# Effects of 5-Week Brain Endurance Training on Fatigue and Performance in Elite Youth Epée Fencers

Giorgio Varesco, Walter Staiano, Maëlle Bracco, Benjamin Pageaux, Lena

Soulas, Maël Goisbault, Julie Doron, Marc Jubeau

► To cite this version:

Giorgio Varesco, Walter Staiano, Maëlle Bracco, Benjamin Pageaux, Lena Soulas, et al. Effects of 5-Week Brain Endurance Training on Fatigue and Performance in Elite Youth Epée Fencers. International Journal of Sports Physiology and Performance, 2025, pp.1-7. 10.1123/ijspp.2024-0396. hal-05080470

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*Note.* This article will be published in a forthcoming issue of the *International Journal of Sports Physiology and Performance*. The article appears here in its accepted, peer-reviewed form, as it was provided by the submitting author. It has not been copyedited, proofread, or formatted by the publisher.

**Section:** Original Investigation

**Article Title:** Effects of 5-week Brain Endurance Training on fatigue and performance in elite youth epee fencers.

**Authors:** Giorgio Varesco,¹ Walter Staiano,²,³ Maëlle Bracco,⁴ Benjamin Pageaux,⁵,⁶,⁷ Lena Soulas,¹ Maël Goisbault,¹ Julie Doron,¹ and Marc Jubeau¹

¹Nantes Université, Laboratory Movement – Interactions – Performance (MIP), UR 4334, F-44000 Nantes, France

²Department of Physical Education and Sport, University of Valencia, Spain

³Department of Psychology, Biological and Cognitive Psychology, University of Southern Denmark, Denmark

⁴Univ Lyon, University Claude Bernard Lyon 1, Laboratory of Vulnerabilities and Innovation in Sport (L-VIS), EA 7428, F-69622, Lyon, France

⁵Université de Montréal, École de kinésiologie et des sciences de l'activité physique (EKSAP), Montréal, Canada.

⁶Centre de recherche de l'Institut universitaire de gériatrie de Montréal (CRIUGM), Montréal, Canada.

⁷Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage (CIRCA), Montréal, Canada

**Journal:** International Journal of Sports Physiology and Performance;

**Acceptance Date:** April 3, 2025

©2015 Human Kinetics, Inc.

**DOI:** 10.1123/ijspp.2024-0396

**Corresponding author:** Marc Jubeau

Laboratoire MIP - Nantes Université
23, rue du Recteur Schmitt Bât F0 - BP 92235
44322 NANTES
marc.jubeau@univ-nantes.fr

**Authors ORCID ID:**

Giorgio Varesco: 0000-0001-9385-6972

Walter Staiano : 0000-0002-1269-0016

Benjamin Pageaux : 0000-0001-9302-5183

Julie Doron: 0000-0002-3967-709X

Marc Jubeau: 0000-0002-4878-7813
# Effects of 5-week Brain Endurance Training on fatigue and performance in elite youth epee fencers.

Varesco G, Staiano W, Bracco M, Pageaux B, Soulas L, Goisbault M, Doron J and Jubeau M.

## Abstract (250 words)

**Purpose:** To examine the effectiveness of five weeks of Brain Endurance Training (BET) in reducing impairments in sustained attention, performance at a specific fencing test and perceived fatigue after a cognitive fatiguing task in youth epee elite fencers during the pre-season.

**Methods:** Using a quasi-randomized controlled trial, 19 elite youth fencers (8 women, 18±1 y) were divided in the BET (n=11) or control (n=8) group. Both groups trained for 5 sessions/week during 5 weeks. The BET group completed the BET sessions before, during or after fencing training, 3 to 4 times/week. The control group performed only fencing training. Before and after the 5 weeks, fencers performed a psychomotor vigilance test (PVT) and fencing test pre and post 40-min of a Reverse Stroop task. Perceived fatigue was scored on a 10-cm visual analog scale.

**Results:** After 5-weeks, perceived fatigue, reaction time and number of lapses at the PVT increased from pre-to post-Reverse Stroop task only in the control group (p≤0.011), with no pre-to-post difference for the BET group (p>0.059). No differences were found in fencing test performance (p>0.07). Effort for the Reverse Stroop task increased for both groups after the 5 weeks (p=0.043). We observed an increase in perceived fatigue, reaction time and number of lapses in the BET group before the fatiguing task (p≤0.028).

