Core stability (CS) training is nowadays largely used in several fields, mainly to enhance athletic performance and to prevent and rehabilitate musculoskeletal injuries. However, in several experimental studies, CS training programs have not delivered as positive results as could be expected. The lack of proper modulation and quantification of the training load parameters (such as intensity, volume, frequency, etc.) may be one of the main explanations. Although training intensity has been manipulated by modifying the CS exercise difficulty through variations in mechanical constraints (i.e. participant posture, lever arms, base of support, unstable surfaces, etc.), to the best of the authors' knowledge no experimental study has quantified the CS training intensity based on objective parameters. The quantification of the load intensity is fundamental to analyze the dose-response relationships between training and CS adaptations. Therefore, the main aim of this study is to evaluate the effectiveness of two individualized CS training programs using smartphone accelerometers placed on the pelvis to quantify the intensity of several of the most common CS exercises employed in fitness, sports and rehabilitation. The expected effect is that the experimental groups will improve CS significantly.

Sixty recreational male athletes will be evaluated twice (pre-test 1 and pre-test 2) before a core stability (CS) training program. Testing sessions will consist in several tests to assess sitting and global dynamic postural control, trunk isometric endurance, neuromuscular function of the lower extremities, trunk response to sudden and unexpected load perturbations and pelvic oscillation during CS exercises evaluated with a smartphone accelerometer. Later, they will be randomly assigned to one of the three groups included in the study: two experimental groups (low and high intensity) and a control group. The intervention will have a training frequency of 2 days per week for 6 weeks. Each CS training session will consist in 4 sets of one variation of four of the most popular stabilization exercises used to challenge core muscles: frontal bridge, back bridge, lateral bridge and bird-dog. Exercise variations will be performed isometrically in increasing order of difficulty through the modifications of the following mechanical constraints: lever-arm, number of supports and/or the use of unstable surfaces. The CS training programs will differ in exercises intensity, mainly. Each participant of the low intensity group will perform those exercise variations in which they have obtained an oscillation ranged between 0.2 and 0.3 m/s2 in pre-test, while participants of the high intensity group will perform the exercise variations in which they have obtained an oscillation ranged between 0.4 and 0.5 m/s2. The exercise duration will be set at 30 s and 15 s for the low intensity and high intensity group, respectively. All participants of the training groups will be revaluated every two weeks during the training period. After the intervention period, all participants will perform a post-test to evaluate the effectiveness of both CS programs. Statistical analysis will consist in repeated-measures ANOVAs for detecting possible significant differences within and between-groups.

Inclusion Criteria:

- Healthy recreative male athletes between 18 and 35 years old

Exclusion Criteria:

• Inguinal hernia or urinary incontinence
• Pathologies that contraindicate physical exercise practice
• Low back pain in the last six months prior to testing
• Pathologies related with Central Nervous System that affect balance
• Professional athletes of sports modalities with high core stability demands

All Individual Participant Data (IPD) that underlie results in a publication.

Data will be available six months after publication

Data access requests will be reviewed by an external Independent Review Panel. Requestors will be required to sign a Data Access Agreement