J Appl Physiol 107: 1864–1873, 2009.
First published October 22, 2009; doi:10.1152/japplphysiol.00392.2009.
Effects of resistance exercise and fortified milk on skeletal muscle mass,
muscle size, and functional performance in middle-aged and older men:
an 18-mo randomized controlled trial
Sonja Kukuljan,1 Caryl A. Nowson,1 Kerrie Sanders,2 and Robin M. Daly1,3
1
Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University,
Melbourne; 2Department of Clinical and Biomedical Sciences: Barwon Health, The University of Melbourne, Geelong;
and 3Department of Medicine, The University of Melbourne, Western Hospital, Melbourne, Australia
Submitted 15 April 2009; accepted in final form 19 October 2009
resistance training; fortified milk; muscle function
PROGRESSIVE RESISTANCE TRAINING (PRT) is one of the few
approaches that has been shown to enhance muscle strength,
mass, and size in older adults and the elderly (19, 20, 30, 34,
35). However, most studies have reported considerable heterogeneity in the skeletal muscle response to training. For muscle
hypertrophy to occur, there must be a net increase in muscle
protein balance, that is, muscle protein synthesis must exceed
protein breakdown (11). While PRT alone stimulates muscle protein synthesis (8, 40), it has been suggested that the greatest
gains in muscle mass will occur with an energy intake that
exceeds requirements to meet the additional demands of train-
Address for reprint requests and other correspondence: R. M. Daly, Dept. of
Medicine, The Univ. of Melbourne, Western Hospital, Footscray, Melbourne
3011, Australia (e-mail: [email protected]).
1864
ing (9, 19) and/or an increased intake of specific nutrients,
particularly dietary protein (18, 35, 36). To date, however, the
findings from several intervention studies in older adults that
have examined whether increased dietary protein or the ingestion of essential amino acids combined with PRT can promote
muscle hypertrophy have produced contrasting results (10 –12,
18, 24, 35, 43). This could be attributed to variations in the
intensity, duration, and frequency of training and/or to differences in the amount or source of protein consumed, habitual
protein intakes, or the timing of ingestion relative to the
resistance training bout.
There is emerging evidence that the ingestion of dairy foods,
particularly whole or fat-free milk, may represent an ideal food
source to enhance muscle protein synthesis and thereby skeletal muscle hypertrophy. Recent findings in young adults have
demonstrated that the consumption of whole milk after resistance training can promote muscle protein synthesis and/or
inhibit protein breakdown, leading to an improved net muscle
protein balance (17, 46). The mechanisms by which whole
milk can enhance the effects of exercise on muscle have been
reported to be related to the fact that milk contains a mix of
casein protein, which is considered a “slow” protein that
inhibits protein breakdown, and whey protein, which is referred to as a “fast” protein that stimulates synthesis (17, 46).
However, there are also likely to be other factors present in
whole milk (e.g., vitamins, minerals, and carbohydrates) that
could contribute to these beneficial effects on muscle. Indeed,
a study (23) in young healthy moderately active men (novice
weightlifters) found that the chronic consumption of fluid skim
milk after PRT was associated with greater gains in lean mass
compared with isoenergetic soy or carbohydrate consumption,
despite similar increases in dietary protein intakes between the
groups throughout the intervention.
Maintaining adequate serum levels of vitamin D (25-hydroxyvitamin D) in the elderly has also been recognized as
being important for optimal musculoskeletal health. This is
because low 25-hydroxyvitamin D levels have been associated
with sarcopenia, an accelerated loss in muscle mass and
strength (44), reduced gait speed and poor balance, and an
increased risk of falling (5, 45). While supplementation with
vitamin D or vitamin D plus calcium can improve lowerextremity muscle performance in the elderly (7, 16, 38, 39), no
studies have examined the potential long-term synergistic skeletal muscle adaptations to PRT and the oral ingestion of fluid
milk containing additional vitamin D3, calcium, and protein in
middle-aged and older men.
8750-7587/09 $8.00 Copyright © 2009 the American Physiological Society
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Kukuljan S, Nowson CA, Sanders K, Daly RM. Effects of
resistance exercise and fortified milk on skeletal muscle mass, size,
and functional performance in middle-aged and older men: an 18-mo
randomized controlled trial. J Appl Physiol 107: 1864 –1873, 2009. First
published October 22, 2009; doi:10.1152/japplphysiol.00392.2009.—
Limited data have suggested that the consumption of fluid milk after
resistance training (RT) may promote skeletal muscle hypertrophy.
The aim of this study was to assess whether a milk-based nutritional
supplement could enhance the effects of RT on muscle mass, size,
strength, and function in middle-aged and older men. This was an
18-mo factorial design (randomized control trial) in which 180
healthy men aged 50 –79 yr were allocated to the following groups:
1) exercise ⫹ fortified milk, 2) exercise, 3) fortified milk, or
4) control. Exercise consisted of progressive RT with weight-bearing
impact exercise. Men assigned to the fortified milk consumed 400
ml/day of low-fat milk, providing an additional 836 kJ, 1000 mg
calcium, 800 IU vitamin D3, and 13.2 g protein per day. Total body
lean mass (LM) and fat mass (FM) (dual-energy X-ray absorptiometry), midfemur muscle cross-sectional area (CSA) (quantitative computed tomography), muscle strength, and physical function were
assessed. After 18 mo, there was no significant exercise by fortified
milk interaction for total body LM, muscle CSA, or any functional
measure. However, main effect analyses revealed that exercise significantly improved muscle strength (⬃20 –52%, P ⬍ 0.001), LM (0.6
kg, P ⬍ 0.05), FM (⫺1.1 kg, P ⬍ 0.001), muscle CSA (1.8%, P ⬍
0.001), and gait speed (11%, P ⬍ 0.05) relative to no exercise. There were
no effects of the fortified milk on muscle size, strength, or function. In
conclusion, the daily consumption of low-fat fortified milk does not
enhance the effects of RT on skeletal muscle size, strength, or function in
healthy middle-aged and older men with adequate energy and nutrient
intakes.
EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
The aim of this study, which was part of an 18-mo factorial
design randomized controlled trial examining the effects of a
multicomponent strength and weight-bearing exercise program
with and without a milk-based nutritional supplement on bone
mineral density in middle-aged and older men (29), was to
investigate the independent and combined effects of these
factors on muscle strength, skeletal muscle mass and size, and
lower-extremity muscle performance. We hypothesized that
exercise combined with fortified milk would result in a greater
skeletal muscle response than either exercise or fortified milk
alone.
