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The Validity and Reliability of the 'MyJump2' Application to Assess Vertical Jumps in Trained Junior Athletes

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Title: The Validity and Reliability of the 'MyJump2' Application to Assess Vertical Jumps in Trained Junior Athletes
Language: English
Authors: Rogers, Simon A. (ORCID 0000-0002-2630-4411), Hassmén, Peter, Hunter, Adam, Alcock, Alison, Crewe, Stewart T., Strauts, Janina A., Gilleard, Wendy L., Weissensteiner, Juanita R.
Source: Measurement in Physical Education and Exercise Science. 2019 23(1):69-77.
Availability: Routledge. Available from: Taylor & Francis, Ltd. 530 Walnut Street Suite 850, Philadelphia, PA 19106. Tel: 800-354-1420; Tel: 215-625-8900; Fax: 215-207-0050; Web site: http://www.tandf.co.uk/journals
Peer Reviewed: Y
Page Count: 9
Publication Date: 2019
Document Type: Journal Articles
Reports - Research
Descriptors: Adolescents, Athletes, Measurement Equipment, Handheld Devices, Computer Oriented Programs, Physical Activities, Muscular Strength, Talent Identification, Motion, Psychomotor Skills, Test Validity, Test Reliability, Interrater Reliability
DOI: 10.1080/1091367X.2018.1517088
ISSN: 1091-367X
Abstract: This study aimed to assess the validity and reliability of jump assessments using the "MyJump2" application. Eleven junior athletes (15 ± 1.4 years) performed five countermovement (CMJ) and drop jumps (DJ) measured simultaneously by a force platform and "MyJump2." Additionally, intra- and inter-day reliability was assessed over two sessions, 7 days apart. "Extremely high" agreement between "MyJump2" and the force platform (intra-class correlation coefficient, ICC = 0.99) and the intra- and inter-operator agreement (ICC = 0.98-0.99) confirmed the validity and reliability of "MyJump2." Mean typical errors (coefficient of variation percentage, CV%) within the first and second sessions were 4.9% and 4.5% respectively for CMJs, and 8.0% to 11.8% for DJ outcomes. CMJ height held acceptable inter-day reliability (CV < 10%; ICC > 0.8), while DJ did not. Results supported "MyJump2" to be a valid and reliable tool for assessing jumps; however, with variability in DJs in this cohort, appropriate caution should be taken if including in a junior assessment battery.
Abstractor: As Provided
Entry Date: 2019
Accession Number: EJ1209857
Database: ERIC
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  Value: &lt;anid&gt;AN0135500789;7mm01jan.19;2019Mar25.10:30;v2.2.500&lt;/anid&gt; &lt;title id=&quot;AN0135500789-1&quot;&gt;The Validity and Reliability of the MyJump2 Application to Assess Vertical Jumps in Trained Junior Athletes&#160;&lt;/title&gt; &lt;p&gt;This study aimed to assess the validity and reliability of jump assessments using the MyJump2 application. Eleven junior athletes (15&#160;&#177;&#160;1.4&#160;years) performed five countermovement (CMJ) and drop jumps (DJ) measured simultaneously by a force platform and MyJump2. Additionally, intra- and inter-day reliability was assessed over two sessions, 7 days apart. Extremely high agreement between MyJump2 and the force platform (intra-class correlation coefficient, ICC ≥&#160;0.99) and the intra- and inter-operator agreement (ICC&#160;=&#160;0.98-0.99) confirmed the validity and reliability of MyJump2. Mean typical errors (coefficient of variation percentage, CV%) within the first and second sessions were 4.9% and 4.5% respectively for CMJs, and 8.0% to 11.8% for DJ outcomes. CMJ height held acceptable inter-day reliability (CV &amp;lt; 10%; ICC &amp;gt; 0.8), while DJ did not. Results supported MyJump2 to be a valid and reliable tool for assessing jumps; however, with variability in DJs in this cohort, appropriate caution should be taken if including in a junior assessment battery.&lt;/p&gt; &lt;p&gt;Keywords: Testing; talent-identification; reactive strength; mobile device&lt;/p&gt; &lt;hd id=&quot;AN0135500789-2&quot;&gt;Introduction&lt;/hd&gt; &lt;p&gt;The increased focus on appropriate strength and neuromuscular training interventions for youth athletes (Bergeron et al., 2015; Lloyd et al., 2016) has led more coaches to seek accessible, low-cost, and reliable assessment tools to understand performance and capacities prior to and during appropriate interventions. Tasks such as the countermovement jump (CMJ) and drop jump (DJ) offer a simple method to assess lower-limb power capacities and reactive strength, requiring athletes to utilize slow and fast muscle stretch-shortening cycle actions, respectively (Komi, 2000). While force platforms are considered the gold standard to capture flight times for subsequent jump outcomes (Cronin, Hing, &amp;amp; Mcnair, 2004; Glatthorn et al., 2011), recent tools such as contact mats, accelerometers, linear position transducers, high-speed cameras, and mobile phone applications may negate the need for expensive laboratory equipment, expert operation, and time-consuming analysis. One such tool is the &lt;emph&gt;MyJump&lt;/emph&gt; mobile application (APP), and the most recent version of this is &lt;emph&gt;MyJump2&lt;/emph&gt;, which utilizes video captured by the high-speed camera in smartphones and iPad devices. This APP guides operators to manually select foot &#39;take-off&#39; and &#39;touch-down&#39; video frames, with the time between these video frames used in the calculation of jump outcomes (Balsalobre-Fern&#225;ndez, Glaister, &amp;amp; Lockey, 2015). The appeal for practitioners is evident through a series of recent publications reporting various validity and reliability data on the first &lt;emph&gt;MyJump&lt;/emph&gt; release (Balsalobre-Fern&#225;ndez et al., 2015; Carlos-Vivas, Martin-Martinez, Hernandez-Mocholi, &amp;amp; Perez-Gomez, 2016; Driller, Tavares, McMaster, &amp;amp; O&#39;Donnell, 2017; Gallardo-Fuentes et al., 2016; Stanton, Wintour, &amp;amp; Kean, 2017), and most recently using &lt;emph&gt;MyJump2&lt;/emph&gt; (Haynes, Bishop, Antrobus, &amp;amp; Brazier, 2018).