High Frequency Mechanical Vibration Research Articles

Light orthodontic force with high-frequency vibration accelerates tooth movement with minimal root resorption in rats.

To determine and compare the effects of high-frequency mechanical vibration (HFV) with light force and optimal force on the tooth movement and root resorption in rat model. Seventy-two sites in 36 male Wistar rats were randomly assigned using a split-mouth design to control (no force/no vibration) or experimental groups: HFV (125Hz), light force (5g), optimal force (10g), light force with HFV, and optimal force with HFV for 14 and 21days. The amount of tooth movement, 3D root volume, and root resorption area were assessed by micro-computed tomography and histomorphometric analysis. Adjunction of HFV with light force significantly increased the amount of tooth movement by 1.8-fold (p = 0.01) and 2.0-fold (p = 0.01) at days 14 and 21 respectively. The HFV combined with optimal force significantly increased the amount of tooth movement by 2.1-fold (p = 0.01) and 2.2-fold (p = 0.01) at days 14 and 21 respectively. The root volume in control (distobuccal root (DB): 0.60 ± 0.19 mm3, distopalatal root (DPa): 0.60 ± 0.07 mm3) and HFV (DB: 0.60 ± 0.08 mm3, DPa: 0.59 ± 0.11 mm3) were not different from the other experimental group (range from 0.44 ± 0.05 to 0.60 ± 0.1 mm3) with the lowest volume in optimal force group. Adjunction of HFV with orthodontic force significantly increased tooth movement without causing root resorption. Using light force with HFV could help to identify alternative treatment option to reduce the risk of root resorption.

Effects of mechanical vibration on bone – a critical review

The benefits of reduced treatment time and comfort for patients undergoing corrective dental treatment with devices gave rise to the creation and modification of long-standing treatment protocols. One of the protocols used for these purposes is mechanical vibration. Objective: This review aimed to study the effects of mechanical vibration on bone. Methods: Portal Capes (periodicos.capes.gov.br) database was searched using the keywords “vibration” and “bone” with no date limit. Based on the title and abstract, the first 50 relevant studies were retrieved. The measured frequencies were between 4 and 150 Hz. Regarding exposure time and the number of applications, the variation is so wide that the average or median would not represent a realistic sample pattern. Results: In the retrieved studies, 41 reported improvements in bone conditions. Research studies show that a reproducible protocol is being applied in most studies on the effects of mechanical vibration on bone tissue. Conclusion: There is stimulation of bone biology, regardless of species, in the sense of osteogenesis in individuals exposed to high frequency mechanical vibration. To improve research protocols on the effects of vibrations on the body, more studies are needed.

Differential analysis of the influence mechanism of ultrasonic vibrations on laser cladding

Although the laser cladding technology is widely used in various fields, the laser cladding layer is prone to pores, inclusions and microcracks, severely limiting the popularization and application of this technology. High-frequency mechanical vibration can effectively reduce the micro defects in the cladding layer and strengthen the solidification structure of the cladding layer. In this paper, a laser cladding system for a disc laser assisted by ultrasonic vibration is built, and the dynamic response of ultrasonic vibration of the cladding experiment platform is tested. A finite element model of the dynamic response of the cladding experiment platform under ultrasonic vibration was established, and the difference of the vibration of the experimental platform substrate at different positions under the ultrasonic vibration was calculated. The internal amplitude of the substrate is differentiated in a hemispherical shape with the vibration source as the center and is distributed under the influence of ultrasonic vibration. On this basis, the phase field method was used to establish the ultrasonic-assisted disc laser cladding solidification model to obtain the dendrite growth state during the solidification process. The calculation reveals the change law of single crystal and polycrystalline solidification growth under the influence of ultrasonic amplitude at different substrate positions. Calculations show that ultrasonic vibration can effectively increase the growth rate of dendrites and promote the formation of secondary dendrite arms. The polycrystalline solidification growth model is closer to reality. The competitive growth of dendrites suppresses the growth of primary dendrites to a certain extent and affects the selective growth of dendrites. The results show that the larger the ultrasonic amplitude, the more rapid the formation of secondary dendrite arms.

Three-dimensional imaging and molecular analysis of the effects of photobiomodulation and mechanical vibration on orthodontic retention treatment in rats : Effects of photobiomodulation and mechanical vibration on orthodontic retention treatment.

