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Water-Based Concurrent Training Improves Peak Oxygen Uptake, Rate of Force Development, Jump Height, and Neuromuscular Economy in Young Women

Pinto, Stephanie S.1,2; Alberton, Cristine L.1,2; Cadore, Eduardo L.1; Zaffari, Paula1; Baroni, Bruno M.1,3; Lanferdini, Fábio J.1; Radaelli, Régis1; Pantoja, Patrícia D.1; Peyré-Tartaruga, Leonardo A.1; Wolf Schoenell, Maira C.1; Vaz, Marco A.1; Kruel, Luiz F.M.1

Journal of Strength and Conditioning Research: July 2015 - Volume 29 - Issue 7 - p 1846–1854
doi: 10.1519/JSC.0000000000000820
Original Research
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Pinto, SS, Alberton, CL, Cadore, EL, Zaffari, P, Baroni, BM, Lanferdini, FJ, Radaelli, R, Pantoja, PD, Peyré-Tartaruga, LA, Wolf Schoenell, MC, Vaz, MA, and Kruel, LFM. Water-based concurrent training improves peak oxygen uptake, rate of force development, jump height, and neuromuscular economy in young women. J Strength Cond Res 29(7): 1846–1854, 2015—The study investigated the effects of different intrasession exercise sequences on the cardiorespiratory and neuromuscular adaptations induced by water-based concurrent training in young subjects. Twenty-six healthy young women (25.1 ± 2.9 years) were placed into 2 water-based concurrent training groups: resistance before (RA, n = 13) or after (AR, n = 13) aerobic training. Subjects trained resistance and aerobic training during 12 weeks, 2 times per week performing both exercise types in the same training session. Peak oxygen uptake (V[Combining Dot Above]O2peak), rate of force development (RFD) obtained during an isometric peak torque knee extension protocol, jump height, and neuromuscular economy (normalized electromyography at 80% of pretraining knee extension isometric peak torque) in young women were determined. After training, there was a significant increase (p < 0.001) in both RA and AR in the V[Combining Dot Above]O2peak, with no differences between groups (7 vs. 5%). The maximal isometric knee extension RFD showed significant increases (p = 0.003) after training (RA: 19 vs. AR: 30%), and both groups presented similar gains. In addition, the countermovement jump height also increased (p = 0.034) after training (RA: 5% vs. AR: 6%), with no difference between groups. After training, there were significant improvements on vastus lateralis (p < 0.001) (RA: −13% vs. AR: −20%) and rectus femoris (p = 0.025) (RA: −17% vs. AR: −7%) neuromuscular economy, with no difference between groups. In conclusion, 12 weeks of water-based concurrent training improved the peak oxygen uptake, RFD, jump height, and neuromuscular economy in young women independent from the intrasession exercise sequence.

1Exercise Research Laboratory, Physical Education School, Federal University of Rio Grande do Sul, Porto Alegre, Brazil;

2Neuromuscular Evaluation Laboratory, Physical Education School, Federal University of Pelotas, Pelotas, Brazil; and

3Department of Physical Therapy, Federal University of Health Sciences of Porto Alegre, Porto Alegre, Brazil

Address correspondence to Stephanie S. Pinto, tetisantana@yahoo.com.br.

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Introduction

The combination of resistance and aerobic training (i.e., concurrent training) is an optimal strategy to improve the cardiorespiratory fitness and muscle strength in young population (4,5,28,36). However, some studies have reported that concurrent training may result in lower strength increases when compared with a resistance training performed alone. This phenomenon has been called in the literature “interference effect” (4,5,11,20,27), and it may occur because of the negative influence of the aerobic training on the neuromuscular adaptations induced by resistance training (17,27). Notwithstanding, this effect is not often observed for cardiorespiratory capacity, because similar adaptations on this parameter have been observed in both concurrent and aerobic training groups (4,12,24,26).

Some studies have assessed the influence of the intrasession exercise sequence (i.e., resistance and aerobic or aerobic and resistance) on the adaptations induced by concurrent training in elderly (8,9) and young subjects (13,14,18,19,31,35). Current evidences suggest that the intrasession exercise order during concurrent training in dryland environment may influence the magnitude of neuromuscular and cardiorespiratory adaptations in elderly men (7,8,9); however, such influence was not found in young subjects (14,19,35).

