Clinical Research Directory

Effects of Short-Term Creatine Supplementation on Cognitive Function in Healthy Young Adults

This study examined whether short-term creatine supplementation affects cognitive function in healthy young adults. Participants were randomly assigned to take either creatine monohydrate or a placebo for 10 days. Participants took 30 grams per day, divided into six 5-gram doses. Before and after the supplementation period, participants completed cognitive tests designed to assess areas such as memory, attention, reaction time, and processing speed. Participants also completed a 30-minute mentally challenging Stroop task, and brain oxygenation was measured during cognitive testing using functional near-infrared spectroscopy (fNIRS). The purpose of the study was to determine whether 10 days of high-dose creatine supplementation improves cognitive performance compared with placebo following a mentally challenging task.

Predicting Declines in Attention and Memory During a Prolonged Mental Task

This study will investigate whether heart activity and changes in the skin's ability to conduct electricity can help predict performance during a demanding computer task. These signals reflect how the body responds to mental effort. The main question is whether measurements taken at rest and near the beginning of the task help predict later accuracy, beyond information about sleep the previous night, current sleepiness, and initial task performance. Healthy young adults will attend one visit lasting approximately 50-60 minutes. Participants will complete a questionnaire and wear sensors that record heart activity and skin responses. After a five-minute resting measurement, participants will learn a computer task involving letters and numbers. The task requires remembering the previous letter and deciding whether numbers are odd or even. A short calibration will adjust the presentation speed to each participant. Participants will then perform the task for 16 minutes at the selected speed and rate their fatigue and the demands of the task. After these ratings, participants will rest quietly for five minutes and repeat the task for four minutes at the same speed. The researchers will also examine how performance, fatigue, and body responses change during the task and after rest. The study is intended to improve understanding of sustained mental effort and is not a medical diagnostic assessment.

tAN for First Responders

This study is designed as an open label, single arm, decentralized clinical study in which first responders will receive transcutaneous auricular neurostimulation (tAN), which targets the auricular branch of the vagus nerve (ABVN) via the mastoid and the auriculotemporal nerve (ATN) anterior to the tragus. Participants will be enrolled in the study over the course of eight weeks (56 days). Participants will respond to daily and weekly questionnaires regarding mood, stress, sleep, energy/fatigue, and burnout. Each week, participants will complete consolidated online questionnaires (intended to last no longer than 15 minutes) comprised of the Perceived Stress Short-Form (PSS-4), Well-Being Index (WHO-5), Mini-Z Burnout (5-item), PROMS Sleep Disturbance (PROMIS-SD), GAD-7 (every 2 weeks), and Perceived Stress (PSS-10; monthly). The PSS-10 will replace the PSS-4 on Days 0, 28, and 56. No tAN treatment will be delivered during the Baseline Period (days between Study Introduction and Day 0). Participants will complete the weekly set of questionnaires ("Weekly Questionnaires") on Day 0. Participants will be recommended to complete the daily set of questionnaires ("Daily Questionnaires ") on the other days of the Baseline Period. On Days 1 - 28, participants will self-administer one session of one to two hours of tAN therapy each day. Participants will be recommended to complete the daily tAN session post-shift prior to sleep. Weekly Questionnaires will be completed by participants on Study Days 0, 7, 14, 21, 28, 35, 42, 49, and 56. Participants will be recommended to complete Daily Questionnaires on all other study days, up to Day 28. Daily Questionnaires will not be required to be completed by participants. Daily tAN sessions and Daily Questionnaires will cease after Day 28. Participants will complete a Study Satisfaction Questionnaire with the Weekly Questionnaires on Day 56. Following Day 56, participants will schedule a Study Exit Interview with the Research Coordinator.

Acute Mental Fatigue and Muscle Strength

This study will investigate the acute effects of mental fatigue on lower-extremity muscle strength and limb symmetry in healthy young adults. Participants will complete lower-extremity strength testing before and after a standardized computer-based mental fatigue protocol involving tasks of attention, reaction time, concentration, and working memory. Muscle strength and limb symmetry will be assessed using isokinetic dynamometry, with muscle activity measured using surface electromyography. Participants will also complete subjective measures of mental fatigue, sleepiness, mental effort, and perceived physical exertion. Heart rate will be monitored throughout the study, and brain activity may be assessed during cognitive tasks. The study will determine whether acute mental fatigue is associated with changes in muscle strength, limb symmetry, and neuromuscular performance.

