Aerobic and Anaerobic Changes with High-Intensity Interval Training in Active College-Aged Men

Abstract

We investigated the aerobic and anaerobic benefits of high-intensity interval training performed at a work-to-rest ratio of 1:2 because little performance enhancement data exist based on this ratio. Recreationally active male volunteers (21 years, 184 cm, 81.5 kg) were randomly assigned to a training (interval training [IT] n = 10) or control group (n = 11). Baseline assessments were repeated after the last training session. Each participant underwent basic anthropometric assessment and performed a VO2max test on an electronically braked cycle ergometer and a 30-second Wingate test. Venous samples were acquired at the antecubital vein and subsequently processed for lactate (LA); samples were obtained at rest, and 5 and 15-minute post-Wingate test. The interval training used a cycling power output equivalent to 80% of VO2max (80% p VO2max) applied for 6 90-second bouts (each followed by 180-second rest) per session, 3 sessions per week, for 6 weeks. The control group maintained their normal routine for the 6-week period. Group × time repeated-measures analyses of variance revealed that IT improved VO2max (5.5 ml · kg(-1) · min), anaerobic threshold (3.8 ml · kg(-1) · min), work output (12.5 J · kg(-1)), glycolytic work (11.5 J · kg(-1)), mean power (0.3 W · kg), peak power (0.4 W · kg(-1)), and max power (0.4 W · kg(-1)); p < 0.05. Posttesting LA was lower on average for IT at the 5-minute mark but significantly so at the 15-minute mark. Twenty-seven minutes of cycling at 80% p VO2max applied with a work-to-rest ratio of 1:2 and spread over 3 sessions per week for 6 weeks provided sufficient stimulus to significantly improve markers of anaerobic and aerobic performance in recreationally active college-aged men. Inclusion of such a protocol into a training program may rapidly restore or improve a client's or athlete's maximal functional capacity.

Full text

AEROBIC AND ANAEROBIC CHANGES WITH
HIGH-INTENSITY INTERVAL TRAINING IN ACTIVE
COLLEGE-AGED MEN
EWA ZIEMANN,
1
TOMASZ GRZYWACZ,
1
MARCIN LUSZCZYK,
1
RADOSLAW LASKOWSKI,
1
ROBERT A. OLEK,
2
AND ANN L. GIBSON
3
1
Department of Physiology, Academy of Physical Education and Sport, Gdan
´sk, Poland;
2
Department of Biochemistry,
Academy of Physical Education and Sport, Gdan
´sk, Poland; and
3
Department of Health, Exercise, and Sport Sciences,
University of New Mexico, Albuquerque, New Mexico
ABSTRACT
Ziemann, E, Grzywacz, T, Luszczyk, M, Laskowski, R, Olek, RA,
and Gibson, AL. Aerobic and anaerobic changes with high-intensity
interval training in active college-aged men. JStrengthCondRes
25(4): 1104–1112, 2011–We investigated the aerobic and
anaerobic benefits of high-intensity interval training performed at
a work-to-rest ratio of 1:2 because little performance enhance-
ment data exist based on this ratio. Recreationally active male
volunteers (21 years, 184 cm, 81.5 kg) were randomly assigned to
a training (interval training [IT] n= 10) or control group (n= 11).
Baseline assessments were repeated after the last training
session. Each participant underwent basic anthropometric
assessment and performed a
_
VO
2
max test on an electronically
braked cycle ergometer and a 30-second Wingate test. Venous
samples were acquired at the antecubital vein and subsequently
processed for lactate (LA); samples were obtained at rest, and
5 and 15-minute post-Wingate test. The interval training used a
cycling power output equivalent to 80% of
_
VO
2
max (80%
p
_
VO
2
max) applied for 6 90-second bouts (each followed by
180-second rest) per session, 3 sessions per week, for 6 weeks.
The control group maintained their normal routine for the 6-week
period. Group 3time repeated-measures analyses of variance
revealed that IT improved
_
VO
2
max (5.5 mlkg
21
min
21
), anaerobic
threshold (3.8 mlkg
21
min
21
), work output (12.5 Jkg
21
),
glycolytic work (11.5 Jkg
21
), mean power (0.3 Wkg
21
), peak
power (0.4 Wkg
21
), and max power (0.4 Wkg
21
); p,0.05.
