Nonuniform Changes in MRI Measurements of the Thigh Muscles After Two Hamstring Strengthening Exercises

Article (PDF Available)inThe Journal of Strength and Conditioning Research 27(3):574-581 · March 2013with 1,078 Reads 
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DOI: 10.1519/JSC.0b013e31825c2f38 · Source: PubMed
Cite this publication
Abstract
Mendiguchia, J, Garrues, MA, Cronin, JB, Contreras, B, Los Arcos, A, Malliaropoulos, N, Maffulli, N, and Idoate, F. Nonuniform changes in MRI measurements of the thigh muscles after two hamstring strengthening exercises. J Strength Cond Res 27(3): 574-581, 2013. Although many different hamstring strengthening exercises exist, the effect on site specific activation of these exercises on different muscles of the leg is unclear. This study investigated the effects of the eccentric leg curl (LC) and lunge (L) exercises on the biceps femoris long head (BFl), biceps femoris short head (BFs), semitendinosus (ST), semimembranosus (SM), and adductor magnus (AM). Each leg of 11 male professional soccer players was randomly assigned to an LC or L exercise protocol (3 sets of 6 repetitions). Functional magnetic resonance imaging (fMRI) of the subjects' thighs were performed before and 48 hours after the intervention. Fifteen axial scans of the thigh interspaced by a distance of 1/15 right femur length (Lf) were obtained. The fMRI data were analyzed for signal intensity changes. No significant changes were observed in absolute short tau inversion recovery values for the SM and BFs. Significant changes for the ST (∼21-45%) from sections 4 to 10, AM (∼2-13%) at section 4, and BFl (∼ -3 vs. 8%) at section 7 were noted. LC exercises load all the regions of the ST muscle. The L exercises load the proximal regions of the BFl and AM. These findings may have relevance when designing protocols for prevention and rehabilitation of hamstring injuries.
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TITLE
Non-uniform changes in MRI measurements of the thigh
muscles following two hamstring strengthening exercises
Authors:
Jurdan Mendiguchia1, Mirian Aranzazu Garrues2, John Barry Cronin3,4, Bret Contreras3,
Asier Los Arcos5, Nikos Malliaropoulos6, Nicola Maffulli7, Fernando Idoate8.
1. Zentrum rehab and performance Center.Department of Physical Therapy.Pamplona,
Spain.
2. Public University of Navarre, Health Science Department .Graduate School for
Health Sciences, Physical Therapy School, Tudela, Spain.
3. Sport Performance Research Institute New Zealand, AUT University, Auckland,
New Zealand
4. School of Biomedical and Health Sciences, Edith Cowan University, Joondalup,
Australia.
5. Club Atletico Osasuna.Pamplona. Spain.
6. National Track & Field Centre, Sports Medicine Clinic of S.E.G.A.S., Thessaloniki,
Greece
7. The London School of Medicine and Dentistry Institute of Health Sciences
Education Centre for Sports and Exercise Medicine Mile End Hospital.
8. Radiology Department, Clinica San Miguel, Pamplona, Spain
Corresponding Author:
Jurdan Mendiguchia1
Zentrum rehab and performance Center
Calle B Nº 23
Department of Physical Therapy
Pamplona, Spain
Jurdan24@hotmail.com
011-34 948229459
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Competing Interest
“ None to declare."
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Abstract
This study investigated the effects of the eccentric leg curl (LC) and lunge (L) on the
biceps femoris (BF), semitendinosus (ST), semimembranosus (SM), adductor magnus
(AM) and gluteus maximus (GM). Each leg of eleven male professional soccer
players were randomly assigned to an eccentric leg curl (LC) or lunge (L) exercise
protocol (3 sets of 6 repetitions). Functional magnetic resonance imaging (fMRI) of the
subjects’ thighs were performed before and 48 hours after the intervention. Fifteen
axial scans of the thigh interspaced by a distance of 1 / 15 of the length of the right
femur (Lf) were obtained from the level of 1/15 Lf to 15/15 Lf . The fMRI data were
analyzed for signal intensity (SI) changes. While no significant changes were observed
in absolute short tau inversion recovery (STIR) values for the semimembranosus and
gluteus maximus, significant changes for the semitendinosus (~21-45%) from sections 4
to 10, adductor magnus (~2-13%) at section 4, and biceps femoris (~ -3 vs 8%) at
section 7 were noted. These two hamstring exercises did not result in a uniform
response (training stimulus) for the same muscles and regions. The ELC exercise was
better suited for loading all regions of the ST muscle, while the L exercise was more
effective for loading the proximal regions of biceps femoris and adductor magnus.
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Introduction
Acute hamstring injuries are the most prevalent muscle injuries reported in sport,
accounting for 6 to 37% of all injuries in Australian Rules football, rugby union,
football, basketball, cricket and track sprinters. [1-8] Appropriate training and
strengthening of the hamstring muscles for many sports is a fundamental focus of
prevention and rehabilitation. Although selective strengthening of the hamstring
muscles has been recommended as a key component in the management of hamstring
injury, [9-13] only limited literature exists to guide clinicians in designing effective
strengthening programs.
The architectures and innervation patterns of the various muscles in the posterior aspect
of the thigh (the biceps femoris muscle long head (BFl), the biceps femoris short head
(BFs), the semimembranosus (SM), and semitendinosus (ST)) differ [14-16], and each
muscle has unique inherent functions. If this were indeed the case, it would be of value
to strength and conditioning coaches as well as clinicians to understand which exercises
preferentially activate different muscle groups, so as programming is guided to better
effect.
Functional magnetic resonance imaging (fMRI) may be a sensitive method for
displaying the physiological changes that occur in muscles activated during exercise, as
it provides detailed anatomical analysis of associated soft tissues, which is lacking in
electromyography (EMG) experiments.[17-22] The short tau inversion recovery (STIR)
sequence is a T2-weighted sequence that suppresses signals from fat and displays
sensitivity in enhancing differences between the water content of tissues. [19-22].
Exercise produces changes in the distribution of water both intra- and inter-cellularly.
