Study of energy expenditure (oxygen consumption, EPOC, and lactate) for different running distances

troduction: This study addressed the metabolic demands of running by analyzing the contri- butions of oxygen consumption during exercise, excess post-exercise oxygen consumption (EPOC), and lactate accumulation to total energy expenditure. Understanding the interaction between these components is essential for optimizing training strategies and improving phys- iological monitoring in elite athletes. Objective: To evaluate the relative contributions of aerobic and anaerobic energy systems across different running distances using a validated physiological approach in elite-level male runners. Methodology: The study involved sixteen elite male runners from Nineveh, Iraq, who completed 100-meter, 400-meter, and 3000-meter running trials under controlled environmental condi- tions. Metabolic data were collected using a portable gas analyzer, while lactate concentrations were assessed via capillary blood sampling. Results: The results revealed significant differences in energy expenditure components across the running distances (p < 0.001). During the 100-meter sprint, anaerobic metabolism domi- nated, with oxygen consumption accounting for 8.57%, EPOC 68.87%, and lactate 22.56%. In the 400-meter trial, energy contributions were more balanced, with 16.78% from oxygen, 53.04% from EPOC, and 30.17% from lactate. The 3000-meter run was characterized by aero- bic dominance, with oxygen contributing 68.00%, EPOC 25.96%, and lactate 6.04%. Statistical tests confirmed the significant role of anaerobic metabolism in short-duration efforts. Discussion: The discussion emphasized that earlier studies often underestimated anaerobic contributions. Incorporating lactate kinetics and EPOC provides a more complete understand- ing of energy demands during intense exercise. Conclusions: It is concluded that integrating anaerobic components yields a more accurate es- timation of total energy expenditure, supporting improved performance modeling and health- oriented interventions. Keywords Lactic acid, energy expenditure, oxygen consumption, EPOC,

discussion emphasized that earlier studies often underestimated anaerobic contributions. Incorporating lactate kinetics and EPOC provides a more complete understand- ing of energy demands during intense exercise. Conclusions: It is concluded that integrating anaerobic components yields a more accurate es- timation of total energy expenditure, supporting improved performance modeling and health- oriented interventions. Keywords Lactic acid, energy expenditure, oxygen consumption, EPOC, anaerobic metabolism. Resumen Introducción: este estudio examinó las demandas metabólicas de la carrera, analizando las con- tribuciones del consumo de oxígeno durante el ejercicio, el epoc y la acumulación de lactato al gasto energético total. comprender su interacción es clave para mejorar el entrenamiento y el monitoreo fisiológico en atletas de élite. Objetivo: evaluar las contribuciones relativas de los sistemas energéticos aeróbico y anaeróbico en distintas distancias de carrera mediante un enfoque fisiológico validado en corredores va- rones de élite. Metodología: participaron dieciséis corredores de élite de nínive, irak, quienes realizaron prue- bas de 100, 400 y 3000 metros bajo condiciones ambientales controladas. se recolectaron datos metabólicos con un analizador de gases portátil y se midió el lactato en sangre capilar. Resultados: se observaron diferencias significativas entre distancias (p < 0.001). en 100 m pre- dominó el metabolismo anaeróbico (8.57% oxígeno, 68.87% epoc, 22.56% lactato). en 400 m, el perfil fue mixto (16.78% oxígeno, 53.04% epoc, 30.17% lactato). en 3000 m dominó el meta- bolismo aeróbico (68.00% oxígeno, 25.96% epoc, 6.04% lactato). los análisis confirmaron la relevancia del metabolismo anaeróbico en esfuerzos breves. Discusión: estudios previos subestimaron los componentes anaeróbicos. incluir la cinética del lactato y el epoc mejora la comprensión del gasto energético en ejercicios intensos. Conclusiones: integrar los componentes anaeróbicos permite una estimación más precisa del gasto energético total, favoreciendo mejores modelos de rendimiento y estrategias de salud. Palabras clave Ácido láctico, gasto energético, consumo de oxígeno, EPOC, metabolismo anaeróbico. Study of energy expenditure (oxygen consumption, EPOC, and lactate) for different running distances Un estudio del gasto energético (consumo de oxígeno, EPOC y lactato) en diferentes distancias de carrera

