RESEARCH ARTICLE
Effects of a period without mandatory
physical training on maximum oxygen uptake
and anthropometric parameters in naval
cadets
A´ lvaro Huerta OjedaID*☯, Guillermo Barahona-FuentesID☯, Sergio Galdames Maliqueo☯
Grupo de Investigacio´n en Salud, Actividad Fı´sica y Deporte ISAFYD, Escuela de Educacio´n Fı´sica,
Universidad de Las Ame´ricas, sede Viña del Mar, Chile
☯ These authors contributed equally to this work.
* achuertao@yahoo.es
Abstract
The effects of a period without physical training on the civilian population are well estab-
lished. However, no studies show the effects of a period without mandatory physical training
on maximum oxygen uptake (VO2 max) and anthropometric parameters in naval cadets.
This study aimed to investigate changes in VO2 max and anthropometric parameters after
12 weeks without mandatory physical training in naval cadets. The sample was 38 healthy
and physically active naval cadets. The measured variables, including VO2 max and anthro-
pometric parameters, were evaluated through the 12-minute race test (12MRT) and the
somatotype. Both variables had a separation of 12 weeks without mandatory physical train-
ing. A t-test for related samples was used to evidence changes between the test and post-
test; effect size was calculated through Cohen’s d-test. Distance in 12MRT and VO2 max
showed significant decreases at the end of 12 weeks without mandatory physical training (p
< 0.001). Likewise, the tricipital skinfold thickness and the endomorphic component showed
significant increases (p < 0.05). 12 weeks without mandatory physical training significantly
reduces the VO2 max in naval cadets. Simultaneously, the same period without physical
training increases both the tricipital skinfold thickness and the endomorphic component in
this population.
Introduction
Increased physical capabilities through strength training [1, 2] and aerobic capacity [3] have
been associated with health, quality of life, and sports performance benefits [1–3]. In this
sense, people included in strength training have shown neuronal and morphological adapta-
tions [4]; these two adaptations, generated by strength training, allow for the improvement of
both the metabolic health [5] and the quality of life of people [6]. At the same time, aerobic
training has reported significant decreases in cardiovascular risk factors [7], as well as an
increase in maximum oxygen uptake (VO2 max) [3]. Specifically, the VO2 max has a direct
PLOS ONE
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
1 / 15
a1111111111
a1111111111
a1111111111
a1111111111
a1111111111
OPEN ACCESS
Citation: Huerta Ojeda A´, Barahona-Fuentes G,
Galdames Maliqueo S (2021) Effects of a period
without mandatory physical training on maximum
oxygen uptake and anthropometric parameters in
naval cadets. PLoS ONE 16(6): e0251516. https://
doi.org/10.1371/journal.pone.0251516
Editor: Randy Wayne Bryner, West Virginia
University, UNITED STATES
Received: October 10, 2020
Accepted: April 27, 2021
Published: June 2, 2021
Copyright: © 2021 Huerta Ojeda et al. This is an
open access article distributed under the terms of
the Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: The data underlying
this study are publicly available at: https://doi.org/
10.6084/m9.figshare.14049590.
Funding: The author(s) received no specific
funding for this work.
Competing interests: The authors have declared
that no competing interests exist.
association with the quality of life of people [8]. These morphological and metabolic changes,
triggered by force training or aerobic training, are experienced by both the civilian population
[9] and the military and naval population [10–12]; in the latter, they provide specific physical
characteristics that allow missions to be carried out efficiently and with a low risk of injury
[13].
Scientific evidence shows that physical training acts as a physiological stressor, increasing
energy expenditure [14], anabolic hormone concentrations [15], arterial diameter, and blood
flow [16]. These responses to physical training contribute to a physiological adaptation of the
body [17], specifical adaptations of muscles [18], and bone tissues [19]. In this sense, a recently
published meta-analysis showed the benefits of eccentric strength training through isoinertial
devices; the study results showed increases in strength, power, and muscle size with this train-
ing [20]. Concerning aerobic training, these stimuli have been considered as the primary
method to improve markers of cardiorespiratory fitness, mainly VO2 max [21]. Additionally,
physical training carried out regularly, and with the principles of intensity, volume, and fre-
quency, will minimize muscular fatigue [22] and favor the physiological adaptations of the
body [17]. Despite the above, there is also a transition phase in sports periodization [23]; this
stage corresponds to the interruption of physical training [24], which can be short term (less
than four weeks) or long term (more than four weeks) [25]. However, if professionals do not
control the transition phase, there is a high probability of provoking a detraining [25]. In this
way, a period without physical training can generate a partial or total loss of morphological
adaptations, physiological adaptations, and physical performance [26], as well as cause alter-
ations in the psychological well-being of the population [27].
The sports transition phase is an opportunity for the physical recovery of athletes [23].
However, there are unplanned situations that generate periods of non-physical training in the
population [28–30], for example, the period of vacation experienced by students each year [28]
or the current period of confinement generated by COVID-19 [30]. Regardless of the reasons,
an extended time-period without physical training has been shown to negatively influence ath-
letes’ body composition [23], increasing fat mass and decreasing lean mass [31–33]. It has also
been shown that a period without physical training of fewer than eight weeks leads to a
decrease in muscle cross-section [34], decreases in maximum strength [35], and a reduction in
VO2 max in both the civilian [36] and naval [37] populations.
Currently, naval personnel has been the subject of several research studies [38, 39]. One of
the reasons for the growing number of investigations in this sample is that the Chilean Navy
comprises more than 25,000 personnel. Of this number, 9.6% (equivalent to 2,400 personnel)
corresponds to naval officers, all trained at the Arturo Prat Naval Academy [40]. These figures
show several aspects, such as the high number of officers [40] and, therefore, the need for this
population to be studied from a psychological [11, 13], health [12] and physical [10, 38] perfor-
mance perspective. This last dimension includes the transition phase considering that we
hypothesize that naval cadets decrease their physical condition, associated with VO2 max and
anthropometric parameters, after a period without mandatory physical training; thus, with
correctly applied training loads, physical fitness loss in this phase could be avoided [23–25].
