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The purpose of this study was to determine the effectiveness of brief intense interval training as exercise intervention for promoting health and to evaluate potential benefits about common interventions, that is, prolonged exercise and strength training. Thirty-six untrained men were divided into groups that completed 12 wk of intense interval running (INT; total training time 40 min wk(-1)), prolonged running (approximately 150 min wk(-1)), and strength training (approximately 150 min wk(-1)) or continued their habitual lifestyle without participation in physical training. The improvement in cardiorespiratory fitness was superior in the INT (14% +/- 2% increase in V˙O2max) compared with the other two exercise interventions (7% +/- 2% and 3% +/- 2% increases). The blood glucose concentration 2 h after oral ingestion of 75 g of glucose was lowered to a similar extent after training in the INT (from 6.1 +/- 0.6 to 5.1 +/- 0.4 mM, P < 0.05) and the prolonged running group (from 5.6 +/- 1.5 to 4.9 +/- 1.1 mM, P < 0.05). In contrast, INT was less efficient than prolonged running for lowering the subjects' resting HR, fat percentage, and reducing the ratio between total and HDL plasma cholesterol. Furthermore, total bone mass and lean body mass remained unchanged in the INT group, whereas both these parameters were increased by the strength-training intervention. INT for 12 wk is an effective training stimulus for improvement of cardiorespiratory fitness and glucose tolerance, but in relation to the treatment of hyperlipidemia and obesity, it is less effective than prolonged training. Furthermore and in contrast to strength training, 12 wk of INT had no impact on muscle mass or indices of skeletal health.
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High-Intensity Training versus Traditional
Exercise Interventions for Promoting Health
LARS NYBO
1
, EMIL SUNDSTRUP
1,2
, MARKUS D. JAKOBSEN
1,2
, MAGNI MOHR
1
, THERESE HORNSTRUP
1
,
LENE SIMONSEN
2
, JENS BU
¨LOW
2
, MORTEN B. RANDERS
1
, JENS J. NIELSEN
1
, PER AAGAARD
2,3
,
and PETER KRUSTRUP
1
1
Section of Human Physiology, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen,
DENMARK;
2
Bispebjerg University Hospital, Copenhagen, DENMARK; and
3
Institute of Sports Science and Clinical
Biomechanics, University of Southern Denmark, Odense, DENMARK
ABSTRACT
NYBO, L., E. SUNDSTRUP, M. D. JAKOBSEN, M. MOHR, T. HORNSTRUP, L. SIMONSEN, J. BU
¨LOW, M. B. RANDERS,
J. J. NIELSEN, P. AAGAARD, and P. KRUSTRUP. High-Intensity Training versus Traditional Exercise Interventions for Pro-
moting Health. Med. Sci. Sports Exerc., Vol. 42, No. 10, pp. 1951–1958, 2010. Purpose: The purpose of this study was to deter-
mine the effectiveness of brief intense interval training as exercise intervention for promoting health and to evaluate potential benefits
about common interventions, that is, prolonged exercise and strength training. Methods: Thirty-six untrained men were divided into
groups that completed 12 wk of intense interval running (INT; total training time 40 minIwk
j1
), prolonged running (È150 minIwk
j1
),
and strength training (È150 minIwk
j1
) or continued their habitual lifestyle without participation in physical training. Results: The
improvement in cardiorespiratory fitness was superior in the INT (14% T2% increase in V
˙O
2max
) compared with the other two
exercise interventions (7% T2% and 3% T2% increases). The blood glucose concentration 2 h after oral ingestion of 75 g of glucose
was lowered to a similar extent after training in the INT (from 6.1 T0.6 to 5.1 T0.4 mM, PG0.05) and the prolonged running group
(from 5.6 T1.5 to 4.9 T1.1 mM, PG0.05). In contrast, INT was less efficient than prolonged running for lowering the subjects’
resting HR, fat percentage, and reducing the ratio between total and HDL plasma cholesterol. Furthermore, total bone mass and lean
body mass remained unchanged in the INT group, whereas both these parameters were increased by the strength-training intervention.
Conclusions: INT for 12 wk is an effective training stimulus for improvement of cardiorespiratory fitness and glucose tolerance, but
in relation to the treatment of hyperlipidemia and obesity, it is less effective than prolonged training. Furthermore and in contrast
to strength training, 12 wk of INT had no impact on muscle mass or indices of skeletal health. Key Words: BONE MASS, BLOOD
PRESSURE, CHOLESTEROL, GLUCOSE TOLERANCE, LEAN BODY MASS, V
˙O
2max
It is well established that factors such as poor cardio-
respiratory fitness, adiposity, impaired glucose toler-
ance, hypertension, and arteriosclerosis are independent
threats to health and that physical inactivity increases the
risk for premature death and elevates the incidence of the
abovementioned unhealthy conditions, which independently
or in combination may be considered risk factors for chronic
diseases (21). Epidemiologic cross-sectional investigations
and longitudinal intervention studies have provided experi-
mental evidence for the effectiveness of prolonged aerobic
exercise training such as continuous running, brisk walking,
or bicycling as interventions that may lower the relative risk
for developing several metabolic diseases (3,5,14,25,26). In
accordance, a recent pronouncement from the American
College of Sports Medicine concludes that between 150 and
250 min of moderate physical activity per week is sufficient
and effective to prevent weight gain (8), and the Centers for
Disease Control and Prevention published national guide-
lines on physical activity and public health as well as the
Committee on Exercise and Cardiac Rehabilitation of the
American Heart Association have previously endorsed and
supported these recommendations for healthy adults to im-
prove and to maintain health (13).
However, lack of time is a common reason why many
people fail to accomplish the ‘‘traditional training pro-
grams,’’ and metabolic-related disorders arising secondary
to a sedentary lifestyle have become a large and expanding
health problem in the modern society (4). In this relation, it
is interesting that short but very intense exercise training
may induce similar improvements in cardiorespiratory fit-
ness and skeletal muscle oxidative capacity as prolonged
training (6,11), and a recent study (1) reported that very
short duration high-intensity interval training substantially
improves insulin action. Accordingly, it has been speculated
that short-term high-intensity interval training could be a
Address for correspondence: Lars Nybo, Department of Exercise and Sport
Sciences, Copenhagen Muscle Research Centre, University of Copenhagen,
The August Krogh Building, Universitetsparken 13, Copenhagen 2100-K,
Denmark; E-mail: lnnielsen@ifi.ku.dk.
Submitted for publication November 2009.
Accepted for publication February 2010.
0195-9131/10/4210-1951/0
MEDICINE & SCIENCE IN SPORTS & EXERCISE
Ò
Copyright Ó2010 by the American College of Sports Medicine
DOI: 10.1249/MSS.0b013e3181d99203
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time-efficient strategy for health promotion (10). Further-
more, in relation to reducing cardiovascular risk factors,
studies by Schjerve et al. (28) and Tjonna et al. (30,31) ele-
gantly demonstrate that high-intensity training has a major
advantage compared with ‘‘isocaloric’’ moderate intense
training. However, because the total energy turnover during
training was matched across the different groups in the
studies by Schjerve et al. (28) and Tjonna et al. (30,31), the
overall exercise time was not markedly reduced in the in-
tense compared with the moderate training group. Although
the abovementioned studies indicate that intense training
has the potential to improve various health parameters, it
remains unknown if very intense but short-lasting exercise
training can completely substitute for the higher training
volume and consequently larger energy expenditure associ-
ated with prolonged moderate physical activity.
