Abstract
Background: Concurrent and aerobic physical exercise are strategies for treating overweight and obesity. Most interventions have utilized cardiovascular or guided execution machines, which often involve high-cost materials not easily accessible to the general population.
Objective: Identify the effect of 12 weeks of exercise (concurrent vs. aerobic training) based on the polarized training intensity distribution model on maximal oxygen consumption, muscle strength, and body composition.
Materials and methods: A randomized controlled trial with two groups, concurrent vs. aerobic training (n = 28), in overweight and obese individuals. Both groups will perform 36 sessions, 3 times a week, on alternate days.
Results: Current evidence has not demonstrated the superiority of concurrent over aerobic exercise on VO2max, muscle strength, and body composition. Additionally, the few randomized studies with concurrent exercise and the methodological limitations in their designs justify the importance of comparing both types of exercise to determine the best strategies for overweight and obese individuals regarding the mentioned outcomes.
Keywords: Cardiorespiratory fitness, circuit-based exercise, obesity, body composition, resistance training, concurrent training, endurance training, strength.
Resumen
Antecedentes: El ejercicio físico concurrente y el entrenamiento aeróbico son estrategias para tratar el sobrepeso y la obesidad. La mayoría de las intervenciones han usado máquinas cardiovasculares o de ejecución guiada, que frecuentemente implican materiales de alto costo no fácilmente accesibles para la población general.
Objetivo: Identificar el efecto de 12 semanas de ejercicio (entrenamiento concurrente vs. aeróbico), basado en el modelo de distribución de intensidad de entrenamiento polarizado, sobre el consumo máximo de oxígeno, la fuerza muscular y la composición corporal.
Materiales y métodos: Ensayo controlado aleatorizado con dos grupos, entrenamiento concurrente vs. aeróbico (n = 28), en personas con sobrepeso y obesidad. Ambos grupos realizarán 36 sesiones, 3 veces por semana, en días alternos.
Resultados: La evidencia actual no ha demostrado la superioridad del ejercicio concurrente frente al aeróbico sobre el VO2max, la fuerza muscular y la composición corporal. Además, los pocos estudios encontrados con ejercicio concurrente y las limitaciones metodológicas justifican en sus diseños la importancia de comparar ambos tipos de ejercicio y así identificar las mejores estrategias para las personas con sobrepeso y obesidad en relación con los desenlaces mencionados.
Palabras clave: Aptitud cardiorrespiratoria, ejercicio en circuito, obesidad, composición corporal, entrenamiento de resistencia, entrenamiento concurrente, entrenamiento aérobico, fuerza.
Study protocol
Concurrent and Aerobic Exercise on Maximal Oxygen Consumption in Adults with Obesity: Study Protocol for a Randomized Controlled Trial
Ejercicio Concurrente y Aeróbico sobre el Consumo Máximo de Oxígeno en Adultos con Obesidad: Protocolo de estudio para un ensayo controlado aleatorizado
Felipe Madrid Zapata
Jonathan Orozco Osorio
Jerman Jesyd Cruz-González Jerman.cruz@udea.edu.co
Víctor Hugo Arboleda-Serna
Received: 11 March 2024
Revised document received: 10 May 2024
Accepted: 11 June 2024
Overweight is characterized by excessive fat deposits, whereas obesity is defined as a disease marked by a significant increase in adipose tissue, which is detrimental to health [1]. It is a risk factor for developing different diseases such as diabetes, hypertension, and cancer [2]. Excess weight is generated by different causes in which the following stand out: excessive consumption of food and sedentary behaviors [2].
By 2030, one in five women and one in seven men are expected to be obese, which is equivalent to more than 1 billion people worldwide [2]. In Latin America, overweight affects 59.5% of the adult population, and obesity affects almost 25% of adults [3]. The increase in overweight has brought different consequences worldwide, such as the annual cost of treatments related to this disease, which oscillates around USD 2.0 trillion.
A protective factor for obesity is the increase in maximum oxygen consumption (VO2max). Due to having high levels, the probability of morbidity and mortality from any cause decreases [4]. A systematic review that inquired about VO2max in this population reported that low VO2max values are associated with obesity [5].
