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How much stronger are muscles
eccentrically than concentrically? Meta-
analysis of the influences of sex, age,
joint action, and velocity
Received: 13th Sept. 2022
Supplementary materials:
https://osf.io/8vt9h/
*For correspondence:
j.nuzzo@ecu.edu.au
Twitter: @JamesLNuzzo
James L. Nuzzo,1 Matheus D. Pinto,1 Kazunori Nosaka,1 James Steele,2
1 Centre for Human Performance, School of Medical and Health Sciences, Edith Cowan University, Joondalup,
Australia
2 Faculty of Sport, Health, and Social Sciences, Solent University, Southampton, United Kingdom
ABSTRACT
For decades, researchers have observed that eccentric (ECC) muscle strength is greater than concentric
(CON) strength. However, knowledge of the ECC:CON strength ratio is incomplete and might inform ECC
exercise prescriptions. Our purposes were to determine the magnitude of the ECC:CON ratio and explore
if sex, age, joint actions/exercises, and movement velocity impact it. A total of 1,393 ECC:CON ratios, ag-
gregated from 11,477 individuals who made up 502 groups in 290 studies, were examined. Approximately
98% of measurements occurred on isokinetic machines. Bayesian meta-analyses were performed using
log-ratios as response variables then exponentiated back to raw ratios. The overall main model estimate
for the ECC:CON ratio was 1.41 [95% credible interval (CI): 1.38–1.44]. The ECC:CON ratio was slightly less
in men (1.39 [CI: 1.35–1.42]) than women (1.46 [CI: 1.42–1.51]), but greater in older (1.65 [CI: 1.59–1.72])
than younger adults (1.38 [CI: 1.36–1.41]). The ratio was similar between grouped upper-body (1.43 [CI:
1.40–1.47]) and lower-body joint actions/exercises (1.40 [CI: 1.37–1.43]). However, heterogeneity in the
ratio existed across joint actions/exercises, with point estimates ranging from 1.32 to 2.75. The ECC:CON
ratio was mostly greatly impacted by movement velocity, with a 0.21% increase in the ratio for every 1°/s
increase in velocity. The results show ECC strength is ~40% greater than CON strength. However, the
ECC:CON ratio is greatly affected by movement velocity and to a lesser extent by age. Differences between
joint actions/exercises likely exist but more data are needed to provide more precise estimates.
Please cite as: Nuzzo, J.L., Pinto, M.D., Nosaka, K., & Steele, J., (2022). How much stronger are muscles
eccentrically than concentrically? Meta-analysis of the influences of sex, age, joint action, and velocity. DOI:
https://doi.org/10.51224/SRXIV.197
DOI:
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1.0 Introduction
A repetition of a resistance exercise usually involves both an active muscle
shortening phase (concentric; CON) and active muscle lengthening phase (eccentric;
ECC). For several decades, researchers have reported that volitional muscle forces
are greater during the ECC than CON phase of exercise repetitions [1-3]. However,
the magnitude of this difference, which is often reported as the ECC:CON strength
ratio, is not entirely clear, and it might be impacted by factors such as sex [4-7], age
[7], injury [8, 9], muscle group [5, 6], and movement velocity [4, 5]. In one study, Col-
liander and Tesch [4] submitted 27 healthy men and 13 healthy women to maximal
strength testing on an isokinetic dynamometer and found that the ECC:CON strength
ratio was greater in women than men (1.74 vs 1.40), the quadriceps than hamstrings
(1.35 vs 1.10), and at faster than slower movement velocity (2.01 vs 1.35). Hollander
et al. [6] reported somewhat similar results when measuring ECC:CON strength ratios
with the one repetition maximum (1RM). In their study, the ECC:CON strength ratio
for the leg curl was 1.83 for women and 1.30 in men [6]. Moreover, across the six
exercises they assessed, the ECC:CON strength ratio ranged from 1.57 to 2.87 in
women and 1.30 to 1.51 in men [6].
Though differences between ECC and CON muscle strength have been ob-
served in human appendicular muscles since at least the 1960s [1-3], a review of the
ECC:CON strength ratio, and the factors that impact it, appears lacking. Knowledge
of this ratio might have implications for the way resistance exercise is prescribed. In
recent years, researchers and practitioners have expressed great interest in accen-
tuated ECC and ECC-only resistance exercise. A number of reviews on ECC resistance
exercise have been published in sports science journals [10-18], and 75-95% of
strength and conditioning coaches now say they prescribe ECC resistance exercise
[19-21]. Moreover, new resistance exercise technologies, such as connected adaptive
resistance exercise (CARE) machines [22], have potential to deliver accentuated ECC
loads in a more feasible way than free weights, plate-loaded machines, and weight
stack machines – the equipment most commonly used by coaches to deliver ECC
overload [20, 23, 24]. Nevertheless, there is no consensus on the magnitude of ECC
overload that should be prescribed and whether factors such as the exercise per-
formed should impact the magnitude of overload.
