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International Journal of
Environmental Research
and Public Health
Article
Using Machines or Free Weights for Resistance
Training in Novice Males? A Randomized
Parallel Trial
Dirk Aerenhouts * and Eva D’Hondt
Department of Movement and Sport Sciences, Faculty of Physical Education and Physiotherapy,
Vrije Universiteit Brussel, 1050 Brussels, Belgium; eva.dhondt@vub.be
*Correspondence: dirk.aerenhouts@vub.be; Tel.: +32-2-629-27-31
Received: 6 October 2020; Accepted: 23 October 2020; Published: 26 October 2020
Abstract:
This study compared the effect of a resistance training (RT) program with machines,
free weights, or a combination of both on changes in anthropometrics, strength, and functional ability
in novice adult males. Thirty-six male novices in RT (18–45 years) followed a 10-week RT program.
Participants were randomly assigned to one of three groups (N =12 each): machines only; free weights
only; or switching from machines to free weights (after 5 weeks). Muscle size (circumferences of
upper arm, thigh and chest), strength (1 Repetition Maximum) on both machines and free weights,
and functional ability (Functional Movement Screen
TM
(Functional Movement Systems Inc., Chatham,
VA, USA)) were assessed prior to the RT program, halfway at 5 weeks, and within one week after
the final training bout. Repeated measures MANOVAs showed no significant time by RT group
interactions for the different outcome measures. Regardless of RT group, significant improvements
over time were observed for anthropometrics (F =9.144, p<0.001), strength (F =6.918, p<0.001),
and functional ability (F =25.578, p<0.001). To conclude, similar gains in muscularity, strength,
and functional ability can be expected for male novices in RT regardless of the equipment being used
and without a fallback when changing from machines to free weights. Accordingly, any choice of RT
equipment can be made, considering individual preferences.
Keywords:
strength; exercise prescription; physical fitness; learning transfer; progression; untrained
1. Introduction
Performing resistance training (RT) on a regular basis provides a safe and effective method
to increase muscular strength, local muscular endurance, fat free mass, as well as overall physical
function [
1
]. This increase in physical function has been related to improved body coordination [
2
],
whereas impaired functional ability (i.e., the ability to perform activities of daily living) may lead to
higher injury prevalence [3,4].
For novices, RT frequency is recommended to be two to three nonconsecutive days per week [
1
].
The American College of Sports Medicine (ACSM) also states that: ”The choice to incorporate free
weights or machines should be based on level of training status and familiarity with specific exercise
movements as well as the primary training objective” [
5
]. Machines are training devices that have pin
loaded weight stacks with fixed lever arms and range of motion. They provide a safer use than free
weights and can be used relatively easy without supervision under any circumstances [
6
]. In contrast,
free weights, including dumbbells, barbells, kettlebells, cables, etc., allow free movement and thus
need to be stabilized by the executioner himself [6].
Because of leading to a higher inter- and intramuscular coordination, free weight RT exercises
may result in a better overall body coordination and are generally considered to be more functional
Int. J. Environ. Res. Public Health 2020,17, 7848; doi:10.3390/ijerph17217848 www.mdpi.com/journal/ijerph
Int. J. Environ. Res. Public Health 2020,17, 7848 2 of 13
compared to using machines for RT [
5
]. Accordingly, free weight exercises provide a higher neuromotor
stimulus as shown in electromyography (EMG) studies [
7
–
9
]. For example, unstable squats result in
higher EMG activity in synergistic muscles [
7
], and EMG activity is also found to be higher in the
medial deltoid muscle during a free weight bench press as compared to the more stable Smith or chest
press machine alternative [
8
,
9
]. In addition, a recent study by Schott et al. (2019) observed that the
relative increase in exercise load from baseline was higher in older adults training with free weights
as compared to those using the machine alternative, but only for the triceps brachialis and knee and
hip extensor muscles [
10
]. Also, Rossi et al. (2018) concluded that free weight squat training elicited
better strength outcomes than training with the leg press machine, whilst balance improved equally
regardless of the exercise used [
11
]. In contrast, Schwartz et al. (2019) observed a higher increase in
peak jump power in recreationally active women training on the machine squat as compared to peers
performing free weight squat training, whilst similar improvements in agility and sprint performances
were observed in both training groups [
12
]. A higher activation and recruitment of more muscle mass
when using free weights should increase testosterone levels to a greater extent [
13
], and thus induce
more hypertrophic effects [
14
]. However, a possible disadvantage of using free weights might be the
(lack of) necessary experience to perform certain exercise movements correctly, since poor technical
skills and inferior movement patterns might increase injury risk [
15
]. Therefore, free weight exercises
are typically not recommended for novices, but are often only introduced when some level of RT
experience is attained [5].
The training principle of specificity is a well-accepted concept of transfer in motor learning [
16
],
indicating that improvements in performance are specific to the exercise and equipment being used.
Boyer (1990) already demonstrated this training specificity in the context of RT a few decades ago [
17
].