MATERIALS AND METHODS
J Appl Physiol • VOL
During the first 12-wk introductory training cycle, participants
completed 3 sets of 15–20 repetitions at 50 – 60% of their 1 repetition
maximum (1-RM) strength. Thereafter, the training volume was set at
2 sets of 8 –12 repetitions. This consisted of a warm-up set at 60 – 65%
of 1-RM followed by a single training set at the following loads: for
the first 4 wk of each 12-wk training cycle, the training load was set
at an intensity of 60 –70% of 1-RM, which increased to 80 – 85% for
the remaining 8 wk. For the first 12 mo, all participants were
instructed to perform each repetition in a slow, controlled manner,
with a rest of 1–2 min between sets. For the final 6 mo of training, the
program switched from maximal strength to high-velocity powerbased training in which the participants were instructed to perform all
repetitions for each exercise as rapidly as possible during the concentric (rising) phase and then return the resistance (load) through the
eccentric (lowering) phase at a slow and controlled speed. The same
training intensity (60 – 85% of 1-RM) was prescribed during this
period. Analysis of the average resistance training load lifted per
session, which was calculated from the sum of the number of repetitions completed multiplied by the weight (in kg) lifted for each set of
all exercises completed throughout the program, revealed that the
average load increased from 7,635 kg at 12 mo to 8,515 kg during the
final 6 mo.
The weight-bearing impact exercises were designed to load the
lower extremities. For each session, three impact exercises were
interspersed between the resistance training exercises. Participants
were initially required to complete 3 sets of 10 repetitions for each
exercise, which progressively increased to a maximum of 20 repetitions that varied in magnitude, rate, and distribution (direction) by
either increasing the height of jumps and/or by introducing more
complex movement patterns (29). Exercise compliance was computed
from daily exercise cards completed by the men at the gymnasium and
checked by records completed daily by the trainers, which were
returned to the research staff every month. The personal trainers also
recorded any adverse events or injuries associated with the program.
Calcium- and vitamin D3-fortified milk. Participants assigned to the
fortified milk were asked to consume 400 ml/day (2 ⫻ 200-ml tetra
packs) of reduced-fat (⬃1%) ultrahigh temperature (UHT) milk,
which was specifically formulated by Murray Goulburn Cooperative
(Brunswick, Australia). This is equivalent to ⬃1.5 glasses of milk per
day, which is in line with the current Australian dietary recommendations of 2–3 servings of dairy per day. Participants were encouraged
to consume one tetra pack in the morning and another in the afternoon
or evening, but not specifically before or after training. Each 200-ml
milk tetra pack was fortified with additional calcium and vitamin D3
(total ⬃500 mg calcium and 400 IU vitamin D3 per 200 ml) and also
contained 418 kJ energy, 6.6 g protein, 2.2 g fat, 11 g lactose, 100 mg
sodium, and 250 mg phosphorous. The milk was fortified with a
calcium salt derived from fresh milk whey. The vitamin D (vitamin
D3) that was used to fortify the milk was obtained from DSM
Nutritional Products (New South Wales, Australia). Six batches of the
milk were produced over the 18-mo intervention with participants
receiving a new batch every 3 mo. The calcium and vitamin D3 levels
of each batch were analyzed by Murray Goulburn Cooperative before
being distributed. The average (⫾SD) calcium and vitamin D3 levels
per 100 ml for the six batches were 247 ⫾ 17 mg and 190 ⫾ 26 IU,
respectively. Participants recorded the number of tetra packs consumed per day on compliance calendars, which were collected and
checked every 3 mo. Compliance was calculated as a percentage by
dividing the number of tetra packs consumed by the expected consumption each month and multiplied by 100.
Anthropometry and body composition. Height was assessed using a
Holtain wall stadiometer (Crymych, Dyfed). Weight was measured
using an A&D UC-321 electronic scale to the nearest 0.1 kg. BMI (in
kg/m2) was calculated as body weight (in kg) divided by height (in
m2). Total body lean mass, fat mass, and percent body fat were
assessed by dual-energy X-ray absorptiometry (Prodigy, GE Lunar,
Madison, WI) with analysis software version 8.10.027. The short-term
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Participants. As described previously (29), 180 healthy communitydwelling Caucasian men aged 50 –79 yr were recruited from within
the local community in Geelong and the surrounding areas in Victoria,
Australia. Participants were excluded if they had taken calcium and/or
vitamin D supplements, had participated in resistance training in the
past 12 mo, participated in high-impact weight bearing activities for
⬎30 min for 3 times/wk in the preceding 6 mo, had a body mass index
(BMI) of ⬎35 kg/m2, had a history of osteoporotic fracture or any
medical condition or used medication known to affect bone metabolism, were lactose intolerant, consumed ⬎4 standard alcoholic drinks/
day, were current smokers, or had any chronic condition that might
limit their ability to be involved in the intervention. In addition, men
with normal to below average areal bone mineral density (total hip or
femoral neck T-score between ⫹0.4 and ⫺2.4 SD) were included in
the study. All men were required to obtain a medical clearance from
their local physician to ensure that they were free of any contraindicated medical conditions to exercise based on American College of
Sports Medicine guidelines (1). The study was approved by the
Deakin University Human Ethics Committee and Barwon Health
Research and Ethics Advisory Committee, and written consent was
obtained from all participants.
Study design. This 2 ⫻ 2 factorial design study was an 18-mo
randomized controlled trial. The two factors were exercise and calciumand vitamin D3-fortified milk; each were tested on two levels so that
the 180 participants were randomly allocated to one of the four
groups: 1) exercise plus fortified milk (n ⫽ 45), 2) exercise alone (n ⫽
46), 3) fortified milk alone (n ⫽ 45), or 4) control (n ⫽ 44). Before
randomization, participants were stratified according to age (⬍65 or
ⱖ65 yr) and baseline dietary calcium intake (⬍800 or ⱖ800 mg/day).
