Investigation of the effect of circadian rhythm on the performances of NBA teams

Figures & data

Table 1. The time zones and the DST characteristics of the NBA teams’ home cities (for the 21 seasons between 2000–2021 years).

UTC	DST	Teams
Pacific UTC-8	In use	Golden State Warriors – Los Angeles Lakers – Los Angeles Clippers – Portland Trail Blazers – Sacramento Kings – Seattle SuperSonics – Vancouver Grizzlies
Mountain UTC-7	In use	Denver Nuggets – Utah Jazz
Arizona Mountain UTC-7	Not in use	Phoenix Suns
Central UTC-6	In use	Chicago Bulls – Dallas Mavericks – Houston Rockets – Memphis Grizzlies – Milwaukee Bucks – Minnesota Timberwolves – New Orleans Pelicans – Oklahoma City Thunder – San Antonio Spurs – New Orleans Hornets – Oklahoma City Hornets
Eastern UTC-5	In use	Atlanta Hawks – Boston Celtics – Brooklyn Nets – Cleveland Cavaliers – Toronto Raptors – Washington Wizards – Philadelphia 76ers – Indiana Pacers – Orlando Magic – New York Knicks – Detroit Pistons – Miami Heat – Charlotte Hornets – New Jersey Nets – Charlotte Bobcats

UTC: Universal Time Coordinated, DST: Daylight Saving Time.

Table 2. The abbreviations and short definitions of the variables.

Variable	Abbreviations	Definitions
Win/Loss^#	W/L	Results of the games either win or loss
Points scored^#	P	Number of points scored
Opponent points^#	OP	Number of points scored by the opposing team
2-point field goals made*	FG2M	Number of successful 2-point shots
2-point field goals attempt*	FG2A	Number of 2-point shot attempts
3-point field goals made*	FG3M	Number of successful 3-point shots
3-point field goals attempt*	FG3A	Number of 3-point shot attempts
Points differential^#	PD	P – OP difference
Field goals made^#	FGM	Sum of FG2M + FG3M
Field goals attempt^#	FGA	Sum of FG2A + FG3A
Field goal percentage^#	FG%	The ratio of FGM/FGA
2-point percentage*	FG2%	The ratio of FG2M/FG2A
3-point percentage*	FG3%	The ratio of FG3M/FG3A
Free throw made*	FTM	Number of successful free throws
Free throw attempt*	FTA	Number of free throw attempts
Free throw percentage*	FT%	The ratio of FTM/FTA
Offensive rebounds*	OR	A rebound at the basket a team is attacking
Defensive rebounds*	DR	A rebound at the basket a team is defending
Total rebounds^#	TR	Sum of DR + OR
Assists*	AS	A pass thrown to a player who immediately scores
Steals*	ST	To intercept a pass or dribble and gain possession of the ball
Turnovers*	TO	A loss of possession of the ball
Blocks*	BL	A tipped or deflected shot belonging to opponent’s team which alters its flight so the shot misses
Personal fouls*	PF	Number of fouls committed
Assists/Turnover ratio*	AS/TO	Ratio of AS/TO

^#: Results of the variable were given in the main text, *: Results of the variable were given only in the tables and supplemental materials.

Table 3. Examples of CR phase shift and CR adaptation by considering only two consecutive games.

Examples of CR Adaptation of a Team Traveling from UTC-8 to UTC-5
Example 1	Travel Day	Rest Day	Rest Day	Rest Day	Game Day
Local UTC	−8	−5	−5	−5	−5
Internal UTC	−8	−8	−7	−6	−5
CR phase shift (direction)	0 (-)	−3 (East)	−2 (East)	−1 (East)	0 (-)
Example 2	Travel Day	Game Day	-	-	-
Local UTC	−8	−5	-	-	-
Internal UTC	−8	−8	-	-	-
CR phase shift (direction)	0 (-)	−3 (East)	-	-	-
Example of CR Adaptation of a Team Traveling from UTC-4 to UTC-6
Example 3	Travel Day	Rest Day	Game Day	-	-
Local UTC	−4	−6	−6	-	-
Internal UTC	−4	−4	−5	-	-
CR phase shift (direction)	0 (-)	+2 (West)	+1 (West)	-	-

CR: Circadian Rhythm, UTC: Universal Time Coordinated.

