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Strength training is as effective as stretching for improving range of motion: A systematic review and meta-analysis.

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Background: Range of motion (ROM) is an important feature of sports performance and health. Stretching is usually prescribed to improve promote ROM gains, but evidence has suggested that strength training (ST) also improves ROM. However, it is unclear if its efficacy is comparable to stretching. Objective: To perform a systematic review and meta-analysis of randomized controlled trials (RCTs) assessing the effects of ST and stretching on ROM. Protocol: INPLASY: 10.37766/inplasy2020.9.0098. Data sources: Cochrane Library, EBSCO, PubMed, Scielo, Scopus, and Web of Science were consulted in early October 2020, followed by search within reference lists and consultation of four experts. No constraints on language or year. Eligibility criteria (PICOS): (P) humans of any sex, age, health or training status; (I) ST interventions; (C) stretching interventions (O) ROM; (S) supervised RCTs. Data extraction and synthesis: Independently conducted by multiple authors. Quality of evidence assessed using GRADE; risk-of-bias assessed with RoB 2. Results: Eleven articles (n = 452 participants) were included. Pooled data showed no differences between ST and stretching on ROM (ES = -022; 95% CI = -055 to 012; p = 0206). Sub-group analyses based on RoB, active vs. passive ROM, and specific movement-per-joint analyses for hip flexion and knee extension showed no between-protocol differences in ROM gains. Conclusion: ST and stretching were not different in improving ROM, regardless of the diversity of protocols and populations. Barring specific contra-indications, people who do not respond well or do not adhere to stretching protocols can change to ST programs, and vice-versa.
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Strength training is as effective as stretching for improving range of motion: A systematic
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review and meta-analysis.
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José Afonso, Ph.D. 1*, Rodrigo Ramirez-Campillo, Ph.D. 2,3, João Moscão4, Tiago Rocha,
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M.Sc. 5, Rodrigo Zacca, Ph.D. 1,6,7, Alexandre Martins, B.Sc. 1, André A. Milheiro, M.Sc.1,
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João Ferreira, B.Sc. 8, Hugo Sarmento, Ph.D. 9, Filipe Manuel Clemente, Ph.D. 10,11
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1 Centre for Research, Education, Innovation and Intervention in Sport, Faculty of Sport of the University of Porto.
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Rua Dr. Plácido Costa, 91, 4200-450 Porto, Portugal.
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2 Department of Physical Activity Sciences. Universidad de Los Lagos. Lord Cochrane 1046, Osorno, Chile.
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3 Centro de Investigación en Fisiología del Ejercicio. Facultad de Ciencias. Universidad Mayor. San Pio X, 2422,
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Providencia, Santiago, Chile.
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4 REP Exercise Institute. Rua Manuel Francisco 75-A 2º C 2645-558 Alcabideche, Portugal.
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5 Polytechnic of Leiria, Rua General Norton de Matos, Apartado 4133, 2411-901 Leiria, Portugal.
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6 Porto Biomechanics Laboratory (LABIOMEP), University of Porto, Rua Dr. Plácido Costa, 91, 4200-450 Porto,
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Portugal.
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7 Coordination for the Improvement of Higher Educational Personnel Foundation (CAPES), Ministry of Education
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of Brazil, Brasília, Brazil.
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8 Superior Institute of Engineering of Porto, Polytechnic Institute of Porto. Rua Dr. António Bernardino de
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Almeida, 431, 4249-015 Porto, Portugal.
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9 Faculty of Sport Sciences and Physical Education, University of Coimbra, 3040-256, Coimbra, Portugal.
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10 Escola Superior Desporto e Lazer, Instituto Politécnico de Viana do Castelo, Rua Escola Industrial e Comercial
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de Nun’Álvares, 4900-347, Viana do Castelo, Portugal.
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11 Instituto de Telecomunicações, Department of Covilhã, 1049-001, Lisboa, Portugal.
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*Corresponding author: José Afonso | jneves@fade.up.pt.
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Summary box
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What is already known?
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Stretching is effective for improving in range of motion (ROM), but promising findings
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have suggested that strength training also generates ROM gains.
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What are the new findings?
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Strength training seems to be as effective as stretching in generating ROM gains.
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In contradiction with existing guidelines, stretching is not strictly necessary for improving
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ROM, as strength may provide an equally valid alternative.
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These findings were consistent across studies, regardless of the characteristics of the
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population and of the specificities of strength training and stretching programs.
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ABSTRACT
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Background: Range of motion (ROM) is an important feature of sports performance and
45
health. Stretching is usually prescribed to improve promote ROM gains, but evidence has
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suggested that strength training (ST) also improves ROM. However, it is unclear if its efficacy
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is comparable to stretching. Objective: To perform a systematic review and meta-analysis of
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randomized controlled trials (RCTs) assessing the effects of ST and stretching on ROM.
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Protocol: INPLASY: 10.37766/inplasy2020.9.0098. Data sources: Cochrane Library,
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EBSCO, PubMed, Scielo, Scopus, and Web of Science were consulted in early October 2020,
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followed by search within reference lists and consultation of four experts. No constraints on
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language or year. Eligibility criteria (PICOS): (P) humans of any sex, age, health or training
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status; (I) ST interventions; (C) stretching interventions (O) ROM; (S) supervised RCTs. Data
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extraction and synthesis: Independently conducted by multiple authors. Quality of evidence
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assessed using GRADE; risk-of-bias assessed with RoB 2. Results: Eleven articles (n = 452
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participants) were included. Pooled data showed no differences between ST and stretching on
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ROM (ES = -0×22; 95% CI = -0×55 to 0×12; p = 0×206). Sub-group analyses based on RoB,
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active vs. passive ROM, and specific movement-per-joint analyses for hip flexion and knee
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extension showed no between-protocol differences in ROM gains. Conclusion: ST and
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stretching were not different in improving ROM, regardless of the diversity of protocols and
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populations. Barring specific contra-indications, people who do not respond well or do not
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adhere to stretching protocols can change to ST programs, and vice-versa.
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KEYWORDS: systematic review; meta-analysis; strength training; flexibility; stretching;
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range of motion.
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Introduction
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Improving range of motion (ROM) is a core goal for the general population,[1] as well
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as in clinical contexts,[2] such as when treating acute respiratory failure,[3] plexiform
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neurofibromas,[4] and total hip replacement.[5] Unsurprisingly, ROM gains are also relevant
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in different sports,[6] such as basketball, baseball and rowing,[7-9] among others. ROM is
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improved through increased stretch tolerance, augmented fascicle length and changes in
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pennation angle,[10] as well as reduced tonic reflex activity.[11] Stretching is usually
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prescribed to increase ROM in sports,[12, 13] clinical settings such as chronic low back
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pain,[14] rheumatoid arthritis,[15] and exercise performance in general.[16] Stretching
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techniques include static (active or passive), dynamic, or proprioceptive neuromuscular
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facilitation (PNF), all of which can improve ROM.[1, 17-20]
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However, reduced ROM and muscle weakness are deeply associated.[21-23] Therefore,
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although strength training (ST) primarily addresses muscle weakness through methods such as
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resistance training or similar protocols, it has been shown to increase ROM in athletic
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populations,[24, 25] as well as in healthy elderly people[26] and women with chronic
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nonspecific neck pain.[27] ST focused on concentric and eccentric contractions has been
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shown to increase fascicle length. [28-30] Better agonist-antagonist co-activation[31],
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reciprocal inhibition,[32] and adjusted stretch-shortening cycles[33] may also explain why ST
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is a suitable method for improving ROM.
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Nevertheless, studies comparing the effects of ST and stretching in ROM have
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presented conflicting evidence,[34, 35] and many have small sample sizes.[36, 37] Developing
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a systematic review and meta-analysis (SRMA) may help summarize this conflicting evidence
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and increase statistical power, thus providing clearer guidance for interventions.[38] Therefore,
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the aim of this SRMA was to compare the effects of supervised and randomized ST versus
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stretching protocols on ROM in participants of any health and training status.
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METHODS
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Protocol and registration
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The methods and protocol registration were preregistered prior to conducting the
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review: INPLASY, no.202090098, DOI: 10.37766/inplasy2020.9.0098.
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Eligibility criteria
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Articles were eligible for inclusion if published in peer-reviewed journals, with no
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restrictions in language or publication date. The Preferred Reporting Items for Systematic
104
Reviews and Meta-Analyses (PRISMA) guidelines were adopted.[39] Participants,
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interventions, comparators, outcomes, and study design (P.I.C.O.S.) were established as
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follows: (i) participants with no restriction regarding health, sex, age, or training status; (ii) ST
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interventions supervised by a certified professional, using resistance training or similar
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protocols; (iii) comparators were supervised groups performing any form of stretching (iv)
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outcomes were ROM assessed in any joint; (v) randomized controlled trials (RCTs). RCTs
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reduce bias and better balance participant features between the groups,[38] and are important
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for the advancement of sports science.[40] There were no limitations regarding intervention
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length.
