A Benefit of Being Heavier Is Being Strong: a Cross-Sectional Study in Young Adults
Hoor et al. Sports Medicine - Open
A Benefit of Being Heavier Is Being Strong: a Cross-Sectional Study in Young Adults
Gill A. ten Hoor 0 1
Guy Plasqui 1
Annemie M. W. J. Schols 3
Gerjo Kok 0
0 Department of Work and Social Psychology, Maastricht University , P.O. Box 616, 6200 MD Maastricht , The Netherlands
1 Department of Human Biology, Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre
2 , P.O. Box 616, 6200 MD Maastricht , The Netherlands
3 Department of Respiratory Medicine, Research School NUTRIM, Maastricht University Medical Centre , P.O. Box 616, 6200 MD Maastricht , The Netherlands
Background: In this study, the main hypothesis is that heavier people enjoy strength exercises more than normalweight people, mediated by fat-free mass and muscle strength. Further, it is hypothesized that heavier people are better in strength exercises and enjoy strength exercises more compared to aerobic exercises. Methods: In a cross-sectional study, height, weight, body composition (i.e., fat mass and fat-free mass by underwater weighing), muscle strength (i.e., one-repetition maximal strength for the leg press and chest press), maximal aerobic exertion (VO2max) during cycle ergometry, and psychological determinants (i.e., attitudes, intentions, and self-determined motivations for strength exercises and aerobic exercises using questionnaires) were measured in 68 participants (18-30 years). Results: Significant correlations between weight/BMI and fat-free mass (index) (r values = .70-.80, p values < .001), fat-free mass and muscle strength (r values = .35-.55, p values < .05), and muscle strength and attitudes, intentions, and motivation for strength exercises were found (r values = .29-.43, p values < .05); BMI was related to psychological determinants via fatfree mass and muscle strength. Furthermore, participants with a higher BMI are significantly better in strength exercises, more intrinsically motivated, and less motivated to do strength exercises compared to aerobic exercises (all p values < .05). Trends in the same direction were found for the following variables: instrumental attitude, experiential attitude, and intention (p values < .1). Conclusions: Strength exercises could be more appropriate for heavier people and might therefore be a valuable component in physical activity programs for people who are overweight or obese.
Overweight; Body composition; Strength; Motivation; Attitude
Heavier people not only have more fat mass but also
more fat-free mass, likely making them stronger (in
absolute sense) compared to normal-weight people.
Heavier people are more positive about strength
exercises compared to (
) normal-weight people and
) aerobic exercises.
Performing strength exercises has beneficial effects
on body composition and, with that, on metabolic
and cardiovascular health.
Obesity is a worldwide problem with high costs to society
and well-being [1, 2]. Being physically active can prevent
and decrease obesity  but is often challenging for
people who are overweight or obese [4–6]. In this study,
we try to bridge the gap between biological and
psychological insights in the management of obesity, by
examining the putative physiological and psychological benefits
of strength exercises for heavier people [4–6]. People who
are overweight do not only have more fat mass but also
more fat-free mass . With that, people who are
overweight or obese are likely to have more muscle mass and
to be stronger compared to people who are not
overweight. Compared to aerobic exercises, strength exercises
are easier for people who are overweight, and therefore,
compliance to an exercise program focused on strength
exercises is greater . By being better in strength
exercises than aerobic exercises, people who are
overweight might be more positive about strength exercises
compared to normal-weight people, and with that,
longterm behavior change may be achieved [4–6]. Additionally,
performing strength exercises has beneficial effects on
overweight or obese people’s body composition and, with
that, on their metabolic and cardiovascular health . In
this study, we cross-sectionally test the “chain of
assumptions” that (
) heavier people have more fat mass and
more fat-free mass, (
) they are stronger and better in
strength exercises, and (
) they have more positive
associations with strength exercises. This chain resulted in two
hypotheses. The main hypothesis is that (
) heavier people
are more positive about strength exercises compared to
normal-weight people, because they have more fat-free
mass and a higher muscle strength. Further, it is
hypothesized that (
) people who are heavier are not only better in
strength exercises but also more positive about strength
exercises compared to aerobic exercises.
