Maiduguri is the largest city and the capital city in the state of Borno. This state is located in North-Eastern Nigeria, and has an estimated population of 4, 151, 193 people, consisting of Kanuri, Shuwa Arabs, Hausa, Fulfude and other ethnic groups [19, 20]. The state covers an area of 72, 609 sq kilometer with a population density of 57 people/square kilometer, and attracts immigrants from the Republic of Cameroon, the Republic of Niger and the Chad Republic [20, 21]. The diverse inhabitants of Maiduguri predominantly use the Hausa language as the common means of communication and commercial activities .
The International Physical Activity Questionnaire
The questionnaire collects information on the time (i.e., number of days and average time per day) spent being physically active and measures vigorous-intensity activity, moderate-intensity activity, walking activity, and sitting in the last seven consecutive day period. These activity categories may be treated separately to obtain the specific activity patterns or multiplied by their estimated value in Metabolic Equivalent of Tasks (METs) and summed to gain an overall estimate of physical activity in a week http://www.ipaq.ki.se. One MET represents the energy expended while sitting quietly at rest and is equivalent to 3.5 ml/kg/min of VO2 Max . The MET intensity values used to score IPAQ questions in this study were vigorous (8 METs), moderate (4 METs) and walking (3.3 METs) http://www.ipaq.ki.se. The IPAQ sitting question is an indicator of the time spent in sedentary activity and was not included as part of the summary score of total physical activity. Data were cleaned to ensure that the daily time spent on each of vigorous, moderate and walking activities ranged between 10 and 180 minutes for all participants http://www.ipaq.ki.se.
The outcomes measures used in the present study were (1) minutes reported in vigorous, moderate, walking and sedentary activities per week (Min week-1) and (2) MET minutes per week. Time spent in each activity category was derived by multiplying the number of days per week with the minutes spent doing the activity per day, while total weekly physical activity (MET-Min week-1) was calculated by multiplying the number of minutes spent in each activity category with the specific MET score for each activity.
To establish good face and content validity, the translation and cultural adaptation of the IPAQ-SF was performed in several steps following the guidelines prescribed by the IPAQ core group http://www.ipaq.ki.se. The English version of IPAQ-SF was translated into the Hausa language by two independent translators, both native speakers of Hausa who speak, read and write Hausa as well as speak, read and write English. One of the translators was a Hausa language expert based in the Linguistic Department of the University of Maiduguri, and the second translator was a physiotherapist clinician at a teaching hospital who was knowledgeable about the concept of cardiorespiratory fitness examined in IPAQ. The two translations, one each from the translators, were synthesized into a single Hausa version by a panel of experts consisting of the translators, two physiotherapists who specialize in exercise physiology and sports physiotherapy, the principal investigator, and a university student who was raised in Hausa language and culture. Following back translations of the synthesized Hausa version by two university lecturers from the Hausa ethnic group in Nigeria, each of them with over seven years of professional experience in health sciences, the panel of experts compared the two back translations with the original English version to ensure that the concept measured by IPAQ had not been lost during the translations.
The synthesized translation and the two back translations were then merged into one pre-final version of the Hausa IPAQ-Short Form (Hausa IPAQ-SF). The expert panel then compared the original English IPAQ and the pre-final Hausa version for conceptual equivalence (conceptual meaning to terms and concept in the Hausa population), experiential equivalence (cultural relevance of the tasks and examples used in the questionnaire), linguistic equivalence (meaning and grammatical correctness), and metric equivalence (ensuring that the substituting cultural items and examples of activity are equivalent in intensity with the original items and examples). The compendium of physical activity (available at http://prevention.sph.sc.edu) was used by the expert panel to ensure that the substitute culturally acceptable examples and items were equivalent in MET to the original examples and items in the English version.
The pre-final version of the Hausa IPAQ-SF was self-administered to 12 Hausa-speaking and Hausa-writing volunteers from a broad range of backgrounds. After the completion of the survey, each of the volunteers was separately interviewed by the principal investigator for their understanding of the words in the questionnaire, the clarity of each item, and their opinion and suggestions for improvement. They were also asked to indicate if any question made them feel uncomfortable and if any relevant items were not included in the questionnaire. Items that were difficult to understand as expressed by two or more volunteers were referred to the expert panel for consideration and the panel's recommendations were incorporated in all such cases.
