Effects of High-Intensity Interval Training vs. Sprint Interval Training on Anthropometric Measures and Cardiorespiratory Fitness in Healthy Young Women

Abstract

Purpose: To compare the effects of 8 weeks of two types of interval training, Sprint Interval Training (SIT) and High-Intensity Interval Training (HIIT), on anthropometric measures and cardiorespiratory fitness in healthy young women.
Methods: A randomized clinical trial in which 49 young active women (age, 30.4±6.1 years; body mass index, 24.8±3.1 kg.m-2; peak oxygen consumption (VO2peak), 34.9±7.5 mL.kg-1.min-1) were randomly allocated into a SIT or HIIT group. The SIT group performed four bouts of 30 s all-out cycling efforts interspersed with four minutes of recovery (passive or light cycling with no load). The HIIT group performed four bouts of four-minute efforts at 90–95% of peak heart rate (HRpeak) interspersed with three minutes of active recovery at 50–60% of HRpeak. At baseline and after eight weeks of intervention, waist circumference, skinfolds (triceps, subscapular, suprailiac, abdominal and thigh), body mass and BMI were measured by standard procedures and cardiorespiratory fitness was assessed by cardiorespiratory graded exertion test on an electromagnetically braked cycle ergometer.
Results: The HIIT and SIT groups improved, respectively, 14.5±22.9% (P<0.001) and 16.9±23.4% (P<0.001) in VO2peak after intervention, with no significant difference between groups. Sum of skinfolds reduced 15.8±7.9% and 22.2±6.4% from baseline (P<0.001) for HIIT and SIT groups, respectively, with greater reduction for SIT compared to HIIT (P<0.05). There were statistically significant decreases in waist circumference (P<0.001) for the HIIT (-3.1±1.1%) and SIT (-3.3±1.8%) groups, with no significant difference between groups. Only SIT showed significant reductions in body weight and BMI (p<0.05).
Conclusions: Eight weeks of HIIT and SIT resulted in improvements in anthropometric measures and cardiorespiratory fitness, even in the absence of changes in dietary intake. In addition, the SIT protocol induced greater reductions than the HIIT protocol in the sum of skinfolds. Both protocols appear to be time-efficient interventions, since the HIIT and SIT protocols took 33 and 23 minutes (16 and 2 minutes of effective training) per session, respectively.

Full text

ORIGINAL RESEARCH
published: 05 December 2018
doi: 10.3389/fphys.2018.01738
Frontiers in Physiology | www.frontiersin.org 1December 2018 | Volume 9 | Article 1738
Edited by:
Robinson Ramírez-Vélez,
Universidad del Rosario, Colombia
Reviewed by:
Elvira Padua,
Università telematica San Raffaele,
Italy
Justin Keogh,
Bond University, Australia
Giovani Dos Santos Cunha,
Universidade Federal do Rio Grande
do Sul (UFRGS), Brazil
*Correspondence:
Paulo Gentil
paulogentil@hotmail.com
Specialty section:
This article was submitted to
Exercise Physiology,
a section of the journal
Frontiers in Physiology
Received: 27 June 2018
Accepted: 19 November 2018
Published: 05 December 2018
Citation:
Naves JPA, Viana RB, Rebelo ACS,
de Lira CAB, Pimentel GD, Lobo PCB,
de Oliveira JC, Ramirez-Campillo R
and Gentil P (2018) Effects of
High-Intensity Interval Training vs.
Sprint Interval Training on
Anthropometric Measures and
Cardiorespiratory Fitness in Healthy
Young Women. Front. Physiol. 9:1738.
doi: 10.3389/fphys.2018.01738
Effects of High-Intensity Interval
Training vs. Sprint Interval Training
on Anthropometric Measures and
Cardiorespiratory Fitness in Healthy
Young Women
João Pedro A. Naves 1, Ricardo B. Viana 1, Ana Cristina S. Rebelo 2,
Claudio Andre B. de Lira 1, Gustavo D. Pimentel 3, Patrícia Cristina B. Lobo 3,
Jordana C. de Oliveira 2, Rodrigo Ramirez-Campillo 4and Paulo Gentil 1
*
1Department of Physical Education, Faculty of Physical Education and Dance, Federal University of Goiás, Goiânia, Brazil,
2Department of Morphology, Biological Sciences Institute, Federal University of Goiás, Goiânia, Brazil, 3Clinical and Sports
Nutrition Research Laboratory, Nutrition Faculty, Federal University of Goiás, Goiânia, Brazil, 4Laboratory of Measurement
and Assessment in Sport, Department of Physical Activity Sciences, Research Nucleus in Health, Physical Activity and Sport,
Universidad de Los Lagos, Osorno, Chile
Purpose: To compare the effects of 8 weeks of two types of interval training, Sprint
Interval Training (SIT) and High-Intensity Interval Training (HIIT), on anthropometric
measures and cardiorespiratory fitness in healthy young women.
