https://orcid.org/0000-0002-1968-4452
Figures
Abstract
Background
Hip osteoarthritis (HOA) is a major contributor to functional impairment in older adults. Physical inactivity and comorbidities are commonly associated with declines in functional ability. However, the relationship between physical inactivity and functional outcomes in individuals with HOA, particularly those aged 80 years and older, remains underexplored.
Objective
This study investigated the association between physical inactivity and functional limitations in older adults with HOA, focusing on two age groups: 60–79 years and 80–100 years.
Methods
We analyzed data from Wave 5 of the Survey of Health, Aging, and Retirement in Europe (SHARE), constructing univariate and multivariable logistic regression models. Functional limitations served as dependent variables, with physical inactivity as the primary explanatory variable and number of chronic conditions, body mass index (BMI), gender, education, and depression as covariates.
Results
The study included 2,088 participants (mean age 73.1 ± 8.5 years; 73.7% female). Physical inactivity was reported by 16.8% (n = 261) of participants aged 60–79 years (n = 1,556; 72.5% female) and 49.6% of those aged 80–100 years (n = 532; 22.5% female). Poor handgrip strength and difficulty rising from a chair were significantly more prevalent among females aged 60–79 years (p < 0.002 for both). A marked decline in both physical activity and functional ability was observed between the two age groups. Physical inactivity emerged as an independent risk factor for reduced functioning across all outcomes, with stronger associations in the 80–100 years age group.
Citation: de Mello GMdV, Frajácomo FTT, Haagsma AB, Souza DLB, de Oliveira VB, Olandoski M, et al. (2025) Physical activity and functional preservation in older adults with hip osteoarthritis: A comparative analysis of age cohorts in the SHARE study. PLoS ONE 20(3): e0317578. https://doi.org/10.1371/journal.pone.0317578
Editor: Domiziano Tarantino,, University of Naples Federico II: Universita degli Studi di Napoli Federico II, ITALY
Received: July 29, 2024; Accepted: December 31, 2024; Published: March 26, 2025
Copyright: © 2025 de Mello et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: Data was accessed and is available at https://1drv.ms/x/s!AimG31vLYOkgjJ9QZ7sLHOBWkcxT4g?e=CswQbR. The SHARE database is open for any researcher who wants to analyze data and after a procedure which is stated in: https://share-eric.eu/data/.
Funding: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) number 88887.309822/2018-00. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Introduction
According to data from the European Project on Osteoarthritis (EPOSA), osteoarthritis (OA) is the leading cause of pain and disability among older people [1]. The Global Burden of Disease Study [2] projected that 595 million people (7.6% of the world’s population) lived with OA in 2020, with higher incidence amongst females. In people with OA, movement limitation is standard, with one in every four people over 60 unable to perform activities of daily living such as dressing, getting out of a chair, or walking rapidly [3].
Physical inactivity, obesity, comorbidities and biomechanical variables all represent modifiable risk factors that can affect the progression of pain and physical function in people with OA [4] and current research suggests that higher levels of physical activity (PA) are inversely associated with the prevalence and incidence of comorbidities in people with hip and knee OA [5,6]. Still, the relationship between PA and function remains to be described, particularly among the oldest-old population. A Cochrane review of twenty-one trials found that involvement in exercise programs slightly enhanced physical function in those with OA aged 45 and over [7]. Furthermore, clinical guidelines recommend exercise and PA programs as the primary components for managing and preventing significant OA [8]. However, programs aimed to increase both self-reported and accelerometry-measured PA demonstrated limited effectiveness [9] and the relationship between PA and other risk factors for physical function is still unknown in early older and late older people with OA.
Population-based research is essential for understanding the pattern and link between PA, comorbidities, and physical function. A previous systematic review has described a complex interplay of physical, psychological, and social factors influences PA engagement in individuals with lower limb OA [10]. Still, there is scarce evidence on the factors influencing physical function in older people with hip osteoarthritis (HOA) in an older than 80 years population. Utilizing the European Health, Aging, and Retirement Survey (SHARE), we aimed to analyse the association between PA levels and self-reported daily activities among older adults with symptomatic HOA, segmented by two age groups (60–79 and 80–100).
