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We have read with great interest and care the study carried out by García-Orea, Belando-Pedreño, Merino-Barrero, and Heredia-Elvar (2019 García-Orea, G. P., Belando-Pedreño, N., Merino-Barrero, J. A., & Heredia-Elvar, J. R. (2019) Validation of an opto-electronic instrument for the measurement of execution velocity in squat exercise. Sports Biomechanics. doi:10.1080/14763141.2019.1597156 [Taylor & Francis Online], , [Google Scholar] ) entitled ‘Validation of an opto-electronic instrument for the measurement of execution velocity in squat exercise’ DOI: 10.1080/14763141.2019.1597156. We applaud the authors for their thoughtful approach to the study. The general idea of the study is good and has an important practical utility, unfortunately there are some aspects, regarding both statistics and results that, in our modest opinion, need to be addressed.
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Sports Biomechanics
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Letter to editor
Iker J. Bautista & Fernando Martín
To cite this article: Iker J. Bautista & Fernando Martín (2019): Letter to editor, Sports
Biomechanics, DOI: 10.1080/14763141.2019.1640280
To link to this article: https://doi.org/10.1080/14763141.2019.1640280
Published online: 30 Jul 2019.
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Letter to editor
We have read with great interest and care the study carried out by García-Orea,
Belando-Pedreño, Merino-Barrero, and Heredia-Elvar (2019) entitled Validation of
an opto-electronic instrument for the measurement of execution velocity in squat
exerciseDOI: 10.1080/14763141.2019.1597156. We applaud the authors for their
thoughtful approach to the study. The general idea of the study is good and has an
important practical utility, unfortunately there are some aspects, regarding both statis-
tics and results that, in our modest opinion, need to be addressed.
The use of devices to control velocity execution while training with external resis-
tances is an interesting issue (García-Ramos et al., 2017; Spitz, Gonzalez, Ghigiarelli,
Sell, & Mangine, 2019). The cost of these devices ranges from the most economical (i.e.,
video camera and app) to the most expensive (T-Force system) (Courel-Ibañez et al.,
2019). However, regardless of the price, it is crucial that all devices that evaluate
execution velocity do so as accurately as possible. Systematic and/or random errors in
the measurement of the velocities at which the bar moves could generate large errors in
the determination of the intensity of the exercise according to its maximum repetition
(1RM) or when comparing the performance between dierent athletes.
Here is a list of what are, in our opinion, errors that we have detected in the study
mentioned above:
Page 3, experimental designsection. The authors express that they have used
a unifactorial repeated subject design. That is not true. Two independent variables are
available in this study (i.e., load [6 levels] and devices [2 levels]). Therefore, the most
appropriate design for the data collection they have carried out would be a factorial design
(since there is more than 1 independent variable) of repeated measurements. At the
statistical level, this could be solved with an analysis of the variance of repeated measure-
ments (ANOVA RM [2, devices x 6, loads]) where we would nd the following eects:
(i) Main eect of device. Regardless of the load factor, the ANOVA compares the
mean of all velocities across both devices (i.e., Velowin vs. T-Force). This is an
interesting eect.
(ii) Main eect of load. Regardless of the device factor, the ANOVA compares the
mean of all velocities across all loads (i.e., 20 vs. 30 vs. 40 . . .). This is not an
interesting eect.
(iii) Interaction device x load. The ANOVA compares the mean of all velocities
across load and intensity factors. This is an interesting eect.
It would be interesting for the reader to be able to interpret the results obtained in
terms of main eect of device factorand interaction eect device x loadof the
aforementioned ANOVA.
SPORTS BIOMECHANICS
https://doi.org/10.1080/14763141.2019.1640280
© 2019 Informa UK Limited, trading as Taylor & Francis Group
Page 6, statistical analysis section. The authors express that they have used the
intraclass correlation coecient (ICC). However, there are more than 6 dierent
types of ICC depending on the treatment that receives the term error, i.e., whether to
include the systematic and/or random error, if a 1-way or 2-way ANOVA is performed,
if a xed or random model is used, and if the data come from one single measurement
or from an average of measurements (Weir, 2005). On the other hand, measurement
reliability is dened as stability against multiple repetitions at dierent times. As we
have been able to read in the study, no measurements have been made on dierent days
and only the best repetition of each load has been analysed. Therefore, we do not
understand how the authors can speak about reliability.
