Original Research
Effects of Training With Free Weights Versus
Machines on Muscle Mass, Strength, Free
Testosterone, and Free Cortisol Levels
Shane R. Schwanbeck,1 Stephen M. Cornish,2 Trevor Barss,3,4,5 and Philip D. Chilibeck1
1
College of Kinesiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada; 2Faculty of Kinesiology and Recreation
Management, University of Manitoba, Winnipeg, Manitoba, Canada; 3Faculty of Medicine and Dentistry, Neuroscience and Mental
Health Institute, University of Alberta, Edmonton, Alberta, Canada; 4Division of Physical Medicine & Rehabilitation, Department of
Medicine, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, Alberta, Canada; and 5Sensory Motor Adaptive
Rehabilitation Technology (SMART) Network, University of Alberta, Edmonton, Alberta, Canada
Abstract
Schwanbeck, SR, Cornish, SM, Barss, T, and Chilibeck, PD. Effects of training with free weights versus machines on muscle mass,
strength, free testosterone, and free cortisol levels. J Strength Cond Res 34(7): 1851–1859, 2020—Free weights offer a more
unstable training environment, which enhances muscle recruitment, whereas some machines have the advantage of using a “cam”
pulley system that better matches strength curves. We compared the effect of training with free weights vs. machines on muscle
mass, strength, free testosterone, and free cortisol concentrations. Forty-six subjects (26 women; 22 6 3 years) were randomized
to train using free weights or machines for 8 weeks (with each muscle group trained 2–3/weeks, 3–4 sets of 4–10 repetitions).
Muscle thickness and strength were measured at 0 and 8 weeks. Salivary hormone concentrations were assessed before and at the
end of workouts at the beginning, midway (4 weeks), and end (8 weeks) of the training intervention. Biceps and quadriceps muscle
thickness increased (p , 0.01) with no difference between groups. There was a group 3 time interaction for machine bench press
strength (p 5 0.05) with the machine group increasing more than the free-weight group (13.9 vs. 8.6%). Free-weight bench press
and squat, and Smith machine squat strength increased in both groups (11–19%; p , 0.01) with no difference between groups.
Men in the free-weight group had a greater increase in free testosterone from before to after acute training sessions than men in the
machine group and all women (p , 0.01); however, there was no differences between groups in free cortisol response to acute
resistance exercise. Training sessions with free weights induced greater increases in free testosterone in men; however, training
with free weights or machines resulted in similar increases in muscle mass and strength.
Key Words: resistance training, hormones, lean body mass
Introduction
One of the controversies when prescribing resistance training
programs is whether the use of free weights or machines is better
for building muscle mass and strength. Free weights provide
isotonic resistance, which provides the same amount of resistance
throughout the range of motion. This does not always match the
strength curve of the muscle; that is, the constant resistance
throughout the range of motion offered by free weights does not
always match the strength of a muscle, which varies throughout
the range of motion. Some machines use “cam” pulley systems,
elastics, hydraulics, and pneumatic resistance, which may better
match the strength curves of typical movements.
Despite these potential benefits of training with machines, training with free weights may allow for greater recruitment of muscle
mass. A major difference between training with free weights and
machines is that training with most machines provides a very
stable environment, whereas training with free weights requires
more stabilization and balance, which may result in greater
recruitment of muscle. Using free weights compared with more
stable machines results in greater muscle activation (as measured by
Address correspondence to Philip D. Chilibeck, phil.chilibeck@usask.ca.
Journal of Strength and Conditioning Research 34(7)/1851–1859
ª 2020 National Strength and Conditioning Association
electromyography) during upper- (15) and lower-body (25) strength
exercises. The increased muscle recruitment during free-weight activities can potentially provide a more anabolic stimulus. For example, acute training sessions with free-weight squat exercise results
in greater release of anabolic hormones such as free testosterone and
growth hormone compared with the more stable leg press exercise
(26). This greater anabolic hormone response could potentially lead
to greater muscle hypertrophy and strength over time (21).
The purpose of our study was to compare the effects of training
with only free weights or machines on anabolic hormone response,
measured by free testosterone levels, muscle mass, and strength.
This was performed by randomly dividing men and women into 2
different training groups: one that trained exclusively with free
weights and the other that trained exclusively with machines for 8
weeks. The hypothesis was that free-weight training would result in
greater increases in free testosterone concentration, muscle mass,
and strength compared with training with machines over 8 weeks.
