Feasibility and effectiveness of a foam rolling intervention in pregnant women requiring bed rest for foetal protection: a randomised controlled trial

Abstract

Background

Bed rest during pregnancy can lead to reduced physical activity, impairing lower limb venous blood flow and increasing the risk of deep vein thrombosis (DVT) and muscle atrophy. We investigated the clinical efficacy of foam rolling intervention (FRI) in enhancing lower limb venous blood flow, mitigating the risk of DVT and muscle atrophy in pregnant women on bed rest.

Methods

This single-blind, randomised controlled trial enrolled 86 pregnant women with long-term bed rest for foetal protection (≥ 7 days), gestational age ≥ 20 weeks, and maternal age < 40 years. Participants were randomly assigned to a control or experimental group using a random number table. The control group received standard care, whereas the experimental group underwent FRI. Researchers and statisticians were aware of the treatment groups, however, the participants were blinded. Lower limb blood flow velocity, D-dimer levels, incidence of DVT, and the extent of lower limb muscle atrophy were assessed in both groups at baseline and post-intervention (day 7). To account for a 5% attrition rate and potential sampling error, the estimated sample size for each experimental and control group was 40.

Results

Before the intervention, no significant differences were observed between the experimental and control groups in peak blood flow, mean flow velocity, D-dimer values, or leg circumference (P > 0.05), however, the peak blood velocities of the popliteal veins were significantly higher in the control group (P = 0.031). On the seventh day post-intervention, the experimental group had significantly higher mean and peak blood velocities in femoral and popliteal veins, significantly (P < 0.05), lower mean D-dimer levels (P = 0.035), and a significantly smaller reduction in thigh and calf circumference (P < 0.001). Consequently, the rate of thigh muscle atrophy was significantly slower in the experimental group (P = 0.011).

Conclusions

FRI is an effective intervention for improving lower limb venous blood flow, mitigating the risk of DVT and muscle atrophy in pregnant women on bed rest.

Trial registration

This trial was retrospectively registered with the Chinese Clinical Trial Registry on June 18, 2024 (registration number: ChiCTR2400085770).

Introduction

Advancements in medical technology, particularly assisted reproductive technology (ART), and pro-fertility policies in China have led to an increase in pregnancies among older women and those with increased risk factors [1]. Bed rest is frequently recommended for prenatal care in these women following in vitro fertilisation and embryo transfer, threatened miscarriage or preterm labour because of weak or short cervix, premature membrane rupture, preeclampsia, intrauterine growth restriction, placenta previa, and other pregnancy complications. Although limited studies have evaluated the effectiveness of bed rest in improving obstetric or neonatal outcomes, it remains a standard recommendation for the management of complicated pregnancies [2, 3].

Pregnancy-induced physiological changes in the coagulation and fibrinolytic systems can lead to a hypercoagulable state. Bed rest, a standard recommendation for prenatal care in certain high-risk pregnancies, can increase the risk of deep vein thrombosis (DVT) due to reduced physical activity and blood flow in the lower limbs [4]. Pregnant women are five times more likely to develop DVT than non-pregnant women [5]. If a thrombus detaches and travels to the lungs, it can cause pulmonary embolism, a life-threatening condition for both the mother and foetus [6]. In addition, prolonged bed rest in pregnant women leads to changes in muscle metabolism and function [3], and without timely rehabilitation treatment, disuse muscular atrophy is easily induced [3, 7].

Atrophy of the thigh muscles can significantly limit physical activity and recovery in pregnant women on bed rest, affecting pregnancy and childbirth outcomes. Therefore, the prevention of lower-limb DVT and muscle atrophy is essential. Current clinical prevention strategies primarily involve pharmacological and physical measures [4, 6, 8, 9]. Although effective in some instances, current prevention strategies for DVT and muscle atrophy in pregnant women on bed rest have limitations. Anticoagulants, such as low-molecular-weight heparin, can easily cause subcutaneous bleeding and pain, leading to emotional distress [10]. The misuse of physical preventive measures, such as medical compression stockings, can lead to lower limb oedema and phlebitis, while foot vein pumps and inflatable pressure devices are expensive and complex, their misuse can cause arterial ischaemia [11]. Furthermore, studies on the prevention and treatment of lower limb muscle atrophy in pregnant women on bed rest remain limited, hindering the development of targeted preventive methods.

Foam rollers, also known as yoga columns or foam rolling tubes, originated in Europe. Although initially made from wood, foam rollers were later made with foam materials due to their light weight and moderate hardness and are commonly used in rehabilitation [12]. Foam rolling involves applying pressure to a muscle using a foam roller and one’s body weight to achieve muscle relaxation and is a method of self-myofascial release. Foam rolling is mainly used to improve body awareness, balance, coordination, flexibility, and strength and is primarily used in recovery training for athletes or sports rehabilitation [12, 13].

