Considerations of the Principles of Resistance Training in Exercise Studies for the Management of Knee Osteoarthritis: A Systematic Review

Abstract

Objective:
To evaluate the methodological quality of resistance training interventions for the management of knee osteoarthritis.

Data sources:
A search of the literature for studies published up to 10(th) August 2015 was performed on Medline (OVID platform), PubMed, EMBase and PEDRo databases. Search terms associated with 'osteoarthritis'; 'knee' and 'muscle resistance exercise' were used..

Study selection:
Studies were included in the review if they were published in the English language and met the following criteria : 1) muscle resistance training was the primary intervention; 2) RCT design; 3) treatment arms included at least a muscle conditioning intervention and a non-exercise control group; 4) participants had osteoarthritis of the knee; . Studies employing pre-operative (joint replacement) interventions with only post-operative outcomes were excluded. The search yielded 1574 results. The inclusion criteria were met by 34 studies.

Data extraction:
Two reviewers independently screened the papers for eligibility. Critical appraisal of the methodology was assessed according to the principles of resistance training (PoRT) and, separately for the reporting of adherence using a specially designed scoring system. A rating for each was assigned.

Data synthesis:
34studies described a strength training focus of the intervention, however, the PoRT were inconsistently applied and inadequately reported across all. Methods for adherence monitoring were incorporated in to the design of 28 of the studies but only 13 reported sufficient detail to estimate average dose of exercise.

Conclusions:
These findings impact the interpretation of the efficacy of muscle resistance exercise in the management of knee osteoarthritis. Clinicians and health-care professionals cannot be confident whether non-significant findings are due to lack of efficacy of muscle resistance interventions, or occur through limitations in treatment prescription and patient adherence. Future research that seeks to evaluate the effects of muscle strength training interventions on symptoms of OA should be properly designed and adherence diligently reported.

Full text

REVIEW ARTICLE (META-ANALYSIS)
Considerations of the Principles of Resistance
Training in Exercise Studies for the Management of
Knee Osteoarthritis: A Systematic Review
Claire Minshull, PhD,
a,b
Nigel Gleeson, PhD
b
From the
a
School of Clinical Sciences, University of Edinburgh, Edinburgh; and
b
School of Health Sciences,
Queen Margaret University, Edinburgh, UK.
Current affiliation for Gleeson, Carnegie School of Sport, Leeds Beckett University, Leeds, UK.
Abstract
Objective: To evaluate the methodologic quality of resistance training interventions for the management of knee osteoarthritis.
Data Sources: A search of the literature for studies published up to August 10, 2015, was performed on MEDLINE (OVID platform), PubMed,
Embase, and Physiotherapy Evidence Database databases. Search terms associated with osteoarthritis,knee, and muscle resistance exercise were
used.
Study Selection: Studies were included in the review if they were published in the English language and met the following criteria: (1) muscle
resistance training was the primary intervention; (2) randomized controlled trial design; (3) treatment arms included at least a muscle conditioning
intervention and a nonexercise group; and (4) participants had osteoarthritis of the knee. Studies using preoperative (joint replacement)
interventions with only postoperative outcomes were excluded. The search yielded 1574 results. The inclusion criteria were met by 34 studies.
Data Extraction: Two reviewers independently screened the articles for eligibility. Critical appraisal of the methodology was assessed according
to the principles of resistance training and separately for the reporting of adherence using a specially designed scoring system. A rating for each
article was assigned.
Data Synthesis: There were 34 studies that described a strength training focus of the intervention; however, the principles of resistance training
were inconsistently applied and inadequately reported across all. Methods for adherence monitoring were incorporated into the design of 28 of the
studies, but only 13 reported sufficient detail to estimate average dose of exercise.
Conclusions: These findings affect the interpretation of the efficacy of muscle resistance exercise in the management of knee osteoarthritis.
