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The purpose of the study was to examine the effects of sprint interval training (SIT) and moderate-intensity continuous cycle training (MICT), with equal estimated energy expenditure during training on body composition and aerobic capacity. Body composition measured via dual-energy X-ray absorptiometry and aerobic capacity were assessed following 6 weeks of training in previously inactive overweight/obese young women (n = 52; age, 20.4 ± 1.5 years; body mass index, 30.3 ± 4.5 kg·m⁻², 67.3% white). Training was performed in a group-exercise format that mimicked cycling classes offered by commercial fitness facilities, and included 3 weekly sessions of either 30-s “all-out” sprints followed by 4 min of active recovery (SIT), or continuous cycling at 60%–70% heart rate reserve to expend a similar amount of energy. Participants were randomized to SIT or MICT, attended a similar number of sessions (15.0 ± 1.5 sessions vs. 15.8 ± 1.9 sessions, P = 0.097) and expended a similar amount of energy (541.8 ± 104.6 kJ·session⁻¹ vs. 553.5 ± 138.1 kJ·session⁻¹, P = 0.250). Without significant changes in body mass (P > 0.05), greater relative reductions occurred in SIT than in MICT in total fat mass (3.6% ± 5.6% vs. 0.6% ± 3.9%, P = 0.007), and android fat mass (6.6% ± 6.9% vs. 0.7% ± 6.5%, P = 0.002). Aerobic capacity (mL·kg⁻¹·min⁻¹) increased significantly following both interventions (P < 0.05), but the relative increase was 2-fold greater in SIT than in MICT (14.09% ± 10.31% vs. 7.06% ± 7.81%, P < 0.001). In conclusion, sprint-interval cycling reduces adiposity and increases aerobic capacity more than continuous moderate-intensity cycling of equal estimated energy expenditure in overweight/obese young women.
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Sprint interval and moderate-intensity cycling
training differentially affect adiposity and aerobic
capacity in overweight young-adult women.
Authors: Simon Higgins1; Michael V. Fedewa1,2; Elizabeth D. Hathaway1; Michael D.
Schmidt1; Ellen M. Evans1
Corresponding Author: Simon Higgins, Department of Kinesiology, Office 101D, Ramsey
Center, 330 River Road, University of Georgia, Athens, GA 30602-6554. Telephone: 706-461-
6776. E-mail: sh@uga.edu
Author Affiliations:
1 Department of Kinesiology, University of Georgia, 330 River Road, Athens, GA 30602-6554.
Email: Simon Higgins sh@uga.edu, Elizabeth D. Hathaway lizhath@uga.edu, Michael D.
Schmidt schmidtm@uga.edu, and Ellen M. Evans emevans@uga.edu.
2Department of Kinesiology, The University of Alabama, 2003 Moore Hall, Box 870312,
Tuscaloosa, AL 35487-0231. E-mail: Michael V. Fedewa - mvfedewa@ua.edu
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Abstract
Purpose: To examine the effects of sprint interval training (SIT) and moderate-intensity
continuous cycle training (MICT), with equal estimated energy expenditure during training, on
body composition and aerobic capacity. Methods: Body composition measured via dual-energy
x-ray absorptiometry and aerobic capacity (VO2peak) were assessed following 6 weeks of training
in previously inactive overweight/obese young women (n=52, 20.4 ± 1.5 yr, 30.3 ± 4.5 kg·m-2,
67.3% white). Training was performed in a group-exercise format that mimicked cycling classes
offered by commercial fitness facilities, and included 3 weekly sessions of either 30-second all-
out sprints followed by 4 minutes of active recovery (SIT), or continuous cycling at 60-70%
heart rate reserve to expend a similar amount of energy. Results: Participants were randomized to
SIT or MICT, attended a similar number of sessions (15.0 ± 1.5 sessions vs. 15.8 ± 1.9 sessions,
P=.097) and expended a similar amount of energy (541.8 ± 104.6 kJ·session-1 vs. 553.5 ± 138.1
kJ·session-1, P=.250). Without significant changes in body mass (P>.05), greater relative
reductions occurred in SIT than in MICT in total fat mass (3.6 ± 5.6% vs. 0.6 ± 3.9%, P=.007)
and android fat mass (6.6 ± 6.9% vs. 0.7 ± 6.5%, P=.002). Aerobic capacity (mL·kg-1·min-1)
increased significantly following both interventions (P<.05), but the relative increase was 2-fold
greater in SIT than in MICT (14.09 ± 10.31% vs. 7.06 ± 7.81%, P<.001). Conclusion: Sprint
interval cycling reduces adiposity and increases aerobic capacity more than continuous
moderate-intensity cycling of equal estimated energy expenditure in overweight/obese young
women.
Keywords: High-intensity, Moderate-intensity, Central Adiposity, Equal Energy Expenditure,
Body Composition.
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Introduction
High-intensity interval training (HIIT) is a mode of exercise that is characterized by brief,
intermittent bursts of vigorous activity, interspersed by periods of rest or low-intensity exercise
(Gibala et al., 2012). HIIT has been investigated in many populations with consistent
improvements in body composition (Boutcher, 2011; Heydari et al., 2012) and aerobic capacity
(Gist et al., 2013; Sloth et al., 2013; Trilk et al., 2011; Weston et al., 2014). It has been suggested
that HIIT may be more efficient than traditional moderate-intensity continuous exercise training
protocols (MICT), producing greater adaptation from a similar training duration, comparable to
that produced by high-volume endurance-type training (Gillen and Gibala, 2014). The popularity
of HIIT reaches beyond the physiological adaptations (Gibala and McGee, 2008), with research
suggesting that it may also be more enjoyable than MICT (Bartlett et al., 2011). These
advantages give HIIT the potential to have a greater adherence rate than conventional exercise
interventions (Jung et al., 2015).
A category of HIIT which employs bouts of efforts at an even higher intensity and power
output than traditional HIIT protocols is sprint interval training (SIT). A typical SIT protocol
includes 30-second ‘all out’ efforts followed by 4 minutes of active recovery at a low-intensity
(Freese et al., 2015; Gibala et al., 2006). The effects of SIT have been explored in healthy
populations (Hazell et al., 2014; Macpherson et al., 2011; Whyte et al., 2010), and in some
clinical populations (Gibala et al., 2012). With regard to overweight/obese women who are
underrepresented in the SIT literature, positive effects on aerobic capacity and cardiovascular
function, post-exercise blood lipids, and perceived health status and mood have been reported
(Freese et al., 2014; Freese et al., 2015; Trilk et al., 2011). While studies have shown that the
benefits of SIT are similar to those of continuous exercise involving a greater volume of work in
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different populations (Gist et al., 2013; Kessler et al., 2012), the feasibility of overweight/obese
women adhering to these ‘all out’ efforts is unclear, as are the relative effects of the two types of
training when energy expenditure during training is equal. It is likely that in most studies, greater
effects of the higher exercise intensity and power output of SIT have been offset by greater
energy expenditure in the continuous training exercise regimens to which they have been
compared, resulting in relatively similar changes in outcomes of interest.
The ability of continuous exercise training to facilitate weight loss and positive body
composition change, in the absence of dietary compensation, is well established (Swift et al.,
2014). Studies examining SIT suggest similar effects (Gibala and McGee, 2008), with the
potential for greater benefits to body composition (Boutcher, 2011) than MICT. The few
reported SIT interventions in women have used training durations of 6-15 weeks (Hazell et al.,
2014; Trapp et al., 2008) and reported significant reductions in weight and adiposity. Moreover,
there is a small amount of research comparing SIT to MICT in inactive overweight/obese
women; one study to do so did not ensure equal exercise energy expenditure during training
(Keating et al., 2014). Indeed, total energy expenditure during an exercise session is a key
mechanism responsible for weight and body composition changes (Swift et al., 2014); however,
few studies involving SIT have controlled for this factor making it difficult to compare the
independent effects of exercise intensity on body composition. One study to investigate the
effects of exercise intensity on body composition showed that high-intensity continuous exercise,
matched on energy expenditure with a lower-intensity regimen, led to greater losses of visceral
fat and abdominal subcutaneous fat over 16 weeks in obese middle-aged women (Irving et al.,
2008); however, both regimens used continuous exercise protocols. Contrary to these findings,
some have argued that it is the volume, not the intensity, of exercise that leads to reductions in
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abdominal adiposity (Ross et al., 2015), thus, the potential for exercise intensity to mediate
magnitude of fat loss warrants further research.