Cognitive Reserve and Post-Fatigue Recovery in Older Adults

As people grow older, it is common to experience a drop in physical stamina and memory functions. This can make recovering from daily physical and mental fatigue more difficult, which directly impacts an individual's independent daily life and overall quality of life. "Cognitive reserve" is a term that describes the brain's built-in resilience. Built over a lifetime through education, work, and social activities, a higher cognitive reserve acts like a buffer, helping the brain adapt to stress and aging. While research shows that a high cognitive reserve protects against conditions like dementia, we still do not fully understand how it helps older adults bounce back from normal, everyday physical and mental exhaustion. The goal of this study is to investigate how cognitive reserve levels influence how individuals aged 65 and older perceive their recovery after experiencing physical and mental fatigue. What the Study Involves The researchers will evaluate participants aged 65 and older to measure their baseline cognitive reserve levels. The study will look closely at how these levels affect the participants': Ability to cope with daily physical and mental fatigue. Need for rest and rest patterns. Time and ability to return to normal daily activities. Overall perception of their mental and physical recovery. Expected Outcome By understanding this relationship, the study aims to fill a gap in medical literature and help healthcare providers design better, more personalized rehabilitation and lifestyle support programs to improve the quality of life for older adults.

Exploring Immunological Markers Associated With Mental Fatigue in Graves' Disease

Mental fatigue occurs in many diseases and the reasons are mostly unknown. The investigators hypothesize that remaining mental fatigue after restored hyperthyroidism in Graves' disease is an autoimmune complication. The aim of this study is to explore immunological markers possibly associated with mental fatigue in Graves' disease, which the investigators plan to validate in another study (ImmunoGraves wp 2). Using a cross-sectional study design, mental fatigue is scored using a questionnaire to find 60 patients with and 60 without mental fatigue 15-60 months after diagnosis of Graves disease. The patients and 60 thyroid healthy controls without mental fatigue are assessed for thyroid hormones, quality of life, anxiety and depression, self-evaluated stress, coping strategies, eye symptoms and background variables. SciLifeLab in Stockholm, the national facility for autoimmune profiling, has pre-set large arrays including 42000 human proteins. Serum and cerebrospinal fluid will be separately pooled and analysed for a subgroup of patients with or without mental fatigue and for a subgroup of the control group. Proteins that preferably bind to antibodies in sera and/or cerebrospinal fluid from Graves' patients with mental fatigue in comparison to non-mental fatigue patients, will be screened against the Human Protein Atlas and the Allen brain map to identify those proteins that are expressed in the brain. Antibodies at higher concentration in the mental fatigue pools compared to the group without mental fatigue will be selected for further analyses on an individual level in the whole cohort together with antibodies targeting g-protein coupled receptors, thyroid autoantibodies, cytokines and biomarkers indicating organic and structural nerve damage.

Phosphatidylserine, Taurine, and Caffeine for Cognitive Fatigue in Professional Football Players

This randomized, double-blind, placebo-controlled, parallel-group trial evaluated neurocognitive fatigue resistance and football-specific decision-making following 28 days of taurine-caffeine supplementation with or without phosphatidylserine in professional male football players. Sixty-five male outfield football players from two professional clubs were randomized to placebo, taurine plus caffeine, or taurine plus caffeine plus phosphatidylserine. Neurocognitive fatigue resistance was evaluated during a standardized high-load Stroop/Flanker task, while football-specific tactical decision-making, visual-search behavior, and field-based reactive decision performance were assessed at baseline and after 28 days of supplementation.