Table 4. CR phase shift and CR adaptation examples as a result of local UTC change without adaptation.

The Local UTCs before and after the change are in the same direction
Example 1	Game Day 1	Rest Day	Game Day 2	Rest Day	Game Day 3
Local UTC	−8	−6	−6	−5	−5
Internal UTC	−8	−8	−7	−6	−5
CR phase shift (direction)	0 (-)	−2 (East)	−1 (East)	−1 (East)	0 (-)
The Local UTCs before and after the change are in the opposite direction
Example 2	Game Day 1	Rest Day	Game Day 2	Rest Day	Game Day 3
Local UTC	−5	−7	−7	−4	−4
Internal UTC	−5	−5	−6	−6	−5
CR phase shift (direction)	0 (-)	+2 (West)	+1 (West)	−2 (East)	−1 (East)

CR: Circadian Rhythm, UTC: Universal Time Coordinated.

Table 5. Time zones that the games played in (n = 24,985).

Time Zone	n	%
Pacific UTC-8	4,557	18.24
Mountain UTC-7	1,676	6.71
Arizona Mountain UTC-7	839	3.36
Central UTC-6	7,099	28.41
Eastern UTC-5	10,814	43.28

UTC: Universal Time Coordinated.

Table 6. CR phase shift data of teams during games according to local UTC (n = 49,970).

CR Phase Shift Volume	Home Teams (n = 24,985)		Away Teams (n = 24,985)
	n	%	n	%
3 Hours Ahead	1	<0.01	3	0.01
2 Hours Ahead	174	0.70	185	0.74
1 Hour Ahead	1,254	5.02	1,898	7.60
Adapt	22,363	89.51	20,617	82.52
1 Hour Behind	1,089	4.36	2,061	8.25
2 Hours Behind	103	0.41	220	0.88
3 Hours Behind	1	<0.01	1	<0.01

CR: Circadian Rhythm, UTC: Universal Time Coordinated.

Table 7. CR phase shift data of teams during games according to the opponent’s internal UTC (n = 49,970).

CR Phase Shift Volume	Home Teams (n = 24,985)		Away Teams (n = 24,985)
	n	%	n	%
3 Hours Ahead	1	<0.01	0	0
2 Hours Ahead	405	1.62	290	1.16
1 Hour Ahead	2,658	10.64	2,357	9.43
Adapt	19,274	77.14	19,274	77.14
1 Hour Behind	2,357	9.43	2,658	10.64
2 Hours Behind	290	1.16	405	1.62
3 Hours Behind	0	0	1	<0.01

CR: Circadian Rhythm, UTC: Universal Time Coordinated.

Table 8. Post-hoc test (Tukey HSD) results and chi-square values for variables showing significant difference for home teams according to the local UTC (n = 24,985).

	Chi-Square Values of the Groups (χ^2)
Variable	LA	LS	LB
W/L*	1.40	0.05	4.79
	Adj. Sig. (p)
Variable	LA and LS	LA and LB	LS and LB
P	0.121	0.001	0.014
PD	0.092	0.004	0.062
FGM	0.089	<0.001	0.010
FGA	<0.001	<0.001	0.003
FG3A	0.872	0.164	0.012
FG2M	0.016	0.009	0.374
FG2A	<0.001	0.016	1.000
OR	<0.001	<0.001	0.004
DR	0.766	0.027	<0.001
TR	0.078	<0.001	<0.001
AS	0.014	<0.001	0.001
TO	0.089	0.738	0.010
AS/TO	<0.001	0.032	0.941

LA: The group with the internal UTC ahead of the local UTC, LS: The group with the same internal UTC as the local UTC, LB: The group with the internal UTC behind the local UTC, UTC: Universal Time Coordinated, W/L: Win/Loss, P: Points scored, PD: Points differential, FGM: Field goals made, FGA: Field goals attempt, FG3A: 3-point field goals attempt, FG2M: 2-point field goals made, FG2A: 2-point field goals attempt, OR: Offensive rebounds, DR: Defensive rebounds, TR: Total rebounds, AS: Assists, TO: Turnovers, AS/TO: Assists/Turnover ratio, *: Chi-Square Test Applied.

