The effects of whole-body vibration on human biodynamic response

The objective of vibration research at the Armstrong Laboratory includes the expansion and improvement of the measurement, quantification, analysis, and modeling of human vibration response. The driving-point impedance and transmissibility techniques have been expanded and are rigorously applied in the research efforts. Driving-point impedance is defined as the ratio between the transmitted force and input velocity at the point of load application. Transmissibility is typically defined as the ratio between the acceleration level measured at some location on the body and the input acceleration at the seat. These two ratios are used to assess the magnitude and frequency location of resonance behaviors where maximum motions occur in the body. From these data, analytical models are developed which can simulate the motions and coupling behaviors, and predict the stiffness and damping characteristics of the affected anatomical structures. The ultimate goal of the research is to provide new and improved data and modeling capability for revising exposure standards and for developing equipment design guidelines and criteria for improving tolerance and reducing physiological consequences. This paper describes the results of recent studies conducted to identify the biodynamic behavior of major anatomical structures affected by seated whole-body vibration, to develop an analytical model for simulating human vibration response, and to apply the model to evaluate the effects of seat cushion materials on the transmission/attenuation pathways.     

Abdominal movements, heartbeats and gas exchange in pupae of the Colorado potato beetle, Leptinotarsa decemlineata

The rhythms of abdominal movements, heartbeats and gas exchange in the pupae of Leptiontarsa decemlineata (Say) were recorded simultaneously using an electrolytic respirometer and infrared gas analyser, both combined with contact thermography. Abdominal pulsations and heartbeat occurred periodically with little variance among individuals. The abdominal pulsations and heartbeat pauses varied individually within large limits, with the frequency of abdominal pulsations being six to seven times lower than that of the heart pulses. A proportion of the pupae (20%) showed discontinuous gas exchange with large, actively ventilated CO₂ bursts, whereas others (≈ 25%) exhibited continuous regular microcycles (flutter) with abrupt intake of air into the tracheae before discrete microbursts of carbon dioxide. The abdominal pulsations exerted only a minor influence on ventilation during the microcycles. More than 90% of the bursts of abdominal movement coincided with a series of forward directed heartbeats, but interspersed between the bouts of abdominal movement commonly two to three heartbeat pulses were observed that were not associated with abdominal movements. A period of abdominal movement associated with a heartbeat pulse was commonly initiated by one or two vigorous strokes of abdominal rotation.     

The effects of movement velocity during squatting on energy expenditure and substrate utilization in whole-body vibration

The purpose of this study was to examine whether and how cycle time duration affects energy expenditure and substrate utilization during whole-body vibration (WBV). Nine men performed 3 squatting exercises in execution frequency cycles of 6, 4, and 2 seconds to 90 degrees knee flexion with vibration (Vb+) (frequency was set at 30 Hz and the amplitude of vibration was 4 mm) and without vibration (Vb-) during 3 minutes, each with an additional load of 30% of the subject's body weight. A 2-way analysis of variance for VO2 revealed a significant vibration condition main effect (p < 0.001) and a cycle time duration effect (p < 0.001). When differences were analyzed by Fisher's LSD test, cycle time duration of 2 seconds was significantly different from 4 and 6 seconds, both in Vb+ and Vb-. Total energy expenditure (EE(tot)), carbohydrate oxidation rate (EE(cho)), and fat oxidation rate (EE(fat)) demonstrated a significant vibration condition main effect (EE(tot): p < 0.01; EE(cho): p < 0.001; EE(fat): p < 0.001) and cycle time duration main effect (EE(tot) and EE(cho): p < 0.001; EE(fat): p < 0.01). EE(tot), EE(cho), and EE(fat) post hoc comparisons indicated that values for the 2-second test significantly differed from 4 and 6 seconds when compared in the same vibration condition. VO2 and EE values were greater in Vb+ than in Vb- conditions with the same cycle time duration. Our study confirms that squatting at a greater frequency helps to maximize energy expenditure during exercise with or without vibration. Therefore, cycle time duration must be controlled when vibration exercise is prescribed.     