Posttesting LA was lower on average for IT at the 5-minute mark
but significantly so at the 15-minute mark. Twenty-seven minutes of
cycling at 80% p
_
VO
2
max applied with a work-to-rest ratio of 1:2
and spread over 3 sessions per week for 6 weeks provided
sufficient stimulus to significantly improve markers of anaerobic and
aerobic performance in recreationally active college-aged men.
Inclusion of such a protocol into a training program may rapidly
restore or improve a client’s or athlete’s maximal functional capacity.
KEY WORDS blood lactate, Wingate, Training adaptations,
cycling
INTRODUCTION
Short duration, high-intensity interval training (HIIT)
has been proposed as an effective way to improve
aerobic capacity (11–13,27) and found to be bene-
ficial when training for endurance sports such as
running, cycling, and swimming (12,21,26–28). Diverse HIIT
protocols are well documented (13,20,26), and extensive
reviews of training adaptations to short-sprint (33)and interval
training (6,7) detail the variety in volume, duration, recovery,
frequency, or sample (33).
Accordingto Daniels and Scardina (17), short-duration work
intervals performed at or near velocities associated with
_
VO
2
max can prolong the time at which intensities of 95–100%
_
VO
2
max can be maintained during a training session (17).
Consequently, previous studies have mostly focused on work-
to-rest ratios of 1:1 or greater (2:1, 4:1) with interval durations
ranging from 15 seconds to 2.5 minutes (8,34). In these studies,
an increase in
_
VO
2
max and the velocity associated with
_
VO
2
max has been presented. Additionally, various passive and
active recovery periods after exertion at intensities of 50–70%
_
VO
2
max combining to make work-to-rest ratios of 1:1, 2:1, and
4:1 have been examined. The results obtained in these studies
confirmed a beneficial impact of interval training while at the
same time presenting limitations to completion of the entire
training program when the exercise intensity was too high and
the recovery time too short even though the subjects had an
excellent level of physical conditioning (8,34).
In various sport disciplines, training with a work-to-rest
ratio of 1:2 or 1:3 is often recommended to prepare for
competition that requires a similar physical effort and
development of particular energetic systems. For example,
randori training (fighting practice) in judo uses this pattern of
Address correspondence to Dr. Ann Gibson, alg@unm.edu.
25(4)/1104–1112
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Ó2011 National Strength and Conditioning Association
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work-to-rest ratio (14). A work-to-rest ratio of 1:2 is also
specific for ice-hockey players during the game (25). Time–
motion analysis of an ice-hockey match indicated that the
average shift lasts about 85 seconds with 225-second
recoveries between shifts (22). In tennis, recent research
has shown that the duration of work and rest periods during
a match is 5–10 and 10–20 seconds, respectively, for a work-
to-rest ratio in the range of 1:1 and 1:2 to 1:4 (18).
Sport-specific training programs are designed to optimize
players’ skills and should also mimic the physiological and
energetic demands of a particular sport. For most sports, the
adenosine triphosphate-phosphocreatine (ATP-PC), glyco-
lytic, and oxidative phosphorylation systems play important
roles. The first 2 energy systems are the main sources of ATP
during high-intensity exercise, whereas the mitochondrial
system plays a crucial role in terms of recovery periods.
Most of the published reports focus mainly on the changes
in aerobic capacity as a result of HIITwith a work-to-rest ratio
of 1:2. Fox suggested that a work-to-rest ratio of 1:2 is optimal
for improving the glycolytic system (19). Recently, Laursen
et al. (27) confirmed this observation, reporting that 4 weeks
of HIIT increased anaerobic capacity as evaluated through
accumulated oxygen deficit. The main goal of the present
study was to determine if a 6-week training program using
a work-to-rest ratio of 1:2 with passive rest periods between
bouts could improve both anaerobic and aerobic capacities
in a sample of recreationally active, college-aged men. We
hypothesized that a protocol using 6 90-second cycling bouts
at 80% p
_
VO
2
max (power at 80%
_
VO
2
max) separated by
180-second passive recovery periods over a 6-week period
would significantly enhance both anaerobic (lactic and
alactic) and aerobic capacity.