Methods: A randomized clinical trial in which 49 young active women [age, 30.4 ±
6.1 years; body mass index, 24.8 ±3.1 kg.m−2; peak oxygen consumption (VO2peak),
34.9±7.5 mL.kg−1.min−1] were randomly allocated into a SIT or HIIT group. The SIT
group performed four bouts of 30 s all-out cycling efforts interspersed with 4 min of
recovery (passive or light cycling with no load). The HIIT group performed four bouts
of 4-min efforts at 90–95% of peak heart rate (HRpeak) interspersed with 3 min of active
recovery at 50–60% of HRpeak. At baseline and after 8 weeks of intervention, waist
circumference, skinfolds (triceps, subscapular, suprailiac, abdominal, and thigh), body
mass and BMI were measured by standard procedures and cardiorespiratory fitness
was assessed by cardiorespiratory graded exertion test on an electromagnetically braked
cycle ergometer.
Results: The HIIT and SIT groups improved, respectively, 14.5 ±22.9% (P<0.001) and
16.9 ±23.4% (P<0.001) in VO2peak after intervention, with no significant difference
between groups. Sum of skinfolds reduced 15.8 ±7.9 and 22.2 ±6.4 from baseline
(P<0.001) for HIIT and SIT groups, respectively, with greater reduction for SIT compared
to HIIT (P<0.05). There were statistically significant decreases in waist circumference
(P<0.001) for the HIIT (−3.1 ±1.1%) and SIT (−3.3 ±1.8%) groups, with no significant
difference between groups. Only SIT showed significant reductions in body weight and
BMI (p<0.05).
Conclusions: Eight weeks of HIIT and SIT resulted in improvements in anthropometric
measures and cardiorespiratory fitness, even in the absence of changes in dietary intake.

Naves et al. HIIT vs. SIT: Anthropometric Measures and Fitness
In addition, the SIT protocol induced greater reductions than the HIIT protocol in the
sum of skinfolds. Both protocols appear to be time-efficient interventions, since the HIIT
and SIT protocols took 33 and 23 min (16 and 2 min of effective training) per session,
respectively.
Keywords: interval training, exercise, physical fitness, weight loss, cardiorespiratory fitness
INTRODUCTION
Interval training (IT) has been used for many decades with
different purposes, such as improvements to health parameters
(Wisløff et al., 2009; Kemi and Wisløff, 2010; Weston et al., 2013),
performance (McMillan et al., 2005; Gibala and McGee, 2008;
Gibala and Jones, 2013), and weight loss (Trapp et al., 2008;
Boutcher, 2011). Typically, IT implicates alternating periods of
relatively intense exercise with periods of lower-intensity effort or
complete rest for recovery (Gibala et al., 2014). Two of the most
common forms of IT are high-intensity interval training (HIIT)
and sprint interval training (SIT) (Gibala et al., 2014). The target
intensity during HIIT is usually “near maximal” or between 80
and 100% of maximal heart rate (HRmax) or maximum oxygen
consumption (VO2max), while SIT protocols usually involve
“all-out” efforts (Buchheit and Laursen, 2013).
Regarding the applications for weight loss, a review found that
fat loss after IT was greater than that after moderate-interval
continuous training (MICT) (60–80% of HRmax) (Boutcher,
2011). Moreover, studies on the effects of IT on post exercise
energy expenditure and fat oxidation (Treuth et al., 1996;
Laforgia et al., 1997; Greer et al., 2015) and weight loss (Tremblay
and Bouchard, 1994; Trapp et al., 2008; Burgos et al., 2017)
suggest that IT is more efficient than continuous models,
including MICT (Zhang et al., 2017). In fact, weight loss seems
to be higher, even if the caloric expenditure obtained with IT is
lower than (Tremblay and Bouchard, 1994) or equal to that of
MICT (Trapp et al., 2008). These results can be attributed to the
effects of IT on metabolism, promoting increased resting energy
expenditure and fat utilization (Kiens and Richter, 1998; Knab
et al., 2011; Kelly et al., 2013). Moreover, it seems that fat loss
is greater at higher exercise intensities (Tremblay and Bouchard,
1994). However, we were not able to find any study in relation to
the effects of SIT vs. HIIT on body composition in healthy young
women.
Considering the meaningful differences between IT variations
(Viana et al., 2018), it is important to analyze each protocol
in detail to get further insight on how variations would be
more suitable for a specific purpose in a given population.