Exercise-based strategies such as aerobic training (AT), strength training (ST) and combined training (CT) have been used. These three types of training generate effects on VO2max, muscle strength (MS) and body composition (BC) in overweight and obese people [4].
Treadmill [6] cycle ergometer [7] tests have been used to determine the intensities of the AT and CT interventions. The control of the intensity in the interventions has been carried out by heart rate (HR) reserve [8] % VO2max [6], VO2peak [9], and ventilatory thresholds (VT) [10]. Table 1 presents the dosage of the load components for AT, ST, and CT.
There is a scarcity of studies on training intensity distribution models (TID) to determine the load in AT or CT [6,8,11]. These models are defined by the total time spent in each training zone during a microcycle or mesocycle and quantify the intensity based on physiological markers such as VT and lactate threshold (LT) [13]. Using these parameters, 3 training zones are established. Zone 1: low intensity, below VT 1 (<VT1) or LT1 (<LT1). Zone 2: moderate intensity, between VT1 and VT2 or LT1 and LT2. Zone 3: high intensity, above VT2 (>VT2) or LT2 (>LT2) [13]. Some of the TID include:
Pyramidal TID: primarily focuses on Zone 1 (<VT1), 80%, with a lower percentage in Zone 2 (between VT1 and VT2) and minimal in Zone 3 (>VT2) [14].
High intensity TID: focused around 70% in Zone 3 (>VT2) [15].
Low-intensity and high-volume TID: predominantly in Zone 1 (<VT1), almost 100% [16].
Polarized TID: 75-80% in Zone 1 (<VT1), 15-20% in Zone 3 (>VT2); rest in Zone 2 (between VT1 and VT2) [16].
The polarized TID increases VO2max in overweight and obese individuals. In a study with obese women, it compared continuous moderate-intensity training, high-intensity interval training, and polarized TID. Polarized training showed superior effects, with a 2.6 ml/min [95% Confidence Interval (CI) 1.5 - 3.8] in VO2peak compared to the other interventions. This also allowed for greater exercise tolerance in this population. However, further investigation is needed regarding the effects of polarized TID on cardiometabolic factors [17].
The following tables describe the effects of AT, CT, and ST on VO2max, MS, visceral adipose tissue (VAT), free fat mass (FFM), fat mass (FM), and waist circumference (WC).
Observe the effects of AT and CT on VO2max in Table 2.
As seen in Table 3, to date the superiority of one training over the other cannot be determined, since there are no statistically significant or important differences for practice.
The benefits of physical exercise on visceral adipose tissue (VAT), fat-free mass (FFM), waist circumference (WC), fat mass (FM), and muscular strength (MS) are shown in Table 4.
However, when comparing these interventions (AT, CT, and ST) to determine which is the best for BC, no statistically significant differences or practically important results were found [20,21]. Conversely, when evaluating MS, CT seemed to be superior to AT in muscle strength gains in both the lower limbs [4] and upper limbs [23]. See Table 5.
The formulation of randomized controlled trials (RCTs) for CT and its effects on this variable becomes relevant. In addition, a greater number of RCTs for AT compared to CT is evident in the following systematic reviews and meta-analyses on VO2max in overweight and obese individuals. For example, Batrakoulis et al. [4] included 45 studies for AT and 15 for CT, Van Baak et al. [18] reported 24 studies for AT and 7 for CT, Scapini et al. [19] selected 21 for AT and 12 for CT, and O’Donoghue et al. [21] considered 35 studies for AT and 11 for CT.
For the aerobic component, most of the interventions used activities, such as walking or running, a cycle ergometer or treadmill [4,18,19,21] and exercises in water [26]. For ST, Van Baak et al. and Ratajczak et al. used body-building machines [18,20] and Slentz et al. and Jin et al. used guided machines [6,11]. There have been few studies on outdoor exercise [4,24,27], and limited interventions have been conducted using block circuits. In these circuits, each block focuses on a specific component, such as strength or aerobic training, and includes self-loading and short-duration cardiovascular exercises [18,20]. Additionally, there is limited evidence regarding the aerobic component of CT, particularly involving coordinated aerobic steps [28,29].
