Paraspinal strength and electromyographic fatigue in patients with sub-acute back pain and controls: Reliability, clinical applicability and between-group differences

Table 5 Reliability of initial median frequency, median frequency-slope and root mean square for the isometric endurance test in both groups

	Controls (n = 26)			Patients (n = 66)
Parameter	ICC3,1	SEM	SDD	ICC3,1	SEM	SDD
IMF (Hz)
L2/3 R	0.91 (0.80-0.96)	3.32	9.19	0.80 (0.69-0.87)	7.56	20.95
L2/3 L	0.82 (0.63-0.92)	4.57	12.66	0.80 (0.69-0.87)	6.88	19.06
L4/5 R	0.82 (0.61-0.92)	7.99	22.13	0.82 (0.73-0.89)	9.64	26.70
L4/5 L	0.81 (0.60-0.91)	8.31	23.02	0.86 (0.79-0.92)	8.61	23.85
L 2/3	0.94 (0.87-0.98)	3.45	9.56	0.90 (0.84-0.94)	6.41	17.75
L 4/5	0.91 (0.79-0.96)	7.27	20.14	0.94 (0.90-0.96)	7.59	21.02
MF slopes (raw, Hz/s)
L2/3 R	0.61 (0.27-0.81)	0.07	0.19	0.75 (0.62-0.84)	0.08	0.22
L2/3 L	0.67 (0.36-0.85)	0.06	0.17	0.66 (0.50-0.78)	0.09	0.25
L4/5 R	0.52 (0.14-0.77)	0.13	0.36	0.73 (0.60-0.83)	0.12	0.33
L4/5 L	0.55 (0.18-0.78)	0.13	0.36	0.62 (0.45-0.75)	0.15	0.41
L 2/3	0.77 (0.46-0.90)	0.06	0.17	0.86 (0.77-0.91)	0.08	0.22
L 4/5	0.73 (0.35-0.89)	0.11	0.30	0.88 (0.80-0.92)	0.10	0.28
MF slopes (normalised, %/min)
L2/3 R	0.67 (0.36-0.85)	5.79	16.03	0.69 (0.55-0.80)	8.59	23.79
L2/3 L	0.65 (0.33-0.84)	5.36	14.85	0.69 (0.54-0.80)	8.44	23.38
L4/5 R	0.64 (0.31-0.83)	7.11	19.69	0.62 (0.45-0.75)	8.59	23.79
L4/5 L	0.50 (0.11-0.75)	7.60	21.05	0.57 (0.38-0.71)	8.66	23.99
L 2/3	0.82 (0.57-0.92)	4.93	13.66	0.85 (0.75-0.91)	7.47	20.69
L 4/5	0.78 (0.49-0.91)	6.02	16.67	0.83 (0.73-0.90)	6.75	18.69
RMS slopes (normalised, %/min)
L2/3 R	0.73 (0.46-0.88)	21.00	58.17	0.48 (0.27-0.65)	14.48	40.11
L2/3 L	0.76 (0.51-0.89)	14.83	41.08	0.71 (0.56-0.81)	10.83	30.00
L4/5 R	0.44 (0.04-0.72)	24.07	66.67	0.73 (0.60-0.83)	11.26	31.19
L4/5 L	0.54 (0.17-0.78)	24.20	67.03	0.61 (0.44-0.74)	12.44	34.46

Hz: Hertz; ICC: Intraclass correlation coefficient; SEM: Standard error of the measurement; SDD: Smallest detectable difference; IMF: Initial median frequency; MF: Median frequency; RMS: Root mean square.