Methods
SHARE database
This is a cross-sectional analysis of SHARE, a global prospective survey that aims to investigate the aging process within different social and cultural backgrounds across Europe. The SHARE Project complies with the Declaration of Helsinki’s guidelines for participant confidentiality; all participants and/or their legal guardians provided informed consent for study participation. SHARE is subject to continuous revisions by ethical committees, waves 1–4 were approved by the Manheim University Ethical Committee, while the subsequent waves were approved by the Ethics Council of the Max Planck Society. Additional information on sampling processes, data collection, and other methodological features can be obtained at www.share-project.org [11].
The SHARE study has gathered socio-demographic characteristics, medical history, functionality, and cognitive function scores of individuals age => 50 in 28 different European countries. All households with at least one person born in 1954 or earlier and speaking the national language were included. More details about SHARE can be found elsewhere [11]. SHARE provides specific training before the evaluators visit the respondents’ homes for each wave. The SHARE survey started in 2004 with its first wave, and was repeated every two years, with new participants, nations, and factors added each time [12].
For this analysis, we included those participants with => 60 years of age that reported hip osteoarthrosis.
Outcome measurements
Functional limitations were assessed using self-reported mobility and other physical functioning issues. Difficulty getting up from a chair after sitting for long periods was assessed using self-reports of mobility and other physical functioning characteristics using “yes” or “no” questions that potentially predict mobility capacity [13]. Difficulty putting on shoes and socks also indicates HOA [14].
HGS was determined in kilograms using a portable dynamometer (Smedley, dynamometer S, TTM, Tokyo, 100 kg). HGS is known for being able to predict disability, morbidity, frailty, and mortality [15,16] and is utilized as a general health indicator, with levels decreasing with age [17]. Participants were instructed on HGS measurement techniques and allowed to use the dynamometer twice in each hand. They were advised to sit with their arms resting on their torso and their elbows flexed at 90°. The final HGS value was determined by combining the maximum HGS measurements from both hands. The variable was generated exclusively for respondents with two valid measurements for each hand, defined as values ranging from 0 to 100 kg with a difference of no more than 20 kg. The European Working Group on Sarcopenia in Older People 2, 2019 edition [18] establishes cutoff values to diagnose sarcopenia for men and women at < 27 kg and < 16 kg, respectively.
Exposure measurement
Physical inactivity was originally described as two categorical variables according to the frequency of vigorous and moderate PA (1. more than once a week; 2. once a week; 3. once to three times per month; and 4. virtually never or never). Vigorous activities included sports, heavy housework, and physically demanding employment, while mild activities included gardening, car cleaning, and walking. For this study, physical inactivity was defined as low level of PA or lack of moderate or vigorous activity.
Covariables measurements
Within the demographic variables, respondents indicated whether and how frequently they drank alcohol (“never,” “1 to 2 times a month,” “1 to 2 times a week,” “3 to 4 times a week,” and “almost every day”). Their smoking status was determined to be either current smokers or nonsmokers. The number of chronic conditions were self-reported, which limited the study’s scope. The chronic conditions included hypertension, high cholesterol, stroke, cerebrovascular disease, diabetes, chronic lung disease, asthma, arthritis, osteoporosis, cancer, duodenal ulcer, Parkinson’s disease, cataracts, and hip and femoral fractures. Multimorbidity was characterized by three or more chronic conditions, which are associated with a lower quality of life and mortality [19,20].
Self-reported weight and height were used to compute BMI (kg/m2), which was then classified according to the World Health Organization categories: underweight (<18.5), average (18.5-24.9), overweight (25-29.9), and obese (≥30).
Euro-D, a mental health questionnaire composed of a scale through several symptoms (depression, pessimism, suicidal tendencies, guilt, sleep, interest, irritability, appetite, fatigue, concentration, pleasure, and crying), was used to measure depression symptoms (yes if 4-12 points and no if ≤ 3 points).
Statistical analysis
Statistical analyses were conducted using IBM SPSS Statistics software, version 29.0.2 (IBM Corp., Released 2020, Armonk, NY). All variables were categorical and are presented as absolute frequencies and percentages.
Comparisons between genders were performed using Fisher’s exact test. Logistic regression models were fitted for univariate and multivariable analyses to identify factors associated with the outcomes of interest, limitations in activities of daily living (none or at least one), poor handgrip strength (defined as ≤ 26 kg for men or < 16 kg for women), difficulty in dressing including shoes and socks (yes or no), and difficulty getting up from a chair (yes or no).
