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Reliability and validity of two measurement systems in the quantification of jump performance
Abstract
There are different devices on the market for assessing strength and power in vertical jumping as a fundamental requisite of an athlete's performance. The purpose of this study was to assess the reliability and validity of two instruments measuring force, power, velocity, and jump height in squat jumps. Myotest® (MYO) (Myotest SA, Switzerland) was compared with force plate measurements (Quattro Jump® [QUATTRO], Kistler, Switzerland & SPSport Software, Trins, Austria). Forty-three frontier-guards (age range 25-58 years) performed twice a series of five squat jumps (SJ) simultaneously using MYO device along with QUATTRO force plate. Reliability was analysed using ICC, CV and RMSE. Results for reliability for both devices show good results with ICCs ranging from 0.910 to 0.955, and CVs ranging from 2.33% to 6.59% for discrete outcome variables. The validity of the methods was investigated using the Limits of Agreement (LoA) method. MYO overestimated jump performance compared to QUATTRO with a bias of 4.38 cm (±2.59) for jump height, 1.82 Watt/kg (±4.08) for power, and 0.85 N/kg (±1.24) for force. For velocity the two methods displayed good agreement. In conclusion, based on the variability of the measurements, coaches may use complemental variables in addition to jump data in the realm of performance testing and training control to better understand the performance of their athletes. In addition, on the basis of the results regarding the validity interchangeability of the two systems is limited.
... Naturally, force plates are considered to be the gold standard for measuring vertical jump performance (Hatze, 1998;Linthorne, 2001;Vanrenterghem, De Clercq, & Cleven, 2001), but are often costly, difficult to transport, and require specialized computer equipment to collect and analyse data. On the contrary, accelerometers may also be used to estimate force (Crewther et al., 2011;Mauch, Rist, & Kaelin, 2014) and offer exceptional portability, often without the need for additional equipment other than a mobile phone or laptop computer. ...
... to .75). As for JH, the data from this study agree with previous research (Casartelli et al., 2010;Choukou et al., 2014;Mauch et al., 2014) in that the ACC and OPT are reliable (r = .93 to .94) ...
... supports the idea of less agreement between F ACC and F FP , meaning ACC should not be used to measure force during a CMJ. The accuracy of peak force estimation could be increased using the squat jump and place the accelerometer on the bar (Bampouras et al., 2013;Crewther et al., 2011;Mauch et al., 2014), where the accuracy of the ACC has been shown to increase with increasing loads (Crewther et al., 2011). Therefore, we recommend reconsidering the use of ACC to estimate peak force during unloaded vertical jumps. ...
Background:
Previous research has determined the validity and reliability of accelerometer-based devices, but the
findings are not consistent.
Objective:
The purpose of this study was to determine the validity of an accelerometer (Myotest PRO) for measuring explosive strength indicators (jump height, peak force, peak velocity, and peak
power) during the countermovement jump.
Methods:
Thirty-three university students (22 males and 11 females;
178.6 ± 5.6 cm, 69.3 ± 6.5 kg, 21.8 ± 1.7 years) performed five individual countermovement jumps. Jump height
was derived from an accelerometer (Myotest, frequency 200 Hz), optic timing system (Optojump) and from a force
plate (Kistler, frequency 800 Hz) using both flight time and force impulse algorithms. Peak force, peak velocity, and
peak power were calculated by the accelerometer and force plate.
Results:
The Myotest resulted in systematic bias, overestimating jump height by 8.0 ± 2.1 cm (p< .001) compared to force impulse algorithm; flight time algorithm by 5.5 ± 2.0 cm (p < .001) using the force plate and by 5.9 ± 2.0 cm (p < .001) using the Optojump. The Myotest also
underestimated peak force by 167 ± 182 N (p < .001). Compared to force impulse algorithm, the Myotest displayed less agreement for peak velocity (r2 = .245) and peak power (r2 = .557).
Conclusion:
Accelerometers are valid and may be used consistently to evaluate countermovement jump height. However, they are not valid, and should neither be used to measure peak force, velocity, or power nor be compared against other methods due to a bias.
