Eur J Appl Physiol DOI 10.1007/s00421-017-3636-7
ORIGINAL ARTICLE
Acute effects of high‑intensity interval training and moderate‑intensity continuous training sessions on cardiorespiratory parameters in healthy young men Gustavo Zaccaria Schaun1 · Cristine Lima Alberton1 · Diego Oliveira Ribeiro1 · Stephanie Santana Pinto1
Received: 28 November 2016 / Accepted: 5 May 2017 © Springer-Verlag Berlin Heidelberg 2017
Abstract Purpose The aim of the present study was to compare the energy expenditure (EE) during and after two treadmill protocols, high-intensity interval training (HIIT) and moderate continuous training (CONT), in young adult men. Methods The sample was comprised by 26 physically active men aged between 18 and 35 years engaged in aerobic training programs. They were divided into two groups: HIIT (n = 14) which performed eight 20 s bouts at 130% of the velocity associated with the maximal oxygen consumption on a treadmill with 10 s of passive rest, or CONT (n = 12) which performed 30 min running on a treadmill at a submaximal velocity equivalent to 90–95% of the heart rate associated with the anaerobic threshold. Data related to oxygen consumption (V˙ O2) and EE were measured during the protocols and the excess post-exercise oxygen consumption (EPOC) was calculated for both sessions. Results No difference was found between groups for mean V˙ O2 (HIIT: 2.84 ± 0.46 L min−1; CONT: 2.72 ± 0.43 L min−1) and EE per minute (HIIT: 14.36 ± 2.34 kcal min−1; CONT: 13.21 ± 2.08 kcal min−1) during protocols. Regarding total EE during session, CONT resulted in higher values compared to HIIT (390.45 ± 65.15; 55.20 ± 9.33 kcal, respectively). However, post-exercise EE and EPOC values were higher after HIIT (69.31 ± 10.88; 26.27 ± 2.28 kcal, respectively)
Communicated by Guido Ferretti. * Gustavo Zaccaria Schaun
[email protected] 1
Neuromuscular Assessment Laboratory, Physical Education School, Federal University of Pelotas, Rua Luís de Camões, 625, Três Vendas, Pelotas, RS, Brazil
compared to CONT (55.99 ± 10.20; 13.43 ± 10.45 kcal, respectively). Conclusion These data suggest that supramaximal HIIT has a higher impact on EE and EPOC in the early phase of recovery when compared to CONT. Keywords Exercise · Interval training · Continuous training · Oxygen uptake · Energy expenditure · EPOC Abbreviations ANOVA Analysis of variance CE Caloric equivalent CONT Moderate-intensity continuous training EE Energy expenditure EPOC Excess post-exercise oxygen consumption HIIT High-intensity interval training HR Heart rate HRmax Maximal heart rate Intensity associated with maximal oxygen iV˙ O2max consumption ˙ V O2 Maximal oxygen consumption VT2 Second ventilatory threshold
Introduction Aerobic exercises play an important role to increase energy expenditure (EE) during or immediately after exercise sessions (Borsheim and Bahr 2003). Therefore, it is relevant to investigate the optimal exercise volume and intensity to reach a time-efficient EE. In this context, EE derived from an exercise session is related to the type of protocol employed, as there may be variations in EE based on manipulation of both its volume and intensity (Borsheim and Bahr 2003; LaForgia et al. 2006) in
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addition to exercise mode performed (Borsheim and Bahr 2003). In this context, sessions EE can be split into the following: (1) energy expended during the session itself and (2) energy demanded after it, which is directly influenced by excess post-exercise oxygen consumption (EPOC; Gaesser and Brooks 1984) as both contribute to a considerable volume to the maintenance of a negative daily energetic balance (Borsheim and Bahr 2003). Researchers suggest that the increased metabolic demand during recovery, expressed by EPOC, seems to be higher after intermittent activities when compared to lower intensity continuous isocaloric ones (Cunha et al. 2016). Nevertheless, there are still conflicting results regarding the influence of exercise mode, intensity, volume, and duration in EPOC (Greer et al. 2015). This way, two training methods have been highlighted