This research aims to look at how warm-up programs and types of footwear affect movement patterns that are associated with injury risk during change-of-direction tasks, also known as cutting, in youth soccer players. Specifically, this research is conducted in two parts with two different study designs: a quasi-randomized controlled trial and a crossover design. The main questions it aims to answer are:

• [Part 1: Quasi-RCT] How does sex and a shortened FIFA11+ warm-up program, lasting 3 months, affect movement patterns during cutting compared to a standard warm-up program in youth soccer players?
• [Part 2: Crossover design] How does female-specific footwear affect movement patterns during cutting, compared to unisex footwear, in youth female players? Secondarily, whether specific shoe properties (comfort, functional traction, pressure distribution) differ between the two types of footwear.

For part 1 of the research:

• Researchers will compare a shortened FIFA11+ with a Brazilian warm-up program (standard) to see its effect on movement patterns during cutting.
• Participants will perform their assigned warm-up program twice a week for 3 months (12-weeks).
• To assess movement patterns, participants will perform an unplanned sidestep cutting task, captured with markerless cameras, before and after the training period.

For part 2, only female participants will be involved:

• Researchers will compare the effects of female-specific soccer cleats (designed exclusively for female) with unisex soccer cleats on cutting patterns and certain shoe properties.
• All participants will test both types of footwear and perform an unplanned sidestep task captured with markerless cameras, run through a slalom course (multiple acceleration and change of directions) to test for shoe traction, and complete an online survey on shoe comfort and perceived performance.
• A subset of participants will perform a planned sidestep task with wireless insoles to test for pressure distribution.

With the rise of soccer's global prominence, injury risks among players remain a concern. Deceleration and change of direction maneuvers are frequently employed as an evasive strategy during games. However, they often contribute to higher risk of non-contact anterior cruciate ligament (ACL) injuries. Sidestep cutting involves planting with one foot and pushing off in the opposite direction. Improper movement patterns may increase loads on the planted leg leading to injuries. Injury prevention initiatives such as the FIFA11+ have been introduced to reduce injury rates, but it is unclear whether these programs can correct movement patterns during cutting. Moreover, the length of these programs (often lasting 20 minutes) can reduce adherence and hinder their practical implementation in the real-world. This results in alternative programs like the Brazilian warm-up to be used instead.

In addition, females are significantly more at-risk of ACL injuries than males. This is often attributed to differences in movement pattern and anatomy. Variations in foot anatomy can affect how players interact with footwear, which may in turn, influence cutting patterns. Yet, soccer footwear is typically designed using a male foot template (i.e. last), resulting in a one-size for all approach for female athletes.

In order to address current limitations, this study aims to estimate the effect of a shortened FIFA11+ and sex-specific footwear on cutting kinematics in youth soccer players. This will be done in two parts, where part 1 examines two warm-up programs, and part 2 examines two types of footwear. Ethics approval and informed participants and parental consent as well as assent have been obtained.

For part 1 of the study, 64 healthy soccer players will be recruited from Soccer Montréal (formerly known as Association Régionale de Soccer Concordia (ARSC)) sport study program. Soccer Montréal provides soccer sport study programs to high schools for high performance soccer players. Soccer Montréal conducts soccer training with pre-established cohorts separated by sex and age. Two male and 2 female cohorts will be allocated to either the intervention or control group. Male cohorts of similar age groups will be selected, and the entire cohort will be randomly allocated using a computer. The female cohorts have different age groups, and thus allocation to intervention or control will be divided within each cohort following a quasi-randomized fashion. During the testing, participants are required to perform an unanticipated sidestep maneuver at 45 (±10) degrees on artificial turf. Data will be collected with markerless motion capture systems. A total of 7 trials will be captured in each direction, only 5 out of 7 will be analyzed.

For part 2 of the study, female participants from part 1 (32 females) will test two types of footwear: Female-specific and unisex soccer cleats. Testing will be done at one time point. Female-specific cleats are provided from IDA sports, specifically the IDA centra FG/AG model. Unisex cleats are the Nike Tiempo Legend 10 Academy. Proper fit of shoe sizes will be examined manually by the research team prior to testing. Kinematic data will be collected using the same unanticipated sidestep task as part 1. Additional testing will include a slalom course to examine functional traction of the shoes. Participants will complete an online comfort survey, following the slalom course, once for each shoe. A subset of female participants will also complete a sidestep cutting task with wireless insoles to measure pressure data.

Findings of this study will advance knowledge of ACL injury mechanism during cutting tasks, aid in the design of more practical injury prevention programs and guide the development of female-specific footwear.

Inclusion Criteria:

• Soccer players
• Enrolled in Association Régionale de Soccer Concordia (ARSC), now known as Soccer Montréal, soccer sport study program.
• Age between 13-17 years old.

Exclusion Criteria:

• Any history of major lower limb or back injuries (e.g., torn ACL, herniated vertebrae)
• History of any lower extremity surgery
• Current medical/neurological condition preventing cutting maneuver or training.

The open-access content, encompass only de-identified biomechanical and demographic data. This will include metrics such as joint waveforms, plantar pressure, performance metrics, and anonymized demographic information including age, sex, height, weight, BMI, years of soccer experience, shoe size, and leg dominance.

Available following publication. No end date

Our study data will be published in an open-access format (available to anyone who wishes to access the information), while protecting participant anonymity. It will encompass only de-identified biomechanical and demographic data, which will be shared via a dedicated repository on the McGill IHRG (Ice Hockey Research Group) server.

All the participants are within the same soccer organization and therefore complete masking of participants to group allocation is not possible. Coaches will be aware of allocations given that they will need to supervise the groups and give appropriate feedback if required. The primary investigator will be implicated in all aspects of the study (recruitment, data collection, supervision of training sessions, analysis) and thus will be aware of group allocations. Other research members that will help with data collection procedures will not be aware of group allocations.