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[Applied Sciences: Physical Fitness And Performance]
Medicine & Science in Sports & Exercise
Issue: Volume 31(9), September 1999, pp 1320-1329
Copyright: © 1999 Lippincott Williams & Wilkins, Inc.
Publication Type: [Applied Sciences: Physical Fitness And Performance]
ISSN: 0195-9131
Accession: 00005768-199909000-00014
Keywords: DIET, STRENGTH TRAINING, LIPOPROTEINS, TESTOSTERONE, CORTISOL, ENDURANCE TRAINING
Influence of exercise training on physiological and performance changes with weight loss in men
KRAEMER, WILLIAM J.; VOLEK, JEFF S.; CLARK, KRISTINE L.; GORDON, SCOTT E.; PUHL, SUSAN M.; KOZIRIS, L. PERRY; McBRIDE, JEFFREY M.; TR
PUTUKIAN, MARGOT; NEWTON, ROBERT U.; HÄKKINEN, KEIJO; BUSH, JILL A.; SEBASTIANELLI, WAYNE J.
Author Information
Department of Kinesiology, Noll Physiological Research Center, and Center for Sports Medicine, The Pennsylvania State University, Universit
Human Performance Laboratory, Ball State University, Muncie, IN 47306
Submitted for publication January 1998.
Accepted for publication June 1998.
This study was supported in part by a grant from Matol Botanical International LTD (Montreal, Canada). Additional support was from the Rob
Leitzinger Research Fund in Sports Medicine at the Pennsylvania State University. We would like to thank a dedicated group of subjects who mad
special thanks to Kathy Buhl, and Laura Gerace for their technical assistance and Brenda Sinclair for her contributions related to nutritional aspe
are fortunate to have a great staff at the Center for Sports Medicine/Noll Physiological Research Center and would like to thank all of clinical an
in data collection, medical monitoring, and nutritional support.
Current affiliations for Susan M. Puhl: State University of New York at Cortland, Park Center E-253, Box 2000, Cortland, NY 13045; N. Travis
M. McBride at the University of Wisconsin-LaCrosse, LaCrosse, WI 54601; Keijo Häkkinen, University of Jyväskylä, Jyväskylä, Finland; and L. Perr
Kinesiology, North Texas State University, Denton, TX.
Address for correspondence: William J. Kraemer, Ph.D., Professor/Director, The Human Performance Laboratory, Ball State University, Mun
wkraemer@bsu.edu.
ABSTRACT
Influence of exercise training on physiological and performance changes with weight loss in men.
Med. Sci.
Sports Exerc.,
Vol. 31, No. 9, pp. 1320-1329, 1999.
Purpose: The purpose of this study was to examine the physiological effects of a weight-loss dietary regimen
with or without exercise.
Methods:
Thirty-five overweight men were matched and randomly placed into either a control group (C;
N
= 6) or
one of three dietary groups; a diet-only group (D;
N
= 8), a diet group that performed aerobic exercise three times
per week (DE;
N
= 11); and a diet group that performed both aerobic and strength training three times per week
(DES;
N
= 10).
Results:
After 12 wk, D, DE, and DES demonstrated a similar and significant (
P
<= 0.05) reduction in body mass
(-9.64, -8.99, and -9.90 kg, respectively) with fat mass comprising 69, 78, and 97% of the total loss in body mass,
respectively. The diet-only group also demonstrated a significant reduction in fat-free mass. Maximum strength, as
determined by 1-RM testing in the bench press and squat exercise was significantly increased for DES in both the
bench press (+19.6%) and squat exercise (+32.6%). Absolute peak O
2
consumption was significantly elevated in DE
(+24.8%) and DES (+15.4%). There were no differences in performance during a 30-s Wingate test for the DE and DES,
whereas D demonstrated a significant decline in peak and mean power output. Resting metabolic rate (RMR)
(kcal·d
-1
) was not significantly different for any of the groups except for the DE group. There were no significant
changes in basal concentrations of serum glucose, BUN, cortisol, testosterone, and high density lipoprotein (HDL)
cholesterol for any of the groups. Serum total cholesterol and low density lipoprotein (LDL) cholesterol were
significantly decreased for all dietary groups. Serum triglycerides were significantly reduced for D and DES at week 6
and remained lower at week 12 for D, while triglycerides returned to baseline values for DES.