Palabras clave Ácido láctico, gasto energético, consumo de oxígeno, EPOC, metabolismo anaeróbico. Study of energy expenditure (oxygen consumption, EPOC, and lactate) for different running distances Un estudio del gasto energético (consumo de oxígeno, EPOC y lactato) en diferentes distancias de carrera

2025 (julio), Retos, 68, 716-731 ISSN: 1579-1726, eISSN: 1988-2041 https://recyt.fecyt.es/index.php/retos/index 717 Introduction Total energy expenditure (TEE) represents the total energy used within a 24-hour timeframe and is comprised of three primary components: resting energy expenditure (REE), the thermic effect of food (TEF), and activity energy expenditure (AEE) (Ndahimana & Kim, 2017). Physical activity accounts for approximately 20–30% of overall energy output in humans (Ainsworth et al., 2011). The energy ex- pended can differ based on the intensity and nature of the exercise performed. There are various methods to measure and assess physical activity and energy expenditure, each with its advantages and limitations (Coyle, 1995 : Brito et.al,2024). Understanding these methods is crucial for determining which one should be used in a specific study context. Therefore, anaerobic exercises should be described as an example, as oxygen consumption may not accurately explain energy expendi- ture. Factors such as blood flow restriction during intense muscle contractions, breath-holding, and ox- ygen deficiency due to short-duration exercises, along with the absence of physiological steady state, reveal the incomplete capacity of oxygen uptake to determine energy expenditure (Scott, 2000). Oxygen consumption and the oxygen debt do not represent the total energy measurement, especially in anaer- obic activities (Kemp et al., 2005). However, it can be argued that interpretations of oxygen debt do not accurately define anaerobic energy expenditure, as oxygen uptake accounts for both the hydrolysis of ATP and its resynthesis, similar to aerobic ATP turnover (Scott & Kemp, 2005). It is assumed that the ATP-PC component forms part of the excess post-exercise oxygen consumption (EPOC) (Børsheim & Bahr, 2003). Since EPOC measurements do not adequately explain anaerobic energy transfer as fast ATP turnover at the substrate level with lactate production, it is possible that the greatest error in interpret- ing total energy expenditure may not arise from measurement contradictions but rather from com- pletely ignoring lactate production and/or EPOC. Thus, we set out to determine whether combining blood lactate measurements and approximating them to estimate anaerobic energy expenditure would significantly increase total energy expenditure. Meas- urements of anaerobic energy expenditure via blood lactate provided a

greatest error in interpret- ing total energy expenditure may not arise from measurement contradictions but rather from com- pletely ignoring lactate production and/or EPOC. Thus, we set out to determine whether combining blood lactate measurements and approximating them to estimate anaerobic energy expenditure would significantly increase total energy expenditure. Meas- urements of anaerobic energy expenditure via blood lactate provided a reasonable estimate of anaero- bic ATP turnover from glucose, which may be more beneficial than a hindrance to the quantitative esti- mation of total energy expenditure (Scott, 2006 ; Mitchell et al., 2024)). The study by Christopher B. Scott (1997) examined energy expenditure during and after exercise from both aerobic and anaerobic perspectives, along with the energy needs for aerobic recovery. Current methods for measuring energy expenditure involve assessing oxygen uptake in conjunction with excess post-exercise oxygen consumption (EPOC) or oxygen deficit, alongside oxygen uptake measurements (Scott, 1997). This research highlights how interpretations of oxygen debt and deficit can influence total energy expenditure calculations. It suggests that while oxygen uptake effectively reflects aerobic me- tabolism during exercise and recovery, it may not adequately account for anaerobic energy production (fermentation) (Kemp et al., 2005). In practice, differences in energy expenditure are more realistically observed in high-intensity, intermittent exercises rather than in low-intensity activities. The study by Christopher B. Scott and Richard B. Kemp (2005) indicates that energy expenditure de- pends on oxygen uptake during exercise and calculates oxygen consumption through EPOC, which con- sumes energy following the end of exercise, as well as through blood lactate measurements. The results of this study suggest that both lactate production and rapid glycolytic ATP turnover and lactate oxida- tion are independently associated with heat production, and thus represent separate and additive com- ponents for measuring total energy expenditure during exercise and recovery (Scott & Kemp, 2005). In the study by Christopher B. Scott (2006), four indirect estimates of anaerobic energy expenditure were measured: (1) oxygen debt (O2), (2) oxygen deficit, (3) blood lactate concentration, and (4) in- creased carbon dioxide production during and after six exercise intervals (2, 4, 10, 15, 30, and 75