Evaluation of Psychometric Properties
The final version of the Hausa IPAQ-SF (Additional file 1) was evaluated for validity and reliability in a non-probability sample of 102 apparently healthy individuals, age 20-65 years. Participants for the psychometric study were recruited directly from various workplaces (e.g., university, teaching hospital, private establishments) and neighborhoods in Maiduguri city. Demographic characteristics including educational level and employment status of the participants were obtained on their first day of contact for the study. Height and weight were measured using standardized equipment. Body mass index (BMI) was calculated as body weight divided by the square of height (kg m-2). Participants were eligible for this study if they were willing to complete surveys in both English and Hausa languages and were not having any disability that prevented independent walking. One of the researchers (F.O.O) was in attendance to provide translation and interpretation assistance to participants (n = 7) who were unable to independently complete the survey.
Concurrent validity of the Hausa IPAQ-SF was assessed by comparing the durations (Min week-1) of physical activity (vigorous, moderate, walking and sitting) from the Hausa IPAQ-SF with that obtained from the original English version of IPAQ-SF. A simple random technique (flip of coin) was used to determine the order of administration of the two questionnaires. Participants whose coin returned with heads completed the Hausa IPAQ-SF first, while those with tails completed the original English version first. An interval of one hour was allowed between administrations of the two questionnaires. Craig et al. , in a 12-country international study on validity and reliability of IPAQ, directly compared different versions of IPAQ and described the process as concurrent or inter method validation.
For construct validity, the participants' rate pressure product (RPP) was compared with duration (Min week-1) of physical activity (vigorous, moderate, walking and sitting) from the Hausa IPAQ-SF. Rate pressure product (RPP) is an index of cardiorespiratory fitness and was derived by multiplying participants' resting systolic blood pressure and heart rate . The systolic blood pressure and heart rate were measured with the Dinamap (model 8100/8101) digital blood pressure measuring device. Three measurements were taken at intervals of 3-5 minutes, and the mean systolic blood pressure and heart rate were used for computing the RPP used in the analysis. A correlation between duration in physical activity and RPP would suggest that the Hausa IPAQ-SF was sensitive to construct of physical activity such as cardiorespiratory fitness. Other important construct validity measures, such as VO2 max, motion sensors, diaries and indicators of lipid and glucose metabolism [12–14], were not used in this study due to cost and ease of utility.
Test-retest reliability was completed by administering the Hausa IPAQ-SF twice within a 1-week time frame. Participants during the retest administration were asked to focus on the 7-day physical activity recalled during the first testing. The 7-day time interval was chosen because IPAQ asks about activity in the last 7 days. All participants provided informed consent and the Research Ethical Committee of the University of Maiduguri Teaching Hospital, Nigeria gave approval for the protocol of the study before its commencement.
Descriptive data were reported as mean, standard deviation and percentages. Mean group differences in physical activity (Min week-1) by gender and socioeconomic status were examined by independent t-test. To assess validity, the non-parametric Spearman correlation coefficients (ρ) were calculated to assess the relationship between Min week-1 of physical activity from the Hausa IPAQ-SF and rate pressure product and body mass index for construct validity, and with Min week-1 in physical activity from the English version of IPAQ for concurrent validity. Pearson correlation coefficients were also used for comparisons, but we only present results from the Spearman correlation analyses, because our results and conclusions were similar. The two-way mixed model (single measure) intraclass correlation coefficient (ICC) was calculated to evaluate the test-retest reliability. A 95% confidence interval was used to describe the variety/differences in the ICCs by gender and socioeconomic status. Percent agreement was not reported because it overestimated the reliability estimates of our data. To prevent type 2-error due to the small sample size in the socioeconomic status-based analyses, education and employment status were respectively grouped into two categories: high school education or no high school education, and employed or not employed (homemaker, student, retired, or unable to work). The agreement levels ratings of poor (0-0.2), fair (0.2-0.4), moderate (0.4-0.6), substantial (0.6-0.8) and almost perfect (0.8-1.0), suggested by Landis and Koch, were used when interpreting the reliability results .
The Bland-Altman analysis was used to provide an indication of the heteroscedasticity of the data, and 95% limits of agreement were used for describing the total error between the Hausa IPAQ-SF and the original English IPAQ, and the retest Hausa IPAQ. Variables used for the Bland-Altman analysis were weekly time spent in moderate activity according to the Hausa IPAQ-SF versus the original English IPAQ, and weekly time in moderate activity on first administration of Hausa IPAQ-SF versus the retest administration. Data were entered and analyzed using Statistical Package for the Social Science (SPSS), version 15.0 for windows (SPSS Inc., Chicago, Illinois, USA) and the level of significance was set at p < 0.05.