and compared in the literature: high-intensity interval training (HIIT), in which exercise volume may be low with exercises performed at high intensity interspersed with recovery intervals (Buchheit and Laursen 2013) and moderate-intensity continuous training (CONT), in which a higher exercise volume is used with a relatively lower intensity when compared to HIIT. Previously, sprint interval exercise (i.e., 4 × 30 s Wingate-based) was shown to elicit similar oxygen consumption (V˙ O2) and EE post-exercise when compared to 30 min (~70% iV˙ O2max) and 60 min (~65% iV˙ O2peak) of CONT along 30 min (Williams et al. 2013) and 24 h post-exercise (Hazell et al. 2012). This is supported by Skelly et al. (2014) who also found the same result when comparing an HIIT protocol (10 × 60 s at 90% H Rmax interspersed with 60 s rest) to a CONT one (50 min at ~70% H Rmax) up to 24 h post-exercise. On the other hand, CONT tended to present a higher EE during the session itself in all the above-mentioned studies (Hazell et al. 2012; Skelly et al. 2014; Williams et al. 2013). Despite this fact, submaximal or maximal HIIT protocols examined up to the present generally have similar duration or workload compared to CONT (LaForgia et al. 1997) and investigated supramaximal protocols commonly employed relatively long recovery periods (Hazell et al. 2012; Williams et al. 2013). Within this context, evaluation of time-efficient HIIT protocols may highlight interesting facts in understanding EE and EPOC. Having said that, the aim of the present study was to compare the acute effects of a very low-volume supramaximal HIIT protocol and a standard 30-min moderate-intensity continuous session on EE and EPOC along 30 min in young healthy men, which was not performed yet. It was hypothesized that total EE and EE during session would be greater following CONT compared with HIIT, whereas session EE per minute, postexercise EE and EPOC would be higher following HIIT compared to CONT.
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Methods Subjects Twenty-six healthy physically active men (23.3 ± 2.9 years; 76.7 ± 12.6 kg; 1.76 ± 0.06 cm; and V˙ O2max = 45.9 ± 5.8 ml kg−1 min−1) volunteered to participate in the study. This study was part of a larger research in which participants were already randomly assigned (simple randomization) to one of two experimental groups: HIIT (n = 14) or CONT (n = 12). Therefore, we opted not to use a cross-over design to avoid bias, since participants were already accustomed to one protocol. Specifically, subjects were engaged in training, three times per week, for less than 30 days at the time of the assessments. All were nonsmokers and did not present previous history of cardiovascular, endocrine, metabolic, or neuromuscular diseases as well as could not be using any type of medication that could interfere in the cardiorespiratory or neuromuscular systems. Prior to any procedure, all participants read, agreed, and signed an informed consent which was previously approved by the Federal University of Pelotas Research Ethics Committee (CAAE 49499415.0.0000.5313). Procedures For the present study, participants attended three separate sessions at the university laboratory. Physical and anthropometrical measures On the first day, weight and height were assessed using a digital scale (FILIZOLA, São Paulo, Brazil) and stadiometer, respectively, to calculate subject’s body mass index (BMI). In addition, seven-site skinfold thickness (chest, axilla, triceps, subscapular, abdominal, suprailium, and thigh) were measured with a skinfold caliper (CESCORF, Porto Alegre, Brazil). Based on the sum of skinfolds, body density was estimated (Jackson and Pollock 1978) and body fat calculated (Siri 1993). Skinfolds were measured in circuit, totaling a maximum of three attempts per skinfold. Finally, subjects were familiarized with the laboratory, treadmill, and masks which they would perform the following procedures. Incremental test measures On a second occasion, separated by at least 48 h from the previous one, subjects performed a maximal incremental test on a treadmill to determine V˙ O2max and the corresponding intensities for the HIIT and CONT protocols. The