Page 6, statistical analysis section. The authors express that only the fastest repetition
at each load is used for the reliability analysis (page 7). They declare to have carried out,
among others, the ICC test, it is therefore impossible to evaluate the reliability of the
device, since to carry this out, at least two measurements should have been taken into
account for each load, and preferably in dierent experimental sessions. We understand
that the ICC has been made to study the concordance between both devices, but the
latter is not a reliability test, only a validation. Moreover, this is not the best statistical
procedure to evaluate that. Bland-Altman plot would be the best procedure to evaluate
the concordance between devices and also assess systematic and random error. Finally,
we understand that the best repetition on device 1 (e.g., T-Force) does not have to
match with the best repetition on device 2 (e.g., Velowin).
Page 7, the authors state that Pearsons Correlation Coecient showed values from
r= 0.70 to r= 0.96. This is not consistent with Lins CCC results, since Lins CCC value
can never be higher than Pearsons Correlation Coecient value, a fact that the same
authors take into account on page 6 when they explain the statistical procedures they
have performed.
Page 7, normal test results section. The authors state that the variable Mean Velocity
for Velowin did not have a normal distribution, but they express a p= 0.172, a value
that evidences the normality of the variable. This is probably a writing error.
Page 7, Table 2. The authors state Table 2. Coecient of Variation (CV), Intra-class
Correlation Coecient (ICC) and Lins Concordance Coecient (CCC) for each variable
with both devices in Squat exercise. However, the variable deviceis not observed
anywhere.
Page 7, Table 2. The authors present the SEM values for each of the loads and as
a function of each of the variables analysed (i.e., mean velocity, mean propulsive
velocity and peak velocity). It is striking that the SEM average of all loads is equal to
0.296 m/s; that the ICC is, on average, 0.94; and that Pearsons correlation coecient
has uctuated between 0.70 and 0.96 (the authors have not expressed in which loads
they have obtained such coecients). The ICC, depending on which formula it is used,
may or may not include systematic error. However, the SEM is aected by the
systematic and random error. In this case, Pearsons correlation coecient cannot
detect systematic errors, but it can detect random errors (Weir, 2005). For this reason,
a type of statistical analysis such as the Bland-Altman graph is missing. Firstly, the error
could have been expressed in terms of systematic and random components. Secondly,
the presence of heterocedasticity could have been analysed.
2LETTER
Page 8, ANOVAsection. As I have previously argued, the experimental design of
the cited study was an ANOVA RM (2 x 6). The authors should have expressed, for
each dependent variable (i.e., VM, VMP and VP), the statistics of Snedecors F, the
degrees of freedom and the eect size.
We rmly believe that the main problem lies in the experimental design of the manuscript
itself. On one hand, one thing is to evaluate the reliability of a device and/or evaluation
procedure and, on the other hand, to evaluate the concordance between dierent devices
(T-Force vs. Velowin). Due to all the arguments we have presented above, we consider that
the assertion made by the authors in the conclusions of the study The main nding of this
study was the high reliability and concurrent validation of the Velowin opto-electronic system
for measuring the execution velocityis not supported by the results presented in the manu-
script. We are not saying that such a device (i.e., Velowin) is not valid or reliable, however,
with the results obtained in the study, making such a claim is risky. In fact, a paper recently
published by Courel-Ibañez et al. (2019) reported a correlation coecient between T-Force
and Velowin of r= 0.991 in full squat exercise and the limits of agreementsvalueswere
0.08 m/s and 0.05 m/s for systematic and random error, respectively.
Disclosure statement
No potential conict of interest was reported by the authors.