&lt;/p&gt; &lt;p&gt;Previous studies have compared jump height estimations between a criterion (force platform) and field-based tools including several with mobile devices (Balsalobre-Fern&#225;ndez et al., 2015; Carlos-Vivas et al., 2016; Driller et al., 2017; Haynes et al., 2018; Stanton et al., 2017), high speed video (Balsalobre-Fern&#225;ndez, Tejero-Gonz&#225;lez, del Campo-Vecino &amp;amp; Bavaresco, 2014), and a linear position transducer (O&#39;Donnell, Tavares, McMaster, Chambers, &amp;amp; Driller, 2018), with consistent findings appearing in estimations of CMJ and DJ heights, with high levels of agreement between the criterion and field-based tool used in each study. This agreement may, however, depend on different study designs including, mobile device models, cohorts assessed, criterion sampling frequencies, and types of reliability reported; future recommendations for longitudinal tracking with multiple &lt;emph&gt;MyJump2&lt;/emph&gt; outputs may therefore be problematic. The majority of reports assessing validity and reliability of the original &lt;emph&gt;MyJump&lt;/emph&gt; APP to assess DJs have relied only on jump height (Gallardo-Fuentes et al., 2016; Stanton et al., 2017). Yet the primary outcome of a DJ assessment is not only jump height but a combination of both height (or flight time) and the ground contact time to absorb and generate force following the initial landing (Beattie &amp;amp; Flanagan, 2015). As such, the reactive strength index (RSI) or reactive strength ratio (RSR) outcomes incorporate jump height or flight time values, respectively (Flanagan &amp;amp; Comyns, 2008). The reactive strength outcomes are an indicator of rapid muscle stretch-shortening cycle capability, which can be associated with effective neuromuscular activity and control (Flanagan, Ebben, &amp;amp; Jensen, 2008). Lower RSI values have previously also been associated with injury risk in pre-elite athletes (Raschner et al., 2012). Following the release of &lt;emph&gt;MyJump2&lt;/emph&gt;, Haynes et al. (2018) assessed validity and reliability of RSI in adult male students performing DJs; they found near-perfect agreement between &lt;emph&gt;MyJump2&lt;/emph&gt; and a force platform when the APP was used by one operator. Nonetheless, both intra- and inter-operator reliability are important considerations when using assessment tools which require human input to manually identify visual landmarks - these were not included in the Haynes et al.&#39;s (2018) study. For example, the same athlete may be assessed by one or more APP operators (multiple coaches/training environments), each of which can hold different biases or experience toward the analysis. Stanton et al. (2017) reported that intra-operator differences were small, but a statistically significant mean difference in DJ jump height was nevertheless detected when assessing the same jumps 7-days apart. This is yet to be reported for the RSI outcome from the APP directly, or RSR calculated outside the APP using the flight and contact times provided by the APP. To date, only two studies using MyJump (Balsalobre-Fern&#225;ndez et al., 2015; Driller et al., 2017) have examined the inter-operator reliability between two different APP users assessing CMJ height, and high agreement was reported (intra-class correlation coefficient, ICC&#160;=&#160;0.999 and 0.97). Yet, as operators in the original &lt;emph&gt;MyJump&lt;/emph&gt; publication were both novice users (Balsalobre-Fern&#225;ndez et al., 2015), it remains unknown how prior APP experience affects this level of agreement.&lt;/p&gt; &lt;p&gt;Reliability of any athletic assessment can be specific to the context in which the performance takes place (Markwick, Bird, Tufano, Seitz, &amp;amp; Haff, 2015). To date, only Gallardo-Fuentes et al. (2016) have performed both intra- and intersession reliability assessments using &lt;emph&gt;MyJump&lt;/emph&gt; in highly trained adult athletes. In practice, when youth athletes formally undergo assessments for the first time, familiarization is often not feasible on a separate day prior to testing. This can be due to time constraints or large cohorts within school or sporting settings when testing occurs (Hackett, Davies, Ibel, Cobley, &amp;amp; Sanders, 2018). Thus, even with ample on the day familiarization, changes in performance from one assessment point to the next, can be due to learning effects, rather than a true change in performance. To assess the intersessional performance of younger athletes, &lt;emph&gt;MyJump2&lt;/emph&gt; may be utilized in the future by those working with this population. Thus, more information is needed for the between-day reliability of this cohort when assessed with mobile technology.&lt;/p&gt; &lt;p&gt;To our knowledge, there are no studies that have employed &lt;emph&gt;MyJump&lt;/emph&gt; or &lt;emph&gt;MyJump2&lt;/emph&gt; to assess youth athletes, who are likely to display a wider range of jump capabilities than senior athletes or recreationally trained adults (Radnor et al., 2017). This study therefore aimed to assess the concurrent validity and reliability of a practical tool in assessing trained junior athletes, in order to confidently monitor impacts of training interventions. Specifically, we aimed to (&lt;reflink idref=&quot;bib1&quot; id=&quot;ref1&quot;&gt;1&lt;/reflink&gt;) assess the validity of CMJ and DJ variables measured by &lt;emph&gt;MyJump2&lt;/emph&gt; against a force platform; (&lt;reflink idref=&quot;bib2&quot; id=&quot;ref2&quot;&gt;2&lt;/reflink&gt;) assess the intra- and inter-tester reliability of experienced and novice operators of &lt;emph&gt;MyJump2&lt;/emph&gt;; and (&lt;reflink idref=&quot;bib3&quot; id=&quot;ref3&quot;&gt;3&lt;/reflink&gt;) report the intra- and intersessional reliability of adolescent athletes being measured by &lt;emph&gt;MyJump2&lt;/emph&gt;.