**Conclusion:** BET reduced the negative effects of a cognitive fatiguing task on sustained attention, without a clear improvement in performance at the fencing test and represents a possible tool to mitigate fatigue in Fencing.

**Keywords:** Mental fatigue; Sport performance; Combat sport; Stroop task; young athletes.
INTRODUCTION

Fencing is an open-skill, interceptive combat sport characterized by fast and intense technical actions that require mastering offensive and defensive sets of movements such as displacements, lunges or *flèches* to perform at a high level.¹,² On top of that, the continuous interaction with the opponent makes cognitive functions such as attention, anticipation, visual discrimination, and decision-making of the utmost importance.¹,³ Thus, as in other combat sports,⁴ fencing psychomotor performance is greatly influenced by physical and psychological factors, with fatigue affecting both.⁵

Fatigue is a symptom traditionally associated with increased feelings of tiredness and lack of energy that can be caused by physical and/or mental exertion.⁶ We have previously shown that, in fencing, the presence of a high mental workload is associated with increased fatigue.⁵ Specific interventions aiming to reduce the harmful effects of fatigue on sport-specific psychomotor performance are currently lacking in fencing and other combat sports. In other sports, previous research aimed to reduce the deleterious effects of fatigue induced by cognitive tasks on sports performance by increasing the cognitive load of habitual training sessions.⁷⁻⁹ The rationale behind this approach is that, being more frequently exposed to high cognitive loads, athletes would become more resistant to fatigue, improving sustained attention capacity and sport-specific performance by fostering neural adaptability.¹⁰ Such intervention has been previously labeled Brain Endurance Training (BET).¹¹ BET has been shown to improve cycling¹² and running⁹,¹³ endurance performance, lowering the rating of perceived effort for a given submaximal intensity. BET also reduced the deleterious effects of a cognitive fatiguing task on sustained attention (index of cognitive performance captured by a Psychomotor Vigilance Task; PVT⁸,⁹,¹²) and, importantly, on agility tests in soccer players⁹ and a shooting test in padel players.⁸ A clear advantage of BET is its adaptability to the field with the possibility to easily increase the cognitive load of training sessions by including inhibitory tasks lasting 20 to 30 min. These tasks can be implemented before,¹⁴ during⁷,⁸ and after⁹,¹² the training sessions.

In the present study, we aimed to evaluate the feasibility and effects of five weeks of BET in reducing the deleterious effects of fatigue on fencing performance, sustained attention and perceived fatigue in elite youth fencers during the pre-season. To do so, we implemented a five-week BET intervention targeting a similar number of sessions, total intervention duration and modalities to previous studies on BET.⁸,⁹,¹²,¹⁴ Half of the fencers of the French U17 and U20 epee fencing national team, completed BET on top of their fencing training. The other half served as control, and performed only the fencing training. We hypothesized that, following a cognitive fatiguing task, the decrease in sustained attention and the increase in perceived fatigue would be lower in the BET group than in the control group, with greater performance at a fencing test.
# METHODS

## Participants

All athletes of the French U17 and U20 epee fencing national team were invited to participate in the present study (n=24, 12 women, 178±9 cm, 72±11 kg, 18±1 years old, fencing experience: 11±2 years). A-priori sample size calculation was not performed due to the lack of preliminary data on this specific population,¹⁵ and because we planned to recruit the whole available population of French elite youth athletes. Before the first session, epee fencers were fully informed of the testing procedures and the aim of the study before obtaining written consent. For minors, written consent was signed by a legal tutor. Exclusion criteria were the presence of injury or surgery resulting in a stop of training activities and were applied after recruitment. Of the 24 fencers invited, four (3 women and 1 man) were injured and thus could not train and enter in the study. Of the 20 fencers recruited, one woman quit the training program in the third week because it was perceived as too stressful with a negative effect on sleep. Based on a sensitivity analysis (GPower v3.1) for a repeated-measures ANOVA with within and between subject factor, with a sample size of 19, α = 0.05, and 80% power, it would be possible to detect a minimum effect size of Cohen's f=0.14, corresponding to a η²p of ~0.05, assuming a correlation among repeated measures of 0.8 and a nonsphericity correction of 0.75. The study was approved by the Nantes University Ethical Committee (N.13092023-1) and met the requirements of the Declaration of Helsinki (2013) for research on human beings.