Methods
Experimental Approach to the Problem
Subjects were randomly assigned to either a free-weight or machine training group after stratifying by sex, months of training
experience, and whether they used mostly free weights, mostly
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Training With Free Weights Versus Machines (2020) 34:7
machines, or an equal mix of both during their typical training.
The total duration of the exercise study was 8 weeks. Hormone
levels were assessed using saliva samples collected before and
after workouts at the beginning, midway (4 weeks), and end of the
study (8 weeks). Body composition, muscle thickness, and
strength were measured during the week before the training intervention and during the week after the training intervention.
Subjects
Ethical approval was obtained from the University of Saskatchewan biomedical review board for research in humans, and
subjects were informed of the benefits and risks of the investigation before signing an institutionally approved informed
consent document to participate in the study. Forty-six healthy
subjects volunteered for this study (20 men and 26 women, age
range 18–30 years) and were randomized to machine or freeweight training groups using a computerized random number
generator. The free-weight group did not differ compared with
the machine group for baseline age (23 6 4 vs. 22 6 3 years), mass
(67 6 8 vs. 74 6 6 kg), height (172 6 10 vs. 171 6 10 cm), or
previous resistance training experience (27 6 25 vs. 26 6 24
months).
Procedures
Lean Tissue Mass. Lean tissue mass was measured before and
after the exercise program by air displacement plethysmography
(BOD POD: Life Measurement Instruments, Concord, CA) using
methods previously described in detail (4). Our laboratory has
a coefficient of variation of 0.80% for lean tissue mass using the
BOD POD and a correlation coefficient of 0.98 when comparing
BOD POD with dual-energy X-ray absorptiometry.
Muscle Thickness. Muscle thickness was measured at the quadriceps and biceps before and after the exercise program with Bmode ultrasound (Aloka SSD-500, Tokyo, Japan), as previously
described (4). The coefficients of variation for these measurements in our laboratory are 0.9 and 2.6% for the quadriceps and
biceps, respectively.
Strength Measurements. Strength was assessed by performing a 1repetition maximum (1RM) on a free-weight bench press,
6–10RM free-weight squat, 1RM Smith machine bench press,
and a 6–10RM Smith machine squat. The free-weight strength
tests were performed at least 2 days apart from the Smith machine
strength tests. The order in which subjects performed their bench
presses and squats and the mode in which they were tested on first
were randomized. A predicted 1RM was determined based on the
6–10RM value for the squat exercises (12) for safety reasons. The
Life Fitness Smith machine consisted of an Olympic bar that has
each end attached to an upright rail. The free-weight bench press
was performed using a barbell and flat bench press. The freeweight squat used a power rack and a barbell. For all exercises,
subjects warmed up using a light weight of their choice, and they
then performed up to 5 trials for a maximal lift. There was 3–5
minutes of rest given between each trial.
During the free-weight bench press 1RM, hands were placed
approximately shoulder-width apart, feet on the floor, and back
against the bench. The subject received help unracking the bar,
and they lowered the bar until it contacted their chest at which
point they pushed the bar back up to full elbow extension where
they received help reracking the bar. If the subject was unsuccessful, a spotter helped rerack the bar. For the free-weight
squat 6–10RM, subjects’ feet were approximately shoulderwidth apart. The subject received help unracking the bar, and they
squatted down until their knees were approximately at 90° where
they stood back up until full hip extension was achieved. Once
they had reached their 6–10RM, they received help reracking the
weight. Depth of each repetition was controlled for by attaching
a TheraBand between the frames at a height that when the bar
touched the band at the bottom range of motion, the subject was
at a 90° knee angle. Once the bar touched the band, the subject
received a verbal cue to stand back up. The height of the TheraBand was recorded for the post-test strength assessment. If the
subject could not complete the repetition, they lowered the bar
onto the safety rails.
For the Smith machine bench press 1RM, the subject received
help unracking the bar by slightly rotating the safety hooks off of
the latches located on the frame of the machine and lowered the
bar until it contacted their chest and then pushed the bar back up
to full elbow extension where they received help reracking the bar
by slightly rotating the safety hooks back onto the latches. If the
subject was unsuccessful, a spotter helped rerack the bar. For the
Smith machine squat 6–10RM, subjects’ feet were approximately
shoulder-width apart. The subjects received help unracking the
bar, and they squatted down until their knees were approximately
at 90° where they stood back up until full hip extension was
completed. Once they had completed their 6–10RM, they received help reracking the weight (same as the Smith machine
bench press). Depth of each repetition was controlled for by
placing a box on the outside of the frame and stacking mats high
enough that when the bar touched the mat at the bottom range of
motion, the subject was at an approximately 90° knee flexion
angle. Once the bar touched the mat, the subject received a verbal
cue to stand back up. The height of the box and mats was
recorded for post-test strength assessments. If the subject could
not complete the repetition, they lowered the bar onto the safeties.
