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Effects Of Variable Resistance Training On Maximal Strength: A Meta-Analysis



Variable resistance training (VRT) methods improve the rate of force development (RFD), coordination between antagonist and synergist muscles, the recruitment of motor units, and reduce the drop in force produced in the sticking region. However, the beneficial effects of long-term VRT on maximal strength both in athletes and untrained individuals have been much disputed. The purpose of this study was to compare in a meta-analysis the effects of a long-term (>= 7 weeks) VRT program using chains or elastic bands and a similar constant resistance program in both trained adults practicing different sports and untrained individuals. Intervention effect sizes were compared among investigations meeting our selection and inclusion criteria using a random effects model. The published studies considered were those addressing VRT effects on the one repetition maximum (1RM). Seven studies involving 235 subjects fulfilled the selection and inclusion criteria. VRT led to a significantly greater mean strength gain (weighted mean difference: 5.03 kg; 95% CI: 2.26-7.80 kg; Z = 3.55; P < 0.001) than the gain recorded in response to conventional weight training. Long-term VRT training using chains or elastic bands attached to the barbell emerged as an effective evidence-based method of improving maximal strength both in athletes with different sports backgrounds and untrained subjects.
Department of Physical Education and Sport, University of Granada, Granada, Spain
Effects of variable resistance training on maximal strength: A meta-
analysis. J Strength Cond Res 29(11): 3260–3270, 2015—
Variable resistance training (VRT) methods improve the rate of
force development, coordination between antagonist and syner-
gist muscles, the recruitment of motor units, and reduce the drop
in force produced in the sticking region. However, the beneficial
effects of long-term VRT on maximal strength both in athletes and
untrained individuals have been much disputed. The purpose of
this study was to compare in a meta-analysis the effects of a long-
term ($7 weeks) VRT program using chains or elastic bands and
a similar constant resistance program in both trained adults prac-
ticing different sports and untrained individuals. Intervention effect
sizes were compared among investigations meeting our selection
and inclusion criteria using a random-effects model. The published
studies considered were those addressing VRT effects on the 1
repetition maximum. Seven studies involving 235 subjects fulfilled
the selection and inclusion criteria. Variable resistance training led
to a significantly greater mean strength gain (weighted mean dif-
ference: 5.03 kg; 95% confidence interval: 2.26–7.80 kg; Z=
3.55; p,0.001) than the gain recorded in response to conven-
tional weight training. Long-term VRT training using chains or
elastic bands attached to the barbell emerged as an effective
evidence-based method of improving maximal strength both in
athletes with different sports backgrounds and untrained subjects.
KEY WORDS one repetition maximum, elastic bands, chains,
Over the past few years, strength training proto-
cols designed to optimize the efficiency and ben-
efits of training have gained popularity (20,33).
Strength training programs including variable
resistance (VR) exercises are typically performed using
accessories, such as elastic bands or chains, and machines
that allow for variation in the velocity of load displacement
and its magnitude. One of the main objectives of the use of
chains or elastic bands is to induce a high variation of stimuli
and thus provoke neural adaptations improving the different
expressions of strength, including maximal strength or the
1 repetition maximum (1RM) (3,28). These methods com-
bine the resistance generated by fixed loads (e.g., barbell and
disks) with the VR produced by elastic bands and chains
attached to the barbell. The most characteristic feature of
this training modality is that resistance directed against the
target muscle or muscle group can be varied over the range
of athletic movement (1,20). Many authors claim that this
type of resistance training reduces the mechanical disadvan-
tage of the sticking point encountered in free weight training
(2–4,33,38). The sticking point or sticking region refers to
the loss of velocity produced in external resistance exercise
and was first described by the authors of classic studies such
as Elliott et al. (18). More recently, van der Tillar and Ettema
(44) discovered that the sticking region is dependent on
loading and accounts for 35–45% of the range of movement.
The sticking region is the most inefficient stage of a joint
movement in that the muscle groups involved cannot meet
the demands of exercise when working with loads as high as
90% of the 1RM (36) or even 80% (18). In this region, move-
ment velocity decreases most likely because of compromised
neural intermuscular and intramuscular coordination, result-
ing in a reduction in the force sustained (44). The rationale
for variable resistance training (VRT) is that a greater abso-
lute external load will be supported if this neuromechanical
disadvantage is minimized by applying lower resistances
(loads lower than 85% 1RM, Table 1 indicating the loads
sustained at the end of the athletic movement) across less
efficient movement ranges (2,18). According to van den
Tillaar and Saterbakken (45), in practical terms, this means
that these movement ranges could be avoided by controlling
exercise velocity to increase the mechanical impulse of each
exercise repetition for workloads greater than 80% 1RM at
the start of the sticking region.
During a variable intrarepetition stimulus weight lifting
protocol, a load increase takes place as the barbell is moved
through the concentric phase of the range of motion, making
it increasingly more difficult to maintain a high velocity and
Address correspondence to Miguel A
´. Soria-Gila,
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TABLE 1. Details of the studies included in the meta-analysis.*
Reference n
Subject characteristics
Age (6SD)
Weight (6SD)
Height (6SD)
(cm) Training level Sports activity
Anderson et al. (2) 44 Mixed 20 61 66.2 613.8 zTrained (4 62 y) Basketball, wrestling, and hockey
Bellar et al. (9) 11 Men 23.6 63.2 84.4 618.8 179 68.5 Untrained z
Cronin et al. (15) 40 Mixed 23.1 64.8 76.3 611 175 69 Trained (3 y) z
Ghigiarelli et al. (22) 36 Men 19.96 61.03 96.3 615 180.83 66.24 Trained American football (36 Division
McCurdy et al. (31) 27 Men 20.63 61.33 84.79 65.84 178.89 65.46 Trained (4.8 62.7 y) Baseball (Division II)
Rhea et al. (40) 48 Men 21.4 62.1 zzTrained Athletics (NCAA) Division I
Shoepe et al. (42) 29 Mixed 19.76 61.33 66.8 611.1 168.77 610.3 Scarce training (12 mo) Free weight lifting
Training characteristics
VRT Duration Sets Repetitions Rest (s)
Anderson et al. (2) Elastic bands 3 d$wk
37 wk 3–6 2–10 120–180 85 15 85
Bellar et al. (9) Elastic bands 2 d$wk
313 wk 5 5 90 85 15 85
Cronin et al. (15) Elastic bands 2 d$wk
310 wk 3 8–15 zzzz
Ghigiarelli et al. (22) Elastic bands and chains 4–5 d$wk
37 wk 5–6 4–6 zzz85
McCurdy et al. (31) Chains 2 d$wk
39 wk 5–7 5–10 z80–90 10–20 z
Rhea et al. (40) Elastic bands 2–3 d$wk
312 wk 4 10 zzz75–85
Shoepe et al. (42) Elastic bands 3 d$wk
324 wk 3–6 6–10 60–120 80–65 20–35 65–95
= days per week; VRT = variable resistance training; PCR = percentage constant resistance; PVR = percentage variable resistance; PMR = percentage maximum
resistance; NCAA = National Collegiate Athletic Association.
