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Background: British Army Phase One training exposes men and women to challenging distances of 13.5 km·d- 1 vs. 11.8 km·d- 1 and energy expenditures of ~ 4000 kcal·d- 1 and ~ 3000 kcal·d- 1, respectively. As such, it is essential that adequate nutrition is provided to support training demands. However, to date, there is a paucity of data on habitual dietary intake of British Army recruits. The aims of this study were to: (i) compare habitual dietary intake in British Army recruits undergoing Phase One training to Military Dietary Reference Values (MDRVs), and (ii) establish if there was a relative sex difference in dietary intake between men and women. Method: Researcher led weighed food records and food diaries were used to assess dietary intake in twenty-eight women (age 21.4 ± 3.0 yrs., height: 163.7 ± 5.0 cm, body mass 65.0 ± 6.7 kg), and seventeen men (age 20.4 ± 2.3 yrs., height: 178.0 ± 7.9 cm, body mass 74.6 ± 8.1 kg) at the Army Training Centre, Pirbright for 8-days in week ten of training. Macro and micronutrient content were estimated using dietary analysis software (Nutritics, Dublin) and assessed via an independent sample t-test to establish if there was a sex difference in daily energy, macro or micronutrient intakes. Results: Estimated daily energy intake was less than the MDRV for both men and women, with men consuming a greater amount of energy compared with women (2846 ± 573 vs. 2207 ± 585 kcal·day- 1, p < 0.001). Both sexes under consumed carbohydrate (CHO) when data was expressed relative to body mass with men consuming a greater amount than women (4.8 ± 1.3 vs. 3.8 ± 1.4 g·kg- 1·day- 1, p = 0.025, ES = 0.74). Both sexes also failed to meet MDRVs for protein intake with men consuming more than women (1.5 ± 0.3 vs. 1.3 ± 0.3 g·kg- 1·day- 1, p > 0.030, ES = 0.67). There were no differences in dietary fat intake between men and women (1.5 ± 0.2 vs. 1.5 ± 0.5 g·kg- 1·day- 1, p = 0.483, ES = 0.00). Conclusions: Daily EI in men and women in Phase One training does not meet MDRVs. Interventions to increase macronutrient intakes should be considered along with research investigating the potential benefits for increasing different macronutrient intakes on training adaptations.
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R E S E A R C H A R T I C L E Open Access
Sex differences in dietary intake in British
Army recruits undergoing phase one
Shaun Chapman
, Justin Roberts
, Lee Smith
, Alex Rawcliffe
and Rachel Izard
Background: British Army Phase One training exposes men and women to challenging distances of 13.5 km·d
11.8 km·d
and energy expenditures of ~ 4000 kcal·d
and ~ 3000 kcal·d
, respectively. As such, it is essential that
adequate nutrition is provided to support training demands. However, to date, there is a paucity of data on
habitual dietary intake of British Army recruits. The aims of this study were to: (i) compare habitual dietary intake in
British Army recruits undergoing Phase One training to Military Dietary Reference Values (MDRVs), and (ii) establish if
there was a relative sex difference in dietary intake between men and women.
Method: Researcher led weighed food records and food diaries were used to assess dietary intake in twenty-eight
women (age 21.4 ± 3.0 yrs., height: 163.7 ± 5.0 cm, body mass 65.0 ± 6.7 kg), and seventeen men (age 20.4 ± 2.3 yrs.,
height: 178.0 ± 7.9 cm, body mass 74.6 ± 8.1 kg) at the Army Training Centre, Pirbright for 8-days in week ten of
training. Macro and micronutrient content were estimated using dietary analysis software (Nutritics, Dublin) and
assessed via an independent sample t-test to establish if there was a sex difference in daily energy, macro or
micronutrient intakes.
Results: Estimated daily energy intake was less than the MDRV for both men and women, with men consuming a
greater amount of energy compared with women (2846 ± 573 vs. 2207 ± 585 kcal·day
,p< 0.001). Both sexes under
consumed carbohydrate (CHO) when data was expressed relative to body mass with men consuming a greater
amount than women (4.8 ± 1.3 vs. 3.8 ± 1.4 g·kg
,p= 0.025, ES = 0.74). Both sexes also failed to meet MDRVs for
protein intake with men consuming more than women (1.5± 0.3 vs. 1.3 ± 0.3 g·kg
,p> 0.030, ES = 0.67). There
were no differences in dietary fat intake between men and women (1.5 ± 0.2 vs. 1.5 ± 0.5 g·kg
ES = 0.00).
Conclusions: Daily EI in men and women in Phase One training does not meet MDRVs. Interventions to increase
macronutrient intakes should be considered along with research investigating the potential benefits for increasing
different macronutrient intakes on training adaptations.
Keywords: Dietary intake, Military, Sex differences, Exercise training
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* Correspondence:
HQ Army Recruiting and Initial Training Command, UK Ministry of Defence,
Upavon, UK
Cambridge Centre for Sport and Exercise Sciences, School of Psychology
and Sport Science, Anglia Ruskin University, East Road, Cambridge CB1 1PT,
Chapman et al. Journal of the International Society of Sports Nutrition
(2019) 16:59
British Army standard entry Phase One training is a 14-
week training syllabus that includes physical training, field
exercises and training on a variety of military-specific skills
including load carriage, marching, military drill and
weapon and equipment handling [1]. It is characterised by
high rates of injury and medical discharge (MD) [13]. In
Phase One training the overall rate of injury is 0.07 people
injured per 100 person-days and that the overall MD rate
is 0.02 people injured per 100 person-days [2]. Recruits are
exposed to high daily training loads and energy expendi-
tures (EE) which, without adequate nutrient provision, may
contribute to a reduction in mood state [4] compromised
physical performance, increased musculoskeletal injury
(MSKi) risk [5,6] and medical discharge (MD). Estimated
daily EE and training distance covered in Phase One train-
ing in men has been reported to be ~ 4000 kcal and 13.5 ±
6.6 km and in women was ~ 3000 kcal and 11.8 ± 4.9 km
for men and women, respectively [1]. Women are at
greater risk of MSKi during British Army Phase One train-
ing and this is supported by evidence that demonstrates
women to be 23 times at greater risk of injury [2]. The in-
creased risk is not due to sex differences per se but likely
due to lower aerobic fitness levels in women, resulting in
higher internal load [1,2,7]. Therefore, women may re-
quire additional dietary support, such as energy and/or
protein intake, to facilitate skeletal muscle repair and sup-
port the higher training load compared to men [1]. To
date, however, there is no suggestion that separate protein
intakes should be recommended for men and women. To
maintain muscle mass, strength and performance during
periods of substantial metabolic demands and concomitant
negative energy balance it is recommended a protein intake
of at least 1.5 g·kg
is consumed [8].
In response to a similar training load women have been
shown to have greater fatigue resistance and maintenance
of muscle function to men [9]. Following a loaded march
during British Army training, men had a greater loss in
maximal voluntary contractions (MVC) of the knee exten-
sors than women (12 ± 9% vs. 9 ± 13%, p= 0.03). The au-
thors suggested that this may have been due to woman
possessing a greater proportion of type 1 muscle fibres in
the knee extensor muscles. Nevertheless, the MVC and
vertical jump height of men following load carriage was
still higher than the pre-exercise values for the women
and therefore, muscle performance rather than fatigability
per se, may contribute to the sex difference in injury inci-
dence [2,9]. The higher baseline values in the men per-
haps allows for greater degradation [9]. Therefore, the
lower baseline values in the women may indicate a re-
quirement for nutritional interventions to enhance skeletal
muscle recovery. Women may also require other dietary
interventions to support training, particularly as recent
evidence has shown women to under consume various
micronutrients such as iron and calcium, during military
training by 77 and 75%, respectively [10].
Dietary intake should match energy expenditure to
maintain health and performance and evidence to support
this has been extensively reviewed [1113]. Specifically, an
inadequate energy intake (EI) is harmful to performance
[4], bone health [5,14,15], immune function [16], cogni-
tion [17], mood [4] and MSKi risk [5]. It has therefore
been recommended to consume 31004100 kcal·d
cific to Phase one training [18]. Moreover, a negative en-
ergy balance of > 500 kcal·d
is detrimental to health in
the longer term. It has been shown that an energy deficit
of this magnitude suppresses the hormone milieu, reduces
thyroid function and reduces exercise performance by
9.8% [19]. Reduced thyroid function is of particular con-
cern in military populations due to the suppression on
bone formation markers and subsequent risk of a stress
fracture [20]. In a crossover study, endurance trained run-
ners undergoing an intense 11-day training programme
whilst habitually consuming a diet lower in CHO (5.4
) experienced a greater deterioration in global
mood scores, than when consuming a diet with a higher
CHO content (8.5 g·kg
)[4]. In military populations
it is generally found that soldiers fail to meet recom-
mended energy and nutrient intakes [10,2127]. McA-
dam et al. (2018) found that recruits undergoing Basic
Training in the United States (U.S.) experienced a 595±
896 kcal·d
deficit and 70% of recruits consumed less
than the lower limit (6 g·kg
) for recommended
carbohydrate intake (CHO). Given the large standard de-
viation for energy intake (896 kcal·d
would have been in a larger energy deficit across the train-
ing phase. It is possible that this deficit was underesti-
mated due to the use of an accelerometer to quantify EE.
