Lower Limb Strength and Power as Predictors of Brain Blood Flow During Exercise

Lincoln University College256 enrolled

Overview

This study aims to investigate the predictive value of lower limb muscle strength and explosive power on exercise-induced prefrontal hemodynamic responses. Using an interpretable machine learning framework (GCAT-Net), the research analyzes how various physical performance indicators-such as isokinetic muscle strength, 1RM leg press, and vertical jump metrics-can predict oxygenated hemoglobin (ΔHbO) changes in the bilateral dorsolateral prefrontal cortex (DLPFC) during moderate-intensity cycling.

Study Type

INTERVENTIONAL

Allocation

Purpose

BASIC_SCIENCE

Masking

NONE

Enrollment

256

Conditions

Prefrontal Hemodynamics Muscle Strength Physical Performance

Interventions

Participants undergo a comprehensive physiological and biomechanical assessment protocol divided into three phases. First, demographic and morphological data (Age, Sex, BMI, and Body Fat %) are collected, followed by a maximal oxygen consumption (VO\_2max) test using a Bruce-modified ramp protocol on a cycle ergometer. Second, participants complete a standardized lower-limb neuromuscular battery, including isokinetic strength testing at 60°/s (peak torque for knee, hip, and ankle) via a Biodex System 4 Pro, a 1RM leg press, and explosive power assessments comprising Countermovement Jumps (CMJ), Squat Jumps (SJ), and 30m sprints. Finally, cortical hemodynamic activity is monitored using a 16-channel fNIRS system (NIRSport2) over the bilateral dorsolateral prefrontal cortex (DLPFC) during a 6-minute constant-load cycling task at 60% VO\_2max.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 60 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: 1. Healthy adults aged between 18.00 and 60.00 years. 2. Must be able to perform standardized lower-limb physical assessments, including isokinetic strength testing and explosive power tests (e.g., CMJ, SJ, and 30m sprints). 3. Capability to complete a 6-minute aerobic cycling task at a moderate intensity (60% VO\_2max). 4. Physically cleared for exercise as determined by a Physical Activity Readiness Questionnaire (PAR-Q). 5. Willingness to undergo functional near-infrared spectroscopy (fNIRS) monitoring with a Scalp Coupling Index (SCI) ≥ 0.7. Exclusion Criteria: 1. History of musculoskeletal injuries to the lower limbs within the past 6 months that would impede maximum voluntary contraction (MVC) or high-intensity efforts. 2. Known cardiovascular, respiratory, or neurological conditions that contraindicate maximal exercise testing (VO\_2max ramp protocol). 3. Body Mass Index (BMI) or health status that prevents the safe completion of high-impact explosive power tests like the 30cm drop jump (RSI assessment). 4. Presence of excessive motion artifacts or poor fNIRS signal quality, specifically a Signal-to-Noise Ratio (SNR) \< 5 dB or motion artifact frame ratio ≥$ 10%.

Outcomes

Primary Outcomes

Area Under the Curve of Oxygenated Hemoglobin (Δ HbO AUC) during Aerobic Exercise

Cortical hemodynamics are measured using the NIRSport2 fNIRS system over the bilateral dorsolateral prefrontal cortex (DLPFC).

Time frame: Measured during the 6-minute constant-load cycling task (60%VO_2max), which occurs approximately 120 minutes after the start of the experimental session.

Secondary Outcomes

Demographic and Morphological Baseline Profile

Collection of foundational participant data including Age, Height (InBody H20N), Weight, BMI, and Body Fat % (InBody 770 via multi-frequency bioelectrical impedance). Resting Heart Rate (RHR) is recorded after 5 minutes of quiet rest.

Time frame: Baseline (Minutes 0-20 of the session).

Isokinetic Neuromuscular Strength Battery

Evaluation of lower-limb strength using a Biodex System 4 Pro at an angular velocity of 60°/s. Metrics include peak torque for knee extension/flexion, hip extension, and ankle plantarflexion, as well as the 1RM leg press and Hamstring/Quadriceps (H:Q) ratio.

Time frame: Post-baseline assessment (Minutes 30-60 of the session).

Explosive Power and Functional Performance Metric

Assessment of neuromuscular power through Countermovement Jump (CMJ), Squat Jump (SJ), Reactive Strength Index (RSI via 30cm drop jump), 30m sprint time, and standing long jump. Functional strength is measured using the Five Times Sit-to-Stand (FiveTSTS) test.

Time frame: Following isokinetic testing (Minutes 70-90 of the session).

Peak Cardiorespiratory Capacity (VO_2max)

Maximal oxygen consumption determined through a Bruce-modified ramp protocol (25 W starting load, increasing 25 W/min) on a cycle ergometer until volitional exhaustion.

Time frame: Final physical assessment before the hemodynamic task (Minutes 100-120 of the session).