Train Velocity Research Articles

Research on aerodynamic characteristics of high-velocity train bogies

The bogie is a critical component of high-velocity trains. As train velocity rises, the operational quality is increasingly influenced by aerodynamic forces. The aerodynamic characteristics of bogies significantly impact the safety of train operations. This article examines a real high-velocity train model, constructing a 3-group train model, and developing a mathematical model of high-velocity train operation on open lines. Using three-dimensional steady-state Navier–Stokes equations, the flow field characteristics, pressure spread, aerodynamic forces, and torque characteristics on the bogie and body of high-velocity locomotives operating at velocities of 200 km/h, 250 km/h, 300 km/h, and 350 km/h are calculated, with measurement spots set to study the trend of pressure variation with train velocity. The research findings indicate that pressure at the same location on the body surface rises with vehicle velocity, with a quadratic link between the two. The uneven pressure spread between two bogies of the same vehicle and between two axles of the same bogie indicates that aerodynamic forces can cause axle load transfer in high-velocity trains. The highest values of aerodynamic resistance and lift happen at the front bogie, and the resistance and lift of both a single carriage and the entire vehicle increase with velocity, following a quadratic relationship. The highest nodding torque of the train body occurs on one vehicle, while the highest nodding torque of the bogie occurs on the 6th bogie, with both torques increasing with velocity, also in a quadratic relationship.

A novel method for reducing the effect of doppler frequency shift in high-speed railway mobile communication using machine learning

Currently, high-speed railway systems are rapidly expanding worldwide, necessitating reliable and efficient mobile communication solutions. However, the Doppler frequency shift caused by the high speeds of trains presents significant challenges to communication systems, particularly those using OFDM in LTE. This paper presents a novel for Doppler frequency compensation in high-speed railway communication based on the results of estimating the train's velocity using machine learning algorithms. By leveraging advanced algorithm such as neural networks, our method dynamically predicts and compensates for Doppler shifts in real-time. In this proposed novel, the Doppler frequency value is calculated based on the actual train’s velocity and the scenario of a high-speed railway, then the Doppler frequency is used to compensate the carrier frequency offset (CFO) directly at the Access Point (AP) device on the train. We conduct simulations to evaluate the effectiveness of our proposed solution in a high-speed railway scenario. The results demonstrate a marked improvement in communication reliability and data integrity, highlighting the potential of machine learning to enhance the performance of mobile communication systems in high-speed railways. The results of the proposed model are evaluated based on the system’s bit error rate BER after the CFO compensation decreases and the ratio of average energy per bit (Eb) to noise power density (N0) (Eb/N0) increases. This shows that the proposed solution works effectively and reduces the system’s bit errors while improving the communication performance. This study opens new avenues for integrating intelligent systems in transportation networks, ensuring seamless connectivity, and improving passenger experience

Prediction of fatigue life of a bolted joint in railway steel arch bridge using multiaxial fatigue criteria

Fatigue represents a critical condition for infrastructure subjected to repeated cyclic loads, such as steel railway bridges. The literature offers several methods to estimate fatigue life, consisting of three main phases: cycle counting, fatigue damage criterion, and damage accumulation criterion. Applying S-N curves might not be conservative in the case of railway bridges subjected to traffic because the stress-time history is complex and cannot be reduced to a sinusoidal history. Additionally, the presence of a multiaxial stress state must be considered. Therefore, this work compares eight multiaxial fatigue damage criteria for evaluating fatigue life in a scenario between high and low-cycle fatigue. Specifically, the authors considered four low-cycle fatigue criteria, namely Smith–Watson–Topper (SWT), Kandil, Brown and Miller (KBM), Glinka, Fatemi and Socie (FS), and four high-cycle fatigue criteria, Crossland, Basquin and the methods recommended by Eurocode 3 and British Standard. The rainflow counting method in ASTM E1049-85 (2011) and Miner’s rule for damage accumulation were used. The Polcevera railway steel bridge was selected as a case study. A 3D numerical model was developed for this purpose using Midas Civil software, taking into account the material non-linearity of the bridge’s elements. Once the area with the highest stress concentration was identified, a detailed analysis was conducted to estimate the stress and strain time histories induced by train traffic. A sensitivity analysis was conducted after critically comparing the eight methods for predicting fatigue life to assess the impact of traffic parameters, train velocity, axle load, and convoy length on fatigue life. It has been found that the criteria considering axial stress tend to overestimate the number of fatigue cycles to failure compared to the criteria, including the effect of shear stress components.

