Participants characteristics
A total of 19 subjects with a nutritional diagnosis of OW-OB according to BMI ≥ 25 kg/m2, physically inactive according to the World Health Organization (WHO) classification [19], and no diagnosis of NCDs participate in the study. Before the evaluations, the subjects signed an informed consent approved by the Scientific Ethics Committee of the Universidad Finis Terrae (resolution Nº21/2017). All procedures were performed in compliance at Helsinki Declaration principles for human experiments.
Study Design
The participants visited the laboratory in five separate days. Subjects arrived between 08:00 and 10:00 am and were evaluated in a randomized order for the following procedures: body composition, cardiorespiratory fitness test, TTT, and ATT.
Body Composition
Fat, lean, and fat-free body mass were measured by double energy X-ray absorptiometry (DEXA) using manufacturer-supplied algorithms (Total Body Analysis, version 3.6; Lunar, Madison, WI, United States). The general characterization of subjects is presented in Table 1.
Table 1
Participant’s characteristics.
| Women (n = 6) | Men (n = 12) | Total (n = 19) |
Age (years) | 33.2 ± 6.4 | 35.8 ± 7.0 | 34.9 ± 6.7 |
Height (cm) | 164.7 ± 5.6 | 173.3 ± 7.3 | 170.4 ± 7.8 |
Weight (kg) | 86.2 ± 14.9 | 91.2 ± 16.7 | 89.5 ± 15.8 |
BMI (kg·m− 2) | 31.8 ± 5.7 | 30.3 ± 4.7 | 30.8 ± 5.0 |
Fat mass (%) | 46.9 ± 3.6 | 31.6 ± 5.7 | 37.0 ± 9.1 |
Lean mass (%) | 49.8 ± 3.2 | 64.8 ± 5.5 | 59.4 ± 8.8 |
Fat-free mass (%) | 53.3 ± 3.5 | 68.4 ± 5.7 | 63.0 ± 9.0 |
Data are shown as mean ± SD. |
Abbreviation: BMI: Body mass index. |
Cardiorespiratory Fitness
After a 5-min warm-up at 50 watts and a constant cadence of 55 ± 5 rpm, the participants performed a maximal incremental test on an electronic automatized cycle-ergometer (Cyclus2, Germany). An initial workload of 40 watts (W) was used, with increments of 15 W (women) and 20 W (men) every 1 min until exhaustion. The test was performed with a constant cadence of 55 ± 5 revolutions per minute (rpm). Gas exchange was recorded continuously with a portable breath-to-breath gas analyzer (Cortex Metalyzer 3B, Leipzig, Germany) and was calibrated according to the manufacturer’s instructions before each trial. Pulmonary ventilation (VE), oxygen uptake (VO2), expired carbon dioxide (VCO2), and respiratory exchange ratio (RER) were averaged over 10 s in the mixing chamber mode, with the highest 30 s value (i.e., three consecutive 10 s averages) used in the analysis. VO2max was determined according to previously established criteria [20]: (i) plateau in VO2 (i.e., increase < 150 ml·min − 1), (ii) RER > 1.1, and (iii) ≥ 90% of theoretical maximal heart rate. The VO2max was expressed both as absolute values (L·min − 1) and relative to body mass (ml·kg − 1·min − 1). The power output at VO2max (pVO2max) was determined as the minimum workload at which VO2max was reached. Ventilatory threshold 1 (VT1) and ventilatory threshold 2 (VT2) were identified separately by three researchers according to the following criteria (24): an increase in VE/VO2 and PETO2 without a concomitant increase in VE/VCO2 for VT1, and an increase in VE/VO2 and VE/VCO2 and a decrease in PETCO2 for VT2. The cardiorespiratory fitness and ventilatory threshold are shown in Table 2.
Table 2
Cardiorespiratory fitness and ventilatory threshold.
| VT1 | VT2 | VO2max |
VO2max (ml·kg− 1·min− 1) | 14.5 ± 2.5 | 22.4 ± 5.4 | 28.2 ± 7.0 |
METs | 4.2 ± 0.8 | 6.3 ± 1.2 | 8.2 ± 2.0 |
VO2max (L·min− 1) | 1.3 ± 0.3 | 2.0 ± 0.5 | 2.6 ± 0.7 |
% VO2max | 51.8 | 77.1 | 96.5 |
Power (Watts) | 65.3 ± 20.8 | 133 ± 36.0 | 190.8 ± 55.3 |
HR (beats·min− 1) | 109 ± 12 | 139 ± 15.0 | 163.6 ± 14.5 |
HR (%) | 65.7 | 82.0 | 98.7 |
Ventilation (L·min− 1) | 34.2 ± 8.1 | 59.5 ± 16.0 | 103.8 ± 28.7 |
Data are shown as mean ± SD. |
Abbreviations: VO2max: maximal oxygen consumption; VT: ventilatory threshold; HR: heart rate; METs: Metabolic equivalent. |
Talk Test
After a 10-minute warm-up, subjects performed an incremental test on an electronic automatized cycle-ergometer (Cyclus2, Germany). The protocol considered load (W) increments every 3 minutes, the time necessary to stabilize ventilation, primary variable for voice production [21, 22]. During the last 30 seconds of each stage, out loud reading of 40 words from the text “Lectura del Abuelo” was requested. Two methods evaluated the ability to converse during exercise: (i) traditional talk test (TTT) by answering “yes”, “no”, or “I do not know” to the question “was talking comfortably?”, and (ii) alternative talk test (ATT) using a 1 to 10 visual analog scale (VAS) [23]. Both, text “Lectura del Abuelo” and VAS are shown in Fig. 1.
Statistical Analyses
Data in the text and figures are presented as mean ± SD and 90% confidence limit/interval (CL/CI). All data were first log-transformed to reduce bias arising from nonuniformity error. The magnitude of differences was interpreted in comparison to the smallest worthwhile change (SWC) (0.6 x pre-tests between-subjects SDs) [24]. This SWC was setting as the equivalence region, representing about one stage of difference during the incremental test and was used to determine agreement. The probability of any substantial difference or realistic equivalence relative to the predefined target values was interpreted using the following scale: <0.5%, most unlikely; 0.5–5%, very unlikely; 5–25%, unlikely; 25–75%, possibly; 75–95%, likely; 95–99.5%, very likely; >99.5%, most likely [25]. Effects were declared relevant if the outcome probability was likely (≥ 75%) (i.e., methods were considered in agreement and, therefore, interchangeable). Statistical analysis was performed with the “mbir” package of the R software [26].