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©Journal of Sports Science and Medicine (2015) 14, 747-755
http://www.jssm.org
The Effects of High Intensity Interval Training vs Steady State Training on
Aerobic and Anaerobic Capacity
Carl Foster 1
, Courtney V. Farland 1, Flavia Guidotti 2, Michelle Harbin 1, Brianna Roberts 1, Jeff
Schuette 1, Andrew Tuuri 1, Scott T. Doberstein 1 and John P. Porcari 1
1 Department of Exercise and Sport Science,University of Wisconsin-La Crosse, La Crosse, WI, USA
2 Department of Human Movement and Sports Sciences, University of Rome Foro Italico, Rome, Italy
Abstract
High intensity interval training (HIIT) has become an increas-
ingly popular form of exercise due to its potentially large effects
on exercise capacity and small time requirement. This study
compared the effects of two HIIT protocols vs steady-state
training on aerobic and anaerobic capacity following 8-weeks of
training. Fifty-five untrained college-aged subjects were ran-
domly assigned to three training groups (3x weekly). Steady-
state (n = 19) exercised (cycle ergometer) 20 minutes at 90% of
ventilatory threshold (VT). Tabata (n = 21) completed eight
intervals of 20s at 170% VO2max/10s rest. Meyer (n = 15)
completed 13 sets of 30s (20 min) @ 100% PVO2 max/ 60s
recovery, average PO = 90% VT. Each subject did 24 training
sessions during 8 weeks. Results: There were significant (p <
0.05) increases in VO2max (+19, +18 and +18%) and PPO (+17,
+24 and +14%) for each training group, as well as significant
increases in peak (+8, + 9 and +5%) & mean (+4, +7 and +6%)
power during Wingate testing, but no significant differences
between groups. Measures of the enjoyment of the training
program indicated that the Tabata protocol was significantly less
enjoyable (p < 0.05) than the steady state and Meyer protocols,
and that the enjoyment of all protocols declined (p < 0.05)
across the duration of the study. The results suggest that alt-
hough HIIT protocols are time efficient, they are not superior to
conventional exercise training in sedentary young adults.
Key words: training, Wingate, interval training, Tabata
Introduction
Interest in optimizing the magnitude of adaptation result-
ing from physical training, while minimizing the time and
effort devoted to training, is a topic of considerable inter-
est within the exercise community. Including classical
studies of interval training for athletic performance
(Astrand et al., 1960; Muller, 1953) the substantial body
of evidence regarding the effects and side effects of varia-
tions in the Frequency, Intensity, Time and Type (FITT)
of training are effectively codified in ACSM’s Guidelines
for Exercise Testing and Prescription (Pescatello et al.,
2014). This evidence is further addressed in the broad
public health recommendation that healthy adults should
accumulate 30 min of moderate intensity exercise on most
if not all days of the week (Haskell et al., 2007), and that
individuals interested in enhanced outcomes (including
competitive performance) should regularly do both a
larger volume of training and higher intensity training
(Billat, 2001; Selier et al., 2013). Active research contin-
ues designed to determine how specific variations of FITT
might further optimize adaptations to exercise training.