Despite the existence of studies showing a decrease in the physical condition and anthropo-
metric parameters after a period without physical training in some segments of the population
[23, 31–33], the available evidence in the naval population is scarce and limited [37]. Likewise,
and as far as knowledge goes, no studies evidence the effects of periods without physical train-
ing on VO2 max and anthropometric parameters in naval cadets from 18 to 25 years old. Con-
sequently, this study aimed to evidence the changes in VO2 max and anthropometric
parameters after 12 weeks without mandatory physical training in naval cadets from 18 to 25
years old.
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
2 / 15
Materials and methods
Research design
This study was empirical research with a manipulative, quasi-experimental strategy with a lon-
gitudinal design with repeated means [41]. To highlight the changes in VO2 max and anthro-
pometric parameters, the 12-minute race test (12MRT) and the somatotype were evaluated 12
weeks apart, a period without mandatory physical training (Fig 1).
Procedures
As a first action, all participants who voluntarily accepted to be part of the study (non-probabi-
listic sample) were recruited. The purpose and procedures of the study were indicated in an
informative talk. The inclusion criteria were that all participants should be healthy, physically
active [21] and between 18 and 25 years of age, while the exclusion criteria were: prevalence of
musculoskeletal injuries, pre-existing cardiac pathologies, abnormal respiratory and cardiac
responses during the familiarization period and inability to perform the 12MRT. All partici-
pants were asked not to engage in physical training that would generate nervous or musculo-
skeletal fatigue 48 hours before the measurements and refrain from ingesting caffeine or any
substance that could increase their metabolism during the assessment. Finally, only those par-
ticipants who signed informed consent were subjected to 12MRT and somatotype evaluations.
Participants
Thirty-eight healthy and physically active naval cadets volunteered to participate in this study
(Table 1). The type of sampling was non-probabilistic for convenience. All participants were
informed of the study objective and possible risks of the experiment. Indeed, all participants
signed the informed consent form before the implementation of the protocols. The informed
consent and the study were approved by the Human Research Committee of the University of
Las Americas (registry number CEC-FP-2020011). The informed consent and the study were
conducted under the Declaration of Helsinki (WMA 2000, Bosˇnjak 2001, Tyebkhan 2003),
which sets out the fundamental ethical principles for research with human subjects.
Fig 1. Research design. 12MRT: 12-minute race test.
https://doi.org/10.1371/journal.pone.0251516.g001
Table 1. Characterization of the participants.
Women (n = 8)
Men (n = 30)
All (n = 38)
mean ± SD (min–max)
Mean ± SD (min–max)
mean ± SD (min–max)
Age (years)
21.0 ± 1.51 (19–23)
20.5 ± 1.22 (18–24)
20.6 ± 1.28 (18–24)
BMI (kg/m2)
21.9 ± 1.79 (20.2–25.5)
22.7 ± 1.69 (20.4–26.7)
22.5 ± 1.72 (20.2–26.7)
% Fat
23.3 ± 4.7 (18.5–33.1)
12.6 ± 2.2 (9.3–18.1)
14.9 ± 5.2 (9.3–33.1)
VO2 max (mLO2kg–1min–1)
46.7 ± 3.9 (42.6–51.5)
59.3 ± 4.7 (50.9–65.5)
56.6 ± 6.9 (42.6–65.5)
SD: standard deviation; kg/m2: kilograms per square meters; min: minimum; max: maximum; %: percentage; VO2 max: maximum oxygen uptake; mLO2kg–1min–1:
milliliters of oxygen per kilogram of body mass per minute.
https://doi.org/10.1371/journal.pone.0251516.t001
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
3 / 15
Somatotype evaluation
The somatotype corresponds to the shape of the human body. It is obtained by analyzing the
arm and leg’s circumferences, the humerus and femur’s diameters, four skinfolds (tricipital,
subscapular, supra-iliac, and mid-calf), and the weight and height of a person. Body shape can
be represented two-dimensionally through the somatochart or three-dimensionally through
the compogram; the latter representation corresponds to three numerical values representing
the endomorphic, mesomorphic, and ectomorphic components of a participant (always in that
order) [42]. To represent a participant’s morphology, Berral [42] recommends using both the
somatochart and the compogram since using only the somatochart can generate an error in
interpreting the results; for example, values 3–5–3 and 4–6–4 would be represented with the
same point on the somatochart [42].
Body mass and height.
The method used to determine the participants’ somatotype was pro-
posed by Carter & Heath [43]. The body mass (kg) was evaluated through a Tanita Inner Scan
BC-5541 digital scale, with the participants barefoot, in shorts, and wearing a light shirt. The height
was measured through a Seca1 stadiometer from the feet to the vertex (Frankfort plane) [44].
Circumferences.
Arm and leg circumferences, humeral and femoral diameters, and skin
folds were evaluated with the FAGA SLR1 anthropometric kit. The circumference of the
right leg was evaluated in this segment’s bulkiest area, in a standing position and with the gas-
trocnemius relaxed; in contrast, the circumference of the right arm was evaluated in the bulki-
est area of the contracted biceps; this evaluation was performed standing with the elbow in
front and bent at 90 [43].
Diameters.
The humeral epicondyle distance was considered the humerus’s diameter,
which is the distance between the epicondyle and the right arm’s epitrochlea. For this evalua-
tion, participants were standing with the elbow bent at 90˚. The distance between the femoral
condyles (medial and distal) was considered the femur’s diameter, which evaluation was per-
formed in a sitting position with the right knee bent at 90˚ [43, 44].
Skinfold thickness.
Four skinfolds were considered to determine the participants’
somatotype: tricipital, subscapular, supra-iliac, and mid-calf [43–45].
Body Mass Index (BMI).
The BMI’s interpretation was made according to anthropomet-
ric standards to evaluate nutritional status [46].
Percentage of fat (%). The fat percentage was evaluated through impedance measurement
with the Tanita Inner Scan BC-5541 digital scale.
Waist-Hip Index (WHI).
The WHI was obtained by dividing the waist perimeter, mea-
sured at a point equidistant from the lower edge of the last rib and the iliac crest, by the perim-
eter of the hips, measured at the greatest prominence of the buttocks [44, 47].
