Female Marathon Study with Holly Archer

The latest marathon fuelling research conducted by Science in Sport in trained male runners provides important new insights into the relationship between carbohydrate intake, metabolic response, and performance potential in (Redefining Marathon Fuelling Guides).

The findings demonstrate, for the first time, a clear dose-response relationship between carbohydrate ingestion and both whole-body and exogenous carbohydrate oxidation during simulated marathon running. An intake of 120 g·h⁻¹ not only maintained higher carbohydrate oxidation rates throughout the protocol but also appeared to confer a metabolic advantage, as evidenced by improved running economy, compared with more traditional strategies of 60 and 90 g·h⁻¹.

Peak exogenous oxidation rates, which represent how much of the carbohydrate being consumed was being utilised, reached 1.64 – 1.99 g·min⁻¹, among the highest ever reported in runners. At the same time, the findings highlighted real-world challenges: the high prevalence of gastrointestinal symptoms across all conditions underscored the importance of gut training and tolerance strategies.

Taken together, the message was compelling; high-carbohydrate fuelling can translate into potential metabolic advantages, but it must be done intelligently.

However, much of the sport nutrition science underpinning marathon performance has historically been derived from male data, leaving female-specific responses comparatively underexplored.
Science in Sport has therefore taken the next step. Using the same robust experimental design, we investigated how carbohydrate intakes of 60, 90, and 120 g·h⁻¹ influence physiological and metabolic outcomes in elite female runners.

THE SCIENCE BEHIND THE STUDY

To bring the science to life, we will step inside Holly Archer‘s journey, from the study to exploring her physiological responses, metabolic outcomes, and lived experience through participation in the research. This closer examination highlights how personalised, evidence-based fuelling strategies may help female marathoners unlock new performance ceilings.

For Holly, the testing revealed a clear, practical takeaway: the more carbohydrate she consumed, the better her body could support the demands of marathon-pace running. When Holly fuelled at 120 g·h⁻¹, she achieved higher carbohydrate oxidation and showed signs of improved running economy compared with 60 g·h⁻¹. When consuming 60 g·h⁻¹, her mean whole body carbohydrate oxidation rate across the 2 hours was 1.66 g·min⁻¹, increasing to 1.85 g·min⁻¹ at 90 g·h⁻¹ and 2.2 g·min⁻¹ at 120 g·h⁻¹. Her peak exogenous oxidation rate followed the same pattern: 60 g·h⁻¹: 0.91 g·min⁻¹; 90 g·h⁻¹: 1.31 g·min⁻¹; and 120 g·h⁻¹: 1.75 g·min⁻¹.

Holly’s heart rate stayed similar across trials, but what really changed was how the effort felt; her rating of perceived exertion was noticeably lower at 90 and 120 g·h⁻¹, meaning the same pace felt more controlled and sustainable when she fuelled more aggressively.

As her carbohydrate intake increased, her body relied more on carbohydrate and less on fat as fuel, helping her maintain the preferred and more efficient fuel source for marathon performance. Importantly, Holly was also able to oxidise more of the carbohydrate she consumed at the higher doses, directly turning race nutrition into usable energy. From a performance perspective, these point Holly toward a fuelling target of around 90 – 120 g·h⁻¹ for marathon racing to help sustain pace and delay fatigue. But the testing also highlighted a real-world challenge: higher intakes brought gastrointestinal discomfort.

Holly’s key learning? Race-day fuelling needs rehearsal. By regularly practising higher carbohydrate intakes in long runs and race-pace sessions, using a mix of gels and drinks, she can train her gut, improve tolerance, and arrive on the start line with a strategy her body is well adapted to.