Headgear mandates in high school girls’ lacrosse: investigating differences in impact rates and game play behaviors

Figures & data

Table 1. Head, body and overall impacts in girls’ high school lacrosse.

	Headgear mandate			No headgear mandate
	Head	Body	Overall	Head	Body	Overall
Games	64	64	64	125	125	125
Impact count	172	5649	5821	158	10361	10519
IR (95% CI)	2.7 (2.3–3.1)	88.3 (86.0–91.0)	90.6 (88.6–93.3)	1.3 (1.0–1.5)	82.9 (81.3–84.5)	84.2 (82.6–85.8)
IRR (95% CI)	2.1 (1.7–2.6)*	1.1 (1.0–1.1)	1.1 (1.0–1.1)

Note: IR = impact rate per game; IRR = impact rate ratio (HM Cohort is reference), *statistically significant.

Table 2. Head and body impacts by headgear cohort and player position.

	Headgear mandate (HM)		No headgear mandate (NHM)		HM vs NHM
Position	n (%)	IR (95% CI)	n (%)	IR (95% CI)	IRR (95% CI)
Head impacts
Attacker	58 (33.7)	0.9 (0.7–1.2)	38 (24.1)	0.3 (0.2–0.4)	3.0 (2.0–4.5)*
Midfield	105 (61.0)	1.6 (1.3–2.0)	101 (63.9)	0.8 (0.7–1.0)	2.0 (1.5–2.7)*
Defender	9 (5.2)	0.1 (0.1–0.3)	19 (12.0)	0.2 (0.1–0.2)	0.9 (0.4–2.0)
Body impacts
Attacker	1245 (22.0)	19.5 (18.4–20.6)	2,120 (20.5)	17.0 (16.2–17.7)	1.1 (1.1–1.2)
Midfield	3612 (63.9)	56.4 (54.6–58.3)	6667 (64.3)	53.3 (52.1–54.6)	1.1 (1.0–1.1)
Defender	792 (14.0)	12.4 (11.5–13.3)	1,574 (15.2)	12.6 (12.0–13.2)	1.0 (0.9–1.1)

Note: IR = impact rate per game; IRR = impact rate ratio (HM Cohort is reference), *statistically significant.

Table 3. Impacts to the head and body by headgear cohort and mechanism.

	Headgear mandate (HM)		No headgear mandate (NHM)		HM vs NHM
Mechanism	n (%)	IR (95% CI)	n (%)	IR (95% CI)	IRR (95% CI)
Head impacts
Ball	3 (1.7)	0.0 (0.0–0.1)	4 (2.5)	0.0 (0.0–0.1)
Stick	145 (84.3)	2.3 (1.9–2.7)	126 (79.7)	1.0 (0.8–1.2)	2.2 (1.8–2.9)*
Player	20 (11.6)	0.3 (0.2–0.5)	19 (12.0)	0.2 (0.1–0.2)	2.1 (1.1–3.9)*
Ground	4 (2.3)	0.1 (0.0–0.1)	9 (5.7)	0.1 (0.0–0.1)
Body impacts
Ball	11 (0.2)	0.2(0.1–0.3)	14 (0.1)	0.1 (0.1–0.2)	1.5 (0.7–3.4)
Stick	2034 (36.0)	31.8 (30.4–33.2)	3740 (36.1)	29.9 (29.0–30.9)	1.1 (1.0–1.1)
Player	2911 (51.5)	45.5 (43.9–47.2)	5359 (51.7)	42.9 (41.7–44.0)	1.1 (1.0–1.1)
Ground	692 (12.2)	10.8 (10.0–11.6)	1246 (12.0)	10.0 (9.4–10.5)	1.1 (0.1–1.2)
Other	1 (0.0)	0.0 (0.0–0.1)	2 (0.0)	0.0 (0.0–0.1)

Note: IR = impact rate per game; IRR = impact rate ratio (HM Cohort is reference), *statistically significant.

Table 4. Penalties administered for stick and player impacts to the head and body by headgear mandate cohort.

		Headgear mandate (HM)		No headgear mandate (NHM)		HM vs NHM
	Mechanism	n (%)	IR (95% CI)	n (%)	IR (95% CI)	IPR (95% CI)
Penalty	Head
	Stick	60 (41.4%)	0.9 (0.7–1.2)	53 (31.4%)	0.3 (0.2–0.4)	0.1 (0.8–1.2)
	Player	5 (25.0%)	0.1 (0.1–0.3)	3 (27.3%)	0.2 (0.1–0.2)	1.4 (1.2–1.5)
	Total	65 (39.4%)	1.6 (1.3–2.0)	56 (31.6%)	0.8 (0.7–1.0)
	Body
	Stick	617 (23.1%)	9.6 (8.9–10.4)	1040 (19.4%)	8.3 (7.8–8.8)	1.0 (0.6–1.4)
	Player	389 (19.1%)	6.1 (5.5–6.7)	684 (18.3%)	5.5 (5.1–5.9)	0.1 (0.6–1.4)
	Total	1006 (20.1%)	15.7 (14.8–16.7)	1724 (19.1%)	13.8 (13.2–14.1)
No Penalty	Head
	Stick	85 (58.6%)	19.5 (18.4–20.6)	113 (68.6%)	17.0 (16.2–17.7)	0.9 (0.7–1.1)
	Player	15 (75.0%)	12.4 (11.5–13.3)	8 (72.7%)	12.6 (12.0–13.2)	2.3 (2.1–2.5)*
	Total	100 (60.6%)	56.4 (54.6–58.3)	121 (68.4%)	53.3 (52.1–54.6)
	Body
	Stick	2294 (76.9%)	35.8 (34.4–37.3)	4319 (80.6%)	34.5 (33.6–35.6)	1.0 (0.6–1.4)
	Player	1645 (80.9%)	25.7 (23.5–27.0)	3056 (81.7%)	24.4 (23.6–25.3)	1.0 (0.6–1.4)
	Total	3939 (79.9%)	61.5 (59.6–63.5)	7375 (80.9%)	59.0 (57.7–60.4)

Note: IR = impact rate per game; IPR = impact proportion ratio (HM cohort is reference), *statistically significant.

Data availability statement

The authors agree to make data supporting the results presented in their paper available upon reasonable request.