Conclusions: These data indicate that a weight-loss dietary regimen in conjunction with aerobic and resistance
exercise prevents the normal decline in fat-free mass and muscular power and augments body composition, maximal
strength, and maximum oxygen consumption compared with weight-loss induced by diet alone.
Weight loss occurs when energy output (i.e., RMR plus the thermic effect of activity and food) is greater than
energy input (i.e., dietary intake). Reducing dietary energy intake certainly provides a simple and effective method
to lose total body mass, at least temporarily. Decreases in body mass with dietary restriction can result in a loss of
fat-free mass
(30)
. However, the loss of fat-free mass (i.e., primarily skeletal muscle) can be undesirable because of
the important functional and metabolic roles the muscle plays in force production and metabolic rate. It was
hypothesized that concurrent dieting and heavy resistance training may spare the loss of fat-free mass, thereby
leading to improvements in muscular strength, body composition, and metabolic rate over dieting alone.
There is a distinct need for a greater understanding of the combined effects of resistance training and endurance
training performed simultaneously during a weight loss program. While many studies have certainly described the
physiological responses to dietary-induced weight loss in men, fewer studies have examined the impact of specific
(i.e., endurance or resistance exercise) training programs performed with dietary restriction in men
(3,4,9)
. To our
knowledge, no data are available in men examining the combined influence of performing both heavy resistance and
endurance training as a part of an overall weight loss program
(7,9)
.
Resistance training has resulted in skeletal muscle hypertrophy and had positive effects on body composition and
muscular strength and power
(15,19)
. These physiological adaptations are dependent upon the program design and
several acute program variables (e.g., load used, number of sets and repetitions, rest periods between sets, etc.)
(16)
. Further data are needed to gain insights into the question of whether a diet adequate in protein, fiber, and
vitamins and minerals but low in total energy, can help mediate the expected chronic adaptations to heavy
resistance training? Despite the fact that resistance training may result in only very small improvements in peak
oxygen consumption
(11)
, endurance oriented training has been shown to induce much greater increases in aerobic
capacity, even during weight loss
(23)
. Endurance training also has positive effects on serum lipids
(36)
. Therefore,
we hypothesized that the incorporation of both heavy resistance training and endurance training into a weight-loss
dietary regimen would appear to offer several simultaneous advantages over those provided by weight loss induced
by dietary restriction alone or dieting with only one form of exercise training. Therefore, the primary purpose of this
investigation was to examine the effects of diet alone and diet combined with endurance training and diet combined
with endurance and heavy resistance training on physiological and performance adaptations in overweight adult men.
METHODS
Subjects and experimental design.
Prior approval by the Institutional Review Board for the Use of Human
Subjects at the Pennsylvania State University was obtained for the investigation. Each subject had the risks of the
experiment explained to them and signed an informed consent document. This study conformed with the policy
statement regarding the use of human subjects as published by
Medicine and Science in Sports and Exercise.
All of
the 35 healthy men who completed the study were screened by a physician and demonstrated no endocrine,
orthopedic, or any other pathological disorders, except for being overweight (i.e., >= 120% of desirable weight
defined as the midpoint of the range of weights for a medium frame man from the 1983 Metropolitan Height and
Weight tables). Our first goal was to match the groups for age and percent body fat. Except for the control group
(statistically set at
N
= 6), we attempted to recruit 10 to 12 men for each group. The men were then randomly placed
into one of four groups. After an attrition of one to four men per group because of scheduling difficulties, the
following
N
sizes were observed and used for all analyses in this study. However, no significant differences were
observed among the groups at the beginning of the study in any of the variables. Control group (C;
N
= 6) which just
performed the testing, maintained body weight, and normal activities; a diet group (D;
N
= 8) which maintained
normal activities while reducing calories for weight loss; a diet group which performed an aerobic endurance training
program 3 d·wk
-1
(DE;
N
= 11); and a diet group which performed an aerobic endurance training program combined
with a heavy resistance training program 3 d·wk
-1
(DES;
N
= 10). The experimental testing took place before the
program (Week 0), at the midpoint of the study (Week 6), and the end of the program (Week 12). Descriptive data
for the experimental groups are presented in
Table 1
.
TABLE 1. Descriptive data of the experimental groups (mean ± SD).
Training protocols.
