Reliability of ADR Jumping Photocell: Comparison of Beam Cut at Forefoot and Midfoot

The ability to detect small changes in a vertical jump is crucial when data are used by sports science specialists to monitor their athletes. This study aimed to analyze the intrasession reliability of the ADR jumping photocell and the reliability relative to the position of the transmitter when it is located facing the phalanges of the foot (forefoot) or the metatarsal area (midfoot). A total of 12 female volleyball players performed 240 countermovement jumps (CMJ), alternating both methods. The intersession reliability was higher for the forefoot method (ICC = 0.96; CCC = 0.95; SEM = 1.15 cm; CV = 4.11%) than for the midfoot method (ICC = 0.85; CCC = 0.81; SEM = 3.68 cm; CV = 8.75%). Similarly, the sensitivity values were better for the forefoot method (SWC = 0.32) than for the midfoot method (SWC = 1.04). Significant differences were found between the methods (13.5 cm, p 0.1). In conclusion, the ADR jumping photocell is shown to be a reliable tool for measuring CMJs. However, the reliability of the instrument can be influenced depending on the placement of the device. Comparing the two methods, the midfoot placement was less reliable as indicated by higher values of SEM and systematic error, and thus its use is not recommended.This work was supported by Generalitat Valenciana (grant number GV/2021/098)

Reliability of My Jump 2 Derived from Crouching and Standing Observation Heights

The crouching or prone-on-the-ground observation heights suggested by the My Jump app are not practical in some settings, so users usually hold smartphones in a standing posture. This study aimed to analyze the reliability of My Jump 2 from the standardized and standing positions. Two identical smartphones recorded 195 countermovement jump executions from 39 active adult athletes at heights 30 and 90 cm, which were randomly assessed by three experienced observers. The between-observer reliability was high for both observation heights separately (ICC~0.99; SEM~0.6 cm; CV~1.3%) with low systematic (0.1 cm) and random (±1.7 cm) errors. The within-observer reliability for the three observers comparing the standardized and standing positions was high (ICC~0.99; SEM~0.7 cm; CV~1.4%), showing errors of 0.3 ± 1.9 cm. Observer 2 was the least accurate out of the three, although reliability remained similar to the levels of agreement found in the literature. The reliability of the mean observations in each height also revealed high reliability (ICC = 0.993; SEM = 0.51 cm; CV = 1.05%, error 0.32 ± 1.4 cm). Therefore, the reliability in the standing position did not change with respect to the standardized position, so it can be regarded as an alternative method to using My Jump 2 with practical added benefits.This research was funded by Generalitat Valenciana, grant number GV/2021/098

Reliability of countermovement jump estimation using the Chronojump jump mat: intra-session and within-session

Vertical jump is a fundamental metric for monitoring and regulating lower body capacities, especially in assessing sports performance through the countermovement jump (CMJ). In recent years, various instruments aimed at estimating vertical jump heights have emerged. However, ensuring effective performance monitoring requires that jump mats prove consistency in measuring jumps across repeated tests, i.e., they must prove reliability. This study focuses on evaluating the intra-session and within-session test-retest reliability of the Chronojump jump mat in highly trained female volleyball players. Ten athletes from the Spanish Superliga 2 league participated in 100 CMJs over two sessions spaced a week apart. A repeated measures design collected jump height data using Chronojump jump mat. The protocol included a 10-min warm-up, a 5-min rest, and the execution of 5 CMJs with 2 min of rest between trials. Intra-session test-retest consistency was assessed by analyzing consecutive pairings of the first five trials. The study reveals moderate noise for SEM (1.56 cm) and standardized SEM (0.37), accompanied high SDC (4.33 cm) and SWC (0.44 cm). Correlation analysis indicated very high reliability (ICC =0.89), high concordance (CCC = 0.82) and a moderate CV (5.97%). Regarding within-session reliability, no significant differences were observed (Paired t-test p = 0.08; Hedges effect size g = 0.09). Additionally, very high correlations between both sessions were observed (r = 0.86). Absolute reliability analysis revealed a noise of 1.65 cm (SEM), resulting in high SDC (4.59 cm) and SWC (0.47 cm). Relative reliability, assessed through correlation coefficients, displayed very high values (ICC = 0.89 and CCC =0.89), although a moderate standardized SEM of 0.44 was observed. The Bland-Altman plot indicated systematic errors of the mean of 0.41 cm without substantial dispersion. Linear regression analyses between sessions showed a high correlation (r = 0.86), with a systematic error of 6.65 cm (intercept) and a random error of 2.01 cm (SEE). To sum up, the Chronojump jump mat proves reliability in measuring CMJ in female volleyball players across both intra-session and within-session contexts. High reliability suggests that this instrument can be deemed reliable for such measurements.This work was supported by Generalitat Valenciana (grant number GV/2021/098). Article developed during Dr. Jimenez-Olmedo's research intership with the Sports Biomechanics Research Group (GIBD) (GIUV2019-454) at University of Valencia

