Table 1.

Participant demographic information and time intervals

		Noncollar			Collar
		n	Range	Median	n	Range	Median	U value	Critical U value	P
Age (years) Time 1		10	16.0–17.9	16.90	13	15.5–17.8	16.87	63	33	0.928
	Time 2	10	16.4–19.0	17.25	13	15.8–18.2	17.24	60	33	0.779
	Time 3	10	17.2–19.7	17.97	13	16.5–18.9	17.92	57.5	33	0.667
	Time 3*	7	17.2–18.1	17.73	9	16.5–18.2	17.67	30.5	12	0.960
	Time 4	7	17.4–18.4	18.02	9	16.9–18.4	18.05	28	12	0.749
Gender	All male				All male
Time btw MR imaging (days)
	Time 1 to Time 2	10	96–148	131	13	104–153	133	64	33	0.976
	Time 2 to Time 3	10	256–277	263	13	242–270	252	28	33	0.024
	Time 3 to Time 4	7	91–113	106	9	99–140	135	13	12	0.056
Time from last game/practice to postseason imaging (days)
	Season 1	10	3–20	6.50	12 **	0–11	5	35.5	29	0.114
	Season 2	7	3–26	12.00	9	0–16	4.00	11	12	0.034

Time 1–3: for athletes who had data at all three time points. Group size was 10 and 13 for the noncollar and collar groups, respectively.

Time 3* and Time 4: for athletes who had data at both time points in Season 2. Group size was 7 and 9 for the noncollar and collar groups, respectively.

Time btw MR imaging: The time interval (days) between the preseason imaging and postseason imaging.

** The accelerometer data were not recorded in one of the 13 participants in the collar group.

Between group difference was tested using Mann–Whitney U test (two‐tailed).