不同干预疗法对去卵巢骨质疏松大鼠肱骨骨矿物质含量影响

目的:对比观察不同干预疗法对去卵巢骨质疏松大鼠肱骨骨矿物质含量的影响。方法:按体重将80只成年雌性SD大鼠分层后随机分为假手术组和去卵巢组。手术11周时,将去卵巢组大鼠按体重分层后又随机分为去卵巢组、跑台运动组、振动组、金雀异黄酮组、氯化锂组和雌激素组。跑台运动组每周进行4次45 min、速度18 m/min、跑道倾角5°的跑台训练;振动组每天进行2次15 min、频率90 HZ/min、7次/周的振动治疗;金雀异黄酮组每天按体重灌胃1次金雀异黄酮,剂量为1 mg/kg体重;氯化锂组每周按体重腹腔注射氯化锂3次,剂量为15 mg/kg;雌激素组每周按体重颈部皮下注射3次17β-雌二醇,剂量为25μg/kg。持续处理8周时,于末次处理结束36-48小时内,按解剖位置截取双肱骨,称量肱骨湿重、去脂肪干重以及煅烧后的灰重。结果:与假手术组比较,去卵巢组肱骨湿重/体重、去脂肪干重/体重和灰重/体重均显著下降;与去卵巢组比较,跑台运动组、振动组、金雀异黄酮组和雌激素组肱骨湿重/体重、去脂肪干重/体重、灰重/体重均显著增加,而氯化锂组虽有所升高,但差异无显著性。结论:除氯化锂处理外,其他几种处理均能减缓去卵巢骨质疏松大鼠肱骨骨量的丢失,对防治去卵巢骨质疏松大鼠的骨质疏松有一定的作用。     

A model analysis of internal loads, energetics, and effects of wobbling mass during the whole-body vibration

The internal loads, energetics, and the effects of wobbling mass during the whole-body vibration are studied in terms of analysis and comparison of two models: one is a system of four degrees-of-freedom with rigid and wobbling masses in both lower body and upper body (Model A), while the other one (Model B) is a system of three degrees-of-freedom with a rigid upper body and is otherwise identical to Model A. The main findings are the following: (1) The wobbling mass in the upper body is able to reduce the total internal load on the rigid mass of the upper body considerably. (2) "Partial" internal loads on a certain part of the body may be even larger than the total load on the same part of the body because of the phase differences among the partial loads. Therefore, a full consideration of safety during the whole-body vibration has to take not only the total, but also all the partial internal loads into account. (3) The fluctuation of power input and the fluctuation of mechanical energy could be much larger than the fluctuation of dissipation rate. (4) For frequencies higher than the resonance frequency range, the amplitude of the oscillation of the centre of mass of the body is so reduced that only the change of elastic potential energy dominates in the change of mechanical energy. Thus, a simple picture of energy flow is obtained as follows: for approximately one half of the oscillation period, the energy flows from the vibrator into the human body and is mainly stored in the muscle-tendon system, while for the remaining approximate half of the period, the energy flows from the muscle-tendon system back to the vibrator with a slightly smaller amount because a small part of the flown-in energy has been dissipated.     

Acute effect of whole-body vibration on electromechanical delay and vertical jump performance

Objectives:To determine if a change in vertical jump performance from acute whole-body vibration can be explained by indirectly assessing spindle sensitivity from electromechanical delay.Methods:Using a counter-balanced design, twenty college-aged participants performed whole-body vibration (WBV) and control treatments. WBV included 10 intervals (26 Hz, 3.6 mm) of 60 s in a half-squat followed by 60 s of rest. After 5 intervals, participants rested for 6-minutes before commencing the final 5 intervals. For the control, the exact same protocol of whole-body vibration was performed but without vibration. Electromechanical delay and vertical jump were assessed at baseline, during the 6-minute rest period and immediately after whole-body vibration and control.Results:There were no differences between treatments, for both electromechanical delay (F(2, 38)=1.385, p=0.263) and vertical jump (F(2, 38)=0.040, p<0.96). Whole-body vibration had no effect on vertical jump performance.Conclusion:The current whole-body vibration protocol is not effective for acute vertical jump or electromechanical delay enhancement. Also, since there was no effect on electromechanical delay, this suggests that whole-body vibration did not enhance muscle spindle sensitivity for the parameters examined.     

