# Influence of Two Exercise Programs on Heart Rate Variability, Body Temperature, Central Nervous System Fatigue, and Cortical Arousal after a Heart Attack PMID: 36612521 Journal: International Journal of Environmental Research and Public Health Published: 2022-12-23 Authors: Gonçalves C, Parraca JA, Bravo J, Abreu A, Pais J, Raimundo A, Clemente-Suárez VJ ## Question What physiological differences in thermography, heart-rate variability, blood pressure, central nervous system fatigue, and cortical arousal occur during HIIT versus MICT in heart-attack patients in cardiac rehabilitation compared with healthy participants? ## Summary This very small case-control study compared acute treadmill HIIT and moderate-intensity continuous exercise responses in two male heart-attack patients in phase III cardiac rehabilitation and two healthy male controls. One participant was assigned to each of four groups: cardiac HIIT, cardiac MICT, control HIIT, and control MICT. The study measured thermography, heart-rate variability, blood pressure, subjective fatigue, and cortical arousal before, during, or after one supervised treadmill session. The authors reported that heart-attack patients showed higher sympathetic modulation and that MICT produced higher subjective fatigue in heart-attack patients than HIIT, but the sample size makes the evidence exploratory. ## Population - Two male heart-attack patients in phase III cardiac rehabilitation two months after angioplasty plus two healthy male controls without cardiovascular disease. - Sample size: 4 - Age: Heart-attack patients 35 and 48 years; controls 38 and 46 years. - Sex: All male. - Fitness level: VO2peak: HAP HIIT 30.7, HAP MICT 30.4, control HIIT 33.3, control MICT 32.7 mL/kg/min. - Health status: Heart-attack patients had LVEF 52% and 46%, diabetes mellitus and dyslipidemia; one had hypertension. Controls had no cardiovascular disease. ## Methodology - Case-control acute exercise study with randomized 1:1:1:1 allocation to cardiac HIIT, cardiac MICT, control HIIT, or control MICT - Single treadmill exercise session - Hospital and laboratory cardiac rehabilitation context in Evora, Portugal - Randomized and controlled study design. ## Protocol - HIIT. - Modality: Treadmill. - Work intervals: Unclear; article states a total of 20 min at 85-95% peak heart rate. - Recovery: 1 min at 40% peak heart rate. - Intensity: 85-95% peak heart rate, with Borg 15-17 target during high-intensity exercise. - Session duration: 5-10 min warm-up plus HIIT trial plus 5 min cool-down; exact total duration unclear. - Program length: Single acute treadmill session. - Progression: Participants were motivated to gradually increase intensity toward Borg 15-17 during high-intensity exercise. - MICT. - Modality: Treadmill. - Work intervals: Continuous exercise. - Sets or repetitions: One continuous bout. - Intensity: 70-75% peak heart rate. - Session duration: 27.5 min continuous bout, plus 5-10 min warm-up and 5 min cool-down. - Program length: Single acute treadmill session. ## Outcomes ### Subjective fatigue Status: mixed In heart-attack patients, fatigue increased from 10.0 +/- 0.0 to 67.5 +/- 3.5 after HIIT and from 10.0 +/- 0.0 to 85.5 +/- 3.5 after MICT; controls changed from 10 to 65 after HIIT and 10 to 40 after MICT. ### Stress index Status: mixed Heart-attack patients had higher stress index than controls. In HAP HIIT, stress index was 12.4 +/- 1.9 pre, 25.3 +/- 6.6 during exercise, and 21.3 +/- 6.2 post; in HAP MICT it was 16.3 +/- 2.1 pre, 19.4 +/- 2.9 during exercise, and 35.7 +/- 15.4 post. ### RMSSD Status: no clear change The authors reported no significant interaction or main effects in RMSSD. No significant interaction or main effects reported; exact p-values not provided in extracted text. ### Thermography Status: mixed Temperature generally decreased from pre to post in most body variables, except right hand temperature increased in both HIIT groups and MICT groups maintained right hand temperature. Chest temperature difference was greater in heart-attack patients than controls. ### Blood pressure Status: mixed Heart-attack patient systolic blood pressure decreased from 130.0 +/- 26.9 to 121.0 +/- 12.7 after HIIT and from 132.5 +/- 19.1 to 124.0 +/- 18.4 after MICT; diastolic blood pressure changed from 80.0 +/- 14.1 to 77.0 +/- 2.8 after HIIT and from 66.5 +/- 13.4 to 73.0 +/- 1.4 after MICT. Authors concluded no differences in systolic and diastolic blood pressure between HIIT and MICT in heart-attack patients. ### Cortical arousal Status: no clear change The results section states there were no differences in cortical arousal outcomes between groups. ## Practical Insights - This paper is best used as safety-boundary and monitoring context for clinical HIIT after heart attack, not as a consumer programming source. - The protocol combined heart-rate targets, Borg RPE, cardiac symptom monitoring, medical evaluation, and supervised graded exercise testing. - The article suggests interval recovery may reduce subjective fatigue versus continuous training in heart-attack patients, but the sample is too small for firm claims. - Exact HIIT interval count and work-bout duration are not reported clearly enough for direct workout reproduction. ## Limitations - Only four male participants, with one participant in each group cell. - Case-control/case-report evidence with acute responses only. - No longitudinal training outcomes, adherence, or clinical events were measured. - Indirect cortical arousal measurement; authors state EEG would better explain cortical responses. - Exact HIIT work-interval duration and repetition count are unclear. ## Safety And Adherence - No adverse event results were explicitly reported. - Heart-attack patients were referred by cardiologist with low-risk medical recommendations and evaluated by a cardiologist. - Participants completed a supervised graded exercise test before intervention to record volitional fatigue, risks, or symptoms of ischemia. - ECG was recorded continuously during the graded test and blood pressure was measured every 3 minutes. - During training, heart rate, Borg RPE, and cardiac symptoms were considered. ## Original Sources - [PubMed](https://pubmed.ncbi.nlm.nih.gov/36612521/) (pubmed) - [DOI](https://doi.org/10.3390/ijerph20010199) (doi) - [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9819636/) (full text) ## Agent Guidance Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.