Analyzing walking speeds with ankle and wrist worn accelerometers in a cohort with myotonic dystrophy

Figures & data

Table 1. Demographic characteristics of study sample presented by group. Data are presented as mean values or scores (standard deviation).

	DM1	Healthy-controls
N (N = males)	30 (20)	14 (6)
Age – years (min–max)	48 (25–72)	32 (23–47)^a
Height – cm (SD)	171 (8)	168 (11)
BMI (SD)	25 (5)	24 (4)
6MWT (m)	440 (147)	685 (82)^a

BMI: body mass index (weight/height²); 6MWT: 6-min walking test; SD: standard deviation.

^a Difference between groups is statistically significant (sig < 0.001).

Figure 1. Box plots representing the accelerometer reports for each test per limb-placement. (a) The 10-m walking at comfortable pace test (10-mWT); and (b) the 10-m walk/run test (10-mW/RT) which implies the fastest pace performed. (c) The DM1 group sub-divided into classic and mild phenotypes (classification explained in methods). Values on the y-axis represent the average of acceleration (ENMO-mg) per minute for each test. Values on the x-axis showed the two groups tested: DM1 and healthy controls.

Table 2. Mean acceleration units for each performed task presented by group.

		DM1	Healthy-controls
Task	Location	Mean (95% CI)	Mean (95% CI)	Sig.
Stand Still	Left wrist	2.3 (1.5−3.2)	2.7 (1.5−4.0)	0.26
	Right wrist	2.3 (1.7−3.0)	2.5 (1.4−3.4)	0.65
	Left ankle	1.2 (0.7−1.7)	1.9 (0.7−3.1)	0.40
	Right ankle	1.3 (0.8−1.7)	1.7 (0.6−2.7)	0.30
10-mWT	Left wrist	13.2 (11.8−14.6)	17 (13.5−20.5)	0.03^a
	Right wrist	12.1 (10.9−13.3)	18.1 (13.0−23.2)	0.001
	Left ankle	37.4 (33.8−41.0)	46.0 (41.8−50.2)	0.001
	Right ankle	37.6 (34.2−40.9)	48.1 (41.9−54.3)	0.001
6MWT	Left wrist	21.3 (15.5−27.1)	40.6 (27.5−53.7)	< 0.001
	Right wrist	20.3 (15.2−25.5)	41.9 (26.3−57.4)	0.002
	Left ankle	47.6 (41.5−53.7)	74.4 (65.1−83.8)	< 0.001
	Right ankle	47.8 (41.6−54.0)	75.5 (66.4−84.7)	< 0.001
10-mW/RT	Left wrist	99.3 (66.8−131.8)	210.6 (189.5−231.6)	< 0.001
	Right wrist	94 (62.8−125.3)	214.9 (188.0−241.9)	< 0.001
	Left ankle	101.6 (82.1−121.1)	183.6 (160.9−206.3)	< 0.001
	Right ankle	98.1 (80.9−115.3)	176.5 (155.0−198.1)	< 0.001

Walking tests are presented from slow to fast: 10-mWT (10 m walk test), 6MWT (6 min walking test), 10-mW/RT (10 m walk/run test).

^aWhen adjusted to age and gender the significance level changed to 0.08 and estimated marginal means of 16.7 for healthy controls and 13.4 for the DM1 group. 95% CI (95% confidence interval for mean).

Table 3. Spearman’s (rho) correlation values estimated between total distance (m) completed during the 6-min walking test (6MWT) and each of the accelerometer units reports (ENMO per minute).

Accelerometer location	DM1	Healthy-controls	Whole sample
Left Wrist	0.14	0.62*	0.46**
Right Wrist	0.16	0.63*	0.46**
Left Ankle	0.38*	0.86**	0.65**
Right Ankle	0.42*	0.78**	0.68**

* p < 0.05; **p < 0.01 (correlation significance).