The methodological designs have limitations, including small sample sizes [11,30], absence of reported sample size calculation [4,18,21], and lack of intergroup comparisons despite having three intervention arms (AT, ST, CT) [8,23]. The authors of the systematic review also declared limitations, including few studies of high methodological quality [11,20,23].
This study aims to assess the effect of a CT program compared to an AT program, both following a polarized TID, on various health parameters including VO2max, lower limb MS, FM, VAT, FFM, and WC in overweight and obese adults aged 18 to 59 years. The goal is to detect a minimum difference of 3.5 ml/kg/min in VO2max between the CT and AT groups [21,27]. Previous research has shown values close to 3.5 ml/kg/min, but this difference between groups has not been achieved. This study proposes a novel intervention that may produce this significant difference, which holds practical significance [31].
We used an RCT involving two parallel groups, designed under the CERT [32] and CONSORT [33] guidelines. This protocol is registered on ClinicalTrials.gov with the identifier NCT05867498.
Participants will be individuals aged 18-59 from the Municipality of Girardota, Antioquia, Colombia, who are overweight or obese. The sample was calculated using the Epidat 4.2 program, with a mean difference of 3.5 ml/kg/min in VO2max, standard deviations (SDs) of 1.3 and 3.1 [11], 95% confidence level, 90% power, 5% alpha error, with a 1:1 ratio between groups. A sample size of 12 people per group was obtained, plus a 15% oversampling due to potential dropouts.
Twenty-eight (28) individuals, both men and women, between 18 and 59 years old, who have a Body Mass Index (BMI) >25.0, WC ≥85 cm in women and ≥94 cm in men will be included. All participants must voluntarily consent to participate in the study by signing an informed consent form, which will detail the objectives of the research, the benefits, the possible risks and the strategies to mitigate those risks. The University of Antioquia Research Ethics Committee of the University Institute of Physical Education in Medellín, Colombia, has approved the protocol of this RCT, along with the informed consent form (ACEI 33-2023). Smokers, individuals with a history of cardiovascular and pulmonary diseases, those with uncontrolled psychiatric problems, those being treated with anticoagulants, beta-blockers, calcium antagonists, or bronchodilators, individuals with musculoskeletal injuries that may affect participation in exercise sessions, pregnant women, and individuals following a nutritional plan for weight loss will be excluded.
The Sports and Recreation Institute (INDER Girardota) database will be searched to identify potential participants who meet the inclusion criteria. Additionally, information will be sent through the INDER Girardota social networks.
The initial and final assessments of VO2max, MS, and BC will be conducted at the laboratory of the National Learning Service (SENA) located at the POMAR headquarters Medellín, Colombia. The interventions will take place at sports centers within the Municipality of Girardota.
The randomization sequence will be generated using Sealed Enveloped software [34], employing blocks of four and six. To ensure concealment, the sequence will be enclosed in opaque, sealed envelopes numbered from 1 to 28. The assignment will be made according to the order of initial evaluation. These procedures will be conducted by personnel external to the research team.
A presentation will be held to discuss the benefits of participation, the project's cost (which is free for participants), and the study schedule will be outlined to identify individuals with available time to participate. The training plans will be implemented by professionals according to training principles, ensuring participant safety and minimizing the risk of injury and dropout during exercise sessions. Messages will be sent via WhatsApp to users, reminding them of upcoming sessions and inquiring about their absence if it occurs. Everyone will receive the results of both initial and final evaluations along with their respective interpretation.
The previously presented inclusion and exclusion criteria will allow us to control selection biases. Confounding biases will be controlled through the randomization process and statistical analyses will include analyses of covariance to control for sources of bias arising from potential confounding variables. To control information biases during evaluations, specialized personnel including a sports medicine specialist physician and laboratory technicians will be involved. Valid and reliable equipment will be utilized, and tests will be conducted at consistent times of the day, following established protocols. The personnel in charge of this process will be blinded to the interventions. Participants will receive detailed instructions on the necessary preparation for evaluations, and their compliance with these requirements will be confirmed before the evaluations begin.
