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Effects of Unilateral vs. Bilateral Resistance Training Interventions on Measures of Strength, Jump, Linear and Change of Direction Speed: A Systematic Review and Meta-analysis

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Exercises can be categorized into either unilateral or bilateral movements. Despite the topic popularity, the answer to the question as to which (unilateral or bilateral) is superior for a certain athletic performance enhancement remains unclear. To compare the effect of unilateral and bilateral resistance training interventions on measures of athletic performance. Keywords related with unilateral, bilateral and performance were used to search in the Web of Science, PubMed databases, and Google Scholar and ResearchGate™ websites. 6365 articles were initially identified, 14 met the inclusion criteria and were included in the final analysis, with overall article quality being deemed moderate. The quantitative analysis comprised 392 subjects (aged: 16 to 26 years). Sub-group analysis showed that unilateral exercise resistance training resulted in a large effect in improving unilateral jump performance compared to bilateral training (ES = 0.89 [0.52, 1.26]). In contrast, bilateral exercise resistance training showed a small effect in improving bilateral strength compared to unilateral (ES = -0.43 [-0.71, -0.14]). Non-significant differences were found in improving unilateral strength (ES = 0.26 [-0.03, 0.55]), bilateral jump performance (ES = -0.04 [-0.31, 0.23]), change of direction (COD) (ES = 0.31 [-0.01, 0.63]) and speed (ES = -0.12 [-0.46, 0.21]) performance. Unilateral resistance training exercises should be chosen for improving unilateral jumping performance, and bilateral resistance training exercises should be chosen for improving bilateral strength performance.
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Biology of Sport, Vol. 39 No3, 2022 485
Effects of unilateral vs. bilateral training on performance
INTRODUCTION
Resistance training is one of the most widely used methods of en-
hancing athletic performance[1–3]. One of the challenging problems
faced by practitioners is the issue of how to optimally choose the
exercises to maximize training effects when prescribing resistance
training programs. Typically, exercises in the weight room can be
categorized into either unilateral or bilateral. Aunilateral exercise is
aweight bearing movement mainly or completely involving one limb
(e.g. single leg squat, Bulgarian split squat and single leg jump),
whereas, abilateral exercise is aweight bearing movement executed
evenly and simultaneously by both limbs (e.g. back squat, deadlift
and countermovement jump). Traditionally, bilateral exercises are
selected as the primary exercises for athletic development[4, 5] due
to their effects on improving strength and power[6–9]. In contrast,
Effects of unilateral vs. bilateral resistance training interventions
on measures of strength, jump, linear and change of direction
speed: asystematic review and meta-analysis
AUTHORS: Kai-Fang Liao1,2, George P. Nassis3,4, Chris Bishop5, Wei Yang1, Chao Bian1,
Yong-MingLi1,6
1School of Physical Education and Sport Training, Shanghai University of Sport, Shanghai, China
2 Department of Strength and Conditioning, Guangdong Vocational Institute of Sport, Guangzhou, China
3 Physical Education Department, College of Education (CEDU), United Arab Emirates University, Al Ain, Abu
Dhabi, United Arab Emirates
4 Department of Sports Science and Clinical Biomechanics, Faculty of Health Sciences, SDU Sport and Health
Sciences Cluster, University of Southern Denmark, Odense, Denmark
5 School of Science and Technology, London Sport Institute, Middlesex University, London, UK
6 China Institute of Sport Science, Beijing, China
ABSTRACT: Exercises can be categorized into either unilateral or bilateral movements. Despite the topic
popularity, the answer to the question as to which (unilateral or bilateral) is superior for a certain athletic
performance enhancement remains unclear. To compare the effect of unilateral and bilateral resistance training
interventions on measures of athletic performance. Keywords related with
unilateral
,
bilateral
and
performance
were used to search in the Web of Science, PubMed databases, and Google Scholar and ResearchGate™
websites. 6365articles were initially identied, 14 met the inclusion criteria and were included in the nal
analysis, with overall article quality being deemed
moderate
. The quantitative analysis comprised 392subjects
(aged: 16 to 26years). Sub-group analysis showed that unilateral exercise resistance training resulted in alarge
effect in improving unilateral jump performance compared to bilateral training (ES = 0.89 [0.52, 1.26]). In
contrast, bilateral exercise resistance training showed asmall effect in improving bilateral strength compared
to unilateral (ES=-0.43[-0.71, -0.14]). Non-signicant differences were found in improving unilateral strength
(ES=0.26[-0.03, 0.55]), bilateral jump performance (ES = -0.04 [-0.31, 0.23]), change of direction (COD)
(ES=0.31[-0.01, 0.63]) and speed (ES = -0.12 [-0.46, 0.21]) performance. Unilateral resistance training
exercises should be chosen for improving unilateral jumping performance, and bilateral resistance training
exercises should be chosen for improving bilateral strength performance.
CITATION: Liao KF, Nassis GP, Bishop C et al. Effects of unilateral vs. bilateral resistance training interventions
on measures of strength, jump, linear and change of direction speed: asystematic review and
meta-analysis Biol Sport. 2022;39(3):485–497.
Received: 2021-01-11; Reviewed: 2021-03-21; Re-submitted: 2021-05-15; Accepted: 2021-05-21; Published: 2021-07-03.
unilateral exercises have been commonly considered to be ‘more
supplementary’ for injury prevention[10]. However, many key sport-
specic skills involved with the basic lower-body movements (e.g.
running, changing direction, jumping, kicking) are executed com-
pletely or predominantly unilaterally. Under the specicity of training
adaptation and to maximize the transfer of training[11], it could be
argued that unilateral exercises similar to sport-specic skills, may
be the best choice to improve athletic performance[10, 12], and
prioritized as akey exercise in such training programs. But the answer
to the question of which one (unilateral vs. bilateral) is better for
athletic performance enhancement remains unclear.
Specicity of training exercises is crucial for transference of train-
ing-induced adaptations to the target performance[13]. Young[5]
Review Paper
DOI: https://doi.org/10.5114/biolsport.2022.107024
Key words:
Exercise selection
Unilateral exercises
Bilateral exercises
Performance
Specicity
Corresponding author:
Yongming LI
1School of Physical Education
& Sport Training, Shanghai
University of Sport,
Changhai Road 399, Yangpu
District, Shanghai 200438,
P.R.China
2China Institute of Sport
Science, Beijing 100061, China
Fax: +86 (0) 21 65507122
Tel.: +86 (0) 21 65507122
E-mail: liyongming@sus.edu.cn
ORCID:
Kai-Fang Liao
0000-0001-6893-1491
George P. Nassis
0000-0003-2953-3911
Chris Bishop
0000-0002-1505-1287
Wei Yang
0000-0002-1564-6862
Chao Bian
0000-0002-0451-7459
Yong-Ming Li
0000-0001-9654-0199
486
Kai-Fang Liao et al.
studies have found no differences between methods[25, 31]. There
is also confusion about which method is superior for the improvement
of change of direction (COD) speed performance, with some favoring
unilateral training methods[32] and others favoring bilateral meth-
ods[26]. Furthermore, there is also conicting evidence on the effects
of these training methods on bilateral strength, jump and speed
performance[24–26, 28, 31, 32]. Recently, ameta-analysis carried
by Moran etal.,[33] concluded that there was no difference between
the effect of unilateral and bilateral resistance training on horizontal
movement speed (ES=0.17, p=0.30), but noted that the effect
size was pooled by 7short sprints, 2CODs, 1ve alternated leg
bounding and 1stair climb outcomes from 11included studies.
Given this review focused purely on the effects on horizontal speed,
it is still unclear how both bilateral and unilateral exercises transfer
to other key physical attributes, such as strength, jumping and COD
speed. Therefore, the purpose of this systematic review and meta-
analysis aimed to compare the effects of unilateral vs. bilateral re-
sistance training on improving athletic performance. The hypothesis
was that the effect of unilateral and bilateral resistance training would
follow the principle of specicity. In other words, the unilateral resis-
tance training would be better for improving the unilateral perfor-
proposed that exercise should be as specic as possible to optimize
the transfer of training. In addition, Bosch[14] proposed that intra-
muscular and inter-muscular coordination, outer movement resem-
blance and energy production are the key factors to evaluate and
predict the specicity of the training methods. Acompelling body of
empirical evidence also supports exercise type specicity with regards
to the range of motions, velocities, postures, and patterns[13, 15–18].
Actually, except for the obvious mechanical differences, unilateral
and bilateral exercises also differ in intra- and inter-muscular aspects
such as interhemispheric mutual activation[19], postural stabili-
ty[20], relationship of force and velocity[21], psychological state[22]
and lumbar load[23]. Based on those distinctions, unilateral and
bilateral resistance training are expected not to transfer equally.
According to the training principle of specicity, unilateral resis-
tance training should improve unilateral performance measures bet-
ter compared with bilateral resistance training, and vice versa. How-
ever, current ndings are conicting with respect to which is better
for the improvement of measures of athletic performance[24–30].