12 weeks without mandatory physical training
In regular class periods, the naval cadets had an average of two hours of daily mandatory phys-
ical training (Monday through Saturday). This physical training was mandatory and consid-
ered loads with the orientation to all physical capacities (strength, power, flexibility, speed,
aerobic capacity and aerobic power). However, upon leaving school, whether for vacation or
unplanned situations such as the current COVID 19 pandemic [30], the physical training regi-
men was not mandatory. During the 12 weeks without mandatory physical training, the naval
cadets voluntarily took part in walking, cycling, and ball games, among other activities.
Standardized warm-up
For both the first and the second evaluation of the 12MRT, the warm-up consisted of 10 min-
utes of jogging, then 5 minutes of ballistic movements of the lower limb (adduction, abduction,
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
4 / 15
flexion, and extension of hips, and flexion and extension of knees and ankles). To finish, par-
ticipants performed three 80-meter accelerations. After this warm-up and before running the
12MRT, there was a 5-minute break.
12-minute race test
The evaluation of the 12MRT was carried out on a 400-meter athletic track. Before the evalua-
tion, participants were instructed to perform as much distance as possible within the test’s 12
minutes. During the application of the test, the participants received verbal incentives from
the researchers. The distance achieved in meters was converted into kilometers, and then the
VO2 max was obtained through the following equation [48]:
VO2 max ðmLO2  kgthe tricipital skinfold participants, a very large, negative correlation was observed between
both variables (r = -0.76, p = 0.01). At the end of the 12 weeks without mandatory physical
training (post-test), a very large, negative correlation was observed between VO2 max and the
participants’ tricipital skinfold (r = -0.81, p = 0.01). The graphic representation of these analy-
ses is presented in Fig 4.
Discussion
Concerning this study’s primary objective, the variables of VO2 max and anthropometric
parameters showed changes after the 12 weeks without mandatory physical training in naval
cadets from 18 to 25 years old. The findings revealed that the analysis initial point relates phys-
ical training to quality of life [6, 8] and sports performance [1–3]. In this way, detrimental
physiological changes and a decline in performance observed after a period without physical
training can be reversed by applying correct training loads and professional supervision [17].
Specifically, the present study’s findings showed a significant decrease in the VO2 max of naval
cadets, both men and women, after 12 weeks without mandatory physical training (p < 0.001,
ES = 0.34). Similarly, Liguori et al. [37] determined changes in VO2 max after a vacation period
without mandatory training; at the end of the vacation period, the researchers reported signifi-
cant decreases in relative (p = 0.009) and absolute (p = 0.001) VO2 max in both men and
women. Likewise, Sotiropoulos et al. [33] evaluated changes in VO2 max after a four-week
transition period in soccer players. The experimental group (EG) conducted a directed
Table 2. Mean values and SD before and after 12 weeks without mandatory physical training (n = 38).
Test
mean ± SD
Post test
mean ± SD
Related differences
Mean
SD
SEM
95% confidence
interval
t
p
d
Lower
Upper
Weight (kg)
67.1 ± 8.0
67.5 ± 8.3
-0.32
1.78
0.28
-0.91
0.25
-1.13
ns
0.01
BMI (kg/m2)
22.5 ± 1.7
22.7 ± 1.8
-0.16
0.58
0.09
-0.35
0.02
-1.78
ns
0.10
% Fat
14.9 ± 5.2
14.9 ± 5.4
0.05
1.24
0.2
-0.35
0.46
0.26
ns
0.01
WHI
0.84 ± 0.05
0.83 ± 0.04
0.00
0.03
0.00
0.00
0.01
0.71
ns
0.08
WHeI
0.46 ± 0.03
0.46 ± 0.02
0.00
0.01
0.00
0.00
0.00
0.84
ns
0.08
Tricipital skinfold (mm)
11.1 ± 3.9
11.8 ± 4.0
-0.69
1.83
0.29
-1.29
-0.09
-2.34
ns
0.18
Subscapular skinfold (mm)
10.7 ± 3.1
10.9 ± 3.0
-0.26
1.32
0.21
-0.7
0.17
-1.22
ns
0.09
Suprailiac skinfold (mm)
9.4 ± 3.4
10.4 ± 3.8
-0.97
3.02
0.49
-1.97
0.01
-1.99
ns
0.27
Mid-calf skinfold (mm)
10.2 ± 4.6
9.9 ± 3.6
0.30
2.34
0.37
-0.46
1.07
0.79
ns
0.07
Arm circumference (cm)
31.6 ± 2.9
31.8 ± 3.0
-0.16
1.62
0.26
-0.7
0.36
-0.62
ns
0.06
Leg circumference (cm)
36.7 ± 2.0
36.8 ± 2.1
-0.11
0.77
0.12
-0.37
0.13
-0.91
ns
0.06
Humerus diameter
6.77 ± 0.42
6.76 ± 0.40
0.00
0.15
0.02
-0.04
0.05
0.21
ns
0.01
Femur diameter
9.76 ± 0.53
9.69 ± 0.52
0.06
0.17
0.02
0.01
0.12
2.4
ns
0.13
Endomorphic component
3.12 ± 0.96
3.32 ± 1.00
-0.20
0.55
0.08
-0.38
-0.02
-2.32
ns
0.21
Mesomorphic component
5.07 ± 0.96
5.10 ± 0.93
-0.02
0.39
0.06
-0.15
0.10
-0.41
ns
0.03
Ectomorphic component
2.51 ± 0.76
2.44 ± 0.77
0.06
0.27
0.04
-0.02
0.15
1.39
ns
0.08
12MRT (m)
3100.8 ± 348.6
2978.1 ± 364.7
122
115
18.6
84.9
160.5
6.57

0.34
VO2 max (mLO2kg–1min–1)
56.6 ± 6.9
54.2 ± 7.2
2.45
2.3
0.37
1.69
3.21
6.57

0.34
SD: standard deviation; SEM: standard error of the mean; WHI: waist-hip index; WHeI: waist-height index; BMI: muscle mass index; kg/m2: kilograms per square
meters; 12MRT: 12-minute race test; mm: millimeters; cm: centimeters; m: meters; VO2 max: maximum oxygen consumption; mLO2kg–1min–1: milliliters of oxygen
per kilogram of body mass per minute
 p < 0.002; ns: not significant; d: Cohen’s d.