Following pleas for full disclosure [9, 10], all research
materials and data are combined in Additional files 1, 2,
3 and 4. This study was approved by the Ethics
Committee of the Maastricht University Medical Center+
(NL43929.068.13/METC 13-3-018) and conforms with
the Code of Ethics of the World Medical Association
(Declaration of Helsinki).
A total of 70 participants (18–30 years of age) were
recruited among students of Maastricht University. Two
participants did not return on day 2 of the study and were
therefore excluded from the analyses. To get a better
range in body mass index (BMI) and body composition,
we advertised the study using flyers, including a statement
that we were especially interested in students with a
BMI > 24. All participants were screened for good health
using a general medical questionnaire (see Additional files
1 and 3) to ensure that participants were able to perform
exercises. Participants were excluded when they had any
condition that prevented them from performing the
exercise protocols (e.g., sports injuries or severe asthma). Prior
to participation, written informed consent was obtained.
Procedure and Measures
Participants were invited to participate in a 2-day
crosssectional study. Participants that expressed their interest
(by responding to the advertisement) and were found
eligible (based on the medical screening questionnaire;
see Additional files 1 and 3) were invited to visit the
university on 2 days, with an 8–10-day interval.
For day 1 (that always started between 8 and 8.30 am),
the participant was asked to refrain from any high
intensity physical exercise 24 h prior to the testing and
to come to the laboratory in a fasted state (overnight fast
from 10 pm onwards). In the Metabolic Research Unit
at Maastricht University, Maastricht, The Netherlands,
height and weight of the participant were measured, and
body composition was assessed using underwater weighing
(see section “Body Composition”). Subsequently, participants
were asked to eat a light breakfast (such as one slice of bread
with cheese). One hour after having eaten a light breakfast,
cardiovascular fitness was assessed with a maximal exercise
test (VO2max test; see section “Maximal Aerobic Exertion
Test (VO2max)”) on a bicycle ergometer. Approximately 1 h
after the VO2max testing, the participant performed a
familiarization session with the exercise equipment to
estimate one-repetition maximum (1RM; see also section
“Maximal Strength Exertion Test (1RM Test)”) strength in
the fitness lab at Maastricht University. During the
familiarization session, proper lifting techniques were
demonstrated for leg press and chest press exercises by a
At day 2, 8–10 days after day 1, the actual 1RM testing
took place in the fitness lab at Maastricht University (see
section “Maximal Strength Exertion Test (1RM Test)”).
Subsequently, the participant was asked to perform a
series of standardized strength and aerobic exercise
activities (see “Standardized Exercise Protocols”). Directly
after each exercise activity (both the strength and aerobic
exercise), a questionnaire was filled out to measure social
cognitive determinants (see “Questionnaires”). All data were
collected by the first author and three research assistants
(always under close supervision of the first author; see
“Acknowledgements”). For the biological measurements,
validated and reliable protocols were used (see sections
“Body Composition” and “Maximal Strength Exertion Test
(1RM Test)”). The exercise protocol (section “Standardized
Exercise Protocols”) was always performed under
supervision of two researchers to ensure proper execution. The
psychological questionnaires were based on validated
constructs (see section “Questionnaires”).
After completion of both days, participants received a
gift voucher and travel expenses. Participants from the
Faculty of Psychology and Neuroscience at Maastricht
University were able to choose between the gift
vouchers, or participation credits (part of the psychology
bachelor curriculum) (see also Fig. 1 and Additional file
4 for a clear overview of the study protocol).