METHODS
Experimental Approach to the Problem
An overview of the experimental protocol is presented in
Table 1. Participants (Table 2) completed the same battery of
body composition, aerobic, and anaerobic assessments before
and after the intervention period. The exercise tests were
performed on separate days before and after the HIIT inter-
vention. Aerobic measurements were performed 5 days
before and 2 days after the training intervention; anaerobic
measurements were repeated 2 days after the aerobic
assessments. The variables of interest included those
indicative of maximal aerobic performance (Table 3) and
maximal anaerobic performance (Table 4) as determined
through graded exercise cycling trials to volitional exhaustion
and a maximal exertion 30-second Wingate anaerobic test
(WAnT), respectively. Blood lactate (LA) responses (Table 5)
were investigated during rest and at 2 time intervals after the
final WAnT. These variables were selected because of their
universal applicability to the research question, ease of study
replicability, financial constraints, and the logistical need
to reduce the level of invasiveness. Based on earlier reports,
the combined measurements of the mechanical power and
underlying anaerobic and aerobic energy metabolism have
clearly demonstrated that, for adults, the metabolic profile of
the WAnT is highly anaerobic (ca. 80%) with a minor
(ca. 20%) aerobic component (1,3–5,15,24,30,32,36,37). Using
the Multi Cyclo Ergometer System (MCE v 5.1 Software,
Sport Institute, Warsaw, Poland), the phosphagenic and
nonphosphagenic components of work were determined
from the 30-second Wingate sprint data for each participant.
The basic anaerobic parameters achieved with MCE and the
original Wingate software have shown a strong correlation
(r= 0.98). The identification of the phosphagenic and
nonphosphagenic components is an authorized complement
of the MCE 5.1 version, previously investigated by our team
in collaboration with Sport Institute (38).
Subjects
Twenty-one healthy, physically active but not highly trained,
college-aged men volunteered to take part in the experiment.
The participants were fully informed of the risks and stresses
associated with the study and gave written informed consent
to participate in this study as approved by the Medical
Research Ethics Committee of the Academy of Physical
Education and Sport. Each participant underwent
TABLE 1. High-intensity interval training investigational timeline.*
I. Protocol before interval training
A Anthropometric measurements,
_
VO
2
max test aerobic performance
2-d rest WAnT anaerobic
performance
3-d rest
B (6 wk/3 times/wk); 6 390 s 80%
p
_
VO
2
max work with 180-s rest†
II. Protocol after interval training
C 2-d rest Anthropometric measurements,
aerobic performance
3-d rest Anaerobic
performance
*HIIT = high-intensity interval training
†Total single session of exercise values was 155 kJ; 1-week session was 465 kJ and total training program was 2,795 kJ.
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preliminary exercise testing to become familiar with the
exercise model and to obtain a measure of their maximal
aerobic work capacity 1 week before the experimental trial.
The participants were randomly assigned to either the
interval training (IT; n= 10) or control (C; n= 11) group.
The first stage of the study (baseline measurements and first
3 weeks of training) was conducted during the semester break.
The last 3 weeks of training was performed during the first
3 weeks of the semester. Nevertheless, the 6 weeks of the
protocol were contiguous. The participants’ class schedules
included both theoretical and physical activity units, respec-
tively, 23 and 7 h wk
21
.
During the study, neither group reported participating in
any organized or recreational physical activity outside the
protocol; only the IT group performed the interval training.
The physical activity classes in which the participants were
enrolled were designed with a primary focus on the methods
of teaching physical education, not for promoting fitness. All
participants, according to self-reports, strictly adhered to
the study’s physical activity restrictions, thereby increasing
the likelihood that the changes observed resulted from the
interval training instead of other outside influences.
Procedures
Anthropometric Measurements. Body mass (BM) and body
composition were estimated using a bioelectrical impedance
floor scale (TBF-300 Body Fat Monitor/Scale Analyzer,
Tanita, Japan) calibrated in accordance with manufacturer
guidelines before each test session. One hour after a light
breakfast, participants voided their bladder and bowels and,
TABLE 2. Participant demographic and anthropometric characteristics.*†‡
Variable
Pretraining Posttraining
IT group C group IT group C group
Age (y) 21.6 61.1 21.0 60.9
Height (cm) 182.5 62.5 186.0 65.7
Weight (kg) 81.6 66.2 81.4 67.1 82.0 65.3 81.7 67.0
FFM (kg) 68.2 64.6 69.9 65.7 68.6 64.1 70.0 65.4
Fat (kg) 13.4 63.2 11.0 63.0 13.5 62.2 11.6 62.8
Fat % 16.2 63.2 13.5 63.0 16.4 62.2 14.1 62.7
BMI (kgm
22
) 24.5 61.8 23.0 61.9 24.6 61.5 23.6 62.0
*Fat = fat mass; FFM = free fat mass; BMI = body mass index; IT = interval training group; C = control group.