Essentially, one can expect that training with machines will result in greater improvements in machine
strength test outcomes compared to using other types of testing equipment. The same principle applies
when training with free weights, even when the same muscles and muscle groups are used in both
types of RT exercises. However, training with free weights has been suggested to produce a more
effective learning transfer than training with machines [
18
]. Therefore, with regard to changing from
using machines to free weights for RT purposes, a stagnation or fallback in performance progression
may be possible because the practitioner needs to acquire a new motor program before the desired
load can be applied. To date, however, no evidence is available to support this particular hypothesis.
The few existing studies that compare the effect of different RT modes on anthropometric and
performance parameters have shown conflicting results. Furthermore, there is a paucity of studies
on novice practitioners and, thus far, no research exists in which the influence of RT equipment
on the learning transfer to the opposite training mode (i.e., using machines vs. free weights) is
examined in novices. Therefore, the primary purpose of the present randomized parallel trial was
to compare changes in anthropometric estimations of muscle size, strength and functional ability in
novice male adults when participating in a 10-week whole-body RT program using either machines
only, free weights only, or when changing halfway the program from using machines to free weights.
Previous research leads to the hypothesis that participants using free weights only during the RT
program will show a greater gain in muscularity, strength, and functional ability as compared to
those using machines only. A secondary purpose was to investigate the bidirectional learning transfer
in terms of strength and functional ability gains between using machines and free weights. It was
hypothesized that a greater positive learning transfer will be observed to strength testing with machines
when training with free weights as compared to strength testing with free weights when training
with machines.
Int. J. Environ. Res. Public Health 2020,17, 7848 3 of 13
2. Materials and Methods
2.1. Experimental Approach to the Problem
A randomized parallel trial was designed to compare changes over time in anthropometric
estimations of muscle size, strength, and functional ability between three different RT groups
(i.e., following a 10-week whole-body RT program using machines only (M), free weights only
(FW), or changing halfway (i.e., after 5 weeks) from using M to FW (COMB)) in male adults being
novice in RT. A 10-week RT program should be sufficiently long to induce hypertrophic effects on
top of initial neurological adaptations (i.e., greater fiber recruitment, rate of discharge, intermuscular
coordination), both resulting in strength increases [
19
,
20
]. In the present study design we only
implemented a COMB group switching from M to FW, and not vice versa, as it is common in novice
RT practitioners to start with relatively easy M exercises and later on switch to the more technical FW
exercises [5].
2.2. Participants
An a priori power analysis with G*Power 3.1.9.2 was performed, using a predefined power of
0.80, an alpha level of 0.05 and an effect size of 0.25 [
21
]. These parameters lead to a required sample
size of at least 36 participants in total (N =12 in each RT group). To be eligible, participants had
to be male, between 18 and 45 years old, and free of musculoskeletal disorders that could hinder
them from exercising. None of these participants had any experience with RT exercises using either
machines or free weights, and they were not allowed to take supplements to promote muscle mass or
strength gains. Recruitment continued until the desired sample size effectively completing the 10-week
RT program was reached. This way, 50 male participants were recruited for the present study by
means of advertisement on social media and via word of mouth. After baseline screening and testing,
all 50 eligible participants were allocated to one of three groups (M, FW, or COMB) by a third person in
a blinded manner (i.e., only using the subject number without knowledge of any other identification or
baseline test result) using block randomization targeting group sizes of N =12. Fourteen participants
dropped out and reported lack of motivation (N =10), not having enough time (N =3), or experiencing
work-related injury (N =1) as a reason.
According the Declaration of Helsinki, participants were informed about the benefits and risks of
the experiment and were given the opportunity to ask any questions in relation to the study, prior to
signing an informed consent. The associated study protocol was approved by the local university’s
ethical committee (B.U.N. 143201630122, dd. 12-07-2016).
2.3. Procedures
2.3.1. RT Program
The whole-body RT program was designed to ascertain that every RT group trained the same
muscles or muscle groups during the 10-week period of the study. For each machine exercise,
a corresponding free weight exercise targeting the same prime movers was provided, as shown in
Table 1. Technical execution of each exercise is demonstrated in Supplementary File S1. All participants
trained two times a week performing three sets per exercise with 12-RM weights (i.e., the load that
can be lifted correctly up to 12 times), which is a generally recommended load to apply in RT for
novices [
1
,
5
]. After each training session, the participant informed the responsible researcher per
e-mail about the number of repetitions performed in each set. When a participant could perform 12
repetitions or more during two sets on two consecutive training sessions, the participant was asked to
increase the resistance with 2 to 10 percent, depending on the available equipment [
5
]. Before and after
the actual training session, a 5-min cycling warm-up and cooldown was performed on a stationary
cycle ergometer at a moderate intensity (i.e., 60% of the theoretical maximal heart rate, calculated as
220 minus the participant’s age) [22].