The literature, particularly with reference to high intensity
interval training (HIIT), has recently been reviewed
(Buchiet and Laursen, 2013a; 2013b; Kessler et al. 2012;
Weston et al., 2014). Since one of the chief barriers to
broad public participation in exercise programs is a per-
ceived lack of time (Salmon et al. 2003), one of the ap-
peals of HIIT training has been that it potentially repre-
sents a more time efficient way to accomplish the adap-
tive goals of exercise training. Indeed, Gillen et al (2014)
have shown that as little as three 10 min sessions weekly,
with only 3 x 20s high intensity, could effect both muscle
oxidative capacity and several markers of cardiometabolic
health. Beyond the importance of time efficiency, there
are a number of known motivations for participation in
exercise programs (extrinsic motivators generally associ-
ated with changes in the body) and sport (intrinsic moti-
vators related to pleasure and mastery) (Kilpatrick et al.,
2002, 2005). These motivators can be contextualized
within the concept of self-determination theory, which
suggests that human activity can be understood within the
context of seeking autonomy, competence and relatedness
(Kilpatrick et al. 2002). Amongst the predictors of contin-
uing an exercise program is recognition of the importance
of enjoyment to long-term adherence with exercise pro-
grams (Dishman et al., 2005). There are relatively little
data available regarding how different types of exercise
programs are perceived by exercisers. Early evidence
suggests that high-intensity interval running might be
more enjoyable than moderate-intensity continuous exer-
cise (Bartlett et al., 2011 Jung et al. 2014), although eve-
ryday experience suggests that higher intensity exercise is
inherently less comfortable (i.e. enjoyable). This is im-
portant because even if exercise programs can be con-
structed in a very effective and time efficient format, if
they are not perceived as enjoyable there is little likeli-
hood that the program will be sustained for long enough
to achieve reasonable health and fitness outcomes.
Beginning with studies demonstrating the value of
interval training in clinical populations (Smodlaka, 1963;
Meyer et al., 1990), and inspired by evidence that very
high-intensity training can simultaneously produce adap-
tations in both aerobic and anaerobic exercise capacity
(Tabata et al., 1996), interest in the potential value of
HIIT, as an alternative to conventional training, has been
considerable during the past 20 years. Studies from a
number of laboratories, with protocols designed more to
Research article
Received: 23 June 2015 / Accepted: 22 August 2015 / Published (online): 24 November 2015
HIIT vs continuous training
748
demonstrate the rapidity of molecular signaling events
following high-intensity training (Babraj et al., 2009;
Burgomaster et al., 2005; Gibala and McGee, 2008;
Gibala et al., 2012; Helgerud et al., 2007, Whyte et al.,
2010) than to have practical use (Bayati et al., 2011;
Guiraud et al., 2010; Little et al., 2009; Matsuo et al.,
2014; Nybo et al., 2010; Osawa et al., 2014; Rognmo et
al., 2004) have demonstrated the ability of HIIT to pro-
duce large gains in both aerobic and anaerobic exercise
ability, often with a remarkably reduced direct exercise
time requirement. However, since these protocols have
widely different levels of experimental control (sedentary
vs aerobic exercise), there is still debate over the relative
value of HIIT training relative to steady- state training.
Further, since many of the HIIT protocols can present
significant discomfort to the exerciser, the likelihood that
long term adherence to HIIT training will be high enough
to promote long term beneficial outcomes is of concern.
However, we have little direct evidence about how differ-
ent training programs are perceived. Accordingly, the
purpose of this study was to compare physiologic re-
sponses of two basic HIIT variants against a steady-state
training control in previously inactive young adults, as
evidenced by changes in both aerobic and anaerobic exer-
cise capacity. Additionally, we sought to evaluate how
training was perceived in these groups, from the perspec-
tive of factors that might influence long term adherence.
Methods
Sixty-five (23 male, 42 female) relatively-sedentary sub-
jects volunteered for the study. Their ages ranged from
18-28 years. The protocol, purpose, and risks of the study
were explained to all interested participants. The Physical
Activity Readiness Questionnaire (PAR-Q) was adminis-
tered to the subjects prior to participation to rule out con-
traindications to participation. In order to be eligible for
the study, subjects could not have been exercising more
than twice per week at low-to-moderate intensity during
the preceding three months (e.g. < 2 hr per week). Quali-
fied subjects provided written informed consent before
participating. The study was approved by the University
Institutional Review Board for the Protection of Human
Subjects, and conformed to the principles outlined in the
Declaration of Helsinki.