†Values are means 6SD.
‡Values are not significantly different for group or time.
TABLE 3. Comparison of aerobic parameters before and after HIIT intervention.*†
Variable
Pretraining Posttraining
IT-group C-group IT-group C-group
_
VO
2
max (Lmin
21
) 4.1 60.3 3.9 60.3 4.5 60.4ठ3.9 60.4
_
VO
2
max (mlkg
21
min
21
) 50.1 63.1 48.2 64.7 55.6 65.5ठ48.5 63.9
Power at
_
VO
2
max (W) 360 635 330 627 406 638ठ347 627
Power at
_
VO
2
max (Wkg
21
) 4.4 60.3 4.0 60.5 5.0 60.3 4.3 60.4
Power at AT (W) 277 644 255 634 307 629 250 631
Power at AT (Wkg
21
) 3.4 60.5 3.1 60.5 3.7 60.2‡3.0 60.4
_
VO
2
at AT (mlkg
21
min
21
) 39.6 64.7 38.6 65.3 43.4 62.7‡§ 36.5 62.4§
AT as percentage of
_
VO
2
max 79.0 67.5 79.6 65.5 78.5 66.7 75.7 67.1
*
_
VO
2
max = maximal oxygen uptake; AT = anaerobic threshold; IT = interval training group; C = control group; HIIT = high-intensity
interval training.
†Values are mean 6SD.
‡Significant differences (p#0.05) vs. C-group.
§Significant differences (p#0.05) vs. pretraining.
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clad only in briefs, underwent duplicate measures while in the
standing position recommended by the manufacturer guide-
lines. The average of the 2 values was used for final analysis.
Aerobic Power Measurement. To determine
_
VO
2
max and
anaerobic threshold (AT), participants performed a graded
cycle ergometry test on an electromagnetically braked cycle
ergometer (ER 900 Jaeger, Germany/Viasys Health Care).
The ergometer seat height was individually adjusted to attain
a5°bend in the knee at the lowest point in the pedal
revolution. Participants were allowed a 5-minute warm-up
period at an intensity of 1.5 Wkg
21
with a pedaling cadence
of 60 rpm. Immediately after the warm-up, the participants
began
_
VO
2
max testing by cycling at increasingly difficult
workloads in which resistance was increased by 25 Wmin
21
until the participant reached the point of volitional
exhaustion. The recovery was passive with the participant
in a seated position. Breath-by-breath pulmonary gas
exchange was measured (Oxycon-Pro, Jaeger-Viasys Health
Care, Hochberg, Germany) throughout the
_
VO
2
max test; the
O
2
and CO
2
analyzers were calibrated before each test using
standard gases of known concentrations in accordance with
manufacturer guidelines. The nonlinear increase in ventila-
tion (ventilatory threshold) was used to determine AT. Heart
rates were monitored continuously by telemetry (S-625,
Polar Electro-Oy, Finland) during each test session and the
first 5 minutes of passive recovery in a seated position.
Anaerobic Power Measurement. Participants performed the
WAnTon a mechanically braked cycle ergometer (884E Sprint
Bike, Monark, Sweden) according to the procedures described
previously (2,23). The testing session started with
TABLE 4. Comparison of anaerobic parameters before and after HIIT intervention.*†
Variable
Pretraining Posttraining
IT-group C-group IT-group C-group
Work output (Jkg
21
) 261.1 611 262.9 615 272.3 613ठ266.7 613
Phosphagenic work (Jkg
21
) 76.8 611 80.6 613 75.5 68.9 80.8 614.1
Phosphagenic work (% of total work) 29.5 64.7 30.7 64.7 27.8 62.1 30.4 65.8
Nonphosphagenic component of work (Jkg
21
) 184.3 616.0 182.2 616.0 196.8 616.7 186.0 621.9
Nonphosphagenic component of work (% of total work) 70.5 64.7 69.3 64.2 72.1 63.7 69.5 65.8
Mean power (Wkg
21
) 8.7 60.3 8.7 60.5 9.0 60.4ठ8.7 60.4
Peak power (Wkg
21
) 11.4 60.4 10.9 61.0 11.8 60.7 10.9 60.8
Max power (Wkg
21
) 11.3 60.4 10.9 60.9 11.7 60.7 10.8 60.9
Fatigue index (%) 23.7 63.6 20.0 65.7 19.2 62.4 18.6 64.5
Time to max power (s) 5.1 61.2 5.4 61.0 4.2 60.6‡4.9 60.9
Time at max power (s) 4.6 61.2 4.6 61.0 3.3 60.7 3.7 61.1
*IT = interval training group, C = control group; nonphosphagenic component of work – glycolytic work and oxidative
phosphorylation.
