Author(s): ALLEN PULUC, C., ABELN, V., ROJAS, S., Institution: DEUTSCHE SPORTHOCHSCHULE KÖLN, Country: GERMANY, Abstract-ID: 2497

INTRODUCTION:
High-intensity exercise is widely used in health promotion due to its time efficiency and cardiometabolic benefits. High-intensity interval training (HIIT) is well established, whereas high-intensity functional training (HIFT) integrates multimodal strength and endurance elements (Feito et al., 2018). Although cardiovascular responses to high-intensity exercise are well documented (Weston et al., 2014), its immediate effects on resting-state brain dynamics remain unclear. EEG microstates provide a validated framework to assess the temporal organization of whole-brain activity at rest (Michel & Koenig, 2018). This study compared the acute physiological and neurophysiological responses to HIIT and HIFT.


METHODS:
In a randomized, counterbalanced crossover design, thirty-nine healthy adults completed three conditions: HIIT, HIFT, and a non-exercise control session. Resting-state EEG was recorded before (PRE), 5 min after (POST1), and 45 minutes after (POST2) each condition. Physiological measures included oxygen uptake (VO2), carbon dioxide production (VCO2), heart rate (HR), blood lactate (LA), and blood pressure. EEG microstate parameters (global explained variance, duration, coverage, and occurrence) were extracted for four microstate classes. Statistical analyses were conducted using repeated-measures models with correction for multiple comparisons.
RESULTS:
HIFT elicited lower VO2, VCO2, and HR compared to HIIT (p < .001), while peak LA was higher following HIFT (p = .012). Immediate post-exercise systolic blood pressure was lower after HIFT compared to HIIT (p < .001), with no differences observed at 5 minutes post-exercise. Resting-state EEG microstate analysis revealed significant time-dependent modulation of several parameters across sessions. However, no statistically robust condition × time interaction survived correction for multiple comparisons. Time-dependent changes were also observed in the non-exercise control condition.
CONCLUSION:
Acute high-intensity exercise induced marked physiological stress responses that differed between HIIT and HIFT. In contrast, EEG microstate dynamics exhibited comparable temporal trajectories across all conditions. These findings indicate that exercise modality differentially affects acute cardiovascular load, whereas resting-state microstate reorganization primarily reflects a general time-related effect rather than a modality-specific neural response. These differences may be relevant for health-oriented exercise prescription, particu-larly in preventive contexts where cardiovascular load management is critical.