Validating Immunological Markers Associated With Mental Fatigue in Graves' Disease

Mental fatigue occurs in many diseases and the reasons are mostly unknown. The investigators hypothesize that remaining mental fatigue after restored euthyroidism in Graves' disease is an autoimmune complication. This is a confirmatory study of the biomarkers from ImmunoGraves WP1 in which immunological markers with possible association with mental fatigue in Graves' disease are explored. In ImmunoGraves WP2, 310 patients with Graves' disease are assessed for symptoms of mental fatigue, quality of life, anxiety and depression, self-evaluated stress, coping strategies, personality traits, eye symptoms and background variables. Participants are examined in hyperthyroidism at inclusion, within three weeks from diagnosis, and in euthyroidism after 15 months. Serum and cerebrospinal fluid (in a subsample of participants) is collected at both visits and will be evaluated for the immunological markers identified in WP1 as well as for thyroid hormones, thyroid autoantibodies and biomarkers indicating organic and structural nerve damage. Significant predictors for mental fatigue will be identified by logistic regression. To assess functional changes in the brain, magnetoencephalography will be performed in a subset of patients and in healthy controls at inclusion and after 15 to 18 months. Combined with magneto resonance imaging (MRI), magnetoencephalography gives information on neuronal activation during attention testing.

Mindfulness, Mental Fatigue, Inhibitory Control and Endurance Performance in Athletes

This study investigated whether trait mindfulness in athletes is associated with impairments in neurocognitive function and endurance performance resulting from mental fatigue.

Sleep, Mental Fatigue, and Performance in Students

This observational, prospective, within-subject study will examine how the volume and timing of physiotherapy and psychology classes and exams at LUDES Institute influence mental fatigue, sleepiness, motivation, executive function, and physical performance in university students. Approximately 30 students aged 18 years or older will complete repeated assessments at baseline (no formal academic activities), during a regular theoretical class, and, when feasible, during an exam session. At each time point, participants will undergo non-invasive measurements including self-reported mental fatigue (visual analogue scale), sleepiness (Karolinska Sleepiness Scale), motivation (Motivational States Scale), cognitive performance (Encephalapp Stroop task), and handgrip strength and endurance with perceived exertion ratings, alongside sleep diaries and wrist actigraphy. The primary endpoint is the pre-to post-session change in mental fatigue and cognitive performance, with secondary endpoints capturing sleep and circadian metrics, physical performance, motivation, and exam grades. Mixed-effects models will be used to test how class/exam duration, time of day, sleep quantity and quality, and chronotype relate to psychobiological responses, with the goal of informing evidence-based scheduling and workload policies in health-profession education.

Mental Fatigue, Attentional Focus, and Countermovement Jump Performance

This study examines whether short-term mental fatigue and different jump instructions affect how high people can jump. Thirty-two physically active university students will complete two testing sessions in random order: one after a 30-minute mentally tiring computer task and one after a 30-minute relaxing video. In both sessions, participants will perform vertical jumps while receiving one of three types of instructions: no special instruction, focusing on their own body movements, or focusing on pushing the ground away. The study will compare jump height across these conditions to better understand how mental tiredness and coaching cues affect jumping performance, which may help coaches and athletes design better training and competition preparation.

Monitoring the Effect of Mental Fatigue on Physical Performance Using Wearable Sensors and Physiological Parameters

Mental fatigue (MF) negatively affects both cognitive and physical performance, increasing the risk of errors in high-stakes environments such as sports and surgery. Traditional methods to assess MF rely on subjective self-report scales, which are prone to bias, or on complex brain measurements (e.g. EEG) that are impractical outside laboratory settings. This study aims to develop a real-time, objective monitoring method for MF using wearable physiological sensors. The study will recruit healthy, trained runners (18-35 years old) who will complete both an MF-inducing cognitive task (Stroop test) and a control condition (watching a documentary) in a randomized, counterbalanced, crossover design. Heart rate variability, respiration rate, and pupil metrics will be continuously recorded using wearable devices. Machine learning models will be used to predict MF-level as well as the effect of MF on physical performance (5-km time trial on a treadmill) using the physiological data as input.

