Accepted Manuscript
Regular Article
Title:
Changes in neurocognitive function after acute high-intensity exercise: Decreasing thebiomechanical risk factors of ACL injury
Author names and affiliations:Mika Konishi, MS, PT1
1
Doctoral Program in Sports Medicine, Degree Programs in Comprehensive Human
Sciences,
Graduate School of Comprehensive Human Sciences,
University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japane-mail: s2230471@u.tsukuba.ac.jp
ORCiD: 0009-0007-7248-1893
Satoshi Shibata, PhD, PT2
2
Department of Physical Therapy, School of Health Sciences,
Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-Machi, Inashiki-gun,Ibaraki 300-0394, Japane-mail: satoshibata96@gmail.com
ORCiD: 0000-0002-9917-7847
Masahiro Takemura, MPhty (Sports), PT3 *3Faculty of Health and Sports Sciences,
University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japane-mail: takemura.masahiro.gw@u.tsukuba.ac.jp
ORCiD: 0000-0003-4870-9257
Number of Figures: 3
Number of Tables: 3
Running Title: Changes in neurocognitive function*

Corresponding Author: Masahiro Takemura (takemura.masahiro.gw@u.tsukuba.ac.jp)

1Abstract: Lower baseline neurocognitive ability could be a risk factor for anterior
cruciate ligament (ACL) injuries. We investigated the effects of high-intensity exercise(HIE) on neurocognitive function in athletes, and if any changes in neurocognitive
function after the HIE had effects on an unanticipated cutting motion. Fourteen collegiate
female athletes performed a bicycle ergometer HIE exercise at 80% of their heart rate
reserve. Neurocognitive function was evaluated by the Stroop Interference Test (SIT) preand post-HIE. Biomechanical variables were captured using a motion analysis system
while participants performed side-step cutting tasks in anticipated and unanticipatedconditions. Participants were divided into two groups according to the changes of SIT
scores after HIE: increased performers (IP; n = 7) and decreased performers (DP; n = 7).
The average SIT score of the IP group significantly increased, while that of the DP group
significantly decreased after the HIE (Paired t-test, P < 0.001). The main effect of the HIE
using repeated-measures ANOVA, was a significant decrease in peak knee valgus
moment (pre: anticipated-condition − 0.1 ± 0.1Nm/kg, unanticipated 0.0 ± 0.2Nm/kg;
post: anticipated 0.0 ± 0.1Nm/kg, unanticipated 0.1 ± 0.2Nm/kg, P = 0.024) and peakground reaction force (pre: anticipated 3.3 ± 2.1%BW, unanticipated 3.8 ± 2.1%BW;
post: anticipated 3.1 ± 3.4%BW, unanticipated 3.6 ± 3.6%BW, P = 0.035) only in the IP
group. The athletes with improved neurocognitive functions had decreased thebiomechanical ACL injury risk factors during the side-step cuttings. Improving
neurocognitive function may contribute to ACL injury prevention.
(Word Count: 246, *limited 250)

Keywords: ACL injury, neurocognitive function, anticipation, biomechanics2表題：高強度一過性運動後の神経認知機能の変化：ACL 損傷バイオメカニカルリ
スクファクターの減少
著者名：
小西 美佳 1, 柴田 聡 2, 竹村 雅裕 3
著者所属：
1
筑波大学大学院 人間総合科学学術院 人間総合科学研究群 スポーツ医学学位プログラム
2
茨城県立医療大学 保健医療学部理学療法学科
3
筑波大学体育系
和文抄録：
ベースラインの神経認知機能が低値であることは，前十字靭帯（ACL）損傷のリスクファクターである可能性が示唆されている．我々は，高強度一過性運動（HIE）がアスリートの神経認知機能に及ぼす影響と，HIE 後の神経認知機能の変化が非予測的カッティング動作に与える影響を調査した．対象者は，大学
女子アスリート 14 名であった．HIE は，自転車エルゴメーターを使用し心拍数
予備能の 80％の運動強度にて実施した．HIE 前後の神経認知機能は，ストルー
プ干渉テスト（SIT）によって評価された．予測・非予測的カッティング動作
中のバイオメカニカル変数は，三次元動作解析装置を用いて測定した．対象者
は，HIE 前後の SIT スコアの変化に基づいて 2 群に分けられた：神経認知機能向上（IP; n = 7）群と減少（DP; n = 7）群．HIE 後，IP 群の平均 SIT スコアは有意に増加し，DP 群の平均 SIT 得点は有意に減少した（Paired t-test, P <0.001）．二元配置分散分析の結果では，IP 群においてのみ，膝関節の最大外反モーメント（HIE 前：予測条件 − 0.1 ± 0.1Nm/kg，非予測条件 0.0 ± 0.2Nm/kg；
HIE 後: 予測条件 0.0 ± 0.1Nm/kg，非予測条件 0.1 ± 0.2Nm/kg，P = 0.024）と最大地面反力（HIE 前：予測条件 3.3 ± 2.1%BW，非予測条件 3.8 ± 2.1%BW；HIE
後: 予測条件 3.1 ± 3.4%BW，非予測条件 3.6 ± 3.6%BW，P = 0.035）の減少に対して HIE による有意な主効果が認められた．神経認知機能が向上した選手は，
カッティング動作中の ACL 損傷バイオメカニカルリスクファクターが減少した．したがって，神経認知機能の向上は，ACL 損傷予防に寄与する可能性が示
唆された．