†Values are means 6SD.
‡Significant differences (p#0.05) vs. C-group.
§Significant differences (p#0.05) vs. pretraining.
TABLE 5. Blood lactate levels after Wingate tests before and after HIIT training.*†
Variable
Pretraining Posttraining
IT-group C-group IT-group C-group
LA at rest (mmolL
21
) 1.0 60.3 1.8 60.3 1.0 60.3 1.5 60.3
LA after (5 min) WAnT (mmolL
21
) 15.5 60.8 15.0 60.6 12.4 60.5ठ15.5 60.7
LA after (15 min) WAnT (mmolL
21
) 11.4 61.7 13.6 61.6 9.4 62.1‡12.1 62.2
*LA = lactic acid, WAnT = Wingate anerobic test, IT = interval training group, C = control group.
†Values are means 6SD.
‡Significant differences (p#0.05) vs. C-group.
§Significant differences (p#0.05) vs. pretraining.
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a standardized 5-minute warm-up cycling at 1.0 Wkg
21
BM
21
including 2 all-out sprints lasting 3–5 seconds each against the
resistance used for the actual test. After a 5-minute rest,
the WAnT began from a stationary starting position with the
participant seated and the right pedal at approximately 45°as
previously described (23,30). The participants were instructed
to accelerate to their maximal pedaling rate and were verbally
encouraged to maintain this pedaling cadence as long as
possible throughout the 30-second test. Only during the first
few, initial movements of the test, was each participant able to
pedal in a standing position; this helped overcome the
resistance and achieve the maximal pedaling rate. The
remaining part of the test was performed with the participant
in a seated position. A flywheel resistance equaling 0.075
kgkgBM
21
(corresponding to 7.5% of each individual’s BM)
was applied at the onset of the WAnT (10). After test
termination, the participants were supervised during a 15-min-
ute recovery in a seated or supine position. All tests were
performed at similar times in the morning at least 2 hours after
a light breakfast.
The computer software automatically calculated mechan-
ical power by multiplying braking force by velocity (pedaling
cadence) for each 5-second segment of the WAnT. Four other
indices describing the participant’s WAnT performance were
also calculated programmatically. Peak power (PP), defined as
the highest mechanical power achieved at any stage of the
test, typically occurred in the first few seconds of the WAnT
and was used to represent the explosive characteristics of the
participant’s muscle power. Mean power (MP), the average
power sustained throughout the 30-second period, was used
to represent the average local muscle endurance throughout
the WAnT. The fatigue index (FI) or degree of power drop
from PP to the lowest power at the end of the test, and was
expressed in Ws
21
,WkgBM
21
and as a percentage of PP. Total
work (Wtot) was used to de-
scribe muscle endurance and
was calculated by multiplying
MP by 30 seconds (duration of
the WAnT protocol) and ex-
pressed in Joules (J) or J kgBM
21
(2). It was assumed that PP
primarily reflected the partici-
pant’s ability to convert alactic
(phosphagenic) energy, whereas
MP mainly reflected the com-
bined rate of lactic (glycolytic–
nonphosphagenic), phospha-
genic, and aerobic energy
conversion.
In the present study, the
phosphagenic and nonphospha-
genic components of work were
calculated as previously de-
scribed (38). This mathematical
method is based on calculating the total area under the curve
from the beginning to the end of WAnT (from 0 to 30 seconds
on the horizontal axis). The total diagram area (Figure 1) is
subsequently separated into 2 components, divided at the
perpendicular line from point A on the power course curve to
point B on the time axis; point B corresponds to the onset of
power drop from PP (point A). The first of the 2 parts
corresponds to the phosphagenic (W
anaphosph
) component of
work, and the second one represents the nonphosphagenic
(W
ananonphosph
) component of work. This method provides an
estimation of the proportion of W
anaphosph
and W
ananonphosph
contribution to the total anaerobic energy turnover during the
WAnT. W
anaphosph
and W
ananonphosph
may be expressed as
percentages of total anaerobic work (W
anatot
).