The coefficients of variation for the free-weight and Smith machine bench press and squat exercises in our laboratory ranged
from 5 to 8% (intraclass correlation coefficients 5 0.90–0.95).
Hormone Collection. A standardized workout was performed at
the first, midpoint (4 weeks), and last workout (8 weeks). This
workout consisted of performing only the bench press and squat
on their designated mode of training. These 2 exercises consisted
of performing 4 sets of 6–10 repetitions with 1.5 minutes of rest
between sets. Loads for the first hormone collection workout
were calculated as 70% of 1RM based on their pre-test strength
assessments. Loads for the midway and final workout were based
on the weights being used during the workouts just before the
hormone assessment day. Salivary samples were collected before
the start of these 3 workouts and 15 minutes after the workouts.
Salivary hormone levels reflect the free plasma concentration and
bioactive component of steroid hormones (10). Time of the day
was recorded for the first workout so that the midway workout
and the final workout were performed at the same time of the day.
This is important because of the circadian rhythm that affects free
testosterone and free cortisol levels (9,10). Subjects were asked to
ensure they were fully hydrated before hormone assessment sessions. A food record was recorded one day before the hormone
collection so that the same food could be ingested on each of the
days before the next 2 hormone collection days. To minimize the
effect of recent exercise, subjects were told not to exercise for 2
hours before their hormone collection sessions. Salivary free
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Training With Free Weights Versus Machines (2020) 34:7
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Figure 1. Subject flow.
testosterone and free cortisol were measured using enzyme-linked
immunoassay kits according to the manufacturer’s instructions
(Salimetrics, State College, PA). Saliva was collected from passive
drool through a short straw and into a polypropylene vial.
Samples were frozen at 230° C until analysis. Once thawed, the
saliva samples were pipetted into the appropriate wells, mixed on
a plate rotator for 5 minutes at 500 rpm, and incubated in the
dark at room temperature for an additional 25 minutes. The
samples were read in a plate reader at 450 nm. Three samples
were taken, and an average value was calculated. Our laboratory
had intra-assay coefficients of variation ranging from 4.0 to 7.2%
for free cortisol and 4.6–8.6% for free testosterone. All samples
for a given individual were assessed within the same assay so that
individual results were not affected by inter-assay variability.
Exercise Program. The exercise program lasted for 8 weeks and
consisted of a 2 days on and one day off cycle (e.g., half the muscle
groups were trained on one day and half the next day, followed by
a day of rest). Eight weeks was chosen as it is an adequate amount
of time to realize hypertrophy and increases in strength for most
muscle groups (30). Day one trained the chest, back, and triceps.
The free-weight exercises included the flat barbell bench press,
incline barbell bench press, bent over barbell row, chin-ups, supine elbow extension, and dumbbell kickbacks. The machine
exercises were performed on Technogym (Seattle, WA), Hammer
Strength (Cincinnati, OH), Life Fitness (Schiller Park, IL), and
APEX (Saanichton, BC, Canada) equipment. The Technogym
equipment uses a cam pulley system, which is designed to match
the strength curve of the specific movement. The machine exercises for the chest, back, and triceps included the Smith machine
(Life Fitness) bench press, Smith machine incline bench press,
Hammer Strength–seated row, Technogym lat pulldown, Technogym machine triceps press-down, and rope press-down (Life
Fitness pulley system). Day 2 trained the legs, shoulders, and biceps. Free-weight exercises included the squat, straight leg deadlift, lunge, single-leg calf raise, dumbbell shoulder press, dumbbell
lateral raise, camber bar curl, and preacher curl. The machine
exercises for the legs, shoulders, and biceps included the Smith
machine squat, Technogym quadriceps extension, Technogymseated hamstring curl, APEX machine calf raise, Technogym
machine shoulder press, Technogym machine lateral raise,
Technogym machine biceps curl, and Hammer Strength machine
preacher curl. For the first 3 weeks, all exercises were performed
for 4 sets of 8–10 repetitions with 1 minute of rest between sets.
