Considerations for the Use of Brain Endurance Training in Elite Sport: A Narrative Review

Authors: Sam D. Joseph, Suzanna Russell, Paul J. Tofari, Shona L. Halson, Rich D. Johnston, Ryan G. Timmins, Nick B. Murray, Stuart J. Cormack

Abstract

Brain endurance training (BET) has been proposed as a method to enhance resistance to mental fatigue (MF) and mitigate the negative effects of MF on performance. The use of BET has been associated with improvements in endurance performance, cognitive function, skill performance, and reduced perception of effort under conditions of MF in amateur and professional athletes. However, the effectiveness and optimal application of BET in elite athletes (performance tier 4–5) has yet to be identified in the preliminary investigations available. This narrative review examined 12 published BET intervention studies to review BET methodology, performance impacts, and identify if BET may be beneficial to elite athlete performance. This review identified potential barriers and facilitators to the practical implementation for elite athletes. Existing research indicates that BET may be useful to maximize resistance to MF or enhance resistance to performance decrements resulting from MF in performance tier 0–3 athletes and should be examined to assess potential benefit for elite athletes. Benefits may exist in enhancing endurance performance, skill execution, and during injury rehabilitation. However, clear guidelines regarding efficacy and implementation are limited by substantial variation in research methodology and a lack of ecologically valid studies. Future research should aim to assess BET in elite athletes in an ecologically valid context to determine if it offers similar benefits shown in non‐elite athletes. Furthermore, research should examine the effect of varying dosages of BET in elite athletes.

Introduction

Mental fatigue (MF) is a psychobiological state caused by prolonged periods of demanding cognitive activity, which impacts cognitive, physical, and psychological function [1]. The precise mechanisms responsible for MF and its subsequent performance impacts are yet to be fully established, with multiple proposed mechanisms [1, 2, 3]. It has been postulated that increased cognitive stimuli result in excessive adenosine concentration in certain brain regions such as the anterior cingulate cortex (ACC) [1]. This accumulation of adenosine potentially increases the perception of effort and reduces motivation to continue a task, resulting in an earlier time to volitional fatigue [1]. Further, excess adenosine may downregulate dopamine release due to its action as a synaptic inhibitor [1]. This likely results in lower levels of enjoyment or motivation for any given task, as dopamine impacts task motivation [1, 4, 5].

Additionally, increased MF has also been associated with reductions in various cognitive functions including working memory, self‐regulation, attention direction, reaction time, and response inhibition [6, 7, 8, 9]. Recent theoretical models suggest that when the perceived cost of sustaining mental effort outweighs the expected reward, cognitive and motivational resources are reallocated toward alternative goals or affective priorities [6, 10, 11, 12, 13]. Therefore, it has been argued that self‐regulatory capacities likely impact someone's ability to maintain task performance when motivation drops, which is symptomatic of MF [6, 14].

Increased MF has been associated with diminished skill execution, impaired decision‐making ability, and altered activity profile in elite athletes, potentially due to detrimental changes in the aforementioned cognitive functions impairing athlete performance [15, 16, 17, 18]. During competitive matches, elite rugby league athletes have demonstrated reductions in positive impacts on team performance, and elite padel athletes displayed reduced shot accuracy when mentally fatigued [15, 16, 18]. In elite Australian football, increased MF was associated with increased use of pacing strategies and alterations in technical execution to avoid dispossession [16]. As performance at the elite level is often decided by very small margins, it is possible that increased MF may have negative performance implications [19, 20].

Given the potential impact MF can have on performance, several approaches have been investigated to mitigate the negative impacts of MF [21, 22]. Behavioral and psychological interventions including mindfulness, meditation, listening to music, caffeine ingestion, and nature exposure have been utilized as acute methods to modify the negative effects of increased levels of MF [21, 22, 23, 24]. It has been hypothesized that some of these methods (mindfulness, meditation, listening to music, and nature exposure) restore limited cognitive abilities of attention direction and self‐regulation, which are reduced when mentally fatigued [21, 22]. Alternatively, caffeine acts as an adenosine receptor antagonist, counteracting some inhibitory effects of adenosine including dopamine suppression [24]. For elite athletes, these acute methods may have utility in certain situations including immediately prior to competition.

Recent evidence has highlighted that brain endurance training (BET) may be beneficial for elite athletes in mediating the effects of MF. Brain endurance training combines an intense cognitive stimulus with physical stimulus and after repeated exposure to BET sessions, can improve resistance to MF and augment exercise performance [25]. The use of BET was first highlighted by Marcora et al. [25], who exposed participants to an intense cognitive task whilst completing 60‐min of cycling at 65% VO2max twice per week for 12 weeks. Compared to cycling alone, the BET intervention significantly improved time to exhaustion by 113% and reduced rating of perceived exertion during a cycling task at 75% of peak power output (PPO). Unlike the transient restoration of an individual's limited cognitive abilities or adenosine‐blocking actions that acute methods (e.g., caffeine, nature exposure) aim to achieve to alleviate MF, BET aims to increase an individual's resistance to MF‐related decrements by augmenting the ability to use limited cognitive capacities and reduce the perceived effort required for a given task [3, 7, 26, 27]. In their novel review of BET, Andre et al. [3] hypothesized that BET may influence brain networks related to these cognitive capacities which may explain BET‐related performance improvements [3]. Compared to acute interventions that offer short‐term reductions in MF‐related performance decrements, BET may provide additional utility for elite athletes by inducing long‐term adaptations that enhance cognitive resilience and reduce perceived effort during performance.

