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Scand J Med Sci Sports. 2019;1–12. wileyonlinelibrary.com/journal/sms
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© 2019 John Wiley & Sons A/S.
Published by John Wiley & Sons Ltd
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INTRODUCTION
Age‐associated degenerative loss in skeletal muscle size is
typically accompanied by a decrease in muscle strength and
function.1 These degenerative changes are associated with
an increased risk of falls, which are a leading cause of in-
jury, permanent disability, and high rates of mortality2 in
older adults. Improved falls prevention strategies are there-
fore a primary healthcare target for older adults.3
Multimodal exercise programs incorporating balance and
resistance training reduce the rate and risk of falls in older
Received: 15 May 2018
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Revised: 22 February 2019
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Accepted: 27 February 2019
DOI: 10.1111/sms.13415
ORIGINAL ARTICLE
Trunk exercise training improves muscle size, strength, and
function in older adults: A randomized controlled trial
BehnazShahtahmassebi1
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Jeffrey J.Hebert1,2
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MarkHecimovich1,3
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Timothy J.Fairchild1
Trial registration number: Australian New Zealand Clinical Trials
Registry (ACTRN12613001176752).
1Discipline of Exercise Science,Murdoch
University, Perth, Western Australia,
Australia
2Faculty of Kinesiology,University of New
Brunswick, Fredericton, New Brunswick,
Canada
3Division of Athletic Training,University
of Northern Iowa, Cedar Falls, Iowa
Correspondence
Timothy John Fairchild, School of
Psychology and Exercise Science, Murdoch
University, Murdoch, WA, Australia.
Email: T.Fairchild@murdoch.edu.au
Funding information
Support was provided via the PhD research
scheme in the School of Psychology and
Exercise Science at Murdoch University.
The aim of this study was to assess the effectiveness of a multimodal exercise pro-
gram to increase trunk muscle morphology and strength in older individuals, and
their associated changes in functional ability. Using a single‐blinded parallel‐group
randomized controlled trial design, 64 older adults (≥60 years) were randomly allo-
cated to a 12‐week exercise program comprising walking and balance exercises with
or without trunk strengthening/motor control exercises; followed by a 6‐week walk-
ing‐only program (detraining; 32 per group). Trunk muscle morphology (ultrasound
imaging), strength (isokinetic dynamometer), and functional ability and balance (6‐
Minute Walk Test; 30 second Chair Stand Test; Sitting and Rising Test; Berg Balance
Scale, Multi‐Directional Reach Test; Timed Up and Go; Four Step Square Test) were
the primary outcome measures. Sixty‐four older adults (mean [SD]; age: 69.8
[7.5] years; 59.4% female) were randomized into two exercise groups. Trunk training
relative to walking‐balance training increased (mean difference [95% CI]) the size of
the rectus abdominis (2.08 [1.29, 2.89] cm2), lumbar multifidus (L4/L5:0.39 [0.16,
0.61] cm; L5/S1:0.31 [0.07, 0.55] cm), and the lateral abdominal musculature (0.63
[0.40, 0.85] cm); and increased trunk flexion (29.8 [4.40, 55.31] N), extension (37.71
[15.17, 60.25] N), and lateral flexion (52.30 [36.57, 68.02] N) strength. Trunk train-
ing relative to walking‐balance training improved 30‐second Chair Stand Test (5.90
[3.39, 8.42] repetitions), Sitting and Rising Test (1.23 [0.24, 2.23] points), Forward
Reach Test (4.20 [1.89, 6.51] cm), Backward Reach Test (2.42 [0.33, 4.52] cm), and
Timed Up and Go Test (−0.76 [−1.40, −0.13] seconds). Detraining led to some de-
clines but all outcomes remained significantly improved when compared to pre‐train-
ing. These findings support the inclusion of trunk strengthening/motor control
exercises as part of a multimodal exercise program for older adults.
KEYWORDS
ageing, aging, core, detraining, exercise therapy, walking
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SHAHTAHMASSEBI ET Al.
adults.4 Resistance‐based training has typically focused on
exercises for peripheral musculature.5 An important role for
strengthening the trunk musculature in older adults6 has more
recently emerged, due to the importance of these muscles in
performing activities of daily living, balance, and mobility.7,8
Trunk strengthening exercises are generally recommended in
older populations, although the efficacy of trunk strength-
ening exercises on function and balance in older adults re-
quire further investigation.6 Training programs combining
motor control exercises with non‐machine‐based resistance
exercises result in the greatest changes in trunk muscle mor-
phology.9 Functional decline (ie, decreased muscle strength,
morphology, and balance) associated with detraining has
previously been examined in older populations.10-12 To our
knowledge, only one study 13 examined the effect of detrain-
ing on the trunk musculature (changes in maximum back
extensor strength). Specifically, Chen et al13 revealed that
in all exercise groups (resistance, aerobic, combination, and
control), 4 weeks of detraining led to some declines in train-
ing‐induced improvement in trunk strength (extension); how-
ever, trunk strength (extension) after detraining still remained
significantly higher than baseline values across all exercise
groups.