Many health-promoting exercise programs also include
strength training, aiming with the intension to develop
strength and to induce muscle hypertrophy (18). The in-
creased lean body mass may increase the basal energy ex-
penditure and favor the loss of body fat (29); in addition, it
could benefit health by other means. Thus, heavy strength
training is not only a stimulus for muscle hypertrophy, this
type of training also appears to be a potent stimulus for os-
teogenesis and increased bone mass, and bone mineral
density may increase bone strength, which is of major im-
portance for the prevention of osteoporosis later in life. As
an alternative to strength training, exercise with a high-
impact load may also provide a significant osteogenic stim-
ulus. High-intensity interval running may be considered as
high-impact exercise and could therefore be speculated to
have an effect on bone mineral density (12,27). Further-
more, strength training for 30 min three times per week in-
creased insulin action in skeletal muscle in both normal
subjects and patients with type 2 diabetes (15). This effect
may in part relate to increased muscle mass and reduced
body fat, but it also involves up-regulation of several key
proteins in the insulin signaling cascade. In contrast, strength
training has limited impact on cardiorespiratory fitness, and
the influences on the metabolic capacity of the skeletal mus-
cles and on the plasma lipoprotein profile seem to be minor
importance (23).
The present study was undertaken to clarify how an in-
tervention with brief but very intense aerobic training con-
ducted as high-intensity interval running would influence
specific parameters such as plasma lipid profile, glucose tol-
erance, fat mass, and blood pressure and compare changes in
these physiological variables of with adaptations achieved
through traditional training interventions. With the ambition
to evaluate the efficiency of different training modes for the
prevention or treatment of different types of metabolic and
musculoskeletal disorders, 36 untrained subject were there-
fore divided into a control group (CON), a strength-training
group (STR), a high-intensity interval running group (INT),
and a group that performed ‘‘traditional’’ moderate-intensity
running (MOD).
METHODS
Thirty-six untrained men that had not participated in any
type of regular physical training for at least 2 yr were
recruited for the study. The participants had a mean age of
31 yr (range = 20–43 yr; for anthropometric details, see
Table 1), and they were all nonsmokers, without diagnosed
metabolic or cardiovascular diseases. The study was carried
out in accordance with the guidelines contained in the
Declaration of Helsinki and approved by the local ethical
committee of Copenhagen (14606; H-C-2007-0012), and
informed written consent was obtained from all subjects.
Design. The subjects were divided into four groups: 1)
a group that performed intense interval running (INT; n= 8);
2) a strength-training group (STR; n= 8); 3) a group that
performed prolonged moderate intense continuous running
(MOD; n= 9); and 4) a control group performing no phys-
ical training (CON; n= 11). The participant in the three
training groups completed three different 12-wk training
programs as described below, whereas the participants in
CON continued their daily life activities during the period.
Before and after the 12-wk intervention period, the subjects
completed a series of tests that consisted of an exercise test,
an oral glucose tolerance test (OGTT), measurements of
resting blood pressure, a plasma lipoprotein profile, and
obtainment of a muscle biopsy for determination of capil-
larization and metabolic enzyme levels.
TABLE 1. Subject characteristics, fat percentage, lean body mass, and bone mass before and after the 12-wk intervention period for the three training groups and controls.
Intense Interval Running Prolonged Running Strength Training Control
Before After Before After Before After Before After
Age (yr) 37 T331T236T230T2
Body mass (kg) 96.3 T3.8 94.9 T4.2 85.8 T5.5 84.8 T5.3* 95.0 T8.4 96.7 T8.586.5 T3.8 86.4 T3.7
Fat percentage 24.7 T1.5 24.2 T1.7 24.3 T1.6 22.6 T1.7* 24.9 T2.3 25.3 T2.4 22.3 T2.7 22.1 T2.8
Lean body mass (kg)
Total 66.6 T1.8 66.8 T2.1 61.3 T2.8 61.9 T2.7 61.0 T2.3 62.8 T2.763.3 T1.7 63.4 T1.5
Legs 23.1 T0.6 23.2 T0.8 21.0 T1.0 21.6 T1.1 21.4 T1.2 22.8 T1.320.3 T0.7 20.0 T0.6
Bone mass (kg)
Total 3.52 T0.12 3.59 T0.14 3.36 T0.11 3.40 T0.11 3.31 T0.07 3.37 T0.083.24 T0.05 3.26 T0.06
Legs 1.38 T0.05 1.39 T0.07 1.36 T0.06 1.38 T0.06 1.29 T0.04 1.32 T0.051.30 T0.04 1.30 T0.04
Age, body mass, fat percentage, total and leg lean body mass, and total and leg bone mass before and after training. Values are presented as mean TSE for the four groups.
* Significantly lower than pretraining value (PG0.05).
Significantly higher than pretraining value (PG0.05).
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Except for the training regimens and for the days before
the testing days, the subjects were instructed to continue
their habitual lifestyle and to maintain their normal dietary
practices throughout the 12-wk period. However, before
the experimental days, the subjects were required to refrain
from alcohol and exercise for 48 h before the resting mea-
surement and the experimental exercise trials.
Measurements and test procedures. Subjects were
familiarized with the exercise test and with the blood pres-
sure measurements at least one time before the experiment.
Fasting blood glucose, lipoproteins, resting HR, and blood
pressure were determined in the morning under standardized
conditions and after an overnight fast. Blood pressure was
measured at least six times, with the subjects in a supine
position, by an automatic upper arm blood pressure mon-
itor (M-7 or HEM-709; OMRON, Schaumburg, IL), and an
average of the six values for diastolic and systolic blood
pressure was recorded. Mean arterial pressure (MAP) was
calculated as 1/3 systolic pressure + 2/3 diastolic pres-
sure. With this procedure, the coefficient of variation (CV)
for repeated measures on the same day was less than 2%, and
the day-to-day variation (CV for the control group) was 2.6%.
Exercise test. Pulmonary gas exchange (CPX Med-
Graphics, St. Paul, MN), HR (Polar Team System; Polar
Electro Oy, Kempele, Finland), and venous blood sampling
were performed during a standardized treadmill test con-
sisting of 6 min of walking at 6.5 kmIh
j1
and 6 min of
submaximal running at 9.5 kmIh
j1
, followed by a 15-min
rest period and thereafter an incremental test to exhaustion.
Pulmonary oxygen uptake (V
˙O
2
)andRERweremeasured
during the last 3 min of walking at 6.5 kmIh
j1
and similarly
during the last 3 min of running at 9.5 kmIh
j1
.V
˙O
2max
and
HR
max
were determined as the peak value reached in a 30-s
period during the incremental test. Fat oxidation during
walking was calculated from the RER and the steady state
V
˙O
2
measured at 6.5 kmIh
j1
and similarly for submaximal
running at 9.5 kmIh
j1
.
Oral glucose tolerance test. Subjects refrained from
performing any strenuous physical activity for 2 d before
the OGTT and attended the laboratory having fasted over-
night. Venous blood samples were collected from an an-
tecubital venous catheter before and 15, 30, 60, 90, and
120 min after ingestion of 75 g of glucose.
Furthermore, before the OGTT, while the subject was
still fasting, 2 mL of blood was drawn into heparinized sy-
ringes for determination of fasting insulin and glucose levels
(ABL 615; Radiometer Medical, Copenhagen, Denmark).
