Effect of head position and dual tasking on landing movement patterns using the Landing Error Scoring System

This is a randomised cross-over study with repeated measures performed in a biomechanics laboratory. Participants will complete the Landing Error Scoring System (LESS) testing procedures, jumping horizontally from a 30-cm box to 50% of their body height and jumping vertically as high as possible upon landing. Participants will jump three times in two conditions for the head turned condition: (1) original control LESS, and (2) with their head turned to approximately 65-90 degrees looking at a visual target placed on the wall to their right side. For the dual-tasking, different participants will jump three times in two conditions: (1) original control LESS, and (2) while tone counting high and low pitched tones during the task. A tone will be played each second with a duration of one second and a 1:1 ratio of high and low pitched tones, provided at random. Participants will use their own habitual athletic footwear. There will be 5 minutes rest between conditions, and 1 minute rest between trials. Participants will be allowed up to three familiarisation trials before formal experimentation. Before each trial, participants will be reminded to jump to 50% of their body height (indicated by the line) with two feet, and jump upwards as high as possible upon landing. Trials will be disregarded when participants do not land at 50% of their body height or do not perform the task in one fluid motion, up to a maximum of five trials per condition. Unless the task is preformed inappropriately, feedback on performance will not given to avoid influencing outcomes. All sessions will be supervised by a trained physiotherapist with research experience, and assessments conducted in groups of up to 4 individuals. The total duration from consent to baseline data collection, familiarisation, and experimentation of the two conditions will not exceed 30 minutes, performed within a single session. The completion of three valid trials for each of the two experimental conditions of interest will be monitored and documented using a checklist. Two video cameras will be use to capture the jumps at 120 frames per second. One camera will be placed to the right hand side of participants, and the other in front of participants. Cameras will be placed 3.5 m away from the landing area on 1.3 m high tripods. The videos will be analysed in a video processing software (Kinovea) and the original Landing Error Scoring System template from Padua et al. (2009) used to extract Landing Error Scoring System scores. The order of conditions will be block randomized prior to study commencement by a third party to ensure an equal number of participants starting in each condition, and allocated sequentially to participants upon study enrolment by a single researcher. Participants will be pre informed of the aims of the study. Participants will complete an informed consent document, and baseline characteristics will be collected (height, mass, gender, age, and self-administered short-form International Physical Activity Questionnaire).