Exercise training. Supervised exercise was performed 3 nonconsecutive days/wk for 18 mo in one of four community leisure facilities
under the supervision of qualified exercise trainers. Each session
lasted 60 –75 min and consisted of warm-up and cool-down activities,
PRT, and moderate-impact weight-bearing exercises. During the first
4 wk of the program, all exercise sessions were supervised to ensure
correct lifting and landing techniques and to monitor the appropriate
amount of exercise and rest intervals. Thereafter, 1 session/wk was
supervised to provide ongoing personal attention, tuition, and supervision to ensure that participants adhered to the principle of progressive overload. For the remaining two sessions, participants were
instructed to seek assistance from local trained gymnasium staff when
needed. As reported previously (29), the PRT included a combination
of upper and lower body machine and free weights and exercises to
strengthen the core musculature. The primary exercises used throughout the program included the following: squats (or leg presses),
lunges, hip abduction and adduction, latissimus dorsi pull down (or
seated row), back extension, and a combination of abdominal and core
stability exercises. Additional exercises, including leg extensions, calf
raises, bench presses, military presses, bicep curls, tricep extensions,
and lumbopelvic and spine stabilization exercises, were also rotated
throughout the program to ensure the development of muscle balance.
1865
1866
EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
dicted basal metabolic rate (22). On this basis, we excluded 18% and
27% of the all food diaries at 12 and 18 mo, respectively. Leisure time
and habitual physical activity outside of the exercise intervention (in
kJ/wk) were assessed using the Community Healthy Activities Model
Program for Seniors physical activity questionnaire (42). Information
on disease history was determined by questionnaire, and medication
use (including calcium and vitamin D supplementation) was determined by a questionnaire at each visit (baseline, 12 mo, and 18 mo)
and confirmed by an interview.
Serum 25-hydroxyvitamin D levels. Fasting morning (8 –10 AM)
blood samples (10 ml) were obtained from each participant’s antecubital vein at 12 and 18 mo. All serum samples were subaliquoted and
stored at ⫺80°C until assayed (in duplicate). Serum 25-hydroxyvitamin D levels were measured using a DiaSorin immunoassay (Stillwater, MN). The mean interassay CV ranged from 3.9% to 5.8%.
Statistical analysis. Statistical analyses were conducted using Stata
Statistical Software release 10.0 (Stata, College Station, TX). Baseline
characteristics between the groups were compared using ANOVA
with a Tukey post hoc test. Pooled time series regression analysis for
longitudinal data was used to test for an interaction between exercise
and fortified milk. If no significant interactions were detected, the
main effects of exercise (exercise plus fortified milk and exercise
alone vs. fortified milk and control) and fortified milk (exercise plus
fortified milk and fortified milk vs. exercise and controls) were
examined. Serum 25-hydroxyvitamin D, gait speed, step test, and all
sway measures were log transformed before analyses. Between-group
differences were calculated by subtracting within-group changes from
the baseline values in each group for each parameter. Separate models
were used to assess the within-group changes, which were expressed
either as absolute changes or as percent changes from baseline.
RESULTS
Baseline characteristics. As previously reported (29), there
were no significant differences between the four groups for any
of the baseline characteristics (Tables 1–3), with the exception
that back and leg muscle strength were greater in the control
group relative to the exercise or exercise plus fortified milk
groups. On average, daily dietary protein and calcium intakes
for all participants were above or equivalent to the current
Australian recommended dietary intake (RDI) for men aged
51–70 yr (Table 2; RDI for protein: 0.84 g/kg and RDI for
calcium: 1,000 mg/day) (36a). Mean baseline serum 25-hydroxyvitamin D levels were no different between the groups
and averaged 86.2 ⫾ 35.9 nmol/l; no participants had severe
vitamin D deficiency (25-hydroxyvitamin D ⬍12.5 nmol/l),
one participant had moderate deficiency (25-hydroxyvitamin
D ⫽ 12.5–25 nmol/l), and 17 participants (9.4%) had mild
deficiency (25-hydroxyvitamin D ⫽ 25–50 nmol/l) (29).
Table 1. Baseline characteristics of the participants according to group
n
Age, yr
Height, cm
Body mass index, kg/m2
Body fat, %
Physical activity (moderate), h/wk
Muscle strength
Chest (bench press), kg
Back (lateral pull down), kg
Legs (leg press), kg
Exercise ⫹ Milk Group
Exercise Group
45
61.7⫾7.6
174.3⫾6.3
27.4⫾3.7
28.0⫾7.8
3.7⫾3.9
46
60.7⫾7.1
174.2⫾6.6
28.1⫾3.3
28.3⫾5.5
3.6⫾3.4
49.1⫾12.7
61.4⫾14.5
63.4⫾18.0
55.0⫾13.1
65.8⫾11.7
64.7⫾16.5
Milk Group
45
61.7⫾7.7
174.4⫾5.8
27.7⫾3.3
29.4⫾7.0
3.3⫾3.8
49.1⫾13.5
66.3⫾11.2
71.4⫾13.7
Control Group
44
59.9⫾7.4
175.0⫾6.6
26.7⫾2.9
26.5⫾6.8
3.4⫾4.1
52.7⫾11.8
68.7⫾12.1*
74.4⫾18.1†
Values are means ⫾ SD; n, no. of subjects/group. *P ⬍ 0.05 vs. the exercise group; †P ⬍ 0.05 vs. the exercise ⫹ milk group and the exercise group.
J Appl Physiol • VOL
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coefficients of variation (CVs) for total body lean mass and fat mass
in our laboratory were 0.7% and 1.0%, respectively.
Midfemur muscle cross-sectional area (CSA) was measured using
quantitative computed tomography (QCT; Philips Mx8000 Quad CT
scanner, Philips Medical Systems). The scan parameters were 120
kVp, 85 mAs, and 2.5-mm slice thickness. The midpoint of the left
femur was determined by drawing a line from the femoral head to the
lateral femoral condyle using the QCT ruler function. A series of four
2.5-mm slices were taken at the midpoint, with the middle two slices
from the left leg analyzed and averaged. All cross-sectional QCT
images were analyzed using the Geanie software program (BonAlyse
Oy, Jyvakyla, Finland). Muscle CSA was obtained by measuring the
area defined within an attenuation range from 0 to 200 HU excluding
the bone and marrow. The short-term CV for two consecutive measurements in our laboratory was 0.40%.
