Effect of the Ultrasound-guided Percutaneous Neuromodulation on the Mean Velocity in Crossfit Practitioners.

CrossFit training requires the integration of strength, power, trunk stability, and efficient force transmission during complex multi-joint movements. The back squat is one of the most frequently used exercises in CrossFit and is commonly applied to assess lower-limb performance through force-velocity profiling. Variables such as mean velocity, mean propulsive velocity, and velocity loss between sets provide relevant information regarding neuromuscular performance and fatigue resistance.

The transversus abdominis is a deep abdominal muscle involved in trunk stabilization and lumbopelvic control. Adequate activation of this muscle may contribute to improved force transmission between the lower and upper extremities during strength exercises. Ultrasound-guided percutaneous neuromodulation (UGPNM) is an invasive physiotherapy technique that delivers electrical stimulation through a needle placed near a peripheral nerve under ultrasound guidance. This intervention has been proposed as a method to modulate neuromuscular function and potentially enhance motor performance.

Despite the increasing use of ultrasound-guided percutaneous neuromodulation in clinical and sports settings, evidence regarding its immediate effects on sport performance variables remains limited. In particular, the influence of neuromodulation targeting the innervation of the transversus abdominis on force-velocity profile characteristics during the squat has not been thoroughly investigated.

The objective of this randomized controlled trial is to evaluate the immediate effects of ultrasound-guided percutaneous neuromodulation of the nerves supplying the transversus abdominis on mean velocity during the back squat in CrossFit practitioners. Secondary outcomes include mean propulsive velocity, fatigue resistance assessed through velocity loss between sets, perceived exertion, and potential differences in response according to baseline transversus abdominis activation capacity.

A total of 42 healthy CrossFit practitioners, both male and female, aged 18 to 60 years with at least one year of training experience, will be recruited. During baseline assessment, participants will undergo ultrasound evaluation of the transversus abdominis muscle at rest and during voluntary contraction. Muscle thickness will be measured in both conditions, and the percentage of activation will be calculated based on the relative change in thickness. Participants will then be classified into higher and lower activation subgroups according to the median value of transversus abdominis activation.

Following this classification, participants will be randomly allocated to either the experimental or sham group using block randomization performed with R statistical software, ensuring balanced distribution of activation levels between groups.

A blinded randomized controlled design with third-party outcome assessment will be used. Outcome assessments will be performed by a blinded evaluator responsible for ultrasound measurements of transversus abdominis thickness and for collecting squat performance variables obtained via a linear velocity transducer. The evaluator will not be involved in the randomization process and will remain unaware of group allocation throughout the study.

A separate clinician, not involved in outcome assessment, will administer either the active ultrasound-guided percutaneous neuromodulation intervention or the sham procedure. Participants will remain blinded to treatment allocation throughout the study.

The baseline performance assessment will include squat testing using a linear velocity transducer. Participants will perform three sets of two repetitions at 80% of their individual one-repetition maximum (1RM), following a standardized warm-up. Mean velocity, mean propulsive velocity, velocity loss, and rating of perceived exertion will be recorded.

The experimental intervention will consist of ultrasound-guided percutaneous neuromodulation applied to the iliohypogastric and ilioinguinal nerves using electrical stimulation at 10 Hz in 10-second cycles. The sham condition will involve identical needle insertion without electrical stimulation. Immediately after the intervention, all performance variables will be reassessed under identical testing conditions.

This study aims to determine whether ultrasound-guided percutaneous neuromodulation can produce immediate improvements in squat performance variables and whether baseline transversus abdominis activation capacity influences the response to the intervention.

Inclusion criteria

• Age between 18 and 60 years
• At least 1 year of CrossFit training experience
• Training frequency between 2 and 6 sessions per week

Exclusion criteria

• Belonephobia (fear of needles)
• Presence of cardiac conditions or implanted cardiac devices (e.g., pacemaker)
• Pregnancy
• Active oncological process
• Skin conditions or lesions in the intervention area
• Neurological or neurosensory disorders
• Epilepsy
• Current febrile condition
• Recent use of antibiotics
• Treatment with anticoagulant medication
• Use of medications that may affect physical performance
• Autoimmune diseases or use of immunosuppressive therapy
• Active lumbar or abdominal pathology
• Recent lumbar surgery or operations related to the intervention area
• Active musculoskeletal injury or pain affecting squat technique or -performance
• Undiagnosed pain affecting execution of the sporting movement.