In the aquatic environment, few studies have investigated the effects of water-based resistance and aerobic training on neuromuscular and cardiorespiratory variables (38,41). Regarding the cardiorespiratory capacity, the studies by Taunton et al. (39) and Takeshima et al. (38) demonstrated that 3-week session during 12 weeks of water-based aerobic and resistance training improved the V[Combining Dot Above]O2max in elderly women (12%). In relation to the neuromuscular parameters, the height jump and the rate of force development (RFD) have been investigated during water-based exercise programs (i.e., resistance and combined training), and significant improvements in the jump height (i.e., squat and countermovement jump [CMJ]) were demonstrated in elderly (9–25%) and young (3%) subjects (16,38,41). In addition, significant increases in maximal knee extension RFD in isometric condition (11%) were observed in elderly by Bento et al. (6), which was the only study that investigated this variable in water-based programs. Nevertheless, the effects of aquatic programs on neuromuscular economy (i.e., neuromuscular activity observed to perform a determined submaximal load) (10–12) were not yet investigated. Some authors have suggested that, after concurrent training performed on dry land, the subjects would need fewer motor units, especially faster type (i.e., type 2), which resulted in lower electromyography (EMG) amplitude to the same absolute load (10–12). Thus, because of the strength gains induced by water-based resistance training, it is possible that young women performing water-based concurrent training would be more economical at neuromuscular level. However, this neuromuscular outcome has not been assessed after water-based concurrent training.

In the studies mentioned above, only 1 intrasession exercise sequence was used (i.e., aerobic followed by resistance exercises). Recently, Pinto et al. (31) demonstrated that the intrasession exercise sequence during water-based concurrent training influences the dynamic strength gains and muscle hypertrophy in young women, because greater improvements were observed in the resistance-aerobic sequence when compared with the inverse order (i.e., aerobic-resistance). However, the possible influence of intrasession exercise order during water-based concurrent training on muscle power performance, for example, RFD (i.e., explosive force) and jump height (i.e., reactive force), remains to be elucidated. It would be interesting to determine its influence because water-based resistance exercises are performed at maximal velocity against the water resistance, and this type of training could stimulate the rapid force development. However, it has been previously shown that concurrent training may affect especially skeletal muscle power increases (20). However, this effect has not been investigated in aquatic environment. In addition, to broaden the knowledge related to the prescription in water-based programs, it is important and relevant to determine the most effective intrasession exercise sequence to promote greater cardiorespiratory and neuromuscular gains during concurrent training in the aquatic environment. Thus, the aim of this study was to investigate the effects of the intrasession exercise sequence during water-based concurrent training on peak oxygen uptake, RFD, jump height, and neuromuscular economy in young women. Our hypothesis was that performing resistance exercises before aerobic exercises would result in greater neuromuscular gains than in the opposite sequence (i.e., aerobic followed by resistance exercises). However, we also hypothesized that the cardiorespiratory adaptations would be similar between both orders.

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Methods

Experimental Approach to the Problem

To investigate the effects of the intrasession exercise sequence during water-based concurrent training in young subjects, the cardiorespiratory and neuromuscular adaptations were compared between resistance before aerobic training and the aerobic before resistance training. To analyze the stability and reliability of the variables, 11 subjects (23.4 ± 2.5 years) were evaluated twice before the start of training (weeks −4 and 0), which served as a control period. Both groups (i.e., resistance-aerobic and aerobic-resistance) trained for 12 weeks, and each subject was evaluated before and after (weeks 0 and 13) the water-based concurrent training. The postmeasurements started 72 hours after the last training session, and the subjects completed all the evaluations within a week with an interval of 48 hours between the tests. Different tests were conducted on different days to prevent fatigue. Each specific test at pre- and postintervention was overseen by the same investigator, who was blinded to the training group of the subjects, and was conducted using the same equipment with identical subject/equipment positioning. The subjects were instructed to maintain their dietary habits for the whole duration of the study. Throughout the training period, the water temperature was maintained at 31.0 ± 0.1° C. In addition, the water depth for each subject was fixed between the xiphoid process and shoulders.

