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IMPACT OF RANGE OF MOTION DURING ECOLOGICALLY
VALID RESISTANCE TRAINING PROTOCOLS ON MUSCLE
SIZE,SUBCUTANEOUS FAT,AND STRENGTH
GERARD E. MCMAHON,
1,2
CHRISTOPHER I. MORSE,
1
ADRIAN BURDEN,
1
KEITH WINWOOD,
1
AND
GLADYS L. ONAMBE
´LE
´
1
1
Institute for Performance Research, Department of Exercise & Sport Science, Manchester Metropolitan University, Crewe,
United Kingdom; and
2
Sports Institute Northern Ireland, University of Ulster, Newtownabbey, Belfast, Ireland
ABSTRACT
McMahon, GE, Morse, CI, Burden, A, Winwood, K, and
Onambe
´le
´, GL. Impact of range of motion during ecologically
valid resistance training protocols on muscle size, subcutane-
ous fat, and strength. J Strength Cond Res 28(1): 245–255,
2014—The impact of using different resistance training (RT)
kinematics, which therefore alters RT mechanics, and their sub-
sequent effect on adaptations remain largely unreported. The
aim of this study was to identify the differences to training at
a longer (LR) compared with a shorter (SR) range of motion
(ROM) and the time course of any changes during detraining.
Recreationally active participants in LR (aged 19 62.6 years;
n= 8) and SR (aged 19 63.4 years; n= 8) groups undertook
8 weeks of RT and 4 weeks of detraining. Muscle size, archi-
tecture, subcutaneous fat, and strength were measured at
weeks 0, 8, 10, and 12 (repeated measures). A control group
(aged 23 62.4 years; n= 10) was also monitored during this
period. Significant (p.0.05) posttraining differences existed
in strength (on average 4 62 vs. 18 62%), distal anatomical
cross-sectional area (59 615 vs. 16 610%), fascicle length
(23 65 vs. 10 62%), and subcutaneous fat (22 68 vs. 5 6
2%), with LR exhibiting greater adaptations than SR. Detrain-
ing resulted in significant (p.0.05) deteriorations in all muscle
parameters measured in both groups, with the SR group expe-
riencing a more rapid relative loss of postexercise increases in
strength than that experienced by the LR group (p.0.05).
Greater morphological and architectural RT adaptations in the
LR (owing to higher mechanical stress) result in a more signif-
icant increase in strength compared with that of the SR. The
practical implications for this body of work follow that LR
should be observed in RT where increased muscle strength
and size are the objective, because we demonstrate here that
ROM should not be compromised for greater external loading.
KEY WORDS detraining, hypertrophy, muscle architecture,
range of motion, stress, strength training
INTRODUCTION
To the strength and conditioning practitioner, the
design of a resistance training (RT) program will
incorporate a selection of exercises that will ideally
reflect both functional tasks of a chosen sport and
also the ability of the exercise to bring about a desired set of
adaptations to enhance function and ideally, therefore, phys-
ical performance. Because muscle force is proportional to
muscle cross-sectional area (29), is intimately linked with
power, and is a key determinant to success in many sports,
muscular hypertrophy is often a key outcome after RT. The
degree of hypertrophy arises from the manipulation of the
training stimulus: exercise selection and order, mode of con-
traction, intensity, recovery, and volume (38). Although
studies on several of these variables are numerous, effects
of training kinematics on training mechanics remain largely
unreported. Taking the squat exercise (which is an exercise
often used to overload the knee extensor muscle group dur-
ing a hypertrophic training phase) as an example, studies
have investigated the relationship between range of motion
(ROM) of the squat and its effects on thigh muscle activation
and joint moments (51), tibiofemoral shear and compressive
forces (36), and on peak velocity and force (10). One poten-
tial important aspect of training kinematics (i.e., ROM) that
practitioners may not have previously taken into consider-
ation is the effects of ROM on muscle mechanics during RT,
and the subsequent adaptations as a result. Suboptimal or
inadequate loading of the muscle group therefore could lead
to the goals of the RT program not being met.
As muscle length changes during force production to
bring about movement, the moment arm of the series elastic
component (i.e., the tendon) also changes. Therefore, the
internal tension a muscle experiences at different joint angles
will change despite there being no alterations in external
Address correspondence to Gladys Onambe
´le
´-Pearson, g.pearson@
mmu.ac.uk.
28(1)/245–255
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VOLUME 28 | NUMBER 1 | JANUARY 2014 | 245
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absolute load. Simultaneous to the change in moment arm is
the effect of changing muscle length on actin-myosin
interactions and thus crossbridge states (18). A changing
muscle length will vary both these cellular factors, thus im-
pacting on the force-length relationship in the muscle (37).
The magnitude of mechanical stress is known to induce
muscle hypertrophy (30); therefore, increased mechanical
stress at 1 joint angle compared with another could act as
a signal for additional sarcomerogenesis at that muscle
length based on the differential stress imposed through the
moment arm changes. To further augment sarcomerogenesis
at different muscle lengths are the effects stretch has on
muscle. Muscles undergoing different amounts of stretching
and shortening have been shown to adapt to their new func-
tional lengths by the addition or removal of sarcomeres in
series (12,46,50), with an increase in functional length asso-
ciated with increased protein synthesis (13).