Int. J. Environ. Res. Public Health 2020,17, 7848 4 of 13
Table 1. Test order and targeted muscle groups for each exercise in the RT program
Machine Exercise Free Weight Exercise Primary Movers
Leg press Squat (barbell)
M. Quadriceps femoris +M. Hamstrings +M. Glutei
Chest press Bench press (dumbbells)
M. Pectoralis major and minor +M. Triceps brachii +
M. Deltoideus pars clavicularis
Hip extension Deadlift (barbell) M. Hamstrings +M. Glutei +M. Erector spinae
Seated row Bent over row (dumbbells) M. Latissimus dorsi +M. Trapezius
Shoulder press Standing shoulder press (dumbbells) M. Deltoideus +M. Triceps brachii
2.3.2. Outcome Measures
At baseline (i.e., pre-intervention), after 5 weeks (i.e., mid-intervention) and after 10 weeks RT
(i.e., post-intervention), all outcome measures of interest were assessed on the same day per test occasion
in the following order: anthropometrics, strength and functional ability. To control for variations in
body weight during the day, measurements for each test occasion were scheduled systematically at the
same time of day per participant.
Anthropometrics—Standardized anthropometric measurements were conducted according to
the guidelines of the International Society for the Advancement of Kinanthropometry (ISAK) [
23
].
Body height was determined to the nearest 0.1cm with a mobile stadiometer (Seca 217). Body weight
was measured to the nearest 0.1kg using an analogue scale (Seca 762). Circumferences of chest, thigh,
and upper arm (both relaxed and maximally contracted) were measured to the nearest 0.1 cm with
a Cescorf anthropometric tape and used to estimate muscle size. Because of corresponding well
with the overall body fat percentage in men, participants’ waist circumference was measured to the
nearest 0.1 cm with a Cescorf anthropometric tape and used as an estimate to control their change in
(abdominal) fat mass during the course of the study [24].
Strength—To ensure correct technical execution (e.g., range of motion, movement velocity,
body posture), familiarization with the strength tests was conducted with minimal loads, about one
week before baseline testing. For strength testing sessions, all participants followed a standardized
test order, which was specifically developed to target the different muscle groups involved with each
corresponding exercise (Table 1).
Because participants were unexperienced in RT, direct 1-RM testing was not performed [
25
].
Instead, 10- to 12-RM weights used to determine the correct training load were converted to 1-RM values
using the Oddvar Holten Diagram [
26
]. First, for warming-up purposes, a series of 6–10 repetitions
was performed with approximately 50% of the workload established. After a two-minute rest
period, the actual strength test was initiated. Participants were encouraged to perform the most
of repetitions (aimed around 10–12 repetitions) until the imposed resistance could no longer be
sustained and an additional repetition could not be performed with the proper technique anymore [
5
].
Technical execution of the test exercises was continuously monitored by an experienced researcher,
who told the participant to stop whenever the observed technique was no longer satisfactory.
This testing protocol for 1-RM estimation was applied at baseline for all RT groups on both
machines and free weights. At mid- and post-intervention, the same testing protocol was applied to
estimate participants’ 1-RM on the equipment that they had not used in the preceding 5 weeks of the
RT program, whilst the 1-RM on the equipment that had been used was estimated and derived from
the 12-RM weight participants used in the first set of each exercise in the last training bout preceding
the mid- and post-intervention assessments (Table 2).
Int. J. Environ. Res. Public Health 2020,17, 7848 5 of 13
Table 2. Training and testing protocol
Pre Tests Week 1–5 Mid Tests Week 6–10 Post Tests
Using machines in RT program M +COMB M
Using free weights in RT program FW FW +
COMB
1-RM test for machines +free weights M+FW +
COMB
1-RM test for free weights +1-RM machines
derived from preceding training M+COMB M
1-RM test for machines +1-RM free weights
derived from preceding training FW FW +
COMB
Anthropometric tests +SBJ +Functional
Movement ScreenTM
M+FW +
COMB
M+FW +
COMB
M+FW +
COMB
RT, Resistance training; M, group using machines (N =12); FW, group using free weights (N =12); COMB, RT
group changing from machines to free weights after 5 weeks (N =12); RM, Repetition maximum; SBJ, Standing
Broad jump.
In addition, a standing broad jump (SBJ) was conducted as a neutral functional strength test.
To this end, participants had to stand behind a line marked on the floor with their feet at shoulder width.
Subsequently, they had to jump as far as possible, landing on both feet without falling backwards.
A counter movement and arm swing were allowed. The distance between the start line and the rear
foot was measured to the nearest 0.5 cm. The highest value from three attempts was retained for
further analysis.
Functional ability—The Functional Movement Screen
TM
(FMS) consists of seven specific exercises
(i.e., deep squat, hurdle step, in-line lunge, active straight-leg raise, trunk stability push-up,
rotary stability, and shoulder mobility) and is a screening tool to assess individuals’ functional
ability [
27
]. Procedures to perform the test are described in detail elsewhere [
28
]. A score of three
indicates that the participant can perform the prescribed movement correctly and without pain; a score
of two indicates that the participant can complete an easier alternative of the movement without pain;
a score of one is given when the participant is unable to complete the easier alternative correctly;
and a score of zero is recorded if the participant experiences pain during any phase of the movement.
Accordingly, the total FMS score equals the sum of all exercises, ranging between 0 and 21 points.
2.4. Statistical Analysis
Data were analyzed using SPSS 26.0 (SPSS Inc., Chicago, IL). A normal distribution for the outcome
measures of interest was confirmed using the Shapiro–Wilk Normality Test.
A one-way analysis of variance (ANOVA) was used to compare baseline values of the basic
demographic and anthropometric variables (age, body height, and body weight) between the three
RT groups.