It is also well established that aerobic exercise training improves aerobic capacity (Garber
et al., 2011; Gormley et al., 2008). Recent work comparing the relative effects of SIT and MICT
interventions on aerobic capacity in sedentary adults over 6 (Burgomaster et al., 2008; Cocks et
al., 2013), 12 (Keating et al., 2014), and 15 weeks (Trapp et al., 2008) reported similar
significant improvements in aerobic capacity regardless of training mode. Interestingly, although
SIT interventions lasted up to 4 months, SIT interventions of just 2 weeks have also significantly
improved aerobic capacity by an average of 9.5% (Whyte et al., 2010). The positive relationship
between the intensity of aerobic work and the magnitude of improvement in aerobic capacity is
accepted (Gormley et al., 2008); however, if the greater increase in aerobic capacity following
higher intensity work holds true with a SIT protocol of an even higher intensity and intermittent
nature is unknown, especially when work or exercise energy expenditure is equal. As interval
training becomes increasingly popular, more research is needed regarding the effect of exercise
intensity/pattern on body composition and aerobic capacity when using a SIT protocol,
controlling for energy expenditure, especially in overweight/obese women as SIT is understudied
in this cohort.
Thus in this context, the primary aim of this study was to examine the relative effects of 6
weeks of SIT compared to a MICT protocol of equal estimated energy expenditure on body
composition and aerobic capacity in inactive overweight/obese young women. We hypothesized
that the magnitude of changes in body composition and aerobic capacity would be greater in SIT
compared to MICT under training conditions of equal estimated energy expenditure.
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Methods
Study Population and Recruitment. This analysis was part of a parent study examining
the effect of SIT and MICT protocols on markers of metabolic syndrome risk. Women (n=60)
were recruited via email and print advertising and excluded if they were: current smokers (within
6 months), physically active (≥30 minutes of physical activity, ≥2 days per week), not aged 18-
24 yr, not enrolled at the University, <25 kg·m-2 BMI, varsity athletes, currently pregnant, or had
been pregnant within the previous 12 months. Individuals with any health condition that could
have been exacerbated by the exercise protocols, or for which the exercise may be unsafe were
not enrolled. The Institutional Review Board of the university approved all aspects of the
protocol and all participants provided written informed consent prior to participation.
Study Design and Exercise Interventions. This research study used a parallel-arm design
with participants stratified on BMI and subsequently randomized to a SIT or MICT group. All
sessions were performed on a friction-loaded stationary cycle ergometer which has the ability to
estimate energy expenditure based on power output (Keiser, Keiser M3 Indoor Cycle, Fresno,
California). Heart rate (HR) during exercise, ratings of perceived exertion (RPE), and estimated
energy expenditure from the Keiser ergometers were recorded during each exercise session to
ensure compliance with the training protocol. Participants assigned to the SIT group began each
exercise session with a 4-minute warm-up at a low resistance and pedal rate, followed by
repeated 30-second ‘all out’ sprints interspersed with 4 minutes of active recovery pedaling
against minimal resistance at a low pedal frequency. This exercise stimulus equated to 2.5-3.5
minutes of near-maximal effort interspersed with 16-28 minutes of recovery, along with a brief
cool-down period following each session. Training progression increased the number of sprint
repetitions from 5 during weeks 1 and 2, to 6 sprints during weeks 3 and 4, and 7 sprints during
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weeks 5 and 6. Participants assigned to the MICT group were instructed to cycle continuously at
an intensity of 60-70% heart rate reserve (HRR) for 20-30 minutes, with the duration of training
sessions systematically increased to maintain equal estimated energy expenditure between
groups. Training protocols were performed 3 times weekly in a supervised group-training format
which were led by trained research staff and mimicked cycling classes offered by commercial
fitness facilities.
Weight Status and Body Composition. Standing height was measured by a stadiometer
(Seca 242, SECA Corp, Hamburg, Germany) to the nearest 0.1 cm. Body mass was measured
with a digital scale (Tanita WB-110A class III, Tanita Corporation, Tokyo, Japan) to the nearest
0.1 kg. Subsequently, BMI was calculated as mass divided by height squared (kg·m-2). Whole
body and regional composition including absolute and relative adiposity (%Fat) and mineral free
soft tissue mass, designated herein as fat free mass (FFM), were measured via dual x-ray
absorptiometry (DXA; Lunar iDXA, v 11.30.062, GE Healthcare, Madison, Wisconsin).
Aerobic Capacity. Aerobic capacity (VO2peak) was measured with a maximal exercise test
whereby participants pedaled continuously on an electronically braked cycle ergometer, with the
workload increasing every 3 minutes in a graded manner (Lode Excalibur Sport 2000, Lode
B.V., Groningen, Netherlands). Oxygen uptake was measured using a computerized indirect
calorimetry system (ParvoMedics True Max 2400; ParvoMedics, Sandy, UT). HR was measured
continuously throughout the test (Polar FT1; Polar Electro, Kempele, Finland). The test was
terminated when traditional termination criteria were met for respiratory exchange ratio, HR,
RPE, volitional fatigue, or pedal rate dropped below 50 rpm. Aerobic capacity is expressed in
absolute terms (L·min-1), relative to body mass (mL·kg-1·min-1), and relative to fat free mass
(mL·kgFFM-1·min-1).
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Habitual Energy Expenditure and Reported Energy Intake. Energy expenditure was
measured objectively over a minimum 3-day continuous period using the Actiheart monitor
(CamNtech, USA), which uses both HR and an omnidirectional accelerometer movement sensor.
Reported energy intake was measured using the Automated Self-Administered 24-hour Recall
(ASA24), a Web-based tool modeled on the USDA’s Automated Multiple Pass Method (Subar et
al., 2012). Energy intake and expenditure data were collected over 3-day periods including 2
weekdays and 1 weekend day at baseline and during weeks 5-6 of the intervention (endpoint),
and are reported as average values.
Statistical Analysis. Statistical analyses were performed using SPSS for Windows (SPSS
22.0, Chicago, IL). After testing for violation of assumptions using standard procedures, baseline
differences between groups were assessed using independent t-tests. Pre- to post-intervention
changes in outcome variables were analysed using a 2x2 (GROUP*TIME) repeated measures
analysis of covariance (ANCOVA) with GROUP included as the between training group factor,
and TIME included as the within factor. Baseline values for outcome variables served as a
covariate. Post hoc pairwise comparisons with a Bonferroni adjustment for repeated contrasts
were used to identify specific treatment effects. As this is a secondary analysis from a parent
study, an a priori power analysis was not possible. However, given the sample size (n =52) in the
designated primary (fat mass) and secondary (VO2peak [mL·kg-1·min-1]) outcomes of interest,
post hoc power anaylsis revealed statistical power well in excess of 0.90 for both outcomes. To
further characterize the magnitude of change in SIT relative to the comparison group (MICT),
effect sizes (ES) are reported as unbiased standardized mean change using the equation 


 (Lipsey and Wilson, 2001) which was subsequently corrected for
sample size bias using hedges unbiased effect size estimate    
 (Hedges,
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1981). Statistical significance was set at an α level of P<.05. All data are expressed as mean ±
standard deviation (M±SD), unless otherwise indicated.
Results
Participant Characteristics and Adherence. Of the participants that completed the
intervention (n=60), seven participants were excluded based on <70% attendance (n=5 SIT; n=2
MICT) and one was excluded from analysis as an outlier (baseline fat mass values >3 SD from
the mean). Thus, the cohort (n=52) of young women (20.4 ± 1.5 yr) were on average obese (30.3
± 4.5 kg·m-2) and mostly white (67.3%) paralleling university racial/ethnic demographics (19.2%
Black, 5.8% Asian, 1.9% Hispanic, and 5.8% other). Groups did not differ on baseline
characteristics (P>.05; data not shown). Session attendance (15.0 ± 1.5 sessions vs. 15.8 ± 1.9
sessions, P=.097) and average energy expenditure (541.8 ± 104.6 kJ·session-1 vs. 553.5 ± 138.1
kJ·session-1, P=.250) was not different between SIT and MICT. No adverse events were reported
within either intervention group. Available complete total daily energy expenditure data (n=44)
indicated no change from pre- to post- intervention in either SIT (10,859.6 ± 1,406.7 kJ·d-1 vs.
10,719.4 ± 1,170.7 kJ·d-1, P=.544) or MICT (10,506.9 ± 1,315.0 kJ·d-1 vs. 10,591.8 ± 1,195.4
kJ·d-1, P=.956), with no significant GROUP*TIME interaction (P=.632). Complete dietary data
(n=51) indicated a main effect of time (P<.001) but no GROUP*TIME interaction (P=.308). Post
hoc analysis revealed no change in response to SIT (7,930.4 ± 2,203.7 kJ·d-1 vs. 7,688.5 ±
2,165.6 kJ·d-1, P=.356), but a significant reduction in MICT (8,367.2 ± 2,869.4 kJ·d-1 vs. 7,388.5
± 2,051.0 kJ·d-1, P=.013).