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Reviews, letters to editors, trial registrations, proposals for protocols, editorials, book
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chapters, and conference abstracts were excluded. Exclusion criteria based on P.I.C.O.S.: (i)
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research with non-human animals; (ii) non-ST protocols or ST interventions combined with
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other methods (e.g., endurance); unsupervised interventions; (iii) stretching or ST + stretching
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interventions combined with other training methods (e.g., endurance); protocols without
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stretching; unsupervised interventions; (iv) studies not reporting ROM; (v) non-randomized
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interventions.
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Information sources and search
122
Six databases were used to search and retrieve the articles in early October 2020:
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Cochrane Library, EBSCO, PubMed (including MEDLINE), Scielo, Scopus, and Web of
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Science (Core Collection). Boolean operators were applied to search the article title, abstract
125
and/or keywords: (“strength training” OR “resistance training” OR “weight training” OR
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“plyometric*” OR calisthenics”) AND (“flexibility” OR “stretching”) AND “range of
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motion” AND “random*”. Specificities of each search engine: (i) in Cochrane Library, items
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were limited to trials, including articles but excluding protocols, reviews, editorials and similar
129
publications; (ii) in EBSCO, the search was limited to articles in scientific, peer-reviewed
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journals (iii) in PubMed, the search was limited to title or abstract; publications were limited
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to RCTs and clinical trials, excluding books and documents, meta-analyses, reviews and
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systematic reviews; (iv) in Scielo, Scopus and Web of Science, the publication type was limited
133
to article; and (v) in Web of Science, “topic” is the term used to refer to title, abstract and
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keywords.
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An additional search within the reference lists of the included records was conducted.
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The list of articles and inclusion criteria were then sent to four experts to suggest additional
137
references. The search strategy and consulted databases were not provided in this process to
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avoid biasing the experts’ searches. More detailed information is available as supplementary
139
material.
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Search strategy
142
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Here, we provide the specific example of search conducted in PubMed:
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((("strength training"[Title/Abstract] OR "resistance training"[Title/Abstract] OR
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"weight training"[Title/Abstract] OR "plyometric*"[Title/Abstract] OR
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"calisthenics"[Title/Abstract]) AND (“flexibility”[Title/Abstract] OR
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“stretching”[Title/Abstract])) AND (“range of motion”[Title/Abstract])) AND
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(“random*”[Title/Abstract]).
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After this search, the filters RCT and Clinical Trial were applied.
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Study selection
151
J.A. and F.M.C. each conducted the initial search and selection stages independently,
152
and then compared result to ensure accuracy. J.F. and T.R. independently reviewed the process
153
to detect potential errors. When necessary, re-analysis was conducted until a consensus was
154
achieved.
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Data collection process
157
J.A., F.M.C., A.A.M. and J.F. extracted data, while J.M., T.R., R.Z. and A.M.
158
independently revised the process. Data for the meta-analysis was extracted by JA and
159
independently verified by A.A.M. and R.R.C. Data is available for sharing.
160
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Data items
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Data items: (i) Population: subjects, health status, sex/gender, age, training status,
163
selection of subjects; (ii) Intervention and comparators: study length in weeks, weekly
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frequency of the sessions, weekly training volume in minutes, session duration in minutes,
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number of exercises per session, number of sets and repetitions per exercise, load (e.g., %
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1RM), full vs. partial ROM, supervision ratio; in the comparators, modality of stretching
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applied was also considered; adherence rates were considered a posteriori; (iii) ROM testing:
168
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joints and actions, body positions (e.g., standing, supine), mode of testing (i.e., active, passive,
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both), pre-testing warm-up, timing (e.g., pre- and post-intervention, intermediate assessments),
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results considered for a given test (e.g., average of three measures), data reliability, number of
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testers and instructions provided during testing; (iv) Outcomes: changes in ROM for
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intervention and comparator groups; (vi) funding and conflicts of interest.
173
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Risk of bias in individual studies
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Risk of bias (RoB) in individual studies was assessed using the Cochrane risk-of-bias
176
tool for randomized trials (RoB 2).[41] J.A. and A.M. independently completed RoB analysis,
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which was reviewed by F.M.C. Where inconsistencies emerged, the original articles were re-
178
analyzed until a consensus was achieved.
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Summary measures
181
Meta-analysis was conducted when ≥3 studies were available.[42] Pre- and post-
182
intervention means and standard deviations (SDs) for dependent variables were used after
183
being converted to Hedges’s g effect size (ES).[42] When means and SDs were not available,
184
they were calculated from 95% confidence intervals (CIs) or standard error of mean (SEM),
185
using Cochrane’s RevMan Calculator for Microsoft Excel.[43] When ROM data from different
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groups (e.g. men and women) or different joints (e.g. knee and ankle) was pooled, weighted
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formulas were applied.[38]
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Synthesis of results
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The inverse variance random-effects model for meta-analyses was used to allocate a
191
proportionate weight to trials based on the size of their individual standard errors,[44] and
192
accounting for heterogeneity across studies.[45] The ESs were presented alongside 95% CIs
193
10
and interpreted using the following thresholds:[46] <0×2, trivial; 0×2–0×6, small; >0×6–1×2,
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moderate; >1×2–2×0, large; >2×0–4×0, very large; >4×0, extremely large. Heterogeneity was
195
assessed using the I2 statistic, with values of <25%, 25-75%, and >75% considered to represent
196
low, moderate, and high levels of heterogeneity, respectively.[47]
197
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Risk of bias across studies
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Publication bias was explored using the extended Egger’s test,[48] with p<0×05
200
implying bias. To adjust for publication bias, a sensitivity analysis was conducted using the
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trim and fill method,[49] with L0 as the default estimator for the number of missing studies.[50]
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Moderator analyses
204
Using a random-effects model and independent computed single factor analysis,
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potential sources of heterogeneity likely to influence the effects of training interventions were
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selected, including i) ROM type (i.e., passive vs active), ii) studies RoB in randomization and
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iii) studies RoB in measurement of the outcome.[51] These analyses were decided post-
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protocol registration.
209
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All analyses were carried out using the Comprehensive Meta-Analysis program
211
(version 2; Biostat, Englewood, NJ, USA). Statistical significance was set at p≤0×05. Data for
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the meta-analysis was extracted by JA and independently verified by A.A.M. and R.R.C.
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Quality and confidence in findings
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Although not planned in the registered protocol, we decided to abide by the Grading of
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Recommendations Assessment, Development, and Evaluation (GRADE),[52] which addresses
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five dimensions that can downgrade studies when assessing the quality of evidence in RCTs.
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RoB, inconsistency (through heterogeneity measures), and publication bias were addressed
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above and were considered a priori. Directness was guaranteed by design, as no surrogates
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were used for any of the pre-defined P.I.C.O. dimensions. Imprecision was assessed on the
221
basis of 95% CIs.
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RESULTS
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Study selection
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Initial search returned 194 results (52 in Cochrane Library, 11 in EBSCO, 11 in
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PubMed, 9 in Scielo, 88 in Scopus, and 23 in Web of Science). After removal of duplicates,
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121 records remained. Screening the titles and abstracts for eligibility criteria resulted in the
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exclusion of 106 articles: 26 were not original research articles (e.g., trial registrations,
230
reviews), 24 were out of scope, 48 did not have the required intervention or comparators, five
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did not assess ROM, two were non-randomized and one was unsupervised. Fifteen articles
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were eligible for full-text analysis. One article did not have the required intervention,[53] and
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two did not have the needed comparators.[54, 55] In one article, the ST and stretching groups
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performed a 20-30 minutes warm-up following an unspecified protocol.[56] In another, the
235
intervention and comparator were unsupervised[57], and in one the stretching group was
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unsupervised[58]. Finally, in one article, 75% of the training sessions were unsupervised.[59]
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Therefore, eight articles were included at this stage.[24, 34-37, 60-62]
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A manual search within the reference lists of the included articles revealed five
239
additional potentially fitting articles. Two lacked the intervention group required[63, 64] and
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two were non-randomized.[65, 66] One article met the inclusion criteria.[67] Four experts
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revised the inclusion criteria and the list of articles and suggested eight articles based on their
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titles and abstracts. Six were excluded: interventions were multicomponent;[68, 69]
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comparators performed no exercise;[70, 71] out of scope;[72] and unsupervised stretching
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group.[73] Two articles were included,[74, 75] increasing the list to eleven articles,[24, 34-37,
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60-62, 67, 74, 75] with 452 participants eligible for meta-analysis (Figure 1).
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247
248
13
249
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Figure 1. Flowchart describing the study selection process.
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Records identified through
database search
(n = 194)
Records after duplicates removed
(n = 121)
Records screened
(n = 121)
Records excluded
(n = 106)
Full-text articles assessed for
eligibility
(n = 15)
(n = 7)
3 articles did not have the required intervention
and/or comparators.