To compare changes over time in circumferences of chest, thigh, and upper arm (both relaxed
and maximally contracted), a two-way repeated measures multivariate ANOVA (MANOVA) was
conducted with RT group as the between-subjects factor (three levels: M, FW, or COMB) and time as the
within-subjects factor (three levels: pre-, mid-, and post-intervention). Likewise, to compare changes
over time in strength, two two-way repeated measures MANOVAs (i.e., once for machine exercises and
once for free weight exercises) were executed, again with RT group (three levels) as the between-subjects
factor and time (three levels) as the within-subjects factor. For waist circumference, SBJ and total FMS
score, similar separate repeated measures ANOVAs were performed. Homogeneity of variance and
sphericity were verified and in case Mauchly’s test indicated a violation of the assumption of sphericity,
Greenhouse–Geisser correction was applied. In case of significance, the RT group by time interaction
effects as well as the main effects for RT group and time were further elaborated at the univariate level
and assessed using a Bonferroni correction for multiple comparisons. Partial eta squared (
ηp2
) effect
sizes were calculated for interaction, within and between effects. The probability level of statistical
significance was set at p<0.05.
Int. J. Environ. Res. Public Health 2020,17, 7848 6 of 13
3. Results
At baseline the three RT groups were comparable for age (F(2,35) =0.862, p=0.431,
ηp2=0.05
;
M: 24.8
±
7.3 yrs; FW: 25.0
±
7.8 yrs; COMB: 28.6
±
7.9 yrs), body height (F(2,35) =1.302,
p=0.286
,
ηp2=0.077
; M: 183.0
±
6.8 cm; FW: 181.4
±
9.9 cm; COMB: 181.1
±
8.9 cm) and body weight
(F(2,35) =0.205, p=0.815, ηp2=0.012; M: 78.3 ±9.0 kg; FW: 80.6 ±11.1 kg; COMB: 80.4 ±9.1 kg).
3.1. Anthropometrics
Anthropometric outcomes are reported in Table 3. The repeated measures MANOVA for chest,
thigh, and upper arm (both relaxed and maximally contracted) circumferences showed no significant
RT group by time interaction effect (F(16,52) =0.818, p=0.659), nor a significant main effect of RT group
(F(8,60) =1.007, p=0.441). However, a significant multivariate main effect of time (
F(8,26) =9.144
,
p<0.001) was found.
Table 3. Anthropometric measurements (mean ±SD) according to RT group and time
Anthropometric
Outcomes RT Group Pre-Intervention
(0 Weeks)
Mid-Intervention
(5 Weeks)
Post-Intervention
(10 Weeks)
Univariate p-Value
and (ηp2) of the
Interaction Effect
Body weight (kg) M 78.3 ±9.0 77.7 ±9.2 78.4 ±8.9 0.465
FW 80.6 ±11.1 80.4 ±10.8 80.1 ±10.7 (0.05)
COMB 80.4 ±9.1 80.1 ±8.9 80.5 ±9.3
Total 79.7 ±9.5 79.4 ±9.4 79.7 ±9.4
Upper arm
circumference
relaxed (cm)
M 30.5 ±2.7 31.1 ±2.6 31.7 ±2.6 0.044
FW 30.5 ±3.1 31.0 ±2.9 31.1 ±2.9 (0.146)
COMB 30.4 ±2.0 31.4 ±2.2 32.0 ±2.4
Total 30.4 ±2.6 31.2 ±2.5 31.6 ±2.7
Upper arm
circumference
flexed (cm)
M 33.0 ±2.7 33.5 ±3.0 33.9 ±3.0 0.757
FW 33.1 ±2.6 33.6 ±2.8 34.1 ±3.2 (0.022)
COMB 33.1 ±2.8 33.8 ±2.8 34.3 ±3.0
Total 33.0 ±2.7 33.6 ±2.8 34.1 ±3.0
Thigh
circumference (cm)
M 51.6 ±3.7 52.5 ±3.1 53.1 ±2.8 0.386
FW 53.8 ±2.9 54.0 ±2.4 54.2 ±2.2 (0.057)
COMB 52.7 ±1.8 53.4 ±1.6 54.0 ±1.8
Total 52.7 ±2.9 53.3 ±2.4 53.8 ±2.3
Chest
circumference (cm)
M 93.1 ±7.8 93.8 ±7.0 94.7 ±6.2 0.728
FW 95.5 ±9.2 96.7 ±8.2 97.7 ±7.6 (0.024)
COMB 95.5 ±9.0 97.1 ±7.9 97.9 ±7.3
Total 94.7 ±8.5 95.9 ±7.6 96.7 ±7.0
Waist
circumference (cm)
M 86.1 ±12.0 85.4 ±12.4 85.6 ±11.2 0.657
FW 85.6 ±8.0 84.9 ±7.7 84.8 ±7.8 (0.037)
COMB 83.2 ±8.4 83.0 ±8.5 83.4 ±8.1
Total 85.0 ±9.4 84.4 ±9.5 84.6 ±9.0
ηp2
: partial eta squared effect size; RT, Resistance training; M, RT group using machines (N =12); FW, RT group
using free weights (N =12); COMB, RT group changing from machines to free weights after 5 weeks (N =12).
