Cardiorespiratory, Metabolic and Muscular Responses during a Video-Recorded Aerobic Dance Session on an Air Dissipation Platform

: Aerobic dance (AD) is an appropriate physical activity for improving cardiorespiratory tness. This study aimed to compare cardiorespiratory and metabolic responses, and muscle fatigue between an air dissipation platform (ADP) and a hard surface during a video-recorded AD session. Methods: 25 healthy young women (23.3 2.5 years) completed three sessions. In session 1, participants performed an incremental test to exhaustion on a treadmill. One week after session 1, participants were randomly assigned in a crossover design to perform video-recorded AD sessions on an ADP and on a hard surface (sessions 2 and 3). Cardiorespiratory and metabolic responses were assessed during AD sessions. Muscular fatigue was measured before and after AD sessions by a countermovement jump test. Results: Signi cantly higher heart rate, respiratory exchange ratio, pulmonary ventilation, ventilatory oxygen equivalent, and ventilatory carbon dioxide equivalent were observed on an ADP than on a hard surface (p<0.05). Despite a signi cant increase in lactate levels on an ADP (p 0.01), muscular fatigue and perceived exertion rating were similar on both surfaces (p>0.05). Conclusions: Video-recorded AD on an ADP increased the cardioventilatory and metabolic responses compared to a

ventilation, ventilatory oxygen equivalent, and ventilatory carbon dioxide equivalent were observed on an ADP than on a hard surface (p<0.05). Despite a signi cant increase in lactate levels on an ADP (p 0.01), muscular fatigue and perceived exertion rating were similar on both surfaces (p>0.05). Conclusions: Video-recorded AD on an ADP increased the cardioventilatory and metabolic responses compared to a hard surface, preventing further muscle fatigue. Keywords:ventilatory threshold; cardiopulmonary exercise test; tness class; blood lactate; fatigue 1. Introduction Group classes in tness centers are a very popular physical activity among women and, particularly, aerobic dance (AD) is one of the most practiced worldwide. In this period of pandemic due to severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), thousands of practitioners who performed AD classes in tness centers have stopped training due to conditions of con nement. EHealth and exercise videos, television and mobiles are technologies that could be used to maintain physical function and mental health [1] during periods of con nement. AD led by tness instructors Int. J. Environ. Res. Public Health2020,17, 9511; doi:10.3390 /ijerph17249511 /journal/ijerph

Int. J. Environ. Res. Public Health2020,17, 9511 2 of 12 through a video-recorded session could be a very interesting alternative to maintain or improve cardiorespiratory and metabolic tness during periods of con nement. Heart rate (HR), blood lactate levels and oxygen uptake (VO2) have been used as measurement parameters to assess the exercise intensity in AD classes [2]. De Angelis et al. proved that AD increased HR, VO2and blood lactate concentrations to a greater extent than expected, showing a high exercise intensity, metabolic demand and a non-steady state [2]. The cardiorespiratory and metabolic requirements for regular bipedal work are conditioned by the mechanical properties of the surface [3,4]. Hardin et al. [3] concluded that a harder surface decreased VO2compared to a softer surface. Rodrigues et al. demonstrated that an elastic surface (i.e., mini-trampoline) increased cardiovascular responses compared to a hardwood surface during a stationary running [5]. The authors assumed that the higher physiological demands induced by the mini-trampoline could be due to constant rebounds and instability produced by an elastic surface. This increased physiological demand would involve greater e ort to carry out the exercise and maintain balance on the mini-trampoline. Moreover, soft surfaces may reduce the risk of joint injuries from high impact [6]. The physiological demands of AD classes could depend, at least in part, on the exercise intensity (i.e., percentage of maximal heart rate, percentage of maximal VO2, energy expenditure, blood lactate, etc.) and the type of surface. The type of surface has been demonstrated to a ect muscle fatigue [7], mechanical work [8] and energy cost [9]. Several studies have proposed that a compliant elastic surface reduces mechanical work and energy cost of generating muscle force compared with hopping or running on a hard surface [8,9]. In human motor actions, the energy cost is determined by the energy required to generate muscle force and the energy required to perform mechanical work [10,11]. During human hopping on a compliant elastic surface, part of the mechanical work is supplied by the musculoskeletal system. Another important part is provided by storage and recovery of elastic energy in the surface.