https://doi.org/10.1371/journal.pone.0251516.t002
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
6 / 15
training program, while the control group (CG) executed a free training program. At the end
of the research, the EG decreased from 57.66 ± 2.56 to 56.85 ± 2.52 mLO2kg-1min-1. In con-
trast, the CG decreased from 58.08 ± 2.60 to 54.52 ± 2.80 mLO2kg-1min-1. Additionally, the
researchers reported significant decreases in VO2 max when comparing the EG to the CG in
the post-test (t = 16.06; p < 0.0001). Likewise, the endomorphic somatotype has a greater fat
mass than the mesomorphic and ectomorphic somatotype [43], and subjects with endomor-
phic predominance have shown a lower VO2 max than subjects with a mesomorphic or
ectomorphic predominance (endomorphic: 37.3 ± 0.77; mesomorphic: 40.2 ± 0.46; and ecto-
morphic: 43.5 ± 0.52) [51]. For this reason, the increase in the endomorphic component
observed in naval cadets after 12 weeks without mandatory physical training could condition
the decrease of VO2 max at the end of this period (p < 0.001, TE = 0.34). However, it is impor-
tant to analyze the ES for each variable studied, which allows us to observe each phenomenon’s
degree of presence, independent of the alpha level calculated [52]. In this study, like in research
by Parpa & Michaelides [24], all ES in the tests with significant differences in VO2 max, includ-
ing men and all data analysis, oscillated between 0.2–0.6. This was considered a small effect.
Fig 2. Changes in VO2 max and anthropometric parameters before and after 12 weeks without mandatory physical training. 12MRT: 12-minute race test;
mLO2Kg–1min–1: milliliters of oxygen per kilogram of body mass per minute; mm: millimeters; cm: centimeters; kg: kilograms; : p < 0.002.
https://doi.org/10.1371/journal.pone.0251516.g002
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
7 / 15
On the other hand, the significant differences in women had an ES between 0.6–1.2 (which
was considered as a moderate effect). Furthermore, the large and negative correlation between
VO2 max and the fat percentage observed in the test (r = -0.69, p = 0.01) increased after the
period without mandatory physical training (r = -0.75, p = 0.01). Up to this point, the decrease
in VO2 max has been attributed to two leading causes; on the one hand, a transition period
without mandatory and controlled physical training, while on the other hand, an increase in
fat mass, reflected in the endomorphic component of naval cadets [51].
Periods without physical training have also been associated with a decrease in muscle cross-
section [34]. This unfavorable consequence could be related to lower levels of muscle strength
[35]. In this case, Koundourakis et al. [31] examined the effects of six weeks without physical
training on performance parameters in soccer players; at the end of the study, the researchers
reported significant decreases in both squat jump (Team A: 39.70 ± 3.32 vs 37.30 ± 3.08 kg;
p < 0.001; Team B: 41.04 ± 3.34 vs 38.18 ± 3.03 kg; p < 0.001) and countermovement jump
(Team A: 41.04 ± 3.99 vs 39.13 ± 3.26%; p < 0.001); Team B: 42.82 ± 3.60 vs 40.09 ± 2.79 kg;
p < 0.001) in both experimental groups. The researchers also concluded that the observed
reductions in jumping ability (considered to be a negative effect) could be related to mis-
matches of rapidly contracting muscle fibers [25, 53]. In parallel, the endomorphic somatotype
has lesser muscle mass than the mesomorphic and ectomorphic somatotype [43]. In turn, Mir-
oshnichenko et al. [51] showed a high correlation between the predominance of the mesomor-
phic component and VO2 max. Likewise, an increase in the endomorphic component and
lower muscle mass could be associated with a lower VO2 max of the participants. Therefore,
Fig 3. Somatotype before and after 12 weeks without mandatory physical training.
https://doi.org/10.1371/journal.pone.0251516.g003
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
8 / 15
an increment of the endomorphic component in naval cadets may decrease the lower extremi-
ties’ strength, generating biomechanical and neuronal changes [54]. These last changes could
affect the economy of the race [55] and, consequently, decrease the performance in 12MRT
(p < 0.001, ES = 0.34). Although the evidence shows the negative influence of periods without
training on strength and muscular power [31, 35], mainly due to loss of muscle mass [34, 51],
the present study did not consider assessing naval cadets’ anaerobic capacity. Therefore, the
possible effects of 12 weeks without mandatory physical training on strength or power in both
the lower and upper extremities should be considered in future studies.
On the other hand, this study also showed increases in some anthropometric parameters
after 12 weeks without mandatory physical training, specifically in the tricipital skinfold thick-
ness in men (p = 0.02, ES = 0.18), arm circumference in women (p = 0.04, ES = 0.19) and the
endomorphic component in both men and women (p = 0.02, ES = 0.25). In this sense, evi-
dence shows that a period without physical training leads to increased fat mass and a decreased
lean mass [31–33]. Also, the tricipital fold, together with the subscapular and suprailiac folds,
are anthropometric indicators with a high explanatory power of VO2 max in both sexes [56].