This identifies “average muscle length-specific training” as
a potential modulator of the training-induced hypertrophic
response. Only 1 previous study to our knowledge (26) has
investigated training at different joint angles on muscle size
and function in vivo, but the results do not reflect what the
theory would have predicted. Nine men completed a 12-
week unilateral isometric training program (70% maximum
voluntary contraction 315 seconds 36 sets) on the knee
extensors at either a short (508of knee flexion) or a long
(1008) muscle length. The authors found that whole quadri-
ceps volume increased significantly in both short (+10 6
1%) and long (+11 62%) muscle lengths, although there
was no significant difference between the groups. However,
it should be noted that the isometric-only protocol adopted
by Kubo et al. (25) may not reflect the practices of individ-
uals training to optimize gains in strength and hypertrophy
in addition to the limited transfer of the functional aspect of
an isometric exercise.
Architectural adaptations have also been shown to occur
with RT. Alterations to the fascicle angle of pennation impacts
on the physiological cross-sectional area (CSA) and therefore
force-generating capacity (1) of muscle, whereas changes to
fascicle length are associated with alterations to the force-
velocity relationship (48), which therefore impacts potential
power output. Regarding fascicle angle, there appears to be
a strong relationship between increases in muscle size and
increases in pennation angle (4,19,20). Although an increase
in pennation angle is expected to allow an increase muscle
force (up to an upper limit of 458), at greater pennation angles,
the effective contractile force exerted on the aponeurosis is
reduced to a greater extent, off-setting the increase in force
production from the increased number of actomyosin cross-
bridges activated in parallel (35,42). Hence, it is important to
monitor both fascicle angle and functional changes in strength
in the muscle of interest. To systematically determine what
changes are evident in the muscle in terms of hypertrophic
and architectural changes is therefore key to optimizing train-
ing protocols with the associated training adaptations.
It is also important to describe how the muscle responds
to a reduction in loading. Detraining is the partial or
complete loss of training-induced adaptations, in response
to an insufficient loading stimulus (32). Significant decre-
ments in strength, electromyography (EMG), and mean
fiber CSA have been reported in as little as 2 weeks of de-
training (16), with similar observations in chronic detraining
periods ($4 weeks) alluding to either losses in mass, strength
or neural activation, or combinations of these factors
(15,25,34). Also, most studies have tended to report changes
after detraining after similar time courses to the preceding
RT, that is, between 3 and 6 months. If there appears to be
a greater hypertrophic response at 1 muscle length over
another, it would also be of interest to determine whether
there is a differential modulation of detraining-induced mal-
adaptations after greater initial gains from RT at different
muscle lengths. Thus, if these greater gains are still evident
after detraining, it would further highlight the value of using
more optimal training mechanics within an RT program.
The purpose of this study was to therefore describe the
changes to vastus lateralis (VL) anatomical CSA (aCSA),
architecture, subcutaneous fat content, and strength after 8
weeks of dynamic resistance exercise at 508compared with 908
of knee flexion, using an ecologically valid training regime. In
brief, the specified angle is the position at which the training
load is held isometrically for 2 seconds. With 508, this involves
ashorterROM(SR)inthedynamicphaseoftheexerciseand
thus a shorter “average muscle length,” whereas with 908,this
involves a longer ROM (LR) in the dynamic phase of the
exercise and thus a longer “average muscle length.” A second
objective was to describe the effects of the detraining time
course over 4 weeks on the aforementioned variables. It was
hypothesized that the group training at longer muscle length
(908joint angle) would undergo a greater amount of skeletal
muscle hypertrophy because of increased physiological stress
and stretch on sarcomeres compared with the group training at
508. It was also expected that the LR group would continue to
have a large muscle mass after detraining, because of greater
initial gains. Strength-related parameters were expected to fol-
low the same pattern as those associated with hypertrophy.
METHODS
Experimental Approach to the Problem
We sought to compare changes in muscle size, architecture,
function, and subcutaneous fat after 8 weeks of RT and 4
weeks of detraining covering 2 distinctly different ROMs
(the between-subjects independent variable) to identify the
most effective method of RT based on the adaptations
observed (dependent variables described below). The par-
ticipants performed isoinertial RT at either a shorter average
muscle length (ROM 0–508knee flexion) or a longer average
muscle length (ROM 0–908knee flexion) 3 times per week at
80% 1RM during the training period and performed habitual
activity during detraining. Dependent variables were
Range-of-Motion Specific Muscle Loading
246
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measured at baseline, posttraining, after 2 weeks of detrain-
ing and again after a further 2 weeks of detraining (the
within-subject independent variable). Testing was completed
within 3 hours of the time of day at weeks 0, 8, 10, and 12
to minimize any impact of diurnal variability in muscle func-
tion (28). The participants were allowed to drink water ad
libitum during testing and training sessions.
Subjects
Twenty-six volunteers (14 men and 12 women; age range of
18 to 26 years old) from the local university campus gave
written informed consent to participate in this study with all
procedures and experimental protocols approved by the local
Ethics Committee within the Department of Exercise and
Sport Science. Exclusion criteria included the presence of any
known musculoskeletal, neurological, and inflammatory and
metabolic disorders or injury. The participants took part in
recreational activities such as team sports and had either never
taken part in lower limb RT or over the last 12 months.
Sixteen activity-matched men and women were randomly
assigned to either the SR (n= 8–4 men, 4 women) training
group or to the long ROM (LR; n= 8–4 men, 4 women)
training group. Ten participants (6 men and 4 women) were
assigned to the nontraining control group (Con) to monitor
for random variation in the muscle parameters investigated in
this population over the training and detraining periods. The
physical characteristics of the study population are outlined in
Table 1. A 1-way analysis of variance (ANOVA) revealed that
the population was homogeneous at baseline for all parame-
ters of interest and in physical characteristics (p.0.05). As
body mass and external load provide the total training stim-
ulus in a number of the leg exercises adopted in the training
program (2 out of the 6), it should be noted that the partic-
ipant groups showed no difference in body mass at baseline,
week 8, 10, or 12. Furthermore, it was felt that training at
loads relative to 1RM provided greater external validity to
the practices of individuals undertaking RT.
