1. Introduction
Regular physical activity is vital for preserving fitness, health, and living standards [
1]. It can regulate weight, improve mental health and vitality, and control heart diseases and type 2 diabetes [
2]. Physical activity can help people with physical disabilities achieve independence and do their daily activities [
3].
Lower Limb Amputation (LLA) causes several physical activity problems, such as gait abnormalities [
4], decreased gait velocity [
5], and activities of daily living [
6]. Previous studies have revealed that physical activity is important for the gait efficiency of people with LLA, affecting their health-related quality of life [
7, 8].
An essential purpose of the rehabilitation program is to return people with LLAs to the community and activities of daily living through prescribing a suitable prosthesis. Prescribing a prosthesis can improve the indoor and outdoor walking abilities of people with LLA, helping them return to vocational, leisure, and work-related activities [
9]. These activities might be essential in making them feel happier [
10]. Previously published studies are limited to evaluating the physical activities of individuals with lower limb amputation. Recent studies have established that many individuals with lower limb amputation engage in low-intensity physical activities [
11, 12]. For these people, physical activity is possibly equally important as the general population. Because individuals with lower limb amputation are at considerable risk for ongoing cardiovascular disease, comorbidities, and mortality [
13], standard and valid tools are needed for their accurate evaluations in a clinical setting and to understand better the functional performance and mobility of people with LLAs while using prostheses.
Different self-reported tools such as the prosthesis evaluation questionnaire [
14], the Prosthetic Limb User Survey Of Mobility (PLUS-MTM) [
15], and the locomotor capabilities index [
16] have been prepared to investigate the evaluation outcomes of people with LLAs. The prosthesis evaluation questionnaire [
14] evaluates the prosthesis and prosthesis-related quality of life. It has four domains of functional, mobility, psychosocial, and health aspects. The PLUS-MTM [
15] examines the perceived ability of people with lower-limb amputations in various physical functions, from basic ambulation to complex tasks while using their lower limbs. The locomotor capabilities index [
16] assesses the ambulatory proficiencies with a prosthesis and the level of independence to do the daily activities in people with LLAs. However, there is no item in these questionnaires to evaluate the average hours of daily physical activity of people with lower-limb amputations. Therefore, a standard, valid, and reliable tool for individuals with a physical disability, such as lower limb amputation, is required to assess the average daily activities associated with the tasks’ intensity. This measure can help prosthetists accurately assess the extent of an individual’s daily physical activity in each visit.
The Physical Activity Scale For Individuals with Physical Disabilities (PASIPD) is a self-reported measure that assesses the average hours of daily physical activity [
17]. It evaluates the activity of daily living of individuals with a physical disability during leisure time, as well as domestic and work-related activities. The PASIPD is applied for individuals with spinal cord injury, cerebral palsy, low-back pain, whiplash injury, lower limb amputation, and Parkinson disease. Also, its psychometric characteristics have been assessed in different languages [
18, 19, 20, 21, 22]. The results of these studies revealed that the PASIPD has acceptable reliability and validity.
This study aimed to translate and cross-culturally adapt the PASIPD into the Persian language and evaluate its psychometric characteristics in persons with unilateral LLA. LLA is a detrimental incident that can change an individual’s life and is perceived as “one of the major causes of permanent disability” [
23]. A critical part of the rehabilitation program following lower limb amputation is evaluating individuals to participate in usual physical activity for physical, mental, and psychosocial well-being [
24].
2. Materials and Methods
Study participants
This research was a cross-sectional study. The Ethics Committee of Iran University of Medical Sciences approved this research (No.: 1398.879). Data collection was conducted face-to-face or online from July 2019 to June 2020. The inclusion criteria were being a community-dwelling Persian-speaking person with unilateral LLA, having a minimum of 18 years old, having the ability to read and understand the Persian language, and having worn the present prosthesis for a minimum of three months [
25].
All cases signed written consent forms before filling out the questionnaires. For those participants that filled the online questionnaires, the consent was achieved through ticking a statement of consent which was included at the beginning of the survey.
Translation and cultural adaptation
The corresponding author contacted the original developers of PASIPD before conducting the research to achieve approval for translating it.
Using an internationally accepted guideline proposed by Beaton et al. [
26], the translation and cultural adaptation procedures were conducted in five stages.
First, the original English version of PASIPD was translated to Persian separately by two experienced translators. In the second stage, two translators and the research team compared the two translated versions and prepared a consensus. In the third stage, the Persian version attained from the previous stage was back-translated into English by two separate translators. Any differences in translations were taken care of with consensus. An expert committee, including the translators and four certified prosthetists, reviewed all the translations to prepare a pre-final P-PASIPD (Persian version of PASIPD).
The back-translated version of the questionnaire was then sent to the original developer of the PASIPD. After achieving proof from the original developer, the final P-PASIPD was used for reliability and validity study.
The pre-final P-PASIPD draft was randomly assessed on 30 Persian-speaking people with unilateral LLAs. Using a 5-point Likert scale, the participants were asked to rate items of the questionnaire. The aim was to identify and address potential deficiencies, such as incorrect spelling of phrases, culturally inappropriate words, ambiguity, or difficulty in understanding the content. All participants understood the questionnaire items correctly. Finally, the final version of the P-PASIPD was prepared by the expert committee to evaluate its reliability and validity.
