annually , 80,000 anterior cruciate ligament ( acl ) injuries occur in the united states with an estimated cost of almost a billion dollars
. the most common mechanisms of acl injury are noncontact in nature , characterized by sudden deceleration prior to a landing motion or change of direction [ 2 , 3 ] .
these noncontact injuries may be due to coordination failure involving a complete and momentary loss of normal protective muscle support .
people at high risk of acl injury frequently demonstrate high dynamic knee valgus ( i.e. , knee abduction moment ) during landing from jumping , which may be due to decreased neuromuscular control [ 3 , 5 ] .
current literature has proposed several laboratory - based tools to identify risk factors for acl injury . however , these screening tools require expensive 3d motion capture equipment , highly trained staff , and significant amount of time to administer and analyze rendering these tools inefficient and impractical for a clinical setting .
several jumping and landing tests are used in the clinical setting , including the landing error scoring system ( less ) , the drop jump video screening test , and the tuck jump assessment ( tja ) [ 69 ] .
for example , the tja protocol , unlike the other two tests , starts and stops from ground level instead of jumping from a box ; this better represents techniques encountered in normal jumping activities [ 6 , 8 ] .
the tja protocol also requires participants to jump for 10 seconds , while the less and drop jump video screening test require only 1 to 2 jumps [ 69 ] .
therefore , the tja evaluates a measure of performance endurance , introducing a potential fatigue effect that might highlight landing flaws not observable in 1 to 2 jumps [ 69 ] .
plyometric assessment , identifying jumping and landing technique flaws pertaining to risk of acl injury [ 8 , 10 ] .
although there are no published reports of the tja being widely used , the availability of test protocol and minimal equipment required may make this a favored tool to use in varied clinical settings with diverse personnel .
the tja includes 10 technique flaws related to jumping and landing that are scored qualitatively as either having the flaw or not [ 6 , 8 ] .
empirical evidence suggests a participant who demonstrates greater than or equal to 6 out of 10 technique flaws during the tja should be targeted for intervention to address flaws , such as correcting lower extremity valgus at landing [ 6 , 8 , 10 ] .
the tja requires minimal equipment ( e.g. , video cameras and tape markers ) and takes only several minutes to administer .
scoring follows standard criteria for each technique flaw and can be completed relatively quickly by watching video playback .
these features make the tja a practical screening tool for injury risk assessment in a clinical setting for people of different educational backgrounds and levels of experience , as it is currently being used .
previous literature reported the interrater reliability of the tja as high with percentage exact agreement ( pea ) of two testers across all scoring criteria of 93% ( range 80%100% ) when scoring 10 participants .
the same study also reported intrarater reliability to be high ( pea of 96%100% ) . although reliability was reported high , several limitations in study design necessitate further study of reliability of the tja .
specific information concerning training and background of tja scoring for the raters was not included , limiting generalizability to clinicians unfamiliar with jumping assessment .
additionally , the small sample size may have allowed raters to remember previous scores , introducing bias , resulting in higher intrarater reliability .
reliability has not been tested with raters of different educational backgrounds or levels of experience .
demonstrating that scoring is consistent between raters of different educational and experiential backgrounds would allow implementation of the tja in the clinical and performance settings with improved understanding of accuracy .
the purpose of this study was to investigate intrarater and interrater reliability of the tja with raters of different educational backgrounds and levels of clinical experience with healthy injury - free men and women .
the hypothesis for this study was that the raters would demonstrate good intra- and interrater reliability for the tja and that there would be no difference in tja total score between raters of different educational and/or experiential backgrounds .
a sample of 108 , both undergraduate and graduate , recreationally active students who were not currently involved in college athletics , were recruited for participation .
all participants were healthy , injury - free men and women , 18 to 24 years old , without prior tuck jump training . from this cohort ,
the videos of 40 participants ( n = 13 men and n = 27 women ) were randomly selected for this reliability study .
participants received a full explanation of the nature , purpose , and risks of the study and were given the opportunity to ask questions .
the physical activity readiness questionnaire ( par - q ) was administered to screen for contraindications for testing .
all participants signed an informed consent document approved by the institutional review board at northern arizona university before participating in the study . prior to participants completing the tja , height and weight
were measured with a wall - mounted stadiometer and digital scale ( cardinal scale , webb city , mo , usa ) .
the tja was performed using instructions from a previously published tja study by the developers of the test .
initial set up for the tja required 2 two - dimensional video cameras ( sony handycam , sony corporation , san diego , ca and jvc camcorder jvc americas corporation , wayne nj ) on tripods to provide sagittal and frontal views of the participants .
two pieces of masking tape were placed on the ground , parallel to each other 8 inches apart .
participants were instructed to stand with one foot on each tape strip to ensure proper positioning for the cameras ( figure 1 ) .
the participants were instructed in purpose and protocol of tja test which included : jumping repeatedly for 10 seconds with high effort level , bringing knees up as high as possible so both thighs were parallel with the ground , landing softly in the same footprint ( 2 pieces of tape ) with each jump , and then immediately begin the next jump . no feedback was given to participants while performing the assessment .