Procedures
Resistance Training Program. Resistance training was per-
formed 3 times per week (twice supervised and 1 home-
based session) by both the SR and LR training groups for 8
weeks, using a combination of free, machine (Pulse Fitness,
Congleton, United Kingdom) and body weights. A general-
ized warm-up was completed at 70–75% age-predicted max-
imum heart rate on a treadmill for 5 minutes, after which
a goniometer was attached to the center of rotation of the
knee. As the subject performed each exercise (Table 2), the
goniometer rotated from 08(full extension), and a training
partner confirmed from the scale when the participant had
reached 50 or 908of knee flexion during the eccentric phase
and therefore could hold the load steady over 2 seconds,
before beginning the concentric phase of movement. Move-
ment speed was dictated by a 1-second metronome. All ex-
ercises involved eccentric and concentric loading, except for
the Sampson chair, which was isometric loading. The subjects
completed 2 familiarization sessions at 70% of 1RM before
commencing the RT program. Exercises were performed at
80% of the 1RM as determined at the training angle, for
example, the SR group 1RM was the greatest weight lifted
whilst performing at 508knee flexion. The 1RMs were mea-
sured every 2 weeks, and the training loads were adjusted
accordingly. Manipulation of the exercise variables (exercise
selection and order, repetitions, sets, recovery, and intensity
shown in Table 2) were all chosen based on empirical evi-
dence presented in the American College of Sports Medicine’s
Progression Models for RT for Healthy Adults for increasing
muscle hypertrophy (38).
Muscle Architecture and Subcutaneous Fat. Architecture was
measured at rest with each participant seated in an upright
position on an isokinetic dynamometer (Cybex, Phoenix
Healthcare Products, Nottingham, United Kingdom). After
calibration, each participant was positioned with a hip angle
of 808(straight back 908) and knee at 908knee flexion
(straight leg 08). All muscle architectural measurements were
determined using real-time ultrasonography (AU5, Esaote
Biomedica, Genoa, Italy) at rest, with images captured at
25 Hz using a digital video recorder (Tevion, Medion Aus-
tralia Pty Ltd, St Leonards, Australia). Vastus Lateralis fasci-
cle pennation angle (u) was measured as the angle of fascicle
insertion into the deep aponeurosis (42). Images were ob-
tained perpendicular to the dermal surface of the VL and
oriented along the midsagittal plane of the muscle. Images
were taken at 25, 50, and 75% of the total femur length (as
described below) and 50% of muscle width at each point
(where 50% muscle width is defined as the midpoint
between the fascia separating the VL and rectus femoris,
and fascia separating the VL and biceps femoris muscles).
Fascicle length was defined as the length of the fascicular
path between the deep aponeurosis and superficial aponeu-
rosis of the VL. The majority of fascicles extended off the
acquired image, where the missing portion was estimated by
linear extrapolation. This was achieved by measuring the
linear distance from the identifiable end of a fascicle to the
intersection of a line drawn from the fascicle and a line
drawn from the superficial aponeurosis. This method has
TABLE 1. Participants’ physical characteristics at
baseline.*
Group Age (y) Mass (kg) Height (cm)
SR 19 63.4 74.9 610.1 174 613.3
LR 19 62.6 73.8 614.9 171 611.8
Con 23 62.4 77.9 613.1 176 69.5
*SR = shorter range of motion; LR = longer range of
motion; Con = control group.
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been shown to produce reliable results previously (4). All
images were analyzed and measured using Image J (Wayne
Rasband, National Institutes of Health, Bethesda, MD, USA).
Subcutaneous fat was estimated using the same images as
taken for muscle architecture. After calibration in Image J to
coincide with the scale of the ultrasound image, a line from
the top to the bottom of the layer of fat visualized was drawn
at 3 regular intervals on the ultrasound image. The average
lengths of these 3 lines were taken to estimate the average
thickness of the subcutaneous fat layer in millimeters. Care
was taken not to deform or compress the subcutaneous fat
with minimal pressure applied to the dermal surface with the
ultrasound probe.
Muscle Force Modeling. Because of the changing moment arm
length of the patella tendon at discrete knee joint angles,
differences in muscle force produced between the groups
had to be accounted for. Thus, quadriceps forces at the
patella tendon were calculated as follows:
QuadForce ¼QuadMaxTorque þHamCoTorque
Moment ArmPT ;
(1)
where
HamCoTorque ¼Co ConEMG 3 FlexMaxTorque
ðMax BFEMGÞ;
(2)
where Co-Con
EMG
is co-contraction of the antagonist muscle
(biceps femoris), and Max BF
EMG
is the maximum antagonist
EMG. The Flex
MaxTorque
is
maximum flexion torque and
Moment Arm
PT
being the
moment arm of the patellar
tendon (values obtained from
dual energy x-ray absorptiom-
etry scans).
Muscle Anatomical Cross-Sec-
tional Area. The VL muscle
aCSA was measured using
real-time ultrasonography at
rest. The aCSA was measured
at 3 sites—25, 50, and 75% of
the total femur length. Femur
length was defined as the line
passing from the greater tro-
chanter to the central palpable
point of the space between the
femur and tibia heads when
thekneewasflexedat908.