measuring total energy expenditure during exercise and recovery (Scott & Kemp, 2005). In the study by Christopher B. Scott (2006), four indirect estimates of anaerobic energy expenditure were measured: (1) oxygen debt (O2), (2) oxygen deficit, (3) blood lactate concentration, and (4) in- creased carbon dioxide production during and after six exercise intervals (2, 4, 10, 15, 30, and 75 sec- onds) performed at three different intensities (50%, 100%, and 200% of VO2 max). The results of the study indicate that the greatest error occurs in not accounting for ATP turnover at the substrate level in lactate's contribution to calculating total energy expenditure in anaerobic efforts (Scott, 2006). In Christopher B. Scott's study (2006) titled "Lactate Contribution to Energy Expenditure from Re- sistance Training," it was found that conventional oxygen uptake measurements do not fully capture the rapid anaerobic ATP turnover that occurs with lactate production. The study compared two weight training protocols: one at 60% of one-repetition maximum (1RM) to failure and another at 80% of 1RM

2025 (julio), Retos, 68, 716-731 ISSN: 1579-1726, eISSN: 1988-2041 https://recyt.fecyt.es/index.php/retos/index 718 with limited repetitions. The aim was to assess whether blood lactate levels, reflecting rapid substrate- level ATP turnover, significantly enhance the interpretation of total energy expenditure when compared to oxygen uptake measurements alone. The total energy expenditure analysis incorporated blood lac- tate, oxygen uptake, and post-exercise oxygen consumption (EPOC). When the results were analyzed by gender, blood lactate frequently played a significant role in total energy expenditure during endurance- type training (Scott, 2006). In the study by (Irvine, C., Laurent, & et al., 2017), "Determining Total Energy Expenditure During and After High-Intensity Interval Running," the aim was to examine the variations in the contribution of ox- idized O2 and glycolytic analysis during two distinct types of high-intensity interval training, with work ratios of (1:1) and (1:2), namely (30:30) seconds and (15:30) seconds, on a sample consisting of 6 men and 8 women. The researchers measured oxygen consumption (VO2) and carbon dioxide production (VCO2), and the respiratory exchange ratio (RER) to represent the oxidative contribution, along with capillary blood lactate analysis to represent the glycolytic contribution during both high-intensity speed workouts. Post-exercise lactate values showed a significant contribution from the glycolytic system. In a recent study involving professional soccer players, [Tortu & Deliceoglu, 2024) compared energy expenditure during repeated sprint tests conducted via running and cycling. The analysis was based on key physiological measurements, including oxygen consumption (VO₂), excess post-exercise oxygen consumption (EPOC), and blood lactate concentration. The findings revealed that running induced higher total energy expenditure and a greater contribution from the ATP-PCr energy system, suggesting that running more accurately reflects the physical demands of field-based sports. The significance of this study lies in its comparative analysis of energy expenditure across different run- ning distances—short, medium, and long—with the aim of identifying the dominant physiological de- terminants in each category. The research offers valuable practical implications for the design of more effective training programs, especially in running-based sports, where a precise understanding of en- ergy distribution can enhance performance optimization and reduce the risk of muscular fatigue. This study

