Vastus Lateralis Architecture Changes During Pregnancy - A Longitudinal Study.

Area of Science:

• Physiology
• Biomechanics
• Obstetrics

Background:

• Increased incidence of falls during pregnancy is documented.
• The underlying mechanisms, particularly changes in lower extremity muscle function, remain unclear.
• Pregnancy-associated alterations in muscle strength may influence injury risk.

Purpose of the Study:

• To longitudinally investigate muscle strength and architectural properties of lower limbs.
• To compare these properties across different stages of pregnancy and postpartum.
• To explore the relationship between muscle changes and body composition during pregnancy.

Main Methods:

• Longitudinal study involving 19 pregnant women and 15 non-pregnant controls.
• Assessment of vastus lateralis muscle strength and architecture using dynamometry, ultrasound, kinematic, and electromyographic measurements.
• Body mass and composition determined via bioimpedance analysis at multiple time points.

Main Results:

• Significant increases in vastus lateralis muscle thickness and pennation angle observed at late pregnancy (LP).
• Muscle strength remained constant throughout pregnancy and postpartum.
• Body mass, skeletal muscle mass, fat mass, and water content peaked at LP; postpartum values normalized.

Conclusions:

• Pregnancy induces muscle hypertrophy in the vastus lateralis, altering muscle architecture.
• Despite muscle architectural changes, muscle strength does not increase to match rising body mass.
• Pregnant women may have an impaired ability to manage balance perturbations due to a mismatch between physical demand and muscle strength.