input-output curve parameters. MVC was significantly increased for VIB at MID for right and left legs [+7.4% (P = 0.001) and +6.2% (P < 0.01), respectively] and remained significantly greater than PRE at POST [+12.0% (P < 0.001) and +10.1% (P < 0.001), respectively]. VATMS was significantly increased for right and left legs at MID [+4.4% (P < 0.01) and +4.7% (P < 0.01), respectively] and at POST [+4.9% (P = 0.001) and +6.2% (P = 0.001), respectively]. These parameters remained enhanced in both legs at POST2W MEP and CSP recorded during MVC and input-output curve parameters did not change at any time point for either leg. Despite no changes in excitability or inhibition being observed, LVT seems to be a promising method to improve strength through an increase of maximal voluntary activation, i.e., neural adaptations. Local vibration may thus be further considered for clinical or aging populations.NEW & NOTEWORTHY The effects of a local vibration training program on cortical voluntary activation measured with transcranial magnetic stimulation were assessed for the first time in dorsiflexors, a functionally important muscle group. We observed that training increased maximal voluntary strength likely because of the strong and repeated activation of Ia spindle afferents during vibration training that led to changes in the cortico-motoneuronal pathway, as demonstrated by the increase in cortical voluntary activation.

Sex differences in active tibialis anterior stiffness evaluated using supersonic shear imaging

This study aimed to evaluate the sex difference in active muscle stiffness of the tibialis anterior muscle (TA) through shear modulus measurements performed using supersonic shear imaging (SSI) technique. Twenty-five women and twenty-one men participated in this study. Joint torque, electromyographic (EMG) activity and shear modulus were measured during two sets of submaximal dorsiflexions performed at 20, 30, 40, 50 and 60% of maximal voluntary contraction (MVC) in a random order. The first set was devoted to the EMG recordings and the second set was devoted to the elastographic measurements. For each set, subjects performed three 5-s trials at each level of submaximal voluntary contraction. Stiffness indexes were calculated as the slopes of the linear regressions established between shear modulus and joint torque (SITORQUE) or estimated TA EMG levels (SIEMG). In the present study, no sex effect was reported for SITORQUE, SIEMG (p=0.76 and p=0.86, respectively), and shear modulus measured at various contraction levels. The results highlight that men and women presented similar TA active stiffness indexes determined using SSI. Regardless of sex, this result suggests similar intrinsic stiffness for the contracting TA.

Forms of interdisciplinarity in four sport science research centres in Europe.

Abstract Interdisciplinarity is often presented as a significant element of sport science. We present here the results of an investigation conducted in four European Sport Science Research Centres applying interdisciplinarity. Four main dimensions, that we have called “forms”, have been investigated. The “scientific”, “organisational”, “academic” and “societal” forms cover a wide range of activities run by these Centres. We have compared their situations using indicators. Globally they present quite similar combinations of forms, with dominant roles in the construction of interdisciplinarity played by the organisational and societal forms. The scientific form is never quite supported by an epistemological setting and the academic form, mostly characterised by the position of the university, plays an influential role when it is hostile to that kind of research. Following Klein classification, all of them remain at a multidisciplinary stage, one of them exploring interdisciplinary tracks in some research projects. The development of a common culture and a curiosity regarding disciplines other than its own is a key factor for a sustainable situation, as is the capacity to secure long-term financial resources, often linked to a high academic recognition for the director(s).