Effects of Menstrual Cycle Phases on Gait, Pelvis, and Sleep

This cross-sectional, prospective observational study investigates the influence of menstrual cycle phases on gait spatiotemporal characteristics, pelvic kinematics, and sleep quality in healthy women aged 18-35 years with regular menstrual cycles (28 ± 7 days). Hormonal changes during the cycle may affect musculoskeletal performance, balance, and sleep quality, yet the extent of these effects on gait and pelvic motion has not been fully clarified.

Participants will be evaluated in three phases of their menstrual cycle:

Early follicular phase (days 1-3), determined by the onset of menstrual bleeding, Ovulation phase (days 7-9), confirmed by a salivary ovulation test, Luteal phase (days 20-23), approximately 6-8 days after ovulation. At each phase, gait spatiotemporal parameters (speed, cadence, stride length, stance and swing phases, gait cycle duration) and pelvic kinematics (tilt, obliquity, rotation symmetry) will be assessed using the BTS-G walk wireless sensor system. Sleep quality will be measured with the Pittsburgh Sleep Quality Index (PSQI).

Primary outcomes

• Change in Gait Speed Across Menstrual Phases [Within one menstrual cycle (~3-4 weeks).]: Within-subject change in comfortable gait speed (meters/second (m/s)) measured by BTS-G walk sensor in three phases: early follicular (days 1-3), ovulation (days 7-9; salivary test-confirmed), luteal (days 20-23).
• Change in Cadence Across Menstrual Phases [Within one menstrual cycle (~3-4 weeks).]: Within-subject change in step cadence( steps/min) recorded by BTS-G walk across the same three phases.
• Change in Stride Length Across Menstrual Phases [Within one menstrual cycle (~3-4 weeks).]: Within-subject change in stride length (centimeters/cm) captured by BTS-G walk across the three phases.
• Change in Stance and Swing Phase Percentages [Within one menstrual cycle (~3-4 weeks).]: Within-subject change in stance (%) and swing (%) durations during gait across phases using BTS-G walk.
• Change in Pelvic Kinematics [Within one menstrual cycle (~3-4 weeks).]: Within-subject change in pelvic tilt (degree), obliquity (degree), and rotation symmetry (degree) indices obtained from BTS-G walk across phases.
• Change in Sleep Quality [Within one menstrual cycle (~3-4 weeks).]: Within-subject change in Pittsburgh Sleep Quality Index (PSQI) global score across phases. The PSQI is scored between 0 and 21. Higher scores indicate poorer sleep quality.

Sex: Female, ages: 18 Years to 35 Years, accepts healthy volunteers

Inclusion Criteria:

* Female, aged 18-35 years
* Voluntarily agrees to participate and provides informed consent
* Regular menstrual cycle (28 ± 7 days)
* Able to comply with study assessments and procedures

Exclusion Criteria:

* History of surgery within the past 6 months
* Current or chronic low back pain
* Dysmenorrhea complaints
* Neurological or orthopedic disorders affecting gait or muscle strength
* Presence of spinal deformities
* Rheumatologic disease
* Climacteric or menopausal period
* Any condition that may affect gait, pelvic kinematics, or sleep quality

• Aylin Baykal, Principal investigator, Yuksek Ihtisas University
• Busra Kalkan Balak, Study director, Yuksek Ihtisas University
• Gungor Beyza Ozvar Senoz, Principal investigator, Yuksek Ihtisas University