Unique to this study was that all exercise programs were individually supervised by our
laboratory's trained team of certified "personal trainers." The cardiovascular conditioning programs followed the
American College of Sports Medicine guidelines for intensity, frequency, and duration of exercise
(14)
. Subjects in
the DE and DES groups participated in a program of whole body aerobic endurance exercise individually designed to
elicit a target heart rate of 70-80% of the functional capacity as determined by treadmill testing. During the first
week, each session lasted ~30 min (not including warm-up and cool-down) and this was gradually increased to 50 min
over the subsequent weeks. Intensity and duration of exercise were individually increased for each subject as
improvement and toleration occurred. For variety, endurance activities included a cross-training mix of treadmill
walking/jogging, stationary cycling, seated rowing, and stationary stair climbing.
In contrast to the DE group, the DES group also performed a strength training workout after their aerobic training
session. The strength training program consisted of a squat exercise performed on a Tru-Squat machine (Southern
Xercise Inc., Cleveland, TN) and additional Nautilus machine (Nautilus Intl. Huntersville, NC) exercises for each of the
major muscle groups consisting of the following exercises: military press, bench press, lat pull down, seated rows,
sit-ups, lower back, leg press, hamstring curls, calf raises, and arm curls. The programs followed typical repetition
maximum (RM) resistance training principles for progression in the resistance and volume of exercise in a program
(18)
. The resistance training protocol also used a nonlinear periodization model, meaning that the loads were
changed within the week with subjects varying their resistance loads for the exercises on different days alternating
between heavy day (5-7 RM) and moderate day (8-10 RM) loads. Target RM zones were maintained for the load
intensity, but subjects did not always go to complete failure to limit joint stress. Subjects progressed from 1-3 sets
over the first 2-3 wk with short rest between sets and exercises when using moderate loads (i.e., 1 min) and longer
rest periods (2-3 min) when using the heavier loads. This program variation reduced boredom and has been shown to
enhance short-term resistance training adaptations when compared with constant loading programs
(16)
. Throughout
the 12 wk subjects were highly encouraged to increase the amount of weight lifted within each designated repetition
range.
Experimental tests.
All experimental dependent variables demonstrated very good test-retest reliability as
intraclass correlation coefficients were determined for all tests; they ranged from R = 0.95 to R = 0.98. All subjects
were completely familiarized with all testing procedures before the experiment to reduce the influence of any
learning effects caused solely by the mechanics of performing the test protocol.
Body mass was measured on a balance scale to the nearest 100 g and body density was determined via
hydrodensitometry. A description of the equipment used for underwater weighing is provided by Akers and Buskirk
(1)
. Underwater weight of the subject was determined by a scale utilizing four electronic force cubes (load cells)
attached to a chart recorder. Following a maximal exhalation subjects were weighed underwater and residual volume
measurements were performed while subjects were still in the tank using an open-circuit nitrogen washout
technique. Percent body fat was calculated from body density using the Siri equation
(31)
. Fat mass was determined
by multiplying percent fat times body mass, and fat-free mass was determined by subtracting fat mass from body
mass.
Maximal force production (1-RM) in the upper body was determined via a Nautilus straight bar bench press and in
the lower body via the Tru-Squat machine. The 1 RM test protocols were performed using methods previously
described and used extensively in our laboratory
(17)
. These tests are specific to the exercise training protocol and
provided the best representation of maximal muscular strength of the upper and lower body musculature.
Maximal oxygen consumption was determined using a graded exercise test on a Quinton (Seattle, WA) motor
driven treadmill using a modified Bruce protocol
(31)
. During each stage of the test, heart rate was monitored
continuously via a 12-lead EKG (Marquette, Model Case-15, Milwaukee, WI), and ratings of perceived exertion (RPE)
were recorded each minute. Blood pressure was obtained every 2 min via brachial auscultation. Expired gases were
analyzed during the last 6 min of the test using an automated metabolic system. The gas analyzers consisted of a
Beckman LB-2 CO
2
analyzer (Beckman Instruments, Schiller Park, IL) and S3A O
2
Analyzer (Applied Electrochemistry,
AEI Technologies, Pittsburgh, PA) and were calibrated before each test with standard gases. Standard gas tanks were
calibrated via Scholander methodology. Flow was measured by a Hans Rudolph model 4813 pneumotach and
transduced to volume by a Fitco Micro-Flow model FLO-1 instrument. These signals were integrated in a software
package by Fitco (Farmingdale, NY).
