Influence Of Running Experience On Respiratory Quotient At Submaximal And Maximal Intensities

Respiratory quotient (RQ) is a value obtained via indirect calorimetry that measures the ratio of carbon dioxide produced to oxygen consumed by the body, typically differentiating fuel sources used during exercise. Both RQ and rating of perceived exertion (RPE) rise with increasing exercise intensity; however, the exact relationship between RQ and RPE can vary depending on individual factors like fitness level and training status. Thus, running experience of the individual may influence RQ at different perceived intensities during exercise. PURPOSE: Evaluate differences in RQ at submaximal and maximal intensities for individuals of different levels of running experience. METHODS: 112 recreational runners (age 39 ± 14 yrs; BMI: 24.1 ± 4.4 kg/m2) completed a graded maximal cardiopulmonary exercise test using indirect calorimetry. Test protocol was dictated by self-selected half marathon race pace with 1 km/hr increments every 3 min until volitional fatigue. RQ was recorded at maximal exertion (RQmax) and for those that reported a common submaximal RPE (14; RQsubmax). Participants were grouped by self-reported years running (<1; 1-5; 5-10; >10 yrs), kilometers (km) run per day (< 3; 3-5; 5-10; >10 km), and average days run per week (1-2, 3-4, 5-7dys). One-way ANOVAs were used to assess group differences in RQmax and RQsubmax. RESULTS: There were no significant differences in RQmax or RQsubmax between years of running, km run per day, or average days run per week (p > 0.05, Table). CONCLUSION: RQ values, both at maximal and submaximal intensities are similar between individuals regardless of years running, km run per day, and average days run per week. RPE may be used as a training metric to estimate substrate utilization at different exercise intensities, regardless of running experience.Supported by: This study received funding from Samsung Electronics Co., Ltd.