Two of the most popular types of interval training protocol
are those presented by the Wisløff group (Wisløff et al., 2007)
and the Gibala group (Gibala et al., 2006), which can be
classified as HIIT and SIT, respectively. Such protocols have
gained notoriety for inducing cardiovascular and performance
adaptations equal to or greater than those induced by MICT
despite the lower volume of exercise. However, despite their
popularity, the effects of these protocols on markers of body
fatness need more clarification, and we are not aware of any
comparison between them. Thus, the aim of the present study
was to compare the effects of two types of IT (HIIT and SIT) on
anthropometric measures and cardiorespiratory fitness in healthy
young women.
MATERIALS AND METHODS
Study Design
The participants performed a HIIT or SIT protocol on a
mechanically braked cycle ergometer (Evolution SR, Schwinn,
USA) three times per week (Monday, Wednesday, and Friday)
for 8 weeks. One week before and 1 week after the intervention,
anthropometric evaluation, and a cardiorespiratory graded
exertion test (GXT) on a cycle ergometer were performed. The
volunteers were asked to not perform any other exercise activity
apart from the study protocol. The HIIT and SIT sessions
lasted 33 and 23 min, respectively. Due to the nature of the
interventions, it was not possible to blind the participants and
supervisors involved in the study. However, all assessments were
completed by blinded technicians. When a participant missed
fewer than three training sessions non-consecutively, the sessions
were replaced at the end of the period, but when three or more
sessions were missed, the participant was excluded from the
study.
Participants were advised to maintain their usual diet. Six 24-
h dietary recalls were performed at the beginning and end of the
intervention.
Participants
Forty-nine healthy women (Table 1) were recruited through
advertisements on social media and through word of mouth.
The following inclusion criteria were adopted: (i) body mass
index (BMI) between 18.5 and 29.9 kg.m−2, (ii) physically active
(≥150 min per week), (iii) pre-menopause, and (iv) not using
stimulants (e.g., caffeine, energy drinks, or thermogenic drugs).
Exclusion criteria were (i) contraindications to physical activity
assessed through the Physical Activity Readiness Questionnaire—
PAR-Q (Canadian Society for Exercise Physiology, 2002) and
(ii) any history of interventions for body mass loss (surgical
or hormonal treatment). Figure 1 shows the flow diagram with
all reasons for participants’ exclusion and abandonment of the
intervention.
All participants were informed of the potential risks and
benefits of the study and signed an informed consent form.
All experimental procedures were approved by the University
Ethics Committee (Approval number: 1.542.353). The study
conformed to the principles outlined in the Declaration of
Helsinki.
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Naves et al. HIIT vs. SIT: Anthropometric Measures and Fitness
TABLE 1 | Anthropometric and physiological characteristics of participants before and after 8 weeks of exercise training.
HIIT (n=25) SIT (n=24) Between
groups
(Pre)
Between
groups
(Pre-Post)
Pre Post ES PPre Post ES P P P
Age (years) 31.0 ±6.0 – – – 29.8 ±6.4 – – – 0.823 –
Height (m) 1.63 ±0.05 – – – 1.64 ±0.05 – – – 0.814 –
HRpeak (beats/min) 182 ±10 – – – 179 ±13 – – – 0.021 –
Body mass (kg) 66.3 ±10.2 65.9 ±9.9 −0.039(trivial) 0.280 67.8 ±8.1 67.0 ±8.1 −0.098(trivial) 0.015 0.156 0.360
Body mass index (kg.m−2) 24.5 ±3.3 24.4 ±3.2 −0.030(trivial) 0.402 25.2 ±3.2 24.9 ±3.3 −0.092(trivial) 0.019 0.950 0.293
Skinfolds (mm)
Triceps 22.0 ±6.3 18.8 ±5.2 −0.553(medium) <0.001 27.6 ±7.7 22.8 ±5.6 −0.712(medium) <0.001 0.213 0.909
Subscapular 21.2 ±9.9 17.3 ±7.3 −0.448(small) <0.001 27.4 ±8.6 20.3 ±5.8 −0.967(large) <0.001 0.393 0.074
Suprailiac 21.0 ±11.2 17.4 ±8.8 −0.357(small) <0.001 30.4 ±8.3 23.2 ±5.3 −1.033(large) <0.001 0.084 0.374
Abdominal 25.0 ±11.2 19.7 ±8.5 −0.533(medium) <0.001 35.5 ±6.9 25.8 ±4.7 −1.643(large) <0.001 0.029 0.111
Thigh 32.7 ±8.6 28.2 ±7.7 −0.551(medium) <0.001 38.3 ±7.9 30.7 ±6.8 −1.031(large) <0.001 0.883 0.020
Pskinfolds (mm) 121.9 ±43.8 101.4 ±34.6 −0.519(medium) <0.001 159.1 ±35.1 122.8 ±24.8 −1.194(large) <0.001 0.310 0.045
Waist circumference (cm) 74.6 ±8.0 72.3 ±7.8 −0.291(small) <0.001 77.6 ±7.0 75.1 ±6.8 −0.362(small) <0.001 0.483 0.739
VO2peak (mL.kg−1.min−1) 37.7 ±7.2 42.1 ±5.5 0.686(medium) <0.001 32.0 ±7.2 36.5 ±6.7 0.647(medium) <0.001 0.860 0.097
iVO2peak (watts) 159 ±31 167 ±27 0.275(small) 0.028 138 ±26 149 ±20 0.474(small) 0.003 0.303 0.402
Data are expressed as means ±standard deviation. p (values) for within-group (time) effect and interaction (time ×group) effect. ES, effect size; HIIT, high-intensity interval training; SIT,
sprint interval training; HRpeak, peak heart rate; PSkinfolds, sum of five skinfolds; VO2peak, peak oxygen uptake; iVO2peak, intensity associated to peak oxygen uptake.