Practitioners and researchers appear to prescribe a wide range of relative
loads for accentuated ECC and ECC-only resistance exercise. According to one survey,
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coaches prescribe ECC overload ranging from 100 to 150% of the CON 1RM [20]. Ac-
cording to our brief review (Table 1), researchers prescribe ECC loads that range from
105% to 190% of the CON 1RM or CON training load. Thus, knowledge of the magni-
tude of the ECC:CON strength ratio, and the factors that impact it, could help to in-
form and optimize delivery of ECC overload for specific exercises and populations,
particularly as exercise technology continues to evolve to make accentuated ECC ex-
ercise safer and more feasible. Therefore, the purpose of this review was to deter-
mine how much stronger muscles are during ECC than CON muscle actions. Specifi-
cally, we examined the extent to which sex, age, joint actions/exercises, and move-
ment velocity impact the ECC:CON strength ratio. These moderators were tested to
provide more specific guidance to exercise practitioners on factors that warrant con-
sideration for ECC overload prescriptions.
Table 1. Magnitude of eccentric (ECC) overload in acute exercise studies and longer-
term training studies.
Study
Sex
Age
(y)
Exercise
ECC overload
Acute exercise studies
Doan et al. [46]
M
< 60
Bench press
1.05 CON 1RM
Ojasta and Hakkinen [47]
M
< 60
Bench press
1.05–1.2x CON 1RM
Sheppard et al. [48]
M
< 60
Bench press
1.2x CON 1RM
Montalvo et al. [49]
M
< 60
Bench press
1.05x–1.2x CON 1RM
Sarto et al. [50]
M
< 60
Leg press
1.5x CON 1RM
Wagle et al. [51]
M
< 60
Squat
1.05x CON 1RM
Wagle et al. [52]
M
< 60
Squat
1.05x CON 1RM
Training studies
Coratella et al. [53]
M
< 60
Knee extension
1.2x CON 1RM
Godard et al. [54]
MF
< 60
Knee extension
1.4x CON training load
Walker et al. [55]
M
< 60
Knee extension
1.4x CON training load
Hortobgyi et al. [56]
F
≥ 60
Knee extension
1.5x CON training load
Friedmann-Bette et al. [57]
M
< 60
Knee extension
1.9x CON training load
Brandenburg and Docherty
[58]
M
< 60
Elbow flexion, extension
1.1x–1.2x CON 1RM
English et al. [59]
M
< 60
Leg press, calf raise
1.38x CON 1RM
Tøien et al. [60]
M
< 60
Leg press
1.5x CON 1RM
Franchi et al. [61]
M
< 60
Leg press
80% of ECC 1RM
Seliger et al. [62]
M
< 60
Squat
1.4x–1.5x CON 1RM
Schroeder et al. [63]
F
< 60
Various upper- and
lower-body exercises
1.25x CON 1RM
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2.0 Methods
2.1 Literature search
To determine the extent to which ECC and CON muscle strength differ, we first
searched for relevant literature. The search was thorough, but not necessarily sys-
tematic or exhaustive, and instead was a ‘snowballing’ approach [25]. Relevant key-
word searches were performed in PubMed and Google Scholar (e.g., “isokinetic” AND
“eccentric” AND “concentric”; “eccentric 1RM”; “isokinetic force-velocity”). The authors’
digital files were also searched, and reference lists of eligible articles were screened
to identify additional papers. The searches were performed between May and July
2022 but were otherwise not limited by publication date.
2.2 Eligibility
A paper was eligible for inclusion into the review if the following conditions
were met: (a) data were collected in human subjects; (b) data were acquired during
volitional strength tests; (c) subjects were apparently healthy; (d) the mean age of
subjects was ≥18 years; (d) means of ECC and CON strength, or the ECC:CON ratio,
were reported; and (e) strength data were reported in absolute units rather than
body mass-normalized units. Both cross-sectional and exercise training studies were
eligible for inclusion into the review.
2.3 Data extraction
The data extracted from papers included sample size, number of study
groups, study type (non-training or training study), sex, age group, joint actions/ex-
ercises, movement velocity, and means and standard deviations (SD) of the ECC:CON
strength ratios or the ECC and CON strength values. For age categorization, if the
mean age of a study group was 18-59 years then the group was classified as “younger
adults.” If the mean age was ≥60 years then the group was classified as “older adults.”
Younger adult groups were sometimes comprised of competitive athletes.
In instances of unilateral strength assessments where data were available
from both the right and left limbs, the data extracted from the paper were from the
right limb. In instances of unilateral assessments where data were available from
both the dominant and non-dominant limbs, the data extracted were from the dom-
inant limb. For isokinetic strength tests, peak torques were always extracted instead
of average torques. However, if a study reported only average torques, then average
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torques were extracted. With training studies, baseline strength scores were ex-
tracted for each group. Finally, for papers, in which data were presented in figures,
muscle strength values were estimated using a graph digitzer (WebPlotDigitizer,
https://automeris.io).
