Validity and Reliability of Methods to Determine Barbell Displacement in Heavy Back Squats: Implications for Velocity-Based Training

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

ABSTRACT

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.

The placement of linear transducers affects the magnitude but not the intra-session reliability of kinematic variables during the bench press exercise

BACKGROUND: While linear transducers are the most accurate velocity monitoring devices, the horizontal motion of the barbell seems to affect its measurement error. OBJECTIVE: To explore the effect of cable inclination of the GymAware and T-Force linear transducers on the intra-session reliability and magnitude of kinematic variables during the Smith machine bench press exercise. METHODS: Twenty-eight resistance-trained males performed 2 blocks of 12 repetitions (4 repetitions at 40-60-80%1RM). In half of the repetitions with each load the two measuring systems were either vertically aligned with the barbell or positioned 15-cm away from the vertical projection of the barbell. RESULTS: Displacement and mean velocity variables were recorded with a high and comparable intra-session reliability regardless of the cable position and measuring system (CV=𝑟𝑎𝑛𝑔𝑒 1.79–8.38%; ICC=𝑟𝑎𝑛𝑔𝑒 0.69–0.98). The inclined cable position provided a lower displacement and mean velocity than the vertical cable position and the differences were comparable using both the GymAware (⩽ 1.52 cm; ⩽ 0.05 m⋅s-1) and T-Force (⩽ 1.53 cm; ⩽ 0.04 m⋅s-1). CONCLUSIONS: These results indicate that repeatable findings of kinematic variables can be obtained regardless of the cable position, but for comparative purposes, the cable position should remain constant from the start to the end of the lifts.

Validity of the bench press one-repetition maximum test predicted through individualized load-velocity relationship using different repetition criteria and minimal velocity thresholds

BACKGROUND: More practical and less fatiguing strategies have been developed to accurately predict the one-repetition maximum (1RM). OBJETIVE: To compare the accuracy of the estimation of the free-weight bench press 1RM between six velocity-based 1RM prediction methods. METHODS: Sixteen men performed an incremental loading test until 1RM on two separate occasions. The first session served to determine the minimal velocity threshold (MVT). The second session was used to determine the validity of the six 1RM prediction methods based on 2 repetition criteria (fastest or average velocity) and 3 MVTs (general MVT of 0.17 m⋅s-1, individual MVT of the preliminary session, and individual MVT of the validity session). Five loads (≈ 2540557085% of 1RM) were used to assess the individualized load-velocity relationships. RESULTS: The absolute difference between the actual and predicted 1RM were low (range = 2.7–3.7%) and did not reveal a significant main effect for repetition criterion (P= 0.402), MVT (P= 0.173) or their two-way interaction (P= 0.354). Furthermore, all 1RM prediction methods accurately estimated bench press 1RM (P⩾ 0.556; ES ⩽ 0.02; r⩾ 0.99). CONCLUSIONS: The individualized load-velocity relationship provides an accurate prediction of the 1RM during the free-weight bench press exercise, while the repetition criteria and MVT do not appear to meaningfully affect the prediction accuracy.

Validity and Effects of Placement of Velocity-Based Training Devices

Velocity-based training (VBT) is a resistance training method by which training variables are manipulated based on kinematic outcomes, e.g., barbell velocity. The better precision for monitoring and manipulating training variables ascribed to VBT assumes that velocity is measured and communicated correctly. This study assessed the validity of several mobile and one stationary VBT device for measuring mean and peak concentric barbell velocity over a range of velocities and exercises, including low- and high-velocity, ballistic and non-ballistic, and plyometric and non-plyometric movements, and to quantify the isolated effect of device attachment point on measurement validity. GymAware (r = 0.90-1, standard error of the estimate, SEE = 0.01-0.08 m/s) and Quantum (r = 0.88-1, SEE = 0.01-0.18 m/s) were most valid for mean and peak velocity, with Vmaxpro (r = 0.92-0.99, SEE = 0.02-0.13 m/s) close behind. Push (r = 0.69-0.96, SEE = 0.03-0.17 m/s) and Flex (r = 0.60-0.94, SEE = 0.02-0.19 m/s) showed poorer validity (especially for higher-velocity exercises), although typical errors for mean velocity in exercises other than hang power snatch were acceptable. Effects of device placement were detectable, yet likely small enough (SEE < 0.1 m/s) to be negligible in training settings.