The STIR sequence has previously shown to be valuable in the investigation of signal
intensity (SI) changes in muscles after exercise. [19-22]
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MRI has also been used to assess muscle damage following intensive exercise. [23,24]
The T2 value increased following eccentric exercise [18,25-30], and was positively
correlated with plasma creatine kinase (CK) activity, reflecting exercise-induced muscle
damage.[18,23,26,31] Furthermore, previous studies have investigated the intermuscle
differences and intramuscle regional differences of the T2 value between proximal and
distal regions of the muscles of interest. [18,29,32] For example, Kubota et al. [18]
reported that although all hamstring muscles and regions displayed a T2 increase
immediately following eccentric knee-flexion exercise (prone leg-curl machine), the
relationship between the changes of the plasma CK activity and the T2 value of the ST
was not statistically significant until the second day following exercise , which may be
indicative of severe localised muscle damage. These findings have interesting
implications in terms of the time course and effects of different exercises on the
hamstrings.
Some exercises are used to prevent hamstring injuries in elite athletes, [9,11-13] but
fMRI to our knowledge, has not been used to date to investigate muscle damage
and intermuscle and intramuscle regional differences in STIR values. This study
assessed SI changes in the upper thigh muscles using fMRI at 48 hours following a
lunge and eccentric leg curl exercises.
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Materials and Methods
Subjects
Eleven male professional soccer players participated in this study. Participants were
excluded if they had an injury to their legs or back in the preceding 12 months or if they
were unsuitable for fMRI because of foreign metal bodies, electronic implants or
claustrophobia. Before the start of the investigation, each participant’s height, weight,
age, regular exercise program and any previous injuries to the legs were recorded (see
Table 1). Subjects were instructed to avoid strength training activities for the lower legs
and not to use icing or anti-inflammatory medication for the week preceding and the
week of the experiment. Our institutional Ethics Committee approved the study and all
participants gave informed consent to participate in the study.
Insert Table 1 about here
GENERAL INITIAL
CHARACTERISTICS
n MEAN SD
HEIGHT
(m) 11 1.80 0.05
WEIGHT
(kg) 11 74.6 4.5
AGE
(years) 11 22.1 1.8
Table 1: Initial characteristics of subjects.
Procedures
The left and right legs of the subjects were randomly assigned to an eccentric leg curl
(LC) or lunge (L) exercise protocol. The protocol involved 3 sets of 6 repetitions with at
least a two-minute rest between sets. Following the completion of the exercise protocol
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for one leg (e.g LC), a two minutes rest was taken before starting the second exercise
(e.g. L) for the other leg.
Exercise Protocol
For the L exercise, subjects were instructed to step forward a predetermined distance
marked on the floor whilst the trunk remained upright. The length of the step was
standardized for each subject and was equal to the distance from the greater trochanter
to the floor as measured with the subject standing. This normalized distance was chosen
based on pilot testing, in which a comfortable L step length was determined. Subjects
were asked to lower their trunk by flexing their lead and trailing knees simultaneously
to a point where the trail knee was approximately 2 to 3 cm short of contacting the
ground. The lunge was completed when the subjects returned to the starting position.
For the ELC exercise, subjects performed eccentric hamstring curls (Prone Leg Curl
Technogym, Italy) at 120% of their one repetition maximum (1RM). The ELC 1RM
was quantified via a typical incremental load to failure protocol. Once the subject could
not complete two concentric leg curls at the set load this was determined as their 1RM
to which a 20% load, which resulted in the 120% 1RM eccentric load. Subjects were
instructed to lower the weight from a knee-flexed position (100°) to a knee-extended
position (0°) in 3 seconds, maintaining a constant lowering velocity. The subjects kept
their ankle plantar flexed to reduce the contribution of the gastrocnemius muscle.
Subjects were verbally encouraged to exert maximal force at the starting position and to
resist maximally against the knee-extending action throughout the range of motion. The
weight was raised after each eccentric repetition by an examiner, thereby rendering the
exercise an eccentric-only task for the subject.
Imaging Technique
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MR imaging was performed using a 1 T whole body imager (Magnetom Impact Expert;
Siemens-Erlangen, Germany), with the subjects supine with their knee extended
immediately before and 48 hours after the exercise. Once the subject was positioned
inside the magnet, the thighs of both legs were kept parallel to the MRI table and the
feet were strapped together to prevent rotation. The length of the right femur (Lf), taken
as the distance from the intercondylar notch of the femur to the superior boundary of the
femoral head, was measured in the coronal plane.
Subsequently, 15 axial scans of the thigh interspaced by a distance of 1 / 15 Lf were
obtained from the level of 1/15 Lf to 15/15 Lf . Every image obtained was labelled at its
location (i.e. slice 4 being closer to the coxofemoral joint and slice 12 closer to the
knee). Great care was taken to reproduce the same individual Lf each time by using the
appropriate anatomical landmarks [33] For the final calculation of the signal intensity
of each muscle, slices 4 / 15 – 12 / 15 were used for all muscles examined; the two
cranial slices (closer to the hip) and the three distal slices (closer to the knee) were
discarded given the presence of image artifacts. Then fast STIR MR axial images
[repetition time (TR) = 5,300 ms, echo time (TE) = 60ms, inversion time (TI) 115 ms,
flip angle (FA): 180] were collected using a 256 x 256 image matrix, with a 350 mm
field of view and 10-mm slice thickness using a body coil.
The MRI data were evaluated for SI of each hamstring muscle (BF, ST and SM),
adductor magnus (AM) and gluteus maximus (GM). The MR images were transferred to
a personal computer in the Digital Imaging and Communications in Medicine (DICOM)
format and analysed using image manipulation and analysis software (OSIRIX,
University Hospital of Geneva, Switzerland). Individual baseline SI readings, analysed
with a standardized radius of interest (ROI), were established with the preliminary scan
for each participant. The ROI was placed in the same position within the muscle for
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each measurement, avoiding blood vessels and bone, which may have affected the
analysis of the intensity changes. The SI was measured in a circular region of interest
(ROI, 10-30 mm2) within each muscle assessed before and after exercise and a
percentage difference was calculated. The same technician (FIS) performed the MR
imaging scan and the SI measures.