Individual details of each study in terms of sample size (n), subject characteristics, and resistance training characteristics.
zNot defined.
Journal of Strength and Conditioning Research
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acceleration (11,13,19,48). When using elastic bands, suffi-
cient acceleration is needed in the early lifting stage to over-
come elastic recoil and complete the movement (19).
Contrarily to the use of bands, chains act by adding mass
(19). The magnitude of this system of masses is proportional
to the height reached by the barbell from the ground. The
gradual increase produced in external resistance causes insta-
bility, which could induce an optimal stimulus for strength
gains (32), and a high neuromuscular demand, increasing
both motor unit recruitment and rate coding (25). Such neu-
romuscular adaptations could be the consequence of
improved coordination between antagonist and synergist
muscles controlling movement (2,8,9,16,31,38). Some
authors have argued that greater muscle activation due to
stored elastic energy translates to an improved rate of force
development (RFD) (40). The resistance produced by elastic
bands or chains generates the greatest workload at the end
of the range of motion. In other words, a steady load
increase is produced through the trajectory of movement,
whereas in traditional training using free weights, this great-
est load is sustained at the onset of the concentric phase
(22,23). A further issue to consider is that elastic bands
increase resistance in a curvilinear manner, whereas chains
do so linearly because of their different physical and
mechanical properties (15,19,33,34).
The results of recent studies (2,9) assessing the efficiency
of combining elastic tension with the tension induced by free
weights in traditional back squat exercise suggest that
80–85% of the load should be provided by free weights
and 15–20% by VR. To improve peak power during explo-
sive movements when elastic bands and free weights are
used in the back squat, other authors (28,33,38,48) recom-
mend figures of 20–35% and 65–80% for VR- and free-
weight loaded resistance, respectively.
A further characteristic feature of varying resistance is that,
besides increasing velocity, it increases the eccentric stimulus
of training, and thus the strength needed to slow down or stop
the load at the end of the eccentric phase, inducing greater
myoelectric activity in the muscles (15). Researchers examin-
ing VRT using chains have also reported that this type of
training induces stimulus variations, as a consequence of the
oscillations that chains produce, which provoke better coor-
dination between agonist, synergistic, and stabilizing muscles
to control the load (11,31). Several studies (2,21,48) have
detected improvements in muscular strength and power gen-
erated in bench press and squat exercises in response to elastic
plus free weight loaded training, compared with similar train-
ing in the absence of elastic resistance. In addition, VRT
improves resistance to fatigue through the physiologic
response to an acute effect of fatigue during training (46).
Individual differences in muscle contractile properties can also
lead to different degrees of fatigue (47).
Based on the available literature, it is difficult to extract
whether the different VRT programs show true benefits in
improving muscular strength. The present meta-analysis was
designed to examine research-based information on the
effects on maximal strength, or 1RM, of a long-term VRT
program under different training conditions.
A meta-analysis was designed following the recommenda-
tions and criteria proposed by the Cochrane Review Group
(26). Each step (article identification, filtering, eligibility
assessment, and inclusion/exclusion of a study) was per-
formed by the present authors.
Selection and Inclusion/Exclusion Criteria
All randomized controlled studies assessing the effects of
a 7-week or longer VRT intervention providing maximal
strength as the main outcome variable were identified. There
were no restrictions made on the search regarding gender,
training status, sport specialty, or body mass index.
A study was included if VRT intervention duration was
$7 weeks and involved $2 sessions per week. The former
cutoff was based on the finding that 6 weeks of resistance
training is sufficient to improve the maximal strength of the
knee extensors by 35%, as a consequence of an increase in
the motor unit firing rate (29). The number of sessions per
week was based on the findings of Rhea et al. (39). The use
of elastic bands or chains was also an inclusion criterion
although the training method (e.g., bench press or back
squat) used to improve strength was not a limitation. Only
articles providing preintervention and postintervention 1RM
data were included. Studies were excluded if designed to
treat a disorder or disease.
Articles were required to report on at least 1 subject group
undergoing VRT and to include a control group of individ-
uals training using the more traditional method (i.e., using
free weights). Also as an inclusion criterion, we considered
all valid and reliable methods commonly used to measure
maximum strength in the different studies (14,32,34).
Search Methods
The following databases were searched for articles published
before January 2014: MEDLINE, PubMed; Scopus, SPORT-
Discus, and Web of Science using the keywords bench press,
bungee weight, chain, concentric, eccentric, elastic bands,
exercise, force, free weight, load, lower limb, maximal, muscle,
neuromuscular, output, performance, power, resistance pro-
gram, rubber bands, squat, strength, traditional, training, upper
limb, variable, and velocity. Annual scientific conference
abstracts, comments, or duplicated publications of the same
study were not included. We also examined references listed
and cited in the articles identified, including review articles, to
identify additional studies. The full texts of the all the articles
selected were examined by 3 of the present authors (M.A.S.-G.,
I.J.C., and S.B.).
Statistical Analyses
Study Inclusion. To select the studies for final inclusion in the
meta-analysis, the 3 reviewers independently screened the
Variable Resistance Training
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references identified for eligibility. Abstracts were assessed
for the studies’ fulfillment of inclusion/exclusion criteria.
Study quality criteria were also considered (experimental
design, subject withdrawal, and possible conflicts of interest).
The recently developed QAREL checklist (30) was used to
evaluate the methodological quality of included interrater
reliability and agreement studies. This checklist was chosen
because it seems to be the only available quality appraisal
tool for reliability studies at the moment. Any disagreement
between reviewers was resolved by consensus.
Interstudy Heterogeneity. Variation between studies was as-
sessed in terms of the effect under investigation (i.e., maximal
strength). Effect sizes (ES) are provided as differences in
weighted means, along with the corresponding 95% confi-
dence interval (CI). To estimate interstudy heterogeneity, the
method was used with significance set at p#0.05. The
index I
was also determined,
where 0% indicates homogene-
ity and 100% heterogeneity (27).
Coding of Studies. Each study
was read and coded by the
main investigator according to
the following variables: descrip-
tive information including sam-
ple size, gender, age, weight,
height, training level, sports
ties trained, training duration,
sets, repetitions, rest, percentage
constant resistance, percentage
VR, and percentage maximum
resistance (PMR).
Coder drift was assessed (37)
by randomly selecting 4 studies
for recoding. Per case agree-
ment was determined by divid-
ing the variables coded the
same by the total number of var-
iables. A greater mean agreement
level was observed (93%) than
the minimum accepted level
of 90%.
Effect Size. The effects of the intervention were calculated for
each study using the pretraining and posttraining mean and
SDs recorded for the main outcome measure (1RM) in the
VRTand control (conventional training) groups. The pooled
ES was estimated in terms of the change in SD produced.
When a study lacked the necessary data to estimate the SD
change, the following equation was used:
where, corr is a correlation factor that relates pretraining and
posttraining results based on the data provided by Rhea et al.
(40) (0.96 for the VRT groups and 0.97 for the control
A random-effects model was used to examine the grouped
data extracted from the different studies. The relative
strength of the intervention effect and 95% CIs for each
study were illustrated in a forest plot. The ES of the
intervention was calculated as the difference between
pretraining and posttraining 1RM mean.