Some studies support the notion that unilateral resistance training
(e.g. Bulgarian split squat) improves unilateral strength more than
bilateral exercise training (e.g. back squat)[24, 26], and some
FIG. 1. Flow chart illustrating the different phases of the search and study selection
Biology of Sport, Vol. 39 No3, 2022
487
Effects of unilateral vs. bilateral training on performance
mance, and the bilateral resistance training would be better for im-
proving the bilateral performance.
MATERIALS AND METHODS
Literature research
This systematic review was conducted under the Preferred Reporting
Items for Systematic Reviews and Meta-Analysis Protocol (PRISMA).
One author searched the related articles from Web of Science
(1980–2020) and PubMed (1949 to 2020). The following keywords
inclusive of three main terms as unilateral, bilateral and performance
were used and combined under Boolean’s language with the opera-
tors AND and OR. Term 1: unilateral, split squat, single leg, one
leg, step up, lunge, Bulgarian split squat. Term 2: bilateral, back
squat, deadlift, double leg, two legs, hang clean, hang snatch.
Term 3: performance, strength, resistance, speed, power, jump,
agility, change of direction (COD), endurance. If studies were not
available in relevant electronic databases, then further searches were
conducted in Google Scholar and Research Gate™ websites. Finally,
additional studies were identied by checking the reference list of
the selected articles. The nal search date for literature was October1,
2020.
Inclusion Criteria
Studies were eligible if they met the following criteria: (1) imple-
mented both unilateral and bilateral resistance training interventions;
(2) the duration of training was longer than 4weeks; (3) the training
intensity was moderate to heavy; (4) included healthy participants
aged from 16 to 40years old in both genders; (5) had measured
athletic performance (Speed, strength, COD, power test etc.) before
and after the training intervention; (6) presented full data (mean
andSD) that allowed effect sizes to be calculated; (7) the manuscripts
were written in English and were published in apeer-reviewed journal.
Literature selection
The rst author imported all records into Endnote software (X9.3.3)
and deleted any duplicates. Then, the rst and fourth authors checked
the title and abstract separately to exclude any unrelated articles,
with the remaining full texts screened against the inclusion criteria.
There was no disagreement between the 2authors on that aspect.
Risk of bias assessment
The fourth and fth authors independently assessed the selected
studies. In case of disagreement on certain item scores, the item
scores would be given after discussion. Considering the most risk of
bias assessment scales such as Delphi scale, PEDro scale and Co-
chrane scale are designed for medical research, studies about train-
ing interventions usually get very low score under these method-
ological scales[34]. We preferred the scale (Table1) modied by
Brughelli et al[34] and Hooren etal.[35]. This scale is deemed
more suitable for sport science research, and includes 10items, with
each item rated as: 0=clearly no/not reported, 1 =maybe, and
2=clearly yes. The articles were rated poor with a total score
lower than 10, moderate with ascore between 10 and 15, good
with ascore>15, and excellent with ascore equal to 20.
Coding of the studies
The rst author extracted the data from the selected literatures with
astandard table. The code included: (1) participants: age, gender,
identity and training experience; (2) interventions: frequency, dura-
tion, exercises, intensity and volume; (3) measurements and results:
pre and post test outcome, with means and standard deviation.
Statistical analysis
The review manager software (5.3) was used for the meta-analytic
comparison if more than one outcome were evaluated for acertain
kind athletic performance measure between unilateral and bilateral
resistance training (e.g. Strength, speed), subgroup analyses were
performed.
Chi2 and I2 were calculated to test the heterogeneity. For I2 values
of 25, 50, and 75% represent low, medium, and high heterogeneity,
respectively[36]. For Chi2 with large value and p<0.1 show evi-
dences of heterogeneity. If p>0.1 and I2<50%, the xed effects
model was applied. Otherwise, the random effects model was applied
and provoked further investigation through a subgroup analysis of
moderator variables (Training experience, identity, gender, training
frequency, training modalities, training weeks). In order to identify
the presence of highly inuential studies, asensitivity analysis was
executed by removing one study at atime. Studies were considered
as inuential if removal resulted in achange of heterogeneity (p) from
signicance (p<0. 1) to non-signicance (p>0.1).
TABLE 1. Risk of bias assessment scale[34, 35]
No. Items Scores
1Clear inclusion criteria 0–2
2Clear description of the participants’ training
experience
0–2
3Random allocation of the participants to groups 0–2
4 Clearly dened intervention 0–2
5 Similarity test at baseline for all groups 0–2
6 Use of acontrol group that did not perform
resistance training
0–2
7 Clearly dened outcome variables 0–2
8 Adequate familiarization period 0–2
9 Appropriate between-group statistical analysis 0–2
10 Point measures of variability 0–2
Total 0–20
488
Kai-Fang Liao et al.
moderate,0.8 as large. Values are reported with 95% condence
intervals to describe the range of the true effect. If the absolute
value of aggregated effect and 95% condence interval are above
zero, effect size can be considered as clear evidence: Apositive effect
size indicated that the effect of unilateral exercises training was bet-
ter for the improvement of athletic performance than bilateral exercise
training, and anegative effect size indicates the opposite, i.e. bilat-
eral better than unilateral.
Given that unilateral athletic performance tests in included stud-
ies are generally divided into the left and right leg separately, and
5of included studies have used multiple measures of the same
athletic performance such as 10m sprint, 20m sprint for speed
performance (table 2), which may introduce statistical dependency
into the meta-analytic data set and enlarge the type Ierror due to
the same participants contributing to two or more effect sizes[39],
Standardized mean differences (SMD) was calculated with the
following algorithm[37]:
[(Mpost,unilateral– Mpre, unilateral)
– (Mpost,bilateral– Mpre, bilateral)/pooled SDpre]
This algorithm was selected as it has been recommended for
effect size calculation of independent pre-/post- study designs in
meta-analysis based on simulation results. The algorithm in speed
and COD outcomes was adjusted as[Mpre Mpost], of which the
smaller values represent better results compared with other outcomes.
SMD was used because the studies all evaluate the same outcome
but test it in various methods such as maximum power of leg press
(n.m) and 1RM of leg press (kg) in strength measures. The absolute
values of effect sizes were rated with the following criterion given by
Cohen[38]: <0.2 as trivial, 0.2–0.49 as small, 0.5–0.79 as
TABLE 2. Multiplicity of included studies
Study Athletic performance Multiplicity of Outcome Selected for
meta-Analysis
Botton etal. [29] Bilateral strength Isokinetic knee extension
Knee extension 1RM
Unilateral strength Isokinetic knee extension
Knee extension 1RM
Ramirez-Campillo
etal. [40]
Bilateral strength Knee extension 1RM
Knee exion 1RM
Unilateral Jump Countermovement jump
Horizontal crossover triple jumps
Horizontal triple jumps
Squat jump
Bilateral Jump Countermovement jump
Squat jump
Horizontal jump
Horizontal triple jumps
Stern etal. [25] Unilateral Jump Drop jump
Countermovement jump
Horizontal jump
Bilateral Jump Drop jump
Countermovement jump
Speed 10m
30m
Gonzalo-Skok. [41] Unilateral jump Countermovement jump
Lateral jump
Horizontal jump
Change of Direction 10m shuttle
20m shuttle
25m shuttle
Speed 10m
20m
25m
Javier Nunez et al.
[42]
Change of Direction 5m–90º–5m
5m shuttle
Biology of Sport, Vol. 39 No3, 2022
489
Effects of unilateral vs. bilateral training on performance
we selected asingle most relevant effect size to deal with the mul-
tiplicity according to adecision rule as following: 1) the most used
test in included studies; 2) the right leg test; 3) in accordance with
training practice: a) multiple joint movements>Single joint move-
ments; b) Dynamic movements>isometric movements/isokinetic
movements; 4) shorter links with the true athletic performance: Jump-
ing performance: single jump>multiple jumps; change of direction:
preference to the greater angle and shorter sprint distance.
RESULTS
Search results
The initial search resulted in 6365records. After excluding 2791
duplicates, 3574 studies were selected to be screened by title and
abstract. When applying the inclusion criteria, 3498 papers were
subsequently excluded. The remaining 76articles were read in full,
with 62rejected because they were acute studies (n=21), not
including both unilateral and bilateral training groups (n=19), re-
views (n=10), participants with an age outside the criteria bound-
aries (n=5), not English (n=3), not peer-reviewed (n=3), mul-
tiple publication (n=1). This left 14studies to be included in the
nal analysis.
Risk of bias assessment
In accordance with the modied scale[34, 35], the scores of 14in-
cluded articles ranged from 12 to 18, the mean score was 15.
Therefore, the overall quality was moderate. The majority of the
studies were rated as moderate (n=9studies[24, 27, 29–32, 40,
42, 43]), and 5studies were rated as good[25, 26, 28, 41, 44].
13studies had allocated the participants in arandom manner. Most
of the studies got high score in item 4and 7, but only 28.6% of the
studies used acontrol group. 78.6% of the studies did not clearly
describe the inclusion criteria and training experience of the partici-
pants (Table3).