3

1

Introduction

2

Anterior cruciate ligament (ACL) injury is one of the most severe sports injuries for3

athletes. It leads to considerable short- and long-term problems, including, but not limited

4

to, the decreased length of an athlete's career1), high re-injury rates2), early development

5of post-trauma osteoarthritis3), and high medical costs4). ACL injuries typically occur

6during athletic movement such as cutting in a non-contact manner5),6). Furthermore, it has

7been reported that incidence rates of ACL injury in female athletes are 2–3 times higher

8than males during the same sports7). Therefore, preventing non-contact ACL injuries

9during sport and physical activity for female athletes is especially important.

10

Recently, poor neurocognitive function has been suggested as a new plausible risk factor

11

for non-contact ACL injury8)–11). Swanik et al.8) measured neurocognitive function using

12“ImPACT”; reporting that the non-contact ACL injured group showed lower scores in

13

reaction time, processing speed, and visual/verbal memory. Subsequently, some studies

14

investigated the association of neurocognitive function with biomechanics during

15

unanticipated motion9)–11). Herman et al.9) reported that athletes with lower

16

neurocognitive performance demonstrated knee kinematic and kinetic patterns that are17

linked to ACL injury. In most cases, non-contact ACL injuries have been observed to18

occur under multitasking and unanticipated situations12),13). Processing of multiple tasks

419

reduces motor capabilities, and thus, could induce biomechanical stability deficits14),15).

20

Therefore, neurocognitive function could play an important role in decision making and21

motion execution in unanticipated situations.

22

Although many studies have proved that neurocognitive function is altered by acute23

exercise16)–21), past studies8),9),22) that examined the relationship between neurocognitive24

function and ACL injury have only assessed neurocognitive function at rest. Particularly

25

during team ball sports, athletes need to perform a high-level of motor-cognitive

26

multitasking under high-intensity loads23),24). Intermittent and repetitive high-intensity

27

physical exertion are required in team sports such as basketball, soccer, and handball23)–

28

25)

29

by acute high-intensity exercise (HIE) and to examine the biomechanics during

30

unanticipated motion.

31

A number of literature reviews19)–21),26) have concluded that moderate-intensity exercise

32．
(≈40 to 80 % VO2 max) promotes positive changes in neurocognitive function. On the other33

hand, a consensus on the effect of HIE (> 80 % maximal power output) on neurocognitive34

function in athletes has not been reached27),28). For example, some studies have found35

positive effects29), negative effects18),30)–32), and some no effects33)–35) of HIE on

36

neurocognitive performance in athletes. Thus, future research is needed to clarify the. Therefore, it is necessary to consider any changes in neurocognitive function caused537

effects of HIE on neurocognitive function in trained populations.

38

Therefore, this study aimed to examine; (1) the effects of HIE (80 % of heart rate

39

reserve) on neurocognitive function in athletes, and (2) the effects that any changes in40

neurocognitive function after the HIE have on unanticipated motion.

41
42

Materials and Methods

43

Acute high-intensity exercise (HIE): Definition.

44

In line with previous reviews an “acute” exercise period was defined as “exercise

45

performed within a single day”19). Consistent with the definitions used by guidelines of46

the American College of Sports Medicine (ACSM)36), high-intensity exercise was defined47

as high intensity (80 % heart rate reserve).

48
49

Participants.