Blood Lactate Analysis. Blood samples were collected from an
antecubital vein as part of the baseline and follow-up WAnT
procedures with samples taken before warm-up and 5 and
15 minutes after WAnT. Immediately after collection, the
blood was deproteinized by the addition of ice cold 0.4 M
perchloric acid. After being thoroughly mixed, the samples
were centrifuged at 12,000gfor 10 minutes. Blood LA was
determined using a standard Randox (Crumlin, United
Kingdom) kit based on the LA oxidase method (LC2389);
assays were performed on a Cecil CE9200 spectrophotometer
(Cambridge, United Kingdom).
Training Intervention. Participants in C continued with their
regularly scheduled classes and activities; Participants in IT,
also in the same academic program, continued with these
same regularly scheduled activities in addition to the training
protocol. The IT group met every Monday, Wednesday, and
Friday for 6 weeks. Each training session began at 0900, 1
Figure 1. Thirty-second Wingate test divided into its phosphagenic and glycolytic components.
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hour after the participants ate a light breakfast. The same
research assistant who controlled the flywheel resistance and
also timed the interval and recovery periods supervised all
sessions. The ergometer (884E Sprint Bike, Monark, Sweden)
seat height was individually identified for each participant
(5°bend in the knee at the lowest point in the revolution) and
maintained throughout the intervention period. Each training
session began with a 5-minute warm-up at an intensity
approximating 30% of maximal aerobic power (30% p_
VO
2
max).
Six 90-second cycling bouts at 80% p
_
VO
2
max were then
performed at a cadence of 60 rpm. Each 90-second bout was
followed by 180 seconds of passive rest for a work-to-rest ratio
of 1:2. All laboratory sessions were performed in ambient
conditions of 20–22°C and 60% humidity.
Statistical Analyses
Statistical analyses were performed using Statistica 8.0 for
Windows. A 2 (group) 32 (time) repeated-measures
analysis of variance was used to investigate the significance
of differences between groups and pre and posttraining
sessions. The normality of data was tested using the
Shapiro–Wilks Wtest. To assess the influence of initial
values on power output, Pearson correlations were
performed to compare the relationship between the pre
and postintervention values of power at
_
VO
2
max in absolute
and relative terms. Statistical significance was set at p#0.05
for all analyses. Targeting statistical power at b=0.8withan
effect size of 0.7, a sample size estimate of 12 participants
per group was determined (39).
RESULTS
All participants completed the
study, and no adverse events
were reported. The Shapiro–
Wilks Wtest was significant
(p,0.05). At baseline, there
were no significant differences
in basic anthropometric char-
acteristics between groups
(Table 2) or in aerobic (Table
3) and anaerobic performance
(Table 4). There were significant
(p,0.05) main effects of group
and time for several aerobic
(Table 3) and anaerobic param-
eters (Table 4). Additionally, as
shown in Table 5, there was
a significant main effect of group
for LA at the 5 and 15 minutes
post-WAnT (mmolL
21
)marks
for IT; p,0.05. Significant
interaction effects were noted
for absolute (Lmin
21
) and rel-
ative (mlkg
21
min
21
)
_
VO
2
max,
absolute (W) and relative
(Wkg
21
) power at
_
VO
2
max, power at AT,
_
VO
2
at AT
(mlkg
21
min
21
), work output (Jkg
21
), and MP (Wkg
21
) with
those in IT, but not C, experiencing improvements; p,0.05
(Tables 3 and 4).
The 6-week HIIT program favorably influenced the aerobic
and anaerobic performances for the IT group. Absolute and
relative
_
VO
2
max increased (p,0.05) by an average of
0.5 Lmin
21
(13%) and 5.5 mlkg
21
min
-1
(11%), respectively
(Table 3). The pre and posttraining correlations between
aerobic performance expressed in absolute (r= 0.93) and
relative (r= 0.86; Figure 2) power terms for IT indicate that
their training effect was similar regardless of their respective
initial values. Improvements (p,0.05) of 29.5 W and
0.29 Wkg
21
in absolute and relative power at AT,
respectively, and 3.8 mlkg
21
min
21
in
_
VO
2
max at AT were
recorded for IT on average (Table 3). Mean values for
absolute and relative power at AT decreased slightly for C
between the pre and posttraining periods.