Figure 1. Study selection/inclusion process.
SD change ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
Journal of Strength and Conditioning Research
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In a separate sensitivity analysis, we determined the
contribution of each study to the overall improvement in
maximal strength detected in this meta-analysis by successively
omitting the results of each
study from the comparisons
made using the data from the
remaining studies.
All calculations were per-
formed using the RevMan
software package (Review
Manager–Version 5.2; The Co-
chrane Collaboration, 2012).
Study Characteristics
Seven studies providing results
for 16 subject groups met the
criteria for inclusion in our
meta-analysis (2,9,15,22,31,40,42),
(Figure 1). Publication dates were
2003–2011. An overview of the
characteristics of the 7 studies
included in this meta-analysis
is provided in Table 1. All stud-
ies selected were designed to
address the same issue although
working hypotheses differed
slightly. Some studies compared
the effects on the 1RM of train-
ing using free weights with chains (22,31), whereas others
compared several experimental groups subjected to different
VRT interventions (elastic bands or chains) with a control
group (traditional free weight
training) (15,22). In the study
by Rhea et al. (40), several
experimental groups undertak-
ing different training protocols
with chains were compared.
Another study compared the ef-
fects of training with elastic
in bench presses and squats (42).
Subject Characteristics
The data examined were ob-
tained from 235 subjects aged
18.3–27.9 years (mean 6SD:
21.21 62.11 years) (Table 1).
Four of the 7 studies were con-
ducted only in men (10 groups)
and 3 in both men and women
(6 groups). The participants of 2
studies were untrained subjects
or had less than 12 months of
experience (4 groups). In 5 stud-
ies, subjects had experience of 2
years or longer or were trained
(12 groups). Trained subjects
Figure 2. Forest plot of the results of the meta-analysis of random effects showing the difference in mean
weighted 1RM and 95% CI detected for the bench press, leg press, back squat, and squat (5.03 kg; 95% CI:
2.26–7.80 kg; Z= 3.55; p,0.001) in trained and untrained subjects. Gray squares indicate the intervention
effect. Square sizes are proportional to the weights assigned to each study in the meta-analysis. The horizontal line
joins the lower and the upper limits of the effect at a 95% CI. The diamonds represent the subgroup mean
difference () and pooled mean difference (). BP = bench press; LP = leg press; SQ = squat; BSQ = back
squat; EB = elastic band; CH = chain; FW = free weight; CI = confidence interval; 1 = fast-velocity group;
2 = slow-velocity group.
Figure 3. Forest plot of the results of the meta-analysis of random effects showing the difference in mean
weighted 1RM and 95% CI detected for the bench press, leg press, back squat, and squat (5.03 kg; 95%
CI: 2.26–7.80 kg; Z= 3.55; p,0.001) in upper-body training and lower-body training subjects. Gray squares
indicate the intervention effect. Square sizes are proportional to the weights assigned to each study in the meta-
analysis. The horizontal line joins the lower and the upper limits of the effect at a 95% CI. The diamonds represent
the subgroup mean difference () and pooled mean difference (). BP = bench press; LP = leg press; SQ =
squat; BSQ = back squat; EB = elastic band; CH = chain; FW = free weight; CI = confidence interval; 1 = fast-
velocity group; 2 = slow-velocity group.
Variable Resistance Training
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TABLE 2. Results of the 7 studies included in the meta-analysis.*
Reference Exercise
Control groups Experimental groups
(kg) ES n
(kg) ES
Anderson et al. (2) BP 21 81.07 32.82 84.41 33.37 0.43 23 80.69 35.34 87.37 35.52 0.66
BSQ 21 108.19 35.61 115.28 33.70 0.86 23 105.80 33.70 121.75 35.70 1.58
Bellar et al. (9) BP 11 101.50 19.60 109.00 20.30 1.60 11 100.00 18.90 109.90 19.40 1.80
Cronin et al. (15) LP 12 122.00 34.10 118.95 33.25 0.39 14 128.00 27.50 139.14 29.90 1.30
Ghigiarelli et al. (22) BP 12 141.80 23.00 149.50 23.00 1.44 12 127.70 25.00 137.70 25.00 1.40
BP 12 129.50 15.00 138.60 14.00 2.13
McCurdy et al. (31) BP 27/2102.65 14.42 109.09 12.98 1.85 27/2151.85 27.12 174.26 13.47 1.52
Rhea et al. (40) BSQ 16 115.94 36.07 119.18 35.56 0.38 16 116.00 31.43 125.81 30.69 1.10
BSQ 16 122.31 39.04 131.94 36.43 1.08
Shoepe et al. (42) BP 12 56.30 30.30 66.70 27.00 1.40 12 53.60 21.00 59.30 24.50 0.77
SQ 12 66.90 16.50 88.90 23.20 2.72 12 69.30 27.00 91.40 31.90 2.27
*n = number of subjects in each group; ES = effect size; BP = bench press; BSQ = back squat; SQ = squat; LP = leg press.
Not defined.
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were Division I athletes (National Collegiate Athletic Associ-
ation [NCAA]), baseball players (Division II) and American
football players (36 Division 1AA players).
Variable Resistance Training
Mean training program duration was 12 65 weeks (range,
7–24 weeks). From 2 to 5 training sessions were conducted
per week, with a mean of 3 61 per week. Training took the
form of upper limb exercise (bench press) in 4 studies (10
groups), lower limb exercise (back squat) in 1 study (2
groups), and both upper and lower limb training (bench
press and back squat) in 2 studies (4 groups). Chains
attached to the barbell in the bench press were used in 2
studies (2 groups), and elastic bands attached to the barbell
in bench press or back squat exercise were used in 5 studies
(6 groups each).
Publication Bias and Interstudy Heterogeneity
A scatter plot of intervention effect (1RM) against the study
size showed a funnel-shaped symmetric distribution indicat-
ing no publication bias. The treatment effect, or 1RM,
yielded the values x
(10) = 27.21; p= 0.002; I
indicating moderate interstudy heterogeneity.
Maximal Strength (One Repetition Maximum)
The mean strength gain produced was greater in the subjects
undertaking long-term VRT, the ES being 1.42 60.51 ex-
pressed as the mean 6SD (difference in the weighted mean
1RM was 5.03 kg; 95% CI: 2.26–7.80 kg; Z= 3.55; p,0.001;
Figure 2) than in those subjected to a conventional resistance
training program, with an ES of 1.24 60.71. Furthermore,
a subgroup analysis by training status indicated a significantly
better 1RM gain in response to VRT, ES = 1.35 60.43, vs.
traditional training, ES = 0.98 60.56, for trained subjects
(pooled estimate = 6.12 kg; 95% CI: 2.43, 9.80 kg; Z= 3.25;
p= 0.001; Figure 2). However, in untrained subjects, the
greater improvement produced in the 1RM with VRT, ES
=1.6260.77, compared with conventional training, ES =
1.91 60.71 was nonsignificant (pooled estimate = 2.56 kg;
95% CI: 20.55, 5.68 kg; Z= 1.61; p= 0.11; Figure 2). Another
subgroup analysis revealed that for upper extremity training,
significant differences in 1RM gains existed between the VRT
program, ES = 1.38 60.57, and traditional training program,
ES = 1.36 60.48 (pooled estimate = 3.99 kg; 95% CI: 0.92,
7.06 kg; Z= 2.54; p= 0.01; Figure 3). Similarly, for lower limb
training, VRTalso led to a significantly better improvement in
the 1RM, ES = 1.47 60.49, than conventional training, ES =
1.09 60.96 (pooled estimate = 6.07 kg; 95% CI: 0.95, 11.20
kg; Z= 2.32; p= 0.02; Figure 3). In Table 2, we provide details
of the effects of the VRT program detected in each study.