2.4 Statistical analyses
All analysis code utilized is presented in the supplementary materials
(https://osf.io/8vt9h/). Given the aim of this research, we opted to take an estimation-
based approach [26], based within a Bayesian framework [27]. For all analyses, effect
estimates and their precision, along with conclusions based upon them, were
interpreted continuously and probabilistically, considering data quality, plausibility
of effect, and previous literature, all within the context of each outcome [28]. The
main exploratory meta-analysis was performed using the ‘brms’ package [29] with
posterior draws for visualization taken using ‘tidybayes’ [30] and ‘emmeans’ [31], and
effect sizes calculated using the ‘metafor’ package [32] in R (v 4.1.2; R Core Team,
https://www.r-project.org/) and RStudio (v 2022.02.03+492, RStudio Team,
https://www.rstudio.com/). All data visualizations were made using ‘ggplot2’ [33] and
‘patchwork’ [34]. Tables were produced using ‘formattable’ [35].
We were interested in estimating the ECC:CON strength ratio, thus the log ratio
was used as our effect size measure for modelling purposes. Where both mean and
variance information were available for both ECC and CON strength in the original
study, we calculated this for correlated study designs as per Lajeunesse [36]. When
only the mean of the ratio and its variance were reported in the original study, we
used the log transformed mean [37].
As the included studies often had multiple groups/conditions, and reported
multiple strength measures within these, the data had a nested structure. Therefore,
multilevel mixed-effects meta-analyses were performed with both inter-study and
intra-study groups included as nested random intercepts in the model. Effects were
weighted by inverse sampling variance to account for the within- and between-study
variance. A main model included all ratios reported for all groups in each study. We
conducted meta-regression and sub-group analyses of moderators (i.e., predictors
of effects). Moderators examined included subject sex (male vs females), age
(younger adults vs older adults), upper- vs lower-body joint actions/exercises, and
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velocity of movement
1
. The upper-body group consisted of the shoulder, elbow, and
wrist. The lower-body group consisted of the hip, knee, and ankle, with the trunk
excluded. Additional exploratory models of specific joint actions/exercises
2
were also
performed.
For all models, we used uninformed priors (due to the number of effects we
anticipated that the likelihood would overwhelm posterior estimates) and 23
3
Monte
Carlo Markov Chains with 2000 warmup and 6000 sampling iterations. All models
had 𝑅
value of 1.00 and trace plots were produced to visually examine chain
convergence along with posterior predictive checks, which are included in the
supplementary materials (https://osf.io/8vt9h/; see folder “Trace plots and posterior
predictive checks”). Draws were taken from the posterior distributions to calculate
the mean and 95% quantile interval (referred to as the ‘credible’ interval; CI) for each
parameter estimate. These gave us the most probable value of the parameter, in
addition to the range from the 2.5% to the 97.5% percentiles. We also constructed
95% prediction intervals for the main model. Log ratios were transformed back to
the raw ratio scale for reporting in all instances.
3.0 Results
A total of 290 studies were identified (see https://osf.io/b84ng/ for list of stud-
ies). Nevertheless, not all reported data were included in the meta-analyses. As such,
the summary table of model estimates notes the number of effects, studies, and
groups within studies for each estimate (Table 2). The earliest study was published
in 1965 and the latest in 2022. The studies included 11,477 participants from 502
separate study groups with a median sample size of 15 (range = 2 to 734). Some
studies did not report sex or age. However, 15% of studies included both male and
female subjects, 59% included only males, and 23% included only females. A total of
89% included only younger adults, 9% included only older adults, and 0.3% included
1
Note, for velocity of movement we limited this to studies reporting this in degrees (°) / s as this constituted the majority of
observed effects.
2
Note, this exploratory model included velocity and age (grand mean centred) as a fixed effect to adjust for the fact that
some joints only had low numbers of effects at specific velocities or were from studies in one age group, and we anticipated
that both velocity and age would impact the ECC:CON ratio. Also, bench press, military press, and lat pulldown were excluded
as only one study had measured these exercises.
3
C -1 where C was the number of cores available on the computer used to run the analysis (build available here:
https://uk.pcpartpicker.com/list/C6VXRT).
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both younger and older adults. The proportion of studies that involved exercise train-
ing interventions was 18.7%. The vast majority of studies (98%) measured ECC and
CON strength using isokinetic dynamometry. The velocities used in these isokinetic
assessments ranged from 2º/s to 360º/s.
Table 2. Summary of eccentric:concentric (ECC:CON) strength ratios from all meta-
analysis models.
Model
Esti-
mate
Lower CI
Upper CI
No. Effects
No. Studies
No. Groups
Overall Pooled
1.40
1.38
1.43
1276
270
469
Sex
1036
197
366
Female
1.46
1.42
1.51
Male
1.39
1.35
1.42
Age (y)
1260
267
464
< 60
1.38
1.36
1.41
≥ 60
1.65
1.59
1.72
Joint action /
exercise
1241
259
452
Lower-body
1.40
1.37
1.43
Upper-body
1.43
1.40
1.47
Velocity (°/s)
1213
244
434
30
1.26
1.23
1.29
60
1.34
1.31
1.37
90
1.43
1.40
1.46
120
1.53
1.49
1.56
150
1.62
1.59
1.66
180
1.73
1.69
1.77
210
1.85
1.81
1.89
240
1.97
1.92
2.01
270
2.10
2.05
2.15
300
2.24
2.19
2.29
330
2.39
2.33
2.44
360
2.55
2.48
2.61
CI = Credible Interval
3.1 Main model
The overall estimate from the main model revealed an ECC:CON ratio of 1.40
with CIs suggesting that the parameter value lay between 1.38 to 1.43 with 95% prob-
ability. Prediction intervals were wide suggesting between-effect heterogeneity, with
most of this variance being accounted for at the study level (see https://osf.io/ag83u).