Study on the misalignment deformation threshold of girder end of curved bridge with ballasted track

When a train traverses a curved bridge, it inherently tends to shift laterally outward. To counteract this propensity, the strategy of track superelevation is employed. After earthquake, curved bridges may exhibit diverse degrees of residual deformation. The precise failure mechanisms that compromise train safety and passenger comfort during transit over curved bridges, particularly under the combined influence of residual deformation, centrifugal force, and track superelevation, remain not entirely comprehended. A comprehensive system integrating trains with curved track-bridges is developed to examine the impact of girder end misalignments on residual track irregularities. The analysis concentrated on the dynamic time-history responses of trains traversing bridges featuring girder misalignments, exploring a range of amplitudes, train velocities, and curve radii. The findings revealed significant variances in the dynamic train responses, especially in lateral acceleration and the Nadal index, when contrasting centripetal and centrifugal girder side misalignments. Furthermore, it is discerned that lateral misalignment at the girder ends markedly affects train lateral acceleration and the Nadal index, with a relatively minor influence on other dynamic response metrics. Finally, the thresholds for misalignment deformation were summarized, for curve radii of 800, 1000, and 1200 meters, the comfort deformation thresholds at 100 km/h are determined to be 23, 23, and 20 mm respectively, while the safety deformation thresholds are found to be 26, 30, and 38 mm respectively. At a speed of 120 km/h, the comfort deformation thresholds for the same curve radii are 18, 18, and 15 mm, with the safety deformation thresholds at 12, 15, and 21 mm.

CFD-DEM modelling of particle entrainment in wheel–rail interface: a parametric study on train characteristics

Rail-sanding is employed to improve the train’s wheel–rail traction loss in low adhesion conditions. This can significantly impede trains’ kinematics, operation, and performance by hindering the train’s acceleration and deceleration, resulting in delays and unreliability of transport system as well as causing safety risks and in the worst cases train collisions. Rail-sanding has its own merits in recovering the wheel–rail traction but can result in a sand wastage of more than 80% due to its low sand entrainment efficiency. In this research, computational fluid dynamics is coupled to discrete element modelling to study the behaviour of sand particles during rail-sanding. A parametric study based on the train characteristics, including train velocity, sand flow rate, and the geometry of the sander nozzle, is performed by comparing the entrainment efficiency of the sand particles. It is found that train velocities over 30 m/s result in the entrainment efficiency of almost zero. A moving air layer generated at the wheel–rail interface influences the lower bound of acceptable particle size range. The flow rate and nozzle geometry can be designed to enhance entrainment efficiency.

Comparison of the effects of isokinetic and isotonic strength training in team sport athletes: A randomized controlled trial

