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Eccentric muscle actions (ECC) are characterized by muscle lengthening, despite actin-myosin crossbridge formation. Muscles acting eccentrically are capable of producing higher levels of force compared to muscles acting concentrically. The purpose of this study was to determine if ECC bench press yields greater strength than concentric (CON) as determined by one-repetition maximum (1RM). Additionally, a comparison was made examining differences in the number of repetitions to failure at different relative intensities of 1RM. Thirty healthy men (age = 24.63 + 5.6 years) were tested for 1RM in CON and ECC bench press and the number of repetitions completed at 60%, 70%, 80%, and 90% 1RM. For CON repetitions, the weight was mechanically lowered to the chest and the participant pressed it up until the elbows were fully extended. The ECC bench press consisted of lowering a barbell from a fully extended elbow position to the chest in a continuous, controlled manner for three seconds as determined by electronic metronome. Paired t-tests showed that ECC 1RM (115.99 ± 31.08 kg) was significantly (p < 0.05) greater than CON 1RM (93.56 ± 26.56 kg) and the number of repetitions completed at 90% 1RM was significantly (p < 0.05) greater in ECC (7.67 + 3.24) as compared to CON (4.57 + 2.21). There were no significant differences in number of completed repetitions during CON and ECC bench press at 60%, 70% and 80% 1RM. These data indicate that ECC actions yield increased force capabilities (∼120%) as compared to CON in the bench press and may be less prone to fatigue, especially at higher intensities. These differences suggest a need to develop unique strategies for training eccentrically.
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Department of Kinesiology, Vanguard University, Costa Mesa, California;
Center for Sport Performance, California State
University, Fullerton, California;
School of Nutrition and Health Promotion, Arizona State University, Phoenix, Arizona;
Rocky Mountain University of Health Professions, Provo, Utah; and
College of Allied Health, California Baptist University,
Riverside, California
Kelly, SB, Brown, LE, Hooker, SP, Swan, PD, Buman, MP,
Alvar, BA, and Black, LE. Comparison of concentric and
eccentric bench press repetitions to failure. J Strength Cond
Res 29(4): 1027–1032, 2015—Eccentric muscle actions
(ECC) are characterized by muscle lengthening, despite
actin-myosin crossbridge formation. Muscles acting eccentri-
cally are capable of producing higher levels of force compared
with muscles acting concentrically. The purpose of this study
was to determine whether ECC bench press yields greater
strength than concentric (CON) as determined by 1 repetition
maximum (1RM). Additionally, a comparison was made exam-
ining differences in the number of repetitions to failure at dif-
ferent relative intensities of 1RM. Thirty healthy men (age =
24.63 65.6 years) were tested for 1RM in CON and ECC
bench press and the number of repetitions completed at 60,
70, 80, and 90% 1RM. For CON repetitions, the weight was
mechanically lowered to the chest, and the participant pressed
it up until the elbows were fully extended. The ECC bench
press consisted of lowering a barbell from a fully extended
elbow position to the chest in a continuous controlled manner
for 3 seconds as determined by electronic metronome. Paired
t-tests showed that ECC 1RM (115.99 631.08 kg) was sig-
nificantly (p#0.05) greater than CON 1RM (93.56 626.56
kg), and the number of repetitions completed at 90% 1RM was
significantly (p#0.05) greater in ECC (7.67 63.24) as com-
pared with CON (4.57 62.21). There were no significant
differences in number of completed repetitions during CON
and ECC bench press at 60, 70, and 80% 1RM. These data
indicate that ECC actions yield increased force capabilities
(;120%) as compared with CON in the bench press and
may be less prone to fatigue, especially at higher intensities.
These differences suggest a need to develop unique strategies
for training eccentrically.
KEY WORDS resistance, strength, fatigue
Eccentric (ECC) muscle actions occur when the
force exerted by working muscle is less than that
of an external resistance. This is characterized by
muscle lengthening, despite actin-myosin cross-
bridge formation. Thus, the separation of myosin from actin
is mechanical rather than chemical (11). This is in contrast to
concentric (CON) muscle actions, during which the muscle
shortens as actin filaments are pulled over myosin filaments.
During CON actions, crossbridges are separated through the
cleaving of an ATP molecule. The chemical reaction of
a CON muscle action results in less muscular damage than
ECC muscle action.
ECC actions, when emphasized during resistance training,
may elicit greater strength adaptation (4,18,23) muscular
hypertrophy (13,14,23), and acute increases in subsequent
CON force capabilities (8,21) and favorable acute inflamma-
tory response (13) compared with traditional ECC/CON
actions and CON muscle actions alone. Studies also suggest
that muscles are less prone to fatigue when acting eccentri-
cally (6,10). Based on the emergence of research supporting
the utilization of ECC muscle actions for a variety of out-
comes, programs that emphasize ECC actions through resis-
tance training methods have become increasingly popular.
As evidence of the effectiveness of ECC training emerges,
it is important to ensure that basic scientific principles of
traditional training are applied. A training program using
a prescribed number of sets and repetitions with a specified
intensity remains the most effective way to maximize the
benefits of resistance training and improve the likelihood of
desired adaptations (12,20). This is generally done by mea-
suring or predicting an individual’s 1 repetition maximum
(1RM) in a particular exercise and using that value to deter-
mine submaximal intensities to be used during training.
Address correspondence to Stephen B. Kelly, stephen.kelly@vanguard.
Journal of Strength and Conditioning Research
Ó2015 National Strength and Conditioning Association
VOLUME 29 | NUMBER 4 | APRIL 2015 | 1027
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A number of tables have appeared in the literature (1,7,19),
which may be useful for estimating 1RM based on the num-
ber of repetitions an individual is able to complete with
a given weight. Alternately, the tables can be used for esti-
mating the number of repetitions an individual should be
able to achieve given their 1RM and the percentage of that
1RM they are lifting. These tables are designed through pre-
diction equations extrapolating norms from data, which have
been collected in research studies. Tables suggesting weights
and repetitions per different percentages of 1RM provide
information useful in program design, minimization of injury
potential, and creating a time-efficient reference tool for use
in the manipulation of training variables such as volume and
intensity. However, each of these tables is designed for use
with traditional muscle actions, which consists of an ECC
action immediately followed by a CON action. In these
ECC/CON movements, the limiting factor in whether or
not the repetition is successful is nearly always the CON
action. This is attributed to the fact that ECC force capabil-
ities are 120–200% of CON force capabilities (2,9,10,15,16).
It is unclear how increased force capability and seemingly
greater resistance to fatigue (6,10) translates to the number
of repetitions, which can be completed eccentrically, as com-
pared with existing norms in the research, which describe
ECC/CON repetitions. This study seeks to address the prac-
tical question of how the physiological differences between
CON and ECC muscle actions relate to performance in
a common exercise.