Clinicians and health care professionals cannot be confident whether nonsignificant findings are because of the lack of efficacy of muscle
resistance interventions, or occur through limitations in treatment prescription and patient adherence. Future research that seeks to evaluate the
effects of muscle strength training interventions on symptoms of osteoarthritis should be properly designed and adherence diligently reported.
Archives of Physical Medicine and Rehabilitation 2017;98:1842-51
ª2016 by the American Congress of Rehabilitation Medicine
Knee osteoarthritis (OA) is a common and painful musculoskel-
etal disorder for which there is no cure; the ultimate treatment is
joint replacement. The number of sufferers of knee OA is
increasing annually,
1
and UK figures project a rise from 4.7
million sufferers in 2010 to 5.4 million by 2020.
2
Given the lack
of cure, and the associated deficits in proprioception and muscle
strength,
3,4
the need to effectively manage OA is of paramount
importance to attenuate declines in function and quality of life.
International guidelines highlight the importance of non-
pharmacologic treatments for people with OA.
5,6
Although recent
reviews indicate that treatments (eg, manual therapy, trans-
cutaneous electrical nerve stimulation, acupuncture) are unlikely
to convey benefits to symptoms of OA over and above placebo
effects,
7
exercise conveys a moderate effect in terms of reduced
pain and improved quality of life in patients with knee OA.
8
Muscle atrophy and weakness have been hypothesized to
contribute to the disability and pain of patients with OA
4
;in
particular, knee extensor muscle weakness has been correlated
with knee pain and functional disability.
9
Progressive muscleDisclosures: none.
0003-9993/17/$36 - see front matter ª2016 by the American Congress of Rehabilitation Medicine
http://dx.doi.org/10.1016/j.apmr.2017.02.026
Archives of Physical Medicine and Rehabilitation
journal homepage: www.archives-pmr.org
Archives of Physical Medicine and Rehabilitation 2017;98:1842-51

resistance training, where the resistance is progressively increased
to maintain relative intensity, can lead to significant improvements
in older adults with knee OA
10
by ameliorating sarcopenic
changes and by improving the strength and function of the sur-
rounding connective tissue, which is often damaged by the
disease.
10,11
The body of literature that evaluates muscle strengthening in-
terventions on symptoms of knee OA, however, pays little or no
attention to the principles of resistance training. Consideration of
these principles ensures that the intervention is likely to elicit the
desired outcome. For example, different neuromuscular stimuli
and adaptations will be produced by manipulation of the number
of repetitions, sets, load/intensity, and periods of rest within an
exercise program. The strength-endurance continuum of resistance
training
12
prescribes how programs using low repetitions and high
resistance; 3 to 5 repetitions maximum (RMs) will elicit optimal
adaptation of strength, whereas training with high repetitions and
low resistance (>12 RMs) promotes muscular endurance.
13-15
A
recent Cochrane review of land-based therapeutic exercise on knee
OA
8
highlighted the marked variability across studies with respect
to exercise interventions. The review identified strengthening ex-
ercises that varied from straightening the knee over a rolled
towel
16
to multiple sitting and standing exercises with body
weight only
17
and body-weight squat exercises to strengthen
multiple lower limb muscles.
18
Each of these exercises likely
represents different intensities of resistance and muscular chal-
lenge, may not all be optimal for strength gain, and importantly
could cloud the interpretation of the effects of true muscle
strengthening programs on symptoms of knee OA.
The development of resistance training programs should follow
a predetermined structure to elicit the desired response, incorpo-
rating 3 common principles: specificity, overload, and progression.
The proper use of these principles ensures that the loads assigned
are sufficient to challenge the involved muscles to become
stronger, faster, or more resistant to fatigue.
19
In addition, the
precise principles of the exercise training should be consistently
and accurately reported such that the methods could be repeated.
This is important for the effective and accurate judgment of the
effects of the intervention alongside the dose of exercise and,
importantly, individual adherence to the regimen.
Why it is important to do this review?