We evidenced that those naval cadets with a higher tricipital fold had a reduced VO2 max
Fig 4. Correlation between VO2 max and anthropometric parameters before and after 12 weeks without mandatory physical training.
mLO2Kg–1min–1: milliliters of oxygen per kilogram of body mass per minute; % fat: percentage of fat; mm: millimeter.
https://doi.org/10.1371/journal.pone.0251516.g004
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
9 / 15
(Test: r = 0.76, p = 0.01; post test: r = 0.81, p = 0.01). Likewise, an elevated tricipital fold condi-
tions an elevated endomorphic component [42]. Consequently, anthropometric parameters
influence cardiorespiratory fitness, independent of sex, age, and obesity level [57]. Related to
this, Sotiropoulos et al. [33] evaluated changes in body weight and body fat percentage after a
four-week transition period in soccer players (The EG conducted a directed training program
and the CG a free training program). At the end of the study, the EG increased from 78.14 ±
4.77 to 78.74 ± 5.00 kg, while the CG increased from 76.48 ± 2.65 to 77.90 ± 2.82 kg (t = -4.91;
p < 0.005); and, also reported increased percentage of body fat (EG from 7.92 ± 1.68 to
8.17 ± 1.81%; CG from 7.77 ± 1.79 to 8.59 ± 1.80%; t = -8.42; p < 0.005). On the other hand,
Ormsbee et al. [58] examined the effect of five weeks without physical training on body com-
position in swimmers. At the end of the study, significant differences were observed in body
weight (68.96 ± 9.7 vs. 69.8 ± 9.8 kg; p = 0.03), fat mass (14.7 ± 7.6 vs. 16.5 ± 7.4 kg; p = 0.001),
and waist circumference (72.7 ± 3.1 vs. 73.8 ± 3.6 cm; p = 0.03). Also, Koundourakis et al. [31]
examined the effects of six weeks without physical training on the body composition of soccer
players; at the end of the study, the researchers reported significant increases in both body
weight (Team A: 77.60 ± 5.88 vs. 79.13 ± 6.16 kg; p < 0.001; Team B: 77.89 ± 8.75 vs.
79.49 ± 8.95 kg; p < 0.001) and in the fat percentage (Team A: 9.2 ± 3.33 vs. 11.01 ± 4.11%;
p < 0.001; Team B: 9.43 ± 3.55 vs. 10.40 ± 4.08 kg; p < 0.001) in both experimental groups.
Although some studies have established the body composition of armed forces personnel in
some countries [59] and anthropometric changes have been documented concerning soldiers’
physical training [60], the effects of 12 weeks without mandatory physical training on anthro-
pometric parameters have not been reported for naval cadets. Consequently, in connection
with the studies referred to above, our study’s findings show the importance of verifying and
controlling body composition after a period without mandatory physical training in naval
cadets [61], especially somatotype indicators [43]. However, it is essential to mention that the
present study did not control the participants’ caloric intake [62]. For this reason, we are not
sure that the changes in anthropometric parameters were only due to a decrease in physical
training [63–65]; there is a possibility that higher caloric intake, above the daily energy needs,
has also influenced these physical changes [62, 66].
Finally, the data show that VO2 max is an essential parameter of the physical condition
[38], and a higher VO2 max allows the efficient performance of physical tasks associated with
military personnel [13, 60]. It has also been demonstrated that subjects with a higher percent-
age of body fat have lower VO2 max, lower strength levels, and lower fatigue tolerance [67]. As
demonstrated in this study, a vacation period without mandatory physical training generates
decreases in the VO2 max [37] and negatively affects anthropometric parameters [51]. There-
fore, the vacation periods must be adapted into a transition phase [24, 25]. In this way, with
controlled and directed physical training, both athletes and naval cadets will have optimal
physical recovery and maintenance; this condition will allow them to face better the next cycle
of physical training [23].
One of the limitations of this study was the sample used. As mentioned above, the sample
was by convenience, which would not allow us to generalize the data. However, armed forces
personnel are more homogeneous in body structure [68] and eating behavior [69]. For this
reason, in this specific case, the results could be generalized to this population.
Conclusions
Twelve weeks without mandatory physical training significantly decreases the VO2 max in
naval cadets from 18 to 25 years old. Simultaneously, the same period without mandatory
training increases skinfold thickness and the endomorphic component in this population.
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
10 / 15
Practical applications
After evidence of decreases in VO2 max and negative increases in some anthropometric
parameters after 12 weeks without mandatory physical training, it is suggested that training
loads in the transition phase [25], whether due to vacations [28] or to unforeseen events [30].
Acknowledgments
We thank the 38 naval cadets for their voluntary and disinterested participation in the Arturo
Prat Naval Academy.
Author Contributions
Conceptualization: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames
Maliqueo.
Data curation: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames
Maliqueo.
Formal analysis: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames
Maliqueo.
Funding acquisition: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames
Maliqueo.
Investigation: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames
Maliqueo.
Methodology: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames
Maliqueo.
Resources: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames Maliqueo.
Supervision: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames Maliqueo.
Validation: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames Maliqueo.
Visualization: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Galdames
Maliqueo.
Writing – original draft: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Gal-
dames Maliqueo.
Writing – review & editing: A´lvaro Huerta Ojeda, Guillermo Barahona-Fuentes, Sergio Gal-
dames Maliqueo.
References
1.
Ojeda A´ H, Rı´os LC, Barrilao RG, Rios IC, Serrano PC. Effect of variable resistance on post-activation
potentiation: A systematic review. Arch Med Deporte. 2016; 33(5):338–45.
2.
Barahona-Fuentes G, Huerta Ojeda A´ , Galdames Maliqueo S. The influence of High-Intensity Interval
Training Based Plyometric Exercise on Jump Height and Peak Power of Under-17 Male Soccer Players.
Educacio´n Fı´sica y Ciencia. 2019; 21(2):e080. https://doi.org/10.24215/23142561e080.
3.
Huerta A´ C, Galdames S, Cataldo M, Barahona G, Rozas T, Ca´ceres P. Effects of a high intensity inter-
val training on the aerobic capacity of adolescents. Rev Med Chil. 2017; 145(8):972–9. https://doi.org/
10.4067/s0034-98872017000800972 PMID: 29189854
4.
Gacesa JZ, Jakovljevic DG, Kozic DB, Dragnic NR, Brodie DA, Grujic NG. Morpho-functional response
of the elbow extensor muscles to twelve-week self-perceived maximal resistance training. Clin Physiol
Funct Imaging. 2010; 30(6):413–9. https://doi.org/10.1111/j.1475-097X.2010.00957.x PMID: 20670339
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
11 / 15
5.