Concurrent Validity of the Inertial Measurement Unit Vmaxpro in Vertical Jump Estimation

The aim of this study was to evaluate if the inertial measurement unit (IMU) Vmaxpro is a valid device to estimate vertical jump height (VJH) when compared to a motion capture system (MoCAP). Thirteen highly trained female volleyball players participated in this study which consisted of three sessions. After a familiarization session, two sessions comprised a warm-up followed by ten countermovement jumps, resting two min between each attempt. Jump height was measured simultaneously by Vmaxpro using take-off velocity and MoCAP using center-of-mass vertical excursion. Results show significant differences in jump height between devices (10.52 cm; p < 0.001; ES = 0.9), a very strong Spearman’s correlation (rs = 0.84: p < 0.001), and a weak concordance correlation coefficient (CCC = 0.22; ρ = 0.861; Cb= 0.26). Regression analysis reveals very high correlations, high systematic error (8.46 cm), and a nonproportional random error (SEE = 1.67 cm). Bland–Altman plots show systematic error (10.6 cm) with 97.3 % of the data being within the LoA. In conclusion, Vmaxpro can be considered a valid device for the estimation of VJH, being a cheaper, portable, and manageable alternative to MoCAP. However, the magnitude of systematic error discourages its use where indistinguishable data from Vmaxpro and MoCAP are used unless the corresponding specific fitting equation is applied.This work was supported by Generalitat Valenciana (grant number GV/2021/098)

Test–Retest and Between–Device Reliability of Vmaxpro IMU at Hip and Ankle for Vertical Jump Measurement

The ability to generate force in the lower body can be considered a performance factor in sports. This study aims to analyze the test–retest and between-device reliability related to the location on the body of the inertial measurement unit Vmaxpro for the estimation of vertical jump. Eleven highly trained female athletes performed 220 countermovement jumps (CMJ). Data were simultaneously captured by two Vmaxpro units located between L4 and L5 vertebrae (hip method) and on top of the tibial malleolus (ankle method). Intrasession reliability was higher for ankle (ICC = 0.96; CCC = 0.93; SEM = 1.0 cm; CV = 4.64%) than hip (ICC = 0.91; CCC = 0.92; SEM = 3.4 cm; CV = 5.13%). In addition, sensitivity was higher for ankle (SWC = 0.28) than for the hip method (SWC = 0.40). The noise of the measurement (SEM) was higher than the worthwhile change (SWC), indicating lack of ability to detect meaningful changes. The agreement between methods was moderate (rs= 0.84; ICC = 0.77; CCC = 0.25; SEM = 1.47 cm). Significant differences were detected between methods (−8.5 cm, p < 0.05, ES = 2.2). In conclusion, the location of the device affects the measurement by underestimating CMJ on ankle. Despite the acceptable consistency of the instrument, the results of the reliability analysis reveal a significant magnitude of both random and systematic error. As such, the Vmaxpro should not be considered a reliable instrument for measuring CMJ.This work was supported by Generalitat Valenciana (grant number GV/2021/098)

Squat-based post-activation potentiation improves the vertical jump of elite female volleyball players