## Procedures

This study was carried out on the field and followed a quasi-randomized controlled trial. Participants were allocated to the BET (n=11; women=5) or control group (n=8; women=3; Figure 1A) according to the individual training and academic schedule of each athlete. BET sessions required additional time compared to regular training, potentially conflicting with the academic schedule of some youth fencers, thus allocation was preferred to randomization to maximize attendance and avoid attrition. The academic schedule was considered independent of fencing performance, and therefore we assumed this allocation did not influence responsiveness to BET.

The study was completed during the pre-competition period (pre-season), which ranges from the end of August, when athletes moved to the training center, until the first week of November, when competitions and exams start. The protocol lasted 7 weeks (11th September - 29th October 2023). During this pre-competition period, athletes kept a stable training and academic schedule, with five training days/week, Monday to Friday. The first and seventh week were dedicated to the testing sessions (Figure 1A). During Week 1, fencers participated in 2 visits separated by 24 hours which included the familiarization with all testing procedures and the cycling test (visit 1), and the testing session (visit 2). Before both visits, participants performed the warm-up routine used for competitions and repeated the same routine across all testing sessions. Fencers were asked to keep caffeine consumption, hydration, sleep, and nutritional habits consistent for the duration of the study.
From Week 2 to Week 6 (included) three to four sessions of BET were scheduled weekly in the BET group and added on top of the habitual training sessions (Figure 1). The number of BET sessions per week was planned with the coach to accommodate travels, training schedule and recovery. Details on the weekly BET sessions are available in Supplementary Materials 1. The control group performed only the habitual training sessions.

<figure><img src="image_2.png" /><figcaption>**Figure 1.** Study design and timeline (Panel A). Numbers represent the quantity of Brain Endurance Training (BET) sessions scheduled each week. Men and women trained 5 days a week. Panel B presents the testing session protocol. NASA-TLX: NASA Task-Load Index questionnaire; VAS fatigue: 10-cm Visual Analog Scale for fatigue; PVT: 5-minutes Psychomotor Vigilance Task.</figcaption></figure>

## Brain Endurance Training

BET involves the use of cognitive tasks designed to stress inhibitory control, performed on the SOMA-NPT platform (v.11, Sswitch, Lucern, SUI) for iOS on a 10.9" screen iPad (10th gen., Apple Inc., Cupertino, CA). Tasks were randomized across sessions. Two types of BET sessions were included in the protocol: dual-task sessions and intermixed sessions. The calendar and details on the tasks performed are available in the Supplemental Materials.

**Dual-task sessions.** Fencing practice is characterized by “cognitive-motor interferences”, that appear when cognitive and physical functions compete for attentional resources, increasing the cognitive workload of the task compared to the physical or cognitive task alone.¹⁶ Dual-task sessions aimed to recreate this “cognitive-motor interference”. The dual-task sessions lasted 30 minutes in total, including a 5-minute PVT¹⁷ on iPad, 20 minutes of cognitive task, and another 5-minute PVT. The cognitive task was performed while cycling at a self-selected cadence on a cycle-ergometer (Smart-Bike20, Stages Cycling, Boulder, CO) at the intensity
determined by a cycling test. Participants performed the PVT sitting at rest. Dual-task sessions were performed 3 times per week before or after the regular ~1 hour individual fencing training sessions. We considered both pre- and post-sessions to be effective in eliciting adaptations, and we ensured a balance between pre- and post-training sessions. The difference in PVT reaction time before and after the dual-task indicated impairments in sustained attention.

*Intermixed sessions.* In the training weeks including 4 training sessions, fencers also underwent an intermixed session. This session aimed to increase the cognitive workload of an *assault* training session, which consisted of repeated fencing bouts alternated with rest. A cognitive task was performed during the periods of recovery, which varied between 1 to 5 minutes. As fencing combat has an important cognitive workload, we targeted the recovery periods so fencers had the opportunity to recover from the physical load. Such intermixed sessions have already been proven to improve performance in padel,⁸ with potential benefits for epee fencing considering the sustained but intermittent nature of this discipline. The total duration of this session was ~1.5 hours.