&lt;/p&gt; &lt;hd id=&quot;AN0135500789-3&quot;&gt;Methods&lt;/hd&gt; &lt;p&gt;&lt;/p&gt; &lt;hd id=&quot;AN0135500789-4&quot;&gt;Participants&lt;/hd&gt; &lt;p&gt;Eleven junior athletes (four female; seven male), taking part in regular training and competition for state-level athletics, participated in this study (age&#160;=&#160;15.0&#160;&#177;&#160;1.4&#160;years, height&#160;=&#160;170.9&#160;&#177;&#160;11.0&#160;cm, body mass&#160;=&#160;57.7&#160;&#177;&#160;7.1&#160;kg). Athletes were routinely performing 8.9&#160;&#177;&#160;4.9&#160;hr of training and competition per week across a variety of modalities (sprinting, running drills, gymnastics). To be eligible for inclusion, athletes were free from any musculoskeletal injury or other health concerns. The testing protocol was approved by the University Human Ethics Committee (ECN-16-296), with informed consent from each participant and their parent/guardian obtained prior to study commencement. The experienced APP operator performing analysis held prior experience as a practitioner using the original version of &lt;emph&gt;MyJump&lt;/emph&gt;, coupled with other lower-limb high-speed video analysis experience. In contrast, the novice operator, used as a comparison in this study, had no prior use with any version &lt;emph&gt;MyJump&lt;/emph&gt; or high-speed video analysis of foot contacts.&lt;/p&gt; &lt;hd id=&quot;AN0135500789-5&quot;&gt;Procedures&lt;/hd&gt; &lt;p&gt;Height (SECA, Hamburg, Germany) and body mass (A&amp;amp;D, Thebarton, SA, Australia) were measured prior to testing. Following a standardized warm-up (light jogging, body weight squats, and lunges), participants performed three submaximal and three maximal familiarization attempts of a CMJ and a DJ. Jumps were performed with hands on hips and to a self-selected countermovement depth (Buchheit &amp;amp; Mendez-Villanueva, 2013; Stanton et al., 2017). For CMJs, participants were instructed to jump as high as possible from a rapid countermovement. For DJs, athletes stepped off a 30-cm box positioned 10&#160;cm from the edge of a force platform and then jumped as high as possible with minimal contact time, as outlined previously (Lloyd, Oliver, &amp;amp; Hughes, 2009). After familiarization, each participant performed five CMJs and five DJs on a force platform with each jump videoed with an iPad Pro (see the &#39;Equipment&#39;section). If jump technique criteria were not met (e.g., hands came off hips, knee flexion during flight phase), the trial was discarded. Each jump was separated by 30&#160;sec rest, and approximately 10&#160;min between CMJ and DJ tasks. Participants repeated all procedures after 7 days in the same indoor conditions and at the same time of day. On both testing occasions, athletes reported for testing having not performed any training activities in the previous 24&#160;hours.&lt;/p&gt; &lt;hd id=&quot;AN0135500789-6&quot;&gt;Equipment&lt;/hd&gt; &lt;p&gt;An iPad Pro 9.7″ (A1673, Apple Inc., Cupertino, CA, USA) running iOS 11 was secured to a small tripod with a mount (GripTight Mount Pro, Joby, USA) and positioned 90&#160;cm from the center of the force platform and with the camera lens 5&#160;cm above the ground to minimize foot shadowing. All jumps were recorded at 240&#160;Hz (720 &#215; 1080 pixel resolution). The iPad video files were imported into the &lt;emph&gt;MyJump2&lt;/emph&gt; APP and analyses performed following the APP instructions.&lt;/p&gt; &lt;p&gt;A Kistler 600&#160;&#215;&#160;900&#160;mm force platform (9287C, Kistler Instruments Ltd., Winterthur, Switzerland) sampling at 1200&#160;Hz was used and data captured using BioWare (5.3.0.7, Kistler, Winterthur, Switzerland). The force-time data were extracted and used to compute the same jump variables as the APP using the formulae provided by the &lt;emph&gt;MyJump2&lt;/emph&gt; developer and presented in Table 1. Force platform take-off was defined as the time when vertical ground reaction force (vGRF) was &amp;lt;&#160;10&#160;N and landing when vGRF was &amp;gt;&#160;10&#160;N (Linthorne, 2001; Lloyd et al., 2009). Flight times and contact times were defined as the time between take-off and landing points accordingly.&lt;/p&gt; &lt;p&gt;Summary of variables from data acquired via the MyJump2 application and force platform.&lt;/p&gt; &lt;p&gt; &lt;ephtml&gt; &amp;lt;table border=&quot;1&quot; cellpadding=&quot;4&quot;&amp;gt;&amp;lt;tbody&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td /&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Variables acquired from &amp;lt;italic&amp;gt;MyJump2&amp;lt;/italic&amp;gt; and force platform&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Calculations performed&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Reference&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;/tbody&amp;gt;&amp;lt;tbody&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;CMJ - height (cm)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;&amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;f&amp;lt;/sub&amp;gt;&amp;amp;#160;=&amp;amp;#160;flight time jump (sec)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;&amp;lt;inline-graphic href=&quot;&quot; /&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;Balsalobre-Fern&amp;amp;#225;ndez et al. (&amp;lt;xref ref-type=&quot;ref&quot; rid=&quot;ref2&quot;&amp;gt;2015&amp;lt;/xref&amp;gt;)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;DJ - reactive strength ratio (RSR)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;&amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;f&amp;lt;/sub&amp;gt;&amp;amp;#160;=&amp;amp;#160;flight time (after first contact) &amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt;&amp;amp;#160;=&amp;amp;#160;contact time (sec)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;&amp;lt;inline-graphic href=&quot;&quot; /&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;Markwick et al. (&amp;lt;xref ref-type=&quot;ref&quot; rid=&quot;ref23&quot;&amp;gt;2015&amp;lt;/xref&amp;gt;)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;DJ - reactive strength index (RSI)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;&amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;f&amp;lt;/sub&amp;gt;&amp;amp;#160;=&amp;amp;#160;flight time (after first contact) &amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt;&amp;amp;#160;=&amp;amp;#160;contact time (msec)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;&amp;lt;inline-graphic href=&quot;&quot; /&amp;gt;&amp;lt;inline-graphic href=&quot;&quot; /&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;Flanagan and Comyns (&amp;lt;xref ref-type=&quot;ref&quot; rid=&quot;ref10&quot;&amp;gt;2008&amp;lt;/xref&amp;gt;)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;/tbody&amp;gt;&amp;lt;/table&amp;gt; &lt;/ephtml&gt; CMJ&#160;=&#160;countermovement jump, DJ&#160;=&#160;drop jump, &lt;emph&gt;h&#160;=&#160;&lt;/emph&gt;jump height, &lt;emph&gt;t&lt;/emph&gt;&lt;subs&gt;c&lt;/subs&gt;&#160;=&#160;contact time, &lt;emph&gt;t&lt;/emph&gt;&lt;subs&gt;f&lt;/subs&gt;&#160;=&#160;flight time.