Power production capabilities in the lower body were determined using a 30-s Wingate anaerobic test performed
on a computerized Monark (Varberg, Sweden) cycle ergometer against an opposing force of 0.49 N (0.05 kg)·kg
-1
of
body mass using a protocol described in detail by Kraemer et al.
(31)
. Flywheel revolutions were electronically
monitored during the test via computer interface (Model 55sx, IBM Personal System/2). Maximum power (highest 1 s
value), mean power (average power over the time curve) and percent decline (decline from the highest to the lowest
points on the curve) were calculated by associated software.
RMR was only determined before and following the 12 wk experimental protocol via indirect calorimetry.
Following a 10-h fast, subjects reported to the laboratory from 0500 to 0600 h and were positioned in a
semirecumbant position on a bed. After a 30-min stabilization period, oxygen consumption was determined at 1-min
intervals for 30 min using the same on-line metabolic system used for maximal treadmill testing.
Nutritional protocol.
Each week all intervention participants attended a 1-h group format nutrition education
meeting led by a registered dietitian. The weekly sessions focused on behavior modification techniques and educating
subjects as to how to implement a healthy well balanced eating plan designed to lose body mass. Our objective was
to create a 6- to 9-kg weight loss in each subject by moderate caloric restriction over the 12 wk. Forms for
documenting daily food intake were provided at each session and these food records were reviewed for dietary
compliance at the beginning of each new week. Food record forms were analyzed for total food energy and nutrient
content using Nutritionist IV, Version 4 nutrient analysis software (N-Squared Computing, First Databank Division, The
Hearst Corporation, San Bruno, CA). In addition, subjects were given a 1-week supply of Matola products at each
meeting. Briefly, the Matola products included prepackaged high-fiber meal replacement bars, shakes, and cereal
which contained approximately 50% of the USRDA for vitamins and minerals. These products were consumed in place
of certain meals in a 4-d rotational sequence. In addition to other meals ingested during the day, subjects consumed
the Matola products in the following order: one product on day 1, two products on day 2, three products on day 3,
and no products on day 4. Thus, a total of about 12 products were consumed each week. Protein intake was >= RDA
and >= 1 g·kg
-1
ideal body weight. Subjects were strongly encouraged to drink copious amounts of water throughout
the day. Body mass was also recorded and charted at each meeting to ensure a steady rate of weight loss (0.5 to 1.0
kg·wk
-1
) over the 12 wk. It was not the goal of the study to strictly control what subjects consumed outside of their
scheduled Matola products. Sample menus were provided to help subjects select a variety of foods for their
non-Matola meals. If weight loss was not progressing at an appropriate rate or if subjects were having problems
adhering to the dietary regimen, individual counseling was provided.
Blood collection and analyses.
Blood was obtained from a forearm vein after a 10 h fast between 0500 to 0600
h. Whole blood was processed and the resultant serum samples were stored at -80°C until analyses were performed.
Serum glucose, blood urea nitrogen (BUN), total cholesterol, high-density lipoprotein cholesterol (HDL), and
triglyceride concentrations were determined via spectrophotometry (Novaspec II, Pharmacia LKB Biochrom Limited,
Cambridge, UK) and testosterone and cortisol using standard radioimmunoassay (RIA) procedures. Serum glucose was
assayed in duplicate using an enzymatic (hexokinase) technique at an absorbance of 340 nm (Sigma Diagnostics, St.
Louis, MO). Total cholesterol, HDL cholesterol, triglycerides, and BUN were enzymatically determined in duplicate
using commercially available kits (Sigma Diagnostics). Low-density lipoprotein cholesterol (LDL) concentrations were
calculated according to the method of Friedewald et al.
(8)
. Serum testosterone and cortisol concentrations were
assayed using solid-phase
125
I single antibody RIA (Diagnostic Products Corp., Los Angeles, CA) with detection limits of
0.14 and 5.5 nmol·L
-1
, respectively. Immumoreactivity was measured with an LKB 1272 Clinigamma automatic gamma
counter with an on-line data reduction system (Pharmacia Wallac, Wallac Oy, Finland). Intra- and inter-assay
variances for all assays were <5% and <10%, respectively.
Statistical analyses.