Physical inactivity was the exposure variable and covariables included gender, years of education (≤8, 9-12, > 12 years), current smoking status (yes or no), alcohol consumption (once or twice a month or at least once a week), physical inactivity (yes or no), depression (yes or no), history of heart attack (no or ever diagnosed/currently having), hypertension (yes or no), high blood cholesterol (yes or no), history of stroke (yes or no), and diabetes or high blood sugar (yes or no).
Initially, each variable was analyzed individually to assess its association with each functionality variable.
Only variables with statistically significant associations in the univariate analysis were included in the final multivariable model to determine the independence of effects.
Significance of each variable in the model was assessed using the Wald test, with the association measure reported as the odds ratio (OR) with a 95% confidence interval (95%CI).
Multicollinearity was examined prior to analysis, and model fit was assessed using the Hosmer-Lemeshow test. A complete case analysis was conducted, as missing data were few and considered random, with no observable pattern or bias. Statistical significance was set at p < 0.05.
Results
Study population characteristics
Our analysis included 2,088 participants: 1,540 (73.8%) women and 548 men as shown in Fig 1. The study participants were predominantly nonsmokers (72.8%). The mean age was 72.5 ( ± 8.2) for men and 73.4 ( ± 8.5) for women. The 60-79 subgroup had a mean age of 69.1 ( ± 5.5) for men and 69.3 ( ± 5.5) for women. The mean age between 80 and 100 years was 84.6 ( ± 3.7) for men and 84.6 ( ± 3.9) for women. Among the studied population, 25.1% (n = 525) was physically inactive. The 80-100 group showed the highest rates of physical inactivity (women 49.8% for women and 49.2% for men). Table 1 shows the demographic description of our population. While schooling categories were equally distributed among male and female subgroups in the 60-79 years of age group, females in the 80-100 years of age group majorly reported less than 8 years of education. Man in both age groups reported consuming alcohol more frequently than women. The majority of male and female in both age groups reported 2-4 comorbidities, being high blood pressure and high cholesterol the commonest.
Handgrip strength and PA associations
Mean HGS was 23,8 ± 6,7 and 40,7 ± 9 kgf for female and male among the 60-79 years of age group and 18,6 ± 5,5 and 30,4 ± 7,2 for female and male respectively among the 80-100 years of age group. Low HGS was present in 14.9% of the studied population (n = 264). The 80-100 subgroup presented with the lowest rates of low HGS compared to the 60-79 subgroup (p < 0.001). While 30.5% of women in the older group presented with low HGS, only 12.7% had low HGS in the 60-79 subgroup. The same was observed within the male population (26% vs 5.3%, 80-100 vs 60-79) (Table 2). Multivariable models shown in Fig 2 revealed that being female was associated with decreased HGS among participants aged 60 to 79. Having more than eight years of schooling and alcohol consumption at least once a week were protective factors for HGS in the 60-79-year-old subgroup.
Physical inactivity was an independent and significant predictor of reduced grip strength in the 80–100 years of age group, as shown in Fig 2. Also, being overweight was a significant protective factor for the 80-100 years of age group.
Limitations in everyday activities and PA associations
Limitations in everyday activities were observed in 34.7% of individuals (n = 724) in the overall population. Compared to the 60-79 age group, the 80-100 age group experienced a higher rate of limitation with activities of daily living. Multivariable models identified physical inactivity and stroke as significant predictors of difficulties in activities of daily living in both the 60-79 and 80-100 age groups. Physical inactivity was also associated with a fourfold chance of difficulty in getting dressed in people over 60 with HOA. Regarding comorbidities diabetes was a significant predictor of restrictions in activities of daily living in the 80–100 years of age group.
Dressing difficulties, including putting on shoes and socks, was reported in 25.2% (n = 526) of the overall population (Table 2). Among the of 60-79 years old group, 21.7% (n = 244) of women and 23.4% (n = 100) of men were unable to perform such task, while among the group 80-100 years of age women (34%; n = 140) and men (35%;n = 42) reported it similarly. According to multivariable analysis, physical inactivity was a significant and independent variable associated with difficulties dressing in both age groups.
Stroke, heart attack, and obesity were associated with difficulties with dressing in those in the 60 to 79 years of age group. Meanwhile, high blood cholesterol was associated with difficulty getting dressed among individuals aged 80–99.
It was also observed that 58.7% (n = 1225) of the population reported difficulty getting up from a chair after long periods of sitting. In the 60-79 age group, 57.8% (n = 652) of women and 48.8% (n = 209) of men failed to complete the task, whereas in the 80-100 age group, 69.7% (n = 287) of women and 64.2% (n = 77) of men struggled with such daily activity.