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1 displays the model mean and interval estimates for each study in addition to the
overall estimates and prediction interval.
Figure 1. Means and 95% credible intervals of all eccentric:concentric (ECC:CON) strength ratios included in the
meta-analysis (n = 1,393).
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3.2 Moderators
Estimates of ECC:CON strength ratios by sex, age group, upper- vs lower-body
joint actions/exercises, and velocity are presented in Table 2. The ECC:CON ratio was
lower in men compared to women, but only slightly (men = 1.39 [95% CI: 1.35 to 1.42];
women = 1.46 [95% CI: 1.42 to 1.51]). However, the ratio was greater in older adults
(1.65 [95% CI: 1.59 to 1.72]) compared to younger adults (1.38 [95% CI: 1.36 to 1.41]).
Whilst in general there was little difference in the ECC:CON strength ratio between
upper-body (1.43 [95% CI: 1.40 to 1.47]) and lower-body joint actions/exercises (1.40
[95% CI: 1.37 to 1.43]), there did appear to be some heterogeneity between joint ac-
tions/exercises effects on ECC:CON from our exploratory model
4
(Figure 2). However,
estimates were imprecise for some joint actions/exercises (e.g., squat, trunk lateral
flexion, hip internal and external rotators, and both wrist flexors and extensors).
There was a clear log-linear relationship with velocity of movement where ECC:CON
increased by 0.21% for every 1º/s increase in velocity (Figure 3).
4
The number of effects in the exploratory joint action/exercise model was 1182 across 423 groups from 246 studies.
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Figure 2. Eccentric:concentric (ECC:CON) strength ratios by joint action/exercise. Mean and 95% credible intervals
are shown as the black circle and connected horizonal lines, respectively, with individual effects displayed as
vertical dashes below each estimate as a rugplot.
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Figure 3. Eccentric:concentric (ECC:CON) strength ratios by test velocity. Mean and 95% credible intervals are
shown as the black line and grey shaded area, respectively, with individual effects as circles with the sizes of the
circles scaled to weighting in the model.
4.0 Discussion
The purpose of this meta-analysis was to determine the magnitude of the
ECC:CON strength ratio and explore if sex, age, joint actions/exercises, and move-
ment velocity impact it. We found consistent evidence that ECC strength is greater
than CON strength. Across 290 studies, the main model estimate for the ECC:CON
strength ratio was 1.40. Thus, ECC muscle strength is generally ~40% greater than
CON muscle strength. However, the ECC:CON strength ratio is impacted by move-
ment velocity and age and to a lesser extent sex. No difference in the ECC:CON
strength ratio was observed between upper-body and lower-body joint actions/exer-
cises generally speaking, but exploratory analysis suggested heterogeneity in the
ECC:CON strength ratio across specific joint actions/exercises.
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4.1 Sex
The ECC:CON strength ratio was slightly greater in women (1.46) than men
(1.39). The reason for this slight sex difference appears to be that the magnitude of
the sex difference in muscle strength is greater in CON than ECC muscle actions [38].
One explanation for this result might be that men participate in muscle-strengthen-
ing activities more regularly than women [38]. Such activities typically involve lifting
a constant load, and this load will represent a greater percent of the CON than ECC
1RM. This might then provide disproportionately greater potential for increasing
CON than ECC muscle strength considering specificity in strength gains. A potential
practical implication of this finding is that if an exercise professional chooses to pre-
scribe ECC overload as percent of the CON 1RM, then the multiplication factor for
this computation might need to be slightly higher for women than men.
4.2 Age
The ECC:CON strength ratio was greater in older adults (1.65) than younger
adults (1.38). The likely reason for this result is that ECC strength is better preserved
with aging than CON strength [7, 39, 40]. Also, as aging research usually involves ex-
amination of CON rather than ECC strength, this helps to explain why men exhibit
relatively greater reductions in strength (i.e., CON strength) in both cross-sectional
and longitudinal aging research [41, 42]. In one longitudinal study of older adults,
reductions in CON strength of muscles about the elbow were 2% per decade in
women but 12% per decade in men [41]. A potential practical implication of this find-
ing is that if an exercise professional chooses to prescribe ECC overload as percent
of the CON 1RM, then the multiplication factor for this computation might need to
be higher for older adults than younger adults.