In light of previous findings and recommendations above,
our study sought to determine the effectiveness of a 12‐week
supervised multimodal exercise program, with or without
trunk strengthening/motor control exercises, on trunk muscle
morphology (size), strength, and functional ability in healthy
older adults. We hypothesized that adding trunk strength-
ening/motor control exercises would preferentially increase
trunk muscle morphology (size), strength, and foster greater
improvements in functional ability, compared to a time‐
matched supervised walking and balance exercise program
alone. We also aimed to determine the effect of a subsequent
6‐week detraining phase (walking program) on trunk muscle
morphology (size), strength, and functional ability in healthy
older adults. We hypothesized that training‐induced gains/
improvements in trunk muscle morphology, trunk strength,
and functional ability would decline following detraining.
However, training‐induced gains/improvements following
the exercise program should still remain above baseline even
after detraining.
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METHODS
2.1
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Study design and participant
involvement
This study is a single‐blinded parallel‐group randomized
controlled trial. The trial was prospectively registered
(ACTRN12613001176752) and reported in accordance with
the CONSORT statement (http://www.consort-statement.
org; Table S5). Participants were not involved in setting the
research agenda presented herein. The baseline data from this
study were previously published in a cross‐sectional analy-
sis.14 Participants were randomized to one of two groups
(1:1) using a computer‐generated block randomization list
with random block sizes of 2, 4, or 6. Sequentially numbered,
opaque envelopes containing the participant’s group assign-
ment were prepared by research staff not affiliated with the
delivery of the exercise program. The group allocation was
conducted by the same researcher and occurred after com-
pletion of baseline assessments. Group allocations were con-
cealed from participants and research assistants.
2.2
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Participants
We recruited healthy individuals aged 60 years and older,
who were able to participate in an 18‐week exercise program.
Individuals were excluded from study participation if they
(a) had undergone lumbar spine surgery, (b) had any medical
condition(s) or were taking prescribed medication that may
have precluded safe participation in an exercise program ac-
cording to a standardized adult pre‐exercise screening tool,15
or (c) were unable to communicate in English. Participants
were recruited from the local community via posted flyers,
announcements through local news outlets, and presentations
at local retirement communities. All participants provided
written informed consent on forms approved by the Murdoch
University Human Research Ethics Committee (Protocol No:
2013/140).
2.3
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Exercise programs
All exercise training sessions were conducted and super-
vised by the main instructor (BSH) and the same trainers in
the Rehabilitation, Strength and Conditioning Laboratory
(Sport Science Laboratories), at Murdoch University, Perth,
Western Australia. Each exercise program involved 12 weeks
of training. Participants attended three supervised sessions
per week, and exercise difficulty was progressed over the
course of the program (Table S4). Throughout the interven-
tion, we closely monitored participants, and we asked them to
inform the main instructor (BSH) or one of the main project
coordinators (MH, JH, TF) if they had any issues/concerns
with respect to the assessments or training. All the reports
were recorded in individual participant files. Program adher-
ence was defined a priori as participating in at least 80% of
the exercise sessions.16
2.3.1
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Walking‐balance exercise program
The walking‐balance program comprised the Otago bal-
ance exercises17 (eg, toe raises, figure 8 walking) for 15 and
45 minutes of continuous outdoor walking (around Murdoch
University, South Street Campus, Perth, Western Australia)
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SHAHTAHMASSEBI ET Al.
at approximately 60% of participants’ maximum heart rate18
using the age‐based prediction formula ([20‐age]−[resting
heart rate] × [60%] + [resting heart rate]).19,20 Resting, maxi-
mum, and post‐exercise heart rates of each individual were
checked before, halfway through, and at the end of the walk-
ing session, respectively. We chose an active control group
(walking‐balance exercise group), because it allows us to use
a novel approach to explore whether the inclusion of trunk
strengthening/motor control exercises into the walking‐bal-
ance exercise program might be associated with increased
muscle size, strength, and functional ability in older adults,
instead of using a traditional, placebo‐control group.
2.3.2
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Trunk strengthening
exercise program
The trunk strengthening program comprised the trunk
strengthening/motor control exercises21,22 (eg, abdominal
bracing, front bridge pose, side bridge pose) for 30 minutes
and all components of the walking‐balance program (Otago
balance exercises17 for 15 minutes, and continuous outdoor
walking [around Murdoch University, South Street Campus,
Perth, Western Australia] for 15 minutes [at approximately
60% of participants’ maximum heart rate]). The participant‐
to‐instructor ratio was kept small (eight participants to three
instructors)22 throughout the program. All trunk strengthen-
ing/motor control exercises were conducted on gym mats
using unstable training equipment (eg, Airex mats, Bosu
ball), but without the use of resistance machines. Throughout
the trunk strengthening/motor control exercises, participants
were always in supine, prone, quadruped, and side‐lying po-
sitions on the gym mats to avoid continuous position changes
(from standing to lying/sitting and vice versa), which are
often uncomfortable for older adults.22 Training intensity was
progressively and individually increased over the 12‐week
exercise program by changing the lever lengths, range of mo-
tion, movement velocity (isometric, dynamic), and the level
of stability/instability.