Comparisons between values obtained at baseline, week 6, and week 12 within each group
and between groups at each time point were made using a two-way analysis of variance (ANOVA). In the presence of
a significant
F
value
post-hoc
comparisons of means were provided by Fisher's LSD test. Statistical power calculations
demonstrated power in this investigation ranged from 0.79 to 0.80. The relationship between changes in selected
variables were made using simple regression. The level of significance was
P
<= 0.05.
RESULTS
Estimated dietary intake for the three experimental groups is shown in
Table 2
. There were no significant
differences between groups in any of the examined nutritional variables. The changes in body mass, percent fat, fat
mass, and fat-free mass following the 12-wk experimental period in all four groups are presented in
Table 3
and
Figure 1
. No significant changes in body mass or body composition were observed in the C group. Body mass was
significantly decreased for all dietary intervention groups at week 6 and continued to decline, although at a slower
rate, from week 6 to week 12. Percent body fat and fat mass were also significantly reduced at week 12 for all
dietary groups. The DES achieved a significantly greater loss in percent body fat (-8.42%) at week 12 compared with
the DE group (-4.70%) and the D group (-3.62%). The diet-only group also demonstrated a significant reduction in
fat-free mass at week 6 and week 12. At week 12, the percent of body mass loss attributed to fat for the D, DE, and
DES groups was 69, 78, and 97%, respectively.
TABLE 2. Estimated daily nutrient intake for the three experimental groups (mean ± SD).
TABLE 3. Body composition data (mean ± SD).
Figure 1-Absolute changes (x ± SD) in body mass, fat mass, and fat-free mass (FFM) after 12 wk in the control (C),
diet-only (D), diet + endurance training (DE), and diet + endurance + strength training (DES) groups. * =
P
<= 0.05
from corresponding change in the C group.
Maximum strength, as determined by 1-RM testing in the bench press and squat exercise, was not significantly
different at week 12 for C, D, or DE. However, DES significantly increased the amount of weight lifted at week 12 for
both the bench press (+19.6%) and squat exercise (+32.6%)
(Table 4)
. Maximum oxygen consumption expressed in
relative terms (mL·kg
-1
·min
-1
) was significantly increased at week 12 for D (+28.4%), DE (+39.2%), and DES (+27.4%).
However, peak oxygen consumption expressed in absolute terms (L·min
-1
) was significantly elevated only in the DE
(+24.8%) and DES (+15.4%) groups
(Table 5)
. Control data for maximum oxygen consumption was discarded because of
a problem with the metabolic system and test retest reliabilities determined on a separate group showed an
intra-class R = 0.96. There were no differences in peak power, mean power, or percent fatigue during the Wingate
test at week 12 for the DE and DES groups. The diet-only group demonstrated a significant decline in peak and mean
power output at week 6 which remained lower at week 12
(Table 6)
. RMR was lower after 12 wk for the D, DE, and
DES groups (-80, -122, and -136 kcal·d
-1
, respectively). The only significant reduction in RMR (kcal·d
-1
) was for the DE
group. However, RMR normalized to body mass or fat-free mass was not significantly altered after weight loss
(Table
7)
. Since it has been suggested that dividing RMR by fat-free mass is inappropriate because the intercept of the
relationship does not intersect zero
(28)
,
Figure 2
illustrates the relationship of RMR and fat-free mass at baseline
and week 12.
TABLE 4. One repetition maximum (1-RM) strength in the bench press and squat exercise (mean ± SD).
TABLE 5. Maximum oxygen consumption (mean ± SD).
TABLE 6. Maximum power, mean power, and percent fatigue during a 30-s Wingate test (mean ± SD).
TABLE 7. Resting metabolic rate determinations (mean ± SD).
Figure 2-The relationship between RMR and fat-free mass at baseline ([white circle]) and week 12 (•) in the diet (A),
diet + endurance (B), and diet + endurance + strength (C) groups. A: Baseline, y = 702.66 + 19.37x, r
2
= 0.47; Week
12, y = 1354 + 9.73x, r
2
= 0.30. B: Baseline, y = 387.21 + 23.70x, r
2
= 0.44; Week 12, y = 1064.50 + 11.71x, r
2
= 0.19.
C: Baseline, y = 1298.4 + 9.96x, r
2
= 0.11; Week 12, y = 2358.90-8.40x, r
2
= 0.04.