This study is the first to introduce foam rollers into the field of obstetrics. The purpose of this study was to investigate the feasibility and effectiveness of foam rolling intervention (FRI) in improving lower limb venous circulation and preventing complications. Our research hypothesis was that FRI can effectively enhance lower limb venous blood flow in pregnant women on bed rest, reduce the risk of DVT and muscle atrophy.

Methods

Participant recruitment

A single-blind, randomised controlled trial was conducted at a tertiary-level obstetrics and gynaecology hospital. The study was approved by the ethics committee of the Women’s Hospital School of Medicine, Zhejiang University (IRB No. 20200098-R), and registered with the Chinese Clinical Trial Registry (ChiCTR2400085770, registration date: 2024-06-18).

All pregnant women requiring bed rest for foetal protection were screened for eligibility between July 2021 and August 2022. Participants with premature rupture of foetal membranes, threatened miscarriage/preterm labour (a weak or short cervix or vaginal bleeding), bed rest ≥ 7 days to ensure pregnancy continuation, gestational age ≥ 20 weeks, and maternal age < 40 years were included. Participants with gestational hypertension or preeclampsia, intrauterine growth restriction, placenta previa, pregnancy with pubic symphysis separation, lower limb oedema or varicose veins, antiphospholipid antibody syndrome, obesity or other severe internal or external diseases, recent DVT in the lower limbs, inherited or acquired thrombophilia, coagulation dysfunction or bleeding tendencies were excluded. Informed written consent was obtained from all participants.

Study procedures

Eligible pregnant women who met the inclusion criteria were informed about the study’s purpose, potential benefits, and the importance of preventing lower limb venous thrombosis and muscle atrophy. Family members were briefed on their potential role in supporting the pregnant women. After obtaining informed consent, participants were numbered sequentially (1–106) according to admission time. Simple randomisation (1:1) was used to assign participants to either the experimental or control group, with 53 participants in each group. The random number sequence was generated using SPSS version 22 (IBM Corp., Armonk, NY, USA). Although participants were blinded to their group assignment, researchers affiliated with the obstetrics and gynaecology department were aware of these assignments. Baseline evaluations and randomisation were conducted upon hospital admission.

Intervention

Pregnant participants received FRI and routine venous thrombosis prophylaxis using medical compression stockings. They independently performed lower leg triceps and quadriceps femoris strength training exercises using a foam roller (approximately 33 cm × 14 cm) (Fig. 1). For the lower leg triceps strength training, participants lay supine with flexed limbs, positioning the foam roller beneath their feet and pressing downward (Fig. 2). For the quadriceps femoris muscle strength training, the foam roller was placed at the popliteal fossa while participants straightened their lower limbs and pressed down, alternating between legs (Fig. 3). Participants performed each exercise for 5–10 s, repeating 50 times per session. This regimen was followed for three sessions daily, distributed across the morning, afternoon, and evening. The specific FRI exercises are demonstrated in a supplementary video. Experienced researchers provided initial guidance for foam rolling, ensuring the correct technique for subsequent exercises, and then supervise each subsequent exercise.

Fig. 1

Foam roller

Fig. 2

Lower leg triceps muscle strength training

Fig. 3

Quadriceps femoris muscle strength training

The control group received standard care, including medical compression stockings and regular exercises. Calf muscle strength training involved lying supine and forcefully straightening the lower limbs. Quadriceps muscle strength training required lying supine with extended lower limbs and pressing firmly against the bed surface. The training frequency matched that of the experimental group.

Outcome assessment

Demographic and obstetric data collected included age, education level, body mass index, parity, gestational week, number of foetuses, preterm rupture of membranes status, and fertilisation method. Outcomes assessed were peak and mean blood flow velocities in the popliteal and femoral veins, D-dimer levels, thigh and calf circumference, and the incidence of lower limb DVT and muscle atrophy.

Hemodynamic indicators

Peak and mean blood flow velocities in the popliteal and femoral veins were measured using a Mindray M9 colour Doppler ultrasound (Mindray Ltd., Shenzhen, China). Measurements were taken at admission and within 30 min of completing the lower limb exercise intervention on day 7. Data were recorded from the Doppler system computer screen.

Coagulation indicators

Fasting venous blood samples (2.7 mL) were collected from all participants upon admission and on day 7 post-intervention. Blood was drawn into vacuum tubes containing 0.3 mL of sodium citrate anticoagulant and gently shaken 4–5 times to ensure proper mixing; the serum was separated for subsequent analysis. D-dimer values were used as the detection index. All tests were conducted in accordance with the standardised quality control procedures of the research unit’s testing department, and reagents were used within their expiration dates.