3 had at least one group of interest performing the
intervention unsupervised.
1 had an undisclosed warm-up protocol that was
Studies included in qualitative synthesis
(n = 8+1+2 = 11)
Studies included in quantitative synthesis
(n = 11)
Additional records fitting inclusion criteria
identified after search within the reference
lists of the included articles
(n = 1)
Additional records fitting inclusion criteria
recommended by four external experts from
two countries and three different institutions
(n = 2)
14
254
Study characteristics and results
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The data items can be found in Table 1. The study of Wyon, Smith [62] required
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consultation of a previous paper[76] to provide essential information. Samples ranged from
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27[37] to 124 subjects,[34] including: trained participants,[24, 36, 61, 62] healthy sedentary
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participants,[35, 60, 67] sedentary and trained participants,[75] workers with chronic neck
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pain,[37] participants with fibromyalgia,[74] and elderly participants with difficulties in at least
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one of four tasks: transferring, bathing, toileting, and walking.[34] Seven articles included only
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women[36, 62, 67, 74] or predominantly women,[34, 35, 37] three investigated only men[24,
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75] or predominantly men,[60] and one article had a balanced mixture of men and women.[61]
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Interventions lasted between five[60] and 16 weeks[67]. Minimum weekly training frequency
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was two sessions[37, 74] and maximum was five.[62] Six articles provided insufficient
265
information concerning session duration.[35, 36, 61, 62, 67, 75] Ten articles vaguely defined
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training load for the ST and stretching groups,[24, 34, 37, 60, 61, 74, 75] or for stretching
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groups.[35, 36, 67] Six articles did not report on using partial or full ROM during ST
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exercises.[24, 34, 36, 37, 61, 67] Different stretching modalities were implemented: static
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active,[35, 37, 60, 67, 74, 75] dynamic,[34, 36] dynamic with a 10-second hold,[24] static
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active in one group and static passive in another,[62] and a combination of dynamic, static
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active, and PNF.[61]
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Hip joint ROM was assessed in seven articles,[24, 34, 36, 60-62, 67] knee ROM in
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five,[34-36, 60, 75] shoulder ROM in four,[34, 36, 60, 74] elbow and trunk ROM in two,[34,
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36] and cervical spine[37] and the ankle joint ROM in one article.[34] In one article, active
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ROM (AROM) was tested for the trunk, while passive ROM (PROM) was tested for the other
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joints.[34] In one article, PROM was tested for goniometric assessments and AROM for hip
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flexion.[36] In another, AROM was assessed for the shoulder and PROM for the hip and
278
15
knee.[60] Three articles only assessed PROM[35, 61, 75] and four AROM,[24, 37, 67, 74]
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while one assessed both for the same joint.[62]
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Table 1. Characteristics of included randomized trials.
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Article
Population and common
program features
Strength training group
Comparator group(s)*
ROM testing
Qualitative
results for ROM
Task-Specific
Resistance
Training to
Improve the
Ability of
Activities of
Daily Living
Impaired Older
Adults to Rise
from a Bed and
from a Chair.[34]
Subjects: 161.
Health status: Elderly people
dependent on help for
performing at least one of four
tasks: transferring,
bathing, toileting and walking.
Gender: ST: 84% women;
STRE: 88% women.
Age: ST: 82·0±6·4; STRE:
82·4±6·3.
Training status: Not
participating in regular
strenuous exercise.
Selection of subjects: Seven
congregate housing facilities.
Length (weeks): 12.
Weekly sessions: 3.
Adherence: average 81% of
the sessions.
Funding: National Institute on
Aging (NIA) Claude Pepper
Older Adults Independence
Center (Grant AG0 8808 and
NIA Grant AG10542), the
Department of Veterans
Affairs Rehabilitation
Research and Development,
and the AARP-Andrus
Foundation.
Conflicts of interest: N/A.
n = 81 (60 completed).
Weekly volume (minutes):
180.
Session duration in
minutes: 60.
No. exercises per session:
16.
No. sets and repetitions:
1*7-8 based on maximum
target of 9 (bed-rise
tasks). 1*5 based on
maximum target of 6
(chair-rise tasks).
Load: Unclear. Loads
were incremented if
subjects were not feeling
challenged enough.
Full or partial ROM:
N/A.
Supervision ratio: 1:1.
STRE n = 80 (64 completed).
Weekly volume (minutes): 180.
Session duration in minutes: 60.
No. exercises per session: N/A.
No. sets and repetitions: N/A.
Stretching modality: Dynamic.
Load: Low-intensity, but without a
specified criterion.
Full or partial ROM: N/A.
Supervision ratio: One supervisor
per group, but group size was N/A.
Joints and actions: Elbow
(extension), shoulder
(abduction), hip (flexion and
abduction), knee (flexion and
extension), ankle
(dorsiflexion) and trunk
(flexion, extension, lateral
flexion).
Positions: Supine (elbow,
shoulder, hip, knee and
ankle); standing (lumbar
spine).
Mode: Active for trunk,
passive for the other joints.
Warm-up: N/A.
Timing: Baseline, 6 weeks,
12 weeks.
Results considered in the
tests: N/A.
Data reliability: ICCs of 0·65
to 0·86 for trunk measures.
Unreported for other
measures.
No. testers: N/A.
Instructions during testing:
N/A.
The ST group had
significant
improvements in
all ROM
measures, except
hip flexion and
abduction.
The STRE group
had no significant
change in any of
the ROM values.
Stretching versus
strength training
in lengthened
position in
subjects with
tight hamstring
Subjects: 45 undergraduate
students.
Health status: 30º knee
extension deficit with the hip
at 90º when in supine
position. No injuries in the
n = 15.
Weekly volume (minutes):
N/A.
Session duration in
minutes: N/A.
STRE n = 15.
Weekly volume (minutes): N/A.
Session duration in minutes: N/A.
No. exercises per session: 1.
No. sets and repetitions: 4*30’’.
Stretching modality: Static.
Joints and actions: Knee
(extension).
Positions: Sitting.
Mode: Passive.
Warm-up: Yes, but unclear
with regard to specifications.
None of the
groups
experienced
significant
improvements in
ROM.
17
muscles: A
randomized
controlled
trial.[35]
lower limbs and no lower
back pain.
Gender: 39 women, 6 men.
Age: 21·33±1·76 years (ST);
22·60±1·84 years (STRE).
Training status: No
participation in ST or STRE
programs in the previous year.
Selection of subjects:
announcements posted at the
University.
Length (weeks): 8.
Weekly sessions: 3.
Adherence: N/A.
Funding: N/A.
Conflicts of interest: N/A.
No. exercises per session:
1.
No. sets and repetitions:
3*12.
Load: 60% of 1RM.
Full or partial ROM:
Partial.
Supervision ratio: N/A.
Load: Unclear.
Full or partial ROM: Full.
Supervision ratio: N/A.
Timing: Baseline, 1-week
post-protocol.
Results considered in the
tests: mean of three
measures.
Data reliability: High.
No. testers: 1 (blinded).
Instructions during testing:
N/A.
Group-based
exercise at
workplace: short-
term effects of
neck and
shoulder
resistance
training in video
display unit
workers with
work-related
chronic neck
pain a pilot
randomized
trial.[37]
Subjects: 35 video display
unit workers, 27 completed
the program.
Health status: chronic neck
pain.
Gender: 27 women, 8 men.
Age: 43 (41-45) in ST; 42
(38·5-44) in STRE.
Training status: N/A.
Selection of subjects: intranet
form.
Length (weeks): 7.
Weekly sessions: 2.
Adherence: average 85% of
the sessions in ST and 86% in
STRE.
Funding: Under
“disclosures”, the authors
stated “none”.
Conflicts of interest: Under
“disclosures”, the authors
stated “none”.
n = 14.
Weekly volume (minutes):
90.
Session duration in
minutes: 45.
No. exercises per session:
10.
No. sets and repetitions:
2-3*8-20. Isometric
contractions up to 30’’.
Load: free-weights with a
maximum of 75% MVC
and elastic bands of
unspecified load.
Full or partial ROM:
N/A.
Supervision ratio: ~1:8.
STRE n = 13.
Weekly volume (minutes): 90.
Session duration in minutes: 45.
No. exercises per session: 11.
No. sets and repetitions: 10*10’’.
Stretching modality: Static.
Load: N/A.
Full or partial ROM: N/A.
Supervision ratio: ~1:8.
Joints and actions: Cervical
spine (flexion, extension,
lateral flexion, rotation).
Positions: Sitting (flexion,
extension, lateral flexion) and
supine position (rotation).
Mode: Active.
Warm-up: N/A.
Timing: Baseline, 1-week
post-protocol.
Results considered in the
tests: N/A.
Data reliability: N/A.
No. testers: 1 (blinded).
Instructions during testing:
N/A.