Athletes may benefit from isokinetic training (IK) to improve strength and jump performance. Previous studies comparing IK methods to isotonic resistance training (IT) have utilized high-repetition protocols and a Dynamometer, which are usually reserved for laboratory or rehabilitation settings.This study compared effects of IK and IT using ≤ 6 repetitions on strength and jump performance in 50 male, team-sport athletes (ages 18–35) during COVID-19 lockdown using the commercially-available TechnoGym BioCircuit Dynamometer. This 4-group randomized parallel study assessed the effects of an 8-week isokinetic at 80°/s (IK80; n = 16) and 25°/s (IK25; n = 12) or isotonic training program (IT; n = 15) compared to a control group (CG; n = 7) on anthropometric measurements, peak torque at 80°/s (PT80) and 25°/s (PT25), one-repetition maximum (1-RM) leg extension, and countermovement (CMJ) and squat jump height (SJ).Anthropomorphic data showed minimal differences between groups post-intervention. Strength increased in IT, and IK25 compared to CG, with no difference between intervention groups. SJ increased in all groups compared to the control group, with differences between groups. Counter movement jump (CMJ) improved only in IT and IK80 with no between-group difference.These results do support the hypothesis that low-repetition IK and IT can be used to effectively improve strength and jump performance in athletic populations. However, the efficacy of IK on CMJ depends on training velocity and repetition range, with a higher velocity training protocol (80°/s) being more effective for jump performance and lower speeds potentially more useful for improving maximal strength (25°/s).

Non-linear influences of track dynamic irregularities on vertical levelling loss of heavy-haul railway track geometry under cyclic loadings

Abstract With an emphasis on the combined degradation of railway track geometry and components, a new numerical-analytical method is proposed for predicting the track geometrical vertical levelling loss (VLL). In contrast to previous studies, this research unprecedentedly considers the influence of initial track irregularities (ITI) on VLL under cyclic loadings, elastic-plastic behaviour, and different operational dynamic conditions. The non-linear numerical models are simulated using an explicit finite element package known as LS-Dyna, and their results are validated by full-scale experimental and field measurement data. The outcomes are iteratively regressed by an analytical logarithmic function that cumulates permanent settlements, which innovatively extends the effect of ITI on VLL in a long-term behaviour. For a typical heavy-haul railway operating under 30 tons axle load and 60 km/h train velocity, the result indicates that the set of ITI with the highest standard deviation (SD) of vertical profile (VP) degrades faster (37% on average) than that with the lowest SD. Additionally, our new findings reveal that the worst scenario is related to a train running at 60 km/h and carrying a load of 20 tons/axle in an uneven track whose SD of VP evolves from 3.23 mm at N = 0 (ITI) to 7.20 mm, whereas the best one corresponds to a train at 60 km/h and 30 ton axle load in an uneven track whose SD of VP downgrades from 0.48 to 1.50 mm, both at 3 M cycles (or 60 million gross tons). These findings indicate the importance of considering the ITI for predicting track geometrical VLL under cyclic loadings. Therefore, based on this research, an acceptable condition (thresholds) of ITI can be redefined for a minimum effect on VLL, which can support the development of practical maintenance guidelines to extend the railway track service life.

One-dimensional analysis of pressure variations induced by trains passing each other in a tunnel

In this study, the asymptotic solutions of the pressure variations induced by two trains passing each other in a tunnel are theoretically investigated. The one-dimensional inviscid compressible airflow is analysed, and two methods to obtain numerically exact solutions and $M_{H}$ expansion formulas for approximate equations are presented, where $M_{H}$ is the Mach number of the high-speed train. The pressure coefficient, corresponding to the maximum value of the magnitude of the pressure, is expressed as $|c_{p}|_{max}=|c_{p,min}|=[({R}/({1-R}))$ $(1+\alpha )^{2}+({R(1-R)}/{(1-2R)^{2}})(1-\alpha )^{2}]+O[M_{H}]$ , where $c_{p,min}<0$ , $\alpha =U_{L}/U_{H}$ and $U_{L}$ and $U_{H}$ denote the speeds of the low- and high-speed trains, respectively, and $R$ is the cross-sectional area ratio of the train to the tunnel. The theoretical results indicate the dependence of the speeds of the two trains on the pressure distribution and that the maximum magnitude of the asymptotic pressure for a fixed value of $M_{H}$ is obtained for $\alpha =1$ and $\alpha =0$ when $R< R_{c}$ and $R>R_{c}$ , respectively, where $R_{c}$ denotes the critical blockage ratio. Because the airflow along the side of the low-speed train, induced by the low-speed train, is along the running direction of the high-speed train and reduces the relative velocity of the high-speed train as the two trains pass each other, $|c_{p}|_{max}$ for $\alpha =0$ is larger than $|c_{p}|_{max}$ for $\alpha =1$ when $R>R_{c}$ . It is theoretically demonstrated that, as conventional high-speed railway systems satisfy $R< R_{c}$ , a conservative pressure estimation can be established assuming $\alpha =1$ .