Ingle L, Stephenson A, Sandercock GR. Physical activity profiles and selected muscular fitness vari-
ables in English schoolchildren: A north–south divide? Eur J Sport Sci. 2016; 16(8):1187–96. https://
doi.org/10.1080/17461391.2016.1183714 PMID: 27220086
6.
Sabido R, Peñaranda M, Herna´ndez-Davo´ JL. Comparison of acute responses to four different hyper-
trophy-oriented resistance training methodologies. Eur J Hum Mov. 2016;37109–21.
7.
Cordova A, Villa G, Sureda A, Rodriguez-Marroyo JA, Sa´nchez-Collado MP. Physical Activity and Car-
diovascular Risk Factors in Spanish Children Aged 11–13 Years. Rev Española Cardiol. 2012; 65
(7):620–6. https://doi.org/10.1016/j.recesp.2012.01.026 PMID: 22633280
8.
Ga´lvez Casas A, Rodrı´guez Garcı´a PL, Garcı´a-Canto´ E, Rosa Guillamo´n A, Pe´rez-Soto JJ, Tarraga
Marcos L, et al. Aerobic capacity and quality of life in school children from 8 to 12. Clin Investig Arterios-
cler. 2015; 27(5):239–45. https://doi.org/10.1016/j.arteri.2015.01.001 PMID: 25814171
9.
Patel A V., Hodge JM, Rees-Punia E, Teras LR, Campbell PT, Gapstur SM. Relationship between mus-
cle-strengthening activity and cause-specific mortality in a large US cohort. Prev Chronic Dis.
2020;171–9. https://doi.org/10.5888/pcd17.190408.
10.
Ojeda A´ H, Rı´os LC, Barrilao RG, Serrano PC. Acute effect of a complex training protocol of back squats
on 30-m sprint times of elite male military athletes. J Phys Ther Sci. 2016; 28(3):752–6. https://doi.org/
10.1589/jpts.28.752 PMID: 27134353
11.
Webber BJ, Flower AM, Pathak SR, Burganowski RP, Pawlak MT, Gottfredson RC, et al. Physical and
Mental Health of US Air Force Military Training Instructors. Mil Med. 2019; 184(5–6):e248–54. https://
doi.org/10.1093/milmed/usy418 PMID: 30690457
12.
Vrijkotte S, Roelands B, Pattyn N, Meeusen R. The Overtraining Syndrome in Soldiers: Insights from
the Sports Domain. Mil Med. 2019; 184(5–6):e192–200. https://doi.org/10.1093/milmed/usy274 PMID:
30535270
13.
Taylor MK, Markham AE, Reis JP, Padilla GA, Potterat EG, Drummond SPA, et al. Physical fitness
influences stress reactions to extreme military training. Mil Med. 2008; 173(8):738–42. https://doi.org/
10.7205/milmed.173.8.738 PMID: 18751589
14.
Schneider KL, Spring B, Pagoto SL. Exercise and energy intake in overweight, sedentary individuals.
Eat Behav. 2009; 10(1):29–35. https://doi.org/10.1016/j.eatbeh.2008.10.009 PMID: 19171314
15.
Lovell DI, Cuneo R, Wallace J, McLellan C. The hormonal response of older men to sub-maximum aero-
bic exercise: The effect of training and detraining. Steroids. 2012; 77(5):413–8. https://doi.org/10.1016/
j.steroids.2011.12.022 PMID: 22248672
16.
Stebbings GK, Morse CI, McMahon GE, Onambele GL. Resting arterial diameter and blood flow
changes with resistance training and detraining in healthy young individuals. J Athl Train. 2013; 48
(2):209–19. https://doi.org/10.4085/1062-6050-48.1.17 PMID: 23672385
17.
Mujika I. The influence of training characteristics and tapering on the adaptation in highly trained individ-
uals: A review. Int J Sports Med. 1998; 19(7):439–46. https://doi.org/10.1055/s-2007-971942 PMID:
9839839
18.
Flann KL, Lastayo PC, McClain DA, Hazel M, Lindstedt SL. Muscle damage and muscle remodeling:
No pain, no gain? J Exp Biol. 2011; 214(4):674–9. https://doi.org/10.1242/jeb.050112.
19.
Gunter K, Baxter-Jones ADG, Mirwald RL, Almstedt H, Fuchs RK, Durski S, et al. Impact exercise
increases BMC during growth: an 8-year longitudinal study. J Bone Miner Res. 2008; 23(7):986–93.
https://doi.org/10.1359/jbmr.071201 PMID: 18072874
20.
Maroto-Izquierdo S, Garcı´a-Lo´pez D, Fernandez-Gonzalo R, Moreira OC, Gonza´lez-Gallego J, de Paz
JA. Skeletal muscle functional and structural adaptations after eccentric overload flywheel resistance
training: a systematic review and meta-analysis. J Sci Med Sport. 2017; 20(10):943–51. https://doi.org/
10.1016/j.jsams.2017.03.004 PMID: 28385560
21.
Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, et al. Quantity and quality of
exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in
apparently healthy adults: Guidance for prescribing exercise. Med Sci Sports Exerc. 2011; 43(7):1334–
59. https://doi.org/10.1249/MSS.0b013e318213fefb PMID: 21694556
22.
Barahona-Fuentes G, Ojeda A´ H, Jerez-Mayorga D. Effects of different methods of strength training on
indicators of muscle fatigue during and after strength training: a systematic review. Motriz J Phys Educ.
2020; 26(3):e10200063. https://doi.org/10.1590/S1980-6574202000030063.
23.
Silva JR, Brito J, Akenhead R, Nassis GP. The transition period in soccer: a window of opportunity.
Sport Med. 2016; 46(3):305–13. https://doi.org/10.1007/s40279-015-0419-3 PMID: 26530720
24.
Parpa K, Michaelides MA. The effect of transition period on performance parameters in elite female soc-
cer players. Int J Sports Med. 2020; 41(8):528–32. https://doi.org/10.1055/a-1103-2038 PMID:
32059247
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
12 / 15
25.
Mujika I, Padilla S. Detraining: loss of training-induced physiological and performance adaptations. Part
I. Sport Med. 2000; 30(2):79–87. https://doi.org/10.2165/00007256-200030020-00002.
26.
