The present study was executed between January 2013 and September 2013. The study was conducted following a previous study that was executed to quantify daily PA levels and energy expenditure in newly diagnosed IC patients.16
Patients were recruited from a population presenting with new onset manifestations of IC at outpatient departments of Vascular Surgery of the Catharina Hospital, Eindhoven and Maxima Medical Centre, Veldhoven/Eindhoven, The Netherlands. Following history taking and a physical examination, patients suspected of IC underwent an ankle-brachial index (ABI) measurement using standard equipment. Patients with values below 0.90 at rest or a drop in value of more than 0.15 after a standardised treadmill test (at 3.2 km/hrs. and a 10% incline) were considered eligible.
Exclusion criteria were serious cardiopulmonary limitations (NYHA class 3-4), critical limb ischemia or previous lower-limb amputation, use of walking aids, psychiatric instability or other serious comorbidity which possibly limited the patient's walking ability. Patients who were treated with invasive revascularizations during follow up were excluded as well. Subjects that were willing to participate provided a written informed consent. All procedures described in this study were approved by the Medical Ethical Committee, Catharina Hospital, Eindhoven.
All participants received a detailed instruction on all specifics regarding proper handling and wearing of the DynaPort MoveMonitor (McRoberts BV, The Hague, the Netherlands) and were asked to wear the device correctly for 7 consecutive days. As the device is not waterproof, participants were instructed to remove the device when taking a shower or a bath. Participants were also asked to perform their normal daily activities during this week and not to wear the device during sleeping.
A 3 months period of SET was commenced immediately after the first week monitoring period. Patients were referred to a local physical therapist, who was trained in providing SET according to the Royal Dutch Society for Physical Therapy guidelines and the Dutch ClaudicatioNet network quality standards 24. The educational program ensured that all patients received SET according to the guidelines of the Royal Dutch Society for Physical Therapy. 25 The physical therapist assessed a baseline and a 3 months pain-free walking distance (PFWD) and maximum walking distance (MWD) using a standardised graded treadmill protocol (walking at 3.2 kilometer per hour (km/h) with a 0% incline that increases by 2% every 2 minutes till a maximum of 10%).26,27 Patients were tested for a maximum of 30 minutes (1600m). Evidence-based cardiovascular risk management including antiplatelet and statin therapy was standardly initiated, in case patients were not taking this medication already. After 3 months, SET outcome was discussed with the patient followed by a second 7-day period of wearing the DynaPort MoveMonitor.
Monitoring of physical activity and walking impairment
The DynaPort MoveMonitor, a tri-axial seismic accelerometer, was used to measure PA. The DynaPort MoveMonitor was placed in a belt that was strapped around
the waist. It was positioned at the base of the lumbar column just cranial to the buttocks. This accelerometer was chosen because of an optimal correlation between indirect calorimetry and generated MET output whereas walking speed was correctly measured in a population with chronic obstructive pulmonary disease 28. Moreover, this activity monitor was recently validated in an IC population 29. The device consists of a tri-orthogonal orientated piezo-capacitive acceleration sensor, a rechargeable battery and removable SD card to store the acceleration data. The raw acceleration data lend itself to a pattern recognition approach using logical algorithms (MoveMonitor analysis software, version 2.6) for the classification of postures (lying, sitting and standing) and motions (locomotion and shuffling). General and specifics of the software were provided in several previously published articles 16,30-32..
A Dutch validated version of the Walking Impairment Questionnaire (WIQ) and a 36-item Short Form Health Survey version 2 (SF-36) were assessed at baseline and after the 3 months of SET treatment. 33-35
- Percentage of participants meeting the ACSM lower limit recommendation for PA and public health (67 METs?min a day)
- Percentage of participants meeting the ACSM higher limit recommendation for PA and public health (107 METs?min a day)
- Daily PA level (measured in METs?min)
- Daily PA level performed in bouts of >10 minutes of moderate or vigorous intensity (measured in METs?min)
- Mean time spent per day during different activities (in minutes; lying, standing, sitting, walking, shuffling, locomotion, not wearing the device)
- Mean number of steps walked in one period and maximal number per day (top period of steps)
- Activity per day (in minutes; sedentary activity: intensity <1.5 METs; light: 1.5-3 METs; moderate: 3-6 METs; vigorous: 6-9 METs)
- Change in SF-36 values
Data checks per patient for each study day were deemed necessary to assure proper use of the device. By definition, the device was 'worn correctly' during a day if it detected a minimum of 20 steps and if it was 'worn' =9 hours and if it was 'not worn' for =5 hours a day. Moreover, patients were arbitrarily excluded from analysis if the device was worn during less than 5 days, to filter out incorrect or unrepresentative data. Mean time that was spent per day was determined for each participant depending on the number of 'correctly worn days'. Analysis was performed on patients with both a correct baseline and follow-up measurement.
All analyses were performed using IBM SPSS Statistics Version 21 (SPSS Inc.,
Chicago, IL, USA). Categorical variables are presented as frequencies with percentages. A Pearson Chi-Square test was used to identify differences for categorical variables. To obtain an impression of the distribution, values were analyzed for skewness and kurtosis. Nominal normally distributed variables are depicted as the mean ± standard deviation (SD), while non-normally distributed values are reported as median ± interquartile range (IQR). Statistical differences between the included and excluded study populations were analysed with an independent Students T-test, while differences between time periods were calculated with a paired sample T-test or with Pearson correlation coefficients for continuous normal distributed variables. A Wilcoxon signed-rank test or Spearman's rho were utilized for non-normal distributed continuous variables. A p-value <0.05 was used for statistical significance.