Seismic and vibration control of segmented isolation layer in underground structure-diaphragm wall system

In this paper, a seismic and vibration reduction measure of subway station is developed by setting a segmented isolation layer between the sidewall of structure and the diaphragm wall. The segmented isolation layer consists of a rigid layer and a flexible layer. The rigid layer is installed at the joint section between the structural sidewall and slab, and the flexible layer is installed at the remaining sections. A diaphragm wall-segmented isolation layer-subway station structure system is constructed. Seismic and vibration control performance of the diaphragm wall-segmented isolation layer-subway station structure system is evaluated by the detailed numerical analysis. Firstly, a three-dimensional nonlinear time-history analysis is carried out to study the seismic response of the station structure by considering the effect of different earthquake motions and stiffness of segmented isolation layer. Subsequently, the vibration response of site under training loading is also studied by considering the influence of different train velocities and stiffness of the segmented isolation layer. Numerical results demonstrate that the diaphragm wall-segmented isolation layer-subway station structure system can not only effectively reduce the lateral deformation of station structure, but also reduce the tensile damage of the roof slab. On the other hand, the developed reduction measure can also significantly reduce the vertical peak displacements of site under training loading.

A simplified weak coupling dynamic analysis method for running safety evaluation of train on bridges under earthquake excitation

This study proposes a simplified analysis method that couples the bridge and train-track subsystem in a weak form to facilitate the dynamic analysis of the train-track-bridge coupled system (TTBS) under earthquakes. The method includes three main steps: (i) performing dynamic analysis of the bridge under seismic conditions to obtain the response of the bridge deck; (ii) interpolating the bridge displacement beneath each wheelset based on the train's velocity, departure time, and the initial positions of the wheelsets; and (iii) assessing the running safety of the train by incorporating the interpolated bridge response as track irregularity into the train-track coupled system. Steps (i) and (iii) can be analyzed separately using finite element and multibody dynamics software, eliminating the need to create a complex TTBS model that is challenging to achieve within a single software platform. Additionally, based on the method’s assumptions, the earthquake excitation on the train can be separated into the seismic inertial effect and seismic-induced bridge deformation, enabling a quantitative analysis of the impact of these two types of excitations on train safety. Taking a 10-span simply supported bridge and a long-span cable-stayed bridge as examples, the proposed method’s assumptions are verified by comparing its results with those obtained from a complex TTBS model. Furthermore, the impact characteristics of inertial effects and seismic-induced bridge deformation on train safety for these two types of bridges are analyzed. The proposed method offers robust support for seismic design of bridges and facilitates a comprehensive analysis of the mechanisms through which seismic excitations affect train safety.

Technical Feasibility of a Hydrail Tram–Train in NA: Okanagan Valley Electric Regional Passenger Rail (OVER PR)

Booming population and tourism have increased congestion, collisions, climate-harming emissions, and transport inequities in The Okanagan Valley, Canada. Surveys suggest that over 30% of residents would shift from cars back to public transit and intercity tram–trains if regional service and connections were improved. Intercity streetcars (aka light-rail tram–trains) have not run in Canada since their replacement in the 1950′s by the national highway system. UBC researchers analyzed a tram–train service fashioned after the current Karlsruhe model but powered by zero-emission hydrogen fuel cell/battery hybrid rail power (hydrail) technology, along a 342 km route between Osoyoos, B.C. at the US Border and Kamloops, B.C., the Canadian VIA rail hub. Hydrail trains have operated successfully since 2018 in Germany and were demonstrated in Quebec, Canada in 2023. However, hydrail combined with tram–train technology has never been tried in Canada. Single-train simulations (STSs) confirmed its technical feasibility, showing a roughly 8 h roundtrip travel time, at an average train velocity of 86 km/h. Each hydrail tram–train consumed 2400 kWh of energy, translating to 144 kg of hydrogen fuel per roundtrip. In total, five tons of H2/day would be consumed over 16 h daily by the 16-tram–train-vehicle fleet. The results provide valuable insights into technical aspects and energy requirements, serving as a foundation for future studies and decision-making processes in developing zero-emission passenger tram–train services not just for Okanagan Valley communities but all of Canada and NA.