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Subjects

Twenty-six healthy young women (19–31 years), who were not engaged in any regular and systematic training program in the previous 6 months, volunteered for the study after signing an informed consent. All subjects were recruited from the city of Porto Alegre (Brazil) through sending flyers by e-mail to several young women. Volunteer subjects were randomly assigned into 2 groups: resistance training before aerobic training (n = 13) (mean ± SD, age: 24.9 ± 2.9 years; body mass: 64.5 ± 8.1 kg; height: 165.4 ± 5.3 cm; percent fat: 30.7 ± 6.1%) and aerobic training before resistance training (n = 13) (mean ± SD, age: 25.4 ± 3.1 years; body mass: 58.9 ± 5.3 kg; height: 162.6 ± 5.6 cm; percent fat: 31.8 ± 4.3%). Exclusion criteria included any history of neuromuscular, metabolic, hormonal, and cardiovascular diseases. Subjects were not taking any medication, which could influence on hormonal and neuromuscular metabolism. Body mass and height were measured using an Asimed analog scale (resolution of 0.1 kg) and an Asimed stadiometer (resolution of 1 mm), respectively. Body composition was assessed using the skinfold technique. A 7-site skinfold equation was used to estimate body density (25), and body fat was subsequently calculated using the Siri equation (37). Subjects were carefully informed about the design of the study and the possible risks and discomforts related to the measurements. The study was conducted according to the Helsinki Declaration and was approved by Ethics Committee of Federal University of Rio Grande do Sul, Brazil.

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Peak Oxygen Uptake

Subjects performed a Bruce protocol to determine the peak oxygen uptake (V[Combining Dot Above]O2peak) and the oxygen uptake corresponding to the second ventilatory threshold (

). Each stage of the Bruce protocol consists of 3 minutes. The initial speed was 1.7 miles per hour (mph) and the inclination is 10%. The increase in speed of 0.7–0.8 mph and 2% increase in the inclination are given for each consecutive stage. The test was halted when the subject indicated exhaustion by means of a hand signal. The expired gas was analyzed using a metabolic cart (CPX/D; Medical Graphics, Corp., St. Paul, MN, USA) breath by breath. The maximal V[Combining Dot Above]O2 value (milligram per kilogram per minute) obtained close to exhaustion was considered the V[Combining Dot Above]O2peak. The assessment was considered valid when some of the following criteria were met at the end of the test: estimated maximal heart rate (HR) was reached (220-age), a respiratory exchange ratio greater than 1.15 was reached, and a maximal respiratory rate of at least 35 breaths per minute was reached (21). The second ventilatory threshold was determined using the ventilation slope and confirmed through the slope of the ventilatory equivalent for CO2 (V[Combining Dot Above]E/V[Combining Dot Above]CO2) (42). Two experienced and independent blind physiologists detected the thresholds through visual inspection according to the criteria previously described above. When the results were discordant, the graphs were assessed by a third physiologist (22). The test-retest reliability coefficient (intraclass correlation coefficient [ICC]) was 0.87 for V[Combining Dot Above]O2peak.

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Rate of Force Development

The isometric torque-time analysis on the absolute scale included the maximal RFD (Newton-meters per second) obtained during the isometric knee extension protocol using an isokinetic dynamometer (Biodex System 3; Biodex Medical Systems, Shirley, New York). Before the measurement session, the subjects were carefully familiarized with the testing procedure. The subjects were positioned seated with their hips and thighs firmly strapped to the seat of the dynamometer, with the hip angle at 85°. After that, subjects warmed up for 10 knee extension repetitions at an angular velocity of 90°·s−1, performing a submaximal effort. The dynamometer was connected to an A/D converter (DATAQ Instruments, Inc., Akron, OH, USA), which made it possible to quantify the torque exerted when each subject executed the isometric knee extension at the determined angle. After having their right leg positioned by the evaluators at an angle of 120° in the knee extension (180° represented the full extension), the subjects were instructed to exert maximal knee extension isometric strength as fast as was possible. The subjects had 3 attempts, each lasting for 5 seconds. During the attempts, the researchers provided verbal encouragement so that the subjects would feel motivated to produce their maximal force. The RFD variable was calculated from the torque onset, which was considered the point that the torque exceeded 2.5 times the standard deviations of the mean of the torque signal at rest, and was determined using the LabView software (National Instruments, Austin, TX). Signal processing included filtering with a fifth-order low-pass Butterworth filter, with a cutoff frequency of 9 Hz. The test-retest reliability coefficient (ICC) was 0.96 for the knee extensors maximal isometric peak torque.