Significant
improvements in
both groups for
all ROM
measurements.
No differences
between the two
groups.
18
A randomized
controlled trial of
muscle
strengthening
versus flexibility
training in
fibromyalgia.[74]
Subjects: 68; 56 completed
the program.
Health status: Diagnosed with
fibromyalgia (FM).
Gender: Women.
Age: 49·2±6·36 years in ST,
46·4±8·56 in STRE.
Training status: 87% were
sedentary. Not engaged in
regular strength training
programs.
Selection of subjects: FM
patients referred to
rheumatology practice at a
teaching university.
Length (weeks): 12.
Weekly sessions: 2.
Adherence: 85% of the initial
participants attended ≥13 of
24 classes. N/A for the 46
women that completed the
interventions.
Funding: Individual National
Research Service Award
(#1F31NR07337-01A1) from
the National Institutes of
Health, a doctoral dissertation
grant (#2324938) from the
Arthritis Foundation, and
funds from the Oregon
Fibromyalgia Foundation.
Conflicts of interest: N/A.
n = 28.
Weekly volume (minutes):
120.
Session duration in
minutes: 60.
No. exercises per session:
Presumably 12.
No. sets and repetitions:
1*4-5, progressing to
1*12.
Load: Low intensity.
Slower concentric
contractions with a 4’’
isometric hold in the end,
and a faster eccentric
contraction.
Full or partial ROM:
Full.
Supervision ratio:
Presumably 1:28.
STRE n = 28.
Weekly volume (minutes): 120.
Session duration in minutes: 60.
No. exercises per session:
Presumably 12.
No. sets and repetitions: N/A.
Stretching modality: Static.
Load: Low intensity.
Full or partial ROM: N/A.
Supervision ratio: Presumably
1:28.
Joints and actions: Shoulder
(the authors report on internal
and external rotation, but the
movements used actually
required a combination of
motions).
Positions: Presumably
standing.
Mode: Active.
Warm-up: N/A.
Timing: Baseline, 12 weeks.
Results considered in the
tests: N/A.
Data reliability: referral to a
previous study, but no values
for these data.
No. testers: 1.
Instructions during testing:
Reach as far as possible.
Both groups had
significant
improvements in
ROM.
No differences
between groups.
Influence of
Strength and
Flexibility
Training,
Combined or
Isolated, on
Strength and
Subjects:28 women.
Health status: Presumably
healthy.
Gender: Women.
Age: 46±6·5.
Training status: Trained in
strength and stretching.
n = 7.
Weekly volume (minutes):
N/A.
Session duration in
minutes: N/A.
No. exercises per session:
8.
STRE n = 7.
Weekly volume (minutes): 240.
Session duration in minutes: 60.
No. exercises per session: N/A.
No. sets and repetitions: 3*30.
Stretching modality: Dynamic.
Load: Stretch to mild discomfort.
Joints and actions: Shoulder
(flexion, extension, abduction
and horizontal adduction)
elbow (flexion), hip (flexion
and extension), knee
(flexion), and trunk (flexion
and extension).
None of the
groups
experienced
significant
improvements in
ROM.
19
Flexibility
Gains.[36]
Selection of subjects:
Volunteers that would refrain
from exercise outside the
intervention.
Length (weeks):12.
Weekly sessions: 4. Not
explicit; 48 sessions over 12
weeks.
Adherence: Minimum was 44
of the 48 sessions.
Funding: N/A.
Conflicts of interest: N/A.
No. sets and repetitions:
3*8-12 during the 1st
month; 3*6-10RM in the
2nd month; 3*10-15RM in
the 3rd month.
Load: 6-15RM,
depending on the month.
Full or partial ROM:
N/A.
Supervision ratio: N/A.
Full or partial ROM: Full.
Supervision ratio: N/A.
STRE + ST n = 7.
Completion of both protocols.
Unknown duration.
ST + STRE n = 7.
Completion of both protocols in
reverse order. Unknown duration.
Positions: Supine (shoulder
flexion, abduction, horizontal
adduction, elbow and hip
flexion), prone (shoulder and
hip extension, and knee
flexion) and upright (trunk
flexion and extension) for
goniometric evaluations.
Sitting for sit-and-reach.
Mode: Passive for
goniometry. Active for sit-
and-reach.
Warm-up: 5- minute walking
on treadmill at mild to
moderate intensity and four
stretching exercises.
Timing: Baseline, 12 weeks.
Results considered in the
tests: Best of 3 trials.
Data reliability: Very high.
No. testers: 1.
Instructions during testing:
N/A.
Effects of
Flexibility and
Strength
Interventions on
Optimal Lengths
of Hamstring
Muscle-Tendon
Units.[61]
Subjects: 40 college students.
Health status: No history of
lower extremity injury in the 2
years prior to the study.
Gender: 20 men, 20
women.
Age: 1824 years.
Training status: participating
in exercise 23 times per
week.
Selection of subjects: college
students.
Length (weeks): 8.
Weekly sessions: 3.
Adherence: N/A.
n = 20.
Weekly volume (minutes):
N/A.
Session duration in
minutes: N/A
No. exercises per session:
4.
No. sets and repetitions:
2-4*8-15. For one
exercise, 2*50-60’’.
Load: N/A.
Full or partial ROM:
N/A.
Supervision ratio: N/A.
STRE n = 20.
Weekly volume (minutes): N/A.
Session duration in minutes: N/A.
No. exercises per session: 4.
No. sets and repetitions: 2*15 for
dynamic stretching, 2*40-60’’ for
static stretching, 3*50’’ for PNF
and 3*40-50’’ for foam roll.
Stretching modality: active static,
dynamic and PNF.
Load: N/A.
Full or partial ROM: N/A.
Supervision ratio: N/A.
Joints and actions: Hip
(flexion).
Positions: Supine.
Mode: Passive.
Warm-up: Six-minute warm-
up including jogging and
jumping.
Timing: Baseline, 8 weeks.
Results considered in the
tests: Mean of three trials.
Data reliability: Very high.
No. testers: N/A.
Instructions during testing:
N/A.
Men and women
in both groups
significantly
improved ROM.
No differences
between groups.
20
Funding: Partially supported
by the National Natural
Science Foundation of China
(Grant No.: 81572212) and
the Fundamental Research
Fund for the Central
Universities, Beijing Sport
University (Grant No.:
2017XS017).
Conflicts of interest: N/A.
Resistance
training vs. static
stretching:
Effects on
flexibility and
strength.[60]
Subjects: 37 college students.
Health status: Healthy.
Gender: 30 men, 12 women;
ratio is unclear in the final
sample.
Age: 21·91±3·64 years.
Training status: Untrained.
Selection of subjects:
Recruited from Physical
Education or Exercise Science
Classes.
Length (weeks): 5.
Weekly sessions: 3.
Adherence: N/A.
Funding: N/A.
Conflicts of interest: N/A.
n = 12.
Weekly volume (minutes):
135-180.
Session duration in
minutes: 45-60.
No. exercises per session:
eight in days 1 and 2, four
in day 3.
No. sets and repetitions: 4
sets of unspecified
repetitions.
Load: N/A.
Full or partial ROM:
Full.
Supervision ratio: 1:12.
STRE n = 12.
Weekly volume (minutes): 75-90.
Session duration in minutes: 25-
35.
No. exercises per session: 13.
No. sets and repetitions: 1*30’’ for
most stretches. 3*30’’ for one
exercise and 3*20’’ for two.
Stretching modality: Static.
Load: N/A.
Full or partial ROM: Full.
Supervision ratio: 1:12.
Joints and actions: Hip
(flexion, extension), knee
(extension) and shoulder
(extension).
Positions: Supine (knee and
hip). Prone (shoulder).
Mode: Passive for hip and
knee, active for shoulder.
Warm-up: 5 minutes of
stationary bicycle with
minimal resistance.
Timing: Baseline, 1-week
post-protocol.
Results considered in the
tests: N/A.
Data reliability: N/A.
No. testers: 1.
Instructions during testing:
Technical instructions
specific to each test.
Both groups had
significant
improvements in
knee extension,
hip flexion and
hip extension, but
not shoulder
extension.
No differences
between the
interventions.
Eccentric
training and
static stretching
improve
hamstring
flexibility of high
school men.[75]
Subjects: 69 high-schoolers.
Health status: Healthy, but
with a 30º loss of knee
extension.
Gender: Men.
Age: 16·45±0·96 years.
Training status: Some
sedentary, others involved in
exercise programs.
n= 24.
Weekly volume (minutes):
N/A.
Session duration in
minutes: N/A.
No. exercises per session:
1.
No. sets and repetitions: 6
repetitions with 5’’
STRE n= 21.
Weekly volume (minutes): N/A.
Session duration in minutes: N/A.
No. exercises per session: 1.
No. sets and repetitions: Unknown
number of repetitions, each lasting
30’’.
Stretching modality: Static.
Joints and actions: Knee
(extension).