In human motor actions, the energy cost is determined by the energy required to generate muscle force and the energy required to perform mechanical work [10,11]. During human hopping on a compliant elastic surface, part of the mechanical work is supplied by the musculoskeletal system. Another important part is provided by storage and recovery of elastic energy in the surface. As a consequence of increasing leg sti ness on a compliant elastic surface, the mechanical work done by the surface is increased. In contrast, the mechanical work done by the legs is reduced. Consequently, the energy cost is reduced by generating muscle force [9]. It is tempting to speculate that the di erent mechanical work and energy costs induced by di erent surfaces on the musculoskeletal system could lead to variations in muscular fatigue. Several studies have used vertical jump height (i.e., counter movement jump) before and after exercise to assess the extent of muscular fatigue [12,13]. However, muscular fatigue assessed by a countermovement jump test before and after an AD session has not been explored by comparing an ADP and a hard surface. Recently, an air dissipation platform (ADP) has been incorporated by our research group into AD classes. The ADP consists of an area that rests on an elastomer that contains air and that allows air to enter and exit through holes. One of the main characteristics of this device is instability and rebound damping produced during exercise, just as it occurs on a mini-trampoline [5]. In theory, cardiorespiratory and metabolic responses on an ADP should be increased compared to a hard surface; however, this statement has not yet been scienti cally con rmed. This knowledge would be a key factor in determining whether the exercise intensity during a video-recorded AD class on an ADP is enough to produce improvements in cardiorespiratory tness. This study aimed to assess the acute cardiorespiratory and metabolic responses induced by an ADP and a hard surface (marble oor) during a video-recorded AD session. The secondary aim was to determine the muscular fatigue induced by an ADP and a hard surface as well

a video-recorded AD class on an ADP is enough to produce improvements in cardiorespiratory tness. This study aimed to assess the acute cardiorespiratory and metabolic responses induced by an ADP and a hard surface (marble oor) during a video-recorded AD session. The secondary aim was to determine the muscular fatigue induced by an ADP and a hard surface as well as the rate of perceived exertion (RPE). We hypothesized that a video-recorded AD session on an ADP produces higher acute cardiorespiratory and metabolic responses (blood lactate) compared to AD on a harder surface. In addition, a video-recorded AD session on an ADP is probably an ideal alternative to increase exercise intensity, maintaining similar RPE and muscular fatigue.

Int. J. Environ. Res. Public Health2020,17, 9511 3 of 12 2. Materials and Methods 2.1. Experimental Approach to the Problem Participants completed three test sessions at the Exercise Physiology laboratory. Sessions were conducted under the same environmental conditions (temperature 20–22.5 C, atmospheric pressure: 715–730 mm Hg, and relative humidity 40–50%) and in the same time frame (+1 h). Participants refrained from any high-intensity physical e ort for 48 h and abstained from any type of physical exercise for 24 h before starting the rst session. In session 1, an incremental test until exhaustion was completed on a treadmill to determine cardiorespiratory responses and ventilatory thresholds (VTs). One week after session 1, participants were randomly assigned in a crossover design to carry out AD sessions on an ADP and on a hard surface (session 2 and 3). The AD class was video recorded by a certi ed tness instructor a week before. This video session was projected on a giant screen individually to each participant during the AD classes on an ADP or a marble oor (hard surface). Sessions 2 and 3 were rigorously identical and cardiorespiratory and metabolic responses, muscular fatigue and RPE were evaluated one week apart. 2.2. Participants The participants recruited were 25 healthy young women (age, 23.3 2.5 years; weight, 58.4 6.8 kg; height, 162.6 5.5 cm; and body mass index, 22.1 2.4 kg/m 2 ). All of them performed light or moderate physical activity a maximum of 2–3 times per week. Exclusion criteria were (a) the use of any medication or performance-enhancing drugs, (b) smoking or alcohol intake, (c) the intake of any nutritional supplement that could alter cardiorespiratory performance, (d) any cardiovascular, metabolic, neurological, pulmonary, or orthopedic disorders that could limit exercise performance, (e) being an elite athlete. Participants were informed of all experimental tests and signed an informed consent form. The study protocol received approval from the Ethics Committee of the University (13/2018) and adhered to the tenets of the Declaration of Helsinki. 2.3. Incremental Treadmill Test The incremental cardiopulmonary exercise test (CPET) until exhaustion included a 5-min warm-up on a motorized treadmill (TechnoGym,