Participants will be scheduled to arrive at 6:00 AM for all tests, and their readiness for evaluation will be confirmed, including instructions to have a light breakfast, abstain from caffeine, tea, or alcoholic beverages for 12 hours prior to the tests, maintain adequate hydration, avoid vigorous physical exercise the day before evaluations, wear sportswear and comfortable shoes, and reschedule evaluations if experiencing fever or body discomfort on the day of the test.
To analyze the BC, height (cm) will first be measured with a stadiometer (SECA, Germany) with a measurement range of 3.5-230 cm. Then, the WC (cm) will be measured with a metric tape (GMD, Colombia) with a length of 150 cm. Finally, the information will be entered in the InBody 270 electrical bioimpedance device (InBody, USA) that works at a frequency of (20kHz, -100kHz) for the evaluation of body weight (kg), FFM (kg), GF (%), and VAT estimation (high>10, low<10); this equipment has a Kendall’s concordance correlation of 0.71 in the FM [35], and 0.14 for the FFM [35].
Measurements will begin with height. The participant will stand barefoot, facing forward, with their heels, buttocks, shoulder blades, and occiputs against the wall to record the height. Next, the WC will be measured. With the participant's authorization, cut-off points will be marked with a pencil on the upper edge of the iliac crest and the costal margin. The tape measure will be passed through the midpoint to take the WC measurement. Finally, the participant will stand barefoot without any metallic object on the Inbody 270, which will be placed on a flat, firm surface. The participant's feet will make contact with the four lower electrodes, and they will hold the upper electrodes with their hands, abducting the shoulders maintaining an upright position while the device performs the measurement.
The T-Forcé tf-100 (ERGOTECH, Spain) will be used. It is a linear encoder that measures average propulsive speed (m/s), maximum strength (N) and maximum peak power (W). The mean relative error in velocity measurements <0.25% and the absolute error in displacement is less than ±0.5 mm [36]. The mean propulsive velocity has an intraclass correlation coefficient of 1.00 (95% CI: 1.00-1.00) and a coefficient of variation of 0.57% [36].
To evaluate lower limb strength, the half-squat exercise will be performed on a Smith machine. The participant will stand under the barbell, resting it on their trapezius after scapular retraction. With feet placed shoulder-width apart, the participant will descend in a controlled manner, performing pelvic anteversion and maintaining the natural curvatures of the spine. Upon reaching 90° of knee flexion, the participant will then ascend at the highest possible speed.
The warm-up will last 2 minutes, consisting primarily of mobility exercises (hip, knees, ankles). Participants will be instructed in the squat technique without weight, supported on a bench; when mastery of the technique is noted, they will perform the exercise on the Smith machine without weight. After every 3 repetitions, the load will be increased by 5 kg until the initial load is reached, which will be 40% of the body weight. With this load, they will be asked to perform 3 repetitions at maximum speed to evaluate the average propulsive speed (m/s), maximum strength (N), peak maximum power (W), and mobilized weight (kg). Increases of 10 kg will be made until the average propulsive speed is <0.4 m/sec, this being a criterion to finish the test, or until the person is unable to continue; the breaks will last 2 minutes between each set.
To assess cardiorespiratory capacity, a bicycle ergospirometry (ERGO-FIT, Germany) will be performed with a gas analyzer (METAMAX 3B cortex, Germany). This equipment has a reliability of ICC ≥ 0.969; p = 0.000 and a precision of % SEM ≤ 4.6 [37]. The following variables will be measured: VO2max, HRmax, VT1, and VT2.
The cycle ergometer will be calibrated with the gas analyzer; the characteristics of the test will be explained, and the participant’s weight, height and age will be recorded. Next, their blood pressure (BP) and the HR will be measured. The height of the bicycle seat will be adjusted.