Symptoms and diagnosis of DVT

Pregnant women were monitored daily for symptoms of DVT during hospitalisation, including lower limb pain, swelling, tenderness, and superficial venous congestion, changes in skin colour and temperature of the lower limbs, and Homan’s sign in the thigh or calf. Diagnostic colour Doppler ultrasound was performed on the lower limbs of all pregnant women on day 7 of bed rest for foetal protection by experienced ultrasound physicians. The ultrasound diagnostic criteria for DVT included a significant echo in the venous lumen, non-compressible veins, and no or minimal blood flow signal within the thrombus [14].

Lower limb muscle atrophy

Lower limb muscle atrophy was assessed by measuring changes in thigh and calf circumference. A single nurse measured the circumference of the thighs and calves of all pregnant women using a soft ruler at admission and within 30 min of completing lower limb exercises on day 7 post-intervention. The thigh circumference was measured 10 cm above the upper patellar border, and the calf circumference was measured at the upper third of the calf. A reduction in circumference ≥ 1.5 cm after bed rest compared to before bed rest was considered indicative of muscle atrophy [15].

Sample size calculation

The sample size was calculated using N1 = N2 = 2[(Zα + Zβ)S/δ]². Based on pilot data regarding venous blood flow velocity, the following values were obtained: S = 4.85, δ = 3.59, α = 0.05 (Zα = 1.96), and β = 0.10 (Zβ = 1.282). Applying these values, the estimated total sample size was 76. To account for a 5% attrition rate and potential sampling error, the estimated sample size for each experimental and control group was 40.

Statistical analysis

To ensure data integrity, a database was created and verified by two independent researchers. Statistical analyses were performed using SPSS version 22 (IBM Corp., Armonk, NY, USA). The normality of data was assessed using the Kolmogorov-Smirnov test. Baseline characteristics and post-treatment outcomes were compared between groups using t-tests (for normally distributed continuous data), chi-square tests (for categorical data), or Mann-Whitney U tests (for non-normally distributed continuous data). Data are presented as means ± standard deviations or percentages. P-values < 0.05 were considered statistically significant.

Results

Participant enrolment

In total, 245 pregnant women indicated bed rest for foetal protection and were screened for study participation. Of these, 139 women were excluded for the following reasons: non-adherence to inclusion criteria (n = 84), refusal to participate (n = 35), communication difficulties (n = 5), limited mobility preventing the completion of FRI (n = 5), and active vaginal bleeding (n = 10). Of the remaining 106 participants, 86 (81.1%) completed baseline and post-intervention assessments, resulting in an overall response rate of 81.1%. During the study period, 9 and 11 women in the experimental and control groups were lost to follow-up, respectively. Figure 4 illustrates the participant enrolment process.

Fig. 4

Flowchart of the inclusion procedure

Demographics and obstetric data

Table 1 presents the baseline characteristics of the study participants. No significant differences in demographic or obstetric variables were observed between the experimental (n = 44) and the control (n = 42) groups.

Table 1 Demographic and clinical characteristics of pregnant women on bed rest

Hemodynamic indicators

Table 2 presents the mean (standard deviation) of outcome variables for pretest and post-test measurements across the allocation groups. No statistically significant differences were observed between the experimental and control groups in terms of the mean and peak blood velocities of the femoral veins (Z = -0.095, P = 0.924; Z = -0.795, P = 0.427) or the mean blood velocities of the popliteal veins (Z = -1.331, P = 0.183) before the intervention. However, the peak blood velocities of the popliteal veins were significantly higher in the control group (Z = -2.151, P = 0.031). On the seventh day post-intervention, the experimental group exhibited significantly higher mean and peak blood velocities in both femoral and popliteal veins. See Table 2.

Table 2 Comparative outcomes between groups before and after intervention

Coagulation indicators

Baseline D-dimer levels were comparable between the groups (Z = -1.007, P = 0.314). However, after intervention, the experimental group had significantly lower levels (Z = -2.113, P = 0.035), as shown in Table 2.

Symptoms and diagnosis of DVT

Doppler ultrasonography revealed no cases of DVT in either group. Moreover, neither group reported any DVT-related symptoms.