Muscle strength. Before the determination of upper and lower body
1-RM muscle strength, participants attended two separate familiarization sessions where they were shown correct exercise techniques by a
trained instructor and given the opportunity to become accustomed to
the selected exercises. To determine 1-RM, each participant initially
performed a warm-up set of eight repetitions with a light load. After
the successful completion of a further five to six repetitions at a
heavier weight selected by the instructor and after a brief rest (⬃2
min), the workload was increased incrementally until only one repetition with correct technique could be completed. The leg press,
latissimus dorsi pull down, and bench press exercises were used to
document changes in upper and lower body muscle strength.
Physical function. Dynamic single limb stance was assessed using
the step test. Participants were instructed to step on and off a
7.5-cm-high block as many times as possible in 15 s. One complete
step consisted of stepping onto and off the block. Participants were
instructed to place their entire foot onto the block and then return it
fully to the floor. Gait speed was calculated as the time taken to walk
along a 6-m line, heel to toe, while avoiding any excessive side-toside movements. Time (in s) was recorded manually using a stopwatch. Postural sway was measured using a sway meter, which
measures the displacement of the body at the level of the waist (32).
Participants were tested for 30 s while standing on the floor or a
medium-density foam mat with both eyes open and eyes closed.
Postural sway was calculated as the product of either maximal
anterior-posterior or lateral sway (in mm2) for each of the four tests.
Diet, physical activity, and medication use. Nutrient intakes were
assessed using a 3-day food diary (2 weekdays and 1 weekend day),
with the option of weighing items, and analyzed using the Foodworks
nutrient analysis software program (Xyris Software, Brisbane,
Queensland, Australia). While all participants were provided with
detailed verbal and written instructions for completing their food
diaries, underreporting of habitual food intake is well known. Therefore, we used the Goldberg cutoff method to identify underreporters
(22). Using this method, food diaries were excluded from nutrient
intake analysis if reported energy intakes were ⬍1.5 times the pre-
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EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
Table 2. Mean estimated dietary intakes by group at baseline and mean changes after 12 and 18 mo
Exercise Group
Milk Group
Control Group
9,694⫾2,149
461 (⫺390, 1,313)
⫺249 (⫺1,168, 669)
9,884⫾1,948
250 (⫺525, 1,026)
⫺647 (⫺1,251, ⫺43)*
9,761⫾1,717
846 (84, 1,609)*
⫺337 (⫺1,122, 448)
10,199⫾2,201
⫺318 (⫺1,079, 442)
⫺1,144 (⫺2,085, ⫺203)*
1.26⫾0.32
0.21 (0.08, 0.35)†
0.06 (⫺0.07, 0.19)
1.32⫾0.32
0.08 (⫺0.03, 0.19)
⫺0.10 (⫺0.20, 0.00)*
1.23⫾0.28
0.16 (0.07, 0.26)‡
0.00 (⫺0.11, 0.10)
1.33⫾0.31
⫺0.04 (⫺0.15, 0.08)
⫺0.06 (⫺0.21, 0.08)
257⫾66
6 (⫺21, 34)
⫺11 (⫺44, 21)
257⫾62
18 (⫺8, 44)
⫺15 (⫺35, 5)
260⫾63
16 (⫺8, 41)
⫺11 (⫺39, 17)
266⫾60
⫺3 (⫺26, 19)
⫺28 (⫺59, 4)
84⫾29
4 (⫺8, 15)
⫺3 (⫺13, 6)
83⫾23
⫺3 (⫺15, 8)
⫺5 (⫺14, 5)
86⫾21
9 (⫺2, 19)
⫺6 (⫺14, 3)
87⫾26
⫺3 (⫺13, 7)
⫺13 (⫺24, ⫺2)*
911⫾360
827 (677, 977)‡
607 (444, 770)‡
1,064⫾449
21 (⫺83, 127)
⫺133 (⫺223, ⫺42)†
1,039⫾455
682 (537, 828)‡
551 (391, 711)‡
996⫾293
46 (⫺90, 181)
⫺81 (⫺202, 39)
1.2⫾2.1
19.1 (16.7, 21.4)‡
17.5 (15.2, 19.9)‡
0.8⫾1.1
1.1 (0.6, 2.2)*
0.4 (⫺0.7, 1.6)
1.4⫾3.0
18.3 (16.2, 20.3)‡
19.7 (17.6, 21.9)‡
0.7⫾1.0
1.1 (0.0, 2.2)*
0.6 (⫺0.2, 1.3)
Baseline values are means ⫾ SD, and change at 12 and 18 mo values are means with 95% confidence intervals in parentheses. The number of food diaries
included in the analysis based on the Goldberg method (22) was as follows: for the change at 12 mo, exercise ⫹ milk group, n ⫽ 38; exercise group, n ⫽ 37;
milk group, n ⫽ 39; and control group, n ⫽ 35; and for the change at 18 mo, exercise ⫹ milk group, n ⫽ 34; exercise group, n ⫽ 32; milk group, n ⫽ 39; and
control group, n ⫽ 35. *P ⬍ 0.05, †P ⬍ 0.01, and ‡P ⬍ 0.001 for within-group changes from baseline.
Study attrition and compliance. Eight of the 180 men (4.4%)
withdrew from the study over the 18-mo period (exercise plus
fortified milk group: n ⫽ 2, exercise group: n ⫽ 2, fortified milk
group: n ⫽ 2, and control group: n ⫽ 2). The reasons for
withdrawal included the following: illness unrelated to the study
(n ⫽ 2), work or personal time commitments (n ⫽ 5), and
dissatisfaction with the group allocation after randomization (n ⫽
1). The average compliance with the exercise program was 63%
(95% confidence interval: 57, 69) and did not differ between the
exercise plus fortified milk group and the exercise alone group
(65% vs. 61%). The average compliance in the fortified milk
group was 90% (95% confidence interval: 87, 93) and was no
different between the exercise plus fortified milk group and the
fortified milk group (92% vs. 89%).