As indicated by data presented in Table 4, the IT group
improved in several anaerobic performance variables when
compared to C. Work output (Jkg
21
) increased 4.3% for IT
but only by 1.4% for C. Although the average nonphospha-
genic component of work (Jkg
21
) increased for both groups,
the change was larger for IT (12.5 Jkg
21
; 6.8%); this was also
reflected through an increase in the mean difference of the
relative contribution of nonphosphagenic component of
work to the total amount of work performed (1.6%) and
a corresponding decrease of 1.7% in the relative contribution
Figure 2. Relationship between baseline and follow-up values for relative power (Wkg
21
)at
_
VO
2
max for those in
interval training group. Line of best fit and 95% confidence intervals are presented as the solid and dashed lines,
respectively.
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of the phosphagenic system for IT. Only in IT group, was
a significant correlation between
_
VO
2
max and nonphospha-
genic component of total work (%) observed (Figure 3). The
relative contribution of the anaerobic energy sources
changed by less than 0.5% for C. Mean power improved,
on average, for ITonly. Both groups attained PP more quickly
at the end of the 6-week period; however, the decrease in
time to attain PP was 0.9 seconds for IT compared to 0.5
seconds for C. On the other hand, the mean difference in the
ability to sustain PP revealed that C was able to maintain PP
production 0.4 seconds longer than was IT during follow-up
testing. Both groups demonstrated that LA values increased
from resting values to 5 minutes postexertion with a decline
after an additional 10 minutes of rest (Table 5). Significant
(p,0.05) improvements in LA response were noted only for
IT. Compared to baseline, LA values for IT when 5 and
15 minutes into recovery were 3.1 and 2.0 mmolL
21
lower,
respectively, after HIIT training.
DISCUSSION
The major finding of this study was that 27 minwk
21
of HIIT
performed on a stationary cycle ergometer at a 1:2 work-to-
rest ratio throughout a 6-week period significantly improved
numerous variables associated with aerobic and anaerobic
performance but decreased LA formation. Our protocol
requiring the participants to cycle at 80% of their baseline
p
_
VO
2
max with a 1:2 work-to-rest ratio was tolerated by all in
the IT group.
Unlike in the protocol used by Laursen et al. (27) in which
they adjusted the training workload after a midpoint reassess-
ment, our workload remained constant over the 6-week
intervention. We observed an 11% increase in
_
VO
2
max
(mlkg
21
min
21
) for the IT group, whereas Laursen et al. (27)
reported an increase of 6%. The 5% difference in final
outcome between the 2 studies may be the result of the initial
cardiorespiratory training levels of the participants and the
duration of the interventions.
There are several other studies
showing increases in the max-
imal aerobic capacity (
_
VO
2
max)
after interval training (16,29).
Our results also support the
findings of Creer et al. (16) and
MacDougall et al. (29) even
though these 2 studies used
a 1:8 work-to-rest ratio for a
sample of trained cyclists and
healthy college students, re-
spectively. Although we noted
an average improvement in
_
VO
2
max of 5.5 mlkg
21
min
21
after a 6-week protocol using
a 1:2 work-to-rest ratio,
MacDougall et al. (29) reported
an improvement of 3.5
mlkg
21
min
21
after a 7-week protocol. Creer et al. (16)
assigned their trained male cyclists into endurance-only and
short-sprint-plus-endurance intervention groups; they noted
an increase in
_
VO
2
max of 0.2 Lmin
21
for both groups. As
shown in Table 3, we reported an increase of 0.41 Lmin
21
for
the IT group. Again, the initial conditioning level of the
participants compared to ours cannot be overlooked when
comparing the results from these 2 studies. In terms of indi-
cators of aerobic endurance, those in the IT group of the
present study increased their
_
VO
2
consumption at AT by
3.5 mlkg
21
min
21
; however, ATas a percentage of
_
VO
2
max at
posttesting did not differ from the baseline values. Similarly,
Creer et al. (16) reported no change in the percentage of
maximal heart rate at which ventilatory threshold was observed.