Studies’ Characteristics
The total number of subjects was 392 (Table4) and the participants’
age ranged from 16 to 26 years. Nine studies solely included
males[24–26, 28, 32, 40–42, 44]. Three studies included both
males and females[27, 31, 43], and 2 studies included females
only[29, 30]. All male athletes[24–26, 28, 32, 40, 41] were from
team sports, including soccer[25, 32, 40, 41], basketball[24, 26]
and rugby[28]. Twelve studies had training frequency of twice per
week[24–32, 40–42], and two studies had performed training
3times per week[43, 44]. The training duration ranged from 5to
12weeks.
The training modalities can be categorized into resistance training
and jump training. Among them, 8studies purely utilized resistance
training as the intervention modality[24, 26, 28, 29, 41–44], 1study
purely utilized jump training[30], 5studies combined resistance
with jumping training exercises together[25, 27, 31, 32, 40]. 3kinds
of muscle actions were applied among the included studies, 11stud-
ies used concentric overload training; 2studies used eccentric over-
load training[41, 42]; 1study used isokinetic training[43].
The unilateral multi-joint resistance exercises included step
up[26,31], Bulgarian split squat[24, 25, 28, 31, 32], single leg
deadlift[44], lunge and eccentric lunge[31, 41, 42]. Unilateral
single-joint resistance exercises included single knee extension and
exion[27, 29, 40, 43]. Bilateral multi-joint resistance exercises
included back squat [24–26, 28], deadlift [44], eccentric
squat[41, 42] and front squat[31]. Single-joint exercises included
knee extension and exion[27, 29, 40, 43]. Jump exercises in-
cluded squat jump, broad jump, countermovement jump and differ-
ent variants of box jumps.
The intensity of the resistance training ranged from 45–90% 1RM,
and the volume, which was equal in both groups, ranged from 3to
15repetitions. The intensity of jumps was maximum without exter-
nal loading, with repetitions and sets ranging from 3to 15 and 1to8,
respectively.
The outcome indicators of the 14included studies were various.
The strength-related tests included: 1) 1RM test of back
squat[25, 26, 28, 31, 44], Bulgarian split squat[25, 28, 31, 44],
step up[26], knee extension[29, 40], knee exion[40] and leg
press[27]; 2) maximal power test of 10s Wingate[30], Margaria-
kalamen stair-climb test[31], isokinetic knee extension[43], back
squat and Bulgarian split squat[24]. The jump-related tests (unilat-
eral and bilateral) included squat jump and countermovement
jump[24, 27, 30, 31, 40–42], broad jump [25, 41], drop
jump[25, 27, 40], 3steps and 5 steps jump [30, 40]. The
COD-related tests included the 50° test[26], the Vtest[24], 180°
shuttle[24, 41, 42], the pro-agility test[28], the Ttest[32, 40],
the 505 test[25] and the Illinois test[32]. The speed-related tests
included 10m sprint running[25, 28, 32, 41], 20m sprint run-
ning[26, 41], 25m[24, 41] and 40m sprint running[25, 28].
After dealing with the multiplicity, the nal included outcomes for
analysis were showed in table 2.
TABLE 3. The results of risk of bias assessment
Studies Items
1 2 3 4 5 6 7 8 9 10 Score
Bogdanis etal.[27] 1 2 2 2 0 0 2 2 2 0 13
Appleby etal.[26] 1 1 2 2 2 2 2 2 2 2 18
Gonzalo-Skok etal.[24] 1 2 1 2 0 0 2 0 2 2 12
Speirs etal.[28] 2 2 2 2 2 0 2 2 2 2 18
Botton etal.[29] 1 0 2 2 0 2 2 1 2 2 14
Fisher etal.[32] 1 2 2 2 1 0 2 0 2 2 14
Makaruk etal.[30] 1 2 2 2 2 2 2 0 2 0 15
McCurdy etal.[31] 1 2 2 2 2 0 2 2 2 0 15
Taniguchi etal.[43] 1 0 0 2 1 2 2 1 2 1 13
Ramirez-Campillo etal.[40] 1 2 2 2 1 0 2 1 2 2 15
Stern etal.[25] 1 2 2 2 2 0 2 1 2 2 16
Krajewski etal.[44] 2 2 2 2 2 0 2 1 2 2 17
Javier Nunez et al.[42] 1 1 0 1 2 0 2 2 2 1 12
Gonzalo-Skok etal.[41] 2 2 2 2 2 0 2 2 2 2 18
490
Kai-Fang Liao et al.
TABLE 4. The characteristics of the included studies
Study
Participants Training Program Outcome Measure
Identity
Training
Experience
(years)
Age
(years) Gender N
Frequency
(times/
week)
Weeks Sets Reps Intensity
(%1RM)
Unilateral
Exercises
Bilateral
exercises Performance test
Bogdanis
etal.[27]
College
students None 19.8
±2.9 F/M 15 2 6 2–3
3–4
10
3–8 60–90%
6 Jumps U
KE U
KF U
6 Jumps
B
KE B
KF B
CMJ U
CMJ B
Iso-LP BMP
Iso-LP UMP
DJ B
Gonzalo-Skok
etal.[24]
Basketball
Players >2 16.9
±2.1 M 22 2 6 3 >10%
MP
80–100%
MP Bul squat Back
squat
Back squat MP
Bul Squat MP
CMJ B
25m Sprint
Vtest
15m shuttle
Botton
etal.[29]
Healthy
active
females
None 24.8
±1.4 F43 2 12 2–4 5–15 5–15RM KE U KE B
KE B1RM
KE U1RM
Iso-KE BMP
Iso-KE UMP
Makaruk
etal.[30]
College
students None 20.6
±1.3 M 54 2 12 2–8 4–15 5 Jumps U 5 Jumps
B
10sWingate
SJ U
SJ B
Ramirez-Campillo
etal.[40]
Soccer
Players >2 17.6
±0.5 M 18 2 8 1–2
3
3–5
10 70%
4 Jumps U
KE U
KF B
4 jumps
B
KE B
KF B
KE B1RM
KF B1RM
Ttest
CMJ B
CMJ U
SJ B
SJ U
H3J
HCMJ
H3MJ
Fisher etal.
[32]
Soccer
Players >2 19.8
±1.5 M 20 2 6 1–3
3
6–10
6 80%
5 Jumps U
Bul squat
5 Jumps
B
Back
squat
T test
Illinois test
10m sprint
Appleby
etal.[26]
Basketball
Players >2 22.4
±4.1 M 33 2 6 6–8 4–8 45–85% Step up Back
squat
Back squat 1RM
Step up 1RM
20m sprint
Speirs
etal.[28]
Rugby
Players >1 18.1
±0.5 M 18 2 5 4 3–6 >75% Bul squat Back
squat
Bul squat 1RM
40m sprint
Pro test
Krajewski
etal.[44]
Healthy
active
males
no 26.4
±5.5 M 15 3 4 3 4–6 60–90% Bul squat
Deadlift U
CMJ U
Back
squat
Deadlift
CMJ
Back squat 1RM
Bul squat 1RM
Javier Nunez
etal.[42]
Healthy
active
males
-22.8
±2.9 M 27 2 6 4 7 0.05–0.1
kg/m2ECC lunge ECC
Squat
CMJ
5m shuttle
5m 90º 5m
10m sprint
Gonzalo-Skok
etal.[41]
Football
Players 1–3 20.5
±2 M 48 2 8 6 6–10 0.27
kg/m2
6 ECC
Lunges
ECC
squat
CMJ
CMJ U
HCMJ U
Lateral jump U
25m sprint
20m sprint
10m sprint
10m shuttle
20m shuttle
25m shuttle
Biology of Sport, Vol. 39 No3, 2022
491
Effects of unilateral vs. bilateral training on performance
Study
Participants Training Program Outcome Measure
Identity
Training
Experience
(years)
Age
(years) Gender N
Frequency
(times/
week)
Weeks Sets Reps Intensity
(%1RM)
Unilateral
Exercises
Bilateral
exercises Performance test
Taniguchi
etal.[43]
College
students None 20
±1.1 F/M 18 3 6 3 6 KE Isok U KE Isok
B
Isok-KE U
Isok-KE B
Stern
etal.[25]
Soccer
Players >2 17.6
±1.2 M 23 2 6 4
4
6
3–6 75–85% Bul squat
3Jumps U
Back
squat
3Jumps
B
Back squat 1RM
CMJ B
CMJ U
Broad jump B
Broad jump U
Drop jump B
Drop jump U
10m sprint
30m sprint
505
McCurdy
etal.[31]
College
students None 20.7
±2.6 F/M 38 2 8 3
3–6
5–15
5–15 50–87%
2 Jumps U
Bul squat
2 Jumps
B
Back
squat
Back squat 1RM
Bul squat 1RM
CMJ B
CMJ U
F: female; M: male; U: unilateral; B: bilateral; KE: knee extension; KF: knee exion; Bul squat: Bulgarian split squat; Iso: isometric;
Isok: isokinetic; LP: leg press; CMJ: countermovement jump; MP: maximum power; DJ: drop jump; SJ: squat jump; H3J: horizontal
3jumps; HCMJ: horizontal countermovement jump; ECC: eccentric
TABLE 4. Continue
Quantitative analysis
The performance tests in included studies can be categorized into
6subgroups, namely: unilateral strength, bilateral strength, unilat-
eral jump, bilateral jump, COD and speed performance tests. After
sensitive analysis, the I2<50% in all subgroups suggested anon-
signicant heterogeneity, and the xed effects models were used to
aggregate the SMDs. The total heterogeneity (Chi2= 70.25,
p=0.03; I2=39%) of 44 effects was medium. The overall effect
size was non-signicant and classied as trivial effect (ES=0.09;
p=0.15; 95% CI: -0.03, 0.22) (Figure2). The heterogeneity for
inter subgroup differences was large (I2=86.1%).