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Countermovement Jump

To carry out the CMJ height, subjects were positioned on a force platform (OR6-WP; AMTI, Watertown, MA, USA) and were familiarized to the procedure by performing several jumps. They were instructed to jump with their hands on their waist while avoiding the bending of their legs during flight and trying to achieve the maximal possible time in the air. After the familiarization, the subjects performed 3 CMJs on the force platform with at least 30 seconds of rest intervals. There was no restriction on the angle of knee flexion during the eccentric phase of the CMJ (23). The subjects were instructed to use the same sport shoes during the pre- and postintervention CMJ test. The greatest jump height was used for analyses and was determined by the equation provided by Asmussen and Bonde-Petersen (3): jump height = (flight time)2 × 1.226, using the SAD32 software (Mechanical Measurements Laboratory, Federal University of Rio Grande do Sul, Porto Alegre, Brazil). Signal processing included filtering with a fifth-order low-pass Butterworth filter, with a cutoff frequency of 30 Hz. The test-retest reliability coefficient (ICC) was 0.82 for the CMJ height.

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Neuromuscular Economy

During the isometric knee extension protocol above mentioned, the submaximal neuromuscular activity (neuromuscular economy) of agonist knee extensors muscles was evaluated using surface EMG (RMS values) on the vastus lateralis (VL) and rectus femoris (RF). Subjects had three 10-second attempts to exert 80% of the pretraining isometric knee extension peak torque and maintain it for, at least, 3 seconds receiving a visual feedback of the torque values (11). Electrodes were positioned on the muscular belly in a bipolar configuration (20-mm interelectrode distance) in parallel with the orientation of the muscle fibers, according to SENIAM project (www.seniam.org). Hair was shaved away from the site of electrode placement, and the skin was abraded and cleaned with alcohol to keep the interelectrode resistance low (<3 kΩ). To ensure the same electrode position in subsequent tests, the right thigh of each subject was mapped for the position of the electrodes moles and small angiomas by marking on transparent paper (29). The reference electrode was fixed on the anterior crest of the tibia to record the EMG signal of the knee extensors muscles. The raw EMG was converted by an A/D converter DI-720 with a 16-bit resolution (DATAQ Instruments, Inc., Akron, OH) and a sampling frequency of 2,000 Hz per channel, connected to a PC. After acquisition of the signal, the data were exported to the SAD32 software (Mechanical Measurements Laboratory, Federal University of Rio Grande do Sul, Porto Alegre, Brazil), where they were filtered through a fifth-order band-pass Butterworth filter with cutoff frequencies between 20 and 500 Hz. After that, the EMG records were sliced exactly in 2 seconds when submaximal value of stable torque was determined of the torque-time curve, and the RMS values were then calculated. The submaximal RMS values were normalized using the maximal RMS values from VL and RF obtained during the maximal isometric knee extension protocol. The test-retest reliability coefficients (ICC values) were 0.76 for the EMG of the VL and 0.86 for the EMG of the RF.

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Water-Based Concurrent Training

Subjects of the study trained both resistance and aerobic training in the same session, 2 times a week, on nonconsecutive days. Training groups were differentiated by their intrasession exercise order during the water-based concurrent training. One group trained resistance training before (RA) aerobic training and the other 1 trained aerobic training before (AR) resistance training. Before the start of the concurrent training, subjects completed 2 familiarization sessions in the water environment to practice the exercises they would further perform during the training period. In addition, in the familiarization sessions, the subjects also performed the resistance exercises at their perceived exertion of maximal effort. During the resistance training, the individuals were instructed to perform each repetition at maximal effort and amplitude to achieve the greatest velocity of motion as possible and consequently, a greater resistance. Verbal encouragement was provided by the same instructor during all resistance exercises. The choice for the nonuse of aquatic devices during the resistance exercises is justified as the subjects were unfamiliar with the aquatic movements. In addition, the devices would provide instability during the exercises affecting the velocity of movement. Moreover, studies in the literature showed that muscle activity of upper and lower limbs was similar regardless the use of aquatic devices at submaximal and maximal velocity (30,32).

