Question 1

Does the menstrual cycle affect heart rate during running?

Accepted Answer

Yes. Progesterone in the luteal phase raises core body temperature by approximately 0.3-0.7°C, which increases the cardiovascular demand of running at a given pace. Heart rate at the same speed may read higher than in the follicular phase, with no change in fitness. The effect is more pronounced in warmer conditions.

Question 2

Why do WHOOP or Garmin recovery scores drop in the second half of the cycle?

Accepted Answer

The luteal phase typically produces lower HRV, higher resting heart rate, and elevated skin temperature. Wearables interpret these physiological signals as incomplete recovery. They are registering real hormonal effects, not training errors. Tracking multiple cycles helps distinguish a hormonal pattern from a genuine recovery problem.

Question 3

Can wearables track hormone levels directly?

Accepted Answer

No current consumer device measures oestrogen or progesterone directly. Devices measure downstream effects: skin temperature, HRV, resting heart rate, and respiratory rate. Several companies are developing tools to infer hormonal shifts from these signals, but direct hormonal measurement is not yet available in a validated consumer product.

Question 4

What is RED-S, and how is the menstrual cycle connected to it?

Accepted Answer

RED-S (Relative Energy Deficiency in Sport) is impaired physiological function caused by insufficient energy availability relative to exercise demands. Changes in cycle length or loss of menstruation can be important indicators of low energy availability and the development of RED-S. Any significant change in cycle regularity warrants attention, particularly in athletes who have increased training load or reduced food intake.

Question 5

Does the menstrual cycle increase injury risk?

Accepted Answer

Evidence suggests that ACL laxity increases around ovulation, coinciding with peak oestrogen levels. A 2017 meta-analysis found this effect, though the overall quality of the evidence is graded as low, and the clinical significance is debated. There is no established protocol for modifying training based on the cycle phase to prevent injury. Awareness of the pattern is reasonable; restructuring training around it requires stronger evidence than currently exists.

Tag: menstrual cycle

Hormones and Endurance Training: What Your Cycle Actually Does

RED-S in Female Athletes: What Your Wearable Is Telling You

Cycle-Synced Running: How to Use Your Garmin to Train Smarter Around Your Period.