## Cycling test

The cycling test was performed at the end of the familiarization session in the BET group and used to set the workload of the dual-task sessions. Fencers performed an incremental cycling task starting at 100 W for women and 150 W for men. Then, the workload increased every 3 min by 20 W for women and 25 W for men. Fencers were blinded to power. The rating of perceived effort was collected every 90 seconds using the 6-20 Borg scale.¹⁸ The task stopped once fencers overcame the “hard effort” (≥15 on the scale). Then, they resumed cycling at the intensity corresponding to a “somewhat hard effort” (13 AU) for 3 min. If the Rate of Perceived Effort (RPE) was greater or lower than a “somewhat hard effort”, the intensity was adjusted. Hence, the power output corresponding to a “somewhat hard effort” was recorded. The goal was to find the highest workload associated with the shortest choice reaction time which, on a 6-20 Borg Scale,¹⁸ has been shown to correspond to a “somewhat hard effort” (13 over 20,¹⁹,²⁰). A “somewhat hard effort” has also been shown to correlate with the onset of blood lactate accumulation (OBLA) and lactate threshold.²¹⁻²³ Dual-task training performed at this intensity is proposed to stress the upper limit of cognitive ability.²⁰,²⁴

## Testing Sessions

During the testing session, after warming up, fencers underwent a battery of tests before and after a fatiguing task consisting of 40 minutes of a Reverse Stroop color-word task²⁵,²⁶ (RS; Figure 1B). This duration was selected to be slightly longer than the minimal duration recommended to induce fatigue using a similar cognitive task.²⁷ In the battery of tests, fencers reported fatigue on a 10-cm visual analog scale (VAS)⁵ and performed a 5-minutes PVT. Differences from pre- to post-fatiguing task in VAS fatigue and PVT mean reaction time, accuracy and lapses were recorded. Accuracy was defined as % of responses between 100-500 milliseconds over the total number of trials, while lapses correspond to responses ≥500 ms.¹⁷ The PVT was followed by a fencing test aiming to measure the performance of fencing fundamentals. Successively, the
fatiguing task was administered, which has been previously shown to elicit fatigue and reduce psychomotor performance (see Supplementary Materials).⁹,¹¹,¹²,²⁸ Finally, after the fatiguing task and before the tests, participants filled out the NASA-Task Load Index questionnaire (NASA-TLX)²⁹ to report their perceived workload of the cognitive fatiguing task. The Standard Operating Procedures are available online.³⁰

The fencing test evaluated the execution performance of the so-called "fundamentals" of fencing, i.e. automated moves such as forward and backward displacements and attacks to a target.¹⁵ The test consisted of a total of three sets of 3 min separated by 1 min of rest, simulating the time requirement of an actual epee bout.³¹ The test included 3 shuttles (back and forth) over 2 m for men and 1.75 m for women, to be completed within 9 s.³¹ During the shuttles, fencers were asked to focus their attention on a fixation cross projected on a target board presenting 8 targets equipped with impact sensors. After 9 s, a red circle was projected on a random target using the Superlab software (v6, Cedrus, San Pedro, CA). Fencers were instructed to attack the target as fast as possible using their fencing equipment. Trials were separated by 9 s of rest, each trial lasting ~18 s in total. Measured outcomes were the number of hits landed on the targets and the execution time required to hit a target (i.e. the time difference between the stimulus appearance and the hit). Supplementary Materials 2 presents a visual representation of the test setting. All details on this testing apparatus were previously published.¹⁵

## Statistics

Statistics are reported as mean ± standard deviation, unless otherwise specified. The rate of attendance was compared between men and women using Mann-Whitney U-test, as they train separately. To quantify the impairment induced by the dual-task sessions (i.e. cycling and cognitive task), the difference in PVT reaction time before and after the dual-task was evaluated using mixed repeated measures ANOVAs (RM-ANOVA). An eventual evolution of these impairments over time was checked during the 5 weeks using linear mixed models, with participants as random effect for the intercept. Details and output for these models are available online.³⁰

To assess the effects of BET on fatigue and fencing performance, we evaluated the effect of group (BET vs. control; between-subjects), time (before vs. after the fatiguing task; within-subject), test (baseline and post-5-weeks; within-subject) and possible interactions using RM-ANOVAs on the VAS, PVT variables and fencing test variables. The effects of group and test on the NASA-TLX dimensions were also evaluated using RM-ANOVAs. All RM-ANOVAS were adjusted for sex. For all analyses, Q-Q plots of the residuals for each model and normality distribution of data and equal variance were checked using the Shapiro-Wilk and Levene's test, respectively. In case of significant main effects or interactions, post-hoc analysis was carried out using Tukey correction. Friedman tests for repeated measures were used when RM-ANOVA assumptions were violated (it was the case only for accuracy and lapses at the PVT), with median and IQR used as descriptives. For parametric analyses, partial eta squared (η²p) was used as the measure of effect size, interpreted as small (>0.01), medium (>0.06), and large (>0.14) effects. For all tests, the significance threshold was set at α = 0.05,
two-tailed. Statistical analysis was carried out in the R environment using JASP (v.0.16, JASP team, www.jasp-stats.org).
RESULTS

The results presented are from the 19 athletes who completed the training protocol. Overall results including data from the athlete who dropped from the study did not change, and they are available at.³⁰

Participant's characteristics are presented in Table 1, and did not differ between groups (all p≥0.54).