Eur J Appl Physiol
test started at 6 km h−1 for 5 min (warm-up) which was followed by subsequent 1 km h−1 increments every min until volitional exhaustion. Throughout the test, expiratory gases were directly collected and analyzed using a breath-by-breath portable spirometer with a frequency of acquisition set for the average of every three breaths (VO2000, MedGraphics, Ann Arbor, USA), which was calibrated according to manufacturer’s specifications before every test. The maximum V˙ O2 (ml kg−1 min−1) was considered as the mean 30 s of the last completed stage and second ventilatory threshold (VT2) was determined by the ventilation vs. intensity curve and confirmed by the ventilatory C O2 equivalent curve (V˙ E ˙ /V CO2; Wasserman et al. 1973). Regarding threshold detection, it was performed by visual inspection by two experienced physiologists in a blinded and independently fashion (Reinhard et al. 1979) as previously described (Alberton et al. 2014). When there was no agreement on the determination of the break point, a third physiologist was employed. In addition, heart rate (HR) was assessed using a Polar® monitor (RS800CX, Finland). Incremental tests were considered valid when at least two of the following criterions were achieved: (1) plateau in V˙ O2 despite an increase in exercise intensity; (2) respiratory exchange ratio higher than 1.10; and (3) heart rate predicted by age (220 age) achieved (Ferreti 2014; Howley et al. 1995). In addition, the day before test participants were asked not to perform vigorous physical activity, not to consume any stimulant beverages and to sleep at least 8 h. Exercise measures On a third occasion, participants performed their assigned protocol. First, they remained seated for 30-min pre-exercise. After, subjects performed their respective protocol and, again, remained seated for 30-min post-exercise. During all the procedures, expiratory gases were collected and V˙ O2 (L min−1) was measured for posterior determination of the EE in each protocol, as well as before and after them. Furthermore, pre-exercise EE was subtracted from postexercise EE to determine EPOC. Different caloric equivalents (CE) were used for the determination of EE based on the moment and protocol performed (Wilmore et al. 1978). For the CONT group, a CE of 4.85 kcal L−1 of O2 was used on the pre-exercise, exercise, and post-exercise moments. As for the HIIT group, the same CE was used on the pre- and post-exercise (i.e., 4.85 kcal L−1); however, during the exercise, a CE of 5.05 kcal L−1 was adopted due to the high intensity arising from the session. In addition, we chose to perform the calculation of the area corresponding to the V˙ O2 (L) through integration, as already frequently employed (Jacobsen et al.
2005). In this regard, for both protocols (CONT or HIIT) V˙ O2, area was calculated (in liters) according to the specific moment (i.e., 30-min pre-; CONT, HIIT; 30-min post) and was multiplied by the corresponding CE. Exercise protocols HIIT group performed a standard warm-up corresponding to 90–95% VT2 for 4 min. Following a 3-min passive interval, participants performed eight 20 s bouts on a motorized treadmill (KIKOS KX 9000, São Paulo, Brazil) at 130% of the velocity associated with V˙ O2max interspersed with 10 s passive recovery between bouts. As for the CONT group, subjects exercised on the same treadmill for 30 min with an intensity corresponding to 90–95% of the HR associated with VT2. Statistical analysis Descriptive and inferential statistics were used for data analysis. After testing the normality of the data with Shapiro–Wilk’s test, data were presented as mean and standard deviations (±SD). For V˙ O2, EE and EPOC comparison between HIIT and CONT groups, a t test for independent measures was applied. Moreover, an ANOVA two-way for repeated measures followed by Bonferroni post hoc was applied to evaluate the EE between moments and protocols. In addition, a value of α = 0.05 was adopted and all tests were performed in the SPSS 20.0 program.