&lt;/p&gt; &lt;hd id=&quot;AN0135500789-7&quot;&gt;Statistical analyses&lt;/hd&gt; &lt;p&gt;Descriptive statistics (mean &#177;&#160;&lt;emph&gt;SD&lt;/emph&gt;) were calculated for each jump outcome across the two testing sessions. To assess concurrent validity between the APP and the force platform for both CMJ and DJs, the five successful jump trials from each of the 11 participants were recorded and pooled from the two sessions, giving a total of 110 individual trials of each jump task. The percentage difference, typical error of measurement (TEM), and ICCs (&lt;reflink idref=&quot;bib2&quot; id=&quot;ref4&quot;&gt;2&lt;/reflink&gt;,&lt;reflink idref=&quot;bib1&quot; id=&quot;ref5&quot;&gt;1&lt;/reflink&gt;) were calculated. This was complimented with Bland-Altman plots (Altman &amp;amp; Bland, 1983). To assess the intra-operator reliability, the experienced APP user reassessed a subset of jump videos (&lt;emph&gt;N&#160;&lt;/emph&gt;=&#160;22 for each jump task), 4 weeks apart, while blinded to the first assessment results. Paired &lt;emph&gt;t&lt;/emph&gt; tests, mean differences with 95% confidence intervals (95% CIs), and correlation coefficients were used to compare the jump outcomes assessed over the two occasions by the same operator, and between the two operators (defined above). For intra-session reliability of the five recorded attempts of each jump by each participant, the TEM was calculated (Hopkins, 2000) and then converted to a percentage (coefficient of variation, CV%) using an open-source spreadsheet (Hopkins, 2015) as published previously (Lombard, Reid, Pearson, &amp;amp; Lambert, 2017; Roe et al., 2016; Sawczuk et al., 2018). For intersession reliability, the mean of the best three jumps for outcomes from &lt;emph&gt;MyJump2&lt;/emph&gt; were compared between the 2 days, using the TEM as a CV%. In addition, ICC (&lt;reflink idref=&quot;bib2&quot; id=&quot;ref6&quot;&gt;2&lt;/reflink&gt;,&lt;reflink idref=&quot;bib1&quot; id=&quot;ref7&quot;&gt;1&lt;/reflink&gt;) was also calculated to provide an additional criteria for acceptable intersession reliability. A jump outcome was regarded as reliable if it had a CV &amp;lt;&#160;10% and ICC ≥&#160;0.80 (Beattie &amp;amp; Flanagan, 2015). For the intra- and inter-rater analyses, the level of statistical significance was set at &lt;emph&gt;p&lt;/emph&gt;&#160;&amp;lt;&#160;0.05 and tests performed using SPSS V 19 (IBM Co., Chicago, IL, USA). ICCs were reported with the flowing thresholds: &amp;gt;&#160;0.99, &lt;emph&gt;extremely high&lt;/emph&gt;; 0.99-0.90, &lt;emph&gt;very high&lt;/emph&gt;; 0.90-0.75, &lt;emph&gt;high&lt;/emph&gt;; 0.75-0.50, &lt;emph&gt;moderate&lt;/emph&gt;; 0.50-0.20, &lt;emph&gt;low&lt;/emph&gt;; &amp;lt;&#160;0.20, &lt;emph&gt;very low&lt;/emph&gt; (Buchheit &amp;amp; Mendez-Villanueva, 2013).&lt;/p&gt; &lt;hd id=&quot;AN0135500789-8&quot;&gt;Results&lt;/hd&gt; &lt;p&gt;There were &lt;emph&gt;extremely high&lt;/emph&gt; agreements between the force platform and &lt;emph&gt;MyJump2&lt;/emph&gt; for assessing jump height in the CMJ, and the RSR and RSI in 30&#160;cm DJs (Figure 1). The &lt;emph&gt;extremely high&lt;/emph&gt; ICCs (≥&#160;0.99), with tight 95% CIs are presented in Table 2. Further analysis of the Bland-Altman plots revealed very low &lt;emph&gt;R&lt;/emph&gt;&lt;sups&gt;2&lt;/sups&gt; values (&lt;emph&gt;R&lt;/emph&gt;&lt;sups&gt;2&lt;/sups&gt;&#160;≤&#160;0.13), meaning outcomes estimated from &lt;emph&gt;MyJump2&lt;/emph&gt; had no predisposition to overestimate or underestimate jump performance.&lt;/p&gt; &lt;p&gt;Jump measures from a force platform and MyJump2 application for 110 trials for each jump metric.&lt;/p&gt; &lt;p&gt; &lt;ephtml&gt; &amp;lt;table border=&quot;1&quot; cellpadding=&quot;6&quot;&amp;gt;&amp;lt;tbody&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td /&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Force plate&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;&amp;lt;italic&amp;gt;MyJump2&amp;lt;/italic&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Mean bias raw&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;TEM raw&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Agreement&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;Metric&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Mean &amp;amp;#177;&amp;amp;#160;&amp;lt;italic&amp;gt;SD&amp;lt;/italic&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Mean &amp;amp;#177;&amp;amp;#160;&amp;lt;italic&amp;gt;SD&amp;lt;/italic&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Mean &amp;amp;#177;&amp;amp;#160;&amp;lt;italic&amp;gt;SD&amp;lt;/italic&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;(95% CI)&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;ICC&amp;lt;sub&amp;gt;2,1&amp;lt;/sub&amp;gt; (95% CI)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;/tbody&amp;gt;&amp;lt;tbody&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;CMJ - height (cm)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;30.09&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;3.48&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;29.49&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;3.48&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.59&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.32&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.22 (0.20-0.26)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.996 (0.994-0.997)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;DJ - reactive strength ratio &amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;f&amp;lt;/sub&amp;gt;/&amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;2.05&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.33&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;1.96&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.31&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.09&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.04&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.03 (0.03-0.03)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.992 (0.988-0.994)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;DJ - reactive strength index &amp;lt;italic&amp;gt;h&amp;lt;/italic&amp;gt; (mm)/&amp;lt;italic&amp;gt;t&amp;lt;/italic&amp;gt;&amp;lt;sub&amp;gt;c&amp;lt;/sub&amp;gt;&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;1.11&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.23&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;1.05&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.23&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.06&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.03&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.02 (0.02-0.02)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;0.993 (0.990-0.995)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;/tbody&amp;gt;&amp;lt;/table&amp;gt; &lt;/ephtml&gt; CMJ&#160;=&#160;countermovement jump, DJ&#160;=&#160;drop jump &lt;emph&gt;t&lt;/emph&gt;&lt;subs&gt;c&lt;/subs&gt;&#160;=&#160;contact time, &lt;emph&gt;t&lt;/emph&gt;&lt;subs&gt;f&lt;/subs&gt;&#160;=&#160;flight time, &lt;emph&gt;h&#160;=&#160;&lt;/emph&gt;jump height, TEM&#160;=&#160;typical error of measurement, ICC&#160;=&#160;intraclass correlation coefficient, 2,1&#160;=&#160;two-way random effects, absolute agreement, CI&#160;=&#160;confidence interval.&lt;/p&gt; &lt;p&gt;PHOTO (COLOR): Figure 1. Level of agreement (Bland-Altman) with 95% limits of agreement (dashed lines) and the mean difference (solid line) between MyJump2 and the force platform for (A) CMJ height, (B) drop jump RSR, and (C) drop jump RSI.&lt;/p&gt; &lt;p&gt;The small mean differences between tools are a result of the different temporal landmarks selected and detected by the two measurement tools (i.e., &lt;emph&gt;MyJump2&lt;/emph&gt; and the force platform). The mean difference in the raw flight times for all analyzed CMJs (&lt;emph&gt;N&lt;/emph&gt;&#160;=&#160;110) was 0.00492&#160;&#177;&#160;0.00267&#160;sec. While for DJs (&lt;emph&gt;N&lt;/emph&gt;&#160;=&#160;110), the mean difference in raw contact and flight times was 0.00620&#160;&#177;&#160;0.00255 and 0.00631&#160;&#177;&#160;0.00280&#160;sec, respectively. The agreement in outcome variables reported are a direct result of these time differences, as temporal values were used in the jump output equations (Table 1).&lt;/p&gt; &lt;p&gt;The &lt;emph&gt;MyJump2&lt;/emph&gt; analysis performed by the experienced operator on the first occasion held &lt;emph&gt;extremely high&lt;/emph&gt; correlations (ICC&#160;=&#160;0.996) to the reanalysis of the same jumps 4 weeks later, with no significant differences (&lt;emph&gt;p&#160;&lt;/emph&gt;&amp;gt;&#160;0.05) across CMJ or DJ metrics (Figure 2). The inter-operator reliability analysis between the experienced and a novice operator revealed small, but significant (&lt;emph&gt;p&lt;/emph&gt;&#160;&amp;lt;&#160;0.01), mean differences in RSR and RSI outcomes (Figure 2), while still producing extremely high agreement between operators (&lt;emph&gt;r&lt;/emph&gt;&#160;≥&#160;0.99). For CMJ height, the novice operator produced slightly lower, but nonsignificant (&lt;emph&gt;p&lt;/emph&gt;&#160;&amp;gt;&#160;0.05) differences in jump height estimation (0.21&#160;cm), with &lt;emph&gt;very high&lt;/emph&gt; agreement to the experience operator (ICC&#160;=&#160;0.985). On all three outcomes, the experienced operator was slightly closer to the force plate values than the novice operator.&lt;/p&gt; &lt;p&gt;PHOTO (COLOR): Figure 2. Comparisons between force platform (FP) outcomes, experienced (EXP) MyJump2 operator performing the analysis twice (T1 and T2) and a novice (NOV) MyJump2 operator for (A) Countermovement jump height, (B) Reactive Strength Ratio, and (C) Reactive Strength Index. Plot illustrates all individual samples of 22 trials per jump metric. Means reported on central horizontal line, with error bars the upper and lower 95% confidence intervals. #&#160;=&#160;no significant difference (p&#160;≥&#160;0.05), *significant difference (p&#160;&amp;lt;&#160;0.05), **significant difference (p&#160;&amp;lt;&#160;0.01).&lt;/p&gt; &lt;p&gt;The junior athletes in this study showed a range of intra-sessional variability in jump performance. The variability within trials was smallest in the CMJ, with the CV &amp;lt;&#160;5% across both sessions. The RSR and RSI values had acceptable intra-sessional reliability within session one. However, in the second session 7 days later, athletes showed greater RSR and RSI variability (Table 3).&lt;/p&gt; &lt;p&gt;Intra-sessional reliability from five jump attempts in junior athletes using the MyJump2 APP.&lt;/p&gt; &lt;p&gt; &lt;ephtml&gt; &amp;lt;table border=&quot;1&quot; cellpadding=&quot;5&quot;&amp;gt;&amp;lt;tbody&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td /&amp;gt;&amp;lt;td align=&quot;center&quot; colspan=&quot;2&quot;&amp;gt;Trials from Session 1&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot; colspan=&quot;2&quot;&amp;gt;Trials from Session 2&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td /&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Mean &amp;amp;#177;&amp;amp;#160;SD&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;CV% (90% CIs)&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;Mean &amp;amp;#177;&amp;amp;#160;SD&amp;lt;/td&amp;gt;&amp;lt;td align=&quot;center&quot;&amp;gt;CV% (90% CIs)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;/tbody&amp;gt;&amp;lt;tbody&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;CMJ - height (cm)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;29.5&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;3.9&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;4.9 (4.1-6.3)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;29.3&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;3.5&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;4.5 (3.7-5.8)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;DJ - reactive strength ratio&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;1.9&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.3&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;8.0 (6.7-10.3)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;2.0&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.3&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;11.8 (9.7-15.2)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;tr&amp;gt;&amp;lt;td&amp;gt;DJ - reactive strength index&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;1.0&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.2&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;9.8 (8.1-12.6)&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;1.1&amp;amp;#160;&amp;amp;#177;&amp;amp;#160;0.2&amp;lt;/td&amp;gt;&amp;lt;td&amp;gt;11.6 (9.6-15.0)&amp;lt;/td&amp;gt;&amp;lt;/tr&amp;gt;&amp;lt;/tbody&amp;gt;&amp;lt;/table&amp;gt; &lt;/ephtml&gt; CV%&#160;=&#160;coefficient of variation as the typical error expressed as a percentage of the mean, CIs&#160;=&#160;conference intervals, CMJ&#160;=&#160;countermovement jump, DJ&#160;=&#160;drop jump.&lt;/p&gt; &lt;p&gt;Test-retest reliability, taken from the mean of the best three trials of each day, was found to be acceptable for CMJ height (CV ≤&#160;10% and ICC ≥&#160;0.8), while the intersession or between-day reliability for both DJ calculations (RSR and RSI) did not meet these thresholds previously suggested and utilized in studies assessing DJ reliability in athletes (Beattie &amp;amp; Flanagan, 2015) (Figure 3). In support of this finding, as shown in Figure 4, in the current cohort of junior athletes, there was wide individual variation across participants in the degree of change from session one to session two in RSR and RSI compared to CMJ height.&lt;/p&gt; &lt;p&gt;PHOTO (COLOR): Figure 3. Intersessional reliability for jump outcomes from the mean of the best three trials. Shaded areas represent acceptable reliability criteria (TEM as a CV ≤&#160;10% &amp;amp; ICC ≥&#160;0.8). Error bars are upper and lower 90% confidence intervals.&lt;/p&gt; &lt;p&gt;PHOTO (COLOR): Figure 4. Individual athlete intersessional change in the mean of the best three trials for (A) countermovement jump height, (B) reactive strength ratio (RSR), and (C) reactive strength index (RSI).&lt;/p&gt; &lt;hd id=&quot;AN0135500789-9&quot;&gt;Discussion&lt;/hd&gt; &lt;p&gt;This study aimed to assess validity and intra- and inter-operator reliability of the &lt;emph&gt;MyJump2&lt;/emph&gt; APP for CMJ and DJ variables, and to report the intra- and intersessional reliability of these tasks in trained junior athletes as reference for practitioners working with this cohort. Our results supported previous findings of validity of &lt;emph&gt;MyJump and MyJump2&lt;/emph&gt; for assessing CMJ height and DJ metrics, producing near-perfect agreement with the force platform. Furthermore, this is the first study to report multiple forms of reliability using &lt;emph&gt;MyJump2&lt;/emph&gt;. Our test-retest design in the current cohort of junior athletes revealed only CMJ height appears a reliable assessment outcome (CV &amp;lt;&#160;10% and ICC &amp;gt;&#160;0.80), with wider between-day variability in the athlete&#39;s DJ outcomes of RSR and RSI over the two sessions.&lt;/p&gt; &lt;p&gt;The current results showed small mean differences of 0.59&#160;cm in CMJ height, and ratio differences of 0.06 and 0.09 in RSR and RSI values, respectively. &lt;emph&gt;MyJump2&lt;/emph&gt; slightly underestimated all values when compared to the criterion force platform. In the CMJs, the current &lt;emph&gt;MyJump2&lt;/emph&gt; underestimation was slightly larger than reported previously, where Gallardo-Fuentes et al. (2016) compared &lt;emph&gt;MyJump&lt;/emph&gt; on an iPhone6 (240&#160;Hz) to a contact mat, finding a mean difference of 0.20&#160;cm. However, the original &lt;emph&gt;MyJump&lt;/emph&gt; study (Balsalobre-Fern&#225;ndez et al., 2015), led by the APP&#39;s designer, quantified the mean underestimation was between 1.1 and 1.3&#160;cm across two operators. This is likely due to the lower sampling rate (iPhone 5s; 120&#160;Hz) available at the time, showing the enhancement in mobile technology aiding in improving &lt;emph&gt;MyJump2&lt;/emph&gt; outputs. Mean differences in CMJ height, yet in the inverse direction, have also been reported, with &lt;emph&gt;MyJump&lt;/emph&gt; producing overestimates of 0.21&#160;cm using a force platform sampling at 1,000&#160;Hz (Stanton et al., 2017) and of 0.90&#160;cm with a platform sampling at 200&#160;Hz (Driller et al., 2017). In the present study, the Bland-Altman plots (Figure 1) suggested only the RSR values showed a small indication toward the higher values (RSR &amp;gt;&#160;2.0) having slightly greater bias between instruments than lower jumps (&lt;emph&gt;R&lt;/emph&gt;&lt;sups&gt;2&lt;/sups&gt;&#160;=&#160;0.13 for Figure 1B). These differences across the literature highlighted how the criterion tool employed (i.e., sampling rate) and the level of performance may affect these reported differences between two tools. Therefore, this study corroborates work showing jump height estimates are within 1&#160;cm when captured via &lt;emph&gt;MyJump2&lt;/emph&gt; on devices capable of video capture at 240&#160;Hz.