Table 9. Post-hoc test (Tukey HSD) results and chi-square values for variables showing significant difference for away teams according to the local UTC (n = 24,985).

	Chi-Square Values of the Groups (χ^2)
Variable	LA	LS	LB
W/L*	7.76	0.84	0.01
	Adj. Sig. (p)
Variable	LA and LS	LA and LB	LS and LB
PD	<0.001	0.273	0.227
FGM	0.033	0.192	0.972
FGA	0.030	0.021	0.562
FG%	<0.001	<0.001	0.949
FG2%	<0.001	0.017	0.992
OR	<0.001	0.001	0.513
AS	0.624	0.019	0.017
PF	0.030	0.733	0.241

LA: The group with the internal UTC ahead of the local UTC, LS: The group with the same internal UTC as the local UTC, LB: The group with the internal UTC behind the local UTC, UTC: Universal Time Coordinated, W/L: Win/Loss, PD: Points differential, FGM: Field goals made, FGA: Field goals attempt, FG%: Field goal percentage, FG2%: 2-point percentage, OR: Offensive rebounds, AS: Assists, PF: Personal fouls, *: Chi-Square Test Applied.

Table 10. Post-hoc test (Tukey HSD) results for variables showing significant difference for home teams according to the opponent’s internal UTC (n = 24,985).

	Adj. Sig. (p)
Variable	OA and OS	OA and OB	OS and OB
P	0.004	0.122	0.877
FGM	0.001	0.109	0.741
FGA	<0.001	<0.001	0.766
FG3M^#	0.078	0.975	0.184
FG3A	0.030	0.883	0.008
FG2M	<0.001	0.067	0.091
FG2A	<0.001	0.026	0.045
OR	<0.001	<0.001	0.306
TR	0.079	0.035	0.478
AS^#	0.202	0.942	0.106
AS/TO	0.002	0.138	0.718

OA: The group with the internal UTC ahead of the opponent’s internal UTC, OS: The group with the same internal UTC as the opponent’s internal UTC, OB: The group with the internal UTC behind the opponent’s internal UTC, UTC: Universal Time Coordinated, P: Points scored, FGM: Field goals made, FGA: Field goals attempt, FG3M: 3-point field goals made, FG3A: 3-point field goals attempt, FG2M: 2-point field goals made, FG2A: 2-point field goals attempt, OR: Offensive rebounds, TR: Total rebounds, AS: Assists, AS/TO: Assists/Turnover ratio, #: Despite the result of the variance analysis was statistically significant, the result of the post-hoc analysis was not statistically significant.

Table 11. Post-hoc test (Tukey HSD) results for variables showing significant difference for away teams according to the opponent’s internal UTC (n = 24,985).

	Adj. Sig. (p)
Variable	OA and OS	OA and OB	OS and OB
OP	0.877	0.122	0.004
FG3M^#	0.223	0.968	0.091
FG3A	0.321	0.696	0.023
FG2M	0.508	0.287	0.003
FG2A	0.223	0.542	0.004

OA: The group with the internal UTC ahead of the opponent’s internal UTC, OS: The group with the same internal UTC as the opponent’s internal UTC, OB: The group with the internal UTC behind the opponent’s internal UTC, UTC: Universal Time Coordinated, OP: Opponent points, FG3M: 3-point field goals made, FG3A: 3-point field goals attempt, FG2M: 2-point field goals made, FG2A: 2-point field goals attempt, #: Despite the result of the variance analysis was statistically significant, the result of the post-hoc analysis was not statistically significant.