No known literature exists, which describes a prediction
equation for ECC-only muscle actions, and as previous
research suggests, muscles performing ECC actions may
respond differently than muscles acting concentrically
(4,10,17). It remains to be examined whether CON and
ECC muscle actions react similarly in terms of repetitions to
failure at the same relative intensity. Therefore, it is important
to understand the unique characteristics of ECC muscle ac-
tions, including force capabilities, fatigue patterns, neural pat-
terns, and training adaptations to ECC-emphasized exercise.
The purpose of this study was to determine differences
between CON 1RM and ECC 1RM values on the bench
press and to examine the number of repetitions completed
at each percentage of 1RM between CON and ECC muscle
actions. These comparisons offer a practical examination of
how CON and ECC muscle actions may require unique train-
ing strategies for maximal health and performance adaptation.
Experimental Approach to the Problem
One repetition maximum loads were measured in the bench
press exercise for both CON and ECC actions. A mechanical
hoist allowed for the load to be passively lowered to the
chest (CON) or raised to the starting position (ECC). One
repetition maximum values were compared between muscle
actions. Loads of 60, 70, 80, and 90% mode-specific 1RM
were then lifted to volitional failure. The number of
repetitions completed at each intensity was compared
between muscle actions. This design allows for comparison
of 1RM data, as well as the mode-specific patterns of fatigue
as expressed in repetitions completed.
Thirty men (age = 24.63 65.6 years, age range 19–40 years;
height = 178.61 66.58 cm; mass = 83.72 611.43 kg) with
a self-report of at least 1 year of resistance training experi-
ence volunteered to participate in this study. Resistance
training experience was defined as having performed the
bench press exercise a minimum average of once per week
during the past year. The specific training goals of the partic-
ipants’ previous programs (i.e., hypertrophy, strength, and
muscular endurance) were not considered, nor were the
typical volume, intensity, rest, or frequency (beyond
the minimum once weekly criteria). Exclusion criteria
included orthopedic injuries and pain in the upper extremities
within the past year, current hypertension (defined as resting
blood pressure higher than 160/90 mm Hg), and cardiovas-
cular risk factors as reported as one or more items selected on
the Physical Activity Readiness Questionnaire. Before partic-
ipation, all subjects read and signed an informed consent
approved by the university Institutional Review Board.
This study consisted of 6 testing sessions per participant over
a 4-week period at approximately the same time of day for
each individual. Study participants were asked to maintain
a consistent routine before each test session in terms of diet,
hydration, and rest. Participants were measured for anthro-
pometric measures of height, and mass. After anthropomet-
ric measures in the initial session, and before lifting in each
subsequent session, participants performed a general warm-
up by pedaling a Monark cycle ergometer (Monark, Varberg,
Sweden) for 5 minutes at 90 rpm. During each session, the
cycle ergometer warm-up was followed by a specific bench
press warm-up consisting of 10, 5, and 3 repetitions at self-
selected, but increasing, loads for a traditional bench press
exercise (characterized as the ECC [lowering] action imme-
diately followed by the CON action [raising]). Repetitions
were completed in succession without rest with 1-minute
rest between sets.
The initial 2 sessions included testing 1RM in either CON
or ECC bench press in random order as determined by flip
of a coin. Participants were allowed to practice each method
of lift with the unloaded barbell to become accustomed to
the timing of the lifts and familiar with the procedures. The
CON bench press was performed with the participant supine
on a bench and pushing the barbell from a resting position
on the chest to complete extension of the elbows. The
weight was passively lowered to the chest before each
repetition through mechanical hoist (2000 lb Minsize
Electric Rope Hoist; Northern Tool and Equipment,
Burnsville, MN) mounted on a 2000-lb capacity gantry
crane (Figure 1). A failed CON repetition was defined as
Concentric vs. Eccentric Bench Press
Journal of Strength and Conditioning Research
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the participant being unable to completely extend the elbows
to complete the movement. The ECC bench press consisted
of lowering a barbell with weight from a fully extended elbow
position to the chest in a continuous, smooth, controlled
manner for 3 seconds as determined by a Korg MA-30 Ultra
Compact digital metronome (Korg, Melville, NY). The barbell
and weight were then returned to the starting position
through the mechanical hoist. A failed ECC repetition was
defined as the participant being unable to control the velocity
of the descent of the bar at any time or allowing the barbell to
touch the chest before the full 3-second count expired. This
protocol is similar to those reported in previous studies (5,16).
Participants were given 2- to 5-minute rest between 1RM
attempts as per National Strength and Conditioning Associa-
tion guidelines (1). Two to six attempts were performed to
determine each participant’s 1RM load. The greatest weight
attained in each lift was used as the 1RM.
The third through sixth sessions included the warm-up
protocols followed by the maximal repetition testing. Each
of the 4 testing days was used to determine the number of
repetitions the participant was able to complete for 1 ECC
and 1 CON percentage (60, 70, 80, and 90%) of each
respective 1RM. The order of exercise and percentage of
1RM was randomized without replacement. Percentage
values of either ECC or CON were written on strips of
paper the participants blindly picked when they arrived for
testing. Participants were aware of the percentage and
amount of weight they were using. Once a specific percent-
age/test combination was performed, it was removed from
the choice selections for the subsequent visits until each
participant completed each percentage for each CON and
ECC tests. All sets were performed to volitional failure,
defined as the first failed repetition in the set. Ten minutes of
rest were given between testing sets at all percentages. The
number of repetitions completed at each percentage of 1RM
was recorded.
To ensure the safety of all participants, trained spotters
were used during all warm-up and testing sets on the bench
press. Additionally, at the commencement of each testing
session, the mechanical hoist was lowered to the appropriate
height, with the barbell lightly touching the participant’s
chest. The cable was marked with a small piece of tape,
indicating where the operator should stop the hoist. This
ensured the cable would prevent the bar from falling onto
the participant in the event of a failed lift. Gym chalk was
available for participants who wished to use it but was not
Statistical Analyses
Data were analyzed using SPSS software (version 19.0; SPSS,
Inc., Chicago, IL, USA). Data were examined for normality
using test statistics for skewness and kurtosis as well as visual
inspection of the data. Data, which were not normally
distributed, were transformed using a natural logarithmic
transformation for analysis and back-transformed for pre-
sentation. Intraclass correlation coefficients were performed
for 1RM, and repetitions to failure. Paired t-tests were used to
determine differences between CON and ECC 1RM. Paired
t-tests were also used to determine differences in number of
repetitions completed at each
1RM percentage (60, 70, 80,
and 90%) between CON and
Concentric 1 Repetition
Maximum vs. Eccentric 1
Repetition Maximum
Intraclass correlation coeffi-
cients for 1RM was 0.964 (p,
0.01). A paired t-test showed
significantly (p#0.05) greater
1RM in ECC (115.99 631.08
kg) when compared with CON
(93.56 626.56 kg) muscle
Figure 1. Bench press and crane setup.
