Landing Error Scoring System: Data from Youth Volleyball Players

The Landing Error Scoring system (LESS) is a reliable screening tool for Anterior Cruciate Ligament (ACL) injury. The test is focused on biomechanical errors of landing motion and is used to evaluate the risk of knee injuries in several sports, such as football and basketball, which involve repeated jumping demands. Presently, available LESS data from youth volleyball players is limited, thus screening for injury risk has not been comprehensively undertaken in this cohort. The LESS is typically performed by jumping from a box while video motion in 2 sagittal and frontal planes is recorded, with the jump landing rated against 17-items. A total of 233 players performed three jump landing trials resulting in a total of 1398 videos being recorded. Each LESS score item was rated by two physical therapists and one sports scientist and the data were separated into four separate LESS score categories: excellent (≤4), good (4 - 5), moderate (5 - 6), and poor (>6). Descriptive analysis (percentage) was employed to describe the data, with scores subdivided by gender. The data may be applied to identify youth volleyball players at potential risk of sustaining a lower body injury from poor landing biomechanics.


a b s t r a c t
The Landing Error Scoring system (LESS) is a reliable screening tool for Anterior Cruciate Ligament (ACL) injury. The test is focused on biomechanical errors of landing motion and is used to evaluate the risk of knee injuries in several sports, such as football and basketball, which involve repeated jumping demands. Presently, available LESS data from youth volleyball players is limited, thus screening for injury risk has not been comprehensively undertaken in this cohort. The LESS is typically performed by jumping from a box while video motion in 2 sagittal and frontal planes is recorded, with the jump landing rated against 17-items. A total of 233 players performed three jump landing trials resulting in a total of 1398 videos being recorded. Each LESS score item was rated by two physical therapists and one sports scientist and the data were separated into four separate LESS score categories: excellent ( ≤4), good (4 -5), moderate (5 -6), and poor ( > 6). Descriptive analysis (percentage) was employed to describe the data, with scores subdivided by gender. The data may be applied to identify youth volleyball players at potential risk of sustaining a lower body injury from poor landing biomechanics. ©

Value of the Data
• These data are useful for screening biomechanical risk factors of anterior cruciate ligament (ACL) injuries in youth volleyball players [1][2][3] • The data may benefit physiotherapists, sports scientist and coaches when applying the LESS screening to test athletes; helping to evaluate ACL injury risk. • The data provide details of each LESS item, which may useful as a reference to identify the item/s which incur the most error (when landing) during the test in this cohort. Therefore, correcting and training to reduce these errors may reduce potential injury occurrence.
Descriptive data of participant characteristics are presented in Table 1 .

Participants
The participants were youth volleyball players who competed in junior school volleyball competitions and from central region schools in Thailand (see Table 2 ). Participants were included if they were aged 10-13 years old, male or female, and had been training for volleyball competition for at least 2 years. Participants were excluded if they had sustained a musculoskeletal injury within the previous 3 months prior to commencing experimental testing or encountered any other injury that could obstruct their performance at the time of testing. The participant characteristics of the 233 participants (male = 97, female = 136) are shown in Table 1 . The purpose and procedures of the study were explained to the participants and responsible guardian. All participants and guardians read and signed informed consent forms that were approved by the Mahidol University Central Institutional Review Board (COA no.2016/118.1209).

Procedure
Two video cameras were positioned perpendicular to the plane of motion (sagittal and frontal planes) and set at 3.64 m from the area of landing [1] . Prior to commencing the test, masking   tape was placed at 50% of the player's height on the floor in front of a box that was 30 cm in height. After a warm-up, participants stood atop of the box and jumped forward beyond the tape marker, immediately jumping upwards as high as possible upon foot contact with the ground. A total of three jump landing motions were recorded with a 2 min rest period between each trial. A total of 1398 videos were recorded using a VLC media player to allow the evaluation of LESS scores by 3 raters (2 physical therapists and a sports scientist). The LESS has 2 different versions, a fulI version (17 items) and a real-time version (10 items aka LESS-RT), with both versions possessing high reliability [ 4 , 5 ]. In this report, the full version was employed. Microsoft Excel (Microsoft corp., Redmond, WA) was used to estimate ICC and 95% confident intervals based on mean-ratings ( k = 3), absolute-agreement, and a 2-way mixed-effects model. The ICC indicated high interrater reliability (ICC = 0.81, 95% CI 0.708-0.883) [2] .

Statistical analysis
The LESS scores obtained from each participant's three trials were averaged. Descriptive statistical analysis was performed and presented using google data studio (Google Inc., Mountainview CA) ( https://datastudio.google.com/s/pIUH9cEmAgM ).

Ethics Statement
All participants and guardians had the experimental procedures and associated risk and benefits fully explained prior to providing their informed consent to participate. All procedures were granted ethical approval from the Mahidol University Central Institutional Review Board (COA no.2016/118.1209).

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have, or could be, perceived to have influenced the work reported in this article.