Simplified method to detect resonance effects in railway bridges. Viaduct over Aragón River and Almonte bridge application

Detecting resonant effects in bridges has been studied for many years, but it has only been solved in a closed form for simple bridges. This article presents a simplified method that enables the calculation of resonance velocities in all types of bridges in an easy manner. The method is based on the concept of dynamic influence line and is validated through finite element models. These models range from simply supported bridges to complex real bridges such as the Almonte Viaduct, the world’s longest arch bridge of its typology. In the real bridge models, a dynamic analysis is performed according to the Eurocode to identify train velocities that induce resonant effects, and these velocities are checked against the simplified method with very good results.

Numerical study on wind-loading characteristics of a high-speed train running over the bridge under tornado-like vortices

With global warming intensifying, weather patterns become more volatile and extremes more common. Tornadoes are the most destructive natural disasters causing significant damage to infrastructure. Meanwhile, high-speed railways now face greater risks from tornado events as the national railway network and mass transit trains expand. Thus, studying the tornado flow characteristics and associated effects on high-speed trains is necessary. A study is presented regarding the wind-loading characteristics of a high-speed train running over a railway bridge induced by a tornado belonging to the future railway network. The wind-loading characteristics analyses are performed using the improved delayed detached eddy simulation method. After verifying the numerical approach and mesh strategy, computational studies are conducted to produce a tornado-like vortex and investigate the tornado-induced wind-loading characteristics of a high-speed train running on the bridge by combining a tornado simulation with a moving mesh technique. For the wind-loading parameters studied herein, the selected train's velocity range is between 50 and 350 km/h, the typical operation speed of either regular or high-speed trains. The numerical results show that the time histories of aerodynamic forces on the train revealed a pattern in tornadic flow variability, the time evolutions of the wind loads on the train were affected by train speeds, and the fluctuation was the greatest when the train ran at 50 km/h. Moreover, the train is subjected to larger aerodynamic forces and moments when it operates along with the rotating vortex flow, especially in the core region, and the train is more dangerous when it runs at a lower speed. The results in this study provide references for assessing operation safety, while a train running on the bridge encounters tornadoes.

NUMERICAL METHODS OF HYDRO-DYNAMIC COUPLING IN SATURATED SOIL AND ITS APPLICATION TO RAILWAY ENGINEERING

Recent field case study shows that the roadbed of ballastless high-speed railway experienced water-induced defect such as excessive fines pumping and even local subgrade-track contact loss affecting the normal operation of highspeed train due to water immersion through gaps of waterproof materials in expansion joints between the concrete base, particularly in rainy seasons. However, the study about the dynamic behavior of high-speed railway subgrade involving water is currently rare. Based on the theory of fluid dynamics in porous medium and the vehicle-track coupling vibration theory, a numerical method of hydraulic-dynamic coupling was established to evaluate the dynamic responses of saturated roadbed surface layer under the high-speed train loading with the validation by comparing the calculated values and field data. The temporal and spatial characteristics of dynamic behaviors (stress, pore water pressure, seepage velocity, displacement) of saturated roadbed surface layer are fully discussed. Also, the effects of train velocity, permeability, on aforementioned dynamic responses of the saturated roadbed surface layer are evaluated. The study shows that improving the drainage of ballastless track roadbed has a significant effect on minimizing the mud pumping of ballastless track, and the influence zone of hydraulic-mechanical coupling is mainly within 0.1 m of the roadbed.