Table 3. Body composition characteristics by group at each time point and within-group changes relative to baseline
Within Group
Weight, kg
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Fat mass, kg
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Lean mass, kg
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Midfemur CSA, cm2
Ex ⫹ Milk
Ex
Milk
Controls
Baseline
12 mo
18 mo
Change at 12 mo
Change at 18 mo
83.2⫾11.9
85.2⫾10.9
84.1⫾9.8
81.9⫾10.7
83.9⫾12.1
85.3⫾11.1
84.7⫾9.4
81.9⫾11.0
83.8⫾12.2
85.2⫾11.5
85.1⫾9.9
81.6⫾10.5
0.6 (⫺0.1, 1.4)
0.0 (⫺0.8, 0.8)
1.3 (0.7, 2.0)‡
0.0 (⫺0.6, 0.6)
0.7 (⫺0.2, 1.6)
0.0 (⫺0.9, 0.9)
1.7 (0.9, 2.5)‡
0.1 (⫺0.7, 0.8)
22.9⫾8.7
23.5⫾6.6
24.2⫾7.4
21.2⫾7.5
22.5⫾8.7
22.8⫾6.8
24.4⫾7.5
21.1⫾7.7
22.3⫾8.5
23.0⫾6.8
25.2⫾7.6
21.1⫾7.4
⫺0.4 (⫺1.0, 0.3)
⫺0.8 (⫺1.6, 0.0)*
0.7 (0.2, 1.2)*
⫺0.1 (⫺0.6, 0.4)
⫺0.3 (⫺1.0, 0.3)
⫺0.4 (⫺1.2, 0.4)
1.3 (0.7, 2.0)‡
0.1 (⫺0.5, 0.7)
57.0⫾6.4
58.5⫾6.5
56.6⫾5.3
57.5⫾5.8
58.2⫾6.1
59.1⫾6.4
56.8⫾5.4
57.5⫾5.6
58.2⫾6.1
58.8⫾6.6
56.5⫾5.0
57.1⫾5.9
1.0 (0.4, 1.5)‡
0.7 (0.2, 1.1)†
0.4 (⫺0.1, 0.8)
0.1 (⫺0.4, 0.5)
0.9 (0.3, 1.6)†
0.3 (⫺0.2, 0.9)
0.2 (⫺0.4, 0.8)
⫺0.2 (⫺0.5, 0.1)
145.9⫾17.6
151.9⫾18.3
143.9⫾17.4
148.5⫾20.0
147.8⫾18.2
153.1⫾20.2
143.5⫾18.9
144.8⫾19.5
1.4 (0.1, 2.7)*
0.7 (⫺0.5, 1.8)
⫺0.1 (⫺1.0, 0.8)
⫺1.5 (⫺2.5, ⫺0.5)‡
Values for baseline, 12 mo, and 18 mo are means ⫾ SD, and values for within-group changes represent means with 95% confidence intervals in parentheses.
Values for weight, fat mass, and lean mass are absolute changes (in kg), and values for midfemur cross-sectional area (CSA) are percent changes. *P ⬍ 0.05,
†P ⬍ 0.01, and ‡P ⬍ 0.001 for within-group changes from baseline.
J Appl Physiol • VOL
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Energy, kJ/day
Baseline
Change at 12 mo
Change at 18 mo
Protein, g 䡠 kg⫺1 䡠 day⫺1
Baseline
Change at 12 mo
Change at 18 mo
Carbohydrate, g/day
Baseline
Change at 12 mo
Change at 18 mo
Fat, g/day
Baseline
Change at 12 mo
Change at 18 mo
Calcium, mg/day
Baseline
Change at 12 mo
Change at 18 mo
Vitamin D, ␮g/day
Baseline
Change at 12 mo
Change at 18 mo
Exercise ⫹ Milk Group
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EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
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Adverse events. There were no serious injuries or adverse
events associated with the exercise program. The limited number of minor injuries included the exacerbation of longstanding
gout of the foot (n ⫽ 1), aggravated knee or hip pain (n ⫽ 2;
both subjects were able to continue with exercise after program
modification), lower back injury (n ⫽ 2; one subject recovered
with 2-wk rest and one subject withdrew from the exercise
program due to aggravated pain associated with a long-standing prolapsed disc but remained in the study), and the aggravation of a long-standing shoulder injury (n ⫽ 2; both participants returned to exercise after treatment). Three men were
diagnosed with an inguinal hernia, but all were able to continue
with the exercise program after treatment.
Nutrient intake and physical activity. As expected, consumption of the fortified milk led to significant (⬃16%) increases in
dietary protein intake (in g 䡠 kg⫺1 䡠day⫺1) after 12 mo but not 18
mo relative to baseline (Table 2). Dietary intakes of calcium
and vitamin D, but not total fat or carbohydrate intake, increased significantly in the fortified milk groups and were
greater than in the nonsupplemented groups after both 12 and
18 mo (all P ⬍ 0.001). For the exercise group, there were no
significant differences for any of the dietary parameters compared with the nonexercise group. Leisure time and recreational activity habits did not differ between the groups
throughout the intervention.
Serum 25-hydroxyvitamin D levels. There was a significant
main effect of fortified milk on serum 25-hydroxyvitamin D
levels after 12 mo (P ⬍ 0.001). This was due to a mean 11.3%
increase (P ⬍ 0.01) in the fortified milk group compared with
an 11.6% reduction (P ⬍ 0.01) in the nonsupplemented group,
resulting in a net difference of 22.9% (29). After 18 mo, the
mean increase in the fortified milk group remained significant
relative to baseline (10.8%, P ⬍ 0.01), but the change in the
nonsupplemented group was no longer significant (3.2%).
There was no main effect of exercise on serum 25-hydroxyvitamin D levels.
Body composition, muscle size, strength, and function. After
18 mo, the gains in total body lean mass and midfemur muscle
CSA were two- to threefold greater in the exercise plus
fortified milk group compared with either group alone or the
control group, but the interaction terms were not statistically
significant for any muscle or functional parameter (Fig. 1 and
Table 3). Subsequent analysis of the main effects of exercise
revealed that there was a net gain of 0.6 kg (P ⬍ 0.05) in total
body lean mass relative to the nonexercise groups after 12 mo,
and this difference remained after 18 mo (P ⬍ 0.05; Table 4*/).
There was also a net 1.8% exercise-induced gain in midfemur
muscle CSA (P ⬍ 0.001; Table 4). There were no significant
effects of exercise on body weight, but there was a net
exercise-related reduction of 0.8 and 1.1 kg in fat mass relative
to nonexercise after 12 and 18 mo, respectively (P ⬍ 0.01 and
⬍0.001; Fig. 1 and Table 4). Upper and lower body muscle
strength improved by 22–56% (all P ⬍ 0.001) after 12 mo of
training and tended to plateau thereafter with the exception of
leg muscle strength, which decreased in the exercise groups
from 12 to 18 mo (both P ⬍ 0.05; Fig. 2). Gait speed improved
by 11% (P ⬍ 0.05) after 18 mo in the exercise group relative
to the nonexercise group (Tables 4 and 5). There were no other
beneficial effects of exercise on any functional parameter,
although various measures of sway improved in all four groups
after 12 and/or 18 mo.