<table><caption>**Table 1.** Participants' characteristics divided by group and sex.</caption><thead><tr><th rowspan="2"></th><th colspan="2">BET (n=11)</th><th colspan="2">Control (n=8)</th></tr><tr><th>Women (n=5)</th><th>Men (n=6)</th><th>Women (n=3)</th><th>Men (n=5)</th></tr></thead><tbody><tr><td>Age (years)</td><td>18±1</td><td>17±1</td><td>18±1</td><td>19±1</td></tr><tr><td>Height (m)</td><td>1.68±0.08</td><td>1.86±0.09</td><td>1.78±0.09</td><td>1.80±0.04</td></tr><tr><td>Body Mass (kg)</td><td>64±10</td><td>82±13</td><td>67±7</td><td>74±5</td></tr><tr><td>Cycling intensity (W)</td><td>130±16</td><td>204±32</td><td>135±5</td><td>189±23</td></tr></tbody></table>

Note: Age distribution per group is available at.³⁰

The number of BET sessions performed was 16 and 18 for women and men, respectively. The attendance rate was high and similar between men (98±3%) and women (95±5%; Mann-Whitney U=8.00; p=0.19). When evaluating the effectiveness of BET sessions in inducing fatigue, PVT reaction time showed an increase from pre- to post-dual task session, from 328±35 ms to 341±33 ms (F=32.9; p<0.001; η²p= 0.185). The mixed effect model estimated an increase in reaction time of 2.62 ms per session (F=54.1; p<0.001).

Mean response time at RS showed a test effect (F=8.08; p=0.012; η²p=0.336), being higher post 5-week (778±156 ms) compared to baseline (744±122 ms). Accuracy was similar across tests and groups, being on average 97±2% (all p>0.16). The PVT, reaction time demonstrated a test × time × group interaction (F=11.92, p=0.004, η²p=0.443; Figure 2A). At baseline, reaction time increased from pre- to post-RS, in both the control group (+11±4%, p=0.012) and the BET group (+14±9%, p<0.001; Figure 2A). When comparing reaction times at pre-RS, an increase was observed post-5-week in the BET group compared to baseline (+17±8%, p<0.001), whereas no change was noted in the control group (p=0.75; Figure 2A). Post-5-week, when comparing reaction times from pre- to post-RS, the control group showed an increase (+19±6%, p<0.001), while the BET group did not (p=0.059; Figure 2A). Lastly, post-5-week reaction time following RS was greater compared to baseline in both the BET (p=0.003) and control (p=0.013; Figure 2A) groups. No difference in group, time or test was found for accuracy (Friedman: χ²=6.96; p=0.433; Figure 2B). Number of lapses (Friedman: χ²=16.3; p=0.022) did not change from pre- to post-RS in both groups at baseline (all p>0.22; Figure 2C). Comparing tests at pre-RS, a higher number of lapses was observed post-5-week compared to baseline in the BET group [median increase: 2 lapses (IQR=3); p=0.028], with no difference in the control group (p=0.897; Figure 2C). Post-5-week, the number of lapses increased only in the control group pre-RS [median increase: 3 lapses (IQR=3.5); p=0.011], reaching similar values to those of the BET group at post-fatigue (Figure 2C).
At the fencing test, no main effect of test, time, or group, nor test × time or test × time × group interaction was observed for the number of hits (all p>0.07; Figure 2D) or execution time (all p>0.08, Figure 2E).

For the VAS fatigue, a test × time × group effect was found (F=5.82; p=0.028; η²p=0.267; Figure 2F). In the BET group and pre-RS, the VAS score was higher post-5-week compared to baseline (+2.98±2.35 cm; p=0.008), remaining similar in the control group (p=0.349; Figure 2F). Finally, at post-RS the VAS score was lower at baseline compared to post-5-week in the control group (p=0.006) but not in the BET group (p=0.188; Figure 2F).

