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Defining the number of bouts and oxygen uptake during the “Tabata protocol” performed at different intensities
Physiology & Behavior 189 (2018) 10–15
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Defining the number of bouts and oxygen uptake during the “Tabata protocol” performed at different intensities
T
Ricardo B. Vianaa, João P.A. Navesa, Claudio A.B. de Liraa, Victor S. Coswigb, ⁎ Fabrício B. Del Vecchioc, Carlos A. Vieiraa, Paulo Gentila, a
Department of Physical Education, Faculty of Physical Education and Dance, Federal University of Goiás, Goiânia, Brazil Department of Physical Education, Faculty of Physical Education, Federal University of Pará, Castanhal, Brazil c Department of Physical Education, Superior School of Physical Education, Federal University of Pelotas, Pelotas, Brazil b
A R T I C L E I N F O
A B S T R A C T
Keywords: Exercise performance High-intensity interval training Metabolism Aerobic exercise Intermittent exercise
It is usually reported that the Tabata protocol (TP) is performed with eight bouts of 20:10 intervals at a load equivalent to 170% of i V̇ O2max. However, the feasibility of accumulating 160 s of work at 170% i V̇ O2max has been questioned. This article tested the intensity that would allow the performance of the original TP on a cycle ergometer, and measured the highest value of oxygen consumption (V̇ O2) obtained during the TP and the time spent above 90% of the maximal oxygen uptake (V̇ O2max) during the TP performed at different intensities. Thirteen young active males (25.9 ± 5.5 years, 67.9 ± 9.2 kg, 1.70 ± 0.06 m, 23.6 ± 3.1 kg·m−2) participated in the study. Participants performed a graded exertion test (GXT) on a cycle ergometer to obtain maximum oxygen consumption (V̇ O2max) and the intensity associated with V̇ O2max (i V̇ O2max). V̇ O2, maximal heart rate (HRmax), and number of bouts performed were evaluated during the TP performed at 115%, 130%, and 170% of i V̇ O2max. V̇ O2max, HRmax, and iV̇ O2max were 51.8 ± 8.0 mL.kg−1·min−1, 186 ± 10 bpm, and 204 ± 26 W, respectively. The number of bouts performed at 115% (7 ± 1 bouts) was higher than at 130% (5 ± 1 bouts) and 170% (4 ± 1 bouts) (p < .0001). The highest V̇ O2 achieved at 115%, 130%, and 170% of iV̇ O2max was 54.2 ± 7.9 mL·kg−1·min−1, 52.5 ± 8.1 mL·kg−1·min−1, and 49.6 ± 7.5 mL·kg−1·min−1, respectively. Non significant difference was found between the highest V̇ O2 achieved at different intensities, however qualitative magnitude-inference indicate a likely small effect between 115% and 170% of iV̇ O2max. Time spent above 90% of the V̇ O2max during the TP at 115% (50 ± 48 s) was higher than 170% (23 ± 21 s; p < 0.044) with a probably small effect. In conclusion, our data suggest that the adequate intensity to perform a similar number of bouts in the original TP is lower than previously proposed, and equivalent to 115% of the iV̇ O2max. In addition, intensities between 115 and 130% of the iV̇ O2max should be used to raise the time spent above 90% V̇ O2max.
1. Introduction The Tabata protocol (TP) was first presented in an article by Tabata et al. [1] that compared a moderate intensity protocol with a highintensity interval training (HIIT) protocol involving eight to nine bouts of 20 s exercise interspaced by 10 s of rest (20:10). According to the results, a TP lasting ~4 min significantly increased aerobic power and anaerobic capacity of physically active individuals, while one hour of moderately intense activities only resulted in a significantly increased aerobic power. Considering that a lack of time is the most cited barrier for exercise adoption [2], the possibility of increasing physical fitness through training sessions of very short duration (4 min of exercise time
without warm-up and cool-down) gained high popularity through the TP. In subsequent years, many researchers, coaches, and exercise enthusiasts have tried to replicate the TP in many different settings [3,4]. However, one problem in reproducing the TP is that the original article was not clear concerning the load used in the study. The study only mentioned that participants cycled at a constant load for 20 s and rested for 10 s (20:10) until they were not able to maintain at least 85 rpm, with load increments whenever the participant was able to perform more than nine bouts [1]. Later, the same research group reported high levels of oxygen uptake (V̇ O2) when young physically active males performed five to six bouts of 20:10 exercise at 170% of the intensity at
⁎ Corresponding author at: FEFD – Faculdade de Educação Física e Dança, Universidade Federal de Goiás – UFG, Avenida Esperança s/n, Campus Samambaia, CEP 74.690-900, Goiânia, Goiás, Brazil. E-mail address: [email protected] (P. Gentil).
https://doi.org/10.1016/j.physbeh.2018.02.045 Received 23 November 2017; Received in revised form 15 February 2018; Accepted 23 February 2018 Available online 24 February 2018 0031-9384/ © 2018 Elsevier Inc. All rights reserved.
Physiology & Behavior 189 (2018) 10–15
R.B. Viana et al.
which maximal oxygen uptake (V̇ O2max) was achieved (iV̇ O2max) [5]. Apparently, both studies were merged to form the recommendation to perform seven to eight bouts of 20:10 intervals at a load equivalent to 170% of i V̇ O2max, a suggestion that was used in many subsequent studies [3,4,6]. However, the feasibility of accumulating 160 s of work at 170% i V̇ O2max has been questioned [7,8]. Thus, a better understanding of the adequate intensity to complete eight 20:10 is relevant to clarify this popular HIIT method known and applied worldwide. One of the most relevant reasons for performing HIIT would be V̇ O2max achievement, since in training-related studies, increasing V̇ O2max is generally explained by achieving a high percentage of V̇
form. All experimental procedures were approved by the Federal University of Goiás Ethics Committee (no 1.542.353) and conformed to the principles outlined in the Declaration of Helsinki. Participants were informed about the aims and methods of the study and were recommended to continue their normal diets throughout the study. In all visits, they ingested an easy-to-digest meal two hours before the test. They were advised not to ingest alcoholic beverages, stimulants (coffee, caffeine, and energetic drinks), tobacco, or drugs prior to the test; have a regular night of sleep (6 to 8 h); and not to perform intense physical activity 24 h before the tests. All of these requests were checked in a pre-test anamnesis.
O2max (90–100%) during a training session [9]. It has also been suggested that the time spent at high levels of V̇ O2 (i.e., above 90% V̇ O2max) could serve as a good criterion to judge the effectiveness of the stimulus to improve aerobic fitness [10,11]. Therefore, to achieve optimal increases in cardiorespiratory fitness, it has been recommended to perform a certain amount of training at intensities of 90–100% of V̇ O2max. If the intensity is too high, the exercise duration would be too short for V̇ O2max to be reached or maintained [12], which may interfere with the results. While Tabata et al. [5] reported that the TP induced maximum levels of V̇ O2, other studies indicate that the mean percentage of V̇ O2max achieved ranged from approximately 43% [13] to 71% [14]. To date, no studies have been found measuring the time spent at high V̇ O2 during the TP or the best load to match the effort:pause ratio and the number of bouts proposed by Tabata et al. [1]. Analyzing both V̇ O2max and time spent at near V̇ O2max are important for understanding physiological response to exercise Moreover, there is a lack of a clear definition how many bouts of 20:10 stimuli are possible to perform at different intensities in cycle ergometer. Therefore, the main purpose of the present study was to estimate the number of bouts performed by active young males at different intensities on a cycle ergometer. In addition, the secondary purposes were measured the highest V̇ O2 obtained during the TP at different intensities and the time spent above 90% of the V̇ O2max. We hypothesized that the optimal intensity for the TP is < 170% iV̇ O2max and that V̇ O2 remains high most of the time (above 90% of the V̇ O2max) during the TP.