Energy expenditure was estimated via an Actigraph
wGT3X monitor using the Sasaki equation which has
been shown to have a mean bias of 0.23 compared to in-
direct calorimetry [28]. It is also possible that EI was also
underestimated due to an acute food diary collection
period being used for analysis [29]. In the United King-
dom (UK), the Scientific Advisory Committee on Nutri-
tion (SACN) have developed Military Dietary Reference
Values (MDRVs) for British Army recruits [18], but no
study has yet quantified dietary intake to establish if these
are habitually met.
The aim of this study was therefore to quantify energy,
macro and micronutrient intake of British Army recruits
to determine if these were adequate compared to MDRVs
and Recommended Daily Allowances (RDA). A secondary
aim was to compare dietary intake between sexes to estab-
lish if future dietary interventions during training needed
to be sex specific. Based on other studies in military popu-
lations, we hypothesized that men and women would not
meet MDRVs for energy intake and that women would be
Chapman et al. Journal of the International Society of Sports Nutrition (2019) 16:59 Page 2 of 9
at greater risk of nutrient deficiency compared to men
due to a lower energy intake. The findings of this investi-
gation will provide novel data into the nutritional intake
of British Army recruits in Phase One training. This data
may be used to inform future interventions aimed at im-
proving nutrient intake in this population during British
Army training.
Materials/ methods
Ethical approval
This study was approved by the U.K. Ministry of Defence
Research Ethics Committee (MODREC). For inclusion, re-
cruits at the Army Training Centre Pirbright (ATC(P)),
Surrey, UK in week ten of training, were invited to take
part. Interested participants received verbal explanation of
the study from the research team and provided written in-
formed consent. Twenty-eight women (mean ± SD: age
21.4 ± 3.0 yrs., height: 163.7 ± 5.0 cm, body mass 65.0 ± 6.7
kg, body mass index: 24.2 ± 2.6 kg·m
) and seventeen men
(mean ± SD: age 20.4 ± 2.3 yrs., height: 178.0 ± 7.9 cm,
body mass 74.6 ± 8.1 kg, body mass index: 22.5 ± 1.7
) volunteered for this study, which was conducted in
accordance with the declaration of Helsinki.
Study design
This was an observational cross-sectional study over an
8-day period. Sample size was based on a priori power
analysis using G*power (v3.1.9.2, Dusseldorf) based on
previously collected energy intake data in the literature
[26]. It was determined that 24 participants (12 men and
12 women) were required to replicate the highest signifi-
cant effect size of 1.05 for a between-sex difference in
energy intake using α= 0.05, β= 0.80. Participant demo-
graphics were collected on day one and diet analysis was
collected on each day (days 1 to 8).
Physical characteristics
Height (cm) and body mass (kg) were recorded with re-
cruits wearing Army uniform except for boots using a
seca 213 mobile stadiometer and pre-calibrated seca flat
scales (Hamburg, Germany).
Diet logs
Dietary intake was recorded using researcher-led food
weighing at breakfast, lunch and dinner in the training
centre dining facility. On arrival, participants chose their
food and each portion was weighed using pre-calibrated
food scales (Salter, 1066 BKDR15, Kent, UK). After each
meal, participants were instructed to leave food discards
so that these could also be weighed and subtracted from
the original weight; to give the actual food portion con-
sumed for that meal [30]. To capture dietary intake be-
tween meals and off-camp, participants completed food
diaries following guided instructions and estimated the
portion size using practical measures (1 cup, 2 handfuls,
1 palm size etc.) [29] and kept any snack or ration dis-
cards in discard bags to cross examine against food diar-
ies. Participants were briefed on how to accurately
complete a food diary and these were then checked by a
member of the research team each day to clarify any un-
clear information.
Nutritics analysis
Food records were entered into nutritional analysis soft-
ware (Nutritics, Dublin, Ireland) for the generation of
mean daily energy, macronutrient and micronutrient in-
takes using the UK Scientific Advisory Committee on
Nutrition (SACN) database. The recipes of foods which
did not already exist in the database (i.e. ration pack
foods) were manually entered using the recipe or nutri-
tional content information provided by the caterer. All
data was inputted by the same researcher to reduce data
processing variability [31].
Data presentation and statistical analysis
Physical characteristics and mean nutrient intakes were
compared between sexes using an independent samples
t-test. Prior to this, dietary intake data was tested for
normality using a Shapiro-Wilks test (IBM SPSS v24).
Where data showed a significant deviation from a nor-
mal distribution, a non-parametric equivalent (Mann
Whitney U test) was used. Cohens d effects (small = 0.2,
medium = 0.5, large = 0.8) were calculated for differences
in nutrient intakes between men and women. Following
an appropriate Bonferroni adjustment, an alpha level of
p< 0.001 was set.
Physical characteristics
There was a statistically significant difference between
sexes in stature (t [22]= 6.521, p= < 0.001) and body
mass (t [32]= 3.920, p= < 0.001) but not age (Z =
1.126, p= .260) or BMI (t [32]= 1.224, p= 0.228).
Energy intake
There was a statistically significant difference between
sexes with men consuming more than women (t [32]=
3.508, p= 0.001, ES = 1.10). Both men and women con-
sumed less than the MDRVs, with men consuming 69%
and women consuming 72% of the recommended energy
intake (Table 2). When data was expressed as relative to
body there was no differences in energy intake between
sexes (t [32]=1.396, p= 0.170, ES = 0.46) (Table 2).
Macronutrient intake
Compared to the MDRVs, men and women under con-
sumed CHO and protein with men consuming a greater
absolute total daily amount of CHO than women (Z = -
Chapman et al. Journal of the International Society of Sports Nutrition (2019) 16:59 Page 3 of 9
3.708, p< 0.001, ES = 1.27). Men also consumed a greater
total daily amount of protein than women (Z = -3.708, p <
0.001, ES = 1.28). Total fat intake was not different between
sexes t [32]=1.113, p= 0.272, ES = 0.37) but under con-
sumed by men. Men consumed a greater amount of fibre
than women (t [32]=2.422, p= 0.020, ES = 1.16) (Table 1).
When data was expressed relative to body mass there was
no difference between sexes for CHO (t [32]=2.333, p=
0.025, ES = 0.74), protein (t [32]=2.241, p=0.030, ES=
0.67), fat (t [32]= 0.708, p= 0.483, ES = 0.00) or fibre in-
take (t [32]=0.840, p= 0.406, ES = 0.00) (Table 2).