This review is important because international guidelines advocate
various nonpharmacologic treatments, including muscle
strengthening, as important in management of knee OA
10
;how-
ever, there is a lack of systematic consideration of the principles of
training within those criterion standard randomized controlled
trials (RCTs) that should provide the best evidence regarding the
effectiveness of exercise interventions. RCTs with an inadequate
methodologic approach promoting suboptimal gains may be
reporting inaccurately the true effects of muscle resistance
training, and may be biased in assessing causal attributions. This
precludes a proper critical appraisal of the quality of clin-
ical evidence.
The objective of this review is to evaluate RCTs with a primary
focus of muscle resistance training in patients with knee OA,
specifically concerning (1) the application of the principles of
resistance training in the development of the prescribed exercise
within the experimental design; (2) the detailed reporting of the
components of the exercise prescription in the methods, as cate-
gorized by the principles of resistance training; and (3) the
collection and reporting of data of adherence of patients to the
prescribed intervention. An RCT aims to reduce bias when testing
a new treatment against a standard treatment. Given there is no
standard treatment for management of knee OA, we chose to
exclude studies from this systematic review that compared resis-
tance training with another form of exercise only.
Methods
Search strategy and eligibility
A search of the literature for studies published up to August 10,
2015, was performed on the following databases: MEDLINE
(OVID platform), PubMed, Embase, and Physiotherapy Evidence
Database using the Preferred Reporting Items for Systematic
Reviews and Meta-Analyses guidelines.
The following search terms were used, with appropriate ad-
justments for each database: Osteoarthritis: [MeSH] OR osteoar-
thritis [ti; ab] AND knee [MeSH] OR knee joint [MeSH] OR knee
[ti; ab]; for muscle resistance exercise/therapy: Exercise [MeSH]
OR exercise* [ti; ab] OR muscle contraction [MeSH] OR
strengthening [ti; ab] OR weight lifting [MeSH] OR weight lifting
[ti; ab].
This combined search yielded 1574 results. Results were
filtered by study type, using the following filters: clinical trial;
comparative study; controlled clinical trial; randomised controlled
trial [exp clinical trial/OR clinical trial, phase i/OR clinical trial,
phase ii/OR clinical trial, phase iii/OR clinical trial, phase iv/OR
controlled clinical trial/OR multicenter study/OR observational
study/OR randomized controlled trial/OR comparative study/].
This yielded 703 results. Cross-referencing of other relevant ar-
ticles and reviews yielded a further 5 results.
There were 708 titles and abstracts screened for eligibility
independently by 2 reviewers (C.M. and N.G.). The full text of the
article was obtained if it was judged eligible by at least 1 reviewer.
There were 78 full texts obtained, and eligibility was judged
independently by the same reviewers. Consensus on inclusion was
reached by discussion in the event of any discrepancies.
Studies were included in the review if they were published in
the English language and met the following criteria: (1) muscle
resistance training was the primary intervention; (2) RCT
design; (3) treatment arms included at least a muscle condi-
tioning intervention and a nonexercise group; and (4) partici-
pants had OA of the knee. Studies using preoperative (joint
replacement) interventions with only postoperative outcomes
were excluded.
After exclusions based on inclusion and exclusion criteria,
duplicate publishing of studies, and the inability to obtain the
relevant methodologic data from publishers,
20
34 studies were
included in the final review. The full text of the 34 articles was
assessed for (1) the application of the principles of resistance
training in the design of the prescribed exercise; (2) the detailed
reporting of the components of the exercise prescription, as
categorized by the principles of resistance training; and (3) the
List of abbreviations:
OA osteoarthritis
RCT randomized controlled trial
RM repetition maximum
Resistance training in knee osteoarthritis 1843
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collection and reporting of data of adherence of patients to the
prescribed intervention. See figure 1 for a diagram of the search
strategy and results.
The strength-endurance continuum for resistance training
12
was used as reference to assess the focus of the stated training
stimulus. The number of repetitions allowed by the resistance will
result in very specific training adaptations, namely training for
muscle strength <6 RMs, training muscle hypertrophy between 6
and 12 RMs, and training for muscular endurance >12 RMs,
19
where RMs define the maximum number of repetitions that can
be successfully performed.