Likely because of the recency of BET research, the precise best‐practice protocols for conducting BET are not well established. To conduct a BET session, a cognitive stimulus (typically 1–3 different cognitive tasks of varying duration and intensity) is combined with a physical training stimulus [26, 28, 29, 30, 31]. Crucially, this cognitive stimulus must be placed immediately before, during, or immediately after the physical stimulus, which can be of varying lengths [7, 26, 28, 30]. The application of the cognitive stimulus increases the perceived difficulty of the combined session by expending cognitive functions, including working memory, directed attention, and response inhibition, and cognitive effort more than what the physical stimuli would have if applied in isolation [7, 26, 28, 30]. This also triggers an increased MF response from the training, relative to physical‐only training [31]. The use of combined cognitive and physical stimuli in BET differs from other cognitive training protocols, which use physical tasks to improve cognitive function and vice versa.

Beyond general application to athletes, BET may have some benefits to athletes in specific scenarios including rehabilitation or return to performance protocols. Athletes in rehabilitation may have difficulties in transitioning back to competition level intensity, which may include significant cognitive demand and can be difficult to replicate in modified training sessions [32, 33, 34]. The cognitive adaptations from BET may help practitioners overcome this challenge. Additionally, technological advances are enabling BET to be increasingly easier to administrate. Applications such as SOMA‐NPT (SSwitch, Switzerland) or Inquisit 7 (Millisecond, USA) provided through smartphones and tablets give practitioners accessible tools to implement interventions in applied settings [7, 35]. These smartphone apps give practitioners access to a variety of cognitive tasks (e.g., Stroop tasks, Flanker task) which can be configured to suit a particular environment or usage to create a BET intervention for athletes.

As BET is a relatively new approach to mitigating MF, there is a limited understanding regarding the optimal dose including timing, duration, volume, and intensity [36]. Currently, the literature base consists of a small number of experimental studies and a recent review summarizing BET methodologies, outcomes and potential neurological mechanisms of action [3]. To date, research has focussed on performance in zero to tier 3 athletes with no work being undertaken with elite athletes (performance tier 4–5) [37]. Further, it is unclear whether BET may be more beneficial for some athletes than others or whether there are any potential negative consequences (e.g., increased MF) that may result from the inappropriate application of BET [38]. The limited evidence available suggests that the periodisation of cognitive demand from BET may be of benefit, particularly to endurance performance and skill execution when mentally fatigued [17, 28, 30, 34, 39]. Therefore, this review aims to broaden knowledge by providing practical perspectives in conjunction with current mechanistic understanding to encourage usage in elite athlete settings. This will be achieved through a critique of the available BET research in at performance tier 0–3 athletes and provide practical recommendations for how BET may be used in this elite (tier 4–5) populations and suggest avenues for future research and applications.

Methods

Due to the relatively recent emergence of the application of BET to elite sport and the small number of studies utilizing the methodology, a narrative review was considered the most appropriate review to conduct. It is acknowledged that many studies exist that utilize cognitive tasks to improve cognitive function with some connection to physical activity [40]. Potentially due to the recency of BET literature, a strict definition of BET does not exist within the literature. However, for this work we have operationally defined BET as training that specifically requires the intervention to combine intense cognitive stimuli with physical stimuli, with the intention of improving athletic performance through enhanced MF resistance [3, 14, 26, 28]. This varies from other cognitive/physical training as these methods typically aim to improve cognitive functions or physical skills in the absence of MF [3]. Therefore, to be eligible for inclusion, studies were required to specifically fit the above description and state that BET was being conducted as part of the study methodology. McKay et al. [37] developed a 6‐tier (0–5) framework for classifying athletic populations in research, noting that different standards of athletes possess a range of training volume and performance standards. Elite athletes are classified as tier 4 (elite/international level) or tier 5 (world class) [37]. To assist the review in examining BET in the context of elite athletes, the population used in each study included was classified by this tier structure using the reported population details. Given the limited number of studies available using BET, and no study using a tier 4 or 5 sample, populations other than tier 4 and 5 were eligible for inclusion. Included literature was gathered from the following Google Scholar, CINAHL, PubMed, Web of Science, MEDLINE, SPORTDiscus, and Scopus. The search was performed on the above databases using a combination of the following search “brain endurance training,” “brain training,” “exercise,” and “mental fatigue.” Where possible, Medical Subject Headings (MeSH) terms were applied to enhance the search. A supplementary hand search was conducted to identify articles that were not found with the search terms. This included forward and backward citation searches using the Web of Science database. The search was conducted in April 2025, and no date limit was applied to the search. Studies were only included if they both described methodology fitting the definition of BET above and explicitly described the study as “brain endurance training” within the manuscript. Studies that achieved one inclusion criterion but not both were excluded. A total of 12 studies were included in the review which are summarized in Table 1.

Proposed Mechanisms of Action

The physiological mechanisms responsible for the improvement in resistance to MF due to BET are not fully established [26]. The proposed mechanisms are visualized in Figure 1. Two studies have examined neurophysiological function in conjunction with physical, cognitive and sport‐specific performance when utilizing BET [7, 26]. To assess neurophysiological function, both studies examined brain haemodynamics during BET and demonstrated that prefrontal cortex (PFC) oxygenation is higher throughout physical tasks, representing an intensified response from brain tissue [7, 26]. These studies investigated BET interventions on performance in a 5‐min rhythmic handgrip task compared to control groups [7, 26]. Following the intervention, the BET group showed no change in PFC tissue oxygenation index (TOI) after a physically demanding task whilst mentally fatigued, whereas the control group PFC TOI significantly declined [26]. Further, the BET group demonstrated better maintenance of PFC blood flow (normalized total hemoglobin index—nTHI) and higher oxygenation (oxyhaemoglobin—O2Hb) than the control group [26]. In the other study to have investigated haemodynamics which used the same experimental design, the BET group demonstrated increases in PFC TOI and O2Hb [7]. Interestingly, nTHI and change in deoxyhaemoglobin (HHb) from the task was greater in the control group, with the authors suggesting that the control group required higher blood flow and oxygenation to maintain performance due to increased task difficulty [7]. Increased HHb resulting from increased cognitive demand has also been demonstrated in competitive sport, supporting this hypothesis [43]. Increased HHb was demonstrated in cricketers in association with increased error rate after a mentally fatiguing high strike‐rate task [43]. Due to the actions of the PFC, these findings have led authors to hypothesize that increased PFC oxygenation capacity may be a potential mechanism for improved cognitive function due to BET [7, 26]. A visual representation of the potential differences in neurophysiological function between BET and control populations after intervention are presented in Figure 2.