Unilateral strength performance
After dealing with the multiplicity (Table2), 9outcomes were se-
lected for meta-analysis. The heterogeneity was low (Chi2=10.30,
p=0.24; I2=22%). In xed effects model, overall effect was not
signicant (p=0.07). Pooled effect size and 95% CI were 0.26
(-0.03, 0.55) and classied as asmall effect.
Bilateral strength performance
After dealing with the multiplicity, 9outcomes were selected to do
meta-analysis. The heterogeneity test was not statistically signicant
(Chi2=6.77, p =0.56; I2=0%). In xed effects model, overall
effect was signicant (p=0.004). Pooled effect size and 95%CI
were -0.43 (-0.71, -0.14) and classied as asmall effect.
Unilateral jump performance
After dealing with the multiplicity, 6outcomes were selected for me-
ta-analysis. The original heterogeneity was high (I2=60%), after
alternated sensitive analysis, one study with eccentric overload train-
ing different from others was excluded, and the adjusted heterogene-
ity was low (Chi2=4.85, p =0.30, I2 =18%). In xed effects
model, the pooled effect size and 95% CI was 0.89 (0.52, 1.26) with
statistical signicance (p<0.0001) and classied as alarge effect.
Bilateral jump performance
After dealing with the multiplicity, 8outcomes were selected for
meta-analysis. The heterogeneity was not statistically signicant
(Chi2=1.68, p=0.98; I2=0%), in xed effects model, the pooled
effect size and 95%CI was -0.12 (-0.40, 0.15) with non-signicance
(p=0.79) and classied as atrivial effect.
COD performance
After dealing with the multiplicity, 7outcomes were selected for
meta-analysis. The heterogeneity was not statistically signicant
(Chi2=5.83, p=0.44; I2=0%). The pooled effect size and 95%CI
was 0.31 (-0.01, 0.63) with non-signicance (p=0.06) and clas-
sied as asmall effect.
Speed performance
After dealing with the multiplicity, 6outcomes were selected for
meta-analysis. The heterogeneity was not statistically signicant
492
Kai-Fang Liao et al.
FIG. 2. Forest plot comparing the effects of bilateral and unilateral exercises training on athletic performance. Bul s: Bulgaria split
squat; LP: leg press; ISO:isokinetic; MP:Maximum power; KE: knee extension; U: unilateral; B:bilateral; L: left; R: right; CMJ:
countermovement jump; SJ: squat jump; Tmod: Tmodied test.
Biology of Sport, Vol. 39 No3, 2022
493
Effects of unilateral vs. bilateral training on performance
(Chi2=2.38, p=0.67; I2=0%). in xed effects model, the pooled
effect size and 95%CI was -0.12 (-0.46, 0.21) with non-signicance
(p=0.82) and classied as atrivial effect.
DISCUSSION
This systematic review with meta-analysis aimed to compare the
training effects of unilateral vs. bilateral resistance training on mea-
sures of athletic performance. The results showed that: 1) both uni-
lateral and bilateral resistance training improve athletic performance;
2) with respect to all performance measures, overall effect showed
no difference between unilateral resistance training and bilateral
resistance training; 3) based on the subgroup analysis, the unilat-
eral resistance training showed alarge effect on improving unilat-
eral jumping performance, but non-signicant difference on improv-
ing unilateral strength performance in comparison to bilateral
exercises. In contrast, bilateral resistance training exhibited asmall
effect on improving bilateral strength performance, but non-signicant
differences on improving bilateral jumping performance in compari-
son to unilateral training. Finally, COD and speed performance im-
provement showed no differences between unilateral and bilateral
resistance training; however COD, which involves unilateral propuslive
force production, did show asmall effect in favor of unilateral resis-
tance training.
Strength performance
The outcome of bilateral strength performance subgroup supported
our hypothesis that bilateral resistance training followed the training
principle of specicity, which demonstrated asmall effect (ES=-0.43)
on improving bilateral strength performance in comparison with uni-
lateral resistance training. It is clear that the muscle cross-sectional
area and neuromuscular adaptation are the main factors for develop-
ing maximum strength[45]. There is evidence that unilateral and
bilateral strength traning had asimilar impact on muscle mass[46],
girth[29] and cross-sectional area[47]. However, Helme etal.,[48]
found that almost 15% of the load was placed on the rear leg during
the Bulgarian split squat. It could be inferred that the rear leg might
be contributed to the concentric phase, which means that the lead
leg might decrease force development. Anderson et al.,[49] and
McCurdy et al[50] found that the bilateral squat activated the knee-
joint agonists (e.g., quadriceps) greater than the Bulgarian split squat,
while the Bulgarian split squat showed greater antagonists such as
the hamstrings, hip abductors and trunk musculature. Cumulatively,
it could be speculated that bilateral strength training may produce
greater knee agonist neuromuscular adaptation owing to higher load
other than the muscle growth.
Four studies in this systematic review showed that the bilateral
group mitigated the bilateral force decit (BLD), but unilateral resis-
tance training increased the BLD in measures of knee extension,
isometric leg press and squat with one leg and both legs, respec-
tively[24, 27, 29, 43]. BLD is described as the sum of the maximum
forces exerted by the left and right limbs unilaterally as being
greater than the simultaneous exertion of both limbs bilaterally[51].
More recently, Bishop etal. found that acombination of bilateral and
unilateral resistance training had superior effects on unilateral jump
performance compared to bilateral. Consequently, it stands to reason
that if greater improvements in unilateral jump performance are
evident (compared to bilateral), it will have an effect on the BLD
outcome (remembering that the BLD is aproduct of both unilateral
and bilateral scores, presented as asingle ratio number)[52]. In line
with the denition and the ndings by Bishop etal., the results of
these 4studies might be explained by the reason of specicity. Sim-
ply put, that unilateral resistance training is likely to enhance unilat-
eral performance measures more than bilateral performance mea-
sures, and vice versa. Given the inherent differences in study design
of these 4studies (e.g.different levels of stability requirements in the
chosen methods but still with similar effects on the BLD), it is spec-
ulated that neuromuscular factors induced by the mechanism of BLD
may be more of acontributing factor to changes than stability.
The results of unilateral strength performance subgroup indicated
that unilateral resistance training had asmall effect (ES=0.26) on
improving unilateral strength. However, there were not statistically
signicant between-group differences. Our nding did not correspond
well with included studies which found clear evidence that unilat-
eral resistance training was better for improving unilateral strength
performance[24, 26]. The possible explanation was that these stud-
ies did not adjust each intervention group’s mean changes between
pre and post tests for analysis as in the current study, which may
enlarge the probability to make the false inference due to the selec-
tion effect. For example, McCurdy etal.,[31] found that 8weeks’
unilateral resistance training was more effective in improving 1RM
of aBulgarian split squat than the bilateral resistance training. How-
ever, after adjusting the pretest difference, both groups exhibited
similar effects on the 1RM of Bulgarian split squat. In addition, the
unilateral exercises may stimulate the stabilizing muscles in the core
and knee to agreater extent than bilateral exercises[50, 53], which
are likely to be benecial for improving stability and force transference
through the kinetic chain. However, the greater agonist neuromus-
cular adapation of bilateral resistance training may counteract the
superiority of stability and specicity of unilateral exercises in unilat-
eral strength tests. Therefore, it is up to coaches to determine what
the athlete needs and program accordingly.
Jump performance
The larger improvement in unilateral jump performance induced by
unilateral rather than bilateral resistance training corresponded with
the training principle of specicity. Five studies were included in the
unilateral jump subgroups, all of which applied jumping exercises as
intervention modalities[25, 27, 30, 31, 40] and found that the
effect of unilateral jumping training were better (ES: 0.24–1.66) than
bilateral jumping training. These ndings might result from the dif-
ferences in stability and neuromuscular adaptation of agonists. In
unilateral jumping, the smaller supporting surface triggers ahigher
494
Kai-Fang Liao et al.
push relative higher load, which may result in greater range of motion
and deeper squat depth for producing greater force, subsequently
increase the contact time. Thus, it is conceivable that the unilateral
jump group might be unable to adapt in the shorter exertion time to
develop similar force as the bilateral jump group in the measure of
bilateral jump test[58]. In contrast, bilateral jump exercises similar
with the test modality may have apriority of familiarization and be
adapted to exert force in shorter time.