&lt;/p&gt; &lt;p&gt;The present study is the first to report both the intra- and inter-operator differences of &lt;emph&gt;MyJump2&lt;/emph&gt; concurrently. In the blinded, 4-week repeat analysis of a subsample of CMJ and DJ trials, the present study found a mean difference of 0.04&#160;cm in CMJ height, with only 6 of the 22 jumps producing a different jump height value (i.e., a different take-off/landing frame selected 4 weeks later). This is a smaller mean intra-operator difference than reported previously by Stanton et al. (2017) (0.43&#160;cm), suggesting there is room to reduce the error made when selecting jump landmarks. The present inter-operator findings support previous work (Balsalobre-Fern&#225;ndez et al., 2015; Driller et al., 2017) with &lt;emph&gt;very&lt;/emph&gt; to &lt;emph&gt;extremely high&lt;/emph&gt; levels of agreement between two operators for CMJ height (ICC&#160;=&#160;0.985). There were small significant differences between the experienced and novice operators in this study for RSR and RSI (mean differences&#160;=&#160;−0.06 and −0.03, respectively). This outcome may be explained by DJs requiring three manual frame selections (contact, take-off, and second contact) compared with two for CMJ (take-off and contact), and thus a greater likelihood of a disagreement in frame selection.&lt;/p&gt; &lt;p&gt;To minimize other sources of random error between trials and testing sessions, we ensured the iPad remained securely mounted to a tripod, at the same height and angle to the athlete each time. Furthermore, the iPad was positioned on a surface free from vibration caused by landing, which was a previously reported limitation (Stanton et al., 2017). To maximize the reliability and accuracy of frame selection, the use of an iPad over devices with smaller displays (iPhone) may also offer explanation for this current study&#39;s stronger intra- and inter-operator reliability, with greater accuracy in manual frame selection. Taken together, these findings confirm &lt;emph&gt;MyJump2&lt;/emph&gt; to be a valid tool for coaches to use in the field. We would encourage users to assess the same jump more than once when first familiarizing themselves with the APP. Furthermore, our results suggest the possibility that prior experience may enhance accuracy of frame selection, and thus producing closer outcomes to the criterion force platform (see Figure 2). However, it should be noted we provided the novice user with a short familiarization session of approximately 5 min to demonstrate the applications functionality (i.e., selecting each athlete, take-off frames, etc.).&lt;/p&gt; &lt;p&gt;When both a CMJ and DJ task are administered as part of an assessment battery, these tasks are designed to assess athletes&#39; slow and fast stretch-shortening cycle abilities respectively. As such, the aim of a DJ is not solely focused on height, but also the quickness of the ground contact time. Reporting an athlete&#39;s DJ height is only one part of the picture, as they are commonly instructed to land and jump as quickly and as high as possible (Read, Oliver, Mark, Myer, &amp;amp; Lloyd, 2016). To our knowledge, this is the first study to utilize such DJ metrics from &lt;emph&gt;MyJump2&lt;/emph&gt; to investigate intra- and inter-operator and intersessional reliability for RSR and RSI. The present study included the RSI metric from &lt;emph&gt;MyJump2&lt;/emph&gt; and calculated the common alternative, RSR, from the flight and contact times provided by the APP. We found in this cohort of junior athletes, there was large intersessional variation in reactive strength from DJs. This suggests that despite familiarization prior to measurement on both testing occasions, the ability to execute DJs consistently from 30&#160;cm, and to maximum effort, is highly varied over a short 7-day period in this cohort (CV &amp;gt;&#160;10%). RSRs are not the only variable with greater variation in youth performing DJs. Large CVs (mean 20.5%) were reported in a sample of 25 pre-peak high velocity academy level soccer players (boys), when Read et al. (2016) examined peak ground reaction forces from DJs at 30&#160;cm, also in a 7-day test-retest design. Therefore, establishing the variability of skill level within athletes of varying maturation should be undertaken at multiple testing occasions if DJ assessments and outcomes are to be included in an assessment battery in junior athletes. A multiple baseline approach can be taken with the ease of data collection and analysis with valid field tools such as &lt;emph&gt;MyJump2&lt;/emph&gt;.&lt;/p&gt; &lt;p&gt;The present findings indicated CMJ heights held acceptable reliability in junior athletes, with good intra- and intersessional agreement with only on-the-day familiarization, a typical scenario in the field. The CMJ heights in the current cohort (range from 22.1 to 37.8&#160;cm) were lower than those reported previously in U16 elite male junior football players undergoing extensive training, with a mean of 39.6&#160;&#177;&#160;5.1&#160;cm (Buchheit &amp;amp; Mendez-Villanueva, 2013), while at a similar level of 29.5&#160;&#177;&#160;5.2&#160;cm to active boys aged 13.5&#160;&#177;&#160;0.5&#160;years (Lloyd et al., 2009). While a limitation of this study is the small, mixed-gender sample for the between session comparisons, the strength was that athletes were recruited from the same training squad, and performed similar amounts and types of training together between testing sessions. This should be considered when interpreting the current results as values would likely differ in adolescents of different age ranges and training or sport backgrounds. Nevertheless, the range of performance across both jump tasks provided a wide spectrum to access &lt;emph&gt;MyJump2&lt;/emph&gt; validity and reliability and address the aims of this study.&lt;/p&gt; &lt;p&gt;In conclusion, &lt;emph&gt;MyJump2&lt;/emph&gt; was confirmed to be a valid tool for both CMJ height and DJ outcomes. Using an iPad Pro, &lt;emph&gt;MyJump2&lt;/emph&gt; showed &lt;emph&gt;very-&lt;/emph&gt; to &lt;emph&gt;extremely-high&lt;/emph&gt; intra- and inter-operator agreements. To maximize the accuracy of data collection and subsequent manual frame selection, we recommend standardizing the iPad placement while securing to a tripod and allowing novice APP operators at least 20 familiarization trials before using &lt;emph&gt;MyJump2&lt;/emph&gt; for analysis. Intra- and intersessional analysis indicated CMJ height is a reliable assessment in this cohort, while wider variability was evident in the performance of the DJs. This may be influenced by the greater coordination required for this skill and practitioners should be cautious of such daily variation if assessing DJs in junior athletes.