The effect of chronotype on sport-specific performance in professional basketball players

Circadian rhythm refers to the biological processes that regulate the sleep/wake cycle and the 24-h oscillations that occur in several psychobiological responses. Differences in the diurnal variation in responses regarding circadian rhythms across individuals has led to the establishment of three distinguished chronotypes: morning types (M-types), neither types (N types), and evening types (E-types). Variations in acrophases of several physiological variables associated with each chronotype has led to the notion that peak athletic performance varies according to time of day in a chronotype-specific manner. Limited research has examined the effect of chronotype on sport-specific performance with most data exploring the effect on diurnal variation on sport-specific skills. Most data exploring the effect of diurnal variation on sport-specific skills indicate that a preference for neither morningness or eveningness (N types), is associated with superior performance between the afternoon and evening. Preliminary data examining the role of chronotype on sport-specific skill performance suggest morningness (M-types) is associated with superior performance earlier in the day (<14:00h), while a preference for eveningness (E-types) is associated with superior performance at night (>20:00h). However, no research has examined the effect of chronotype on basketball specific performance according to time of day. This is of particular importance to basketball teams in various leagues where players are exposed to fluctuating schedules across the season requiring completion of games with a variety of start times typically alternating between the afternoon and evening. Thus, the aims of this research were to 1) examine diurnal variations in shooting accuracy between chronotypes at different times of the day and, 2) identify the effect of evening games (>18:00h) on in-game basketball performance between different chronotypes in male basketball players. Professional basketball players (n = 13) were recruited from the same team registered in the National Basketball League (NBL) and each player completed a Horne-Östberg Morningness Eveningness Questionnaire (HÖ-MEQ) to determine their self-reported chronotype. Three players were categorised as M-types, nine players as N-types, and one player as an E-type. To examine differences in shooting accuracy between chronotypes according to time of day, players completed a shooting accuracy test consisting of 100 shots from five different locations on separate days in the morning (08:00h-09:30h) and afternoon (15:00-16:30h). To equilibrate sample sizes, the data were split into tertiles for analysis (Anderson et al., 2018), where five players were assigned to the first tertile representing the M-types (HÖ-MEQ >54), four players were assigned to the second tertile representing the N-types (HÖ-MEQ 47-53), and four players were assigned to the third tertile representing the E-types (HÖ-MEQ <46). Shooting accuracy in each test was determined via the cumulative score of the 100 shots using a 0–3-point scoring scale classifying each shot’s accuracy. To examine differences between chronotypes in in game performance during evening games played after 18:00h, box score data from the 2019/20 season (31 games) were retrieved and analysed. Using the results of each player’s HÖ-MEQ score (n = 11), players were split into M-types (n = 4) and N-types (n = 6). Due to only one player identifying as an E-type, E-type data were excluded from the analysis of in-game performance. In this way, separate linear mixed models were conducted to determine the effect of chronotype (fixed effect) on each player (random effect). Results from the shooting accuracy testing revealed no significant (p >0.05) differences in shooting accuracy scores between chronotype groups in either the morning or afternoon testing sessions. However, effect size analysis showed each chronotype group shot more accurately (small-large effects) in the morning trial (M-types: 213.0; N-types: 218.0; E-types: 206.0) compared to the afternoon trial (M-types: 201.5; N-types: 211.5; E-types: 191.0). Findings regarding the in-game analyses revealed no significant (p >0.05) differences in in-game performance between M-type and N-type chronotype groups. However, effect size analysis yielded small to very large differences in 3-point shots made and attempted, assists, and steals in favour of N-types compared to M-types during games. Shooting accuracy at different times of the day and in-game performance during the evening appear to be largely unaffected by chronotype among professional, male basketball players. The lack of observed effects suggest coaching staff may not need to closely consider player chronotype when scheduling training sessions or developing match strategies to optimise player shooting accuracy or in-game performance. However, considering the plausible effect of the time at which habitual training sessions are conducted (i.e., morning) on shooting accuracy, coaching staff may endeavour to schedule training sessions in line with that of times that games are typically held to ensure greatest specificity in aligning player circadian rhythms to competition.