Regardless of RT group, significant improvements were observed between pre-, mid-,
and post-intervention measurements (univariate p- and
ηp2
values ranging from <0.001 to 0.003
and 0.209 to 0.568, respectively). Pairwise comparisons demonstrated a significant increase from pre-
to mid-intervention for the upper arm relaxed (p<0.001), upper arm flexed (p<0.001) and chest
circumference (p=0.001), while a similar positive trend was found for thigh circumference (p=0.060).
In addition, a significant increase was also observed from mid- to post-intervention for the upper arm
relaxed (p<0.001), upper arm flexed (p=0.002), thigh (p=0.002), and chest (p=0.004) circumference.
Accordingly, a significant increase from pre- to post-intervention was found for the upper arm relaxed
(p<0.001), upper arm flexed (p<0.001), thigh (p=0.008), and chest (p<0.001) circumference. As an
illustration, Figure 1a shows the evolution of chest circumference.
Int. J. Environ. Res. Public Health 2020,17, 7848 7 of 13
Figure 1.
Evolution over the three test occasions of the three RT groups for (
a
) chest circumference,
(
b
) 1-RM on chest press, (
c
) 1-RM on dumbbell bench press, (
d
) FMS total score. M, RT group using
machines (N =12); FW, RT group using free weights (N =12); COMB, RT group changing from
machines to free weights after 5 weeks (N =12); FMS, Functional Movement Screen
TM
; *: significant
time effect at p<0.001.
For waist circumference, no significant RT group by time interaction effect was observed
(
F(4,64) =0.610
,p=0.657,
ηp2
=0.037). In addition, there were no significant main effects of RT
group (
F(2,33) =0.227
,p=0.798,
ηp2
=0.014) nor time (F(2,32) =1.949, p=0.159,
ηp2
=0.109) at the
univariate level for this outcome measure.
3.2. Strength
All strength outcomes are reported in Table 4according to the type of exercise used for
the assessment.
3.2.1. 1-RM Estimations on Machines
No significant RT group by time interaction effect (F(20,48) =0.790, p=0.711), nor a significant
main effect of RT group (F(10,58) =0.579, p=0.824) was found executing the repeated measures
MANOVA for machine exercises. However, a significant multivariate main effect of time was observed
(F(10,24) =11.659, p<0.001). Regardless of RT group, significant improvements were shown between
pre-, mid-, and post-intervention measurements for all machine exercises (univariate p-values all
<0.001 and
ηp2
values ranging from 0.517 to 0.692). Pairwise comparisons demonstrated statistically
significant increases in performance from pre- to mid-intervention, mid- to post-intervention, and pre-
to post-intervention (all p-values <0.001). As an illustration, Figure 1b shows the evolution of 1-RM on
chest press.
Int. J. Environ. Res. Public Health 2020,17, 7848 8 of 13
Table 4. Strength and functional ability assessments (means ±SD) according to RT group and time
Strength Outcomes RT Group Pre-Intervention
(0 Weeks)
Mid-Intervention
(5 Weeks)
Post-Intervention
(10 Weeks)
Univariate p-Value and (ηp2)
of the Interaction Effect
Leg press (kg) aM 117.8 ±47.6 132.3 ±46.2 153.2 ±48.3 0.756
FW 128.6 ±56.8 150.1 ±61.3 167.5 ±67.5 (0.021)
COMB 124.8 ±32.2 150.2 ±36.3 166.5 ±44.9
Total 123.7 ±45.6 144.2 ±48.3 162.4 ±54.6
Squat (kg) bM 50.9 ±20.6 61.0 ±20.7 76.0 ±18.6 0.481
FW 53.8 ±23.2 65.9 ±24.8 74.8 ±25.7 (0.047)
COMB 50.6 ±9.6 59.9 ±9.6 70.1 ±14.1
Total 51.7 ±18.3 62.3 ±19.1 73.6 ±19.6
Chest press (kg) aM 50.0 ±15.5 61.8 ±17.0 71.1 ±16.2 0.657
FW 55.6 ±15.1 64.5 ±13.5 72.8 ±15.1 (0.033)
COMB 53.9 ±13.5 67.8 ±13.7 76.2 ±16.3
Total 53.2 ±14.5 64.7 ±14.6 73.4 ±15.6
Dumbbell bench press
(kg) bM 17.4 ±5.9 20.2 ±6.1 23.3 ±6.4 0.974
FW 18.0 ±5.1 21.4 ±5.9 24.2 ±5.5 (0.005)
COMB 19.0 ±3.8 21.8 ±4.1 24.8 ±4.8
Total 18.1 ±4.9 21.1 ±5.3 24.1 ±5.5
Hip extension (kg) aM 46.6 ±13.7 55.6 ±13.6 65.6 ±16.5 0.724
FW 55.7 ±18.1 66.9 ±17.9 73.0 ±14.7 (0.025)
COMB 48.9 ±18.0 62.7 ±19.8 70.5 ±21.3
Total 50.4 ±16.7 61.7 ±18.5 60.0 ±18.8