Musumeci G. Sarcopenia and exercise “the state of the art.” J Funct Morphol Kinesiol. 2017; 2(4):.
https://doi.org/10.3390/jfmk2040040.
27.
Maugeri G, Castrogiovanni P, Battaglia G, Pippi R, D’Agata V, Palma A, et al. The impact of physical
activity on psychological health during Covid-19 pandemic in Italy. Heliyon. 2020; 6(6):e04315. https://
doi.org/10.1016/j.heliyon.2020.e04315 PMID: 32613133
28.
Katzmarzyk PT, Barreira T V., Broyles ST, Champagne CM, Chaput JP, Fogelholm M, et al. Physical
activity, sedentary time, and obesity in an international sample of children. Med Sci Sports Exerc. 2015;
47(10):2062–9. https://doi.org/10.1249/MSS.0000000000000649 PMID: 25751770
29.
Prentice-Dunn H, Prentice-Dunn S. Physical activity, sedentary behavior, and childhood obesity: a
review of cross-sectional studies. Psychol Health Med. 2012; 17(3):255–73. https://doi.org/10.1080/
13548506.2011.608806 PMID: 21995842
30.
Paoli A, Musumeci G. Elite athletes and COVID-19 lockdown: future health concerns for an entire sec-
tor. J Funct Morphol Kinesiol. 2020; 5(2):10–2. https://doi.org/10.3390/jfmk5020030 PMID: 33467246
31.
Koundourakis NE, Androulakis NE, Malliaraki N, Tsatsanis C, Venihaki M, Margioris AN. Discrepancy
between exercise performance, body composition, and sex steroid response after a six-week detraining
period in professional soccer players. PLoS One. 2014; 9(2):. https://doi.org/10.1371/journal.pone.
0087803.
32.
Reinke S, Karhausen T, Doehner W, Taylor W, Hottenrott K, Duda GN, et al. The influence of recovery
and training phases on body composition, peripheral vascular function and immune system of profes-
sional soccer players. PLoS One. 2009; 4(3):1–7. https://doi.org/10.1371/journal.pone.0004910.
33.
Sotiropoulos AS, Travlos AK, Gissis I, Souglis AG, Grezios A. The effect of a 4-week training regimen
on body fat and aerobic capacity of professional soccer players during the transition period. J Strength
Cond Res. 2009; 23(6):1697–703. https://doi.org/10.1519/JSC.0b013e3181b3df69 PMID: 19675494
34.
Hakkinen K. Effect of combined concentric and eccentric strength training and detraining on force-time,
muscle fiber and metabolic characteristics of leg extensor muscles. Scand J Sport Sci. 1981;350–8.
35.
Izquierdo M, Ibanez J, Gonzalez-Badillo JJ, Ratamess N, Kraemer WJ, Hakkinen K, et al. Detraining
and tapering effects on hormonal responses and strength performance. J Strenght Cond Res. 2007; 21
(3):768–75. https://doi.org/10.1519/R-21136.1 PMID: 17685721
36.
De Paiva PRV, Casalechi HL, Tomazoni SS, MacHado CDSM, Ribeiro NF, Pereira AL, et al. Does the
combination of photobiomodulation therapy (PBMT) and static magnetic fields (sMF) potentiate the
effects of aerobic endurance training and decrease the loss of performance during detraining? A rando-
mised, triple-blinded, placebo-controlled trial. BMC Sports Sci Med Rehabil. 2020; 12(1):1–11. https://
doi.org/10.1186/s13102-020-00171-2.
37.
Liguori G, Krebsbach K, Schuna J. Decreases in maximal oxygen uptake among army reserve officers’
training corps cadets following three months without mandatory physical training. Int J Exerc Sci. 2012;
5(4):354–9. PMID: 27182392
38.
Ojeda A´ H, Maliqueo SG, Serrano PC. Validacio´n del test de 6 minutos de carrera como predictor del
consumo ma´ximo de oxı´geno en el personal naval. Rev Cuba Med Mil. 2017; 46(4):1–11.
39.
Galdames S, Huerta A´ , Pastene A. Effect of acute sodium bicarbonate supplementation on perfor-
mance on the obstacle run in professional military pentathlete. Arch Med Deporte. 2020; 37(4):220–6.
40.
Armada-de-Chile. ¿Quie´nes la componen? Armada de Chile. 2014;
41.
Ato M, Lo´pez JJ, Benavente A. A classification system for research designs in psychology. An Psicol.
2013; 29(3):1038–59. https://doi.org/10.6018/analesps.29.3.178511.
42.
Berral F. Protocolo de medidas antropome´tricas. Jornadas Me´dico Sanit. sobre Atlet., 2004;, p. 115–
22.
43.
Carter JEL, Heath BH. Somatotyping: development and applications. vol. 5. New York, USA: Cam-
bridge university press; 1990;
44.
National Health and Nutrition Examination Survey. Anthropometry procedures manual. 2005;
45.
Durnin J, Womersley J. Body fat assessed from total body density and its estimation from skinfold thick-
ness: measurements on 481 men and women aged from 16 to 72 years. Br J Nutr. 1974;3277–97.
https://doi.org/10.1079/bjn19740060 PMID: 4843734
46.
Barrera A, Gladys M. Esta´ndares antropome´tricos para evaluacio´n del estado nutritivo. INTA. Santi-
ago, Chile: 2004;
47.
Mederico M, Paoli M, Zerpa Y, Briceño Y, Go´mez-Pe´rez R, Martı´nez JL, et al. Reference values of
waist circumference and waist/hip ratio in children and adolescents of Me´rida, Venezuela: comparison
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
13 / 15
with international references. Endocrinol y Nutr. 2013; 60(5):235–42. https://doi.org/10.1016/j.endoen.
2012.12.006.
48.
Cooper KH. A means of assessing maximal oxygen intake: correlation between field and treadmill test-
ing. Jama. 1968; 203(3):201–4. PMID: 5694044
49.
Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine
and exercise science. Med Sci Sports Exerc. 2009; 41(1):3–12. https://doi.org/10.1249/MSS.