Effects of Mental Fatigue Duration on Cortical Activity and Jump Performance

"This study investigates whether the length of time spent on a mentally demanding task affects brain activity and jumping performance in physically active young men. Twelve healthy male university students, all regularly engaged in sport, completed four separate testing sessions on different days, each at least 72 hours apart. In one session (the control condition), participants watched a calm nature documentary. In the other three sessions, mental fatigue was induced by having participants perform a demanding attention task (the Stroop color-word test) continuously for 10, 15, or 30 minutes. Before and after each session, brain activity was recorded using electroencephalography (EEG), a painless method that measures electrical activity through sensors placed on the scalp. Immediately afterward, participants performed a countermovement jump test, a standard measure of explosive leg power used in sports science. The study examines whether longer periods of mental fatigue produce progressively larger changes in brain activity and jump performance, and whether changes in brain activity are related to changes in jumping ability. The findings may help athletes, coaches, and students better understand how mentally tiring activities, such as studying or exams, could affect physical performance shortly afterward."

The Effect of Brain Endurance Training on Motor Skill Learning in Adolescents With Mild Mental Fatigue

Objective: To investigate the effects of brain endurance training on improving motor skill learning in adolescents with mild mental fatigue. Methods: Fifty-eight adolescents experiencing mild mental fatigue were recruited. A 6-week training program was conducted using a 2 (BET group, control group) × 2 (pre- and post-Stroop task) × 3 (0, 3, 6 weeks) mixed-design experimental design. Assessments included basketball free throws, the Visual Analog Scale (VAS-MF), the 3-minute Psychomotor Vigilance Test (PVT-B), the Borg Rating of Perceived Exertion (RPE) to assess performance before and after a 30-minute Stroop task.

The Effects of Caffeine and Vitamin C on Maximum Strength and Strength Endurance in Adolescents With Mild Mental Fatigue

Objective To investigate the independent and combined effects of caffeine and vitamin C on maximal strength and strength endurance in female adolescents with mild mental fatigue. Methods A randomised, double-blind, crossover experimental design was adopted. Forty female college students presenting mild mental fatigue were recruited as participants. Each participant completed five laboratory sessions in total. The first session determined their one-repetition maximum (1RM) for bench press and back squat. The remaining four experimental sessions involved four supplement interventions administered in random order: placebo control, vitamin C (VC) alone, caffeine (CAF) alone, and combined caffeine plus vitamin C (CAF+VC). A one-week washout interval was arranged between every two supplementation trials. In each test session, participants completed a 45-min Stroop task to induce mental fatigue prior to exercise assessments. Measurements included the Visual Analogue Scale for Mental Fatigue (VAS-MF), 1RM bench press and squat performance, as well as the maximal number of repetitions at 65% 1RM for both movements. Immediately after the strength endurance test, perceived exertion and muscle pain were rated. Blood glucose and blood lactate concentrations were sampled before and after all exercise protocols. Supplementation was administered 1 hour prior to testing: a standard caffeine dosage of 3.0 mg per kg body mass and a single 500 mg dose of vitamin C were provided for the corresponding intervention groups.

Effects of Cognitive Fatigue on Gait

The goal of this study is to comprehend how mental fatigue could affect human gait. The main questions to answer are: * Does mental fatigue change how people walk? * How long does it take for walking patterns to return to normal after mental fatigue sets in? * What role do constructs like boredom, sleepiness, and motivation play in this relationship? To achieve this, participants will take part in the experiment, split into two sessions: Day 1 (online, about 25 minutes): Practice session. Participants will practice a computer task that will be used to induce mental fatigue in the next session. Day 2 (in-person, about 1.5 to 2 hours): Participants will wear several wearable sensors: motion sensors on their legs, feet, and back, sensor insoles in their shoes, a cap that measures brain activity, and glasses that track eye movement. After sensor placement, participants will walk in a straight line for 10 meters to measure their normal walking pattern. They will then complete a 32-minute computer task designed to induce mental fatigue. Afterward, participants will walk in a straight line for 10 meters again, rest for 3 minutes, and repeat this walk-and-rest cycle 3 more times. Participants will also answer short questions about how tired, bored, and alert they feel throughout the session.