We aimed to evaluate and compare effects of photobiomodulation (PBM) and low-magnitude high-frequency mechanical vibration (HFMV) on orthodontic retention. Sixty-four female Wistar albino rats were divided into 9groups (2negative and positive controls each, 3PBM and 2HFMV groups) and studied for 25days. In the experimental groups, closed nickel-titanium closed coil springs with a50 cN force were placed for 10days between the maxillary incisor and molar. PBM and HFMV were applied daily over long- (15days) and short-term (7days) retention periods. The PBM groups received PBM with asingle wavelength (650 nm) or higher wavelengths (532, 650, 940 nm) for 9 min per day. HFMV groups received HFMV of 10, 20, and 30 Hz for 10 min per day. Right and left maxilla were assessed using micro-computed tomography imaging and real-time polymerase chain reaction. The amount of tooth movement during the retention period, expression levels of cyclooxygenase‑2 (COX-2), osteoprotegerin (OPG), and receptor activator of nuclear factor-kappaB ligand (RANKL) mRNA gene expression levels, OPG/RANKL ratios, alveolar bone trabecular thickness (Tb.Th), trabecular number (Tb.N), and structure model index were analyzed. Kruskal-Wallis and Mann-WhitneyU tests were used for multiple comparisons of the nonparametric distributed data and binary comparisons, respectively. When using the long-term retention protocol, PBM and HFMV treatment increased Tb.N (p < 0.05) and decreased COX‑2 mRNA gene expression levels (p < 0.05) and Tb.Th (p < 0.05) compared to controls. For short-term retention, PBM and HFMV decreased the amount of relapse tooth movement compared to controls. In addition, Tb.Th (p < 0.05) and the mRNA gene expression levels of COX‑2 and RANKL (p < 0.05) were decreased. PBM and HFMV might be able to support retention after orthodontic tooth movement by reducing bone resorption and increasing bone quality.

Building of Longitudinal Ultrasonic Assisted Turning System and Its Cutting Simulation Study on Bulk Metallic Glass.

Bulk metallic glass (BMG) is a new kind of material which is made by rapid condensation of alloy. With excellent properties like high strength, high hardness, corrosion resistance, BMG is increasingly applied in mold manufacturing, weapon equipment and other fields. However, BMG is also one of hard-to-machine materials, which is arduous to be processed precisely and efficiently by the means of conventional cutting. Compared with conventional cutting, ultrasonic machining has a multitude of technological advantages such as reducing the cutting force, extending the tool life, etc. In ultrasonic machining, the ultrasonic electric signal is transformed into high frequency mechanical vibration on the tool, which changes the relationship between the tool and the workpiece in the process of machining. In this study, the longitudinal ultrasonic assisted turning (LUAT) system is established for processing BMG. Its resonant frequency and vibration characteristics are first simulated by modal analysis and harmonic response analysis, and then tested by displacement testing experiments, so that the suitable frequency and the amplitude for BMG turning can be selected and verified. On this basis, the two-dimensional turning finite element model is established to study the effect of ultrasonic vibration on cutting force under different cutting speeds. The research manifest that during the BMG turning, the assistance of longitudinal ultrasonic vibration can significantly reduce the average cutting force as well as the von Mises stress when the turning speed is below the critical turning speed. In addition, the tip of the tool contacts the workpiece discontinuously during cutting process which makes the instantaneous turning force in LUAT more periodic than that in conventional turning (CT).

Mechanical impact stimulation platform tailored for high-resolution light microscopy

High frequency (HF) mechanical vibration has been used in vitro to study the cellular response to mechanical stimulation and induce stem cell differentiation. However, detailed understanding of the effect of the mechanical cues on cellular physiology is lacking. To meet this limitation, we have designed a system, which enables monitoring of living cells by high-resolution light microscopy during mechanical stimulation by HF vibration or mechanical impacts. The system consists of a commercial speaker, and a 3D printed sample vehicle and frame. The speaker moves the sample in the horizontal plane, allowing simultaneous microscopy. The HF vibration (30–200 Hz) performances of two vehicles made of polymer and aluminum were characterized with accelerometer. The mechanical impacts were characterized by measuring the acceleration of the aluminum vehicle and by time lapse imaging. The lighter polymer vehicle produced higher HF vibration magnitudes at 30–50 Hz frequencies than the aluminum vehicle. However, the aluminum vehicle performed better at higher frequencies (60–70 Hz, 90–100 Hz, 150 Hz). Compatibility of the system in live cell experiments was investigated with epithelial cells (MDCKII, expressing Emerald-Occludin) and HF (0.56 Gpeak, 30 Hz and 60 Hz) vibration. Our findings indicated that our system is compatible with high-resolution live cell microscopy. Furthermore, the epithelial cells were remarkable stable under mechanical vibration stimulation. To conclude, we have designed an inexpensive tool for the studies of cellular biophysics, which combines versatile in vivo like mechanical stimuli with live cell imaging, showing a great potential for several cellular applications.