References
Courel-Ibañez, J., Martínez-Cava, A., Morán-Navarro, R., Escribano-Peñas, P., Chavarren-
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of ve dierent technologies for bar velocity measurement in resistance training. Annals of
Biomedical Engineering,47, 15231538. doi:10.1007/s10439-019-02265-6
García-Orea, G. P., Belando-Pedreño, N., Merino-Barrero, J. A., & Heredia-Elvar, J. R. (2019)
Validation of an opto-electronic instrument for the measurement of execution velocity in
squat exercise. Sports Biomechanics. doi:10.1080/14763141.2019.1597156
García-Ramos, A., Torrejón, A., Feriche., B., Morales-Artacho, A. J., Pérez-Castilla, A., Padial, P.,
&Ha,G.G.(2017). Prediction of the máximum number of repetitions and repetitions in
reserve from barbell velocity. International Journal of Sports Physiology and Performance,13,
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Spitz, E. W., Gonzalez, A. M., Ghigiarelli, J. J., Sell, K. M., & Mangine, G. T. (2019). Load-velocity
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Iker J. Bautista
Physical Education and Sport Science, University of Granada, Granada, Spain
ikerugr@gmail.com http://orcid.org/0000-0002-7409-6290
Fernando Martín
Physical Education and Sports, University of Valencia, Valencia, Spain
http://orcid.org/0000-0003-1996-8276
Received 13 June 2019; Accepted 1 July 2019
SPORTS BIOMECHANICS 3
Article
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The purpose of this study was to analyse the reliability and validity of an opto-electronic sensor system (Velowin) for assessment of the bar-velocity in the deep squat exercise. Mean velocity, mean propulsive velocity and peak velocity generated in the deep squat exercise performed in the Smith machine bar were analysed compared to a linear velocity transducer considered as the gold standard. The study was conducted with a sample of 26 men with experience in resistance training. Six measurements were analysed for squat exercise in concentric phase using a progressive loading increase. Three consecutive repetitions were performed per load with a 3–4 min recovery between loads. Analysis of variance confirmed that there were no significant differences (p > 0.05) for the velocity variables between Velowin and T-Force for each of the loads. The reliability analysis showed high values of the intraclass correlation coefficient (ICC = 0.94–0.99), an ‘almost perfect’ Lin’s concordance coefficient (CCC = 0.99) and a low coefficient of variation (CV <3.4%) for each of the loads and velocities. These results confirm the reliability and validity of the Velowin device for measuring the execution velocity in deep squat exercise.
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This study aimed to analyze the agreement between five bar velocity monitoring devices, currently used in resistance training, to determine the most reliable device based on reproducibility (between-device agreement for a given trial) and repeatability (between-trial variation for each device). Seventeen resistance-trained men performed duplicate trials against seven increasing loads (20-30-40-50-60-70-80 kg) while obtaining mean, mean propulsive and peak velocity outcomes in the bench press, full squat and prone bench pull exercises. Measurements were simultaneously registered by two linear velocity transducers (LVT), two linear position transducers (LPT), two optoelectronic camera-based systems (OEC), two smartphone video-based systems (VBS) and one accelerometer (ACC). A comprehensive set of statistics for assessing reliability was used. Magnitude of errors was reported both in absolute (m s⁻¹) and relative terms (%1RM), and included the smallest detectable change (SDC) and maximum errors (MaxError). LVT was the most reliable and sensitive device (SDC 0.02–0.06 m s⁻¹, MaxError 3.4–7.1% 1RM) and the preferred reference to compare with other technologies. OEC and LPT were the second-best alternatives (SDC 0.06–0.11 m s⁻¹), always considering the particular margins of error for each exercise and velocity outcome. ACC and VBS are not recommended given their substantial errors and uncertainty of the measurements (SDC > 0.13 m s⁻¹).
