An Analysis of Variability in “CatWalk” Locomotor Measurements to Aid Experimental Design and Interpretation

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Figure 1.
Scatter plot between run speed and right hind/right fore (RH/RF) coupling in normal rats on the CatWalk. There is no apparent correlation between these variables (r = −0.012; p = 0.885).
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Figure 2.
RH stride length at week 3 and week 6 after rats had received a unilateral C5 spinal cord impact injury (SciCrunch data).

Table 1

CatWalk detection settings

Camera detection settings	Results	Auto detection settings
Camera gain (dB): 12.00 Green intensity threshold: 0.14 Red ceiling light (V): 17.70 Green walkway light (V): 16.0	Maximum green intensity: 0 Minimum green intensity: 256 Range: –256	Maximum range from 197 to 203 Frames before Delta: 5 Intensity minimum: 85

Table 3

RCVs

Test	Mean	RCV (%)
Overall measures of hindlimbfunction
Run duration	3.29 s	69.3
Average speed	36.87 cm/s	72.5
Base of support	2.71 cm	34.4
Coupling RHRF	45.12%	31.6
Coupling LHLF	45.40%	30.8
Hindlimb function, right
Stride length	17.68 cm	29.1
Print area	1.82 cm²	65.0
Swing duration	0.16 s	25.7
Swing speed	112.52 cm/s	34.8
Stance duration	0.23^* s	Up: 121.5;down: 54.9
Max contact area	1.39 cm²	73.2
Mean intensity	103.61 AU	19.6
Duty cycle	58.60%	24.2
Hindlimb function, left
Stride length	17.71 cm	27.1
Print area	1.83 cm²	66.1
Swing duration	0.16 s	27.2
Swing speed	112.45 cm/s	31.0
Stance duration	0.23^* s	Up: 136.6;down: 57.7
Max contact area	1.41 cm²	71.5
Mean intensity	103.63 AU	20.4
Duty cycle	58.33%	24.9

Table 4

Pearson correlation matrix for commonly measured variables, RH

	Runduration	Stridelength	Base ofsupport	Printarea	Swingduration	Swingspeed	Maxcontact	Stancetime	Runspeed	Meanintensity	Dutycycle
Run duration	1
Stride length	–0.454	1
Base of support	0.090	–0.268	1
Print area	0.219	–0.140	0.098	1
Swing duration	0.218	0.0207	0.046	–0.004	1
Swing speed	–0.487	0.720	–0.223	–0.071	–0.660	1
Max contact	0.183	–0.107	0.062	0.97	–0.021	–0.039	1
Stance time	0.568	–0.558	0.260	0.202	0.202	–0.546	0.354	1
Run speed	–0.770	0.588	–0.161	–0.326	–0.326	0.660	–0.305	–0.716	1
Mean intensity	0.057	0.123	0.115	0.509	0.016	0.090	0.579	0.079	–0.060	1
Duty cycle	0.437	–0.673	0.235	0.515	–0.176	–0.361	0.458	0.773	–0.617	0.114	1

Table 5

Application of RCI analysis to previously published data on RH stride length following unilateral 12.5-mm NYU impactor injury at C5

Ratnumber	Week 3 Stridelength (mm)	Week 6 Stridelength (mm)	RCV (fromour study)	Upper RCIboundary(= week 3 + RCV)	Lower RCIboundary(= week 3 – RCV)	Week 6 exceedsupper RCIboundary?	Week 6 lessthan lower RCIboundary?
1	150.70	158.39	42.20	192.90	108.50	No	No
2	159.17	184.74	44.57	203.74	114.60	No	No
3	138.41	176.61	38.76	177.17	99.66	No	No
4	150.63	161.65	42.18	192.81	108.46	No	No
5	146.08	148.88	40.90	186.98	105.18	No	No
6	143.36	143.85	40.14	183.50	103.22	No	No
7	169.21	169.29	47.38	216.58	121.83	No	No
8	168.78	188.33	47.26	216.04	121.52	No	No
9	169.94	154.81	47.58	217.52	122.36	No	No
10	197.48	169.24	55.29	252.77	142.19	No	No
11	190.84	193.31	53.43	244.27	137.40	No	No
12	128.59	145.83	36.00	164.59	92.58	No	No
13	172.51	180.00	48.30	220.81	124.21	No	No
14	137.35	179.32	38.46	175.80	98.89	Yes	No
15	122.18	175.32	34.21	156.39	87.97	Yes	No
16	110.61	198.19	30.97	141.58	79.64	Yes	No
17	117.51	192.55	32.90	150.41	84.61	Yes	No
18	125.85	135.39	35.24	161.09	90.61	No	No
19	142.68	150.32	39.95	182.63	102.73	No	No
20	153.95	147.86	43.11	197.06	110.85	No	No
21	153.02	170.64	42.85	195.87	110.18	No	No
22	154.96	166.54	43.39	198.34	111.57	No	No
23	154.82	189.25	43.35	198.18	111.47	No	No
24	149.06	176.97	41.74	190.79	107.32	No	No
25	126.54	140.62	35.43	161.97	91.11	No	No
26	156.21	183.76	43.74	199.95	112.47	No	No
27	163.30	170.99	45.72	209.02	117.57	No	No
28	130.30	172.69	36.49	166.79	93.82	Yes	No
29	150.85	132.10	42.24	193.09	108.61	No	No
30	164.72	153.03	46.12	210.85	118.60	No	No
31	172.34	167.85	48.26	220.60	124.09	No	No
32	141.57	158.13	39.64	181.21	101.93	No	No