Experimental Evidence of the Tonic Vibration Reflex during Whole-Body Vibration of the Loaded and Unloaded Leg

Increased muscle activation during whole-body vibration (WBV) is mainly ascribed to a complex spinal and supraspinal neurophysiological mechanism termed the tonic vibration reflex (TVR). However, TVR has not been experimentally demonstrated during low-frequency WBV, therefore this investigation aimed to determine the expression of TVR during WBV.  Whilst seated, eight healthy males were exposed to either vertical WBV applied to the leg via the plantar-surface of the foot, or Achilles tendon vibration (ATV) at 25Hz and 50Hzfor 70s. Ankle plantar-flexion force, tri-axial accelerations at the shank and vibration source, and surface EMG activity of m. soleus (SOL) and m. tibialis anterior (TA) were recorded from the unloaded and passively loaded leg to simulate body mass supported during standing.  Plantar flexion force was similarly augmented by WBV and ATV and increased over time in a load- and frequency dependent fashion. SOL and TA EMG amplitudes increased over time in all conditions independently of vibration mode. 50Hz WBV and ATV resulted in greater muscle activation than 25Hz in SOL when the shank was loaded and in TA when the shank was unloaded despite the greater transmission of vertical acceleration from source to shank with 25Hz and WBV, especially during loading. Low-amplitude WBV of the unloaded and passively loaded leg produced slow tonic muscle contraction and plantar-flexion force increase of similar magnitudes to those induced by Achilles tendon vibration at the same frequencies. This study provides the first experimental evidence supporting the TVR as a plausible mechanism underlying the neuromuscular response to whole-body vibration.     

The apparent mass of the seated human exposed to single-axis and multi-axis whole-body vibration

Most workplaces where workers are exposed to whole-body vibration involves simultaneous motion in the fore-and-aft (x-), lateral (y-) and vertical (z-) directions. Previous studies reporting the biomechanical response of people exposed to vibration have almost always used single-axis vibration stimuli. This paper reports a study where apparent masses of 15 subjects were measured whilst exposed to single-axis and tri-axial whole-body vibration. Each subject was exposed to 28 vibration conditions comprising every combination of single-axis and tri-axial vibration with magnitudes of 0.4 and 0.8 ms(-2) r.m.s. in each direction, once with backrest contact and once without backrest contact. Results show that increasing the magnitude of vibration in directions orthogonal to that being measured affects the apparent mass, causing a reduction in the resonance frequency as the total magnitude of vibration increases. It is demonstrated that the apparent mass resonance frequency is a function of the total vibration magnitude in all axes rather than a function of the vibration magnitude in the direction being measured. It is also shown that, for individuals, the frequency of the peak in the apparent mass in one direction is not related to the frequency of the peak in another direction. It is concluded that more complex biomechanical models are required in order to simulate human response to multi-axis vibration.     

Excitatory neural control of posterograde heartbeat by the frontal ganglion in the last instar larva of a lepidopteran, Bombyx mori

The frontal ganglion of the silkworm (Bombyx mori) gives rise to a visceral nerve, branches of which include a pair of anterior cardiac nerves and a pair of the posterior cardiac nerves. Forward-fill of the visceral nerve with dextran labeled with tetramethyl rhodamine shows the anterior cardiac nerves innervate the anterior region of the dorsal vessel. Back-fill of the anterior cardiac nerves with Co²⁺ and Ni²⁺ ions and the fluorescent dye reveals that the cell bodies of two motor neurons are located in the frontal ganglion. Injection of 5, 6-carboxyfluorescein into the cell body of an identified motor neuron shows that the neuron gives rise to an axon running to the visceral nerve. Unitary excitatory junctional potentials (EJPs) were recorded from a myocardial cell at the anterior end of the heart. They responded in a one-to-one manner to electrical stimuli applied to the visceral nerve, or to impulses generated by a depolarizing current injected into the cell body. EJPs induced by stimuli at higher than 0.5 Hz showed facilitation while those induced at higher than 2 Hz showed summation. Individual EJPs without summation, or a train of EJPs with summation, caused acceleration in the phase of posterograde heartbeat and heart reversal from anterograde heartbeat to posterograde heartbeat. It is likely that the innervation of the anterior region of the dorsal vessel by the motor neurons, through the anterior cardiac nerves is responsible for the control of heartbeat in Lepidoptera, at least in part.     

