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Validation of the 4-second exercise test in the orthostatic position
Marcos Bezerra de Almeida1, Djalma Rabelo Ricardo, Claudio Gil Soares de Araújo
1Physical Education Graduate Program, Universidade Gama Filho, Rio de Janeiro, RJ, Brazil.
Arquivos Brasileiros De Cardiologia
|August 24, 2004
Summary
The 4-second exercise test (4sET) in the orthostatic position is a valid, low-cost alternative for assessing cardiac vagal tone, especially when a cycloergometer is unavailable.
Area of Science:
- Physiology
- Cardiovascular Research
Background:
- Assessing cardiac vagal tone is crucial for understanding autonomic nervous system function.
- Conventional methods like the cycloergometer (CYCLO) protocol may not be accessible in all laboratory settings.
Purpose of the Study:
- To evaluate the operational viability and clinical validity of the 4-second exercise test (4sET) performed in the orthostatic position (ORTHO).
Main Methods:
- The study compared the ORTHO protocol (stationary walking during inspiratory apnea) with the conventional CYCLO protocol.
- Cardiac vagal index (CVI) was calculated using RR intervals from electrocardiographic tracings.
- Forty-seven participants underwent both protocols to assess CVI, RRB, and RRC.
Main Results:
- While statistically significant differences in CVI were observed between protocols, they lacked physiological relevance.
- Strong correlations were found between RRB, RRC, and CVI measurements from both ORTHO and CYCLO protocols (r=0.84-0.93).
- Clinically significant differences in CVI were noted in only 11% of cases.
Conclusions:
- The ORTHO protocol is a valid and simple alternative for assessing vagal cardiac tonus in labs without a cycloergometer.
- This method maintains clinical interpretability and offers low operational costs.
- The 4sET in the orthostatic position provides a practical option for evaluating cardiac autonomic function.