The progression of the water-based resistance training was previously described in the study conducted by Pinto et al. (31). The resistance exercises were separated into 2 blocks, and each block had 1 exercise for the upper limbs and 1 exercise for the lower limbs, starting from the anatomical position. The block 1 consisted of elbow flexion and extension (simultaneously), right or left hip flexion and extension (separately). Additionally, the block 2 consisted of shoulder flexion and extension (simultaneously), right or left knee flexion and extension (starting from hip flexion at 90°) (separately). In the weeks 1–4, the subjects performed 3 sets of 20 seconds of each block with the following sequence: 20 seconds of exercise for the upper limbs, 5 seconds for swapping, 20 seconds of exercise for the lower limbs (right leg), 5 seconds for swapping, and 20 seconds of exercise for the lower limbs (left leg). This sequence was repeated 3 times with an active interval (stationary running for 1 minute and 20 seconds) between each set. The training was divided into 2 different blocks (1 and 2), and the block sequences and intervals were as follows: 3 times block 1 (6 minutes and 10 seconds), active interval between blocks (1 minute), and 3 times block 2 (6 minutes and 10 seconds). In weeks 5–8, the subjects performed 4 sets of 15 seconds of each block with an active interval (stationary running for 1 minute and 30 seconds) between each set. The block sequences and intervals were as follows: 4 times block 1 (7 minutes and 55 seconds), active interval between blocks (1 minute), and 4 times block 2 (7 minutes and 55 seconds). In weeks 9–12, the subjects performed 6 sets of 10 seconds of each block with an active interval (stationary running for 1 minute and 40 seconds) between each set. The block sequences and intervals were as follows: 3 times block 1 (5 minutes and 20 seconds), active interval between blocks (1 minute), 3 times block 2 (5 minutes and 20 seconds), active large interval (5 minutes), 3 times block 1 (5 minutes and 20 seconds), active interval between blocks (1 minute), and 3 times block 2 (5 minutes and 20 seconds). The resistance training sessions lasted for 13 minutes and 20 seconds in the first mesocycle, 16 minutes and 50 seconds in the second mesocycle, and in 28 minutes and 20 seconds in the third mesocycle.

The aerobic training program was performed using 3 water-based exercises performed at the HR corresponding to the second ventilatory threshold (VT2). During the first 4 weeks, subjects performed 2 sets of 3 minutes with the following sequence, without interval between the sets: 3 minutes of stationary running, 3 minutes of cross-country skiing, and 3 minutes of frontal kick, totaling 18 minutes. In the weeks 5–8, subjects performed 3 sets of 3 minutes with the same above-mentioned sequence, totaling 27 minutes and in the last 4 weeks (7–10), subjects performed 4 sets of 3 minutes, totaling 36 minutes. The 3 water-based exercises are described in the study of Alberton et al. (2). During the sessions of aerobic training, all the subjects used a coded Polar monitor to control the HR corresponding to VT2. Three experienced water-based trainers carefully supervised all training sessions.

The VT2, used as a parameter to prescribe the intensity of aerobic training, was determined during a maximal progressive test at the water environment with the stationary running exercise, because Alberton et al. (1) have demonstrated there were no differences in the HR corresponding to VT2 among the stationary running, cross-country skiing, and frontal kick water-based exercises. Thus, the maximal test with stationary running was conducted with an initial cadence of 85 b·min−1 for 3 minutes, with 15 b·min−1 increases in cadence every 2 minutes until maximal effort was obtained. The cadences were set by a digital metronome (MA-30; KORG, Tokyo, Japan).

To evaluate the ventilatory data, a mixing-box-type portable gas analyzer (VO2000; MedGraphics, Ann Arbor, MI, USA) was used and had been previously calibrated according to the manufacturer's specifications. The HR was measured using a Polar monitor (FS1, Shangai, China). The sampling rate of the collected HR and ventilatory data was 10 seconds, and the data were acquired using the Aerograph software. The second ventilatory threshold analyses were the same described in the Bruce protocol. The VT2, used to prescribe the intensity of aerobic training, corresponded to 73.8 ± 9.6% and 87.6 ± 4.1% of the V[Combining Dot Above]O2peak and maximal HR (HRmax), respectively. The VT2 was also evaluated in the week 6 to adjust the training intensity, and no significant change was observed in this parameter compared with the week 0 (VT2: 73.8 ± 7.5% of the V[Combining Dot Above]O2peak; 87.8 ± 4.2% of the HRmax). The water-based concurrent training periodization is shown in Table 1.

Table 1

Table 1

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Statistical Analyses

The SPSS statistical software package was used to analyze all data. Results are reported as mean ± SD. Statistical comparisons in the control period (from week −4 to week 0) were performed using Student's paired t-tests. In addition, the test-retest reliability for each dependent variable between the weeks −4 and 0 was determined using the ICC. The training-related effects were assessed using a 2-way analysis of variance with repeated measures (group × time). The effect size (ES) of main effects was calculated using the formula pre-post ES = (posttest mean − pretest mean)/pretest SD, and the threshold values for assessing the magnitude of standardized effects were 0.20, 0.60, 1.2, and 2.0 for small, moderate, large, and very large, respectively (34). Significance was accepted when α = 0.05.