2.2. Study design This is a randomized cross-over study in which each participant reported to the laboratory on four different occasions separated by at least 48 h. During the first session, anamnesis, anthropometric evaluation, and a cardiorespiratory graded exertion test (GXT) on a cycle ergometer were performed to assess the V̇ O2max, iV̇ O2max, and maximal heart rate (HRmax). On the subsequent visits, the TP was performed at different intensities in a randomized order: 115%, 130%, and 170% of iV̇ O2max. The randomization was performed through opaque envelope with six possible sequences. During the tests, the V̇ O2, heart rate (HR), rating of perceived exertion (RPE), and number of bouts performed were evaluated. 2.3. Cardiorespiratory graded exertion test Participants performed a GXT on an electromagnetic braked cycle ergometer (CG04, Inbramed, Brazil) to determine their V̇ O2max, iV̇ O2max, and HRmax. Briefly, following a 2 min warm-up at 50 W, the resistance was increased by 25 W every 1 min until volitional exhaustion or the point at which the participant was not able to sustain a pedal cadence of at least 80 rpm. Despite 50 rpm is often used as the cutting point for interrupting the test, we choose 80 rpm because, in practical terms, after dropping the cadence to below 80 rpm the cycling pattern changed abruptly, and the participants interrupted the exercise in a few seconds. Participants wore a mouthpiece and nose clip, and gas were collected breath by breath by a specific pneumotach connected to the analyzer. V̇ O2 and carbon dioxide production (V̇ CO2) were analyzed by a metabolic gas collection system (VO2000, MedGraphics, USA) every 10 s. After exhaustion, the load was reduced to 50 W to perform a recovery of 2 min. V̇ O2max was measured as the mean maximum oxygen uptake during 10 s periods. To identify iV̇ O2max, the lower workload that elicited V̇ O2max was considered. HR was constantly monitored throughout the test using a HR monitor (Polar RS800, Kempele, Finland). The RPE was evaluated every minute using the 6–20 Borg Scale [16].
2. Material and methods 2.1. Participants The sample size was calculated using data from Aguiar et al. [15], considering the absolute time spent above 90% of the V̇ O2max as the main outcome using GPower (Brunsbüttel, Germany). Therefore, 9 participants were necessary to achieve a power of 80% and p-value of 5% with effect size of 0.58. Thus, 12 physically active men were recruited (Table 1). Recruitment was carried out through advertisements on social media and direct contact. The inclusion criteria was to be in regular involvement in physical exercise at least three times a week in the last six months. Exclusion criteria were: i) cardiovascular diseases, ii) hypertension, iii) orthopedic limitation, and iv) contraindications for performing physical activity evaluated through the Physical Activity Readiness Questionnaire (PAR-Q). All participants were informed of the potential risks and benefits of the study and signed an informed consent
2.4. Tabata protocol at 115%, 130%, and 170% of iV̇ O2max The TP involved bouts of 20 s of effort interspaced by 10 s of rest (20:10). During the bouts, the subjects were oriented to pedal at around 90–100 rpm at three different constant intensities: 115%, 130%, and 170% of i V̇ O2max obtained in GXT. TP sessions were performed in the same electromagnetic braked cycle ergometer used in the GXT. The equipment allowed the power to be adjusted objectively independently of velocity. Participants received visual feedback from ergometer's screen in order to self-control cadence. Rest was performed at 50 W at a self-selected cadence. All sessions were preceded by 2 min of rest and 2 min of warm-up at 50 W and succeeded by 2 min of cool-down at 50 W. As the intensity in each TP was maintained constant, to avoid the effect of inertia, participants were instructed to increase the number of rpm 3–4 s before finishing the rest intervals. The participants were encouraged to complete the test through verbal encouragement. The exercise ended when the participant was unable to keep rotations above
Table 1 Participants' physical characteristics (n = 12).
Age (y) Body mass (kg) Height (m) Body mass index (kg·m−2)
Mean ± standard deviation
Minimum–maximum
25.93 ± 5.45 67.94 ± 9.22 1.70 ± 0.06 23.57 ± 3.10
21.4–41.9 55.8–84.0 1.60–1.81 18.86–29.39
All variables presented normal distribution.
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Table 2 Tabata protocol performance evaluated at 115%, 130%, and 170% of iV̇ O2max. Variables
115% iV̇ O2max
130% iV̇ O2max
Effect size
170% iV̇ O2max
115% vs. 130% iV̇ O2max
115% vs. 170% iV̇ O2max
130% vs. 170% iV̇ O2max
(Unclear, but possibly/small)
1.9 3.4 0.3
(Probably/small)
3.1 2.3 0.1
(Unclear, but possibly/small)
0.3
(Probably/small)
0.1
Overall time test (seconds) Number of bouts V̇ O2mean (mL·kg−1·min−1)
196 ± 37 7±1 38.2 ± 5.0
153 ± 47⁎ 5 ± 1⁎ 37.0 ± 7.0
98 ± 16⁎,# 4 ± 1⁎,# 36.3 ± 4.8
1.1 1.1 0.2
%V̇ O2max HR reached (beats·min−1) RPE (6–20 Borg scale)
74.8 ± 11.0
71.9 ± 12.5
70.8 ± 8.2
0.2
182 ± 7 20 ± 0
181 ± 5 20 ± 0
179 ± 10 20 ± 0
0.1 –
(Almost certainly/large) (Almost certainly/large)
(Unclear, but possibly/trivial)
0.4 –
(Almost certainly/very large) (Almost certainly/very large)
(Probably/small)
0.2 –
(Almost certainly/very large) (Almost certainly/very large) (Unclear, but possibly/trivial) (Unclear, but possibly/trivial) (Unclear, but possibly/small)
V̇ O2mean, mean oxygen uptake; HRmax, maximum heart rate; RPE, rate of perceived exertion; iV̇ O2max, intensity associated at maximal oxygen uptake.). Data are presented as mean ± standard deviation. ⁎ p < 0.01 from the Tabata protocol at 115% iV̇ O2max. # p < 0.01 from the Tabata protocol at 130% iV̇ O2max.
3. Results
85 rpm for 10 s. The number of bouts performed and RPE values reported by participants was registered immediately after the end of exercise. HRmax in each session was established as the highest HR value during exercise. V̇ O2max in each session was taken as the mean V̇ O2max for 10 s period. The time spent above 90% of the V̇ O2max was calculated by summing the number of times that mean V̇ O2 values were above 90% of the V̇ O2max, and then multiplied by 10, since the mean V̇ O2 values were recorded every 10 s by the metabolic gas collection system (VO2000, MedGraphics, USA). All sessions were performed at a minimum interval of 48 h, always at the same time of day and supervised by two physical education professionals. Before each TP session the participants were asked about presence of delayed onset muscle soreness or other possible discomforts that could disturb the performance on the test. If so, the session would be relocated to another day. However, it was not necessary in any case.
3.1. Cardiorespiratory graded exertion test There were no intercurrences in the GXT. The V̇ O2max, HRmax, and iV̇ O2max obtained were 51.80 ± 8.10 mL·kg−1·min−1, 186 ± 10 bpm, and 204 ± 26 W, respectively.
3.2. Tabata protocol performance The TP performance is shown in Table 2. Considering that iV̇ O2max was 204 ± 26 W, protocol intensities performed at 115%, 130%, and 170% of iV̇ O2max were 235 ± 30 (CI 95% = 216–254 W), 266 ± 34 (CI 95% = 244–287 W), and 347 ± 44, (IC 95% = 320–375 W) respectively. There was a significant difference in the number of bouts between three intensities (χ2 = 24.000; p < 0.001), and post hoc testing identified that 115% (7 ± 1) and 130% (5 ± 1) of iV̇ O2max allowed significantly more bouts to be completed than 170% (4 ± 1) of iV̇ O2max (p < 0.001; ES = 3.4 [almost certainly very large] and p = 0.018; ES = 2.3 [almost certainly very large], respectively). The average of number of bouts decreased 17 ± 13% (1 ± 1) and 46 ± 10% (3 ± 1) when using 130% and 170% in comparison to 115% of iV̇ O2max, respectively. The mean V̇ O2 corresponded to approximately 70% of V̇ O2max with no significant difference between the three intensities (F [2.33] = 0.729; p = 0.494; η2p = 0.062). However, the non-clinical inferences were unclear, but possibly small or trivial (Table 2). No significant differences were found (F [2.33] = 3.979; p = .056; η2p = 0.266) between the highest V̇ O2 achieved at 115% (54.2 ± 7.9 mL.kg−1·min−1; CI 95% = 49.2–59.2 mL·kg−1·min−1) and 130% (52.5 ± 8.1 mL·kg−1·min−1; CI 95% = 47.4–57.8 mL·kg−1·min−1; ES = 0.1 [almost certainly trivial]), 115% and 170% (49.6 ± 7.5 mL·kg−1·min−1; CI 95% = 44.8–54.3 mL·kg−1.min−1; ES = 0.2 [Likely small]), and 130% and 170% of iV̇ O2max (ES = 0.1 [almost certainly trivial]). Fig. 1A and 1B compare the average highest V̇ O2 reached in each TP session performed and the V̇ O2max obtained in the GXT, and shows the individual analysis, respectively. Participants spent 25.9 ± 20.0% (CI 95% = 13.2–38.6%), 25.1 ± 20.5% (CI 95% = 12.0–38.1%), and 23.1 ± 21.7 (CI 95% = 9.3–36.8%) of the total TP time at 115%, 130%, and 170% of iV̇ O2max above 90% of V̇
2.5. Statistical analysis Data were entered into an Excel spreadsheet (Microsoft) and imported into Statistical Package for the Social Science (SPSS) version 23.0 for statistical analysis. HRmax, iV̇ O2max, number of bouts, time test, and the absolute time spent above 90% of V̇ O2max during the TP at 115%, 130%, and 170% of iV̇ O2max presented a non-normal distribution (p > 0.05) according to the Shapiro - Wilk tests. All other variables presented a normal distribution (p < 0.05). Repeated measurements ANOVA was used to compare the independent variables, with normal distribution. When necessary, post-hoc testing was performed by multiple comparisons using the Bonferroni correction. For number of bouts and all other variables with non-normal distribution Friedman H test was used, and when necessary, post-hoc Dunn's test was performed. In addition, qualitative magnitude inferences are presented based on Batterham and Hopkins [17] suggestions. For that, the post-only crossover spreadsheet available at http://sportsci.org/ was used. For % V̇ O2max the non-log transformed data was used, while log transformed data was applied for all other variables. The smallest worthwhile change was set at 0.2* the between-subject SD. The magnitude of the effect sizes (ES) was evaluated according to the criteria reported by Batterham and Hopkins [17]: Threshold for standardized differences (0.1, trivial; 0.2, small; 0.6, moderate; 1.2, large; > 2.0, very large) was used to describe the qualitative magnitude of the differences. Thresholds for non-clinical inferences probabilities was used to provide the qualitative probability based on the following scale: most unlikely, almost certainly not (< 0.5%); very unlikely (< 5%); unlikely, probably not (< 25%); possibly, possibly not (25–75%); likely, probably (> 75%); very likely (> 95%); most likely, almost certainly (> 99.5%). Data are presented as number and percentages for categorical variables, and continuous data are expressed as mean ± standard deviation and confidence intervals (CI). A significance level of 0.05 was adopted for all statistical tests.