2.3.3
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Detraining
Following completion of the 12‐week exercise program, par-
ticipants in both groups were instructed to continue with a
walking‐only program (45 minutes of continuous walking at
approximately 60% of their maximum heart rate), three times
per week, over the subsequent 6 weeks. We chose a walking‐
only program and termed it the “detraining phase,” because
walking has no apparent effect on the main outcome meas-
ures of the trial, namely trunk muscle morphology (size)9 or
most (except 6‐minute walk test) functional tasks adopted
in the current study. Prior to detraining, each participant
was given a walking diary (walking log) to record the ses-
sion date/time, as well as heart rates (resting, maximum, and
post‐heart rates), and the Borg Rating of Perceived Exertion
(RPE) Scale (perceived intensity of physical activity) to as-
sess adherence. During detraining, participants were not di-
rectly supervised but contacted systematically (eg, twice per
week via telephone calls, emails, or text messages) about
their exercise engagement to assess compliance with the
walking program. Participants were advised to contact the
main instructor (BS) or one of the main project coordinators
(TJF), (JJH), and (MH) whether they encountered any issues/
problems during detraining. Participants were considered
compliant if they completed at least 80% of the 18 sessions
of the walking program over the 6 weeks of detraining.
2.4
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Measurements
Demographic and anthropometric data were recorded at base-
line along with all primary outcome measures. The primary
outcomes were trunk muscle morphology (ultrasound imag-
ing), strength (isokinetic dynamometer), and functional abil-
ity and balance (6‐Minute Walk Test, 30‐second Chair Stand
Test, Sitting and Rising Test, Berg Balance Scale, Multi‐
Directional Reach Test, Timed Up and Go, and Four Step
Square Test). All outcome measures were readministered at
week 6, week 12, and week 18. All assessments (ultrasound
imaging, isokinetic dynamometer, and functional ability and
balance) were carried out by the same trained assessor (BSH)
in the Rehabilitation, Strength and Conditioning Laboratory
(Sport Science Laboratories), at Murdoch University, Perth,
Western Australia.
2.4.1
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Anthropometric and demographic
characteristics
Participants filled in a demographic questionnaire and an-
swered one question on self‐reported physical activity. This
question was adapted from Question 27 of The Falls Risk for
Older People in the Community (FROP‐Com). We measured
body weight using a digital scale (Scales Plus, Perth, WA,
Australia) and height (standing and seated) using a wall‐
mounted stadiometer (Surgical Medical Supplies Pvt Ltd,
Adelaide, SA, Australia).
2.4.2
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Trunk muscle morphology
A high‐resolution ultrasound unit with a 60 mm broad-
band curved array ultrasound transducer probe (5‐2 MHz;
SonoSite M‐Turbo, SonoSite™, Bothell, WA, USA) was
used to measure the size of the rectus abdominis (RA),
internal oblique (IO), external oblique (EO), transversus
abdominis (TrA), and lumbar multifidus (LM). Previous
studies using ultrasound imaging to measure trunk muscle
size in older adults have demonstrated high inter‐rater and
intra‐rater reliability (ICC ≥ 0.86).23-25 Image acquisition
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SHAHTAHMASSEBI ET Al.
was performed three times bilaterally and exported for of-
fline analysis using Image J (National Institutes of Health,
version 1.41). All measures were averaged across the three
repetitions to reduce measurement error.26 We created total
lateral abdominal muscles size variable by summing the
thickness of TrA, IO, and EO muscles. We calculated the
intra‐rater variability (the percentage coefficient of varia-
tion; %CV) across three ultrasound images of the selected
trunk muscles (ie, rectus abdominis, lumbar multifidus
L4/L5, lumbar multifidus L5/S1, total lateral abdominal
muscles [internal oblique + external oblique + transversus
abdominis]) among 30 participants (Trunk strengthening
exercise = 15, Walking‐balance = 15; Table S6). The co-
efficient of variation was calculated (CV in %: Standard
Error of Measurement [SEM]/mean value × 100). The
SEM was calculated using the formula: [SEM = SD √1−r]
where SD is the standard deviation, and r is the reliability
coefficient for that measurement.27 The ultrasound imag-
ing procedure of trunk muscles size has been described
previously.14
2.4.3
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Trunk muscle strength
Maximal isometric strength in trunk flexion, extension,
and lateral flexion was measured using the Humac NORM
Isokinetic dynamometer (Humac NORM, Computer Sports
Medicine, Stoughton, MA, USA) with the trunk extension‐
flexion modular component. Isokinetic dynamometry has
previously been reported to be a reliable and valid method
for measuring trunk muscle strength.28,29 The measurement
procedure of maximal isometric trunk strength has been de-
scribed previously.14
2.4.4
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Functional ability and balance
Functional ability and balance were assessed using reliable
and valid tests (the 6‐Minute Walk Test,30,31 the 30‐second
Chair Stand Test,32 the Sitting and Rising Test,33 the Berg
Balance Scale,34,35 the Multi‐Directional Reach Test,36,37 the
Timed Up and Go,38 and the Four Step Square Test).39 The
6‐Minute Walk Test31 assesses distance (meters) walked over
6 minutes which should be performed indoors, along an en-
closed, flat, straight, hard‐surfaced 25‐m corridor. The walk-
ing track was marked with two cones at turn‐around points
(start, turn around‐go back).30 Performance on the 30‐second
Chair Stand Test32 was derived from the number of success-
ful repetitions in 30 seconds. The 30‐second Chair Stand Test
requires participants to stand fully upright (with arms crossed
over the chest) from a chair without arms (approximate seat
height of 43.18 cm) then return to the seated position as many
times as possible, within 30 seconds.32 The Sitting and Rising
Test33 measures the individual’s ability to sit and rise unas-
sisted from the floor, with partial scores assigned from the
two required actions of sitting (5 points) and rising (5 points),
along with a final composite score ranging from 0 to 10. The
Berg Balance Scale35 comprises 14 items of static and dy-
namic balance tasks, and scores are presented as a summed
score with a maximum of 56 points. The Multi‐Directional
Reach Test36 requires participants to voluntarily reach and
shift their center of gravity to the limits of the base of support
with the feet stationary, in order to measure the limits of sta-
bility in four directions: forward, backward, rightward, and
leftward.36 The results from the Multi‐Directional Reach Test
are presented as Forward Reach Test (cm); Backward Reach
Test (cm); Right Reach Test (cm); and Left Reach Test (cm).