Furthermore, 10 mL was drawn into dry syringes for deter-
mination of plasma fatty acid, HDL cholesterol, and plasma
triacylglycerol concentrations measured by commercial kits
(Wako Chemicals, Neuss, Germany) on a Hitachi autoana-
lyzer (Roche Diagnostic, Basel, Switzerland). The analytical
variations (CV) for these measures are reported to be less
than 1.5%. LDL cholesterol was calculated in accordance
with the Friedewald–Levy–Fredrickson equation (27b) as to-
tal cholesterol minus HDL cholesterol and one-fifth of total
plasma triacylglycerol. Plasma concentrations of insulin were
determined using a RIA kit (Pharmacia Insulin Radioimmu-
noassay 100; Pharmacia & Upjohn Diagnostics, Uppsala,
Sweden; intra-assay CV 3%).
Body weight was measured in the morning after an
overnight fast on a platform scale (Ohaus, Germany). Body
composition was determined by dual-energy x-ray absorp-
tiometry (DEXA scan, DPX-IQ version 4.6.6; Lunar Corp.,
Madison, WI).
Muscle biopsies were obtained at rest from musculus
vastus lateralis under local anesthesia using the Bergstrom
technique. The posttraining biopsy was obtained between
48 and 72 h after the final training session, and the pre-
training biopsies were also obtained with no physical activ-
ity for 48 h before the biopsy. All biopsies were frozen in
liquid nitrogen within 15 s and stored at j80-C for subse-
quent analysis. Muscle tissue was subsequently freeze dried
and dissected free of all visible exogenous adipose tissue,
connective tissue, and blood under a stereo microscope
(Stemi 2000-C; Zeiss, Oberkochen, Germany).
Approximately 30 mg of wet weight muscle tissue was
mounted in an embedding medium (OCT Tissue-Tek; Sakura
Finetek, Zoeterwoude, The Netherlands), frozen in precooled
isopentane, and analyzed histochemically for capillaries.
Maximal citrate synthase (CS) and beta-hydroxyacyl-CoA-
dehydrogenase (HAD) activities were determined fluorimet-
rically on a separate piece of muscle from the biopsy. The
muscle fibers were mixed, and pooled fibers were used for
the determination of maximal enzyme activity as expressed
in micromole per gram (dry weight muscle) per minute (22).
Training. The high-intensity training consisted of a brief
5-min warm-up with light jogging followed by five intervals
of 2 min of near-maximal running (HR above 95% of their
HR
max
at the end of the 2-min period; total exercise time per
session = 20 min, including warm-up). For all training
groups, there were three scheduled training sessions per
week. However, because of injuries or absence for other rea-
sons, the participants in the INT group completed 2.0 T0.1
sessions per week corresponding to a total training time
during the 12 wk of approximately 480 min, including
warm-up. Three of the subjects in INT missed between one
and four training sessions because of overuse injuries (shin
splints—periostitis tibialis medialis and/or lateralis); how-
ever, no acute injuries were registered. Furthermore, one of
the subjects suffered from inflammation of the hollow foot
tendon (fasciitis plantaris), and another had bilateral unspe-
cific knee pain. The prolonged running sessions consisted
of 1 h of continuous running at 80% of individual HR
max
approximately 65% of V
˙O
2max
(as evaluated from the cor-
relation between V
˙O
2
and HR during the treadmill test). The
average number of completed training sessions was 2.5 T0.2
per week for the participants in MOD corresponding to
a total training time of approximately 1800 min. In the
MOD group, two subjects missed training sessions because
of overuse injuries similar to those reported for the INT
group. The strength-training program consisted of 12 wk of
HEALTH EFFECTS OF INTENSE INTERVAL RUNNING Medicine & Science in Sports & Exercise
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progressive heavy-resistance strength training (2.0 T0.1
times a week; total time, È1500 min). The training consisted
of three to four sets of the following exercises: squat, hack
squat, incline leg pres, isolated knee extension, hamstring
curls, and calf raises. The loads corresponded to 12–16
repetition maximum (RM) during the first 4 wk and 6–10
RM during the remaining 8 wk of the training period, with
the absolute loads gradually adjusted to match the individual
progressions in muscle strength. The total exercise time
was 60 min per session, and the subjects completed training
with 1-min breaks between sets (average HR during training,
È50% of HR
max
).
Statistics. Between- and within-group data were evalu-
ated both by two-factor mixed ANOVA design and with one-
way ANOVA on repeated measurement. When a significant
interaction was detected, data were subsequently analyzed
using a Newman–Keuls post hoc test. The significance level
was set at PG0.05. Data are presented as means TSE unless
otherwise indicated.
RESULTS
Aerobic fitness and cardiovascular adaptations.
Although the total training time in the INT group was less
than one-third of the time completed by the two other
training groups, the intense interval training induced an in-
crease in maximal oxygen uptake, which was superior to the
other two training interventions (Fig. 1). Thus, the im-
provement in V
˙O
2max
was almost twofold higher in INT as
compared with MOD, whereas there were no significant
changes in the STR and CON groups. Systolic blood pres-
sure was reduced by 8 mm Hg in all three training groups.
In contrast, resting HR and diastolic blood pressure were
reduced to a lesser extend in INT compared with MOD
(Table 2). The prolonged running group also had a signifi-
cant increase in capillaries per fiber, whereas capillarization
remained unchanged in the INT group. HR during walking
and during submaximal running was reduced to a similar
degree in the INT and MOD groups (Table 2).
Metabolic fitness. Although aerobic fitness was en-
hanced in the INT group and the relative exercise intensity
at a given submaximal load accordingly became reduced,
there were no changes in fat oxidation during walking at
6.5 kmIh
j1
or submaximal running at 9.5 kmIh
j1
(Table 3).
Fat oxidation during walking also remained unchanged in
the other groups, but energy turnover from fat oxidation was
enhanced during submaximal running in the MOD group
(Table 3). The enhanced capacity for fat oxidation was not
related to changes in HAD activity, and neither HAD nor
CS measured in the biopsy from musculus vastus lateralis
was significantly changed in any of the three training groups
(Table 3).
HDL, LDL, and total cholesterol and accordingly the ratio
between total and HDL cholesterol remained unchanged
during the 12-wk period in the INT group (Table 3). In con-
trast, the ratio between total and HDL cholesterol decreased
significantly in the MOD group and tended to be lower in
STR after the 12 wk of training (see Fig. 2 and Table 3).
Both fasting blood glucose and blood glucose concentra-
tion 2 h after oral ingestion of 75 g of glucose were reduced
to a similar extent in INT and MOD, whereas fasting glucose
TABLE 2. Aerobic fitness and cardiovascular factors before and after the 12-wk intervention period for the three training groups and controls.
