This randomized controlled trial will compare the effectiveness of Post-Isometric Relaxation (PIR) versus Simple Stretching Exercises (SSE), each combined with standard physiotherapy modalities, for reducing menstrual pain and improving physical activity in young unmarried women with primary dysmenorrhea. Forty-four participants will be randomly assigned (1:1) to receive either PIR or SSE three times per week for eight weeks (24 total sessions). The study will identify which non-pharmacological intervention provides superior benefits for pain relief and daily function.

Primary dysmenorrhea is defined as menstrual cramps without underlying disease. This condition affects 50-90% of women of reproductive age and can significantly impair daily activities and quality of life. While pharmacologic treatments exist, non-drug interventions which include muscle energy techniques and stretching are under investigation for their safety and efficacy.

In this single-center, parallel-group randomized controlled trial, 44 unmarried female students aged 18-30 years with documented regular menstrual cycles and moderate to severe primary dysmenorrhea (WaLIDD score ≥5) will be enrolled. After baseline screening and informed consent, participants will be randomized (via OpenEpi) to one of two groups of post-isometric relaxation technique and simple stretching exercises.

Pain intensity (NPRS 0-10) and physical activity levels (IPAQ MET·min/week) will be assessed at baseline, 4 weeks, and 8 weeks by blinded assessors. Secondary measures include dysmenorrhea severity (WaLIDD questionnaire) and range of motion. Data will be analyzed with RM-ANOVA for within-group changes and independent-samples t-tests for between-group comparisons, after testing normality with Shapiro-Wilk. A p-value <0.05 denotes significance.

This trial will clarify which non-pharmacological intervention more effectively reduces menstrual pain and enhances activity, informing evidence-based physiotherapy protocols for primary dysmenorrhea.

Inclusion Criteria:

• Female participants aged 18-30 years.
• Self-identification as female.
• Unmarried students with regular menstrual cycles (24-35 days).
• Diagnosed primary dysmenorrhea with a WaLIDD score ≥ 5.
• Able and willing to participate in thrice-weekly physiotherapy sessions for eight weeks.
• Provide written informed consent.

Exclusion Criteria:

• Secondary dysmenorrhea (e.g., endometriosis, pelvic inflammatory disease).
• Current use of hormonal contraceptives or any medication for menstrual pain.
• History of hip or pelvic surgery in the past year.
• Acute musculoskeletal injury or chronic pain conditions unrelated to dysmenorrhea.
• Neurological disorders affecting lower-limb muscle function.
• Contraindications to TENS or heat therapy (e.g., skin lesions, implanted electronic devices).
• Pregnancy or breastfeeding.
• Participation in another interventional trial within the past three months.

Participants must self-identify as female.

De-identified individual participant data (IPD) for all enrolled subjects-including demographic variables, baseline and follow-up outcomes (NPRS scores, IPAQ MET-min/week, WaLIDD scores, hip range of motion, and session compliance)-will be made available to qualified researchers. Data will be stripped of direct identifiers in accordance with HIPAA Safe Harbor guidelines. Requests must include a methodologically sound proposal and Institutional Review Board (IRB) approval or exemption documentation.

Data and supporting documents will become available 12 months after publication of the primary trial results and will remain accessible for up to 5 years thereafter.

Researchers must submit:

A formal request describing the research question and analysis plan.

Evidence of ethics approval.

A signed data use agreement committing to protect participant confidentiality and use data only for the approved purpose.

Outcome assessors will be blinded to each participant's group assignment. Participants, care providers, and investigators will be aware of group allocation (open-label for all other roles).