Statistical Analysis
The STIR absolute values were reported as mean ± SD. Given the differences between
exercises utilized in this study, the principal comparison of interest was the within
exercise pre-post changes in absolute values of STIR of the muscles (BF, SM, ST, AM
and GM) for all the different sections (3, 4, 5, 6, 7, 8, 9, 10,11 and 12). To disentangle
the main effects a two factor (time x section) repeated measures ANOVA with post hoc
contrasts was used to determine significant differences between sections. Paired t-tests
were used to determine significant pre-post exercise changes in L and ELC and for the
relative change between the ELC and L exercises. Statistical significance was set at p <
0.05.
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Results
Typical STIR of the right (ELC) and left (L) before and after exercise can be observed
in Figure 1. No statistical differences (p < 0.05) were found in any muscle or section
between left and right legs in the pre-exercise MRI’s. The changes in absolute values
pre and post exercise of the different muscles (BF, SM, ST, AM and GM) and sections
3 to 12 for the ELC and L exercises can be observed in Table 2. The following is a
summary of the main findings from these tables.
Insert Figure 1 about here.
Insert Table 2 about here.
STIR Absolute Values for ELC and L before and after exercise
ELC L
ANOVA
RM p
Muscle
and
Section
TIME n Mean +SD
T-
TEST
p
Muscle
and
Section
TIME n Mean +SD
T-
TEST
P
ST4 Before 11 128.0
915.33 0.048 ST4 Before 11 133.4 13.0 0.718 0.033
After 11 189.0
089.37 After 11 131.00 14.3
ST5 Before 11 134.4
510.71 0.021 ST5 Before 11 132.3 12.3 0.068 0.019
After 11 267.3
6
165.2
5
After 11 139.9 13.4
ST6 Before 11 146.2
720.70 0.005 ST6 Before 11 132.00 15.1 0.057 0.004
After 11 342,4
5
186,4
5
After 11 143.7 18.0
ST7 Before 11 135,9
118,66 0,007 ST7 Before 11 126.3 15.9 0.085 0.005
After 11 321,4
5
183,1
3
After 11 136.3 16.4
ST8 Before 11 130,7
317,82 0,016 ST8 Before 11 124.4 12.9 0.028 0.018
After 11 234,6
4
115,6
4
After 11 134.7 16.1
10
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208
10
ST9 Before 10 131,8
014,70 0,054 ST9 Before 10 126.2 15.2 0.696 0.048
After 10 204,6
0
105,1
0
After 10 127.9 13.6
ST10 Before 10 131,1
012,78 0,029 ST10 Before 10 130.6 9.5 0.268 0.012
After 10 185,3
064,00 After 10 124.00 12.9
BF7 Before 11 157,2
745,35 0,260 BF7 Before 11 147.3 40.2 0.110 0.048
After 11 152,0
041,05 After 11 162.1 43.6
AM4 Before 10 137,1
08,69 0,047 AM4 Before 9 142.1 9.9 0.042 0.152
After 10 145,1
09,71 After 9 164.2 23.5
AM5 Before 11 136,2
79,03 0,143 AM5 Before 11 134.8 6.5 0.002 0.010
After 11 144,0
914,77 After 11 170.2 24.7
AM6 Before 11 140,4
514,10 0,145 AM6 Before 11 137.4 12.8 0.002 0.003
After 11 146,7
312,23 After 11 181.7 31.4
AM7 Before 11 145,1
810,09 0,211 AM7 Before 11 148.0 12.6 0.003 0.001
After 11 140,2
713,56 After 11 172.8 16.1
Table 2: STIR absolute values of muscles before and after exercise. ST=
semitendinosus, BF = biceps femoris, AM= adductor magnus. The number after the
muscle represents the section. ELC= eccentric leg curl. L =Eccentric Lunge, RM=
repeated measures. Significant differences are marked in cursive.
For the semitendinosus, significant changes (~21-45%, Table 2) in the STIR values for
the ELC exercise were noted along the length of the ST belly from sections 4 to 10 (see
Figure 2A); whereas only section 8 was found to differ significantly (p<0.028) from
pre-testing for the L exercise (see Figure 2B). In terms of the adductor magnus,
significant changes were observed for the L exercise proximally (sections 4 to 7,
Figures 3A) (~2-13%) whereas a significant increase in STIR was only found for
section 4 for the ELC exercise (See Figure 3B).
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Insert Figure 2A-2B, 3A-3B.
In terms of biceps femoris, significant differences (p=0,048, see figure 4A and 4B) were
found post exercise for the ELC and L exercise at section 7 (~ -3 vs 8%). No significant
changes were observed in absolute STIR values for the semimembranosus and gluteus
maximus.
Insert Figure 4A and 4B about here.
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Discussion
This study measured whether the hamstring muscles responded in a uniform manner to
two different exercises, as quantified by the absolute changes in the STIR values of
fMRI. It has been assumed previously that during hamstring strengthening exercises,
individual hamstring muscles are activated in a similar manner. However, this is not the
case, as we observed that each hamstring muscle responded differently during the L and
ECL exercises respectively. The mechanics of the exercises used in this investigation
differ in many ways: 1) the ELC is an open kinetic chain exercise with differences in
hip flexion and tibial rotation [34,35] compared to the L which is a closed kinetic chain
exercise;[36,37] 2) the ELC is principally a monoarticular exercise, whereas the L is
biarticular; 3) as a result, the moments around the joints as well as the length-
tension/torque angle relationship of individual muscles will differ; 4) there is no
concentric component in the ELC which is not the case for the L; and, 5) the ELC is
supramaximally loaded at 120% 1RM which is not the case for the L. Given these
differences, it is difficult to ascertain whether a given exercise is ‘superior’ to the other,
and we shall focus on the site specific activation of each exercise and how each exercise
may be used for the conditioning of the hamstring muscle group.