Cell adhesion and culture medium dependent changes in the high frequency mechanical vibration induced proliferation, osteogenesis, and intracellular organization of human adipose stem cells

High frequency (HF) mechanical vibration appears beneficial for in vitro osteogenesis of mesenchymal stem cells (MSCs). However, the current mechanobiological understanding of the method remains insufficient. We designed high-throughput stimulators to apply horizontal or vertical high magnitude HF (HMHF; 2.5 Gpeak, 100 Hz) vibration on human adipose stem cells (hASCs). We analyzed proliferation, alkaline phosphatase (ALP) activity, mineralization, and effects on the actin cytoskeleton and nuclei using immunocytochemical stainings. Proliferation was studied on a standard tissue culture plastic (sTCP) surface and on an adhesion supporting tissue culture plastic (asTCP) surface in basal (BM) and osteogenic (OM) culture medium conditions. We discovered that the improved cell adhesion was a prerequisite for vibration induced changes in the proliferation of hASCs. Similarly, the adhesion supporting surface enabled us to observe vibration initiated ALP activity and mineralization changes in OM condition. The horizontal vibration increased ALP activity, while vertical stimulation reduced ALP activity. However, mineralization was not enhanced by the HMHF vibration. We performed image-based analysis of actin and nuclei to obtain novel data of the intracellular-level responses to HF vibration in BM and OM conditions. Our quantitative results suggest that actin organizations were culture medium and stimulation direction dependent. Both stimulation directions decreased OM induced changes in nuclear size and elongation. Consequently, our findings of the nuclear deformations provide supportive evidence for the involvement of the nuclei in the mechanocoupling of HF vibration. Taken together, the results of this study enhanced the knowledge of the intracellular mechanisms of HF vibration induced osteogenesis of MSCs.

Effect of contact area with fixture on dynamic behaviour of joint interface in ultrasonic welding of thermoplastics

Ultrasonic welding is one of the most common methods for joining thermoplastics. The two plastic parts to be joined are placed on the fixture before high frequency mechanical vibration is applied to the parts through an ultrasonic horn. This generates heat at the joint area and locally melts thermoplastics. The parts are welded together. In this paper, we investigate the effect of the contact area between the lower part and the fixture on the dynamic behaviour of the joint interface, which affects heat generation. The displacements and elastic strains of the interface are predicted using finite element dynamic contact analysis and compared for different contact areas. The results show that the dynamic behaviour of the interface depends on the dynamic characteristics of the two parts. When both natural frequencies are close to the horn vibration frequency, the displacements and strains are small. Conversely, when the lower part has no natural frequency near the horn vibration frequency, the displacements and strains are large. The contact area significantly affects the dynamic behaviour of the interface. This is because its dynamic behaviour depends on the natural frequencies of the parts to be joined while the natural frequency of the lower part is easily improved by the contact area.

High-Performance Pressure Sensor for Monitoring Mechanical Vibration and Air Pressure.

To realize the practical applications of flexible pressure sensors, the high performance (sensitivity and response time) as well as more functionalities are highly desired. In this work, we fabricated a piezoresistive pressure sensor based on the micro-structured composites films of multi-walled carbon nanotubes (MWCNTs) and poly (dimethylsiloxane) (PDMS). In addition, we establish efficient strategies to improve key performance of our pressure sensor. Its sensitivity is improved up to 474.13 kPa−1 by minimizing pressure independent resistance of sensor, and response time is shorten as small as 2 μs by enhancing the elastic modulus of polymer elastomer. Benefiting from the high performance, the functionalities of sensors are successfully extended to the accurate detection of high frequency mechanical vibration (~300 Hz) and large range of air pressure (6–101 kPa), both of which are not achieved before.

Effect of the application of high-frequency mechanical vibration on tooth length concurrent with orthodontic treatment using clear aligners: A retrospective study.