4.3 Joint action/exercise
In the current analysis, muscle strength measurements acquired from joint
actions/exercises about the wrist, elbow, and shoulder were combined into one up-
per-body ECC:CON strength ratio. Similarly, strength measures acquired from joint
actions/exercises about the ankle, knee, and hip were combined into one lower-body
ECC:CON strength ratio. The ECC:CON strength ratio was generally similar between
the upper-body (1.43) and lower-body (1.40). However, exploratory analysis revealed
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heterogeneity between some joint actions/exercises. We consider this analysis ex-
ploratory, in part, because of a relative lack of ECC versus CON strength data for
some joint actions/exercises. Indeed, this is reflected in the imprecision in estimates
for some joint actions/exercises (e.g., squat, trunk lateral flexion, hip internal and
external rotators, and wrist flexors and extensors). The knee extension was the joint
action/exercise studied most frequently, with 518 effects, and this was more than
double the next most frequently studied joint action/exercise (i.e., knee flexors, 205
effects) (Table 3). Nevertheless, heterogeneity in the ECC:CON strength ratio between
specific joint actions/exercises appears to exist. Future research should systemati-
cally explore different joint actions/exercises with large samples to obtain more pre-
cise estimates of their ECC:CON ratios. Moreover, 98% of ECC:CON strength ratios
came from tests of isokinetic muscle strength, with few researchers attempting to
measure both ECC and CON 1RM with free weights, weight stack machines, or plate-
loaded machines. The ECC 1RM is often impractical to examine given the design of
most contemporary resistance exercise equipment. However, emerging resistance
exercise technologies, discussed briefly in Section 4.5., could make evaluation of
maximal ECC strength safer and more feasible in coming years. Such machines might
then be used to establish ECC:CON muscle strength ratios for various joint ac-
tions/exercises.
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Table 3. Number of effects for each joint action/exercise
Joint Action/Exercise
No. Effects
Knee extensors
518
Knee flexors
205
Ankle plantarflexors
106
Elbow flexors
106
Shoulder external
84
Ankle dorsiflexors
81
Shoulder internal
70
Elbow extensors
30
Trunk extensors
23
Trunk flexors
17
Leg press
16
Hip extensors
13
Hip flexors
10
Shoulder abductors
8
Hip abductors
7
Hip external
6
Shoulder adductors
6
Shoulder extensors
6
Shoulder flexors
6
Wrist flexors
6
Hip adductors
5
Hip internal
5
Squat
5
Trunk lateral
4
Wrist extensors
2
4.4 Velocity
The factor that impacted the ECC:CON strength ratio the most was movement
velocity. The ECC:CON strength ratio was largest at fast velocities and smallest at slow
velocities. The greater ECC:CON strength ratio at faster velocities is due primarily to
the substantial reduction in CON phase torque that occurs at faster velocities. Our
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analysis revealed a log-linear relationship between test velocity and the ECC:CON ra-
tio such that the ratio increased 0.21% for every 1°/s increase in velocity. A potential
practical implication of this finding is that resistance exercise technologies that can
control ECC and CON phase velocities independently can account for such differ-
ences to optimize force generation during the ECC and CON phases.
4.5 Implications overview
Historically, ECC resistance exercise has been difficult to prescribe because of
limitations of free weights and weight machines. “Releasers,” which dispose of a pro-
portion of the eccentric load after the ECC phase, have been used with free weights
and weight machines to overcome such limitations [18]. However, “releasers” can be
difficult to use beyond the first repetition. The lack of feasibility to implement ECC
resistance exercise with such equipment also explains why, in the current review, so
few studies assessed ECC 1RMs, i.e., isoinertial load testing. The lack of feasibility of
using such equipment for ECC testing and training also explains why, in one survey,
23% of strength and conditioning coaches said inadequate equipment was the most
significant barrier to implementation of ECC resistance exercise [43]. Moreover, in
another survey, 57% coaches who had never prescribed ECC resistance exercise said
the main reason was equipment inaccessibility [20]. Nevertheless, new exercise tech-
nologies have the potential to make ECC resistance exercise more accessible, safe,
and feasible. Examples of such equipment include connected adaptive resistance ex-
ercise (CARE) machines [22], flywheels [44], and motorized isokinetic devices [45].
Other ECC resistance exercise machines also exist and have been reviewed by Tin-
wala et al. [17]. With such equipment, independent load prescriptions for the ECC
and CON phases is sometimes possible. Thus, knowledge of ECC:CON strength ratios
might be useful for coaches who use such equipment to prescribe ECC overload.
Currently, coaches [20] and researchers prescribe ECC loads ranging from 1.05 to 2.0
times the CON 1RM or CON training load (Table 1). Results from the current analysis
suggest factors such as velocity, joint action/exercise, age, and to a lesser extent sex
warrant consideration when determining how much ECC overload to prescribe in
athletic, clinical, and research settings. For example, if ECC overload is computed
based on CON 1RM, then higher multiplication factors are likely necessary for older
than younger adults and for faster than slower velocities. New exercise technologies
have potential to allow for isokinetic exercise and independent control of ECC and
DOI:
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CON resistances in non-laboratory environments. Isokinetic modes in such machines
might account for the impact of velocity on force. To allow participants to generate
their greatest CON forces, slow movement velocities would be necessary. For the ECC
phase, more leniency could be provided, as force output in the ECC phase is less
impacted by velocity.
