Marie Gernigon

Feasibility and validity of self-reported walking capacity in patients with intermittent claudication

OBJECTIVE The primary aim of this study was to assess if self-reported measures of walking limitation correlate better with a community-based assessment of maximum walking distance (MWD) than they do with laboratory-based tests in patients with intermittent claudication. A secondary aim was to examine the effect of prior objective testing on these correlations. METHODS Thirty-one patients completed three self-report tools (self-reported MWD; Walking Impairment Questionnaire [WIQ]; Estimation of Ambulatory Capacity by History-Questionnaire [EACH-Q]) immediately before and approximately 1 week after a series of objective tests (incremental treadmill walking test, 6-minute walk test, 1-hour global positioning system [GPS] recording of a community walk). We analyzed the feasibility of the self-report tools in terms of number of errors and their correlation (r) with objective measures. RESULTS The correlations of self-report tests to GPS-MWD (range, .579-.808) were consistently higher than with the treadmill test (range, .310-.584) and 6-minute walk test (range, .414-.613). The WIQ had the highest proportion of errors, both at first and second completion (58% and 42%, respectively), compared with self-reported MWD (23% and 13%, respectively) and the EACH-Q (6.5% and 13%, respectively). Correlations were improved with the second set of self-report tests (range, .310-.595 to .414-.808). CONCLUSIONS The fact that all self-report tools correlated better with a community-based measure of MWD using GPS than with laboratory results confirms that they measure what they aim to: community-based MWD. In addition, prescription of a community walk might help patients to better estimate their walking limitation.

The inter-and intra-unit variability of a low-cost GPS data logger/receiver to study human outdoor walking in view of health and clinical studies

Purpose The present study evaluates the intra- and inter-unit variability of the GlobalSat® DG100 GPS data logger/receiver (DG100) when estimating outdoor walking distances and speeds. Methods Two experiments were performed using healthy subjects walking on a 400 m outdoor synthetic track. The two experiments consisted of two different outdoor prescribed walking protocols with distances ranging from 50 to 400 m. Experiment 1 examined the intra-unit variability of the DG100 (test-retest reproducibility) when estimating walking distances. Experiment 2 examined the inter-unit variability of four DG100 devices (unit to unit variability) when estimating walking distances and speeds. Results The coefficient of variation [95% confidence interval], for the reliability of estimating walking distances, was 2.8 [2.5–3.2] %. The inter-unit variability among the four DG100 units tested ranged from 2.8 [2.5–3.2] % to 3.9 [3.5–4.4] % when estimating distances and from 2.7 [2.4–3.0] % to 3.8 [3.4–4.2] % when estimating speeds. Conclusion The present study indicates that the DG100, an economical and convenient GPS data logger/receiver, can be reliably used to study human outdoor walking activities in unobstructed conditions. This device let facilitate the use of GPS in studies of health and disease.

The effects of exercise modality on the incidence of plateau at V·O2max

The purpose of this study was to determine the effect of exercise modality on the incidence of plateau at V·O2max . Twelve recreationally active men (age, 21·7 ± 2·3 year; mass, 74·8 ± 6·5 kg; height, 177·6 ± 5·6 cm) completed four incremental tests to volitional exhaustion, of which two were completed on a treadmill (TRE) and two were completed using a cycle ergometer (CYC). The work rate employed for CYC was 1 W·2 s−1 from an initial loading of 100 W with cadence being maintained at 60 rpm. For TRE, the workload (gradient) increased at a rate of 0·5% · 30 s−1while maintaining a constant running speed of 10 kph. Throughout all the trials, V·O2 was determined on a breath‐by‐breath basis using a precalibrated metabolic cart. The criteria adopted for determination of a plateau was a Δ V·O2 over the final two consecutive 30‐s sampling periods of ≤50 ml · min−1. Averaging across the two trials per each exercise modality showed a significant difference for plateau incidence between CYC (8%) and TRE (58%) (P = 0·017). This was aligned with a significant difference in the slope of the regression line during the final 60 s of the V·O2max test, CYC (99·9 ± 49·7 ml · min−1) and TRE (49·6 ± 42·6 ml · min−1) (P = 0·017). Repeat measures ANOVA of these data suggests that plateau incidence rates at V·O2max differ between treadmill‐ and cycle ergometry‐based exercises. Future studies need to address whether these response rates are replicated in well‐trained athletes.