Interval Training Intervention
During the study period, the participants were requested to
avoid any form of physical activity besides the study protocols.
The research team constantly monitored and questioned the
participants to verify if they complied with the recommendations
and to record any adverse event (dizziness, nausea, muscle
soreness. . . ). The intervention lasted 8 weeks, with three sessions
per week (Monday, Wednesday, and Friday).
The SIT group performed a warm-up of 5 min at light load
and self-selected speed, followed by four 30-s all-out bouts
interspersed with 4 min of recovery (passive or light cycling
with no load). If necessary, the load was adjusted to allow the
participant to maintain cycling cadence ≥60 rpm.
The HIIT protocol consisted of a warm-up of 5 min at 50%
of peak heart rate (HRpeak) (FT1, Polar, Finland), followed by
four bouts of 4-min efforts at 90–95% of HRpeak interspersed
with 3 min of active recovery at 50–60% of HRpeak. The load
was adjusted when the HR deviated from the established zone.
During recovery, the cadence was self-selected and the load was
reduced to the minimum by one of the researchers. All training
sessions for both groups were directly supervised by professionals
experienced with the training prescription in a ratio of one
supervisor per volunteer. During both protocols, standardized
verbal stimuli were offered.
Outcomes Measures
Cardiorespiratory Graded Exertion Test
Participants performed a GXT on an electromagnetically braked
cycle ergometer (CG04, Inbramed, Brazil) to determine their
peak oxygen consumption (VO2peak), intensity associated with
VO2peak (iVO2peak), and HRpeak. Testing was performed 3–
7 days before and after the training period. Briefly, following
a 2-min warm-up at 50 W, the load was increased by 25 W
every minute until volitional exhaustion, defined as the point
at which the participant was not able to sustain a cadence
≥50 rpm. Participants wore a mouthpiece and nose clip, and
gas was collected breath by breath by a specific pneumotach
connected to the analyzer. VO2and carbon dioxide production
(VCO2) were analyzed by a metabolic gas collection system
(VO2000, MedGraphics, USA) every 10 s. After exhaustion, the
load was reduced to 50 W for 2 min of recovery. The highest VO2
measured at the cessation of exercise was called VO2peak because
no participants reached the criteria for VO2max (Howley, 2007).
To identify iVO2peak, the highest workload was considered.
HR was constantly monitored throughout the test using a
HR monitor (Polar RS800, Kempele, Finland). The rating of
perceived exertion (RPE) was assessed every minute using the
6–20 Borg scale (Borg, 1982).
Anthropometric Measures
Each participant’s height and body mass were measured to
the nearest 0.1 cm and 0.1 kg, respectively. All anthropometric
measurements (3–7 days before and after the training period)
were carried out at the same phase of the menstrual cycle
(follicular phase) and by the same examiner (to avoid
inter-examiner variability), who was previously trained and
experienced in these types of measurements and was blinded
to group allocation. BMI was calculated from these data.
Waist circumference was measured at the level of the smallest
circumference above the umbilicus and below the xiphoid
appendix (American College of Sports Medicine, 2011).
Five subcutaneous skinfolds (triceps, subscapular, suprailiac,
abdominal, and thigh) were measured on the right side of
the body using an adipometer (Premier, Cescorf, Brazil) and
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Naves et al. HIIT vs. SIT: Anthropometric Measures and Fitness
FIGURE 1 | Flow diagram of participants through all phases of the trial.
following the recommendations of the American College of
Sports Medicine (2011). The mean of three valid measurements
obtained at each skinfold site was used in the analysis. Intraclass
correlation coefficient was 0.991 for triceps, 0.993 for subscapular,
0.996 for suprailiac, 0.995 for abdominal, and 0.986 the thigh
skinfold. The Typical Error Measurement (TEM) was 0.7 mm
for triceps, 0.8 mm for subscapular, 0.7 mm suprailiac, 0.7 mm
for abdominal, 1.0 mm for thigh, and 11.2 mm for sum of five
skinfolds (Σskinfolds).