Altered feeding response as a cause for the altered heartbeat rate and locomotor activity of Schistosoma mansoni-infected biomphalaria glabrata

Biomphalaria glabrata infected with Schistosoma mansoni for 33 days fed more often than uninfected snails. Whereas uninfected snails had nocturnal increases in feeding, snails with a 33-day-old infection of S. mansoni fed as often during the day as in the night. Using direct observation and film analysis, we found that feeding increased the heartbeat rate and locomotor activity of B. glabrata. When snails were allowed to feed ad lib., infected snails had higher heartbeat rates than uninfected snails both during the day (P less than 0.01) and the night (P less than 0.001). However, when the snails were deprived of food for 24 hr, infected snails had slightly higher heartbeat rates than uninfected snails only during the day (P less than 0.05). There was no difference between the heartbeat rates of feeding, infected snails and the heartbeat rates of uninfected snails that were starved for 8 hr, and then allowed to feed. Uninfected snails had nocturnal increases in heartbeat rate regardless of feeding schedule, but infected snails had greater nighttime heartbeat rate than daytime heartbeat rate only when they were not allowed to feed. Infected snails had less nocturnal locomotor activity than uninfected snails when feeding, but there was no difference between the locomotor activity of infected and uninfected snails when the snails were deprived of food for 24 hr. Absence of food also resulted in an increased nighttime to daytime ratio of locomotor activity of infected snails. These results suggest that the increased heartbeat rate and altered rhythms of heartbeat rate and locomotor activity in B. glabrata infected with S. mansoni for 33 days were caused by the altered feeding response of these snails.     

Effects of muscular strength, exercise order, and acute whole-body vibration exposure on bat swing speed

The purposes for this study were to investigate effects of acute whole-body vibration (WBV) exposure and exercise order on bat speed and to examine relationship between muscular strength and bat speed. All participants were recreationally trained men (n = 16; 22 ± 2 years; 181.4 ± 7.4 cm; 84.7 ± 9 kg), with previous baseball experience and were tested for 1 repetitive maximum (1RM) strength in squat and bench press. Subjects then participated in 4 randomized sessions on separate days, each consisting of 3 sets of 5 bat swings. Exercises (upper and lower body dynamic and static movements related to bat swing) with or without WBV exposure were performed after sets 1 and 2. Trials were as follows: no-exercise Control (CTRL), upper body followed by lower body exercises without WBV (Arm-Leg NOVIB), upper body followed by lower body exercises with WBV (Arm-Leg VIB), and lower body followed by upper body exercises with WBV (Leg-Arm VIB). Bat speed was recorded during each swing and averaged across sets. Statistical analyses were performed to assess differences across sets and trials. Linear regressions analyzed relationship between strength and bat speed. A significant relationship existed between bat speed and lower body strength (r = 0.406, p = 0.008) but not for upper body strength. The exercise order of Arm-Leg VIB significantly increased bat speed by 2.6% (p = 0.02). Performing identical order of exercises without vibration (Arm-Leg NOVIB) significantly decreased bat speed by 2% (p = 0.039). It was concluded that adding vibration exposure to total-body exercises can provide acute enhancements in bat speed. Additionally, leg strength was shown to influence bat speed suggesting that increasing leg strength may enhance bat speed.     

The Subjective Visual Vertical and the Subjective Haptic Vertical Access Different Gravity Estimates

The subjective visual vertical (SVV) and the subjective haptic vertical (SHV) both claim to probe the underlying perception of gravity. However, when the body is roll tilted these two measures evoke different patterns of errors with SVV generally becoming biased towards the body (A-effect, named for its discoverer, Hermann Rudolph Aubert) and SHV remaining accurate or becoming biased away from the body (E-effect, short for Entgegengesetzt-effect, meaning “opposite”, i.e., opposite to the A-effect). We compared the two methods in a series of five experiments and provide evidence that the two measures access two different but related estimates of gravitational vertical. Experiment 1 compared SVV and SHV across three levels of whole-body tilt and found that SVV showed an A-effect at larger tilts while SHV was accurate. Experiment 2 found that tilting either the head or the trunk independently produced an A-effect in SVV while SHV remained accurate when the head was tilted on an upright body but showed an A-effect when the body was tilted below an upright head. Experiment 3 repeated these head/body configurations in the presence of vestibular noise induced by using disruptive galvanic vestibular stimulation (dGVS). dGVS abolished both SVV and SHV A-effects while evoking a massive E-effect in the SHV head tilt condition. Experiments 4 and 5 show that SVV and SHV do not combine in an optimally statistical fashion, but when vibration is applied to the dorsal neck muscles, integration becomes optimal. Overall our results suggest that SVV and SHV access distinct underlying gravity percepts based primarily on head and body position information respectively, consistent with a model proposed by Clemens and colleagues.     