Deadlift (kg) bM 44.9 ±17.4 51.4 ±18.8 59.9 ±18.8 0.446
FW 50.6 ±23.6 62.4 ±28.4 73.3 ±28.3 (0.051)
COMB 45.3 ±15.1 51.4 ±16.3 63.2 ±22.8
Total 46.9 ±28.3 55.0 ±21.7 65.5 ±23.7
Seated row (kg) aM 53.6 ±15.3 61.7 ±14.2 71.6 ±17.8 0.753
FW 62.5 ±14.0 71.1 ±12.0 77.3 ±14.5 (0.021)
COMB 59.2 ±19.5 68.1 ±14.3 73.1 ±14.9
Total 58.4 ±16.4 67.0 ±13.8 74.0 ±15.6
Dumbbell bent over
row (kg) b
M 16.7 ±5.4 19.2 ±4.7 21.2 ±5.8 0.935
FW 18.6 ±5.4 21.7 ±5.6 23.0 ±5.5 (0.008)
COMB 16.1 ±3.6 19.1 ±4.7 21.2 ±4.8
Total 17.1 ±4.8 20.0 ±5.0 21.8 ±5.3
Shoulder press (kg) aM 35.3 ±13.4 40.2 ±12.7 47.6 ±15.2 0.662
FW 36.5 ±8.8 42.9 ±11.6 50.3 ±13.4 (0.029)
COMB 43.0 ±17.0 52.0 ±20.3 56.3 ±20.9
Total 38.3 ±12.6 45.1 ±15.8 51.4 ±16.7
Standing dumbbell
shoulder press (kg) b
M 11.7 ±2.8 14.1 ±2.9 15.8 ±3.1 0.832
FW 12.1 ±3.3 14.5 ±3.0 16.1 ±3.1 (0.015)
COMB 12.0 ±3.2 13.8 ±3.6 15.5 ±3.8
Total 11.9 ±3.0 14.1 ±3.1 15.8 ±3.3
Standing broad jump
(cm)
M 179.7 ±28.2 184.0 ±28.6 185.5 ±28.2 0.108
FW 184.4 ±29.9 193.1 ±32.3 198.2 ±31.8 (0.115)
COMB 200.7 ±22.5 213.7 ±17.9 217.1 ±20.9
Total 188.2 ±27.8 196.9 ±29.1 200.3 ±29.6
FMS total score
M 14.9 ±1.4 15.9 ±1.3 17.5 ±1.4 0.578
FW 14.8 ±3.1 15.9 ±2.3 17.5 ±1.8 (0.041)
COMB 14.3 ±1.1 15.7 ±1.6 16.3 ±2.0
Total 14.6 ±2.0 15.9 ±1.7 17.1 ±1.8
a
, Machine exercise;
b
, Free weight exercise;
ηp2
: partial eta squared effect size; RT, Resistance training; M, RT group
using machines (N =12); FW, RT group using free weights (N =12); COMB, RT group changing from machines to
free weights after 5 weeks (N =12); FMS, Functional Movement Screen TM.
3.2.2. 1-RM Estimations on Free Weights
No significant RT group by time interaction effect (F(20,48) =1.098, p=0.382), nor a significant
main effect of RT group (F(10,58) =0.597, p=0.810) was found executing the repeated measures
MANOVA for free weight exercises. However, a significant multivariate main effect of time was
observed (
F(10,24) =12.982
,p<0.001). Regardless of RT group, significant improvements were shown
between pre-, mid-, and post-intervention measurements for all free weight exercises (univariate
p-values all <0.001 and
ηp2
values ranging from 0.511 to 0.733). Pairwise comparisons demonstrated
statistically significant increases in performance from pre- to mid-intervention (all p-values <0.001),
mid- to post-intervention (p-values ranging from p=0.007 to p<0.001) and pre- to post-intervention
(all
p-values <0.001
). As an illustration, Figure 1c shows the evolution of 1-RM on dumbbell bench press.
Int. J. Environ. Res. Public Health 2020,17, 7848 9 of 13
3.2.3. Standing Broad Jump
No significant RT group by time interaction effect (F(2.9,47.9) =2.149, p=0.108,
ηp2
=0.115).
However, a significant univariate main effect of group (F(2,33) =3.357, p=0.047,
ηp2
=0.169) was
observed with higher values found in the FW group as compared to the COMB group (p-values of
0.005 and 0.006). Also a significant main effect of time was observed (F(1.5,47.9) =28.098,
p<0.001
,
ηp2
=0.460), with significant improvements from pre- to mid-intervention (p<0.001), mid- to
post-intervention (p=0.009) and pre- to post-intervention (p<0.001).
3.3. Functional Ability
Total FMS scores at pre-, mid-, and post-intervention are also presented in Table 4and in
Figure 1d. No significant RT group by time interaction effect (F(4,64) =0.824, p=0.514,
ηp2
=0.049),
nor a significant main effect of RT group (F(2,33) =0.599, p=0.555,
ηp2
=0.035) was found at the
univariate level. However, a significant univariate main effect of time was observed (F(2,32) =25.578,
p<0.001
,
ηp2
=0.615). Regardless of RT group, significant improvements in total FMS score were
shown between pre-, mid-, and post-intervention measurements. Pairwise comparisons demonstrated
statistically significant increases in total FMS score from pre- to mid-intervention (p<0.001), mid- to
post-intervention (p=0.001) and pre- to post-intervention (p=0.001).
