The effect of concussion on batting performance of major league baseball players

Figures & data

Table 1 Glossary

Metric	Definition	Calculation
Isolated power	A measure of raw power	Slugging Percentage–Batting Average
On-base percentage	How frequently a batter reaches base per plate appearance	(Hits+Walks+Hit by Pitch)/(At Bats+Walks+Hit by Pitch+Sacrifice Flies)
Slugging percentage	Total number of bases a player records per at-bat	(Singles+Doubles×2+Triples×3+Home runs×4)/At Bats

Table 2 Player characteristics by position in control and concussion groups

	Control (n=212)	Concussion (n=85)	P-value
Age in years, mean (SD)	28.8 (4)	28.1 (3.7)	0.19
Days missed, mean (SD)	49.1 (96.7)	54.5 (107.6)	0.69
Position, number of players (%)
Catcher	32 (15.1)	14 (16.5)	0.77
1B	16 (7.5)	7 (8.2)	0.84
2B	14 (6.6)	2 (2.4)	0.14
SS	18 (8.5)	9 (10.6)	0.57
3B	16 (7.5)	6 (7.1)	0.89
RF	43 (20.3)	14 (16.5)	0.45
CF	19 (9)	10 (11.8)	0.46
LF	5 (2.4)	4 (4.7)	0.29
DH/Other	49 (23.1)	19 (22.4)	0.89
Year, number of players (%)
2008	30 (14.2)	5 (5.9)	0.05
2009	21 (9.9)	8 (9.4)	0.90
2010	19 (9)	12 (14.1)	0.19
2011	29 (13.7)	14 (16.5)	0.54
2012	24 (11.3)	12 (14.1)	0.50
2013	33 (15.6)	12 (14.1)	0.75
2014	37 (17.5)	16 (18.8)	0.78

Figure 1 Comparison of traditional batting statistics of concussed and control players before and after event. (A) Batting average; (B) On-base percentage; (C) Slugging percentage; and (D) Isolated power.

Notes: *Indicates a P<0.05 for a comparison between the concussed players at a given time vs their own pre-concussion performance. ^# indicates a P<0.05 for a comparison between concussed players vs controls.
Abbreviations: AVG, battling average; SLG, slugging percentage; OBP, on-base percentage; ISO, isolated power.