50

Participants were 14 collegiate female athletes (mean ± SD age: 19.9 ± 1.6 years; height51

1.62 ± 4.9 m; weight: 57.0 ± 4.3 kg). Inclusion criteria were (1) female sex, (2) age older

52

than 18 years, (3) participate in jumping/cutting sports (e.g., basketball, soccer, lacrosse,

53

rugby) in university athletic clubs, and (4) engagement in regular physical activity

54(training of these sports at least 2–3 hours per day, 5–6 days per week). Exclusion criteria

655

were (1) any current injuries in the lower limbs, (2) concussion within the past six months,

56(3) any disorder of the peripheral sensory system, (4) a past history of surgery in the57

lumbar spine or lower limbs, (5) being color-blind, (6) previously taking the Stroop Color58

and Word Test, (7) taking medication that might affect neurocognitive ability, and/or (8)59neurocognitive impairment that would inhibit motor learning. This study was approved60

by the Ethical Committee of the Faculty of Health and Sports Sciences at the University

61

of Tsukuba (approval number. 020-165) and each participant provided written informed

62

consent before data collection. Participants were required to abstain from alcohol and63

caffeine consumption for at least 24 hours prior to the experiment, and to get adequate

64

sleep the day before in order to control for external factors that might affect65

neurocognitive function.

66
67

Experimental procedure.

68

Each participant completed a consent form and questionnaire, and then heart rate (HR)69

at rest was measured in a quiet room. After that, any anatomical characteristics that could70

be a risk factor of ACL injury; Q-angle, thigh-foot angle, leg-heel alignment, and71

navicular drop height37) were collected from the dominant leg. The dominant leg was

72

defined as the leg with which the participants would prefer to kick a ball38). An outline of7

73

the experimental procedures is shown in Fig. 1.

74

The first section of the pre-session was the Stroop Interference Test (SIT) as a75

neurocognitive test. Before the SIT, sufficient explanation was given to each participant

76

and practice was conducted until the participant became familiar with the SIT, to prevent77

any change between pre- and post-session due to habituation. We believe that the78

familiarization phase and the full randomization of the SIT trials reduced the risk of79

observing a repetition effect.

80

After the neurocognitive test, participants warmed up with 2 minute jog at a self-selected81

pace followed by 3 minutes of dynamic quadriceps and hamstrings stretching39).

82

Participants then completed the motor tasks including side-step cutting (CUT), single-leg

83landing (LAND), and forward stepping (STEP) tasks in unanticipated and anticipated84

conditions11).

85

After the motor tasks, participants were seated on a cycle ergometer (Power Max VIII,

86

Konami Corp., Tokyo, Japan) and HIE was performed. The HIE intensity was determined87

as target heart rate (THR). The definition of THR is given in detail later. During the88

exercise, the workload and pedal speed were gradually increased until the individual

89

reached the desired THR, based on a previous study16) and our pilot study. The method of90

gradually increasing workload is explained later. Immediately after reaching the THR,8

91

the participants were asked to perform SIT simultaneously as a post-neurocognitive test92

and to continue pedaling while maintaining pedal speed until the end of the93

neurocognitive test. Finally, the post-motor task was performed within 1 minute after the94

end of the HIE.

95

[Fig. 1 about here.]

96
97
98

Neurocognitive test.

99

High-order neurocognitive function, which is also referred to as executive function, was100

tested with SIT40),41). This is a test of how fast the participants can say the colors of the101

ink words are printed in, ignoring the word that is printed for each item. The participants

102

continued to say the ink colors according to the order of the columns for 45 seconds. The

103

score was calculated as the number of correct responses in 45 seconds. In this study, the104participants were divided into two groups. The increased performance (IP) group was

105

participants whose neurocognitive test scores increased post compared to pre, and the106

decreased performance (DP) group was participants whose neurocognitive test scores

107

decreased post compared to pre. By chance, the scores resulted in two groups with an108

equal number of participants.

9

109
110

Motor tasks.

111

Participants performed the motor tasks in the order of unanticipated condition, and then112

anticipated condition. The motor tasks consisted of three motions in which the113

participants hopped down to the center of a force plate from a 30-cm-tall box using the114

dominant leg. The dominant leg was defined as the leg with which the participants would

115

prefer to kick a ball38), and the box was placed at a distance of 50 % of their leg length

116(anterior superior iliac to medial malleolus) away from the center of the force plate. The

117

participants were required to perform one of 3 tasks according to an instruction by a118

projector screen (KIJ Corporation, Tokyo, Japan) which was set 10 m away from the box.

119

The size of the screen was width 215.4 cm and height 134.6 cm. The instructions for each120

motor task were: (1) CUT: when a yellow horizontal arrow is displayed, perform a side-

121

step cutting 45 degrees toward the nondominant leg side, (2) LAND: when a blue circle

122

is displayed, perform a single-leg landing, and (3) STEP: when a red upward arrow is123

displayed, step forward11) (Fig. 2).