5.0 Conclusion
Researchers have known for many decades that ECC strength is greater than
CON strength. However, prior to the current review, the magnitude of this strength
difference, and the factors that impact it, had never been submitted to review and
meta-analysis. We report a main model estimate for the ECC:CON strength ratio of
1.40. However, the ratio is higher at faster than slower movement velocities and in
older adults than younger adults. The ratio is also slightly higher in women than men.
The ratio does not differ between upper- and lower-body muscles generally speak-
ing, but an exploratory analysis indicated that there is likely heterogeneity in ratios
across different joint actions/exercises. Further systematic study will be necessary to
identify more precise estimates of exercise-specific ECC:CON strength ratios. Exer-
cise practitioners can use the ECC:CON ratios discovered in the current analysis to
guide prescriptions of ECC overload in athletic, clinical, and research settings.
Funding information
No financial support was received for the conduct of this article or for the preparation of
this manuscript.
Data and Supplementary Material Accessibility
All materials, data, and code are available on the Open Science Framework project page for
this study https://osf.io/8vt9h/
Author contributions
JLN wrote the first draft of the manuscript. JLN performed the literature search. JS per-
formed the meta-analyses. All authors were involved in the interpretation of the meta-anal-
yses, read, revised, and approved the final manuscript.
REFERENCES
DOI:
https://doi.org/10.51224/SRXIV.197
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1. Doss WS, Karpovich PV. A comparison of concentric, eccentric, and isometric
strenth of elbow flexors. J Appl Physiol. 1965;20(2):351-3.
2. Singh M, Karpovich PV. Strength of forearm flexors and extensors in men and
women. J Appl Physiol. 1968;25(2):177-80.
3. Singh M, Karpovich PV. Isotonic and isometric forces of forearm flexors and
extensors. J Appl Physiol. 1966;21(4):1435-7.
4. Colliander EB, Tesch PA. Bilateral eccentric and concentric torque of
quadriceps and hamstring muscles in females and males. Eur J Appl Physiol
Occup Physiol. 1989;59(3):227-32.
5. Griffin JW, Tooms RE, vander Zwaag R, Bertorini TE, O'Toole ML. Eccentric
muscle performance of elbow and knee muscle groups in untrained men and
women. Med Sci Sports Exerc. 1993;25(8):936-44.
6. Hollander DB, Kraemer RR, Kilpatrick MW, Ramadan ZG, Reeves GV, Francois
M, et al. Maximal eccentric and concentric strength discrepancies between
young men and women for dynamic resistance exercise. J Strength Cond Res.
2007;21(1):34-40.
7. Porter MM, Myint A, Kramer JF, Vandervoort AA. Concentric and eccentric knee
extension strength in older and younger men and women. Can J Appl Physiol.
1995;20(4):429-39.
8. Damiano DL, Martellotta TL, Quinlivan JM, Abel MF. Deficits in eccentric versus
concentric torque in children with spastic cerebral palsy. Med Sci Sports Exerc.
2001;33(1):117-22.
9. Marshall PW, Mannion J, Murphy BA. The eccentric, concentric strength
relationship of the hamstring muscles in chronic low back pain. J Electromyogr
Kinesiol. 2010;20(1):39-45.
10. Cowell JF, Cronin J, Brughelli M. Eccentric muscle actions and how the strength
and conditioning specialist might use them for a variety of purposes. Strength
Cond J. 2012;34(4):33-48.
11. Douglas J, Pearson S, Ross A, McGuigan M. Chronic adaptations to eccentric
training: a systematic review. Sports Med. 2017;47(5):917-41.
12. Fisher JP, Ravalli S, Carlson L, Bridgeman LA, Roggio F, Scuderi S, et al. The
"Journal of Functional Morphology and Kinesiology" journal club series: utility
and advantages of the eccentric training through the isoinertial system. J Func
Morphol Kinesiol. 2020;5(1).
DOI:
https://doi.org/10.51224/SRXIV.197
SportRxiv is free to access, but not to run. Please consider
donating at www.storkinesiology.org/annual 18
13. Mike J, Kerksick CM, Kravitz L. How to incorporate eccentric training into a
resistance training program. Strength Cond J. 2015;37(1):5-17.
14. Schoenfeld BJ, Grgic J. Eccentric overload training: a viable strategy to enhance
muscle hypertrophy? Strength Cond J. 2018;40(2):78-81.
15. Suchomel TJ, Wagle JP, Douglas J, Taber CB, Harden M, Haff GG, et al.
Implementing eccentric resistance training-part 2: practical recommendations.
J Func Morphol Kinesiol. 2019;4(3).
16. Suchomel TJ, Wagle JP, Douglas J, Taber CB, Harden M, Haff GG, et al.
Implementing eccentric resistance training-part 1: a brief review of existing
methods. J Func Morphol Kinesiol. 2019;4(2).
17. Tinwala F, Cronin J, Haemmerle E, Ross A. Eccentric strength training: a review
of the available technology. Strength Cond J. 2017;39(1):32-47.
18. Wagle JP, Taber CB, Cunanan AJ, Bingham GE, Carroll KM, DeWeese BH, et al.
Accentuated eccentric loading for training and performance: a review. Sports
Med. 2017;47(12):2473-95.