Non-linearities in apparent mass and transmissibility during exposure to whole-body vertical vibration

The causes of low back pain associated with prolonged exposure to whole-body vibration are not understood. An understanding of non-linearities in the biomechanical responses is required to identify the mechanisms responsible for the dynamic characteristics of the body, to allow for the non-linearities when predicting the influence of seating dynamics, and to predict the adverse effects caused by various magnitudes of vibration. Twelve subjects were exposed to six magnitudes, 0.25-2.5ms(-2) rms, of vertical random vibration in the frequency range 0.2-20Hz. The apparent masses of the subjects were determined together with transmissibilities measured from the seat to various locations on the body surface: the upper and lower abdominal wall, at L3, over the posterior superior iliac spine and the iliac crest. There were significant reductions in resonance frequencies for both the apparent mass and the transmissibilities to the lower abdomen with increases in vibration magnitude. The apparent mass resonance frequency reduced from 5.4-4. 2Hz as the magnitude of the vibration increased from 0.25-2.5ms(-2) rms. Vertical motion of the lumbar spine and pelvis showed resonances at about 4Hz and between 8 and 10Hz. When exposed to vertical vibration, the human body shows appreciable non-linearities in its biodynamic responses. Biodynamic models should be developed to reflect the non-linearity.     

不同干预方法对去卵巢骨质疏松大鼠子宫GSK-3β蛋白表达的影响

目的观察全身垂直振动、跑台运动和金雀异黄酮对去卵巢骨质疏松大鼠子宫重量指数和组织形态学以及糖原合成激酶3β（GSK-3β）蛋白表达的影响。方法将72只3月龄雌性SD大鼠按体重分层后随机分为假手术组（12只）和去卵巢组（60只）。去卵巢10周时,将去卵巢组大鼠按体重分层后又随机分为去卵巢组、振动组、跑台组、金雀异黄酮组和雌激素组（每组8~10只）,并开始进行不同干预处理。干预处理8周时,于末次处理结束36~48h内,腹主动脉取血处死各组大鼠,用电子天平称量大鼠子宫的重量,用HE染色方法观察子宫形态学的变化,用Western blot方法检测子宫GSK-3β和P-GSK-3β蛋白表达的变化。结果与去卵巢组比较,雌激素组大鼠子宫重量指数显著增加,而振动组、跑台组、金雀异黄酮组大鼠子宫重量指数均无显著变化;与去卵巢组比较,雌激素组、跑台组和振动组大鼠子宫P-GSK-3β/GSK-3β蛋白的比值均显著增加,而金雀异黄酮组无显著变化。结论全身垂直振动和跑台运动均能刺激去卵巢骨质疏松大鼠子宫GSK-3β蛋白的磷酸化,而金雀异黄酮无此效应。     

Apparent mass of the standing human body when using a whole-body vibration training machine: Effect of knee angle and input frequency

Several studies have investigated the transmission of vibration from the vibrating plate of a whole-body vibration training machine (WBVTM) to different locations on the human body. No known work has investigated the interface force between the vibrating plate of the machine and the human body. This paper investigates the effect of bending the knees and the vibration frequency on the interface force (presented as apparent mass (AM)) between the vibrating plate and the body. Twelve male subjects stood with four different knee angles (180, 165, 150 and 135°) and were exposed to sinusoidal vertical vibration at eight frequencies in the range of 17–42 Hz. The vertical acceleration and the interface force between the body and the vibrating plate were measured and used to calculate the AM. The acceleration and force depended on the frequency and were found to vary with both the adopted posture and subject. The AM generally decreased with increasing the frequency but showed a peak at 24 Hz which was clearer when the knees were bent. Bending the knees showed an effect similar to increasing the damping of a system with base excitation; increasing the damping reduced the AM in the resonance region but increased the AM at higher frequencies. Users of WBVTMs have to be careful when choosing the training posture: although, as shown in previous studies, bending the knees reduces the transmission of vibration to the spine, it increases the interface forces which might indicate increased stresses on the lower legs and joints.     

How chimpanzees look at pictures: a comparative eye-tracking study

Surprisingly little is known about the eye movements of chimpanzees, despite the potential contribution of such knowledge to comparative cognition studies. Here, we present the first examination of eye tracking in chimpanzees. We recorded the eye movements of chimpanzees as they viewed naturalistic pictures containing a full-body image of a chimpanzee, a human or another mammal; results were compared with those from humans. We found a striking similarity in viewing patterns between the two species. Both chimpanzees and humans looked at the animal figures for longer than at the background and at the face region for longer than at other parts of the body. The face region was detected at first sight by both species when they were shown pictures of chimpanzees and of humans. However, the eye movements of chimpanzees also exhibited distinct differences from those of humans; the former shifted the fixation location more quickly and more broadly than the latter. In addition, the average duration of fixation on the face region was shorter in chimpanzees than in humans. Overall, our results clearly demonstrate the eye-movement strategies common to the two primate species and also suggest several notable differences manifested during the observation of pictures of scenes and body forms.     

