Cardiopulmonary resuscitation (CPR) is essential in the management of cardiorespiratory arrest (CA) to improve survival rates. High-quality chest compressions are the primary intervention to maintain circulation and oxygenation of vital organs during cardiac arrest, making them a key determinant in CPR effectiveness.

Guidelines emphasize that the quality of chest compressions is a critical factor in the effectiveness of basic life support (BLS). To ensure efficacy, a compression rate of 100 to 120 per minute is recommended, with a depth of at least 5 cm but not exceeding 6 cm, proper arm and hand alignment, full chest recoil after each compression, minimal interruptions during CPR, and rescuer rotation every 2 minutes to prevent performance decline due to fatigue.

As we can see, these guidelines refer to performing compressions using the upper limbs. However, it is essential to acknowledge that some individuals have physical limitations that may impair their ability to apply effective force with their upper limbs (e.g., amputations, fractures, neuromuscular dysfunctions). This presents important challenges regarding accessibility and inclusive CPR training. In addition, the use of the lower extremities has been proposed as an alternative to potentially reduce rescuer fatigue, although evidence regarding its effectiveness and impact on physiological fatigue is still limited.

There are studies comparing chest compressions performed with the hands (Hands Method, HMM) and with the feet (Foot Method, FMM); however, these studies have certain limitations and a limited number of participants. Although the quality of CPR was lower when using the feet technique, the results were positive.

However, to date, no specific guidelines have been established on how to perform CPR using the feet (Foot CPR), and it remains unclear whether the position of the feet on the chest or whether compressions are performed with or without shoes are variables that influence compression quality.

Furthermore, during CPR, it is recommended to rotate rescuers every 2 minutes when two or more rescuers are available due to fatigue associated with the procedure. Current evidence suggests that CPR is most effectively performed in the kneeling position, rather than standing or using a stool, due to the lower levels of fatigue in this position.

Traditionally, exercise-induced fatigue is assessed using subjective perception of exertion (RPE), performance monitoring (e.g., power or speed), or biochemical markers (e.g., blood lactate). More recently, heart rate variability (HRV) has been proposed as a valuable tool for assessing the autonomic nervous system response to exercise stress and quantifying physiological fatigue.

After exercise, especially if it is intense or prolonged, the body experiences significant physiological stress. This stress affects multiple systems, including the cardiovascular and autonomic nervous systems. Post-exercise fatigue is a complex sensation involving muscular, metabolic, and neuronal factors. Therefore, HRV becomes a valuable biomarker.

Numerous studies have shown a correlation between decreased HRV and the subjective perception of fatigue after exercise. People with lower heart rate variability (HRV) after exercise tend to report higher levels of fatigue. HRV analysis provides an objective and physiological measure of the stress the body experiences after short-duration, high-intensity exercise, such as that performed during resuscitation.

Therefore, measuring HRV after 2 minutes of chest compressions can indicate the degree of exercise-induced physiological fatigue, which could vary depending on the technique used (Hands-on CPR [H-CPR] vs. Feet-on CPR [F-CPR]).

Efforts to improve outcomes should focus on optimizing the chain of survival through training in Basic Life Support and Automated External Defibrillation (BLS + AED). Offering these courses to the general population presents significant challenges in terms of accessibility and implementation of comprehensive and inclusive training.

The objective of our randomized simulation study using mannequins, with a population of Basic Life Support students, was to compare the quality of chest compressions and the fatigue produced by this technique, in compressions performed with the hands and with the foot.

This is a single-center, randomized, crossover, controlled study conducted in the Skills Laboratory of the Faculty of Medicine and Health Sciences, Campus Clínic. Each participant will act as their own control, performing chest compressions with both hands and their foot. The order of compression method (hand or foot) will be randomly assigned, and participants will subsequently perform the alternative method they did not initially complete.

Participants will be enrolled in a Basic Life Support and Automated External Defibrillation (BLS+AED) course from the Catalan Resuscitation Council - European Resuscitation Council.

Data collection will be consecutive and open-label.

Variable-size block randomization, generated using statistical software, will be used to ensure balanced assignment of participants to the study groups while maintaining unpredictability.

To implement this randomization, the R programming language will be used, widely used in scientific research and statistical analysis due to its robustness and reliability. R offers specialized tools for this type of randomization, ensuring a rigorous, transparent, and reproducible process.

We will use the R package blockrand, specifically designed for efficient and controlled block randomization.

Primary objectives:

To compare the depth of uninterrupted chest compressions (without ventilation) delivered over a 2-minute period during a simulated cardiac arrest on the floor, using either the hands (HM) or feet (FM).

To assess CPR-associated fatigue in the two groups using:

Subjective measures: Rating of perceived exertion (Borg score). Direct objective measures: Use of a wearable health monitoring device (abdominal strap-based) to measure rescuer heart rate variability (HRV), a parameter correlated with fatigue during CPR.

Indirect objective measures: heart rate and oxygen saturation.

Data will be collected using the SkillReporter® app (Laerdal Medical®) during 2 minutes of continuous chest compressions on a Resusci Anne QCPR manikin, a certified medical-grade abdominal strap (Movesense®), and a pulse oximeter.

Inclusion Criteria:

• Age 18 years or older
• Signed informed consent
• First-year postgraduate trainees in health-related fields such as medicine or nursing
• Enrolled in a Basic Life Support and Automated External Defibrillation (BLS+AED) course from the Consell Català de Resuscitació - European Resuscitation Council

Exclusion Criteria:

• Physical limitations preventing chest compressions with hands or feet
• Contraindications for physical exercise (e.g., arthritis, heart disease, advanced lung disease, severe physical disability, morbid obesity, chronic fatigue, pregnancy).

At the time of inclusion in the study and after signing the informed consent, personal data will be coded. The data (with coded information) will be collected in an Excel® database, which will be accessible to the collaborating researchers. Access to identifiable data will be restricted to the principal investigator, who will keep it for a maximum of 5 years.