In each comparison (preintervention vs. postintervention) in
which the results of 1 study were omitted, no significant
differences were detected (p,0.001) in each case indicating
the significant contribution of all the studies to the overall
strength gains observed.
In this meta-analysis, we compared the effects of traditional
vs. VRT on the adaptive response produced in terms of
maximal strength. The studies meeting the selection and
inclusion criteria for the meta-analysis were those by Cronin
et al. (15), Anderson et al. (2), Ghigiarelli et al. (22),
McCurdy et al. (31), Rhea et al. (40), Bellar et al. (9), and
Shoepe et al. (42). Participants were either untrained (with
under 12 months’ experience in strength training) or trained
(longer than 2 years’ experience). Our results indicate that
VRT over at least 7 weeks ($2 sessions per week) leads to
a significantly greater strength gain (p,0.001) than that
produced in response to a traditional strength training pro-
gram. When subjects were stratified according to training
status, trained individuals achieved a significantly greater
strength gain with the VRT than the traditional training pro-
gram (p= 0.001). However, the strength gains observed for
the nontrained subjects undertaking a VRT program vs. a tra-
ditional program did not vary significantly (p= 0.11). When
stratified according to the extremities trained, for both the
lower and upper limbs, VRT gave rise to significantly better
gains in 1RM than conventional training (p#0.02).
According to the Rhea scale (38) used to determine the
magnitude of the ES in a study comparing the effects of resis-
tance training as a function of training status, in trained sub-
jects who undertook a VRT (ES = 1.35 60.43) vs.
conventional training program (ES = 0.98 60.56), the ES
was moderate, although sufficient for a significant difference
to exist between the 2 groups. This indicates that in individuals
with more experience in resistance exercises such as the bench
press and back squat, $7 weeks of VRT is an effective stimulus
for them to show a performance peak during training.
However, in our study, a moderate ES was also observed in
untrained subjects undertaking both a VRT program (ES =
1.62 60.77) or conventional training program (ES = 1.91 6
0.71). It should be noted that subjects labeled in our study as
“trained subjects,” would according to Rhea classification (38),
be considered “recreationally trained” given they had more
than 1 year of experience but a training duration of less than
5 years.
It also remains unclear whether a VRT program of
duration under 7 weeks or longer than 12 weeks would be
adequate for athletes to develop sufficient neural and
muscular adaptations in a short time span to improve their
1RM while also continuing to improve their 1RM over the
ensuing weeks. Only one of the studies reviewed here (42)
examined a VRTprogram lasting longer than 12 weeks. This
24-week intervention in untrained subjects produced no sig-
nificant impact on 1RM.
Evidence has only recently started to mount indicating that
VRT leads to a greater RFD and muscular power than the
more conventional form of resistance training (42). The find-
ings of the latter study suggest that during VRT, the training
impulse and muscle activation achieved on completion of
Variable Resistance Training
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each repetition are enhanced. According to Shoepe et al. (42),
this means that the lifter develops greater force in the final
portion of the concentric phase. Despite this, no significant
strength differences were detected in response to a 24-week
program of traditional training and VRT training combining
elastic and free weight loading in subjects with limited RT
experience. McCurdy et al. (31) also noted improved strength
gains in individuals undertaking the VRT program but again
differences with respect to controls were not significant.
These authors attributed the strength gains observed to the
different stability involved in the variable and conventional
training protocols, such that the neuromuscular activity
required for a strength improvement depends on the stabili-
zation needed to control resistance (5). Accordingly, for
a more unstable load, greater neuromuscular activation is nec-
essary and force production is significantly reduced (6). Our
findings confirm those of the study by Shoepe et al. (42) in
that subjects unaccustomed to free weight training showed no
significant differences when comparing the effects of conven-
tional and VRT. Thus, an optimal level of stability could be
a prerequisite for an improvement in maximal strength.
Chain-loaded VRT is slightly more unstable than free weight
resistance training (31). Consequently, once an individual
becomes accustomed to VRT and acquires more neuromus-
cular control, VRT can be an optimal stimulus to develop the
different expressions of strength.
The general trend detected in this meta-analysis is in line
with the findings of the study by Anderson et al. (2), in which
significant 1RM improvements were obtained both in the
bench press and squat. Participants of this study were trained
athletes who showed no muscle cross-section increase at the
end of the training period, suggesting improvements at the
neural level. Variable resistance training emerged as a beneficial
strategy for trained athletes, offering new stimuli inducing
fitness adaptations. The strength gains produced in these ath-
letes could also be attributed to increased muscle tension in
the more mechanically productive regions of the range of
movement, accompanied by reduced loading in the less effi-
cient sticking region. According to Anderson et al. (2), during
traditional free weight training, the barbell gains velocity dur-
ing muscle shortening until the sticking region. In the latter
study, subjects executing VRT achieved approximately 10%
less resistance in the lower region of the range of movement
and 10% more resistance toward the top, or end, of the ath-
letic movement. Acceleration remained constant over a long
period within each repetition, determining that deceleration is
reduced in VRT. Bellar et al. (9) argue that another method of
modifying resistance during a traditional resistance exercise is
to add elastic resistance. Thus, variable-resistance loading dur-
ing the bench press makes the lifting movement no longer
isoinertial. The percentage-load variation produced by elastic
bands here was 15%, and this modified the strength produc-
tion pattern during lifting. This type of variable stimulation
could be responsible for beneficial neural adaptations. In the
subject populations entered in our meta-analysis, resistance
exercise led to improved performance in terms of maximal
strength gains (2,9,15,22,31,40,42).
Elastic recoil during eccentric contraction in VRT training
may differently challenge the neuromuscular system during
each repetition (2). Ha
¨kkinen et al. (24) reported increased
electromyographic activity and a controlled increase in veloc-
ity during eccentric actions. In another study, Cronin et al.
(15) concluded that VRT using elastic bands attached to
a jump squat machine induced greater electromyographic
activity in eccentric contractions compared with traditional
training methods. Anderson et al. (2) proposed that greater
muscle fiber recruitment and stimulation during the eccentric
portion of each repetition may bring about greater neuromus-
cular adaptations and/or type IIx fiber recruitment with VRT
than with free weights alone. This explanation offered by
Anderson et al. (2) is consistent with the preferential recruit-
ment of high-threshold motor units during high-force eccen-
tric contractions reported by Nardone et al. (35).