Echo-absorptive tape was
placed at regular intervals
(;3 cm) along the muscle width at each site so that when
the probe was placed on the leg, 2 distinct shadows were
cast on the ultrasound image. Therefore, each ultrasound
image provided a section of VL within the boundaries set
by the 2 shadows and fascia surrounding the muscle. Each
of these sections was analyzed for the total area using
Image J to provide a total aCSA at that particular site. This
method has been validated previously (40).
Strength Measurement. Maximal isometric knee extension
torque was measured with the knee at a range of angles,
that is, 30, 50, 60, 65, 70, 75, and 908(full knee extension =
08) on the right leg of all the participants. The order of
testing by knee angle was randomized so as to minimize
any systematic fatigue effect. After a series of warm-up trials
consisting of 10 isokinetic contractions at 608$s
21
at 50–85%
maximal effort, the participants were instructed to rapidly
exert maximal isometric force against the dynamometer
(Cybex NORM, Medway, MA, USA) lever arm. The partic-
ipants were given both verbal and visual encouragement and
feedback throughout their effort. Joint torque data were dis-
played on the screen of a Mac Book Air computer (Apple
Computer, Cupertino, CA, USA), which was interfaced with
an A/D system (Acknowledge, Biopac Systems, Santa
Barbara, CA, USA) with a sampling frequency of 200 Hz.
Isometric contractions were held for approximately 2 sec-
onds at the plateau with a 60-second rest period between
contractions. Peak torque was expressed as the average of
data points over a 200-millisecond period at the plateau
phase (i.e. 100 milliseconds either side of the instantaneous
peak torque). The peak torque of 3 extensions was used as
the measure of strength in each participant.
TABLE 2. Resistance training program outline.*†
Exercise Reps Sets Recovery (s) Intensity (1RM %)
Day 1
BB back squat 10 3 90 80
Knee extension 10 3 60 80
Bulgarian split squat 10 3 90 80
DL Sampson chair 4 310-s holds 3 60 -
Day 2
BB back squat 10 3 90 80
Knee extension 10 3 60 80
Leg press 10 3 90 80
DB lunges 10 3 60 80
Day 3
BW squats 30 3 90 -
DL Sampson chair 4 320-s holds 3 60 -
BW lunges 30 3 90 -
SR Sampson chair 5 35-s holds 3 60 -
*BB = barbell; DB = dumbbell; DL = double-legged; SR = single-legged; BW = body
weight; RM = repetition maximum.
†Exercises were carried out at 80% 1RM where appropriate or using body mass.
Range-of-Motion Specific Muscle Loading
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Statistical Analyses
Data were parametric and were therefore analyzed using
a mixed-design repeated measures ANOVA. The within
factor was the phase of training (i.e., weeks 0, 8, 10, and 12)
and the between factor was training group (i.e., SR, LR, or
Con). Post Hoc contrast analyses with Bonferroni correc-
tions were used to compare data to baseline (“within” factor)
and to control group (“between” factor). All data are pre-
sented as mean 6SEM. Statistical significance was set with
alpha at #0.05. In terms of the sample size in this study, the
average statistical power of the measured muscle parameters
(CSA, pennation angle, fascicle length, and strength) was
statistically adequate at beta = 0.86.
Repeatability of the Measurements. A small pilot study was
conducted at the onset of the study on a similar population
(i.e., age and physical characteristics). Repeated measures of
VL muscle anatomical CSA, architecture, and strength on
a group of 5 individuals (2 men, 3 women) were collected on
3 separate occasions. Within-day coefficients of variation
(CVs in percent) of 1.5, 1.9, 1.3, 2.6, and 0.8%, and between-
day CVs of 2.6, 2.1, 1.6, 2.9, and 1.8% were yielded for
aCSA, fascicle length, fascicle pennation angle subcutane-
ous fat, and strength, respectively. Therefore, the repeat-
ability of the measurements was within an acceptable range
of error (3).
RESULTS
Total Training Load
To allow internal force comparisons, external training
loads were monitored in each group. Total average loads
(mean 6SD) lifted for externally loaded (i.e., not just using
body mass) exercises completed were (a) Squat: SR 99 6
10 kg, LR 80 68 kg; (b) Leg Press: SR 60 619 kg, LR 48 6
17 kg; (c) Leg extension: SR 51 617 kg, LR 46 615 kg. To
accurately assess internal muscle forces produced, the
change in resistance moment arms of the CAM pulley
machine used during leg extensions were also measured.
Based on the training load for the leg extension exercise
stated above for each group, the resistance machine load
component yielded on average a 7% increase in external
torque produced in the SR group compared with LR (SR:
137 vs. LR: 128 N$m).
The results in the subsequent sections describe paired
physiological changes relative to baseline.