Fig. 1. Mean absolute changes (⫾SE) from baseline for total body fat mass
and lean mass and percent changes for midfemur muscle cross-sectional area
(CSA) according to group. There were no exercise by fortified milk interactions, but exercise resulted in significant improvements in total body lean mass,
fat mass, and muscle CSA relative to the nonexercise group (main effects: P ⬍
0.05 to P ⬍ 0.001).
In the fortified milk group compared with the nonsupplemented groups, body weight and fat mass increased by 1.0 kg
(P ⬍ 0.01) and 0.6 kg (P ⫽ 0.07) after 12 mo, respectively, and
these differences persisted after 18 mo (Fig. 1 and Tables 3 and
4). This was largely due to a significant increase in the fortified
107 • DECEMBER 2009 •
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EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
Table 4. Main effects for exercise and fortified milk for the
changes in body weight, total body fat mass, total lean mass,
midfemur muscle CSA, and gait speed
Main Effects
Exercise
Weight
Change at 12
Change at 18
Fat mass
Change at 12
Change at 18
Lean mass
Change at 12
Change at 18
Midfemur CSA
Change at 18
Gait speed
Change at 12
Change at 18
1869
due to the fact that our participants were healthy communitydwelling men with adequate energy and protein intakes and
sufficient circulating 25-hydroxyvitamin D levels and/or that
the timing of milk consumption was not controlled. In partial
support of the latter explanation, the findings from a recent
Milk
mo
mo
⫺0.3 (⫺1.1, 0.3)
⫺0.6 (⫺1.4, 0.3)
1.0 (0.3, 1.6)†
1.2 (0.4, 2.0)‡
mo
mo
⫺0.8 (⫺1.5, ⫺0.2)†
⫺1.1 (⫺1.8, ⫺0.4)‡
0.6 (0.0, 1.3)
0.7 (0.0, 1.4)*
mo
mo
0.6 (0.1, 1.1)*
0.6 (0.1, 1.2)*
0.3 (⫺0.2, 0.8)
0.5 (0.0, 1.0)*
mo
1.8 (0.7, 2.9)‡
1.0 (⫺0.1, 2.1)
mo
mo
⫺7 (⫺16, 2)
⫺11 (⫺21, ⫺2)*
2 (⫺7, 11)
6 (⫺4, 15)
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Values are mean net differences with 95% confidence intervals in parentheses. Values for weight, fat mass, and lean mass are net absolute differences
between the groups (in kg), values for midfemur CSA are net percentage
differences between the groups, and values for gait speed are net percentage
differences between the groups based on log-transformed data. *P ⬍ 0.05,
†P ⬍ 0.01, and ‡P ⬍ 0.001 for between-group differences.
milk alone group; neither weight nor fat mass increased significantly in the exercise plus fortified milk group at any time.
There was also a net benefit in the fortified milk group for total
body lean mass (0.5 kg, P ⬍ 0.05) and a trend for a greater
increase in midfemur muscle CSA (1.0%, P ⫽ 0.07) after 18
mo. However, these benefits were largely attributed to significant gains in the exercise plus fortified milk group and/or
marked losses in the control group. There were no significant
within-group changes for lean mass or muscle CSA in the
fortified milk alone group. Finally, there were no main effects
of fortified milk on muscle strength or any functional measure.
DISCUSSION
The findings from this 18-mo factorial design randomized
controlled trial indicate that the provision of a daily milk-based
nutritional supplement providing additional energy, protein,
vitamin D3, and calcium did not significantly enhance the
effect of exercise on any muscle or functional performance
measure in healthy community-dwelling middle-aged and
older men. Consistent with these findings, Rankin et al. (41)
reported that milk consumption after each bout of resistance
training over 10 wk was associated with a twofold, but nonsignificant, greater gain in total body lean mass in young
healthy men compared with those participants given an isocaloric carbohydrate solution. In this study, the lack of a significant additive effect of exercise and milk on lean mass was
likely due to the small sample size (n ⫽ 19) and/or relatively
high habitual dietary protein intakes (⬃1.2 g䡠kg⫺1 䡠 day⫺1). In
our 2 ⫻ 2 factorial design study, the gains in total body lean
mass and lower-extremity muscle CSA were two- to threefold
greater in the exercise plus fortified milk group compared with
either of these groups alone or the control group, but the
“synergistic” interaction terms were not significant despite our
larger sample size (n ⫽ 180). This lack of a statistically
significant exercise by fortified milk interaction is most likely
J Appl Physiol • VOL
Fig. 2. Mean percentage changes (⫾SE) from baseline for upper body (bench
press), back (lat pull down), and lower body (leg press) muscle strength
according to group. Exercise resulted in significant increases in all muscle
strength measures relative to both baseline and to the nonexercise group (main
effects: all P ⬍ 0.001).