Micronutrient intake
When compared to men, women consumed less calcium
(t [32]= 3.645, p= 0.001, ES = 1.06),iron (t [32]=4.262, p<
0.001, 1.18), sodium (t [32]=2.700, p= 0.010, ES = 0.77),
vitamin B
(Z = -3.123,p= 0.002, ES = 0.91), vitamin B
(Z = -3.477,p= 0.001, ES = 1.11), potassium (Z = -2.537,
p= 0.011, ES =0.86), niacin (Z = -4.062, p<0.001,ES=
1.42), iodine (Z = -2.733, p= 0.006, ES = 0.91), thiamine
(Z = -2.355, p= 0.010), riboflavin (Z = -3.576, p<0.001,
ES = 0.97), phosphorus (Z = -2.976, p= 0.003, ES = 0.97)
and folate (Z = -3.391, p= 0.001, ES = 1.17). Men and
women consumed less than the RDA for copper, magne-
sium and vitamin D with women consuming significantly
less magnesium (Z = -2.464, p= 0.014, ES = 0.84) and vita-
min D (Z = -2.257, p= 0.024, ES = 1.00) but not copper (t
[32]=1.035, p= 0.306, ES = 0.47). Women consumed an
inadequate amount of vitamin A when compared to the
RDA and this was significantly less than men (Z = -2.562,
p= 0.010, ES = 0.84). Both men and women consumed ad-
equate amounts of vitamin C when compared to the RDA
with no differences between sexes (Z = -1.049, p=0.294,
ES = 0.45). When micronutrient data was expressed rela-
tive to body mass there was no difference for iron (t [32]=
2.468, p= 0.18, ES = 0.75), calcium (t [32]=2.28, p=0.027,
ES = 0.71), magnesium (t [32]=1.513, p= 0.138, ES = 0.46),
vitamin A (t [32]=1.808, p= 0.078, ES = 0.58), vitamin C (t
Table 1 Absolute nutrient intake for participants compared to MDRVs and RDA
Nutrient All Men MDRV Women MDRV
Energy (kcal·day
) 2439 ± 653 2846 ± 573* 4100.0 2207 ± 585* 3100.0
CHO (g·day
) 283 ± 98 352 ± 92* 513615 243 ± 79* 388465
PRO (g·day
) 94 ± 27 114 ± 29 123154 83 ± 18 93116
Fat (g·day
) 103 ± 25 109 ± 21 128159 100 ± 27 96121
Fibre (g·day
) 20±6 25 30 18±1 30
Calcium (mg·d
) 837.0 ± 383.0 1078.0 ± 418.0* 700.0 699.0 ± 287.0* 700.0
Copper (mg·d
) 0.9 ± 0.3 1.0 ± 0.0 1.2 0.9 ± 0.3 1.2
Folate (μg·d
) 173.0 ± 84.0 231.0 ±95.0* 200.0 140.0 ± 55.0* 200.0
Iodine (μ·d
) 99.0 ± 64.0 135.0 ± 79.0 140.0 77.0 ± 44.0 140.0
Iron (mg·d
) 8.7 ± 3.0 10.0 ± 3.0* 8.7 7.0 ± 2.0* 14.8
Magnesium (mg·d
) 198.0 ± 77.0 239.0 ± 94.0 300.0 174.0 ± 55.0 270.0
Niacin (mg·d
) 14.8 ± 6.3 19.9 ± 7.3* 16.5 12.0 ± 3.0* 13.2
Phosphorus (mg·d
) 997.0 ± 382.0 1227.0 ± 461.0 550.0 865.0 ± 254.0 550.0
Potassium (mg·d
) 2386.0 ± 877.0 2859.0 ± 1051.0 3500.0 2115.0 ± 634.0 3500.0
Riboflavin (mg·d
) 1.1 ± 0.7 1.6 ± 0.8* 1.3 0.8 ± 0.4* 1.1
Selenium (μg·d
) 39.0 ± 21.0 57.0 ± 25.0 75.0 29.0 ± 11.0 60.0
Sodium (g·d
) 2.7 ± 0.7 3.0. ± 0.6 2.4 2.5 ± 0.7 2.4
Thiamin (mg·d
) 1.3 ± 0.5 1.5 ± 0.5 1.0 1.1 ± 0.3 0.8
Vitamin A (μg·d
) 634.0 ± 410.0 840.0 ± 388.0 700.0 516.0 ± 380.0 600.0
Vitamin B
) 4.3 ± 2.6 6.0 ± 3.2* 1.5 3.3 ± 1.3* 1.5
Vitamin B
) 1.5 ± 0.9 2.0 ± 1.2 1.4 1.2 ± 0.3 1.2
Vitamin C (mg·d
) 55.0 ± 38.0 67.0 ± 49.0 40.0 49.0 ± 29.0 40.0
Vitamin D (μg·d
) 2.0 ± 1.0 2.0 ±1.0 10.0 1.0 ± 1.0 10.0
Zinc (mg·d
) 7.1 ± 2.5 8.0 ± 3.0 9.5 6.0 ± 1.0 7.0
Energy, macronutrient and micronutrient intake of all participants and with data grouped according sex to establish differences in intakes. Intakes for each sex
were then compared to recommendations. The recommended MDRV for CHO, protein and fat towards total energy intake is 50-60%, 12-15% and 28-35%,
respectively. These values were used to calculate the absolute amount of CHO, protein and fat needed to achieve the required energy intake in men (4100
) and women (3100 kcal·day
). EI Energy intake , MDRV Military Dietary Reference Value , CHO Carbohydrate , grams·body mass
) and micrograms·day
). *indicates a statistically significant differecnce between sexes
Chapman et al. Journal of the International Society of Sports Nutrition (2019) 16:59 Page 4 of 9
[32]=0.289, p= 483, ES = 0.21), vitamin B
(t [42] = 3.043,
p= 0.004, ES = 0.95), phosphorus (t [32]=1.913, p=0.063,
ES = 0.58), potassium (t [32]=1.584, p= 0.121, ES = 0.48),
selenium (t [19.791] = 3.351, p= 0.003, ES = 1.11), sodium
(t [32]=0.733, p= 0.468, ES = 0.00), zinc (t [32]=0.2130,
p= 0.039, ES = 0.57), iodine (t [32]=2.228, p=0.031, ES=
0.67), niacin (t [20.989] = 3.249, p= 0.004, ES = 1.10), fol-
ate (t [32]=2.756, p= 0.009, ES = 0.70), vitamin D (Z =
1.786, 0.074, ES = 0.00), vitamin B
(Z = -1.837, p=0.066,
ES = 0.63), copper (Z = -0.266, p= 0.790, ES = -0.45),
thiamine (Z = -1.102, p= 0.271, ES = 0.00) or riboflavin (Z
=2.807, p= 0.005, ES = 0.57) (Table 2).
The aim of this study was to quantify daily energy, macro
and micronutrient intake of British Army recruits in Phase
One training and to compare intakes between men and
women. Our primary finding was that men and women
under consumed daily energy intake by ~ 1200 and ~ 800
, respectively when compared to MDRVs. The
MDRVs are based on measurements of daily energy ex-
penditures via the doubly labelled water method in a simi-
lar cohort within this population whilst undertaking the
same programme in British Army Phase One training
[18]. The reported underconsumption of daily energy in-
take in this population observed in this study is typical of
military populations and values estimated here are similar
to other research [21,23,2527]. The observed under
consumption of total calories in this study, meant that re-
cruits did not meet MDRV and RDAs for specific macro
and micronutrients. Furthermore, due to a lower daily en-
ergy intake of women compared to men, and higher RDA
for some micronutrients (i.e. iron), women are at greater
risk of inadequate intakes when compared to guidelines
and need to increase habitual iron intake by ~ 53% to
meet the RDA of 14.8 mg·d
(Table 1).
equate when compared to MDRVs (Table 1)andthismay
increase the incidence of reduced energy availability [33]
which, in turn, may in increase the risk of injury [5,14].
Table 2 Relative daily nutrient intakes for participants compared to MDRVs/RDA and Sport Nutrition guidelines
Nutrient All Men MDRV Women MDRV
Energy (kcal·kg
) 35.7 ± 9.5 38.3 ± 7.3 55.0 34.2 ± 10.3 48.0
CHO (kcal·kg
) 4.1 ± 1.4 4.8 ± 1.3 6.08.0 3.8 ± 1.4 6.07.0
PRO (kcal·kg
) 1.4 ± 0.4 1.5 ± 0.3 1.62.0 1.3 ± 0.3 1.41.8
Fat (kcal·kg
) 1.5 ± 0.4 1.5 ± 0.2 1.72.1 1.5 ± 0.5 1.51.9
Fibre (kcal·kg
) 0.3 ± 0.1 0.3 ± 0.1 0.4 0.3 ± 0.1 0.5
Calcium (mg·kg
) 12.17 ± 5.18 14.43 ± 5.21 9.38 10.88 ± 4.78 10.80
Copper (mg· kg
) 0.01 ± 0.01 0.01 ± 0.01 0.02 0.02 ± 0.01 0.02
Folate (μg· kg
) 2.50 ± 1.12 3.08 ± 1.19 2.68 2.18 ± 0.95 3.08
Iodine (μg· kg
) 1.44 ± 0.91 1.83 ± 1.06 1.88 1.22 ± 0.74 2.15
Iron (mg· kg
) 0.12 ± 0.04 0.15 ± 0.04 0.12 0.12 ± 0.04 0.23
Magnesium (mg·kg
) 2.90 ± 1.07 3.22 ± 1.21 4.02 2.72 ± 0.96 4.15
Niacin (mg· kg
) 0.41 ± 0.15 0.51 ± 0.17 0.22 0.36 ± 0.09 0.20
Phosphorus (mg·kg
) 14.54 ± 5.18 16.46 ± 5.89 7.37 13.45 ± 4.48 8.46
Potassium (mg· kg
) 34.74 ± 11.86 38.42 ± 13.70 46.91 32.63 ± 10.35 53.85
Riboflavin (mg· kg
) 0.02 ± 0.01 0.02 ± 0.01 0.02 0.01 ± 0.01 0.02
Selenium (μg· kg
) 0.57 ± 0.29 0.77 ± 0.35 1.00 0.46 ± 0.18 0.92
Sodium (g· kg
) 0.04 ± 0.01 0.04 ± 0.01 0.03 0.04 ± 0.01 0.04
Thiamin (mg· kg
) 0.02 ± 0.01 0.02 ± 0.01 0.01 0.02 ± 0.01 0.01
Vitamin A (μg· kg
) 9.25 ± 5.94 11.34 ± 5.12 9.38 8.05 ± 6.13 9.23
Vitamin B
) 0.06 ± 0.04 0.08 ± 0.04 0.02 0.05 ± 0.02 0.02
Vitamin B
(mg· kg
) 0.02 ± 0.01 0.03 ± 0.02 0.02 0.02 ± 0.01 0.02
Vitamin C (mg·kg
) 0.81 ± 0.54 0.89 ± 0.62 0.54 0.77 ± 0.49 0.62
Vitamin D (μg· kg
) 0.03 ± 0.02 0.03 ± 0.02 0.13 0.03 ± 0.02 0.15
Zinc (mg· kg
) 0.10 ± 0.03 0.12 ± 0.04 0.13 0.10 ± 0.03 0.11
Daily nutrient intakes of all participants with data separated for sex to establish relative differences. Data was compared to recommendations. Military dietary
reference values (MDRVs) were used for energy, macro and micronutrient intake recommendations. Recommended relative intakes were calculated by dividing
the recommended absolute intake by the average body mass for each sex. Data presented as mean ± standard deviations. No statistically significant differences
between sexes were observed.
