The new racewalking event at the 2024 Paris Olympics was a mixed marathon relay. This poses new physiological challenges, as this competition format has never been attempted before. Therefore, this study will help generate new insights into how metabolism and the endocrine system function and interact in this novel format. This would allow for the identification of limitations and adjustments in the future for this type of protocol. A pilot study was conducted to characterize glycemic and hormonal responses-including glucose (GLUv), insulin (IN), adrenaline (A), noradrenaline (NA), glucagon (GG), and cortisol (C) in plasma during a structured protocol designes mimic the event. The protocol consisted of two high-intensity exercises with an interspersed rest period (40 min of exercise at 90% of HRmax + 40 min of active recovery + 40 min of exercise at 90% of HRmax), conducted under a predefined fluid and carbohydrates (CH) intake strategy. During this protocol, subjects ingested 50 g CH in 500 ml in each phase of the protocol and, in addition, a 45 g CH gel during recovery. No hypoglycemia or dehydration >2% of body mass (BM) was observed throughout protocol. In addition, IN (+~84%) and GLUv (+~41%) evolved similarly in both exercise sectors. Despite the carbohydrate and fluid intake strategy, increases in counterregulatory hormones, particularly in NA (161%) and GG (42%), were observed during the second phase of exercise. Within the limitations of this exploratory study, these findings describe the hormonal and metabolic response patterns observed under the conditions tested, without implying causal or functional effects of the intake strategy. The high interindividual variability and small sample size prevent any statistical inferences from being made. In addition, high carbohydrate intake during recovery was accompanied by an increase in IN concentration, with no evidence of hypoglycemia before the second exercise segment.
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