Dietary Intake Evaluation
Six dietary recalls were applied by a dietitian, with three 24-
h food recalls in the first and three in the eighth week. The
quantification of the home measures to their equivalent in
grams was made according to values of the Table for Evaluation
of Food Consumption in Domestic Measures (Pinheiro et al.,
2009).
Food intake was calculated in the Dietpro R
Clinical software,
version 5.8.1 (S. SISTEMAS, Minas Gerais, Brazil), using as
reference the values of the Food Composition Table (Philippi,
2015), Brazilian Food Composition Table (TACO) (Núcleo de
Estudos e Pesquisas em Alimentação, 2011), and United States
Department of Agriculture (USDA). Total energy (kcal),
carbohydrates (g), proteins (g), and lipids (g) were obtained.
After the quantification, the mean initial and final intakes were
compared for the results.
Statistical Analysis
Data were entered into an Excel spreadsheet (Microsoft) and
imported into Statistical Package for the Social Sciences (version
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Naves et al. HIIT vs. SIT: Anthropometric Measures and Fitness
20.0; SPSS Inc., Chicago, IL). Based on tests and retests for 49
participants, the standard error of the measurement (SEM) was
calculated for triceps, subscapular, suprailiac, abdominal, and
thigh skinfolds as previously described (Barbalho et al., 2017).
Responsiveness was defined as changes that exceeded two times
the SEM in favor of beneficial changes, since this response is
supposed to be a true physiological adaptation beyond what
might be expected to result from technical and/or biological
variability (Barbalho et al., 2017). The responsiveness threshold
was set at 0.7 mm for triceps, 0.8mm for subscapular, 0.7 mm for
suprailiac, 0.7 mm for abdominal, 1.0 mm for thigh, and 11.2 mm
for sum of skinfolds. Paired t-tests were used to compare pre and
post values of anthropometry measures, ˙
VO2peak, and i˙
VO2peak
within each group. Analysis of covariance (ANCOVA) was used
to compare post-intervention values, using baseline values as
covariate. Pearson’s chi-squared test was used to analyze the
distribution of R and NR between groups. Measures of the effect
size (ES) for differences were calculated by dividing the mean
difference by the standard deviation (SD) of the pre-training
measurement. The magnitude of the ES was classified according
to the following criteria: d<0.2 was considered “trivial,”
0.2 <d<0.5 was considered “small,” 0.5 <d<0.8 represented
“medium,” and d >0.8 constituted “large” (Cohen, 1988).
Data are presented as numbers and percentages for categorical
variables and are expressed as mean ±SD. A significance level of
0.05 was adopted for all statistical tests.
RESULTS
Adherence to training in HIIT and SIT groups was 76.5 and
74.2%, respectively. Only one participant from each group
needed to replace one exercise session at the end of the
intervention period. Moreover, one participant from the HIIT
group reported vomiting and two participants from the SIT
group reported dizziness after a training session.
Cardiorespiratory Fitness
The HIIT and SIT groups improved (P<0.001) VO2peak by 14.5
±22.9 and 16.9 ±23.4%, respectively, as well as iVO2peak by 6.2
±12.2 and 10.6 ±18.1%, respectively (Table 1). The ANCOVA
revealed no significant difference between groups for the changes
in VO2peak and iVO2peak (P>0.05).
Anthropometric Measures
Decreases (P<0.05) in body mass (−1.2 ±2.6 kg) and BMI
(−1.2 ±2.6 kg.m−2) were observed only for the SIT group
(Table 1).
The sum of the five skinfolds was reduced by 15.8 ±7.9
and 22.2 ±6.4% from baseline (P<0.001) for the HIIT
and SIT groups, respectively (Figure 2 and Table 1). The results
of ANCOVA revealed that the reductions were greater for
SIT than for HIIT. The HIIT and SIT groups significantly
decreased (P<0.001) triceps (−13.8 ±9.4 and −16.4 ±7.8%),
subscapular (−15.7 ±11.8 and −24.0 ±10.6%), suprailiac
(−13.8 ±14.9 and −22.0 ±9.5%), abdominal (−19.8 ±10.4
and −26.8 ±6.7%), and thigh skinfolds (−13.6 ±8.0 and
−19.6 ±8.1%) (Table 1). There were no significant differences
FIGURE 2 | Changes in the sum of skinfolds (1Σ 5 skinfolds) induced by High
intensity interval training (HIIT, n=25) and Sprint interval training (SIT, n=24).