O2max, respectively. There was a significant difference only in the absolute time spent above 90% of V̇ O2max between intensities (χ2 = 9.150; p = 0.010) and post hoc testing identified that it was only between 115% (53.3 ± 48.5 s; CI 95% = 22.5–84.1 s) and 170% (23.3 ± 21.5 s; CI 95% = 9.7–37.0 s) of iV̇ O2max (p = .018; ES = 0.3 [probably small]) (Fig. 2).
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Fig. 1. Mean (A) and individual (B) oxygen uptake reached in all session. GXT, cardiorespiratory graded exertion test; 115%, 130%, 170%, intensities associated at maximal oxygen uptake used in the Tabata protocol sessions.
Fig. 2. Mean (A) and individual (B) time spent above 90% V̇ O2max in the Tabata protocol performed at different intensities. 115%, 130%, 170%, intensities associated at maximal oxygen uptake used in the Tabata protocol sessions. *p = .018 from the Tabata protocol at 115% of the intensity associated at maximal oxygen uptake.
to six bouts at 170% iV̇ O2max. Divergence between studies may lie in the initial measurement of V̇ O2max, since variations in iV̇ O2max can greatly influence any factors dependent upon it. For example, an underestimation of an individual's V̇ O2max (e.g., due to different training experiences) in previous studies would have resulted in underestimated calculations of subsequent intensities. The suggestion that participants trained at lower intensities in previous studies is supported by the observation that the RPE were not maximum [18], whereas in the present study all participants reported maximal values of RPE in all tests. In the present study, we were very rigorous in orienting and stimulating participants to perform exercise until their cadence was below 85 rpm. In practical terms, when it happened participants were not able to pedal at all, which might explain the high RPE. Our results showed that similar values of V̇ O2 were obtained at 115% and 130% iV̇ O2max. In addition, all intensities' high values of V̇
3.3. HR and RPE There was no significant difference (χ2 = 2.651; p = 0.266) between HR reached in the TP performed at 115% (182 ± 7 bpm; CI 95% = 178–187 bpm), 130% (181 ± 5 bpm; CI 95% = 178–185 bpm), and 170% of iV̇ O2max (179 ± 10 bpm; CI 95% = 172–187 bpm). However, non-clinical inferences showed a probably small effect between 115% and 170% of iV̇ O2max. All participants reported maximum values of the RPE in the Borg scale in all three sessions (Table 2).
4. Discussion The aims of this study were to investigate the intensity that would allow participants to perform the original TP on a cycle ergometer and to measure the highest V̇ O2 achieved and the time spent above 90% of the V̇ O2max during a TP performed at different intensities in active young males. Our primary finding suggests that adequate intensity to perform seven to eight bouts using the 20:10 effort:pause protocol [1] in an electromagnetic braked cycle ergometer is equivalent to 115% of the iV̇ O2max. This value is considerably less than the popular recommendation of using 170% iV̇ O2max. According to our results, the number of bouts at 170% iV̇ O2max ranged between three and five, and no participant performed more than five bouts. This is in agreement with the findings of previous authors who questioned the feasibility of performing eight to nine bouts of 20:10 at 170% iV̇ O2max [7,8]. However, this conflicts with studies that involved eight or more bouts at 170% iV̇ O2max [3,6,18] and also challenged the study published by Tabata et al. [5], which involved five
O2 were close to the values obtained during the GXT. However, time spent above 90% V̇ O2max was lower at 170% and similar at both 115% and 130% of iV̇ O2max. Our results support the suggestion that if the intensity is too high, the exercise duration would be too short for V̇ O2max to be maintained [12]. The present results are consistent with previous studies on running in which velocities closer to 100% iV̇ O2max allowed more time to be spent at high V̇ O2 than much higher intensities [19,20]. Despite a significant effect of intensity on time spent above 90% V̇ O2max, the present study reported values considerably shorter (approximately 4 [198 s] to 13 [678 s] times) than those found in previous studies with well-trained cyclists and young endurance-trained athletes [10,21]. This was not surprising, since the overall exercise duration was
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low. This finding challenges the suggestion that the TP would impose a high demand on the cardiorespiratory system. Therefore, increases in V̇ O2max obtained from the TP might be more related to neuromuscular/ peripheral factors (e.g., increased glycogen depletion) than cardiorespiratory improvements per se. In agreement with this suggestion, in previous studies using the TP, increases in V̇ O2max were accompanied by increases in mitochondrial proteins and PGC1-α activity, which may suggest peripheral factors might be associated with results obtained by the TP [3,22]. According to the authors, fiber-type distribution, fiber-type specific oxidative and glycolytic capacity, glycogen and IMTG storage, and whole-muscle capillary density and whole-muscle glycolytic capacity could influence the results [3,22]. Indeed, neuromuscular adaptations have been shown to affect performance in previous studies involving HIIT [23,24]. It has been suggested that shorter intervals at higher intensities might induce greater neuromuscular load than longer intervals at lower intensities [25]. This might be related to a greater firing rate and relative force developed per fiber during short intervals at higher intensities, and also to increased metabolic and muscle force demands caused by frequent accelerations and decelerations associated with shorter intervals [25]. These neuromuscular adaptations, combined with high cardiopulmonary and metabolic demand, might highlight the important role of HIIT, specifically the TP, in stimulating a complex integrative physiology [26]. While the current study provides valuable insight into the acute physiological effect of the TP performed at different intensities, some limitations must be considered. First, blood lactate concentration was not measured, which could provide interesting information about participation of the anaerobic pathway. Second, as the current study involved healthy and active young male adults, it is difficult to generalize our findings to other populations (i.e., unfit, overweight, obese, sedentary, with some disease, elite athletes). Third, V̇ O2 was measures only once per 10 s and it was not possible to identify the intermediate values. In addition, future works should consider to apply the reserve power (delta between maximal aerobic power and maximal power) in order to raise individualization of training intensity and to consider betweensubjects differences in physical fitness, as previously suggested (Buchheit and Laursen [26]).