Keywords:
accelerometer, optic timing, force plate, peak forc
... The peak power estimates, however, were similarly inaccurate with errors of 10.7-21.2% [25][26][27]. These Newtonian approaches are highly sensitive to the small errors that arise from corrections needed to the sensor's changing orientation [28][29][30]. ...
... Estimates based on jump height had errors of 6.0-16.5% [17][18][19][20][21][22] while the Newtonian sensor-based calculations resulted in errors of 10.7-21.2% [25][26][27]. The lowest error reported in those studies was for the Canavan-Vescovi equation [18], but it was based on data from only 20 . ...
External peak power in the countermovement jump is frequently used to monitor athlete training. The gold standard method uses force platforms, but they are unsuitable for field-based testing. However, alternatives based on jump flight time or Newtonian methods applied to inertial sensor data have not been sufficiently accurate for athlete monitoring. Instead, we developed a machine learning model based on characteristic features (functional principal components) extracted from a single body-worn accelerometer. Data were collected from 69 male and female athletes at recreational, club or national levels, who performed 696 jumps in total. We considered vertical countermovement jumps (with and without arm swing), sensor anatomical locations, machine learning models and whether to use resultant or triaxial signals. Using a novel surrogate model optimisation procedure, we obtained the lowest errors with a support vector machine when using the resultant signal from a lower back sensor in jumps without arm swing. This model had a peak power RMSE of 2.3 W·kg ⁻¹ (5.1% of the mean), estimated using nested cross validation and supported by an independent holdout test (2.0 W·kg ⁻¹ ). This error is lower than in previous studies, although it is not yet sufficiently accurate for a field-based method. Our results demonstrate that functional data representations work well in machine learning by reducing model complexity in applications where signals are aligned in time. Our optimisation procedure also was shown to be robust can be used in wider applications with low-cost, noisy objective functions.
... Vale la pena notare che l'affidabilità, la precisione e la validità del dispositivo force-plate portatile nella valutazione del salto verticale sono state riportate in studi precedenti. 15,16 Inoltre, diversi studi [17][18][19][20][21] hanno utilizzato il Quattro Jump come modello di riferimento (cioè, gold standard) per convalidare altri strumenti per valutare le prestazioni del salto verticale. ...
... It is worth noting that the reliability, accuracy, and validity of the portable force-plate device in the vertical jump assessment have been reported in previous study. 15,16 In addition, several studies [17][18][19][20][21] have used the Quattro Jump as a reference model (i.e., gold standard) to validate other tools for evaluating vertical jump performance. ...
... Vale la pena notare che l'affidabilità, la precisione e la validità del dispositivo force-plate portatile nella valutazione del salto verticale sono state riportate in studi precedenti. 15,16 Inoltre, diversi studi [17][18][19][20][21] hanno utilizzato il Quattro Jump come modello di riferimento (cioè, gold standard) per convalidare altri strumenti per valutare le prestazioni del salto verticale. ...
... It is worth noting that the reliability, accuracy, and validity of the portable force-plate device in the vertical jump assessment have been reported in previous study. 15,16 In addition, several studies [17][18][19][20][21] have used the Quattro Jump as a reference model (i.e., gold standard) to validate other tools for evaluating vertical jump performance. ...
BACKGROUND: The aim of this study was to validate the accuracy of ground-reaction force measurement using inverse body dynamic analysis via video motion analysis system versus portable force-plate direct measurement system (i.e., gold standard model). METHODS: Six elite-level male gymnasts (age =23.70±1.94 years; height =1.66±0.06 m; body mass =58.67±8.24 kg) participated in this study. The concurrent kinematic and dynamic analysis of the ground-reaction forces during snapdown
take-off to back somersault were performed in the acrobatic series (i.e., round-off flic-flac back somersault). RESULTS: The finding of the present study showed very good relative and absolute reliability of the motion analysis system outcomes (intraclass correlation coefficient [ICC] =0.953, typical error of measurement [TEM] =85.31 N, and TEM(%) =1.17%). Further, the motion analysis device demonstrated good ability to detect small and meaningful performance change (TEM< smallest worthwhile change [SWC]). No statistically significant differences were observed when comparing the ground-reaction force outcome between repetitions and devices (P>0.05; d=0.048). Additionally, results showed a nearly perfect association between the two methods (r=0.965 and R2=93%). The mean (bias)±95% limits of agreement between the two measurement devices was 341.0±508.8 N. CONCLUSIONS: In conclusion, inverse body dynamic analysis could be a good alternative to force-plate device for coaches to evaluate ground-reaction force in male artistic gymnastics.