19. McNeill C, Beaven CM, McMaster DT, Gill N. Survey of eccentric-based strength
and conditioning practices in sport. J Strength Cond Res. 2020;34(10):2769-75.
20. Harden M, Bruce C, Wolf A, Hicks KM, Howatson G. Exploring the practical
knowledge of eccentric resistance training in high-performance strength and
conditioning practitioners. Int J Sports Sci Coach. 2020;15(1):41-52.
21. Weldon A, Duncan MJ, Turner A, LaPlaca D, Sampaio J, Christie CJ. Practices of
strength and conditioning coaches: a snapshot from different sports,
countries, and expertise levels. J Strength Cond Res. 2022.
22. Nuzzo JL, Nosaka K. Comment on: “Stepwise load reduction training: a new
training concept for skeletal muscle and energy systems”. Sports Med. 2022.
23. Durell DL, Pujol TJ, Barnes JT. A survey of the scientific data and training
methods utilized by collegiate strength and conditioning coaches. J Strength
Cond Res. 2003;17(2):368-73.
24. Judge LW, Petersen CB, Bellar DM, Craig BW, Cottingham MP, Gilreath EL. The
current state of NCAA Division I collegiate strength facilities: size, equipment,
budget, staffing, and football status. J Strength Cond Res. 2014;28(8):2253-61.
25. Greenhalgh T, Peacock R. Effectiveness and efficiency of search methods in
systematic reviews of complex evidence: audit of primary sources. BMJ.
2005;331(7524):1064-5.
DOI:
https://doi.org/10.51224/SRXIV.197
SportRxiv is free to access, but not to run. Please consider
donating at www.storkinesiology.org/annual 19
26. Gardner MJ, Altman DG. Confidence intervals rather than P values: estimation
rather than hypothesis testing. BMJ. 1986;292(6522):746-50.
27. Kruschke JK, Liddell TM. The Bayesian New Statistics: hypothesis testing,
estimation, meta-analysis, and power analysis from a Bayesian perspective.
Psychon Bull Rev. 2018;25(1):178-206.
28. McShane BB, Gal D, Gelman A, Robert C, Tackett JL. Abandon statistical
significance. The American Statistician. 2019;73:234-45.
29. Burkner P-C. brms: An R package for Bayesian multilevel models using Stan. J
Stat Softw. 2017;80(1):1-28.
30. Kay M. tidybayes: Tidy data and geoms for Bayesian models. R package
version 3.0. 0. . 2021.
31. Lenth RV. emmeans: Estimated Marginal Means, aka Least-Squares Means. R
package version 1.6.1. . 2021.
32. Viechtbauer W. Conducting meta-analyses in R with the metafor package. J Stat
Softw. 2010;36(3):1-48.
33. Wickham H, Chang W. An implementation of the grammar of graphics. 2016.
34. Pedersen TL. The composer of plots [R package patchwork version 1.1.1].
2020.
35. Ren K, Russell K. formattable: Create 'Formattable' Data Structures. R package
version 0.2.1. 2021.
36. Lajeunesse MJ. On the meta-analysis of response ratios for studies with
correlated and multi-group designs. Ecology. 2011;92(11):2049-55.
37. Nakagawa S, Poulin R, Mengersen K, Reinhold K, Engqvist L, Lagisz M, et al.
Meta-analysis of variation: ecological and evolutionary applications and
beyond. Methods in Ecology and Evolution. 2015;6(2):143-52.
38. Nuzzo JL. Narrative review of sex differences in muscle strength, endurance,
activation, size, fiber type; and strength training participation rates,
preferences, motivations, injuries, and neuromuscular adaptations. J Strength
Cond Res. In press.
39. Poulin MJ, Vandervoort AA, Paterson DH, Kramer JF, Cunningham DA. Eccentric
and concentric torques of knee and elbow extension in young and older men.
Can J Sport Sci. 1992;17(1):3-7.
DOI:
https://doi.org/10.51224/SRXIV.197
SportRxiv is free to access, but not to run. Please consider
donating at www.storkinesiology.org/annual 20
40. Roig M, Macintyre DL, Eng JJ, Narici MV, Maganaris CN, Reid WD. Preservation
of eccentric strength in older adults: Evidence, mechanisms and implications
for training and rehabilitation. Exp Gerontol. 2010;45(6):400-9.
41. Hughes VA, Frontera WR, Wood M, Evans WJ, Dallal GE, Roubenoff R, et al.
Longitudinal muscle strength changes in older adults: influence of muscle
mass, physical activity, and health. J Gerontol A Biol Sci Med Sci.
2001;56(5):B209-B17.
42. Wu R, Delahunt E, Ditroilo M, Lowery M, De Vito G. Effects of age and sex on
neuromuscular-mechanical determinants of muscle strength. Age
2016;38(3):57.
43. Drury B, Clarke H, Moran J, Fernandes JFT, Henry G, Behm DG. Eccentric
resistance training in youth: a survey of perceptions and current practices by
strength and conditioning coaches. J Func Morphol Kinesiol. 2021;6(1).