The PFC is likely responsible for the cognitive capacities of decision‐making, attention control, impulse control, self‐regulation and effort perception [6, 44, 45, 46]. It has been proposed that the endurance capacity of these outcomes is modifiable and can be improved when exposed to appropriate stimuli through directed training [23, 47]. Further, these cognitive capacities have been suggested to be important to maintaining physical and sport‐specific task performance, which potentially explains performance reductions associated with increased MF, from reduced self‐regulation capacities [1, 8, 14, 48]. When fatigued, PFC oxygenation decreases, signaling a reduced usage of the area and may potentially result in limitations to cognitive capacities [49]. After exposure to a BET intervention, it has been suggested the PFC adapts to the repeated intensified cognitive stimuli and as a result, may improve resistance to exhaustion of the aforementioned cognitive capacities when exposed to increased mental demand [7, 26]. However, measures of PFC activity and the associated cognitive capacities can be influenced by several environmental and physiological factors. For example, ambient temperature, hypoxia and altered glycaemic state have all been shown to reduce PFC oxygenation and impair executive functioning [50, 51, 52]. Similarly, inadequate sleep, heightened psychological stress, and the use of stimulants or ergogenic aids can modify attentional control, response inhibition and mental fatigue responses independent of training effects [53, 54, 55]. These influences should therefore be considered when interpreting BET‐related changes to ensure they reflect true neurocognitive adaptations rather than contextual confounders. Although evidence is still limited, it appears that BET potentially improves cognitive and physical performance through improved neurophysiological function of the PFC and subsequent improvements in cognitive abilities [26].

Intervention Methodologies

Types of BET

Despite a limited number of investigations using BET, a range of methodologies have been used [7, 14, 17, 25, 26, 27, 28, 29, 30, 31, 38, 41, 42, 56, 57]. These methodologies are summarized in Table 1 including participant types, participant numbers, performance tier, type of BET, type of exercise used and intervention duration. As previously mentioned, Marcora et al. [25] were the first to demonstrate the benefits of BET, exposing participants to an intense cognitive stimulus whilst completing 60‐min of cycling at 65% VO2max [25]. This study involved completing cognitive stimuli while simultaneously performing physical training, which has been termed Concurrent‐BET [26, 58]. Three other types of BET have been Prior‐BET, Intermixed‐BET, and Post‐BET [7, 28, 29, 41]. These labels refer to the timing of the cognitive stimulus relative to the physical stimulus. Prior‐BET and Post‐BET utilize the cognitive stimulus before and after the physical stimulus, respectively. Intermixed‐BET exposes participants to cognitive stimuli interspersed with physical stimuli multiple times (e.g., 3 × 5‐min periods of cognitive stimuli between three periods of 10‐min resistance training [27, 59]). Figure 3 visualizes each of four types of reported types of BET. The use of each type of BET in the literature varies, with Prior‐BET and Post‐BET used three times each, Concurrent‐BET used twice, and Intermixed‐BET used six times. However, it is unclear whether any particular type of BET is advantageous over another. This is largely due the variations in BET prescriptions and athletic contexts where it has been utilized and the fact it has been used in only a small number of studies. More BET studies are required to increase the ability to analyze and compare the efficacy of differing types of BET and their potential application.

Session Volume, Intervention Frequency and Intervention Duration

A range of acute programming variables, including cognitive stimuli durations, physical stimuli durations and total training durations have been utilized in conjunction with different types of BET [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. These variations make drawing conclusions about the efficacy of particular combinations of volume and intensity of BET interventions challenging. Training volumes for each study are presented in Tables 1 and 2 along with a summary of BET types in Table 3. Table 2 reports individual study cognitive stimuli duration whereas Table 3 reports cognitive, physical and total stimulus time for each type of BET. Prior‐BET, Post‐BET and Concurrent‐BET studies used longer durations of cognitive stimuli, ranging from 20 to 60 min per session, whereas 4–6 exposures of 3–5 min per session have been used in Intermixed‐BET studies [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42].

A range of physical stimuli durations have also been utilized in studies using sport‐specific training and resistance or endurance training [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. Sport‐specific sessions (soccer, padel, cycling, tennis) have reported physical stimuli durations exceeding 60 min per session, whereas resistance and endurance training only designs have reported physical training times of 20–60 min per session [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. Sport‐specific study designs incorporated multiple training types (sport‐specific skill training, conditioning and resistance training), which likely increased total physical stimulus time per session relative to resistance and endurance training only studies [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. Increased session physical stimuli duration in sport‐specific training studies is likely a product of incorporating BET as part of a normal training program, rather than specific interventions as seen in resistance or endurance training BET studies. In terms of total training time for BET sessions (application of both physical and cognitive stimuli), Concurrent‐BET designs have reported the lowest durations (30–60 min), due to the simultaneous completion of both cognitive and physical stimuli [25, 41]. Intermixed‐BET studies reported durations of 27–109 min of training time, whereas Prior‐BET and Post‐BET both reported 40–< 120 min [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42].