Concurrent Validity of Field-Based Diagnostic Technology Monitoring Movement Velocity in Powerlifting Exercises

ABSTRACT

Mitter, B, Hölbling, D, Bauer, P, Stöckl, M, Baca, A, and Tschan, H. Concurrent validity of field-based diagnostic technology monitoring movement velocity in powerlifting exercises. J Strength Cond Res 35(8): 2170-2178, 2021-The study was designed to investigate the validity of different technologies used to determine movement velocity in resistance training. Twenty-four experienced powerlifters (18 male and 6 female; age, 25.1 ± 5.1 years) completed a progressive loading test in the squat, bench press, and conventional deadlift until reaching their 1 repetition maximum. Peak and mean velocity were simultaneously recorded with 4 field-based systems: GymAware (GA), FitroDyne (FD), PUSH (PU), and Beast Sensor (BS). 3D motion capturing was used to calculate specific gold standard trajectory references for each device. GA provided the most accurate output across exercises (r = 0.99-1, ES = -0.05 to 0.1). FD showed similar results for peak velocity (r = 1, standardized mean bias [ES] = -0.1 to -0.02) but considerably less validity for mean velocity (r = 0.92-0.95, ES = -0.57 to -0.29). Reasonably valid to highly valid output was provided by PU in all exercises (r = 0.91-0.97, ES = -0.5 to 0.28) and by BS in the bench press and for mean velocity in the squat (r = 0.87-0.96, ES = -0.5 to -0.06). However, BS did not reach the thresholds for reasonable validity in the deadlift and for peak velocity in the squat, mostly due to high standardized mean bias (ES = -0.78 to -0.63). In conclusion, different technologies should not be used interchangeably. Practitioners who require negligible measurement error in their assessment of movement velocity are advised to use linear position transducers over inertial sensors.

Validity and Reliability of the Inertial Measurement Unit for Barbell Velocity Assessments: A Systematic Review

The use of inertial measurement unit (IMU) has become popular in sports assessment. In the case of velocity-based training (VBT), there is a need to measure barbell velocity in each repetition. The use of IMUs may make the monitoring process easier; however, its validity and reliability should be established. Thus, this systematic review aimed to (1) identify and summarize studies that have examined the validity of wearable wireless IMUs for measuring barbell velocity and (2) identify and summarize studies that have examined the reliability of IMUs for measuring barbell velocity. A systematic review of Cochrane Library, EBSCO, PubMed, Scielo, Scopus, SPORTDiscus, and Web of Science databases was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. From the 161 studies initially identified, 22 were fully reviewed, and their outcome measures were extracted and analyzed. Among the eight different IMU models, seven can be considered valid and reliable for measuring barbell velocity. The great majority of IMUs used for measuring barbell velocity in linear trajectories are valid and reliable, and thus can be used by coaches for external load monitoring.

Velocity Loss Thresholds Reliably Control Kinetic and Kinematic Outputs during Free Weight Resistance Training

Exercise velocity and relative velocity loss thresholds (VLTs) are commonly used in velocity-based resistance training. This study aims to quantify the between-day reliability of 10%, 20%, and 30% VLTs on kinetic and kinematic outputs, changes in external load, and repetition characteristics in well-trained athletes. Using a repeated, counter-balanced crossover design, twelve semi-professional athletes completed five sets of the back squat with an external load corresponding to a mean concentric velocity of ~0.70 m·s^-1 and a VLT applied. The testing sessions were repeated after four weeks of unstructured training to assess the long-term reliability of each VLT. A coefficient of variation (CV) <10% was used to classify outputs as reliable. Kinetic and kinematic outputs and external load were largely reliable, with only peak power during sets 2-5 within the 10% VLT condition demonstrating a CV >10% (CV: 11.14-14.92%). Alternatively, the repetitions completed within each set showed large variation (CV: 18.92-67.49%). These findings demonstrate that by utilizing VLTs, kinetic and kinematic outputs can be prescribed and replicated across training mesocycles. Thus, for practitioners wishing to reliably control the kinetic and kinematic stimulus that is being applied to their athletes, it is advised that a velocity-based approach is used.