OBJECTIVES:To evaluate the possible change in teeth lengths as an indicator of orthodontically induced tooth root resorption (OITRR) after high-frequency mechanical vibration (HFV) treatment concurrent with Invisalign Smart Track® aligners as evaluated by cone beam computed tomography (CBCT).MATERIALS AND METHODS:The sample, composed of 30 patients with an average age of 26 ± 11 years and Class I malocclusion with an initial anterior crowding ranging from 3 to 5 mm, was divided equally into two groups; Group I received adjunctive high-frequency mechanical vibration (HFV); Group II, the control, did not receive adjunctive mechanical treatment. The maxillary incisor's teeth lengths were measured using Mimics software before (T1) and after (T2) treatment. All data were analyzed using Student's t-test. Reliability testing was completed by randomly selecting 10 patients’ CBCTs, and their teeth lengths were measured twice by the same investigator over a 15-day interval and compared confirming intra-operator accuracy.RESULTS:The control group showed a statistically significant decrease in tooth lengths compared to the HFV group which showed nonstatistically significant change of tooth lengths.CONCLUSION:Patients treated with HFV showed minimum tooth length changes after treatment, which may indicate that HFV can reduce OITRR with treatment using clear aligners.

Sensing flexural motion of a photonic crystal membrane with InGaAs quantum dots

Optical coupling between quantum dots and photonic crystal cavities and waveguides has been studied for many years in order to explore interesting physics and to advance quantum technologies. Here, we demonstrate strain-based coupling between mechanical motion of a photonic crystal membrane and embedded single InGaAs quantum dots. The response to high frequency mechanical vibration is measured for a series of quantum dots along the length of a photonic crystal waveguide for several flexural modes by optically driving the membrane while measuring high resolution time-resolved photoluminescence. The position-dependent response is similar to the measured and calculated displacement profile of the membrane but falls off less rapidly at higher frequencies. These results indicate potential for nanoscale strain sensing with high bandwidth and sensitivity.

A new type of high frequency mechanical vibration table

This paper puts forward a new type of mechanical vibration table. First of all, the structure and working principle of this vibration table is described. Then the kinetic equation and the three-dimensional model of the eccentric exciter are established, the simulation experiments are carried out, and the displacement curves, velocity curves and acceleration time curves at different frequencies are analyzed. Finally, finite element analysis of eccentric wheels is carried out based on solidwork2012. The simulation results show that the mechanical vibration of this new mechanical vibration table is achievable at 0-100 Hz.

Effects of low magnitude high frequency mechanical vibration combined with compressive force on human periodontal ligament cells in vitro.

Vibration can be used to accelerate tooth movement, though the exact mechanisms remain unclear. This study aimed to investigate the effects of low magnitude high frequency (LMHF) vibration combined with compressive force on periodontal ligament (PDL) cells in vitro. Human PDL cells were isolated from extracted premolar teeth of four individuals. To determine the optimal frequency for later used in combination with compressive force, three cycles of low-magnitude (0.3 g) vibrations at various frequencies (30, 60, or 90 Hz) were applied to PDL cells for 20 min every 24 h. To investigate the effects of vibration combined with compressive force, PDL cells were subjected to three cycles of optimal vibration frequency (V) or 1.5 g/cm2 compressive force for 48 h (C) or vibration combined with compressive force (VC). Cell viability was assessed using MTT assay. PGE2, soluble RANKL (sRANKL), and OPG production were quantified by ELISA. RANKL, OPG, and Runx2 expression were determined using real-time PCR. Cell viability was decreased in groups C and VC. PGE2 and RANKL, but not OPG, were increased in groups V, C, and VC, thus increasing the RANKL/OPG ratio. The highest level was observed in group VC. sRANKL was increased in groups V, C, and VC; however, no significant different between the experimental groups. Runx2 expression was reduced in groups C and VC. Vibration increased PGE2, RANKL, and sRANKL, but not OPG and Runx2. Vibration had the additive effects on PGE2 and RANKL, but not sRANKL in compressed PDL cells.