Positions: Supine.
Mode: Passive.
Warm-up: No warm-up.
Timing: Baseline, 6 weeks.
Results considered in the
tests: Two measures for
previous reliability
Both groups
improved ROM.
No differences
between the
interventions.
21
Selection of subjects:
Volunteers with tight
hamstrings.
Length (weeks): 6.
Weekly sessions: 3 for STRE.
N/A for ST.
Adherence: N/A for ST.
STRE: subjects missing >4
sessions were excluded.
Funding: N/A.
Conflicts of interest: N/A.
isometric hold between
each.
Load: N/A.
Full or partial ROM:
Full.
Supervision ratio:
Description suggests a
1:1 ratio.
Load: Stretch until a gentle stretch
was felt on the posterior thigh.
Full or partial ROM: Full.
Supervision ratio: Description
suggests a 1:1 ratio.
calculations, but unclear for
the groups’ evaluation.
Data reliability: Very high.
No. testers: 2 (1 blinded).
Instructions during testing:
N/A.
Effects of
flexibility
combined with
plyometric
exercises vs.
isolated
plyometric or
flexibility mode
in adolescent
men
hurdlers.[24]
Subjects: 34 trained hurdlers.
Health status: No lower
extremity injury in the
previous 30 days.
Gender: Men.
Age: 15±0·7 years.
Training status: ≥3 years of
experience in hurdle racing.
Selection of subjects:
Recruited from three athletic
teams.
Length (weeks): 12.
Weekly sessions: 4.
Adherence: N/A.
Funding: No funding.
Conflicts of interest: No
conflicts of interest.
n= 9.
Weekly volume (minutes):
320.
Session duration in
minutes: 80.
No. exercises per session:
4.
No. sets and repetitions:
3*30’’.
Load: Evolved from low
to hard intensity, but no
criteria were provided.
Full or partial ROM:
N/A. Supervision ratio:
N/A.
STRE n = 8.
Weekly volume (minutes): 320.
Session duration in minutes: 80.
No. exercises per session: 7.
No. sets and repetitions: 5*10’’.
Stretching modality: Dynamic with
10’’ static hold.
Load: Evolved from low to hard
intensity, but no criteria were
provided.
Full or partial ROM: N/A.
Supervision ratio: N/A.
STRE+ ST n = 9.
Weekly volume (minutes): 320.
Session duration in minutes: 80.
No. exercises per session: 11 (4
plyometric; 7 flexibility).
No. sets and repetitions: 3*30’’ for
plyometrics, 5*10’’ for stretching.
Stretching modality: Dynamic with
10’’ static hold.
Load: Evolved from low to hard
intensity, but no criteria were
provided.
Full or partial ROM: N/A.
Supervision ratio: N/A.
Joints and actions: Hip
(flexion and extension).
Positions: Supine.
Mode: Active.
Warm-up: N/A.
Timing: Baseline, 12 weeks.
Results considered in the
tests: Best of 3 attempts.
Data reliability: Referral to a
previous study, but no values
for these data.
No. testers: 2.
Instructions during testing:
N/A.
All interventions
had significant
improvements in
ROM.
No differences
between the
interventions.
22
The influence of
strength,
flexibility, and
simultaneous
training on
flexibility and
strength
gains.[67]
Subjects: 80 women.
Health status: Healthy.
Gender: Women.
Age: 35±2·0 (ST), 34±1·2
(STRE), 35±1·8 (ST +
STRE), 34±2·1 (non-
exercise).
Training status: Sedentary.
Selection of subjects:
Volunteers that were
sedentary ≥12 months.
Length (weeks): 16.
Weekly sessions: 3.
Adherence: Minimum was 46
of the 48 sessions.
Funding: N/A.
Conflicts of interest: N/A.
n = 20.
Weekly volume (minutes):
N/A.
Session duration in
minutes: N/A.
No. exercises per session:
8.
No. sets and repetitions:
3*8-12 in the 1st and 4th
months; 3*6-10 in 2nd
month; 3*10-15 in 3rd
month.
Load: 8-12RM (1st and
4th months); 6-10RM (2nd
month); 10-15RM (3rd
month).
Full or partial ROM:
N/A.
Supervision ratio: N/A.
STRE n = 20.
Weekly volume (minutes): N/A.
Session duration in minutes: N/A.
No. exercises per session: N/A.
No. sets and repetitions: 4*15-
60’’. Duration of each set started at
15’’ and progressed to 60’’ during
the intervention.
Stretching modality: Static.
Load: Performed at the point of
mild discomfort.
Full or partial ROM: N/A.
Supervision ratio: N/A.
ST + STRE n = 20.
STRE protocol followed by the ST
protocol.
Joints and actions: Hip
(flexion) and knee
(extension) combined.
Positions: Sitting.
Mode: Active.
Warm-up: 4 stretching
exercises (2*10’’).
Timing: Baseline, 16 weeks.
Results considered in the
tests: Maximum of 3
attempts.
Data reliability: Very high.
No. testers: 1.
Instructions during testing:
N/A.
The interventions
significantly
improved ROM.
No differences
between the
interventions.
A comparison of
strength and
stretch
interventions on
active and
passive ranges of
movement in
dancers: a
randomized
control trial.[62]
Subjects: 39 dance students,
35 completed.
Health status: N/A.
Gender: Women (39).
Age: 17±0·49 years (ST
group); 17±0·56 years (low-
intensity STRE); 17±0·56
years (moderate to high
intensity STRE).
Training status: Moderately
trained dance students.
Selection of subjects:
Recruited from dance college.
Length (weeks): 6.
Weekly sessions: 5.
Adherence: N/A.
Funding: N/A.
Conflicts of interest: N/A.
n = 11.
Weekly volume (minutes):
N/A.
Session duration in
minutes: N/A.
No. exercises per session:
1.
No. sets and repetitions:
3*5, increasing to 3*10
during the program. Each
repetition included a 3’’
isometric hold.
Load: Unclear, but using
body weight.
Full or partial ROM:
Partial (final 10º).
Supervision ratio: N/A.
Low-intensity STRE n = 13.
Weekly volume (minutes): N/A.
Session duration in minutes: N/A.
No. exercises per session: 5.
No. sets and repetitions: N/A, but
1’ for each stretch.
Stretching modality: Active static.
Load: 3/10 perceived exertion.
Full or partial ROM: N/A.
Supervision ratio: N/A.
Moderate-intensity or high-
intensity STRE n = 11.
Weekly volume (minutes): N/A.
Session duration in minutes: N/A.
No. exercises per session: 5.
No. sets and repetitions: N/A.
Stretching modality: Passive.
Load: 8/10 perceived exertion.
Full or partial ROM: N/A.
Joints and actions: Hip
(flexion).
Positions: Standing.
Mode: Active and passive.
Warm-up: 10 minutes of
cardiovascular exercise and
lower limb stretches.
Timing: Baseline, 6 weeks.
Results considered in the
tests: N/A.
Data reliability: N/A.
No. testers: N/A.
Instructions during testing:
Positioning cues for ensuring
proper posture.
The three groups
significantly
improved passive
ROM, without
differences
between the
groups.
The moderate-to-
high intensity
STRE group did
not improve in
active ROM. The
two other
interventions did.
23
Supervision ratio: N/A.
Legend: N/A Information not available. ST Strength training. STRE - Stretching. ROM Range of motion. MVC Maximum voluntary contraction. PNF
284
Proprioceptive neuromuscular facilitation. * Non-exercise groups are not considered in this column.
285
286
287
24
288
289
In seven articles,[24, 37, 60, 61, 67, 74] ST and stretching groups significantly
290
improved ROM, and the differences between the groups were non-significant. In one article,
291
the ST group had significant improvements in 8 of 10 ROM measures, while dynamic
292
stretching did not lead to improvement in any of the groups.[34] In another article, the three
293
groups significantly improved PROM, without between-group differences; the ST and the
294
static active stretching groups also significantly improved AROM.[62] In two articles, none of
295
the groups improved ROM.[35, 36]
296
297
Risk of bias within studies
298
Table 2 presents assessments of RoB. Bias arising from the randomization process was
299
low in four articles,[34, 36, 62, 74] moderate in one,[37] and high in six.[24, 35, 60, 61, 67,
300
75] Bias due to deviations from intended interventions, missing outcome data, and selection of
301
the reported results was low. Bias in measurement of the outcome was low in six articles,[35-
302
37, 67, 74, 75] but high in five.[24, 34, 60-62]
303
304
305
25
306
Table 2. Assessments of risk of bias.
307
Cochrane’s
RoB 2
Alexander
, Galecki
[34]
Aquino,
Fonseca
[35]
Caputo,
Di Bari
[37]
Jones,
Burckhard
t [74]
Leite, De
Souza
Teixeira
[36]
Li, Garrett
[61]
Morton,
Whitehead
[60]
Nelson and
Bandy [75]
Racil, Jlid
[24]
Simão,
Lemos [67]
Wyon,
Smith
[62]
1.Bias arising from the randomization process
1.1.Was the
allocation
sequence
random?