In the study by Ghigiarelli et al. (22), significant maximal
strength increases were observed in VR compared with tradi-
tional resistance-trained individuals, regardless of the use of
chains or elastic bands. Wallace et al. (48) observed that add-
ing elastic-loaded resistance to free weight training in the back
squat led to maximal strength and power improvements when
working with loads approaching 85% of the 1RM.
According to Cronin et al. (15), the ability to quickly com-
plete a stride and return to the starting position or move in
another direction is a determining factor for success in sports,
such as squash, badminton, tennis, and fencing, among others.
In their study, subjects undertaking VRT using elastic bands
on the leg press machine showed improvement in the move
toward the stride, especially in the last part of the eccentric
phase. These subjects were able to complete a stride faster
than their peers who trained on the same machine in the
traditional way. Thus, it seems that VRT serves to improve
the transition from eccentric to concentric phase exercise, and
thus, shortens the stretch-shortening cycle, which would
potentiate the concentric phase (12) and expedite the stride.
Despite an increased prevalence of VRT programs using
heavy chains and elastic bands, some studies have generated
contradictory results (4,10,48), whereas others have found
that VRT programs offer promising results in the long
term (15,22).
Variable resistance training using heavy chains modifies
the kinetics of the barbell for all movement ranges,
increasing the mechanical advantage of the athlete’s move-
ment (4,10,38). However, because of the gradual resistance
reduction at the end of the eccentric phase, the time taken to
reach maximum acceleration (at the start of the concentric
phase) decreases in that range of movement zone causing
neural adaptation (22,31). McCurdy et al. (31) identified the
individual range of movement as an important factor to con-
sider when quantifying the workload. Behm and Sale (7)
described the user’s intention to displace the barbell as rap-
idly as possible as the main force driving neural adaptations
Journal of Strength and Conditioning Research
VOLUME 29 | NUMBER 11 | NOVEMBER 2015 | 3267
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
of muscular power and strength. Neuromuscular adaptations
are specific to the nature of the training load (43). Thus, it
has been proposed that the different characteristics of load
distribution during VRT affect muscle recruitment patterns
(2). In the study by Anderson et al. (2), subjects in the VRT
group were able to complete the prescribed exercise sets,
whereas some of the control group subjects had to pause
for 5–10 seconds between some repetitions to complete
a set.
In their study, Rhea et al. (40) noted maximal strength gains
when they compared subjects in whom VRT involved high-
velocity movements (0.6–0.8 m$s
) with subjects in the tra-
ditional training group working at slower velocities (0.2–0.4
). These results support the idea that the RFD can be
improved through VRT training using elastic bands
(2,15,16,22). Wallace et al. (48) suggested that the RFD
increase could correspond to an earlier phase in which the
peak velocity is reached in VRT. This is because as resistance
progressively increases with the mechanical advantage, higher
levels of force are generated during the concentric phase just
at the moment when muscles approach their optimal length-
tension relationship (17). A further factor inducing an increase
in RFD is a shorter muscle tissue stretch-shortening cycle
(40). The muscle is able to store elastic energy during the
eccentric phase of movement and then releases this energy
as kinetic energy during the concentric phase of the lift (15).
According to Rhea et al. (40), when the time taken needed to
reach maximal force is not limited, strength relates more to
activation of muscle mass with some relationship to synchro-
nization. Athletes using elastic bands as the VRT stimulus
showed both improved muscular strength and power, most
likely because of simultaneously improved motor unit syn-
chronization and coding velocity, although this needs to be
confirmed in further work (40).
The finding of this meta-analysis that VRT training using
chains or elastic bands leads to strength gains has obvious
implications to be considered by coaches and specialists in
sport sciences. This new training modality enables both elite
athletes and untrained individuals to more rapidly and
efficiently achieve adaptations in their functional capacity
than the more traditional resistance training methods.
As a limitation to this meta-analysis, we should mention
that many studies were excluded because of the strict
inclusion criteria established. Similarly, because of missing
data in some of the selected studies, a correlation factor
(Equation 1) had to be calculated from the data provided by
Rhea et al. (40). A further limitation was the possible effects
of publication bias (41). Despite these limitations, this meta-
analysis provides an overview of the research in this field and
offers an explanation based on the scientific literature of the
benefits of the use of VRT to increase maximal strength.
This meta-analysis provides research-based data supporting
the benefits of VRT using chains or elastic bands as an
effective strategy to increase maximal strength (1RM) in
athletes of different sports disciplines. Thus, VRT could be
used as a complement to traditional training to vary the
athletic stimulus once the user has adapted to the previous
stimulus, leading to faster training-induced adaptations.
This training modality could help avoid overload during
the range of athletic movement and may therefore be used
throughout a sport’s season to gradually improve a competi-
tion skill. It is also a useful tool to strengthen certain muscle
groups while subjecting injured muscles to lower resistances
during a rehabilitation process.
Variable resistance training is an economic simple strategy
for use with barbells in exercises such as the bench press or
back squat. The chains or elastic bands are quick to attach
and unattach meaning that strength conditioning coaches
can readily prescribe a different exercise after a variable-
resistance exercise without wasting valuable training time.
Our results indicate that training status affects the impacts of
conventional and VRT. For untrained subjects, we would not
recommend VRT, because similar strength gains are pro-
duced with traditional free weight training. In contrast, in
trained individuals, VRTwill lead to improved strength gains
over traditional training. This type of protocol would be
ideal in adults with training experience to achieve stimulus
variations and thus avoid plateaus in their physical fitness.
This issue should be borne in mind by strength conditioning
experts and coaches to better design training regimens.
Based on our findings, it would also seem that both upper
and lower limb VRT produces greater adaptations than
conventional free weight training, indicating similar effects of
this training form on both halves of the body.
Our findings provide direction for future studies designed
to determine whether other percentages of VR work and/or
PMR will produce the same 1RM adaptations or whether
single-joint exercises will give rise to similar results as
multijoint actions. Future research efforts should also explore
whether the impacts of VRT are reduced with training
duration and establish the minimum period for VRT to
produce the strength gains detected here.
The authors thank Pedro Femia Marzo for help with the
data analysis and useful comments. This study received no
funds from an external source. The results of this study do
not represent the endorsement of any product by the
authors or National Strength and Conditioning Association.
This article was based on data from a PhD thesis in
Biomedicine (Universidad de Granada, Spain) by M.A.
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... Table 1 depicts the findings of the systematic review. We excluded one meta-analysis [46] after determining that it was retracted in 2018 [47] because of statistical errors resulting in an incorrect conclusion [48]. We replaced this retracted meta-analysis with the 21st most cited meta-analysis from our search. ...
... This is problematic because dividing by the standard deviation of the change scores yields information about statistical significance but not about the magnitude of the effect [21]; yet the authors of these meta-analyses incorrectly Effects of low-volume high-intensity interval training (HIT) on fitness in adults: a meta-analysis of controlled and non-controlled trials [36] to weight studies Focus on within-group rather than between-group comparisons 16 The optimal load for maximal power production during lower-body resistance exercises: a meta-analysis [42] As described in the search method, Scopus and Google Scholar were searched for 20 highly cited meta-analysis or meta-regression studies between 2000 and 2020 as of February 2021. All papers identified in the top 20 except Soria-Gila et al. [46] were present in the Scopus and Google Scholar search. The means of Google Scholar and Scopus citations are presented for all papers except Soria-Gila et al. [46] interpreted the pooled effect sizes as giving information about magnitude. ...
