Impact of Acute Exercise on Autonomic Nervous System Regulation in College-Aged Adults: A Comparative Study Using Heart Rate Variability and Baroreflex Sensitivity

Project Abstract

Acute aerobic exercise is known to transiently alter autonomic nervous system (ANS) balance, yet comparative data on heart rate variability (HRV) indices and baroreflex sensitivity (BRS) in college-aged adults remain limited. This study investigates the immediate and short-term autonomic responses to a standardized bout of moderate-intensity exercise and contrasts HRV-derived autonomic modulation with baroreflex function, providing a comprehensive profile of ANS adjustments. A randomized, crossover design was employed involving 40 healthy college-aged participants (18–25 years; 20 males, 20 females) who completed two sessions a graded treadmill exercise bout at 60–70% maximal heart rate reserve and a resting control condition, separated by a one-week washout period. HRV metrics were derived from 5-minute resting and post-exercise electrocardiogram (ECG) recordings, including time-domain measures (SDNN, RMSSD, pNN50), frequency-domain components (LF, HF, LF/HF ratio), and non-linear indices (Poincaré plot descriptors). Baroreflex sensitivity was assessed using sequences (up-up and down-down) and the transfer function method to quantify spontaneous BRS in both pre- and post-exercise windows. Primary outcomes focused on time- and frequency-domain HRV changes and BRS magnitude and gain, with secondary analyses examining sex differences and correlations between HRV indices and BRS estimates. The results demonstrated an immediate rise in heart rate and a reduction in overall HRV following exercise, characterized by decreased RMSSD and HF power and an elevated LF/HF ratio, consistent with a rapid withdrawal of parasympathetic tone and heightened sympathetic modulation during recovery. BRS showed a transient attenuation immediately post-exercise, indicated by lower sequence slope values and reduced transfer function gain, suggesting diminished baroreceptor-cardiovascular reflex sensitivity in the post-exercise period. Over the 30-minute recovery interval, HRV parameters gradually returned toward baseline, with partial restoration of parasympathetic markers and normalization of the LF/HF ratio, while BRS gradually recovered but remained suppressed relative to baseline at 30 minutes. Sex-specific analyses revealed a tendency for females to exhibit faster parasympathetic reactivation post-exercise, reflected by quicker RMSSD and HF recovery, though HRV-BRS relationships remained broadly concordant across sexes. Correlation analyses indicated that post-exercise reductions in HRV, particularly RMSSD and HF power, were moderately associated with decreases in BRS, implying a linked autonomic downregulation of cardiac vagal activity and baroreflex control during acute stress. The study underscores the complementary value of combining HRV and BRS assessments to capture nuanced ANS dynamics following acute exercise in young adults. Findings have implications for exercise prescription, cardiovascular risk stratification in populations with autonomic dysfunction, and the design of interventions aiming to optimize autonomic recovery after strenuous activity. Limitations include the homogeneous, healthy sample and the short-term observation window, suggesting avenues for future work to explore diverse populations, longer follow-up, and the influence of varying exercise modalities.

Project Overview

What This Project Is About

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A plain-language overview of how the body’s automatic system controls heart and blood vessel function changes after a short period of exercise. The project compares how these changes show up in different people by looking at two measures: heart rate variability (how heart rate varies over time) and baroreflex sensitivity (how well the body adjusts blood pressure). It asks whether quick exercise affects these controls in a similar way across college-aged adults and what that might mean for health or exercise planning.

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The Problem It Addresses

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Many studies focus on long-term fitness or clinical patients, but less is known about how a single session of exercise immediately shifts autonomic regulation in normal young adults. Understanding this helps explain who benefits most from physical activity, guides safe exercise recommendations, and could point to simple tests that track how well the body adapts to exercise in everyday settings.

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Objectives of the Project

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1. Describe how acute exercise changes heart rate variability and baroreflex sensitivity in college-aged adults.
2. Compare responses between individuals of different fitness levels.
3. Identify patterns that indicate good autonomic adjustment after exercise.
4. Discuss practical implications for exercise guidance and health monitoring.

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What You Will Do Step by Step

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1. Recruit a small group of college-aged participants with varying fitness backgrounds.
2. Have participants perform a standardized short exercise session.
3. Record heart rate data before, during, and after exercise using a wearable or chest strap sensor.
4. Estimate heart rate variability from the data and assess baroreflex sensitivity with simple, noninvasive tests.
5. Analyze how the measurements change post-exercise and compare across participants.
6. Interpret findings in light of existing literature and discuss limitations.

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Expected Outcome

The project is expected to show measurable short-term shifts in autonomic control after acute exercise, with clearer patterns in some fitness groups. It should provide practical takeaways for tailoring exercise plans and highlight potential simple indicators for monitoring post-exercise autonomic recovery.