Table 3 Plate discipline and batted ball statistics

Measure	Timing	Concussion	Control	P-value concussed players at given time vs concussed players pre-event	P-value concussed players vs control
Swing	Non-injury season	46.4%	45.5%	<0.01	0.12
	Pre-event	45.5%	45.4%	Reference	0.95
	15 days after return	46.2%	46.5%	0.14	0.75
	15–30 days after return	47.6%	46.0%	0.00	0.06
	Rest of season	46.7%	45.6%	<0.01	0.10
Swing at strike	Non-injury season	30.5%	29.8%	<0.01	0.03
	Pre-event	29.8%	29.8%	Reference	1.00
	15 days after return	30.0%	30.0%	0.67	0.97
	15–30 days after return	31.0%	29.8%	0.03	0.06
	Rest of season	30.6%	29.9%	0.03	0.10
Swing and miss	Non-injury season	10.1%	10.0%	0.10	0.85
	Pre-event	10.4%	9.8%	Reference	0.19
	15 days after return	10.9%	10.7%	0.08	0.63
	15–30 days after return	10.4%	10.2%	0.80	0.64
	Rest of season	10.6%	10.2%	0.39	0.40
Swing at ball	Non-injury season	15.8%	15.6%	0.19	0.64
	Pre-event	15.6%	15.6%	Reference	0.96
	15 days after return	16.2%	16.5%	0.13	0.56
	15–30 days after return	16.6%	16.2%	0.02	0.59
	Rest of season	16.1%	15.7%	0.08	0.50
Take ball	Non-injury season	36.4%	36.8%	0.02	0.20
	Pre-event	36.9%	36.9%	Reference	0.88
	15 days after return	36.4%	36.4%	0.33	0.88
	15–30 days after return	35.5%	36.8%	0.01	0.05
	Rest of season	36.1%	37.0%	0.01	0.03
Swing and miss at strike	Non-injury season	4.2%	4.2%	0.04	0.80
	Pre-event	4.4%	4.0%	Reference	0.06
	15 days after return	4.4%	4.2%	0.91	0.42
	15–30 days after return	4.3%	4.1%	0.73	0.53
	Rest of season	4.5%	4.2%	0.85	0.36
Swing at strike or take ball	Non-injury season	66.9%	66.6%	0.52	0.53
	Pre-event	66.7%	66.7%	Reference	0.89
	15 days after return	66.5%	66.3%	0.58	0.85
	15–30 days after return	66.4%	66.6%	0.60	0.84
	Rest of season	66.6%	66.9%	0.70	0.51
Ground ball	Non-injury season	43.6%	39.6%	0.65	0.56
	Pre-event	40.9%	40.6%	Reference	0.79
	15 days after return	40.4%	41.0%	0.71	0.75
	15–30 days after return	38.0%	42.4%	0.06	0.02
	Rest of season	40.1%	40.3%	0.41	0.87
Line drive	Non-injury season	17.8%	21.2%	0.99	0.53
	Pre-event	17.9%	18.2%	Reference	0.57
	15 days after return	16.8%	18.7%	0.29	0.10
	15–30 days after return	16.3%	19.0%	0.18	0.04
	Rest of season	18.4%	19.3%	0.51	0.19
Fly ball	Non-injury season	38.6%	33.6%	0.23	0.45
	Pre-event	31.8%	34.2%	Reference	0.02
	15 days after return	33.3%	32.4%	0.25	0.59
	15–30 days after return	33.9%	31.6%	0.16	0.19
	Rest of season	31.6%	32.8%	0.81	0.31
Home run/fly ball ratio	Non-injury season	11.1	3.6	0.21	0.11
	Pre-event	6.1	7.2	Reference	0.10
	15 days after return	4.6	6.1	0.09	0.15
	15–30 days after return	6.0	6.7	0.91	0.57
	Rest of season	5.8	6.2	0.59	0.62
Pull	Non-injury season	33.7%	34.7%	0.28	0.88
	Pre-event	39.9%	40.4%	Reference	0.65
	15 days after return	41.3%	39.2%	0.32	0.19
	15–30 days after return	37.8%	40.4%	0.18	0.17
	Rest of season	41.6%	39.1%	0.10	0.03
Central	Non-injury season	35.9%	34.4%	0.71	0.82
	Pre-event	33.8%	33.8%	Reference	0.96
	15 days after return	34.1%	36.5%	0.87	0.09
	15–30 days after return	35.1%	35.9%	0.41	0.59
	Rest of season	34.1%	35.4%	0.74	0.14
Opposite field	Non-injury season	30.5%	31.0%	0.40	0.92
	Pre-event	26.2%	25.7%	Reference	0.54
	15 days after return	24.6%	24.3%	0.21	0.83
	15–30 days after return	27.1%	23.7%	0.51	0.03
	Rest of season	24.2%	25.4%	0.02	0.18
Soft contact	Non-injury season	21.0%	20.8%	0.68	0.96
	Pre-event	19.1%	17.5%	Reference	0.02
	15 days after return	19.1%	18.5%	0.97	0.64
	15–30 days after return	19.4%	17.2%	0.83	0.13
	Rest of season	18.7%	18.3%	0.65	0.54
Medium contact	Non-injury season	44.6%	53.4%	0.09	0.21
	Pre-event	54.6%	54.6%	Reference	0.11
	15 days after return	54.1%	54.1%	0.71	0.40
	15–30 days after return	54.1%	54.1%	0.76	0.68
	Rest of season	54.3%	54.3%	0.78	0.14
Hard contact	Non-injury season	34.3%	25.8%	0.13	0.17
	Pre-event	26.2%	29.2%	Reference	0.00
	15 days after return	26.8%	28.7%	0.68	0.18
	15–30 days after return	26.4%	29.3%	0.91	0.08
	Rest of season	26.7%	28.8%	0.58	0.05