the exercise should be performed at a lower intensity in the next session. Using RPE per se might not be useful because all sessions would end with maximal values, independent of the number of bouts performed, as reported in Table 2, since they all are supposed to lead to maximum effort. In addition, based on our results, previous TP studies should be critically analyzed, since applications and responses to training could be quite different from what is originally expected. Future research should completely describe test and protocol prescriptions in order to facilitate analysis and practical application. In conclusion, this study showed that the adequate intensity to perform a similar number of bouts in the original TP is equivalent to 115% of the iV̇ O2max reached in an incremental V̇ O2max test. In addition, the time spent above 90% V̇ O2max was lower at the highest intensity (170%) and similar at both 115% and 130%. Author contributions RV, JN, and PG: conceived and designed the research. RV and JN: performed experiments. RV, VC, and FV: analyzed data. RV, CL, VC, FV, CV, and PG: interpreted results of experiments. RV and PG: drafted manuscript. CL, VC, FV, CV, and PG: edited and revised manuscript. All authors approved final version of manuscript. Funding The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Acknowledgments We would like to thank the participants for their effort and commitment to the research project. References [1] I. Tabata, K. Nishimura, M. Kouzaki, Y. Hirai, F. Ogita, M. Miyachi, K. Yamamoto, Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max, Med. Sci. Sports Exerc. 28 (1996) 1327–1330. [2] K. Silliman, K. Rodas-Fortier, M. Neyman, A survey of dietary and exercise habits and perceived barriers to following a healthy lifestyle in a college population, Californian J, Health Promot. 2 (2004) 10–19. [3] T.D. Scribbans, B.A. Edgett, K. Vorobej, A.S. Mitchell, S.D. Joanisse, J.B.L. Matusiak, G. Parise, J. Quadrilatero, B.J. Gurd, Fibre-specific responses to endurance and low volume high intensity interval training: striking similarities in acute and chronic adaptation, PLoS One 9 (2014) e98119. [4] G.R.M. Logan, N. Harris, S. Duncan, L.D. Plank, F. Merien, G. Schofield, Low-active male adolescents: a dose response to high-intensity interval training, Med. Sci. Sports Exerc. 48 (2016) 481–490. [5] I. Tabata, K. Irisawa, M. Kouzaki, K. Nishimura, F. Ogita, M. Miyachi, Metabolic profile of high intensity intermittent exercises, Med. Sci. Sports Exerc. 29 (1997) 390–395. [6] S. Joanisse, B.R. McKay, J.P. Nederveen, T.D. Scribbans, B.J. Gurd, J.B. Gillen, M.J. Gibala, M.A. Tarnopolsky, G. Parise, Satellite cell activity, without expansion, following non-hypertrophic stimuli, Am. J. Phys. Regul. Integr. Comp. Phys. 309 (2015) R1101–R1111. [7] V.S. Coswig, P. Gentil, J.P.A. Naves, R.B. Viana, C. Bartel, F.B. Del Vecchio, Commentary: the effects of high intensity interval training vs steady state training on aerobic and anaerobic capacity, Front. Physiol. 7 (2016) 495. [8] P. Gentil, J.P.A. Naves, R.B. Viana, V. Coswig, M. Dos Santos, C. Bartel Vaz, F.B. Del Vecchio, Revisiting Tabata's protocol: does it even exist? Med. Sci. Sports Exerc. 48 (2016) 2070–2071. [9] A.M. Jones, H. Carter, The effect of endurance training on parameters of aerobic fitness, Sports Med. 29 (2000) 373–386. [10] B.R. Rønnestad, J. Hansen, Optimizing interval training at power output associated with peak oxygen uptake in well-trained cyclists, J. Strength Cond. Res. 30 (2016) 999–1006. [11] T. Turnes, R.A. de Aguiar, R.S. de O. Cruz, F. Caputo, Interval training in the boundaries of severe domain: effects on aerobic parameters, Eur. J. Appl. Physiol. 116 (2016) 161–169. [12] F. Caputo, B.S. Denadai, The highest intensity and the shortest duration permitting attainment of maximal oxygen uptake during cycling: effects of different methods and aerobic fitness level, Eur. J. Appl. Physiol. 103 (2008) 47–57. [13] R.G. Timmins, M.N. Bourne, A.J. Shield, M.D. Williams, C. Lorenzen, D.A. Opar, Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk
4.1. Practical applications An important practical aspect of the present study is that HR values during protocols reached values near the maximum estimated HR. Due to this high cardiovascular stress, performance of the TP should be preceded by an adequate clinical examination and should be limited to populations without cardiovascular risks. Although benefits of HIIT protocols for health and fitness are warranted [27,28], we must analyze each protocol individually to assure that it is adequate for the proposed population. It is our opinion that the TP might be of value, especially because of its reported benefits with a reduced time commitment [29]. However, the high cardiovascular stress combined with the great discomfort brings into question the cost–benefit of the TP in a real-world setting [30]. Moreover, use of the TP should be preceded by careful examination, and its performance should be closely supervised to assure compliance, especially in initial stages. Considering that in a real-world setting exercise practitioners usually do not have access to equipment to assess V̇ O2max, we suggested for these practitioners to perform a GXT without metabolic gas collection system and used the percentage of the intensity reached at the end of the test (“iV̇ O2max”) as the mechanical parameter to prescribe exercise intensity. If it is not possible to perform a GXT test, one can aim to reach failure after performing 7–9 bouts at a constant intensity (fixed load and/or velocity). If more than nine bouts were performed, the intensity should be increased for the next session. On the other hand, if the practitioner fatigues before the seventh bout, 14
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[14]
[15]
[16] [17] [18]
[19]
[20]
[21]
Appl. Physiol. 102 (2007) 19–26. [22] T.D. Scribbans, J.K. Ma, B.A. Edgett, K.A. Vorobej, A.S. Mitchell, J.G.E. Zelt, C.A. Simpson, J. Quadrilatero, B.J. Gurd, Resveratrol supplementation does not augment performance adaptations or fibre-type-specific responses to high-intensity interval training in humans, Appl. Physiol. Nutr. Metab. 39 (2014) 1305–1313. [23] A. Ross, M. Leveritt, S. Riek, Neural influences on sprint running: training adaptations and acute responses, Sports Med. 31 (2001) 409–425. [24] T. Turnes, R. de Aguiar, R. de Oliveira Cruz, K. Pereira, A. Salvador, F. Caputo, High-intensity interval training in the boundaries of the severe domain: effects on sprint and endurance performance, Int. J. Sports Med. 37 (2016) 944–951. [25] M. Buchheit, P.B. Laursen, High-tntensity tnterval training, solutions to the programming puzzle: part II: anaerobic energy, neuromuscular load and practical applications, Sports Med. 43 (2013) 927–954. [26] M. Buchheit, P.B. Laursen, High-intensity interval training, solutions to the programming puzzle: part I: cardiopulmonary emphasis, Sports Med. 43 (2013) 313–338. [27] U. Wisløff, Ø. Ellingsen, O.J. Kemi, High-intensity interval training to maximize cardiac benefits of exercise training? Exerc. Sport Sci. Rev. 37 (2009) 139–146. [28] M.J. Gibala, A.M. Jones, Physiological and performance adaptations to high-intensity interval training, in, Nestle Nutr. Inst. Workshop Ser, 2013, pp. 51–60. [29] F.B. Del Vecchio, P. Gentil, V.S. Coswig, D.H. Fukuda, Commentary: why sprint interval training is inappropriate for a largely sedentary population, Front. Psychol. 6 (2015) 1359. [30] S.J. Hardcastle, H. Ray, L. Beale, M.S. Hagger, Why sprint interval training is inappropriate for a largely sedentary population, Front. Psychol. 5 (2014) 1505.
of hamstring injury in elite football (soccer): a prospective cohort study, Br. J. Sports Med. 50 (2016) 1524–1535. H.A. Fortner, J.M. Salgado, A.M. Holmstrup, M.E. Holmstrup, Cardiovascular and metabolic demads of the kettlebell swing using Tabata interval versus a traditional resistance protocol, Int. J. Exerc. Sci. 7 (2014) 179–185. R.A. de Aguiar, J. Schlickmann, T. Turnes, F. Caputo, Effect of intensity of intermittent running exercise 30s:15s at the time maintenance at or near VO2max, Motriz. 19 (2013) 207–216. G.A. Borg, Psychophysical bases of perceived exertion, Med. Sci. Sports Exerc. 14 (1982) 377–381. A.M. Batterham, W.G. Hopkins, Making meaningful inferences about magnitudes, Sportscience. 9 (2005) 6–13. C. Foster, C.V. Farland, F. Guidotti, M. Harbin, B. Roberts, J. Schuette, A. Tuuri, S.T. Doberstein, J.P. Porcari, The effects of high intensity interval training vs steady state training on aerobic and anaerobic capacity, J. Sports Sci. Med. 14 (2015) 747–755. L.V. Billat, Interval training for performance: a scientific and empirical practice. Special recommendations for middle- and long-distance running. Part II: anaerobic interval training, Sports Med. 31 (2001) 75–90. B.R. Wakefield, M. Glaister, Influence of work-interval intensity and duration on time spent at a high percentage of VO2max during intermittent supramaximal exercise, J. Strength Cond. Res. 23 (2009) 2548–2554. D. Thevenet, M. Tardieu, H. Zouhal, C. Jacob, B.A. Abderrahman, J. Prioux, Influence of exercise intensity on time spent at high percentage of maximal oxygen uptake during an intermittent session in young endurance-trained athletes, Eur. J.