... All papers identified in the top 20 except Soria-Gila et al. [46] were present in the Scopus and Google Scholar search. The means of Google Scholar and Scopus citations are presented for all papers except Soria-Gila et al. [46] interpreted the pooled effect sizes as giving information about magnitude. Had the correct standard deviation been used, this likely would have resulted in lower effect sizes. ...
Full-text available
Background and Objective Meta-analysis and meta-regression are often highly cited and may influence practice. Unfortunately, statistical errors in meta-analyses are widespread and can lead to flawed conclusions. The purpose of this article was to review common statistical errors in meta-analyses and to document their frequency in highly cited meta-analyses from strength and conditioning research. Methods We identified five errors in one highly cited meta-regression from strength and conditioning research: implausible outliers; overestimated effect sizes that arise from confusing standard deviation with standard error; failure to account for correlated observations; failure to account for within-study variance; and a focus on within-group rather than between-group results. We then quantified the frequency of these errors in 20 of the most highly cited meta-analyses in the field of strength and conditioning research from the past 20 years. Results We found that 85% of the 20 most highly cited meta-analyses in strength and conditioning research contained statistical errors. Almost half (45%) contained at least one effect size that was mistakenly calculated using standard error rather than standard deviation. In several cases, this resulted in obviously wrong effect sizes, for example, effect sizes of 11 or 14 standard deviations. Additionally, 45% failed to account for correlated observations despite including numerous effect sizes from the same study and often from the same group within the same study. Conclusions Statistical errors in meta-analysis and meta-regression are common in strength and conditioning research. We highlight five errors that authors, editors, and readers should check for when preparing or critically reviewing meta-analyses.
... The descending variable resistance from the landmine is kinetically dissimilar to the ascending variable resistance from bands and chains (42,43,68). Research on variable resistance using free weight equipment focuses predominantly on the application of bands and chains to exercises with ascending strength curves (66,73). The revised statistics of a meta-analysis reporting improved strength with variable resistance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 training relative to constant resistance training showed no significant difference in effects (49,66). ...
... Research on variable resistance using free weight equipment focuses predominantly on the application of bands and chains to exercises with ascending strength curves (66,73). The revised statistics of a meta-analysis reporting improved strength with variable resistance 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 training relative to constant resistance training showed no significant difference in effects (49,66). Interestingly, variable resistance training has been shown to improve resistance to lower body fatigue, enabling greater volume-load to be lifted (72). ...
The landmine row is an upper-body pulling exercise using a barbell as a lever. This column provides the strength and conditioning coach with a summary of trained musculature, technique descriptions for common landmine row variations, suggested instructional cues for improving technique and performance, an overview of unique exercise biomechanics, and programming recommendations.
... As the time-force curve increases throughout the concentric phase (as the barbell moves upwards) of the movement, the load increases in order to accommodate the resistance to the easier part of the lift 9, 10 . This will result in the greatest workload being at the top of the lift whereas in the CPL, the greatest workload would be at the bottom (start of the concentric phase) 11 . Characteristics will vary between the different barbell AR training techniques. ...
... Characteristics will vary between the different barbell AR training techniques. Chains will provide mostly vertical resistance (especially if they remain in contact with the floor as shear forces will remain minimal) and affect the force-time relationship in a linear manner (as chains are raised or lowered vertically loading or unloading chain links on to the floor), while elastic bands will also provide some type of resistance, in addition to vertical loading and unloading, in other planes that will affect the force-time relationship in a logarithmic manner 9,11 . Furthermore, the double looped chain technique will provide nearly twice the resistance than the single looped technique at the top of a squat 12 . ...
This study compared the absolute (kg) and relative (Wilks pts) maximal strength (MS) gains between the accommodated resistance (AR) and the classic plate loaded (CPL) training methods. Seventeen (17) powerlifters were separated into two groups [experimental (EG; n=9) and control (CG; n=8)]. Both followed the same 9-week, 4 times a week, 2 hour, wave-like percentage-based training program with pre and post MS powerlifting testing measures except that the EG trained with a 25% added AR (elastic bands or chains) and 80% of the CPL bar weight. Elastic band resistance relative to bar height for all powerlifting movements was measured with a stadiometer. A two-way repeated measure ANOVA was performed. Effect sizes (ES) were calculated with Morris’ estimate effect size. The EG significantly (p<0.05) improved more in the Deadlift Wilks pts and Total Wilks pts (+6.3±3.9% vs 0.1.±5.9%; ES=0.55 and 6.3±5.1% vs 2.1±2.3%; ES=0.24 respectively), that the EG trended (p>0.05) towards improving more in the Squat Kg (+6.5±9.7% vs 2.8±3.0%; ES= 0.04), Squat Wilks pts (+9.5±11.6% vs 2.9±3.2 %; ES=0.21), Deadlift Kg (3.5±3.7% vs 0.0±5.4%; ES=0.19) and Total Kg (3.4±3.5% vs 2.0±2.4%; ES=0.03). In contrast, the CG trended (p>0.05) towards improving more in the Bench Kg (4.3±3.5% vs -0.1±6.9%; ES=-0.16) and Bench Wilks pts (4.3 ± 4.0 % vs 2.6±7.5%; ES=0.1). Thus, the present AR technique produces significantly greater relative MS gains when prescribing deadlifts twice a week, non-significant greater MS gains when prescribing squats twice a week, but CPL produces non-significant greater MS gains when prescribing presses four times a week.
... Regardless of the method used, when planning training loads, coaches and athletes must consider the training objectives and the magnitude of the effect of the different methodologies available [8]. These processes could consider using any available training methods to develop muscular strength and power, such as variable resistance (VR). 2 of 21 VR is another methodology that has shown good results for developing muscle strength and power [5,9,10]. The main characteristic of VR is the variation of intensity within the training load [11]. ...
Full-text available
Variable resistance (VR) is a methodology that has shown good results in developing muscular strength and power. However, no updated information relates to the use of VR as an activation to trigger post-activation performance enhancement (PAPE). The primary objective of this systematic review and meta-analysis was to review and qualitatively describe studies published between 2012 and 2022 that used VR to generate PAPE in muscle power-dominant sports. The secondary objective was to calculate the effect size of the different power outcomes reported in the selected studies. The search was designed following the PRISMA ® guidelines for systematic reviews and meta-analyses and performed in the Web of Science (WOS), Scopus, SPORTDiscus, PubMed, and MEDLINE between 2012 and 2022. The methodological quality and risk of bias were evaluated with the Cochrane Collaboration tool. The main variables were the throwing speed, time in sprint tests, and jump height. The analysis was conducted with a pooled standardized mean difference (SMD) through a Hedges' g test (95% CI). Twenty-two studies were included in the systematic review and ten in the meta-analysis, revealing a trivial effect for throwing speed (SMD = 0.06; CI = 95%: −0.23-0.35; p = 0.69), a small effect for the time in sprint tests (SMD = −0.37; CI = 95%: −0.72-−0.02; p = 0.04), and a moderate effect for jump height (SMD = 0.55; CI = 95%: 0.29-0.81; p < 0.0001). All forms of VR used for neuromuscular activation effectively triggered PAPE. Specifically, the results showed that activation with VR generates performance increases in time, in sprint tests and jump height, and a trivial effect in throwing tests (speed and distance).
