Objective To systematically review the impact of prehabilitation on objectively measured physical activity (PA) levels in elective surgery patients.
Data sources Articles published in Web of Science Core Collections, PubMed, Embase (Ovid), CINAHL (EBSCOHost), PsycInfo (EBSCOHost) and CENTRAL through August 2020.
Study selection Studies that met the following criteria: (1) written in English, (2) quantitatively described the effect(s) of a PA intervention among elective surgery patients prior to surgery and (3) used and reported objective measures of PA in the study.
Data extraction and synthesis Participant characteristics, intervention details, PA measurement, and clinical and health-related outcomes were extracted. Risk of bias was assessed following the revised Cochrane risk of bias tool. Meta-analysis was not possible due to heterogeneity, therefore narrative synthesis was used.
Results 6533 unique articles were identified in the search; 21 articles (based on 15 trials) were included in the review. There was little evidence to suggest that prehabilitation is associated with increases in objectively measured PA, but this may be due to insufficient statistical power as most (n=8) trials included in the review were small feasibility/pilot studies. Where studies tested associations between objectively measured PA during the intervention period and health-related outcomes, significant beneficial associations were reported. Limitations in the evidence base precluded any assessment via meta-regression of the association between objectively measured PA and clinical or health-related outcomes.
Conclusions Additional large-scale studies are needed, with clear and consistent reporting of objective measures including accelerometry variables and outcome variables, to improve our understanding of the impact of changes in PA prior to surgery on surgical and health-related outcomes.
PROSPERO registration number CRD42019151475.
- sports medicine
- adult surgery
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information. All data generated or analysed during this study are included in this published article.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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Strengths and limitations of this study
This review is the first to synthesise the findings of prehabilitation interventions in which objective measurements of physical activity were used.
A systematic approach was used and evidence across surgery types was included.
Meta-analysis and meta-regression were not possible due to heterogeneity in measurements and reporting conventions.
Preoperative levels of physical fitness have been positively associated with surgical outcomes, including lower risk of postoperative morbidity and mortality.1–3 This may be because preoperative physical fitness is indicative of the body’s capacity to withstand the stress of surgery,3 which may in turn contribute to a faster recovery from surgery and a quicker return to preoperative physical functioning levels. As postoperative morbidity is a substantial burden on health systems and can have adverse impacts on patients’ health and well-being,4 interventions to reduce the risk of poor postoperative outcomes are important.
In recent years, exercise interventions prior to surgery (‘prehabilitation’) have become increasingly recognised as a way to improve surgical outcomes across surgery types.5 6 There is diversity in prehabilitation programme methods and contents (eg, supervised exercise training, home-based physical activity (PA) programmes, educational sessions), but all share the key goal of improving patients’ functional capacity in advance of surgery in order to improve clinical outcomes following surgery.7 8 Across surgery types, a number of systematic reviews and meta-analyses have concluded that prehabilitation is effective for increasing patients’ functional capacity,9 reducing patients’ length of hospital stay10–12 and reducing the likelihood of postoperative complications.11–16
A key element that has received little attention within the context of prehabilitation is the use of objective measures of PA such as accelerometry. Accelerometers capture free-living movement of all intensities, usually over a week-long period, and can be used to estimate time spent in moderate-to-vigorous physical activity (MVPA) or light-intensity PA, average daily acceleration or average steps per day.17 18 While there is some variation in the validity of accelerometer measurements (driven largely by variation in wear protocol specifications), accelerometers have been shown to have near-perfect agreement with direct observation for the classification of PA intensity19–22 and have higher measurement validity than subjective methods.22 To date, most prehabilitation interventions have used self-report methods to estimate changes in PA levels across the intervention period.23–25 However, self-reported measures of PA are not well-suited to capturing changes in PA levels over time26 and the high measurement error of self-report methods for estimating total PA severely limits the interpretability of the findings. Use of accelerometry within the context of prehabilitation could overcome these limitations, enabling stronger estimates of the impact that prehabilitation may have on PA levels prior to surgery and the subsequent impact on clinical outcomes. The extent to which accelerometry has been used in prehabilitation interventions is not currently known.
This review seeks to synthesise the available literature that has used objective (ie, device-based) measures of PA within the context of prehabilitation. The specific aims of this systematic review are (1) to assess the impact of prehabilitation interventions on objectively measured PA levels and (2) to determine meta-associations between objectively measured PA levels during the prehabilitation period on health-related and clinical outcomes.