Intense Interval Running Prolonged Running Strength Training Control
Before After Before After Before After Before After
Resting HR (bpm) 55 T252T259T253T2* 57 T256T260T361T3
Systolic blood pressure (mm Hg) 127 T4 119 T4* 131 T4 123 T3* 129 T6 121 T4 129 T2 127 T3
Diastolic blood pressure (mm Hg) 75 T473T381T376T2* 82 T475T374T376T3
MAP (mm Hg) 92 T389T3* 98 T392T3* 97 T590T392T392T3
Maximal oxygen uptake (mLImin
j1
Ikg
j1
) 36.3 T1.7 41.4 T2.239.3 T2.5 42.2 T1.836.8 T3.2 37.9 T3.3 39.2 T2.7 38.9 T2.4
HR (bpm)
6.5 kmIh
j1
121 T4 112 T3* 121 T6 107 T5* 125 T7 121 T6 115 T3 109 T4
9.5 kmIh
j1
177 T3 160 T5* 167 T5 146 T6* 169 T6 163 T5* 162 T6 157 T6
Capillaries per fiber 2.2 T0.2 2.0 T0.2 1.8 T0.1 2.1 T0.12.0 T0.1 2.1 T0.1 2.2 T0.1 2.3 T0.1
Resting values for HR, systolic and diastolic blood pressure, and MAP. Capillarization expressed as capillaries per muscle fiber, exercise values for maximal oxygen uptake, and HR during
walking at 6.5 kmIh
j1
and submaximal running at 9.5 kmIh
j1
.
Values are presented as mean TSE for the four groups.
* Significantly lower than the pretraining value (PG0.05).
Significantly higher than the pretraining value (PG0.05).
FIGURE 1—Percentage changes in maximal oxygen consumption for
the intense interval running (INT), prolonged moderate intense run-
ning (MOD), strength training (STR), and control (CON) groups dur-
ing the 12-wk intervention period. *Significant increase from pre- to
posttraining (PG0.05); #Significant larger response compared with the
MOD group (PG0.05).
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and blood glucose response to the OGTT remained unaltered
in STR and CON (Table 3). Fasting insulin levels were not
changed in any of the three training groups.
Lean body, bone mass, and fat percentage. There
were no significant changes in total body weight, total and
leg lean body mass, fat percentage, total bone mass, or leg
bone mass in the INT group (Table 1). In contrast, MOD
training induced a significant reduction in the subject body
weight and fat percentage, and the group that performed
strength training increased their body weight and had signif-
icant increases in total and leg lean body mass (Table 1).
Furthermore, the DEXA scans revealed that the STR group
had significant increases in total and leg bone mass (Table 1).
DISCUSSION
The present investigation reveals that INT is an effective
training stimulus for improvement of cardiorespiratory fit-
ness and glucose tolerance, and in untrained subjects it may
induce a significant reduction in systolic blood pressure.
However, in relation to the treatment of hyperlipidemia and
obesity, it is less effective than prolonged training, and in
contrast to strength training, 12 wk of INT had no impact on
muscle mass or indices of skeletal health.
Blood pressure, aerobic fitness, and CV risk
factors. The present results reveal that brief but intense
training has the potential to reduce arterial blood pressure
and counteract the development of hypertension. Thus, the
group that completed the high-intensity training interven-
tion had a significant reduction in systolic blood pressure
and consequently a lowering of the MAP. The 8-mm Hg
reduction in systolic pressure was similar to the changes in
the MOD and STR groups, whereas diastolic pressure ap-
peared to be less affected in the INT group compared with
the MOD group. However, from a statistical perspective,
the study included relatively few subjects, and therefore we
cannot conclude whether brief intense training is less or
equally efficient compared with prolonged moderate-intensity
exercise interventions. In contrast, it seems clear that reduc-
tion in systolic or MAP after aerobic training is not directly
related to the concomitant improvements in cardiorespira-
tory fitness. Accordingly, the study by Cornelissen et al. (7)
supports the findings that reductions in systolic blood pres-
sure are not correlated to changes in V
˙O
2max
because they
reported similar reductions in systolic blood pressure after
moderate-intensity exercise training and training with a very
low intensity, although the low-intensity training had a lower
impact on V
˙O
2max
as compared with the moderate-intensity
training (7).
The improvement of maximal oxygen consumption and
performance during incremental treadmill running test was
superior in the INT group compared with the MOD and STR
groups, supporting the notion that the training intensity is
more important than the training volume for the develop-
ment of cardiorespiratory fitness (33). However, the larger
improvement of cardiorespiratory fitness was not accompa-
nied by superior adaptations in relation to metabolic fitness.
TABLE 3. Indices of metabolic fitness before and after the 12-wk intervention period for the three training groups and controls.
Intense Interval Running Prolonged Running Strength Training Control
Before After Before After Before After Before After
Fat oxidation during walking (kJImin
j1
) 10.2 T2.7 12.3 T2.8 11.5 T1.1 11.3 T1.5 11.9 T1.3 8.8 T1.5 13.9 T1.6 9.7 T2.6
Fat oxidation during running (kJImin
j1
) 2.8 T2.3 4.1 T3.0 5.0 T3.1 11.1 T2.53.0 T2.7 2.0 T1.5 6.3 T2.6 9.9 T2.2
Fasting total cholesterol (mM) 5.1 T0.2 5.0 T0.2 4.1 T0.3 3.8 T0.4 4.8 T0.3 5.3 T0.34.1 T0.2 4.1 T0.3
Fasting HDL cholesterol (mM) 1.2 T0.1 1.2 T0.1 1.2 T0.1 1.3 T0.1 1.2 T0.1 1.2 T0.1 1.3 T0.1 1.4 T0.1
Fasting LDL cholesterol (mM) 3.4 T0.2 3.3 T0.3 2.5 T0.2 2.4 T0.3 3.1 T0.3 3.5 T0.3 2.7 T0.2 2.7 T0.2
CS (KmolIg
j1
Imin
j1
) 35.5 T3.4 37.7 T3.2 33.0 T2.8 35.4 T2.3 41.4 T3.4 39.2 T2.7 42.1 T3.2 37.5 T4.4
HAD (KmolIg
j1
Imin
j1
) 23.6 T1.9 25.9 T2.6 28.1 T1.9 29.6 T2.4 29.3 T2.3 26.2 T2.6 31.0 T1.5 27.6 T2.3
Fasting glucose (mM) 5.7 T0.2 5.2 T0.1* 5.6 T0.7 5.1 T0.4* 5.3 T0.4 5.3 T0.3 4.7 T0.5 4.9 T0.4
OGTT end glucose (mM) 6.1 T0.6 5.1 T0.4* 5.6 T1.5 4.9 T1.1* 5.5 T0.5 5.7 T0.5 5.3 T1.7 5.5 T1.0
Fasting insulin (KUImL
j1
) 7.1 T1.1 7.8 T2.2 5.0 T1.7 4.1 T0.9 7.3 T2.5 5.7 T1.2 —
Fasting values for total, HDL and LDL cholesterol, blood glucose, and insulin concentrations. The oral glucose tolerance test (OGTT) end glucose value represents the blood glucose
concentration 2 h after oral ingestion of 75 g of glucose. Citrate synthase (CS; per gram of dry weight muscle) and beta-hydroxyacyl-CoA-dehydrogenase (HAD) activity measured
from vastus lateralis muscle biopsy obtained at rest. Fat oxidation during walking and running are the values for energy turnover from fat oxidation during walking at 6.5 kmIh
j1
and running at 9.5 kmIh
j1
. Values are presented as mean TSE for the four groups.
* Significantly lower than the pretraining value (PG0.05).
Significantly higher than the pretraining value (PG0.05).
FIGURE 2—Reductions in the ratio between total cholesterol and HDL
cholesterol for the intense interval running (INT), prolonged moderate
intense running (MOD), strength training (STR), and control (CON)
groups during the 12-wk period. *Significant change from pre- to
posttraining (PG0.05).
