During pregnancy period, a woman’s body undergoes many transformations due to changes in endocrine system, cardiovascular system, musculoskeletal system reproductive system, respiratory system, gastrointestinal system and renal system . Among them changing spinal curvatures, balance, gait, joint laxity and pelvic tilt can be considered as biomechanical changes in pregnancy period.. This can greatly impact quality of life by increasing back pain, groin pain, sciatica( pain along the lower limbs), postural abnormalities, gait abnormalities and risk of falls.
Changes in spinal curvatures
Normally, the human spine shows both inward and outward curvature. Lordosis (inwards curvature) is observed in the lumbar and cervical regions of the spine. Kyphosis (outward curvature) is observed in the thoracic and sacral regions of the spine.
During pregnancy period, centre of gravity (COG) of the body no longer falls over the feet and it goes forward due to increasing abdominal size. Therefore overall equilibrium of the body alters. For that woman leans backward to gain equilibrium resulting increase the lumbar lordosis and thoracic kyphosis. It is lead to cause low back pain and this causes increased tension in the paraspinal muscles and reduced activity & strength of the gluteal muscles.
Changes in the pelvic
Pelvis is the bones that form a bowl-shaped structure in the area below the waist at the top of the legs, and to which the leg bones and spine are joined. Pelvic tilt has been shown to be more anterior in pregnant women in their third trimester. It is major reason for the increasing lumbar lordosis. The pelvis is connected to the lumbar spine via a group of muscles known as “hip flexors”; an anteriorly-tilted pelvis shortens the hip flexors.
Weakened abdominal muscles during pregnancy due to increased levels of Relaxing and progesterone (which relax the muscles), or as a result of the overstretching of the muscles due to increased abdominal size, are thought to be responsible for an increase in anterior pelvic tilt.
Changes in the balance
During pregnancy period, both static and dynamic balances are reduced. One of the major factors leading to balance was the shift forward of a woman’s centre of gravity as her stomach and abdomen expanded outward to account for a growing fetus and joint laxity. This unstability leads to compensate the posture and gait to maintain the stability during walking and standing.
Changes in the walking pattern
A single gait cycle (A gait cycle is the time period or sequence of events or movements during locomotion in which one foot contacts the ground to when that same foot again contacts the ground, and involves propulsion of the centre of gravity in the direction of motion) can be separated into the stance phase and the swing phase. The stance phase begins with the first moment of contact of the foot with the floor and continues while the foot remains in contact with the floor. The swing phase begins the moment the foot leaves the floor and continue while the foot touch the floor. Any point when both limbs are touching the floor is determined as ‘double support,’ and when only one limb has contact with the floor is defined as ‘single support’.
Spatially, stride length is decrease in pregnancy period. Alongside this, pregnant women display an increased step width. The increased step width is a method use by pregnant women to increase their base of support and therefore increase their stability during gait. Pregnant women also display shorter swing phases, longer stance phases, short single limb support period and long double limb support period. It’s harder to maintain balance during walking due to change in centre of gravity, weak pelvic girdle muscles and joint laxity. Body swings side to side to maintain balance. Abnormal gait pattern during pregnancy is called ‘pregnancy waddling gait’.
Joint laxity
The nature has provided a way to help create more space in and around a woman’s pelvis by loosening of the joint and ligaments of the pelvis by secreting of pregnancy hormones such as relaxin. Relaxin not only relaxes ligaments in a woman’s pelvis to prepare her labour. But it also loosens the joints and ligaments all over the body. This can lead to lots of physical deformities such as sciatica, low back pain, gait abnormalities and abnormalities in posture.
To correct biomechanical changes during pregnancy period
Should maintain the good postures
doing regular prenatal exercises under supervision of physiotherapist
maintain the good physical activity level
avoiding heavy weight lifting wearing
Sameesha Devindi
References
Conder, Rebecca & Zamani, Reza & Akrami, Mohammad. (2019). The Biomechanics of Pregnancy: A Systematic Review. Journal of Functional Morphology and Kinesiology. 4. 10.3390/jfmk4040072.
Branco, M., Santos-Rocha, R. and Vieira, F. (2014) ‘Biomechanics of gait during pregnancy’, Scientific World Journal, 2014.
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