Yes.
No
information
.
Yes.
Yes.
No
information
.
No
information
.
No
information
.
No
information.
No
information
.
No
information
.
Yes.
1.2.Was the
allocation
sequence
concealed
until
participants
were enrolled
and assigned
to
interventions
?
Yes.
Probably
no.
Yes.
Yes.
Yes.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Yes.
1.3.Did
baseline
differences
between
groups
suggest a
problem with
the
randomizatio
n process?
No.
No
information
.
Yes.
No.
No.
No.
Probably
no.
No.
No.
No.
No.
1.4.RoB
judgement
Low risk.
High risk.
Some
concerns
.
Low risk.
Low risk.
High risk.
High risk.
High risk.
High risk.
High risk.
Low
risk.
2.Bias due to deviations from intended interventions
26
(effect of assignment to intervention)
2.1.Were
participants
aware of their
assigned
intervention
during the
trial?
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
2.2.Were
carers and
people
delivering the
interventions
aware of
participants’
assigned
intervention
during the
trial?
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
2.3.If
Y/PY/NI to
2.1 or 2.2:
Were there
deviations
from the
intended
intervention
because of
the trial
context?
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probabl
y no.
2.4.If Y/PY
to 2.3: Were
these
deviations
likely to have
affected the
outcome?
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
27
2.5.If
Y/PY/NI to
2.4: Were
these
deviations
from the
intended
intervention
balanced
between
groups?
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
2.6.Was an
appropriate
analysis used
to estimate
the effect of
assignment to
intervention?
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
Probabl
y yes.
2.7.If
N/PN/NI to
2.6: Was
there
potential for a
substantial
impact (on
the result) of
the failure to
analyze
participants
in the group
to which they
were
randomized)?
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
2.8.RoB
judgement
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low
risk.
3.Bias due to missing outcome data
3.1.Were data
for this
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
28
outcome
available for
all, or nearly
all,
participants
randomized?
3.2.If
N/PN/NI to
3.1.: Is there
evidence that
the result was
not biased by
missing
outcome
data?
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
3.3.If N/PN
to 3.2: Could
missingness
in the
outcome
depend on its
true value?
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
3.4.If
Y/PY/NI to
3.3: Is it
likely that
missingness
in the
outcome
depended on
its true value?
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
N/A.
3.5.RoB
judgement
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low
risk.
4. Bias in measurement of the outcome
4.1.Was the
method of
measuring the
outcome
No.
No.
No.
No.
No.
No.
No.
No.
No.
No.
No.
29
inappropriate
?
4.2.Could
measurement
or
ascertainment
of the
outcome have
differed
between
intervention
groups?
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probabl
y no.
4.3.If
N/PN/NI to
4.1. and 4.2:
Were
outcome
assessors
aware of the
intervention
received by
study
participants?
Probably
yes.
No.
No.
No.
No.
Probably
yes.
Probably
yes.
Probably
yes.
Probably
yes.
No.
Probabl
y yes.
4.4.If
Y/PY/NI to
4.3: Could
assessment of
the outcome
have been
influenced by
knowledge of
intervention
received?
Probably
yes.
N/A.
N/A.
N/A.
N/A.
Probably
yes.
Probably
yes.
Probably no
[blinded
goniometer]
.
Probably
yes.
N/A.
Probabl
y yes.
4.5.If
Y/PY/NI to
4.4: Is it
likely that
assessment of
Probably
yes.
N/A.
N/A.
N/A.
N/A.
Probably
yes.
Probably
yes.
N/A.
Probably
yes.
N/A.
Probabl
y yes.
30
the outcome
was
influenced by
knowledge of
intervention
received?
4.6.RoB
judgement
High risk.
Low risk.
Low risk.
Low risk.
Low risk.
High risk.
High risk.
Low risk.
High risk.
Low risk.
High
risk.
5.Bias in selection of the reported results
5.1.Were the
data that
produced this
result
analyzed in
accordance
with a pre-
specified
analysis plan
that was
finalized
before
unblinded
outcome data
were
available for
analysis?
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
Yes.
5.2.Is the
numerical
result being
assessed
likely to have
been selected,
on the basis
of the results,
from multiple
eligible
outcome
measurement
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probabl
y no.
31
s (e.g., scales,
definitions,
time points)
within the
outcome
domain?
5.3.Is the
numerical
result being
assessed
likely to have
been selected,
on the basis
of the results,
from multiple
eligible
analyses of
the data?
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probably
no.
Probabl
y no.
RoB
judgement
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low risk.
Low
risk.
308
309
32
310
311
Synthesis of results
312
Comparisons were performed between ST and stretching groups, involving eleven
313
articles and 452 participants. Global effects on ROM were achieved pooling data from the
314
different joints. One article did not have the data required,[35] but the authors kindly supplied
315
it upon request. For another article,[36] we also requested data relative to the goniometric
316
evaluations, but obtained no response. Therefore, only data from the sit-and-reach test was
317
used. For one article,[37] means and SDs were obtained from 95% CIs, while in another SDs
318
were extracted from SEMs,[74] using Cochrane’s RevMan Calculator.
319
Of the five articles including both genders, four provided pooled data, with no
320
distinction between genders.[34, 35, 37, 60] One article presented data separated by gender,
321
without significant differences between men and women in response to interventions.[61]
322
Weighted formulas were applied sequentially for combining means and SDs of groups within
323
the same study.[38] Two studies presented the results separated by left and right lower limbs,
324
with both showing similar responses to the interventions;[24, 62] outcomes were combined
325
using the same weighted formulas for the means and SDs. Five articles only presented one
326
decimal place,[24, 34, 37, 61, 67] and so all values were rounded for uniformity.
327
Effects of ST versus stretching on ROM: no significant difference was noted between
328
ST and stretching (ES = -0×22; 95% CI = -0×55 to 0×12; p = 0×206; I2 = 65×4%; Egger’s test p =
329
0×563; Figure 2). The relative weight of each study in the analysis ranged from 6×4% to 12×7%
330
(the size of the plotted squares in Figure 2 reflects the statistical weight of each study).
331
332
333
33
334
335
Figure 2. Forest plot of changes in ROM after participating in stretching-based compared to strength-based
336
training interventions. Values shown are effect sizes (Hedges’s g) with 95% confidence intervals (CI). The size
337
of the plotted squares reflects the statistical weight of the study.
338
339
Additional analysis
340
Effects of ST versus stretching on ROM, moderated by study RoB in randomization: No
341
significant sub-group differences in ROM changes (p = 0·256) was found when programs with
342
high RoB (6 studies; ES = -0·41; 95% CI = -1·02 to 0·20; within-group I2 = 77·5%) were
343
compared to programs with low RoB (4 studies; ES = -0·03; 95% CI = -0·29 to 0·23; within-
344
group I2 = 0·0%) (Supplementary figure 1).
345
Effects of ST versus stretching on ROM, moderated by study RoB in measurement of
346
the outcome: No significant sub-group difference in ROM changes (p = 0·320) was found
347
when programs with high RoB (5 studies; ES = -0·04; 95% CI = -0·31 to 0·24; within-group
348
I2 = 8·0%) were compared to programs with low RoB (6 studies; ES = -0·37; 95% CI = -0·95
349
to 0·22; within-group I2 = 77·3%) (Supplementary figure 2).
350
Effects of ST versus stretching on ROM, moderated by ROM type (active vs. passive):
351
No significant sub-group difference in ROM changes (p = 0·642) was found after training
352
Study name Hedges's g and 95% CI
Hedges's
g
Alexander et al. (2001) 0.045
Aquino et al. (2010) 0.087
Caputo et al. (2017) 0.220
Jones et al. (2002) -0.282
Leite et al. (2015) -0.229
Li et al. (2020) -0.616
Morton et al. (2011) 0.123
Nelson & Bandy (2004) -0.101
Racil et al. (2020) -0.000
Simão et al. (2011) -1.922
Wyon et al. (2013) 0.247
-0.215
-3.00 -1.50 0.00 1.50 3.00
Favo urs s tre tc hin g Favo urs st ren gth
Stretching
(n)
Strength
(n)
34
programs that assessed active (8 groups; ES = -0·15; 95% CI = -0·65 to 0·36; within-group I2
353
= 78·7%) compared to passive ROM (6 groups; ES = -0·01; 95% CI = -0·27 to 0·24; within-
354
group I2 = 15·3%) (Supplementary figure 3).
355
Effects of ST versus stretching on hip flexion ROM: Seven studies provided data for hip
356
flexion ROM (pooled n = 294). There was no significant difference between ST and stretching
357
interventions (ES = -0·24; 95% CI = -0·82 to 0·34; p = 0·414; I2 = 80·5%; Egger’s test p =
358
0·626; Supplementary figure 4). The relative weight of each study in the analysis ranged from
359
12·0% to 17·4% (the size of the plotted squares in Figure 6 reflects the statistical weight of
360
each study).
