Lower extremity kinetics and muscle activation patterns during gait in early postpartum women: 42-day and 3-month comparison with nulliparous controls.

Background: Musculoskeletal problems are common during and after pregnancy. Biomechanical adaptations in postpartum females, particularly in pelvic stability and lower extremity mechanics, may contribute to long-term health issues. The postnatal period from 42-day to 3-month is a critical recovery window. This study aimed to compare early postpartum gait adaptations and muscle activation patterns between females at 42 days and 3 months postpartum and nulliparous females.

Methods: Nine postpartum females were assessed at 42 days (PT1) and 3 months (PT2) postpartum for lower extremity kinematics, kinetics, and muscle activation during walking. A control group of nine nulliparous females was tested at a single time point. Lower extremity kinematics, moments, and work were calculated. Non-negative matrix factorization decomposed the sEMG data into muscle synergy patterns and activation time courses.

Results: At PT1, postpartum participants showed increased pelvic obliquity, reduced knee extension moment and power, and increased ankle plantarflexion compared to controls. Muscle activation analysis revealed greater tibialis anterior activation in postpartum compared to controls. Rectus femoris activation was lower at PT1 than at PT2 during the stance phase, but higher at PT1 during the swing phase. By PT2, pelvic stability and muscle synergy patterns were similar to nulliparous controls.

Conclusion: Early postpartum gait mechanics show increased pelvic obliquity and altered muscle activation, indicating neuromuscular instability and compensation. Partial neuromuscular recovery was observed by 3 months postpartum, highlighting the need for rehabilitation targeting pelvic stability and muscle coordination to prevent long-term dysfunction.