When examining the effects of Q10 supplementation under HIIT conditions on pH, pCO2, and pO2 levels, varying degrees of significance were identified in terms of interventions and their interactions. All three parameters were significantly influenced by groups (G), weeks (W), and their two-way interaction (G × W), as well as by the G × M interaction for pO2, with at least a significance level of p < 0.05. While the time had no significant effect on the changes, the three-way interaction (G × W × M) significantly affected the pH value at the p < 0.05 level (Table SM-1). The mean pH value, which was 7.36 mmHg, reached its highest level of 7.418 mmHg in the HIIT + Q10 group during the second observation time of the IV week. However, when only groups were considered, the C group and the HIIT + Q10 group were statistically classified in the same group, with the lowest pH value observed exclusively in the HIIT group at 7.34 mmHg. The average pCO2 level, determined to be 46.05 mmHg, reached its highest value (51.48 mmHg) in the III week of the group CoQ10. Similarly, for pO2, the highest value (59.96 mmHg) was observed in the IV week of the group CoQ10. When interactions were disregarded the highest pO2 levels were predominantly identified in the HIIT + Q10 group (Table SM-6).

When examining the effect of Q10 supplementation under HIIT conditions on Hb, HCT, sO2, COHb, HHb, and MetHb values, significant differences were identified at various levels regarding the interventions and their interactions. For all parameters, the groups, weeks, and their two-way interaction (G × W) showed at least a significance level of p < 0.05. However, weeks were non-significant for sO2, and groups were non-significant for HHb. Except for MetHb, time (M) had no significant effect on the changes, but the three-way interaction (G × W × M) significantly influenced HCT levels at p < 0.05 (Tables SM-1, 2) (Tables SM-1, 2). For Hb, with an overall mean value of 14.68 g/dl, the highest level, 16.36 g/dl, was reached in the III week in the HIIT + Q10 group. When only groups were considered, the HIIT + Q10 group had the highest Hb level at 15.22 g/dl. Similarly, for HCT, which had an overall mean of 44.54, the HIIT + Q10 group recorded the highest value (47.19), while the C group had the lowest value (41.92). In the two-way interaction (G × W), the HIIT + Q10 group exhibited the highest HCT value (50.13), while the C group showed the lowest. In the three-way interaction (G × W × M), particularly during the second observation time in the II week of supplementation, the HIIT + Q10 group demonstrated significant increases. The highest Hb value, 15.22 g/dl, was identified in the HIIT + Q10 group. For sO2, the CoQ10 group, HIIT group, and HIIT + Q10 group belonged to the same statistical category, while the lowest value, %50.41, was observed in the C group. Regarding COHb, which had an overall mean of %1.45, the lowest value, %1.07, was statistically distinct and observed in the HIIT + Q10 group. In the G × W interaction, COHb reached its highest level during the I week in the HIIT group (3.02) and the II week in the CoQ10 group (2.81). The lowest COHb value, %0.53, was recorded in the III week in the HIIT + Q10 group. For HHb, which had an overall mean of %43.65, the highest values were observed in the II (%46.12) and III (%47.42) weeks, while the lowest value occurred in the IV week (%38.68). MetHb, with an overall mean of %0.42, reached its highest value in the IV week in the CoQ10 group (%1.17). Among the groups, the HIIT group recorded the lowest MetHb value at %0.16 (Table SM-7).

The effect of Q10 supplementation under HIIT conditions on Lac was significant at the p < 0.01 level for all factor and their two-way and three-way interactions. For Glu, significance was observed in G, W, G × W, and G × W × M interactions (Tables SM-2, 3). The average Lac value, calculated as 3.72 mmol/L, reached its highest level of 7.76 mmol/L in the HIIT group during the first observation time in the III week. However, the HIIT + Q10 group had the lowest Lac level at the same observation time, with a value of 2.42 mmol/L. At the second observation time in the IV week, the HIIT group exhibited the highest Lac value at 4.68 mmol/L, while the HIIT + Q10 group recorded the lowest Lac value during the second observation time in the II week. Furthermore, when only the groups were compared, the HIIT + Q10 group and the CoQ10 group were found to belong to the same statistical category, while the highest Lac value, 5.33 mmol/L, was exclusively observed in the HIIT group. Regarding weeks, the Lac level, which was at its peak during the I week, declined in subsequent weeks following supplementation intervention (Fig. 2). As for Glu, the overall study average was 186.24 mg/dL, with the CoQ10 group reaching the highest value (259.68 mg/dL) in the IV week. Among the groups, the highest Glu value (205.71 mg/dL) was identified in the HIIT + Q10 group (Table SM-8).