Mass & Body Composition. Changes in outcome variables are expressed in relative terms
within the main text and in absolute terms within Table 1. No changes in body mass occurred in
response to either of the exercise interventions (ES=.07, P=.118). A significant GROUP*TIME
10
interaction was found for reductions in total fat mass (ES=.12, P=.007), with SIT reducing total
fat mass by 3.6% (P<.001) compared to 0.6% (P=.757) in MICT (Table 1, Figure 1A). A
significant interaction was also found for changes in %Fat (ES=.14, P=.013), with further
analysis indicating a 1% decrease in SIT (P<.001) and no change (-0.3%, P=.315) in MICT.
Similarly, a significant GROUP*TIME interaction (ES=.16, P=.002) existed indicating that
exercise intensity had differential effects on android fat mass with a 6.6% reduction in SIT and
no change (-0.7%) in MICT. Total body FFM did not change differentially (ES=.00, P=.983) or
within either group (both P>.05). The change in leg FFM was similar in both groups (ES=.03,
P=.557), increasing by 2.0% in MICT (P=.001) and 1.9% in SIT (P<.001).
Aerobic Capacity. A significant GROUP*TIME interaction (ES=.48, P<.001) existed
with SIT demonstrating a 2-fold (14.1%) increase in VO2peak (mL·kg-1·min-1) compared to the
7.1% increase in MICT (Table 1, Figure 1B). Similar interactions and changes were observed for
VO2peak expressed in absolute terms (L·min-1; ES=.49, P=.001) and relative to FFM (mL·kgFFM-
1·min-1; ES=.46, P=.002).
Discussion
The effect of exercise intensity on body composition and aerobic capacity in
overweight/obese young women was examined with 6-week SIT and MICT interventions
involving equal estimated exercise energy expenditure. In agreement with our hypothesis, the
major findings were: 1) exercise training intensity/pattern differentially affected adiposity, with
SIT eliciting significantly greater losses of total and central fat mass compared to MICT, and 2)
although both interventions led to a significant increase in aerobic capacity, SIT led to a nearly
2-fold greater increase in VO2peak than in MICT, regardless of expression.
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Body Mass and Composition. The absence of substantial change in body mass is not
surprising in light of the low energy expenditure of each session ~550 kJ, totaling ~10,000 kJ
over the 6-week intervention. However, the reported reductions in total and central fat mass in
favor of SIT are mirrored by an absolute reduction in body mass which neared significance
(p=.06) and was not seen following MICT. In support of these findings, a recent study using a 6-
week running SIT protocol of a similar duration and intensity to the present study (Hazell et al.,
2014), reported a 1.2 kg reduction in fat mass with only a 0.5 kg reduction in body mass, despite
presumably low exercise energy expenditure and no changes to dietary energy intake. The
significant reduction in energy intake within MICT of ~1000 kJ/day in the absence of body
composition change, along with the ~2500 kJ discrepancy between energy intake and
expenditure reported by participants is paradoxical and highlights the limitations of
methodologies for measuring free living energy intake. Indeed, part of the variance in body
composition change could be accounted for by changes in energy balance not captured by these
methodologies; however, these limitations are present in all such studies, similarly affecting
intervention groups. Moreover, most studies are consistent in their findings of reduced adiposity
following similar SIT protocols (Hazell et al., 2014; Macpherson et al., 2011), along with other
forms of high intensity interval work (Gillen et al., 2013; Heydari et al., 2012), which speaks to
the validity of the findings and strength of the lipolytic effect of high intensity interval training.
However, one study comparing SIT and MICT failed to show a beneficial effect of SIT, nor one
which was greater than MICT (Keating et al., 2014). In overweight/obese adults, 12 weeks of
MICT reduced android fat by 2.7%, whereas SIT led to no reductions in adiposity (P=.04)
(Keating et al., 2014). Notably, this intervention showed similar discrepancies in energy intake
and expenditure to the current data, and did not have equal work or exercise energy expenditure
12
between groups which could have played a role in the contradictory findings, as by the final
week of training, exercise duration was 2-fold greater in MICT compared to SIT (Keating et al.,
2014).
Though reductions in adiposity have been consistently noted following SIT (Hazell et al.,
2014; Macpherson et al., 2011), much debate exists regarding the mechanisms that drive the
lipolytic effect of SIT (Boutcher, 2011), and how they might differ from MICT. One theory is
that an intensity driven hormone release occurs with SIT, which augments lipolysis (Bracken et
al., 2009; Nevill et al., 1996; Williams et al., 2013; Zouhal et al., 2008). Nevill et al., showed that
elevations in growth hormone were linked to peak power output, with greater concentrations
occurring following SIT than endurance work (Nevill et al., 1996). Furthermore, increased
production of the catecholamines epinephrine and norepinephrine in comparison to MICT has
also been reported in some studies (Bracken et al., 2009; Williams et al., 2013; Zouhal et al.,
2008), but not others (Sevits et al., 2013). Indeed, these hormones are important contributors to
lipolysis, however, in the case of increased catecholamine production, the high rate of lipolysis
does not appear to translate into augmented fat oxidation, leading only to high re-esterification
rates (Mora-Rodriguez and Coyle, 2000; Williams et al., 2013). More research is needed to
define the relationships among training regimen type, hormones released at supramaximal
intensities, and subsequent fat oxidation.
A second theory that has been considered to explain favorable changes in adiposity is a
higher excess post-exercise oxygen consumption (EPOC) throughout the remainder of the day.
Although the positive relationship between exercise intensity and EPOC is well accepted (Bahr
and Sejersted, 1991), investigations into EPOC following SIT suggest that energy expenditure is
similar to that of MICT protocols (Kelly et al., 2013; Sevits et al., 2013; Williams et al., 2013),
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with changes in total daily energy expenditure being attributable to the energy cost of exercise
and any differences between protocols being too small in magnitude (~6-15% of the total oxygen
cost of exercise) to explain the changes in body composition (Kelly et al., 2013; LaForgia et al.,
2006). It is noteworthy that the recovery period between sprints is accompanied by an increased
EPOC, which contributes to overall energy expenditure above that which is captured by
measurement methods other than calorimetry (LaForgia et al., 2006). As such, the use of Keiser
ergometers to estimate energy expenditure and the lack of oxygen uptake data post-training
limits the mechanistic interpretation of our data as we cannot confirm differences in EPOC;
however notably, these limitations are balanced by the greater translational utility of this exercise
intervention.
A third, more recent hypothesis focuses on the potentially satiating effect of SIT,
reducing perceptions of hunger (Deighton et al., 2013; Williams et al., 2013), and in some cases
energy intake (Alkahtani et al., 2014; Sim et al., 2015). However, there remains question as to
whether a change in measured appetite translates to a reduction in energy intake, as
malalignment between the two have been reported (Deighton et al., 2013). As we were unable to
measure specific aspects of these proposed mechanisms, the explanation of greater fat loss
following SIT remains elusive and warrants further investigation.
Aerobic Capacity. Studies using a similar SIT protocol that employed an equal work or
exercise energy expenditure design between intervention groups are sparse. One study compared
6 sessions of 4-7 SIT bouts over 2 weeks to a MICT group working at an intensity below their
ventilatory threshold, with an equal estimated energy expenditure. This study found no
significant improvements in VO2peak in MICT but 7.5% (L·min-1) and 6.7% (mL·kg-1·min-1)
increases with SIT (Bailey et al., 2009). Conversely, a study by Keating et al. showed that in
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overweight adults, 12 weeks of training improved aerobic capacity to a similar extent in SIT
(22.3 ± 3.5%) and MICT (23.8 ± 3.0%) groups (Keating et al., 2014). A number of potential
moderators may explain the conflicting results from previous SIT and MICT comparisons
including study duration, MICT intensity, and lack of energy expenditure control in each
exercise group subsequently leading to different training volumes and limiting the interpretation
of the findings.
A recent meta-analysis summarizing the effect of SIT on aerobic capacity in young
healthy participants suggested that a SIT intervention would be expected to induce on average an
8% increase in VO2max relative to non-exercise control groups (Cohen’s d=.69) and that changes
would not be different from a moderate-to-vigorous-intensity continuous training intervention of
a similar duration (Cohen’s d=.04) (Gist et al., 2013). With the similarities between Cohen’s d
and the ES used in this analysis, an effect size of ES=.48 for increases in VO2peak (mL·kg-1·min-1)
suggests that the SIT protocol used in this study had a stronger effect on aerobic capacity than
reported in previous literature. However, this and similar reviews did not explore relationships
between equal exercise energy expenditure or work-matched interventions and outcomes of
interest, which makes the comparison of results difficult (Gist et al., 2013; Weston et al., 2014).