For each eligible study, details of the intervention protocols
were abstracted using defined criteria. Each study was assigned a
score rating for each of the principles of resistance training
(specificity, overload, or progression) separately for the applica-
tion of the principle within the design of the study and the
adequate reporting of that principle within the methodology. This
scoring system was also applied to the criterion of adherence for
the study design (Were data collected on adherence?) and
reporting (Was adherence described in sufficient detail?). Appli-
cation of the specific principle/criterion was assigned a 1, and
0 was assigned if the principle/criterion was not used or described
adequately. Details of the scoring criteria are shown in tables 1
and 2. A total score for the principles of resistance training and
adherence criteria were obtained for each study reviewed.
Results
The details and overall scores of the 34 individual studies are
listed in table 3. Of the 34 studies, 6 failed to attend to any of the
principles of resistance training in the design of the exercise
intervention and 5 studies failed to report in adequate detail on
these specific components (see table 3). Only 24% of the studies
appropriately applied the principle of specificity, 59% applied the
principle of overload, and 74% applied the principle of progres-
sion within the experimental design. The reporting of the
component of specificity was more widely achieved across studies
(nZ20; 59%); however, 16 of these same studies failed to score on
specificity within the design. The reporting of the components of
overload and progression of the exercise interventions was ach-
ieved adequately by 35% and 62% of the studies, respectively
(appendices 1 and 2).
Focus
All the studies reviewed described a strength training focus within
the rationale, hypothesis, and/or methods. One study involved
both separate strength and power training interventions,
30
and
another study described both low- and high-intensity strength
training.
42
The methods of resistance training ranged across
resistance training machines, free weights, ankle weights and
Records idenƟfied through
database searching
(n = 1574 )
Screening
Included
Eligibility
Identification
AddiƟonal records idenƟfied
through other sources
(n = 5)
Total records screened (Ɵtles and
abstracts)
(n = 708)
Abstracts excluded with
reasons
(n = 630)
Full-text arƟcles assessed
for eligibility
(n = 78)
Studies included in
qualitaƟve synthesis
(n = 34)
‘Secondary analysis’
(arƟcle excluded)
(n = 1)
Records filtered by
study type
(n = 1579)
Fig 1 Flow diagram of the search strategy and results.
1844 C. Minshull, N. Gleeson
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sandbags, elastic resistance bands, and isometric holds both
against an immovable restraint and at the end range of motion.
Specificity, overload, and progression
Strengthening interventions ranged from 3 repetitions of 8 sets at
80% 1 RM with 1 to 2 minutes interset rest interval
33
to 20 rep-
etitions of 1 set at an unspecified intensity/load over 6 exercises
with no specified interset rest interval.
51
The overload intensity of
exercises ranged across achievement of a subjective ratings of
perceived exertion score,
49
a prescribed predetermined percent of
1RM
22
or 10 RM,
28
to the subjectively judged production of
maximal voluntary contractions
24,52
(see table 3). Progression of
exercise, where documented, ranged across increasing the resis-
tance of the exercise to maintain 80% 1 RM, which was measured
biweekly,
30
a 5% biweekly increment of resistance of the initial
50% 1 RM,
38,39
and increased hold times of isometric
contractions.
21
Adherence
Six studies (18%) failed to score on the adherence criteria.
Methods for adherence monitoring to exercise interventions
were incorporated into the design of 82% (nZ28) of the
studies. These were principally constrained to the monitoring of
dropouts and the reporting of the final number of patients who
completed the trial. The detailed monitoring and reporting of
adherence data on the average volume (dose) of exercise
completed per individual was only achieved by 38% (nZ13) of
studies.
26,27,30-35,42,44-46,48,50,51
Table 1 Application and reporting of the principles of resistance training in the prescribed exercise
Principle/Criterion Description
Specificity Specificity of the training intervention will elicit improvements in specific outcomes.