An incremental exercise test, performed on an
electrically braked cycle ergometer (Lode Excalibur,
Groningen, NL), was used to assess aerobic capacity. The
subjects were instructed to abstain from caffeine for 6
hours before the test, which was conducted (within sub-
ject) in a period of ±2 hours of each day. A practice test
was not administered. The test began with a 5-min rest-
ing period to allow measurement of resting HR, followed
by a 3-minute warm up at 25 W. After 3 minutes, the load
was increased by 25 W per minute. Subjects pedaled at a
cadence ~80 rpm. The test was terminated when subjects
were too fatigued to continue, or when the cadence fell
below 60 rpm. Maximal HR was measured using radiote-
lemetry (Polar Electro-Oy, Kempele, Finland). The Rat-
ing of Perceived Exertion (RPE) was measured during the
test using the Category Ratio (0-10) RPE scale (Borg,
1998). Respiratory metabolism was measured using open-
circuit spirometry, with a mixing chamber based metabol-
ic cart (Parvo Medics, Sandy, Utah). Calibration was
completed before each test using a reference gas (16% O2
& 4% CO2) and room air. A 3-L syringe was used to
calibrate the pneumotach. VO2 was summated every 30s,
and the highest 30s value during the test was accepted as
VO2max. A verification trial was not performed as we
have previously found that there is no systematic change
in VO2max during a second exercise effort at higher
muscular power output (Foster et al., 2007). The peak
aerobic power, expressed per kg BW (PaerPO) was accept-
ed as the PO for the highest stage completed plus propor-
tional credit for incomplete stages.
As a measure of anaerobic power-capacity, the
subjects performed the Wingate Anaerobic Test (Bar-Or,
1987). The test was performed, on a different day, on an
electronically braked cycle ergometer (Lode Excalibur,
Groningen, NL), in the constant torque mode. The sub-
jects warmed up for 5-min at 25W. In the last 5-s of the
warm-up period, the subject increased their pedaling rate
to >100 rpm (with no resistance on the flywheel). At the
beginning of the test the resistance was increased to 0.075
kg.kg-1 BW and the subject attempted to maximize their
pedaling rate for the next 30s. Peak power output (PPO)
(the highest PO observed during 1s during the test) and
the mean power output (MPO)(the average PO over the
30s duration of the test) were recorded from the ergome-
ter software. The PPO and MPO were expressed relative
to BW. As an additional marker of exercise capacity, the
Combined Exercise Capacity (CEC) was calculated as the
mean of PaerPO + PPO + MPO, and expressed as W.kg-1
BW. One day during each week of the 8-week training
program the subjects completed the Exercise Enjoyment
Scale (EES) (Stanley et al., 2010). The ESS was adminis-
tered pre-, during- and post-training to determine the
subject’s perceived level of enjoyment. A rank of zero
indicated the absence of enjoyment, while a rank of seven
indicated high enjoyment. All subjects were directed to
rank their perceived level of enjoyment at the exact mo-
ment in time that the scale was administered. Within
subjects, the ESS was admininstered on the same day of
each week. For logistic reasons, between subjects the
administration of the ESS was distributed throughout the
week.
Training
Following pre-testing, the subject’s exercise capacity was
ranked based on the CEC. Males and females were ranked
separately. From these rankings, subjects were stratified
into groups (best 3, next three, …..worst three) and from
these groups were randomly assigned to the three training
groups: steady-state, very brief, very high intensity inter-
val training (Tabata et al.. 1996), or moderate intensity
interval training (Meyer et al., 1990). Training was per-
formed on mechanically braked ergometers (Monarch
GBH, Varburg, Sweden) with the pedaling rate controlled
by a metronome. All training sessions were supervised 1
to 1 by laboratory assistants.
Identical five-minute warm-up and cool-down pe-
Foster et al.
749
riods were performed by all three training groups (2 min
at 25 W, 1 min at 50 W, 1 min at 75 W, 1 min at 25 W).