Four-week follow-up of the lactate (Lac) mmol/L value at two different observation times. Lac Lactate concentration in blood, C Control group, CoQ10 Coenzyme Q10 supplement group, HIIT High-Intensity Interval Training group, HIIT + Q10 High-Intensity Interval Training + Coenzyme Q10 supplement group, 5 m: 5th minute (first observation time), 10 m: 10th minute (second observation time), the letters above the columns (a, b, c, d, e, f, g, h, j) indicate statistical differences between groups analyzed by the One-Way ANOVA test followed by the LSD multiple comparison test

When examining the effect of Q10 supplementation under HIIT conditions on pH (T), pCO2 (T), and pO2 (T) values, varying levels of significance were identified in terms of the interventions and their interactions. Among these, the parameters pH (T), pCO2 (T), and pO2 (T) showed significant differences between groups and weeks, as well as in their interaction (G × W) at the p < 0.01 level, while pCO2 (T) was influenced by weeks at the p < 0.05 level (Table SM-3). The mean pH (T) value, recorded at 7.36, reached its highest level of 7.40 in the IV week in the HIIT + Q10 group. When only groups were considered, the CoQ10 group, HIIT group, and HIIT + Q10 group were found to belong to the same statistical group, with the highest pH (T) value observed exclusively in the C group at 7.38 mmHg. In terms of weeks, the lowest pH (T) value was observed in the I week, while the highest was recorded in the IV week. The mean pCO2 (T) value, calculated at 45.95, was found to be highest in the CoQ10 group (47.64) when only groups were analyzed. In terms of weeks, the highest pCO2 (T) value was observed in the III week. Regarding the interaction (G × W), the HIIT group (48.82) and the HIIT + Q10 group (46.67) were above the overall mean in the I week, while the HIIT + Q10 group was below the mean in the II and III weeks. The mean pO2 (T) value, recorded at 46.94, showed the highest value in the HIIT group (51.15) when only groups were considered. In terms of weeks, the highest pO2 (T) value was observed in the IV week (Table SM-9).

The effects of Q10 supplementation under HIIT conditions on p50 and O2 (vol%) values were analyzed, revealing significant differences based on G, W, M, and their interactions. The p50 value was significantly influenced by G, W, T, and pairwise interactions (G × W and G × M) at p < 0.01, and by the three-way interaction (G × W × M) at p < 0.05 (Table SM-3,4). The mean p50 value was 37.35 mmHg, with the highest value (41.71 mmHg) recorded in the HIIT + Q10 group during the first observation time of the I week. Among the groups, the lowest p50 value (35.27 mmHg) was observed in the C group. The O2 (vol%) value was significantly affected by G and W at p < 0.05 and by pairwise interactions (G × W) at p < 0.01. The mean O2 (vol%) value was 12.40, with the lowest value (11.11) observed in the C group and the highest value (13.65) recorded in the IV week. The CoQ10 group and HIIT + Q10 group reached the highest O2 (vol%) values during the IV week, placing them in the same statistical group (Table SM-10).

The effects of Q10 supplementation on metabolic parameters under HIIT conditions were evaluated. When examining Base (Ecf), Base (B), HCO3- (st), and HCO3- values, statistically significant differences were identified in terms of interventions and interactions at least at the p < 0.05 and p < 0.01 levels (Table SM-4). The overall mean of HCO3- (st) was 23.38 mmol/L, showing an increase from the I week and reaching its peak level. In the HIIT + Q10 group, the lowest value was recorded in the I week, followed by an increase in subsequent weeks. The mean Base (Ecf) value was 0.67 mmol/L, with the negative value in the I week transitioning to a positive increase. The lowest positive value was observed in the HIIT + Q10 group, while the highest was recorded in the CoQ10 group. The mean Base (B) value was 0.13 mmol/L, where the initially negative value in the I week turned positive in subsequent weeks. The mean HCO3- value was calculated as 25.51 mmol/L, with the maximum level reached in the IV week in the HIIT + Q10 group (Table SM-11).

When examining the effects of Q10 supplementation under HIIT conditions on K+, Na+, and Ca+ levels, significant differences were identified at various levels in terms of treatments and their interactions. The K+ and Ca+ levels were influenced by G, W, and their two-way interaction (G × W), with Ca+ also being affected by the interaction (G × M), and K+ by the interaction (W × M), all at a significance level of at least p < 0.05. The Na+ level was significantly influenced by G and W (p < 0.05) and by two-way interactions (G × W and W × M) at a significance level of at least p < 0.01 (Table SM-5). The mean K+ level, recorded as 3.96 mmol/L, showed that the HIIT group and the HIIT + Q10 group were within the same statistical category, with the highest K+ level observed in the C group at 4.64 mmol/L. The Na+ level, with an overall mean of 142.46 mmol/L, was lowest in the HIIT group at 141.47 mmol/L. For Ca+, the highest level (1.42 mmol/L) was observed in the C group, while the lowest level (1.32 mmol/L) was found in the HIIT + Q10 group. At the second observation time, the HIIT group and HIIT + Q10 group were within the same statistical category, although the Ca+ level in the HIIT + Q10 group was lowest (1.33 mmol/L) at the first observation time (Table SM-12).