361
Effects of ST versus stretching on hip flexion ROM, moderated by study RoB in
362
randomization: No significant sub-group difference in hip flexion ROM changes (p = 0·311)
363
was found when programs with high RoB in randomization (4 studies; ES = -0·46; 95% CI =
364
-1·51 to 0·58; within-group I2 = 86·9%) were compared to programs with low RoB in
365
randomization (3 studies; ES = 0·10; 95% CI = -0·20 to 0·40; within-group I2 = 0·0%)
366
(Supplementary figure 5).
367
Effects of ST versus stretching on hip flexion ROM, moderated by ROM type (active vs.
368
passive): No significant sub-group difference in hip flexion ROM changes (p = 0·466) was
369
found after the programs assessed active (4 groups; ES = -0·38; 95% CI = -1·53 to 0·76; within-
370
group I2 = 87·1%) compared to passive ROM (4 groups; ES = 0·08; 95% CI = -0·37 to 0·52;
371
within-group I2 = 56·5%) (Supplementary figure 6).
372
Effects of ST versus stretching on knee extension ROM: Four studies provided data for
373
knee extension ROM (pooled n = 223). There was no significant difference between ST and
374
stretching interventions (ES = 0·25; 95% CI = -0·02 to 0·51; p = 0·066; I2 = 0·0%; Egger’s test
375
p = 0·021; Supplementary figure 7). After the application of the trim and fill method, the
376
adjusted values changed to ES = 0·33 (95% CI = 0·10 to 0·57), favoring ST. The relative
377
35
weight of each study in the analysis ranged from 11·3% to 54·2% (the size of the plotted
378
squares in Supplementary figure 7 reflects the statistical weight of each study).
379
One article behaved as an outlier in all comparisons (favoring stretching),[67] but after
380
sensitivity analysis the results remained unchanged (p>0·05), with all ST vs. stretching
381
comparisons remaining non-significant.
382
383
Confidence in cumulative evidence
384
Table 3 presents GRADE assessments. ROM is a continuous variable, and so a high
385
degree of heterogeneity was expected.[77] Imprecision was moderate, likely reflecting the fact
386
that ROM is a continuous variable. Overall, both ST and stretching consistently promoted
387
ROM gains, but no recommendation could be made favoring one protocol.
388
389
390
36
391
Table 3. GRADE assessment for the certainty of evidence.
392
Outcome
Study
design
RoB1
Publication
bias
Inconsistency
Indirectness
Imprecision
Quality
of
evidence
Recommendation
ROM
11 RCTs,
452
participants
in meta-
analysis.
Randomizationlow in
four articles, moderate in
one, and high in six.
No
publication
bias.
9 RCTs showed
improvements in ROM
in both groups.
2 RCTs showed no
changes in ROM in
either group.
11 RCTs
showed effects of equal
magnitude for ST and
stretching.2
No serious
indirectness.
Moderate.3
Moderate.
⨁⨁⨁
Strong
recommendation
for either strength
training or
stretching4.
No
recommendation
for choosing one
of the protocols
over the other, as
their efficacy in
ROM gains was
statistically not
different.
Deviations from intended
interventionsLow.
Missing outcome data
Low.
Measurement of the
outcomelow in six
articles and high in five.
Selection of the reported
resultsLow.
1 - Meta-analyses moderated by RoB showed no differences between studies with low and high risk.
2 - Because ROM is a continuous variable, high heterogeneity was expected. However, this heterogeneity is mostly between small and large beneficial effects. No adverse
effects were reported.
3 - Expected because ROM is a continuous variable. Furthermore, imprecision referred to small to large beneficial effects.
4 Both strength training and stretching presented benefits without reported adverse effects.
Legend: ROM Range of motion. RCTs: randomized controlled trials. RoB: risk of bias.
393
394
395
37
396
DISCUSSION
397
Summary of evidence
398
The aim of this SRMA was to compare the effects of supervised and randomized ST
399
compared to stretching protocols on ROM, in participants of any health and training status.
400
Qualitative synthesis showed that ST and stretching interventions were not statistically
401
different in improving ROM, regardless of the nature of the interventions and moderator
402
variables such as gender, health, or training status. Meta-analysis including 11 articles and 452
403
participants showed that ST and stretching interventions were not statistically different in
404
active and passive ROM changes, regardless of RoB in the randomization process, or in
405
measurement of the outcome. RoB was low for deviations from intended interventions, missing
406
outcome data, and selection of the reported results. No publication bias was detected.
407
High heterogeneity is expected in continuous variables,[77] such as ROM. However,
408
more research should be conducted to afford sub-group analysis according to characteristics of
409
the analyzed population, as well as protocol features. For example, insufficient reporting of
410
training volume and intensity meant it was impossible to establish effective dose-response
411
relationships, although a minimum of 5 weeks of intervention,[60] and two weekly sessions
412
were sufficient to improve ROM.[37, 74] Studies were not always clear with regard to the
413
intensity used in ST and stretching protocols. Assessment of stretching intensity is complex,
414
but a practical solution may be to apply scales of perceived exertion,[62] or the Stretching
415
Intensity Scale.[78] ST intensity may also moderate effects on ROM,[79] and ST with full vs
416
partial ROM may have distinct neuromuscular effects[70] and changes in fascicle length.[28]
417
Again, information was insufficient to discuss these factors, which could potentially explain
418
part of the heterogeneity of results.
419
38
Most studies showed ROM gains in ST and stretching interventions, although in two
420
studies neither group showed improvements.[35, 36] Though adherence rates were unreported
421
by Aquino, Fonseca [35], they were above 91.7% in Leite, De Souza Teixeira [36], thus
422
providing an unlikely explanation for these results. In the study of Aquino, Fonseca [35], the
423
participants increased their stretch tolerance, and the ST group changed the peak torque angle,
424
despite no ROM gains. The authors acknowledged that there was high variability in
425
measurement conditions (e.g., room temperature), which could have interfered with
426
calculations. Leite, De Souza Teixeira [36] suggested that the use of dynamic instead of static
427
stretching could explain the lack of ROM gains in the stretching and stretching + ST groups.
428
However, other studies using dynamic stretching have shown ROM gains.[24, 34]
429
Furthermore, Leite, De Souza Teixeira [36] provided no interpretation for the lack of ROM
430
gains in the ST group.
431
Globally, however, both ST and stretching were effective to improve ROM. Why would
432
ST improve ROM in a manner that is not statistically distinguishable from stretching? ST with
433
an eccentric focus demands the muscles to produce force on elongated positions, and a meta-
434
analysis showed limited to moderate evidence that eccentric ST is associated with increases in
435
fascicle length.[80] Likewise, a recent study showed that 12 sessions of eccentric ST increased
436
fascicle length of the biceps femoris long head.[29] However, ST with an emphasis in
437
concentric training has been shown to increase fascicle length when full ROM was
438
required.[28] In a study with nine older adults, ST increased fascicle length in both the eccentric
439
and concentric groups, albeit more prominently in the former.[81] Conversely, changes in
440
pennation angle were superior in the concentric group (35% increase versus 5% increase).
441
Plyometric training can also increase plantar flexor tendon extensibility.[33]
442
One article showed significant reductions in pain associated with increases in
443
strength.[37] Thus, decreased pain sensitivity may be another mechanism through which ST
444
39
promotes ROM gains. An improved agonist-antagonist coactivation is another possible
445
mechanism promoting ROM gains, through better adjusted force ratios.[31, 62] Also, some
446
articles included in the meta-analysis assessed other outcomes in addition to ROM, and these
447
indicated that ST programs may have additional advantages when compared to stretching, such
448
as greater improvements in neck flexors endurance,[37] ten repetition maximum Bench Press
449
and Leg Press,[36, 67] and countermovement jump and 60-m sprint with hurdles,[24] which
450
may favor the choice of ST over stretching interventions.
451
452
453
Limitations
454
After protocol registration, we chose to improve upon the design, namely adding two
455
dimensions (directness and imprecision) that would provide a complete GRADE assessment.
456
Furthermore, subgroup analyses were not planned a priori. There is a risk of multiple subgroup
457
analyses generating a false statistical difference, merely to the number of analyses
458
conducted.[38] However, all analyses showed an absence of significant differences and
459
therefore provide a more complete understanding that the effects of ST or stretching on ROM
460
are consistent across conditions. Looking backwards, perhaps removing the filters used in the
461
initial searches could have provided a greater number of records. Notwithstanding, it would
462
also likely provide a huge number of non-relevant records, including opinion papers and
463
reviews. Moreover, consultation with four independent experts may hopefully have resolved
464
this shortcoming.