15
Contents lists available at ScienceDirect
Physiology & Behavior journal homepage: www.elsevier.com/locate/physbeh
Defining the number of bouts and oxygen uptake during the “Tabata protocol” performed at different intensities
T
Ricardo B. Vianaa, João P.A. Navesa, Claudio A.B. de Liraa, Victor S. Coswigb, ⁎ Fabrício B. Del Vecchioc, Carlos A. Vieiraa, Paulo Gentila, a
Department of Physical Education, Faculty of Physical Education and Dance, Federal University of Goiás, Goiânia, Brazil Department of Physical Education, Faculty of Physical Education, Federal University of Pará, Castanhal, Brazil c Department of Physical Education, Superior School of Physical Education, Federal University of Pelotas, Pelotas, Brazil b
A R T I C L E I N F O
A B S T R A C T
Keywords: Exercise performance High-intensity interval training Metabolism Aerobic exercise Intermittent exercise
It is usually reported that the Tabata protocol (TP) is performed with eight bouts of 20:10 intervals at a load equivalent to 170% of i V̇ O2max. However, the feasibility of accumulating 160 s of work at 170% i V̇ O2max has been questioned. This article tested the intensity that would allow the performance of the original TP on a cycle ergometer, and measured the highest value of oxygen consumption (V̇ O2) obtained during the TP and the time spent above 90% of the maximal oxygen uptake (V̇ O2max) during the TP performed at different intensities. Thirteen young active males (25.9 ± 5.5 years, 67.9 ± 9.2 kg, 1.70 ± 0.06 m, 23.6 ± 3.1 kg·m−2) participated in the study. Participants performed a graded exertion test (GXT) on a cycle ergometer to obtain maximum oxygen consumption (V̇ O2max) and the intensity associated with V̇ O2max (i V̇ O2max). V̇ O2, maximal heart rate (HRmax), and number of bouts performed were evaluated during the TP performed at 115%, 130%, and 170% of i V̇ O2max. V̇ O2max, HRmax, and iV̇ O2max were 51.8 ± 8.0 mL.kg−1·min−1, 186 ± 10 bpm, and 204 ± 26 W, respectively. The number of bouts performed at 115% (7 ± 1 bouts) was higher than at 130% (5 ± 1 bouts) and 170% (4 ± 1 bouts) (p < .0001). The highest V̇ O2 achieved at 115%, 130%, and 170% of iV̇ O2max was 54.2 ± 7.9 mL·kg−1·min−1, 52.5 ± 8.1 mL·kg−1·min−1, and 49.6 ± 7.5 mL·kg−1·min−1, respectively. Non significant difference was found between the highest V̇ O2 achieved at different intensities, however qualitative magnitude-inference indicate a likely small effect between 115% and 170% of iV̇ O2max. Time spent above 90% of the V̇ O2max during the TP at 115% (50 ± 48 s) was higher than 170% (23 ± 21 s; p < 0.044) with a probably small effect. In conclusion, our data suggest that the adequate intensity to perform a similar number of bouts in the original TP is lower than previously proposed, and equivalent to 115% of the iV̇ O2max. In addition, intensities between 115 and 130% of the iV̇ O2max should be used to raise the time spent above 90% V̇ O2max.
1. Introduction The Tabata protocol (TP) was first presented in an article by Tabata et al. [1] that compared a moderate intensity protocol with a highintensity interval training (HIIT) protocol involving eight to nine bouts of 20 s exercise interspaced by 10 s of rest (20:10). According to the results, a TP lasting ~4 min significantly increased aerobic power and anaerobic capacity of physically active individuals, while one hour of moderately intense activities only resulted in a significantly increased aerobic power. Considering that a lack of time is the most cited barrier for exercise adoption [2], the possibility of increasing physical fitness through training sessions of very short duration (4 min of exercise time
without warm-up and cool-down) gained high popularity through the TP. In subsequent years, many researchers, coaches, and exercise enthusiasts have tried to replicate the TP in many different settings [3,4]. However, one problem in reproducing the TP is that the original article was not clear concerning the load used in the study. The study only mentioned that participants cycled at a constant load for 20 s and rested for 10 s (20:10) until they were not able to maintain at least 85 rpm, with load increments whenever the participant was able to perform more than nine bouts [1]. Later, the same research group reported high levels of oxygen uptake (V̇ O2) when young physically active males performed five to six bouts of 20:10 exercise at 170% of the intensity at
⁎ Corresponding author at: FEFD – Faculdade de Educação Física e Dança, Universidade Federal de Goiás – UFG, Avenida Esperança s/n, Campus Samambaia, CEP 74.690-900, Goiânia, Goiás, Brazil. E-mail address: [email protected] (P. Gentil).
https://doi.org/10.1016/j.physbeh.2018.02.045 Received 23 November 2017; Received in revised form 15 February 2018; Accepted 23 February 2018 Available online 24 February 2018 0031-9384/ © 2018 Elsevier Inc. All rights reserved.
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which maximal oxygen uptake (V̇ O2max) was achieved (iV̇ O2max) [5]. Apparently, both studies were merged to form the recommendation to perform seven to eight bouts of 20:10 intervals at a load equivalent to 170% of i V̇ O2max, a suggestion that was used in many subsequent studies [3,4,6]. However, the feasibility of accumulating 160 s of work at 170% i V̇ O2max has been questioned [7,8]. Thus, a better understanding of the adequate intensity to complete eight 20:10 is relevant to clarify this popular HIIT method known and applied worldwide. One of the most relevant reasons for performing HIIT would be V̇ O2max achievement, since in training-related studies, increasing V̇ O2max is generally explained by achieving a high percentage of V̇
form. All experimental procedures were approved by the Federal University of Goiás Ethics Committee (no 1.542.353) and conformed to the principles outlined in the Declaration of Helsinki. Participants were informed about the aims and methods of the study and were recommended to continue their normal diets throughout the study. In all visits, they ingested an easy-to-digest meal two hours before the test. They were advised not to ingest alcoholic beverages, stimulants (coffee, caffeine, and energetic drinks), tobacco, or drugs prior to the test; have a regular night of sleep (6 to 8 h); and not to perform intense physical activity 24 h before the tests. All of these requests were checked in a pre-test anamnesis.
O2max (90–100%) during a training session [9]. It has also been suggested that the time spent at high levels of V̇ O2 (i.e., above 90% V̇ O2max) could serve as a good criterion to judge the effectiveness of the stimulus to improve aerobic fitness [10,11]. Therefore, to achieve optimal increases in cardiorespiratory fitness, it has been recommended to perform a certain amount of training at intensities of 90–100% of V̇ O2max. If the intensity is too high, the exercise duration would be too short for V̇ O2max to be reached or maintained [12], which may interfere with the results. While Tabata et al. [5] reported that the TP induced maximum levels of V̇ O2, other studies indicate that the mean percentage of V̇ O2max achieved ranged from approximately 43% [13] to 71% [14]. To date, no studies have been found measuring the time spent at high V̇ O2 during the TP or the best load to match the effort:pause ratio and the number of bouts proposed by Tabata et al. [1]. Analyzing both V̇ O2max and time spent at near V̇ O2max are important for understanding physiological response to exercise Moreover, there is a lack of a clear definition how many bouts of 20:10 stimuli are possible to perform at different intensities in cycle ergometer. Therefore, the main purpose of the present study was to estimate the number of bouts performed by active young males at different intensities on a cycle ergometer. In addition, the secondary purposes were measured the highest V̇ O2 obtained during the TP at different intensities and the time spent above 90% of the V̇ O2max. We hypothesized that the optimal intensity for the TP is < 170% iV̇ O2max and that V̇ O2 remains high most of the time (above 90% of the V̇ O2max) during the TP.