Anthropometric measurements, body mass, and height
were taken in the morning after an overnight fast on
day 1 of testing. Body mass was measured on an
electronic scale to the nearest 0.01 kg. Height was measured
to the nearest 0.1 cm. Body composition was calculated
based on underwater weighing with simultaneous
measurement of residual lung volume using the helium
dilution technique (Volugraph 2000, Mijnhardt). For this
measurement, participants are in a fasted state and are
completely submerged under water, for approximately
90 s to measure their weight under water, while breathing
oxygen through a mouthpiece. The measurement was
repeated three times. Body volume was calculated using the
following formula: ((body massdry − body massunder water) /
water density) − lung volume. Body density was derived
from body weight and body volume, which was used to
calculate fat mass and fat-free mass by the Siri equation .
Maximal Aerobic Exertion Test (VO2max)
Cardiovascular fitness was assessed with an incremental
test on a bicycle ergometer using the protocol of Kuipers
et al. . During this test on day 1, oxygen consumption
(VO2) and CO2 production were measured continuously
(Omnical, Maastricht University) and heart rate was
monitored using a polar heart rate monitor (RS400, Polar
Electro, Kempele, Finland; watch worn by the instructor).
After a warming up of 5 min at 100 watts (W) for men
and 75 W for women, the workload increases with 50 W
every 2.5 min. When one’s heart rate reached a value of
35 beats per minute (bpm) below the age predicted
maximal HR (220 bpm − age) or the respiratory quotient
(RQ = CO2 production / oxygen consumption) exceeded
1, workload was increased with 25 W (instead of 50 W)
every 2.5 min until exhaustion. VO2max was presented
relative to fat-free mass (ml/kg fat-free mass/min).
Maximal Strength Exertion Test (1RM Test)
Approximately 1 h after VO2max testing on day 1,
participants performed a familiarization session with
the exercise equipment to estimate 1RM strength. During
the familiarization session, proper lifting technique was
demonstrated for leg press and chest press exercises.
Guided-motion exercise machines (one for leg press, one
for chest press) were used to establish safe and proper lifting.
Maximum strength was estimated in all participants using
the multiple-repetition testing procedure . In a separate
session (8–10 days later; day 2), the actual 1RM testing took
place. After warming up (5 min on light load on cycle
ergometer), two sets of 12 repetitions were performed on
the exercise machines at a light load (15 and 25 kg on the
chest press and 70 and 80 kg on the leg press, for female
and male participants, respectively). Next, the load was set
at 95% of the estimated 1RM and one repetition was
performed. Thereafter, the load was increased by 2.5–5.0%
after each successful lift until the participant was able to
perform a maximum of one repetition .
Standardized Exercise Protocols
On day 2, standardized exercise protocols were carried
out before each questionnaire (i.e., a strength exercise
protocol before the strength exercise questions, and an
aerobic exercise protocol before the questions about
aerobic activities). The goal of the protocols was to let
participants experience strength and aerobic exercises to
improve the validity of the questionnaires that were
filled out immediately afterwards (to measure the
socalled “experiential” attitudes and motivations). In both
the aerobic and strength exercise protocols, two different
exercises were included to ensure that people did not
answer questions about “cycling” but about “aerobic
exercises.” The duration of the strength and aerobic
fitness protocol was similar (~ 20 min), and the order of
the protocols was randomized to control for a possible
order effect. For both protocols, we chose to work on
70% of their maximum. A higher percentage unnecessarily
increased the chances of injury/anaerobic training, while a
lower percentage would be too low (i.e., warming up or
too low exertion). The strength protocol was based on the
two different 1RM tests (for leg press and chest press).
The 70% of maximal strength on the leg press exercise
and chest press exercise was calculated. After a 5-min
warmup (75 W; bicycle ergo meter—to minimize the
chance for injuries), participants were asked to do three
sets of 8–10 repetitions on the chest press apparatus and
three sets of 8–10 repetitions on the leg press apparatus.