Global Positioning System Use in the Community to Evaluate Improvements in Walking After Revascularization A Prospective Multicenter Study With 6-Month Follow-Up in Patients With Peripheral Arterial Disease

AbstractRevascularization aims at improving walking ability in patients with arterial claudication. The highest measured distance between 2 stops (highest-MDCW), the average walking speed (average-WSCW), and the average stop duration (average-DSCW) can be measured by global positioning system, but their evolution after revascularization is unknown.We included 251 peripheral artery diseased patients with self-reported limiting claudication. The patients performed a 1-hour stroll, recorded by a global positioning system receiver. Patients (n = 172) with confirmed limitation (highest-MDCW <2000m) at inclusion were reevaluated after 6 months. Patients revascularized during the follow-up period were compared with reference patients (ie, with unchanged lifestyle medical or surgical status). Other patients (lost to follow-up or treatment change) were excluded (n = 89).We studied 44 revascularized and 39 reference patients. Changes in highest-MDCW (+442 vs. +13 m) and average-WSCW (+0.3 vs. −0.2 km h−1) were greater in revascularized than in reference patients (both P < 0.01). In contrast, no significant difference in average-DSCW changes was found between the groups. Among the revascularized patients, 13 (29.5%) had a change in average-WSCW, but not in highest-MDCW, greater than the mean + 1 standard deviation of the change observed for reference patients.Revascularization may improve highest-MDCW and/or average-WSCW. This first report of changes in community walking ability in revascularized patients suggests that, beyond measuring walking distances, average-WSCW measurement is essential to monitor these changes. Applicability to other surgical populations remains to be evaluated.Registration: http://www.clinicaltrials.gov/ct2/show/NCT01141361

Real-life adaptations in walking patterns in patients with established peripheral arterial disease assessed using a global positioning system in the community: A cohort study

Lower extremity peripheral arterial disease (PAD) is a chronic condition most commonly presenting with intermittent claudication (IC). Intermittent claudication limits walking ability and may negatively affect health‐related quality of life. Treadmill assessment of maximal walking distance (MWD) is the gold standard to assess PAD symptom severity. Despite being a well‐established and reproducible tool, it may be inappropriate (due to frailty or fear) for some patients and only describes maximal abilities for a single walk test. Global positioning systems (GPS) have been proposed as reliable and reproducible tool to measure total, mean and maximal walking distances in patients with PAD, in the community setting. Using GPS, our study attempted to explore what happens to the walking ability of patients with IC following no intervention under ‘real‐life’ conditions.

Accuracy of a low-cost global positioning system receiver for estimating grade during outdoor walking

The aim of this study was to assess, for the first time, the accuracy of a low-cost global positioning system (GPS) receiver for estimating grade during outdoor walking. Thirty subjects completed outdoor walks (2.0, 3.5 and 5.0 km · h-1) in three randomized conditions: 1/level walking on a 0.0% grade; 2/graded (uphill and downhill) walking on a 3.4% grade; and 3/on a 10.4% grade. Subjects were equipped with a GPS receiver (DG100, GlobalSat Technology Corp., Taiwan; ~US

Predicting metabolic rate during level and uphill outdoor walking using a low-cost GPS receiver

75). The GPS receiver was set to record at 1 Hz and its antenna was placed on the right shoulder. Grade was calculated from GPS speed and altitude data (grade  =  altitude variation/travelled distance  ×  100). Two methods were used for the grade calculation: one using uncorrected altitude data given by the GPS receiver and another one using corrected altitude data obtained using map projection software (CartoExploreur, version 3.11.0, build 2.6.6.22, Bayo Ltd, Appoigny, France, ~US

Using GPS, accelerometry and heart rate to predict outdoor graded walking energy expenditure