Chapman et al. Journal of the International Society of Sports Nutrition (2019) 16:59 Page 5 of 9
Reduced chronic energy availability may lead to impaired
physiological functions such as metabolic rate, protein syn-
thesis, bone health, menstrual function and cardiovascular
health [33]. Musculoskeletal injury risk (MSKi) may be in-
creased during periods of reduced energy availability with
concomitant reductions in skeletal muscle mass are ob-
served due to reduced protein turnover [34,35]Further-
more, skeletal muscle response to the training stimulus
maybe downregulated during periods of reduced energy
availability. For example, a daily energy surplus of ~ 358
478 kcal·d
is recommended to maximise muscle hyper-
trophy with resistance training [36]. Energy restriction has
been shown to downregulate mTOR signalling activity and
this is likely due to the inhibited protein translation and
subsequently lower phosphorylation of protein kinase B
(AKt), the mammalian target of rapamycin (mTOR), ribo-
somal protein S6 kinase (P70S6K) and ribosomal protein
S6 (rps6) [37]. An energy deficit of ~ 40% upregulates
mRNA of the skeletal muscle ubiquitin proteasome system
(UPS) which regulates skeletal muscle proteolysis [38]. Our
data demonstrates men and women consumed adequate
energy to prevent an estimated deficit vs. the MDRVs of
40% and consumed ~ 31% and ~ 29% less than the
MDRVs, respectively, which may still be considered as a
considerable energy deficit. In relation to bone health, re-
duced energy availability reduces calcium absorption,
bone turnover and bone mineral density [5], and thus,
increases stress fracture risk [39] with women appear-
ing to be more affected than men [40]. Furthermore, a
reduced energy availability will increase the risk of in-
adequate supply of macro and micronutrients, which
will likely impair physical performance and increase the
risk of injury further [6].
Men and women both consumed less than the mini-
mum recommended intake for CHO compared to
MDRVs (Table 1-2). These results are similar to intakes
of U.S. Army personnel, which found ~ 70% of personnel
consumed less than 6 g·kg
carbohydrate [27].
Given that participants undergoing Phase One training
have energy expenditures between ~ 3000 to ~ 4000
[1] which is comparable to athletes in team
sports [41] it may be appropriate to aim for similar
CHO intakes per day (57 g·kg
)[42]. As such,
British Army recruits may not be maintaining muscle
glycogen stores to support training. Lower intakes of
CHO during intensified training periods have been
shown to reduce exercise performance and mood state
in athletes [4] and contribute to immunosuppression
[32]. Sub-optimal intakes of CHO during hard training
periods in athletes, increases concentrations of cortisol
whilst attenuating the secretion of immunoglobin-A
(SlgA), and thus, increases the risk of contracting an
upper respiratory tract infection [32,43]. Taken to-
gether, CHO intakes below recommended intakes whilst
undergoing military training may result in missed train-
ing days and possibly failure to complete training due to
increased illness and injury risk. Future research should
assess the effects of additional CHO intake on training
outcomes, illness and injury incidence. Furthermore, re-
search investigating the impact of nutrient timing in this
population is also warranted given the influence this
may have on recovery, tissue repair, muscle protein syn-
thesis and psychological mood [44]. It has been shown
that British Army officer cadets may under consume
suboptimal levels of CHO and protein between meal-
times [45] but data in the recruit population is currently
Protein intakes in men and women were less than the
MDRVs but were in-line with sport nutrition guidelines
(1.22.0 g·kg
)[12] although women did have a
lower relative intake than men (Table 2). To date, how-
ever, specific protein intakes are not recommended for
British Army recruits. Intakes in the range of 1.22.0
are recommended in athletes to support
metabolic adaptation, repair, remodelling, and for pro-
tein turnover [12]. Despite both sexes meeting this range
in this study, it should be noted that intakes were at the
lower end of this, and that true protein requirements
may be at the upper limit of this range to meet training
demands (1.52.0 g·kg
). In fact, evidence now sug-
gests endurance athletes require more than the original
recommended intake of 1.21.4 g·kg
and instead
should consume 1.61.8 g·kg
on intense training
days [46]. Given the arduous nature of military training
and that military type exercise (i.e. load carriage) stimu-
lates muscle protein synthesis more than endurance type
exercise (i.e. running) [47], military personnel may re-
quire a daily protein intake of 1.5 g·kg
[8]. Further-
more, intakes of > 2.0 g·kg
during energy restriction
may be needed to maximise the loss of fat-mass whilst
also maintaining lean-tissue mass [13]. A protein intake
higher than that observed in the current study has been
shown to have physiological and performance benefits
[4850]. A protein intake of 3.0 g·kg·
resulted in a
30% possibility that the decrement in time trial perform-
ance pre-and-post the intervention was attenuated vs. a
moderate protein intake (1.5 g·kg
)[49]. U.S. Marines
who were supplemented daily with protein (12 g protein,
9.6 g CHO, 3.6 g fat) for 54-days had 14% fewer visits to the
medical centre compared to the placebo group (0 g protein,
9.6 g CHO, 3.6 g fat) and 40% less visits to the medical
centre compared to the control group [48]. More recently,
U.S. Army soldiers participating in Initial Entry Training
who supplemented daily with whey protein (77 g, 580 kcal)
had a greater reduction of fat-mass (4.5 kg, Cohensd=
0.67 vs. -2.7 kg, Cohensd=0.40) compared to a group
who supplemented daily with CHO (127 g, 580 kcal). The
total daily protein intake was 2.8 g·kg
in the protein
Chapman et al. Journal of the International Society of Sports Nutrition (2019) 16:59 Page 6 of 9
group, which is far greater than both men and women in
the current study (Table 2)[50]. An increased protein in-
take > 1.5 g·kg
may also have psychological benefits.
Endurance trained cyclists undergoing three weeks of high-
intensity training had a 97% chance that a higher protein
intake (3 g·kg
) attenuated increased symptoms of
stress compared to a moderate protein intake (1.5 g·kg
) when participants were weight stable and when CHO in-
take was matched between conditions (6 g·kg
This provides the rationale that protein intake should
be considered in relation to other functions other
than muscle protein synthesis and that a daily protein
intake > 1.5 g·kg
may provide psychological benefits
to individuals undergoing intense training (i.e. military
training). Given the apparent benefits on increasing
dietary protein to > 2.0 g·kg
in periods of ardu-
ous training, it should be investigated if an additional
protein intake to that of habitual intakes in British
Army recruits in Phase One training influences train-
ing adaptions and training outcomes.
The total micronutrient intake data for the cohort
showed that there was an inadequate intake of magne-
sium, vitamin D, potassium, selenium, copper, iodine
and folate (Table 1-2). Similarly, data collected in men
and women during Basic Combat Training in the U.S.