The Timed Up and Go Test38 measures functional mobility,
gait speed, and risk of falls. For the timed Up and Go Test,
participants were timed (in seconds) to stand from a standard
armchair (approximately seat height 46 cm and arm height
65 cm) without using the arms or any physical assistance,
walk at a comfortable and safe pace to a line on the floor 3 m
away, turn, walk back return to the chair, and sit down on the
chair.38 The Four Step Square Test39 is a timed agility, bal-
ance, quick stepping, and coordination test in four different
directions. For the Four Step Square Test, four canes (height
2.5 cm and length 90 cm) were placed flat on the floor in a
cross formation to mark four squares (1,2,3,4). Participants
were timed (in seconds) to step forward, sideways, and back-
wards over the four canes. Participants were then asked to
stand and touch the floor with both feet in square 1, and then
step as fast as possible from one square to another in the
order; 2‐3‐4‐1‐4‐3‐2 and 1.39
2.5
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Sample size
An a priori power analysis revealed 64 participants (32 per
group) would be required to detect a small‐moderate effect
(f = 0.165; type I error = 0.05; type II error = 0.80) between
two groups assuming four repeated measurements with a cor-
relation between measures of 0.50 and an anticipated 20%
dropout rate. The effect size was computed from changes in
trunk muscle morphology (abdominal muscle morphology)
following an exercise training intervention.40
2.6
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Statistical
Data management and statistical analyses were performed
using IBM SPSS version 22.0 software (IBM Corp,
Armonk, NY). The primary outcomes were trunk muscle
morphology (ultrasound imaging), strength (isokinetic dy-
namometer), and functional ability and balance (6‐Minute
Walk Test; 30‐second Chair Stand Test; Sitting and Rising
Test; Berg Balance Scale; Multi‐Directional Reach Test;
Timed Up and Go; Four Step Square Test). Treatment ef-
fects were estimated with separate, random‐intercept linear
mixed models for each outcome variable. Time [baseline
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SHAHTAHMASSEBI ET Al.
(week 0), 6, 12, 18 weeks] and exercise group (trunk
strengthening, walking‐balance) were modeled as fixed ef-
fects. The hypothesis of interest was the group by time in-
teraction, which was examined with pairwise comparisons
of the estimated marginal means. Consistent with the inten-
tion‐to‐treat principle, the linear mixed models estimated
values for missing data based on the available scores;
therefore, all participants were included in the analyses.
The level of significance was set at P 0.05.
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RESULTS
Between February 2014 and November 2015, 105 individu-
als were screened for study inclusion (the first participant
was enrolled on February 14, 2014, the last participant was
assessed May 21, 2015, and the project was finalized on
November 25, 2015). Sixty‐four participants met the inclu-
sion criteria. Thirty‐two participants were randomly allo-
cated to the trunk strengthening exercise group, and 32 to the
walking‐balance exercise group (Figure S1). Exercise adher-
ence (trunk strengthening: 90% and walking‐balance: 93.5%)
was considered high, and loss to follow‐up (trunk strengthen-
ing: 12.5% and walking‐balance: 6.2%) low. We had three
medically related withdrawals (eg, back pain, brain, and jaw
surgeries) in the current study. However, none of these medi-
cal conditions were deemed to be related to any training or
test‐related injury or other adverse events by the review team
(MH, JH, TF). All the reports were recorded in individual
participant files. Baseline characteristics of participants are
presented in Table 1.