With regards to the ST, it appears that the greatest changes in the MRI measurements
followed the ELC loading, in agreement with previous research. [18,38] The changes
in fMRI measurements of the ST may relate to its architectural characteristics as it has
the longest fascicle length and smallest physiological cross-sectional area (PSCA) of the
hamstring muscles [16], and it is a fusiform muscle compared with more pennate BF
and SM muscles. Muscles containing long fascicles produce forces over large length
ranges and at high shortening speeds, because they have a large number of
simultaneously contracting, serially arranged sarcomeres. [39] Such morphological
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properties of ST may be selectively used to perform eccentric knee flexion more
efficiently.
The region-specific activation within the proximal, middle and distal regions of the
same muscle found in this study were in contrast to the Kubota et al. [18] findings,
where significant differences between proximal and distal regions were detected. This
was explained by the fact that the ST is the only hamstring muscle that was
anatomically partitioned as defined by its architecture and innervation [16]. In addition,
this division into partitions was augmented by the presence of a tendinous inscription
with each partition receiving innervation from one muscle nerve, or from a primary
branch of the nerve [16]. The differences between ours and Kubota et al.’s findings [18]
could be attributed to methodological differences, as we divided the thigh into fifteen
regions while they only divided the thigh into three regions. Only in one instance did
one section (Section 8) of the ST show changes after the lunge exercise.
In the AM, significant changes (section 4,~12%; section 5, ~19%; section 6, ~22%; and
section 7, ~14%s) were observed for the L exercise proximally (sections 4 to 7), as
compared to section 4 ( 5%) for the ELC exercise. The greater evidence of
intramuscular changed of the AM during lunges may result from greater hip extension
moments when the hip is flexed. The large hip extension moment arm in addition to
adduction has been noted previously for this muscle. [40,41] The lesser involvement of
the AM during the ELC may be due to a fixed hip angle position (15º) during the
exercise.
No significant changes in fMRI were observed for the BF after ECL loading. In
contrast, significant absolute changes in STIR values were observed at one region
(Section 7) for the BF after L loading. As T2 values are more sensitive to eccentric
exercise [18,25-30] compared to concentric exercise[26] this study may support
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previous findings where a very short and rapid period of eccentric hamstring contraction
during the forward lunge has been documented .[36,37] Hamstring length depends on
both knee and hip joint angles since the hamstrings are biarticular muslces. The angle of
the hip has more impact on the length of the biceps femoris than the angle of the knee,
[42,43] given the longer moment arm at the hip, and this relationship increases with
increasing knee angle. Hip flexion-extension exercise resulted in greater BF activation
as measured by MRI compared with a hip fixed exercise .[18,38] Given this
information and based on muscle mechanics and physiology, greater BF damage during
lunges may arise from larger internal hip extension moments when the hip is flexed.
It is difficult to ascertain which variables differ between exercises to produce site
specific activation differences. However, greater proximal activation (section 5, 23%;
section 6, 10%; section 7, 8%; and section 8, 7%) is present after the L exercise ( see
figure 3) while minimal or negative changes after ELC exercise (section 5, 11%; section
6, -3%; section 7, -3%; and section 8, -4%) are evident. It is possible that exercise
intensity accounts for the finding that only one region showed significant changes for
the BF. Exercise-induced changes in fMRI vary according to exercise intensity:
previous studies have reported greater SI changes after maximal loads compared to
lower loads. [19,21,22,44-46] To better define this load effect, more research is needed
investigating whether a loaded lunge produces greater changes across the proximal BF
in comparison to the bodyweight lunge.
This study used fMRI to assess the relative damage to lower leg muscles after two
different exercises. Different exercises can increase hamstring strength, [11,47] but
various hamstring exercises do not result in a uniform response, and therefore training
stimulus, for the same muscles and the same regions of the muscles. Because hamstring
strains affect different hamstring muscles, proper exercise selection is crucial to target
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the desired muscle/s. When the goal of a therapeutic intervention is to specifically
strengthen the ST, AM, and/or BF, a progressive resistive training program that
incorporates ELC or L is indicated, as these exercises selectively and effectively
activate the aforementioned muscles. In conclusion, the present study demonstrates that
the ELC exercise is better suited for loading all regions of ST muscle and the L exercise
is more effective for loading the proximal regions of biceps femoris and adductor
magnus.
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Supplementary resource

  • ... Proper exercise selection potentially allows the clinician to better succeed in (re-)injury prevention, but this is challenging for many reasons. For example, non-uniform adaptations to exercise interventions 11,15,16 may be associated with non-uniform hamstring activity patterns across exercises 11,[17][18][19] . Moreover, study results are inconsistent concerning which hamstring muscles are activated in different exercises, as well as the extent of activation 20 , and it is questionable whether these differences are real or at least partly reflect the (in)accuracy with which different methods can define muscle activity. ...
    ... In conventional EMG studies, electrodes are placed over the mid-belly of hamstring muscles, ignoring possible proximal-distal differences in muscle activity. Studies have shown non-uniform proximal-distal metabolic activity patterns within hamstring muscles 18,19,21 . Similarly, during two common hamstring exercises, we recently observed large differences in muscle activity within the semitendinosus (ST) and biceps femoris long head (BFlh) using high-density EMG (HD-EMG) 22 . ...
    ... In addition to recent studies using muscle functional magnetic resonance imaging (mfMRI) 18,19,21 and our previous results using HD-EMG 22 , the exercise-dependent changes in proximal-distal activity patterns observed in this study reinforce the notion that spatially robust methods are needed to accurately describe the activity level of ST and BFlh muscles. This is further supported by the substantially different proximal-distal EMG activity patterns between muscles in most of the exercises. ...
    Article
    Proximal‐distal differences in muscle activity are rarely considered when defining the activity level of hamstring muscles. The aim of this study was to determine the inter‐muscular and proximal‐distal electromyography (EMG) activity patterns of hamstring muscles during common hamstring exercises. Nineteen amateur athletes without a history of hamstring injury performed 9 exercises while EMG activity was recorded along the biceps femoris long head (BFlh) and semitendinosus (ST) muscles using 15‐channel high‐density electromyography (HD‐EMG) electrodes. EMG activity levels normalized to those of a maximal voluntary isometric contraction (%MVIC) were determined for the eccentric and concentric phase of each exercise and compared between different muscles and regions (proximal, middle, distal) within each muscle. Straight‐knee bridge, upright hip extension and leg curls exhibited the highest hamstrings activity in both the eccentric (40‐54%MVIC) and concentric phases (69‐85%MVIC). Hip extension was the only BF‐dominant exercise (Cohen's d = 0.28 (eccentric) and 0.33 (concentric)). Within ST, lower distal than middle/proximal activity was found in the bent‐knee bridge and leg curl exercises (d range = 0.53‐1.20), which was not evident in other exercises. BFlh also displayed large regional differences across exercises (d range = 0.00–1.28). This study demonstrates that inter‐muscular and proximal‐distal activity patterns are exercise‐dependent, and in some exercises are affected by the contraction mode. Knowledge of activity levels and relative activity of hamstring muscles in different exercises may assist exercise selection in hamstring injury management. This article is protected by copyright. All rights reserved.