... For athletic profiling, these assessments should comprise both measures of the athlete's maximal velocity (explosive performance, also referred to as ballistic performance [13]) and maximal strength (possibly when lifting a set of increasing loads in classical overload exercises). Both types of assessment have been performed using MIMUs that provide instantaneous acceleration (and therefore force) data along with an integrated measurement of velocity to determine muscular power: explosive performance was assessed for the lower limbs during jumps [13,83,84,92,93,97,100,117,150,166,167,199,213,[218][219][220]233,244,251,257,258,281,286] and for the upper limbs [78,141,151,190,236,310]. Force and power production capacity were quantified during maximum dynamic strength tests for the upper limbs [76,97,103,172,186,198,252,261,305] and lower limbs [64,65,76,82,97,172,252,265,289]. ...
... This data is quantified for the lower limbs in terms of jump height, maximal velocity, and peak power, eventually separating concentric and eccentric contributions. Several studies tested the accuracy, reliability, and validity of MIMUs in providing jump height [13,83,84,92,93,115,117,167,199,213,218,220,233,244,251] or other jump related parameters, such as peak knee flexion and trunk lean during landing [115], take-off velocity, contact and flight time [93,167,220,233,257,258], and force and power [97,100,281]. Upper limb ballistic performance has been analysed in terms of maximum velocity, estimated strength, peak power during explosive bench press [141,151,236], and also upper limb ability to elevate the centre of mass during upper limb jumps [190]. ...
Recent technological developments have led to the production of inexpensive, non-invasive, miniature magneto-inertial sensors, ideal for obtaining sport performance measures during training or competition. This systematic review evaluates current evidence and the future potential of their use in sport performance evaluation. Articles published in English (April 2017) were searched in Web-of-Science, Scopus, Pubmed, and Sport-Discus databases. A keyword search of titles, abstracts and keywords which included studies using accelerometers, gyroscopes and/or magnetometers to analyse sport motor-tasks performed by athletes (excluding risk of injury, physical activity, and energy expenditure) resulted in 2040 papers. Papers and reference list screening led to the selection of 286 studies and 23 reviews. Information on sport, motor-tasks, participants, device characteristics, sensor position and fixing, experimental setting and performance indicators was extracted. The selected papers dealt with motor capacity assessment (51 papers), technique analysis (163), activity classification (19), and physical demands assessment (61). Focus was placed mainly on elite and sub-elite athletes (59%) performing their sport in-field during training (62%) and competition (7%). Measuring movement outdoors created opportunities in winter sports (8%), water sports (16%), team sports (25%), and other outdoor activities (27%). Indications on the reliability of sensor-based performance indicators are provided, together with critical considerations and future trends.
... Also, in recent years, different studies have been published on the reliability and concurrent validity of accelerometry-based devices (Casartelli, Müller, & Maffiuletti, 2010;Castagna et al., 2013;Choukou, Laffaye, & Taiar, 2014;Lesinski, Muehlbauer, & Granacher, 2016;Mauch, Praxisklinik-Rennbahn, Hans-Joachim, & Xaver, 2014;Monnet et al., 2014;Nuzzo et al., 2011;Picerno, Camomilla, & Capranica, 2011;Requena et al., 2012) andvideo-analysis (Balsalobre-Fernández, Glaister, &Lockey, 2015;Carlos-Vivas, Martín-Martinez, Hernández-Mocholi, & Pérez-Gómez, 2016) to determine the height of the vertical jump starting from flight time. As a whole, these instruments show an acceptable reproducibility and reliability of the vertical jump measurement without load (CV 'low': <6%; CCI 'medium-high': ≥0.8; SEM: 1-5 cm). ...