Steady-state training consisted of 20-min of continuous
exercise at a PO calculated to require a VO2 of 90% of
ventillatory threshold (VT) (Foster and Cotter, 2005),
based on the pre-training VO2max test, and to fit into the
moderate to vigorous intensity as defined by ACSM (Pes-
catello et al. 2013). Meyer interval training consisted of
20 minutes (13 sets) of 30s work intervals (at 100%
PaerPO from the pre-training VO2max test) paired with
60S of active recovery (at a PO calculated to yield a mean
PO @ 90% VT). Tabata training consisted of 20s of work
at a PO calculated to require 170% of Paer paired with 10s
of unloaded pedaling for a total of 8 sets, or 4 min.
Steady-state and Meyer subjects cycled at a cadence of 80
rpm, while Tabata subjects pedaled at 90 rpm during the
loaded period.
At the end of each day of training the session RPE
(sRPE) was assessed (Foster et al., 1995). When sRPE
decreased by 2 units or greater, the PO was increased ~
10% for the next training session. In the two HIIT groups,
PO was increased in the loaded segment by increasing
flywheel torque; recovery PO remained constant. All
subjects completed 24 exercise sessions over the 8-week
training period. To further document the training intensi-
ty, HR and [blood lactate] (Lactate Pro) were measured
during one training session each week. However, deci-
sions regarding progression of the training load were
based solely on sRPE.
Statistical analysis
Standard descriptive statistics were used to characterize
the subject population. A one-way analysis of variance
(ANOVA) was performed across pre-training scores to
determine if the groups were similar at the beginning of
the study. A three-way ANOVA with repeated measures
was then performed (pre/post x group x gender) to deter-
mine if there were any between group changes as a result
of training. When there was a significant F-ratio, Tukey’s
post-hoc tests were used to determine pairwise differ-
ences. Alpha was set at .05 to achieve statistical signifi-
cance. Analysis was performed on data from the subjects
who completed the entire protocol.
Results
Fifty-five of the original 65 subjects completed the study
(17 male, 38 female). Descriptive characteristics of the
subjects are presented in Table 1. The steady-state group
lost one male due to loss of interest (unwillingness to
continue the protocol). The Tabata group lost three female
subjects, two due to loss of interest and one other to an
unrelated injury. The Meyer group lost a total of six sub-
jects. One female was lost due to loss of interest, four
males due to unrelated injury/illness, and one female due
to unrelated injury. No significant differences existed
between the three training groups with regards to age,
height, and weight at the start of the study.
The acute responses during the training program
are presented in Figure 1. There was a progressive in-
crease in training PO in all groups, amounting to 50 W in
the steady state group (+50%), 45 W in the PO of the hard
segment of the Meyer group (+45%), and 70 W in the PO
of the hard segment in the Tabata group (+18%). Despite
these progressions of the external training load training,
markers of the internal training load (%HRR, sRPE, blood
lactate) remained constant during the 8-week training
period (Figure 1). The HR at the end of the training bout
was 75-80% HRR in the steady-state and Meyer groups,
whereas in the Tabata group the HR approximated 85%
HRR. Blood lactate concentration at the end of the train-
ing bouts was 5-6 mmol.l-1 in the steady-state group, ~8
mmol.l-1 in the Meyer group, and ~12 mmol.l-1 in the
Tabata group. The sRPE was 4-5 (somewhat hard to
hard), 5-6 (hard+) and 7-8 (very hard) in the steady-state,
Meyer and Tabata groups, respectively.
Table 1. Descriptive characteristics of the subjects who
completed the study. Data are means (±SD).
Steady-State
(n=19)
Tabata
(n=21)
Meyer
(n=15)
Age (yrs)
Males
19.5 (1.4)
20.3 (2.1)
19.3 (1.3)
Females
19.6 (2.9)
19.5 (1.2)
19.9 (2.8)
Height (m)
Males
1.82 (.09)
1.75 (.06)
1.79 (.11)
Females
1.65 (.05)
169 (.04)
1.65 (.05)
Weight (kg)
Males
94.3 (7.2)
81.0 (13.9)
76.4 (12.5)
Females
68.6 (15.1)
68.2 (14.0)
71.9 (18.6)
There were no significant differences between
groups for any variable pre-training. There were no sig-
nificant differences in responses of males vs. females over
the course of the study, thus training group data were
collapsed across gender.