124

In the unanticipated condition, the projector screen was synchronized with a footswitch

125

placed on the box, and one of the three instructions was set to display randomly.

126

Participants were asked to stand with their dominant foot on the foot switch and perform

10

127

the task which appeared on the screen the moment they left the box. Whereas, in the128

anticipated condition, the instruction was displayed in advance, then the participants

129

performed the task after they sufficiently recognized the task to be performed. The motor

130

tasks were finished when the participants successfully completed each task three times

131

under both conditions. In this study, only the first successful CUT tasks in each session

132

and condition were analyzed.

133
134

[Fig. 2 about here.]

135
136

Kinematic and Kinetic data collection and processing.

137

A three-dimensional motion analysis system, the VICON MX motion analysis system

138(VICON, Oxford, England) was used to capture the task motions with a 250 Hz sampling

139

rate through 12 infrared cameras. Ground reaction force data (GRF) was obtained at 1,000140

Hz from a force platform (Kistler Instruments, Inc., model 9281C, Winterthur,

141

Switzerland) which was synchronized with the kinematic data. Thirty-five retroreflective

142

markers were attached to the whole body of each participant in a standard Plug-in Gait

143

model (Helen Hays marker-set) on anatomical landmarks42),43). The participants wore the144

athletic shoes they normally wear when engaging in sports activities and the motion

11

145

capture suit. A matched 15Hz fourth-order Butterworth filter was used for the marker and146

force data44). All kinetic data were normalized to body weight. As described in a previous

147

study45), the ‘initial contact’ (IC) was defined as the time where vertical GRF was higher

148

than 10 N. Peak value was defined as the maximum (joint flexion, adduction (varus), and149

GRF) or minimum (joint extension and abduction (valgus)) value of any dependent

150

variable between the IC and 100 milliseconds (msec) after the IC because most non-151

contact ACL injuries occur within 100 msec after the IC46). Furthermore, the difference

152

between the maximum and minimum joint angles from the IC to 100 msec after the IC

153

was calculated as angular displacement.

154
155

Acute high-intensity exercise.

156

A cycle ergometer (Power Max VIII, Konami Corp., Tokyo, Japan) was used for the157

HIE protocol. At first, a 6 minute warm-up was performed at a low-intensity workload of158

0.4 kp and a pedaling speed of 70 rpm16). Following the warm-up phase, the workload

159

was gradually increased by increasing the resistance by 0.1 kp every 30 seconds while160

maintaining pedal speed at 80–90 rpm until each participant reached the THR. We applied161

this incremental method because it had allowed participants to maintain pedal speed based162

on our pilot study. Until the participants could not hold the pedaling speed above 80 rpm,

12

163

gradual increases in workload were continued. Immediately after the target heart rate was164

reached, the participants were asked to perform SIT and to maintain the pedal speed and165

THR until the end of the test16). Workload and pedal speed during the HIE were recorded

166

every 2 minutes excluding the warm-up period, and then the mean of each variable was167

calculated.

168
169

Acute high-intensity exercise intensity manipulation check.

170

Heart Rate. The heart rate (HR) was measured using the wearable sensors POLAR V800

171

HR and POLAR H10 (Polar Electro Oy, Kempele, Finland). In the experiment, two HR

172

variables (resting HR and exercise HR) were identified. Resting HR was assessed173

following a 10-minute sitting rest. Exercise HR was defined as the mean of the HR values

174

assessed at 2 minute intervals during the HIE excluding the warm-up period16).

175
176

The target heart rate. The target heart rate (THR) was calculated using the heart rate

177

reserve (HRR)47) which is a common means of establishing a target heart rate for exercise

178

intensity36). HRR was estimated as the difference between the age-predicted maximum179

HR (207 − 0.7 × age)48) and resting HR. THR was applied with the following formula:180[(desired intensity percentage × HRR) + resting HR]. In this study, the desired intensity

13

181

was chosen as high intensity (80 % HRR) based upon guidelines of the American College

182

of Sports Medicine (ACSM)36).

183
184

Rating of Perceived Exertion. Borg’s rating of perceived exertion (RPE)49) is commonly

185

used to assess a participant’s subjective perception of exertion during exercise. The rating

186

ranges from 6 to 20, where the values from 6 to 11 are categorized as “no exertion to187

light,” the values from 12 to 14 are categorized as “some exertion,” the values from 15 to188

20 are categorized as “hard to maximal exertion”. The RPE was assessed at 2 minute189

intervals during the HIE excluding the warm-up period, and then the mean and maximum

190

values were calculated16).