  • ... Mendiguchia et al. (34) studied posterior thigh muscles of soccer players and showed that MRIs are an effective method to capture the acute post-practice muscular changes through the T2 signal. Meanwhile, Mendiguchia et al. (34) showed greater metabolic activity in recto-femoral muscles, vastus medialis, and gluteus maximus using the MRI T2 map immediately after training using the Pilates Method. ...
    ... Mendiguchia et al. (34) studied posterior thigh muscles of soccer players and showed that MRIs are an effective method to capture the acute post-practice muscular changes through the T2 signal. Meanwhile, Mendiguchia et al. (34) showed greater metabolic activity in recto-femoral muscles, vastus medialis, and gluteus maximus using the MRI T2 map immediately after training using the Pilates Method. Both studies are similar to the present study, which showed an increase in the T2 map after a series of exercises of the quadriceps muscle, a finding that indicates an increase in metabolic activity of muscle cells. ...
    Article
    Full-text available
    OBJECTIVES: Menopause marks the end of women’s reproductive period and can lead to sarcopenia and osteoporosis (OP), increasing the risk of falls and fractures. The aim of this study is to evaluate the influence of normal and low bone mineral density (BMD) on muscular activity, observed through inflammatory edema when mapping using magnetic resonance imaging (MRI) on the quadriceps muscle of postmenopausal women. METHODS: This was a cross-sectional study involving 16 older women, who were divided into two groups: osteoporosis group (OG), older women with OP, and control group (CG), older women without OP. The groups were evaluated in terms of nuclear MRI exam before and after carrying out fatigue protocol exercises using an isokinetic dynamometer and squatting exercises. RESULTS: The results of the present study showed that in intragroup comparisons, for both groups, there was a significant increase (p<0.05) in the T2 signal of the nuclear MRI in the quadriceps muscle after carrying out exercises using both thighs. In the intergroup comparison, no statistically significant difference was observed between the OG and CG, pre- (p=0.343) and postexercise (p=0.874). CONCLUSION: The acute muscular activation of the quadriceps evaluated by T2 mapping on nuclear MRI equipment is equal in women with and without OP in the postmenopausal phase. BMD did not interfere with muscle response to exercise when muscle fatigue was reached.
  • ... The first stage of the frustum method estimates gross thigh volume by performing (typically three) requisite linear extrapolation of thigh circumference measures, however, is not representative of a complex thigh structure, where muscle hypertrophy can be local. Therefore, using the initial part of the frustum method to measure total thigh volume can mask local hypertrophy, which reduces sensitivity (Mendiguchia et al., 2013). As such, the gross thigh volume which is used as part of the frustum method should be considered an emblematic measure rather than a valid representation of thigh volume. ...
    ... First, it minimises inter-and intra-practitioner error as it only requires a practitioner to mark one point subsequent to the first measure of a participant rather than having to make three separate circumference measures. Second, the higher resolution from the depth camera system gives a better representation of gross thigh morphology, capturing the non-homogenous structure and growth of the thigh, which can be lost with the frustum method (Mendiguchia et al., 2013;Wells et al., 2014). ...
    Article
    Full-text available
    Gross thigh volume is a key anthropometric variable to predict sport performance and health. Currently, it is either estimated by using the frustum method, which is prone to high inter-and intra-observer error, or using medical imaging, which is expensive and time consuming. Depth camera 3D-imaging systems offer a cheap alternative to measure thigh volume but no between-session reliability or comparison to medical imaging has been made. This experiment established between-session reliability and examined agreement with magnetic resonance imaging (MRI). Forty-eight male cyclists had their thigh volume measured by the depth camera system on two occasions to establish between-session reliability. A subset of 32 participants also had lower body MRIs, through which agreement between the depth camera system and MRI was established. The results showed low between-session variability (CV = 1.7%; Absolute Typical Error = 112 cm³) when measuring thigh volume using the depth camera system. The depth camera systematically measured gross thigh volume 32.6cm³ lower than MRI. These results suggest that depth camera 3D-imaging systems are reliable tools for measuring thigh volume and show good agreement with MRI scanners, providing a cheap and time-saving alternative to medical imaging analysis.
  • ... [2][3][4] In the pre-season, rectus femoral strains injuries (29%) are more frequent than biceps femoral injuries incidence (11%), composition (47, 1% fiber type I and 52, 4% fiber type ii) 5 but during the season, the risk of injury to posterior thigh muscles is higher. 3,6 overall, hamstring muscle injuries are the most prevalent, accounting for 12-16% of all injuries. 7 The fiber structural damage can be produced by the collisions and the metabolic stress from prolonged high-intensity exercise that contribute to tissue damages in the players. ...
    Article
    Background: To measure the impact of training models on injury incidence, data of health and performance were integrated to study fiber adaptation during a competitive season. We studied football players over a season, analyzing hours of exposure to sport by serum changes in fast and slow myosin, creatine kinase and lactate dehydrogenase. Methods: A new assay was developed to measure the myosin isoforms in 49 non-sporting volunteers and in 27 professional football players. Results: Myosin isoforms in volunteers with mean ages of 30±8 were 1553 µg/L fast and 1284 µg/L slow; in the group with of 56±7 were 1426 µg/L fast and 1046 µg/L slow. Slow myosin was significantly lower in older subjects (-18%). Samples from the players in preseason had lower mean scores for fast myosin (1123 µg/L) and higher for slow myosin (2072 µg/L) than reference volunteers. During the season, myosins reached the maximum with the maximum load (1537 µg/L fast, 2195 µg/L slow but decreased and adapted to the high level of demand (425 µg/L fast, 1342 µg/L slow). CK and LDH were maximal at the pre-season (227 U/L, 333 U/L) while myosin levels were maximal at the beginning of season (1537 µg/L, 2195 µg/L). Conclusions: Measuring serum myosin isoforms we identify the type and amount of damage caused by training and matches, making it a new control tool capable of advising training towards a minimum of blood slow myosin but controlling the fast fiber participating and be able to improve the performance of the players.