Between each set, there was a 2-min break. Between the
leg press and the chest press, there was a 5-min transition
time break. Also, the order of the chest press and leg press
was randomized to control for a possible order effect.
The aerobic exercise protocol (conducted on day 2)
was based on maximal heart rate and maximal workload
measured during the VO2max test conducted on day 1,
and included both cycling and running. After a 5-min
warmup (75 W, bicycle ergo meter), participants were
asked to cycle for 10 min on 70% of their Wmax
(70 RPM; the same as during the VO2max test) and to
run 3 × 3 min at 70% of their maximal heart rate on a
treadmill (no inclinations, and the speed was continuously
adjusted by the instructor to keep the participant at 70%
of their maximal heart rate). The running was introduced
to also have two different aerobic exercises. Between the
three sets of running, participants walked for 1 min.
Between the cycling and running, there was a 5-min
transition time break. The order of the cycling and
running was counterbalanced as well.
Participants completed a questionnaire, based on the
reasoned action approach  and the self-determination
theory . This questionnaire included specific and
general questions about resistance and aerobic exercises
and was divided accordingly into two sections for
completion (i.e., resistance exercise questions were answered
following completion of the strength exercise protocol,
and the aerobic exercise questions were answered
following completion of the aerobic exercise protocol; see
also Fig. 1). Filling out the questionnaires took about 3–
5 min per stage. The measured constructs are as follows:
) instrumental attitudes (cognitive feelings about
) experiential attitudes (affective feelings about
the exercises), (
) intentions (whether the participant
intends to do the specific exercise in the near future), (
intrinsic motivation (how fun the exercise is), and (
amotivation (no motivation to do the specific exercise at
all). All items were rated on a 7-point Likert scale. Scores
on items that measured the same construct were averaged
into one scale where internal consistency was sufficient
(α > .60). One item was deleted (“After doing this exercise,
I’m satisfied no matter what my performance is”) for both
aerobic and strength exercises, as reliability analysis
showed low-scale reliability when this item was added to
the intrinsic motivation construct. Scores were recoded
such that a higher score reflected a higher value on the
variable (see also Table 1 for all exact items, scoring, and
IBM SPSS statistics and Excel were used to analyze the
data (see also Additional file 2). Frequencies (n), means
(M), and standard deviations (SD) were calculated to
provide an overall picture of the sample. Paired sample
t-tests were conducted to calculate differences between
male and female participants. Pearson’s correlations were
calculated to examine associations between the various
determinants. We tested the direct and indirect
associations linking BMI scores with psychological constructs
regarding strength exercises using the PROCESS
software including the bootstrapping method with
biascorrected confidence estimates (see also Fig. 3) [17, 18].
Bootstrapping, a non-parametric sampling procedure, was
used to assess the significance of indirect effects. In the
present study, the 95% confidence interval of the indirect
effects was obtained with 5000 bootstrap resamples; results
are statistically significant when 95% confidence intervals
did not include zero. To compare correlations of BMI with
strength and BMI with aerobic outcomes, first, the
difference in Fisher’s z was calculated. Based on the z score of
this difference, p values were estimated .
A total of 68 participants participated in this study (BMI
ranged from 18 to 38). Male (n = 33) and female (n = 35)
participants did not differ in age, BMI, VO2max, or
selfreported physical activity (all p values > .05), but male
participants were taller, heavier, and stronger. Female
participants had a higher fat mass compared to male
participants (see Table 2). Self-reported activity levels
ranged from very high (14 h/week) to not active at all
(mean [SD], 4 h/week [3 h]; median 3.5 h; not reported
in the table).