&lt;/p&gt; &lt;hd id=&quot;AN0135500789-10&quot;&gt;Acknowledgments&lt;/hd&gt; &lt;p&gt;The authors are grateful for the support during data collection from Alexandra H. Roberts and to John S. Warmenhoven for feedback in drafting this manuscript. We thank the athletes and their parents for giving their time to attend and participate in this study.&lt;/p&gt; &lt;hd id=&quot;AN0135500789-11&quot;&gt;Disclosure statement&lt;/hd&gt; &lt;p&gt;No benefits in any form have been or will be received from any source, which may have affected this study in any capacity. None of the authors are associated with the application &lt;emph&gt;MyJump2&lt;/emph&gt;, and have no conflicts of interest to declare.&lt;/p&gt; &lt;ref id=&quot;AN0135500789-12&quot;&gt; &lt;title&gt; References &lt;/title&gt; &lt;blist&gt; &lt;bibl id=&quot;bib1&quot; idref=&quot;ref1&quot; type=&quot;bt&quot;&gt;1&lt;/bibl&gt; &lt;bibtext&gt; Altman, D., &amp;amp; Bland, J. ( 1983 ). Measurement in medicine: The analysis of method comparison studies. &lt;emph&gt;Statistican&lt;/emph&gt;, 307 - 317. doi: 10.2307/2987937&lt;/bibtext&gt; &lt;/blist&gt; &lt;blist&gt; &lt;bibl id=&quot;bib2&quot; idref=&quot;ref2&quot; type=&quot;bt&quot;&gt;2&lt;/bibl&gt; &lt;bibtext&gt; Balsalobre-Fern&#225;ndez, C., Glaister, M., &amp;amp; Lockey, R. A. ( 2015 ). 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  Data: The Validity and Reliability of the &#39;MyJump2&#39; Application to Assess Vertical Jumps in Trained Junior Athletes
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  Data: &lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Rogers%2C+Simon+A%2E%22&quot;&gt;Rogers, Simon A.&lt;/searchLink&gt; (ORCID &lt;externalLink term=&quot;http://orcid.org/0000-0002-2630-4411&quot;&gt;0000-0002-2630-4411&lt;/externalLink&gt;)&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Hassm&#233;n%2C+Peter%22&quot;&gt;Hassm&#233;n, Peter&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Hunter%2C+Adam%22&quot;&gt;Hunter, Adam&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Alcock%2C+Alison%22&quot;&gt;Alcock, Alison&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Crewe%2C+Stewart+T%2E%22&quot;&gt;Crewe, Stewart T.&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Strauts%2C+Janina+A%2E%22&quot;&gt;Strauts, Janina A.&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Gilleard%2C+Wendy+L%2E%22&quot;&gt;Gilleard, Wendy L.&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;AR&quot; term=&quot;%22Weissensteiner%2C+Juanita+R%2E%22&quot;&gt;Weissensteiner, Juanita R.&lt;/searchLink&gt;
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  Data: Routledge. Available from: Taylor &amp; Francis, Ltd. 530 Walnut Street Suite 850, Philadelphia, PA 19106. Tel: 800-354-1420; Tel: 215-625-8900; Fax: 215-207-0050; Web site: http://www.tandf.co.uk/journals
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  Data: &lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Adolescents%22&quot;&gt;Adolescents&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Athletes%22&quot;&gt;Athletes&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Measurement+Equipment%22&quot;&gt;Measurement Equipment&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Handheld+Devices%22&quot;&gt;Handheld Devices&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Computer+Oriented+Programs%22&quot;&gt;Computer Oriented Programs&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Physical+Activities%22&quot;&gt;Physical Activities&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Muscular+Strength%22&quot;&gt;Muscular Strength&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Talent+Identification%22&quot;&gt;Talent Identification&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Motion%22&quot;&gt;Motion&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Psychomotor+Skills%22&quot;&gt;Psychomotor Skills&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Test+Validity%22&quot;&gt;Test Validity&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Test+Reliability%22&quot;&gt;Test Reliability&lt;/searchLink&gt;&lt;br /&gt;&lt;searchLink fieldCode=&quot;DE&quot; term=&quot;%22Interrater+Reliability%22&quot;&gt;Interrater Reliability&lt;/searchLink&gt;
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  Data: 10.1080/1091367X.2018.1517088
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  Data: 1091-367X
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  Label: Abstract
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  Data: This study aimed to assess the validity and reliability of jump assessments using the &quot;MyJump2&quot; application. Eleven junior athletes (15 &#177; 1.4 years) performed five countermovement (CMJ) and drop jumps (DJ) measured simultaneously by a force platform and &quot;MyJump2.&quot; Additionally, intra- and inter-day reliability was assessed over two sessions, 7 days apart. &quot;Extremely high&quot; agreement between &quot;MyJump2&quot; and the force platform (intra-class correlation coefficient, ICC = 0.99) and the intra- and inter-operator agreement (ICC = 0.98-0.99) confirmed the validity and reliability of &quot;MyJump2.&quot; Mean typical errors (coefficient of variation percentage, CV%) within the first and second sessions were 4.9% and 4.5% respectively for CMJs, and 8.0% to 11.8% for DJ outcomes. CMJ height held acceptable inter-day reliability (CV &lt; 10%; ICC &gt; 0.8), while DJ did not. Results supported &quot;MyJump2&quot; to be a valid and reliable tool for assessing jumps; however, with variability in DJs in this cohort, appropriate caution should be taken if including in a junior assessment battery.
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      – SubjectFull: Measurement Equipment
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      – TitleFull: The Validity and Reliability of the 'MyJump2' Application to Assess Vertical Jumps in Trained Junior Athletes
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