Degree of atrophy of lower limb muscles

Baseline thigh and calf circumferences were comparable between the experimental and control groups (Table 2). On the 7th day after the intervention, there was no statistically significant difference in the thigh or calf circumference between the two groups (t = -0.166, P = 0.868; Z = -1.194, P = 0.233). However, a reduction in the thigh and calf circumference was observed in both groups, with the reduction in the experimental group being smaller than that in the control group (t = -5.494, P<0.001; Z = -4.744, P <0.001). Consequently, the rate of atrophy of the thigh muscle was significantly slower in the experimental group (P = 0.011), while there was no significant difference in the rate of calf muscle atrophy between the two groups (P = 0.152). See Table 2.

Discussion

This study is the first to demonstrate the clinical efficacy of FRI in enhancing venous blood flow of the lower limb, mitigating the risk of DVT and muscle atrophy in pregnant women on bed rest. The mean and peak velocities of femoral and popliteal vein blood flow were significantly higher in the experimental group on day 7; these findings emphasise the efficacy of FRI in improving lower limb flow in pregnant women on bed rest. Furthermore, mean D-dimer levels were significantly lower in the experimental group following the intervention, suggesting its effectiveness in preventing lower limb DVT in this population, in line with previous studies showing that lower limb exercise effectively enhances blood flow and reduces the risk of DVT [16, 17]. Tanaka et al. [18] developed a specialised in-bed leg exercise apparatus, the Leg Exercise Apparatus (LEX), designed to prevent DVT. The tool led to significantly increased lower leg venous blood flow and vessel diameter. However, our results contrast with those of Schroeter et al. who reported that intramuscular microvascular blood flow did not significantly increase within 30 min following foam rolling intervention [19]. This discrepancy may be attributed to variation in exercise modality, frequency, and intensity; moreover, the two studies focused on distinct types of blood vessels. In our study, the diameter of the femoral and popliteal veins was larger than that of intramuscular microvessels, leading to disparate changes in blood flow velocity following FRI.

Nakanishi et al. demonstrated that intermittent pneumatic compression (IPC) applied solely to accelerated venous blood return in the thigh and improved haemodynamics [8]. Another study revealed that resistance exercise using a lower limb resistance exercise device (LRD) achieved a comparable effect to thigh-targeted IPC, increasing femoral vein blood flow velocity and volume [9]. The FRI incorporates resistance movement while wearing elastic socks and activating the lower limbs. Our findings are comparable to those of thigh-focused IPC and LRD, suggesting a similar mechanism of action. Similarly, the FRI promotes blood return by engaging bone joints and deep veins, establishing a pressure gradient in the plantar and leg regions and facilitating the transfer of blood from superficial to deep veins. This ultimately accelerates deep vein blood flow, potentially reducing the incidence of DVT.

The experimental group experienced a smaller reduction in thigh and calf circumference and lower rate of atrophy of the thigh muscle. Thus, the FRI, which entails multiple sets of low-intensity, high-frequency resistance exercises, effectively prevented muscle atrophy, consistent with prior studies [20]. Yu et al. [21] reported that a vibrating foam shaft can significantly enhance lower limb stability control, sensitivity, muscle strength, joint mobility, and stress and pain threshold in young women. The mechanism underlying muscle atrophy involves increased protein degradation and decreased synthesis within skeletal muscle. Resistance exercise, a cornerstone of exercise therapy, is pivotal in the prevention and treatment of muscle atrophy. Moreover, multiset exercises stimulate muscle protein synthesis more effectively than single-set exercises [20].

Strengths and limitations

To the best of our knowledge, this is the first study to evaluate the efficacy of FRI in the prevention of lower limb DVT and muscle atrophy in pregnant women on bed rest. In this study, a foam roller, typically used for yoga exercises, served as resistance exercise equipment; the intervention combined FRI with elastic sock use and active movement.

Our study had several limitations. First, despite randomisation, there were baseline differences in the peak blood velocities of the popliteal vein between groups. Although these differences had minimal effect, future studies should use more rigorous randomisation methods. Second, as a resistance exercise, the duration and timing of FRI can influence its effectiveness. However, we focused solely on training frequency. Third, uterine contractions were primarily assessed through manual palpation and patient reports. Future studies should use more objective monitoring tools to further verify the impact of this intervention on uterine contractions. Finally, the single-centre design, short follow-up period, and relatively small sample size may limit the generalisability of our findings. Larger, multicentre studies are needed to validate these results and assess long-term clinical outcomes.

Conclusions

FRI is an effective intervention for improving lower limb venous blood flow, mitigating the risk of DVT and muscle atrophy in pregnant women on bed rest. It is inexpensive and portable, enhancing exercise adherence among pregnant women. In particular, it is suitable for women who manage their pregnancy at home. Considering these benefits, the promotion and application of FRI in obstetrics are warranted. Further studies are needed to investigate the optimal duration, frequency, and timing of FRI and its long-term effects.