Change of direction (COD) and speed performance
COD speed and sprint have been suggested to be largely unilateral
exercises in previous research[12, 59]. However, our results indi-
cated that the effect size in the speed subgroup showed no difference
between unilateral and bialteral resistance training, similar to recent
ndings[33]. However, COD was likely to be in favor of unilateral
resistance training with asmall effect.
Four of the 7studies in the COD subgroup that adopted both the
Bulgarian split squat versus back squat as the modalities of resistance
intervention[24, 25, 28, 32] supported use of the Bulgarian split
squat over the back squat. McCurdy etal. found that the Bulgarian
split squat could produce greater activation in glutes maximus and
hamstring compared with back squat[50]. Another 2studies in this
subgroup used eccentric overload as the intervention modality also
supported the unilateral group as being the more favourable method
on enhancing COD performance. Chaabene etal.,[60] obtained
amoderate to very large correlation (r=0.45–0.89) between ec-
centric strength and the COD performance through a systematic
review. The concentric force of push, the eccentric force during de-
celerating, and the ground contact time are the key factors affecting
the ability to COD effectively[61,62]. Alarger eccentric braking
force can shorten the deceleration time, increase the elastic force of
the muscles and connective tissue, and generate agreater subsequent
push force, which collectively results in a shorter ground contact
time, greater acceleration, and thereby improving overall COD per-
formance[62]. Accordingly, the unilateral exercises such as Bulgar-
ian split squat emphasizes the use of eccentric force in apredomi-
nantly unilateral manner, which could explain the greater improvement
on COD performance.
The current data also demonstrated that bilateral resistance train-
ing had atrivial effect on improving linear speed performance. Vari-
ous factors account for the improvement of speed performance.
Empirical evidence shows that the rate of force development in short
time and large propulsive forces in initial acceration stage are the
main attributes of speed performance. Wilkau etal.[63] found that
the contact time, vertical force and peak propulsive forces (r=–0.64,
r=0.57 and r=0.66, respectively) contributed most to the step
velocity. In ameta analysis of 15studies, Seitz etal.[64] reported
astrong relationship between squat strength and sprint performance
(r=-0.77; p=0.001). In the current study, the strength subgroup
showed that bilateral exercise training had alarger effect in improv-
ing bilateral strength with statistical signicance. Collectively, the
co-activation in the stabilizing muscle groups (e.g. hamstrings), and
helps maintain the head, arms, trunk and lower limbs in the same
direction during both landing and taking off. As aresult, the stabil-
ity of the lower limbs are improved, and the absorption of the reac-
tion force of the lower limbs decreases during the landing phase[54].
Bogdanis etal.[27] found that unilateral jumping training was more
effective at improving unilateral squat jump performance and
RFD0–50ms and RFD0–100ms (Rate of force development) in unilat-
eral isometric seated leg extension in comparison to bilateral jump
training. Turki etal. [55] also found that the electromyographic
level of the vastus intermedius and gastrocnemius in unilateral body
weight vertical jump was 10–25% higher than that in bilateral body
weight vertical jumps. According to the force-velocity relationship,
unilateral jumping without asecond limb to ‘spread the load’ needs
to push agreater relative load with alonger time to take off. It could
be inferred that unilateral jumping might make the muscles generate
more force, and more strongly stimulate the muscles such as the
extensors of the ankle, knee and hip to result in greater neuromus-
cular adaptation when considering individual limbs. It should be
noted that 1study not included for aggregating effect size after
sensitive analysis purely used eccentric overload resistance exer-
cises as intervention modalities and found bilateral training group
improved unilateral countermovment jump better than the unilat-
eral exercise group[41]. Although speculative, the results may be
attributed to the eccentric force improvement in bilateral group which
help to stablize the posture during testing. In addition, the training
status of subjects will also have an effect on results. For example, it
is plausible that high-level athletes might exhibit less improvements
in bilateral jump performance (compared to non-athletes), as there
is arguably areduced ‘window of opportunity’ for enahnced adapa-
tation[56]. However, it could be suggested that improvements in
unilateral jump performance may be more likely for all, owing to the
use of unilateral resistance training methods being employed less
frequently. This concept is partly supported by the ndings of Bish-
op etal.[53] who showed sigicant improvements in unilateral jump
height (but not bilateral), after an 8-week combined bilateral and
unilateral strength training programme. Collectively, these evidences
may explain why unilateral resistance training had alarger effect on
improving unilateral jumping performance in comparison with bilat-
eral resistance training.
The overall effect size of bilateral jumping subgroup was trivial in
favor of bilateral exercises training, but the value was not statisti-
cally signicant. The results may be the contribution of the mechanism
of bilateral decit and differences in kinetics[57]. When both legs
contract simultaneously, the nerve activation of the left and right
interhemisphere may be mutually inhibited, and there was alack of
bilateral activation while training unilaterally, so it would be ex-
pected that muscles would not achieve maximum voluntary contrac-
tion in unilateral jump group. Furthermore, the contact time for bi-
lateral and unilateral jumps (CMJ) was 178–190ms and >250ms
respectively[21]. As above explained, the unilateral jump needs to
Biology of Sport, Vol. 39 No3, 2022
495
Effects of unilateral vs. bilateral training on performance
improvement of bilateral strength may explain the trivial effect in
favor of bilateral exercises training on improving speed.
It should be noted that the overall effect of each training method
(unilateral vs bilateral) on COD and speed were not statistically sig-
nicant. This could be attributed to the studies’ small sample size,
the lack of specicity of training methods with regards to the tests
measures, and/or the low transference of jump and resistance train-
ing adaptations to sprint and COD performance measures [65].
However, Hopkins etal.[66] stated the smallest worthwhile enhance-
ment (SWE) by 10% will help the athletes to win the game. SWE
was calculated by the coefcient of the variablility (CV) of within-
athlete’s performance from competition to competition. With respect
to short running events, it was found SWE was even lower to
0.3–0.5%[67]. This indicated that although the effect sizes were
rather small or not signicance between unilateral vs. bilateral resis-
tance training, when inter-athlete variability was counted, the small
difference in improving performance caused by the exercise selection
were within arange that was meaningful for elite athletes. Thus,
these ndings still have signicant implications for understanding
how to choose unilateral or bilateral resistance exercise for optimiz-
ing speed performance.
It should be acknowleged that some limitations exist in our paper.
Firstly, the lower number (<10) of studies in subgroup analyses
means it was not possible to do further meta-regression analysis.
Thus, as is often the case in science, more research is likely needed
to provide greater clarity between the two training methods. Sec-
ondly, all included studies for this meta-analysis applied lower body
exercises as training intervention, thus, whether the present ndings
based on lower limbs studies can be applied to the upper limbs re-
mains unclear. Future research should attempt to investigate the
difference between bilateral and unilateral exercises training for the
upper limbs. Thirdly, the included participants’ age ranged 16 to
26years, which means that our results may not be extrapolated to
those participants with age out of this range. But it still can provide
references for these practitioners.
CONCLUSIONS
This study set out to establish the different effects between unilateral
and bilateral resistance training on strength, jump, linear and COD
speed performance. The most interesting ndings was that unilateral
resistance training was superior for enhancing unilateral jump perfor-
mance, and bilateral resistance training was superior for enhancing
bilateral strength performance. But both had no signicant difference
in enhancing unilateral strength, bilateral jump, linear and COD speed
performance. The results suggest that both kinds of training should
likely be considered by practitioners. Specically, bilateral exercises
should be chosen for enhancing bilateral strength performance, and
unilateral exercises should be chosen for enhancing unilateral jump
performance. With regards to other performance outcomes (e.g., lin-
ear and COD speed), practitioners can probably choose any kind of
exercises based on their interest and the availability of facilities.
Funding
This work was supported by the Winter Olympics Founda-
tion[2018FF0300901] and China Institute of Sport Science Basic
Foundation[Basic 17–30] grants to Yong-ming Li.
Conict of interest
The authors declare that they have no competing interests.
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... Unilateral strength training can increase jumping performance compared to bilateral training (Liao et al., 2022). Several studies by Bogdanis et al., (2019);Makaruk et al., (2011);Stern et al., (2020) also stated that unilateral training was more effective in increasing jumping performance (Makaruk et al., 2011;Bogdanis et al., 2019;Stern et al., 2020). ...
... This is because unilateral training can increase muscle strength more than bilateral exercises (Gonzalo-Skok, Tous-Fajardo, Suarez-Arrones, et al., 2017). This also relates to the principle of specific training (Liao et al., 2022). The specific training principle is crucial for specific adaptation to the planned performance improvement targets (Brearley and Bishop, 2019). ...