Design Score 1/0 Reporting Score 1/0
Have the authors designed the intervention
appropriately to achieve the desired
outcome: conditioning of muscle
strength, muscle power, or muscle
endurance (correct manipulation of
repetitions, velocity, and type of
muscle action)?
Have the authors adequately described
the specificity of the intervention to
condition muscle strength, muscle power,
or muscle endurance within the methods
and/or results?
Overload Assigning a training regimen of greater intensity than the individual is accustomed to to achieve
the desired outcome.
Design Score 1/0 Reporting Score 1/0
Have the authors appropriately manipulated
training load/intensity, sets, frequency,
and rest to achieve the specific outcome?
Have the authors described adequately
issues of load/intensity, sets, frequency,
and rest within the methods and/or
results?
Progression Intensity of the intervention must become progressively greater as improvements occur.
Design Score 1/0 Reporting Score 1/0
Have the authors appropriately manipulated
the training load, repetitions, and/or
volume over time to progress the
intervention?
Have the authors described adequately how
progression of the intervention was
achieved and assured within the
methods and/or results?
Table 2 Design and reporting of adherence to the prescribed exercise
Principle/Criterion Description
Adherence Extent to which an individual acts in accordance with the advised interval, exercise dose,
and exercise dosing regimen.
Design Score 1/0 Reporting Score 1/0
Have the authors designed and described
methods for adherence monitoring?
Have the authors reported adequately the
adherence of individuals to the
intervention, including exercise dose per
individual over the full time period
(number of sessions completed as a
proportion of the total)?
Resistance training in knee osteoarthritis 1845
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Table 3 Details of individual studies reviewed
Authors
Total Score
(PoRT þAD)
Exercise Characteristics
Reps Sets Intensity Rest Mode/Type
Frequency, Times Per
Week Weeks Progression
Crossley et al
21
351to153 At least 5/10 on NRS ? 3 strengthening
exercises: inner- and
midrange (OKC) and
wall squat
412 Increased hold times
and resistance tubing
Jorge et al
22
682 50% and 70% 1 RM 1min 4 exercises on resistance
training equipment
212 Loads evaluated every
2wk
Park and Hwangbo
23
3103? 50%, 75%, 100% 10 RM ? PRT group: KEs with
sandbags on ankles
38 10 RM evaluated each
week
Anwer and Alghadir
24
3101e3(2/d) MVIC ? 3 exercises: SLRs,
isometric KE (over
rolled towel), and hip
abduction
55 Progression of number
of sets per week
Samuel et al
25
4105 50% 1 RM þ? KEs with ankle weights 54 5% increment per week
Bruce-Brand et al
26
2103 RPE 14/15 ? 3 exercises with
resistance bands
36 RPE <14
McKay et al
27
282 60% 1RM ? 3 exercises on resistance
equipment (þBW calf
raises)
361e2kg/wk
Imoto et al
28
1153 50%e60% 10 RM 45s KEs weighted 28?
Chang et al
29
4103 13 RPE for 10 RM 1e2min Leg press with
resistance bands
28 12 RM at RPE 13
Sayers et al
30
3 Power 12e143 (fast) 40% 1 RM ? Leg press and KEs on
resistance equipment
312 1 RM assessment
Sayers et al
30
Strength 8e103 80% 1 RM ? 312 Assessed every 2wk
de Olivera et al
31
0153 50%e60% of 10 RM 30e45s KEs (mode?) 28?
Swank et al
32
2101e2 ? ? 9 exercises with
resistance bands
34e8?
Foroughi et al
33
583 80% 1 RM 1e2min 6 exercises on RT
equipment
324 1 RM assessment every
2wk; 3% RPE
increments between
Bennell et al
34
1103 ? 6 exercises with
resistance bands and
ankle weights
512 ?
Farr et al
35
46e81e2 Up to 50%e75% 3 RM ? 3 lower limb exercises
(resistance bands to
resistance equipment)
336 50%e75% 3 RM
Shakoor et al
36
0?????6?