expenditure across different run- ning distances—short, medium, and long—with the aim of identifying the dominant physiological de- terminants in each category. The research offers valuable practical implications for the design of more effective training programs, especially in running-based sports, where a precise understanding of en- ergy distribution can enhance performance optimization and reduce the risk of muscular fatigue. This study also introduces a comprehensive scientific model for estimating energy expenditure by inte- grating three essential physiological indicators: oxygen consumption during exercise (VO₂), oxygen debt (EPOC), and blood lactate concentration. This advanced theoretical framework surpasses traditional models that rely solely on oxygen uptake by incorporating the metabolic costs associated with lactate accumulation. Additionally, the study identifies critical variables that influence the estimation of energy expenditure and quantifies their relative contributions. These include estimated oxygen consumption during activity, EPOC, and lactate-derived energy output. By integrating lactate metrics with post-exer- cise oxygen uptake, the study provides a more accurate and holistic assessment of total energy expendi- ture. Method The researcher employed a cross-sectional descriptive approach to investigate energy expenditure pat- terns among runners in Nineveh Governorate. This design was selected to analyze the relationships be- tween oxygen consumption, EPOC (excess post-exercise oxygen consumption), and lactate levels across varying race distances at a single time point. By focusing on a defined population of runners in their natural training environment, the approach allowed for: 1. Comprehensive data collection on physiological variables (e.g., lactate measurements via blood sampling, VO₂ monitoring during runs). 2. Identification of influencing factors (e.g., distance-specific metabolic demands, recovery dynam- ics). 3. Accurate description of energy expenditure trends without manipulating participants’ running routines.

2025 (julio), Retos, 68, 716-731 ISSN: 1579-1726, eISSN: 1988-2041 https://recyt.fecyt.es/index.php/retos/index 719 Participants The study sample consisted of 21 runners from Iraqi university teams in Nineveh Governorate partici- pating in the Iraq Athletics Championship for Universities (mean age = 20.03 years), with the analysis focused on 16 elite runners (mean age = 20.52 years) as the main group. Although selecting elite com- petitive athletes enhances the credibility of the results in the context of high performance. Table 1. Shows the ages, training experience, and gender distribution of the sample. Variable Total Group (n=21) Main Group (n=16) Mean Age (years) 20.03 ± 1.1 20.52 ± 0.9 Gender (Male/Female) 100% Male 100% Male Years of Experience 4.8 ± 1.5 4.3 ± 1.2 Recent Injuries 5 athletes (23.8%) 0 athletes (0%) Inclusion: Regular training (≥5 days/week, ≥50 km/week). No musculoskeletal injuries within the preceding 3 months. Exclusion: Five players were excluded due to injuries or missed training sessions prior to competitive matches Chronic metabolic/cardiovascular conditions (e.g., diabetes, heart disease). Use of metabolism-altering supplements (e.g., creatine, hormones). Incomplete laboratory measurements (e.g., missing lactate or VO₂ data). Ethical Approval The study protocol was approved by Al-Noor University’s Research Ethics Committee (Ref. No. 22112025, 22 January 2025) and adhered to the Declaration of Helsinki. Participants provided written informed consent, with data anonymized and physical/psychological risks minimized. Measurements and Data Collection Oxygen Consumption (VO₂) Oxygen consumption during running trials was assessed using the Cosmed K5 portable metabolic sys- tem (Cosmed, Rome, Italy), a widely recognized and validated device for measuring gas exchange in both controlled laboratory settings and dynamic field environments. According to Macfarlane (2017), the K5 demonstrates high validity and reliability when compared with traditional stationary metabolic carts, making it suitable for sport-specific, on-field applications where mobility and real-time data acquisition are critical. Prior to data collection, rigorous calibration procedures were implemented in accordance with the man- ufacturer’s specifications to ensure the accuracy, reproducibility, and stability of all measurements. Flowmeter calibration was performed using a 3-liter calibration syringe (Hans Rudolph, USA), with the procedure repeated until flow accuracy was confirmed within ±2%, as recommended by technical vali-