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This study aimed to determine the effect of 10 weeks of unilateral training on asymmetry and jumping performance in sub-elite badminton athletes. 23 out of 41 badminton athletes who met the inclusion criteria were taken as samples in this study. Selected samples will be given unilateral exercise interventions in the form of Swiss ball hamstring curl exercises and single leg bridge for ten weeks with a frequency of exercise 3 times a week. Data were collected two times before the intervention (pretest) was given and after the intervention (posttest). The measurement uses the Norbord test to determine the condition of hamstring asymmetry and the Counter Movement Jump (CMJ) jump test to determine jump height. The results showed that there was a significant decrease in the percentage of hamstring asymmetry p ≤ 0.001 (Pretest: 20.26±10.25 % to Posttest: 9.20±3.51 %) and has a large effect size with a Cohen's d value of 1.443, and an increase in jump height p ≤ 0.001 (Pretest: 33.06±4.93 cm to Posttest: 35.17±4.54 cm) and has a medium effect size with a Cohen's d value of 0.447. The conclusion is that 30 unilateral exercises for ten weeks can improve hamstring asymmetry above 10% and increase jumping performance in badminton athletes.
... A convincing body of empirical evidence also supports the specificity of the type of exercise with regard to the range of motion, speed, posture, and movement patterns. Furthermore, we use a lower external load than in the case of BIL exercises, which can translate into lumbar load [15]. BIL exercises are usually used in micro-cycles in which one championship match is played. ...
... Given the structure of the exercises in the UNI mesocycle, they may stimulate stabilizing muscles of the core and knee joint to a greater extent than BIL exercises, which may be beneficial for improving stability and strength transfer through the kinematic chain. However, the greater neuromuscular adaptation of agonists with BIL training may counteract the stability and evasiveness of UNI exercises [15,83]. We assume that this effect may be further increased by extending the eccentric phase, which may be an additional argument for the use of this periodization. ...
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The purpose of the investigation was to determine the influence of a four-week unilateral (UNI) and bilateral (BIL) resistance training program on peak torque and peak power of the lower limbs in soccer players. Background: We evaluated the effects of a 3:1 step load training program using UNI and BIL forms of exercises on the level of peak torque and peak power of the knee joint extensors and flexors. Methods: The study included 16 division I soccer players having the highest number of matches played in the first round of the season. The motor tests included isokinetic evaluation of peak torque and peak power of the extensors and flexors of the knee joint. Results: The results showed that both types of training sessions were equally effective. Only in terms of power during knee flexion, unilateral training contributed to improvement, whereas bilateral training did not. Conclusions: The use of periodization using a step load progression based on an extended eccentric phase of the movement during the preseason period in combination with UNI training may increase peak torque and peak power of knee flexors and extensors in soccer players.
... Conventional resistance training with dumbbells can be improved to duplicate the unique biomechanics of an athlete's selected sport, which maximizes athletes' performance. In addition, it permits unilateral training, which helps balance out asymmetries and enhances general stability, which are both essential for explosive movements on track and field [15,16]. ...
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Background: In sports and for physical fitness capacity explosive strength is of great significance, as the players regularly require high-intensity actions as fast as possible. Objective: to compare the effects of resistance training with resistance bands and resistance training with dumbbells on the explosive strength performance of male track & field athletes Materials & Methods: A randomized control trial study design was used for this study, the participants were male track & field athletes, aged above 18 years and above actively involved in any competitive sports. a total of n=60 participants were equally divided into three groups i.e., Resistance band group (RBG), Dumbbells Resistance Group (DRG), and control group (CG). The vertical jump and standing board jump tests were performed to evaluate the explosive power at the baseline and after the 8th-week intervention. Results: There was a significant difference among the groups when comparing the vertical jump (p<0.001) and standing board tests (p<0.001). The group that received resistance band and dumbbell training showed significant (p<0.05) better results than the control group in the vertical jump test. There was no significant difference between resistance band and dumbbell (p=0.215) training after the 8-week intervention. When comparing the standing board jump test, the resistance band group was significantly improved (p<0.05) than the group that received Dumbbell training and the control group. But no significant difference (p=0.234) between the control and dumbbell groups. Conclusion: Resistance band training is a great option for increasing explosive strength. Although dumbbells are useful in strength training, bands make it easier to lift heavy weights quickly. Keywords: athletes; dumbbells; physical performance; resistance band training; standing broad test; vertical jump test
... Swings, snatches, and throws involve rapid and forceful movement, which is necessary to develop explosive strength. Kabaddi players who regularly incorporate these explosive motions into their training regimen might increase their ability to generate short bursts of power during tackles, raids, and defensive manoeuvres throughout the game (Liao et al., 2022). ...
Article
Background: Hypertension, a prevalent cardiovascular condition, is linked to autonomic nervous system dysregulation, often evidenced by reduced heart rate variability (HRV). Yoga, particularly Uddiyana Bandha, may influence autonomic control and improve HRV, thus offering potential benefits for hypertension management. Background: Hypertension, a prevalent cardiovascular condition, is linked to autonomic nervous system dysregulation, often evidenced by reduced heart rate variability (HRV). Yoga, particularly Uddiyana Bandha, may influence autonomic control and improve HRV, thus offering potential benefits for hypertension management. Methods: This randomized controlled study included 60 hypertensive patients aged 40-60 years. Participants were randomized into an intervention group practicing Uddiyana Bandha (n=30) and a control group with no intervention (n=30). The outcome parameters were time and frequency domain HRV variables including standard deviation of the NN interval (SDNN), and the square root of the mean squared differences of successive NN intervals (RMSSD), high-frequency (HF) and low-frequency (LF) components in normalized units (n.u), and LF/HF ratio, measured before and immediately after the intervention. The intervention group performed three rounds of Uddiyana Bandha under supervision, while the control group rested quietly for an equivalent duration. Results: The Uddiyana Bandha group demonstrated significant (p<0.05) improvements in HRV parameters post-intervention compared to the control group. Mean RR interval, SDNN and RMSSD increased immediately after Uddiyana Bandha practice. The HF component (n.u) increased, while the LF component (n.u) and LF/HF ratio decreased (p<0.05), indicating enhanced parasympathetic activity. No significant changes were observed in the control group. Conclusion: Uddiyana Bandha practice results in immediate notable effects on HRV in hypertensive patients, showing better autonomic balance and cardiovascular performance. These results suggest Uddiyana Bandha as a possible non-pharmacological strategy for hypertension management. Future studies with larger sample sizes and longer durations are needed to support these results and explore long-term effects.
... Swings, snatches, and throws involve rapid and forceful movement, which is necessary to develop explosive strength. Kabaddi players who regularly incorporate these explosive motions into their training regimen might increase their ability to generate short bursts of power during tackles, raids, and defensive manoeuvres throughout the game (Liao et al., 2022). ...
Article
Full-text available
Kabaddi demands high bio-motor fitness and physiological robustness in players. The Bulgarian Bag, known for its dynamic training potential, offers multi-planar movements to enhance strength, endurance, and coordination. However, its impact on Kabaddi players still needs to be explored. To assess the effects of Bulgarian Bag training (BBT) on bio-motor fitness, physiological, hematological, and performance measures in young adult Kabaddi players. A total of 30 participants were randomly assigned to either the BBT Group (BBTG) (n = 15; age = 20.73 ± 1.83 years; weight = 72.56 ± 7.27 kg; height = 175.20 ± 6.03 cm) or the active Control Group (CG) (n = 15; age = 20.80 ± 1.69 years; weight = 71.86 ± 4.75 kg; height = 171.46 ± 6.06 cm). The training intervention lasted 12 weeks and was conducted during the in-season period. All outcome parameters tests were conducted before and after the intervention, including agility (AG), explosive strength (ES), shoulder strength (SS), muscular strength (MS), resting heart rate (RHR), VO2max, red blood cells (RBC), white blood cells (WBC), hemoglobin (HG), and playing ability (PA). The ANCOVA analysis revealed significant between-group differences in all physical fitness measures at post-test. Specifically, the BBTG showed significant improvements in AG, ES, SS, MS, RHR, VO2Max, RBC, WBC, HG, and PA (d = 0.75 to 3.28; Δ0.50% to 16.37%). Moreover, the BBTG group significantly reduced resting heart rate (d = 0.75; Δ-3.31%). In contrast, no significant changes were reported in the Control Group (CG) between pre- and post-tests (d = 0.00 to 0.78; Δ-0.08% to 4.59%). Integrating BBTG into the training program of young adult male Kabaddi players yielded beneficial effects across multiple parameters of bio-motor fitness, physiological, hematological, and playing ability. The findings reveal the potential of BBTG as a valuable training method for enhancing Kabaddi performance and overall athletic condition-ing.
... their preference and available equipment. Given the marginal differences in performance outcomes, adherence and effort are likely to be far more important variables than the uni-or bilateral status of an exercise, and we correspondingly arrive upon a similar conclusion as the previously mentioned authors(Liao et al. 2022). ...