Army showed an inadequate intake of vitamin D, mag-
nesium and potassium with women under consuming
calcium and iron [10]. Given the reported intake of
calcium (699 ± 287 mg·d
) and iron (7 ± 2 mg·d
women in this study, the risk of an inadequate intake of
these micronutrients in this population is highlighted.
Previously, it has been observed that training increase
bone mineral content (BMC) and bone mineral density
(BMD) of the arms, legs and pelvis in men and women
undergoing the same training course at ATC(P). Con-
versely, it was observed training reduced BMC for the
trunk and ribs and BMD for the ribs in both men and
women (unpublished observations). These changes in
BMD and BMC may be explained by habitual calcium
intakes (837 ± 383 mg·d
) with some consuming less
than the RDA as shown by the reported standard devi-
ation. Furthermore, it has previously been reported that
only 9% of men and 36% of women entering Phase one
training are vitamin D sufficient [51]. Given the inad-
equate intake of vitamin D and calcium, it should be in-
vestigated if increasing the intake of these micronutrients
benefits training outcomes. For instance, female U.S. Navy
recruits undergoing basic training who supplemented
daily with 2000mg calcium and 800IU vitamin D had a
21% reduction in stress fracture incidence compared to a
control group [52]. It is unknown, however, if the reduc-
tion was due to an increased calcium or vitamin D intake.
The low habitual intake of iron in women compared to
the RDA (Table 1-2) is comparable to that of their U.S.
Army counterparts [10]. British Army training appears to
have a deleterious effect on iron status with ferritin and
haemoglobin decreasing significantly pre and post Phase
One training in men and women. Ferritin has been shown
to reduce from 105.1 to 78.7 μg·L
in men and from 52.7
to 47.7 μg·L
in women. Haemoglobin has been shown
to reduce from 149.7 to 147.1 g·dL
in men and from
139.2 to 132.1 g·dL
in women in 14 weeks of training.
These changes in iron status contributed to a 6.9 and 2.3%
development of anaemia in women and men, respectively
[53]. As such, research investigating iron requirements
and the potential benefits of iron supplementation in
British Army recruits undergoing Phase One training may
be warranted. It is possible that recruits may require 70%
more than the RDA [12]. For example, similar to athletes,
British Army recruits who engage in regular exercise in-
crease hepcidin levels which then inhibits iron absorption
and contributes to a decrease in iron status [54]. There-
fore an intervention may be to increase dietary iron intake
particularly during periods not in close proximity to exer-
cise to promote iron absorption and thus iron status [12].
One training is inadequate when compared to MDRVs.
When considered to MDRVs, men and women both under
consume CHO and protein and therefore interventions to
combat this should be considered. Given this and the po-
tential benefits of increasing protein intakes above 1.5
in military populations, future research investi-
gating this should be explored. Furthermore, research aim-
ing to better understand habitual protein requirements
may be warranted. Given the low vitamin D intakes in both
sexes and low iron and calcium intakes in women, research
investigating the effects of micronutrient supplementation
on training outcomes is needed. Finally, research which in-
vestigates changes in habitual dietary intake during Phase
timing of daily energy and macronutrients intakes due to
the potential effects on training adaptations and the impli-
cations of nutritional based interventions.
Akt: Protein kinase B; ATC(P): Army training centre pirbright; BMC: Bone
mineral content; BMD: Bone mineral density; CHO: Carbohydrate; EE: Energy
expenditure; EI: Energy intake; Kcal: Kilocalorie; LBM: Lean body mass;
MD: Medical discharge; MDRV: Military dietary reference values;
MODREC: Ministry of defence research ethics committee; MRNA: Messenger
RNA; MSKi: Musculoskeletal injury risk; mTOR: Mammalian target of
rapamycin; P70S6K: Ribosomal protein S6 kinase; RDA: Recommended daily
allowance; rps6: Ribosomal protein S6; SACN: Scientific advisory committee
on nutrition; SD: Standard deviation; SIgA: Secretory immunoglobulin A;
U.K.: United Kingdom; U.S.: United States
The authors would like to acknowledge Miss Louise Corfield, Miss Bethan
Moriarty, Mr. Luke Davies and Mr. Alfie Gordon for their assistance with
Chapman et al. Journal of the International Society of Sports Nutrition (2019) 16:59 Page 7 of 9
participant recruitment and data collection. As well as the training staff and
recruits who volunteered to take part.
SC and RI designed the study. SC and AR recruited participants and
conducted data collection. SC and AR undertook analysis of all data. SC, JR
and LS interpreted the data. SC wrote the paper. All authors reviewed and
approved the final manuscript.
This study was funding by the Army Recruiting and Initial Training
Command, U.K. Ministry of Defence.
Availability of data and materials
Datasets used and/or analysed during the study are available from the
corresponding author in reasonable request.
Ethics approval and consent to participate
This study was conducted in accordance with the declaration of Helsinki and
was approved by the United Kingdom Ministry of Defence Ethics Committee
(843/MODREC/18). Written informed consent was provided by all individual
participants in this study.
Consent for publication
Not applicable
Competing interests
There are no competing interests from the authors.
Received: 30 August 2019 Accepted: 26 November 2019
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Chapman et al. Journal of the International Society of Sports Nutrition (2019) 16:59 Page 9 of 9
... Based on a typical body mass in this population for men (74.6 kg), this corresponds to a relative intake of 1.6-2.0 g·kg −1 ·d −1 [18]. To date, no study has assessed protein requirements in British Army recruits undergoing BT to determine if nutritional interventions are required to optimise dietary patterns, particularly protein intake, that may improve training adaptations. ...
... The aims of this study were: (i) compare habitual dietary intake to recommendations and to determine the change in energy and macronutrient intake in male British Army infantry recruits undergoing BT; (ii) measure urinary nitrogen balance to estimate habitual protein requirements during BT. It was hypothesised that participants would not meet nutrient recommendations and that energy and macronutrient intake would not significantly change during BT as military populations undergoing training typically do not meet dietary recommendations [18,30]. It was also hypothesised that participants would not be in nitrogen balance during BT based on previously recorded daily protein intakes in this population [18]. ...
... It was hypothesised that participants would not meet nutrient recommendations and that energy and macronutrient intake would not significantly change during BT as military populations undergoing training typically do not meet dietary recommendations [18,30]. It was also hypothesised that participants would not be in nitrogen balance during BT based on previously recorded daily protein intakes in this population [18]. ...
Full-text available
We assessed dietary intake and nitrogen balance during 14 weeks of Basic Training (BT) in British Army Infantry recruits. Nineteen men (mean ± SD: age 19.9 ± 2.6 years, height: 175.7 ± 6.5 cm, body mass 80.3 ± 10.1 kg) at the Infantry Training Centre, Catterick (ITC(C)) volunteered. Nutrient intakes and 24-h urinary nitrogen balance were assessed in weeks 2, 6 and 11 of BT. Nutrient intake was assessed using researcher-led weighed food records and food diaries, and Nutritics professional dietary software. Data were compared between weeks using a repeated-measures analysis of variance (ANOVA) with statistical significance set at p ≤ 0.05. There was a significant difference in protein intake (g) between weeks 2 and 11 of BT (115 ± 18 vs. 91 ± 20 g, p = 0.02, ES = 1.26). There was no significant difference in mean absolute daily energy (p = 0.44), fat (p = 0.79) or carbohydrate (CHO) intake (p = 0.06) between weeks. Nitrogen balance was maintained in weeks 2, 6 and 11, but declined throughout BT (2: 4.6 ± 4.1 g, 6: 1.6 ± 4.5 g, 11: −0.2 ± 5.5 g, p = 0.07). A protein intake of 1.5 g·kg −1 ·d −1 may be sufficient in the early stages of BT, but higher intakes may be individually needed later on in BT.
... 2 3 Furthermore, when considering specific macronutrient intakes, British Army recruits generally consume diets containing excessive fat, alongside insufficient consumption of fruit, vegetables and whole grains, in comparison with reference values. 5 This issue is problematic given that inadequate nutrition negatively affects multiple body systems, influencing overall health (eg, mood state, immunity, bone strength) and physical performance. 5 6 Therefore, to achieve, maintain and retain a healthy, effective and operationally deployable military workforce, a healthy diet containing adequate macronutrient and micronutrient intake is a fundamental requirement. ...