The test will begin with a resistance of 30 Watts, maintaining a pedaling cadence of 50 revolutions per minute (rpm) for 3 minutes; this will be the first ergometric charge. Subsequently, 30 Watts will be increased while maintaining the cadence at >50 rpm for another 3 minutes. This process will continue until the participant reaches exhaustion or decides to stop voluntarily. The following criteria will be considered to identify VO2max: Respiratory Quotient (≥1.10) and Heart Rate (≥95%) of the theoretical maximum. HR and BP will be recorded at the end of each load. The recovery phase will last 5 minutes, with a load of 30 Watts at 30 rpm, the HR and BP will be measured at minutes 1, 3, and 5.
Two groups, CT and AT, will undergo a 12-weeks program, 3 sessions per week on alternate days, each lasting 60 minutes. Participants will have a HR monitor (MI BAND 4) to control the intensity. Training zones for the polarized TID will be determined based on ergo spirometry results
Both groups will start each session with an 8-minute warm-up. AT will perform aerobic steps at an intensity <VT1 for 12 weeks. CT will do the same for 6 weeks and then switch to joint mobility exercises for the remaining 6 weeks. The session will conclude with 4-minute stretch of the main muscle groups.
The main part of the session, lasting 48 minutes, will consist of 2 components: strength and aerobics; each lasting 24 minutes. The strength component will involve a circuit of 7 exercises. (As seen in Tables 6, 7 and 8).
The aerobic component will include 18 minutes of variable continuous method with rumba-aerobic (ballroom and folk-dance steps), followed by 6 minutes of interval method with combat gestures (fists, knees, and plantar flexions).
This group will perform the same rumba steps, combat gestures, intensities, and time as the CT group during the aerobic component. However, in the AT group, the variable continuous method will last 36 minutes and the interval method will last 12 minutes (see Table 9).
The data analyses will follow the intention-to-treat principle and per protocol analyses (compliance ≥70% of the sessions, only for the primary outcome). The Shapiro-Wilk and Levene tests assess normality and homogeneity of variances. Analysis of covariance (ANCOVA) [38] will be used to identify mean differences between CT and AT groups, adjusting for initial outcome variable values and controlling for possible confounding variables. Summary measures will include means and standard deviations. In case of non-normality or heterogeneous variances, the Mann-Whitney U test will be used, and data will be presented in medians and interquartile ranges. Statistical significance will be set at p<0.05 with a 95% confidence interval. Analysis will be conducted using SPSS v27.
Multiple data imputation will be made, for VO2max and FM.
The SPSS license was acquired by the University of Antioquia in a Campus Agreement modality. Epidat 4.2 is freely distributed.
Based on the Declaration of Helsinki of 2013, participant privacy will be ensured. Sources of financing, conflicts of interest, benefits, and potential risks associated with the research will be disclosed. Additionally, compliance with Resolution 8430 of 1993 from the Colombian Ministry of Health and Social Protection will be considered. Participants will receive training on the informed consent process, providing them with comprehensive knowledge of the study's objectives, justification, benefits, and potential risks, which will enable them to make an informed decision to participate freely.
The data share in this research will uphold participants' privacy and consent. They will be informed about the data's public use, ensuring confidentiality. Privacy measures include restricted access to electronic files solely by researchers, participant identification through codes, and no disclosure of information compromising privacy. Participants' consent will be consistently obtained.
Obesity, a detrimental health condition [1], increases the risk of various cardiovascular and metabolic diseases such as diabetes, hypertension, and cancer [2]. Increasing VO2max can mitigate risks, lowering morbidity and mortality rates [4]. Therefore, it is important to compare the effectiveness of AT and CT in improving VO2max, MS, and BC in overweight and obese individuals. Furthermore, using polarized TID with outdoor music dynamics and easily accessible materials is an innovative approach that has been relatively under-researched until now.
Using electrical bioimpedance for BC evaluation is preferred due to its cost-effectiveness, although it lacks precision in assessing VAT. Financial and logistical limitations hinder the use of advanced equipment like computed tomography, magnetic resonance imaging, or dual-energy X-ray absorptiometry, which offer greater accuracy.
*Correspondence: Jerman Jesyd Cruz-González. Email: Jerman.cruz@udea.edu.co