2.2. Study design This is a randomized cross-over study in which each participant reported to the laboratory on four different occasions separated by at least 48 h. During the first session, anamnesis, anthropometric evaluation, and a cardiorespiratory graded exertion test (GXT) on a cycle ergometer were performed to assess the V̇ O2max, iV̇ O2max, and maximal heart rate (HRmax). On the subsequent visits, the TP was performed at different intensities in a randomized order: 115%, 130%, and 170% of iV̇ O2max. The randomization was performed through opaque envelope with six possible sequences. During the tests, the V̇ O2, heart rate (HR), rating of perceived exertion (RPE), and number of bouts performed were evaluated. 2.3. Cardiorespiratory graded exertion test Participants performed a GXT on an electromagnetic braked cycle ergometer (CG04, Inbramed, Brazil) to determine their V̇ O2max, iV̇ O2max, and HRmax. Briefly, following a 2 min warm-up at 50 W, the resistance was increased by 25 W every 1 min until volitional exhaustion or the point at which the participant was not able to sustain a pedal cadence of at least 80 rpm. Despite 50 rpm is often used as the cutting point for interrupting the test, we choose 80 rpm because, in practical terms, after dropping the cadence to below 80 rpm the cycling pattern changed abruptly, and the participants interrupted the exercise in a few seconds. Participants wore a mouthpiece and nose clip, and gas were collected breath by breath by a specific pneumotach connected to the analyzer. V̇ O2 and carbon dioxide production (V̇ CO2) were analyzed by a metabolic gas collection system (VO2000, MedGraphics, USA) every 10 s. After exhaustion, the load was reduced to 50 W to perform a recovery of 2 min. V̇ O2max was measured as the mean maximum oxygen uptake during 10 s periods. To identify iV̇ O2max, the lower workload that elicited V̇ O2max was considered. HR was constantly monitored throughout the test using a HR monitor (Polar RS800, Kempele, Finland). The RPE was evaluated every minute using the 6–20 Borg Scale [16].
2. Material and methods 2.1. Participants The sample size was calculated using data from Aguiar et al. [15], considering the absolute time spent above 90% of the V̇ O2max as the main outcome using GPower (Brunsbüttel, Germany). Therefore, 9 participants were necessary to achieve a power of 80% and p-value of 5% with effect size of 0.58. Thus, 12 physically active men were recruited (Table 1). Recruitment was carried out through advertisements on social media and direct contact. The inclusion criteria was to be in regular involvement in physical exercise at least three times a week in the last six months. Exclusion criteria were: i) cardiovascular diseases, ii) hypertension, iii) orthopedic limitation, and iv) contraindications for performing physical activity evaluated through the Physical Activity Readiness Questionnaire (PAR-Q). All participants were informed of the potential risks and benefits of the study and signed an informed consent
2.4. Tabata protocol at 115%, 130%, and 170% of iV̇ O2max The TP involved bouts of 20 s of effort interspaced by 10 s of rest (20:10). During the bouts, the subjects were oriented to pedal at around 90–100 rpm at three different constant intensities: 115%, 130%, and 170% of i V̇ O2max obtained in GXT. TP sessions were performed in the same electromagnetic braked cycle ergometer used in the GXT. The equipment allowed the power to be adjusted objectively independently of velocity. Participants received visual feedback from ergometer's screen in order to self-control cadence. Rest was performed at 50 W at a self-selected cadence. All sessions were preceded by 2 min of rest and 2 min of warm-up at 50 W and succeeded by 2 min of cool-down at 50 W. As the intensity in each TP was maintained constant, to avoid the effect of inertia, participants were instructed to increase the number of rpm 3–4 s before finishing the rest intervals. The participants were encouraged to complete the test through verbal encouragement. The exercise ended when the participant was unable to keep rotations above
Table 1 Participants' physical characteristics (n = 12).
Age (y) Body mass (kg) Height (m) Body mass index (kg·m−2)
Mean ± standard deviation
Minimum–maximum
25.93 ± 5.45 67.94 ± 9.22 1.70 ± 0.06 23.57 ± 3.10
21.4–41.9 55.8–84.0 1.60–1.81 18.86–29.39
All variables presented normal distribution.
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Table 2 Tabata protocol performance evaluated at 115%, 130%, and 170% of iV̇ O2max. Variables
115% iV̇ O2max
130% iV̇ O2max
Effect size
170% iV̇ O2max
115% vs. 130% iV̇ O2max
115% vs. 170% iV̇ O2max
130% vs. 170% iV̇ O2max
(Unclear, but possibly/small)
1.9 3.4 0.3
(Probably/small)
3.1 2.3 0.1
(Unclear, but possibly/small)
0.3
(Probably/small)
0.1
Overall time test (seconds) Number of bouts V̇ O2mean (mL·kg−1·min−1)
196 ± 37 7±1 38.2 ± 5.0
153 ± 47⁎ 5 ± 1⁎ 37.0 ± 7.0
98 ± 16⁎,# 4 ± 1⁎,# 36.3 ± 4.8
1.1 1.1 0.2
%V̇ O2max HR reached (beats·min−1) RPE (6–20 Borg scale)
74.8 ± 11.0
71.9 ± 12.5
70.8 ± 8.2
0.2
182 ± 7 20 ± 0
181 ± 5 20 ± 0
179 ± 10 20 ± 0
0.1 –
(Almost certainly/large) (Almost certainly/large)
(Unclear, but possibly/trivial)
0.4 –
(Almost certainly/very large) (Almost certainly/very large)
(Probably/small)
0.2 –
(Almost certainly/very large) (Almost certainly/very large) (Unclear, but possibly/trivial) (Unclear, but possibly/trivial) (Unclear, but possibly/small)
V̇ O2mean, mean oxygen uptake; HRmax, maximum heart rate; RPE, rate of perceived exertion; iV̇ O2max, intensity associated at maximal oxygen uptake.). Data are presented as mean ± standard deviation. ⁎ p < 0.01 from the Tabata protocol at 115% iV̇ O2max. # p < 0.01 from the Tabata protocol at 130% iV̇ O2max.
3. Results
85 rpm for 10 s. The number of bouts performed and RPE values reported by participants was registered immediately after the end of exercise. HRmax in each session was established as the highest HR value during exercise. V̇ O2max in each session was taken as the mean V̇ O2max for 10 s period. The time spent above 90% of the V̇ O2max was calculated by summing the number of times that mean V̇ O2 values were above 90% of the V̇ O2max, and then multiplied by 10, since the mean V̇ O2 values were recorded every 10 s by the metabolic gas collection system (VO2000, MedGraphics, USA). All sessions were performed at a minimum interval of 48 h, always at the same time of day and supervised by two physical education professionals. Before each TP session the participants were asked about presence of delayed onset muscle soreness or other possible discomforts that could disturb the performance on the test. If so, the session would be relocated to another day. However, it was not necessary in any case.
3.1. Cardiorespiratory graded exertion test There were no intercurrences in the GXT. The V̇ O2max, HRmax, and iV̇ O2max obtained were 51.80 ± 8.10 mL·kg−1·min−1, 186 ± 10 bpm, and 204 ± 26 W, respectively.
3.2. Tabata protocol performance The TP performance is shown in Table 2. Considering that iV̇ O2max was 204 ± 26 W, protocol intensities performed at 115%, 130%, and 170% of iV̇ O2max were 235 ± 30 (CI 95% = 216–254 W), 266 ± 34 (CI 95% = 244–287 W), and 347 ± 44, (IC 95% = 320–375 W) respectively. There was a significant difference in the number of bouts between three intensities (χ2 = 24.000; p < 0.001), and post hoc testing identified that 115% (7 ± 1) and 130% (5 ± 1) of iV̇ O2max allowed significantly more bouts to be completed than 170% (4 ± 1) of iV̇ O2max (p < 0.001; ES = 3.4 [almost certainly very large] and p = 0.018; ES = 2.3 [almost certainly very large], respectively). The average of number of bouts decreased 17 ± 13% (1 ± 1) and 46 ± 10% (3 ± 1) when using 130% and 170% in comparison to 115% of iV̇ O2max, respectively. The mean V̇ O2 corresponded to approximately 70% of V̇ O2max with no significant difference between the three intensities (F [2.33] = 0.729; p = 0.494; η2p = 0.062). However, the non-clinical inferences were unclear, but possibly small or trivial (Table 2). No significant differences were found (F [2.33] = 3.979; p = .056; η2p = 0.266) between the highest V̇ O2 achieved at 115% (54.2 ± 7.9 mL.kg−1·min−1; CI 95% = 49.2–59.2 mL·kg−1·min−1) and 130% (52.5 ± 8.1 mL·kg−1·min−1; CI 95% = 47.4–57.8 mL·kg−1·min−1; ES = 0.1 [almost certainly trivial]), 115% and 170% (49.6 ± 7.5 mL·kg−1·min−1; CI 95% = 44.8–54.3 mL·kg−1.min−1; ES = 0.2 [Likely small]), and 130% and 170% of iV̇ O2max (ES = 0.1 [almost certainly trivial]). Fig. 1A and 1B compare the average highest V̇ O2 reached in each TP session performed and the V̇ O2max obtained in the GXT, and shows the individual analysis, respectively. Participants spent 25.9 ± 20.0% (CI 95% = 13.2–38.6%), 25.1 ± 20.5% (CI 95% = 12.0–38.1%), and 23.1 ± 21.7 (CI 95% = 9.3–36.8%) of the total TP time at 115%, 130%, and 170% of iV̇ O2max above 90% of V̇
2.5. Statistical analysis Data were entered into an Excel spreadsheet (Microsoft) and imported into Statistical Package for the Social Science (SPSS) version 23.0 for statistical analysis. HRmax, iV̇ O2max, number of bouts, time test, and the absolute time spent above 90% of V̇ O2max during the TP at 115%, 130%, and 170% of iV̇ O2max presented a non-normal distribution (p > 0.05) according to the Shapiro - Wilk tests. All other variables presented a normal distribution (p < 0.05). Repeated measurements ANOVA was used to compare the independent variables, with normal distribution. When necessary, post-hoc testing was performed by multiple comparisons using the Bonferroni correction. For number of bouts and all other variables with non-normal distribution Friedman H test was used, and when necessary, post-hoc Dunn's test was performed. In addition, qualitative magnitude inferences are presented based on Batterham and Hopkins [17] suggestions. For that, the post-only crossover spreadsheet available at http://sportsci.org/ was used. For % V̇ O2max the non-log transformed data was used, while log transformed data was applied for all other variables. The smallest worthwhile change was set at 0.2* the between-subject SD. The magnitude of the effect sizes (ES) was evaluated according to the criteria reported by Batterham and Hopkins [17]: Threshold for standardized differences (0.1, trivial; 0.2, small; 0.6, moderate; 1.2, large; > 2.0, very large) was used to describe the qualitative magnitude of the differences. Thresholds for non-clinical inferences probabilities was used to provide the qualitative probability based on the following scale: most unlikely, almost certainly not (< 0.5%); very unlikely (< 5%); unlikely, probably not (< 25%); possibly, possibly not (25–75%); likely, probably (> 75%); very likely (> 95%); most likely, almost certainly (> 99.5%). Data are presented as number and percentages for categorical variables, and continuous data are expressed as mean ± standard deviation and confidence intervals (CI). A significance level of 0.05 was adopted for all statistical tests.