191
192

Statistical analysis.

193

All statistical analyses were performed using SPSS statistics 27 (IBM, SPSS Tokyo,

194

Japan), with the level of statistical significance set at P < 0.05. Unpaired t-tests compared195

the differences of demographic characteristics and the HIE manipulation between the IP

196

and DP groups. Analyses of SIT scores from the pre- to post-session for each group were197

conducted using the paired t-test for each group. Each point of the kinematic and kinetic

198

data was subjected to a two-way repeated-measures ANOVA to determine the effect of

14

199

the HIE (pre- versus post-session), the condition (anticipated versus unanticipated) and200

any interaction effects.

201
202

Results

203

Demographic and acute high-intensity exercise manipulation analyses.

204

The mean and standard deviation for each participant’s demographic characteristics and205

the physiological effects of the HIE excluding the warm-up period are displayed in Table

206

1. There were no significant differences between the groups in height, weight, any

207

anatomical characteristics, HR variables, or RPE, except age and THR.

208

[Table 1 about here.]

209
210
211

Neurocognitive function.

212

SIT scores were not significantly different between the pre- and post-sessions.

213

Comparing the pre- with the post-session, the participants were divided into an IP group214(7 participants with increased scores) and a DP group (7 participants with decreased

215

scores), respectively. The average score of the IP group significantly increased, while that216of the DP group significantly decreased between the sessions (Table 2).

15

217

[Table 2 about here.]

218
219
220

Biomechanical analysis.

221Interaction effect. Fig. 3 demonstrates the interaction effect on hip biomechanics during

222

the side-step cutting tasks. In the IP group, the interaction effect of condition and time for223

peak hip abduction angle was significant. In the DP group, the interaction effect of224

condition and time for peak hip extension moment was significant.

225
226

Main effect for acute high-intensity exercise. Table 3 presents the main effects of the227

HIE on trunk and lower limb biomechanics, and ground reaction force during the side-228

step cutting tasks. In the IP group, the HIE led to decreased peak knee valgus moment

229(KVM), decreased peak GRF, increased angular displacement of pelvis rotation toward230

the dominant leg side, and increased knee flexion. In the DP group, the HIE resulted in231

increased angular displacement knee flexion.

232
233

[Table 3 about here.]

234

16

235

Main effect for anticipation. No significant effect for anticipation was observed for the236

main measurements.

237
238

Discussion

239

The effects of acute high-intensity exercise on neurocognitive function in athletes.

240

The results of the current study showed that neurocognitive performances improved in241

7 participants (IP group) and decreased in 7 participants (DP group) after the HIE (Table

242

2). However, there were no significant differences between the groups in acute high-243

intensity exercise total time, HR, or RPE during the HIE (Table 1).

244

In the current study, we applied 80 % HRR, defined as high intensity according to the245

guidelines of the ACSM36) for the HIE. Wang et al.16) indicated that neurocognitive

246

performances were significantly impaired in college-aged adults who conducted a bicycle

247

ergometer exercise until reaching 80 % HRR and who then performed the Wisconsin Card

248

Sorting Test as a neurocognitive test. While a general notion that HIE negatively affects

249

neurocognitive performance has been proposed50), this theory does not always apply to250

trained individuals with high fitness levels and there is no consensus specifically for251

athletes28). As athletes are typically required to perform quickly and make critical252

decisions during exposure to high physical workloads23),24), they may be less cognitively

17

253

affected by HIE than those with lower levels of fitness28). Neurocognitive function may

254

influence an athlete's decision-making and quick response in unanticipated athletic

255

situations, resulting in performance level and injury risk8)–11). Therefore, we set the HIE

256

at an 80 % HRR intensity level16),36) to explore the effects of high-intensity load on

257

neurocognitive function in athletes.

258

The results of the current study included athletes who had improved (IP group) and those259

who had decreased (DP group) neurocognitive function due to HIE (Table 2), suggesting

260

that the effects of HIE on neurocognitive function may vary among individuals.

261

Additionally, most of the HIE manipulation variables, such as the total HIE time, exercise

262

HR, and RPE, which could affect neurocognitive function19),50), were not significantly

263

different between the groups; however, age was significantly higher in the IP group

264

compared to the DP group (Table 1). Therefore, there is a possibility that the IP group265

was more experienced in training and had a higher psychological stress tolerance for high-266

intensity physical loads51).