<figure><img src="image_3.png" /><figcaption>**Figure 2.** Effect of 5 weeks of Brain Endurance Training (BET) on PVT's reaction time (Panel A), Accuracy (Panel B), number of Lapses (Panel C), and fencing test's number of targets hit (Panel D) and execution time (Panel E) in the control (in orange) and BET (in blue) groups. Perceived fatigue on the 10-cm VAS Fatigue is presented in Panel F. Median and Interquartile Range were used for panels B and C. In panel C, number of fencers scoring zero lapses are presented on the bottom. RS= Reverse Stroop task; \*=significant difference from pre Stroop task; \*=p<0.05, \*\*\*=p<0.001. \#=significant difference from pre Stroop task at baseline; \#\*=p<0.05, \#\#\*=p<0.01, \#\#\#\*=p<0.001. $=significant difference from post Stroop task at baseline; $=p<0.05, $$=p<0.01.</figcaption></figure>
From all the NASA TLX scale dimensions, only effort presented a test effect (F=4.84; p=0.043; η²p=0.232), with effort being lower post-5-week than baseline (Table 2). No other test or group main effects, nor test × group interaction were found for the other dimensions (all p>0.057, Table 2).

<table><caption>**Table 2.** Group comparison in perceived workload of the fatiguing task, measured using the NASA Task-Load Index (NASA-TLX).</caption><thead><tr><th rowspan="2">NASA-TLX dimensions (AU)</th><th colspan="2">BET (n=11)</th><th colspan="2">Control group (n=8)</th></tr><tr><th>Baseline</th><th>Post 5-week</th><th>Baseline</th><th>Post 5-week</th></tr></thead><tbody><tr><td>Mental Demand</td><td>86±8.5</td><td>79±16.5</td><td>79±14</td><td>80.5±15.5</td></tr><tr><td>Physical Demand</td><td>14±8.5</td><td>19.5±11.5</td><td>14±8</td><td>21.5±14.5</td></tr><tr><td>Time Pressure</td><td>61.5±26.5</td><td>48±24.5</td><td>51.5±21</td><td>46.5±22</td></tr><tr><td>(Perceived) Performance</td><td>68±21</td><td>76.5±11</td><td>65±14</td><td>66.5±10.5</td></tr><tr><td>Effort*</td><td>75±19</td><td>66.5±21.5</td><td>84.5±9.5</td><td>72.5±18</td></tr><tr><td>Frustration</td><td>56.5±27</td><td>39.5±25</td><td>59±20.5</td><td>59.5±25.5</td></tr></tbody></table>

Note: *=significant test main effect (p=0.043). BET: Brain Endurance Training. Perceived was added to Performance dimension to avoid confusion with the objective performance at the Reverse Stroop task.
DISCUSSION

In the present study, we aimed to evaluate the effects of BET in reducing the deleterious effects of fatigue on fencing performance, sustained attention and mitigate perceived fatigue in elite youth fencers during the pre-season. Number of sessions, total time dedicated to each session, training duration and modalities were in line with the previous literature.⁸,⁹,¹²,¹⁴ We observed an excellent attendance rate at the BET sessions (>90%).

The first main result was a difference in the impairments induced by the fatiguing task between groups. After the 5 weeks, there were no changes in reaction time, lapses, and perceived fatigue caused by the fatiguing task in the BET group, while impairments manifested in the control group. These results support our hypothesis on the benefits of BET in reducing the negative effect of the cognitive fatiguing task on sustained attention and fatigue. While we did not measure brain activation, we could speculate that the BET led to an improvement in the efficiency of the pre-frontal cortex or anterior cingulate cortex during RS, thus reducing the overall cognitive exertion.⁷,¹⁴,³² However, it is also possible that a ceiling effect exists in the task-induced impairments observed in the PVT, and that the increased baseline fatigue masked some potential impairments from pre- to post-RS. Future studies exploring the mechanism behind fatigue and BET-related improvements in fencers are needed. It could be expected that the deterioration in sustained attention following RS would impair fencing performance, with lower alterations in the BET group. Contrary to our hypothesis, execution time or number of hits at the specific fencing test was not different between groups, tests, or time. On one hand, the accumulation of cognitive workload with the consequent alteration in sustained attention before RS could halt or mask some positive adaptations derived from the BET, as discussed below. On the other hand, previous research has shown that interventions reducing attentional capacity, such as sleep deprivation, do not impair the performance of automated skills that are repetitive and standardized, and which requires minimal conscious attention due to extensive practice and proficiency.³³ This includes the execution of fencing fundamentals such as displacements, lunges, and flèches in elite fencers. This could partially explain the differences between the current and previous studies showing an increase in sport-specific performance after BET in football⁹ and padel.⁸ Another possibility is that BET is less effective in elite fencers compared to amateurs, but further evidences are needed to confirm a tendency toward an upper limit in BET-derived adaptations dependent on fencer's level.