Data are expressed as means ±standard deviation*P<0.05.
between the groups (P>0.05) in triceps, subscapular, suprailiac,
and abdominal skinfold reductions. However, decreases in thigh
skinfold were greater for the SIT group (P=0.020). Waist
circumference was reduced (P<0.001) for the HIIT (−3.1 ±
1.1%) and the SIT groups (−3.3 ±1.8%), with no significant
difference (P=0.739) between groups (Table 1).
Dietary Intake
No significant difference (P>0.05) was found in dietary intake
between the HIIT and SIT groups at baseline and after 8 weeks of
training. In addition, no significant difference was found after the
intervention period for both groups (Table 2).
Responders and Non-responders
Forty-one participants were classified as responders (R) to triceps
skinfold (20 in the HIIT and 21 in the SIT group), 41 to
subscapular skinfold (20 in HIIT and 21 in SIT), 44 to suprailiac
(21 in HIIT and 23 in SIT), 45 to abdominal (21 in HIIT and 24 in
SIT), 47 to thigh (23 in HIIT and six in 24), and 43 to Pskinfolds
(20 in HIIT and 23 in SIT) (Figure 3). The SIT group presented
more R in abdominal skinfolds when compared with the HIIT
group; however, no significant difference was found (P>0.05) in
the prevalence of R between HIIT and SIT protocols for triceps,
subscapular, suprailiac, thigh, and Pskinfolds.
DISCUSSION
To the best of our knowledge, this is the first study to compare
the effects of HIIT and SIT on anthropometric measures and
cardiorespiratory fitness in healthy young females. Our results
suggest that 8 weeks of HIIT and SIT improve markers of
body fatness and cardiorespiratory fitness, even in the absence
of changes in dietary intake. However, our results suggest that
the SIT protocol is more efficient than the HIIT protocol for
some parameters. In addition, we found greater prevalence of
responders for abdominal and suprailiac skinfolds in the SIT
group than in the HIIT group.
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Naves et al. HIIT vs. SIT: Anthropometric Measures and Fitness
TABLE 2 | Dietary intake of participants before and after 8 weeks of exercise training.
HIIT (n=25) SIT (n=24) Between
groups
Pre Post ES PPre Post ES P P
Energy intake (kcal) 1594.6 ±429.9 1577.8 ±424.9 −0.039(trivial) 0.894 1442.8 ±657.1 1420.6 ±384.8 −0.041(trivial) 0.863 0.243
Carbohydrate (g) 184.7 ±67.5 186.1 ±65.8 0.021(trivial) 0.930 171.9 ±79.6 163.5 ±56.6 −0.121(trivial) 0.620 0.258
Protein (g) 75.5 ±23.8 69.9 ±20.4 −0.252(small) 0.272 64.4 ±21.6 65.6 ±21.6 0.055(trivial) 0.822 0.893
Lipids (g) 61.4 ±20.2 61.3 ±22.9 −0.004(trivial) 0.988 53.9 ±33.0 55.9 ±16.9 0.076(trivial) 0.762 0.420
Monounsaturated fat (g) 17.1 ±6.8 16.6 ±8.0 −0.067(trivial) 0.824 14.7 ±10.9 15.5 ±6.6 0.088(trivial) 0.729 0.645
Polyunsaturated fat (g) 9.3 ±5.0 9.5 ±4.1 0.043(trivial) 0.881 9.9 ±6.3 10.2 ±4.8 0.053(trivial) 0.876 0.594
Saturated fat (g) 17.0 ±7.2 16.3 ±6.8 0.099(trivial) 0.726 14.6 ±10.7 14.8 ±4.3 0.024(trivial) 0.946 0.469
Calcium (g) 501.7 ±266.5 536.8 ±235.6 0.139(small) 0.616 572.2 ±392.9 488.3 ±193 −0.271(small) 0.242 0.322
Sodium (g) 43.6 ±159.1 12.1 ±4.9 −0.279(small) 0.691 11.8 ±7.1 11.7 ±6.2 −0.015(trivial) 0.571 0.362
Dietary fiber (g) 1539.9 ±730.9 1628.5 ±566.1 0.135(trivial) 0.192 1575.6 ±962.9 1446.7 ±781.9 −0.146(trivial) 0.996 0.884
Data are expressed as means ±standard deviation. p (values) for within-group (time) effect and interaction (time ×group) effect. ES, effect size; HIIT, high-intensity interval training; SIT,
sprint interval training.