3.1
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Changes in trunk muscle morphology
in response to exercise program and detraining
A significant time by group interaction was identified for all
trunk muscle morphology outcomes (Figure 1; see Table S1,
Changes in trunk muscle morphology in response to exer-
cise program and detraining). At week 12, participants in the
trunk strengthening exercise group had greater hypertrophy
(mean difference [95% CI] or percentage %) in the CSA of
rectus abdominis (2.08 [1.29‐2.89] cm2 or 47.2%), and thick-
ness of the lumbar multifidus at L4/L5 (0.39 [0.16‐0.61] cm
or 12.1%) and L5/S1 (0.31 [0.07‐0.55] cm or 9.6%), as well
as the mean thickness of the lateral abdominal muscles (0.63
[0.40‐0.85] cm or 36%) compared with participants in the walk-
ing‐balance exercise group (Figure 1; see Table S1, Changes
in trunk muscle morphology in response to exercise program
and detraining). Following the subsequent 6 weeks of detrain-
ing, between‐group differences were no longer present (week
18) for rectus abdominis CSA, or lumbar multifidus thickness.
However, participants in the trunk strengthening exercise group
retained greater muscle size (mean difference [95% CI]) only
in the total lateral abdominal muscles (mean of right and left;
0.28 [0.01‐0.55] cm) compared with participants in the walk-
ing‐balance exercise group (Figure 1; see Table S1, Changes in
trunk muscle morphology in response to exercise program and
detraining).
FIGURE 1 Changes in trunk muscle
morphology in response to exercise
program and detraining. All differences
were estimated using linear mixed‐effect
models with random intercepts. Values are
presented as mean values (95% CIs). CSA:
cross‐sectional area, L4/L5: lumbar spinal
level L4/L5, L5/S1: lumbar spinal level L5/
S1. *Significant difference between groups
at P ≤ 0.05, †significant difference from
week 0 (baseline) at P ≤ 0.05, #significant
difference from week 12 at P ≤ 0.05
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SHAHTAHMASSEBI ET Al.
3.2
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Changes in trunk muscle strength in
response to exercise program and detraining
A significant time by group interaction was identified for all
trunk strength outcomes (Figure 2; see Table S2, Changes in
trunk muscle strength in response to exercise program and
detraining). Participants in the trunk strengthening exercise
group experienced larger increases (mean difference [95%
CI] or percentage %) in trunk flexion (29.8 [4.4‐55.3] N or
23.2%), trunk extension (37.7 [15.1‐60.2] N or 41.6%), and
trunk lateral flexion strength (52.3 [36.5‐68.0] N or 83.6%)
at week 12 compared with participants in the walking‐bal-
ance exercise group (Figure 2; see Table S2, Changes in
trunk muscle strength in response to exercise program and
detraining). Following the subsequent 6 weeks of detrain-
ing, participants in the trunk strengthening exercise group
largely retained the improvements from the trunk strength-
ening training program (Figure 2; see Table S2, the changes
in trunk muscle strength in response to exercise program
and detraining). Specifically, at week 18, participants in
the trunk strengthening exercise group had greater (mean
difference [95% CI]) trunk extension (40.0 [14.9‐65.2] N)
and trunk lateral flexion strength (50.6 [32.9‐68.4] N)
compared with participants in the walking‐balance exer-
cise group.
3.3
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Changes in functional
ability and balance in response to exercise
program and detraining
A significant time by group interaction was identified
for some of the functional ability and balance outcomes
(Figures 3 and 4; see Table S3, Changes in functional
ability and balance in response to exercise program and
detraining). At 6 weeks, performance in the 30‐second
Chair Stand Test was better (mean difference [95% CI] or
TABLE 1 Baseline characteristics of study’s participants stratified by exercise group
Characteristics All (n = 64)
Trunk strengthening
(n = 32)
Walking‐balance
(n = 32)
Age, years 69.8 ± 7.5 70.1 (7.7) 69.4 (7.3)
Sex n (%) female 38 (59.4) 18 (56.3) 20 (62.5)
Height, cm 165.1 (9.0) 166.5 (9.2) 163.8 (8.9)
Weight, kg 74.9 (14.8) 74.3 (14.0) 75.4 (15.8)
BMI, kg/m227.3 ± 4.7 26.6 (3.2) 28.1 (5.8)
Sitting height, cm 80.5 ± 5.0 81.5 (4.9) 79.5 (4.9)
Living status
Lived with one or more than one persons (%) 18 (28.1) 9 (28.1) 9 (28.1)
Lived alone (%) 46 (71.9) 23 (71.9) 23 (71.9)
Could drive (%) 62 (96.9) 32 (100) 30 (94)
Used glasses or contact lens (%) 55 (85.9) 25 (78.1) 30 (93.8)
Used hearing aids (%) 8 (12.5) 4 (12.5) 4 (12.5)
Used walking aid (%) 0 0 0
History of falls over past 1 mo
Falls n (%) 6 (9.4) 2 (6.3) 4 (12.5)
History of falls over past 12 mo
Falls (%) 12 (18.8) 6 (18.8) 6 (18.8)
Medications
1‐2 Medications n (%) 27 (42.2) 14 (43.7) 13 (40.6)
3 Medications or more n (%) 22 (12.5) 10 (31.3) 12 (37.6)
No medications n (%) 15 (23.4) 8 (25.0) 7 (21.8)
Self‐reported physical activity
Moderately active (1‐2 times/week) n (%) 34 (53.1) 14 (43.7) 20 (62.5)
Very active (3 times/week) n (%) 28 (43.8) 16 (50.0) 12 (37.5)
Not very active (rarely leaves house) n (%) 2 (3.1) 2 (6.3) 0 (0)
Values are presented as mean (SD) or as number and percentage.