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EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
Table 5. Measures of physical function at each time point and within-group changes relative to baseline
Within Group
Step test, no. of steps
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Gait speed, m/s
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Baseline
12 mo
10.2⫾2.1
10.3⫾2.7
9.9⫾2.9
10.3⫾2.8
11.2⫾3.1
11.7⫾3.0
10.2⫾3.0
11.2⫾3.2
2.58⫾0.94
2.92⫾1.04
2.84⫾0.96
3.08⫾1.36
18 mo
Change at 12 mo
Change at 18 mo
12.2⫾2.6
12.6⫾3.0
11.4⫾3.0
12.0⫾3.3
6 (⫺1, 13)*
12 (5, 19)‡
3 (⫺4, 10)
10 (4, 17)‡
17 (11, 24)‡
19 (11, 27)‡
13 (6, 20)‡
15 (9, 22)‡
2.32⫾0.79
2.52⫾0.76
2.74⫾1.06
2.86⫾1.07
2.15⫾0.73
2.44⫾0.80
2.79⫾1.17
2.66⫾1.12
⫺9 (⫺18, 0)*
⫺14 (⫺24, ⫺4)†
⫺6 (⫺13, 2)
⫺4 (⫺14, 6)
⫺18 (⫺28, ⫺8)‡
⫺20 (⫺31, ⫺9)‡
⫺3 (⫺12, 5)
⫺12 (⫺21, ⫺3)†
241⫾185
343⫾303
294⫾282
320⫾366
300⫾354
288⫾319
252⫾211
227⫾154
180⫾153
205⫾159
326⫾420
179⫾147
12 (⫺23, 47)
⫺39 (⫺76, ⫺1)*
⫺19 (⫺52, 14)
⫺18 (⫺54, 17)
⫺48 (⫺87, ⫺9)*
⫺42 (⫺77, ⫺7)*
⫺17 (⫺58, 23)
⫺30 (⫺59, ⫺2)*
235⫾158
279⫾210
364⫾318
285⫾232
294⫾286
291⫾272
372⫾384
362⫾344
279⫾277
287⫾333
241⫾192
320⫾373
6 (⫺31, 43)
⫺9 (⫺43, 25)
⫺3 (⫺40, 33)
6 (⫺19, 31)
⫺3 (⫺29, 23)
⫺19 (⫺53, 14)
⫺45 (⫺78, ⫺11)†
⫺21 (⫺57, 15)
492⫾241
565⫾455
737⫾762
597⫾532
412⫾302
331⫾270
572⫾783
347⫾249
391⫾267
367⫾275
596⫾733
348⫾266
⫺29 (⫺53, ⫺5)*
⫺59 (⫺87, ⫺32)‡
⫺39 (⫺70, ⫺9)*
⫺56 (⫺85, ⫺27)‡
⫺38 (⫺67, ⫺9)†
⫺48 (⫺78, ⫺17)‡
⫺38 (⫺71, ⫺4)*
⫺51 (⫺75, ⫺28)‡
1,201⫾981
1,332⫾930
1,317⫾875
1,437⫾1217
1,041⫾1,044
875⫾675
925⫾781
1,086⫾831
933⫾1,085
864⫾662
1,045⫾787
1,254⫾1489
⫺31 (⫺61, ⫺1)*
⫺44 (⫺70, ⫺19)‡
⫺46 (⫺72, ⫺20)‡
⫺38 (⫺70, ⫺6)*
⫺46 (⫺74, ⫺19)†
⫺48 (⫺74, ⫺21)‡
⫺32 (⫺60, ⫺4)*
⫺29 (⫺55, ⫺3)*
Sway, mm2
Values for baseline, 12 mo, and 18 mo are means ⫾ SD, and values for within-group changes are means with 95% confidence intervals in parentheses. All
within-group percent changes are based on the log-transformed data, which represent the absolute differences from baseline multiplied by 100. *P ⬍ 0.05,
†P ⬍ 0.01, and ‡P ⬍ 0.001 for within-group changes from baseline.
12-wk intervention in 56 healthy young novice male weightlifters with baseline protein intakes of ⬃1.2–1.4 g 䡠kg⫺1 䡠day⫺1
revealed that milk consumption immediately and 1 h after
exercise led to a significant ⬃1.5-fold greater gain in lean
mass compared with isoenergetic soy or carbohydrate consumption (23).
Habitual dietary protein intakes of the men in our study were
above current RDIs. The mean baseline dietary protein intake
across all groups was 1.30 g 䡠kg⫺1 䡠day⫺1, which exceeds the
current Australian RDI value of 0.84 –1.07 g 䡠kg⫺1 䡠 day⫺1 for
men aged ⬎50 yr (36a). Although there are some reports that
dietary protein requirements should increase in older adults
engaged in resistance training (33), a recent review concluded
that the additional intake of dietary protein in older people who
consume adequate dietary protein (in excess of 0.8
g䡠kg⫺1 䡠day⫺1) does not enhance the effects of resistance training on muscle mass and strength in older people (11). However, as already indicated, an important factor that could
explain the lack of an interactive effect in our study relates to
the timing in which the fortified milk was consumed. In a
12-wk study of elderly men, Esmarck et al. (18) reported that
protein delivery immediately after each bout of resistance
training, as opposed to 2 h later, augmented the exerciseinduced gains in muscle hypertrophy. In our study, the timing
of milk consumption in relation to the exercise program was
J Appl Physiol • VOL
not controlled, and thus it is possible that the men may have
missed the important “window of anabolic opportunity” to
enhance muscle protein synthesis (8). Indeed, the findings from
a 10-wk resistance training trial in recreational male body
builders revealed that the ingestion of a supplement containing
protein, creatine, and glucose before and after each workout
resulted in significantly greater skeletal muscle gains compared
with a matched group who consumed the supplement outside
of the pre- and postworkout time frames (14). However,
several other acute resistance training studies have indicated
that the window of opportunity for feeding may be extended
for up to 24 h after resistance training, although it has been
suggested that earlier feeding provides some additional advantages since this is when muscle protein synthesis is stimulated
to the greatest extent (8). Interestingly, however, the findings
from several intervention studies in older men have reported
that ingesting additional protein either before and/or after a
bout of resistance training does not provide additional skeletal
muscle benefits (12, 13, 42). It has been suggested that the
potential benefits of timed (protein) supplementation might be
limited to specific elderly subpopulations, such as the frail
elderly or malnourished (28).
Vitamin D deficiency has also been associated with reduced
muscle strength, slower walking speed, and impaired balance
in the elderly (4, 44, 45), which have been reported to improve
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Eyes open, on floor
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Eyes closed, on floor
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Eyes open, on foam
Exercise ⫹ milk group
Exercise group
Milk group
Control group
Eyes closed, on foam
Exercise ⫹ milk group
Exercise group
Milk group
Control group
EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
J Appl Physiol • VOL
improvements in gait speed were related to the inclusion and
progressive difficulty of the weight-bearing activities throughout the intervention. A recent systematic review on the effects
of PRT alone on balance in older adults reported that only 22%
of all balance tests reported showed significant improvement in
balance performance after training (37). In contrast, there is a
growing body of evidence to support the findings that highvelocity resistance training can effectively improve muscle
function in older adults, including gait and stair climbing speed
(3, 25, 26).
