This study aims to investigate the effects of different phases of the menstrual cycle on gait spatiotemporal characteristics, pelvic kinematics, and sleep quality in healthy women aged 18-35 years with regular menstrual cycles. Participants will be assessed in three phases of the cycle: early follicular (days 1-3), ovulation (days 7-9, confirmed by ovulation test), and luteal (days 20-23). Gait parameters and pelvic kinematics will be evaluated using the BTS-G walk sensor system, while sleep quality will be assessed with the Pittsburgh Sleep Quality Index (PSQI). The study seeks to determine whether physiological and hormonal changes during menstrual phases lead to measurable differences in gait, pelvic motion, and sleep quality.

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).

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

Healthy women aged 18-35 years with regular menstrual cycles (28 ± 7 days). Participants will be assessed during three phases of their menstrual cycle (early follicular, ovulation, and luteal) to examine changes in gait parameters, pelvic kinematics, and sleep quality.