Results Initially, no significant difference was identified between groups regarding V˙ O2 at rest (p > 0.05), which corresponded to 0.29 ± 0.07 and 0.30 ± 0.04 L min−1 for CONT and HIIT groups, respectively, totaling 8.78 ± 2.02 and 9.21 ± 1.61 L of O2 over the 30-min period. Similar behavior has been verified for all other descriptive variables (Table 1). All t tests for independent variables revealed that there were no statistical differences between these variables (all p > 0.05) at the onset of the study. In addition, it should be noted that all subjects reached at least two out of the three criteria for V˙ O2max attainment during the incremental test. Results regarding exercise and post-exercise comparisons between sessions are presented in Table 2. Differences between protocols were observed for absolute V˙ O2 and EE during and after session, as well as for V˙ O2 and EE per minute after the session. Absolute V˙ O2 and EE during exercise were higher in CONT when compared to HIIT, while HIIT presented higher absolute and per minute V˙ O2 and EE
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Table 1 Physical and anthropometrical characteristics of a healthy and physically active men’s sample according to group (n = 26)
Age (years) Body weight (kg) Height (m) BMI (kg/m2) BF (%) ∑Skinfolds (mm) V˙ O2max (ml kg−1 min−1)
CONT (n = 12)
HIIT (n = 14)
Mean
±s
Mean
±s
23.3 79.9 1.79 25.0 17.0 127.5
±3.1 ±12.6 ±5.0 ±3.3 ±6.7 ±51.5
23.3 73.8 1.75 24.0 15.9 108.5
±2.9 ±12.6 ±4.8 ±3.4 ±5.3 ±39.3
47.5
±6.9
44.5
±4.4
CONT moderate-intensity continuous training session, HIIT highintensity interval training session, BMI body mass index, BF percentage of body fat, ∑Skinfolds sum of seven-site skinfold thickness, V˙ O2max maximal oxygen consumption. No statistical difference between groups was identified
Table 2 Comparisons of oxygen consumption (V˙ O2), energy expenditure (EE), and excess post-exercise oxygen consumption (EPOC) according to protocol in healthy young man (n = 26) CONT (n = 12)
HIIT (n = 14)
Mean
±s
Mean
13.43
10.45*
±s
2) V˙ O2 exercise (L O V˙ O2 exercise (L O2 min−1)
80.50 2.68
0.45
2.73
0.46
V˙ O2 post (L O2) V˙ O2 post (L O2 min−1)
11.55
2.10
14.29*
2.25
0.39
0.07
0.48*
0.08
390.45 13.02 55.99 1.87 2.77
65.15 2.17 10.20 0.34 2.15
52.78* 13.20 69.31* 2.31* 5.41*
7.50 1.87 10.88 0.36 1.30
13.43
10.45
26.27*
6.28
EE exercise (kcal) EE exercise (kcal min−1) EE post (kcal) EE post (kcal min−1) EPOC (L O2) EPOC (kcal)
1.48
CONT moderate-intensity continuous training session, HIIT highintensity interval training session * Significant difference between protocols (p ≤ 0.005)
post-exercise. Moreover, a greater EPOC was verified after HIIT when compared to CONT. When considering EE in relation to values at rest (Fig. 1), it was observed that CONT already had similar values to the resting condition on the fifth minute after the protocol (p > 0.05). However, HIIT had not returned to resting values at this point (p = 0.001), but only in the 25th minute (p > 0.05). Although no difference was identified in the mean EE between protocols (HIIT 52.78 ± 7.50 kcal; CONT 390.45 ± 65.15 kcal) during the sessions (Table 1), Fig. 1 shows that on the last minute of the exercise session, HIIT was promoting significantly greater EE when compared to CONT (p = 0.011). Figure 2 presents the
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Fig. 1 Energy expenditure between moments according to protocol performed. CONT moderate-intensity continuous training session (n = 12), HIIT high-intensity interval training session (n = 14), Pre twenty-fifth minute at rest, Exercise last minute of exercise session, Post 5 fifth minute post-exercise, Post 25 twenty-fifth minute postexercise. *Significant difference between protocols (p ≤ 0.01), †Significant difference from exercise to the other moments (Pre, Post 5, and Post 25) in both protocols (p