For the next 3 weeks, weight was increased, and all exercises were
Table 1
Lean tissue mass (kg) before and after 8 weeks of training.*
Free-weight group
Males†
Females
Combined
Machine group
Males†
Females
Combined
Before
After
Effect size
65 6 4 (61–69)
47 6 4 (44–50)
56 6 4 (53–58)
65 6 5 (61–69)
46 6 4 (43–49)
56 6 5 (53–58)
0
20.25
0
72 6 8 (68–75)
48 6 4 (44–51)
60 6 6 (57–62)
70 6 7 (66–73)
48 6 4 (45–51)
59 6 6 (56–61)
20.25
0
20.17
*All values are mean 6 SD (95% confidence intervals).
†Significant sex main effect (p , 0.01).
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Training With Free Weights Versus Machines (2020) 34:7
Figure 2. Individual responses for lean tissue mass (A), biceps muscle thickness (B), and quadriceps muscle thickness (C)
from baseline to 8 weeks. The machine group subjects are indicated by dashed lines, and the free-weight group subjects are
indicated by a solid line.
performed for 4 sets of 6–8 repetitions with 1.5 minutes of rest
between sets. For the last 2 weeks, weight was increased again,
and all exercises were performed for 3 sets of 4–5 repetitions with
2 minutes of rest between sets. Intensity was increased throughout
the program once a subject was able to complete their required
repetitions with good form, to achieve progressive overload. The
exercise program also increased load as volume decreased to
mimic a taper effect, which has been shown to promote strength
increases (7). If the subject performed a set outside of the desired
repetition range, they were instructed to adjust the weight for the
following sets so that they would complete the appropriate
number of repetitions required. This allowed for an adequate
progression in training load. Workouts were recorded in a detailed activity log. All workouts took place in our university’s
fitness center where fully qualified exercise professionals
(i.e., Canadian Society for Exercise Physiology Certified Exercise
Physiologists or Certified Personal Trainers) were available to
provide assistance during the workouts. Over the 8 weeks, there
were approximately 38 training sessions; therefore, with the splitbody program, each muscle group was trained over 19 sessions.
Statistical Analyses
A 2 3 2 3 2 mixed (between–within) analysis of variance
(ANOVA) was conducted with group (free-weight group vs.
machine group), sex (men vs. women), and time (baseline vs. 8
weeks) as factors to determine the differences between groups for
lean tissue mass, muscle thicknesses, and strength over time.
A 2 3 2 3 2 3 3 mixed (between–within) ANOVA was conducted with group (free-weight group vs. machine group), sex
(male vs. female), time during workout (pre vs. post), and time of
the training program (baseline vs. 4 vs. 8 weeks) as factors to
determine the difference between groups for hormone levels
during workouts and over time. Tukey’s post hoc tests were run
when significant interactions were found. All statistical analyses
were conducted using STATISTICA 7.0 (Tulsa, OK). All values
are expressed as means 6 SD, except in graphs, where standard
errors were used for clarity. A p value of 0.05 was accepted as
significant.
Results
The subject flow through the study is indicated in Figure 1.
Fifteen men and 21 women completed the study (7 men and 11
women in the free-weight group, 8 men and 10 women in the
machine group). The reason for dropout was the time commitment needed to complete the workouts. There was no difference
between groups for compliance to the training with the freeweight group attending 83 6 29% and the machine group attending 81 6 12% of their training sessions. As an indication of
the subjects’ training experience, the ratio of their squat and
bench press strength to body mass at baseline was as follows:
machine-group men: Smith machine bench press 1.0 6 0.2,
Smith machine squat 1.6 6 0.5, free-weight bench press 1.0 6
0.2, and free-weight squat 1.6 6 0.4; machine-group women:
Smith machine bench press 0.7 6 0.1, Smith machine squat 1.7
6 0.2, free-weight bench press 0.7 6 0.1, and free-weight squat
1.6 6 0.3; free-weight group men: Smith machine bench press
1.2 6 0.3, Smith machine squat 2.1 6 0.2, free-weight bench
press 1.1 6 0.2, and free-weight squat 2.0 6 0.2; free-weight
Table 2
Muscle thickness before and after 8 weeks of training.*
Biceps (cm)
Free-weight group
Males‡
Females
Combined
Machine group
Males‡
Females
Combined
Quadriceps (cm)
Before
After†
Effect size
Before
After†
Effect size
4.1 6 0.5 (3.8–4.4)
3.4 6 0.4 (3.1–3.6)
3.7 6 0.5 (3.4–3.9)
4.3 6 0.4 (4.1–4.5)
3.5 6 0.4 (3.3–3.6)
3.9 6 0.4 (3.5–4.1)
0.40
0.25
0.40
5.6 6 0.7 (5.2–6.1)
5.7 6 0.6 (5.3–6.0)
5.6 6 0.7 (5.2–5.9)
6.0 6 0.7 (5.5–6.5)
5.9 6 0.8 (5.5–6.3)
5.9 6 0.7 (5.6–6.2)
0.57
0.33
0.43
4.2 6 0.3 (3.9–4.5)
3.2 6 0.3 (3.0–3.5)
3.7 6 0.3 (3.4–3.9)
4.4 6 0.3 (4.2–4.6)
3.4 6 0.2 (3.2–3.6)
3.9 6 0.4 (3.6–4.1)
0.67
0.67
0.67
6.4 6 0.5 (5.9–6.8)
5.6 6 0.5 (5.2–6.0)
5.9 6 0.5 (5.6–6.2)
6.7 6 0.5 (6.2–7.1)
5.9 6 0.5 (5.5–6.3)
6.2 6 0.5 (5.9–6.6)
0.60
0.60
0.60
*All values are mean 6 SD (95% confidence interval).