The purpose of this study was to confirm if a squat-based conditioning activity was effective in generating post-activation potentiation (PAP), and, as a consequence of this activation, improve the vertical jump (VJ) performance of national female volleyball players. Eleven trained volleyball players (22.6 ± 3.5 years) were randomly divided into two groups: an experimental group (N=6) and a control group (N=5). They completed 2 sessions. In the first session, a back squat one-repetition maximum (1RM) was determined for the experimental group by using an optoelectronic encoder and an incremental protocol until reaching the maximum load lifted for each subject. On the second day, the experimental group performed a PAP procedure consisting of three repetitions of 90% of 1RM. Before and after performing the activation protocol, both groups completed a countermovement jump (CMJ) to verify whether any improvements were accomplished in the VJ. The height of the vertical jump was estimated by using a jump mat. The data obtained were analysed using an ANOVA test to determine the significant differences intra-group and between groups. The pre-PAP test did not establish any differences between the results of the control group (31.35±4.28 cm) and that of the experimental group (34.08±3.98cm), Therefore, the groups were, at first, homogeneous. On the other hand, there were significant differences in the CMJ percentage of improvement between the experimental and control groups in the post-PAP test F(1,9)=6.074; p=0.036; ▢2=0.40. The control group presented a loss in jump height in the CMJ, thus obtaining negative values in the improvement percentage (-5.36%). The experimental group improved its jump height (4.11%). These differences between groups were statistically significant F(1,9)=6.673; p=0.030; ▢2=0.43. Finally, no significant differences were found intragroup between the pre and post-PAP test in both groups. To conclude, squat-based PAP protocols can generate positive effects on the vertical jump performance of elite female volleyball players. It may therefore be relevant to introduce these activation methods in the warm-up protocols of volleyball players.This study was supported by a pre-doctoral grant (ACIF/2018/209) from the Generalitat Valenciana, Spain, and vice-rectorate program of research and knowledge transfer for the promotion of R+D+I at the University of Alicante (Ref. GRE18-19)

Validity and reliability of smartphone high-speed camera and Kinovea for velocity-based training measurement

The aim of this study was to validate the combination of smartphone high-speed camera and motion analysis software Kinovea methodology (SHSC-Kinovea) to measure kinematic variables of velocity-based training during back squat exercises. Fifteen athletes were voluntarily recruited for the study (age 22.8 ± 2.9 years, height 182.9 ± 8.9 cm, body mass 79.5 ± 9.6 kg). High-speed video recordings with a smartphone at 240 fps were used against a criterion linear force transducer (LPT) for measuring displacement of the barbell (RB), mean velocity (MV), maximum velocity (Vmax) and concentric phase time (CPT). The intra-class correlations coefficient between LPT and SHSC-Kinovea showed almost perfect agreement for consistency (.992, .995, .997, .993) and absolute agreement (.975, .978, .980, .964) for RB, MV, Vmax and CPT, respectively. The mean differences between instruments were 1.11 mm for RB, 0.03 m/s for MV, 0.05 m/s for Vmax and 65.91 ms for CPT, all p < .001. Bland-Altman plots showed low systematic bias ± random error for RB: 1.11 ± 1.50 cm (r2: .006), MV: 0.03 ± 0.33 m/s (r2: .001) and Vmax: 65.91 ± 63.82 m/s (r2: .11), whereas Vmax showed overestimation for the high range of measures: 0.55 ± 0.42 m/s (r2: .31). Pearson’s product moment correlation coefficient showed almost perfect association between all variables: (r = .985 - .990) (p < .001). The SHSC-Kinovea methodology resulted in similar kinematic values than criterion so it can be considered as a trustworthy instrument for measuring velocity-based training.This study was supported by vice-rectorate program of research and knowledge transfer for the promotion of R+D+I at the University of Alicante (Ref. GRE18-19)