Investigation of Ti-6Al-4V alloy acoustic softening

High power ultrasonic vibration is widely used for improving manufacturing processes such as machining and metal forming. High frequency mechanical vibration affects material properties and friction forces in contacting surfaces. Flow stress reduction under superimposed ultrasonic vibration is called as acoustic softening. The amount of this parameter should be determined for ultrasonic assisted metal forming processes. For determination of this parameter for workhorse Ti-6Al-4V alloy, experimental setup was designed and fabricated. Then tensile test under longitudinal ultrasonic vibration was performed for different ultrasonic powers. Results show that ultrasonic vibration has considerable effect on plastic behavior of the alloy and decreases flow stress. Also, increasing ultrasonic power leads to higher acoustic softening. Yield stress reduction up to 9.52%, ultimate stress reduction up to 4.55% and elongation up to 13% were obtained at 340W ultrasonic power. After applying ultrasonic vibrations and its termination, hardness of specimens were measured in which increase up to 9% was observed.

Mechanical vibration may be a novel adjuvant approach to promoting stability and retention following orthodontic treatment

Introduction: Orthodontic tooth movement occurs as a consequence of paradental tissue remodeling in response to applied mechanical forces. Retention is a necessary procedure to prevent relapse when orthodontic appliances are removed. Developing new methods to promote stability and retention following orthodontic treatment has always been desired. Recent studies have demonstrated the favorable effects of low magnitude, high frequency (LMHF) mechanical vibration on bone homeostasis through an ability to stimulate cell metabolism and to enhance osteoblast proliferation, osteoblastic gene expression and bone formation. The Hypothesis: In this paper, we propose that LMHF mechanical vibration is a viable adjuvant method to accelerate bone and periodontal tissue remodeling, thereby promoting stability and shortening retention time. Evaluation of the Hypothesis: Much effort has been made to explore therapies to prevent relapse and shorten orthodontic retention time with limited success. LMHF mechanical vibration may be a promising approach to accelerate alveolar bone remodeling, ultimately promote stability and shorten retention time.

CRosser As First choice for crossing Totally occluded coronary arteries (CRAFT Registry): focus on conventional angiography and computed tomography angiography predictors of success

We investigated the use of the CROSSER catheter, a CTO crossing device based upon high frequency mechanical vibration, as a first resort to treat patients with chronic total occlusions (CTO) while describing angiographic and computed tomography coronary angiography (CTCA) serving as predictors for success. Eighty consecutive patients were enrolled in this prospective multicentre registry of patients treated for a CTO. For 76.3% of the patients, this was the first attempt to open the CTO. Overall success rate was 75%. By conventional coronary angiography, the length of the occlusion was 26.7±14.1 mm and there was a difference in successful vs. unsuccessful cases (24.5±13.9 and 32.8±13.1, p=0.02). The presence of angulation, as defined qualitatively, was more prevalent in failed cases (60.0% vs. 32.2%, p=0.03). The mean ratio CROSSER distance within the occlusion site and length of the occlusion showed a trend towards statistical significance in successful procedures (0.56±0.90 vs. 0.30±0.34, p=0.08). During hospitalisation, two patients had a non-fatal myocardial infarction. One patient experienced delayed onset of tamponade six hours postprocedure. At 30 days, two patients had PCI in a non-treated vessel and one patient had a transient ischaemic attack. Relation to the CROSSER catheter was inconclusive. The success rate of the use of a dedicated-CTO device--the CROSSER catheter--as a first choice to open a chronic total occlusion was 75%. By multivariate analysis, in a subset of patients that were imaged with computed tomography coronary angiography, the absence of angulation was related with higher success rate.

Mechanical effect of muscle spindles in the canine external intercostal muscles

High-frequency mechanical vibration of the ribcage increases afferent activity from external intercostal muscle spindles, but the effect of this procedure on the mechanical behaviour of the respiratory system is unknown. In the present study, we have measured the changes in external intercostal muscle length and the craniocaudal displacement of the ribs during ribcage vibration (40 Hz) in anaesthetized dogs. With vibration, external intercostal inspiratory activity increased by approximately 50 %, but the respiratory changes in muscle length and rib displacement were unaltered. A similar response was obtained after the muscles in the caudal segments of the ribcage were sectioned and the caudally oriented force exerted by these muscles on the rib was removed, thus suggesting that activation of external intercostal muscle spindles by vibration generates little tension. Prompted by this observation, we also examined the role played by the external intercostal muscle spindles in determining the respiratory displacement of the ribs during breathing against high inspiratory airflow resistances. Although resistances consistently elicited prominent reflex increases in external intercostal inspiratory activity, the normal inspiratory cranial displacement of the ribs was reversed into an inspiratory caudal displacement. Also, this caudal rib displacement was essentially unchanged after section of the external intercostal muscles, whereas it was clearly enhanced after denervation of the parasternal intercostals. These findings indicate that stretch reflexes in external intercostal muscles confer insufficient tension on the muscles to significantly modify the mechanical behaviour of the respiratory system.