an elite athlete. Participants were informed of all experimental tests and signed an informed consent form. The study protocol received approval from the Ethics Committee of the University (13/2018) and adhered to the tenets of the Declaration of Helsinki. 2.3. Incremental Treadmill Test The incremental cardiopulmonary exercise test (CPET) until exhaustion included a 5-min warm-up on a motorized treadmill (TechnoGym, Runrace 1400HC, Forl½, Italy) at a self-selected light intensity (~5–6 km h 1 ), followed by 5-min of dynamic joint mobility drills and stretching exercises. After 3-min rest time, the CPET on a treadmill commenced at an initial load of 5 km h 1 (1% slope) which was increased in steps of 0.5 km h 1 every 30 s. Respiratory exchange data were recorded during the CPET using a breath-by-breath open-circuit gas analyzer (Vmax spectra 29, Sensormedics Corp., Yorba Linda, CA, USA). VO2max, minute ventilation (VE), carbon dioxide production (VCO2), ventilatory equivalent for oxygen (VE VO2 1), ventilatory equivalent for carbon dioxide (VE VCO2 1), respiratory exchange ratio (RER), oxygen partial pressure on expiration (PetO2), partial pressure of carbon dioxide on expiration (PetCO2) were monitored. HR was checked every 5 s by telemetry (RS-800CX, Polar Electro OY, Kempele, Finland). In the CPET, maximum or peak cardiorespiratory indices and VTs ( rst ventilatory threshold: VT1 and second ventilatory threshold: VT2) were determined to identify the relative exercise intensity of AD classes. As in a previous study [14], two investigators separately identi ed VT1 and VT2. If there was lack of agreement, the opinion of a third observer was considered. VT1 was de ned as the workload (velocity) at which both VE VO2 1and PetO2increase, without a concomitant increase in VE VCO2 1. Similarly, VT2 was de ned as the workload (velocity) at which VE VO2 1and VE VCO2 1 increase, accompanied by a drop in PetCO2[15]. 2.4. Aerobic Dance Sessions AD sessions were conducted on an ADP and on a marble oor (hard surface) (sessions 2 and 3). The ADP consists of an area of one meter in diameter and 20 cm high that rests on an elastomer that

at which VE VO2 1and VE VCO2 1 increase, accompanied by a drop in PetCO2[15]. 2.4. Aerobic Dance Sessions AD sessions were conducted on an ADP and on a marble oor (hard surface) (sessions 2 and 3). The ADP consists of an area of one meter in diameter and 20 cm high that rests on an elastomer that

Int. J. Environ. Res. Public Health2020,17, 9511 4 of 12 contains air at atmospheric pressure and that allows air to enter and exit through holes. The same general warm-up was carried out as in the CPET. After a 3-min rest period, each subject performed a 40-min AD session of individual exercise on an ADP or a marble oor. The AD class consisted of three phases: a 5-min of speci c warm-up, a 30-min aerobic or principal phase, and 5-min cool-down. The aerobic phase of the AD session was structured by an experienced instructor to be of light intensity at most 75% HRmax (RPE ~11–12), moderate intensity at most 85% HRmax (RPE ~13–14), or heavy intensity at most 90% HRmax (RPE ~15–17) [16]. The AD sessions were based on global and multi-articular movements in which large muscle groups participated, including jumps, arm and leg movements, trunk exions, etc. The exercise intensity of the AD classes was controlled by varying the muscle mass involved (deeper movements, increased bending, arm activity) as well as modifying the direction, the impact of the movements and the range. To verify that both AD classes (ADP vs. hard surface) were rigorously the same, a video of an AD class was recorded a week before. Participants were instructed to imitate the motor tasks to be performed by an expert instructor to the rhythm of the music (Figure). Since all participants were familiarized with AD classes, the motor tasks were not di cult to replicate.Int. J. Environ. Res. Public Health 2020, 17, 9511 4 of 12 2.4. Aerobic Dance Sessions AD sessions were conducted on an ADP and on a marble floor (hard surface) (sessions 2 and 3). The ADP consists of an area of one meter in diameter and 20 cm high that rests on an elastomer that contains air at atmospheric pressure and that allows air to enter and exit through holes. The same general warm-up was carried out as in the CPET. After a 3-min rest period, each subject performed a 40-min AD session of individual exercise on an ADP or a marble floor. The AD