HEALTH EFFECTS OF INTENSE INTERVAL RUNNING Medicine & Science in Sports & Exercise
d
1955
APPLIED SCIENCES
by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.Copyright @ 2010
Thus, CS and HAD activity as well as fat oxidation during
walking was not significantly altered in any of the three
training groups, and only the MOD group appeared to have
an improved capacity for fat oxidation during submaximal
running. The lack of significant change in CS and HAD
activity is in opposition to previous observations in our
laboratory after bicycle (24) and soccer training (19) in
subjects with a similar starting level. Considering the rela-
tively low number of subjects, there is a risk of a type II
error. However, the divergence may also relate to the dif-
ferent exercise modes because soccer and especially bi-
cycling training may provide a strong stimulus for metabolic
changes in vastus lateralis, whereas the training modes in-
vestigated in the present study do not appear to be as ef-
fective for vastus lateralis oxidative enzyme adaptations.
In contrast to the prolonged training program, the intense
intermittent training intervention failed to lower the ratio
between total and HDL cholesterol. Intense but short-lasting
training therefore seems to be less efficient than prolonged
training for improving the plasma lipoprotein–lipid profiles
in untrained subjects, and in contrast to the stimuli for car-
diorespiratory fitness, it seems that training volume rather
than intensity is of importance for the improvement of the
plasma lipoprotein–lipid profile (9). The observed lipopro-
tein responses may relate to the concomitant changes in the
subjects fat percentage, which was lowered in the MOD
group but remained unaltered in the INT group. Accord-
ingly, previous training studies have observed correlations
between changes in lipoprotein–lipid profile and loss of
body fat (17), and the higher training volume and the larger
total energy turnover in MOD compared with INT may ex-
plain both the significant loss of body fat and the improved
lipoprotein–lipid profile in the MOD group, whereas total
energy expenditure may have been insufficient in the INT
group. The American College of Sports Medicine concludes
that between 150 and 250 min of moderate physical activity
per week is needed to counteract weight gain (8), and al-
though the INT intervention induced a significant increase
in the subjects aerobic metabolic capacity, it included only
40 min of training per week, with 20 min of high-intensity
running and 20 min of low-intensity warm-up activities. It
has been speculated that short-term high-intensity interval
training could be a time-efficient strategy for health pro-
motion (10), and the present results support that such train-
ing may influence some health parameters. However, it also
demonstrates that in relation to treatment of hyperlipidemia
and obesity, a certain training volume is needed, and the
present study therefore supports the previously mentioned
recommendations from the American College of Sports
Medicine (8,13). Nevertheless, for individuals with the
metabolic syndrome and overweight subjects, it appears that
an exercise program that includes high-intensity training is
more effective than a program that only includes moderate-
intensity exercise (28,30,31). Consequently, the total weekly
training time may be reduced to some extent when high-
intensity bouts are included, but it appears that a certain
volume is needed and that the total energy utilization is also
of importance.
Glucose tolerance. The present results indicate that
INT with a relatively low volume was equally efficient to
moderate training with a substantially larger total training
volume. Previously, Houmard et al. (16) suggested that the
total exercise duration should be considered when designing
training programs with the intent of improving insulin ac-
tion. Thus, they observed that exercise prescription that in-
corporated approximately 170 min of exercise per week
improved insulin sensitivity more substantially than a pro-
gram using only 115 min of exercise per week—both exer-
cise interventions with intensities comparable with the MOD
group in the present study. However, recently the same
group (2) concluded that although the weekly exercise du-
ration may be of importance for insulin action measured
less than 24 h after the last exercise bout, it appears that
moderate-intensity exercise and vigorous-intensity exercise
appear to result in similar beneficial long-term effects. The
present study supports the later conclusion and indicates
that when the intensity is close to maximal, as little as
40 min of training per week may result in similar improve-
ments in glucose tolerance as 150 min of moderate intense
exercise per week.
Muscle and bone mass. Both bone and muscle mass
were significantly increased after the strength-training in-
tervention, whereas both these parameters remained un-
changed in the INT group as well as in the MOD running
group. The observation of increased bone mass after 12 wk
of strength training indicates that such training besides
being an effective stimulus for muscle growth also provides
a significant osteogenic stimulus. Similar effects have been
demonstrated by intervention studies, which have included
strength training for a prolonged period (in general, 1 yr or
more (20)). Longitudinal studies also signify that exercise
with a so-called high-impact load may provide an effective
osteogenic stimulus. For example, it has been observed
that short-term participation in intermittent sports such as
soccer training increases bone mineral content (19), and
cross-sectional studies have demonstrated that participants
in sports that are characterized by multiple turns, jumps,
and short sprints with accelerations and decelerations have
higher bone mass and mineral density compared with seden-
tary subjects or athletes participating in non-weight-bearing
or so-called low-impact sports (12,27). A high strain rate
and a large magnitude of ground reaction and muscle forces
seem to be important factors for providing the anabolic ef-
fect, and the loading pattern in sports that include running at
different speeds and in multiple directions appears to be at
least as effective as specific strength training (32). However,
the present investigation indicates that a training program
with ‘‘normal’’ straight forward running, although performed
in interval with a high intensity, does not provide the ade-
quate stimulus for enhancing bone mass or strength. In op-
position, a recent cross-sectional study by Rector et al. (27)
concluded that that long-term running and resistance training
http://www.acsm-msse.org1956 Official Journal of the American College of Sports Medicine
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by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.Copyright @ 2010
increase BMD compared with cycling, and running may have
a greater positive effect on BMD than resistance training. The
contradicting observation from the cross-sectional study and
the present longitudinal investigation may illustrate the pit-
fall from drawing conclusions from cross-sectional studies
because these may be influenced by other factors than the
actual training that the subjects have conducted.
In conclusion, the present study investigated various
health effects of brief but very intense exercise training, and
the marked improvements in cardiovascular fitness, glucose
tolerance, and exercise endurance as well as the lowering of
systolic blood pressure put emphasis on the potential benefits
of high-intensity training and its ability to improve certain
physiological health parameters. However, the intense low-
volume training regimen had limitations, and for the short-
term intervention period, it was less effective than prolonged
training in relation to the treatment of hyperlipidemia and
obesity. Furthermore, 12 wk of INT had no impact on muscle
mass or leg bone mass, whereas strength training besides in-
creasing the subjects muscle mass also provided a significant
osteogenic stimulus that may have both acute and prolonged
effects for musculoskeletal health.
This study was supported by the Danish Ministry of Culture
(Kulturministeriets Udvalg for Idr&tsforskning).
The authors acknowledge the great effort by the subjects in
the present study. They also thank Jens Bangsbo, Jesper Frank
Christensen, Henrik Pedersen, Birgitte Rejkj&r Krustrup, Edward
Petersen, Mads Bendiksen, and Rikke Leihof for excellent technical
support.
The results of the present study do not constitute endorsement
by the American College of Sports Medicine.