267

The SIT used as the neurocognitive test in this study reflects executive functions (i.e.,268high-order neurocognitive function)40),41). Factors contributing to the improvement of

269

executive function include exercise-induced prefrontal activation, as well as increased

270

psychological arousal and pleasure levels52). On the other hand, acute psychological stress

18

271

is considered as one of the factors that impair executive function53). Response to an acute272

stressor includes activation of the hypothalamus-pituitary-adrenal axis and subsequent273

release of adrenal hormones such as cortisol, noradrenergic or inflammatory activity53). It274

has been suggested that the limited managerial resources of cognition are allocated to275

complex stress responses, thereby impairing executive function54). Thus, the IP group276

may not have experienced significant psychological stress or biological processing when277

exposed to high-intensity physical loads. Consequently, the increase in exercise-induced

278

neurocognitive performance among the IP group might have been facilitated by factors

279

such as prefrontal activation, as well as increased psychological arousal and pleasure280

levels52).

281

In contrast, the DP group may have been vulnerable to the psychological stress of the282

HIE and consumed neurocognitive resources for biologic responses, leading to the283

impaired executive function51). Additionally, multiple factors such as hypoxia,284

hypoglycemia, dehydration, and heat stress could have also led to the decreased285

neurocognitive performance20),55).

286

It would be difficult to explain changes in neurocognitive function with a single factor,

287

as the neurocognition of healthy individuals results from the interaction of multiple

288

processes and complex mechanisms19)-21),52)-54). In the current study, direct measurements

19

289

of physiological mechanisms such as neurotransmitters, hormones, and brain functions

290

were not conducted, making it difficult to provide evidence to support the results.

291

Additionally, the history of sports experience periods was not recorded. Future studies

292

should employ a systematic approach to investigate the mechanisms underlying any

293changes in neurocognitive function. This would contribute to the development of training294

methods and conditioning techniques aimed at improving neurocognitive performance.

295
296

Effects of changes in neurocognitive function after acute high-intensity exercise on

297

unanticipated motion.

298

The findings of the current study showed that peak KVM and peak GRF decreased in299

both conditions after the HIE in the IP group. An increase in KVM and GRF after ground300

contact have been established as biomechanical risk factors of ACL injuries by previous

301

research56)–59). Therefore, the improvement of neurocognitive function after the HIE may

302

have contributed to the reduction of ACL injury risk during the side-step cutting tasks.

303

The decrease in peak KVM after the HIE could have been related to the increase in304

angular displacement of pelvis rotation toward the dominant leg side. Villa et al.6)

305

conducted systematic video analysis of ACL injuries and reported that the trunk rotated306

toward the uninjured limb in more than 50 % of the injuries. In the IP group, rotation of

20

307

the pelvis toward the dominant leg side may have prevented knee abduction associated308with hip internal rotation and contributed to the reduction in peak KVM. In addition,309

increasing the angular displacement of knee flexion may have reduced peak GRF by

310

absorbing the impact from the ground.

311

SIT used in this study is widely known to reflect high-order neurocognitive functions39).

312

High-order neurocognitive functions enable us to complete goal-oriented behavior and313

decision-making in complex situations60). Weiss et al.61) suggested that higher

314

neurocognitive function could reduce the reaction time from stimulus presentation to315

movement onset. Giesche et al.22) revealed that high-level neurocognitive functions are316

related to task-related decision-making in unplanned landings. Therefore, the317

improvement of high-order neurocognitive function because of the HIE could have318

improved reaction time and decision-making, and as a result, led to stable motion.

319

On the other hand, the reason that the biomechanical risk factor of ACL injury did not320change significantly in the DP group may be related to the persistence time of the effects

321

of the HIE on neurocognitive function. A few studies have suggested that an improvement322

of neurocognitive function can be induced by short periods of exercise lasting as little as323

10 minutes19),62), whereas a decrease of neurocognitive performance could be found after

324

long period exercise lasting as long as 40 minutes16),17). Additionally, previous studies

21

325

have shown that neurocognitive performance is less affected by acute exercise after

326

exercise than during exercise63). Therefore, although the improvement of neurocognitive327

function in the IP group remained, the neurocognitive performance of the DP group could

328

have returned to near-baseline levels after the HIE, and did not affect the dynamic trunk329

and knee movements.