Article
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This investigation assessed the effects of bilateral and unilateral strength training on strength and power development, as measured by uni- and bi-lateral 3-repetition maximum leg press and vertical jump tests, respectively. 14 college-aged participants were randomized into either bilateral or unilateral training conditions. The participants engaged in biweekly strength training sessions for a period of 4 weeks, with strength and power pre- and post-testing in the weeks immediately before and after the training protocol, respectively. There was no significant (F = 0.98, p = 0.33) main effect of condition for vertical jump height. There was no significant (F = 2.48, p = 0.13) main effect of condition for 1RM bilateral strength. There was no significant (F = 1.86, p = 0.19) main effect of condition for 1RM unilateral strength between both right and left legs. While our investigation yielded no significant results, there may be reason to further investigate this area of research, due to professionals wanting to develop weight training protocols for the athletic and/or injured populations to facilitate greater improvements in performance and/or quicker recovery from injuries.
... Unilateral squatting has been reported to have a greater peak ground reaction force than bilateral squatting [19]. In addition, a meta-analysis summarizing the effects of unilateral versus bilateral training [20] reported that jumping performance is more effective with unilateral training than with bilateral training. Although CMJ is expected to exert less muscle power than is exerted in the 6s peak power test, the correlation coefficient between the two is stronger than 0.7, so we do not need to consider the effect of bilateral hypofunction in this study. ...
... Unilateral and bilateral training tactics have arisen as a result of the explosive action of the modified neuromuscular system. Both of these exercises are equally effective in promoting strong growth and increased strength (Hung et al., 2019;Liao et al., 2022). These two exercises when combined can have a huge impact (Núñez et al., 2018). ...
Article
Full-text available
Study purpose. The study was aimed to identify exercise techniques used to improve the physical condition of volleyball players through literature studies. Materials and methods. A systematic review of these previous studies was conducted. We studied articles published between 2014 and 2023 that explained how to prepare volleyball players to have better physical condition. Scopus, Web of Science, Google Scholar, and PubMed were used for the electronic search. We collected all the articles that discussed how to improve physical performance through exercise. Results. To improve the physical condition of volleyball players, 50 publications used exercise techniques, which were categorized based on the physical condition that was evaluated and repaired. The following techniques are some of the ones that can be used: Neuromuscular, unilateral and bilateral, ballistic, plyometric exercises, combined weight and plyometric, mixed training with optimal load, COD & plyometric complex, strength, combined strength, eccentric trainings, repetitive sprint, resistant/non-resistant sprint, resistance training, exercises with elastic band, core training, combined core training; small-sided games training, aerobic interval training, blood flow restriction, intermittent training, and anaerobic speed endurance. Conclusions. Following a thorough analysis, a number of training regimens were found to be effective in enhancing volleyball players’ physical attributes, including muscular strength, aerobic and anaerobic endurance, speed and acceleration, explosive power, flexibility, agility, and balance.
... The IRFD measurement was performed using a single-leg, while the VJs were measured using a bilateral leg. A previous study has suggested that a single-leg VJ had a longer movement duration than a double-leg VJ [16] and that movements on the frontal plane significantly influence performance in single-leg VJ [17]. These characteristics of the single-leg VJ suggest that it is a more technically complex than the double-leg VJ and is thus more likely to reflect anything other than the sagittal leg-extension explosive force. ...
Article
Full-text available
Purpose This study aimed to elucidate characteristics of explosive force-production capabilities represented by multi-phase rate of force developments (IRFDs) during isometric single-leg press (ISLP) through investigating relationships with countermovement (CMJ) and rebound continuous jump (RJ) performances. Methods Two-hundred-and-thirty male athletes performed ISLP, CMJ with an arm swing (CMJAS), and RJ with an arm swing (RJAS). IRFDs were measured during ISLP using a custom-built dynamometer, while CMJAS and RJAS were measured on force platforms. The IRFDs were obtained as rates of increase in force across 50 ms in the interval from the onset to 250 ms. Jump height (JH) was obtained from CMJAS, while RJAS provided JH, contact time (CT), and reactive strength index (RSI) values. Results All IRFDs were correlated with CMJAS-JH (ρ = 0.20–0.45, p ≤ 0.003), RJAS-JH (ρ = 0.22–0.46, p ≤ 0.001), RJAS-RSI (ρ = 0.29–0.48, p < 0.001) and RJAS-CT (ρ = −0.29 to −0.25, p ≤ 0.025). When an influence of peak force was considered using partial rank correlation analysis, IRFDs during onset to 150 ms were correlated with CMJAS-JH (ρxy/z = 0.19–0.36, p ≤ 0.004), IRFDs during onset to 100 ms were correlated with RJAS-JH and RJAS-RSI (ρxy/z = 0.33–0.36, p < 0.001), and IRFD during onset to 50 ms was only correlated with RJAS-CT (ρxy/z = −0.23, p < 0.001). Conclusion The early phase (onset to 150 ms) IRFDs measured using ISLP enabled the assessment of multiple aspects of leg-extension strength characteristics that differ from maximal strength; these insights might be useful in the assessment of the athletes’ leg-extension strength capabilities.
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The aim of this study was to determine the effects of pre-season strength training on bilateral and unilateral jump performance and the bilateral deficit (BLD) in Premier League academy soccer players. Fourteen male academy players (age: 16.36 ± 0.50 years; body mass: 73.45 ± 8.43 kg; height: 1.80 ± 0.09 m) performed one upper body and one lower body strength session per week, for eight weeks. Bilateral and unilateral countermovement jumps (CMJ) were assessed pre and post-intervention with jump height, mean force, reactive strength index modified (RSI-Mod) and time to takeoff reported for each test. In addition, the BLD was also computed for each metric. Results showed meaningful and significant increases in unilateral jump height on the left (g = 1.00; p = 0.02) and right (g = 0.77; p = 0.039) legs, and for the BLD for jump height (g = 0.67; p = 0.046). No other significant changes in jump performance were evident. Despite numerous non-significant changes in jump performance at the group level, individual analysis showed numerous players exhibited percentage improvements greater than the variance in the test (as depicted by the coefficient of variation), across all metrics. Thus, the results illustrate that a single lower body strength session per week is enough to elicit positive improvements in jump performance for all metrics when assessed on an individual basis, but only for unilateral jump height, when assessed at the group level. Significant increases were also evident for jump height BLD. Despite the majority of players exhibiting improvements in jump performance, some small reductions in performance were also evident. Given the requirement for soccer players to be competent during unilateral movement patterns, an increase in the BLD may be favourable, as it shows greater improvements in unilateral test scores compared to bilateral.
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Purpose:To examine the effects of ‘operationally-relevant’ loads on postural stability and to determine the effects of unilateral and bilateral strength training programs on postural stability in healthy, recruit-aged males. Methods: 15 participants were randomly assigned to either a unilateral (UL; n=7) or bilateral (BL; n=8) strength training group, which performed strength training three times a week for four weeks. Participants completed the following pre-test and post-test assessments: one repetition maximum in bilateral (1RM-BL) and unilateral (1RM-UL) stance positions and bilateral and unilateral balance tasks with eyes open and eyes closed. Balance tasks were performed over three loading conditions: body weight, 50% body weight, 70% body weight. Sample entropy (SE) and root mean square (RMS) were calculated from the center of pressures (COP) collected during each balance assessment. Results: The UL strength training group showed significant improvement following training in both 1RMUL (p<.01) and 1RM-BL (p<.01). The BL strength training group only showed significant improvement in 1RM-BL (p=.01). There was a significant main effect of load on RMS (p<.05) across all balance tasks with RMS increasing with increasing load. SE was found to decrease with increasing load in the unilateral eyes open and bilateral stance tasks. Conclusions: Significant increases in strength (~10-29%) were observed, however increased strength alone is not enough to mitigate the effects of load carriage on postural control, even when training is performed in stance positions that are posturally challenging. Therefore, ‘operationally-relevant’ loads negatively impact postural stability in novice load carriers when assessing nonlinear measures.
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Background: The ability to perform a rapid change of direction (COD) is a critical skill in numerous court- and field-based sports. The aim of this review is to investigate the effect of different physical training forms on COD performance. Methods: A systematic review of the literature was undertaken using the following databases: PubMed, SPORTDiscus and Google Scholar. Studies were eligible if they met the following criteria: (1) a COD test measuring performance before and after the training intervention, with specific description of the test in terms of length and number of changes in a direction with specified angles, (2) involve training intervention like plyometric, strength, sprint, specific COD training, or a combination of these training forms targeting the lower extremities, (3) the study had to state training background in terms of which sport they participated in and their competitive level and a detailed methodological description. Non-English articles were excluded. Percentage difference and effect sizes were calculated in order to compare the effects of different training interventions. Results: A range of studies performing plyometrics, strength, sprint, specific COD training, training with post-activation potentiation or a combination of these training forms were examined. The percentage of change and effect size (ES) were calculated. Seventy-four studies met the inclusion criteria, comprising 132 experimental groups and 1652 unique subjects. The review revealed no clear consensus on which training form is optimal to develop COD performance. All training forms resulted in an increase in performance from almost no ES to large ES. Conclusions: The results of the study indicate that COD ability is a specific skill, whereas the COD task, the sports require determines which training form is the most effective to develop COD ability. Training targeting improvement in COD performance should address the duration of the training in line with which energy system is utilized. The complexity of the COD task with respect to the individual athlete must be considered. Consequently, the number of changes in direction and the angles of the task are relevant when organizing training.