and real-time data acquisition are critical. Prior to data collection, rigorous calibration procedures were implemented in accordance with the man- ufacturer’s specifications to ensure the accuracy, reproducibility, and stability of all measurements. Flowmeter calibration was performed using a 3-liter calibration syringe (Hans Rudolph, USA), with the procedure repeated until flow accuracy was confirmed within ±2%, as recommended by technical vali- dation protocols. For gas calibration, the K5 device was exposed to both ambient air (approximately 20.9% O₂ and 0.03% CO₂) and a certified calibration gas mixture (16.0% O₂ and 5.0% CO₂), ensuring sensor accuracy across the physiological range of interest, as supported by (Nicolò et al., 2017). Envi- ronmental conditions, including temperature, barometric pressure, and humidity, were monitored and factored into the calibration process to reduce their influence on gas exchange measurements. To effec- tively capture the dynamic fluctuations in oxygen consumption during high-intensity intermittent exer- cise, VO₂ data were collected at 10-second intervals, providing an optimal balance between temporal resolution and data stability. Additionally, the K5 system employs breath-by-breath analysis, which of- fers a highly responsive method for tracking oxygen kinetics. This feature is particularly valuable in re- peated sprint protocols, where rapid physiological changes occur. Previous research has validated the reliability of the K5’s breath-by-breath methodology, provided the system is correctly calibrated and properly fitted during running trials.

2025 (julio), Retos, 68, 716-731 ISSN: 1579-1726, eISSN: 1988-2041 https://recyt.fecyt.es/index.php/retos/index 720 Excess Post-Exercise Oxygen Consumption (EPOC) EPOC was quantified via indirect calorimetry using the K5 system for 30 minutes post-exercise, a dura- tion consistent with protocols for assessing post-exercise metabolic recovery (Børsheim & Bahr, 2003). Participants remained seated in a controlled environment (25°C, 40% humidity) to minimize external metabolic influences. Lactic Acid Accumulation Blood lactate concentration was assessed using the Lactate Pro LT-1730 (Arkray, Japan), a portable an- alyzer with a coefficient of variation (CV) of <3% (Pyne et al., 2000). Sampling followed standardized intervals: - Pre-run: Baseline measurement after 10 minutes of seated rest. - Post-run: 5 minutes after exercise cessation, a timepoint selected to capture peak lactate accumulation as per exercise physiology literature (Retty, 2022). Capillary blood samples (5 ml) were drawn from the earlobe, cleaned with alcohol swabs, and analyzed immediately to prevent glycolysis-induced measurement errors (Moran et al., 2012). Lactate Timing Rationale: The 5-minute post-exercise sampling aligns with evidence that blood lactate peaks 3–7 minutes after high-intensity exercise Environmental Control All trials were conducted in a climate-controlled laboratory (25 ± 1°C, 40 ± 5% humidity) to standardize thermal and hygrometric influences on metabolic measurements. Scientific Integrity The study adhered to COPE (Committee on Publication Ethics) guidelines, with full methodological transparency and no evidence of data fabrication or falsification. Raw datasets are archived in anony- mized form and available for independent verification. Devices and Tools Used in the Research •Electronic Device for Measuring Weight and Height (Type: Detecto) •Electronic Stopwatches (4 units) for measuring time to the nearest one-hundredth of a second •Pulse Measuring Watches •Measuring Tape for distances to the nearest centimeter, 40 meters in length •Plastic Markers (25 units) •K5 Device for measuring CO2 and O2 •Lactate Measuring Device (Lactate PrO2 LT-1730) •Colored Adhesive Strips for use in tests •Chalk in Various Colors for drawing on the ground during pre- and post-tests •Whistle Tests and Measurements Used in the Research •Body Measurements: Body measurements included two measurements: (Height measurement and Body mass measurement). •Measurement of Lactic Acid Concentration in Capillary Blood: The level of lactic

O2 •Lactate Measuring Device (Lactate PrO2 LT-1730) •Colored Adhesive Strips for use in tests •Chalk in Various Colors for drawing on the ground during pre- and post-tests •Whistle Tests and Measurements Used in the Research •Body Measurements: Body measurements included two measurements: (Height measurement and Body mass measurement). •Measurement of Lactic Acid Concentration in Capillary Blood: The level of lactic acid concentration in capillary blood was measured using the device (Lactate PrO2 LT-1730) five minutes before warm-up. The researcher will then conduct several pilot experiments to measure lactate after aerobic and anaerobic exertion, using strips with a chemical detector that sends an electrical signal in response to the interaction with the blood sample. This signal varies according to the concentration of lactic acid in the tested blood sample.

The study evaluates energy expenditure across different running distances in elite male runners.