... 3. Accommodating resistance: including two technologies systems (1) Isokinetic in which the movement velocity is controlled while the applied force changes over the range of motion at a relatively constant velocity [65] and (2) Isotonic that controls the force and measures changes in movement velocity over a range of motion at a constant force. 4. Nongravitational resistance: vibration machines [66] and rotary inertial machines (flywheel-based equipment) [67]. 5. Combining different mode of resistances: (1) hydraulic and pneumatic-based equipment which combines nongravity with accommodating resistance [65] (2) simple pieces of equipment such as bands, springs that combine non-gravity with progressive resistance [68] or chains that use gravity while is applied progressively [69]. ...
Resistance training (RT) configures a specialized method of training that involves the progressive use of a wide range of resistive loads, different rate of muscle activation or movement velocities, and a variety of training modalities. RT is currently considered essential in athletic preparation. It is a key component for optimizing growth and maturation in children, promoting health and quality of life in the elderly, or to attenuate the incidence of injuries in physically active populations. Qualified professionals are necessary to design individualized RT programs for athletes from varying disciplines with very specific performance outcomes. The professional must consider specific needs for all ages, not only the athletic population, making the necessary adaptation to meet their level of ability and desired outcomes. Effective training stimuli should help increase performance and avoid overtraining. This is accomplished by manipulating physiological, neurological, and biomechanical-related variables. There is hard science behind the importance of menstrual cycle-based periodization, and—although research in this area is scarce—results suggest that designing training programs integrating the menstrual cycle hormonal fluctuation or the ingestion of triphasic contraceptives might be of relevance to optimize performance in premenopausal women.
... However, for these coaches, concentric and eccentric training modalities were still the most common forms of resistance training. Two factors may explain these results: 1) the scarcity of appropriate track and field training facilities throughout the country (i.e., Brazil), which often means that coaches need to develop and use alternative training approaches (e.g., elastic bands as resistance); 2) the proven effectiveness and practical aspects of variable resistance training, especially in terms of maximum strength development, either in isolation or in combination with more traditional training strategies (e.g., free-weight exercises) Soria-Gila et al., 2015). ...
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Olympic coaches are likely to have adequate knowledge and implement effective training programs. This study aimed to describe and critically examine the strength and conditioning practices adopted by Brazilian Olympic sprint and jump coaches. Nineteen Olympic coaches (age: 50.2 ± 10.8 years; professional experience: 25.9 ± 13.1 years) completed a survey consisting of eight sections: 1) background information; 2) strength-power development; 3) speed training; 4) plyometrics; 5) flexibility training; 6) physical testing; 7) technology use; and 8) programming. It was noticed that coaches prioritized the development of explosiveness, power, and sprinting speed in their training programs, given the specific requirements of sprint and jump events. Nevertheless, unexpectedly, we observed: (1) large variations in the number of repetitions performed per set during resistance training in the off-season period, (2) a higher volume of resistance training prescribed during the competitive period (compared to other sports), and (3) infrequent use of traditional periodization models. These findings are probably related to the complex characteristics of modern competitive sports (e.g., congested competitive schedule) and the individual needs of sprinters and jumpers. Identification of training practices commonly used by leading track and field coaches may help practitioners and sport scientists create more effective research projects and training programs.
... Considering this, this elastomeric garment may optimize the neuromuscular response to resistance exercises (Kompf & Arandjelović, 2016). Additionally, and although we have not measured this, systematically repeating this training stimulus may induce greater performance levels compared to traditional resistance training with constant resistance (Soria-Gila et al., 2015). ...
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Resistance training is one key method for improving physical conditioning. With this purpose, Menatechpro System® has designed an avant-garde garment that includes elastomeric technology that may stimulate the neuromuscular system in a better way, but a deeper knowledge of its effects is needed. Objective: To explore the effects of a new garment with elastomeric technology on upper-limb performance, and neuromuscular, perceptual, and cardiovascular responses in two upper-extremities exercises. Methodology: Fit young men trained in resistance exercises performed a seated shoulder press (80% of one-repetition maximum) and push up (bodyweight) until muscle failure with the garment that incorporates the elastomeric technology versus a placebo garment without it. The number of repetitions, mean propulsive velocity, mean and peak muscle activation, rate of perceived effort and perceived velocity, and heart rate were analysed. Possible differences were obtained with a two-way mixed ANOVA of repeated measures with post-hoc analysis. Results: Compared with a placebo garment, the use of this new garment with elastomeric technology improved positively the physical performance and muscular activation during the exercises analysed (p ≤ .05). Conclusion: Menatechpro System®'s elastomeric technology integrated into the garment could provide an optimal neuromuscular stimulus for the development of the performance during the upper extremity training.
... Frequently, comparisons have been made with popular training interventions with relatively minor adjustments, for example, the use of variable resistance (e.g. elastic bands or chains) in comparison to traditional resistance training (31), or alterations to sequence of exercises (e.g. complex vs contrast training) (32). ...
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This study aimed to investigate the effects of combining elastic bands to free weight (EB+FWR) on the acceleration-deceleration and velocity profiles of the bench press in professional rugby players and recreationally-trained subjects. Sixteen male subjects (8 rugby players and 8 recreationally-trained subjects) were randomly assigned to complete 2 experimental conditions in a cross-over fashion: EB+FWR and FWR. In both conditions, subjects performed one bench-press set to volitional exhaustion with a load equivalent to the 85% of one-repetition maximum (1RM). In the EB+FWR condition, the contribution of elastic resistance was approximately the 20% of selected load (85% of 1RM). Results indicate that EB+FWR condition increased significantly the range of concentric movement in which the barbell is accelerated. This increase was significantly higher in rugby players (35%) in comparison with recreationally-trained subjects (13%). Maximal velocity was also increased in EB+FWR (17%), when compared with FWR condition. These results suggest that when combined with variable resistance (i.e. EB), the external resistance seems to be more evenly distributed over the full range of motion, decreasing the need for dramatic deceleration at the end of the concentric phase. The present data also indicate that the kinematic benefits of a EB+FWR approach seems to be more prominent in athletes from modalities in which high level of strength and power are required (i.e. rugby players).