The second important result of the present study is that we observed evidence of cognitive workload accumulation: effort in completing RS increased and the objective RS performance decreased in both groups after 5 weeks. This is in agreement with a recent study finding that elite netball players experienced increasing levels of perceived fatigue during the pre-season.³⁴ Indeed, pre-season in elite athletes is characterized by an important volume of intensive training, that could increase fatigue.³⁴ On top of that, our sample was composed of students whose academic life would impose an additional cognitive load.³⁵ Importantly, the BET group showed also increased subjective fatigue and lower sustained attention ability post-5-week compared to baseline before RS, which was not observed in the control group. Despite we did not administer VAS at the training sessions, we observed a linear increase in PVT reaction time along the 5 weeks of BET, further
suggesting an important accumulation of fatigue in the BET group. Of note, the only fencer abandoning the protocol justified the choice stating that BET was perceived as too demanding. We did not perform PVT in the control group, which is a limitation of the present study. Overall, our results differ from previous results on open-skills sports, which showed no evidence of BET-induced fatigue accumulation on the pre-fatigue task,⁸,⁹ suggesting possible situation specific mediating mechanisms (e.g. sport discipline, level, occupation etc.). Accumulation of cognitive workload and fatigue are essential to trigger adaptations, however, the recovery might have been slower than expected, or the cognitive workload too excessive, leading to non-functional overreaching. Due to the athletes' busy schedules, we could not impose a rest period (e.g., one week) after the 5 weeks and re-test thereafter. Future research should explore sport-specific recovery and adaptation kinetics following BET, as well as the period-effect (e.g., pre-competitive, competitive, or off-season; or class vs. exam periods) to optimize intervention timing and ensure adequate recovery from the additional workload.

## Practical implications

- BET is beneficial in reducing the negative effects of fatigue on sustained attention and perceived fatigue in youth elite fencers.

- BET increased the level of fatigue over the five weeks, most likely due to the additive effect of the pre-season and the academic load.

- Coaches aiming to implement BET in elite youth epee fencers are advised to carefully consider the academic workload on top of the training workload to minimize potential fatigue accumulation over time.

## Conclusions

Five weeks of BET intervention in elite youth fencers during the pre-season could reduce the negative effects of a fatiguing cognitive task on perceived fatigue, PVT reaction time and lapses. However, the accumulation of cognitive workload displayed in the BET group might mask some potential additional benefits of the BET. Performance at a specific fencing test was not improved. Future studies are needed to understand whether moving the intervention to periods with low volumes of training and academic load are needed, as it could considerably reduce the risk of overload and produce additional benefits.

## Acknowledgements

We sincerely thank all the coaches (Pierre Moigneteau, Frédéric Chottin, Jérôme Roussat and Robin Rieu) and the athletes for their participation and interest. We would like to thank the Federation Francaise d'Escrime, the CREPS Reims and the CREPS Haute-de-France in Wattignies for their logistic support. We would like to thank Grant Hayes and the Soma NPT team (SSwitch) for their technical support and Kevin Haffner for his help in data collection.

This study was supported by the Agence Nationale de la Recherche with a grant from the Programme d'investissements d'avenir [ref. ANR-20- STHP- 005].
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SUPPLEMENTARY MATERIALS

Supplementary Materials 1. Training session details and cognitive task references