O2max, respectively. There was a significant difference only in the absolute time spent above 90% of V̇ O2max between intensities (χ2 = 9.150; p = 0.010) and post hoc testing identified that it was only between 115% (53.3 ± 48.5 s; CI 95% = 22.5–84.1 s) and 170% (23.3 ± 21.5 s; CI 95% = 9.7–37.0 s) of iV̇ O2max (p = .018; ES = 0.3 [probably small]) (Fig. 2).
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Fig. 1. Mean (A) and individual (B) oxygen uptake reached in all session. GXT, cardiorespiratory graded exertion test; 115%, 130%, 170%, intensities associated at maximal oxygen uptake used in the Tabata protocol sessions.
Fig. 2. Mean (A) and individual (B) time spent above 90% V̇ O2max in the Tabata protocol performed at different intensities. 115%, 130%, 170%, intensities associated at maximal oxygen uptake used in the Tabata protocol sessions. *p = .018 from the Tabata protocol at 115% of the intensity associated at maximal oxygen uptake.
to six bouts at 170% iV̇ O2max. Divergence between studies may lie in the initial measurement of V̇ O2max, since variations in iV̇ O2max can greatly influence any factors dependent upon it. For example, an underestimation of an individual's V̇ O2max (e.g., due to different training experiences) in previous studies would have resulted in underestimated calculations of subsequent intensities. The suggestion that participants trained at lower intensities in previous studies is supported by the observation that the RPE were not maximum [18], whereas in the present study all participants reported maximal values of RPE in all tests. In the present study, we were very rigorous in orienting and stimulating participants to perform exercise until their cadence was below 85 rpm. In practical terms, when it happened participants were not able to pedal at all, which might explain the high RPE. Our results showed that similar values of V̇ O2 were obtained at 115% and 130% iV̇ O2max. In addition, all intensities' high values of V̇
3.3. HR and RPE There was no significant difference (χ2 = 2.651; p = 0.266) between HR reached in the TP performed at 115% (182 ± 7 bpm; CI 95% = 178–187 bpm), 130% (181 ± 5 bpm; CI 95% = 178–185 bpm), and 170% of iV̇ O2max (179 ± 10 bpm; CI 95% = 172–187 bpm). However, non-clinical inferences showed a probably small effect between 115% and 170% of iV̇ O2max. All participants reported maximum values of the RPE in the Borg scale in all three sessions (Table 2).
4. Discussion The aims of this study were to investigate the intensity that would allow participants to perform the original TP on a cycle ergometer and to measure the highest V̇ O2 achieved and the time spent above 90% of the V̇ O2max during a TP performed at different intensities in active young males. Our primary finding suggests that adequate intensity to perform seven to eight bouts using the 20:10 effort:pause protocol [1] in an electromagnetic braked cycle ergometer is equivalent to 115% of the iV̇ O2max. This value is considerably less than the popular recommendation of using 170% iV̇ O2max. According to our results, the number of bouts at 170% iV̇ O2max ranged between three and five, and no participant performed more than five bouts. This is in agreement with the findings of previous authors who questioned the feasibility of performing eight to nine bouts of 20:10 at 170% iV̇ O2max [7,8]. However, this conflicts with studies that involved eight or more bouts at 170% iV̇ O2max [3,6,18] and also challenged the study published by Tabata et al. [5], which involved five
O2 were close to the values obtained during the GXT. However, time spent above 90% V̇ O2max was lower at 170% and similar at both 115% and 130% of iV̇ O2max. Our results support the suggestion that if the intensity is too high, the exercise duration would be too short for V̇ O2max to be maintained [12]. The present results are consistent with previous studies on running in which velocities closer to 100% iV̇ O2max allowed more time to be spent at high V̇ O2 than much higher intensities [19,20]. Despite a significant effect of intensity on time spent above 90% V̇ O2max, the present study reported values considerably shorter (approximately 4 [198 s] to 13 [678 s] times) than those found in previous studies with well-trained cyclists and young endurance-trained athletes [10,21]. This was not surprising, since the overall exercise duration was
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low. This finding challenges the suggestion that the TP would impose a high demand on the cardiorespiratory system. Therefore, increases in V̇ O2max obtained from the TP might be more related to neuromuscular/ peripheral factors (e.g., increased glycogen depletion) than cardiorespiratory improvements per se. In agreement with this suggestion, in previous studies using the TP, increases in V̇ O2max were accompanied by increases in mitochondrial proteins and PGC1-α activity, which may suggest peripheral factors might be associated with results obtained by the TP [3,22]. According to the authors, fiber-type distribution, fiber-type specific oxidative and glycolytic capacity, glycogen and IMTG storage, and whole-muscle capillary density and whole-muscle glycolytic capacity could influence the results [3,22]. Indeed, neuromuscular adaptations have been shown to affect performance in previous studies involving HIIT [23,24]. It has been suggested that shorter intervals at higher intensities might induce greater neuromuscular load than longer intervals at lower intensities [25]. This might be related to a greater firing rate and relative force developed per fiber during short intervals at higher intensities, and also to increased metabolic and muscle force demands caused by frequent accelerations and decelerations associated with shorter intervals [25]. These neuromuscular adaptations, combined with high cardiopulmonary and metabolic demand, might highlight the important role of HIIT, specifically the TP, in stimulating a complex integrative physiology [26]. While the current study provides valuable insight into the acute physiological effect of the TP performed at different intensities, some limitations must be considered. First, blood lactate concentration was not measured, which could provide interesting information about participation of the anaerobic pathway. Second, as the current study involved healthy and active young male adults, it is difficult to generalize our findings to other populations (i.e., unfit, overweight, obese, sedentary, with some disease, elite athletes). Third, V̇ O2 was measures only once per 10 s and it was not possible to identify the intermediate values. In addition, future works should consider to apply the reserve power (delta between maximal aerobic power and maximal power) in order to raise individualization of training intensity and to consider betweensubjects differences in physical fitness, as previously suggested (Buchheit and Laursen [26]).