  • ... These data have a logical rationale from a functional anatomical perspective given that the hamstring muscles act as prime movers in both a hip extension and knee flexion, which in turn suggests its length would remain relatively constant during MJ lower-body exercise [29]. Adding further insight to the findings, Mendiguchia et al. [30] found differences in region-specific activation within the proximal, middle, and distal regions of the hamstrings between the leg curl and the lunge as determined by magnetic resonance imaging (MRI), indicating that SJ and MJ may not be interchangeable when determining prescription for exercise volume for this muscle complex. ...
    Article
    Full-text available
    Resistance training volume, determined by the number of sets performed (set-volume) is considered one of the key variables in promoting muscle hypertrophy. To better guide resistance exercise prescription for weekly per-muscle training volume, the purpose of this paper is to provide evidence-based considerations for set-volume ratios between multi-joint (MJ) and single-joint (SJ) exercises so that practitioners can better manage prescription of training volume in program design. We analyzed this topic from three primary areas of focus: (1) biomechanical and physiological factors; (2) acute research; and (3) longitudinal research. From a biomechanical and physiological standpoint, when considering force production of different muscle groups, the moment arm of a given muscle, “motor abundance”, the link between biomechanics and exercise-induced fatigue, as well as the amount of time in voluntary muscle activation, a logical rationale can be made for SJ exercises producing greater hypertrophy of the limb muscles than MJ exercises (at least from specific exercises and under certain conditions). This would mean that sets for a MJ exercise should be counted fractionally for select muscles compared to an SJ exercise (i.e., less than a 1:1 ratio) when prescribing set-volumes for given muscles. When considering results from acute studies that measured muscle activation during the performance of SJ and MJ exercises, it seems that MJ exercises are not sufficient to maximize muscle activation of specific muscles. For example, during performance of the leg press and squat, muscle activation of the hamstrings is markedly lower than that of the quadriceps. These results suggest that a 1:1 ratio cannot be assumed. Current longitudinal research comparing the effects of training with MJ vs. SJ or MJ + SJ exercises is limited to the elbow flexors and the evidence is somewhat conflicting. Until more research is conducted to derive stronger conclusions on the topic, we propose the best advice would be to view set-volume prescription on a 1:1 basis, and then use logical rationale and personal expertise to make determinations on program design. Future research should focus on investigating longitudinal hypertrophic changes between MJ and SJ in a variety of populations, particularly resistance-trained individuals, while using site-specific measures of muscle growth to more systematically and precisely compute effective individualized set-volumes.
  • ... The hamstrings consist of three individual muscles, each of which have functional roles related to their anatomy, and demonstrate various electromyography (EMG) patterns and MRI spatial characteristics in response to exercise stimulus. [39][40][41][42][43][44] In sprinting, bicep femoris (BF) is subject to the largest strain, semitendinosus (ST) the greatest lengthening velocities, whereas semimembranosus (SM) acts predominantly as a force producer. [43][44][45] BF is activated more during the acceleration phase of sprinting and terminal swing, ST during maximum-velocity sprinting, whereas SM has an important role in absorbing and generating power in swing and stance. ...
    Article
    Rationale Hamstring injuries are common in elite sports. Muscle injury classification systems aim to provide a framework for diagnosis. The British Athletics Muscle Injury Classification (BAMIC) describes an MRI classification system with clearly defined, anatomically focused classes based on the site of injury: (a) myofascial, (b) muscle–tendon junction or (c) intratendinous; and the extent of the injury, graded from 0 to 4. However, there are no clinical guidelines that link the specific diagnosis (as above) with a focused rehabilitation plan. Objective We present an overview of the general principles of, and rationale for, exercise-based hamstring injury rehabilitation in British Athletics. We describe how British Athletics clinicians use the BAMIC to help manage elite track and field athletes with hamstring injury. Within each class of injury, we discuss four topics: clinical presentation, healing physiology, how we prescribe and progress rehabilitation and how we make the shared decision to return to full training. We recommend a structured and targeted diagnostic and rehabilitation approach to improve outcomes after hamstring injury.
  • ... We believe another strength is the detailed definition of the grading levels and its potential prognostic value and easy clinical application for health-related professionals (i.e., physicians, physiotherapists, and trainers). The classification can help to improve clear communication between healthcare and sports-related professionals and assist them in the decision making regarding rehabilitation protocols and RTP [93,[120][121][122][123][124][125][126][127][128]. In addition, we believe it is a flexible and open system, allowing future adaptation to incorporate any subsequent knowledge shown to be relevant to prognosis or diagnosis. ...
  • ... The different locations where an injury may occur (proximal, medial distal) must be trained at the moment when it may arise. On the other hand, as the hamstring muscles portions are not activated uniformly during different exercises, 48,49 this suggests that a range of exercises should be used. ...
    Article
    Full-text available
    Hamstring strains, mainly in the femoral biceps, are the most common football injury. In spite of all the studies carried out on preventing these injuries, their incidence has not fallen. One of the possible causes of this is incorrect choice of strength exercises and the traditional reductionist vision that fails to consider the interrelation between risk factors. The aim of this article is to review the risk factors presented in the literature and propose a correct choice of exercises for prevention based on the location of muscle activation, as well as offering a multifactor description of risk factors.