TABLE 1. Concentric (CON) and eccentric (ECC) 1RM descriptives.*
Mean (kg) 6SD Skewness
SE of
skewness Kurtosis
SE of
CON 1RM93.56 626.56 1.27 0.427 1.324 0.833
ECC 1RM115.99 631.08 0.874 0.427 0.141 0.833
lnCON 1RMz5.29 60.26 0.715 0.427 0.01 0.833
lnECC 1RMz5.51 60.26 0.367 0.427 20.434 0.833
*1RM = 1 repetition maximum.
Data before logarithmic transformation.
zData after logarithmic transformation (ln = natural log).
Journal of Strength and Conditioning Research
VOLUME 29 | NUMBER 4 | APRIL 2015 | 1029
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actions. These data indicate ECC strength was approximately
124% of that of CON strength (Table 1).
Repetitions Completed for CON vs. ECC
Intraclass correlation coefficients for repetitions to failure
was significant (p#0.05) but low (0.478). Paired t-tests
revealed significantly (p#0.05) greater number of repeti-
tions completed at 90% 1RM for ECC = 7.67 63.24 when
compared with CON = 4.57 62.21 muscle actions. There
were no significant differences between the number of rep-
etitions completed concentrically and eccentrically at any
other intensity (Figure 2).
This study examined differences between CON and ECC
bench press in terms of 1RM and the number of repetitions
completed at various percentages (60, 70, 80, and 90%) of
mode-specific 1RM. Overall, the findings were (a) ECC
1RM was significantly (p#0.05) greater than CON 1RM,
(b) a significant (p#0.05) difference between the number of
repetitions completed at 90% of mode-specific 1RM, and (c) no
differences between the number of repetitions completed at any
of the other mode-specific 1RM relative intensities.
Based on previous research (2,9,10,15,16), it was hypoth-
esized that ECC 1RM would be approximately 120% of
CON 1RM. These data support this as ECC 1RM was
approximately 124% of CON 1RM, a statistically significant
(p#0.05) difference. Our confirmatory results establish the
present research design (5),
particularly the protocol for
testing ECC repetitions, as
a valid measure of ECC
No known studies compare
the number of repetitions par-
ticipants can complete in the
bench press exercise with an
equated relative load concentri-
cally and eccentrically. Studies
comparing fatigue patterns
between CON and ECC muscle
actions have been performed
using isokinetic dynamometry
(3,17,18,22), but testing the
number of repetitions com-
pleted before volitional failure,
as characterized by the inability
to complete a repetition, is dif-
ficult and has not been previ-
ously done to the best of our
knowledge. However, previous
research has focused on de-
creases in muscular force as
a result of repeated bouts of
CON and ECC exercise as
measured by isokinetic dynamometry, but as previously
stated, not on how many repetitions actually completed.
Tesch et al. (22) showed no force decreases as a result of 3
bouts of 32 maximum voluntary ECC repetitions, as com-
pared with the same number of CON repetitions, which re-
sulted in 34–47% decreases in force. Binder-Macleod and Lee
(3) showed very different patterns of fatigue between CON
and ECC exercise over the course of 180 invoked knee ex-
tensions, with CON resulting in a very sharp decline in force
over the first 40 repetitions and no further force decreases
after the 80th repetition, and ECC showing a linear decrease
from the 15th to the 180th repetition. Muscle actions were
invoked at 20% of maximum voluntary isometric force. Force
outputs were statistically greater in ECC actions than CON
actions for both of these studies.
Taken together, these studies indicate that not only can
the muscle produce more force eccentrically but also it can
maintain force production over a longer period of time under
ECC conditions as compared with CON. What is unclear,
however, is whether this apparent heightened resistance to
fatigue results in a greater number of ECC repetitions that
can be completed in a free weight exercise when compared
with CON repetitions, particularly under the same relative
intensities. A key difference between isokinetic dynamome-
try and free weights revolves around the possibility of a failed
repetition: a participant may exhibit fluctuations of force
throughout a set of isokinetic exercise but will still be able to
complete the prescribed number. Conversely, if there is
Figure 2. Comparison of repetitions to failure (mean 6SD) by percentage 1RM between concentric (CON) and
eccentric (ECC). *Significantly greater than CON. 1RM = 1 repetition maximum.
Concentric vs. Eccentric Bench Press
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a sufficient decrease in force during a set of free weight
exercise, the repetition will be unsuccessful and the set
This study indicates that with an equated load (i.e., equal
percentage of mode-specific 1RM), there is a significant
difference between the number of repetitions that can be
completed concentrically and eccentrically at 90% 1RM.
There were no differences in repetitions to failure at any
other relative intensity of 1RM. This seems to support
existing research, which suggests differences between CON
and ECC actions in terms of fatigue rate. Studies by Enoka
(10), Tesch et al. (22), and Binder-Macleod and Lee (3) all
indicated that muscles acting eccentrically are slower to
fatigue. What is unclear throughout the research, however,
is how this slower fatigue rate, which was observed largely
through isokinetic testing and EMG data translates to actual
repetitions of an exercise an individual is able to perform.
The issue remains unclear as noted by the fatigue curves
displayed in this study indicating similar rates of fatigue
between CON and ECC muscle actions at the tested relative
This is the first known study to directly measure ECC
1RM and test participants at various intensities of that 1RM
using free weights. This allows for a truly equated testing
load, which has not been present in studies that estimated
ECC 1RM (15) or used isokinetic dynamometry (3,22). With
an equated load, differences between CON and ECC perfor-
mance capabilities are minimized. Research is still unclear
regarding an accepted methodology for the duration of ECC
repetitions, with previous studies ranging from 2 seconds
(15) to 4 seconds (23). Such a wide range of time under
tension during a repetition could lead to major differences
in the number of repetitions completed. We felt 3 seconds
(16) was an appropriate duration for ECC repetitions, but
acknowledge further research is required to determine the
optimal amount of time under tension during ECC exercise.
Our data show that under free weight conditions and with
an equated load, there remains a different failure rate
between CON and ECC actions. The fact that there was
a significant difference at 90% 1RM, followed by decreasing
differences at 80, 70, and 60% seems to be similar to the
pattern of fatigue reported by Binder-Macleod and Lee (3).
Because of the nature of ECC muscle actions, particularly
in the bench press exercise, it can be difficult to distinguish
between a successful and an unsuccessful repetition. Because
the weight is lowered toward the chest due to gravity, the
participant must control the descent throughout the range of
motion for a repetition to be deemed successful. Because of
the difficulty determining the success of an ECC repetition,
there are very few known studies (5) examining ECC 1RM
or ECC repetitions to failure using free weights. Hollander
et al. (16) tested ECC 1RM in a number of exercises, includ-
ing bench press, using a similar protocol to ours using
a weight stack. A failed repetition is fairly easy to distinguish
whether the muscle is acting concentrically. In the standard
bench press exercise, if a failure occurs during the CON
phase, the bar will stop ascending and will eventually
descend back toward the chest. Another factor, which com-
plicates ECC testing with free weights, is the necessity of
returning the weight to the starting position without requir-
ing a CON muscle action. This can only be done with 1 or
more spotters or mechanical assistance (16), as was used in
this study. This can prove challenging for researchers.