Muscle Anatomical Cross-Sectional Area at 25, 50, 75%
Femur Length
The results at all femur lengths are presented in Table 3. The
VL CSA increased significantly (p,0.05) relative to baseline
after training at all sites in both training groups. The signif-
icant training effect remained during the whole detraining
period in both training groups at both 50 and 75% but was
TABLE 3. Paired changes to VL CSA and pennation angle of fascicles at different femur lengths over the training and
detraining phases.*†
Site (% femur length) Baseline Week 8 Week 10 Week 12
25 CSA SR 2,877 6338 SR 3,425 6303zSR 3,361 6306zSR 3,265 6310
LR 2,684 6427 LR 3,592 6303zLR 3,461 6309zLR 3,328 6295
Con 3,201 6253 Con 3,086 6259 Con 3,079 6240 Con 3,086 6259
50 CSA SR 3,033 6289 SR 3,699 6342zSR 3,526 6334zSR 3,382 6304z
LR 3,004 6385 LR 3,545 6339zLR 3,424 6349zLR 3,233 6338z
Con 3,326 6354 Con 3,314 6364 Con 3,294 6357 Con 3,314 6364
75 CSA SR 1,081 6175 SR 1,162 6127zSR 1,115 6127zSR 1,037 6119z
LR 1,074 6224 LR 1,505 6217z§ LR 1,369 6200zLR 1,219 6191z
Con 1,366 6165 Con 1,370 6185 Con 1,358 6175 Con 1,370 6185
25 PEN SR 10.1 60.3 SR 10.3 60.3zSR 10.0 60.7 SR 9.9 60.2
LR 10.2 60.3 LR 11.2 60.6zLR 11.1 60.6 LR 11.0 60.6
Con 11.9 60.2 Con 12.2 60.1 Con 12.0 60.1 Con 12.2 60.1
50 PEN SR 16.5 60.5 SR 17.2 60.3zSR 16.8 60.9 SR 16.4 60.4
LR 15.9 60.2 LR 17.1 60.8zLR 16.6 60.8 LR 16.0 60.6
Con 16.4 60.8 Con 16.4 60.7 Con 16.3 60.7 Con 16.4 60.7
75 PEN SR 16.0 61.4 SR 17.9 61.2zSR 16.8 60.9zSR 16.8 60.9
LR 15.5 60.6 LR 17.5 60.7zLR 17.2 60.6zLR 16.3 60.5
Con 19.4 60.7 Con 18.5 60.7 Con 18.4 60.6 Con 18.5 60.7
*CSA = cross-sectional area; PEN = pennation; SR = shorter range of motion; LR = longer range of motion.
†Values are millimeters squared and degrees (mean 6SE).
zSignificantly different from other training group.
§Significantly above baseline.
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not evident at 25% of femur length after week 10. There was
a trend for LR to exhibit greater relative gains in aCSA
compared with SR at all sites, which was significant at week
8 at 75% of femur length. It was found that there was not
only a main training effect (p,0.05) but also a main group
effect after week 8 (p,0.05) with LR exhibiting a 59 615%
compared with SR showing 16 610% increment in VL
aCSA. Surprisingly, after the first 2 weeks of detraining,
the group effect was no longer
evident (p= 0.07) although
both training groups were still
significantly above baseline
at weeks 10 and 12. There
was no notable change over
the 12-week period for the
controls.
Muscle Architecture
Fascicle Pennation Angle—25, 50,
75% Femur Length. Table 3
shows the changes in fascicle
pennation angle at each site
for all 3 groups. At 25%, there
was a main effect of training
(p,0.05) for each group, with
no significant effect of group.
Pennation angles recorded at
baseline increased by 2 65
and 9 66% at week 8 for the
SR and LR groups, respec-
tively. However, by weeks 10
and 12, the effect of training
was negated with values return-
ing toward baseline (p.0.05).
This pattern was repeated at
50% of femur length with the
main effect of training (5 6
3% SR, 9 63% LR) reverted
after 2 weeks without the train-
ing stimulus. This was again the
case for pennation angles at
75%; however, the significant
increase because of the RT
was observed until week 10
but had receded toward base-
line after the 4 weeks of de-
training at week 12.
Fascicle Length—25, 50, 75%
Femur Length. There was a sig-
nificant main effect of RT on
fascicle length at all 3 sites
(Figure 1, p,0.05), which re-
mained significantly elevated
above baseline values after the
detraining period, with both
training groups significantly
increasing (p,0.05) fascicle
length at all sites at weeks 8,
Figure 1. Graph showing relative changes in fascicle length (millimeters) during training and detraining. A)
Changes at 25%, B) at 50%, and C) at 75%. *Significant relative change above baseline in both groups.
#Significantly different from the other training group. †Significantly different (p,0.05) from the control group
(mean 6SE).
Range-of-Motion Specific Muscle Loading
250
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10, and 12 compared with controls. Although there was no
group effect at 25%, a significant group effect (p,0.05) did
occur at both 50 and 75% of the femur length. The
LR fascicle lengths increased 23 65, 19 64, 16 64% at
weeks 8, 10, and 12 from baseline in contrast to the SR
group’s less pronounced increments of 10 62, 6 62, and
262% during the same time period. All the values were
significantly enhanced compared with baseline in both
groups except for SR at week 12. At 75%, there was a similar
significant (p,0.05) group effect with relative increases of 19
63, 13 63, and 10 62% at weeks 8, 10, and 12 for LR from
baseline compared with 11 62, 5 64, and 2 62% for SR
during the same period.
Subcutaneous Fat 25, 50, 75 Femur Length. The training
intervention resulted in appreciable reductions in fat in both
SR and LR training groups between weeks 0 and 8 (p,
0.05) at all measured sites. At 25%, the SR group reduced
fat levels from 16.2 63.9 to 15.6 63.8 mm (2461%),
compared with LR (18.1 64.0 to 15.4 63.3 mm [214 6
3%]) posttraining; however, no group effect existed. After
training ceased, both groups remained significantly lower
than baseline at week 10 (2362% SL and 2963%
LR), but by week 12, there was no main effect of training
and detraining on either group (p.0.05), although there
was a strong trend for a group effect at this time point (p=
0.057). The control group did not fluctuate significantly from
baseline values during weeks 8, 10, and 12. There was also
considerable subcutaneous fat loss at 50% after RT, with
greater losses achieved by the LR group. Both lost 6.8 6
1.2 mm after training; however, LR produced a loss of 22 6
8% compared with SL with a 5 62% loss at this phase of the
protocol. The main effect of group remained during weeks
10 and 12, as SR regressed toward baseline by week 12,
whereas LR still possessed significant losses at this phase
(210 66%). There was a similar trend seen at 75% where
a main effect of both group and training existed at week 8
(p,0.05). This difference was
not present at week 10 or 12
although both training groups
had significantly less fat (p,
0.05) compared with that at
baseline during the detraining
period (7 63% SL and 9 6
1% LR).