  • Chapter
    Hamstring strain injury often results in neuromuscular performance deficits that persist beyond rehabilitation and the return to full training and competitive sport. It seems appropriate to address these deficits as a part of a sport-specific training program which primarily aims to enhance performance. Prolonged deficits in horizontal ground reaction forces in sprinting, repeat sprint performance, knee flexor eccentric strength and biceps femoris long head fascicle lengths have been observed in multiple studies of hamstring strain injury. Why such deficits persist beyond the return to sport is not known, although persistent neuromuscular inhibition of the injured muscles has been proposed. There is limited and mixed evidence for sprint running kinematic (technique) differences between previously injured and uninjured limbs or athletes, although more work in this area seems warranted. While there is some uncertainty about the optimal mix of methods for addressing the aforementioned deficits, sport-specific running programs in conjunction with continued monitoring of acceleration phase sprint performance and repeated sprint ability seem appropriate. Heavy strength training with at least some eccentrically biased exercises is also recommended to address deficits in eccentric strength and muscle fascicle lengths.
  • Chapter
    Treatment failure is defined as an unsuccessful result of management, and this is observed frequently in acute and long-standing hamstring injuries. The main causes of treatment failure are an incorrect diagnosis or inefficacy of treatment. This chapter will describe the differential diagnoses that can be considered in patients with treatment failure after acute and long-standing hamstring injuries. Reevaluation of the patient and expanding diagnostic workup can be useful to identify other causes of posterior thigh or buttock pain. If the diagnosis remains within the category of acute hamstring injury, hamstring injury sequela, or hamstring tendinopathy, alternative treatments can be considered. Numerous alternative treatment options are available for this patient group. This chapter describes which treatments can be considered and what the current level of evidence for their efficacy is.
  • Article
    Muscle functional magnetic resonance imaging (mfMRI) is an innovative technique that offers a noninvasive method to quantify changes in muscle physiology following the performance of exercise. The mfMRI technique is based on signal intensity changes due to increases in the relaxation time of tissue water. In contemporary practice, mfMRI has proven to be an excellent tool for assessing the extent of muscle activation following the performance of a task and for the evaluation of neuromuscular adaptations as a result of therapeutic interventions. This article focuses on the underlying mechanisms and methods of mfMRI, discusses the validity and advantages of the method, and provides an overview of studies in which mfMRI is used to evaluate the effect of exercise and exercise training on muscle activity in both experimental and clinical studies.
  • Article
    Full-text available
    Muscle injuries constitute a large percentage of all injuries in football. To investigate the incidence and nature of muscle injuries in male professional footballers. Cohort study; Level of evidence, 2. Fifty-one football teams, comprising 2299 players, were followed prospectively during the years 2001 to 2009. Team medical staff recorded individual player exposure and time-loss injuries. The first-team squads of 24 clubs selected by the Union of European Football Associations as belonging to the best European teams, 15 teams of the Swedish First League, and another 15 European teams playing their home matches on artificial turf pitches were included. A muscle injury was defined as "a traumatic distraction or overuse injury to the muscle leading to a player being unable to fully participate in training or match play." In total, 2908 muscle injuries were registered. On average, a player sustained 0.6 muscle injuries per season. A squad of 25 players can thus expect about 15 muscle injuries per season. Muscle injuries constituted 31% of all injuries and caused 27% of the total injury absence. Ninety-two percent of all muscle injuries affected the 4 major muscle groups of the lower limbs: hamstrings (37%), adductors (23%), quadriceps (19%), and calf muscles (13%). Sixteen percent of the muscle injuries were reinjuries. These reinjuries caused significantly longer absences than did index injuries. The incidence of muscle injury increased with age. When separated into different muscle groups, however, an increased incidence with age was found only for calf muscle injuries and not for hamstring, quadriceps, or hip/groin strains. Muscle injuries are a substantial problem for players and their clubs. They constitute almost one third of all time-loss injuries in men's professional football, and 92% of all injuries affect the 4 big muscle groups in the lower limbs.
  • Article
    To evaluate the activity of neck extensor muscles during different extension exercises with muscle functional magnetic resonance imaging (mfMRI). Cross-sectional. University laboratory. Healthy subjects (N=11; 7 men, mean age +/- SD, 34+/-5.6y; 4 women, mean age +/- SD, 23.3+/-5.2y; group mean age +/- SD, 30.1+/-7.5y). Not applicable. mfMRI measures of T2 relaxation were made for the multifidus (Mul), the semispinalis cervicis (SCe), the semispinalis capitis (SCa), and the splenius capitis (SpC) at C2-3, C5-6, and C7-T1 in response to 2 head/neck orientations: craniocervical neutral (CCN) and craniocervical extension (CCE). Subjects performed three 1-minute repetitions of each condition at 20% maximum voluntary contraction. Significant shifts were observed in all muscle groups at the C5-6 and C7-T1 levels after both conditions (P=.04) except the SpC muscle at C5-6 with CCN (P=.17). T2 shifts in the SCa were significantly greater in response to CCE than CCN at C2-3 (P=.03) and C5-6 (P=.02). Similarly, CCE resulted in larger shifts than CCN in the Mul/SCe at C7-T1 (P=.003). No segmental differences were observed between exercises for SpC (P=.25). The results of this study provide some preliminary insight into the impact of craniocervical orientation on the differential response of the deep and superficial cervical extensor muscles during the performance of cervical extensor exercises.
  • Article
    Full-text available
    The purpose of this study was to clarify the activation patterns among knee flexor muscles during knee flexion exercises by electromyography (EMG) and muscle functional magnetic resonance imaging (mfMRI). Seven male volunteers performed knee flexion exercises with each unilateral limb at 120% of 1 repetition of maximum (1RM) and 50% of 1RM. EMG activity was recorded for the biceps femoris long head, semitendinosus (ST), semimembranosus (SM), and gracilis (G) muscles; mfMRI T2 values in the same muscles were measured at rest and immediately after exercise. The study found that EMG of the ST and G was significantly higher than that of the SM during the exercises at 120% 1RM. T2 value changes in the ST and G were significantly higher than in the biceps femoris long head (BFlh) and SM in both exercises [corrected].It was concluded that the activation patterns among knee flexor muscles during knee flexion were nonuniform for the respective muscles.