With these issues considered, the research team set forth
the guidelines for determining a “successful” ECC repetition.
The subject was to lower the bar toward the chest in
a smooth continuous motion over a 3-second duration in
cadence with a digital metronome. The 3-second ECC
phase was selected as an average between previously re-
ported methods, which ranged from 2 seconds (15) to 4
seconds (23). Hollander et al. (16) also tested ECC 1RM
using a 3-second repetition set to a metronome. In our study,
the same tester was responsible for determining the success
of every repetition for every participant to maximize intra-
rater reliability. Thus, the use of a single trained tester and
digital metronome minimized error in determining the suc-
cess of a repetition.
Eccentric muscle actions are a part of daily living and
a large component of many sport and occupational
demands. Because they are often performed sequentially
with less forceful CON actions, ECC muscle actions are
often underloaded and, therefore, undertrained. Training
with an emphasis on ECC actions yields greater strength
and hypertrophic gains than in programs in which ECC
actions are not emphasized. With greater training potential
for strength increases, hypertrophic gains, and the fre-
quency with which ECC muscle actions are required in
daily life and sport, it seems intuitive that a comprehensive
training program includes exercises, which emphasize ECC
muscle actions. More research is required to establish
proper training protocols regarding frequency, intensity,
and rest required for ECC actions due to differences in
force capabilities, fatigue patterns, and potential muscular
damage. Our findings offer further evidence that muscles
acting eccentrically produce greater force than those acting
concentrically. Our data also indicate differences in the
patterns of fatigue between muscle action. Strength and
conditioning professionals should attempt to account for
these potential differences as they design resistance training
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Journal of Strength and Conditioning Research
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... Eccentric (ECC) muscle actions are characterized by different mechanical and surface electromyographic (sEMG) responses and have lower energy requirements compared with concentric (CON) muscle actions (Clarkson and Newham, 1995;Enoka, 1996;Herzog, 2018). Previous research has shown that the force generated in ECC muscle actions is significantly greater than in CON muscle actions under either dynamic or isokinetic conditions (Kelly et al., 2015;Linnamo et al., 2000). Kelly et al. (2015) found that the ECC maximum strength (1-RM) in the bench press exercise was approximately 124% of CON 1-RM in men. ...
... Previous research has shown that the force generated in ECC muscle actions is significantly greater than in CON muscle actions under either dynamic or isokinetic conditions (Kelly et al., 2015;Linnamo et al., 2000). Kelly et al. (2015) found that the ECC maximum strength (1-RM) in the bench press exercise was approximately 124% of CON 1-RM in men. Despite the greater force capabilities of ECC muscle actions, sEMG responses have been shown to be lower (Kellis and Baltzopoulos, 1998;Potvin, 1997;van den Tillaar and Sousa, 2020;Westing et al., 1991) or equal (Linnamo et al., 2000) compared with CON muscle actions. ...
... In the present study, velocity loss was higher in the CON compared with the ECC phase of the movement. One possible explanation may be that the relative load, i.e., the load expressed as a percentage of maximum strength, was lower in the ECC than in the CON phase, since ECC muscle strength is higher than CON strength (Kelly et al., 2015). A previous study compared maximum strength and repetitions to failure during isolated ECC and CON bench presses and found that ECC maximum strength (1-RM) was 124% of CON 1-RM, while the number of repetitions completed at 90% 1-RM was significantly greater under the ECC compared with the CON condition (7.8 vs. 4.4 repetitions) (Kelly et al., 2015). ...
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We examined changes in barbell velocity and surface electromyographic activity (sEMG) during the concentric (CON) and eccentric (ECC) phases of a bench press set. Ten men executed a set to instant exhaustion as fast as possible, against a low (40% 1-RM) and a heavy load (80% 1-RM), one week apart. The reduction in mean barbell velocity was lower in the ECC compared with the CON phase for both loads (40%1-RM: ECC: −36 ± 21% vs. CON: −63 ± 14%, p < 0.001; 80%1-RM: ECC: −26 ± 15% vs. CON: −59 ± 9%, p < 0.001). Under both loading conditions, sEMG activity of the pectoralis major increased in the last compared to the first repetitions only in the CON phase (by 48.6% and 24.8%, p < 0.01, in the 40% and 80%1-RM, respectively). Similarly, triceps brachii sEMG increased by 15.7% (p = 0.02) and by 21.0% (p < 0.001) during the CON phase in the 40% and 80%1-RM conditions, respectively. However, during the ECC phase, sEMG remained unchanged in the last part of the set for both muscles and loads except for 80%1-RM in the pectoralis major muscle. It was concluded that fatigue measured by velocity loss was lower during the ECC than the CON phase of the bench press movement, when the exercise was performed with maximum velocity to failure, irrespective of the load. sEMG was lower in the ECC than the CON phase for all loads, and increased at the end of the set only during the CON phase, while it remained relatively unchanged in the ECC phase, with the exception of the pectoralis muscle when the load was heavier.
... We identified three studies that examined ECC versus CON repetitions-to-failure with equal relative loads. [67][68][69] These studies were of the barbell bench press, 68 dumbbell bicep curl, 69 and isokinetic knee extension. 67 The loads tested ranged from 60 to 95% of the muscle actionspecific 1RM. ...
... 67 The loads tested ranged from 60 to 95% of the muscle actionspecific 1RM. In the study by Kelly et al., 68 30 healthy men completed ECC and CON repetitions-to-failure tests in the bench press with loads equal to 60, 70, 80, and 90% of 1RM. For the 90% 1RM load comparison, participants completed, on average, three more repetitions during ECC (8 repetitions) than CON tests (5 repetitions). ...
... 72,73 However, as the current review highlights, the number of ECC repetitions that can be completed at a given relative load is sometimes higher than the number CON repetitions that can be completed at that same relative load. [67][68][69]74 Thus, further research will be required to determine the %1RM-repetition relationship for ECC resistance exercise in various populations and across various exercises. ...