Information sources and search strategy
The protocol for this review was registered with PROSPERO. Six databases (Web of Science Core Collections, PubMed, Embase (Ovid), CINAHL (EBSCOHost), PsycInfo (EBSCOHost), Central) were systematically searched in August 2020 using broad search terms to capture exercise interventions related to surgery (online supplemental file 1). The search was not limited by publication date but was restricted to publications written in English. The citations of included articles were checked and, if relevant, were included in the review.
Studies were included in the review if they (1) quantitatively described the effect(s) of a PA intervention among elective surgery patients prior to surgery and (2) used and reported objective measures of PA in the study. There were no limits to the kind of surgery for which patients were scheduled, nor were there restrictions on the prehabilitation programme contents or structure. Exclusion criteria included (1) no reported objective measures of PA and (2) observational studies in which no PA interventions were implemented.
Study selection and data extraction
Titles and abstracts of the search results were screened for relevance. A subsample (10%) was screened independently by two reviewers (JW and Dr Sonia Ahmed) for eligibility to check consistency and agreement (which was high, 97%) before the lead author continued with the remainder of the screening. The full texts for any articles with relevant abstracts were consulted for eligibility.
Eligible studies were read and their data were extracted by the lead author using a prespecified data extraction form adapted from Booth et al27 including general study details, study design and methodology, sample characteristics, statistical analyses and main study findings. Risk of bias was assessed by the lead author (JW) following the revised Cochrane risk of bias tool (RoB 2).28 A second author (AK) independently assessed the risk of bias for a subsample (20%) of articles; agreement between both authors’ assessments was high. Risk of bias was done for each article (even where multiple articles reported on the same trial) because outcome variables and prevalence of missing data differed between articles and thus required separate consideration.
Synthesis of results
Because of lack of data and inconsistencies in the ways in which outcome data were reported, meta-analysis was not possible. A narrative synthesis was used instead to summarise the review findings. Throughout the narrative, we present the findings in order of study rigour, primarily in terms of study design, for example, randomised controlled trials (RCTs) first. We also discuss changes specific to the intervention period (ie, preintervention and postintervention) first before discussing any measurements gathered from the follow-up period.
Patient and public involvement
No patients involved.
Study selection and characteristics
The flow of studies through the review is shown in figure 1. After the removal of duplicates, 6533 unique articles were screened. In many cases, it was not immediately clear from the title and abstract of relevant articles whether PA was measured objectively, thus the full-text was consulted for a large number of articles.
Twenty-one articles reporting on 15 separate trials were eligible for inclusion in the review (table 1). Over half (n=8) of the trials identified themselves as feasibility or pilot studies. The majority of trials (n=9) were based in Europe (n=4 of these in the UK) with the remainder (n=6) based in North America (n=3 in the USA, n=3 in Canada). Nine trials were RCTs with sample sizes ranging from 17 to 118; five were single-arm trials with sample sizes ranging from 12 to 50 and one was a non-randomised parallel group trial (n=35). Most of the trials (n=7) involved patients preparing for cancer-related surgery; the remainder were patients preparing for bariatric surgery (n=2), kidney or liver transplantation (n=2), orthopaedic surgeries (n=2), coronary artery bypass grafting (n=1) or general major surgery (n=1).
The prehabilitation interventions were highly variable and diverse in terms of duration and content (table 2). In 11 of the trials, the interventions consisted of structured exercise training programmes that involved either supervised training sessions in a facility (n=6) or unsupervised home-based programmes (n=5). In four trials, the interventions consisted of education-based or behavioural change programmes in which patients were given advice or counselling regarding PA but were not given a detailed programme to follow. One study used both exercise training and education within the intervention.29 The duration of the interventions ranged from a one-off information session to a structured and supervised 3-month to 6-month programme while patients awaited bariatric surgery.
The measurements of PA used in each trial are described in tables 3 and 4. Ten trials objectively measured PA during the intervention period (table 3) and seven trials objectively measured PA postoperation (table 4); two trials measured PA at both time points and are thus counted two times here. The most common type of accelerometer used was the Actigraph (n=6 trials) and the most common wear protocol (regardless of accelerometer brand) was hip-worn (n=6) followed by wrist-worn (n=4). Daily steps were the most frequently measured metric of PA (n=9) followed by indices of overall PA (eg, mean counts per minute, total active minutes; n=7) and time spent in MVPA (n=6), although the definitions of MVPA varied between trials. Most trials measured more than one metric, for example, three trials measured both steps per day and time spent in MVPA.