Stability of Running Stride Biomechanical Parameters during Half-Marathon Race

This study explores the stability of biomechanical parameters of the running stride of male trained athletes during a half-marathon competition. Using a field-based descriptive design, eight male athletes from a local training group were monitored throughout an official half-marathon race under identical conditions, assessing biomechanical parameters including ground contact time (GCT), leg spring stiffness (LSS), vertical oscillation (VO), and stride length (SL) recorded via the Stryd Summit Power Meter. A repeated measures analysis of variance (RM ANOVA) was conducted to detect significant changes in biomechanical parameters as the race progressed. Results demonstrated minimal changes in all parameters, with no significant differences observed for GCT (F = 0.96, p = 0.38), VO (F = 0.23, p = 0.87), and SL (F = 1.07, p = 0.35), and a small (η2 = 0.004) yet statistically significant difference in LSS (F = 5.52, p = 0.03) between the first and second segments, indicating that athletes were able to maintain stable biomechanical parameters throughout the race. The conclusion highlights the need for personalized training programs tailored to the unique biomechanical adaptations and demands of endurance running.This work was supported by Generalitat Valenciana (grant number GV/2021/098)

Validity and Reliability of the VmaxPro IMU for back squat exercise in multipower machine

Problem Statement: Currently, the application for velocity-based training through a 3D Motion Capture System is discarded due to the economic and personal resources involved, being used mainly as laboratory instruments. As an alternative, different device on the market make it possible to assess and control training loads, although not all use the same technology to measure execution velocity. Approach: Specifically, the inertial measurement unit VmaxPro is one of the new additions to the market of sensors based on accelerometry for the control of execution velocity in resistance training and the reliability and validity of this type of device need to be analysed. Purpose: Thus, this study aimed to conduct a concurrent validation for the velocity and range of displacement of the barbell of VmaxPro against a 3D Motion Capture System as the gold standard. The secondary purposes of this study were to analyse the reliability and measurement errors (both random and systematic) of VmaxPro. Results: The main results of the present study are shown in terms of reliability, validity, and accuracy of the VmaxPro. Firstly, the practical device shows excellent to good ICCs values for the reliability of the velocity and range of displacement of the barbell, respectively. Secondly, VmaxPro presents a small underestimation of the velocity of its systematic error (-0.021 m/s) in comparison to the 3D Motion Capture System, contrary to the random error (0.053 m/s), overestimating the velocity measurement, and a measurement errors both systematic and random close to 2 cm for the range of barbell displacement. Finally, VmaxPro presents valid values for both the velocity and range of displacement of the barbell, being a suitable instrument for this purpose. Conclusions: It would be possible for both coaches and athletes to use the inertial measurement unit VmaxPro for the control, monitoring, and evaluation of strength training.This work was supported by Generalitat Valenciana (grant number GV/2021/098)

Postactivation Performance Enhancement (PAPE) Increases Vertical Jump in Elite Female Volleyball Players

The purpose of this study was to verify if a conditioning activity was effective to elicit postactivation performance enhancement (PAPE) and to increase the performance in vertical jump (VJ) in elite female volleyball players. Eleven national Superliga-2 volleyball players (22.6 ± 3.5 years) were randomly assigned to an experimental and control group. Countermovement jumps (CMJ) were performed on eight occasions: before (Pre-PAPE) and after activation (Post-PAPE), after the match (Pre-Match), and after each of the five-match sets (Set 1 to 5). ANOVA showed significantly increased jump performance for the experiment between baseline (Pre-PAPE) and all the following tests: +1.3 cm (Post-PAPE), +3.0 cm (Pre-Match), +4.8 cm (Set 1), +7.3 cm (Set 2), +5.1 cm (Set 3), +3.6 cm (Set 4), and +4.0 cm (Set 5), all showing medium to large effect size (0.7 < ES < 2.4). The performance of the control group did not show significant increases until Set 3 (+3.2 cm) and Set 5 (+2.9 cm), although jump heights were always lower for the control group than the experimental. The use of conditioning activity generates increased VJ performance in Post-PAPE tests and elicited larger PAPE effects that remain until the second set of a volleyball match.This research was funded by Generalitat Valenciana, grant number GV/2021/098