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Results

During the control period (weeks −4 and 0), no changes were observed in all variables analyzed, except the CMJ height variable, which showed slight changes between weeks −4 and 0 (Table 2). Thus, the changes found in the cardiorespiratory and neuromuscular variables after the intervention period may be attributed to the type of training conducted. No significant differences were observed in training compliance between RA and AR (92.3 ± 7.4 vs. 95.1 ± 5.5%, respectively). In addition, there were no differences between groups before training in the age (p = 0.650), body mass (p = 0.054), height (p = 0.201), and percent fat (p = 0.587).

Table 2

Table 2

After training, there was a significant increase (p < 0.001) in both RA and AR in the V[Combining Dot Above]O2peak (Figure 1), with no differences between groups (p = 0.271) (RA: 6.79 ± 7.40%, ES = 0.39 vs. AR: 5.07 ± 4.32%, ES = 0.70).

Figure 1

Figure 1

The maximal isometric knee extension RFD showed significant increases (p = 0.003) after training (RA: 19.50 ± 30.81%, ES = 0.28 vs. AR: 30.58 ± 31.45%, ES = 0.92) and both groups presented similar gains (p = 0.931). In addition, the CMJ height also increased (p = 0.034) after training (RA: 5.54 ± 11.07%, ES = 0.33 vs. AR: 6.11 ± 13.77%, ES = 0.33), with no difference between groups (p = 0.462) (Figure 2). After training, there were significant improvements on VL (p < 0.001) (RA: −12.75 ± 22.14%, ES = −0.74 vs. AR: −19.78 ± 16.46%, ES = −0.72) and RF (p = 0.025) (RA: −16.79 ± 19.74%, ES = −0.88 vs. AR: −6.65 ± 30.97%, ES = −0.41) neuromuscular economy, with no difference between groups (VL: p = 0.402; RF: p = 0.149) (Figure 3).

Figure 2

Figure 2

Figure 3

Figure 3

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Discussion

The main findings of this study were the improvements in the peak oxygen uptake, RFD, jump height, and neuromuscular economy in young women after water-based concurrent training independent from the intrasession exercise sequence. Therefore, this type of prescription in water-based programs was effective to promote improvements in the cardiorespiratory capacity, muscle power, and neuromuscular function in this population.

Regarding the V[Combining Dot Above]O2peak, it may be observed that the water-based concurrent training was efficient to improve the cardiorespiratory capacity in young women who were previously sedentary (≈7%). Such gains were also found in studies that evaluated the effects of water-based programs on V[Combining Dot Above]O2max in elderly population (≈12%) (38,39). It is important to highlight that no study was found in the literature investigating the effects of water-based aerobic training on V[Combining Dot Above]O2max by direct measure (i.e., metabolic cart) in young individuals. In addition, no difference was found between RA and AR sequences on this variable (7 vs. 5%). Similar pattern was observed in other studies that analyzed the effects of intrasession exercise sequence during concurrent training on dry land in young (35) and elderly population (8). Schumann et al. (35) evaluated the effects of 24-week concurrent training on dry land in both RA and AR sequences in moderately physically active young men (aerobic training on a cycle ergometer) and observed similar cardiorespiratory gains between groups (6.4 vs. 6.1%, respectively). In contrast to these findings, Chtara et al. (13) showed greater improvements in the AR intrasession exercise sequence than the opposite order during concurrent training on dry land in young male sport students. In this study, the aerobic training was carried out through running on a track with 5 sets of 200 m (interval training) at 100% of the velocity corresponding to V[Combining Dot Above]O2max (RA: 11 vs. AF: 14%). Such different result could be explained by the fact that our aerobic training was performed in a continuous form at intensity corresponding to the second ventilatory threshold. Therefore, even performing the resistance training before, subjects were able to perform the aerobic training and, consequently, no deleterious effect was observed on the cardiorespiratory adaptations.