2018): Validation of an opto-electronic instrument for the measurement of weighted countermovement jump execution velocity, Sports Biomechanics, ABSTRACT The purpose of this study was to analyse the reliability and validity of an opto-electronic sensor system (Velowin) compared to a linear velocity transducer (T-Force System) considered as the gold standard. Mean velocity (MV) and peak velocity (PV) generated in the Smith machine bar placed on the shoulders in counter-movement jump exercise (CMJ) were analysed. The study was conducted with a sample of 21 men with experience in resistance training. Five measurements were analysed for CMJ exercise in concentric phase using a progressive loading increase. Three jumps were made per load with a 3-4 min recovery between loads. The analysis of the variance confirmed that there were no significant differences (p > 0.05) in the execution velocity between Velowin and T-Force with each of the loads. The reliability analysis showed, with each of the loads, high values of the intraclass correlation coefficient (ICC = 0.95-0.99) and a 'substantial' Lin´s concordance coefficient in MV (CCC ≥0.96) and between 'substantial' (CCC = 0.98) and 'almost perfect' (CCC = 0.99) in PV. These results confirm the reliability and validity of the Velowin device is reliable for measuring the execution velocity in loaded CMJ exercise. ARTICLE HISTORY
... Take-off was the first crossing at zero and landing was the second crossing at zero of the Y accelerations signals. The equation used to determine jump height was JH= (G*AT^2) / 8 where JH is the jump height, G is acceleration due to gravity (-9.81 m•s -2 ) and AT is the time spent in air (Bosco, Luhtanen, & Komi, 1983;Choukou, Laffaye, & Taiar, 2014;Linthorne, 2001;Mauch, Rist, & Kaelin, 2014;McMahon, Jones, & Comfort, 2016;Monnet, Decatoire, & Lacouture, 2014). From motion capture data and the use of a retroreflective marker, the average of 21 points before take-off when the subject was standing straight was used to determine the standing height of each subject, in other words the "zero" point of the reflective marker. ...
Vertical jumps are vital aspects in many sports. Many technologies are available to determine and calculate jump height. One such portable and easy-to-use technology is an Inertial Measurement Unit (IMU) that uses accelerometers, gyroscopes and magnetometers. The purpose of this study was to compare vertical jump heights calculated from the data captured with an IMU versus true jump height calculated using a gold standard 3-Dimensional Motion Capture system. Ten subjects completed five jumps for six different conditions including vertical counter-movement jumps and jumps involving rotations on the ground and using a trampoline. An average Pearson correlation coefficient of 0.87 was found between the IMU and motion capture for all conditions. Condition correlations ranged from 0.76 to 0.94. Bland-Altman analyses showed that the IMU underestimated the vertical jump height compared to the motion capture by 5.0 to 9.2 cm across all conditions. Results suggest an IMU can be used to measure jump height in a laboratory setting with a reasonable accuracy, even during vertical jumps that include rotations. Keywords: Inertial measurement unit; Accelerometers; Accuracy; Sports.
... An ICC was higher than .75 are reliability acceptance [25]. The value of CV that had been 10% or below showed the indicators of reliability acceptance [26]. Table II showed the mean and the standard deviation of the high school players" Performance Time (the Time Taken and the Penalty Time) from the first and second trials. ...
... Also, in recent years, different studies have been published on the reliability and concurrent validity of accelerometry-based devices (Casartelli, Müller, & Maffiuletti, 2010;Castagna et al., 2013;Choukou, Laffaye, & Taiar, 2014;Lesinski, Muehlbauer, & Granacher, 2016;Mauch, Praxisklinik-Rennbahn, Hans-Joachim, & Xaver, 2014;Monnet et al., 2014;Nuzzo et al., 2011;Picerno, Camomilla, & Capranica, 2011;Requena et al., 2012) andvideo-analysis (Balsalobre-Fernández, Glaister, &Lockey, 2015;Carlos-Vivas, Martín-Martinez, Hernández-Mocholi, & Pérez-Gómez, 2016) to determine the height of the vertical jump starting from flight time. As a whole, these instruments show an acceptable reproducibility and reliability of the vertical jump measurement without load (CV 'low': <6%; CCI 'medium-high': ≥0.8; SEM: 1-5 cm). ...