In agreement with previous studies showing that different
forms of IT significantly increased VO2max (Gibala et al., 2006;
Wisløff et al., 2007; Bacon et al., 2013; Sloth et al., 2013; Gist et al.,
2014), the present study found that 8 weeks of HIIT and SIT
increased VO2peak by 14.5 and 16.9%, respectively. Considering
that low cardiorespiratory fitness is a strong independent risk
factor for cardiovascular disease and all-cause mortality (Kodama
et al., 2009; Barry et al., 2014) and that “lack of time” is a
common barrier to regular exercise adoption (Weston et al.,
2013), IT might help to increase exercise adherence. While the
general recommendations suggest a minimum of 150 min of
moderate aerobic activity or vigorous exercise for 75 min per
week (World Health Organization, 2010), we found that with
only 23 min of SIT performed three times per week, it is possible
to increase cardiorespiratory fitness. Moreover, the increases for
both groups were similar to those found in previous studies
involving protocols with longer durations (Scribbans et al., 2016).
The cardiorespiratory fitness increases observed in the present
study are similar to those reported in previous IT interventions
(Trapp et al., 2008; Macpherson et al., 2011; Bagley et al., 2016;
Higgins et al., 2016). Bagley et al. (2016) submitted 17 women and
24 men to a SIT protocol (4 x 20 s sprints on a cycle ergometer
at 175% VO2max followed by 2 min of active recovery, three
times per week for 12 weeks) and found VO2max increased by
18.7 and 6.0% for women and men, respectively. In the study
of Higgins et al. (2016), 52 inactive, overweight/obese young
women performed one of two experimental interventions: SIT
(5–7 x 30 s sprints “all out” followed by 4 min of active recovery)
and continuous cycling at 60–70% of heart rate reserve. After 6
weeks, the SIT group increased VO2peak by 14.1%. The study of
Macpherson et al. (2011) involved men and women (n=10 per
group) training three times per week for 6 weeks with SIT (30 s
all-out running sprints on a manually driven treadmill, four to
six bouts per session, 4 min of recovery per bout) vs. MICT (65%
VO2max for 30 to 60 min). After the intervention, the SIT and
MICT groups showed increases of 11.5 and 12.5% in VO2peak.
These studies indicate that SIT, involving cycling and running,
provides an efficient stimulus to improve aerobic metabolism
despite its short duration. An important aspect is that the
previously mentioned studies (Macpherson et al., 2011; Bagley
et al., 2016; Higgins et al., 2016) also used active recovery. Active
recovery contributes to increased aerobic metabolic activity and
can also influence performance (Buchheit and Laursen, 2013). It
appears that active recovery may decrease muscle oxygenation
(Buchheit et al., 2009) and impair PCr resynthesis (Spencer
et al., 2006). In addition, the active recovery might decrease
the performance of the next effort when the intensity is ≥45%
iVO2max). Therefore, if active recovery is chosen, it should last
at least 3–4 min at a low intensity (Belcastro and Bonen, 1975)
to allow maintenance of the high intensity of exercise during the
following interval.
Both types of IT promoted reductions in body mass, markers
of subcutaneous fat (skinfolds) and waist circumference, which
is in agreement with the suggestion of Astorino and Schubert
(2018) that HIIT and SIT increase whole-body fat oxidation. An
important aspect of the present study is that the participants
did not present a statistically significant difference between the
groups in the pre-intervention period. In addition, our results
were similar to those of Hazell et al. (2014), who reported that 6
weeks of a running SIT protocol of similar intensity and duration
to the one used in our intervention reduced fat mass by 1.2 kg
with 0.5 kg reduction in body mass despite no changes in dietary
intake.
Previous studies using different forms of IT with longer
periods of training also found fat loss in postmenopausal women
with type II diabetes (Maillard et al., 2016), inactive young
women (Trapp et al., 2008; Panissa et al., 2016), overweight
men and women (Heydari et al., 2012; Higgins et al., 2016),
and mixed samples of young men and women (Tremblay and
Bouchard, 1994; Macpherson et al., 2011). One of the few studies
comparing different IT protocols (Tong et al., 2018) compared
the effects of SIT and HIIT in reducing abdominal visceral fat
in 46 obese women. The participants were assigned to one of
three experimental groups: SIT (6 s all-out sprint followed by a 9 s
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Naves et al. HIIT vs. SIT: Anthropometric Measures and Fitness
FIGURE 3 | Histogram of the relative changes in triceps (A), subscapular (B), suprailiac (C), abdominal (D) thigh (E), and Σ5 skinfolds (F) for each individual after 8
weeks interval training in young women.
passive recovery for 80 cycles), HIIT (4 min exercise bouts at an
intensity of 90% VO2max, followed by a 3-min passive recovery).
and Control group (no exercise). After 12 weeks, there was a
reduction in abdominal visceral and subcutaneous fat. However,
SIT group had lower reduction in subcutaneous abdominal fat
(−17.4 vs. 40.7 cm2) and trunk fat mass (1.2 vs. 2.0 kg) than
HIIT group. No difference was found between SIT and HIIT
for visceral abdominal fat, total fat mass, gynoid, and android
fat mass. Probably, the difference between the results present
by Tong et al. (2018) and our study was related to training
protocol, since the short duration of SIT in the study by Tong
et al. (6 vs. 30 s) might have lead to a less pronounced effect on
fat metabolism and post exercise energy expenditure (Islam et al.,
2017).