The results of the Pearson correlation analysis demonstrated statistically significant but low-level positive and negative correlations among biochemical parameters. Specifically, weak positive or negative correlations were identified among pH, Na+, HCO3⁻, Lac, COHb, Hb, and pO2, while pCO2 was found to be associated with Glu and HTC. Hb exhibited correlations with HCO3⁻ and HHb, whereas HTC showed low-level positive relationships with parameters such as Na+, HCO3⁻, and MetHb. Positive correlations were detected between Lac and Ca+, while negative correlations were observed between Lac and HCO3⁻ or pH. Additionally, Glu exhibited a negative correlation with Ca+ and a positive correlation with p50. pO3 was positively associated with Na+, Base(B), and Base(Ecf), while significant relationships were identified between pCO2(T) and O2(Vol%). These findings are illustrated in Fig. 3.

Correlation between Lac and other blood gas measurements using Pearson correlation analysis. pCO2 Partial pressure of carbon dioxide, pO2 partial pressure of oxygen, Hb hemoglobin, HCT hematocrit, sO2 Oxygen saturation, COHb Carboxyhemoglobin, HHb Deoxyhemoglobin, MetHb Methemoglobin, Lac Lactate, Glu Glucose, O2(vol%) Oxygen concentration, Base(Ecf) Base excess in extracellular fluid, Base(B) Base excess in blood, HCO3-(st) Standard bicarbonate, HCO3- Bicarbonate, K+ Potassium, Na+ Sodium, Ca+ Calcium

Principal component analysis (PCA) was conducted to determine the relative importance of the parameters and their contributions to total variance. The first two components accounted for 67.61% of the total variance, while the first five components, with eigenvalues ≥ 1, explained 99.39% of the variance. The largest contributions to the F1 component were made by K+ (9.1%) and Ca+ (8.3%), followed by Hb, sO2, pO2(T), HCO3⁻(st), and cBase(B). For the F2 component, the highest contributions were from HTC (16.9%), pH (15.2%), and HHb (13.1%), followed by CoHb, O2, pCO2, and MetHb. The PCA biplot graph revealed the adaptive capacity of parameters to variable conditions. The parameters located near the origin represented higher adaptability, while Na+, Lac, p50, and Glu emerged as significant parameters under HIIT and Q10 interventions. Notably, Na+ levels were more stable in the CoQ10 groups, suggesting a potential role in maintaining electrolyte balance during exercise stress. Meanwhile, Lac levels were significantly lower in the HIIT + Q10 group compared to the HIIT group, reinforcing the hypothesis that Q10 enhances lactate clearance and aerobic energy production. Similarly, Glu levels were highest in the HIIT + Q10 group, indicating enhanced glucose utilization and energy availability, possibly due to Q10's role in mitochondrial efficiency. A strong relationship between the HIIT + Q10 group and HTC was evident, while pCO2 demonstrated a notable association with the CoQ10 group. In the HIIT-only group, O2 and Lac were prominent in the early phase, whereas Glu dominated in the later phase. This suggests that O2 emerged as a key parameter in the HIIT + Q10 group. The vector lengths and angles in the PCA biplot indicated relationships between parameters: angles smaller than 90° indicated positive correlations, while those greater than 90° signified negative correlations. For instance, a strong negative correlation was found between pO2 and pH, whereas no significant association was observed with pCO2. Variations in the responses of parameters within the same group were inferred from the tendency of vectors to diverge from or converge toward the center. These findings suggest that CoQ10 supplementation may contribute to metabolic optimization during high-intensity exercise, a trend that was clearly visualized through PCA group separation. Notably, MetHb and K+ were positioned near the C group, whereas pH(T) and HHb distanced themselves from the HIIT and Q10 factors, occupying distinct regions. The correlation findings indicate that biochemical balance is shaped by multiple factors and that Q10 supplementation, in combination with HIIT exercise, significantly contributes to physiological adaptation processes (Fig. 4).

Responses of different parameters to changing conditions, differences between groups, and relationships between parameters using principal component analysis (PCA). pCO2 partial pressure of carbon dioxide, pO2 partial pressure of oxygen, Hb hemoglobin, HCT hematocrit, sO2 oxygen saturation, COHb carboxyhemoglobin, HHb deoxyhemoglobin, MetHb methemoglobin, Lac lactate, Glu glucose, O2(vol%) oxygen concentration, Base(Ecf) base excess in extracellular fluid, Base(B) base excess in blood, HCO3-(st) Standard bicarbonate, HCO3- bicarbonate, K+ potassium, Na+ sodium, Ca+ calcium