†Significant time main effect (p , 0.01).
‡Significant sex main effect for both muscle groups (p , 0.01).
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141 6 29 (124–157) 171 6 33 (150–192)
103 6 15 (89–117) 128 6 23 (111–146)
122 6 22 (111–133) 150 6 28 (136–163)
0.68
1.13
0.84
*All values are mean 6 SD (95% confidence interval).
†Significant time main effect (p , 0.01).
‡Significant sex main effect (p , 0.01).
§Significant group 3 time interaction; the increase in the machine group was greater than that of the free-weight group (p 5 0.05).
142 6 22 (126–157) 157 6 21 (140–175)
101 6 15 (89–113) 118 6 16 (104–133)
122 6 19 (111–131) 138 6 19 (127–149)
0.85
0.75
1.10
0.71
0.55
0.80
85 6 14 (77–93) 95 6 13 (87–103)
42 6 11 (35–49) 48 6 11 (41–55)
63 6 10 (58–69) 71 6 9 (66–77)
90 6 13 (81–99) 101 6 13 (92–110)
44 6 12 (37–52) 55 6 12 (47–63)
67 6 10 (61–73) 78 6 10 (72–84)§
153 6 11 (137–169) 178 6 12 (158–197)
93 6 23 (78–106) 118 6 29 (101–135)
123 6 17 (112–133) 148 6 21 (135–161)
1.93
1.05
1.44
146 6 15 (132–160) 175 6 22 (158–191)
98 6 21 (86–109) 120 6 24 (106–113)
122 6 18 (113–131) 148 6 23 (136–157)
0.38
0.50
0.57
94 6 21 (84–103)
45 6 12 (37–53)
70 6 14 (63–76)
86 6 21 (76–95)
39 6 12 (31–47)
62 6 14 (56–68)
0.53
1.09
0.62
81 6 19 (73–90) 91 6 19 (82–99)
36 6 11 (29–43) 44 6 11 (37–51)
59 6 13 (53–64) 67 6 13 (62–73)
Before
Before
After†
Effect
size
Machine
Effect
size
After†
The major finding of this study is that free weight and machine
training were equally effective for increasing muscle thickness and
strength. These findings do not support our hypothesis that
training with free weights would result in greater gains in muscle
mass and strength. The second major finding is that the men
training with free weights experienced a significant acute increase
in free testosterone from before to after workouts. This finding
partially supports our hypothesis that the group training with free
weights would have greater increases in anabolic hormone response. The hypotheses were based on the evidence that training
with free weights activates more muscle mass (1,15,25), which
should cause a greater increase in free testosterone (26), and over
time causes a greater increase in muscle mass and strength (21).
Before
Discussion
Bench press (kg)
All hormone results are presented in Table 4. There was a significant group 3 sex 3 time during workout interaction for free testosterone (p , 0.05). Tukey’s post hoc analyses indicated that only
the free-weight training men significantly increased free testosterone from before to after workouts (p , 0.01; Figure 4). There was
no significant change in free cortisol at any time point for either sex
or training group. There was a significant sex 3 time during
workout interaction for the free testosterone to free cortisol ratio (p
, 0.05). Only men had significant increases in the free testosterone
to free cortisol ratio during workouts, increasing from 7.0 6 3.7 to
8.8 6 5.3 (p , 0.01). There were no changes over the duration of
the 8 weeks of training in any hormone measure (i.e., there were no
“chronic” changes in any of the hormone measures).