Currently, there is no clear consensus or recommendation regarding frequency or duration of BET protocols, likely due to the limited number of studies using BET. Frequency of BET sessions per week in studies have been reported as 3–5 sessions/week [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 41, 42], with only one study not using this dose [38]. However, the duration of BET protocols seems to vary largely between types of BET. Studies using Concurrent‐BET designs have reported the longest intervention length, with two studies using a 12‐week design and one a 6‐week design [25, 26, 41]. This is in contrast to studies using Intermixed‐BET, Prior‐BET or Post‐BET, which reported generally shorter protocols of 4–8 weeks [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. No multiple exposure study has used a shorter duration than 4 weeks or longer than 12 weeks, which raises questions about the efficacy of ultra‐short and extended duration BET protocols. However, one study has utilized a single‐exposure design, using an Intermixed‐BET during one session [38]. Elite tennis players were given 20‐min of BET before 20‐min of tennis match‐play, which was also interspersed with four 5‐min BET intervals during match‐play. This is the only study that has used this kind of approach. The findings of the study showed inconclusive differences in tennis performance, resulting in uncertainty regarding the efficacy of single‐exposure BET [38]. Until more studies are conducted using single‐exposure, ultra‐short and extended exposure designs, BET prescription recommendations regarding these approaches are largely speculative.

Physical and Cognitive Stimuli

Significant variation also exists within the literature relating to the physical and cognitive stimuli utilized in the BET intervention which further complicates the development of conclusive BET protocol guidelines [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. A range of cognitive stimuli has been reported including the 2‐back task [7, 27, 60], Stroop task [29, 41, 42], color‐word Stroop task [60], modified color‐word Stroop task [60], incongruent color‐word Stroop task [7, 27, 31], Flanker task [17, 28, 30], Go/No‐Go task [17, 28, 30], AX‐Continuous Performance test (AX‐CPT) [17, 28, 30], Switched Stop Visual task [27], Multi‐Source Interference task (MSIT) [27], and Time‐Load Dual‐Back task [27]. Further, the physical training stimuli reported included cycling [25, 30, 42], timed rhythmic handgrip task [7, 26], soccer (on‐field, conditioning and sport‐specific resistance training) [17, 28], running [41], padel (sport‐specific training only) [29], general resistance training [27, 31], and tennis (sport‐specific training only) [38].

Despite the broad range of physical and cognitive stimuli used between studies, limited assessment has been completed to understand the differences in intensity of the BET stimuli. It has been suggested that some cognitive tasks may be more cognitively demanding than others [27, 38, 61]. For example, it has been shown that when using a Stroop task, task design (e.g., mixed or blocked) and stimulus material (e.g., number or letter) for any given task can have considerable impact on cognitive processing and demand required to solve the task [61]. Further, the duration of the cognitive task in isolation is not a strong predictor of subsequent MF, which may suggest that short duration, high intensity tasks have greater utility for BET [62]. Considering the variety of cognitive tasks used in BET, there may be some benefit in understanding the relative intensity of BET tasks to more easily standardize and compare interventions.

Beyond the lack of stimuli standardization in the reviewed literature, some studies have used tasks which change the cognitive stimuli intensity depending upon the ability of the participant, as measured by prior cognitive task performance or performance on cognitive task within a BET session [27]. This may be important, as some cognitive tasks like the AX‐CPT, can induce sleepiness rather than MF, if the cognitive stimulus is inappropriate (too weak or too strong where attention is not maintained) [63]. In conjunction with adapting cognitive stimuli intensity to create equivalent cognitive demand, there have also been some suggestions that the cognitive stimuli requires progression over the course of the BET intervention period, however only three studies have implemented this approach [7, 26, 30]. To do this, these studies either increased the volume of the same cognitive task or changed the cognitive task to be more cognitively demanding after a certain amount of time in the protocol [7, 26, 30]. No information is available about when or how BET stimuli intensity should be progressed (e.g., increases in volume, intensity or both). Furthermore, the insight into factors which might influence the difficulty of BET for different individuals (e.g., sport, level of competition, cognitive ability) would be useful [62, 63, 64]. Further work is needed to explore the optimal intensity and progression of a BET intervention to determine recommendations for BET prescription.

Performance Outcomes

Aerobic and Anaerobic Performance

Several studies have demonstrated BET‐related benefits to endurance performance, which are summarized in Table 4 [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. Crucially, most studies reviewed reported physical performance improvements while subjects were in a state of increased MF [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. Endurance performance in running and cycling significantly improved after BET, relative to exercise‐only controls [17, 25, 26, 27, 28, 30, 65]. Specifically, increases in time to exhaustion (TTE) at 65%, 75%, and 85% peak power output, 5‐min time trial distance (TT), and 20‐min TT distance after a Post‐BET intervention have been observed in cycling tasks in low‐level and highly‐trained cyclists [25, 30]. Further, increased final velocity during a 30–15 Intermittent Fitness Test (IFT) was observed in professional soccer athletes after a Post‐BET intervention [28]. In contrast, Concurrent‐BET did not improve VO2max or TTE at 80% maximal aerobic speed (MAS) in well‐trained runners more than regular endurance training [41]. From the current literature base, it seems likely that BET improves aerobic performance when mentally fatigued.

Strength Endurance

Three studies have also examined the impact of BET on strength endurance, with findings suggesting that BET may improve this physical quality [27, 31]. Dallaway et al. [27] found that Intermixed‐BET in healthy undergraduate students improved strength endurance by measuring dynamic calisthenic exercises to failure across two studies. In the first study, BET increased push ups to failure compared to control whereas in the second study, BET increased burpees, jump‐squats, and leg‐raises to failure more than the control condition did [27]. Further, a Prior‐BET intervention improved number of reps at 40% 1RM chest press to failure, along with number of reps to failure of jump squats in resistance training individuals [31]. Whilst evidence is limited, it does appear that BET can improve strength endurance of bodyweight exercises and loading of 40% 1RM and below when mentally fatigued. If strength endurance is improved at percentages beyond 40% 1RM while mentally fatigued is yet to be investigated.