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Since the 1970s, researchers have studied a potential difference in muscle fatigue (acute strength loss) between maximal eccentric (ECCmax) and concentric (CONmax) resistance exercise. However, a clear answer to whether such a difference exists has not been established. Therefore, the aim of our paper was to overview methods and results of studies that compared acute changes in muscle strength after bouts of ECCmax and CONmax resistance exercise. We identified 30 relevant studies. Participants were typically healthy men aged 20–40 years. Exercise usually consisted of 40–100 isokinetic ECCmax and CONmax repetitions of the knee extensors or elbow flexors. Both ECCmax and CONmax exercise caused significant strength loss, which plateaued and rarely exceeded 60% of baseline, suggesting strength preservation. In upper‐body muscles, strength loss at the end of ECCmax (31.4 ± 20.4%) and CONmax (33.6 ± 17.5%) exercise was similar, whereas in lower‐body muscles, strength loss was less after ECCmax (13.3 ± 12.2%) than CONmax (39.7 ± 13.3%) exercise. Muscle architecture and daily use of lower‐body muscles likely protects lower‐body muscles from strength loss during ECCmax exercise. We also reviewed seven studies on muscle fatigue during coupled ECCmax‐CONmax exercise and found similar strength loss in the ECC and CON phases. We also found evidence from three studies that more ECC than CON repetitions can be completed at equal relative loads. These results indicate that muscle fatigue may manifest differently between ECCmax and CONmax resistance exercise. An implication of the results is that prescriptions of ECC resistance exercise for lower‐body muscles should account for greater fatigue resilience of these muscles compared to upper‐body muscles.
... To the best of our knowledge, only 1 study (11) has examined the relationship between %1RM and RF in an ECC resistance exercise. Kelly et al. (11) compared the RF between CON and ECC bench press exercise at the same relative intensity (60, 70, 80, and 90% of 1RM for CON and ECC bench press exercise, respectively). ...
... To the best of our knowledge, only 1 study (11) has examined the relationship between %1RM and RF in an ECC resistance exercise. Kelly et al. (11) compared the RF between CON and ECC bench press exercise at the same relative intensity (60, 70, 80, and 90% of 1RM for CON and ECC bench press exercise, respectively). They showed a greater RF in the ECC (7.7 6 3.2) than CON exercise (4.6 6 2.2) at 90% 1RM, but no significant difference in the RF between the protocols was evident at 60% (25-30 repetitions), 70% (17-18 repetitions), and 80% 1RM (10-13 repetitions). ...
... To answer the research questions whether the number of RF would be greater in ECC than in CON at the same relative intensity, and whether inter-repetition rest would affect the number of RF, 6 experimental sessions were conducted over 6 weeks with at least 3 days between the sessions. Although a previous study (11) compared the RF in ECC versus CON contractions for bench press, which is a multi-joint exercise, the present study used a dumbbell arm curl exercise as a starting point. It is because an arm curl exercise is less technical than multi-joint exercises, and it was considered to be a good choice for the purpose of the present study to compare the number of RF between ECC and CON conditions. ...
Shibata, K, Yamaguchi, T, Takizawa, K, and Nosaka, K. Comparison in repetitions to failure between concentric-only and eccentric-only dumbbell arm curl exercise at four different relative intensities. J Strength Cond Res XX(X): 000-000, 2022-The repetitions to failure (RF) were compared between concentric-only (CON) and eccentric-only (ECC) arm curl exercise for different intensities based on CON and ECC 1 repetition maximum (1RM), respectively, with 2 different inter-repetition rests. Sixteen healthy male, university students (19-22 years) participated in 6 sessions. In sessions 1 and 2, CON and ECC 1RM strength were determined. In sessions 3 to 6, CON and ECC dumbbell arm curl exercises were performed until momentary failure at the intensity of either 70, 80, 90 or 95% of CON and ECC 1RM, respectively, with the inter-repetition rest of 3 seconds (R3) for one arm and 6 seconds (R6) for the other arm in a pseudo-randomized order. A significant (p < 0.01) muscle contraction type × intensity interaction effect was evident for both R3 and R6 conditions. RF was greater (p < 0.01) in ECC than in CON at 70% (34.2 ± 13.3 vs 20.9 ± 5.4), 80% (22.0 ± 6.7 vs 11.6 ± 2.7), 90% (10.1 ± 3.1 vs 5.2 ± 1.3), and 95% (6.8 ± 2.1 vs 2.7 ± 0.8) for R3. RF was also greater (p < 0.01) for ECC than for CON at 80% (24.5 ± 8.1 vs 15.6 ± 3.6), 90% (10.8 ± 2.8 vs 7.2 ± 1.8) and 95% (6.7 ± 2.4 vs 3.9 ± 1.5) for R6, with greater (p < 0.05) RF for R6 than R3. Significant (p < 0.01) correlations in RF were evident between CON and ECC for R3 (r = 0.86) and R6 (r = 0.76). Equations to estimate 1RM were derived for CON and ECC at R3 and R6 (e.g., ECC 1RM = Load × 110.0/[110.5-RF] for R3). These results suggest that fatigue is less in ECC than in CON performed at the same relative intensity.
... Results from a small number of studies suggest that at equal relative loads, more eccentriconly than concentric-only repetitions can be completed for some exercises and at certain %1RM. 17,37,38 If these results are replicated in future research, a REPS~%1RM table specific to eccentric muscle actions will probably need to be developed, particularly as eccentric resistance exercise is growing in popularity and new technologies are making its prescription more feasible. 11,18,19 Moving forward, more data will be needed to provide more precise point estimates of the number of repetitions that an individual can be expected to ...
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The maximal number of repetitions that can be completed at various percentages of the one repetition maximum (1RM) (REPS~%1RM relationship) is foundational knowledge in resistance exercise programming. The current REPS~%1RM relationship is based on few studies and has not incorporated uncertainty into estimations or accounted for between-individual variation. Therefore, we conducted a meta-regression analysis to estimate the mean and between-individuals standard deviation of number of repetitions that can be completed at various percentages of 1RM. We also explored if the REPS~%1RM relationship is moderated by sex, age, training status, and/or exercise. A total of 952 repetitions-to-failure tests, completed by 7,270 individuals in 450 groups from 266 studies, were identified. Study groups were predominantly male (66%), healthy (97%), <59 years of age (92%), and resistance-trained (60%). The bench press (42%) and leg press (14%) were the most commonly studied exercises. The REPS~%1RM relationship for mean repetitions and standard deviation of repetitions were best described using natural cubic splines and a linear model, respectively, with mean and standard deviation for repetitions decreasing with increasing %1RM. More repetitions were evident in the leg press than bench press across the loading spectrum , thus separate REPS~%1RM tables were developed for these two exercises. Analysis of moderators suggested little influences of sex, age, or training status on the REPS~%1RM relationship, thus the general main model REPS~%1RM table can be applied to all individuals and to all exercises other than the bench press and leg press. More data are needed to develop REPS~%1RM tables for other exercises.
... Only successful repetitions were used for analysis of Ecc1RM. Three seconds during the eccentric muscle action is a time constraint consistently used during eccentric overload repetitions of multi-joint exercises (Kelly et al., 2015;Meneghel et al., 2014;Wirth et al., 2015). ...