and 20 cm high that rests on an elastomer that contains air at atmospheric pressure and that allows air to enter and exit through holes. The same general warm-up was carried out as in the CPET. After a 3-min rest period, each subject performed a 40-min AD session of individual exercise on an ADP or a marble floor. The AD class consisted of three phases: a 5-min of specific warm-up, a 30-min aerobic or principal phase, and 5-min cool-down. The aerobic phase of the AD session was structured by an experienced instructor to be of light intensity at most 75% HRmax (RPE ∼11–12), moderate intensity at most 85% HRmax (RPE ∼13–14), or heavy intensity at most 90% HRmax (RPE ∼15–17) [16]. The AD sessions were based on global and multi-articular movements in which large muscle groups participated, including jumps, arm and leg movements, trunk flexions, etc. The exercise intensity of the AD classes was controlled by varying the muscle mass involved (deeper movements, increased bending, arm activity) as well as modifying the direction, the impact of the movements and the range. To verify that both AD classes (ADP vs. hard surface) were rigorously the same, a video of an AD class was recorded a week before. Participants were instructed to imitate the motor tasks to be performed by an expert instructor to the rhythm of the music (Figure 1). Since all participants were familiarized with AD classes, the motor tasks were not difficult to replicate. Figure 1. Aerobic dance session performed on an air dissipation platform. The video session was projected on a giant screen individually to each participant. 2.5. Cardiorespiratory, Metabolic and Muscular Assessment Respiratory exchange data were recorded during AD classes using a breath-by-breath open- circuit gas analyzer, as previously in the CPET. Blood lactate and RPE were measured at rest (before warm-up) and every 10 min during AD classes (10-min, 20-min, 30-min and 40-min). Blood lactate levels were determined from finger capillary blood using a portable lactate analyzer (Lactate Pro LT-1710, Arkray Factory Inc., KDK Corporation, Siga, Japan), while RPE was determined by using the Borg Scale

as previously in the CPET. Blood lactate and RPE were measured at rest (before warm-up) and every 10 min during AD classes (10-min, 20-min, 30-min and 40-min). Blood lactate levels were determined from finger capillary blood using a portable lactate analyzer (Lactate Pro LT-1710, Arkray Factory Inc., KDK Corporation, Siga, Japan), while RPE was determined by using the Borg Scale [17]. Before and after AD classes, muscular fatigue of lower limbs was evaluated by the countermovement jump (CMJ) test using a force platform (Quattro Jump model 9290AD; Kistler Figure 1. Aerobic dance session performed on an air dissipation platform. The video session was projected on a giant screen individually to each participant. 2.5. Cardiorespiratory, Metabolic and Muscular Assessment Respiratory exchange data were recorded during AD classes using a breath-by-breath open-circuit gas analyzer, as previously in the CPET. Blood lactate and RPE were measured at rest (before warm-up) and every 10 min during AD classes (10-min, 20-min, 30-min and 40-min). Blood lactate levels were determined from nger capillary blood using a portable lactate analyzer (Lactate Pro LT-1710, Arkray Factory Inc., KDK Corporation, Siga, Japan), while RPE was determined by using the Borg Scale [17]. Before and after AD classes, muscular fatigue of lower limbs was evaluated by the countermovement jump (CMJ) test using a force platform (Quattro Jump model 9290AD; Kistler Instruments, Winterthur, Switzerland), as in previous studies [13,18]. The CMJ was initiated while standing on the force platform with hands on hips and legs extended. Next, the knees were rst exed

Int. J. Environ. Res. Public Health2020,17, 9511 5 of 12 to 90 (eccentric action) and immediately explosively extended in a coordinated manner (concentric action) trying to reach maximum vertical height. During the ight stage, the knees were fully extended and contact with the ground was made with the toes rst. The participants were instructed to keep their hands on the hips and avoid any sideways or backward/forward movements during the ight stage. Participants carried out 3 CMJs separated by a rest time of 30 s, and the mean values of vertical ight height and mean power (3 CMJs) were used in the subsequent analyses. Loss of vertical jump height and power output have been used to assess muscle fatigue before and after an exercise session [13,18]. The force platform was connected to a computer and the software package of Kistler (Quattro Jump software, version 1.1.1.4, (Kistler Instruments, Winterthur, Switzerland) was used to quantify the kinetic and kinematic variables. The vertical ground reaction force (GRF) data were obtained during the jump (range 0–10 kN; sampling frequency 0.5 kHz). The vertical component of the center of mass (COM) velocity was estimated using the impulse method [19]. Net impulse was taken by integrating the GRF from 2 s before the rst movement of the participant [20]. The vertical velocity of COM was calculated by dividing the net impulse by the participant's body mass [21]. Maximum velocity reached at the end of the concentric muscle action of the jump was considered as maximum take-o velocity (Vmax). Flight height (cm) was calculated from Vmaxof the COM and the deceleration of gravity. Height=((Vmax) 2 /2 9.81). Power was calculated from the un ltered force–time history using the impulse momentum principle [22]. Mean relative power (watts kg 1 ) was calculated as the product of mean velocity and vertical component of the vertical ground reaction force. 2.6. Statistical Analysis The Shapiro–Wilk test was used to check the normal distribution of data, provided as means, standard deviation (SD), con dence intervals (95% CI) and percentages. A t-student for paired samples was applied to identify signi cant di erences

The study compares responses during aerobic dance on different surfaces.