330

In the results of the current study, the interaction effects of condition and time were331

observed in the peak hip abduction angle in the IP group and in the peak hip extension

332

moment in the DP group, respectively. Hip joint control is more likely to play a vital role333

in preventing high-risk knee movements6),64). Several investigations revealed an

334

association between decreased hip abduction and increased knee valgus, possibly

335

resulting in ACL injury6),64). In the IP group, increased neurocognitive function after the336

HIE may have enabled individuals to make appropriate decisions in unanticipated337

conditions, resulting in an increased hip abduction angle. However, considering that338

KVM decreased in both conditions, it would be difficult to corroborate that the results339

were solely due to the hip joint. Greater external hip extension moments could result from340

increased activity in the rectus femoris muscle as an antagonistic force, leading to a higher

341

amount of anterior tibial shear force and ACL loading65). However, the DP group did not342show an increase in knee extension moments; thus, the hip kinetics were less likely to

22

343

affect the knee biomechanics. In the results of the current study, knee kinematics and344

kinetics that could occur as a result of biomechanical changes in the hip joint were not345

observed in either group. Knee biomechanics result from a complex human kinetic chain

346

involving the trunk, hip, and ankle joints6),58),64). Furthermore, multiple risk factors such347

as neuromuscular and hormonal factors are simultaneously involved66). Thus, it is348

challenging to explain knee biomechanics solely through the planar motion of a single

349

joint. Future research should take these multifactorial aspects into account and investigate

350

their effects on knee biomechanics.

351

There were several limitations to the current study. First, the small sample size and352

inclusion of only collegiate athletes were among the limitations for broad generalization353

of these data. While the main effect of the HIE showed a large effect size67) (peak KVM:

354

η2 = 0.18, peak GRF: η2 = 0.55), future research will need to recruit from a larger and355

more diverse sample size, encompassing various age groups. Second, multiple ACL

356

injury risk factors such as neuromuscular and hormonal factors66) were not assessed in

357

this study. Future studies should examine the combination of diverse risk factors, as it is358

challenging to identify a significant contribution to ACL injury from single planar359

biomechanics alone. Third, the motor tasks used in the laboratory setting could not360

completely mimic a realistic sports scenario. Replicating a more realistic sports

23

361

environment will be required to better understand the potential relationship between

362

neurocognitive function and ACL injury risk factors. Finally, we did not identify any

363

factors associated with changes in neurocognitive function directly. Diverse contributing

364

factors have been suggested to link to the changes in neurocognitive function during acute365

exercise20). However, only SIT was used in this study. It would be difficult to consider all366

the factors because multiple factors are intricately involved in the changes in367

neurocognitive function through interactive processes. Suwabe et al.68) reported that368

evaluating oxygenated hemoglobin using fNIRS is an efficient measurement for

369

identifying changes in cognitive function caused by acute exercise. Future research will370

be necessary using validated evaluations such as fNIRS.

371
372

Conclusion

373

The findings of this study showed that HIE caused some female athletes to have374

improved neurocognitive function and others to have decreased neurocognitive function.

375

When grouped by improved and decreased neurocognitive function, respectively, the376

group with improved neurocognitive function showed a decrease in peak KVM and GRF

377

during side-step cutting tasks in both anticipated and unanticipated conditions.

378

Furthermore, the unanticipated condition post-HIE exercise showed different motion at

24

379

the hip joint from the anticipated condition. These results suggest that the female athletes

380

who improved neurocognitive function after HIE may reduce the biomechanical risk of381

ACL injury during side-step cutting tasks. Future research is required to increase the382sample size and further evaluate factors related to changes in cognitive function.

383
384

Acknowledgements

385

The authors thank all participants involved in this study and members of the laboratory.

386

Especially, we would like to show our appreciation to Dr. Miyazaki Terumitsu in the387

National Institute of Fitness and Sports in Kanoya for his contribution to kinetic and388

kinematic data collection.

389
390

Conflicts of Interest

391

The authors declare that there is no conflict of interest.

392
393

Author Contributions

394

Experiment conception and design: MK, SS and MT. Experiment implementation: MK.

395

Data analysis: MK. Paper composition: MK. Analyzing and writing advisory: SS and MT.

396

All authors approved the final version of the manuscript.