(continued on next page)
1846 C. Minshull, N. Gleeson
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Table 3 (continued )
Authors
Total Score
(PoRT þAD)
Exercise Characteristics
Reps Sets Intensity Rest Mode/Type
Frequency, Times Per
Week Weeks Progression
McKnight et al
37
36e102 3 and 6 RM ? Resistance bands to free
weights and
resistance equipment
?36 (phase 1) Achievement of 10 reps
with given weight;
weight increased
(62)
Lin et al
38
364 50% RM þ1min KEs (on custom
dynamometer)
38 50% 1 RM 5%
increments every 2wk
Jan et al
39
464 50% RM þLeg press, KEs on
resistance training
equipment
38 50% 1 RM 5%
increments every 2wk
Lim et al
40
3102e3 Comfortably able to
complete
? 5 exercises with
resistance bands and
ankle weights
512 Loads progressed when
patients could
achieve given dosages
Jan et al
41
6 Hi Int 83 60% 1 RM (pain
determined)
1min Leg press 38 1 RM assessed every
2wk, 5% increments
to load
Jan et al
41
Low Int 1510 10% 1 RM 1min Leg press 38 1 RM assessed every
2wk, 5% increments
to load
Mikesky et al
42
48e1038e10 RM ? Leg press and KFs on
resistance training
equipment
352 (þ24
unsupervised)
12 reps
reacheddresistance
increased
Foley et al
43
2103 10 RM ? 6 exercises with ankle
weights
36 15 reps reached
Huang et al
44
4 Isokinetic
Isotonic
Isometric
51e6 60% Max torque 5s KEs and KFs (all modes
isokinetic, isotonic,
isometric)
38?
Cheing et al
45
463 MVIC 1min Isometric MVIC KEs at 3
angles KFs 1 angle
54?
Gu¨r et al
46
4 Con/Ecc 126 MVC 2min Isokinetic KE and KF 38?
Topp et al
47
2 Dynamic 81to123 RPE of mild fatigue 2min 6 exercises with
resistance bands
316 Increased resistance
bands
Topp et al
47
Isometric 81to123 RPE of mild fatigue 3min 7 exercises with
resistance bands
316 Increased hold times
and resistance
Baker et al
48
4122 8/10 RPE ? 4 exercises with ankle
weights (knee and
hip)
316 6/<on RPE reached
Sevik et al
49
4102 10 RM ? 4 lower limb exercises
ankle weights
312 12 reps reached
(continued on next page)
Resistance training in knee osteoarthritis 1847
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The mean score across the 6 criteria for the application
and reporting of the principles of resistance training across
the 36 studies was 3.051.48. Of the studies, 6% scored full
marks, and only 71% of the studies scored half-marks or
more (see appendix 2). The overall mean score across the 8
criteria (principles of resistance training plus adherence)
was 4.291.62.
Discussion
This systematic review evaluated RCTs with a primary focus of
muscle resistance training in patients with knee OA that did not
have an exercise control group. Specifically, studies were evaluated
on the extent to which the principles of resistance training had been
applied in the development of the prescribed exercise and the
quality and extent of reporting of the components of the exercise
prescription. Data pertaining to the monitoring and reporting of
participant adherence to the exercise regimen were also evaluated.
The results showed that the principles of resistance training were
inconsistently applied within the exercise design and were inade-
quately reported (see appendix 1). The principle of specificity was
least frequently applied, evident in only 24% of studies, and over-
load was least frequently reported adequately, in 35% of studies.
These findings affect the interpretation of the efficacy of muscle
resistance exercise in the management of knee OA. This is com-
pounded by the lack of detailed reporting of individual adherence, or
average dose of exercise experienced by each patient. Taken
together, none of the 34 studies reviewedscored a full 8 marks across
principles of resistance training and adherence criteria, and only 3
studies scored 7 out of 8
22,33,41
(see table 3 and appendices 1 and 2).
These data illustrate that health care professionals and clinicians
cannot be confident whether nonsignificant findings are because of a
lack of efficacy of muscle resistance interventions, or because of
limitations in treatment prescription and patient adherence.