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SHAHTAHMASSEBI ET Al.
percentage %) in the trunk strengthening group, relative
to the walking‐balance group (3.1 [0.63‐5.6] repetitions
or 17.4%; Figures 3; see Table S3, Changes in functional
ability and balance in response to exercise program and de-
training). After 12 weeks of the exercise program, partici-
pants in the trunk strengthening exercise group performed
better on the 30‐second Chair Stand Test (5.9 [3.3‐8.4] rep-
etitions or 30.8%), Sitting and Rising Test (1.2 [0.24‐2.2]
points or 18.1%), Forward Reach Test (4.2 [1.8‐6.5] cm or
13.7%), Backward Reach Test (2.4 [0.33‐4.5] cm, 12.9%)
and Timed Up and Go Test (−0.76 [−1.4 to −0.13] sec-
onds, 12%), relative to the walking‐balance exercise group
(Figures 3 and 4; see Table S3, Changes in functional abil-
ity and balance in response to exercise program and de-
training). Following the subsequent 6 weeks of detraining,
participants in the trunk strengthening exercise group re-
tained better performance outcomes (mean difference [95%
CI]) in the 30‐second Chair Stand Test (4.4 [1.5‐7.3] repe-
titions) and Forward Reach Test (3.9 [1.4‐6.3]) at week 18,
compared to the walking‐balance exercise group (Figures
3 and 4; see Table S3, Changes in functional ability and
balance in response to exercise program and detraining).
4
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DISCUSSION
The main findings of this study were as follows: inclusion
of trunk strengthening/motor control exercises into a mul-
timodal exercise program (a) increased trunk muscle size
and strength; and (b) improved functional ability and bal-
ance (30‐Second Chair Stand Test, Sitting and Rising Test,
Forward Reach Test, Backward Reach Test, and Timed Up
and Go Test), relative to a walking‐balance control group.
Additionally, training‐induced improvements in trunk mus-
cle strength, and functional ability and balance, but not mus-
cle size, were retained following the subsequent 6 weeks
of detraining (walking program), particularly in the trunk
strengthening exercise group.
Significant hypertrophy (9.6%‐47.2%) occurred in all
trunk muscles in response to the 12‐week exercise program;
this finding is consistent with a recent systematic review that
primarily evaluated younger adults.9 These findings may help
to dispel the myth that older adults do not benefit from train-
ing as much as younger adults. Importantly, in three of the
four assessed muscle groups (rectus abdominis, lumbar mul-
tifidus muscle at L4/L5, and the total lateral abdominal mus-
cles), significant between‐group differences were identified
by week 6. The rate of hypertrophy in the lumbar multifidus
muscle is consistent with the findings of a previous study34
in a similarly aged cohort. Specifically, increases in lumbar
multifidus muscle thickness following our 12‐week exercise
program (1.78% and 1.42% per week over 6 and 12 weeks,
respectively) are comparable to findings of Klizienė et al41
(1.56% and 2.11% increases per week in the lumbar multifi-
dus CSA over 16 and 32 weeks, respectively). To the authors’
knowledge, this study is also the first study that examined
the effect of detraining on trunk muscle morphology (size).
Participants in the trunk strengthening exercise group lost
(−3% to −9.1%) training‐induced trunk muscle size, but these
still remained significantly greater than baseline (Figure 1),
thus demonstrating that participants were still able to retain
training‐induced gains from the exercise program in trunk
muscle size to a certain extent. Together, our findings imply
that older adults should engage consistently in structured and
systematic exercise programs (even for a short duration of
training) that contain trunk strengthening/motor control exer-
cise components, in order to improve and/or maintain trunk
muscle (size), and to protect against age‐related progressive
degeneration of these muscles (Sarcopenia).
The current study demonstrated a significant increase in
all measures of trunk strength by week 12 in participants of
the trunk strengthening exercise program (Figure 2). These
results are consistent with the outcomes of a recent system-
atic review which showed that including trunk strengthen-
ing exercises into exercise programs improved trunk muscle
strength among older adults.6 The increases in trunk flexion
FIGURE 2 Changes in trunk muscle strength in response to exercise program and detraining. All differences were estimated using linear
mixed‐effect models with random intercepts. Values are presented as mean values (95% CIs). *Significant difference between groups at P ≤ 0.05,
†significant difference from week 0 (baseline) at P ≤ 0.05, #significant difference from week 12 at P ≤ 0.05
8
|
SHAHTAHMASSEBI ET Al.
and extension strength with the trunk strengthening exercise
program are consistent with two previous studies13,42 which
showed that the use of an exercise program designed to
specifically target the abdominal and lower back muscles
potentially contributed to this large increase in trunk muscle
strength. Changes in strength associated with the detraining
phase were not significant or as apparent (−1.7% to −6.8%)
as those observed in muscle size. All measures of trunk
FIGURE 3 Changes in functional
ability and balance in response to exercise
program and detraining. All differences
were estimated using linear mixed‐effect
models with random intercepts. Values
are presented as mean values (95% CIs).