Effects of Different Nap Durations on Volleyball Performance and EEG Activity Following Mental Fatigue

Mental fatigue is known to impair cognitive and physical performance in athletes, but the effectiveness of different nap durations in counteracting these effects remains unclear. The purpose of this randomized crossover study is to investigate the effects of mental fatigue and different nap durations (20, 40, 60, and 90 minutes) on volleyball-specific performance and electroencephalographic (EEG) activity in trained male volleyball players. Mental fatigue is induced using a 15-minute Stroop task. Performance outcomes include the Volleyball Agility Test (VAT) and Countermovement Jump (CMJ), while cortical activity is assessed using resting-state EEG recordings. The findings are expected to improve understanding of the neurophysiological mechanisms underlying mental fatigue and recovery and to provide evidence-based recommendations regarding optimal nap duration for athletes.

Muscular Fatigue vs. Mental Fatigue on Balance, Proprioception and Reaction Time

This study aims to understand how different types of fatigue affect balance and reaction time, proprioception, and fine motor in healthy young adults. Fatigue is a common experience in daily life and can arise from physical activity or prolonged mental effort. The study seeks to determine whether fatigue of the upper body, lower body, or mental fatigue from cognitively demanding tasks can negatively affect balance and reaction time, proprioception, and fine motor abilities. To examine this, participants will undergo controlled fatigue protocols designed to tire specific parts of the body or the mind. the Upper body fatigue will be induced through repeated maximal push-up sets performed until the participant can no longer maintain proper form. Lower body fatigue will be created through repeated maximal 1-minute squat jump sets, with participants touching a low box to ensure standardized depth and proper movement. Mental fatigue will be induced using a 20-minute computer-based cognitive task that alternates between the 2-back working memory task and the numerical Stroop task. These tasks are designed to require continuous attention, mental effort, and inhibitory control. Each type of fatigue will be induced independently, and participants' performance will be measured before and after each fatigue protocol. Following fatigue induction, participants will complete a series of tests designed to assess balance and reaction time, proprioception, and fine motor abilities. This includes both static and dynamic postural tasks, as well as reaction time and proprioceptive accuracy assessments. By evaluating these measures before and after fatigue, the study will determine how different forms of physical and mental fatigue impact postural stability, sensory processing, and precise motor control. The study addresses the question: "Do upper body fatigue, lower body fatigue, or mental fatigue reduce balance and reaction time, proprioception, and fine motor performance in healthy young adults?" The hypothesis is that each form of fatigue upper body, lower body, or mental-will meaningfully impair balance and reaction time, proprioception, and fine motor performance compared to non-fatigued conditions.

Virtual Reality Training on Technical Skills, Training Load and Mental Fatigue in Football

Virtual reality (VR) technology has emerged as a promising supplementary training tool in football, yet no study has simultaneously examined its effects on technical skills, training load, and mental fatigue within a randomized controlled design. This study evaluated the effects of an 8-week Rezzil Index® VR training program on football-specific technical skills, training load (sRPE), and mental fatigue in licensed male football players. Twenty-four male football players (age: 18.82±0.85 years) were randomly assigned to a VR training group (n=12) or a control group (n=12). The VR group completed two supplementary sessions per week using the Rezzil Index® application (HTC Vive Pro and Oculus Quest 2) in addition to regular team training. Football-specific technical skills, mental fatigue (Modified Color-Word Stroop Test), and training load (session RPE) were assessed pre- and post-intervention. The VR group demonstrated statistically significant improvements in all technical skill measures (p\<0.05; d=0.91-1.69, large effects). Rezzil Index® VR training is an effective complementary method for improving football-specific technical skills.

A Multi-Dimensional Comparative Study of Exercise Psychological Experience Under AI Fitness Companion and Human Coach Paradigms

This study conducted a comparative analysis of subjective exercise experiences between an AI-based fitness companion and traditional human coaching among 98 university students participating in a standardized 20-minute functional circuit training session. Participants were evaluated across three psychological dimensions: Emotional Resonance (ER), Interactive Dynamics (InD), and Embodied Presence (EP). The results indicated that human coaching elicited significantly higher levels of Emotional Resonance, whereas AI-based companions demonstrated superior performance in Interactive Dynamics. No significant differences were observed in Embodied Presence, suggesting that contemporary AI systems can provide spatial immersion and body-awareness comparable to human coaches. These findings indicate that AI and human coaches offer distinct psychological strengths, suggesting that AI should be viewed as a complementary, scalable tool for exercise guidance rather than a direct replacement for human emotional support.