Multivariable models confirmed that physical inactivity was an independent exposure for difficulties getting up from a chair in both age groups (Fig 2). In addition, past heart attacks and obesity were also associated with difficulties getting up from a chair in the 60–79 years of age group. In the 80-99 years of age group, high blood cholesterol was significantly associated with difficulty getting up from a chair.
Discussion
This population-based study examined the independent associations between physical inactivity, gender, BMI, years of schooling, alcohol intake, and specific comorbidities and functionality in two age subgroups (60-79 and 80-99 years old) of people with HOA.
We found in both age groups that self-reported physical inactivity was an independent predictor of low muscle strength measured by handgrip and functional decline defined by self-reported limitations in daily activities. Morbidities such as stroke, heart attack, and obesity were associated with poor functionality in people aged 60 to 79. In contrast, stroke, diabetes, and high blood cholesterol were major factors for decreased functionality in the 80–100-year-old subgroup.
Our findings highlight that physical inactivity is the primary predictor of impaired functionality in older people with HOA. These results are consistent with previous research. A prospective community-based study using self-reported PA in people with hip or knee OA (mean age 65.4 years) found that regular or very regular PA was linked to long-term improvements in physical function [21]. A systematic and comprehensive review found compelling evidence that PA reduces pain and enhances physical function in adults with hip or knee OA [6]. Despite the known association between PA and functioning, we observed that advanced age (over 80 years old) favours the importance of PA as a key component of physical function in older people with HOA. Given the magnitude and the independence of physical inactivity in both groups, it is possible to hypothesize that the mere fact of not being inactive could lower this impact.
Current OA guidelines recommend using land-based exercise as the first line of treatment for hip and knee OA [8,22]. In the literature on OA, the terms “PA” and “exercise” interchangeably refer to various aspects of human movement. PA is defined as any energy expenditure from skeletal muscle above resting levels, which helps to prevent and manage OA. Meanwhile, planned, structured, and repeatable PA is known as exercise [23]. Our population study only considered self-reported PA levels and discovered an independent link between low PA levels and reduced functioning. These findings highlights the current OA guidelines’ recommendation to enhance PA levels to maintain physical function even though anecdotal evidence shows that some older patients with OA are recommended to make rest.
The maintenance of physical function through PA happens through mechanisms that enhance joint stability while reducing pain and inflammation. Stair patterns, particularly stair ascent, vary among people with HOA. Yet, focused therapy may ease discomfort and improve mobility by transferring load and relieving pressure on hip abductors [24]. Furthermore, regular PA is necessary for adjusting muscle and neuromuscular function to compensate for joint deterioration. Research reveals that neuromuscular training or classical quadriceps strength can reduce muscle discomfort and enhance muscle function without affecting knee alignments in hip or knee OA [25,26].
In addition to biomechanical benefits, PA promotes joint function by enhancing overall physical conditioning and lowering inflammation. Preoperative PA helps to maintain muscle stiffness and function following joint replacement operations, such as total hip arthroplasty [27]. Regular exercise also has anti-inflammatory properties because it helps to break the vicious cycle of local synovial membrane inflammation and systemic inflammation caused by numerous morbidities [28], which can, in turn help reduce OA-related inflammation and discomfort. These physiological advantages underline the need for maintaining an active lifestyle to control OA symptoms, underscoring exercise’s dual role in both mechanical and biochemical disease progression management. Overall, these systems work to alleviate symptoms and improve the quality of life for those with OA.
This study has some limitations. The cross-sectional design of our analysis prevented us from investigating a causal association between physical inactivity and functional outcomes. Also, SHARE is a survey; hence, there were no imaging tests to assess the severity of HOA. Another limitation is the lack of objective measures of PA, such as pedometers and accelerometers. The survey revealed that 25.1% of people in the studied population were physically inactive, indicating a group with high self-reported activity levels. This variation is significant, especially compared to other SHARE research and an age-matched group [29]. One possible explanation is that self-reported PA questionnaires may overestimate data [30].
A strength of this study was the sample size, which represented an exponentially rising but understudied population. Moreover, our study included various functional variables for both sexes and determinants of independence and quality of life, such as strength, mobility, and endurance. Furthermore, after accounting for frequent confounders, our robust models demonstrated the impact of physical inactivity and multimorbidity on functioning. To our knowledge, this is the first study to compare functional measurements and their relationships across these two age groups.