Ejaculatory pattern of llamas during copulation

The objective of this study was to use transrectal digital palpation of urethral pulses to define the ejaculatory pattern of llamas during copulation. Five male llamas were palpated during 5 to 6 copulations each with receptive female llamas (n = 28 copulations). The time from first exposure of a male to a female until mounting was 0.7 +/- 1.1 min (mean +/- SD), time to the first intromission was 1.7 +/- 1.4 min, and time from initial mount to final dismount (copulation duration) was 21.7 +/- 7.8 min. A total of 121.9 +/- 61.0 urethral pulses per copulation (5.6 +/- 1.7 pulses/min) was palpated. During the first 3.9 +/- 3.7 min of copulation, urethral pulses (11.0 +/- 10.1 urethral pulses at 3.5 +/- 2.5 pulses/min) occurred randomly and were not associated with whole-body strains. After the first 4 min of copulation, urethral pulses occurred in a pattern of clusters of frequent urethral pulses associated with whole-body strains, alternating with intercluster intervals of infrequent urethral pulses without whole-body strains. Individual clusters were characterized by 4.3 +/- 2.7 urethral pulses at 16.7 +/- 4.5 pulses/min during strains, and intercluster intervals were characterized by 1.7 +/- 2.3 urethral pulses at 2.2 +/- 1.8 pulses/min. Each cluster of urethral pulses during a strain was preceded by 2.3 +/- 1.8 repositions of the male's hindlegs and by 38.1 +/- 20.8 pelvic thrusts. There were 18.5 +/- 10.6 clusters of urethral pulses accompanied by strains per copulation at 0.9 +/- 0.3 clusters/min. The 18 to 19 clusters of urethral pulses appeared to be individual ejaculations. Therefore, we hypothesize that llamas ejaculated 18 to 19 times during their 22-min copulations.     

Raman amplification of laser pulses near the threshold for plasma wave breaking

Equations are derived for the amplitudes of counter-propagating laser pulses near the threshold for plasma wave breaking, which allow one to describe laser pulses with durations on the order of the plasma oscillation period. In the quasi-monochromatic approximation, they take the form of conventional threewave equations with an additional nonlinearity for the plasma wave. The amplitudes of the amplified laser pulses estimated using these equations agree with results obtained by solving the complete equations. It is shown that Raman amplification of a weak quasi-monochromatic signal (plasma noise) in rarified plasma is significantly suppressed. At the same time, according to numerical simulations, the amplification of laser pulses with durations on the order of the plasma oscillation period is suppressed insignificantly. This result opens new prospects in the application of Raman compression of laser pulses without additional frequency modulation.     

Stimulated Raman microscopy (CARS): From principles to applications

A new technique in microscopy is now available which permits to image specific molecular bonds of chemical species present in cells and tissues. The so called Coherent Anti-Stokes Raman Scattering (CARS) approach aims at maximizing the light matter interaction between two laser pulses and an intrinsic molecular vibrational level. This is possible through a non linear process which gives rise to a coherent radiation that is greatly enhanced when the frequency difference between the two laser pulses equals the Raman frequency of the aimed molecular bond. Similar to confocal microscopy, the technique permits to build an image of a molecular density within the sample but doesn't require any labelling or staining since the contrast uses the intrinsic vibrational levels present in the sample. Images of lipids in membranes and tissues have been reported together with their spectral analysis. In the case of very congested media, it is also possible to use a non invasive labelling such as deuterium which shifts the molecular vibration of the C-H bond down to the C-D bond range which falls in a silent region of the cell and tissue vibrational spectra. Such an approach has been used to study lipid phase in artificial membranes. Although the technique is still under development, CARS has now reach a maturity which will permit to bring the technology at a commercial stage in the near future. The last remaining bottleneck is the laser system which needs to be simplified but solutions are now under evaluation. When combined with others more conventional techniques, CARS should give its full potential in imaging unstained samples and like two photons techniques has the potential of performing deep tissues imaging.