Psychological Impacts of Exercise Snacks Versus Traditional Exercise: A Comparative Study

This study investigates the comparative psychological impacts of a high-frequency "Exercise Snacks" (ESG) protocol versus a traditional continuous exercise (TEG) regimen on healthy young adults. Utilizing a randomized controlled trial design over a 4-week longitudinal period, 180 participants were allocated into two groups of 90, with a standby recruitment protocol employed to ensure sample size stability. The intervention was standardized to equate total weekly exercise volume at 90 minutes. The TEG cohort performed 30-minute continuous cycling sessions three times per week, whereas the ESG cohort executed 15-minute distributed cycling sessions six times per week. To ensure physiological homogeneity and precision in workload prescription, individual baseline maximal aerobic capacity was assessed via incremental cardiopulmonary exercise testing. Based on these individual thresholds, exercise intensity for both cohorts was rigorously maintained at 40% of their respective maximal aerobic capacity throughout the intervention. Psychometric outcomes were evaluated within 24 hours of the intervention's conclusion, focusing on three dimensions: Perceived Stress, Decision Fatigue and Cognitive Load, and Physical Activity Enjoyment. By applying Lazarus and Folkman's Transactional Model of Stress and Coping, Sweller's Cognitive Load Theory, and Self-Determination Theory, this research examines how fragmented exercise protocols interact with daily workflow and self-regulatory resources. The findings provide critical insights into the real-world viability, behavioral resistance, and psychological divergence associated with high-frequency, fragmented exercise routines compared to conventional models.

Mental Fatigue Effects on Posture and Spinal Reflexes

This randomized crossover study investigates the effects of mental fatigue on postural control and spinal reflex excitability in healthy physically active adults aged 18-35 years. Participants will complete two experimental conditions: a mentally fatiguing Stroop task and a control condition involving passive documentary watching, separated by at least 48 hours. Postural control will be assessed using force plate measures of center of pressure displacement during bipedal and unipedal stance, with and without concurrent cognitive dual-tasking. In parallel, spinal reflex excitability will be evaluated using H-reflex recordings from the triceps surae muscles across sitting and standing postures. The primary aim is to determine whether mental fatigue increases postural sway, particularly in more challenging balance conditions such as single-leg stance. The secondary aim is to examine whether mental fatigue alters the normal modulation of spinal reflex excitability across progressively demanding postural tasks. Additional biomechanical and neuromuscular measures, including EMG activity and hip kinematics, will be recorded to provide insight into underlying control mechanisms. The study will include approximately 26 participants, with each serving as their own control. Data will contribute to understanding how cognitive fatigue influences balance control and spinal-level neuromuscular regulation.

The Effect of Mental Fatigue on Upper Extremity Functional Performance

Mental fatigue (MF) is known to impair cognitive performance and may negatively affect physical performance. While its effects on lower-extremity functional performance have been investigated, little is known about the influence of MF on upper-extremity physical performance tests commonly used in sports and rehabilitation settings. This randomized crossover study will investigate the effects of experimentally induced mental fatigue on upper-extremity physical performance in 16 healthy physically active adults. Participants will complete both a mental fatigue condition, involving a prolonged Stroop task, and a control condition consisting of watching an emotionally neutral documentary. Before and after each condition, participants will perform the Upper Quarter Y Balance Test, Reactive Upper Quarter Y Balance Test, Closed Kinetic Chain Upper Extremity Stability Test, and Seated Single-Arm Shot Put Test. Subjective mental fatigue, cognitive performance, motivation, and perceived exertion will also be assessed. The findings will improve understanding of whether mental fatigue influences upper-extremity physical performance test outcomes and may assist clinicians and researchers in interpreting these assessments in sports medicine and rehabilitation contexts.

Impact of Astaxanthin on Cognition in Recreationally Active Females

The purpose of this study is to examine the protentional that the antioxidant Astaxanthin has on mitigating cognitive decline following mental fatigue.