Furthermore, the study findings could imply that sustaining physical exercise is critical even in individuals older than 80 years old. However, the amount of PA in those specific age groups that would increase their levels of functionality remains to be measured by proper interventions. These findings reinforce to health care practitioners, that implementing and maintaining PA-based programs is the foundation of physical functional preservation in older people with HOA.
References
- 1. Kolasinski SL, Neogi T, Hochberg MC, Oatis C, Guyatt G, Block J, et al. 2019 American College of Rheumatology/Arthritis Foundation Guideline for the Management of Osteoarthritis of the Hand, Hip, and Knee. Arthritis Rheumatol. 2020;72(2):220–33. pmid:31908163
- 2. GBD 2021 Osteoarthritis Collaborators. Global, regional, and national burden of osteoarthritis, 1990-2020 and projections to 2050: a systematic analysis for the Global Burden of Disease Study 2021. Lancet Rheumatol. 2023;5(9):e508–22. pmid:37675071
- 3. Jordan JM, Helmick CG, Renner JB, Luta G, Dragomir AD, Woodard J, et al. Prevalence of hip symptoms and radiographic and symptomatic hip osteoarthritis in African Americans and Caucasians: the Johnston County Osteoarthritis Project. J Rheumatol. 2009;36(4):809–15. pmid:19286855
- 4. Lane NE, Brandt K, Hawker G, Peeva E, Schreyer E, Tsuji W, et al. OARSI-FDA initiative: defining the disease state of osteoarthritis. Osteoarthritis Cartilage. 2011;19(5):478–82. pmid:21396464
- 5. Cornwall N, Swaithes L, Woodcock C, Healey EL, Hider SL. Implementation of physical activity interventions for people with inflammatory arthritis: an overview and future recommendations. Rheumatol Adv Pract. 2023;7(1):rkac094. pmid:36699546
- 6. Kraus VB, Sprow K, Powell KE, Buchner D, Bloodgood B, Piercy K, et al. Effects of Physical Activity in Knee and Hip Osteoarthritis: A Systematic Umbrella Review. Med Sci Sports Exerc. 2019;51(6):1324–39. pmid:31095089
- 7. Hurley M, Dickson K, Hallett R, Grant R, Hauari H, Walsh N, et al. Exercise interventions and patient beliefs for people with hip, knee or hip and knee osteoarthritis: a mixed methods review. Cochrane Database Syst Rev. 2018;4(4):CD010842. pmid:29664187
- 8. Bannuru RR, Osani MC, Vaysbrot EE, Arden NK, Bennell K, Bierma-Zeinstra SMA, et al. OARSI guidelines for the non-surgical management of knee, hip, and polyarticular osteoarthritis. Osteoarthritis Cartilage. 2019;27(11):1578–89. pmid:31278997
- 9. Williamson W, Kluzek S, Roberts N, Richards J, Arden N, Leeson P, et al. Behavioural physical activity interventions in participants with lower-limb osteoarthritis: a systematic review with meta-analysis. BMJ Open. 2015;5(8):e007642. pmid:26260348
- 10. Kanavaki AM, Rushton A, Efstathiou N, Alrushud A, Klocke R, Abhishek A, et al. Barriers and facilitators of physical activity in knee and hip osteoarthritis: a systematic review of qualitative evidence. BMJ Open. 2017;7(12):e017042. pmid:29282257
- 11. Börsch-Supan A, Brandt M, Hunkler C, Kneip T, Korbmacher J, Malter F, et al. Data Resource Profile: The Survey of Health, Ageing and Retirement in Europe (SHARE). International Journal of Epidemiology. 2013;42(4):992–1001.
