The goal of this clinical trial is to learn how different running environments affect physiological responses, emotional regulation, exercise motivation, and attentional control in healthy college students. The main questions it aims to answer are:

How do different running environments (indoor treadmill, outdoor road, and outdoor grass) affect physiological stress and recovery, such as heart rate variability, blood pressure, cortisol, and blood lactate levels?

Are there differences in subjective emotional experiences, perceived recovery, and exercise motivation when running in natural versus artificial environments?

Does the running environment influence post-exercise cognitive performance, specifically inhibitory control and sustained attention?

Researchers will compare indoor treadmill running, outdoor road running, and outdoor grass running to see if natural environments provide greater benefits for stress relief, mood improvement, and cognitive enhancement.

Participants will:

Attend three separate 70-minute experimental sessions (one for each environment) with at least 48 hours between sessions.

Complete baseline physiological measurements (HRV, blood pressure, saliva, and blood samples), psychological questionnaires, and computerized cognitive tasks.

Complete a 30-minute moderate-intensity running session in the randomly assigned environment while wearing a heart rate monitor.

Repeat the physiological measurements, psychological questionnaires, and cognitive tasks immediately and 10 minutes after the running session.

This study employs a randomized, counterbalanced crossover design to investigate the acute effects of three different running environments (indoor treadmill, outdoor road, and outdoor grass) on physiological, psychological, and cognitive outcomes. Each of the 30 healthy college student participants will complete three experimental sessions corresponding to the three environments. To eliminate carry-over effects and fatigue accumulation, a minimum washout period of 48 hours is strictly mandated between each experimental session.

The experimental procedures for each session are highly standardized, lasting approximately 70 minutes in total, and are structured into three main phases:

Pre-Exercise Baseline Assessment (approx. 20 minutes) Upon arrival, participants will undergo a brief health and safety screening. Researchers will then collect resting baseline physiological data, including Heart Rate Variability (HRV), Blood Pressure (BP), salivary cortisol, and blood lactate samples. Following physiological sampling, participants will complete subjective psychological scales (assessing mood state, exercise enjoyment, and perceived recovery) and perform three computerized cognitive tasks: the Stroop task (assessing attention control and inhibition), the Go/No-Go task (assessing response inhibition), and the Psychomotor Vigilance Task (PVT) (assessing sustained attention and reaction speed).

Running Intervention Phase (30 minutes) Participants will perform a 30-minute moderate-intensity running session in their randomly assigned environment for that session (indoor sports venue for treadmill, campus athletic track for outdoor road, or campus lawn area for grass). Exercise intensity is continuously monitored and controlled using heart rate devices by the research team to ensure safety and standardization across all conditions.

Post-Exercise Assessment Phase (approx. 20 minutes) Immediately following the 30-minute run, and again at 10 minutes post-exercise, physiological measurements (HRV, BP, salivary cortisol, and blood lactate) will be repeated to evaluate the recovery process. Participants will also complete post-exercise psychological scales and retake the three computerized cognitive tasks (Stroop, Go/No-Go, PVT).

This rigorous methodology ensures that any observed differences in physiological stress regulation, emotional state, and executive function can be reliably attributed to the modulatory effects of the specific running environment.

Inclusion Criteria:

• Full-time college students aged 18 to 25 years old.
• Healthy, with no history of major cardiovascular, respiratory, neurological, or endocrine diseases.
• No exercise contraindications or injuries, capable of safely completing moderate-intensity running (treadmill, outdoor road, and grass running).
• No recent major life events affecting physiological or psychological status (e.g., severe insomnia, anxiety, depression, or extreme fatigue).
• No use of medications or supplements affecting heart rate, blood pressure, mood, or attention within the past week.
• Normal or corrected-to-normal vision, capable of completing computerized cognitive tasks (e.g., Stroop, Go/No-Go, PVT).
• Able to comprehend and truthfully complete psychological scales.
• Voluntary participation and signed informed consent form.

Exclusion Criteria:

• Current or past diagnosis of severe cardiovascular disease (e.g., myocardial infarction, severe arrhythmia, uncontrolled hypertension).
• Severe respiratory disease (e.g., severe asthma, COPD) or recent acute respiratory infection within the past month.
• History of neurological disease or brain injury (e.g., epilepsy, recent concussion) affecting safety or cognitive task performance.
• Endocrine or metabolic diseases (e.g., uncontrolled thyroid disease, severe diabetes) affecting cortisol or metabolic measurements.
• Recent diagnosis or psychiatric treatment for severe psychological disorders within the past month.
• Use of drugs or supplements affecting heart rate, blood pressure, cortisol, or attention within the past 7 days.
• Currently pregnant or lactating.
• Acute illness within the past 48 hours (e.g., fever, acute gastroenteritis).
• Severe bleeding tendencies, blood disorders, or contraindications to blood/saliva sampling.
• Recent substance use interference, such as heavy drinking or substance dependence within the past 2 weeks.
• Inability to meet pre-experiment control requirements (e.g., avoiding caffeine, tobacco, or heavy exercise).
• Inability to complete computerized tasks due to poor vision or lack of familiarity with keyboard/mouse.
• Acute or chronic injuries hindering the safe completion of running intervention (e.g., recent lower limb injury).
• Participation in similar HIT or environmental intervention studies within the past 3 months.
• Unable to understand research procedures or unwilling to sign the informed consent form.