SIT has induced rapid improvements in both aerobic capacity and muscular oxidative
potential, with a meta-analysis showing several studies of a 2-week duration significantly
improving VO2max (Sloth et al., 2013). Within this review, it was suggested that the time-course
of adaptations to SIT may differ from MICT, the former eliciting peripheral adaptations at a
much faster rate than the latter. This has implications when looking at study duration and the
comparison of SIT and MICT interventions, pointing towards interventions with a shorter
duration being more likely to show superior improvements in aerobic capacity with SIT. Further
15
research is needed to elucidate the effects of longer duration SIT interventions, with MICT
comparison groups, to identify the different time-course of adaptations as current reviews have
failed to resolve this issue (Gist et al., 2013; Sloth et al., 2013; Weston et al., 2014).
As suggested, another factor influencing the comparability of SIT and continuous
exercise results is the differing intensity of the continuous exercise comparison groups within the
current literature, with intensities of 65-80% VO2max (Esfarjani and Laursen, 2007; Keating et al.,
2014; Rowan et al., 2012), along with HRmax based methodologies (Sandvei et al., 2012). This
range of ‘moderate-to-vigorous intensities could logically elicit differential improvements in
aerobic capacity as previous research has shown that the intensity of continuous exercise is
generally linearly related to improvements in VO2max (Gormley et al., 2008). In the context of
this study, it is possible that the MICT exercise intensity was not high enough to elicit the same
magnitude of changes in just 6 weeks; however, further research looking at equivalent exercise
stimuli is needed to address this issue.
Conclusion. In summary, compared to a MICT protocol in which the same estimated
energy was expended, 6 weeks of SIT elicited significantly greater reductions in total and central
adiposity, and increases in aerobic capacity in overweight/obese young women. Aerobic capacity
improved 2-fold more with SIT compared to MICT, with increases in VO2peak being greater than
expected based on recent reviews. Our findings suggest that SIT is an effective means to rapidly
improve body composition and aerobic capacity in overweight/obese young women when
performed in a supervised group-training format.
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Acknowledgments: No sources of funding were used in preparation of this manuscript. The authors
declare no conflict of interest. Data collection was performed by SH, MVF, and EDH. Review of
literature and statistical analyses were performed by SH. Manuscript preparation and revision were
performed by SH, MVF, EDH, MDS, and EME. Preparation of the final document for submission was
performed by SH and EME.
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Table 1. Changes in body composition and aerobic capacity
Variable
MICT
(n=29)
Pairwise
P-value
SIT
(n=23)
Pairwise
P-value
GROUP*TIME
P-value
Body Mass (kg)
Baseline
83.1 ± 14.2
81.9 ± 12.2
Post
.814
81.0 ± 11.5
.060
.118
Change
0.1 ± 1.8
-0.9 ± 2.5
Fat Mass (kg)
Baseline
36.1 ± 8.6
33.7 ± 7.9
Post
35.9 ± 8.5
.757
32.5 ± 7.1
<.001
.007
Change
0.2 ± 1.4
-1.2 ± 1.9
Fat Mass (%)
Baseline
44.5 ± 4.8
42.2 ± 4.8
Post
44.2 ± 4.4
.315
41.2 ± 4.8
<.001
.013
Change
-0.3 ± 1.1
-1.0 ± 1.4
Android Fat Mass (kg)
Baseline
3.1 ± 1.0
2.9 ± 0.9
Post
3.1 ± 1.0
.724
2.7 ± 0.8
<.001
.002
Change
0.0 ± 0.2
-0.2 ± 0.3
Whole Body FFM (kg)
Baseline
44.5 ± 6.9
45.6 ± 5.9
Post
44.8 ± 7.0
.149
46.0 ± 6.3
.208
.983
Change
0.4 ± 1.1
0.4 ± 1.5
Leg FFM (kg)
Baseline
24.6 ± 4.5
25.6 ± 4.0
Post
25.1 ± 4.5
.001
26.1 ± 4.1
<.001
.557
Change
0.5 ± 0.7
0.6 ± 0.8
VO2 peak (L/min)
Baseline
2.2 ± 0.3
2.3 ± 0.4
Post
2.4 ± 0.3
<.001
2.7 ± 0.3
<.001
.001
Change
0.2 ± 0.2
0.3 ± 0.2
VO2 peak (ml/kg/min)
Baseline
26.9 ± 4.5
29.1 ± 4.8
Post
28.8 ± 4.3
<.001
33.2 ± 4.4
<.001
<.001
Change
1.9 ± 2.1
4.1 ± 3.0
VO2 peak (ml/kg FFM/min)
Baseline
50.1 ± 7.0
51.6 ± 7.9
Post
53.6 ± 7.2
<.001
58.4 ± 6.4
<.001
.002
Change
3.5 ± 3.8
6.8 ± 4.8
Values are mean ± SD. FFM = Fat-free mineral-free soft tissue mass. All comparisons controlled for
baseline values using Analysis of Covariance with Bonferroni adjustment for multiple comparisons.
25
Figure Captions:
Figure 1. Magnitude of training induced changes in (A) absolute adiposity (kg) and (B) aerobic capacity
(mL·kg-1·min-1). Values are mean ± SEM. *Significant within group difference (P<.001). †Significant
GROUP*TIME interaction (P<.01).
... Interval training refers to the training protocol involving bursts of near maximal (high-intensity interval training, HIIT) or supramaximal (sprint interval training, SIT) intensity exercise interspersed with periods of recovery or rest (MacInnis and Gibala 2017). This modality speeds up V O 2 kinetics (McKay et al. 2009;Schaumberg et al. 2020), and promotes cardiorespiratory fitness (Kokkinos et al. 2022;Yue et al. 2022;De Revere et al. 2021;Astorino et al. 2013Astorino et al. , 2011Astorino et al. , 2017Higgins et al. 2016;Batacan et al. 2017;Martin-Smith et al. 2020), body fat reduction (Higgins et al. 2016;Keating et al. 2017;Maillard et al. 2018) and skeletal muscle adaptations including neuromuscular control (Martinez-Valdes et al. 2017, microvascular O 2 distribution, utilization, and the mitochondrial respiratory capacity (Rosenblat et al. 2022;Robinson et al. 2017;Gibala et al. 2012;Callahan et al. 2021a, b) across the spectra of age and gender. The physiological and functional improvements can be detected in a relatively short training period (~ 4 weeks). ...
... Interval training refers to the training protocol involving bursts of near maximal (high-intensity interval training, HIIT) or supramaximal (sprint interval training, SIT) intensity exercise interspersed with periods of recovery or rest (MacInnis and Gibala 2017). This modality speeds up V O 2 kinetics (McKay et al. 2009;Schaumberg et al. 2020), and promotes cardiorespiratory fitness (Kokkinos et al. 2022;Yue et al. 2022;De Revere et al. 2021;Astorino et al. 2013Astorino et al. , 2011Astorino et al. , 2017Higgins et al. 2016;Batacan et al. 2017;Martin-Smith et al. 2020), body fat reduction (Higgins et al. 2016;Keating et al. 2017;Maillard et al. 2018) and skeletal muscle adaptations including neuromuscular control (Martinez-Valdes et al. 2017, microvascular O 2 distribution, utilization, and the mitochondrial respiratory capacity (Rosenblat et al. 2022;Robinson et al. 2017;Gibala et al. 2012;Callahan et al. 2021a, b) across the spectra of age and gender. The physiological and functional improvements can be detected in a relatively short training period (~ 4 weeks). ...
... Significant adaptations in the V O 2 max and PPO were observed in the HIIT group, consistent with those previously reported in young women (De Revere et al. 2021;Astorino et al. 2011Astorino et al. , 2013Higgins et al. 2016;Schaumberg et al. 2017;Edge et al. 2006). The magnitude of V O 2 max improvements (14%) was similar between the untrained female participants (in this study) and their recreationally active counterparts, with Schaumberg et al. (2017) reported a 13% improvement and Edge et al. (2006) reported a 14% improvement, showing that the lower baseline V O 2 max level does not result in more profound changes for females after short-term HIIT, at least not in the present study. ...