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Studies that examine the effects of inter-limb asymmetry on measures of physical performance are scarce, especially in adult female populations. The aim of the present study was to establish the relationship between inter-limb asymmetry and speed and change-of-direction speed (CODS) in adult female soccer players. Sixteen adult players performed a preseason test battery consisting of unilateral countermovement jump (CMJ), unilateral drop jump (DJ), 10 m, 30 m, and 505 CODS tests. Inter-limb asymmetry was calculated using a standard percentage difference equation for jump and CODS tests, and Pearson's r correlations were used to establish a relationship between asymmetry and physical performance as well as asymmetry scores themselves across tests. Jump-height asymmetry from the CMJ (8.65%) and DJ (9.16%) tests were significantly greater (p < 0.05) than asymmetry during the 505 test (2.39%). CMJ-height asymmetry showed no association with speed or CODS. However, DJ asymmetries were significantly associated with slower 10 m (r = 0.52; p < 0.05), 30 m (r = 0.58; p < 0.05), and 505 (r = 0.52-0.66; p < 0.05) performance. No significant relationships were present between asymmetry scores across tests. These findings suggest that the DJ is a useful test for detecting existent between-limb asymmetry that might in turn be detrimental to speed and CODS performance. Furthermore, the lack of relationships present between different asymmetry scores indicates the individual nature of asymmetry and precludes the use of a single test for the assessment of inter-limb differences.
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Train to perform at the highest level with the lowest risk of injury. The second edition of New Functional Training for Sports produces the best results on the court, field, track, and mat, not just in the weight room. Michael Boyle, one of the world’s leading sport performance coaches, presents the concepts, methods, exercises, and programs that maximize athletes’ movements in competition. A series of functional assessments help in determining the design of a specific plan for each athlete. Self-reinforcing progressions in exercises for the lower body, core, upper body, and ultimately total body give athletes the balance, proprioception, stability, strength, and power they require for excelling in their sports. Sample programs assist in the customization process and cover each aspect of preparation for physical performance. Boyle also draws on the latest research and his wealth of experience to offer programming advice and recommendations on foam rolling, stretching, and dynamic warm-ups. New Functional Training for Sports goes beyond traditional exercise descriptions and explanations, incorporating full-color, high-definition composites of foundational movements as well as online access to video demonstrations, commentary, and analysis of key exercises. New Functional Training for Sports is a refined and expanded version of Boyle’s original work published more than a decade previously. This edition offers the most current functional training expertise to apply to your specific purposes.
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Successful sprinting depends on covering a specific distance in the shortest time possible. Although external forces are key to sprinting, less consideration is given to the duration of force application, which influences the impulse generated. This study explored relationships between sprint performance measures and external kinetic and kinematic performance indicators. Data were collected from the initial acceleration, transition and maximal velocity phases of a sprint. Relationships were analysed between sprint performance measures and kinetic and kinematic variables. A commonality regression analysis was used to explore how independent variables contributed to multiple-regression models for the sprint phases. Propulsive forces play a key role in sprint performance during the initial acceleration (r = 0.95 ± 0.03) and transition phases (r = 0.74 ± 0.19), while braking duration plays an important role during the transition phase (r = −0.72 ± 0.20). Contact time, vertical force and peak propulsive forces represented key determinants (r = −0.64 ± 0.31, r = 0.57 ± 0.35 and r = 0.66 ± 0.30, respectively) of maximal velocity phase performance, with peak propulsive force providing the largest unique contribution to the regression model for step velocity. These results clarified the role of force and time variables on sprinting performance.
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The purpose of the study was to determine the unilateral nature of the rear foot elevated split squat (RFESS). Specifically, the production of force by the rear leg was examined to better understand its role, if any, toward successful completion of the exercise. Male volunteers were recruited, (n = 26, age = 23.8 ±4.6 years, mass = 88.1 8 ±10.7kg, height = 1.79±0.1m), who were recreationally trained and engaged in a structured strength and conditioning program including both bilateral and unilateral exercise and had at least two years supervised training experience. Subjects participated in an incremental five repetition maximum protocol, following familiarisation. Kinetic data was recorded via two independent force plates, one integral to the floor and the second mounted on top of solid weightlifting blocks. Kinematic data was captured through three-dimensional motion analysis. A total of 715 repetitions were analysed, the mean contribution of the lead foot to total vertical 16 force production was 84.36 ±3.6%. An almost certainly small positive correlation (rho 17 = 0.25, CI 0.18, 0.33), was found between percentage of force produced by the lead foot, with increasing exercise intensity. A most likely trivial, non-significant correlation 19 (rho =-0.01, CI-0.09,0.06) with rear foot force production, representing the mass of the rear leg. Data from this study does not indicate that the rear foot contributes to the kinetic demands of the exercise and therefore suggests that the RFESS is a valid unilateral exercise. The paper is now available ahead of print from JSCR here: https://journals.lww.com/nsca-jscr/Abstract/9000/Is_the_Rear_Foot_Elevated_Split_Squat_Unilateral_.94276.aspx
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The aim of the present study was to compare the effects of bilateral and unilateral-biased strength and power training programs on measures of physical performance in male youth soccer players. Twenty-three elite youth players (age: 17.6  1.2 years) were randomly assigned to either a unilateral (n = 11) or a bilateral (n = 12) group, who completed a strength and power intervention, twice per week for 6-weeks. The unilateral group completed rear foot elevated split squats (RFESS), single leg countermovement jumps (SLCMJ), single leg drop jumps (SLDJ) and single leg broad jumps (SLBJ). The bilateral group intervention performed back squats, countermovement jumps (CMJ), drop jumps (DJ) and broad jumps (BJ). A 2 x 2 repeated measures ANOVA showed no between-group differences. However, within-group differences were evident. The bilateral training group showed significant (p < 0.05) improvements in back squat strength (d = 1.27; %Δ = 26.01), RFESS strength (d = 1.64; %Δ = 23.34), BJ (d = 0.76; %Δ = 5.12), 10 m (d =-1.17; %Δ = 4.29) and 30 m (d =-0.88; %Δ = 2.10) performance. The unilateral group showed significant (p < 0.05) improvements in RFESS strength (d = 1.40; %Δ = 33.29), SLCMJ on the left leg (d = 0.76; %Δ = 9.84), SLBJ on the left leg (d = 0.97; %Δ = 6.50), 10 m (d =-1.50; %Δ = 5.20), and 505 on the right leg (d =-0.78; %Δ = 2.80). Standardised mean differences showed that bilateral training favoured improvements in back squat strength and unilateral training favoured improvements in RFESS strength, SLDJ on the right leg and 505 on the right leg. These results show that although both training interventions demonstrated trivial to large improvements in physical performance, the notion of training specificity was evident with unilateral training showing greater improvements in unilateral test measures.
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Appleby, BB, Cormack, SJ, and Newton, RU. Unilateral and bilateral lower-body resistance training does not transfer equally to sprint and change of direction performance. J Strength Cond Res XX(X): 000-000, 2018-Given maximal strength can be developed using bilateral or unilateral resistance training, the purpose of this study was to determine the magnitude of transfer of unilateral or bilateral resistance training to sprint and change of direction (COD) performance. Thirty-three trained participants (average training age = 5.4 ± 2.9 years and 1 repetition maximum [1RM] 90° squat = 177.6 ± 26.7 kg) completed either a bilateral group (BIL, n = 13), unilateral (UNI, n = 10), or comparison (COM, n = 10) 18-week randomized controlled training design. Training involved 2 lower-body, volume-load-matched resistance sessions per week (6-8 sets × 4-8 reps at 45-88% 1RM), differing only in the prescription of a bilateral (squat) or unilateral (step-up) resistance exercise. Strength was assessed through 1RM squat and step-up, in addition to 20-m sprint and a customized 50° COD test. The effect size statistic ± 90% confidence limit (ES ± CL) was calculated to examine the magnitude of difference within and between groups at each time point. BIL and UNI groups improved their trained and nontrained strength exercise with an unclear difference in adaptation of squat strength (ES = -0.34 + 0.55). Both groups improved 20-m sprint (ES: BIL = -0.38 ± 0.49 and UNI = -0.31 ± 0.31); however, the difference between the groups was unclear (ES = 0.07 ± 0.58). Although both groups had meaningful improvements in COD performance, bilateral resistance training had a greater transfer to COD performance than unilateral resistance training (between-groups ES = 0.59 ± 0.64). Both bilateral and unilateral training improved maximal lower-body strength and sprint acceleration. However, the BIL group demonstrated superior improvements in COD performance. This finding potentially highlights the importance of targeting the underlying physiological stimulus that drives adaptation and not exercise selection based on movement specificity of the target performance.