Effectiveness of Tap Water in Reducing the Generation of Ultrafine Wear Particles from the Wheel-Rail Contact by Eliminating the Water Vapor Effect.

This study aimed to assess the impact of tap water application on reducing the generation of ultrafine particles from the wheel-rail contact using a twin-disk rig under dry and wet conditions, with train velocities of 45 and 80 km/h. A small amount of 0.3 L/min tap water was applied at the wheel-rail contact, and a diffusion dryer was used to eliminate water vapor. The Fast Mobility Particle Sizer measured the number concentration (NC) of nano-sized wear particles in the range of 6 to 560 nm. The tap water application method effectively reduced the NC of ultrafine and fine particles by 67-72% and 86-88%, respectively. Positive reduction rates were observed for all diameters at 45 km/h and for most diameters, except for approximately 70 nm and 80 nm, at 80 km/h. Even with a small amount of water, this approach successfully decreased nano-sized wear particle generation. However, the potential influence of mineral crystals in tap water on NC requires further investigation. Overall, this method shows promise for enhancing air quality and public health by mitigating nano-sized wear particle generation in subway systems.

Vibration energy transmission in high-speed train-track-bridge coupled systems

This paper investigates the vibration energy transmission characteristics of high-speed train-track-bridge coupled systems based on a high-speed railway in China. A coupled system composed of a CRH380A high-speed train, CRTS II slab ballastless track, and standard 32-meter girder bridge was analyzed through hybrid simulations that integrated multi-body dynamics and finite element analysis. The hybrid model included the interactions between the train, track, and bridge of the coupled system as well as track irregularity. The vibration energy of the coupled system was quantitatively investigated under various train velocities. The effects of key variables of ballastless track and bridge on energy transmission characteristics were evaluated. The studied variables included fastener stiffness, fastener damping, mortar layer stiffness, bridge cross section, and bridge damages. The results show that these variables have significant effects on vibration energy transmission, suggesting that it is important to consider these variables in the design and operation of high-speed railways.

Stiffness profile spectral composition & geometry deterioration of railway tracks

This work addresses the contribution of the wavelength composition of the spectrum of the rail support stiffness profile to the expected long-term settlement. To that aim, purely harmonic stiffness variations of different wavelength are studied. The frequency-domain model with a double periodicity level previously developed by the first and last authors is adopted to embed the stiffness profile in one of the periodicity layers. Additional resonance velocities at which the resonance frequency of the track system coincides with the support-passing frequency or its multiples are found. The susceptibility to degradation is assessed both by quantifying the mechanical energy dissipated in the substructure under a moving train axle within one wavelength of the support stiffness variation, and the work performed by the wheel-rail contact force. It is shown that shorter wavelengths and larger standard deviations of varying ballast/subgrade stiffness result in an increasing energy dissipation in the substructure, and increase the work performed by the wheel-rail contact force, therefore leading to a reduced lifetime of the track. The energetic quantities increase for lower mean values of the stiffness profile, confirming the proneness of tracks on soft soils to degradation. The influence of varying stiffness vanishes for wavelengths of approximately 16 times the sleeper span, which is equivalent to a track length of about 10 m. High railpad stiffness values result in increased energy dissipation but the influence is limited. In general, an increasing train velocity amplifies the rate of track degradation, with no stabilizing trend in the high-speed regime (300 km/h).

Cooperative Reference Velocity Regulation Control for Virtual Coupling Systems of Heavy-Haul Trains

Virtual coupling systems are important for improving the safety and efficiency of heavy-haul trains by coordinating the velocities of heavy-haul trains. However, the set point change of reference velocity leads to unsafe train operation. To address this issue, in this paper, a cooperative reference velocity regulation control method is proposed for virtual coupling systems of heavy-haul trains, which can smoothly adjust the train velocity during the operation process. Firstly, the heavy-haul trains are characterized by a cyber-physical model, where the physical layer models the longitudinal dynamics of the trains, while the cyber layer represents the communication topology of the trains using graph theory. Secondly, a cooperative control law is designed to achieve velocity consensus and maintain a safe distance between adjacent trains. The set point modulation method is utilized to smoothly adjust the reference velocity of heavy-haul trains, suppressing velocity fluctuations of heavy-haul trains. The proposed approach is validated through extensive simulations under acceleration and deceleration conditions. Simulation results verify that the proposed method can significantly reduce the velocity fluctuations during the operation of virtual coupling systems when compared with the classical cooperative control method.