Consistent across most studies was the lack of documentation
of the rationale for the selected exercise prescription. Despite all
studies describing a strength training focus, only 2 studies used a
repetition range at an appropriate intensity for optimal strength
gains
50,52
(3e5 repetitions of maximum voluntary contraction). A
further 5 studies prescribed 6 repetitions per set
35,37,38,41,45
;
however, only 1 study did so at an intensity (maximum voluntary
contraction) likely to evoke optimal strength changes
45
(see
table 3). The maximum training loads achieved in the remaining
studies
37,38,41
ranged from 65% 1 RM to 75% 3 RM.
Patients with OA may be symptomatic and/or suffer reduced
levels of muscle function capabilities compared with aged-
matched healthy counterparts. Clearly, these factors should be
taken into account during exercise design and prescription. The
rationale used by some of the studies in this review to justify a
low-intensity protocol (50%e60% 10 RM) was to “.avoid the
possibility of injury caused by excessive strain.”
28(p82)
Unfortu-
nately, the evidence for this appears to be drawn from a disser-
tation,
55
which given the wealth of peer-reviewed literature
documenting the efficacy of progressive strength training pro-
grams even in the very elderly, seems to be an inappropriate cri-
terion by which to shape the design of their exercise intervention.
There is also the potential for exercise to elicit a pain response in
OA populations. This is an important consideration in exercise
design; however, to adopt a conservative approach to muscular
loading a priori could potentially result in ineffective strength-
ening exercise prescription. It is encouraging to see recent studies
Table 3 (continued )
Authors
Total Score
(PoRT þAD)
Exercise Characteristics
Reps Sets Intensity Rest Mode/Type
Frequency, Times Per
Week Weeks Progression
Maurer et al
50
333(3 velocities) MVC 1min Isokinetic KEs at 3
velocities
38 Strength assessment
every 2wk
O’Reilly et al
51
1201(5) ? ? 5 exercises (isometric
holds and stepping)
724 Reps increased to 20
Røgind et al
52
2103 70% of “individual
ability”
? 6 exercises with ankle
weights
612 Increased reps and ankle
weights when able
Schilke et al
53
556 MVC ? Isokinetic KE and KF
90/s
38?
Kreindler et al
54
3104e8, different
speeds
? ? Isokinetic KEs and KFs
(60e300/s)
36 Exercises progressed
every week (? details)
Abbreviations: ?, unclear/not stated; AD, adherence; BW, body weight; Con/Ecc, Concentric/Eccentric; Int, intensity; KE, knee extension; KF, knee flexion; Max, maximum; MVC, maximal voluntary contraction;
MVIC, maximal voluntary isometric contraction; NRS, numerical rating scale (maximum score, 10); OKC, open kinetic chain; PoRT, principles of resistance training; PRT, progressive resistance training; Reps,
repetitions; RPE, ratings of perceived exertion; RT, resistance training; SLR, straight leg raise.
1848 C. Minshull, N. Gleeson
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reporting that progressive resistance training and explosive resis-
tance strength training programs are both feasible and tolerable in
preoperative patients with OA and have an adherence of
>90%.
56-59
Tolerance in this group is likely to be facilitated by
adequate warm-up to downgrade the pain response and therefore
should form an important component of any resistance training
intervention in OA groups.
Gains in dynamic muscular strength may be made in the initial
stages of a strength training intervention using suboptimal loads in
those with no background of resistance training
12,60
; however,
heavy loads are required thereafter to increase maximal strength.
Neural adaptations account for early increases in strength,
whereby improvements in motor unit recruitment, firing rate, and
synchronization take place
61
; however, following this adaptation,
light training loads (eg, resistance approximating 12e15 RM [12
RMZ70% 1 RM] or lighter) rarely increase maximal strength, but
are effective for increasing absolute local muscular endurance.