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Purpose This study investigated the physical fitness and oxygen uptake kinetics (τV˙O2pV˙O2p\dot{\text{V}}\text{O}_{2p}) along with the O2 delivery and utilization (heart rate kinetics, τHR; deoxyhemoglobin/V˙O2V˙O2\dot{\text{V}}\text{O}_{2} ratio, ∆[HHb]/V˙O2V˙O2\dot{\text{V}}\text{O}_{2}) adaptations of untrained female participants responding to 4 weeks of high-intensity interval training (HIIT) and 2 weeks of detraining. Methods Participants were randomly assigned to HIIT (n = 11, 4 × 4 protocol) or nonexercising control (n = 9) groups. Exercising group engaged 4 weeks of treadmill HIIT followed by 2 weeks of detraining while maintaining daily activity level. Ramp-incremental (RI) tests and step-transitions to moderate-intensity exercise were performed. Aerobic capacity and performance (maximal oxygen uptake, V˙O2maxV˙O2max\dot{\text{V}}\text{O}_{2\max }; gas-exchange threshold, GET; power output, PO), body composition (skeletal muscle mass, SMM; body fat percentage, BF%), muscle oxygenation status (∆[HHb]), V˙O2V˙O2\dot{\text{V}}\text{O}_{2}, and HR kinetics were assessed. Results HIIT elicited improvements in aerobic capacity (V˙O2maxV˙O2max\dot{\text{V}}\text{O}_{2\max }, + 0.17 ± 0.04 L/min; GET, + 0.18 ± 0.05 L/min, P < 0.01; PO-V˙O2maxV˙O2max\dot{\text{V}}\text{O}_{2\max }, ± 23.36 ± 8.37 W; PO-GET, + 17.18 ± 3.07 W, P < 0.05), body composition (SMM, + 0.92 ± 0.17 kg; BF%, − 3.08% ± 0.58%, P < 0.001), and speed up the τV˙O2pV˙O2p\dot{\text{V}}\text{O}_{2p} (− 8.04 ± 1.57 s, P < 0.001) significantly, extending to better ∆[HHb]/V˙O2V˙O2\dot{\text{V}}\text{O}_{2} ratio (1.18 ± 0.08 to 1.05 ± 0.14). After a period of detraining, the adaptation in body composition and aerobic capacity, as well as the accelerated τV˙O2pV˙O2p\dot{\text{V}}\text{O}_{2p} were maintained in the HIIT group, but the PO-V˙O2maxV˙O2max\dot{\text{V}}\text{O}_{2\max } and PO-GET declined below the post-training level (P < 0.05), whereas no changes were reported in controls (P > 0.05). Four weeks of HIIT induced widespread physiological adaptations in females, and the majority of improvements were preserved after 2 weeks of detraining except for power output corresponding to V˙O2maxV˙O2max\dot{\text{V}}\text{O}_{2\max } and GET.
... The duration of 13 studies [44,46,47,49,51,[53][54][55]58,63,66,67,69] was 3 months, only two studies [42,50] adopted >3 months intervention. Most interventions used HRmax or VO 2peak to measure the intensity of exercise, two studies [44,50] used RPE, three studies [45,59,60] used Wpeak or Wmax, six studies [46,48,52,56,57,61,64] used all-out exercise or maximum effort. A total of 10 HIIT interventions used passive recovery [44,48,51,53,[57][58][59]61,64,69] and the remaining used active recovery. ...
... The exercise time ranged from 9 to 54 min for HIIT and 15 to 60 min for MICT, only two studies [58,68] used energy expenditure formulating exercise time. A total of 19 studies [42,43,[46][47][48][50][51][52][53][54]56,57,[59][60][61][62]64,67,69] instructed participants to exercise 3 times/week, nine studies [41,45,49,55,58,63,65,66,68] instructed > 3 times/week, and only one study [44] instructed once per week. A total of 14 studies [41,46,[49][50][51]53,54,58,61,63,64,[67][68][69] had dropouts, of which four studies [49][50][51]64] had <85% attendance rate. ...
... A total of four studies [48,50,67,68] did not report sex ratio, the sex ratio of the remaining studies was 2:3. The participants in 20 included studies [44][45][46][47][48][49][51][52][53][54][55][57][58][59][60][61]63,66,68,69] were people with sedentary obesity, two studies [30,56] were sedentary only, and seven studies [41][42][43]50,62,64,67] were other medical comorbidities (two Type 1 diabetes, two Type 2 diabetes, one prediabetes, one polycystic ovary syndrome, and one fibromyalgia). ...
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Objectives: This systematic review is conducted to evaluate the effect of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on body composition and cardiorespiratory fitness (CRF) in the young and middle-aged. Methods: Seven databases were searched from their inception to 22 October 2022 for studies (randomized controlled trials only) with HIIT and MICT intervention. Meta-analysis was carried out for within-group (pre-intervention vs. post-intervention) and between-group (HIIT vs. MICT) comparisons for change in body mass (BM), body mass index (BMI), waist circumference (WC), percent fat mass (PFM), fat mass (FM), fat-free mass (FFM), and CRF. Results: A total of 1738 studies were retrieved from the database, and 29 studies were included in the meta-analysis. Within-group analyses indicated that both HIIT and MICT can bring significant improvement in body composition and CRF, except for FFM. Between-group analyses found that compared to MICT, HIIT brings significant benefits to WC, PFM, and VO2peak. Conclusions: The effect of HIIT on fat loss and CRF in the young and middle-aged is similar to or better than MICT, which might be influenced by age (18-45 years), complications (obesity), duration (>6 weeks), frequency, and HIIT interval. Despite the clinical significance of the improvement being limited, HIIT appears to be more time-saving and enjoyable than MICT.
... For females who are planning a pregnancy, interval training can be a means to increase cardiorespiratory fitness, improve insulin sensitivity, and reduce fat mass. Higgins and colleagues showed that 6 weeks with three weekly sessions of 30 s "all-out" sprints, repeated 5-7 times interspersed with 4 min low-intensity recovery, reduced total fat mass and increased VO 2 peak more than MICT of equal estimated energy expenditure in young (∼20 years old) women with overweight/obesity (Higgins et al. 2016). Similarly, Zhang and colleagues showed greater visceral fat reductions after three weekly sessions of interval training for 12 weeks (three separate protocols; two of which were isoenergetic to MICT) than after MICT in young women with obesity (Zhang et al. 2021). ...
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... A short work bout duration of ≤60 s per repetition increased FFM while a longer work bout (>60 s) had no significant effect. In agreement with our finding, multiple studies with short-term intervals have reported reduced body fat [14,63,83,84]. However, a recent study showed both short and long intervals reduced BF% and FM (kg), although short-term intervals (≤60 s) induced a greater reduction. ...
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This systematic review and meta-analysis of randomized controlled trials (RCTs) compared body compositional changes, including fat mass (FM), body fat percentage (BF%), and fat-free mass (FFM), between different types of high-intensity interval training (HIIT) (cycling vs. overground running vs. treadmill running) as well as to a control (i.e., no exercise) condition. Meta-analyses were carried out using a random-effects model. The I2 index was used to assess the heterogeneity of RCTs. Thirty-six RCTs lasting between 3 to 15 weeks were included in the current systematic review and meta-analysis. RCTs that examined the effect of HIIT type on FM, BF%, and FFM were sourced from online databases including PubMed, Scopus, Web of Science, and Google Scholar up to 21 June 2022. HIIT (all modalities combined) induced a significant reduction in FM (weighted mean difference [WMD]: −1.86 kg, 95% CI: −2.55 to −1.18, p = 0.001) despite a medium between-study heterogeneity (I2 = 63.3, p = 0.001). Subgroup analyses revealed cycling and overground running reduced FM (WMD: −1.72 kg, 95% CI: −2.41 to −1.30, p = 0.001 and WMD: −4.25 kg, 95% CI: −5.90 to −2.61, p = 0.001, respectively); however, there was no change with treadmill running (WMD: −1.10 kg, 95% CI: −2.82 to 0.62, p = 0.210). There was a significant reduction in BF% with HIIT (all modalities combined) compared to control (WMD: −1.53%, 95% CI: −2.13, −0.92, p = 0.001). All forms of HIIT also decreased BF%; however, overground running induced the largest overall effect (WMD: −2.80%, 95% CI: −3.89 to −1.71, p = 0.001). All types of HIIT combined also induced an overall significant improvement in FFM (WMD: 0.51 kg, 95% CI: 0.06 to 0.95, p = 0.025); however, only cycling interventions resulted in a significant increase in FFM compared to other exercise modalities (WMD: 0.63 kg, 95% CI: 0.17 to 1.09, p = 0.007). Additional subgroup analyses suggest that training for more than 8 weeks, at least 3 sessions per week, with work intervals less than 60 s duration and separated by ≤90 s active recovery are more effective for eliciting favorable body composition changes. Results from this meta-analysis demonstrate favorable body composition outcomes following HIIT (all modalities combined) with overall reductions in BF% and FM and improved FFM observed. Overall, cycling-based HIIT may confer the greatest effects on body composition due to its ability to reduce BF% and FM while increasing FFM.
