With the exception of the shoulder, the hip is among the most frequently injured areas in swimmers. Despite this, hip injuries are often overlooked in training and prevention programmes. Such neglect can cause significant damage to muscles, particularly the adductors, and the joint itself, potentially requiring arthroscopic surgery or even leading to secondary injuries in related structures such as the knee. Furthermore, hip strength and range of motion directly affect swimmers' underwater kicking speed. Although hip assessments are common in other sports, like football, for injury prevention and performance analysis-both dynamically and isometrically-isometric testing is particularly recommended due to its higher reproducibility.

Therefore, this study aims to validate a multidirectional isometric hip test in swimmers and examine agonist-antagonist muscle ratios in young advanced swimmers.

A comparative analysis will be conducted on 30 elite swimmers. This will include a descriptive analysis of the group and comparative analyses between breaststroke/non-breaststroke swimmers and between genders. Maximum isometric contractions of both lower limbs will be measured using a Chronojump force sensor (Boscosystem, Barcelona, Spain).

Athletes will stand on a step positioned centrally within a rack or cage, either laterally or frontally depending on the movement assessed (ABD-ADD or flexion-extension, respectively). They will grip the appropriate supports with their hands and perform three maximal efforts of each movement lasting 3 seconds, without compensatory actions (any attempt with compensations will be discounted). There will be a 20-second rest between attempts. All three attempts will be recorded.

To assess measurement reliability, tests will be repeated after 48 hours for subsequent comparison.

Inclusion Criteria:

• Aged between 14 and 18 years.
• Swimmers who train at least 15 hours weekly.
• Swimmers who have participated in the national championship this season.

Exclusion Criteria:

• Swimmers with any current hip or lower limb pathology.
• Swimmers who have required hip surgery.
• Swimmers who, for any other reason, are unable to complete an isometric maximal strength test.
• No ability to perform the Multidirectional Isometric Assessment of the Hip without compensatory movements.
• Refusal to sign informed consent (or legal guardian's consent for minors).