نوع مقاله : مقاله پژوهشی
نویسندگان
1 بیومکانیک ورزشی، دانشکده علوم ورزشی و تندرستی، دانشگاه تهران، تهران، ایران.
2 گروه بهداشت و طب ورزش، دانشکده تربیت بدنی و علوم ورزشی، دانشگاه تهران، تهران، ایران
3 گروه بهداشت و طب ورزشی، دانشکده تربیت بدنی و علوم ورزشی، دانشگاه تهران، تهران
4 2. گروه زنان و زایمان، عضو انجمن ناباروری ایران، ایران.
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction
Pregnancy is a critical and complex period in a woman’s life, accompanied by extensive physiological, hormonal, and biomechanical changes. These adaptations occur to support maternal and fetal health and can affect multiple body systems. In particular, weight gain, altered body mass distribution, and anterior displacement of the center of mass increase demands on the musculoskeletal and neuromuscular systems to maintain postural control and stability [1]. Structural adaptations, including increased lumbar lordosis and spinal realignment, although necessary, may increase mechanical load on joints, muscles, and ligaments [2]. Concurrently, biomechanical changes, particularly in gait, serve as strategies to maintain stability and reduce fall risk. These include reductions in walking speed and step length, increases in step width and double-support duration, and temporal-spatial gait alterations, which become more pronounced as pregnancy progresses [3,5].
Static balance and postural control are also significantly affected during pregnancy. Studies have demonstrated that center of pressure (COP) displacement and postural sway in standing increase with gestational age [7], largely due to changes in the center of mass and increased body weight, which challenge neuromuscular control [7,8]. Pregnancy-related low back pain (LBP) is among the most prevalent musculoskeletal disorders, affecting 50–70% of women, with severity increasing as pregnancy advances [2]. LBP can directly impact gait and balance; women with higher pain severity tend to walk more slowly, take shorter steps, have longer double-support phases, and exhibit impaired static postural control [5,8]. Despite numerous studies on gait, balance, and LBP prevalence, comprehensive data comparing the effects of different LBP severities on spatiotemporal gait parameters and static balance across trimesters remain limited [2]. Understanding these effects can inform preventive and rehabilitative interventions aimed at reducing fall risk. This study aimed to compare changes in spatiotemporal gait parameters and static balance from the first to the third trimester in pregnant women with varying LBP severity.
Methods
This descriptive-comparative study was prospective and applied in purpose, approved by the Ethics Committee of the Faculty of Sport Sciences and Health, University of Tehran (Ethics ID: IR.UT.SPORT.REC.1402.015). The minimum sample size was estimated using G*Power software (effect size = 0.5, α = 0.05, power = 0.95), resulting in 50 participants. Pregnant women aged 25–35 years with a normal BMI (18.5–24.5) at the third month of gestation were recruited. Exclusion criteria included a history of lumbar trauma or surgery, chronic LBP before pregnancy, systemic diseases, orthopedic conditions, preterm labor, multiple pregnancy, or occupations affecting spinal health. Among 500 women attending health centers in Borkhar County, Isfahan Province, 53 met the criteria and provided written informed consent. Measurements were conducted at two time points: early first trimester (third month) and late third trimester (ninth month). During the second assessment, 35 participants remained due to dropouts (8 due to miscarriage, 7 due to absolute rest prescribed by a doctor, and 3 withdrew from the study). Height and weight were measured using a tape measure and a digital scale (SECA, Germany).
Gait assessment: Spatiotemporal gait parameters (stride length, right and left step length, stride time, right and left step time) were measured along a 4-meter walkway. A sagittal-plane camera (Xiaomi Redmi Note 12 Pro) mounted on a tripod (250 cm from the wall, 85.5 cm from the floor) recorded at 100 Hz. Participants completed six back-and-forth walking trials; the first three stabilized natural gait, and data from trials four to six (three right steps: trials 4–6) were analyzed. Videos were analyzed using Kinovea software (v0.9.5-x64) with virtual markers on the heel, lateral malleolus, and head of the fifth metatarsal. Linear calibration using a 1-meter reference line converted video measurements to real-world distances. Analyses were restricted to the sagittal plane, and rest periods were provided to prevent fatigue.
Static balance assessment: Participants stood barefoot on a Wii Balance Board (WBB) for 20 seconds with eyes open. COP displacement was recorded at 100 Hz and COP path length calculated as:
COP Path Length = ∑_(i=1)^n▒√((X₂ - X₁)² + (Y₂ - Y₁)²)
Higher COP path length indicated greater postural sway and reduced static balance.
Low back pain assessment: LBP severity was assessed at the ninth month using a 10-cm Visual Analogue Scale (VAS), where 0 = no pain and 10 = worst imaginable pain. Scores of 1–3 indicated mild pain, 4–7 moderate pain, and 8–10 severe pain. Participants were then categorized into two groups: mild LBP and moderate-to-severe LBP. All participants had no prior history of LBP.
Results
All statistical analyses were conducted using SPSS version 27, with significance set at p < 0.05. Parametric Independent-Samples T Test and non-parametric Mann–Whitney U Test were used for group comparisons. Significant differences were observed in all spatiotemporal gait parameters between mild and moderate-to-severe LBP groups: stride length (p = 0.001), right step length (p = 0.001), left step length (p = 0.001), stride time (p = 0.009), right step time (p = 0.018), and left step time (p = 0.008). These results indicate that gait patterns differed significantly between groups throughout pregnancy. Regarding static balance, COP path length was significantly higher in the moderate-to-severe LBP group (p = 0.044), indicating greater postural sway and reduced static balance. In summary, higher LBP severity was associated with a more conservative gait pattern and increased postural instability.
Conclusion
Progression of pregnancy accompanied by higher severity of low back pain is associated with unfavorable changes in spatiotemporal gait parameters and reduced static balance efficiency. These findings reflect compensatory motor strategies in late pregnancy and underscore the importance of monitoring motor performance and implementing targeted rehabilitation interventions for pregnant women experiencing low back pain.
کلیدواژهها [English]
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