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Background Although the efficacy of interval training for improving body composition has been summarized in an increasing number of systematic reviews in recent years, discrepancies in review findings and conclusions have been observed. Objective This study aims to synthesize the available evidence on the efficacy of interval training compared with moderate-intensity continuous training (MICT) and nonexercise control (CON) in reducing body adiposity in apparently healthy adults. Methods An umbrella review with meta-analysis was performed. A systematic search was conducted in seven databases (MEDLINE, EMBASE, Cochrane Database, CINAHL, Scopus, SPORTDiscus, and Web of Science) up to October 2023. Systematic reviews with meta-analyses of randomized controlled trials (RCTs) comparing interval training and MICT/CON were included. Literature selection, data extraction, and methodological quality assessment (AMSTAR-2) were conducted independently by two reviewers. Meta-analyses were performed using a random-effects model. Subgroup analyses were conducted based on the type of interval training [high-intensity interval training (HIIT) and sprint interval training (SIT)], intervention duration, body mass index, exercise modality, and volume of HIIT protocols. Results Sixteen systematic reviews, including 79 RCTs and 2474 unique participants, met the inclusion criteria. Most systematic reviews had a critically low (n = 6) or low (n = 6) AMSTAR-2 score. Interval training demonstrated significantly greater reductions in total body fat percent (BF%) compared with MICT [weighted mean difference (WMD) of − 0.77%; 95% confidence interval (CI) − 1.12 to − 0.32%] and CON (WMD of − 1.50%; 95% CI − 2.40 to − 0.58%). Significant reductions in fat mass, visceral adipose tissue, subcutaneous abdominal fat, and android abdominal fat were also observed following interval training compared to CON. Subgroup analyses indicated that both HIIT and SIT resulted in superior BF% loss than MICT. These benefits appeared to be more prominent in individuals with overweight/obesity and longer duration interventions (≥ 12 weeks), as well as in protocols using cycling as a modality and low-volume HIIT (i.e., < 15 min of high-intensity exercise per session). Conclusions This novel umbrella review with large-scale meta-analysis provides an updated synthesis of evidence with implications for physical activity guideline recommendations. The findings support interval training as a viable exercise strategy for reducing adiposity in the general population.
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Background To determine rates of compliance (i.e., supervised intervention attendance) and adherence (i.e., unsupervised physical activity completion) to high-intensity interval training (HIIT) among insufficiently active adults and adults with a medical condition, and determine whether compliance and adherence rates were different between HIIT and moderate-intensity continuous training (MICT). Methods Articles on adults in a HIIT intervention and who were either insufficiently active or had a medical condition were included. MEDLINE, EMBASE, PsychINFO, SPORTDiscus, CINAHL, and Web of Science were searched. Article screening and data extraction were completed by two independent reviewers. Risk of bias was assessed using RoB 2.0 or ROBINS-I. Meta-analyses were conducted to discern differences in compliance and adherence between HIIT vs. MICT. Sensitivity analyses, publication bias, sub-group analyses, and quality appraisal were conducted for each meta-analysis. Results One hundred eighty-eight unique studies were included (n = 8928 participants). Compliance to HIIT interventions averaged 89.4% (SD:11.8%), while adherence to HIIT averaged 63% (SD: 21.1%). Compliance and adherence to MICT averaged 92.5% (SD:10.6%) and 68.2% (SD:16.2%), respectively. Based on 65 studies included in the meta-analysis, compliance rates were not different between supervised HIIT and MICT interventions [Hedge’s g = 0.015 (95%CI: − 0.088–0.118), p = .78]. Results were robust and low risk of publication bias was detected. No differences were detected based on sub-group analyses comparing medical conditions or risk of bias of studies. Quality of the evidence was rated as moderate over concerns in the directness of the evidence. Based on 10 studies, adherence rates were not different between unsupervised HIIT and MICT interventions [Hedge’s g = − 0.313 (95%CI: − 0.681–0.056), p = .096]. Sub-group analysis points to differences in adherence rates dependent on the method of outcome measurement. Adherence results should be interpreted with caution due to very low quality of evidence. Conclusions Compliance to HIIT and MICT was high among insufficiently active adults and adults with a medical condition. Adherence to HIIT and MICT was relatively moderate, although there was high heterogeneity and very low quality of evidence. Further research should take into consideration exercise protocols employed, methods of outcome measurement, and measurement timepoints. Registration This review was registered in the PROSPERO database and given the identifier CRD42019103313.
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BACKGROUNDː Deep Water Running (DWR) is an exercise model often used for health promotion purposes. This study standardized an aerobic capacity evaluation protocol specific for attached DWR in young healthy adults and monitored a DWR session with normobaric hypoxia exposure addition. METHODSː In Study 1, nine young healthy adults, seven male and two female (22.88 ± 3.14 years old; 72.44 ± 11.38 kg; 174.88 ± 9 cm; 23.58 ± 2.33 kg·m-2), were subjected to two DWR incremental tests with a 48-hour interval between them, and in Study 2, six healthy males were subjected to three (hypoxia, normoxia, and inter-effort recovery hypoxia) attached DWR exercise sessions involving normobaric hypoxia. Data are expressed as average ± standard deviation. Friedman's test was used to compare the groups with a significance level of p<0.05. RESULTS: In Study 1, no significant statistical differences were observed for the physiological variables analyzed. In Study 2, there was no difference in strength and lactate between conditions; values of rates of perceived exertion were higher in the hypoxic session, compared to inter-effort recovery hypoxia, in efforts 1 and 5, respectively, while heart rate was lower in effort 1 in normoxia. In hypoxia, effort 1 was lower than effort 3, with no alteration in recovery hypoxia. CONCLUSIONS: This aerobic capacity evaluation protocol is valid, sensitive, and replicable, and there were no important differences in the physiological variables from high-intensity exercise sessions monitoring in hypoxia, normoxia, and inter-effort recovery hypoxia conditions. Suggested Reviewers: Secondary Full Title: Standardization de l'évaluation et de la prescription d'exercices pour la course en piscine profonde avec exposition à l'hypoxie normobare Secondary Abstract: CONTEXTEː La course en piscine profonde (Deep Water Running; DWR) est un modèle d'exercice souvent proposé pour améliorer la santé. Cette étude a standardisé un protocole d'évaluation de la capacité aérobie spécifique au DWR chez de jeunes adultes en bonne santé et a étudié une séance de DWR avec exposition à l'hypoxie normobare. MÉTHODESː Dans l'étude 1, neuf jeunes adultes en bonne santé, sept hommes et deux femmes (22,88 ± 3,14 ans ; 72,44 ± 11,38 kg ; 174,88 ± 9 cm ; 23,58 ± 2,33 kg·m-2), ont été soumis à deux tests DWR incrémentiels distants de 48 heures, et dans l'étude 2, six hommes en bonne santé ont été soumis à trois séances d'exercices DWR avec hypoxie normobare (hypoxie, normoxie et hypoxie de récupération inter-effort).
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Background/Objective Guidelines on obesity management reinforce regular exercise to reduce body fat. Exercise modalities, including high-intensity interval training (HIIT), appear to produce a similar effect to continuous aerobic training (CAT) on body fat. However, they have not addressed the chronic effect of HIIT vs. CAT on body fat assessed by dual energy X-ray absorptiometry (DEXA). Thus, we compared the effectiveness of CAT vs. HIIT protocols on body fat (absolute or relative) (%BF) and abdominal visceral fat reduction, assessed by DEXA, in adults with overweight and obesity. Methods We conducted a systematic review and meta-analysis of randomized clinical trials (RCTs) including both female or male adults with excess body weight. We performed searches in the databases MEDLINE (PubMed), EMBASE, Scopus, LILACS, Web of Science and Cochrane. Results In our analysis (11 RCTs), we found no greater benefit on %BF of HIIT vs. CAT (MD –0.55%, 95% CI –1.42 to 0.31; p = 0.209). As for abdominal visceral fat, no training modality was superior (SMD: −0.05, 95% CI –0.29 to 0.19; p = 0.997). Regarding secondary outcomes (body weight, BMI, VO2 max, glycemic and lipid profiles), HIIT shows greater benefit than CAT in increasing VO2 max and fasting blood glucose and reducing total cholesterol. Conclusion HIIT is not superior to CAT in reducing %BF or abdominal visceral fat in individuals characterized by excess weight. However, HIIT showed beneficial effects on cardiorespiratory fitness, total cholesterol and fasting blood glucose when compared to CAT.