The purpose of this study was to analyse the reliability and validity of an opto-electronic sensor system (Velowin) compared to a linear velocity transducer (T-Force System) considered as the gold standard. Mean velocity (MV) and peak velocity (PV) generated in the Smith machine bar placed on the shoulders in counter-movement jump exercise (CMJ) were analysed. The study was conducted with a sample of 21 men with experience in resistance training. Five measurements were analysed for CMJ exercise in concentric phase using a progressive loading increase. Three jumps were made per load with a 3–4 min recovery between loads. The analysis of the variance confirmed that there were no significant differences (p > 0.05) in the execution velocity between Velowin and T-Force with each of the loads. The reliability analysis showed, with each of the loads, high values of the intraclass correlation coefficient (ICC = 0.95–0.99) and a ‘substantial’ Lin´s concordance coefficient in MV (CCC ≥0.96) and between ‘substantial’ (CCC = 0.98) and ‘almost perfect’ (CCC = 0.99) in PV. These results confirm the reliability and validity of the Velowin device is reliable for measuring the execution velocity in loaded CMJ exercise.
... For measuring vertical jump variables, it has been used different techniques and sensors, in [23] the authors reviewed some methods used for this purpose. In the estimating of maximum height have been regarded platforms forces, as Quattro Jump Kistler force plate [15]. Although they have high precision, can have limitations in sporting environments because of cost-effectiveness and handling [12,4]. ...
The physical challenges of human development reflected in the sport are increasingly technology-related. This relationship can be demonstrated in several lines; design on sports elements using high technology as well as sports analysis systems that trying to enhance technical indicators in every discipline. The analysis systems facilitate the feedback process to coaches and athletes, based on mathematical models using derived measures, avoiding precision errors of human observations. One meaningful measure for coaches, strength and conditioning professionals, and sport professionals in general is the vertical jump height. In this paper the initial development of a vertical jump height measurement system is presented, that allows to know the flight height of a person in the development of exercise, and his flight time. The system relies on information from an Inertial Measurement Unit (IMU) consisting of an triaxial accelerometer, a triaxial gyroscope and a triaxial magnetometer and two pressure sensors that fuse the jump measured data. The equipment is completely portable and wireless allowing measurements under standard conditions and these can be developed at the same time with the sporting activity. In average were obtained a flight time of 0.4720s and a maximum height of 0.3160m. The results evidence that these systems based on initiatives of low-cost national technology can be at the level of the products used commercially. Finally, it is important to note that the development of these devices can be complemented with specific applications that automatically process data to support the practice of sports.
External peak power in the countermovement jump is frequently used to monitor athlete training. The gold standard method uses force platforms, but they are unsuitable for field-based testing. However, alternatives based on jump flight time or Newtonian methods applied to inertial sensor data have not been sufficiently accurate for athlete monitoring. Instead, we developed a machine learning model based on characteristic features (functional principal components) extracted from a single body-worn accelerometer. Data were collected from 69 male and female athletes at recreational, club or national levels, who performed 696 jumps in total. We considered vertical countermovement jumps (with and without arm swing), sensor anatomical locations, machine learning models and whether to use resultant or triaxial signals. Using a novel surrogate model optimisation procedure, we obtained the lowest errors with a support vector machine when using the resultant signal from a lower back sensor in jumps without arm swing. This model had a peak power RMSE of 2.3 W·kg ⁻¹ (5.1% of the mean), estimated using nested cross validation and supported by an independent holdout test (2.0 W·kg ⁻¹ ). This error is lower than in previous studies, although it is not yet sufficiently accurate for a field-based method. Our results demonstrate that functional data representations work well in machine learning by reducing model complexity in applications where signals are aligned in time. Our optimisation procedure also was shown to be robust can be used in wider applications with low-cost, noisy objective functions.