Muscle Strength. There was
a main effect of training on
the MVCs of both training
groups (p.0.05) at each of
the training end ROMs, with
SR recording an increase of 5
610% at 58and 30 65% for
LR at 908. There were no dif-
ferences (p.0.05) between
absolute MVC in SR and LR at baseline or after training.
In agreement with previous observations after isometric
joint-angle specific training, there was evidence of angular
specificity of training in both the groups with SR signifi-
cantly (p.0.05) increasing MVCs at 50, 60, 65, and 708(i.
e., those closest to the training angle—Table 4), whereas LR
increased MVCs over the entire angular range, that is, 30–
908. The angle of peak torque altered from 75 to 708at week
8 in SR, where it remained for the duration of detraining in
weeks 10 and 12. In LR, the angle of peak torque was orig-
inally 708and did not change after training and detraining.
By week 10, both groups displayed an average 6 62%
strength reduction (relative to the posttraining strength val-
ues), with SR not significantly above baseline (0 62%) in
contrast to LR remaining significantly above both baseline (p
,0.05) and SR (p= 0.027) at weeks 10 and 12. The control
group’s strength did not significantly alter during the 12-week
training and detraining period (p.0.05).
DISCUSSION
The current investigation aimed to study the in vivo effect of
resistance exercise training and detraining over a larger ROM
and hence longer average muscle length (0–908knee flexion—
LR) vs. a smaller ROM and hence shorter average muscle
length (0–508knee flexion—SR) on morphological, architec-
tural, and functional changes in the VL. It was hypothesized
that the group training over a wider range of joint angles (LR)
would undergo a greater amount of skeletal muscle hypertro-
phy because of increased physiological stress and stretch on
sarcomeres compared with the group training over a shorter
range of joint angles (SR). It was also hypothesized that the
LR group would still have a greater muscle mass after detrain-
ing, probably because of greater initial gains. Our findings
partly support these hypotheses in that although there were
no notable changes to any of the muscle parameters in the
control group during a 12-week nontraining period, significant
adaptations were observed in both SR and LR training groups
TABLE 4. Changes in quadriceps MVC over a range of knee flexion angles from
baseline to week 8 (posttraining).
Knee flexion angle (8)
Torque (N$m) baseline—week 8 Relative change (%)
SR LR SR LR
30 106–108 102–127 2 681865*
50 167–175 157–193 5 610* 16 64*
60 191–197 186–213 4 65* 11 67*
65 207–216 194–231 5 64* 19 68*
70 212–225 202–247 6 62* 13 62*
75 218–215 193–232 216318611*
90 216–218 161–208 1 623065*
*Significantly above baseline measures.
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across all the muscle measurements. What is more, there was
a significant main effect of training where strength, VL fascicle
length, VL aCSA increased, whereas midthigh subcutaneous
fat decreased to a greater extent after training at a longer
muscle length compared with a shorter muscle length.
Further, as per our expectation of greater physical demands
of 1 training setup over the other, the stresses experienced by
the knee extensors, although comparable in terms of an eco-
logically valid training program setting and in terms of abso-
lute loads lifted were 10–25% greater in SR, in fact translated
to approximately 32% greater internal stresses in the group
training over the LR. This has a major impact on how both
coach and athlete should view the impact of ROM on mus-
cular adaptations. It is often tempting for an athlete to reduce
joint ROM to accommodate a larger external load in the belief
that lifting heavier will confer an advantage in adaptation.
However, from the evidence presented, without an apprecia-
tion of internal muscle mechanics, this assumption would be
erroneous.
The relative increases in VL size after 8 weeks of RT
reported in this study (21 68% in SR and 44 613% in LR—
averaged across the 3 sites) are much greater than those
previously reported in a similar study (26). It should be how-
ever noted that this study (26) is the only other known study
to our knowledge reporting changes specifically in VL size
after training at shorter vs. longer muscle length (;11 67%
ST and ;13 612% LT—values estimated from Figure 2 in
their Results section). The discrepancy between the 2 sets of
results would not only arise from the differences between
measurements of VL size (volume vs. aCSA) but also from
the difference in training protocols (isometric vs. combined
isoinertial and isometric) between Kubo et al. (26) and this
study. Indeed metabolic cost and work done are greater
during dynamic (i.e., concentric and eccentric) compared
with isometric contractions (49). Therefore, a greater
work-induced hypertrophic effect of the combined training
may have produced the variation in hypertrophy gain differ-
ences between the 2 studies (11). Previous research on
RT-induced whole quadriceps aCSA showed changes of
18.8 67.2, 13.0 67.2, and 19.3 66.7 at distal, central, and
proximal sites, respectively (34). It is nonetheless difficult to
compare the studies directly, however, not only owing to the
fact this study measured aCSA of the VL as opposed to all
4 quadriceps muscles but also the earlier report (34) showed
a significant difference in hypertrophic response between the
components of the quadriceps muscle group. In a review of
hormonal responses and adaptations to exercise (24), the
authors suggest exercises involving large muscle masses are
superior to more isolated exercises to elicit greater hormonal
responses. Therefore, the large mass exercises such as the
bilateral squat in our study would elicit a greater hormonal
response to that of a seated unilateral knee extension on a
dynamometer as in the study of Kubo et al. (26).