It is important to note that, according to our results, women
reduced the Σskinfolds without changes in dietary intake,
which is similar to results previously reported by Zhang et al.
(2017) and Trapp et al. (2008), who observed changes in body
composition after intervention with IT without changes in
dietary intake. Several studies have suggested that the increases
in post-exercise fat oxidation seem to be influenced by glycogen
depletion (Withers et al., 1991; Kiens and Richter, 1998), and
protocols that rely more on the glycolytic system might be
more advantageous in this aspect (Whyte et al., 2013; Tucker
et al., 2016). The higher reduction in the sum of skinfolds
promoted by SIT might be due an increased oxidation of fat
during the rest period, as previously reported (Withers et al.,
1991). In agreement with this, previous studies have shown that
IT protocols that lead to glycogen depletion result in increased
fat oxidation (Withers et al., 1991; Kiens and Richter, 1998;
Whyte et al., 2013; Tucker et al., 2016). Therefore, it appears
that restoration of glycogen has a metabolic priority during
recovery, leading to an increase in fat oxidation (Kiens and
Richter, 1998).
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Naves et al. HIIT vs. SIT: Anthropometric Measures and Fitness
One important aspect of the present study is that training
was performed in a standard fitness facility using commercially
available stationary bicycles, which is important to its practical
application. However, one important aspect that limits the
generalization of our results is that our training sessions were
closely supervised at a 1:1 ratio. Considering that previous
studies show that the results of an exercise intervention depend
on supervision (Gentil and Bottaro, 2010; Knab et al., 2011;
Ramírez-Campillo et al., 2017), the current findings might not
be reproducible in unsupervised situations. Another apparent
limitation is that our study did not identify the responders and
non-responders to VO2peak. In addition, lacks a control group
that did not perform any type of exercise and the lack of a more
accurate instrument for measuring body composition. However,
since the participants did not change their nutritional habits and
were evaluated at the same phase of the menstrual cycle, seasonal
variations are unlikely to have been able to alter the results. As
for the skinfolds measures, whilst we recognize that it might be
a limited method to estimated body composition, it has been
shown to be a highly reproduceable and widely used method
(Jackson et al., 2009; Silva et al., 2009; Alves et al., 2017; Astorino
et al., 2018); therefore, it is our opinion that it might be suitable
to access the changes induced by an intervention on markers of
body fatness.
CONCLUSION
Both HIIT and SIT protocols increased cardiorespiratory fitness
and promoted reductions in adiposity indicators in healthy
young women, even in the absence of dietary changes. Moreover,
the SIT protocol induced greater improvements in some markers
of body fatness than the HIIT protocol.
Considering the low physical activity levels in the population,
the high prevalence of excessive body fat, and the fact
that lack of time is a common barrier to exercise adoption
(Weston et al., 2013; Vella et al., 2017), both protocols
appear to be viable alternatives, since HIIT and SIT protocols
lasted 33 and 23 min, respectively. In addition, one advantage
of SIT is that it does not need complex tests to define
the intensity of the exercise, which might contribute to its
widespread use in cases where no clinical contraindications
exist.
AUTHOR CONTRIBUTIONS
JN and PG conceived and designed the research. JN, PL, and JdO
performed experiments. JN, RV, and PG analyzed data. JN, RV,
AR, CdL, GP, RR-C, and PG interpreted results of experiments.
JN and PG drafted manuscript. AR, CdL, GP, RR-C, and PG
edited and revised manuscript. All authors approved final version
of manuscript.
FUNDING
This work was supported by the Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior (CAPES,
Brazil).
ACKNOWLEDGMENTS
We would like to thank all participants who volunteered their
time to participate in the study. We would like to thank Allysson
Brayan Alves de Lima, Jean Mateus Ferreira Maximiano, Marco
Aurélio Oliveira Braga, and Pablo André Naves Prudente for their
contributions and commitment at the study site. We would like to
thank Eduardo Netto (BodyTech) for providing logistical support
for the research. Finally, we would like to thank the collaborating
authors for their contributions.
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Conflict of Interest Statement: 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.
The handling Editor declared a past co-authorship with the authors RR-C and PG.
Copyright © 2018 Naves, Viana, Rebelo, de Lira, Pimentel, Lobo, de Oliveira,
Ramirez-Campillo and Gentil. This is an open-access article distributed under the
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