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Background of Study: Benefits of training with eccentric overload (EO) include increased concentric strength, eccentric strength, explosiveness, and muscle adaptation. There is a lack of practical strength training protocols that compare traditional methods and EO. Purpose: Compare effects of eccentric overload versus traditional training on strength and performance. Method: Thirty-three trained males (age: 21.4 ± 2.7 years) were divided into three groups: Traditional (TRAD, N =12), EO, (N =11), and Control (CTRL, N =10). Back squat training lasted five weeks. The average intensity (%1RM) for each repetition and the volume was the same between groups. Results: Multiple 3x2 (Group x Time) Analyses of Variance (ANOVAs) were performed on the following: 1RM, eccentric 1RM (Ecc1RM), countermovement jump height (CMJ), and 20-meter sprint times. A significant Group x Time interaction (p =.001) was observed for Ecc1RM. The source was a significant increase in Ecc1RM strength from pre to post-test for the EO group (+16.9 kg) and TRAD group (+12.7 kg). A significant Group x Time interaction (p =.026) was observed for CMJ. The source was a significant increase in CMJ height from pre to post-test for the EO group (+3.8 cm) and TRAD group (+2.9 cm). Conclusions: Using EO and TRAD during a short-term back squat training protocol enhanced vertical jump explosiveness and eccentric strength. Athletes aiming to enhance lower body explosiveness and eccentric strength are likely benefit from EO. Athletes looking to enhance concentric strength should adhere to methods whereby paired concentric-eccentric actions are the primary focus.
... [4][5][6][7] The type of strength training (i.e., eccentric [ecc], concentric [coN], and isometric) is responsible for changes in sensorimotor activation, increasing stability and performance as a result of muscular and neural adaptations. [7][8][9][10][11][12] in general, dynamic exercises are divided into ecc and coN, with numerous studies observing the effectiveness of ecc training on strength, functionality, and performance. [13][14][15][16] eccentric exercise is characterized by the extension of the muscle-tendon complex in conjunction with a contraction of the muscle associated with a greater force production than coN exercise. ...
Background: The purpose of this study was to investigate the effectiveness of different ankle strengthening training programs: eccentric, concentric, and resistance bands, on performance of university level sedentary males. Methods: Sixty-three males between the ages of 18 and 26 years were randomized to either eccentric isokinetic (n=21), concentric isokinetic (n=21), and resistance bands ankle strengthening groups (n=21). Training was performed three days a week, for eight weeks for both sides of ankle. Each program was made progressively harder by increasing the number of repetitions or sets. Measurements evaluating strength, balance and jumping performance were repeated pre, post and at one month (follow-up) after training. Results: Statistical significance was observed for concentric evertor strength for both sides of the ankle for all groups after training (p<0.05). In addition, statistically significant increases were seen in jumping performance for all groups and dynamic balance for eccentric and concentric groups (p<0.05), with the concentric being statistically higher compared to the resistance bands group for all parameters (p<0.05). Conclusions: Ankle isokinetic strength (eccentric, concentric) training is more effective than resistance bands regarding improvement on strength, explosive strength, and dynamic balance. Ankle isokinetic strength training, which includes evertor and invertor muscles, improves performance, especially when applied concentrically. Therefore, the proper strengthening of ankle muscles will prevent the re-injury of ankles with individuals returning to activities.
... Lastly, the seven-parameter function (20) has similar velocity-scaling capabilities to (10); however, its three-parameter activation component is unique [65]. It may be the case that this activation function is better suited for sports simulations as it encompasses the safety mechanisms, intrinsic to skeletal muscle [58], that athletes can encounter while pushing themselves to extreme levels of performance [29]. Further analysis is required to confirm this hypothesis. ...
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Using detailed musculoskeletal models in computer simulations of human movement can provide insights into individual muscle and joint loading; however, these muscle models increase problem dimensionality and require difficult-to-fit parameters. Here, we provide a brief overview of a muscle model alternative, muscle torque generators (MTGs), and highlight how MTG functions have been used by researchers to generate accurate dynamic simulations of optimal sports performance. Multibody dynamic models of a golf drive, track cycling, and wheelchair propulsion were designed and actuated using MTGs. Each MTG was effectively a rotational, single muscle equivalent that contained joint angle/velocity scaling and passive elements to mimic Hill-type muscle model behaviour. Optimal control algorithms were used to predict how each model would execute their respective sports task; these results were compared against experimental data collected from elite athletes. Good agreement between simulated and experimental movement trajectories was observed, with relatively low computational times required for convergence of the MTG-driven multibody simulations.
... Since force development is greater in eccentric contractions compared to concentric Kelly et al., 2015), it is expected that this greater production of force would induce increased activation of the mechanotransduction pathway, which was shown to be extremely important to exercise-derived anabolism. In view of this, the result published by Moore et al. (2012) was predictable. ...
Studies from the 20th century had proposed that exercise-derived anabolism is the result of acute release of anabolic hormones. Recent advances in molecular biology have validated the hormonal theory, but have raised the question of whether exercise-induced anabolic hormones are related to chronic hypertrophy. Intrinsic factors of muscle contraction, on the other hand, seem to play an important role in exercise-induced protein synthesis and hypertrophy. This review seeks to highlight the role of anabolic pathways related to resistance exercise and express its applicability in resistance training considering the following variables: (a) intensity; (b) volume; (c) rest interval; (d) types of contraction; (e) velocity of contraction; (f) exercise order; and (g) frequency. We conclude that resistance training-induced hypertrophy is likely explained by intrinsic factors rather than by the hormonal theory. Regarding the following training recommendations, multiple sets, long rest intervals, dynamic and high-velocity contractions and prioritizing the exercise order are most likely to produce the greatest enhancement in skeletal muscle hypertrophy. Training intensity may vary, as low (30% one-repetition maximum [1RM]) or high (80% 1RM) intensities induce similar improvements in hypertrophy when performed to a maximal level of effort. Likewise, training frequency may vary according to individual needs, as the total volume performed within a training week appears to be more strongly related to hypertrophy than the number of weekly training sessions. This review contributes to the development of sports performance, aesthetics, and quality of life, and to the prevention or treatment of muscle loss caused by aging or illness.