14
Twenty-three of the reviewed studies used a training load of this
intensity or lighter, 6 used a subjective rating of perceived exer-
tion, and 5 studies failed to document the intensity or load (see
table 3). These are important considerations in an ageing popu-
lation where strength is lost at a rate of 2.5% to 4% per year,
62
in
addition to the likely deleterious effects on muscle strength
associated with symptoms of knee OA.
63
Treatment guidelines
recommend strengthening exercises to combat sarcopenia in pa-
tients with knee OA
4
; however, the specifics of the exercise pre-
scription will continue to be unresolved when trials evaluating
strengthening resistance training interventions have been inade-
quately designed, promoting adaptations in muscular endurance
and doing little to attenuate the sarcopenic decline in muscle
strength. Further, other tissues (eg, tendon, bone) respond more
favorably to heavy loading,
15
which may be a particularly
important consideration for patients with knee OA.
The findings of recent Cochrane
8
and systematic meta-
regression reviews
64
describe the marked variability across studies
with respect to exercise interventions and that optimal exercise
programs for knee OA should have one aim and focus (eg, to
improve aerobic capacity or quadriceps muscle strength). The data
from the current review are in agreement with these findings, and
can go one step further and offer the following recommendations.
First, the process of development of muscle resistance in-
terventions should commence with the determination of the
training/rehabilitation goals, including the focus of the interven-
tion (muscle strength, power, or endurance) and the muscle group.
Second, the design of the intervention should reflect these
goals, including the correct selection of type of exercise(s) and the
detailed address of the principles of muscle resistance training
(specificity, overload, and progression). In doing so, the appro-
priate profile of repetitions, sets, intensity, rest, and progression
will be achieved.
Third, the exercise prescription and the rationale for it should
be clearly reported, such that the methods could be repeated.
Finally, data on individual patient adherence should be
collected and clearly reported. Detailed reporting of the dose of
exercise prescribed and subsequently received will allow for an
adequate interpretation of the results, including possible dose-
response effects.
Future research that takes into account each of these recom-
mendations will produce an improved body of literature with
respect to reporting and delivery of muscular conditioning in
patients with knee OA and therefore should provoke improved
responses and efficacy.
Study limitations
This review is unable to present a meaningful estimation of the
dose response of resistance training and the effect of OA on
clinical outcomes. As the review highlights, this is not currently
possible because of the heterogeneity of methodologic
approaches, which includes the inconsistent application of the
principles of resistance training and the reporting of adherence.
Further, it must be acknowledged that this systematic review
included only nonblinded studies in which the control group
received no exercise. Future reviews that seek to evaluate out-
comes and the efficacy of resistance training interventions should
include designs with exercise controls and blinded allocation to
minimize the potential for bias.
Conclusions
Considerable methodologic diversity exists across studies that
describe the evaluation of the effects of muscle strengthening in
patients with knee OA. This review demonstrated that the prin-
ciples of resistance training were inconsistently applied within the
exercise design and were inadequately reported. As such, <10%
of investigations designed their intervention optimally to elicit
strength gains. Furthermore, conclusions regarding the efficacy of
many interventions could not be made because of the inadequate
reporting of adherence and therefore average dose experienced by
each participant. Although some individual studies have shown a
benefit of muscle strength training on symptoms of knee OA, a
proper scientific appraisal of the literature cannot be conducted at
this time. Future research that seeks to evaluate the effects of
muscle strength training interventions on symptoms of OA should
be properly designed and adherence diligently reported.
Keywords
Knee; Osteoarthritis; Rehabilitation; Resistance training; Review
[publication type]
Corresponding author
Claire Minshull, PhD, Carnegie School of Sport, Leeds Beckett
University, Headingly Campus, Leeds LS1 3HE, UK. E-mail
address: minshullc@hotmail.com.
Appendix 1 Number of studies that attended to the principles
of resistance training and distribution of scores between studies
Design Reporting
Specificity Overload Progression Specificity Overload Progression
8 2024 20 1220
Score (Maximum, 3) Count Score (Maximum, 3) Count
0605
19110
214214
3535
Resistance training in knee osteoarthritis 1849
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