Validation of Inertial Sensor to Measure Barbell Kinematics across a Spectrum of Loading Conditions

The aim of this study was to evaluate the level of agreement in measuring back squat kinematics between an inertial measurement unit (IMU) and a 3D motion capture system (3DMOCAP). Kinematic variables included concentric peak velocity (CPV), concentric mean velocity (CMV), eccentric peak velocity (EPV), eccentric mean velocity (EMV), mean propulsive velocity (MPV), and POP-100: a proprietary variable. Sixteen resistance-trained males performed an incrementally loaded one repetition maximum (1RM) squat protocol. A series of Pearson correlations, 2 × 4 RM ANOVA, Cohen’s d effect size differences, coefficient of variation (CV), and standard error of the estimate (SEE) were calculated. A large relationship existed for all variables between devices (r = 0.78–0.95). Between-device agreement for CPV worsened beyond 60% 1RM. The remaining variables were in agreement between devices with trivial effect size differences and similar CV magnitudes. These results support the use of the IMU, regardless of relative intensity, when measuring EMV, EPV, MPV, and POP-100. However, practitioners should carefully select kinematic variables of interest when using the present IMU device for velocity-based training (VBT), as certain measurements (e.g., CMV, CPV) do not possess practically acceptable reliability or accuracy. Finally, the IMU device exhibited considerable practical data collection concerns, as one participant was completely excluded and 13% of the remaining attempts displayed obvious internal error.

Reliability of technologies to measure the barbell velocity: Implications for monitoring resistance training

This study investigated the inter- and intra-device agreement of four new devices marketed for barbell velocity measurement. Mean, mean propulsive and peak velocity outcomes were obtained for bench press and full squat exercises along the whole load-velocity spectrum (from light to heavy loads). Measurements were simultaneously registered by two linear velocity transducers T-Force, two linear position transducers Speed4Lifts, two smartphone video-based systems My Lift, and one 3D motion analysis system STT. Calculations included infraclass correlation coefficient (ICC), Bland-Altman Limits of Agreement (LoA), standard error of measurement (SEM), smallest detectable change (SDC) and maximum errors (MaxError). Results were reported in absolute (m/s) and relative terms (%1RM). Three velocity segments were differentiated according to the velocity-load relationships for each exercise: heavy (≥ 80% 1RM), medium (50% < 1RM < 80%) and light loads (≤ 50% 1RM). Criteria for acceptable reliability were ICC > 0.990 and SDC < 0.07 m/s (~5% 1RM). The T-Force device shown the best intra-device agreement (SDC = 0.01–0.02 m/s, LoA <0.01m/s, MaxError = 1.3–2.2%1RM). The Speed4Lifts and STT were found as highly reliable, especially against lifting velocities ≤1.0 m/s (Speed4Lifts, SDC = 0.01–0.05 m/s; STT, SDC = 0.02–0.04 m/s), whereas the My Lift app showed the worst results with errors well above the acceptable levels (SDC = 0.26–0.34 m/s, MaxError = 18.9–24.8%1RM). T-Force stands as the preferable option to assess barbell velocity and to identify technical errors of measurement for emerging monitoring technologies. Both the Speed4Lifts and STT are fine alternatives to T-Force for measuring velocity against high-medium loads (velocities ≤ 1.0 m/s), while the excessive errors of the newly updated My Lift app advise against the use of this tool for velocity-based resistance training.