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APPLIED SCIENCES
... Estudos vem apontando benefícios da prática do HIIT quanto a doenças cardiovascular (WISLOFF et al., 2009), pulmonar (HASSEL et al., 2014, hipertensão (CIOLAC, 2012), e diabetes (FRANÇOIS e LITTLE, 2015). Segundo estudos, o HIIT resulta em benefícios fisiológicos, incluindo melhorias na capacidade aeróbia, aptidão cardiorrespiratória, tolerância à glicose, resistência ao exercício, capacidade oxidativa do músculo esquelético, conteúdo de glicogênio e reduções na taxa de produção de lactato e utilização de glicogênio (NYBO et al., 2010;GIBALA et al., 2012). ...
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Physical exercise is recognized for its beneficial effects on brain health and executive function, particularly through the careful manipulation of key exercise parameters, including type, intensity, and duration. The aim of this systematic review and meta-analysis was to delineate the optimal types, intensities, and durations of exercise that improve cognitive functions in older adults with mild cognitive impairment (MCI) or dementia. A comprehensive search was conducted in Scopus, Web of Science, and PubMed from their inception until December 2023. The methodological quality and publication bias of the included studies were assessed using the PEDro scale and Egger’s regression test, respectively. Separate meta-analyses were performed to assess the overall impact of exercise on cognitive assessments and to explore the effects of different exercise types (i.e., aerobic, resistance, dual-task, mind-body, and multi-component exercises) and intensities (i.e., low, moderate, and high) on executive function. Results were presented as standardized mean differences (SMD) and 95% confidence intervals (95% CI). A meta-regression analysis was conducted to examine the correlation between exercise duration and mean effects. In total, 15,087 articles were retrieved from three databases, of which 35 studies were included in our final analyses. The results indicated high overall methodological quality (PEDro score = 8) but a potential for publication bias (t = 2.08, p = 0.045). Meta-analyses revealed that all types of exercise (SMD = 0.691, CI [0.498 to 0.885], p < 0.001) and intensities (SMD = 0.694, CI [0.485 to 0.903], p < 0.001) show significant effects favoring exercise. Notably, dual-task exercises (SMD = 1.136, CI [0.236 to 2.035], p < 0.001) and moderate-intensity exercises (SMD = 0.876, CI [0.533 to 1.219], p < 0.001) exhibited the greatest effect. No significant correlation was observed between exercise duration and SMD (R² = 0.038, p = 0.313). Overall, our meta-analyses support the role of physical exercise in enhancing executive function in older adults with MCI or dementia. It is essential to carefully tailor exercise parameters, particularly type and intensity, to meet the specific needs of older adults with MCI or dementia. Such customization is crucial for optimizing executive function outcomes and improving overall brain health.
... The HIIT group received a supervised, three times a week, aerobic HIIT program for 12 weeks. Each HIIT session comprised 2 min of high-intensity exercise (workload corresponding to 85-95% VO 2peak ) followed by 2 min of lightintensity exercise recovery (workload corresponding to 40% VO 2peak ), with progression from 5 to 8 intervals resulting in 28 min to 40 min of exercise (including warm-up and cool-down for 5 min each), which has been found to be effective in improving cardiovascular outcomes in patients with chronic diseases [17][18][19]. Participants in the UC group were asked not to begin any structured high-intensity exercise during the intervention period (i.e., 12 weeks), and they were offered a 4-week HIIT program at our facility or a 12-week community-based exercise program after the intervention period [20]. ...
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Purpose To report the effects of a 12-week high-intensity interval training (HIIT) program on cardiometabolic biomarkers in patients with prostate cancer on active surveillance (AS) from the Exercise During Active Surveillance for Prostate Cancer (ERASE) Trial. Methods Fifty-two men with prostate cancer on AS were randomized to either an exercise (HIIT; n = 26) or usual care (UC; n = 26) group. The HIIT intervention consisted of progressive, supervised, aerobic HIIT at an intensity of 85 to 95% VO2peak for 28 to 40 min per session performed three times/week for 12 weeks. Blood samples were collected at baseline and postintervention to analyze cardiometabolic biomarkers. Analysis of covariance was used to examine between-group mean differences. Results Blood data were obtained from 49/52 (94%) participants at postintervention. Participants were aged 63.4 ± 7.1 years and 40% were obese. The HIIT group attended 96% of the planned exercise sessions. No significant between-group changes in weight were observed after the intervention. Compared to UC, HIIT significantly improved total cholesterol (−0.40 mmol/L; 95% confidence interval[CI], −0.70 to −0.10; p = 0.011), non-high-density lipoprotein-c (−0.35 mmol/L; 95% CI, −0.60 to −0.11; p = 0.006), insulin (−13.6 pmol/L; 95% CI, −25.3 to −1.8; p = 0.025), insulin-like growth factor (IGF)-1 (−15.0 ng/mL; 95% CI, −29.9 to −0.1; p = 0.048), and IGF binding protein (IGFBP)-3 (152.3 ng/mL; 95% CI, 12.6 to 292.1; p = 0.033). No significant differences were observed for fasting glucose, HbA1c, other lipid markers, IGFBP-1, adiponectin, and leptin. Conclusions The ERASE Trial showed that a 12-week aerobic HIIT program improved several cardiometabolic biomarkers in patients with prostate cancer on AS that may contribute to cardiovascular health benefits and potentially influence signaling pathways in the progression of prostate cancer. Further research is needed to confirm the effects of exercise on cardiometabolic markers in men with prostate cancer on AS and determine if these effects are associated with improved long-term clinical outcomes.
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Resistance training (RT) promotes skeletal muscle (Skm) hypertrophy, increases muscular strength, and improves metabolic health. Whether changes in fat-free mass (FFM; a surrogate marker of muscle hypertrophy) moderate RT-induced improvements in glucose homeostasis has not been determined, despite extensive research on the benefits of RT for health and performance. The aim of this meta-analysis is to examine whether RT-induced Skm hypertrophy drives improvements in glucose metabolism and to explore confounders, such as biological sex and training parameters. Random-effects meta-analyses were performed using variance random effects. Meta-regressions were performed for confounding factors depending on the heterogeneity (I²). Analyses from 33 intervention studies revealed significant within-study increases in FFM with a moderate effect size (within-studies: (effect size; ES = 0.24 [0.10; 0.39]; p = 0.002; I2 = 56%) and a tendency for significance when compared with control groups (ES = 0.42 [−0.04–0.88]; p = 0.07). Within-study significant increases in glucose tolerance (2 h glucose: ES = −0.3 [−0.50; −0.11]; p < 0.01; I2 = 43%; glucose area under the curve (AUC): −0.40 [−0.66; −0.13] I2 = 76.1%; p < 0.01) and insulin sensitivity (ES = 0.38 [0.13; 0.62]; I2 = 53.0%; p < 0.01) were also apparent with RT. When compared to control groups, there was no significant difference in 2 h glucose, nor in glucose AUC from baseline in RT intervention groups. Meta-regression analyses failed to consistently reveal increases in FFM as a moderator of glucose homeostasis. Other mixed-effect models were also unsuccessful to unveil biological sex or training parameters as moderators of FFM increases and glucose homeostasis changes. Although Skm hypertrophy and improvements in glycemic control occur concurrently during RT, changes in these variables were not always related. Well-controlled trials including detailed description of training parameters are needed to inform RT guidelines for improving metabolic health. Registration and protocol number (Prospero): CRD42023397362.