Kubo et al. (26) estimated that internal VL force during
isometric MVC at 1008of knee flexion was 2.3 times greater
than that at 508. This is key because mechanical stress mag-
nitude is known to induce muscle hypertrophy (30). Using
the 1RM training loads, patellar tendon moment arm and
aCSA, it was found that the mean force per unit area of
muscle was 5.1 N$mm
22
in the SL group compared with
6.8 N$mm
22
in the LR group. The results of this study
showed a nonsignificant trend for the LR group to exhibit
a greater VL aCSA after RT compared with SR at each site.
Importantly, in support of these beneficial morphological
adaptations in the LR group, this group had a significantly
greater increase in strength than SR group after training at
all knee angles measured, which has previously been dem-
onstrated after isometric training (26). In addition, Campos
et al. (6) found that the subjects who trained with higher
loads (i.e., 3–5 reps and therefore experiencing greater force)
increased maximal strength more significantly than moder-
ate (9–11 reps) or low (20–28 reps) loads, whereas the low to
moderate repetition groups experienced the greatest hyper-
trophic gains in the 3 major fiber types (12.5–26%) after
8 weeks of RT. The above, in addition to previous work from
Staron et al., shows that the hypertrophic training response
is accompanied with a gradual transition in the percentage of
fiber type and myosin heavy chain isoform (6,45), which
may explain the disassociation between muscle strength
and muscle size increments.
The magnitude of hypertrophy at 75% of the femur length
was greater for LR after training. Relative increases were
59 615% for LR and 16 610% for SR, displaying evidence
for region-specific hypertrophy. This has been observed pre-
viously after knee extensor RT (33,34,43). With both force
generation and stretch being effective stimuli for muscle
growth (14), the discrepancies in CSA between the groups
may be because of regional differences in the total stimulus
transmitted along the length of the muscle. Evidence exists
that there is relatively high serial and parallel distribution of
muscle fiber strain during transmission of myofascial force
(17). Thus, the LR group could have experienced a greater
strain at a more distal portion of the VL, which was also
transmitted laterally, resulting in a greater stimulus and
therefore enhanced hypertrophy at this site. Because muscle
force is proportional to CSA, this provides a basis for
enhancing the force output of the muscle, which is reflected
in our strength results.
A major finding of this study was the greater increase in
fascicle length at all sites in the LR group compared with SR
group, although only significantly so at 50 and 75% of total
femur length. In vivo increases in fascicle length are
associated with the addition of sarcomeres in series (assum-
ing a fixed sarcomere length) and appear to be strongly
influenced by muscle length or stretch (12,46,50). A study by
Boakes et al. (5) wherein surgery placed the thigh muscles
under constant stretch to address a leg-length discrepancy,
resulted in a 4-cm femoral lengthening. Fascicle and sarco-
mere length was measured in VL postoperatively and after
12 months. The results showed that in vivo fascicle length
Range-of-Motion Specific Muscle Loading
252
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increased and sarcomere length decreased, with sarcomero-
genesis from approximately 25,000 to 58,650 as a result of
adaptation to stretch. In this study, our protocol increased
the muscle excursion range of the quadriceps to a greater
extent in the LR group compared with that in the SR group.
The results from this investigation support pervious animal
research evidence (22) that “average muscle length” (or excur-
sion range) is a possible primary stimulus for increases in
fascicle length in adult skeletal muscle. As mentioned previ-
ously, changes in fascicle length produce alterations to the
force-velocity relationship in muscle (48) and could therefore
impact on an athlete’s potential for power production.
Further architectural adaptations included a significant
increase of pennation angle (Pu) in both training groups
(Table 3). A functional consequence of an increase in Puis
that more contractile material can be packed in parallel for
a given anatomical cross-section (19,42). The Puhas been
shown to increase after resistance exercise (1,4,20,39,43)
and is usually closely associated with an increase in ana-
tomical CSA in the quadriceps (42). Despite not reaching
between-group significance, the average increase in Pu
across the 3 sites was greater for LR than for SR (11 65
vs. 7 64%, respectively). Thus, this could also have been
a factor in contributing to the LR group’s greater strength
after training.
A further benefit experienced by the LR group was
a greater reduction in subcutaneous fat at 50 and 75% of
the femur length. In the athletic world, it is often considered
beneficial to reduce levels of subcutaneous fat. For example,
in running events (or events where the body is not
supported), excess body weight has been shown to signifi-
cantly decrease relative V
_
O
2
max and performance during
a running test as a direct consequence of an increased energy
cost of running at submaximal speeds (8). Additionally, in
sports where body mass is accelerated against gravity, a more
lean muscle mass would be advantageous for performance
and energetic consumption. This is not to mention the effect
of body composition on cardiovascular risk factors and mor-
tality for the average person (27). It would be tempting to
suggest that the possible mechanism for an increased fat loss
in the LR group may be linked to the greater internal phys-
iological stress on the muscle, because strenuous resistive
exercise may elevate postexercise metabolic rate for a pro-
longed period and may enhance postexercise lipid oxidation
(31). However, more recently, Singhal et al. (44) found that
there was no significant difference in postprandial lipemia in
groups undertaking either moderate-intensity (MI) or high-
intensity (HI) resistance exercise. An alternative explanation
therefore for the physiological processes involved is linked
with the fact that acute resistance exercise has been shown
to increase adenosine monophosphate activated protein
kinase (AMPK) activity (9), which in turn has also been
shown to mediate effects of interleukin-6-stimulated increases
in glucose disposal and free fatty acid oxidation. Further,
AMPKa2 activity has been shown to be intensity dependent
(7); therefore, training at longer muscle lengths could affect
upstream factors of adiposity.