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Background Interval training can be classified into high-intensity interval training (HIIT, 80%-100%V̇O2max) and sprint interval training (SIT, ≥ 100%V̇O2max) according to exercise intensity. HIIT can be further divided into high-volume HIIT (HV-HIIT, pure training time ≥ 15min/session) and low-volume HIIT (LV-HIIT, pure training time < 15min/session). The effectiveness of HV-HIIT in reducing body fat among adults has been well-proven, but there is a lack of comprehensive analysis on the impacts of low-volume interval training (i.e. LV-HIIT and SIT) on fat loss. Objective The systematic review and meta-analysis aim to determine the effectiveness of low-volume interval training in improving whole-body fat, abdominal and visceral fat in adults living with overweight and obesity. Methods Following the PRISMA guidelines and inclusion criteria, eligible articles were extracted from seven electronic databases and the reference lists of key papers in the field. The search was limited to English articles published on and before May 2023. Effect sizes were calculated as standardized mean difference (SMD) for four intervention outcomes, whole-body fat, body fat percentage, abdominal fat, and visceral fat. Results Out of the 4568 identified studies, a total of 50 randomized controlled trials were included, involving 1843 participants (age: 19.8 to 70.5 years, BMI: 25 to 39.5 kg/m²). The low-volume interval training protocol included in this review had an average training duration of 9.5 weeks, a frequency of 3.3 times per week, an exercise session time of 6.2 minutes, and an exercise intensity of ≥ 80%V̇O2max or HRmax. Compared to the comparator groups of no-exercising (CON), low-volume interval training significantly reduced whole-body fat mass (-6.4%, p < 0.001), body fat percentage (-5.3%, p < 0.001), abdominal fat (-5.8%, p = 0.02) and visceral fat (-12.6%, p < 0.001). Compared to moderate-intensity continuous training (MICT), low-volume interval training showed a significant reduction in visceral fat (-3.9%, p = 0.04). No significant differences were observed between low-volume interval training and HV-HIIT in four outcome measures. Conclusion Low-volume interval training (LV-HIIT and SIT) groups show significant reductions in whole-body, abdominal and visceral fat among overweight and obese adults. It is more effective than MICT in reducing visceral fat. These findings emphasize the efficiency of low-volume interval training as an intervention for fat loss. The study protocol was registered (Registration No.: CRD42022341699) with the International Prospective Register of Systematic Reviews (PROSPERO).
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Aims: High-intensity interval training (HIIT) leads to improvements in various markers of cardiometabolic health but adherence to HIIT following a supervised laboratory intervention has yet to be tested. We compared self-report and objective measures of physical activity after one month of independent exercise in individuals with prediabetes who were randomized to HIIT (n = 15) or traditional moderate-intensity continuous training (MICT, n = 17). Method: After completing 10 sessions of supervised training participants were asked to perform HIIT or MICT three times per week for four weeks. Results: Individuals in HIIT (89 ± 11%) adhered to their prescribed protocol to a greater extent than individuals in MICT (71 ± 31%) as determined by training logs completed over one-month follow-up (P = 0.05, Cohen's d = 0.75). Minutes spent in vigorous physical activity per week measured by accelerometer were higher in HIIT (24 ± 18) as compared to MICT (11 ± 10) at one-month follow-up (P = 0.049, Cohen's d = 0.92). Cardiorespiratory fitness and systolic blood pressure assessed at one-month follow-up were equally improved (P's < 0.05). Conclusions: This study provides preliminary evidence that individuals with prediabetes can adhere to HIIT over the short-term and do so at a level that is greater than MICT.
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An acute bout of high intensity intermittent exercise suppresses ad-libitum energy intake at the post-exercise meal. The present study examined the effects of 12 weeks of high intensity intermittent exercise training (HIIT) compared with moderate intensity continuous exercise training (MICT) on appetite regulation. Thirty overweight, inactive men (BMI: 27.2 ± 1.3 kg/m; V˙O2Peak: 35.3 ± 5.3 mL.kg.min were randomised to either HIIT or MICT (involving 12 weeks of training, 3 sessions per week) or a control group (CON) (n = 10 per group). Ad-libitum energy intake from a laboratory test meal was assessed following both a low-energy (LEP: 847 kJ) and a high-energy preload (HEP: 2438 kJ) pre and post-intervention. Perceived appetite and appetite-related blood variables were also measured. There was no significant effect of the intervention period on energy intake at the test meal following the two different preloads (p ≥ 0.05). However, the 95% CI indicated a clinically meaningful decrease in energy intake after the HEP compared with LEP in response to HIIT (516 ± 395 kJ decrease), but not for MICT or CON, suggesting improved appetite regulation. This was not associated with alterations in the perception of appetite or the circulating concentration of a number of appetite-related peptides or metabolites, although insulin sensitivity was enhanced with HIIT only (p = 0.003). HIIT appears to benefit appetite regulation in overweight men. The mechanisms for this remain to be elucidated.
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The purpose of this investigation was to determine whether 6 weeks of sprint interval training (SIT) is associated with changes in mood and perceived health in women at risk for developing metabolic syndrome (MetS). Physically inactive women (30-65 years) were randomized to 6 weeks of nutrition meetings and SIT (n = 23; 3 bouts/week of 4-8 30-s cycle sprints with 4-min recovery) or a nonexercise control condition (CON; n = 24). Before and after the 6-week intervention, perceived health status and mood were assessed. Clinically relevant increases in role-physical scores (ES = 0.64) and vitality (ES = 0.52) were found after 6 weeks of SIT compared with a nonexercise control group. For middle-aged women at risk for MetS, it is concluded that high-intensity, low-volume SIT (1) increases feelings of vitality and perceptions of having fewer physical limitations and (2) does not induce mood disturbances as occurs with high-volume, high-intensity training.
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Individuals diagnosed with the metabolic syndrome (MetS) exhibit elevated postprandial lipemia (PPL). The aims of this investigation were to determine 1) if an acute bout of sprint interval training (SIT) attenuates PPL and 2) if the attenuation of PPL following 6-weeks of SIT is magnified compared to a single session of SIT prior to training in women at-risk for MetS (n = 45; 30-65 yrs). Women were randomized to SIT (n = 22) or a non-exercise control (n=23; CON) for 6-weeks. Postprandial responses to a high-fat meal challenge (HFMC) were assessed in the CON group before (B-HFMC) and after (Post-HFMC) without prior exercise and in the SIT group at baseline (B-HFMC) without prior exercise, after an acute bout of SIT (four 30-s all-out sprints with 4-min recovery) prior to (Pre-HFMC) and after the 6-week intervention (Post-HFMC).Responses to the HFMC were assessed by collecting venous blood samples in the fasted state and at 0, 30, 60, 120, and 180 min postprandial. Compared to baseline, an acute bout of SIT before (Pre-HFMC) and after the 6-week intervention (Post-HFMC) significantly attenuated fasted TG (P<0.05; 16.6% and 12.3%, respectively) and postprandial area under the curve (13.1% and 9.7%, respectively; tAUC) TG responses. There was no difference in fasted or tAUC TG responses between Pre-HFMC and Post-HFMC. SIT is an effective mode of exercise to reduce fasted and postprandial TG concentrations in women at-risk for MetS. Six weeks of SIT does not magnify the attenuation of PPL in response to a single session of SIT. Copyright © 2014, Journal of Applied Physiology.
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Data on whether sprint interval training (SIT) (repeated supermaximal intensity, short-duration exercise) affects body composition are limited, and the data that are available suggest that men respond more favourably than do women. Moreover, most SIT data involve cycling exercise, and running may differ because of the larger muscle mass involved. Further, running is a more universal exercise type. This study assessed whether running SIT can alter body composition (air displacement plethysmography), waist circumference, maximal oxygen consumption, peak running speed, and (or) the blood lipid profile. Fifteen recreationally active women (age, 22.9 ± 3.6 years; height, 163.9 ± 5.1 cm; mass, 60.8 ± 5.2 kg) completed 6 weeks of running SIT (4 to 6, 30-s “all-out” sprints on a self-propelled treadmill separated by 4 min of rest performed 3 times per week). Training decreased body fat mass by 8.0% (15.1 ± 3.6 to 13.9 ± 3.4 kg, P = 0.002) and waist circumference by 3.5% (80.1 ± 4.2 to 77.3 ± 4.4 cm, P = 0.048), whereas it increased fat-free mass by 1.3% (45.7 ± 3.5 to 46.3 ± 2.9 kg, P = 0.05), maximal oxygen consumption by 8.7% (46 ± 5 to 50 ± 6 mL/(kg·min), P = 0.004), and peak running speed by 4.8% (16.6 ± 1.7 to 17.4 ± 1.4 km/h, P = 0.026). There were no differences in food intake assessed by 3-day food records (P > 0.329) or in blood lipids (P > 0.595), except for a slight decrease in high-density lipoprotein concentration (1.34 ± 0.28 to 1.24 ± 0.24 mmol/L, P = 0.034). Running SIT is a time-efficient strategy for decreasing body fat while increasing aerobic capacity, peak running speed, and fat-free mass in healthy young women.