Free weight
Hormones
Table 3
Free-weight and machine bench press and squat strength before and after 8 weeks of training.*
There was a group 3 time interaction (p 5 0.05) for the machine
bench press with the machine training group experiencing a greater
increase in machine bench press strength compared with the freeweight training group (Table 3 and Figure 3A). There were no other
differences between groups over time for any other strength measure (Figure 3B–D). There were significant time main effects for
free-weight bench press, free-weight squat, and machine squat (p ,
0.01), with strength increasing from before to after training. There
was a significant sex main effect (p , 0.01) for all strength tests,
with men higher than women, as would be expected. There were no
sex 3 time interactions for any strength measures, indicating men
and women responded similarly to the training program.
Free weight
Strength
After†
Effect
size
Squat (kg)
Before
Machine
There were no differences in lean tissue mass over time or between
groups (Table 1 and Figure 2A). Biceps and quadriceps muscle
thickness increased over the training program (time main effect p
, 0.01), with no differences between groups (Table 2 and
Figure 2B, C). There was a sex main effect (p , 0.01), for lean
tissue mass, and biceps and quadriceps muscle thickness with
higher values in men compared with women, as would be
expected. There were no sex 3 time interactions, indicating men
and women responded similarly to the training program.
Free-weight
group
Males‡
Females
Combined
Machine group
Males‡
Females
Combined
Lean Tissue Mass and Muscle Thickness
After†
Effect
size
group women: Smith machine bench press 0.6 6 0.1, Smith
machine squat 1.5 6 0.5, free-weight bench press 0.6 6 0.1, and
free-weight squat 1.5 6 0.4.
1.03
1.67
1.27
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2.27
1.09
1.47
Training With Free Weights Versus Machines (2020) 34:7
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Training With Free Weights Versus Machines (2020) 34:7
Figure 3. Individual responses for Smith machine bench press (A), free-weight bench
press (B), Smith machine squat (C), and free-weight squat (D). The machine group
subjects are indicated by dashed lines, and the free-weight group subjects are indicated
by a solid line.
We found no significant changes for either training group in
whole-body lean tissue mass assessed by the Bod Pod but significant increases in biceps and quadriceps muscle thickness across
both groups. Subjects had previous training experience and might
have been close to their ceiling level of lean body mass, and 8 weeks
of resistance training may not have been enough to induce a further
increase. Our results are in agreement with one other study that
previously used the Bod Pod to assess changes in lean tissue mass.
Rossi et al. (22) compared training with free-weight squat vs.
machine-based leg press for 10 weeks and found no differences
between groups for changes in lean tissue mass. Similarly, Maddalozzo and Snow (14) found that 24 weeks of training with
a seated resistance training program or standing free-weight program produced equivalent increases in lean body mass as measured
using dual-energy x-ray absorptiometry. Their free-weight program however also included some machine-based exercises;
therefore, their programs were not exclusively free weight or
machine-based. Boyer (2) compared 3 different training modes
consisting of 2 different types of machines or free weights and
found no significant differences for changes in body composition as
assessed by skinfolds and girths between groups over time. Overall,
these results support the contention that free weight and machinebased training are equally effective for increasing muscle mass.
Both the free-weight training group and the machine training
group had significant increases in free weight and Smith machine
squat strength and free weight and Smith machine bench press
strength. These findings do not support our hypothesis that the
free-weight group would experience greater gains in strength. The
machine-based training group experienced greater increase in
machine bench press strength compared with the free-weight
training group. This finding supports the idea of specificity, which
refers to the concept that the greater the similarity training has to
the actual performance test, the greater the probability of transfer
(23). This training specificity is supported by one other study where
training with free weights or using a Nautilus machine resulted in
greater gains in strength when testing was performed on the
training device (2). Also, 10 weeks of training with free-weight
squat exercise was superior for increasing strength in the squat
exercise compared with training with machine leg press (22). In
contrast to the concept of specificity, our free-weight bench press,
free-weight squat, and Smith machine squat increased in both the
free weight and the machine training groups with no differences
between the 2 groups. One previous study evaluating training with
free-weight squats, the Nautilus Compound Leg Machine, or
Universal Variable Resistance Maximum Overload Leg Press also
found significant increases in all strength measures, which were
similar across free weight or machine training groups (28). These
findings do not support the concept of specificity, but rather, they
show that there was good transfer of strength from one mode
(i.e., free weights or machines) to the other. It is possible that the
training level of our subjects contributed to a lack of specificity for
training. Our subjects had on average over 2 years of resistance
training experience and therefore may have had adequate previous
experience training on different machines and with free weights.
Individuals who are less accustomed to resistance training may
experience greater specificity in their response to training (23).