465
Due to the heterogeneity of populations analysed, sub-group analysis according to sex
466
or age group were not possible, and so it would be important to explore if these features interact
467
with the protocols in meaningful ways. And there was a predominance of studies with women,
468
meaning more research with men is advised. There was also a predominance of assessments of
469
40
hip joint ROM, followed by knee and shoulder, with the remaining joints receiving little to no
470
attention. In addition, dose-response relationships could not be addressed, mainly due to poor
471
reporting.
472
473
CONCLUSIONS
474
Overall, ST and stretching were not statistically different in ROM improvements, both
475
in short-term interventions[60] and in longer-term protocols,[67] suggesting that a combination
476
of neural and mechanical factors is at play. Therefore, if ROM gains are a desirable outcome,
477
both ST and stretching can be prescribed, in the absence of specific contraindications,
478
especially because studies did not report any adverse effects. People that do not respond well
479
or do not adhere to stretching protocols can change to ST programs, and vice-versa.
480
Furthermore, session duration may negatively impact adherence to an exercise program.[82]
481
Since ST generates ROM gains similar to those obtained with stretching, clinicians may
482
prescribe smaller, more time-effective programs when deemed convenient and appropriate,
483
thus eventually increasing patient adherence rates.
484
485
486
41
487
488
Declaration of interests: J.M. owns a company focused on Personal Trainer’s education but
489
made no attempt to bias the team in protocol design and search process and had no role in
490
extracting data for meta-analyses. The multiple cross-checks described in the methods
491
provided objectivity to data extraction and analysis. Additionally, J.M. had no financial
492
involvement in this manuscript. The other authors have no conflict of interest to declare.
493
494
Funding: No funding was used for conducting this meta-analysis.
495
496
497
42
498
Author’s contributions (following ICMJE recommendations)
499
Authors
Substantial
contributions to the
conceptualization
or design of the
study; OR the
acquisition,
analysis, or
interpretation of
data
Drafting the
manuscript; OR
revising the
manuscript
critically for
important
intellectual
content
Final
approval
of the
version to
be
published
Agreement to be
accountable for all
aspects of the work, and
to ensure that issues
related to the accuracy or
integrity of any part of
the work are
appropriately
investigated and resolved
José Afonso
Rodrigo Ramirez-
Campillo
João Moscão
Tiago Rocha
Rodrigo Zacca
Alexandre Martins
André A. Milheiro
João Ferreira
Hugo Sarmento
Filipe Manuel
Clemente
Acknowledgements
Role
Richard Inman
Language editing and proof reading.
Pedro Morouço
Thorough pre-submission scientific review of the manuscript. Signed consent form
below.
Daniel Moreira-
Gonçalves, Fábio
Yuzo Nakamura plus
two experts who
wished to remain
anonymous.
Review of inclusion criteria and included articles, and proposal of additional articles
to be included in the systematic review and meta-analysis.
Signed consent forms below.
500
501
43
502
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Functional tests are used for the assessment and prevention of injuries, as they evaluate physical or physiological imbalances and allow the observation of asymmetries. The main aim of this study has been to detect the asymmetries in the upper limbs (right and left arms) in athletes, using OctoBalance Test (OB), depending on the stage of the season. Two hundred and fifty-two participants (age: 23.33 ± 8.96 years old; height: 178.63 ± 11.12 cm; body mass: 80.28 ± 17.61 kg; body mass index: 24.88± 4.58; sports experience: 12.52 ± 6,28 years), practicing different sports (rugby, athletics, football, swimming, handball, triathlon, basketball, hockey, badminton and volleyball), all of them evaluated with OB in medial, superolateral, and inferolateral directions in both right and left arms, in 4 moments of the season (May 2017, September 2017, February 2018 and May 2018). ANOVA test was used with repeated measures with a p ≤ 0.05, for the analysis of the different studied variances. Significant differences were found (p=0.021) in the medial direction of the left arm, between the first (May 2017) and fourth stages (May 2018), with values of 71.02 ± 7.15 cm and 65.03 ± 7.66 cm. From the detection of asymmetries, using OB, it is possible to use the measures, in the medial, superolateral and inferolateral directions, to evaluate mobility and balance, allowing us to observe functional imbalances, as risk factor for injury, in each of the stages in which the season is divided, which will help in the prevention of injuries and in the individualization of the training.
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Whereas a variety of pre-exercise activities have been incorporated as part of a “warm-up” prior to work, combat, and athletic activities for millennia, the inclusion of static stretching (SS) within a warm-up has lost favor in the last 25 years. Research emphasized the possibility of SS-induced impairments in subsequent performance following prolonged stretching without proper dynamic warm-up activities. Proposed mechanisms underlying stretch-induced deficits include both neural (i.e., decreased voluntary activation, persistent inward current effects on motoneuron excitability) and morphological (i.e., changes in the force–length relationship, decreased Ca²⁺ sensitivity, alterations in parallel elastic component) factors. Psychological influences such as a mental energy deficit and nocebo effects could also adversely affect performance. However, significant practical limitations exist within published studies, e.g., long-stretching durations, stretching exercises with little task specificity, lack of warm-up before/after stretching, testing performed immediately after stretch completion, and risk of investigator and participant bias. Recent research indicates that appropriate durations of static stretching performed within a full warm-up (i.e., aerobic activities before and task-specific dynamic stretching and intense physical activities after SS) have trivial effects on subsequent performance with some evidence of improved force output at longer muscle lengths. For conditions in which muscular force production is compromised by stretching, knowledge of the underlying mechanisms would aid development of mitigation strategies. However, these mechanisms are yet to be perfectly defined. More information is needed to better understand both the warm-up components and mechanisms that contribute to performance enhancements or impairments when SS is incorporated within a pre-activity warm-up.
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This chapter describes the principles and methods used to carry out a meta-analysis for a comparison of two interventions for the main types of data encountered. A very common and simple version of the meta-analysis procedure is commonly referred to as the inverse-variance method. This approach is implemented in its most basic form in RevMan, and is used behind the scenes in many meta-analyses of both dichotomous and continuous data. Results may be expressed as count data when each participant may experience an event, and may experience it more than once. Count data may be analysed using methods for dichotomous data if the counts are dichotomized for each individual, continuous data and time-to-event data, as well as being analysed as rate data. Prediction intervals from random-effects meta-analyses are a useful device for presenting the extent of between-study variation. Sensitivity analyses should be used to examine whether overall findings are robust to potentially influential decisions.
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The revised edition of the Handbook offers the only guide on how to conduct, report and maintain a Cochrane Review ? The second edition of The Cochrane Handbook for Systematic Reviews of Interventions contains essential guidance for preparing and maintaining Cochrane Reviews of the effects of health interventions. Designed to be an accessible resource, the Handbook will also be of interest to anyone undertaking systematic reviews of interventions outside Cochrane, and many of the principles and methods presented are appropriate for systematic reviews addressing research questions other than effects of interventions. This fully updated edition contains extensive new material on systematic review methods addressing a wide-range of topics including network meta-analysis, equity, complex interventions, narrative synthesis, and automation. Also new to this edition, integrated throughout the Handbook, is the set of standards Cochrane expects its reviews to meet. Written for review authors, editors, trainers and others with an interest in Cochrane Reviews, the second edition of The Cochrane Handbook for Systematic Reviews of Interventions continues to offer an invaluable resource for understanding the role of systematic reviews, critically appraising health research studies and conducting reviews.
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This study explores the effect of supervised back extensor strength training on spinal pain, back extensor muscle strength, trunk-arm endurance, kyphosis, functional mobility, and quality of life (QoL) among sixty postmenopausal women with vertebral osteoporotic fractures. Purpose To compare the effects of a 6-week supervised or home-based program of back-strengthening exercise on spinal pain, back extensor strength, trunk-arm endurance, kyphosis, functional mobility, and QoL in osteoporotic postmenopausal women with vertebral fractures. Methods The study was designed as a randomized controlled clinical trial. Sixty osteoporotic postmenopausal women with vertebral fracture (mean age 60.3 ± 9.3 years) were included in the study. Subjects were randomly assigned into three groups (supervised program, home-based program, or control), each consisting of 20 subjects. The subjects underwent the 6-week exercise program which included strengthening exercise for the back extensor muscles. They performed three sets of 8, 10, or 12 repetitions for each of the exercises, biweekly ascending, three times per week. Spinal pain, back extensor strength, trunk and arm endurance, kyphosis, functional mobility, and QoL were measured at baseline and at the end of the exercise program. Results Statistically significant improvements were demonstrated on spinal pain, muscle strength and endurance, functional mobility, and QoL for the supervised exercise program compared with control and home-based exercise groups (p < 0.01). Home-based exercise program did not provide a significant improvement compared with the control group except for mobility parameters of QoL. Conclusions Six-week supervised back extensor strengthening training is superior to home-based program in terms of spinal pain, back extensor muscle strength, trunk endurance, functional mobility, and QoL for postmenopausal osteoporotic women with vertebral fractures.