An unexpected finding in our study was the significant net
gain in total body lean mass and, to a lesser extent, midfemur
muscle CSA in the fortified milk group compared with the
nonsupplemented groups. Despite reports that the ingestion of
milk can stimulate muscle protein synthesis (17), the gains
observed in our study appear to be largely attributed to the
significant within-group increases in the exercise plus fortified
milk group combined with the lack of change or losses in the
control group. Inspection of the changes in the fortified milk
alone group revealed that there were no changes in either lean
mass or muscle CSA throughout the intervention. However, the
ingestion of the fortified milk, particularly without exercise,
resulted in a significant gain in total body fat mass. Although
these changes were similar in magnitude to those reported in
previous milk supplementation trials in older men (15) and
women (13, 31), it is important to note that the consumption of
fortified milk was not associated with an increase in total fat
intake.
While the strength of our study lies in its randomized
controlled design, relatively long-term followup, high study
retention, and compliance to the intervention, there are a
number of limitations. First, our sample size was relatively
small to detect a significant exercise by fortified milk interaction on the muscle outcomes. Post hoc sample size calculations
based on the changes in total body lean mass in our study
indicated that we would require ⬃265 participants/group to
detect a significant synergistic interaction between exercise and
fortified milk. Second, the timing of milk consumption was not
controlled in our study, and we recruited relatively healthy,
ambulatory community-dwelling men with adequate energy
and protein intakes and serum 25-hydroxyvitamin D levels, all
of which may have limited our ability to detect any significant
interactions if they were present. Finally, we did not include a
placebo or energy-matched control drink. Therefore, if any
significant interaction or main effects of fortified milk were
detected, we would not be able to determine whether it was due
to the additional protein, calcium, and/or vitamin D present in
the milk. In addition, it is possible that the nonsupplemented
groups may have increased their daily dairy intake, although
the findings from our dietary analysis indicate that there were
no marked changes in habitual energy, calcium, or protein
intake in these groups.
In conclusion, daily consumption of 400 ml of low-fat
fortified milk providing additional energy, protein, vitamin D3,
and calcium does not significantly enhance the effects of
progressive resistance exercise on muscle mass, size, strength,
or function in healthy community-dwelling middle-aged and
older men with adequate energy and nutrient intakes. However,
we were able to show that a community-based resistance
training program involving a single high-intensity training set
performed 3 days/wk over 18 mo was effective for improving
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with vitamin D and/or calcium supplementation in some (7, 16,
38, 39) but not all (27) studies. In our study, serum 25hydroxyvitamin D levels significantly increased by ⬃10 nmol/l
after supplementation with fortified milk, but it is unlikely that
this would have enhanced the effects of resistance exercise on
muscle mass or function because baseline vitamin D levels
were already sufficiently high (mean ⫾ SD: 86.2 ⫾ 35.9
nmol/l). There is emerging evidence and expert opinion that
serum 25-hydroxyvitamin D levels above 75– 80 nmol/l are
needed for optimal muscle function, after which further increases are unlikely to translate into any marked functional
improvements (6).
Despite the lack of a significant interactive effect, the
present study showed that a community-based progressive
moderate to high-intensity resistance training program in combination with a diverse range of weight-bearing exercises
performed 3 days/wk was safe, feasible, and effective for
improving muscle strength, total body lean mass, lower-extremity muscle size, and gait performance and reducing fat
mass in healthy community-dwelling middle-aged and older
men. The observed 20 –52% improvements in upper and lower
body muscle strength after 18 mo were comparable to the gains
reported in a number of previous resistance training trials in
older men (12, 18, 34, 35, 43). However, the net 1.8% gain in
midfemur muscle CSA was considerably less than the 4 –9%
gains reported in several previous trials after 12 wk (20, 23, 34)
to 2 yr (34) of resistance training. The most likely explanation
for the attenuated gains in our study is that the total volume and
intensity of training were lower than those reported in the
previous studies. Our program consisted of a single warm-up
set at 60 – 65% 1-RM followed by a single training set at
60 – 85% 1-RM, whereas participants in most previous studies
typically performed 3 sets at 75– 80% 1-RM (20, 23, 33). In
support of this notion, previous research has indicated that
greater skeletal muscle gains can be achieved with multiset
resistance training (21). Nevertheless, we believe that the
findings from our study are important because they highlight
that significant, albeit smaller, gains in muscle mass and size
can still be achieved with a single set of moderate to highintensity resistance training performed 3 days/wk in healthy
middle-aged and older men.
An important strength of our study lies in its long-term
followup with repeated measurements. This provided a unique
opportunity to quantify the time course for skeletal muscle
adaptations to resistance training in middle-aged and older
men. For muscle strength, we found that the greatest increases
occurred after 6 to 12 mo of training, after which no further
improvements were detected. This coincides with the plateau
observed in total body lean mass after 12 mo of training. It is
difficult to explain the lack of a continual increase in muscle
strength and lean mass because the average resistance training
load per session increased by ⬃12% from 12 to 18 mo.
Nevertheless, these findings are consistent with the principle of
diminished returns, which suggests that after an initial training
adaptation, any further gains are likely to be slow and of small
magnitude. Importantly, however, we believe that the introduction of the high-velocity training phase during the final 6 mo
contributed to the significant improvements in gait speed in the
exercise group after 18 mo of training; no exercise-induced
improvements were observed in any functional measures after
the initial 12 mo of traditional PRT. It is also possible that the
1871
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EFFECTS OF RESISTANCE EXERCISE AND MILK ON MUSCLE
total body lean mass and fat mass, lower-extremity muscle
CSA, and gait speed. Importantly, the low attrition and relatively good exercise compliance coupled with the low number
of adverse events indicates that this type of program is safe,
feasible, and well tolerated in previously untrained but otherwise healthy middle-aged and older men.
ACKNOWLEDGMENTS
The authors thank Tiana Mahncke for analyzing the QCT scans. The
authors also thank Murray Goulburn Cooperative Company Limited for
providing the calcium- and vitamin D3- fortified low-fat UHT milk used in the
study and the City of Greater Geelong and Ocean View Health Club for the
generous provision of the gymnasium facilities used throughout the study.
The authors also thank the following people for contributions to this study:
Shona Bass, Nicole Petrass, Joanne Daly, and Sam Korn.
GRANTS
DISCLOSURES
No conflicts of interest are declared by the author(s).
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This work was financially supported by a grant from the Australian
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