Group baseline characteristics
A total of 130 participants were considered eligible (IC, n=94; controls, n=36). Analysis of the accelerometer data demonstrated that 56 IC patients and 27 controls met all criteria of a correctly worn device. A significant group difference regarding age, number of correctly worn days, resting ABI, WIQ-score, SF-12 PCS score and MWD was found between both groups. (Table 1)
Time spent in different activities or intensity-levels
IC patients spent almost 8.5 hours a day sitting (508 ± 108 minutes), more than 2.5 hours a day standing (165 ± 60 minutes), more than 2 hours a day lying (132 ± 101 minutes), 1 hour a day walking (65 ± 33 minutes) and 21 ± 12 minutes a day shuffling. (Table 2) Compared to the control group a significant difference was found in the time spent sitting and 'device not worn'. A significant group difference was also found regarding vigorous-intensity activities (IC: 4 ± 8 vs. Controls: 11 ± 10 minutes a day, p=0.002).
Daily number of steps in the IC subgroups was significantly fewer compared to the control group (IC subgroup 1: 4663 ± 3104 vs. IC subgroup 2: 5761 ± 2371 vs. Controls: 6682 ± 2701, p=0.03). The highest number of steps walked in one period (top period of steps) was also significantly lower in IC patients (IC subgroup 1: 1601 ± 1414 vs. IC subgroup 2: 2546 ±1894 vs. Controls: 4584 ± 4680, p<0.001).
Daily physical activity level
A statistically significant difference (p = 0.02) in both daily PA level and daily PA in bouts of >10 minutes of moderate- or vigorous intensity exercise, was found between the IC subgroups and the control group. (Figure 1, 2) Post-hoc analyses showed that this difference was solely due to a significant difference between IC subgroup 1 (WIQ < 0.4) and the control group (p=0.018). In contrast, no significant difference in daily PA level was found between IC subgroup 2 (WIQ = 0.4) and the control group (p=0.28).
Analysis of the number of participants achieving the lower (67 METs?min a day) and upper (107 METs?min a day) limit of the ACSM minimum recommendations showed a significant difference (lower limit: p=0.01, higher limit: p=0.02) between the IC subgroups and the control group in favour of the healthy controls. (Figure 3)
Prediction model for daily physical activity level
Univariable regression analysis revealed that age, a previous history of pulmonary disease, MWD and the WIQ, SF-12 MCS and SF-12 PCS score, all independently influenced the daily PA level. (Table 3) Multivariable regression analysis including five variables (age, pulmonary history, SF-12 PFS, SF-12 MFS, MWD) explained 53% (p<0.001) of the variance in daily PA level:
Daily PA level of IC patients (METs?min) = 369.23 – 7.65 x Age + 4.73 x SF-12 PCS score + 6.53 x SF-12 MCS score + 0.18 x MWD (– 138.65 if pulmonary history is present)