Being Heavier Means More Fat-Free Mass, Means Stron
ger, and Means More Positive Results on Psychological
Correlational analyses revealed significant correlations
between weight and fat mass (r = .85 for female and r = .78
for male participants, all p < .001), and BMI (weight
adjusted for height), and fat mass index (fat mass adjusted
for height; r = .86 for female and r = .82 for male
participants, all p < .001; see Fig. 2a). Weight and BMI were also
highly correlated with the fat-free mass and fat-free mass
indices, respectively (r values ranging from .70 to .80, all
p < .001; see Fig. 2b). Participants with a higher fat-free
mass had a significantly higher chest press 1RM (r = .55
for female and r = .48 for male participants, all p < .005)
and leg press 1RM (r = .55 for female, p = .001, and r = .35
for male participants, p = .046; see Fig. 2c). Finally, a
combined strength score (sum of leg press 1RM and chest
press 1RM) was positively correlated with instrumental
attitude (r = .29, p = .02), experiential attitude (r = .31,
The shown answers for the questions in this table are for the strength questions. The same questions were asked for aerobic exercises (i.e., the word “strength”
was replaced by the word “aerobic”)
p = .008), one’s intention to start with strength
exercises (r = .35, p = .02), and intrinsic motivation (r = .33,
p = .007). An expected negative correlation was found
with a-motivation (r = − .43, p < .001; see Table 3).
There was no direct effect of BMI on attitudes,
intention, or motivations (p values range from .44 to .95;
see Fig. 3 and Table 4). Indirect effects of BMI on all
psychological outcomes were found via fat-free mass and
the combined strength score. No indirect effect from
BMI to psychological outcomes was found via strength
only. BMI had an indirect effect on experiential attitude
(β = − .08, SE = .05, CI SE = − .18 to − .01) and
amotivation (β = .09, SE = .04, CI SE = .01–.19) via fat-free
mass (see Fig. 3 and Table 4).
Strength Versus Aerobic Exercises
To examine whether heavier people are relatively better in
strength exercises than aerobic exercises compared to
normal-weight people, correlations between BMI and
strength outcomes and BMI and aerobic outcomes were
calculated. Based on these correlations, a difference in
Fisher’s z was calculated and p values were estimated .
Comparing aerobic and strength variables shows that
when participants have a higher BMI, they are significantly
better in strength exercises compared to aerobic exercises
(Fisher’s z = .91, p < .001), more intrinsically motivated
(Fisher’s z = .46, p < .008), and less a-motivated
(Fisher’s z = .40, p < .02) for strength exercises
compared to aerobic exercises. For the variables
instrumental attitude, experiential attitude, and intention, the
directions of the relations were the same, but these
variables were not significant (p values ranged from .06 to
.08) (see Table 5).
) confirmed that heavier people have a higher
fatfree mass compared to normal-weight people. This is in
line with biological insights . Additionally, (
) we have
shown that people with a higher fat-free mass are stronger
(in absolute sense) and are better in strength exercises than
in aerobic exercises. We have also confirmed that (
mastery experiences (in this case, resulting from successfully
engaging in strength exercises as opposed to aerobic
exercises) are related to more positive psychological
outcomes. This observation is in line with psychological
insights [20–23]. As hypothesized, we (
) have shown that
heavier people are more positive about strength exercises
compared to normal-weight people, via fat-free mass and
muscle strength. Moreover, (
) heavier people are better in
strength exercises and are more positive about strength
exercises compared to aerobic exercises.
Table 2 Study sample characteristics
N = 68
− 1.03 to 2.04
− 14.66 to − 8.75
− 19.13 to − 8.95
− 3.05 to − 0.01
− 21.57 to 15.47
− 4.80 to 1.94
− 1.09 to 1.77
− 89.85 to − 55.78
− 57.39 to − 40.42
− 0.09 to 0.41
− 0.53 to 0.48
− 0.45 to 0.82
− 0.56 to 0.60
− 0.28 to 0.74
− 0.73 to 0.16
− 1.04 to 0.22
− 1.75 to − 0.04
− 1.51 to 0.21
0.05 to 1.26
Instrumental attitude (
Experiential attitude (
Intrinsic motivation (
To the best of our knowledge, this is the first time that
this chain of relationships has been demonstrated
empirically, thereby bridging the gap between biological and
psychological insights. In light of these results, new exercise
interventions for people with overweight or obesity could
be developed, concentrating on biological strengths and
using psychological principles and techniques to make
them more aware of their strengths . Additionally, for
long-term behavior and health changes, new interventions
might benefit from focusing (and giving feedback; ) on
body composition instead of weight.
