Glucose data regarding extreme elite performances in athletes without diabetes remains limited. The purpose is to characterize continuous glucose monitoring (CGM) responses in elite athletes across distinct high-performance contexts. This descriptive case series includes three separate elite athletes who used a CGM during their respective sporting events. The first is an ultra-endurance relay cycling world-record performance (Race Across the West, RAW), the second is a continuous high-intensity Everesting Challenge cycling record attempt, and the third is a maximal constant-weight no-fins breath-hold depth dive performed in international competition. Glycemic outcomes, as measured by CGM, included mean, maximum, and minimum glucose, glucose standard deviation (SD), and the percentage of time in tight glucose range (TITR: 70–140 mg/dL; 3.9–7.8 mmol/L), time below range (TBR: <70 mg/dL; 140 mg/dL; >7.8 mmol/L). Other performance data, including peak power, heart rate, and lactate, are also provided where available. During the RAW challenge lasting 44 h and 20 min, mean glucose was 91 ± 23.2 mg/dL (mean ± SD) with 9.15% TBR and 35.58% TITR during cycling and 115 ± 24.7 mg/dL with 9.11% TBR and 43.16% TITR during resting periods. In contrast, the Everesting Challenge cycling record attempt demonstrated a persistently elevated glucose profile (160 ± 5.7 mg/dL), minimal variability (CV 3.5%), and 100% TAR140. Following the maximal breath-hold depth dive, interstitial glucose was 100% TAR140 during recovery (187 ± 18.5 mg/dL), alongside marked elevations in blood lactate concentrations (peak 13.4 mmol/L). The series of case studies demonstrate that substantial deviations from traditional euglycemic ranges are common during elite performance in athletes without diabetes. Interpretation of CGM data in athletic settings should therefore be performance- and context-specific rather than based on clinical glycemic thresholds.

Background: High-intensity interval training (HIIT) is increasingly used in exercise-based cardiac rehabilitation (ebCR) after myocardial infarction (MI), yet the temporal sequence of physiological, cardiac, biochemical, and functional adaptations remains incompletely characterized. Methods: Stable post-STEMI (ST-segment elevation myocardial infarction, MI-group) and previously inactive participants without known cardiovascular, metabolic or systemic disease (CTRL group) completed 12-week supervised outpatient HIIT (4 × 4 min intervals at 85–90% HRpeak (peak heart rate), ~80–90% of VO₂peak, 3 sessions/week). Assessments were performed at baseline (T1), 4 (T2), 8 (T3), and 12 weeks (T4), including cardiopulmonary exercise testing (CPET), echocardiography, blood biomarkers, body composition, six-minute walk test (6MWT), and RAND-36. Longitudinal changes were analyzed using Friedman tests with Dunn post hoc comparisons; between-group differences used Mann–Whitney U tests with Holm correction. Results: VO₂peak increased significantly in both groups (p < 0.001), increasing by ~22% from T1 to T4 in MI (median 20.1 to 24.5 mL·kg⁻¹·min⁻¹) and ~23% from T1 to T4 in CTRL (median 22.3 to 27.6 mL·kg⁻¹·min⁻¹). LVEF (left ventricular ejection fraction) improved early in MI, increasing from 52.5% (50.0–55.0) at T1 to 57.5% (55.2–58.7) at T2 and up to 60% (55.8–60.0) at T4 (all p < 0.001), while LV dimensions remained stable. NT-proBNP (N-terminal pro-B-type natriuretic peptide) showed no significant longitudinal change (p = 0.510), and CRP (C-reactive protein) decreased from 2.1 to 0.7 mg·L⁻¹ (p = 0.008) in MI. Both groups improved body fat % and 6MWT distance (p < 0.001). Conclusions: In low-risk stable post-STEMI patients, longitudinal changes during supervised HIIT-based ebCR were consistent with improved VO₂peak and LVEF, without clinically relevant increases in cardiac stress biomarkers. However, due to the observational design and absence of clinical comparator groups, these findings should be interpreted as descriptive and support further evaluation in larger randomized studies.