Study Instruments
The PASIPD
The original version of the PASIPD was prepared by Washburn et al. [
17] to measure the physical activity level of persons with different physical disabilities, including cerebral palsy, stroke, low-back pain, postpolio, spinal cord injury, and locomotor disabilities. This tool is a 13-item self-reported measure. Its items are in three domains of leisure time (items 1 to 6), housework activities (items 7 to 12), and work-related activities (item 13). According to Washburn et al. [
17], its total score is predetermined by multiplying the mean hours per day of each item with a relevant metabolic equivalent of task (MET) value and adding the values of items of 2 to 13. In each item, the activity intensity has been classified as never, seldom (1-2 days per week), sometimes (3-4 days per week), often (5-6 days per week) and how many hours of activity per day the individuals have had physical activity (<1 h, 1-2 h, 2-4 h, and >4 h for items 2 to 12; and , 1 h, 1-4 h, 5-8 h, >8 h for item 13). There is no score for item one. The PASIPD total score ranges from 0 MET hours per day (lowest) to 199.5 MET hours per day (highest).
The PLUS-M™
The PLUS-M is a self-reported measure that evaluates the ability of adults with lower limb amputations to move independently from one place to another using prosthesis over the past 7 days. The original English version of this measure was prepared by Hafner et al. [
15]. The items of the PLUS-M cover movements that range from walking a short distance over even ground to a long distance over uneven ground.
All survey questions utilized a 5-point Likert scale ranging from 1 to 5, in which 1 demonstrates the worst condition (inability to do work) and 5 the best condition (ability to do work without difficulty). The raw total score of the PLUS-M is obtained by summing up the responses to each item. Raw scores range from 12 to 60. However, we need a PLUS-M t-score to report the values of this questionnaire. T-scores are valid and comparable measures of mobility. T-scores range from 21.8 to 71.4 for the 12-item short-form PLUS-M.
Reliability
The internal uniformity and test/re-retest study applying the Cronbach α and Pearson correlation coefficient (r) were used to assess the reliability of the P-PASIPD. According to Cohen’s formula, to attain a power of 0.8, ICC > 0.5, α=0.05, and an effect size of 0.25 [
27], we randomly chose 30 participants to complete the P-PASIPD twice with a two-week interval.
Convergent Validity
All participants were requested to respond to the Persian form of PLUS-M (unpublished results) beside the PASIPD to calculate the convergent validity of the P-PASIPD. In this case, the total and item scores of the PASIPD were compared with the t-score of the PLUS-M.
Known-Groups Validity
The known-groups validity of the P-PASIPD was investigated regarding the participants’ sex, cause of amputation, and level of amputation. Data from previous studies suggest that the amputee’s sex [
28], level of amputation, and cause of amputation [
29] can affect their level of physical activity.
Statistical analysis
Descriptive information was presented as mean, standard deviation, missing answers, interquartile ranges, and extent of ceiling and floor effects. If more than 15% of participants give the best or worst possible score on a questionnaire, a ceiling or floor effect has occurred [
30]. The proposed value for the Cronbach α to be acceptable is 0.45 to 0.98 [
31]. The Pearson correlation coefficient was used to assess the test-retest reliability.
To investigate the relationship between the PASIPD and PLUS-M questionnaires, the Spearman correlation coefficient was performed. Considering the way of relationship, the following criteria were utilized [
32]: strong (r>0.75), moderate (0.50
For factor analysis, the principal component analysis with varimax rotation was applied to 12 questions of the P-PASIPD. Before conducting principal component analysis, the suitability of values was checked by Bartlett’s test of sphericity (<0.05) and the Kaiser-Meyer-Olkin test (>0.5) [33]. Factor extraction was performed by calculating factors with an eigenvalue of 1.0 or higher. All analyses were carried out in SPSS software, v. 20. A P value of 0.05 was considered statistically significant.
3. Results
Translation and cultural adaptation
The PASIPD was adapted and validated for the Persian language. In item 2, “walking the dog shopping” was omitted because this activity is not common in the popular culture of many parts of Persian. In item 3, “use of a standing frame” was replaced with “yoga and walking in the forest.” In item 4, “softball” was replaced with “jogging on even ground.” In item 5, “off-road pushing” was replaced with “jogging on uneven ground.” In item 6, “wheelchair push-ups” was replaced with “sitting up or uphill walking.” All of these changes were made under the supervision of the original developer of the PASIPD.
The participants’ characteristics
A total of 197 people with lower limb amputation (168 men and 29 women) were included in this study. Their Mean±SD age was 43.84±12.51 years (range: 19-72 y). The Mean±SD time since amputation and wearing the current prosthesis were 253.24±159.57 months (range: 12-660 mo) and 62.16±71.70 months (range: 3-448 mo), respectively. Characteristics of the studied population are reported in Table 1.
No significant ceiling effect was observed in the items and total score of the P-PASIPD. However, the P-PASIPD items showed significant floor effects (ranging from 19.3% to 83.3%) (Table 2).
Reliability
The P-PASIPD had a satisfactory internal uniformity (the Cronbach α=0.68) (Table 2). The total score of the P-PASIPD showed moderate test-retest association (r=0.7). For each item, the r values ranged from 0.45 (for item 11) to 0.87 (for item 10).
Factor analysis
A total of four components were extracted for P-PASIPD with eigenvalues higher than 1 as factor 1 (items 2, 3, 4, 5, 6), factor 2 (items 7, 8, 12), factor 3 (items 9, 10, 13), and factor 4 (items 10, 11, 13) (Figure 1 and Table 2).