Methods for calculating aerodynamics inside high-speed railway tunnel lining cracks and predicating stress intensity factors

PurposeThis study aims to propose a series of numerical and surrogate models to investigate the aerodynamic pressure inside cracks in high-speed railway tunnel linings and to predict the stress intensity factors (SIFs) at the crack tip.Design/methodology/approachA computational fluid dynamics (CFD) model is used to calculate the aerodynamic pressure exerted on two cracked surfaces. The simulation uses the viscous unsteady κ-ε turbulence model. Using this CFD model, the spatial and temporal distribution of aerodynamic pressure inside longitudinal, oblique and circumferential cracks are analyzed. The mechanism behind the pressure variation in tunnel lining cracks is revealed by the air density field. Furthermore, a response surface model (RSM) is proposed to predict the maximum SIF at the crack tip of circumferential cracks and analyze its influential parameters.FindingsThe initial compression wave amplifies and oscillates in cracks in tunnel linings, resulting from an increase in air density at the crack front. The maximum pressure in the circumferential crack is 2.27 and 1.76 times higher than that in the longitudinal and oblique cracks, respectively. The RSM accurately predicts the SIF at the crack tip of circumferential cracks. The SIF at the crack tip is most affected by variations in train velocities, followed by the depth and length of the cracks.Originality/valueThe mechanism behind the variation of aerodynamic pressure in tunnel lining cracks is revealed. In addition, a reliable surrogate model is proposed to predict the mechanical response of the crack tip under aerodynamic pressures.

Intentionally Slow Concentric Velocity Resistance Exercise and Strength Adaptations: A Meta-Analysis.

Hermes, MJ and Fry, AC. Intentionally slow concentric velocity resistance exercise and strength adaptations: a meta-analysis. J Strength Cond Res 37(8): e470-e484, 2023-Intentionally slow-velocity resistance exercise (ISVRE) is suggested by some to be equally or more effective than fast or traditional velocities for increasing muscular strength. The purpose of this meta-analysis was to assess the effect ISVRE has on strength adaptations compared with faster or traditional velocities, with subgroup analyses exploring age, sex, and training status as confounding factors on the influence of velocity on strength adaptation. Eligible studies (n = 24) were required to be chronic (multiple weeks) randomized or nonrandomized comparative studies using dynamic constant external resistance for training and testing, and pre-post strength assessments. All studies examined healthy individuals (n = 625; fast or traditional n = 306, intentionally slow n = 319). A random-effects meta-analysis indicated a significant (p ≤ 0.05) effect in favor of fast training (effect size [ES] = 0.21, 95% confidence interval [CI] = 0.02-0.41, p = 0.03). Publication bias was noted through trim and fill analysis, with an adjusted effect size estimate of 0.32 (p < 0.001). Subgroup analyses indicated no difference between trained and untrained subjects (QM = 0.01, p = 0.93), and no difference between older and younger subgroups (QM = 0.09, p = 0.77), despite younger favoring faster (ES = 0.23, p = 0.049) and older not favoring either velocity (ES = 0.16, p = 0.46). Subgroup analysis also indicated women favored faster training (ES = 0.95, p < 0.001) in comparison to men (ES = 0.08, p = 0.58). Contrary to some previous reviews, these results indicate that chronic fast or traditional velocity resistance exercise increases muscular strength to a greater degree than ISVRE training. Resistance training velocity must be considered if strength is a desired outcome.