Our results indicated that men and women responded in
a similar fashion to the training program for increases in muscle
thickness and strength (i.e., there were no sex 3 time interactions). This is in agreement with the early studies by Staron et al.
who found similar increases in muscle fiber size (30) and strength
(29) in response to training programs in women and men.
A surprising finding is that there was no difference in predicted
1RM or actual 1RM for squat or bench press between the Smith
machine and free-weight modalities. One would expect a greater
strength performance with the Smith machine because it offers greater
stabilization. Previous studies comparing Smith machine and freeweight squat did not report 1RMs (1,25). In support of our bench
press results, one other study found no difference for 1RM performance between Smith machine and free-weight bench press (24). They
proposed that the linear motion of the Smith machine is unnatural and
places the lifter at a biomechanical disadvantage, therefore, resulting in
a lower lifting performance than expected. This may account for the
similar 1RM between Smith machine and free-weight modalities.
The only group that experienced a significant acute increase in
free testosterone was the men training with free weights. This
1856
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Baseline
Free-weight males
Machine males
Free-weight females
Machine females
4 weeks
8 weeks
Before
After
Before
After
Before
After
194 6 53 (146–243)
143 6 58 (98–188)
75 6 60 (35–114)
70 6 20 (33–107)
242 6 59 (191–292)
152 6 61 (106–199)
77 6 60 (35–118)
95 6 30 (56–134)
152 6 44 (124–180)
134 6 34 (108–161)
91 6 33 (68–115)
80 6 33 (58–102)
203 6 65 (165–242)
173 6 44 (137–208)
93 6 45 (62–125)
87 6 33 (57–117)
172 6 31 (142–201)
156 6 34 (128–183)
89 6 33 (65–113)
76 6 31 (53–99)
218 6 68 (168–267)
160 6 60 (114–206)
78 6 60 (37–118)
87 6 40 (49–125)
Training With Free Weights Versus Machines (2020) 34:7
Testosterone (pg·ml21)
Cortisol (mg·dl21)
Baseline
1857
Free-weight males
Machine males
Free-weight females
Machine females
4 weeks
8 weeks
Before
After
Before
After
Before
0.21 6 0.22 (0.02–0.39)
0.34 6 0.21 (0.17–0.51)
0.36 6 0.21 (0.21–0.51)
0.37 6 0.21 (0.23–0.52)
0.30 6 0.17 (0.16–0.44)
0.31 6 0.18 (0.18–0.44)
0.32 6 0.15 (0.21–0.44)
0.40 6 0.16 (0.30–0.51)
0.19 6 0.20 (0.02–0.36)
0.32 6 0.21 (0.17–0.48)
0.46 6 0.14 (0.32–0.60)
0.34 6 0.20 (0.21–0.47)
0.31 6 0.22 (0.08–0.53)
0.32 6 0.25 (0.11–0.52)
0.47 6 0.27 (0.29–0.65)
0.32 6 0.24 (0.14–0.49)
0.30 6 0.44 (0.08–0.68)
0.60 6 0.42 (0.25–0.95)
0.33 6 0.45 (0.02–0.64)
0.40 6 0.45 (0.11–0.69)
After
0.28 6 0.12 (0.17–0.039)
0.23 6 0.18 (0.13–0.33)
0.29 6 0.12 (0.20–0.38)
0.40 6 0.12 (0.32–0.49)
Testosterone: Cortisol (ratio) 3 102
Baseline
Free-weight males
Machine males
Free-weight females
Machine females
4 weeks
8 weeks
Before
After
Before
After
Before
After
8.4 6 1.6 (6.1–10.6)
5.5 6 4.5 (3.6–7.4)
2.7 6 1.2 (1.0–4.5)
2.7 6 1.9 (1.1–4.3)
10.0 6 3.7 (6.3–13.8)
7.8 6 8.2 (4.6–11.0)
2.7 6 1.0 (0.2–5.7)
2.9 6 2.0 (0.3–5.6)
8.2 6 3.9 (5.6–10.8)
5.7 6 3.6 (3.5–7.8)
2.9 6 2.3 (0.85–4.9)
3.1 6 1.1 (1.2–4.9)
10.0 6 3.8 (7.5–10.4)
6.7 6 3.4 (4.7–8.8)
2.9 6 1.4 (1.0–4.9)
3.4 6 1.5 (1.8–5.2)
6.7 6 2.1 (3.9–9.4)
6.9 6 6.4 (4.5–9.2)
2.6 6 1.1 (0.41–4.8)
1.9 6 0.6 (0–3.9)
8.8 6 5.6 (5.1–12.6)
9.4 6 7.3 (6.2–12.6)
3.1 6 2.0 (0.1–6.0)
2.1 6 0.7 (0.5–4.8)
*All values are means 6 SD (95% confidence intervals).