<table><thead><tr><th>Week</th><th>Date</th><th>WOMEN-Habitual training</th><th>WOMEN-type of Brain Endurance Training Session</th><th>MEN-Habitual training</th><th>MEN-type of Brain Endurance Training Session</th><th>Brain Endurance Training TASK</th></tr></thead><tbody><tr><td>1</td><td>18sept</td><td>Session Assault</td><td>Intermixed</td><td>Individual Lesson</td><td>50% Pre - DT; 50% Post -DT</td><td>Incongruent Flanker</td></tr><tr><td>1</td><td>19sept</td><td>S&C</td><td>PRE - DT</td><td>Individual Lesson</td><td>50% Pre - DT; 50% Post -DT</td><td>Numerical Inhibition</td></tr><tr><td>1</td><td>20sept</td><td>Fundamentals</td><td>POST - DT</td><td>Session Assault</td><td>Intermixed</td><td>Visual Stop Signal</td></tr><tr><td>1</td><td>21sept</td><td>Individual Lesson</td><td>PRE - DT</td><td>Individual Lesson / S&C</td><td>PRE-DT</td><td>Incongruent Flanker</td></tr><tr><td>2</td><td>25sept</td><td>Crosstraining</td><td>50% PRE - DT; 50% POST -DT</td><td>Individual Lesson / S&C</td><td>50% PRE - DT; 50% POST -DT</td><td>Dots Task</td></tr><tr><td>2</td><td>26sept</td><td>Individual Lesson / S&C</td><td>PRE - DT</td><td>Session Assault</td><td>Intermixed</td><td>MSIT</td></tr><tr><td>2</td><td>27sept</td><td>Individual Lesson / S&C</td><td>PRE - DT</td><td>Individual Lesson</td><td>50% PRE - DT; 50% POST -DT</td><td>Numerical Inhibition</td></tr><tr><td>2</td><td>28sept</td><td>No</td><td>No</td><td>Individual Lesson / S&C</td><td>PRE-DT</td><td>Flanker Compatibility</td></tr><tr><td>3</td><td>02oct</td><td>Session Assault</td><td>50% Pre - Dt; 50% Post -Dt</td><td>Individual Lesson</td><td>50% Pre - Dt; 50% Post -Dt</td><td>MSIT</td></tr><tr><td>3</td><td>03oct</td><td>Individual Lesson / S&C</td><td>POST - DT</td><td>Individual Lesson</td><td>50% PRE - DT; 50% POST -DT</td><td>Go / No-Go Visual Task</td></tr><tr><td>3</td><td>04oct</td><td>Session Assault</td><td>Intermixed</td><td>Session Assault</td><td>Intermixed</td><td>Sudoku (No Ipad)</td></tr><tr><td>3</td><td>05oct</td><td>No</td><td>No</td><td>Individual Lesson / S&C</td><td>PRE-DT</td><td>Sustained Attention Task</td></tr><tr><td>4</td><td>09oct</td><td>Individual Lesson</td><td>POST - DT</td><td>Individual Lesson</td><td>50% Pre - DT; 50% Post -DT</td><td>Spatial Stroop Task</td></tr><tr><td>4</td><td>10oct</td><td>Individual Lesson / S&C</td><td>50% PRE - DT; 50% POST -DT</td><td>Individual Lesson</td><td>POST-DT</td><td>Flanker Compatibility</td></tr><tr><td>4</td><td>11oct</td><td>Session Assault</td><td>Intermixed (Sudoku - No Ipad)</td><td>S&C</td><td>50% Pre - DT; 50% Post -DT</td><td>Incongruent Flanker</td></tr><tr><td>4</td><td>12oct</td><td>Individual Lesson</td><td>PRE - DT</td><td>Session Assault</td><td>Intermixed (Go/No-Go)</td><td>Dots Task</td></tr><tr><td>5</td><td>16 oct</td><td>Session Assault</td><td>POST - DT</td><td>Individual Lesson</td><td>50% Pre - DT; 50% Post -DT</td><td>MSIT</td></tr><tr><td>5</td><td>17 oct</td><td>Individual Lesson</td><td>50% Pre - DT; 50% Post -DT</td><td>Individual Lesson</td><td>50% Pre - DT; 50% Post -DT</td><td>Spatial Stroop Task</td></tr></tbody></table>

Notes: S&C= strength and conditioning session. PRE-DT= Brain endurance training dual-task session performed before the training presented in the column "Habitual training". POST-DT= Brain endurance training dual-task session performed after the training presented in the column "Habitual training". The mention "50%" indicates the percentage of participants undergoing the task at PRE or POST. MSIT= Multi-Source Interference Task. For some intermixed sessions, iPads were not available or used, a sudoku intermediate level numerical puzzle was used instead
We used Simon dots tasks,³¹ congruent and incongruent Flanker tasks,³² go/no-go tasks,³³ numerical inhibition tasks,³⁴ visual stop signal tasks,³⁵ multi-source interference tasks,³⁶ and spatial Stroop tasks.³⁷

Supplementary Materials References:

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Supplementary Materials 2. Experimental setting for the fencing test.

<figure><img src="image_4.png" /></figure>

Experimental setting for the specific epee test. Participants needed to maintain the attention on the fixation cross projected in the center of the target board and perform 3 shuttle run over a given distance (2 m for men, 1.75 m for women) in 9 seconds. This was followed by an attacking phase where a target out of 8 was projected.