VO2max changed significantly in all three groups
(Table 2). This represented ~18% increase across training,
with no differences between training groups. When the
data were expressed as body weight normalized power
output, there were significant changes across training in
all groups, with no differences between groups. When the
body weight normalized power output was expressed as
the combined exercise capacity (CEC), there was a 6-10%
increase with training, but no difference between groups
(Table 2).
The EES demonstrated a significantly declining
score across weeks in all groups, with significantly lower
values in the Tabata group. There was not a significant
weeks x group interaction effect (Figure 2). The EES was
lower during training than either before or after training.
Discussion
The main finding of this study was the substantial equiva-
lence of increases in measures of both aerobic and anaer-
obic exercise performance in all three training groups.
Contrary to the frequent claims in the literature of larger
responses following high- intensity exercise training re-
gimes, in this group of relatively untrained young adults
there was no apparent advantage gained from more in-
tense exercise. Even considering the numerically greater
increase in all measures of exercise capacity in the Tabata
HIIT vs continuous training
750
Figure 1. Acute responses (mean ±sd) during training in the three experimental groups (circles=steady state, trian-
gles=Meyer, Squares=Tabata) across the training program. Power output in the HIIT groups is expressed as Watts during the loaded
segments.
Table 2. Changes in VO2max, PaerPO, Wingate PPO and Wingate MPO in the three training groups. All groups improved
significantly, but there was no evidencce that one group improved significantly more than the others. Data are means (±SD).
Measure
Pre Training
Post Training
Change (%)
VO
2
max (ml.kg-1)
Steady-State
33.6 (5.4)
40.1 (6.3)
19% *
Tabata
34.0 (6.5)
40.1 (6.8)
18% *
Meyer
34.3 (9.1)
40.6 (8.7)
18% *
P
aer
PO (W.kg-1)
Steady-State
2.65 (.61)
3.09 (.76)
17% *
Tabata
2.72 (.77)
3.36 (.69)
24% *
Meyer
2.81 (.70)
3.21 (.69)
14% *
Wingate PPO (W.kg-1)
Steady-State
11.5 (1.6)
12.4 (1.4)
8% *
Tabata
11.7 (1.4)
12.7 (1.4)
9% *
Meyer
11.8 (1.5)
12.4 (1.7)
5% *
Wingate MPO (W.kg-1)
Steady-State
6.1 (1.0)
6.3 (.9)
4% *
Tabata
6.4 (1.0)
6.9 (1.1)
7% *
Meyer
6.2 (1.3)
6.6 (1.0)
6% *
Combined Exercise
Capacity (W.kg-1)
Steady-State
6.75 (1.07)
7.26 (1.02)
7.6% *
Tabata
6.94 (1.06)
7.65 (1.06)
10.2% *
Meyer
6.94 (1.17)
7.40 (1.13)
6.6% *
* p < 0.05
group, there was not a significantly larger increase in the
CEC in any of the groups.
The second major finding was that the EES de-
clined progressively across the duration of the study.
Additionally, the EES was lower during the most intense
(Tabata et al. 1996) training scheme. Put simply, the
subjects were significantly less likely to enjoy the most
intense training protocol, and their enjoyment of all the
protocols declined over time.
The magnitude of improvement in measures of
aerobic exercise performance (VO2max and Paer) is con-
sistent with other short-term training studies in relatively
untrained trained young adults (Bouchard et al., 1999;
Helgerud et al., 2007; Matsuo et al., 2014; Nybo et al.,
2010; Pollock, 1973; Rognmo et al., 2004; Tabata et al.,
1996). In studies with an appropriate steady-state control
group, interval training has usually produced a larger
increase in VO2max than nominally similar steady state-
Foster et al.
