Assumptions and estimations are not direct measurements and, as such, represent guesses, which should be avoided in laboratory and field-based sport-related research.

Assuming or estimating menstrual cycle phases is neither a valid (i.e. how accurately a method measures what it is intended to measure) nor reliable (i.e. a concept describing how reproducible or replicable a method is) methodological approach.

Extra caution should be exercised when drawing conclusions from data linked to assumed or estimated menstrual cycle phases.

Transparent and honest reporting of the limitations associated with assumptions and estimations, as well as the implications of these limitations, must be provided and justified.