35). Linear regression of GPS-estimated versus actual grade with R 2 coefficients, bias with 95% limits of agreement (±95% LoA), and typical error of the estimate with 95% confidence interval (TEE (95% CI)) were computed to assess the accuracy of the GPS receiver. 444 walking periods were performed. Using uncorrected altitude data, we obtained: R 2  =  0.88 (p  <  0.001), bias  =  0.0  ±  6.6%, TEE between 1.9 (1.7-2.2)% and 4.2 (3.6-4.9)% according to the grade level. Using corrected altitude data, we obtained: R 2  =  0.98 (p  <  0.001), bias  =  0.2  ±  1.9%, TEE between 0.2 (0.2-0.3)% and 1.0 (0.9-1.2)% according to the grade level. The low-cost GPS receiver used was weakly accurate for estimating grade during outdoor walking when using uncorrected altitude data. However, the accuracy was greatly improved when using corrected altitude data. This study supports the potential interest of using GPS for estimating energy expenditure during outdoor walking.

Influence of blood donation on the incidence of plateau at \( \dot{V}{\text{O}} \) 2max

The objective of this study was to assess the accuracy of using speed and grade data obtained from a low-cost global positioning system (GPS) receiver to estimate metabolic rate (MR) during level and uphill outdoor walking. Thirty young, healthy adults performed randomized outdoor walking for 6-min periods at 2.0, 3.5, and 5.0 km/h and on three different grades: 1) level walking, 2) uphill walking on a 3.7% mean grade, and 3) uphill walking on a 10.8% mean grade. The reference MR [metabolic equivalents (METs) and oxygen uptake (V̇o2)] values were obtained using a portable metabolic system. The speed and grade were obtained using a low-cost GPS receiver (1-Hz recording). The GPS grade (Δ altitude/distance walked) was calculated using both uncorrected GPS altitude data and GPS altitude data corrected with map projection software. The accuracy of predictions using reference speed and grade (actual[SPEED/GRADE]) data was high [R(2) = 0.85, root-mean-square error (RMSE) = 0.68 MET]. The accuracy decreased when GPS speed and uncorrected grade (GPS[UNCORRECTED]) data were used, although it remained substantial (R(2) = 0.66, RMSE = 1.00 MET). The accuracy was greatly improved when the GPS speed and corrected grade (GPS[CORRECTED]) data were used (R(2) = 0.82, RMSE = 0.79 MET). Published predictive equations for walking MR were also cross-validated using actual or GPS speed and grade data when appropriate. The prediction accuracy was very close when either actual[SPEED/GRADE] values or GPS[CORRECTED] values (for level and uphill combined) or GPS speed values (for level walking only) were used. These results offer promising research and clinical applications related to the assessment of energy expenditure during free-living walking.

Test-retest Reliability of GPS derived Measurements in Patients with Claudication

OBJECTIVES To determine the best method and combination of methods among global positioning system (GPS), accelerometry, and heart rate (HR) for estimating energy expenditure (EE) during level and graded outdoor walking. DESIGN Thirty adults completed 6-min outdoor walks at speeds of 2.0, 3.5, and 5.0kmh-1 during three randomized outdoor walking sessions: one level walking session and two graded (uphill and downhill) walking sessions on a 3.4% and a 10.4% grade. EE was measured using a portable metabolic system (K4b2). Participants wore a GlobalSat® DG100 GPS receiver, an ActiGraph™ wGT3X+ accelerometer, and a Polar® HR monitor. Linear mixed models (LMMs) were tested for EE predictions based on GPS speed and grade, accelerometer counts or HR-related parameters (alone and combined). Root-mean-square error (RMSE) was used to determine the accuracy of the models. Published speed/grade-, count-, and HR-based equations were also cross-validated. RESULTS According to the LMMs, GPS was as accurate as accelerometry (RMSE=0.89-0.90kcalmin-1) and more accurate than HR (RMSE=1.20kcalmin-1) for estimating EE during level walking; GPS was the most accurate method for estimating EE during both level and uphill (RMSE=1.34kcalmin-1)/downhill (RMSE=0.84kcalmin-1) walking; combining methods did not increase the accuracy reached using GPS (or accelerometry for level walking). The cross-validation results were in accordance with the LMMs, except for downhill walking. CONCLUSIONS Our study provides useful information regarding the best method(s) for estimating EE with appropriate equations during level and graded outdoor walking.