What question did this study set out to answer?

To determine whether electroencephalographic (EEG) and autonomic nervous system responses to high-intensity exercise differ between morning and evening exercise sessions in middle-aged women.

October 1, 2026Physical Activity and NutritionOpen Access

Effects of morning versus evening high-intensity exercise on electroencephalographic and autonomic responses in middle-aged women

Q: What are the key findings of this study?

Morning high-intensity exercise elicited significantly greater increases in the theta-to-beta ratio (interaction p=0.010) and decreases in spectral edge frequency compared to evening exercise.

Q: What is the clinical evidence from this study?

Study design: RCT. Population: Healthy middle-aged women (n=30). Intervention: Morning high-intensity exercise (6:00 am) vs. Evening high-intensity exercise (6:00 pm). Primary outcome: Theta-to-beta ratio (TBR) change from pre- to post-exercise (p=0.010).

Q: What does this research mean for the field?

Morning high-intensity exercise elicits significantly greater changes in electroencephalographic and autonomic responses than evening exercise in middle-aged women. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

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Key result

Morning high-intensity exercise boosts post-exercise theta-to-beta ratio significantly more than evening exercise.

P=0.010
n=30

Why the study?

The time of day at which exercise is performed influences physiological responses and performance, but differences in EEG and autonomic responses to morning versus evening exercise in middle-aged women were unclear.

Does morning high-intensity exercise alter electroencephalographic and autonomic responses differently than evening exercise in healthy middle-aged women?

Comparison

Morning high-intensity exercise at 6:00 am vs evening high-intensity exercise at 6:00 pm

Design

Randomized controlled trial

Follow-up

Immediately after exercise

Authors

JKJae-Myun KoYonsei University WSWi-Young SoKorea National University of Transportation JJJae-Hyun Jung

Discussion

Member takes

Implication

Morning high-intensity exercise yields greater acute EEG/autonomic shifts than evening sessions in middle-aged women; extends chronobiology of exercise timing for targeted trials.

Key Points

To determine whether electroencephalographic (EEG) and autonomic nervous system responses to high-intensity exercise differ between morning and evening exercise sessions in middle-aged women.
Thirty women aged 50-60 years were randomly assigned to exercise at either 6:00 am (morning exercise group) or 6:00 pm (evening exercise group) following 7 to 8 hours of sleep.
Resting EEG indices (theta-to-beta ratio [TBR] and spectral edge frequency at 90% [SEF-90]) and photoplethysmography-derived heart rate variability (HRV) indices were recorded pre-exercise and immediately post-exercise.
Outcomes were evaluated using a two-way mixed-design analysis of variance with simple effects and change-score analyses for significant interactions.
TBR and SEF-90 exhibited significant group × time interactions (TBR: F(1, 28) = 7.65, p = 0.010; SEF-90: F(1, 28) = 9.99, p = 0.004), with TBR rising from 3.40 ± 0.21 to 4.18 ± 0.31 in the morning group versus 3.61 ± 0.23 to 3.95 ± 0.26 in the evening group.
SEF-90 decreased from 15.33 ± 0.65 Hz to 14.52 ± 0.57 Hz in the morning group and from 15.71 ± 0.56 Hz to 15.21 ± 0.45 Hz in the evening group, showing a significantly larger pre-to-post change score in the morning group (p = 0.004).
HRV-derived sympathetic-related indices increased (group × time: F(1, 28) = 10.11, p = 0.004) and parasympathetic-related indices decreased (F(1, 28) = 9.27, p = 0.005) in both cohorts, with significantly greater change scores in the morning group (p = 0.004 and p < 0.01, respectively).

Study Design

Type

RCT (n=30)

Randomization

Randomly assigned

Multicenter

Structured PICO

Does morning high-intensity exercise alter electroencephalographic and autonomic responses differently than evening exercise in healthy middle-aged women?

Population

30 healthy middle-aged women aged 50-60 years without neurological or cardiovascular disease who performed a single session of high-intensity exercise.

Intervention

High-intensity exercise performed in the morning at 6:00 am (single session).

Comparator

High-intensity exercise performed in the evening at 6:00 pm (single session).

Outcome

Electroencephalographic (EEG) responses (theta-to-beta ratio [TBR] and spectral edge frequency at 90% [SEF-90]) and photoplethysmography-derived autonomic responses (HRV index, HRV-derived sympathetic-related and parasympathetic-related indices) measured at rest before and immediately after exercise.surrogate

Main Result

p-value: p=0.010

Morning high-intensity exercise elicits greater acute neurophysiological and autonomic responses than evening exercise in middle-aged women, suggesting that exercise timing influences physiological stress and recovery demands.

Limitations

EEG and autonomic indices were derived from device-embedded algorithms, representing indirect measures.
Ultra-short-term recordings may limit the physiological precision and stability of HRV-related measurements.
The single-session design did not account for potential adaptations to repeated exercise.
A significant baseline difference was observed for TBR between groups.
Chronotype, habitual wake-up time, sleep quality, and potential sleep inertia effects were not formally assessed.
The study population was limited to middle-aged women, restricting generalizability.
A between-subject rather than a crossover design was used, so individual differences in circadian responses could not be directly assessed.
EEG and autonomic indices derived from device-embedded algorithms represent indirect measures, and ultra-short-term recordings may limit physiological precision
Single-session design did not account for potential adaptations to repeated exercise
Significant baseline difference was observed for TBR
Chronotype, habitual wake-up time, sleep quality, and potential sleep inertia effects were not formally assessed
Study population was limited to middle-aged women, restricting generalizability
Between-subject rather than a crossover design prevented direct assessment of individual differences in circadian responses

Cite This Study

Ko et al. (2026) conducted an RCT in Healthy middle-aged women (n=30). Morning high-intensity exercise (6:00 am) vs. Evening high-intensity exercise (6:00 pm) was evaluated on Theta-to-beta ratio (TBR) change from pre- to post-exercise (p=0.010). Morning high-intensity exercise elicited significantly greater increases in the theta-to-beta ratio (interaction p=0.010) and decreases in spectral edge frequency compared to evening exercise.

synapsesocial.com/papers/6abda8ff4d657f10339f95a1 https://doi.org/10.20463/pan.2026.0036

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Implication

Morning high-intensity exercise yields greater acute EEG/autonomic shifts than evening sessions in middle-aged women; extends chronobiology of exercise timing for targeted trials.

Effects of morning versus evening high-intensity exercise on electroencephalographic and autonomic responses in middle-aged women

Discussion

Member takes

Implication

Key Points

Study Design

Structured PICO

Main Result

Limitations

Cite This Study

Effects of morning versus evening high-intensity exercise on electroencephalographic and autonomic responses in middle-aged women

Discussion

Member takes

Implication

Key Points

Study Design

Structured PICO

Main Result

Limitations

Cite This Study

Also Consider

Also Consider