Hip adductor strength training is important for groin injuries rehabilitation and prevention. A widely used exercise is the Copenhagen Adduction (CA) exercise. The current study will include young football players (12-16 yrs) individually randomised into two CA groups (isometric, dynamic) training 2 times per week for 6 weeks. Both groups will use 2 sets per side and a range of 6-12 repetitions. Maximal eccentric (EHAD) and isometric (IHAD) hip adduction torque, jump and sprint capacity, delayed onset muscle soreness (DOMS), and perceived exertion will be recorded. A minimum of 42 participants will be required.

Introduction: Groin injuries are one of the most common injuries in sports such as basketball, hockey and handball. They account for 4-19% of all injuries in Association football (soccer), with movements such as shooting or passing, changes of direction, and jumping being the most common injury mechanisms. Previous groin injury and low hip adductor strength have been shown to be risk factors for groin injuries. Exercise has shown a positive effect on adductor muscle strength, groin pain rehabilitation, and prevention. An exercise widely used in adductor strength training and groin pain rehabilitation is the Copenhagen Adduction (CA) exercise. Another exercise used in groin pain rehabilitation and adductor strength training is the adductor squeeze exercise. Although there are investigations comparing the strength effects of the CA with these of other dynamic exercises, and isometric exercises, there is only one study that included the CA using isometric contraction during a progressive training protocol for the hip adductor muscles, and no studies comparing two contraction types of the CA. Although muscle strengthening is an important component in football training, sprint and jump training also plays an important role in athletes' performance. There is only one study which evaluated the effects of the CA and Nordic Hamstring exercise on athletic performance.

Aim: To compare the effects of a dynamic and an isometric CA on adductor muscle strength and athletic performance (sprint, jump) in male football (soccer) players.

Methods: Young football players (12-16 yrs) will be included in the study. They will be individually randomised into two CA groups (isometric, dynamic) and will train 2 times per week for six weeks using 2 sets per side and a range of 6-12 repetitions maintaining the same repetition number and time under tension. The strength and athletic performance testing will be performed by a physiotherapist and an exercise therapist, respectively. They will not participate in the intervention supervision and will be unaware of the group allocation. The physiotherapist and the exercise therapist who will supervise the intervention, as well as the participants, will not be aware of the testing results until the completion of the study.

Inclusion Criteria:

Healthy male soccer players between 12 and 16 years old systematically (≥4 times per week) participating in training and games

Exclusion Criteria:

1. musculoskeletal injury and/or neurological disorder that would affect strength and/or athletic performance testing, and/or exercise execution.
2. adductor muscle injury within 6 months before study initiation.
3. groin pain greater than 2/10 on a Numeric Rating Scale (NRS) during strength and/or athletic performance testing, and/or during exercise execution.
4. any systematic strength training of the adductor muscles during the last month prior to study initiation.

The data that support the findings of this study will be available from the corresponding author upon reasonable request

Beginning after publication with no end date

The data that support the findings of this study will be available from the corresponding author upon reasonable request