751
Figure 2. Changes in the acute Exercise Enjoyment Score
(possible score 1-7)( mean ±sd) measured prior to (top),
during (middle) and after (bottom) training bouts (all meas-
urements on the same day within subjects) in relation to the
type of training and the duration of the study (circles=steady
state, triangles=Meyer, Squares=Tabata). Notably, the ESS is
generally declining across the course of the study, and the most intense
training scheme (Tablata) was rated the least enjoyable.
training. Indeed, studies like that of Gillen et al. (2010)
suggest that even very brief high intensity training proto-
cols can produce stubstantial increases in markers of
cardiometabolic health. Certainly in already well-trained
individuals, interval training seems to be necessary to
provoke additional increases in exercise capacity that
cannot be achieved with steady-state training (Laursen,
2010; Gorostiaga et al., 1991; Seiler et al., 2013; Stepto et
al., 1999). Remarkably, in the present data was the com-
paratively large increase in the magnitude of improve-
ment in the steady-state group. Ignoring the report of
Meyer et al. (1990), which represents early post-bypass
surgery patients (with a very large margin for improving),
other studies have observed ~15% increases in VO2max
per kg BW in HIIT groups over 6-12 weeks of training,
compared to ~10% in control groups performing steady-
state training. In the current results the increase in
VO2max per kg BW was 18-20%. These results do not
appear to be attributable to uniquely high values for train-
ing intensity in the control group, which averaged 75-80%
HRR (e.g. moderate to vigorous training intensity) and an
sRPE of 4-5 on the Category Ratio RPE scale, although
[blood lactate] averaged 4-6 mmol∙l-1 which suggests
training intensity was in the vigorous if not severe train-
ing classification
One of the most remarkable (but perhaps not sur-
prising) findings of this study is the significantly lower
level of enjoyment in the Tabata group, and the progres-
sively declining level of enjoyment in all groups across
the course of the study. Several studies (Bartlett et al.
2011, Jung et al. 2014, Kilpartirck et al., 2012) all suggest
that moderate intensity interval training may be more
pleasant than moderate intensity continuous exercise.
However, Tabata type protocols (very high intensity in-
tervals with very short recovery periods) are so physically
chanllenging that they are very unlikely to be perceived as
pleasant. Regardless of how effective an exercise training
program might be, adherence over any meaningful period
of time is unlikely in programs that are not enjoyable.
Regardless of whether the EES was obtained before, dur-
ing or after training, the very high intensity Tabata proto-
col was rated as the least enjoyable. Despite the contem-
porary popularity of Tabata type training within the fit-
ness industry, it must be remembered that the develop-
ment of this type of training was based on extrapolating
training practices of highly motivated strength-power
athletes (speed skaters) to the general exercising public.
To expect non-athletes to find this type of training enjoy-
able is probably unreasonable. In this context, it is worth
noting that several studies which have been based on very
short-term (2 weeks) models of repetitive Wingate tests
(which are widely known to be unpleasant), were de-
signed to demonstrate the rapidity of the skeletal muscle
and metabolic adaptive response to high levels of molecu-
lar signaling. It seems reasonable to suggest that the
findings of these high intensity studies have been extrapo-
lated by the fitness community into daily practice, without
the benefit of longer term studies supporting short term
experimental results. From what we know of the intra
muscular molecular responses to HIIT (Burgomaster et
al., 2005, Gibala and McGee, 2008, Gibala et al., 2012) it
would be reasonable to suggest that protocols less de-
manding (and likely less unpleasant) than the Burgomater
model of repeat Wingate tests or the Tabata model of
ultra-high intensity exercise with very short recovery
periods, might induce (in previously untrained people)
many of the same skeletal muscle and metabolic adapta-
tions, in a way that is more likely to be enjoyable enough
to be continued for long periods of time. This is supported
by the somewhat briefer, and less demanding, protocol
recommended by Gillen et al. (2010). However, the com-
parability of MRNA expression following iso-energetic
HIIT vs continuous training
752
continuous and interval training (Wang et al. 2009) argues
that in untrained people, the responsiveness of the muscle
to training may be so high that the details of how training
is accomplished may be comparatively less important.