The maximal isometric knee extension RFD increased in both water-based concurrent training groups (RA: 19% and AR: 31%). Bento et al. (6) showed that 12 weeks of water-based aerobic and resistance training were enough to improve the maximal isometric knee extension RFD (11%) in elderly women. In addition, other studies have suggested that water-based concurrent training may be an effective training alternative to stimulate or maintain muscle power development during sports off-season period, returning from injuries, and recovery microcycle (15,40). It is important to highlight that no significant difference on RFD between RA and AR sequences was found in this study, and this result is in line with the results reported by Cadore et al. (9). This study showed that both intrasession exercise sequences during concurrent training on dry land in elderly population presented similar maximal isometric knee extension RFD improvements (RA: 14 vs. AR: 33%). From a practical perspective, the present findings showed that twice-weekly water-based concurrent training performed during 12 weeks is enough to improve the explosive muscle force in young population.

The increases in skeletal muscle power were also evident because CMJ height was increased after both water-based concurrent training groups (RA: 5% and AR: 6%). Adaptations in jump height performance (i.e., squat and CMJ) have been investigated during water-based programs, and significant improvements in this variable have been demonstrated in elderly (9–25%) (38,41) and young (3%) subjects (16). Regarding the intrasession exercise sequence, no significant difference in CMJ height was observed between RA and AR groups, and this result is in accordance with those found by Chtara et al. (14) in young men (3%). It should be noted that the pattern of muscle contraction in multiple repetitions during exercises used in water-based programs is similar to the stretch-shortening cycle (SSC) (33), although the SSC is probably slower in aquatic environment. However, even performing SSC at slower velocities, our results suggest that water-based concurrent training induces jump height increases in previously sedentary young women.

In addition, significant improvements were also verified in VL (RA: −13 vs. AR: −20) and RF (RA: −17 vs. AR: −7) neuromuscular economy after both water-based concurrent training sequences. These results partially corroborate with the findings from Cadore et al. (9), who showed significant improvements in VL neuromuscular economy in elderly men after both intrasession exercise concurrent training sequences on dry land environment (RA: −17 vs. AR: −12%). However, this study observed that only the intrasession sequence RA improved the RF neuromuscular economy (RA: −23 vs. AR: 1%). It is important to highlight that the intensity to evaluate the neuromuscular economy was different between the studies, because in the study by Cadore et al. (9) it was used 50% of maximal knee extension isometric strength and in our study, 80%. The improvement in the neuromuscular economy of the lower limbs has a relevant applicability to the daily living activities, because a specific task after training may be performed with lower muscle recruitment and consequently lower relative effort.

A possible limitation of this study was the absence of comparisons between the 2 concurrent training regimes with groups performing resistance or aerobic training alone. However, in this study, we aimed to compare 2 ways of prescribing water-based resistance and aerobic exercises in the same concurrent training session (i.e., RA and AR), and our results are relevant because they show that both intrasession exercise orders promoted improvements on cardiorespiratory and neuromuscular parameters in young women. In addition, the lack of cardiorespiratory assessment by a maximal test conducted in water to observe the responses of this variable in the specific environment could be a limitation.

In summary, 12 weeks of water-based concurrent training improved the peak oxygen uptake, RFD, jump height, and neuromuscular economy in young women. However, the intrasession exercise sequence had no influence on these parameters. These findings are novel in the literature, because the adaptations induced by water-based activities on peak oxygen uptake and neuromuscular economy had not been investigated in young women. In addition, this is the first study to compare the muscle power (i.e., reactive and explosive force) between RA and AR sequences in water-based concurrent training. It is important to point out that the neuromuscular and cardiorespiratory adaptations were achieved in this study performing resistance exercises as fast as possible and aerobic exercises at intensity corresponding to the second ventilatory threshold (i.e., anaerobic threshold).

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Practical Applications

The primary importance of the present results is that positive adaptations on cardiorespiratory and neuromuscular systems may occur independently of the intrasession exercise sequence during water-based concurrent training. Thus, 12 weeks of water-based concurrent training performed twice a week is a sufficient stimulus to improve the peak oxygen uptake, RFD, jump height performance, and neuromuscular economy in untrained young women. Although caution is necessary to extrapolate our results to power trained women, it could be suggested that water-based concurrent training may be an effective training alternative to stimulate or maintain muscle power development during sports off-season period, returning of injuries, and recovery microcycle. However, these possibilities should be tested in future studies assessing the effects of water-based concurrent training in trained women.

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Acknowledgments

The authors specially thank FAPERGS, CAPES, CNPq, and FINEP Brazilian Government Associations for support to this project. They also gratefully acknowledge all subjects who participated in this research and made this project possible.

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Keywords:

aquatic environment; combined training; cardiorespiratory capacity; neuromuscular function

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