technique flaws included : ( 1 ) lower extremity valgus at landing ( figure 2 ) , ( 2 ) thighs do not reach parallel ( peak of jump ) , ( 3 ) thighs not equal side - to - side ( during flight ) , ( 4 ) foot placement not shoulder width apart , ( 5 ) foot placement not parallel ( front to back ) , ( 6 ) foot contact timing not equal , ( 7 ) excessive landing contact noise , ( 8) pause between jumps , ( 9 ) technique declines prior to 10 seconds , and ( 10 ) does not land in same footprint ( excessive in - flight motion ) .
additional figures depicting these technique flaws can be found in previously published tja studies [ 6 , 8 , 10 ] .
the participants were rated as either demonstrating a technique flaw or not . per previously published literature , the flaws were then summed for the tja total score [ 6 , 8 ] .
five raters of varying educational backgrounds and clinical experiences were chosen to analyze video and score the tja of the 40 participants .
raters included a physical therapist with a doctor of physical therapy degree and 4 years clinical experience ( rater 1 ) ; the head strength and conditioning coach at a division 1 university with a masters of science in exercise science and strength and conditioning specialist certification and 7 years of clinical experience ( rater 2 ) ; the head athletic trainer as a certified athletic trainer at a division 1 university with 17 years of clinical experience ( rater 3 ) ; a third - year doctor of physical therapy student ( rater 4 ) ; and a first - year doctor of physical therapy student ( rater 5 ) .
all raters were given identical flash drives with instructions , a microsoft access database to input scores , a copy of myer et al .   that described the tja and scoring in detail , 80 video files for 40 participants ( frontal and sagittal plane view for each participant ) , and 2 video files for 1 example participant ( frontal and sagittal plane views ) previously scored independently by 3 of the authors of this paper ( l. a. dudley , c. a. smith , and m. warren ) .
the sample video was chosen from the larger sample of 100 to assist with consistency training of the raters and was not included in the 40 participants evaluated by raters .
raters were instructed to read an excerpt from myer et al .   to create consistency between raters regarding the scoring procedures of the tja .
this included looking at the tja scoring tool created with pictures of the first 6 technique flaws to ensure consistency with previously established tja scoring procedures .
raters were then instructed to watch and score the example video , which had the purpose of ensuring consistency in procedures between all raters and establishing the same volume setting to accurately analyze technique flaw number 7 ( excessive contact landing noise ) .
once raters accurately scored the example video , participants ' videos were scored independently , with no discussion amongst raters .
raters were instructed to use frontal plane views to score technique flaws ( 1 ) , ( 3 ) , ( 4 ) , ( 6 ) , and ( 7 ) ; sagittal plane views for ( 2 ) and ( 5 ) ; and frontal and sagittal views for ( 8) , ( 9 ) , and ( 10 ) .
raters were given instructions on how to change playback speed on the computer program to allow viewing of the video in slow motion .
raters were encouraged to watch the videos as many times as necessary to give an accurate score .
approximately 1 month later , 3 of the 5 raters scored the videos again to determine intrarater reliability .
descriptive statistics were calculated as means with standard deviation for interval data and percents for categorical data .
analysis of variance with tja total score as the dependent variable and rater as the independent variable was completed to assess differences in mean values between raters .
intraclass correlation coefficients ( icc , 2,1 ) and associated 95% confidence intervals ( ci ) were calculated to determine intrarater ( 3 different raters at 2 timepoints ) and interrater ( 5 raters for first session and 3 raters for second session ) reliability of the total tja score .
the clinical significance was defined as poor for an icc below 0.50 , moderate for 0.500.75 , and good for 0.75 or higher .
icc was calculated as 
 ( 1)icc=2b2b+2w , 
 where b is the between person variance and w in the within person variance .
maximum likelihood estimates of b and w were obtained from linear mixed models with rater as a fixed effect for interrater reliability .
least square means were calculated for the mean tja scores for each rater , with p values calculated to determine significant differences in tja scores .
all analyses were completed using sas , version 9.2 ( sas institute , inc . ,
cary , nc ) and an a priori alpha level of 0.05 was used to denote statistical significance .
participants in this study were 40 university students , 18 to 24 years of age ( mean age  standard deviation ( sd ) 21.0  1.6 years ) .
there were 13 males and 27 females with an average height and weight of 170.8  8.9  cm and 67.4  14.7  kg , respectively .
the average number of flaws identified on the tja ( tja total score ) were 6.30  1.76 ; and technique flaw ( 2 ) ( thighs do not reach parallel ) was the most frequently identified ( 87.5% of participants ) , using scoring from rater 5 who was randomly chosen . additionally , technique flaw ( 2 ) was the most consistently agreed upon by all raters .
technique flaws ( 5 ) ( foot placement not parallel front to back ) and ( 9 ) ( technique declines prior to 10 seconds ) were the least agreed upon by all raters
. analysis of variance showed differences between raters for mean tja total score ( f = 11.82 ; p < 0.001 ) .