Mechanical effect of muscle spindles in the canine external intercostal muscles.

High-frequency mechanical vibration of the ribcage increases afferent activity from external intercostal muscle spindles, but the effect of this procedure on the mechanical behaviour of the respiratory system is unknown. In the present study, we have measured the changes in external intercostal muscle length and the craniocaudal displacement of the ribs during ribcage vibration (40 Hz) in anaesthetized dogs. With vibration, external intercostal inspiratory activity increased by approximately 50 %, but the respiratory changes in muscle length and rib displacement were unaltered. A similar response was obtained after the muscles in the caudal segments of the ribcage were sectioned and the caudally oriented force exerted by these muscles on the rib was removed, thus suggesting that activation of external intercostal muscle spindles by vibration generates little tension. Prompted by this observation, we also examined the role played by the external intercostal muscle spindles in determining the respiratory displacement of the ribs during breathing against high inspiratory airflow resistances. Although resistances consistently elicited prominent reflex increases in external intercostal inspiratory activity, the normal inspiratory cranial displacement of the ribs was reversed into an inspiratory caudal displacement. Also, this caudal rib displacement was essentially unchanged after section of the external intercostal muscles, whereas it was clearly enhanced after denervation of the parasternal intercostals. These findings indicate that stretch reflexes in external intercostal muscles confer insufficient tension on the muscles to significantly modify the mechanical behaviour of the respiratory system.

Response of the canine inspiratory intercostal muscles to chest wall vibration.

High-frequency mechanical vibration of the rib cage reduces dyspnea, but the effect of this procedure on the respiratory muscles is largely unknown. In the present studies, we have initially assessed the electrical and mechanical response to vibration (40 Hz) of the canine parasternal and external intercostal muscles (third interspace) during hyperventilation-induced apnea. When the vibrator was applied to the segment investigated, prominent external intercostal activity was recorded in the seven animals studied, whereas low-amplitude parasternal intercostal activity was recorded in only four animals. Similarly, when the vibrator was applied to more rostral and more caudal interspaces, activity was recorded commonly from the external intercostal but only occasionally from the parasternal. The two muscles, however, showed similar changes in length. We next examined the response to vibration of the muscles in seven spontaneously breathing animals. Vibrating the rib cage during inspiration (in-phase) had no effect on parasternal intercostal inspiratory activity but induced a marked increase in neural drive to the external intercostals. For the animal group, peak external intercostal activity during the control, nonvibrated breaths averaged (mean +/- SE) 43.1 +/- 3.7% of the activity recorded during the vibrated breaths (p < 0.001). External intercostal activity during vibration also occurred earlier at the onset of inspiration and commonly carried on after the cessation of parasternal intercostal activity. Yet tidal volume was unchanged. Vibrating the rib cage during expiration (out-of-phase) did not elicit any parasternal or external intercostal activity in six animals. These observations thus indicate that the external intercostals, with their larger spindle density, are much more sensitive to chest wall vibration than the parasternal intercostals. They also suggest that the impact of this procedure on the mechanical behavior of the respiratory system is relatively small.

Reflex inhibition of canine inspiratory intercostals by diaphragmatic tension receptors.

1. Electrical stimulation of phrenic afferent fibres in the dog elicits a reflex inhibition of efferent activity to the inspiratory intercostal muscles. However, electrical stimulation has a poor selectivity, so the sensory receptors responsible for this inhibition were not identified. 2. In the present studies, cranial forces were applied during spontaneous inspiration to the abdominal surface of the central, tendinous portion of the canine diaphragm to activate tension mechanoreceptors in the muscle. Vagal afferent inputs were eliminated by vagotomy. 3. The application of force to the central tendon caused a graded, reflex reduction in inspiratory intercostal activity, especially in external intercostal activity. This reduction was commonly associated with a decrease in inspiratory duration and was invariably attenuated after section of the cervical dorsal roots. 4. In contrast, no change in inspiratory intercostal activity was seen when high frequency mechanical vibration was applied to the central tendon to stimulate diaphragmatic muscle spindles. 5. These observations provide strong evidence that tension receptors in the diaphragm, but not muscle spindles, induce reflex inhibition of inspiratory intercostal activity. The expression of this reflex probably involves supraspinal structures.