Cognitive Performance and Perceptual Measures

A range of improvements in cognitive performance have been observed after a BET intervention [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. These improvements have largely been in extended cognitive tasks (Stroop task, 2‐back working memory task, AX‐CPT) lasting between 20 and 30 min [7, 17, 25, 26, 27, 28, 29, 30, 31, 36, 38, 41, 42]. As a result of BET interventions, Stroop task reaction time (RT) improvements have been observed in healthy undergraduate students, professional soccer athletes, and highly‐trained cyclists [27, 28, 30]. Similar to reported improvements in physical performance after a BET intervention, BET has also been reported to improve cognitive performance when mentally fatigued relative to control groups [17, 27, 28, 30]. Professional soccer players have demonstrated decreased psychomotor vigilance task (PVT) RT relative to control groups when mentally fatigued after both Post‐BET and Intermixed‐BET interventions [17, 28]. Similar improvements in AX‐CPT reaction time in mentally fatigued undergraduate students have also been observed relative to control after an Intermixed‐BET intervention [27].

Some evidence exists that a BET intervention can also reduce perception of effort during difficult cognitive and physical tasks [25, 30]. Rating of perceived exertion (RPE) reduced after a Concurrent‐BET intervention in physically active males relative to the control group during TTE cycling at 75% of PPO [25]. Similarly, RPE was lower in a submaximal incremental cycling test and in 65% PPO and 85% PPO TTE tests after a Post‐BET intervention in highly trained cyclists [30]. Lower RPE after a Concurrent‐BET intervention was also demonstrated during a TTE running task at 80% MAS in trained runners [41]. In terms of cognitive tasks, mental demand, effort, and frustration (NASA‐TLX) was lower after a 30‐min Stroop task in highly trained cyclists after a Post‐BET intervention compared to control [30]. Despite being reported on less than physical improvements, BET may be a promising approach to improve cognitive function in difficult tasks. Importantly, these findings also suggest that BET reduces effort perception when mentally fatigued, which may assist athletes in maintaining exercise intensity for longer.

Skill and Sport‐Specific Performance

Due to a lack of studies investigating sport‐specific tasks, evidence to support BET improving sport‐specific tasks, like skill execution and agility, is limited. The few studies to include these measures demonstrate that BET may be potentially useful for mediating MF‐related performance reductions [17, 28, 29, 30, 38]. Aside from the improvements in cycling and running performance previously mentioned, four studies (two soccer, one padel, one tennis) have examined the impact of BET interventions on sport‐specific tasks [17, 28, 29, 38]. After an Intermixed‐BET intervention, professional soccer players demonstrated improved passing and shooting scores in the Loughborough Soccer Passing and Shooting Tests [17] and recreational padel players demonstrated faster and more accurate shots when mentally fatigued after an Intermixed‐BET intervention compared to a control group [29]. In contrast to multi‐week BET interventions, exposure to a single session of BET may negatively impact performance [38]. Elite junior tennis athletes demonstrated some reductions in ball spin rate, ball landing location, and out ratios in match play after one BET exposure of Intermixed‐BET [38]. These negative effects are likely the result of a single BET functioning as a mentally fatiguing task rather than a positive stimulus [38, 66]. This is in comparison to the reported positive adaptations to long‐term BET interventions through repeated increased cognitive demand demonstrated in other literature [17, 38]. Interestingly, BET has also been associated with improvements in sport‐specific decision making in professional soccer athletes [28]. Athletes who completed a Post‐BET intervention made fewer errors than the control group in the Soccer‐specific Reactive Agility test (S‐RAG) [28]. This task required athletes to make a decision based on a soccer‐specific stimulus and then run to a target and return [28]. Whilst not during training or match play, it does suggest that BET may benefit sport‐specific tasks such as decision making that require a cognitive component [28]. Further exploration of BET's effects on sport‐specific tasks would be of benefit to determine the utility of the training method.

Research Summary

Despite the limited number of available studies, the current literature utilizing tier 0–3 athletes suggests that BET may be a useful training methodology for elite athletes (tier 4 and 5). Whilst evidence is limited to a few studies, the use of BET has demonstrated improvements in sport‐specific skill execution. As MF can impact skill execution negatively, use of BET may provide some utility to improving resistance to MF and MF‐related skill execution decrements, which could improve performance for elite athletes. A reduction in perception of effort and resistance to MF in demanding physical (running, cycling) and cognitive (PVT, Stroop, AX‐CPT) tasks has also been observed, which may reduce the magnitude and occurrence of MF‐related performance decrements [25, 27, 28, 30]. Further, BET may be able to improve TTE performance in highly‐trained athletes beyond that of regular physical training alone [28]. Whilst there is inconsistency in the literature in the way BET has been applied to date, the results suggest the potential for it to provide a positive stimulus to minimize the deleterious effects of MF to both physical and cognitive performance experienced in sport. Considering these potential benefits, the following sections will discuss how BET could be specifically used in elite athlete settings with consideration of some of the limitations to implementation.