4. Discussion
The main finding from this randomized parallel trial is that male adults being novice in RT showed
significant increases in anthropometric estimations of muscle size, strength, and functional ability,
regardless of using machines (M) versus free weights (FW) or the combination thereof. Secondly,
an equally positive transfer in strength gains was observed between training with M and with FW
in both directions (i.e., from training with M to testing with FW as well as from training with FW
to testing with M). Our findings do not support the hypothesis that RT with FW would elicit better
training effects in terms of muscularity, strength, and functional ability, nor did it result in a better
learning transfer in performance on machines as compared to the opposite direction.
In the present study, significant increases in upper arm, thigh, and chest circumferences were
found for all RT groups when comparing pre-, mid-, and post-intervention outcomes over the 10-week
RT program applied. This positive change over time in these anthropometric estimations of muscle size
is an expected result as a 10-week RT program should be sufficiently long to induce hypertrophic effects
in the untrained [
19
,
29
–
31
]. Seynnes et al. (2006) observed that changes in muscle size were already
detectable after three weeks of RT in recreationally active young healthy males [
19
]. Interestingly,
in the study of Moro et al. (2020) hypertrophic effects were only observed in recreationally active men
who engaged in 8 weeks of high intensity interval RT but not in their peers performing traditional
RT [
31
]. Muscular adaptation and the role of fitness level, training volume, intensity, and periodization
are indeed topics that can further be explored [32].
For the novice individual, it is known that strength gains experienced over the first 5–8 weeks
of RT are primarily neurological in nature, while gains experienced over the following weeks and
years result from muscular hypertrophy [
33
]. In the present study, participants already demonstrated
significant increases over the first five weeks in upper arm and chest circumferences as well as a similar
trend towards a larger thigh circumference. Since waist circumference did not significantly change
during the 10-week RT program, it can be cautiously assumed that the observed significant changes
in limb and chest circumferences may be mainly attributed to an increase in muscle size instead of
adipose tissue [24].
It was hypothesized that the muscular strength in RT group of participants using FW only would
improve significantly more than in their counterparts using M only during the 10-week RT program
since more muscle fibers and synergistic muscles are activated to maintain postural balance and
stabilization during the FW exercises [
7
–
9
]. This statement was previously confirmed by the study of
Int. J. Environ. Res. Public Health 2020,17, 7848 10 of 13
Schott et al. (2019) conducted in older adults (>60 years old, mixed gender) based on more pronounced
relative strength increases in some muscle groups, but not all, after 26 weeks from baseline when using
FW for RT (i.e., 50% in leg press versus up to 120% in squat) versus when using M [
10
]. However,
people at a more advanced age may initially feel uncertain when performing unfamiliar exercises that
challenge their postural stability, possibly resulting in an underestimation of strength at baseline when
being tested with FW. The results of the present study, however, demonstrate that RT novice adult
males can achieve equal strength gains using either FW, M, or a combination of both (starting with
M). In other words, the strength gains in all of our participants were found to be similar irrespective
of the RT equipment being used during the 10-week program. Regardless of RT group, participants’
mean estimated 1-RM improved with 27% up to 43% from pre- to post-intervention depending on the
targeted muscle groups. Similar gains in strength performance were observed by Rossi et al. (2018),
who compared three groups (i.e., leg press-only group, squat only group, combined squat and leg press
group) and found that squat training was significantly better in comparison to both other training
groups [
11
]. However, an important difference compared to the present study to consider is that in
the study of Rossi et al. (2018) only the leg press and/or squat were trained, targeting the knee and
hip extensors as primary movers, and that a different training volume was administered (6 sets of
squat or leg press vs. 3 sets of each exercise in the present study). Apart from all specific M and/or FW
exercises, this finding of equal (functional) strength gains in each group was also confirmed for the SBJ
as a neutral test. Also, Schwartz et al. (2019) observed that vertical jump height improved equally in
young recreationally active women after 6 weeks of free weight squat versus machine squat training,
as was also the case for agility and 30 m sprint performance [
12
]. However, women who trained with
the machine squat did produce a higher peak power output during vertical jumping as compared to
their counterparts who trained with free weights [
12
]. Thus, Schwartz et al. (2019) concluded that
machine training can elicit equal or even superior training effects. Our study involving a 10 week RT
program in male novices confirms that strength can equally increase regardless of the training mode.