Another element of high-intensity training that has
been widely promoted is the supposed time efficiency of
HIIT protocols. In the current data, substantially equiva-
lent results were realized by the Tabata protocol in 14 min
(warm-up + training + cool-down) versus 30 min in the
steady-state and Meyer protocols. Considering only this
time commitment the Tabata protocol is, indeed, more
time efficient than the more conventional training models.
More strikingly, Gillen et al. (2014) have shown that as
little as three 10 min sessions per week, with only 3 x 20s
at high intensity, could have significant effects on muscle
oxidative capacity and several markers of cardiometabolic
health. Similarly, Hazell et al (2010) have shown that
high intensity bouts as short as 10s (which is much less
onerous than the 30s bouts typical of repeated Wingate
tests) could induce substantial changes in VO2max.
However, the experience during the study was that both
the steady-state and Meyer subjects were fully recovered
and ready to ‘return to normal life’ immediately following
the conclusion of the cool-down period. On the other
hand, subjects in the Tabata protocol were still visibly
distressed at the end of the cool-down period and often
required an extended period of time to recover to the point
where they could again pursue normal activities. Viewed
from the perspective that the time efficiency of training
must be evaluated based on the preparation + training +
recovery time, the Tabata protocol (which we take as
broadly representative of the currently popular HIIT
training models) cannot be considered to be particularly
time efficient. Nevertheless, in a comparison of sprint
interval and high intensity interval training, broadly com-
parable to the Tabata and Meyer protocols in the present
study, Wood et al. (2015) demonstrated that essentially
half of participants preferred the more ‘sprint’ type train-
ing. And, it must be acknowledged that the results of
Gillen et al. (2010) with very brief training bouts are
supportive of the potential of HIIT, certainly considering
that exercise modes that recruit relatively more muscle
fibers (including relatively more Type II motor units) may
have unique cardiometabolic effects that deserve further
investigation.
The logic behind HIIT training models is that they
may produce a large adaptive response by virtue of re-
cruiting a broader population of muscle fibers (Gollnick et
al., 1974) and by providing a larger cardiorespiratory
signal to adapt (Buchheit and Laursen, 2013a; 2013b).
To the degree that there have been large changes demon-
strated in elements of muscle physiology including mark-
ers of molecular signaling (Gibala et al., 2008, 2012) with
high intensity training, this logic seems valid. Higher
intensity training is clearly advantageous for more athletic
individuals who have a smaller adaptive response window
(Billat, 2001; Gunnarsson and Bangsbo, 2012; Seiler et
al., 2013; Stepto et al., 1999, Tschakert and Hofmann,
2013). However, the present results suggest, in the setting
of a practical exercise training protocol, that there is little
unique advantage to HIIT protocols with minimally
trained individuals. Further, given that the enjoyment of
the highest intensity protocol was lower, it seems reason-
able to suggest that long-term adherence to this form of
training may be unfavorable. The generally declining EES
in all three groups suggests that the novelty in the struc-
ture of a training program may be rather the more im-
portant issue. Although we are unaware of evidence re-
garding how the structure of training programs influences
the EES, or for that matter how the EES influences the
long-term adherence to exercise programs, it seems rea-
sonable to suggest that variation in the structure of exer-
cise programs might be important to long term adherence,
just as periodization of the physical stresses of an exercise
program is important to the physiological responses to
training.