post hoc comparisons showed no consistent pattern in scoring by educational and/or clinical experience ( table 1 ) .
interrater reliability between the 5 raters was poor ( icc = 0.47 ; 95% ci : 0.330.62 ) . however , interrater reliability between raters 1 , 2 , and 5 ( raters used for intrarater reliability ) improved in the second scoring session ( icc = 0.52 , 95% ci : 0.350.68 versus icc = 0.69 , 95% ci : 0.550.81 ) .
intrarater reliability testing was completed by raters 1 , 2 , and 5 who scored the tja videos at two different timepoints .
the purpose of this study was to investigate intrarater and interrater reliability of the tja with raters of different educational backgrounds and levels of clinical experience with healthy injury - free men and women .
this study showed intrarater reliability to be poor to moderate for the 3 raters scoring videos of 40 participants .
it is noteworthy that those with more education and experience were not more consistent in scoring the tja than those raters with minimal education and experience .
rater 5 had highest intrarater reliability of the 3 raters and also had the most experience administering the tja .
these results suggest the tja may not be used reliably , following published protocol , by a single clinician regardless of level of education or experience [ 6 , 8 , 11 ] .
this study also showed poor interrater reliability between 5 raters when assessing tja performance of the same 40 participants .
this suggests the tja may not be used reliably , following published protocol , when being scored by different raters [ 6 , 8 , 11 ] . however , interrater reliability improved the second session between the 3 raters that scored the videos in 2 separate sessions .
additional training beyond what was done in the study , as well as practice scoring to achieve consensus between raters , may be required .
these results are in contrast to herrington et al .   who reported the tja had good intrarater and interrater reliability ( greater than 0.75 ) when 2 raters scored videos of 10 recreationally active university students at 2 different scoring sessions .
did not specify raters ' educational background , level of experience , or previous training in the tja .
however , as this study was written by a developer of the tja , the two raters likely had more experience in scoring the tja and were more familiar with the flaws than the 5 raters of this study .
the improved interrater reliability in the current study from session one to session two suggested a possible learning effect .
further , the small sample size used by herrington et al .   could promote bias due to raters remembering the scores of only 10 participants .
the authors of the current study took measures to ensure continuity with previously established tja procedures and scoring criteria .
however , current tja instructions do not specify whether a technique flaw should be scored only if it is seen consistently throughout the test or if the technique flaw may be scored if seen only once during the test . due to this exclusion in the published protocol ,
it is likely that raters may inherently interpret this differently , thus creating scoring inconsistencies between raters .
for example , during a 10 second tja a participant may demonstrate lower extremity valgus at landing only once throughout several jumps .
one rater may score this as a technique flaw because it was demonstrated in the assessment ; however , another rater may not score this as a technique flaw because the majority of jumps did not demonstrate lower extremity valgus at landing .
more training and specific tja instruction prior to administration may correct this issue and promote consistency between raters .
the current study includes the most diverse set of raters to date , representing 3 professions that may administer the tja .
this allows for greater external validity in the clinical and performance setting than other published reliability studies to date . however , there are limitations of the current study .
participants in the current study were not competitive athletes , though were recreationally active university students .
the results of this study suggest the tja may not be consistently scored , following the previously published protocol , although modifications to instructions and rater training may correct this . since ,
further research is necessary to determine whether more specific scoring guidelines or training in tja administration would improve reliability .
using a published protocol and training of raters , the tja has poor to moderate interrater and intrarater reliability
. there may be a learned effect with the tja since interrater reliability improved with repetition .
enhanced training or scoring instructions may be required to improve reliability of the tja among professionals of varying education backgrounds and experience .
 
 objective . 
 the tuck jump assessment ( tja ) , a clinical plyometric assessment , identifies 10 jumping and landing technique flaws . the study objective was to investigate tja interrater and intrarater reliability with raters of different educational and clinical backgrounds . 
 methods . 
 40 participants were video recorded performing the tja using published protocol and instructions . 
 five raters of varied educational and clinical backgrounds scored the tja . 
 each score of the 10 technique flaws was summed for the total tja score . 
 approximately one month later , 3 raters scored the videos again . 
 intraclass correlation coefficients determined interrater ( 5 and 3 raters for first and second session , resp . ) and intrarater ( 3 raters ) reliability . results . 
 interrater reliability with 5 raters was poor ( icc = 0.47 ; 95% confidence intervals ( ci ) 0.330.62 ) . 
 interrater reliability between 3 raters who completed 2 scoring sessions improved from 0.52 ( 95% ci 0.350.68 ) for session one to 0.69 ( 95% ci 0.550.81 ) for session two . 
 intrarater reliability was poor to moderate , ranging from 0.44 ( 95% ci 0.220.68 ) to 0.72 ( 95% ci 0.550.84 ) . 
 conclusion . published protocol and training of raters were insufficient to allow consistent tja scoring . 
 there may be a learned effect with the tja since interrater reliability improved with repetition . 
 tja instructions and training should be modified and enhanced before clinical implementation . 