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Objective Exercise improves postprandial glycaemia and insulin sensitivity in individuals with prediabetes, but the optimal intensity for this metabolic regulation remains unclear. The current study aims to explore the impact of various exercise intensities on metabolic markers in prediabetic individuals to identify the optimal intensity for improving these indicators. Methods In this crossover study, 25 prediabetic individuals participated in exercise sessions at 50 %, 60 %, 70 %, and 80 % intensities of their predicted maximum heart rate using a treadmill. Each session lasted for 30 min, including a 5-min warm-up and a 5-min cool-down period. Blood samples were collected at four distinct time points: during fasting, immediately before exercise, and 30 and 60 min post-exercise. These samples were analyzed for glucose, insulin, and C-peptide levels. The effects of exercise intensity on these parameters were evaluated using repeated measures ANOVA, with post hoc tests conducted to determine specific differences between the intensities. Results The participants had an average age of 34.88 years, a mean height of 170 cm, and a BMI of 30.34 kg/m². A significant reduction in insulin and glucose levels post-exercise was observed at 70 % intensity (p ≤ 0.001). Despite high fasting blood glucose levels (110–115 mg/dL), significant reductions were noted at 30 and 60 min post-exercise (p ≤ 0.001). Insulin levels approached near baseline at 70 % intensity, from fasting (26.74 ± 20.83) to 60 min post-exercise (28.47 ± 20.79), indicating a positive response at this intensity. C-peptide levels also showed significant changes, with the 70 % intensity exercise bringing them closest to fasting levels by 60 min post-exercise. Conclusion This study highlights the importance of exercise intensities in enhancing metabolic parameters in prediabetic individuals. Specifically, 70 % of the predicted maximum heart rate was beneficial, optimizing insulin sensitivity and potentially reducing the risk of progressing from prediabetes to diabetes.
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High-Intensity Interval Training (HIIT) has gained attention as an effective training method for improving basketball performance. This study investigates the impact of an 8-week HIIT program on basketball-specific physiological and performance metrics, compared to traditional endurance training. Basketball is an intermittent sport, requiring both aerobic and anaerobic energy systems for activities like sprints, jumps, and rapid direction changes. Traditional endurance training often focuses on aerobic capacity but neglects the anaerobic demands of the sport. In contrast, HIIT emphasizes short bursts of high-intensity activity, which better replicate the physical demands of basketball. This study involved 40 male basketball players aged 18-25, randomly assigned to either a HIIT group or a control group performing traditional endurance training. Key metrics measured included VO2 max, lactate threshold, sprint performance, and muscle endurance. Results demonstrated that the HIIT group showed significantly greater improvements across all performance metrics. VO2 max increased by 13.3% in the HIIT group compared to 4.8% in the control group. Additionally, the HIIT group exhibited a 10.9% improvement in lactate threshold, 5.3% faster sprint times, and 7.9% higher jump performance, indicating superior muscle endurance. Findings suggest that HIIT is a more effective training method for basketball players, enhancing both aerobic and anaerobic performance and aligning better with the sport's physical demands. Introduction Physical conditioning is a critical component of basketball performance. Players must maintain high levels of cardiovascular fitness, muscular strength, and endurance to perform effectively during games. Traditional training methods, often focusing on steady-state endurance exercises and basic strength training, have been used to develop these attributes. However, such methods may not fully replicate the physiological demands of basketball, which is inherently an intermittent sport. Traditional endurance training, while effective in improving aerobic capacity, does not always address the anaerobic demands required for the explosive movements seen in basketball (Castagna et al., 2007) [9]. High-Intensity Interval Training (HIIT) has emerged as a highly effective training method, particularly for sports that require both aerobic and anaerobic fitness. HIIT involves repeated bouts of high-intensity exercise followed by short periods of rest or low-intensity activity. This form of training is designed to stress the body's energy systems to a greater extent than continuous, moderate-intensity exercise, leading to significant improvements in both aerobic and anaerobic performance (Laursen & Jenkins, 2002) [23]. In the context of basketball, HIIT's emphasis on short, intense bursts of activity closely mimics the physical demands of the sport. Players frequently engage in high-intensity actions such as sprints, jumps, and defensive movements, making HIIT a potentially more effective training method for improving basketball-specific performance metrics (Buchheit & Laursen, 2013) [23]. Furthermore, HIIT has been shown to improve VO 2 max, enhance lactate threshold, and increase muscle endurance all critical factors for maintaining high levels of performance throughout a basketball game.
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In this review, we develop a blueprint for exercise biology research in the new millennium. The first part of our plan provides statistics to support the contention that there has been an epidemic emergence of modern chronic diseases in the latter part of the 20th century. The health care costs of these conditions were almost two-thirds of a trillion dollars and affected 90 million Americans in 1990. We estimate that these costs are now approaching $1 trillion and stand to further dramatically increase as the baby boom generation ages. We discuss the reaction of the biomedical establishment to this epidemic, which has primarily been to apply modern technologies to stabilize overt clinical problems (e.g., secondary and tertiary prevention). Because this approach has been largely unsuccessful in reversing the epidemic, we argue that more emphasis must be placed on novel approaches such as primary prevention, which requires attacking the environmental roots of these conditions. In this respect, a strong association exists between the increase in physical inactivity and the emergence of modern chronic diseases in 20th century industrialized societies. Approximately 250,000 deaths per year in the United States are premature due to physical inactivity. Epidemiological data have established that physical inactivity increases the incidence of at least 17 unhealthy conditions, almost all of which are chronic diseases or considered risk factors for chronic diseases. Therefore, as part of this review, we present the concept that the human genome evolved within an environment of high physical activity. Accordingly, we propose that exercise biologists do not study “the effect of physical activity” but in reality study the effect of reintroducing exercise into an unhealthy sedentary population that is genetically programmed to expect physical activity. On the basis of healthy gene function, exercise research should thus be viewed from a nontraditional perspective in that the “control” group should actually be taken from a physically active population and not from a sedentary population with its predisposition to modern chronic diseases. We provide exciting examples of exercise biology research that is elucidating the underlying mechanisms by which physical inactivity may predispose individuals to chronic disease conditions, such as mechanisms contributing to insulin resistance and decreased skeletal muscle lipoprotein lipase activity. Some findings have been surprising and remarkable in that novel signaling mechanisms have been discovered that vary with the type and level of physical activity/inactivity at multiple levels of gene expression. Because this area of research is underfunded despite its high impact, the final part of our blueprint for the next millennium calls for the National Institutes of Health (NIH) to establish a major initiative devoted to the study of the biology of the primary prevention of modern chronic diseases. We justify this in several ways, including the following estimate: if the percentage of all US morbidity and mortality statistics attributed to the combination of physical inactivity and inappropriate diet were applied as a percentage of the NIH's total operating budget, the resulting funds would equal the budgets of two full institutes at the NIH! Furthermore, the fiscal support of studies elucidating the scientific foundation(s) targeted by primary prevention strategies in other public health efforts has resulted in an increased efficacy of the overall prevention effort. We estimate that physical inactivity impacts 80–90% of the 24 integrated review group (IRG) topics proposed by the NIH's Panel on Scientific Boundaries for Review, which is currently directing a major restructuring of the NIH's scientific funding system. Unfortunately, the primary prevention of chronic disease and the investigation of physical activity/inactivity and/or exercise are not mentioned in the almost 200 total subtopics comprising the IRGs in the Panel's proposal. We believe this to be a glaring omission by the Panel and contend that the current reorganization of NIH's scientific review and funding system is a golden opportunity to invest in fields that study the biological mechanisms of primary prevention of chronic diseases (such as exercise biology). This would be an investment to avoid US health care system bankruptcy as well as to reduce the extreme human suffering caused by chronic diseases. In short, it would be an investment in the future of health care in the new millennium.