Impact of prehabilitation on PA levels
Eight trials reported on changes in objectively measured PA from baseline to postintervention29–35 or the end of the intervention period36 37 (table 3). Among RCTs or non-randomised parallel group trials (n=4), only one study reported a significant difference: Bond et al31 reported a significantly larger improvement in MVPA and steps per day in the intervention group compared with the control group from baseline to postintervention. The remaining RCTs/parallel studies reported no differences between intervention and control groups in objectively measured total PA level29 34 36 or steps per day29 34 36 37 from baseline to postintervention29 34 or baseline to the end of the intervention.36 37 Single-arm trials tended to report significant increases in PA across the intervention period. Grimes et al32 and McAdams-DeMarco et al33 reported significant increases in objectively measured total PA from baseline to the end of the intervention and Williams et al35 reported a significant increase in steps per day. Alejo et al30 found no difference in MVPA from baseline to the end of the intervention.
Seven trials (all RCTs) compared objectively measured PA levels in terms of total PA, time in MVPA and light physical activity (LPA), and steps per day between the intervention and control groups in the postoperative period, ranging from postoperative day 1 to 1 year following surgery29 38–43 (table 4). Four trials made cross-sectional comparisons between the PA levels of the intervention group and control group in the postoperative period, and all four studies found significant differences.38–41 Three of these reported that PA levels were higher among the prehabilitation group in terms of total PA on postoperative day 1,38 steps per day at 6 months40 and steps per day 1 year39 following surgery; the fourth study found that the prehabilitation group had fewer steps per day than the control group in the immediate postoperative period.41 The remaining three trials compared changes in PA levels from baseline to the postoperative period (3 months) and found no significant differences in change in MVPA,42 43 total PA,29 43 steps per day,29 42 light PA42 or sedentary time42 between the intervention and control groups in the postoperative period.
Impact of objectively measured PA on health-related outcomes
Four trials tested associations between changes in objectively measured PA over the intervention period and health- and clinically-related outcomes.44–47 Bond et al44 reported that increases in MVPA (accumulated in bouts lasting ≥10 min) during the intervention period were associated with significant improvements in health-related quality of life in terms of physical function (β=0.43, p=0.04), bodily pain (β=0.39, p=0.03) and general health (β=0.56, p=0.048) (no CIs were reported). Among the same sample, increases in MVPA were not associated with changes in enjoyment, self-efficacy or motivation for PA (only p values were reported, ranging from 0.20 to 0.90).45 Dronkers et al46 reported a significant correlation (rpb=0.50, p=0.02; no CIs reported) such that those with more objectively measured steps per day during the intervention period were less likely to experience postoperative pulmonary complications. In a single-arm trial, Ngo-Huang et al47 reported that accelerometer-measured MVPA and LPA averaged over the prehabilitation period were each associated with improvement in 6 min walk test distance (MVPA β=0.18, p=0.03; LPA β=0.08, p=0.03) and perceived physical functioning (MVPA β=0.03, p<0.01; LPA β=0.01, p=0.02); MVPA was also associated with physical well-being (β=0.01, p=0.04) and LPA was associated with change in health-related quality of life from baseline to end of intervention (β=0.03, p=0.02 and β=0.02, p<0.01 for Functional Assessment of Cancer Therapy-Hepatobiliary and Functional Assessment of Cancer Therapy-General subscales, respectively).
Due to high heterogeneity of the studies included in the review, it was not possible to determine meta-associations between objectively measured PA levels during the prehabilitation period and health-related or clinical outcomes. The findings of each trial in relation to the impacts of the interventions on health and clinical outcomes are detailed in tables 3 and 4. These results are not discussed further in the text because, due to our inclusion criteria, the studies included in this review represent a very small subgroup of the larger body of evidence that has examined impacts of prehabilitation on these outcomes.
Risk of bias
Risk of bias was deemed to be high for nine articles and low for seven articles; some concerns were noted for the remaining five articles (online supplemental file 2). The most common sources of bias came from issues during randomisation or lack of randomisation all together, reflecting the pilot/feasibility nature of most of the studies. We did not identify high risk of bias in the measurement of the outcome in any articles.
This review identified 21 articles based on 15 separate trials that used objective measures of PA within PA interventions prior to surgery. There was a high degree of variability across the studies in terms of surgery type, nature of the prehabilitation intervention, outcome measurements, and completeness in the reporting of PA measurements and outcome variables. The lack of complete and consistent reporting meant that meta-analysis could not be used to estimate pooled effects across studies or to examine the relationships between changes in objectively measured PA and clinical outcomes. Additionally, almost half of the included studies were small feasibility or pilot studies that were not statistically powered to detect associations that were being tested. There is a clear need for more widespread use of accelerometry within large-scale prehabilitation interventions, alongside transparent and consistent reporting of predictor and outcome variables, to improve our understanding of the impact that prehabilitation may have on PA levels and on subsequent clinical outcomes.