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The aim of this project was to investigate the reliability of a new 11-item quality appraisal tool for studies of diagnostic reliability (QAREL). The tool was tested on studies reporting the reliability of any physical examination procedure. The reliability of physical examination is a challenging area to study given the complex testing procedures, the range of tests, and lack of procedural standardisation. Three reviewers used QAREL to independently rate 29 articles, comprising 30 studies, published during 2007. The articles were identified from a search of relevant databases using the following string: “Reproducibility of results (MeSH) OR reliability (t.w.) AND Physical examination (MeSH) OR physical examination (t.w.).” A total of 415 articles were retrieved and screened for inclusion. The reviewers undertook an independent trial assessment prior to data collection, followed by a general discussion about how to score each item. At no time did the reviewers discuss individual papers. Reliability was assessed for each item using multi-rater kappa (κ). Multi-rater reliability estimates ranged from κ = 0.27 to 0.92 across all items. Six items were recorded with good reliability (κ > 0.60), three with moderate reliability (κ = 0.41 - 0.60), and two with fair reliability (κ = 0.21 - 0.40). Raters found it difficult to agree about the spectrum of patients included in a study (Item 1) and the correct application and interpretation of the test (Item 10). In this study, we found that QAREL was a reliable assessment tool for studies of diagnostic reliability when raters agreed upon criteria for the interpretation of each item. Nine out of 11 items had good or moderate reliability, and two items achieved fair reliability. The heterogeneity in the tests included in this study may have resulted in an underestimation of the reliability of these two items. We discuss these and other factors that could affect our results and make recommendations for the use of QAREL.
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Movement is accomplished by the controlled activation of motor unit populations. Our understanding of motor unit physiology has been derived from experimental work on the properties of single motor units and from computational studies that have integrated the experimental observations into the function of motor unit populations. The article provides brief descriptions of motor unit anatomy and muscle unit properties, with more substantial reviews of motoneuron properties, motor unit recruitment and rate modulation when humans perform voluntary contractions, and the function of an entire motor unit pool. The article emphasizes the advances in knowledge on the cellular and molecular mechanisms underlying the neuromodulation of motoneuron activity and attempts to explain the discharge characteristics of human motor units in terms of these principles. A major finding from this work has been the critical role of descending pathways from the brainstem in modulating the properties and activity of spinal motoneurons. Progress has been substantial, but significant gaps in knowledge remain. © 2012 American Physiological Society. Compr Physiol 2:2629-2682, 2012.
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Variable resistance training has recently become a component of strength and conditioning programs. Prior research has demonstrated increases in power and/or strength using low loads of variable resistance. However, no study has examined using high loads of variable resistance as a part of a periodized training protocol. PURPOSE:: to examine variable resistance training within the context of a periodized training program, and to examine a greater load of variable resistance than has been examined in prior research. METHODS:: 14 NCAA Division II male basketball players were recruited for this study. Athletes were divided equally into either a variable resistance or control group. The variable resistance group added 30% of their one repetition maximum as band tension to their prescribed weight one session per week. Rate of power development, peak power, strength, body composition, and vertical jump height were measured pre and post treatment. RESULTS:: No baseline differences were observed between groups for any measurement of strength, power, or body composition. A significant group by time interaction was observed for RPD, in which RPD was greater in VRT post training than in the control group. Significant time effects were observed for all other variables including squat 1RM, bench press 1RM, deadlift 1-RM, clean 3-RM, vertical jump, and lean mass. While there were no significant group X time interactions, the VRT group's percent changes and ESs indicate a larger treatment effect in the squat and bench press 1RM values and the vertical jump performed on the force plate and vertec. CONCLUSIONS:: These results suggest that when using variable resistance as a component of a periodized training program, power and strength can be enhanced. Therefore, athletes whom add variable resistance to one training session per week may enhance their athletic performance.
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Loading using variable resistance devices, where the external resistance changes in line with the force:angle relationship, has been shown to cause greater acute neuromuscular fatigue and larger serum hormone responses. This may indicate a greater potential for adaptation during long-term training. Twelve (constant resistance group) and 11 (variable resistance group) men completed 20 weeks of resistance training with 10 men as non-training controls. Training-induced adaptations were assessed by bilateral leg press one repetition maximum, a repetition to failure test using 75 % 1RM, lower limb lean mass and vastus lateralis cross-sectional area. Only the variable resistance training group improved the total number of repetitions (41 ± 46 %) and volume load (52 ± 37 %) during the repetition to failure test (P < 0.05). Similar improvements in maximum strength and hypertrophy of the lower limbs were observed in both training groups. Also, constant and variable resistance 5 × 10RM leg press loadings were performed before and after training in a crossover design. Acute loading-induced responses were assessed by concentric and isometric force, serum hormone concentrations and phosphorylation of intramuscular signalling proteins (0-30 min post-loading). Greater acute decreases in force (P < 0.05-0.01), and greater increases in serum testosterone and cortisol concentration (P < 0.05) and ERK 1/2 phosphorylation (P < 0.05) were observed following variable resistance loadings before and after training. Greater training-induced improvements in fatigue resistance occurred in the variable resistance training group, which may be due to greater acute fatigue and physiological responses during variable versus constant resistance loadings.
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Electromyographic Activity and Applied Load During High Intensity Elastic Resistance and Nautilus Machine Exercises This study was designed to quantify and compare Electromyographic activity (EMG) and applied load in quadriceps muscle within performing high intensity knee extension exercises by Elastic Resistance (ER) and Nautilus Machine (NM). Sixteen male and female subjects (22.4 ± 4.7 yrs) completed 8 RM seated knee extension by NM, elastic tubing with original length (E0) and elastic tubing with 30% decrement of original length (E30). The mean value of EMG and external force were calculated and synchronized across various segments of motion for the three modes of training. The results demonstrated that in the early concentric and late eccentric segments of contraction, NM elicited significantly higher muscle activation than both E30 and E0 (p < 0.05). However, in the mid-concentric and mid-eccentric as well as late concentric and early eccentric segments no significant differences were observed between NM and E30. These findings supported the approach that developing external recoil of force in ER device by reducing 30% of initial length of elastic material can offer similar neuromuscular activation compared with NM. On this basis, E30 can be suggested as an affordable and non-gym based exercise device which has the capacity to provide an appropriate high resistance stimulus to meet the training requirement of athletes.
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The purpose of this investigation was to assess the effectiveness of variable resistance as provided through elastic plus free weight techniques in college aged males and females. Twenty novice lifters were randomly assigned to a traditional free weight only (6 males and 5 females) or elastic band plus free weight group (5 males and 5 females) and 9 more normally active controls (5 males and 4 females), were recruited to maintain normal activity for the duration of the study. No differences existed between control, free weight and elastic band at baseline for age, body height, body mass, body mass index, and body fat percentage. One-repetition maximums were performed for squat and bench press while both strength and power were assessed using isokinetic dynamometry. Elastic groups and free-weight groups completed 24 weeks of whole body, periodized, high intensity resistance (65-95% of one-repetition maximum) training three times/week. Training programs were identical except that the elastic group trained the barbell squat, bench press and stiff-legged deadlift with 20-35% of their total prescribed training loads coming from band resistance (assessed at the top of the range of motion) with the remainder from free weight resistance. A mixed-model analysis revealed that peak torque, average power and one-repetition maximums for squat were significantly greater after training for the elastic group compared to the control (p<0.05). In addition, the free weight group also showed significantly greater improvements over the control in peak torque and one-repetition maximums for squat and bench press. No significant differences were observed between the elastic band and free weight groups. Combined variable elastic band plus free weight exercises are effective at increasing strength and power similar to free-weights alone in novice college aged males and females. However, due to complexity in set-up and load assignment elastic adoption by novice lifters in an unsupervised situation is not advised.