There are some limitations that should nuance the
drawn conclusions. Most of the study participants are
university students who volunteered to participate which
might limit the generalizability of our study results. The
self-reported physical activity level was higher than
45year-old parents (2.8 h/week) but lower than 13-year-old
children (5.3 h/week) . The sample size is relatively
small, but the used measures were accurate. The BMI
range was limited, making more research necessary
among a broader BMI range. Cross-sectional data
instead of longitudinal data was gathered. With that, we
were not able to show causality. Two additional questions
might be (
) whether the exercise protocols adequately
encompass what strength and aerobic exercises are and
) whether the (possibly different) training loads of the
two different exercises might have influenced the results.
To ensure that we actually worked with strength and
aerobic exercises, we used exercises that are generally
used in our gold standard maximal strength tests and
aerobic tests (the additional running is also used very
often in VO2max tests; see, e.g., . For the protocols,
we limited this to 70% of the maximum and ensured
that the duration (including rest periods) was similar for
both exercises. In future research, it might be helpful to
add an effort perception scale to measure the perceived
intensity of the protocols. For our (correlational)
research question, it is unlikely that difference in training
protocols influences the direction of our outcomes or
conclusions (they could only have weakened the effects at
most in the hypothetical case that there would have been
an “ideal” training intensity). However, most of our results
were significant and in the right direction.
The definition of being “heavier” is based on either a
high weight or BMI, suggesting that someone is less
healthy compared to someone with a normal weight or
BMI. However, an increased weight or BMI is not a very
reliable tool to evaluate body composition and, with that,
individual (metabolic) health . Therefore, to examine
the statement “heavier means more fat-free mass,” we
reported not only correlations of fat-free mass with
weight, and fat-free mass index with BMI, but also
correlations of fat mass with weight and fat mass index
In conclusion, a benefit of being overweight is being
strong. Strength exercise interventions might have the
ability to make people who are overweight more
motivated to be physically active on the long term. They
might improve long-term health by improving one’s
body composition (and energy balance, insulin sensitivity,
blood pressure, cholesterol level, motor skills, and the
chances on cardiovascular disease) [28–31]. In short,
strength exercises might contribute to the management of
obesity. With interventions focusing on strength exercises,
the obesity problem per se will not be solved, but such
programs might positively contribute to obesity-related
Additional file 1: READ ME – medical screening questionnaire for the
study "A benefit of being heavier is being strong: a cross-sectional study in
young adults". (ZIP 32 kb)
The authors thank Margreet Meems, Lena Lütgehetmann, and Gulsen Kadri
for their help during the measurements, and Robert Ruiter and Rik Crutzen
for their critical review of the final manuscript.
This study is funded by the Netherlands Organization for Health Research
and Development (ZonMw; project number 525001004).
Availability of Data and Materials
All research materials and data are combined in a .zip archive labeled
Additional file 1.
GtH, GP, AS, and GK conceived of, designed, and coordinated the study. GtH
and GP performed the analyses. GtH drafted the manuscript. All authors read
and approved the final manuscript.
Ethics Approval and Consent to Participate
This study was approved by the Ethics Committee of the Maastricht
University Medical Center+ (NL43929.068.13/METC 13-3-018) and conforms
with the Code of Ethics of the World Medical Association (Declaration of
Helsinki). Prior to participation, written informed consent was obtained.
Consent for Publication
All authors (Gill A. ten Hoor, Guy Plasqui, Annemie M.W.J. Schols, and Gerjo
Kok) declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
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