Across the studies that examined the impact of prehabilitation on objectively measured PA levels during the intervention period, there was no clear effect. Only one of three RCTs reported a significantly larger increase in MVPA and daily steps among the intervention group compared with the control group.31 It is important to note that this RCT was the only study for which a sample size calculation was reported with change in PA (MVPA) as the primary outcome variable.31 The remaining RCTs had comparatively small sample sizes and were either powered for a different (non-PA) outcome variable29 or were feasibility/pilot studies,34 which may explain their null findings. Data from single-arm studies tended to suggest that prehabilitation was effective for increasing PA levels across the intervention period (three out of four). The trials that reported significant changes in PA were unsupervised home-based interventions,31 32 35 suggesting such interventions might have a more effective impact on objectively measured PA, although it is worth noting that not all home-based interventions reported an effect.34 Further randomised studies that are adequately powered to detect changes in objectively measured PA are needed to improve our understanding of the impact of prehabilitation on PA levels.
Among the very few studies in this review that examined associations between objectively measured PA and health-related outcomes, significant associations were reported. For example, Bond et al44 and Ngo-Huang et al47 reported that changes in MVPA during the intervention were associated with improvements in quality of life and physical functioning in the intervention period. These findings suggest that the effects that prehabilitation interventions have on objectively measured PA levels directly correlate with improvements in clinical outcomes. A larger body of evidence-based on accelerometry is required to be able to quantify the volume and/or intensity of PA that patients might be advised to aim for (on a case-by-case basis) in preparation for surgery to optimise clinical outcomes following surgery, as others have similarly suggested.48 To support the development of this evidence base, prehabilitation studies should use objective measures of PA wherever possible during the intervention. Additionally, studies should endeavour to report descriptive statistics of accelerometry variables and health/clinical outcome variables consistently and in sufficient detail to allow meta-analysis of associations to be possible. As this review has identified, this evidence gap is particularly salient for cardiothoracic surgery patients for whom prehabilitation might be especially important.49
We recommend that best practice be followed when objective measures of PA are integrated in future prehabilitation trials to ensure the validity and interpretability of the measurements. When objectively measuring PA (particularly using accelerometry), a number of decisions are required to be made in terms of what device will be used, wear protocol (eg, waking wear or 24-hour wear), minimum wear required to constitute a valid dataset, how to identify and handle periods of non-wear, and the selection of relevant outcome variables and how they will be defined. Best practice depends on what the outcome of interest is (ie, measurement of sedentary time has different considerations than measurement of MVPA); we refer readers to useful reviews for further details.17 22 50
This review has several limitations that must be acknowledged. Over half of the included studies were small feasibility or pilot studies for which power calculations were not performed. The null findings throughout this review should thus not necessarily be interpreted as a lack of effect of prehabilitation. Additionally, the fidelity of the interventions was generally not assessed or reported, thus we cannot rule out the possibility that issues or inconsistencies in intervention implementation within studies may also be at play. Finally, the small number of eligible studies involving a range of surgery types meant it was not possible to do any subgroup analyses to examine any differences in outcomes according to type of prehabilitation programme or type of surgery.
Few prehabilitation trials have incorporated objective measurements of PA. There is little evidence to suggest that prehabilitation may be effective for increasing patients’ PA levels prior to surgery, although the evidence included in this review primarily consisted of small feasibility studies which may not have sufficient statistical power. There was some evidence to suggest that increases in objectively measured PA were associated with improvements in physical functioning and quality of life. Limitations in the evidence base precluded any assessment of pooled associations between objectively measured PA during the intervention period and surgical outcomes. Additional large-scale studies are needed, with clear and consistent reporting of accelerometry variables and outcome variables, to improve our understanding of the impact of changes in PA prior to surgery on health and clinical outcomes.
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information. All data generated or analysed during this study are included in this published article.
Patient consent for publication
We wish to thank Dr Sonia Ahmed for her assistance in the screening process.
Contributors JW conducted the review and drafted the manuscript with the guidance of AK, and JW and AK conducted risk of bias assessment. EA, RHM and HCH provided input into the study design and protocol, interpreted the results, and revised the manuscript. All authors contributed to and approved the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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