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Low-volume high-intensity interval training (HIT) appears to be an efficient and practical way to develop physical fitness. Our objective was to estimate meta-analysed mean effects of HIT on aerobic power (maximum oxygen consumption [VO2max] in an incremental test) and sprint fitness (peak and mean power in a 30-s Wingate test). Five databases (PubMed, MEDLINE, Scopus, BIOSIS and Web of Science) were searched for original research articles published up to January 2014. Search terms included 'high intensity', 'HIT', 'sprint', 'fitness' and 'VO2max'. Inclusion criteria were fitness assessed pre- and post-training; training period ≥2 weeks; repetition duration 30-60 s; work/rest ratio <1.0; exercise intensity described as maximal or near maximal; adult subjects aged >18 years. The final data set consisted of 55 estimates from 32 trials for VO2max, 23 estimates from 16 trials for peak sprint power, and 19 estimates from 12 trials for mean sprint power. Effects on fitness were analysed as percentages via log transformation. Standard errors calculated from exact p values (where reported) or imputed from errors of measurement provided appropriate weightings. Fixed effects in the meta-regression model included type of study (controlled, uncontrolled), subject characteristics (sex, training status, baseline fitness) and training parameters (number of training sessions, repetition duration, work/rest ratio). Probabilistic magnitude-based inferences for meta-analysed effects were based on standardized thresholds for small, moderate and large changes (0.2, 0.6 and 1.2, respectively) derived from between-subject standard deviations (SDs) for baseline fitness. A mean low-volume HIT protocol (13 training sessions, 0.16 work/rest ratio) in a controlled trial produced a likely moderate improvement in the VO2max of active non-athletic males (6.2 %; 90 % confidence limits ±3.1 %), when compared with control. There were possibly moderate improvements in the VO2max of sedentary males (10.0 %; ±5.1 %) and active non-athletic females (3.6 %; ±4.3 %) and a likely small increase for sedentary females (7.3 %; ±4.8 %). The effect on the VO2max of athletic males was unclear (2.7 %; ±4.6 %). A possibly moderate additional increase was likely for subjects with a 10 mL·kg(-1)·min(-1) lower baseline VO2max (3.8 %; ±2.5 %), whereas the modifying effects of sex and difference in exercise dose were unclear. The comparison of HIT with traditional endurance training was unclear (-1.6 %; ±4.3 %). Unexplained variation between studies was 2.0 % (SD). Meta-analysed effects of HIT on Wingate peak and mean power were unclear. Low-volume HIT produces moderate improvements in the aerobic power of active non-athletic and sedentary subjects. More studies are needed to resolve the unclear modifying effects of sex and HIT dose on aerobic power and the unclear effects on sprint fitness.
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Objective: The purpose of this study was to assess the effect of high intensity interval training (HIIT) versus continuous aerobic exercise training (CONT) or placebo (PLA) on body composition by randomized controlled design. Methods: Work capacity and body composition (dual-energy X-ray absorptiometry) were measured before and after 12 weeks of intervention in 38 previously inactive overweight adults. Results: There was a significant group × time interaction for change in work capacity (P < 0.001), which increased significantly in CONT (23.8 ± 3.0%) and HIIT (22.3 ± 3.5%) but not PLA (3.1 ± 5.0%). There was a near-significant main effect for percentage trunk fat, with trunk fat reducing in CONT by 3.1 ± 1.6% and in PLA by 1.1 ± 0.4%, but not in HIIT (increase of 0.7 ± 1.0%) (P = 0.07). There was a significant reduction in android fat percentage in CONT (2.7 ± 1.3%) and PLA (1.4 ± 0.8%) but not HIIT (increase of 0.8 ± 0.7%) (P = 0.04). Conclusion: These data suggest that HIIT may be advocated as a time-efficient strategy for eliciting comparable fitness benefits to traditional continuous exercise in inactive, overweight adults. However, in this population HIIT does not confer the same benefit to body fat levels as continuous exercise training.
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Exercise reduces obesity and related glucose tolerance, but whether increasing exercise intensity offers additional benefit at fixed exercise amounts is unknown. To determine the separate effects of exercise amount and intensity on abdominal obesity and glucose tolerance. 24-week, single-center, parallel-group trial from 2009 to 2013. (ClinicalTrials.gov: NCT00955071). Kingston, Ontario, Canada. 300 abdominally obese adults. Control (no exercise) (n = 75) or 5 weekly sessions of low-amount, low-intensity exercise (LALI) (180 and 300 kcal/session for women and men, respectively, at 50% of maximum oxygen consumption [V̇o2peak]) (n = 73); high-amount, low-intensity exercise (HALI) (360 and 600 kcal/session, respectively, at 50% of V̇o2peak) (n = 76); or high-amount, high-intensity exercise (HAHI) (360 and 600 kcal/session, respectively, at 75% of V̇o2peak) (n = 76). Daily unsupervised physical activity and sedentary time were measured by accelerometer. Waist circumference and 2-hour glucose level (primary outcomes) and cardiorespiratory fitness and measures of insulin action (secondary measurements). 217 participants (72.3%) completed the intervention. Mean exercise time in minutes per session was 31 (SD, 4.4) for LALI, 58 (SD, 7.6) for HALI, and 40 (SD, 6.2) for HAHI. Daily unsupervised physical activity and sedentary time did not change in any exercise group versus control (P > 0.33). After adjustment for age and sex in a linear mixed model, reductions in waist circumference were greater in the LALI (-3.9 cm [95% CI, -5.6 to -2.3 cm]; P < 0.001), HALI (-4.6 cm [CI, -6.2 to -3.0 cm]; P < 0.001), and HAHI (-4.6 cm [CI, -6.3 to -2.9 cm]; P < 0.001) groups than the control group but did not differ among the exercise groups (P > 0.43). After adjustment for covariates, reductions in 2-hour glucose level were greater in the HAHI group (-0.7 mmol/L [-12.5 mg/dL] [CI, -1.3 to -0.1 mmol/L {-23.5 to -1.5 mg/dL}]; P = 0.027) than the control group but did not differ for the LALI or HALI group versus the control group (P > 0.159). Weight loss was greater in all exercise groups than the control group (P < 0.001); however, reduction in body weight did not differ among the exercise groups (P > 0.182). The clinical importance of reducing 2-hour glucose level in nondiabetic adults remains undetermined. Fixed amounts of exercise independent of exercise intensity resulted in similar reductions in abdominal obesity. Reduction in 2-hour glucose level was restricted to high-intensity exercise. Canadian Institutes of Health Research.
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Compensatory responses may attenuate the effectiveness of exercise training in weight management. The aim of this study was to compare the effect of moderate- and high-intensity interval training on eating behaviour compensation. Using a cross-over design, 10 overweight and obese men participated in 4-week moderate- (MIIT) and high- (HIIT) intensity interval training. MIIT consisted of 5 min cycling stages at ±20% of mechanical work at 45 %VO2peak, and HIIT consisted of alternate 30 s work at 90 %VO2peak and 30 s rests, for 30-45 min. Assessments included a constant-load exercise test at 45 %VO2peak for 45 min followed by 60 min recovery. Appetite sensations were measured during the exercise test using a Visual Analogue Scale. Food preferences (Liking & Wanting) were assessed using a computer-based paradigm, and this paradigm uses 20 photographic food stimuli varying along two dimensions, fat (high or low) and taste (sweet or non-sweet). An ad libitum test meal was provided after the constant-load exercise test. Exercise-induced hunger and desire to eat decreased after HIIT, and the difference between MIIT and HIIT in desire to eat approached significance (p = 0.07). Exercise-induced liking for high-fat non-sweet food tended to increase after MIIT and decreased after HIIT (p = 0.09). Fat intake decreased by 16% after HIIT, and increased by 38% after MIIT, with the difference between MIIT and HIIT approaching significance (p = 0.07). This study provides evidence that energy intake compensation differs between MIIT and HIIT.