RESEARCH: Studies from 20 to 26 Jul 2026

1. Menstrual cycle phase impact on carbohydrate’s ergogenic effect in cycling

2. Effect of substrate oxidation on middle-distance running performance

3. Chronic effects of cluster sets versus traditional sets in resistance training

4. Role of histamine in adaptations to endurance exercise training

5. Which training intensity distribution best improves VO2 Max and time-trial performance?

Study date: Mar 2026

Carbohydrate supplementation is a well-established ergogenic aid during endurance exercise, but hormonal fluctuations across the menstrual cycle could change substrate use and fatigue responses in a way that requires changing nutrition strategies. In this study, the authors set out to “investigate whether carbohydrate supplementation affects endurance performance and fatigue responses across different menstrual cycle phases during heavy-intensity cycling”.

STUDY INTERVENTION

1. 12 recreationally trained females completed four 90-minute constant-power cycling bouts at a heavy intensity, two during the mid-follicular phase and two during the mid-luteal phase.

2. In each phase, one bout involved carbohydrate beverage consumption and the other a placebo, followed immediately by a 4km time trial.

3. Perceived exertion, muscle fatigue (voluntary activation, twitch force), dyspnoea and leg pain were measured throughout.

KEY RESULTS

1. Carbohydrate supplementation significantly improved 4km time trial performance compared with placebo in both the follicular and luteal phases.

2. Carbohydrate ingestion was associated with a greater decline in twitch force (a marker of peripheral muscle fatigue) than placebo.

3. Dyspnoea ratings increased with carbohydrate ingestion in the luteal phase, but no other fatigue measures differed between phases.

AUTHORS’ CONCLUSION

• Carbohydrate supplementation enhanced cycling performance similarly in both the follicular and luteal phases of the menstrual cycle.

• The ergogenic benefit of carbohydrate during heavy-intensity exercise does not appear to depend on menstrual cycle phase.

RESULT CONFIDENCE

• The sample was small (12 participants) and menstrual phase was tracked using calendar-based methods rather than hormone assays in all cases, which can misclassify phase.

PRACTICAL TAKEAWAY

This study showed that carbohydrate supplementation improves heavy-intensity cycling performance regardless of menstrual cycle phase.

My recommendation for female athletes is that carbohydrate intake does not need to be changed based on cycle phase. This means that a simple, consistent nutrition plan can be used all the time.

However, the results of this study do not mean sex is irrelevant to carbohydrate strategy as other research shows female athletes deplete muscle glycogen faster than male athletes during high-intensity exercise. The absence of a menstrual-cycle effect doesn’t rule out a wider sex-based difference in carbohydrate needs; it just means fuelling doesn’t need to be adjusted by cycle phase specifically.

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