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Table 4
Changes in testosterone and cortisol levels during workouts at baseline, 4 and 8 weeks in males and females performing free-weight or machine-based training.*
Training With Free Weights Versus Machines (2020) 34:7
Figure 4. Free testosterone before and after workouts (averaged for all 3 hormone collection workouts). Values are mean 6 SE. *Significant increase from before to after
workouts for men training with free weights (p , 0.01). Effect sizes were as follows: freeweight men 5 1.41; machine men: 0.53; free-weight women 5 20.06; machine women
5 0.44.
result partially supports our hypothesis that the free-weight group
would have a greater anabolic response to training. Recruitment
of large amounts of muscle mass may be needed to elicit an acute
free testosterone response (11). This greater acute anabolic hormone response for men exercising with free weights vs. machines
is supported by one other study (26). In our study, the men
training with machines experienced only a small nonsignificant
increase in free testosterone. Although the acute workouts for the
free-weight group and the machine group followed a protocol
with similar training volume, the men training with machines in
our study may not have received enough mechanical stress by
training in the very stable environment of the Smith machine.
Free-weight exercise requires more stabilization than Smith machine exercise as evidenced by substantially higher muscle recruitment, as assessed by electromyography (25). The stability
and balance needed for the free-weight training session may have
added the needed stress resulting in an acute free testosterone
increase. The women, regardless of the training mode, did not
experience any changes in acute free testosterone levels, similar to
other studies (8,13). Overall, our salivary hormone results are
similar to others who have assessed salivary hormone response to
acute and chronic resistance training. Others have found that
training with free weights (5,6) but not with programs that use
mainly machines (10) results in an acute increase in salivary free
testosterone in men but not women (19). Also, there is generally
a lack of increase in salivary free testosterone with chronic
training programs in men and women (20,27).
Although there was no acute change in free testosterone for
women and men training with machines, they still had increases in
biceps and quadriceps muscle thickness over the 8 weeks of
training. This finding indicates that there may not be a direct
causal relationship between increases in muscle mass and acute
exercise-induced increases in free testosterone. This idea is supported by several recent studies that failed to find correlations
between acute increases in anabolic hormone response and
chronic changes in muscle mass during resistance training programs (16–18).
There are a number of limitations to the study. The machine
program used a variety of machines, some of which had “cam”
pulley systems and some which did not. The machines therefore
would have differed biomechanically, and our results therefore
are not specific to any one design of machine. Another limitation
is that the training program was only 8 weeks in duration. A
longer training program may be necessary to elicit differences in
training responses to machines vs. free weights. In the current
study, we assessed salivary hormones, but these may not always
reflect serum hormone concentrations. For example, Cadore et al.
(3) found that although salivary free cortisol concentrations
correlated with serum free cortisol in response to an acute session
of resistance training, there was no correlation between salivary
and serum free testosterone.
In conclusion, results of this study show that significant
increases in strength and biceps and quadriceps muscle thickness
can be achieved by training with only free weights or only
machines. Men training with free weights have an acute increase
in free testosterone after an acute resistance training session, but
this does not seem to translate into greater increases in muscle size
or lean body mass when compared with resistance training with
machines. These results suggest that muscle size and strength can
be increased to the same degree with either training modality.
Practical Applications
Frequently strength and conditioning practitioners promote
the use of free weights over the use of machines to enhance
muscle size and strength. Our study indicates that the mode of
training (i.e., free weights or machines) does not determine the
degree of muscle hypertrophy or strength increase. The results
of this study indicate that muscle size and strength was increased similarly between a free-weight–only training group
and a weight-machine–only training group during 8 weeks of
training in subjects with about 2 years of previous training
experience. This suggests that if the goal of the training program is to increase muscle size or strength, then either modality of training can be used effectively to accomplish this
outcome. It should be emphasized that these results may differ
if training programs are longer than 8 weeks and in subjects
with less training experience. Our study also indicates that
although there is an increase in free testosterone from an acute
bout of free-weight resistance exercise, this may not translate
into larger gains in lean body mass, muscle size, or strength
when completing a chronic resistance training program.
1858
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Training With Free Weights Versus Machines (2020) 34:7
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Acknowledgments
This study was supported by a grant from the Saskatchewan
Academy of Sports Medicine. The authors declare no conflicts of
interest.
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