This study aims to comprehensively assess the accuracy and precision of five different devices and by incorporating a variety of analytical approaches for measuring countermovement jump height: Qualisys motion system; Force platform; Ergojump; an Accelerometer, and self-made Abalakow jump belt. Twenty-seven male and female physical education students (23.5 ± 3.8 years; height 170 ± 9.1 cm and body mass 69.1 ± 11.4 kg) performed three countermovement jumps simultaneously measured using five devices. The 3D measured displacement obtained through the Qualisys device was considered in this study as the reference value. The best accuracy (difference from 3D measured displacement) and precision (standard deviation of differences) for countermovement jump measurement was found using the Abalakow jump belt (0.8 ± 14.7 mm); followed by the Force platform when employing a double integration method (1.5 ± 13.9 mm) and a flight-time method employed using Qualisys motion system data (6.1 ± 17.1 mm). The least accuracy was obtained for the Ergojump (−72.9 mm) employing its analytical tools and then for the accelerometer and Force platform using flight time approximations (−52.8 mm and −45.3 mm, respectively). The worst precision (±122.7 mm) was obtained through double integration of accelerometer acceleration data. This study demonstrated that jump height measurement accuracy is both device and analytical-approach-dependent and that accuracy and precision in jump height measurement are achievable with simple, inexpensive equipment such as the Abalakow jump belt.
Manufacturers recommend that linear position transducers (LPTs) should be placed on the side of a barbell (or wooden dowel) to measure countermovement jump (CMJ) height, but the validity and reliability of this placement have not been compared to other attachment sites. Since this recommended attachment site is far from the centre of mass, a belt attachment where the LPT is placed between the feet may increase the validity and reliability of CMJ data. Thirty-six physical education students participated in the study (24.6 ± 4.3 years; 177.0 ± 7.7 cm; 77.2 ± 9.0 kg). Parameters from the two LPT attachments (barbell and belt) were simultaneously validated to force plate data, where the nature of bias was analysed (systematic vs random). The within-session and between-session reliability of both attachment sites were compared to force plate data using a test-retest protocol of two sets of 5 CMJs separated by 7 days. The LPT provided highly reliable and valid measures of peak force, mean force, mean power, and jump height, where the bias was mostly systematic (r2 > 0.7; ICC > 0.9). Peak velocity, mean velocity, and peak power were in very good agreement with the force plate and were highly reliable (r2 > 0.5; ICC > 0.7). Therefore, both attachment sites produced similar results with a systematic bias compared to force plate data. Thus, both attachment sites seem to be valid for assessing CMJs when the measuring tool and site remain consistent across measurements. However, if LPT data are to be compared to force plate data, recalculation equations should be used.
Abstract
Background. This systematic review aimed to investigate the psychometric properties of the school health’s assessment tools in primary schools through COSMIN Risk of Bias checklist. We examined the studies that have addressed the measurement properties of school-health instruments to give a clear overview of the quality of all available tools measuring school health in primary schools. This systematic review was registered in PROPERO with the Registration ID: CRD42020158158.
Method. Databases of EBSCOhost, PubMed, ProQuest, Wily, PROSPERO, and OpenGrey were systematically searched without any time limitation to find all full-text English journal articles studied at least one of the COSMIN checklist measurement properties of a school-health assessment tool in primary schools. The instruments should be constructed based on a school health model. The eligible studies were assessed by COSMIN Risk of Bias checklist to report their quality of methodology for each measurement property and for the whole study by rating high, moderate or low quality.
Results. At the final screening, just seven studies remained for review. Four studies were tool development, three of them were rated as “adequate” and the other study as “very good”; five studies examined the content validity, three of them were appraised as “very good”, and the two remaining as “inadequate”. All seven studies measured structural validity, three of them were evaluated as “very good”, three others were scored as “adequate”, and the last study as “inadequate”. All the seven studies investigated the internal consistency, five of them were assessed as “very good”, one was rated as “doubtful”, and the last one as “inadequate”. Just one study examined the cross-cultural validity and was rated as “adequate”. Finally, all seven studies measured reliability, two of them were rated as “very good” and the rest five studies were appraised as “doubtful”. All rating was based on COSMIN checklist criteria for quality of measurement properties assessment.
