LAB REPORT

The effect of incremental exercise on respiratory rate, oxygen consumption and the respiratory exchange ratio (RER)



The effect of incremental exercise on respiratory rate, oxygen consumption and the respiratory exchange ratio (RER)

Introduction

Both the rest-exercise transition (on-transient) and the exercise-recovery transition (off-transient) result in cardiac and metabolic changes that are necessary in order to meet the energy demands of the organism and maintain homeostasis. However, not all individuals respond in a similar fashion as these responses are influences by the health of various physiologic systems. These physiological adaptations can be non-invasively quantified by the kinetic behavior of certain variables, such heart rate (HR) and oxygen consumption (VO2) (Koppo, 2004, pp. 225).

The analysis of the exercise kinetic response through these variables is becoming increasingly recognized as an important tool for the evaluation of exercise performance and health, given their ability to reflect cardiac autonomic modulation and aerobic metabolism1,2. Faster are observed in athletes and young individuals and are reflective of the good health status generally seen in these populations1. Delayed kinetic responses in both of these variables, both during the initial and final transient of exercises, reflect an increased risk of cardiovascular mortality1. Factors that can induce changes in the central and peripheral responses during a physical exercise, such as the exercise intensity, seem to influence the kinetic responses of HR and VO2 kinetics.

Method

This was a prospective, cross-sectional, controlled study involving 28 men separated into two groups: 1) 14 healthy young men aged between 20 and 30 years (young group — YG) and; 2) 14 healthy elderly men aged between 60 and 80 years (elderly group — EG). Additionally all subjects were considered to be in good health based on clinical, physical examination and laboratory tests. Subjects were excluded if they had skeletal muscle and/or joint pain, cardiopulmonary, metabolic or neurologic diseases, or difficulty in performing the exercise protocol used in this study (Javorka, 2003, pp. 8). All participants signed a written informed consent and the study protocol was approved by the Ethics Committee on Human Research at the Universidade Federal de São Carlos (UFSCar), Sao Carlos, SP, Brazil (nº 008/2010).

Incremental exercise testing

Prior to data collection volunteers were evaluated by a physician using a 12-lead electrocardiography at rest (ECG) (Wincardio System, Micromed, Brasília, Brazil), and a symptom-limited exercise testing on a cycle ergometer. The later was performed to ensure a normal physiologic response to exertion and to determine the maximal power to subsequently apply during the discontinuous exercise test. The protocol was performed in an erect position on an calibrated, electromagnetically braked cycle ergometer (Quinton Corival 400, Groninger, Netherlands) with gas exchange and ventilator variables analyzed breath-by-breath through a tightly fitted facial mask, using a portable telemetric system (Oxycon Mobile, Viasys Healthcare, Hoechberg, Germany). The exercise protocol consisted of: a) 1 min at rest; b) 4 min with 4W at 60 rpm; c) an incremental phase with 15 to 30 Watts/min (using a ramping protocol); and d) 4 min of recovery period. During the incremental phase, power (in Watts) was progressively increased ...