Implementation Considerations and Limitations

Whilst BET has potentially positive benefits for elite athletes, several implementation practicalities and limitations need to be acknowledged. First, BET is yet to be widely studied in a variety of elite athlete populations. Two studies have used professional athletes (soccer), whereas two more have used performance tier 2 and 3 cyclists [17, 28, 30]. It is currently unknown if BET would produce similar benefits in performance tier 4–5 athletes (i.e., elite or world‐class) as has been demonstrated at lower levels [37]. Elite athletes with large training histories demonstrate increased self‐regulation capacities, which is a proposed mechanism responsible for BET‐related performance adaptations [14, 26]. However, it remains unclear whether BET can further enhance self‐regulation in these athletes or whether their already advanced capacities limit the potential for additional benefit from utilizing BET. Furthermore, factors such as age, sex, sport experience and fitness may impact the efficacy of BET due to their potential influence on MF susceptibility [67]. Whilst significant variation in reported MF exists between male and female athletes in different sports [68, 69, 70, 71, 72], there is little information available to confirm the role of other factors that may influence MF susceptibility. It is possible that these variations may impact the effect of BET at the individual level in athletes of the same sport and performance tier, due to variations in the ability to tolerate MF. Further, research is yet to evaluate the effects of BET on measures of performance (i.e., skill execution efficiency and success) ore exercise intensity during training or competition in professional or elite athletes. Available studies have employed fitness tests or skill assessments for evaluation, which may lack ecological validity compared to training or competition‐based measures [8, 9, 16, 48]. At present, the prescription of BET in elite athletes is based on assumption that the benefits are similar to those observed in lower‐tier athletes.

Another significant consideration for the application of BET to high performance athletes is the logistics of use in the training and competition environment. Beside the lack of agreement regarding BET programming variables, it may be impractical for some athletes or coaches to add 20–60 min of extra training time per session [73, 74]. However, with the range of BET methodologies reported to improve various performance outcomes, there may be options available to remove time‐based implementation limitations. Intermixed‐BET, with the lowest amount of cognitive task time and multiple short‐duration exposures may be an attractive option to add to training sessions. For example, short (i.e., < 5‐min) BET intervals may be possible to implement during a 10–25‐min team sport warm up or during rest periods within field or resistance training sessions. It may also be more palatable for athletes as they are exposed to short efforts, rather than long blocks of tiresome cognitive tasks (20–60 min) which may reduce their buy‐in [38]. Practitioners need to carefully balance practicality of implementing BET in their environment based on the volumes of BET reported in literature. Creating buy‐in may be assisted by educating athletes and coaches as to the potential benefits of BET [75].

There is also limited knowledge regarding which cognitive tasks to use as part of a BET intervention [56, 76]. Different cognitive tasks stress different cognitive abilities, which may alter the potential training effects of BET [3]. Further, tasks can be highly variable in difficulty and may deliver a different intensity of cognitive stimulus [77]. In the 12 reviewed studies, a Stroop task, incongruent Stroop task, color‐word Stroop task, incongruent color‐word Stroop task and modified color‐word Stroop task were all used as cognitive tasks in a BET intervention [7, 26, 27, 31, 65]. It is likely that these variations of the Stroop task provide a different stimulus to an athlete, with the incongruent color‐word task likely more difficult than a standard Stroop task [61]. Furthermore, it is also likely that different athletes experience a different cognitive load from a given task [62, 78]. As mentioned previously, variation between athletes (e.g., cognitive function) may alter the efficacy of BET. Tasks that adapt difficulty to an athlete's level of cognitive abilities are available and could be a solution to individualizing BET stimuli [27]. For example, smartphone applications like SomaNPT (SSwitch, Lucerne, Switzerland) have features that can adapt to the athlete's cognitive level which could assist this process [27]. However, the cost of these apps and new technology can be prohibitive for organizations and athletes, particularly those that are bound to spending limits from owners or competition rules.

Beyond constraints relating to the prescription and cognitive stimuli of a BET intervention, discussion between practitioners and sport coaches is needed to determine how BET may best be periodized within an athlete's training plan. Practitioners may face difficulty implementing BET if sport coaches see limited value in the approach due to concerns about the ability to improve sport‐specific performance [79]. Equally, the potential negative effects of BET need to be considered when evaluating the implementation of BET [38]. As BET uses an intense cognitive stimulus that athletes may not be accustomed to, there will likely be a subsequent detrimental MF response to the training, particularly early in the intervention [38]. As shown by Ozsoy et al. [38], one BET session had a negative effect on some tennis performance metrics during match play. Skill performance is also negatively affected by prior MF in elite athletes and therefore timing of Prior, Intermixed or Concurrent‐BET designs may need to be considered carefully [15, 18]. Sport coaches may expect potentially poorer skill execution in training and/or match‐play during a BET intervention, particularly if sport performance follows a BET session [35]. One factor that may be important to consider for the delivery of BET is the duration of recovery time needed to return to baseline MF following a BET session, but this is currently unknown due to a lack of research examining cognitive recovery after BET. Although short term negative effects are likely, it could be speculated that there may be a risk of longer‐term detriment in some athletes from a BET intervention when combined with overall training load considerations [39, 80, 81]. This may be augmented during periods of heavy training, which increases the global fatigue response and if BET is applied inappropriately, may subject athletes to an undesirable level of fatigue [82]. Due to these potential residual negative effects on performance from MF, BET may be inappropriate at certain times during a season or cycle (when performance is paramount) such as during important competitive periods (i.e., play‐offs) [34, 83]. However, current literature reports positive adaptations from BET interventions in as little as 4 weeks, suggesting that the period of residual MF is not excessive [28]. Finally, there is currently no understanding of how long BET‐related adaptations last. It is feasible that adaptations will decline over a period of time without a stimulus, therefore is possible that additional doses of BET could maintain adaptations, but this is speculative.