There were no changes in serum concentrations of glucose, BUN, cortisol, and testosterone for any of the groups
(Table 8)
. Serum cholesterol and triglycerides are shown in
Figure 2
. Total cholesterol
(Fig. 3A)
and LDL cholesterol
(Fig. 3C)
were significantly decreased at week 6 and remained lower at week 12. There were no changes in HDL
cholesterol concentrations for any group
(Fig. 3B)
. Serum triglycerides were significantly reduced in the D and DES
groups at week 6
(Fig. 3D)
. While triglyceride concentrations remained significantly lower at week 12 for the D group,
triglycerides returned to baseline values in the DES group.
TABLE 8. Venous blood variables (mean ± SD).
Figure 3-Serum concentrations (mean ± SD) of total cholesterol (A), HDL cholesterol (B), LDL cholesterol (C), and
triglycerides (D). W0, Week 0; W6, Week 6; W12, Week 12; C, Control; D, Diet; DE, Diet/Endurance; DES,
Diet/Endurance/Strength. * =
P
<= 0.05 from corresponding value at week 0. † =
P
<= 0.05 from corresponding value
at week 6.
DISCUSSION
Dietary restriction alone does not appear to be an optimal strategy to promote weight loss for the >33% of U.S.
adults currently classified as overweight
(21)
. Whether exercise offers any physiological advantages over body fat
reduction induced by dietary restriction has been debated for some time. Furthermore, the potential differential
effects of various forms of exercise, including resistance training, have not been well characterized in men with
regard to its influence on changes in body composition, serum lipid responses, and muscular performance during
weight loss. In this investigation we provide evidence that 12 wk of moderate dietary energy restriction in
conjunction with endurance training improves peak oxygen consumption; however, no advantages over diet alone are
apparent in regards to total weight loss or body composition changes, serum lipoprotein profile, metabolic rate,
power production capabilities, and 1-RM strength. In comparison, when heavy resistance training is added to the diet
and endurance program, improvements in body composition changes and maximal strength are apparent. These data
are important to help identify key program design components for development of successful weight loss programs.
As expected, all three dietary intervention groups demonstrated a significant and similar reduction in overall
body mass. Thus, exercise provided no additional stimulus for greater weight loss compared with that obtained from
dietary restriction alone. This finding is consistent with data from a prior study in women from our laboratory
(20)
as
well as data from several other studies
(3,4,12,26,34)
. The composition of weight loss, however, varied among
groups. In a meta-analysis, Garrow and Summerbell
(9)
predict from regression analysis that for a weight loss of 10 kg
by dieting alone the expected loss of fat mass is 71% and when a similar weight loss is achieved by both diet and
endurance exercise the expected loss from fat mass is increased to 83%. These estimations are remarkably close to
the 69 and 78% loss in fat mass observed in the diet-only and diet-plus endurance groups, respectively. Forbes
(7)
suggests that the two major body components, fat-free mass and fat mass, are linked and rise and fall in a
predictable fashion. For exercising humans with an average percent body fat of approximately 29% (similar to that in
the present study) Forbes
(7)
predicts that 75% of the loss in body mass to be from the fat mass component. Again,
our data from the endurance trained group showing that 78% of the total loss in body mass represents fat mass is in
close agreement with this estimation.
However, the proposed relationship between fat-free mass and fat mass is clearly lost when heavy resistance
training is performed during dietary restriction. Our data show that inclusion of both endurance and a periodized
heavy resistance exercise training three times per week resulted in nearly complete preservation of the fat-free mass
component in a group of overweight men. Of the total body mass loss in the resistance training group, 97% was
accounted for by fat mass. Thus, a periodized heavy resistance training program that sufficiently overloads the whole
body musculature appears to provide a unique stimulus to spare catabolism of body protein and thus alter the
relationship between the fat-free mass and fat mass components.
In contrast to our finding that fat-free mass is essentially completely preserved with heavy resistance exercise
combined with endurance training, other investigators have reported that weight training does not offer advantages
in regards to body composition changes over dietary restriction alone
(5,6)
. However, results from studies using
women have reported that combined resistance training and dieting not only attenuates but maintains or increases
fat-free mass
(2,10,23,25,29,30)
. Differences in training intensity and/or incorporation of periodization (i.e., varying
the program over time) into the resistance training program may help to explain these apparent discrepancies.