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The purpose of this Position Stand is to provide guidance to professionals who counsel and prescribe individualized exercise to apparently healthy adults of all ages. These recommendations also may apply to adults with certain chronic diseases or disabilities, when appropriately evaluated and advised by a health professional. This document supersedes the 1998 American College of Sports Medicine (ACSM) Position Stand, "The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory and Muscular Fitness, and Flexibility in Healthy Adults." The scientific evidence demonstrating the beneficial effects of exercise is indisputable, and the benefits of exercise far outweigh the risks in most adults. A program of regular exercise that includes cardiorespiratory, resistance, flexibility, and neuromotor exercise training beyond activities of daily living to improve and maintain physical fitness and health is essential for most adults. The ACSM recommends that most adults engage in moderate-intensity cardiorespiratory exercise training for ≥30 min·d on ≥5 d·wk for a total of ≥150 min·wk, vigorous-intensity cardiorespiratory exercise training for ≥20 min·d on ≥3 d·wk (≥75 min·wk), or a combination of moderate- and vigorous-intensity exercise to achieve a total energy expenditure of ≥500-1000 MET·min·wk. On 2-3 d·wk, adults should also perform resistance exercises for each of the major muscle groups, and neuromotor exercise involving balance, agility, and coordination. Crucial to maintaining joint range of movement, completing a series of flexibility exercises for each the major muscle-tendon groups (a total of 60 s per exercise) on ≥2 d·wk is recommended. The exercise program should be modified according to an individual's habitual physical activity, physical function, health status, exercise responses, and stated goals. Adults who are unable or unwilling to meet the exercise targets outlined here still can benefit from engaging in amounts of exercise less than recommended. In addition to exercising regularly, there are health benefits in concurrently reducing total time engaged in sedentary pursuits and also by interspersing frequent, short bouts of standing and physical activity between periods of sedentary activity, even in physically active adults. Behaviorally based exercise interventions, the use of behavior change strategies, supervision by an experienced fitness instructor, and exercise that is pleasant and enjoyable can improve adoption and adherence to prescribed exercise programs. Educating adults about and screening for signs and symptoms of CHD and gradual progression of exercise intensity and volume may reduce the risks of exercise. Consultations with a medical professional and diagnostic exercise testing for CHD are useful when clinically indicated but are not recommended for universal screening to enhance the safety of exercise.
The purpose of this study was to examine the strength benefits of an eccentric-only protocol versus a standard and concentric-only protocol in a multi-joint lift (bench press). Additionally, a secondary purpose was to examine the same protocol's ability to elicit power benefits (seated medicine ball put). Forty-Two men (mean±SD, age 24.9 ± 5.1 yr., height 71.0 ± 3.0 in, weight 189.2 ±31.1 lbs) with recreational resistance training experience (>6 months at least two times per week) performed two sessions a week for 6 weeks utilizing the bench press exercise. Subjects were tested for concentric, standard and eccentric 1-RM pre and post study. Subjects were randomized into one of three groups, eccentric-only (ECC), standard (ECCON) or concentric-only (CON). Subjects performed 4 sets of 4-8 repetitions with 80% of their 1-RM in the repetition type characterized by their group. Subjects moved up 5% when 4 sets of 8 repetitions were completed successfully. Rest time between sets was fixed at 3-5 minutes. Subjects were also tested for power using a 3-kg seated medicine ball put for distance pre and post study and for body composition using air density plethysmography (Life Measurement Inc., Bod Pod, Concord, CA). All statistics were analyzed using SPSS for Windows 15.0 (Chicago, Ill.). Paired sample t-tests were used to test differences pre to post study. One-Way analysis of variance (ANOVA) was used to analyze percentage differences between groups. Tukey HSD test was used as a post hoc when necessary. The level of significance for statistical analysis was set at p ≤ .05. All three groups significantly increased their strength from pre to post study (p
Inflammation response in exercise of healthy humans is significantly different than that which is commonly reported for chronic inflammatory conditions. Regardless of the scenario, cytokines such as Tumor Necrosis Factor (TNF)-α and Interleukin (IL)-1b have demonstrated pro-inflammatory functions, while IL-6 has demonstrated versatile pro- and anti-inflammatory roles when exercise is a factor. Prolonged skeletal muscle contractions of sufficient intensity have been shown to induce significant muscle protein damage and a complex inflammatory cascade involving IL-6 and, separately, Heat Shock Proteins (HSP), and components of the Mitogen-Activated Protein Kinase (MAPK) pathway. This cascade not completely understood in any scenario, particularly in humans. Thus the role of inflammation in regards to exercise, particularly resistance training, has not been elucidated. To determine the effects of concentric (CON) and eccentric (ECC) contractions on creatine kinase (CK), lactate dehydrogenase (LDH), and IL-6 signaling in regards to IL-1b, TNF-α, HSP-72, Nuclear Factor-kappa B (NF-?B), p38 MAPK, Signal Transducer and Activator of Transcription (STAT)-1 and STAT-3 and the potential cytoprotection HSP-27. Six active males (19.33 ± 1.03 yrs; 181.94 ± 6.40 cm; 72.83 ± 12.78 kg) participated in two separate bouts of 10 × 10 unilateral isokinetic knee extensions at 30°/sec. Each bout consisted of either CON or ECC contractions on either the right or left leg; each contraction type and leg was utilized once for each subject. Isokinetic strength tests were performed five days pre- and 24 and 48 hours post-exercise. Serum CK, LDH, IL-6, IL-1b, and TNF-α were assessed immediately preexercise (PRE), immediately post-exercise (PX), and at 2, 6, 24, and 48 hr PX. IL-6, HSP-27, and HSP-72, NF-?B, p38 MAPK, STAT-1 and STAT-3 protein and mRNA expression of IL-6, HSP-27, and HSP-72 were assessed from vastus lateralis biopsies (Bergstrom ) collected at PRE, PX, and 2 and 6 hr PX. Repeated measures MANOVAs and subsequent univariate analyses were performed on all data. Peak torque decreased (p < 0.05) at 24 and 48 hr PX. CK, but not LDH, increased (p < 0.05) similarly following CON and ECC. Serum cytokines were different (p < 0.05) between CON and ECC, but did not change over time. In muscle, NF-?B (p < 0.05) increased and STAT-1 decreased (p < 0.05). ECC contractions demonstrated significantly greater expression for IL-6, p38 MAPK, and STAT-3 than did CON, with a trend (p = 0.093) for STAT-1. There was significant CON/ECC interaction among NF-?B and STAT-1 and a trend (p = 0.074) for HSP-72. Skeletal muscle mRNA expression demonstrated no significant results. Both CON and ECC bouts demonstrated muscle damage and fatigue, but were not sufficient to induce a systemic inflammatory response. Intramuscular inflammatory response was most robust for NF-?B and STAT-1. The hypothesis of ECC stimulating the IL-6 pathway more so than CON is supported the relationship in expression of IL-6, p38 MAPK, STAT-1 and STAT-3. This is novel evidence of a relationship among these factors. Bouts of resistance exercise that include ECC contractions can favorably affect the exercise inflammation response; perhaps more so than lower intensity CON-only contractions.