A limitation of the study in terms of subject selec-
tion needs to be acknowledged. Recruiting truly seden-
tary subjects, who are not generally interested in exercise
of any form, for a study that includes the possibility of
being randomized to a quite vigorous training program is
difficult. On the other hand, in a university community,
even nominally sedentary subjects may have background
levels of activity that are higher than ideal. We only ac-
cepted ~33% of subjects expressing an interest in the
study. Most of those who were rejected were either too
active currently, or had a recent history of sports partici-
pation (usually in high school).
Exercise training protocols also have to be evalu-
ated in terms of safety. Although exercise training is gen-
erally quite safe (Foster and Porcari, 2008), higher inten-
sity exercise has been shown to be a trigger for acute
myocardial infarction in middle-aged and older individu-
als (Franklin and Billecke, 2012) and there has been re-
cent concern that “excessive” volume and intensity of
exercise training, in athletic individuals, may lead to ad-
verse cardiac remodeling (O’Keefe et al., 2015). Within
this context, it seems reasonable to suggest that HIIT
protocols should be used somewhat sparingly.
Conclusion
In conclusion, in this population of relatively untrained
but healthy young adults, our results suggest no particular
advantage for very high intensity training models, such as
that which has been widely adapted from the results of
Tabata et al. (1996). The observation that the Tabata pro-
tocol was less enjoyable is not surprising. The progressive
loss of enjoyment across all the protocols suggests that
perhaps variety in the type of exercise is as important as
the type of exercise per se. Particularly considering that
the health benefits of exercise have to be viewed in the
context of the likelihood that exercise is continued for
several years, not just the weeks of a controlled study.
Perhaps, in our quest to find the ‘perfect exercise’ we
have missed the more important issue of how to make
exercise enjoyable enough to be continued long term.
Acknowledgements
This study was performed in compliance with the laws of the United
States of America. This study was supported by a grant to John Porcari,
Ph.D. from the American Council on Exericse.
Foster et al.
753
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Key points
• Steady state training equivalent to HIIT in un-
trained students
• Mild interval training presents very similar physio-
logic challenge compared to steady state training
• HIIT (particularly very high intensity variants were
less enjoyable than steady state or mild interval
training
• Enjoyment of training decreases across the course
of an 8 week experimental training program
AUTHOR BIOGRAPHY
Carl FOSTER
Employment
Professor of Exercise and Sport Science,
University of Wiscosnsin-La Crosse
Degree
Ph.D.
Research interests
Exercise physiololgy
E-mail: cfoster@uwlax.edu
Courtney V. FARLAND
Employment
Graduate student, University of Wisconsin-
La Crosse
Degree
M.S.
Research interests
Clinical Exercise Physiology
Flavia GUIDOTTI
Employment
Department of human movement science,
University of Rome, Foro Italico
Degree
Ph.D.
Research interests
Exercise science
Michelle HARBIN
Employment
Graduate student, exercise science, Univer-
sity of Minnesota
Degree
M.S.
Research interests
Exercise physiology
Brianna ROBERTS
Employment
Graduate student, University of Wisconsin-
La Crosse
Degree
M.S.
Research interests
Clinical Exercise Physiology
Jeff SCHUETTE
Employment
Graduate student, University of Wisconsin-
La Crosse
Degree
M.S.
Research interests
Clinical Exercise Physiology
Foster et al.
755
Andrew TUURI
Employment
Graduate Student, University of Wisconsin-
La Crosse
Degree
M.S.
Research interests
Clinical Exercise Physiology
Scott T. DOBERSTEIN
Employment
Senior academic staff—
exercise and sport
science, University of Wisconsin-La Crosse
Degree
M.S., ATC
Research interests
Athletic training
John P. PORCARI
Employment
Professor of Exercise and Sport Science,
University of Wisconsin-La Crosse
Degree
Ph.D.
Research interests
Exercise Physiology
Carl Foster, Ph.D., FACSM
Department of Exercise and Sport Science, University of Wis-
consin-La Crosse, 133 Mitchell Hall, La Crosse, WI 54601 USA