The lack of significant interaction effects for the 1-RM estimations in the present study shows
that there is an equal strength transfer from one RT mode to the other. This means that changing
equipment is not necessarily accompanied with a delayed progression in muscularity, strength or
functional ability, at least not in novice male RT practitioners. This rather surprising finding does
not support the earlier mentioned concept of training specificity, but demonstrates that there was a
positive transfer of strength both from M to FW and from FW to M in the present study. Despite the
advantages of FW in terms of intermuscular coordination and activation of synergistic muscles [7–9],
no difference in learning transfer was found. This unexpected finding might be due to the testing load
of 10-12-RM (corresponding with ~75% of 1-RM) that could have limited the stability role of synergistic
muscles, as was also suggested by Schick et al. (2010) and McCaw and Friday (1994) [
8
,
34
]. Schick et al.
observed a higher recruitment of the stabilizing rear and medial deltoid muscles during free weight
bench press as compared to the stable Smith machine alternative, but only when performed at 60%
of 1-RM and not at 90% of 1-RM. They assumed that while using lighter loads, the lower activity of
the agonist muscles decreases joint stiffness and in turn increases the stabilizing role of synergistic
muscles [
8
]. Thus, other findings may be observed when applying a lower training or testing intensity
or when training effects are evaluated after a longer training period [
28
]. Future studies should thus
provide more insight in this respect.
It is also known that RT enhances one’s body coordination [
2
], which should lead to an improved
functional ability. Our hypothesis that FW exercises would result in a better coordination for real life
movements and thus being more functional than a M only RT program was not confirmed as shown by
equal improvements in total FMS score over time in all three RT groups. The study of Rossi et al. (2018)
showed similar results, using the Star Excursion Balance Test to assess balance in participants training
with M only, FW only, or both [
11
]. Balance improved equally in all three groups over the course of
that 10-week study [
11
]. Despite the difference in assessment tools being used, it seems that M and FW,
or a combination of both (with M preceding FW in our study) can elicit an improved functional ability
Int. J. Environ. Res. Public Health 2020,17, 7848 11 of 13
and a better quality of movement patterns. An increase in strength may be a factor that resulted in a
better overall score on the FMS in each group, as some components in this test battery rely on muscle
strength, such as the deep squat and the trunk stability push-up. Another part of the explanation may
be the occurrence of a learning effect, regardless of the RT program.
There are several aspects of the present study that should be taken into account when interpreting
its findings. First, our study deliberately included only men who were novice in RT and recruited by
means of convenience sampling. Therefore, caution is warranted when generalizing and extrapolating
the presented study findings, more specifically with regard to women and individuals who are already
more familiar with RT. Secondly, we used body segment circumferences as a field-based method
to estimate the evolution in muscularity. Besides its clear advantages—such as being low in cost,
very easy to apply, and non-invasive—one disadvantage of using these anthropometric estimations to
assess changes in muscle size is that they do not correct for changes in fat mass. Therefore, our study
participants’ waist circumference was also considered to control for any changes in overall fat mass,
and thus body fat percentage, since men tend to store their excess fat primarily in the abdominal
region [
24
]. Another disadvantage of using segmental anthropometrics is the lower sensitivity and
possible disturbing effects of hydration as compared to total and/or segmental body composition
assessments using laboratory techniques such as dual energy X-ray absorptiometry [
35
]. Therefore,
possible subtle inter-group differences in body composition may not have been detected. Finally,
the present study design did not allow to control for possible learning effects on the strength tests nor
the FMS. It can be assumed that these would have been equal for each RT group, possibly contributing
to the equal learning transfer and progressions in strength observed in this study.
Nevertheless, some specific strengths of the present study can be highlighted as well. First,
this study, including three test occasions, used a sufficiently high predefined power which lowers the
chance on the probability of false negative results. Secondly, participants were randomly assigned to
one of the three different RT groups. The present study also applied international recommendations for
RT in novices, such as using a whole-body workout instead of focusing on a single muscle or muscle
group and also in terms of training load as well as concerning the timing and magnitude of increasing
intensity. Furthermore, we used a realistic and feasible setting with exercises that are relatively easy to
acquire for novices. Finally, this study applied a holistic approach including anthropometrics, strength,
as well as functional ability outcomes to evaluate RT effects, whilst its particular design allowed to
investigate the learning transfer between RT modes offering new insights for novices in RT.
5. Conclusions
To conclude, adult male novices in RT can expect substantial positive training effects in 10-weeks’
time regardless of using M or FW exercises, without experiencing a fallback when changing from
M to FW exercises. It should be noted, however, that the observed improvements in muscularity,
strength and functional ability as well as the bi-directional transfer of strength between RT modes
might be due to the novice status of the participants engaging in 10 weeks of exercising. Therefore, it is
imperative for future experimental research to include different target populations in terms of gender,
age and RT experience in order to confirm or refute the present findings of similar gains regardless of
RT mode.
Supplementary Materials:
The following are available online at http://www.mdpi.com/1660-4601/17/21/7848/s1,
Video S1: video_exercises_SBJ.
Author Contributions:
Conceptualization, D.A; Methodology, D.A; Formal analysis, D.A and E.D.; Investigation,
D.A and E.D.; Resources, D.A and E.D.; Data curation, D.A and E.D.; Writing—original draft preparation, D.A
and E.D.; Writing—review and editing, D.A and E.D.; Visualization, D.A and E.D.; Supervision, D.A and E.D.;
Project administration, D.A. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Int. J. Environ. Res. Public Health 2020,17, 7848 12 of 13
Acknowledgments:
The authors would like to thank all participants for their commitment as well as Elke
De Maeght, Tomas Van Eecke, and Jens De Backer for their assistance during participant recruitment and
data collection.
Conflicts of Interest: The authors declare no conflict of interest.
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