the exercise should be performed at a lower intensity in the next session. Using RPE per se might not be useful because all sessions would end with maximal values, independent of the number of bouts performed, as reported in Table 2, since they all are supposed to lead to maximum effort. In addition, based on our results, previous TP studies should be critically analyzed, since applications and responses to training could be quite different from what is originally expected. Future research should completely describe test and protocol prescriptions in order to facilitate analysis and practical application. In conclusion, this study showed that the adequate intensity to perform a similar number of bouts in the original TP is equivalent to 115% of the iV̇ O2max reached in an incremental V̇ O2max test. In addition, the time spent above 90% V̇ O2max was lower at the highest intensity (170%) and similar at both 115% and 130%. Author contributions RV, JN, and PG: conceived and designed the research. RV and JN: performed experiments. RV, VC, and FV: analyzed data. RV, CL, VC, FV, CV, and PG: interpreted results of experiments. RV and PG: drafted manuscript. CL, VC, FV, CV, and PG: edited and revised manuscript. All authors approved final version of manuscript. Funding The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Acknowledgments We would like to thank the participants for their effort and commitment to the research project. References [1] I. Tabata, K. Nishimura, M. Kouzaki, Y. Hirai, F. Ogita, M. Miyachi, K. Yamamoto, Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max, Med. Sci. Sports Exerc. 28 (1996) 1327–1330. [2] K. Silliman, K. Rodas-Fortier, M. Neyman, A survey of dietary and exercise habits and perceived barriers to following a healthy lifestyle in a college population, Californian J, Health Promot. 2 (2004) 10–19. [3] T.D. Scribbans, B.A. Edgett, K. Vorobej, A.S. Mitchell, S.D. Joanisse, J.B.L. Matusiak, G. Parise, J. Quadrilatero, B.J. Gurd, Fibre-specific responses to endurance and low volume high intensity interval training: striking similarities in acute and chronic adaptation, PLoS One 9 (2014) e98119. [4] G.R.M. Logan, N. Harris, S. Duncan, L.D. Plank, F. Merien, G. Schofield, Low-active male adolescents: a dose response to high-intensity interval training, Med. Sci. Sports Exerc. 48 (2016) 481–490. [5] I. Tabata, K. Irisawa, M. Kouzaki, K. Nishimura, F. Ogita, M. Miyachi, Metabolic profile of high intensity intermittent exercises, Med. Sci. Sports Exerc. 29 (1997) 390–395. [6] S. Joanisse, B.R. McKay, J.P. Nederveen, T.D. Scribbans, B.J. Gurd, J.B. Gillen, M.J. Gibala, M.A. Tarnopolsky, G. Parise, Satellite cell activity, without expansion, following non-hypertrophic stimuli, Am. J. Phys. Regul. Integr. Comp. Phys. 309 (2015) R1101–R1111. [7] V.S. Coswig, P. Gentil, J.P.A. Naves, R.B. Viana, C. Bartel, F.B. Del Vecchio, Commentary: the effects of high intensity interval training vs steady state training on aerobic and anaerobic capacity, Front. Physiol. 7 (2016) 495. [8] P. Gentil, J.P.A. Naves, R.B. Viana, V. Coswig, M. Dos Santos, C. Bartel Vaz, F.B. Del Vecchio, Revisiting Tabata's protocol: does it even exist? Med. Sci. Sports Exerc. 48 (2016) 2070–2071. [9] A.M. Jones, H. Carter, The effect of endurance training on parameters of aerobic fitness, Sports Med. 29 (2000) 373–386. [10] B.R. Rønnestad, J. Hansen, Optimizing interval training at power output associated with peak oxygen uptake in well-trained cyclists, J. Strength Cond. Res. 30 (2016) 999–1006. [11] T. Turnes, R.A. de Aguiar, R.S. de O. Cruz, F. Caputo, Interval training in the boundaries of severe domain: effects on aerobic parameters, Eur. J. Appl. Physiol. 116 (2016) 161–169. [12] F. Caputo, B.S. Denadai, The highest intensity and the shortest duration permitting attainment of maximal oxygen uptake during cycling: effects of different methods and aerobic fitness level, Eur. J. Appl. Physiol. 103 (2008) 47–57. [13] R.G. Timmins, M.N. Bourne, A.J. Shield, M.D. Williams, C. Lorenzen, D.A. Opar, Short biceps femoris fascicles and eccentric knee flexor weakness increase the risk
4.1. Practical applications An important practical aspect of the present study is that HR values during protocols reached values near the maximum estimated HR. Due to this high cardiovascular stress, performance of the TP should be preceded by an adequate clinical examination and should be limited to populations without cardiovascular risks. Although benefits of HIIT protocols for health and fitness are warranted [27,28], we must analyze each protocol individually to assure that it is adequate for the proposed population. It is our opinion that the TP might be of value, especially because of its reported benefits with a reduced time commitment [29]. However, the high cardiovascular stress combined with the great discomfort brings into question the cost–benefit of the TP in a real-world setting [30]. Moreover, use of the TP should be preceded by careful examination, and its performance should be closely supervised to assure compliance, especially in initial stages. Considering that in a real-world setting exercise practitioners usually do not have access to equipment to assess V̇ O2max, we suggested for these practitioners to perform a GXT without metabolic gas collection system and used the percentage of the intensity reached at the end of the test (“iV̇ O2max”) as the mechanical parameter to prescribe exercise intensity. If it is not possible to perform a GXT test, one can aim to reach failure after performing 7–9 bouts at a constant intensity (fixed load and/or velocity). If more than nine bouts were performed, the intensity should be increased for the next session. On the other hand, if the practitioner fatigues before the seventh bout, 14
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[14]
[15]
[16] [17] [18]
[19]
[20]
[21]
Appl. Physiol. 102 (2007) 19–26. [22] T.D. Scribbans, J.K. Ma, B.A. Edgett, K.A. Vorobej, A.S. Mitchell, J.G.E. Zelt, C.A. Simpson, J. Quadrilatero, B.J. Gurd, Resveratrol supplementation does not augment performance adaptations or fibre-type-specific responses to high-intensity interval training in humans, Appl. Physiol. Nutr. Metab. 39 (2014) 1305–1313. [23] A. Ross, M. Leveritt, S. Riek, Neural influences on sprint running: training adaptations and acute responses, Sports Med. 31 (2001) 409–425. [24] T. Turnes, R. de Aguiar, R. de Oliveira Cruz, K. Pereira, A. Salvador, F. Caputo, High-intensity interval training in the boundaries of the severe domain: effects on sprint and endurance performance, Int. J. Sports Med. 37 (2016) 944–951. [25] M. Buchheit, P.B. Laursen, High-tntensity tnterval training, solutions to the programming puzzle: part II: anaerobic energy, neuromuscular load and practical applications, Sports Med. 43 (2013) 927–954. [26] M. Buchheit, P.B. Laursen, High-intensity interval training, solutions to the programming puzzle: part I: cardiopulmonary emphasis, Sports Med. 43 (2013) 313–338. [27] U. Wisløff, Ø. Ellingsen, O.J. Kemi, High-intensity interval training to maximize cardiac benefits of exercise training? Exerc. Sport Sci. Rev. 37 (2009) 139–146. [28] M.J. Gibala, A.M. Jones, Physiological and performance adaptations to high-intensity interval training, in, Nestle Nutr. Inst. Workshop Ser, 2013, pp. 51–60. [29] F.B. Del Vecchio, P. Gentil, V.S. Coswig, D.H. Fukuda, Commentary: why sprint interval training is inappropriate for a largely sedentary population, Front. Psychol. 6 (2015) 1359. [30] S.J. Hardcastle, H. Ray, L. Beale, M.S. Hagger, Why sprint interval training is inappropriate for a largely sedentary population, Front. Psychol. 5 (2014) 1505.
of hamstring injury in elite football (soccer): a prospective cohort study, Br. J. Sports Med. 50 (2016) 1524–1535. H.A. Fortner, J.M. Salgado, A.M. Holmstrup, M.E. Holmstrup, Cardiovascular and metabolic demads of the kettlebell swing using Tabata interval versus a traditional resistance protocol, Int. J. Exerc. Sci. 7 (2014) 179–185. R.A. de Aguiar, J. Schlickmann, T. Turnes, F. Caputo, Effect of intensity of intermittent running exercise 30s:15s at the time maintenance at or near VO2max, Motriz. 19 (2013) 207–216. G.A. Borg, Psychophysical bases of perceived exertion, Med. Sci. Sports Exerc. 14 (1982) 377–381. A.M. Batterham, W.G. Hopkins, Making meaningful inferences about magnitudes, Sportscience. 9 (2005) 6–13. C. Foster, C.V. Farland, F. Guidotti, M. Harbin, B. Roberts, J. Schuette, A. Tuuri, S.T. Doberstein, J.P. Porcari, The effects of high intensity interval training vs steady state training on aerobic and anaerobic capacity, J. Sports Sci. Med. 14 (2015) 747–755. L.V. Billat, Interval training for performance: a scientific and empirical practice. Special recommendations for middle- and long-distance running. Part II: anaerobic interval training, Sports Med. 31 (2001) 75–90. B.R. Wakefield, M. Glaister, Influence of work-interval intensity and duration on time spent at a high percentage of VO2max during intermittent supramaximal exercise, J. Strength Cond. Res. 23 (2009) 2548–2554. D. Thevenet, M. Tardieu, H. Zouhal, C. Jacob, B.A. Abderrahman, J. Prioux, Influence of exercise intensity on time spent at high percentage of maximal oxygen uptake during an intermittent session in young endurance-trained athletes, Eur. J.
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