... Data collection occurred as part of a wider study designed to investigate sex differences in dietary intake in British Army phase 1 recruits undergoing phase 1 BT. 5 For analysis of nutritional knowledge, a conservative power calculation was conducted using Gpower (V., Germany), which determined a minimum sample size of 14 per group using a medium effect size, α=0.05 and β=0.80. Prior to formal statistical analysis, data were assessed for normality. ...
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Background: Appropriate nutritional intake is essential to optimise both general health and performance in military recruits. General nutritional knowledge is a significant and modifiable determinant of dietary behaviour; however, the level of nutritional knowledge in British Army recruits undertaking basic training is poorly understood. Methods: The Nutritional Knowledge Questionnaire for Athletes was completed by 29 male (age: 22.3±3.8 years) and 26 female (age: 22.0±3.0 years) standard-entry recruits at the end of basic training, and 15 male (age: 20.7±3.2 years) infantry recruits both at the start and end of basic training for the British Army. Between-group and within-group differences in total and subcomponent (ie, carbohydrate, protein, fat, vitamins and minerals, general nutrition, fluid intake, and sporting performance) scores were analysed. Results: Standard-entry male recruits had more correct answers (52%) than standard-entry female recruits (38%) and male infantry recruits (40%) at the end of training. Infantry recruits had similar levels of nutritional knowledge at the start (39% correct) and end (40% correct) of training. Nutritional knowledge related to protein (range: 53%-75% correct answers) and vitamins and minerals (range: 42%-63% correct answers) were the two highest scoring subcomponents within each group. Conclusion: British Army recruits, in particular standard-entry female and infantry recruits, have poor nutritional knowledge, which did not improve throughout basic training. Better nutritional intervention, especially surrounding carbohydrate and fluid education, is required during British Army basic training to optimise career-long dietary behaviour.
... Por consiguiente, el nutriólogo deportivo es parte fundamental del equipo multidisciplinario que interviene en la estructura del macrociclo de entrenamiento al tener que periodizar la ICD a las cargas de entrenamiento y composición corporal de cada deportista (14) evitando factores adversos que limiten el desempeño físico (9,15). Para esto, es importante qué, al inicio, durante y al fi nal de la preparación física, todos los deportistas reciban evaluaciones exhaustivas por un equipo multidisciplinario que permitan la predicción del desempeño físico (16,17) a través de estudios antropométricos, bioquímicos, clínicos, dietéticos, psicológicos y fi siológicos (3,16,18). Además, con la evaluación de la aptitud física se podrá estimar el máximo consumo de oxígeno (VO 2 máx) que permitirá conocer las unidades metabólicas (MET), gasto calórico y metabolitos generados según la intensidad de entrenamiento (12,19). Asimismo, evitar un défi cit nutrimental o calórico que son perjudiciales para el rendimiento físico al afectar la salud ósea, función inmunológica, estado de ánimo y cognición del deportista (18). ...
... Además, con la evaluación de la aptitud física se podrá estimar el máximo consumo de oxígeno (VO 2 máx) que permitirá conocer las unidades metabólicas (MET), gasto calórico y metabolitos generados según la intensidad de entrenamiento (12,19). Asimismo, evitar un défi cit nutrimental o calórico que son perjudiciales para el rendimiento físico al afectar la salud ósea, función inmunológica, estado de ánimo y cognición del deportista (18). ...
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Antecedentes: el propósito del presente estudio fue comparar la ingesta nutrimental, masa grasa y VO2máx entre boxeadores amateur y profesionales al inicio de temporada, así como el requerimiento y consumo nutrimental intra e inter grupos y el porcentaje de adecuación nutrimental intergrupo. Métodos: se realizó un estudio de cohorte transversal y no experimental con 41 boxeadores del sexo masculino (26 profesionales y 15 amateurs; M=20.29±3.29 años). La muestra fue seleccionada por conveniencia y se estratificó por maestría deportiva. Se aplicaron pruebas t de Student para comparar las variables inter e intra grupos y significancia de p≤0.05. Resultados: se observó mayor necesidad energética en boxeadores profesionales, aunque deficiente en ambos grupos respecto a la ingesta calórica diaria (p<0.05) principalmente por el consumo de carbohidratos (5.68±1.72gr/kg/peso corporal; amateurs y 5.63±2.1872gr/kg/peso corporal; profesionales). Ambos grupos presentaron desequilibrio en la ingesta de micronutrimentos, principalmente en hierro, sodio, zinc, ácido ascórbico, tocoferol y retinol. Conclusiones: existió deficiente ingesta calórica diaria en ambos grupos de boxeadores con desequilibrio de micronutrimentos intra e intergrupo los cuales pudieran afectar negativamente el rendimiento físico de los boxeadores en alguna etapa de entrenamiento.
... Whether sex differences in the hepcidin response to physically demanding activity exist and contribute to sex differences in iron homeostasis is unknown. However, compared to males, poor iron status is more prevalent in female recruits entering IMT, iron intakes below recommended levels are more common in females during IMT, and declines in iron status during IMT may be greater in females (Chapman et al., 2019;Lutz et al., 2018;Yanovich et al., 2015). Notably, poor iron status is associated with impaired aerobic performance in female recruits (McClung et al., 2009;Martin et al., 2019), and iron supplementation (100 mg/d ferrous sulfate) during IMT is effective in improving iron status and aerobic performance in female recruits with iron deficiency anaemia (McClung et al., 2009). ...
The importance of diet and nutrition to military readiness and performance has been recognized for centuries as dietary nutrients sustain health, protect against illness, and promote resilience, performance and recovery. Contemporary military nutrition research is increasingly inter-disciplinary with emphasis often placed on the broad topics of: 1) determining operational nutrition requirements in all environments, 2) characterizing nutritional practices of military personnel relative to the required (role/environment) standards, and 3) developing strategies for improving nutrient delivery and individual choices. This review discusses contemporary issues shared internationally by military nutrition research programs, and highlights emerging topics likely to influence future military nutrition research and policy. Contemporary issues include improving the diet quality of military personnel, optimizing operational rations, and increasing understanding of biological factors influencing nutrient requirements. Emerging areas include the burgeoning field of precision nutrition and its technological enablers.
... The primary goal of BT is to transform civilians into soldiers. As such, the BT programme is necessarily arduous, involving cyclic high impact loading activities and tasks such as up and downhill running, foot-drill, circuit training, strength training, and marching with external loads of up to 40 kg (Armstrong et al. 2019;Chapman et al. 2019). Similar cyclic high impact activities involving continuous locomotion and rapid changes in direction are associated with exerciseinduced breast pain in athletic populations, through excessive and repetitive movement in the vertical, medial, and lateral directions (Burbage and Cameron 2017;Mason, Page, and Fallon 1999;White, Scurr, and Smith 2009). ...
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Increasing retention of female recruits throughout Basic Training (BT) is a key priority for the British Army. The aims of this study were two-fold; (i) quantify breast health issues and sports bra usage within female British Army recruits, and (ii) assess the influence of professionally fitted sports bras on breast health and bra fit issues across 13 weeks of BT. A survey was completed by 246 female recruits that identified the incidence of breast health issues during BT. Subsequently, 33 female recruits were provided with professionally fitted sports bras during Week-1 of BT. Recruits completed a survey in Week-1 (Pre) and Week-13 (Post). There was a high incidence of bra issues during BT, which did not reduce following the implementation of professionally fitted sports bras. The authors recommend further research into the specific functional requirements of breast support relative to the demands of BT and the needs of the female recruit. Practitioner Summary: The British Army have a duty of care to ensure female recruits are equipped sufficiently for the demands of training. Despite the implementation of a sports bra fitting and issue service bra fit issues remained high. Further research into the specific functional requirements of breast support during training is recommended. Abbreviations: BT: Basic Training; ATR(W): Army Training Regiment Winchester; ATC(P): Army Training Centre Pirbright; BMI: Body Mass Index; NRS: Numeric Rating Scale; FET: Fisher's Exact Test
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Active members of the military must perform optimally under conditions of thermal stress and/or energy deficiency. Military dietary reference intakes (MDRIs) provide guidelines for energy and nutrient intakes but is based studies largely conducted in Army. Needs may vary by service branch and/or position. New protein recommendations have emerged, which are not reflected in MDRIs. Purpose of Review Compare reported dietary intake in active duty members to MDRIs and 2016 American College of Sports Medicine (ACSM) sports nutrition guidelines. Recent Findings Active duty members are not meeting their energy and carbohydrate needs with low-to-adequate protein intake and adequate-to-high fat intake. Other nutrients of concern are vitamin D, calcium, iron, B-vitamins, and fiber. Thermal stress increases energy needs and suppresses appetite and thus increase risk for energy and nutrition deficiencies. Summary Energy and nutrients needs can vary by branch of armed service, job responsibility, and external stressors.