*Significant difference between groups
at P ≤ 0.05, †significant difference from
week 0 (baseline) at P ≤ 0.05, #significant
difference from week 12 at P ≤ 0.05
FIGURE 4 Changes in functional ability and balance in response to exercise program and detraining. All differences were estimated using
linear mixed‐effect models with random intercepts. Values are presented as mean values (95% CIs). *Significant difference between groups at
P ≤ 0.05, †significant difference from week 0 (baseline) at P ≤ 0.05, #significant difference from week 12 at P ≤ 0.05
|
9
SHAHTAHMASSEBI ET Al.
strength remained significantly higher at week 18 (post the
6‐week detraining phase) compared to baseline in the trunk
strengthening exercise group (Figure 2), which is consistent
with the findings (trunk extension only) of Chen et al.13
Improvements in the 30‐second Chair Stand Test follow-
ing the trunk strengthening exercise program in our study is
consistent with findings from previous studies.6,43 The ability
to sit and rise from the floor unassisted (represented in the
Sitting and Rising Test) has been reported to predict mortal-
ity in older individuals,33 with each one‐point improvement in
test score associated with a 21% reduction in all‐cause mor-
tality.33 Our study clearly showed that the trunk strengthening
exercises improved Sitting and Rising Test performance rela-
tive to the walking‐balance exercise group.
The trunk strengthening exercise program also resulted
in significant improvements in the Multi‐Directional Reach
Test (forward and backward). This increase in Multi‐
Directional Reach Test performance following the trunk
strengthening exercise program is in agreement with pre-
vious studies.6,12,22 Significant within and between‐group
changes were observed for the forward and backward reach
tests, while only within‐group changes were identified for
the Functional Reach Test sideways (right/left) tests, follow-
ing 6 and 12 weeks of both exercise programs (Table S4).
Individuals unable to reach six or more inches (≤15.24 cm)
forward have previously been identified as being at high
risk of falls.44 Notably, the distance achieved in the Multi‐
Directional Reach Test by this study cohort is comparable
to those previously published36 in a similarly aged healthy
cohort (Mean scores of Forward Reach Test = 22.58
[8.63] cm, Backward Reach Test = 11.78 [7.79] cm, Right
Reach Test = 15.62 [7.59] cm, and Left Reach Test = 16.78
[7.31] cm [29]). Although all participants in this study co-
hort achieved scores above clinical cutoff points at base-
line (Table S4), the participants in the trunk strengthening
exercise group still demonstrated significant improvements
in Forward and Backward Reach Test (both ~ 15%) after
12 weeks of the exercise program.
The significant improvements in participants’ perfor-
mance in the Timed Up and Go Test following the trunk
strengthening exercise program was also in agreement with
previous studies.12,22 Longer Timed Up and Go test times
are associated with decreased mobility and may predict
falls in older adults.38 Older individuals who completed the
Timed Up and Go test in <10 seconds (independent individ-
uals in physical mobility) are classified into the first cate-
gory of Timed Up and Go Test scores.38 All the participants
in the current study were classified into the first category
with good functional performance at baseline (mean [SD];
trunk strengthening 7.5 [1.7] seconds, walking‐balance ex-
ercise 7.3 [2.0] seconds). However, participants in the trunk
strengthening exercise group demonstrated significant im-
provements in Timed Up and Go Test performance, whereas
the walking‐balance exercise group’s performance in this test
did not significantly improve.
Although there were no significant between‐group dif-
ferences in Berg Balance Scale performance, there were
significant (3%‐7%) within‐group improvements for all par-
ticipants. Previous research has reported 4 points of improve-
ment as the minimum level of detectable change required
in the Berg Balance Scale among older adults with base-
line scores of 45‐56 points.45 In the current study, only the
trunk strengthening exercise group achieved this magnitude
of change (mean change of 51.7‐55.7 points). Specifically,
six participants from the trunk strengthening group and
five participants in the walking‐balance group met this 4‐
point criterion. With respect to the 6‐Minute Walk Test,
although there were no between‐group differences, meaning-
ful improvements (>50 m)46 were observed in both groups
(11.2%‐16.4%; 64‐101 m; Figure 3) and were comparable to
previous observations.47
With respect to the Four Step Square Test, a cutoff score
of 15 seconds is the criterion used to distinguish older adults
with a history of multiple falls (>15 seconds) from indi-
viduals with no history of falls (15 seconds).39 Participants
in the trunk strengthening exercise group scored (mean
[SD] seconds) (8.5 [1.7] seconds) and participants in the
walking‐balance exercise group scored (8.0 [1.5] seconds).