A second aim of the study was to determine if there was a
differential response to detraining between the training
groups. Both training groups showed that detraining period
resulted in significant losses at weeks 10 and 12 (p= 0.001,
pe
2
= 0.34) in all measured parameters. Although generally
there was no significant difference between groups, the LR
group consistently exhibited a trend (p= 0.07, pe
2
= 0.32)
toward greater absolute and relative decrements in muscle
dimensional parameters over the 4-week detraining period.
This is in agreement with the findings of a previous study
(47) that reported that after 12 weeks of RT, a group of older
adults performing HI training increased total thigh CSA and
strength to a greater (p,0.05) extent than an MI training
group did. After a subsequent 12 weeks of detraining, total
relative thigh CSA and strength in the HI group diminished
significantly more than that in the MI group. Despite these
reductions, HI group strength and CSA remained signifi-
cantly greater than in the MI group because of greater initial
adaptations. In this study in terms of average VL aCSA
across the 3 sites, there was a decrease from 44 613 to
25 611% above baseline between weeks 8 and 12 in the
LR group, whereas SR decreased from 21 68% at weeks 8–
10 67% at week 12. Therefore the relative changes in the
aCSA to the LR group after 4 weeks of detraining (25 6
11%) are still superior to those made by the SR immediately
posttraining (21 68%). This suggests that although greater
initial gains may be lost at a greater rate, training using
a relatively wider ROM may still confer an advantage for
the longer term. This is evident in the strength data where
the LR group was significantly stronger until the conclusion
of the detraining period, whereas the SR group was not
significantly stronger compared with the pretraining data,
at week 10. It is difficult to say why greater gains are lost
more rapidly, such as in the LR group, but it may be because
of an inability to stimulate sufficient protein synthesis to
support a larger muscle mass. One would not expect to
observe a difference in daily protein synthetic rate between
groups with no change in activity levels and dietary habits
(21). Therefore, basal protein synthetic rates would support
a greater relative percentage of a smaller muscle mass than
a larger mass. Also, because resistance exercise causes per-
turbations to the intramuscular environment, and there are
subsequent adaptations, a new homeostatic point is reached,
where only a greater stimulus than the original will stimulate
further adaptations (23). The LR group may have set a higher
threshold to maintain adaptations, where daily activity did
not disturb the internal muscle environment as much as in
the SR group with a lower threshold. Indeed to reiterate,
although the face value load was similar in the 2 groups
(80% 1RM in both cases), the internal loads experienced are
in fact greater under a relatively wide ROM, and therefore,
because the phosphorylation of extracellular signal-regulated
kinase 1 and 2 and the 38-kDa stress-activated protein kinase
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(p38) both appear to be intensity dependent (41) could be
a contributing factor to the difference in cellular response
and adaptation.
It should however be noted that in this study, although
the ROM has been presented as different, the manner in
which the 2 training groups were required to hold the
contractions (over 2 seconds) means that the greatest
difference in the loads experienced by the quadriceps muscle
was because of the internal joint architecture. In other words,
the difference between the 2 training protocols was not so
much owing to the ROM (thought this differed at the start of
the movement) but to the length of the muscle when the
muscle group was experiencing the “isometric hold” phase of
the exercise. Nevertheless, future studies should aim to deter-
mine whether in making the internal loads comparable the
effects of training at the relatively elongated muscle length
we describe here still exhibit the advantage over training at
a relatively shortened muscle length. The authors do also
recognize that in covering a greater ROM the muscle is
loaded for a longer duration in LR (i.e., 0.25–0.50 seconds).
However, previous studies (2) have concluded that measures
of work production during RT do not directly scale with the
adaptation responses seen in skeletal muscle. Furthermore,
it is difficult to give substance to a mechanism whereby
such a small difference in duration of loading (i.e., load-time
product) would lead to serial sarcomerogenesis and give rise
to such striking differences in fascicle length.
In summary, after 8 weeks of RT and 4 weeks of detraining
over different ROM (and thus implied average muscle lengths),
not only were there significant morphological differences
between the 2 groups after training but also the muscle
strength was enhanced to a greater extent after training at
a larger rather than a narrow ROM. Moreover, there was
a significant difference between groups in muscle architec-
ture, with fascicle length increments greater when training
over a large ROM, supporting the notion that muscle length
(or excursion) has a major influence on fascicle length. The
implications of the results may be useful in athletic training
and also deter athletes from reducing their ROM during
exercises to accommodate greater external loads.
PRACTICAL APPLICATIONS
In the field of practice, when choosing an ROM in which
a resistance exercise should be performed, muscle mechanics
must also be considered. We have shown that RT protocols
that enforce a wider ROM enhance the muscle character-
istics that influence force and power production to a greater
extent than protocols where the ROM is not as extensive.
A common error in practice is allowing the ROM to be
compromised to accommodate a greater absolute external
load, in an attempt to increase the stress of mechanical
loading. Following this, it is important for the coach to
reinforce a more complete ROM, even when absolute load
maybe reduced, to provide a greater internal stress and more
potent stimulus for adaptation. Optimization of training
mechanics could therefore potentially reduce the time spent
in the gymnasium achieving sporting and performance goals,
because training time and exercise volume constraints are
pivotal considerations in the periodization of training.
Adherence to a greater ROM also provides a better long-
term prognosis for retention of training adaptations, for
example, after prolonged bed rest and immobilization
(caused by illness and injury) or indeed during tapering.
ACKNOWLEDGMENTS
The authors are ever indebted to the study populations
without whom none of this work would have been possible.
The authors are also grateful for the continued support from
the Institute for Performance Research.
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