To investigate the effects of HITT on anaerobic capacity,
a Wingate test was performed. We noted that total work output
was significantly higher in the IT group. As performance in
WAnT is dependent on phosphagenic, glycolytic and, partially,
oxidative metabolism, these data indicate that at least one of
these energetic systems had improved after interval training.
Our data indicate that the phosphagenic work was the same in
both groups but the nonphosphagenic component of work
tended to be higher in the IT group. Recent evidence suggests
that during exercise lasting up to 30 seconds, a substantial
amount of energy is derived from aerobic metabolism.
Therefore, we consider that improvement in WAnT could be
a result of increase in glycolysis and oxidative phosphorylation.
To evaluate the influence of HIIT on glycolysis, we measured
the blood LA concentration after WAnT. Blood LA values
taken after the WAnT were lower on average for our ITgroup
(Table 5). This 3-mmolL
21
decrease in concentration at the
5-minute mark indicates that LA formation was significantly
lower in the ITgroup. On the other hand, when we compared
changes in LA concentration 15 minutes after WAnT, there
was no difference between groups. These data suggest that 6
weeks of HIIT did not influence the rate of LA removal.
Figure 3. Relationship between
_
VO
2
max (Lmin
21
) and percent contribution of nonphosphagenic work after high-
intensity interval training protocol for training and control groups.
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Effects of High-Intensity Interval Training
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Our data are in agreement with those of Burgomaster et al.
(11); their sprint cycling group had lower rates of
glycogenolysis and, hence, muscle LA accumulation because
the men in that group also had an increased ability to oxidize
pyruvate. Moreover, 8 weeks of endurance training was
sufficient to increase nicotinamide adenine dinucleotide
reduced form (NADH) shuttle enzymes levels by approxi-
mately 50%; this enzymatic system competes with LA
dehydrogenase for NADH (35). Because we had no
capabilities of measuring NADH shuttle enzyme activity,
we can only speculate that our training protocol decreased
LA formation by increasing oxidative capabilities of
cytoplasmic NADH via the shuttle enzymes. Indeed, recent
evidence suggests that 13% of energy during a 10-second
sprint and 27% of energy during a 20-second sprint is
generated aerobically (9,24). Postintervention results for the
IT group in the present study revealed an increased
nonphosphagenic component of total work performed during
WAnT (Figure 3). All together these data indicate that an
increase in total work output during WAnT is a result of an
increase in aerobic metabolism. This conclusion is in direct
opposition to the studies reporting an increase in anaerobic
metabolism as a result of HIIT. For example, Creer et al. (16)
noted higher LA levels for the short-sprint-plus-endurance
training group during posttraining compared to baseline for
each of the 4 sprints and at 3- and 6-minutes into recovery after
the last sprint. Using a sample of college students similar to
those in the present study, MacDougall et al. (29) noted
increases in oxidative and glycolytic enzymes after a 7-week
intervention of 30-second sprint sessions 3 times per week.
Our data indicate that 6 weeks of an HIIT protocol with a 1:2
work-to-rest ratio is an effective means to improve aerobic
capacity and that the increased performance during WAnT is
a result of increased aerobic capacity.
PRACTICAL APPLICATIONS
For coaches, athletes, and fitness practitioners who need to
quickly improve maximal aerobic and anaerobic cycling
performance, using our 1:2 work-to-rest HIIT protocol should
produce notable and favorable changes with minimal time
invested in cycling-specific training per week. This protocol
may shorten preseason training requirements or provide
a time-efficient method to maintain in- and postseason
performance capacities of men similar to those in our study.
Forthe tennis players who lost 4–15% of their aerobic capacity
during a 3–6 week break (31) and for other athletes, our HIIT
protocol with a 1:2 work-to-rest ratio may be a time-efficient
means to counter detraining during the off season.
ACKNOWLEDGMENTS
Gratitude is expressed to all the participants involved in this
study. This project was supported by the Committee of
Scientific Research (KBN), and a grant from the Academy of
Physical Education and Sport funded this project in its
entirety. There are no conflicts of interest to be reported by
the authors, because there are no professional relationships
with companies or manufacturers who will benefit from the
results of the present study. The results presented herein do
not constitute an endorsement of the protocol by the NSCA
nor by the authors as the only method by which to quickly
show such improvements in aerobic and anaerobic perfor-
mance. Disclosure of funding: There was no external funding
for this project.
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