Perhaps the uniqueness of the dietary regimen, which was comprised of moderate energy, adequate protein, vitamins
and minerals, and high dietary fiber, also contributed to our findings. Heavy resistance training has been shown to
increase resting concentrations of testosterone and decrease resting concentrations of cortisol in men in the early
phase (first 16 workouts) of a heavy resistance training program
(32)
; however, other studies have shown unaltered
concentrations of these hormones. No significant changes in circulating testosterone and cortisol were observed in
this study over the training period, indicating that an overt endocrine response reflective of the changes to the
various interventions was not observed under these experimental conditions or was not observed because of a more
rapid homeostatic time course of regulation
(19)
.
Serum total cholesterol decreased at week 6 and remained lower than baseline values at week 12 for all three
dietary intervention groups. At week 6 in the D, DE, and DES groups total cholesterol had declined by 16.3%, 14.6%,
and 11.2%, respectively. From week 6 to week 12 total cholesterol increased in the D, DE, and DES groups by 2.6%,
1.8%, and 1.0%, respectively. Serum LDL cholesterol and triglycerides followed a similar pattern of response as total
cholesterol while HDL cholesterol remained unchanged. These lipid responses are very similar to data reported in
men undergoing either dietary restriction alone or diet combined with aerobic conditioning for 12 wk
(12)
.
Interestingly, Wallace et al.
(35)
observed a positive effect of performing resistance exercise in addition to
endurance training on blood lipids (i.e., greater increase in HDL cholesterol and decrease in triglycerides) in subjects
with hyperinsulinemia. Our data show no additional cholesterol lowering effect of exercise over diet alone. Thus,
exercise (both endurance and resistance) did not "enhance" the positive effects of the dietary regimen in this study.
Whether the weight loss, high fiber content of the diet, moderate dietary energy restriction, or a combination of
these factors contributed to the serum lipid responses is unclear.
A reduction in serum cholesterol has been demonstrated to be directly linked to a reduction in coronary risk
(22)
. It should be pointed out, however, that rapid weight loss may induce a non-steady state that has transient
effects on total cholesterol and that clinical evaluation of serum lipid profiles should not be made until body mass
has stabilized
(27)
. More specifically, total cholesterol and LDL cholesterol may show an initial decline after 2 months
of dieting, a moderate rise as weight loss continues (possibly because of mobilization of adipose tissue cholesterol
stores), followed by a decline when body mass finally stabilizes
(12,27)
. Since subjects in this study may still have
been losing body mass at week 12, firm conclusions regarding the potential response of serum lipoproteins should be
made with caution.
RMR expressed in absolute terms (kcal·d
-1
) declined for the D, DE, and DES groups (-3.8%, -6.4%, and -7.0%,
respectively). However, RMR expressed in relative terms, either kcal·kg FFM
-1
·d
-1
or kcal·kg BM
-1
·d
-1
, was not
significantly altered in any of the dietary groups. Thus, when the changes in body mass are accounted for, all dietary
intervention groups prevented the normal decline in RMR typically observed with dietary energy restriction
(24)
. We
regressed RMR across fat-free mass because of potential errors in interpreting RMR expressed as kcal·kg FFM
-1
·d
-1
(28)
. Interestingly, the lowest correlations between fat-free mass and RMR were observed in the DES. The change in
fat-free mass was not significantly correlated with the change in RMR which is in agreement with the findings of a
meta-analysis on the effects of diet and exercise on metabolic rate
(33)
. Contrary to our hypothesis, the exercise
groups demonstrated similar responses in RMR compared with the diet-only group. Geliebter et al.
(10)
also reported
no advantage of either endurance or strength training over dieting alone on RMR in a group of subjects that lost very
similar amounts of body mass to subjects in the present study. In the present study RMR in the D, DE, and DES groups
declined by -80, -136, -122 kcal·d
-1
, respectively, compared with a decline of -88, -149, and -127 kcal·d
-1
reported by
Geliebter et al.
(10)
. Thus, although strength training prevents the normal loss in FFM during dieting, the decline in
RMR is not prevented. As pointed out by Heshka et al.
(13)
, the elapsed time between weight loss and
remeasurement of RMR is a critical factor in assessing the impact of a weight loss program on RMR. Since subjects
may still have been losing weight at week 12, the same cautions must be taken in interpreting the RMR results as that
for the serum lipid data.