44. Tesch PA, Fernandez-Gonzalo R, Lundberg TR. Clinical Applications of Iso-
Inertial, Eccentric-Overload (YoYo™) Resistance Exercise. Front Physiol.
2017;8:241.
45. Armstrong R, Baltzopoulos V, Langan-Evans C, Clark D, Jarvis J, Stewart C, et al.
Determining concentric and eccentric force-velocity profiles during squatting.
Eur J Appl Physiol. 2022;122(3):769-79.
46. Doan BK, Newton RU, Marsit JL, Triplett-McBride NT, Koziris LP, Fry AC, et al.
Effects of increased eccentric loading on bench press 1RM. J Strength Cond
Res. 2002;16(1):9-13.
47. Ojasto T, Häkkinen K. Effects of different accentuated eccentric load levels in
eccentric-concentric actions on acute neuromuscular, maximal force, and
power responses. J Strength Cond Res. 2009;23(3):996-1004.
48. Sheppard JM, Young K. Using additional eccentric loads to increase concentric
performance in the bench throw. Journal Strength and Conditioning Research.
2010;24(10):2853-6.
49. Montalvo S, Gruber LD, Gonzalez MP, Dietze-Hermosa MS, Dorgo S. Effects of
Augmented Eccentric Load Bench Press Training on One Repetition Maximum
Performance and Electromyographic Activity in Trained Powerlifters. J Strength
Cond Res. 2021;35(6):1512-9.
DOI:
https://doi.org/10.51224/SRXIV.197
SportRxiv is free to access, but not to run. Please consider
donating at www.storkinesiology.org/annual 21
50. Sarto F, Franchi MV, Rigon PA, Grigoletto D, Zoffoli L, Zanuso S, et al. Muscle
activation during leg-press exercise with or without eccentric overload. Eur J
Appl Physiol. 2020;120(7):1651-6.
51. Wagle JP, Cunanan AJ, Carroll KM, Sams ML, Wetmore A, Bingham GE, et al.
Accentuated Eccentric Loading and Cluster Set Configurations in the Back
Squat: A Kinetic and Kinematic Analysis. J Strength Cond Res. 2021;35(2):420-7.
52. Wagle JP, Taber CB, Carroll KM, Cunanan AJ, Sams ML, Wetmore A, et al.
Repetition-to-Repetition Differences Using Cluster and Accentuated Eccentric
Loading in the Back Squat. Sports. 2018;6(3).
53. Coratella G, Milanese C, Schena F. Unilateral eccentric resistance training: A
direct comparison between isokinetic and dynamic constant external
resistance modalities. Eur J Sport Sci. 2015;15(8):720-6.
54. Godard MP, Wygand JW, Carpinelli RN, Catalano S, Otto RM. Effects of
accentuated eccentric resistance training on concentric knee extensor
strength. J Strength Cond Res. 1998;12(1):26-9.
55. Walker S, Blazevich AJ, Haff GG, Tufano JJ, Newton RU, Häkkinen K. Greater
strength gains after training with accentuated eccentric than traditional
isoinertial loads in already strength-trained men. Front Physiol. 2016;7:149.
56. Hortobágyi T, DeVita P. Favorable neuromuscular and cardiovascular
responses to 7 days of exercise with an eccentric overload in elderly women. J
Gerontol A Biol Sci Med Sci. 2000;55(8):B401-B10.
57. Friedmann-Bette B, Bauer T, Kinscherf R, Vorwald S, Klute K, Bischoff D, et al.
Effects of strength training with eccentric overload on muscle adaptation in
male athletes. Eur J Appl Physiol. 2010;108(4):821-36.
58. Brandenburg JP, Docherty D. The effects of accentuated eccentric loading on
strength, muscle hypertrophy, and neural adaptations in trained individuals. J
Strength Cond Res. 2002;16(1):25-32.
59. English KL, Loehr JA, Lee SM, Smith SM. Early-phase musculoskeletal
adaptations to different levels of eccentric resistance after 8 weeks of lower
body training. Eurorpean Journal of Applied Physiology. 2014;114(11):2263-80.
60. Tøien T, Pedersen Haglo H, Unhjem R, Hoff J, Wang E. Maximal strength
training: the impact of eccentric overload. J Neurophysiol. 2018;120(6):2868-
76.
DOI:
https://doi.org/10.51224/SRXIV.197
SportRxiv is free to access, but not to run. Please consider
donating at www.storkinesiology.org/annual 22
61. Franchi MV, Ruoss S, Valdivieso P, Mitchell KW, Smith K, Atherton PJ, et al.
Regional regulation of focal adhesion kinase after concentric and eccentric
loading is related to remodelling of human skeletal muscle. Acta Physiol.
2018;223(3):e13056.
62. Seliger V, Dolejs L, Karas V, Pachlopníková I. Adaptation of trained athletes'
energy expediture to repeated concentric and eccentric muscle contractions.
Int Z Angew Physiol. 1968;26(3):227-34.
63. Schroeder ET, Hawkins SA, Jaque SV. Musculoskeletal adaptations to 16 weeks
of eccentric progressive resistance training in young women. J Strength Cond
Res. 2004;18(2):227-35.