Potential Benefits and Practical Applications

Physical and Sport‐Specific Development

The primary benefit to elite athletes is that BET has been demonstrated to improve cognitive function, which can improve resistance to MF‐related decrements in endurance performance and skill execution during training and match‐play [17, 28, 30]. These findings could be of significant use to practitioners and sport coaches when planning preparation programs for athletes. In terms of physical development, specifically cardiovascular endurance, utilizing BET in conjunction with regular training could increase the efficiency of training. Suggestions of how BET could be used are presented in Table 5. Aligning BET usage at times like pre‐season, where physical and technical capacities are being developed, could be of most benefit and practicality. For example, implementing an Intermixed‐BET intervention and delivering the cognitive aspect of BET (4 × 3‐min periods) within the session warm up or across the training session may be highly effective and easy to administer. This may also provide a cognitive priming stimulus, which could also improve cognitive function in subsequent physical tasks [84]. Further, from early research that BET increases endurance performance, BET may be of benefit for athletes where aerobic capacity is important in their sport (e.g., Australian football or soccer) [85, 86]. These athletes could potentially utilize Intermixed‐BET during aerobic training to augment the efficacy of regular physical training methods through increased effort tolerance. Whilst recommendations regarding which cognitive tasks to use are not available, dual‐task paradigms may be useful for this kind of BET. Dual‐task paradigms fatigue executive control and sustained attention, which mirror the demands of sport performance [87].

Utilizing BET with skill training could have potentially significant benefits, particularly within the pre‐season where skill development is prioritized [7, 17, 26, 29, 83]. Due to BET potentially improving PFC function, athletes may see improvement in cognitive abilities required for successful skill execution when mentally fatigued including working memory, self‐regulation, attention direction, reaction time, and response inhibition [7, 8, 9, 26, 48, 78, 88, 89, 90, 91]. Outside of the previously mentioned Intermixed‐BET options during training, coaches and practitioners may find value in implementing a Prior‐BET intervention with athletes in skill development sessions. This may be of high value leading up to periods of match‐play to enhance MF resistance and tolerance to MF‐related skill decrements. Considering athletes experience elevated MF during match‐play [15, 33], this may help practitioners and coaches bridge the gap between training and competition for athletes more efficiently by increasing tolerance of cognitive effort and reduced fatigability of cognitive abilities used for skill execution. Further, athletes with lower skill levels or athletes in high‐skill sports may see greater benefit from BET due to the potential for MF to negatively impact skill performance [66, 85]. In addition to dual‐task paradigms which may suit as the cognitive task for BET with skill‐related training, continuous performance tasks like the AX‐CPT may also be useful. Tasks like the AX‐CPT demand significant sustained attention which mirrors athletic performance requirements [87, 92].

Mesocycle Demands

Depending on the stage of the athlete's season or competitive cycle, there are some potentially beneficial periods and scenarios where BET may assist athletes in mitigating the effects of MF or improving performance. As a caveat to the implementation of BET, practitioners must consider the extra recovery time needed on top of normal training and competition demands due to the additional cognitive load. In elite Australian football athletes, an increased MF response has been observed at the beginning of the pre‐season [69, 70]. This has been proposed due to the increased cognitive load from returning from time off in the off‐season to full‐time sport participation, increased sport‐specific education, assimilation into new environments, and developing new relationships [69, 70]. Utilizing BET during the off‐season as part of an athlete's program may help reduce the magnitude of the MF response when returning to full‐time training, due to BET's potential effects of improving MF tolerance and cognitive abilities [17, 30]. Similarly, pre‐season periods with large amounts of travel, practice matches, and reduced cognitive recovery can also increase the severity of MF experienced by elite athletes, relative to periods without these demands [93]. Intensified training camps, used commonly in preparation for international competition, also increase MF in athletes similar to pre‐season periods where cognitive recovery is low [69, 72, 93]. By using BET as part of training in the weeks preceding intensified periods, the MF experienced in the period may be less detrimental to performance [17, 28, 36]. When aiming to prepare athletes for increased MF demand prior to pre‐season or intensified camps, utilizing Stroop or n‐back tasks may be most effective. These tasks create significant demand for working memory, executive control, and result in high cognitive load [94, 95]. Exposure to high cognitive demand and subsequent MF may assist practitioners in reducing potential MF‐related performance decrements for athletes and achieving better pre‐season training outcomes. Beyond this, given the likely low cognitive load in off‐season or holiday periods, longer exposures (potentially Prior, Post, or Concurrent‐BET) to these tasks may give greater benefit to reducing MF susceptibility.

Further, BET may also be beneficial for MF tolerance in longer duration competitive seasons, when integrated with adequate cognitive recovery to promote competitive performance. Competition demands such as travel and match schedule may increase MF in athletes through a decreased ability to cognitively recover, which may explain why netball athletes have reported their highest MF during the middle of the competitive season [71, 96]. Further, MF has been demonstrated to be higher after losing compared to winning, which could expose less successful athletes to increased MF compared to successful athletes [68]. Unlike prior to pre‐season and international camps where MF and cognitive load are low, utilizing longer exposures of Stroop or n‐back tasks may not be ideal for in‐season BET prescription due to the potential increased MF response [72, 95]. Practitioners may find benefit in using smaller dosages of Stroop and n‐back tasks (Intermixed‐BET), which maintain intensity of exposure but limit volume to maintain or improve MF susceptibility for athletes. This may be possible on low‐intensity training days within the competition microcycle or on active recovery days.