This study examined the relationship between 1-RM bench press performance and the 225-lb bench press reps-to-fatigue test. Using NCAA Div. II football players at a north central university (N = 98), this study found that the 225-lb bench press reps-to-fatigue test is a valid estimate of 1-RM performance in trained college football players (r = 0.96, p < 0.001) with a standard error of +/-10.8 lbs (4.9 kg). The estimation of 1-RM bench press performance was improved when repetitions were 10 or less (R2 = 0.85 vs. 0.76). Thus this study supported the validity of the 225-lb bench press reps-to-fatigue test as a submaximal estimate of 1-RM bench press performance in college football players who are familiar with the exercise and sufficiently conditioned to perform reps with 225 lbs. (C) 1998 National Strength and Conditioning Association
The purpose of this study was to determine whether superior concentric performance could be achieved in the bench throw with the use of additional eccentric loads. Fourteen male subjects performed bench throws in a smith machine with an eccentric-concentric load of 40-kg (40-40), and 40-kg concentric with additional eccentric loads of 20 (60-40), 30 (70-40), and 40 kg (80-40). A linear position transducer was used to record displacement-time characteristics, allowing for determination of maximum displacement of the barbell. Differences between the conditions were accepted when p < 0.05. Barbell displacements in the 60- to 40-, 70- to 40-, and 80- to 40-kg eccentric-concentric conditions were all significantly greater than for the 40- to 40-kg eccentric-concentric equated load condition, but no significant difference was observed between each eccentric-concentric load condition. Superior concentric peak barbell displacement can be achieved with additional eccentric loads in the 40-kg bench throw when compared to an equated eccentric-concentric 40- to 40-kg condition, possibly because of greater muscle tension and crossbridging during the eccentric action. Strength and conditioning coaches can use accentuated eccentric load bench throws to elicit greater concentric bench throw performance in athletes.
1. A study has been made of the tension responses and sarcomere length changes produced by servo-controlled stretches applied to isometrically contracting frog muscle. Sarcomere lengths were monitored by cine-photography of diffiraction spectra obtained by illuminating a small area of muscle with a laser. 2. The tension increment produced by a ramp-and-hold stretch of approximately 1 mm (ca. 4% of the muscle length) comprises three phases whose limits are defined by two points, S1 and S2, where the slope of the response decreases abruptly. S1 and S2 correspond to extensions of 0.13 and 1.2% of the muscle length. 3. Movements of the first order spectra relative to the zero order recorded during stretch reveal that S2 coincides with an abrupt elongation of the sarcomeres. This is termed sarcomere 'give' and it occurs when the filaments are displaced by 11-12 nm from their steady-state (isometric) position. 4. The stiffness of the sarcomeres, Es, up to S2 decreases with increasing sarcomere length. The maximum force sustained by the muscle at S2, PS2, also shows an inverse dependence on sarcomere length. Both Es and PS2 fall to zero at an extrapolated sarcomere spacing of 3.6-3.7 micrometer, coinciding with the length at which the actin and myosin filaments no longer overlap. 5. The ratio PS2/P0 (where P0 = maximum isometric tension) varies with temperature and speed of stretch. It increases with increasing speeds of stretch until a certain critical velocity, Vc, is reached, beyond which it is almost independent of any further increase. Vc has a positive temperature coefficient, increasing 5-6 in the range 0-30 degrees C (Q10 = 1.8). There is a positive correlation between the maximum speed of isotonic shortening (Vmax.) and Vc in different muscles. 6. Sarcomere 'give' during stretch is considered to be due to forcible detachment of cross-bridges between the actin and myosin filaments. This results in recoil of the extended series elastic elements in the muscle at the expense of the sarcomers. The amount of filament displacement required to induce sarcomere 'give' (11-12 nm) is thought to represent the range of movement over which a cross-bridge can remain attached to actin during a stretch.
Three different training regimens were performed to study the influence of eccentric muscle actions on skeletal muscle adaptive responses to heavy resistance exercise. Middle-aged males performed the leg press and leg extension exercises two days each week. The resistance was selected to induce failure within six to twelve repetitions of each set. Group CON/ECC (n = 8) performed coupled concentric and eccentric actions while group CON (n = 8) used concentric actions only. They did four or five sets of each exercise. Group CON/CON (n = 10) performed twice as many sets with only concentric actions. Eight subjects did not train and served as controls. Tissue samples were obtained from m. vastus lateralis using the biopsy technique before and after 19 weeks of training, and after four weeks of detraining. Histochemical analyses were performed to assess fibre type composition, fibre area and capillarization. Training increased (P less than 0.05) Type IIA and decreased (P less than 0.05) Type IIB fibre percentage. Only group CON/ECC increased Type I area (14%, P less than 0.05). Type II area increased (P less than 0.05) 32 and 27%, respectively, in groups CON/ECC and CON/CON, but not in group CON. Mean fibre area increased (P less than 0.05) 25 and 20% in groups CON/ECC and CON/CON, respectively. Capillaries per fibre increased (P less than 0.05) equally for Type I and Type II fibres. Capillaries per fibre area for both fibre types, however, increased (P less than 0.05) only in groups CON and CON/CON. The changes in fibre type composition and capillary frequency were manifest after detraining.(ABSTRACT TRUNCATED AT 250 WORDS)
Healthy males (n = 14) performed three bouts of 32 unilateral, maximal voluntary concentric (CON) or eccentric (ECC) quadriceps muscle actions on separate days. Surface electromyography (EMG) of the m. vastus lateralis (VL) and m. rectus femoris (RF) and torque were measured. Integrated EMG (IEMG), mean (MPF) and median power frequencies and torque were averaged for seven separate blocks of four consecutive muscle actions. Torque was greater (P less than 0.05) for ECC than for CON muscle actions at the start of exercise. It did not decline throughout ECC exercise, but decreased (P less than 0.05) markedly for each bout and over bouts of CON exercise. Thus, torque overall was substantially greater (P less than 0.05) for ECC than for CON exercise. At the start of exercise IEMG of VL or RF was greater (P less than 0.05) for CON than for ECC muscle actions. This was also true for overall IEMG activity during exercise. The IEMG increased (P less than 0.05) modestly for both muscles during each bout of CON or ECC muscle actions, but did not change for the VL over bouts. The IEMG of RF decreased (P less than 0.05) modestly over CON but not ECC exercise bouts. At the beginning of the first bout of exercise the IEMG/torque ratio was twofold greater (P less than 0.05) for CON than ECC muscle actions. The ratio of IEMG/torque increased (P less than 0.05) markedly during CON but did not change during ECC exercise. Thus, by the end of the third bout there was a fivefold difference (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
This study examined the catchlike property of skeletal muscle during eccentric and concentric isovelocity contractions of fresh and fatigued quadriceps femoris muscles of 10 healthy subjects. During concentric contractions of fresh muscles, stimulation trains that elicited a catchlike response (CITs) produced greater force outputs and rates of rise force than comparable constant-frequency trains. These enhancements became more pronounced during fatigue. CITs were less effective in enhancing forces during eccentric contractions but did improve the rates of rise of force. Overall, the CIT that produced the greatest augmentation had a 5-ms initial interpulse interval. Proposed mechanisms for the catchlike property involve enhanced muscle stiffness for more efficient transmission of tension and increased calcium release. These results suggest that stimulation trains that take advantage of the catchlike property of skeletal muscle may be helpful during clinical applications where neuromuscular electrical stimulation is used to restore function in patients with damaged central nervous systems.