0b013e31818cb278 PMID: 19092709
50.
Martı´nez Camblor P. P-value adjustment for multiple comparisons. Rev Chil Salud Pu´blica. 2012; 16
(3):225–32. https://doi.org/10.5354/0717-3652.2012.23127.
51.
Miroshnichenko VM, Furman YM, Brezdeniuk OY, Onyshchuk VE, Gavrylova N V, Salnykova S-V. Cor-
relation of maximum oxygen consumption with component composition of the body, body mass of men
with different somatotypes aged 25–35. Pedagog Phys Cult Sport. 2020; 24(2):290–6. https://doi.org/
10.15561/26649837.2020.0603.
52.
Casado A, Prieto L, Alonso J. El tamaño del efecto de la diferencia entre dos medias: ¿estadı´stica-
mente significativo o clı´nicamente relevante? Med Clin (Barc). 1999; 112(15):584–8. PMID: 10365387
53.
Perez-Gomez J, Rodriguez GV, Ara I, Olmedillas H, Chavarren J, Gonza´lez-Henriquez JJ, et al. Role of
muscle mass on sprint performance: gender differences? Eur J Appl Physiol. 2008; 102(6):685–94.
https://doi.org/10.1007/s00421-007-0648-8 PMID: 18084774
54.
Trowell D, Vicenzino B, Saunders N, Fox A, Bonacci J. Effect of strength training on biomechanical and
neuromuscular variables in distance runners: a systematic review and meta-analysis. Sport Med. 2020;
50(1):133–50. https://doi.org/10.1007/s40279-019-01184-9 PMID: 31541409
55.
Skovgaard C, Christensen PM, Larsen S, Andersen TR, Thomassen M, Bangsbo J. Concurrent speed
endurance and resistance training improves performance, running economy, and muscle NHE1 in mod-
erately trained runners. J Appl Physiol. 2014; 117(10):1097–109. https://doi.org/10.1152/japplphysiol.
01226.2013 PMID: 25190744
56.
de Andrade E, Gimenes H, Santos D. Which body fat anthropometric indicators are most strongly asso-
ciated with maximum oxygen uptake in adolescents? Asian J Sports Med. 2017; 8(3):e13812. https://
doi.org/10.5812/asjsm.13812.
57.
Yanek LR, Vaidya D, Kral BG, Dobrosielski DA, Moy TF, Stewart KJ, et al. Lean mass and fat mass as
contributors to physical fitness in an overweight and obese african american population. Ethn Dis. 2015;
25(2):214–9. PMID: 26118151
58.
Ormsbee MJ, Arciero P. Detraining increases body fat and weight and decreases VO2peak and meta-
bolic rate. J Strength Cond Res. 2012; 26(8):2087–95. https://doi.org/10.1519/JSC.
0b013e31823b874c PMID: 22027854
59.
Nelson R, Cheatham J, Gallagher D, Bigelman K, Thomas DM. Revisiting the United States Army body
composition standards: a receiver operating characteristic analysis. Int J Obes. 2019; 43(8):1508–15.
https://doi.org/10.1038/s41366-018-0195-x PMID: 30181655
60.
Dyrstad SM, Soltvedt R, Halle´n J. Physical fitness and physical training during norwegian military ser-
vice. Mil Med. 2006; 171(8):736–41. https://doi.org/10.7205/milmed.171.8.736 PMID: 16933814
61.
Pl¸avin¸a L, Umbrasˇko S. Analysis of physical fitness tests and the body composition of the military per-
sonnel. Pap Anthropol. 2016; 25(1):27. https://doi.org/10.12697/poa.2016.25.1.03.
62.
Thomas DT, Erdman KA, Burke LM. Position of the academy of nutrition and dietetics, dietitians of can-
ada, and the american college of sports medicine: nutrition and athletic performance. J Acad Nutr Diet.
2016; 116(3):501–28. https://doi.org/10.1016/j.jand.2015.12.006 PMID: 26920240
63.
Franckle R, Adler R, Davison K. Accelerated weight gain among children during summer versus school
year and related racial/ethnic disparities: a systematic review. Prev Chronic Dis. 2014; 11(12):1–10.
https://doi.org/10.5888/pcd11.130355 PMID: 24921899
64.
Moreno JP, Johnston CA, Woehler D. Changes in weight over the school year and summer vacation:
results of a 5-year longitudinal study. J Sch Health. 2013; 83(7):473–7. https://doi.org/10.1111/josh.
12054 PMID: 23782089
65.
von Hippel PT, Workman J. From kindergarten through second grade, U.S. children’s obesity preva-
lence grows only during summer vacations. Obesity. 2016; 24(11):2296–300. https://doi.org/10.1002/
oby.21613 PMID: 27804271
66.
Cooper JA, Tokar T. A prospective study on vacation weight gain in adults. Physiol Behav.
2016;15643–7. https://doi.org/10.1016/j.physbeh.2015.12.028 PMID: 26768234
67.
Crawford K, Fleishman K, Abt JP, Sell TC, Lovalekar M, Nagai T, et al. Less body fat improves physical
and physiological performance in army soldiers. Mil Med. 2011; 176(1):35–43. https://doi.org/10.7205/
milmed-d-10-00003 PMID: 21305957
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
14 / 15
68.
Maldonado I, Calero S. Anthropometric profile and body composition in aspirants of the Army Soldiers
Training School. Rev Cuba Investig Biome´dicas. 2017; 36(2):1–13.
69.
Kildal CL, Syse KL. Meat and masculinity in the Norwegian Armed Forces. Appetite. 2017; 112(Novem-
ber 2013):69–77. https://doi.org/10.1016/j.appet.2016.12.032 PMID: 28040506
PLOS ONE
Period without physical training on maximum oxygen uptake
PLOS ONE | https://doi.org/10.1371/journal.pone.0251516
June 2, 2021
15 / 15

Effects of a period without mandatory physical training on maximum oxygen uptake and anthropometric parameters in naval cadets.
Huerta Ojeda, Álvaro,Barahona-Fuentes, Guillermo,Galdames Maliqueo, Sergio