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Military personnel experience energy deficit (total energy expenditure higher than energy intake), particularly during combat training and field exercises where exercising energy expenditures are high and energy intake is reduced. Low energy availability (energy intake minus exercising energy expenditure expressed relative to fat free mass) impairs endocrine function and bone health, as recognized in female athletes as the Female Athlete Triad syndrome. More recently, the Relative Energy Deficiency in Sport (RED-S) syndrome encompasses broader health outcomes, physical and cognitive performance, non-athletes, and men. This review summarizes the evidence for the effect of low energy availability and energy deficiency in military training and operations on health and performance outcomes. Energy availability is difficult to measure in free-living individuals but doubly labeled water studies demonstrate high total energy expenditures during military training; studies that have concurrently measured energy intake, or measured body composition changes with DXA, suggest severe and/or prolonged energy deficits. Military training in energy deficit disturbs endocrine and metabolic function, menstrual function, bone health, immune function, gastrointestinal health, iron status, mood, and physical and cognitive performance. There are more data for men than women, and little evidence on the chronic effects of repeated exposures to energy deficit. Military training impairs indices of health and performance, indicative of the Triad and RED-S, but the multi-stressor environment makes it difficult to isolate the independent effects of energy deficiency. Studies supplementing with energy to attenuate the energy deficit suggest an independent effect of energy deficiency in the disturbances to metabolic, endocrine and immune function, and physical performance, but randomized controlled trials are lacking.
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Introduction It is important to collate the literature that has assessed dietary intake within military settings to establish which methods are commonly used and which are valid so that accurate nutrition recommendations can be made. This scoping review aims to identify which methods are typically used to assess dietary intake in military settings and which of these have been validated. This review also aims to provide a recommendation as to which method(s) should be used in military settings. Methods This scoping review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. Searches were conducted in PubMed, Web of Science and SPORTDiscus with the most recent search executed on 12th June 2020. Eligible studies had to report original data, assess and quantify dietary intake and have been published in peer-reviewed academic journals. The reporting bias was calculated for each study where possible. Results Twenty-eight studies used a single method to assess dietary intake and seven studies used a combination of methods. The most commonly used methods were the gold standard food intake/waste method, Food Frequency Questionnaire (FFQ) or a food diary (FD). The only method to date that has been validated in military settings is weighed food records (WFR). Conclusions The food intake/waste method or WFR should be used where feasible. Where this is not practical the FFQ or FD should be considered with control measures applied. There is currently not sufficient evidence to state that using multiple methods together improves validity.
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Resistance training is commonly prescribed to enhance strength/power qualities and is achieved via improved neuromuscular recruitment, fiber type transition, and/ or skeletal muscle hypertrophy. The rate and amount of muscle hypertrophy associated with resistance training is influenced by a wide array of variables including the training program, plus training experience, gender, genetic predisposition, and nutritional status of the individual. Various dietary interventions have been proposed to influence muscle hypertrophy, including manipulation of protein intake, specific supplement prescription, and creation of an energy surplus. While recent research has provided significant insight into optimization of dietary protein intake and application of evidence based supplements, the specific energy surplus required to facilitate muscle hypertrophy is unknown. However, there is clear evidence of an anabolic stimulus possible from an energy surplus, even independent of resistance training. Common textbook recommendations are often based solely on the assumed energy stored within the tissue being assimilated. Unfortunately, such guidance likely fails to account for other energetically expensive processes associated with muscle hypertrophy, the acute metabolic adjustments that occur in response to an energy surplus, or individual nuances like training experience and energy status of the individual. Given the ambiguous nature of these calculations, it is not surprising to see broad ranging guidance on energy needs. These estimates have never been validated in a resistance training population to confirm the “sweet spot” for an energy surplus that facilitates optimal rates of muscle gain relative to fat mass. This review not only addresses the influence of an energy surplus on resistance training outcomes, but also explores other pertinent issues, including “how much should energy intake be increased,” “where should this extra energy come from,” and “when should this extra energy be consumed.” Several gaps in the literature are identified, with the hope this will stimulate further research interest in this area. Having a broader appreciation of these issues will assist practitioners in the establishment of dietary strategies that facilitate resistance training adaptations while also addressing other important nutrition related issues such as optimization of fuelling and recovery goals. Practical issues like the management of satiety when attempting to increase energy intake are also addressed.
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Selecting effective dietary strategies for professional football players requires comprehensive information on their energy expenditure (EE) and dietary intake. This observational study aimed to assess EE and dietary intake over a 14-day period in a representative group (n = 41) of professional football players playing in the Dutch Premier League (Eredivisie). Daily EE, as assessed by doubly labelled water, was 13.8 ± 1.5 MJ/day, representing a physical activity level (PAL) of 1.75 ± 0.13. Weighted mean energy intake (EI), as assessed by three face-to-face 24-h recalls, was 11.1 ± 2.9 MJ/day, indicating 18 ± 15% underreporting of EI. Daily EI was higher on match days (13.1 ± 4.1 MJ) compared with training (11.1 ± 3.4 MJ; P < 0.01) and rest days (10.5 ± 3.1 MJ; P < 0.001). Daily carbohydrate intake was significantly higher during match days (5.1 ± 1.7 g/kg body mass (BM)) compared with training (3.9 ± 1.5 g/kg BM; P < 0.001) and rest days (3.7 ± 1.4 g/kg BM; P < 0.001). Weighted mean protein intake was 1.7 ± 0.5 g/kg BM. Daytime distribution of protein intake was skewed, with lowest intakes at breakfast and highest at dinner. In conclusion, daily EE and PAL of professional football players are modest. Daily carbohydrate intake should be increased to maximize performance and recovery. Daily protein intake seems more than adequate, but could be distributed more evenly throughout the day.
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Purpose: To investigate the skeletal effects of the first all-female trans-Antarctic traverse. Methods: Six women (mean ± SD, age 32 ± 3 years, height 1.72 ± 0.07 m, body mass 72.8 ± 4.0 kg) hauled 80 kg sledges over 1700 km in 61 days from coast-to-coast across the Antarctic. Whole-body areal bone mineral density (aBMD) (dual-energy X-ray absorptiometry) and tibial volumetric BMD (vBMD), geometry, microarchitecture and estimated mechanical properties (high-resolution peripheral quantitative computed tomography) were assessed 39 days before (pre-expedition) and 15 days after the expedition (post-expedition). Serum and plasma markers of bone turnover were assessed pre-expedition, and 4 and 15 days after the expedition. Results: There were reductions in trunk (-2.6%), ribs (-5.0%) and spine (-3.4%) aBMD from pre- to post-expedition (all P ≤ 0.046); arms, legs, pelvis and total body aBMD were not different (all P ≥ 0.075). Tibial vBMD, geometry, microarchitecture and estimated mechanical properties at the metaphysis (4% site) and diaphysis (30% site) were not different between pre- and post-expedition (all P ≥ 0.082). Bone-specific alkaline phosphatase was higher 15 days post- than 4 days post-expedition (1.7 μg∙l-1, P = 0.028). Total 25(OH)D decreased from pre- to 4 days post-expedition (-36 nmol∙l-1, P = 0.008). Sclerostin, procollagen 1 N-terminal propeptide, C-telopeptide cross-links of type 1 collagen and adjusted calcium were unchanged (all P ≥ 0.154). Conclusion: A decline in aBMD of the axial skeleton may be due to indirect and direct effects of prolonged energy deficit. We propose that weight-bearing exercise was protective against the effects of energy deficit on tibial vBMD, geometry, microarchitecture and strength.
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Injuries are an inevitable consequence of athletic performance with most athletes sustaining one or more during their athletic careers. As many as one in 12 athletes incur an injury during international competitions, many of which result in time lost from training and competition. Injuries to skeletal muscle account for over 40% of all injuries, with the lower leg being the predominant site of injury. Other common injuries include fractures, especially stress fractures in athletes with low energy availability, and injuries to tendons and ligaments, especially those involved in high-impact sports, such as jumping. Given the high prevalence of injury, it is not surprising that there has been a great deal of interest in factors that may reduce the risk of injury, or decrease the recovery time if an injury should occur: One of the main variables explored is nutrition. This review investigates the evidence around various nutrition strategies, including macro- and micronutrients, as well as total energy intake, to reduce the risk of injury and improve recovery time, focusing upon injuries to skeletal muscle, bone, tendons, and ligaments.