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Purpose: This study aimed to provide two general equations to estimate (1) the maximum possible number of repetitions (XRM) from the mean velocity (MV) of the barbell, and (2) the MV associated with a given number of repetitions in reserve, as well as (3) to determine the between-sessions reliability of the MV associated with each XRM. Methods: After the determination of the bench press one-repetition maximum (1RM: 1.15±0.21 kg·kg(-1) body mass), 21 men (age: 23.0±2.7 years; body mass: 72.7±8.3 kg; body height. 1.77±0.07 m) completed four sets of as many repetitions as possible against relative loads of 60%1RM, 70%1RM, 80%1RM, and 90%1RM over two separate sessions. The different loads were tested in a randomized order with 10 min of rest between them. All repetitions were performed at the maximum intended velocity. Results: Both general equations to predict the XRM from the fastest MV of the set (CV = 15.8%-18.5%) and the MV associated with a given number of repetitions in reserve (CV = 14.6%-28.8%) failed to provide data with acceptable between-subjects variability. However, a strong relationship (median r(2) = 0.984) and acceptable reliability (CV < 10% and ICC > 0.85) were observed between the fastest MV of the set and the XRM when considering individual data. Conclusions: These results highlight that generalized group equations are not acceptable methods for estimating the XRM-MV relationships or the number of repetitions in reserve. When attempting to estimate the XRM-MV relationship individualized relationships must be utilized in order to objectively estimate the exact number of repetitions that can be performed in a training set.
Article
Spitz, RW, Gonzalez, AM, Ghigiarelli, JJ, Sell, KM, and Mangine, GT. Load-velocity relationships of the back vs. front squat exercises in resistance-trained men. J Strength Cond Res 33(2): 301-306, 2019-The purpose of this investigation was to describe and compare changes in barbell velocity in relation to relative load increases during the back squat (BS) and front squat (FS) exercises. Eleven National Collegiate Athletic Association Division I baseball position players (19.4 ± 1.0 years; 182.4 ± 6.5 cm; and 87.2 ± 7.4 kg) performed trials at maximum speed with loads of 30, 50, 70, and 90% of their predetermined 1 repetition maximum (1RM) for both BS and FS. Peak and mean velocity was recorded during each repetition using an accelerometer. Differences between exercises and relative loading were assessed by separate 2 × 4 (condition × relative load) repeated-measures analysis of variance for mean and peak velocity. In addition, the load-velocity relationship across submaximal loadings in BS and FS were further assessed by calculating their respective slopes and comparing slopes through a paired-samples t-test. No significant condition × relative load interactions were noted for mean velocity (p = 0.072) or peak velocity (p = 0.203). Likewise, no significant differences in the slope for BS and FS were noted for mean velocity (p = 0.057) or peak velocity (p = 0.196). However, significant main effects for relative load were noted for both mean and peak velocity (p < 0.001), whereby mean and peak velocity were progressively reduced across all relative loads (i.e., 30, 50, 70, and 90% 1RM) for both the BS and FS. Our results demonstrate that the load-velocity relationships of the BS and FS exercises seem to be similar; therefore, similar approaches may be used with these squat variations when monitoring barbell velocity or implementing velocity-based strength training.
Article
Reliability, the consistency of a test or measurement, is frequently quantified in the movement sciences literature. A common metric is the intraclass correlation coefficient (ICC). In addition, the SEM, which can be calculated from the ICC, is also frequently reported in reliability studies. However, there are several versions of the ICC, and confusion exists in the movement sciences regarding which ICC to use. Further, the utility of the SEM is not fully appreciated. In this review, the basics of classic reliability theory are addressed in the context of choosing and interpreting an ICC. The primary distinction between ICC equations is argued to be one concerning the inclusion (equations 2,1 and 2,k) or exclusion (equations 3,1 and 3,k) of systematic error in the denominator of the ICC equation. Inferential tests of mean differences, which are performed in the process of deriving the necessary variance components for the calculation of ICC values, are useful to determine if systematic error is present. If so, the measurement schedule should be modified (removing trials where learning and/or fatigue effects are present) to remove systematic error, and ICC equations that only consider random error may be safely used. The use of ICC values is discussed in the context of estimating the effects of measurement error on sample size, statistical power, and correlation attenuation. Finally, calculation and application of the SEM are discussed. It is shown how the SEM and its variants can be used to construct confidence intervals for individual scores and to determine the minimal difference needed to be exhibited for one to be confident that a true change in performance of an individual has occurred.
Bautista Physical Education and Sport Science
  • J Iker
Iker J. Bautista Physical Education and Sport Science, University of Granada, Granada, Spain ikerugr@gmail.com http://orcid.org/0000-0002-7409-6290