Conclusion. The number of studies addressing school health assessment tools was very low and therefore not sufficient. Hence, there is a serious need to investigate the psychometric properties of the available instruments measuring school health at primary schools. Moreover, the studies included in the present systematic review did not fulfill all the criteria of the COSMIN checklist for assessing measurement properties. We suggest that future studies consider these criteria for measuring psychometric properties and developing school health assessment tools.
The paper topic is about the propagation of uncertainty in a multivariate measurement. The Law of Propagation of Uncertainty defined in the Guide to the Expression of Uncertainty in Measurement is used to calculate the standard uncertainties, covariance matrix and correlation coefficient. The procedure is presented for a set of samples, acquired from a balance platform, which are used to calculate the centre of pressure (COP) coordinates. The possibility of evaluating the uncertainty of COP results in different way is also discussed.
Vertical jump is one of the most prevalent acts performed in several sport activities. It is therefore important to ensure that the measurements of vertical jump height made as a part of research or athlete support work have adequate validity and reliability. The aim of this study was to evaluate concurrent validity and reliability of the Optojump photocell system (Microgate, Bolzano, Italy) with force plate measurements for estimating vertical jump height. Twenty subjects were asked to perform maximal squat jumps and countermovement jumps, and flight time-derived jump heights obtained by the force plate were compared with those provided by Optojump, to examine its concurrent (criterion-related) validity (study 1). Twenty other subjects completed the same jump series on 2 different occasions (separated by 1 week), and jump heights of session 1 were compared with session 2, to investigate test-retest reliability of the Optojump system (study 2). Intraclass correlation coefficients (ICCs) for validity were very high (0.997-0.998), even if a systematic difference was consistently observed between force plate and Optojump (-1.06 cm; p < 0.001). Test-retest reliability of the Optojump system was excellent, with ICCs ranging from 0.982 to 0.989, low coefficients of variation (2.7%), and low random errors (±2.81 cm). The Optojump photocell system demonstrated strong concurrent validity and excellent test-retest reliability for the estimation of vertical jump height. We propose the following equation that allows force plate and Optojump results to be used interchangeably: force plate jump height (cm) = 1.02 × Optojump jump height + 0.29. In conclusion, the use of Optojump photoelectric cells is legitimate for field-based assessments of vertical jump height.
In sport and everyday activities, the most important attribute of skeletal muscle is the ability to generate power, a product of strength and speed of movement. Many factors influence the muscle's ability to generate power. Training for muscular power requires special care in developing the proper exercise prescription. The need for muscular power runs across a spectrum of people from elite athletes attempting to optimize sports performance to the frail elderly trying to perform simple tasks. Power development is paramount to optimal neuromuscular function.
This study examined the validity of 2 kinematic systems for estimating force and power during squat jumps. 12 weight-trained males each performed single repetition squat jumps with a 20-kg, 40-kg, 60-kg and 80-kg load on a Kistler portable force plate. A commercial linear position transducer (Gymaware [GYM]) and accelerometer (Myotest® [MYO]) were attached to the bar to assess concentric peak force (PF) and peak power (PP). Across all loads tested, the GYM and MYO estimates of PF and PP were moderately to strongly correlated ( P≤0.05-0.001) with the force plate measurements ( R=0.59-0.87 and R=0.66-0.97), respectively. The mean PF and PP values were not significantly different between the 2 kinematic systems and the force plate, but the estimates did produce some systematic bias and relatively large random errors, especially with the 20-kg load (PF bias >170 N, PF error >335 N, PP bias >400 W, PP error >878 W). Some proportional bias was also identified. In summary, the estimation of PF and PP by a linear position transducer and accelerometer showed moderate to strong relative validity and equivalent absolute validity, but these estimates are limited by the presence of bias and large random errors.
