Test-retest reliability of lower limb isokinetic endurance in COPD: A comparison of angular velocities

Figures & data

Figure 1 Experimental design.

Note: *Randomized order.
Abbreviation: PFT, pulmonary function tests.

Table 1 Subject characteristics (n=14)

Male/female	11/3
Age (years)	65±4
Body mass index (kg/m^2)	26.6±3.9
Fat-free mass index (kg/m^2)	18.6±1.7
FVC (L)	3.6±1.1
FVC (% predicted)	97±25
FEV1 (L)	1.51±0.59
FEV1 (% predicted)	55±18
FEV1/FVC (%)	42±10
TLC (L)	7.1±1.8
TLC (% predicted)	117±10
DLCO (% predicted)	64±16
SpO2 (%)	96±1
Physical activity (Voorrips score)	5±5

Note: Values are shown as the mean ± standard deviation.

Abbreviations: FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; TLC, total lung capacity; DL_CO, diffusing capacity of the lung for carbon monoxide; SpO₂, pulse oximetry oxygen saturation.

Table 2 Comparison between variables of the lower limb isokinetic endurance test at different angular velocities

Variables	90° per second		180° per second*
	Visit 1	Visit 2	Visit 1	Visit 2
Peak torque (Nm)	115±30	118±33	89±26	89±25
Total isokinetic work (Nm)	2,164±553	2,214±535	1,712±508	1,803±514
Work slope (%/rep)	−2.4±0.8	−2.5±0.9	−1.5±0.7	−1.3±0.6
Fatigue index (%)	49.3±8.2	49.5±7.9	40.1±13.0	35.4±14.7
Delta dyspnea (Borg scale)	3±2	3±1	2±1	3±1
Delta leg fatigue (Borg scale)	5±3	6±2	4±2	5±1

Notes: Values are shown as the mean ± standard deviation.

* P<0.05 180° per second vs 90° per second.

Table 3 Test-retest reliability

Variables	90° per second			180° per second
	ICC (95% CI)	MDC95%	MDC95% (95%)	ICC (95% CI)	MDC95%	MDC95% (%)
Peak torque	0.97 (0.92–0.99)	14 Nm	12	0.94 (0.81–0.98)	17 Nm	19
Total isokinetic work	0.98 (0.93–0.99)	220 Nm	10	0.93 (0.78–0.98)	339 Nm	19
Work slope	0.94 (0.83–0.98)	0.58%/rep	23	0.59 (0.13–0.85)	1.21%/rep	86
Work fatigue index	0.92 (0.77–0.97)	6.5%	13	0.30 (−0.24–0.70)	32.2%	85
Δ Dyspnea	0.51 (−0.03–0.81)	3	118	0.24 (−0.26–0.66)	3	121
Δ Leg fatigue	0.51 (−0.02–0.81)	5	86	0.60 (0.15–0.85)	3	75

Abbreviations: CI, confidence level; ICC, intraclass correlation; MDC, minimal detectable change; MDC_95%, absolute value of MDC at the 95% CI; MDC_95% (%), relative value of MDC at the 95% CI; rep, repetition.

Figure 2 Bland-Altman plots.

Notes: llustration by Bland-Altman plots of means differences (solid lines) and 95% confidence intervals (dotted lines) of a 30-maximal repetition isokinetic muscle endurance procedure performed on two separate occasions for peak torque, total work, work slope, work fatigue, dyspnea perception, and leg fatigue perception. Left panels illustrate means differences and 95% confidence intervals for peak torque (A), total work (C), work slope (E), work fatigue (G), dyspnea perception (I), and leg fatigue perception (K) during isokinetic leg extension performed at 90°/s. The right panels illustrate means differences and 95% confidence intervals for peak torque (B), total work (D), work slope (F), work fatigue (H), dyspnea perception (J), and leg fatigue perception (L) during isokinetic leg extension performed at 180°/s.
Abbreviation: SD, standard deviation.