25

397

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Table 1. Participant characteristics and acute high-intensity exercise manipulation (mean625± SD).
IP group

DP group(n = 7)(n = 7)Age (year)

20.7 ± 1.6

19.0 ± 1.1

0.048*

Body height (cm)

161.3 ± 4.3

162.7 ± 5.2

0.616

Body weight (kg)56.2 ± 3.9

57.7 ± 4.5

0.527

Q-angle (°)

3.0 ± 4.2

7.3 ± 2.8

0.059

Thigh-foot angle (°)

7.0 ± 5.9

8.7 ± 5.5

0.611

Leg-heel alignment (°)

3.1 ± 1.8

4.1 ± 1.5

0.313

3.4 ± 2.3

5.5 ± 4.3

0.315

782.4 ± 162.8

736.7 ± 113.9

0.554

Resting HR (bpm)57.0 ± 6.3

61.9 ± 3.90.110

THR (bpm)

165.3 ± 2.1

167.3 ± 1.0

0.043*

Exercise HR (bpm)

141.3 ± 7.2

147.1 ± 3.0

0.085

Mean RPE

14.1 ± 0.9

14.0 ± 1.9

0.926

Maximum RPE

17.3 ± 1.0

16.4 ± 1.7

0.271

Workload (kp)1.8 ± 0.2

1.6 ± 0.1

0.079

Pedal speed (rpm)84.2 ± 1.6

83.6 ± 1.4

0.415

Variables

P value

Participants’ Demographic Characteristics

Navicular drop test (mm)Acute High-intensity Exercise Manipulation
Acute high-intensity exercise total time (s)a626

IP: increased performance; DP: decreased performance; HR: heart rate; THR: target heart

627

rate; RPE: rating of perceived exertion.

628

a

629

*Significant difference between groups (P < 0.05).

Data are shown excluding the warm-up period.

39

630

Table 2. Pre-session and post-session Stroop Interference Test scores (Mean ± SD).
631
Pre

Post

P value

A total of participants (n = 14)

64.6 ± 12.6

65.1 ± 12.7

0.699

IP group (n = 7)

63.7 ± 9.7

68.6 ± 9.0< 0.001*

DP group (n = 7)

65.6 ± 15.7

61.7 ± 15.5

< 0.001*

632
633
634

635

IP: increased performance; DP: decreased performance.

636*Significant difference between groups (P < 0.05).

637

40

638

Table 3. The main effect of the acute exercise on trunk and lower limb biomechanics during the side-step cutting tasks (mean ± SD).
Pre

Post

F (1, 32)

P

η2

Anticipated

Unanticipated

Anticipated

Unanticipated

IP group− 0.1 ± 0.1

0.0 ± 0.2

0.0 ± 0.1

0.1 ± 0.2

9.08

0.024*

0.18

DP group

0.1 ± 0.1

0.1 ± 0.1

0.0 ± 0.1

0.1 ± 0.1

0.11

0.752

0.02

IP group

3.3 ± 2.1

3.8 ± 2.1

3.1 ± 3.4

3.6 ± 3.6

7.37

0.035*

0.55

DP group

3.8 ± 4.9

4.0 ± 5.3

3.7 ± 5.1

3.7 ± 3.9

4.81

0.071

0.45

Pelvis rotation toward thedominant leg side (°)

IP group

4.4 ± 1.6

3.9 ± 2.0

5.5 ± 2.7

6.3 ± 2.5

7.39

0.035*

0.55

DP group

4.1 ± 1.7

7.5 ± 4.5

5.0 ± 3.8

7.1 ± 1.7

0.14

0.719

0.02

Knee Flx/Ext (°)

IP group45.2 ± 3.2

45.0 ± 2.5

46.3 ± 5.0

50.6 ± 2.0

14.58< 0.001*

0.71

DP group45.6 ± 2.8

42.7 ± 4.9

45.8 ± 5.1

49.1 ± 4.4

10.75

0.017*

0.64

Peak Kinetic Variablesa
Knee Var/Val Moment (Nm/kg)
GRF (%BW)
Angular displacementb639

IP: increased performance; DP: decreased performance.

640

a

Peak Variables. Var/Val, varus (+)/valgus (–); GRF, ground reaction force.

641b

The difference between the maximum and minimum joint angles. Flx/Ext, flexion (+)/extension (–).

642

* Significant main effect of the acute exercise (P < 0.05).

41

Fig. 1. Experimental procedures.
Immediately after reaching the target heart rate, the participants were asked to perform the Stroop
Interference Test and to maintain the pedal speed until the end of the test.

aFig. 2. The procedure of experimental tasks.
(1) Participant stood while stepping on the footswitch with their dominant leg on a 30cm high box.
(2) Immediately after the participant jumped off the box, the experimental task was displayed on thescreen.
(3) Participant reacted to the instruction displayed on the screen.

Fig. 3. Interaction effect on hip biomechanics during the side-step cutting tasks (mean±SD).aa

Peak variables. Flx/Ext, flexion(+)/extension(–); Add/Abd, adduction(+)/abduction(–)