The purpose of this investigation was to assess the intrasession and intersession reliability of the Vertec, Just Jump System, and Myotest for measuring countermovement vertical jump (CMJ) height. Forty male and 39 female university students completed 3 maximal-effort CMJs during 2 testing sessions, which were separated by 24-48 hours. The height of the CMJ was measured from all 3 devices simultaneously. Systematic error, relative reliability, absolute reliability, and heteroscedasticity were assessed for each device. Systematic error across the 3 CMJ trials was observed within both sessions for males and females, and this was most frequently observed when the CMJ height was measured by the Vertec. No systematic error was discovered across the 2 testing sessions when the maximum CMJ heights from the 2 sessions were compared. In males, the Myotest demonstrated the best intrasession reliability (intraclass correlation coefficient [ICC] = 0.95; SEM = 1.5 cm; coefficient of variation [CV] = 3.3%) and intersession reliability (ICC = 0.88; SEM = 2.4 cm; CV = 5.3%; limits of agreement = -0.08 ± 4.06 cm). Similarly, in females, the Myotest demonstrated the best intrasession reliability (ICC = 0.91; SEM = 1.4 cm; CV = 4.5%) and intersession reliability (ICC = 0.92; SEM = 1.3 cm; CV = 4.1%; limits of agreement = 0.33 ± 3.53 cm). Additional analysis revealed that heteroscedasticity was present in the CMJ when measured from all 3 devices, indicating that better jumpers demonstrate greater fluctuations in CMJ scores across testing sessions. To attain reliable CMJ height measurements, practitioners are encouraged to familiarize athletes with the CMJ technique and then allow the athletes to complete numerous repetitions until performance plateaus, particularly if the Vertec is being used.
The purpose of this study was to verify the concurrent validity of a bar-mounted Myotest® instrument in measuring the force and power production in the squat and bench press exercises when compared to the gold standard of a computerized linear transducer and force platform system. Fifty-four men (bench press: 39-171 kg; squat: 75-221 kg) and 43 women (bench press: 18-80 kg; squat: 30-115 kg) (age range 18-30 years) performed a 1 repetition maximum (1RM) strength test in bench press and squat exercises. Power testing consisted of the jump squat and the bench throw at 30% of each subject's 1RM. During each measurement, both the Myotest® instrument and the Celesco linear transducer of the directly interfaced BMS system (Ballistic Measurement System [BMS] Innervations Inc, Fitness Technology force plate, Skye, South Australia, Australia) were mounted to the weight bar. A strong, positive correlation (r) between the Myotest and BMS systems and a high correlation of determination (R2) was demonstrated for bench throw force (r = 0.95, p < 0.05) (R2 = 0.92); bench throw power (r = 0.96, p < 0.05) (R2 = 0.93); squat jump force (r = 0.98, p < 0.05) (R2 = 0.97); and squat jump power (r = 0.91, p < 0.05) (R2 = 0.82). In conclusion, when fixed on the bar in the vertical axis, the Myotest is a valid field instrument for measuring force and power in commonly used exercise movements.
The aim of the present study was to verify the validity and reliability of the Myotest accelerometric system (Myotest SA, Sion, Switzerland) for the assessment of vertical jump height. Forty-four male basketball players (age range: 9-25 years) performed series of squat, countermovement and repeated jumps during 2 identical test sessions separated by 2-15 days. Flight height was simultaneously quantified with the Myotest system and validated photoelectric cells (Optojump). Two calculation methods were used to estimate the jump height from Myotest recordings: flight time (Myotest-T) and vertical takeoff velocity (Myotest-V). Concurrent validity was investigated comparing Myotest-T and Myotest-V to the criterion method (Optojump), and test-retest reliability was also examined. As regards validity, Myotest-T overestimated jumping height compared to Optojump (p < 0.001) with a systematic bias of approximately 7 cm, even though random errors were low (2.7 cm) and intraclass correlation coefficients (ICCs) where high (>0.98), that is, excellent validity. Myotest-V overestimated jumping height compared to Optojump (p < 0.001), with high random errors (>12 cm), high limits of agreement ratios (>36%), and low ICCs (<0.75), that is, poor validity. As regards reliability, Myotest-T showed high ICCs (range: 0.92-0.96), whereas Myotest-V showed low ICCs (range: 0.56-0.89), and high random errors (>9 cm). In conclusion, Myotest-T is a valid and reliable method for the assessment of vertical jump height, and its use is legitimate for field-based evaluations, whereas Myotest-V is neither valid nor reliable.