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Background Adequate dietary intake is important for promoting adaptation and prevention of musculoskeletal injury in response to large volumes of physical training such as Army Initial Entry Training (IET). The purpose of this study was to evaluate training volume and dietary intake and estimate energy balance in Army IET soldiers. Methods Dietary intake was assessed by collecting diet logs for three meals on each of three, non-consecutive days during the first week of IET. Training volume was measured across 13 weeks of training using Actigraph wGT3X accelerometers. Training intensity was classified using Sasaki vector magnitude three cut points. Energy expenditure estimates were calculated during weeks two and three of training using the modified Harris-Benedict equation and by estimation of active energy expenditure using metabolic equivalents for each classification of physical activity. All data is presented as mean ± standard deviation. Results A total of 111 male soldiers (ht. = ± 173 ± 5.8 cm, age = 19 ± 2 years, mass = 71.6. ± 12.4 kg) completed diet logs and were monitored with Actigraphs. IET soldiers performed on average 273 ± 62 min low, 107 ± 42 min moderate, 26 ± 22 min vigorous, and 10 ± 21 min of very vigorous intensity physical activity daily across 13 weeks. The estimated total daily energy expenditure was on average 3238 ± 457 kcals/d during weeks two and three of IET. Compared to week one caloric intake, there was a caloric deficit of 595 ± 896 kcals/d on average during weeks two and three of IET. Regression analysis showed that body weight was a significant predictor for negative energy balance (adj. R2 = 0.54, p < 0.001), whereby a 1 kg increase in body mass was associated with a 53 kcal energy deficit. Conclusions Based on week one dietary assessment, IET soldiers did not consume adequate calories and nutrients to meet training needs during red phase (weeks one through three). This may directly affect soldier performance and injury frequency. IET soldiers undergo rigorous training, and these data may help direct future guidelines for adequate nourishment to optimize soldier health and performance. Electronic supplementary material The online version of this article (10.1186/s12970-018-0262-7) contains supplementary material, which is available to authorized users.
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We investigated the effects of whey protein (WP) supplementation on body composition and physical performance in soldiers participating in Army Initial Entry Training (IET). Sixty-nine, male United States Army soldiers volunteered for supplementation with either twice daily whey protein (WP, 77 g/day protein, ~580 kcal/day; n = 34, age = 19 ± 1 year, height = 173 ± 6 cm, weight = 73.4 ± 12.7 kg) or energy-matched carbohydrate (CHO) drinks (CHO, 127 g/day carbohydrate, ~580 kcal/day; n = 35, age = 19 ± 1 year, height = 173 ± 5 cm, weight = 72.3 ± 10.9 kg) for eight weeks during IET. Physical performance was evaluated using the Army Physical Fitness Test during weeks two and eight. Body composition was assessed using 7-site skinfold assessment during weeks one and nine. Post-testing push-up performance averaged 7 repetitions higher in the WP compared to the CHO group (F = 10.1, p < 0.001) when controlling for baseline. There was a significant decrease in fat mass at post-training (F = 4.63, p = 0.04), but no significant change in run performance (F = 3.50, p = 0.065) or fat-free mass (F = 0.70, p = 0.41). Effect sizes for fat-free mass gains were large for both the WP (Cohen’s d = 0.44) and CHO (Cohen’s d = 0.42) groups. WP had a large effect on fat mass (FM) loss (Cohen’s d = −0.67), while CHO had a medium effect (Cohen’s d = −0.40). Twice daily supplementation with WP improved push-up performance and potentiated reductions in fat mass during IET training in comparison to CHO supplementation.
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Background: Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words 'sport nutrition'. Consequently, staying current with the relevant literature is often difficult. Methods: This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches. Conclusions: This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.
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Purpose: To determine the relationship between vitamin D status and exercise performance in a large, prospective cohort study of young men and women across seasons (Study-1). Then, in a randomized, placebo-controlled trial, to investigate the effects on exercise performance of achieving vitamin D sufficiency (serum 25(OH)D ≥ 50 nmol·L) by a unique comparison of safe, simulated-sunlight and oral vitamin D3 supplementation in wintertime (Study-2). Methods: In Study-1, we determined 25(OH)D relationship with exercise performance in 967 military recruits. In Study-2, 137 men received either placebo, simulated-sunlight (1.3x standard erythemal dose in T-shirt and shorts, three-times-per-week for 4-weeks and then once-per-week for 8-weeks) or oral vitamin D3 (1,000 IU[BULLET OPERATOR]day for 4-weeks and then 400 IU[BULLET OPERATOR]day for 8-weeks). We measured serum 25(OH)D by LC-MS/MS and endurance, strength and power by 1.5-mile run, maximum-dynamic-lift and vertical jump, respectively. Results: In Study-1, only 9% of men and 36% of women were vitamin D sufficient during wintertime. After controlling for body composition, smoking and season, 25(OH)D was positively associated with endurance performance (P ≤ 0.01, [INCREMENT]R = 0.03-0.06, small f effect sizes): 1.5-mile run time was ~half-a-second faster for every 1 nmol·L increase in 25(OH)D. No significant effects on strength or power emerged (P > 0.05). In Study-2, safe simulated-sunlight and oral vitamin D3 supplementation were similarly effective in achieving vitamin D sufficiency in almost all (97%); however, this did not improve exercise performance (P > 0.05). Conclusion: Vitamin D status was associated with endurance performance but not strength or power in a prospective cohort study. Achieving vitamin D sufficiency via safe, simulated summer sunlight or oral vitamin D3 supplementation did not improve exercise performance in a randomized-controlled trial.
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Purpose: To compare training loads between men and women during 14-weeks of British Army standard entry basic training. Methods: Thirty-one male (mean ± SD, age 21 ± 4 years, height 1.78 ± 0.08 m, mass 77.1 ± 10.5 kg) and 28 female (age 22 ± 4 years, height 1.65 ± 0.05 m, mass 63.9 ± 8.9 kg) British Army recruits had external (distance) and internal (heart rate [HR], training impulse [TRIMP], ratings of perceived exertion [RPE]) training loads measured during weeks 1, 2, 6, 12 and 13 of basic training. Total energy expenditure (TEE) was measured during weeks 1-2 and 12-13. Results: Daily distance was higher for men than women (13,508 ± 666 vs 11,866 ± 491 m, respectively, P < 0.001). Average daily HR (29 ± 3 vs 30 ± 3% HR reserve) and RPE (4 ± 1 vs 4 ± 1) were not different between men and women, respectively (P ≥ 0.495). Daily TRIMP was higher for women than men (492 ± 130 vs 261 ± 145 au, respectively, P < 0.001). TEE was higher for men than women during weeks 1-2 (4020 ± 620 vs 2847 ± 323 kcal[BULLET OPERATOR]d, respectively) and 12-13 (4253 ± 556 vs 3390 ± 344 kcal[BULLET OPERATOR]d, respectively) (P < 0.001). Daily RPE, HR and TRIMP were related to daily distance (R = 0.18-0.57, P ≤ 0.037), and daily RPE was related to daily TRIMP and HR (R = 0.37-0.77, P ≤ 0.001). Conclusion: Sex differences in training loads could contribute to the greater injury risk for women during basic training. Daily RPE appears a practical option for measuring internal training load during military training.
The impact of iron deficiency is considerable when enhanced physical fitness is required. Female military recruits represent a unique population faced with intense physical and cognitive demands. Purpose: To examine the prevalence of iron deficiency and the impact of dietary habits among female recruits in the Israel Defense Forces (IDF). Methods: 348 recruits completed the study (188 female combatants, 58 male combatants, 92 non-combat females). Dietary intake was assessed using a Food Frequency Questionnaire (FFQ). Blood samples were collected for CBC, iron indices and vitamin B12. The common definitions for anemia and iron store deficiency were used as follows: Hemoglobin (Hgb) < 12gr/dl for females and <14gr/dl for males; Serum ferritin < 12 mg/dl. Results: The prevalence of iron deficiency and iron deficiency anemia was 29.8% and 12.8%, respectively, among female combatants. Similar data were found among non-combat females (27.2% and 17.4% respectively) as compared to 5.2% and 0%, among males. No significant difference in iron or total calorie intake was detected between subjects with iron deficiency (with or without anemia) when compared to subjects with normal iron status in the same study group. Plant sources constituted 85% of dietary iron source for females, in comparison to 73% for males. Conclusions: A high prevalence of iron deficiency was found among female recruits. Coupled with the iron loss during menstruation, inadequate iron intake may have a permissive role for iron deficiency in female recruits, and is an important issue facing females in the military.