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In this review, we develop a blueprint for exercise biology research in the new millennium. The first part of our plan provides statistics to support the contention that there has been an epidemic emergence of modern chronic diseases in the latter part of the 20th century. The health care costs of these conditions were almost two-thirds of a trillion dollars and affected 90 million Americans in 1990. We estimate that these costs are now approaching $1 trillion and stand to further dramatically increase as the baby boom generation ages. We discuss the reaction of the biomedical establishment to this epidemic, which has primarily been to apply modern technologies to stabilize overt clinical problems (e.g., secondary and tertiary prevention). Because this approach has been largely unsuccessful in reversing the epidemic, we argue that more emphasis must be placed on novel approaches such as primary prevention, which requires attacking the environmental roots of these conditions. In this respect, a strong association exists between the increase in physical inactivity and the emergence of modern chronic diseases in 20th century industrialized societies. Approximately 250,000 deaths per year in the United States are premature due to physical inactivity. Epidemiological data have established that physical inactivity increases the incidence of at least 17 unhealthy conditions, almost all of which are chronic diseases or considered risk factors for chronic diseases. Therefore, as part of this review, we present the concept that the human genome evolved within an environment of high physical activity. Accordingly, we propose that exercise biologists do not study "the effect of physical activity" but in reality study the effect of reintroducing exercise into an unhealthy sedentary population that is genetically programmed to expect physical activity. On the basis of healthy gene function, exercise research should thus be viewed from a nontraditional perspective in that the "control" group should actually be taken from a physically active population and not from a sedentary population with its predisposition to modern chronic diseases. We provide exciting examples of exercise biology research that is elucidating the underlying mechanisms by which physical inactivity may predispose individuals to chronic disease conditions, such as mechanisms contributing to insulin resistance and decreased skeletal muscle lipoprotein lipase activity. Some findings have been surprising and remarkable in that novel signaling mechanisms have been discovered that vary with the type and level of physical activity/inactivity at multiple levels of gene expression. Because this area of research is underfunded despite its high impact, the final part of our blueprint for the next millennium calls for the National Institutes of Health (NIH) to establish a major initiative devoted to the study of the biology of the primary prevention of modern chronic diseases. We justify this in several ways, including the following estimate: if the percentage of all US morbidity and mortality statistics attributed to the combination of physical inactivity and inappropriate diet were applied as a percentage of the NIH's total operating budget, the resulting funds would equal the budgets of two full institutes at the NIH! Furthermore, the fiscal support of studies elucidating the scientific foundation(s) targeted by primary prevention strategies in other public health efforts has resulted in an increased efficacy of the overall prevention effort. We estimate that physical inactivity impacts 80-90% of the 24 integrated review group (IRG) topics proposed by the NIH's Panel on Scientific Boundaries for Review, which is currently directing a major restructuring of the NIH's scientific funding system. Unfortunately, the primary prevention of chronic disease and the investigation of physical activity/inactivity and/or exercise are not mentioned in the almost 200 total subtopics comprising t
Conference Paper
Strength training represents an alternative to endurance training for patients with type 2 diabetes. Little is known about the effect on insulin action and key proteins in skeletal muscle, and the necessary volume of strength training is unknown. A total of 10 type 2 diabetic subjects and 7 healthy men (control subjects) strength-trained one leg three times per week for 6 weeks while the other leg remained untrained. Each session lasted no more than 30 min. After strength training, muscle biopsies were obtained, and an isogly-cemic-hyperinsulinemic clamp combined with arterio-femoral venous catheterization of both legs was carried out. In general, qualitatively similar responses were obtained in both groups. During the clamp, leg blood flow was higher (P < 0.05) in trained versus untrained legs, but despite this, arterio-venous extraction glucose did not decrease in trained legs. Thus, leg glucose clearance was increased in trained legs (P < 0.05) and more than explained by increases in muscle mass. Strength training increased protein content of GLUT4, insulin receptor, protein kinase B-␣/␤, glycogen syn-thase (GS), and GS total activity. In conclusion, we found that strength training for 30 min three times per week increases insulin action in skeletal muscle in both groups. The adaptation is attributable to local contraction mediated mechanisms involving key proteins in the insulin signaling cascade. Diabetes 53:294 –305, 2004 I t is an established finding that aerobic endurance training increases insulin action in patients with type 2 diabetes (1–9), and also that the effect of training is predominantly located to the skeletal muscle (10). Glycemic control also improves along with training (11). Furthermore, with the increased insulin action, the need for insulin to mediate the clearance of a given amount of glucose is lessened. Thus, the need for exogenous insulin or oral hypoglycemic agents is decreased (12). Apart from the beneficial effects on glucose metabolism, physical training also exerts marked improvement on most of the components of the metabolic syndrome (13). Despite the scientific evidence of the therapeutic effect of exercise training, it is a well-known clinical experience that it is often very difficult to engage the patients into taking exercise on a regular basis, and even if one succeeds , the adherence is disappointing. The majority of patients with type 2 diabetes are overweight and have usually been sedentary for the major part of their lives. For many reasons, both psychological and sociological, they are not likely to take up endurance training. Obesity may even be a physical problem in the performance of exercise , especially endurance-type exercises. For patients with type 2 diabetes, resistance training probably represents an attractive exercise modality, but little is known about the overall effect, and the effect in muscle has not been studied. Furthermore, dose-response studies on resistance training effects have not been carried out. To provide support for the recommendations about the type and intensity of effective exercise, we have now carried out a study where we investigated the effect of a very low amount of strength training on insulin action in the skeletal muscle in patients with type 2 diabetes. Based on the sparse literature available on strength training regimens in these patients (14 –19), we used a training program that we a priori considered to be minimally effective. We used a one-legged training protocol, a model that is robust against biological variation and that has previously been used to demonstrate the effect of endurance training on skeletal muscle insulin sensitivity (10). Second, we obtained muscle biopsies from both legs and analyzed these for differences in content and activities of proteins and enzymes that could explain a possible effect of strength training.
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Strength training represents an alternative to endurance training for patients with type 2 diabetes. Little is known about the effect on insulin action and key proteins in skeletal muscle, and the necessary volume of strength training is unknown. A total of 10 type 2 diabetic subjects and 7 healthy men (control subjects) strength-trained one leg three times per week for 6 weeks while the other leg remained untrained. Each session lasted no more than 30 min. After strength training, muscle biopsies were obtained, and an isoglycemic-hyperinsulinemic clamp combined with arterio-femoral venous catheterization of both legs was carried out. In general, qualitatively similar responses were obtained in both groups. During the clamp, leg blood flow was higher (P < 0.05) in trained versus untrained legs, but despite this, arterio-venous extraction glucose did not decrease in trained legs. Thus, leg glucose clearance was increased in trained legs (P < 0.05) and more than explained by increases in muscle mass. Strength training increased protein content of GLUT4, insulin receptor, protein kinase B-alpha/beta, glycogen synthase (GS), and GS total activity. In conclusion, we found that strength training for 30 min three times per week increases insulin action in skeletal muscle in both groups. The adaptation is attributable to local contraction-mediated mechanisms involving key proteins in the insulin signaling cascade.