- 12. Börsch-Supan A, Hank K, Jürges H. A new comprehensive and international view on ageing: introducing the “Survey of Health, Ageing and Retirement in Europe”. Eur J Ageing. 2005;2(4):245–53. pmid:28794739
- 13. Leichtenberg CS, van Tol FR, Gademan MGJ, Krom T, Tilbury C, Horemans HLD, et al. Are pain, functional limitations and quality of life associated with objectively measured physical activity in patients with end-stage osteoarthritis of the hip or knee?. Knee. 2021;29:78–85. pmid:33582594
- 14. Austin S, Qu H, Shewchuk RM. Association between adherence to physical activity guidelines and health-related quality of life among individuals with physician-diagnosed arthritis. Qual Life Res. 2012;21(8):1347–57. pmid:22038394
- 15. Gum AM, Segal-Karpas D, Avidor S, Ayalon L, Bodner E, Palgi Y. Grip strength and quality of life in the second half of life: hope as a moderator. Aging Ment Health. 2018;22(12):1600–5. pmid:28956636
- 16. Li Y-Z, Zhuang H-F, Cai S-Q, Lin C-K, Wang P-W, Yan L-S, et al. Low Grip Strength is a Strong Risk Factor of Osteoporosis in Postmenopausal Women. Orthop Surg. 2018;10(1):17–22. pmid:29430846
- 17. Hamad B, Basaran S, Coskun Benlidayi I. Osteosarcopenia among postmenopausal women and handgrip strength as a practical method for predicting the risk. Aging Clin Exp Res. 2020;32(10):1923–30. pmid:31679147
- 18. Cruz-Jentoft AJ, Bahat G, Bauer J, Boirie Y, Bruyère O, Cederholm T, et al. Sarcopenia: revised European consensus on definition and diagnosis. Age Ageing. 2019;48(1):16–31. pmid:30312372
- 19. Breckner A, Glassen K, Schulze J, Lühmann D, Schaefer I, Szecsenyi J, et al. Experiences of patients with multimorbidity with primary care and the association with patient activation: a cross-sectional study in Germany. BMJ Open. 2022;12(8):e059100. pmid:35940827
- 20. Souza DLB, Oliveras-Fabregas A, Minobes-Molina E, de Camargo Cancela M, Galbany-Estragués P, Jerez-Roig J. Trends of multimorbidity in 15 European countries: a population-based study in community-dwelling adults aged 50 and over. BMC Public Health. 2021;21(1):76. pmid:33413239
- 21. Lopes DG, Costa D, Cruz EB, Mendonça N, Henriques AR, Branco J, et al. Association of physical activity with physical function and quality of life in people with hip and knee osteoarthritis: longitudinal analysis of a population-based cohort. Arthritis Res Ther. 2023;25(1):14. pmid:36703210
- 22. Hinman RS, Hall M, Comensoli S, Bennell KL. Exercise & Sports Science Australia (ESSA) updated Position Statement on exercise and physical activity for people with hip/knee osteoarthritis. J Sci Med Sport. 2023;26(1):37–45. pmid:36463000
- 23. Caspersen CJ, Powell KE, Christenson GM. Physical activity, exercise, and physical fitness: definitions and distinctions for health-related research. Public Health Rep. 1985;100(2):126–31. pmid:3920711
- 24. Meyer CAG, Corten K, Fieuws S, Deschamps K, Monari D, Wesseling M, et al. Evaluation of stair motion contributes to new insights into hip osteoarthritis-related motion pathomechanics. J Orthop Res. 2016;34(2):187–96. pmid:26212929
- 25. Ageberg E, Link A, Roos EM. Feasibility of neuromuscular training in patients with severe hip or knee OA: the individualized goal-based NEMEX-TJR training program. BMC Musculoskelet Disord. 2010;11:126. pmid:20565735
- 26. Bennell KL, Hinman RS. A review of the clinical evidence for exercise in osteoarthritis of the hip and knee. J Sci Med Sport. 2011;14(1):4–9. pmid:20851051
- 27. Gilbey HJ, Ackland TR, Wang AW, Morton AR, Trouchet T, Tapper J. Exercise improves early functional recovery after total hip arthroplasty. Clin Orthop Relat Res. 2003;408:193–200. pmid:12616059
- 28. Skou ST, Pedersen BK, Abbott JH, Patterson B, Barton C. Physical Activity and Exercise Therapy Benefit More Than Just Symptoms and Impairments in People With Hip and Knee Osteoarthritis. J Orthop Sports Phys Ther. 2018;48(6):439–47. pmid:29669488
- 29. Lübs L, Peplies J, Drell C, Bammann K. Cross-sectional and longitudinal factors influencing physical activity of 65 to 75-year-olds: a pan European cohort study based on the survey of health, ageing and retirement in Europe (SHARE). BMC Geriatr. 2018;18(1):94. pmid:29661154
- 30. Vogel O, Niederer D, Wilke J, Steinmann M, Vogt L. Relating Lifetime Activity Behavior to the Current Level of Physical Activity of Older Adults. J Aging Phys Act. 2021;29(6):915–21. pmid:34034227