  • Article
    Full-text available
    The organization of fibers within a muscle (architecture) defines the performance capacity of that muscle. In the current commentary, basic architectural terms are reviewed in the context of the major hip muscles and then specific illustrative examples relevant to lower extremity rehabilitation are presented. These data demonstrate the architectural and functional specialization of the hip muscles, and highlight the importance of muscle physiology and joint mechanics when evaluating and treating musculoskeletal disorders.
  • Article
    Full-text available
    Eccentric exercises are commonly used as a treatment for various muscle and tendon injuries. During complex motions such as the forward lunge, however, it is not always clear which muscles may be contracting eccentrically and at what time. Because this exercise is used during rehabilitation, the purpose of this investigation was to determine what type of contractions take place during two different types of forward lunge and assess the implications for rehabilitation. Five experienced athletes performed five cycles for each of the walking and jumping forward lunges. Motion analysis was used to calculate the shortening or elongation of each muscle based on the change of position of their origin and insertion points during the lunge. Electromyography of the lateral hamstrings, rectus femoris and lateral gastrocnemius was combined with the muscle length change data to determine when isometric, concentric and eccentric activations occur during the lunge. Eccentric contractions in both the quadriceps and gastrocnemius were observed during the lunge. No hamstring eccentric contractions were found; however, the hamstrings showed isometric contractions during the first part of the stance phase.
  • Article
    A few studies have shown that eccentric exercise is effective for prevention and treatment of muscle injuries. Most earlier studies on eccentric exercises have used training with advanced equipment. Forward lunges are considered eccentric exercises, and they may be performed without any equipment. These exercises are commonly used by sprint runners. We performed a prospective, randomized, 6-week training study comparing the effects of walking or jumping forward lunges on hamstring and quadriceps strength and function. Thirty-two soccer players were included in the study. The forward lunge training was done as an addition to ordinary soccer training twice a week for 6 weeks. The outcome was measured by the maximal hamstring and quadriceps strength tests and by functional tests with 1-leg hop tests and 30-m sprint runs. Overall muscle pain was evaluated using a visual analogue scale score, and local pain was estimated with an algometer. Whereas the walking lunge improved hamstring strength, the jumping lunge resulted in sprint running improvements. Algometer testing showed a general increase in the pain detection thresholds of all subjects, including the controls. Thus, precautions should be taken when algometers are used for temporal studies of pain. Walking and jumping forward lunges can be used for improving hamstring strength and running speed in young soccer player. The findings may have relevance when designing protocols for prevention and rehabilitation of muscle injuries.
  • Article
    The purpose of this study was to investigate the effect of intensive eccentric exercise on hamstring muscles by using magnetic resonance imaging (MRI) and to elucidate the relationships between the changes in the electromyographic (EMG) parameters and in the transverse relaxation time (T2) of the hamstring muscles. Seven male volunteers performed eccentric knee flexion exercise, and the EMG activity of the hamstring muscles was simultaneously measured. Before and immediately after the exercise, the maximum isometric knee flexion torque was measured and MR images of the hamstring muscles were obtained. For all hamstring muscles, the EMG activity of the fifth set was significantly lower than that of the first set. For each subject, a significant correlation was detected between the percentage change in the value of the post-exercise T2 value and those of EMG signals during the exercise only for the semitendinosus (ST) muscle and not for the biceps femoris (BF) and the semimembranosus (SM) muscles. These results suggested that the EMG-activity reductions in the BF, ST, and SM muscles were due to neuromuscular fatigue, and moreover the reduction in the ST muscle was due to a failure in the E-C coupling, which was caused by excessive muscle-fiber damage.
  • Article
    Electromyography (EMG) is commonly used to determine the electrical activity of skeletal muscle during contraction. To date, independent verification of the relationship between muscle use and EMG has not been provided. It has recently been shown that relaxation- (e.g., T2) weighted magnetic resonance images (MRI) of skeletal muscle demonstrate exercise-induced contrast enhancement that is graded with exercise intensity. This study was conducted to test the hypothesis that exercise-induced magnetic resonance (MR) contrast shifts would relate to EMG amplitude if both measures reflect muscle use during exercise. Both MRI and EMG data were collected for separate eccentric (ECC) and concentric (CON) exercise of increasing intensity to take advantage of the fact that the rate of increase and amplitude of EMG activity are markedly greater for CON muscle actions. Seven subjects 30 +/- 2 (SE) yr old performed five sets of 10 CON or ECC arm curls with each of four resistances representing 40, 60, 80, and 100% of their 10 repetition maximum for CON curls. There was 1.5 min between sets and 30 min between bouts (5 sets of 10 actions at each relative resistance). Multiple echo, transaxial T2-weighted MR images (1.5 T, TR/TE 2,000/30) were collected from a 7-cm region in the middle of the arm before exercise and immediately after each bout. Surface EMG signals were collected from both heads of the biceps brachii and the long head of the triceps brachii muscles. CON and ECC actions resulted in increased integrated EMG (IEMG) and T2 values that were strongly related (r = 0.99, P < 0.05) with relative resistance.(ABSTRACT TRUNCATED AT 250 WORDS)
  • Lengths of muscle tendon complexes of the quadriceps femoris muscle and some of its heads, biceps femoris and gastrocnemius muscles, were measured for six limbs of human cadavers as a function of knee and hip-joint angles. Length-angle curves were fitted using second degree polynomials. Using these polynomials the relationships between knee and hip-joint angles and moment arms were calculated. The effect of changing the hip angle on the biceps femoris muscle length is much larger than that of changing the knee angle. For the rectus femoris muscle the reverse was found. The moment arm of the biceps femoris muscle was found to remain constant throughout the whole range of knee flexion as was the case for the medial part of the vastus medialis muscle. Changes in the length of the lateral part of the vastus medialis muscle as well as the medial part of the vastus lateralis muscle are very similar to those of vastus intermedius muscle to which they are adjacent, while those changes in the length of the medial part of the vastus medialis muscle and the lateral part of the vastus lateralis muscle, which are similar to each other, differ substantially from those of the vastus intermedius muscle. Application of the results to jumping showed that bi-articular rectus femoris and biceps femoris muscles, which are antagonists, both contract eccentrically early in the push off phase and concentrically in last part of this phase.