Association of sedentary behavior and physical activity with occurrence of signs and symptoms in participants of a cardiac rehabilitation program

Study design and participants

This is an observational longitudinal prospective cohort study that was developed between February and March 2019. It is described according to the “Strengthening the Reporting of Observational Studies in Epidemiology” (STROBE) recommendations¹⁴. A total of 65 individuals were recruited for this study. It included those who were participating in an exercise-based CRP conducted in a Brazilian University for at least three months, had a clinical diagnosis of cardiovascular diseases and/or risk factors for cardiovascular diseases, and those who agreed to participate in the study. The recruitment was conducted by a researcher who was not part of the clinical care and had no conflict of interest.

Patients who presented errors in the evaluation of the SB and PA, assessed by an accelerometer, (i.e., did not wear the accelerometer for at least 10 h during 4 days) were excluded from the analyses.

The individuals were informed about the objectives and procedures of the study and provided written informed consent. All procedures used in this study were approved by the Ethical Research Committee of São Paulo State University Campus of Presidente Prudente, São Paulo, Brazil (CAAE: 79213417.0.0000.5402) and all procedures carried out in the study are in accordance with the Declaration of Helsinki, as well as with research regulatory organizations in Brazil.

Sample size

The sample size was determined using the results obtained in a pilot study previously conducted. Data from 10 individuals were considered for analysis. It was based on an estimated correlation of 0.429, alpha risk of 5%, and beta risk of 80%, which resulted in a minimum sample size of 40 individuals. Considering possible sample losses, 10% was added to the sample, which resulted in 44 individuals. The sample size calculation was performed using MedCalc Software bvba – version 19.2.6 (Oostende, Belgium) [https://www.medcalc.org].

Experimental procedure

The study data collection was performed from March to December 2019, in the afternoon (13:30 to 17:30), and occurred in two moments. In the first moment, data for sample characterization were extracted from the patients’ medical records, and anthropometric data (body mass and height) were measured for further body mass index calculation and obesity definition. Subsequently, the SB and PA was assessed using an accelerometer¹⁵.

In the second moment, all participants were followed up for 24 exercise sessions of a CRP for the identification and recording of the occurrence of SS. All the assessments were facilitated by a researcher who was not part of the clinical care and had no conflict of interest.

Characterization and assessment of the individuals

The following information was extracted from the patients’ medical records: sex, age, main clinical diagnosis. The ACSM recommendations¹⁶ were considered for the analysis of risk factors for cardiovascular diseases, and the presence of hypertension, diabetes mellitus, dyslipidemia, and obesity were assessed from the patients’ medical records.

For the assessment of body mass, a digital scale was used (Balmak, Premium Bk − 200Fa, Brazil). Height was measured in an orthostatic position using a stadiometer (Sanny, ES 2020, Brazil). Body mass index was obtained by the formula: body mass (kg)/height² (m)¹⁷.

Cardiac rehabilitation program

The exercise sessions of the CRP occurred at a frequency of three times a week, on alternate days, and had a duration period of 60 min divided into 4 phases: (1) resting phase: initial evaluation [blood pressure, heart rate and SS]; (2) warm-up phase: global stretching, active exercises of lower limbs, upper limbs and combined; with an average duration of 15 min; (3) resistance phase: individualized aerobic protocol performed for 30 min (15 min using a treadmill and 15 min using a stationary bike) and with intensity prescribed according to heart rate reserve values; (4) relaxation phase: cardiovascular deceleration and heart rate monitoring, and if necessary blood pressure monitoring¹⁸. The sessions were performed and supervised by previously trained therapists, with a maximum ratio of 1:2 patients¹⁸.

Identification of signs and symptoms

The identification of the occurrence of SS was performed for 24 exercise sessions of a CRP. Signs were identified by previously trained professionals, and symptoms were reported by the patients at the end of each phase of the session.

SS that are more frequently observed in CRP were assessed¹⁰: (a) Signs: Systolic blood pressure with an abnormal increase during exercise (higher than 200 mmHg), diastolic blood pressure with an abnormal increase during exercise (higher than 120 mmHg), changes in pulse rate, pallor and tachypnea; (b) Symptoms: dizziness, angina, cramps, muscle pain, fatigue, and nausea¹⁰.

The calculation of the occurrence of SS was relative to each session, regardless of the number of times that the same sign and/or symptom occurred during a session. Thus, if the patient presented the same sign and/or symptom in all of 24 sessions, it was calculated as 24 times. More information regarding the assessment and the definition of SS is described in the protocol previously published by Vanzella et al.¹⁸.

Assessment of sedentary behavior and physical activity

The Actigraph GT3X-BT triaxial accelerometer (ActiGraph, LLC, Pensacola, FL, USA) calibrated with a frequency of 30 Hz was used for the objective assessment of SB and PA¹⁵. Patients were previously instructed on how to wear the Actigraph (on the hip – dominant side), and to remove the equipment only while sleeping and performing activities that involves water.

Patients wore the Actigraph for seven consecutive days. The wearing of the device for at least 10 h was defined as a valid day. Data from patients that wore the device for least 4 valid days were considered for analysis¹⁵. After seven days of use, the data were downloaded from the Actigraph and the activity in counts was analyzed considering an epoch of 60 s¹⁹. The ActiLife Software – version 6.11.8 (ActiGraph, LLC, Pensacola, FL, USA) [ was used for analysis. To determine the valid periods, the non-valid periods of 24 h were subtracted, defined as intervals of at least 60 consecutive minutes of zero activity²⁰. These data provided information about individuals SB, characterized by the time in which the patient performed activities at less than 100 counts per minute²¹, and PA, considering MVPA (more than 2020 counts per minute) and total number of steps²⁰. Thus, the following outcomes were used: indicators of SB (daily SB time and % of SB total time) and PA (weekly time in MVPA, % of MVPA total time, steps/day, and steps/minute).

Data analysis

Accelerometer data was presented in median and interquartile range for sample characterization, while categorical information was presented in absolute and relative frequency. The SB and PA parameters were compared according to the occurrence of SS and according to each assessed sign/symptom by Mann-Whitney U test. Proportions of categorical variables were compared by chi-square test. Linear regression models were used do analyze the association between SB and PA parameters with SS occurrence in crude and adjusted models for age, sex, and comorbidities. Due to skewness of SB and PA parameters, these variables were transformed in natural logarithm for standardization and robustness of linear models. The first-order autocorrelation in multivariate model was analyzed by the Durbin-Watson test, whereas the Variance Inflation Factor (VIF) was analyzed in order to check whether covariates did not increase the regression coefficient due to multicollinearity. Statistical significance level was set at 5%. Data analysis was performed using the Statistical Packages for the Social Sciences (SPSS) – version 22.0 (SPSS Inc., Chicago, IL, USA) [