Rehabilitation and Reconditioning

An area where BET could have significant benefit is for athletes in rehabilitation or reconditioning settings. During rehabilitation, athletes are physically compromised due to injury, which may restrict their participation in training and competition [97]. Practitioners can face challenges in maintaining an athlete's training load, musculoskeletal tissue quality, levels of cardiovascular fitness, level of skill exposure, and cognitive load due to the inability to train at the required intensity to maintain these qualities [98, 99, 100]. Complex and long‐term injuries, like anterior cruciate ligament repair, may exacerbate this problem further due to extended recovery time or increased loss of function [101]. Utilizing BET during rehabilitation may assist practitioners in increasing the perceived intensity of the stimulus injured athletes are exposed to during training through additional cognitive load when physical load is low [17]. Without exposure to competition, athletes may experience cognitive detraining, and this may see athletes struggle to tolerate the cognitive load of competition [32, 34, 102]. Utilizing BET during rehabilitation may improve athletes' ability to deal with the cognitive demands of competition. Beyond musculoskeletal injury, BET may also have a role in recovery from concussion, where cognitive function is impaired due to brain injury. Although unexplored in relation to concussion, BET may be useful during return to play protocols, particularly when trying to expose athletes to cognitive demand to improve their tolerance [103].

Given athletes in rehabilitation often have different training schedules to their uninjured counterparts, there may be an increased opportunity to include BET. When prescribing low‐to‐moderate volumes and intensities of reconditioning training, multiple types of BET could be integrated to increase the perceived intensity of the training stimulus [17, 30, 36]. Utilizing BET in the stages prior to complete return to training of skill‐based rehabilitation sessions could also be useful, to increase the cognitive and overall stimulus of the session, along with perception of effort [17, 28]. This may help practitioners enhance athletes' tolerance of cognitive load which may otherwise undermine performance when returning to more difficult skill drills or closer to return to play scenarios [33]. The inclusion of BET may also be a novel stimulus that is useful for maintaining athlete engagement in long‐term return‐to‐play scenarios [32, 100]. Given the lack of cognitive load experienced during long‐term rehabilitation, a variety of cognitive tasks may be useful. During early rehabilitation involving low‐intensity exercise, training, physical training could be supplemented with mentally fatiguing protocols like n‐back and Stroop tasks to increase cognitive load from the session [94, 95]. As the athletes progress through rehabilitation and get closer to normal training, utilizing dual‐task paradigms may better prepare athletes to tolerate the cognitive demands of training and match play [87]. Practitioners may even see benefit in using a combined approach using multiple types of cognitive tasks during a training phase but are encouraged to consider the training goals of the athlete at that time.

Despite these promising applications, practical challenges such as limited training time, cognitive overload, and uncertainty about optimal dosage may constrain BET use in elite environments. Based on current evidence, practitioners are encouraged to integrate BET gradually, starting with short cognitive exposures (2–5 min) during low‐intensity conditioning or skill sessions, and to monitor athlete workload and recovery to avoid excessive MF. Collaboration between practitioners and coaches is essential to ensure BET aligns with existing physical and technical objectives. These provisional recommendations may assist practitioners in safely testing BET in real‐world environments while contributing to a broader evidence base for implementation in elite sport.

Future Research Direction

Despite promising evidence supporting BET usage in elite athletes, a number of future research directions exist to evaluate the efficacy and inform the application of BET. First, it would be beneficial to further understand the physiological mechanisms responsible for improvements in athletic performance following BET. As highlighted, increased PFC function may be a potential hypothesis, but the haemodynamic measures used to assess PFC function are highly susceptible to a range of environmental and physiological states [50, 51, 52]. Research should aim to manipulate these factors to understand if they impact how BET modifies PFC function. Further, it is unknown if BET interventions result in similar cognitive and physical performance improvements for elite athletes as shown for amateur athletes. In an elite athlete setting, this may be addressed by incorporating a BET intervention and assessing the impact on MF and training and match‐based measures of skill performance and activity profile [16]. This approach would be ecologically valid and provide direction for practitioners and coaches to make informed decisions on the potential benefit of BET for their athletes and environments. Several practical implementation questions also remain, including uncertainty related to the optimal type and dosage of BET, in addition to the performance effects of different cognitive tasks, the time to realize BET‐related adaptations and cognitive recovery timeframes from BET sessions. Should these questions be answered by future research it would provide more certainty for the development of guidelines for the use of BET. Considering the difficulty of conducting research in elite athletes, assessing these questions in tier 2 and 3 athletes to form preliminary hypotheses may be useful as they are generally more accessible than tier 4 and 5 athletes [37]. Finally, limited details exist regarding individualization of BET stimuli including the effect of adapting the level of cognitive stimuli difficulty to specific athletes. Future research should aim to compare the differences in effect of volume‐matched individualized cognitive stimuli with generic cognitive stimuli to answer this question. Future works should also look to utilize both male and female athletic populations, which may be important when considering BET stimuli individualization and associated intervention outcomes [104]. Finally, broadening the number of research centres investigating BET may be beneficial and provide increased access to elite athletes, research funding and resources.

Perspectives

Limited evidence currently exists on the application of BET to elite athletes; however, examination of its utility for its use to improve performance in this population appears warranted. Utilizing BET could assist in mitigating MF‐related decrements in skill execution and physical performance. In scenarios such as rehabilitation or pre‐season periods, BET may have particular utility for elite athletes to improve cognitive capability to prepare athletes to resist MF in future competition. However, very little is known about appropriate protocols and periodization of BET including aspects related to duration, frequency, and intervention length. Given the lack of detailed knowledge regarding these factors, practitioners should carefully consider how BET may be used in their environment in order to maximize positive outcomes and limit negative effects. Future research should aim to understand the effect of BET in elite athletes with ecologically valid measures of sport performance.

Author Contributions

S.D.J., S.J.C., S.R., and P.J.T. were responsible for the idea conception. S.D.J. was responsible for literature review, interpretation and production of figures and tables. S.D.J., S.J.C., S.R., and P.J.T. collaborated in writing and the manuscript. S.L.H., R.G.T., N.B.M., and R.D.J. edited the manuscript. All authors contributed to the article, approved the submitted version and approved the final manuscript.

Funding

The authors have nothing to report.

Ethics Statement

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.