These within‐group changes were statistically significant
(7%‐25.4%), following 12 weeks of both exercise programs,
but there were no significant between‐group differences.
Changes in all functional outcomes associated with the
6‐week detraining phase (walking only; weeks 12‐18) were
small (All 3.0% decrement) and remained above baseline val-
ues in both groups.
The study presented herein had multiple strengths, in-
cluding (a) adoption of a randomized controlled design; (b)
the high level of adherence to both exercise programmes and
low loss to follow‐up; and (c) adoption of reliable and valid
outcome measures. Despite these strengths, these findings
should be considered in light of several limitations. The par-
ticipants included in this study were generally healthy and
moderately active older adults. Therefore, the current study
results may not generalize to other populations. Our outcome
measures may not represent all the components of trunk mus-
cle morphology, strength, mobility, and balance; therefore,
the findings of our study should also be generalized with cau-
tion to other experimental assessment techniques (ie, MRI
imaging, isokinetic trunk strength, force‐plate for balance,
and postural sway measurements). The single‐blinded design
resulted in the assessments (ultrasound imaging, isokinetic
dynamometer, and functional ability and balance) being un-
dertaken by the same individual (BSH) involved in the ex-
ercise training program. This individual was, therefore, not
blinded to the group allocation, and this could have intro-
duced measurement bias.
10
|
SHAHTAHMASSEBI ET Al.
Our study did not incorporate any long‐term follow‐up,
thus the impact of these programs over longer periods is
unknown. We measured surrogate outcomes in the present
study, and the effect of these exercise programs on hard end-
points like falls and injury remains unknown.
Future research should thus focus on long‐term outcomes
including falls risk and incidence of falls and related injuries
following similar exercise programs. In addition, the benefits
of this type of exercise program in clinical populations (ie,
sedentary, frail older adults, and musculo‐skeletal disorders)
require further investigation.
5
|
CONCLUSION
Following completion of the 12‐week exercise program, we
found that participants in the trunk strengthening exercise
group experienced (a) greater increases in trunk muscle size
and strength and (b) greater improvement in functional abil-
ity compared to participants in the walking‐balance exercise
group. Six weeks of detraining (walking program only) signifi-
cantly decreased trunk muscle size in the trunk strengthening
exercise group and caused slight declines in trunk strength and
functional ability in both exercise groups. Overall, the inclusion
of trunk strengthening/motor control exercises into a 12‐week
supervised walking‐balance exercise program appeared to be
safe (no training‐related injuries), feasible (high attendance
rates of >90%), and inexpensive (minimal equipment), and was
associated with improvements in trunk muscle size, strength,
and functional ability in healthy older adults.
5.1
|
Perspective
Exercises to strengthen the trunk musculature in older in-
dividuals has been associated with improving strength and
functional outcomes,22 although current evidence is limited
to only a few studies.6 In the current study, we confirm the
benefits of including trunk strengthening/motor control ex-
ercises into a supervised, time‐matched multimodal (walk-
ing and balance) exercise program. Specifically, addition
of trunk strengthening exercises to a 12‐week training
program (a) increased muscle morphology by 9.6%‐47.2%
across the trunk musculature and (b) increased trunk muscle
strength by 23.2%‐83.6%. This translated into significant
between‐group improvements in the functional measures,
including the 30‐second Chair Stand Test (30.8%), Sitting
and Rising Test (18.1%), Forward Reach Test (13.7%),
Backward Reach Test (12.9%), and Timed Up and Go test
(12%). Function, along with trunk muscle morphology and
strength, declined in the subsequent 6‐week detraining
period consisting of walking‐exercise only. However, the
improvements across all outcomes remained significantly
above baseline levels.
ACKNOWLEDGEMENTS
The authors would like to thank Dr Golnaz Shahtahmassebi
for statistical advice.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
AUTHOR CONTRIBUTIONS
BS was involved in the study conception, study design, data
acquisition, and analysis, as well as drafting and approval
of the final manuscript. JJH was involved in the study con-
ception, study design, and data analysis, as well as critical
manuscript revision and final approval. MH was involved
in the data acquisition as well as critical manuscript re-
vision, and final approval. TJF was involved in the study
conception, study design, critical manuscript revision and
final approval.
ETHICS APPROVAL
This study was approved by the Murdoch University Human
Research Ethics Committee (Protocol No: 2013/140).
ORCID
Behnaz Shahtahmassebi https://orcid.org/0000-0002-8105-
1314
Jeffrey J. Hebert http://orcid.org/0000-0002-6959-325X
Timothy J. Fairchild https://orcid.org/0000-0002-3975-2213
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SUPPORTING INFORMATION
Additional supporting information may be found online in
the Supporting Information section at the end of the article.
How to cite this article: Shahtahmassebi B, Hebert
JJ, Hecimovich M, Fairchild TJ. Trunk exercise
training improves muscle size, strength, and function
in older adults: A randomized controlled trial. Scand J
Med Sci Sports. 2019;00:1–12. https://doi.org/10.1111/
sms.13415
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