As expected the DES group experienced the greatest increases in 1-RM strength in the bench press and squat
exercise. The highest gains were made in the first 6 wk with continued improvement by 12 wk of training. The lack of
continued increases in 1-RM strength may have been a result of the lack of muscle mass gains over the training
program
(15)
. Since there was little change in fat-free mass in the DES group, it may be speculated that 1-RM
strength improvements were mediated via changes in neural mechanisms and/or changes in the quality of protein in
the muscle fiber
(32)
. For example, fiber type conversions in the fast-twitch subpopulations from Type IIB to Type IIA
increased anaerobic energy sources and enzymes, enhanced muscle tissue activation of the agonists, and/or
decreased inhibition of the antagonists, and changes in neuromuscular junction are all physiological adaptations that
have been shown to occur from heavy resistance training
(15,19,32)
. The reason that some studies have reported
small or no strength increases may be related to the resistance training program design. (i.e., most resistance
exercise training programs have not used the higher intensities of exercise nor have they periodized heavy and light
training days over the training period)
(16)
. These data demonstrate that with proper exercise prescription and a
sound weight-loss program, despite the dramatic reduction in body mass, positive adaptational responses most likely
caused by neural mechanisms can be achieved with resistance training on strength performance.
Maximum oxygen consumption expressed in absolute terms (L·min
-1
) was increased for both groups who
performed endurance training (DE and DES). When peak oxygen consumption was expressed relative to body mass
(mL·kg
-1
·min
-1
) increases were observed in all dietary groups. Thus, the improvement in relative peak oxygen
consumption observed in the diet-only group most likely reflects the decrease in body mass at week 12
(12)
. In
contrast, the increase in peak oxygen consumption for the DE and DES groups reflect a true functional improvement
in the muscle's oxidative ability and the body's cardiorespiratory capacity. Interestingly, the improvements in peak
oxygen consumption were not detectable at week 6, indicating that training adaptations resulting in improved oxygen
capacity may not be evident during the initial weeks of a training program during weight loss. This finding agrees
with data reported by Phinney et al.
(26)
showing no improvement in peak oxygen consumption after 40 d of a very
low calorie diet and regular endurance exercise. There were also no differences in the increase in maximum oxygen
consumption between the DE and DES groups, indicating that even under conditions of weight loss, the concurrent
resistance training and endurance training can be performed without comprising the expected cardiovascular
improvements as previously demonstrated without weight loss
(19)
. Nevertheless, whether simultaneous resistance
and endurance training compromised the physical performance gains derived from weight training alone remains
unknown because of the experimental design used in this investigation. One might speculate that the rate of strength
gains may have been attenuated by the combination of strength and endurance training, particularly in the lower
body as both forms of exercise involved the leg musculature
(19)
.
No statistically significant changes were observed over the 12-wk training program in the Wingate anaerobic
cycle power test performance except for a decline in peak and mean power output by the diet-only group and a
trend for lower values in the DE group. These declines in power production capabilities most likely reflect the loss in
fat-free mass observed in these groups. The resistance trained DES group did maintain their fat-free mas and their
anaerobic power performance despite a significant reduction in total body mass. The mechanisms responsible for
enhancing fast-velocity strength changes have been shown to be different than those which mediate slow-velocity
strength changes
(16)
. Thus, the lack of improvement in the power component of performance is most likely
attributable to the fact that neither the weight training nor the cycle exercise used in the endurance training were
specifically designed with power development in mind. These data demonstrate that strength increases do not
necessarily contribute to changes in power as the use of controlled movements in training do not promote
improvements in the rate of force development nor can such stack plate equipment be used for explosive lifting
because of deceleration requirements over the range of motion to protect joints involved.
In summary, these data indicate that endurance exercise, when added to a dietary weight loss program, increase
maximum oxygen consumption. However, no additional benefits are detectable over dieting alone in regards to
changes in total body mass, body composition, RMR, serum lipid profile, and muscular strength in men. However, diet
in conjunction with heavy resistance and endurance exercise training not only improves peak oxygen consumption but
also has the largest impact on improving body composition, maximal strength, and maintaining power production
capabilities. Thus, heavy resistance exercise is an important component for weight management programs in men as
it offers several distinct advantages over weight loss accomplished by dieting alone.
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Key Words: DIET; STRENGTH TRAINING; LIPOPROTEINS; TESTOSTERONE; CORTISOL; ENDURANCE TRAINING
IMAGE GALLERY
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