Effect of Pilates exercises on muscle strength and balance after healed lower limb burns

Introduction

Burn injuries are considered one of the most destructive types of injury and rank as the fourth most prevalent form of trauma worldwide. Patients who survive the initial acute phase of burn injuries often experience marked prolonged skeletal muscle weakness, postural imbalance, and diminished functional abilities. These complications hinder the burn victims from performing daily activities and resuming work [1]. Lower extremity burns are prevalent in burn centers, with approximately 35 to 39% of burn patients presenting such injury, either in isolation or with burns in other parts of the body [2].
Pilates is an exercise approach that was first created in the early 20th century by Joseph Pilates, with the aim of integrating body, mind, motor skills, and core stability. Pilates sessions focus on triggering specific muscles in functional patterns at controlled speeds, with an emphasis on breathing and proprioception. The key objectives of Pilates exercises include promoting proper movement patterns, improving core stability, and enhancing overall performance. Pilates enhances motion and function by strengthening minor muscles, subsequently thus strengthening major muscular groups [3]. Pilates exercises stretch the lumbar spine muscle groups and improve the strength of the core muscles, viz. the transverse abdominal, multifidus, pelvic floor, and diaphragm muscles, with the aim of lessening spinal strain and stabilize it [4]. Pilates is a unique method for improving posture and motion control as well as mind-body awareness. Recently, Pilates has drawn attention as a beneficial exercise method [5].
Pilates exercises are performed on the floor or with the aid of specialized apparatus with adjustable spring resistance. Pilates exercises usually relied on the following concepts: breathing, flow, centering, precision, and control. Although Pilates was once only employed by dancers, it has gained popularity in recent years in the general fitness community and in the rehabilitation of injuries. Its emphasis on activating the torso and the stabilizing muscles of the lower back make it a common prescription for individuals with low back pain (LBP). It is therefore assumed that Pilates exercises will aid in the reactivation of these muscles, enhancing the lower back stability and lowering pain and disability [6].
In conjunction with other exercise programs, Pilates aims to strengthen specific muscles, rebalance, and realign the body. It emphasizes improving body awareness to decrease the hazards of injury related to imbalances [7]. In contrast to traditional resistance exercises that train muscles separately, Pilates targets the synchronized recruitment of several muscle groups simultaneously, applying the holistic approach. Pilates has also demonstrated improvements in physical fitness, quality of life (QoL), psychological well-being, mood, depression, and anxiety [8]. Additionally, Pilates exercises have been found to enhance motivation and adherence, which are crucial for successful interventions and improvement [9].
Severe burn injuries covering ≥30% of total body surface area (TBSA) are linked to increased catabolism and hypermetabolic reactions. These result in significant muscle mass loss, diminished strength and endurance, and ultimately crippling contractures due to hypermetabolism, which can persist for two to three years after the burn. This final problem induces a catabolic state that raises insulin resistance, tachycardia, resting energy expenditure, negatively balances muscle protein, reduces bone mass, and ultimately impairs physical abilities. These effects are exacerbated by deconditioning, such as extended bed rest, immobility and inactivity, and affect the capacity to carry out various tasks and function over the short- and long-term [10,11].
Balance deficits following burn injuries can arise from several factors, including loss of tactile sensation, proprioception, muscle strength, limited joint mobility, and cognitive impairments, all of which can be affected in severe cases. Additionally, balance may deteriorate further due to complications associated with burns, such as prolonged hospitalization, poor nutrition, pain, and neuropathies. Burn injuries also damage the dermal tissue that contains sensory neurons responsible for providing both conscious and automatic feedback essential for balance and coordination. Consequently, patients with burn injuries exhibit different walking kinematics and kinetics compared to those without injuries. Factors such as gait pace, stride length, movement quality, and overall balance are significantly impacted after a lower limb burn [12,13].
Some of the potential complications associated with lower limb burns include scarring, contractures, muscle weakness, postural instability, impaired sensation, pain, and low exercise capacity. These problems profoundly impair the patient’s functional abilities [14]. One therapeutic intervention that could reduce the adverse consequences of burns, and enhance the functional outcomes of burn survivors, is exercise [15]. The practice of Pilates has grown in popularity lately and appears to be a useful way to improve QoL, postural balance, and core strength. However, little data exists about the efficacy of Pilates exercises in post burn rehabilitation or its effects when the lower limb muscles are the main focus [16]. Thus, the aim of the current study is to evaluate the impact of Pilates exercises on lower limb muscle strength, balance, and functional status in patients with healed lower limb burns, and to identify the most effective treatment program for lower limb burn rehabilitation.

Materials and methods

Study design
A randomly assigned, double-blind, controlled experiment was performed from July 2023 to March 2024 at the Outpatient Clinic of the Faculty of Physical Therapy and the Burn Unit of Orabi Hospital for Burns, Al Obour City. This study complied with the Helsinki Declaration, obtained approval from the ethical committee of the College of Physical Therapy, Cairo University (approval No.: P.T.REC/012/004642), and was enrolled on ClinicalTrials.gov (ID: NCT05991479). Following the ethical approval, participants provided informed consent before enrolment.
Participants
Seventy-six patients of both sexes with thermal burn injuries were enrolled based on specific inclusion criteria: age 20 to 40 years, with a body mass index (BMI) ranging between 25 and 30 kg/m², a total body surface area (TBSA) of 30% to 40% determined by rule of nines, and having experienced second-degree thermal burns (partial thickness burns) affecting the lower limbs. All patients received the treatment from one to three months after full wound healing. Patients involved in the study presented with second-degree burns located on the anterior and posterior thighs, anterior and posterior legs, and the foot.
Patients with second degree burns, i.e. both superficial and deep partial-thickness burns, were selected through clinical assessment. Superficial partial-thickness burns mostly damage the dermal layer. When first examined, blisters are common and frequently stay intact. After the blister has unroofed, the underlying wound bed is always red or pink and will blanch when pressure is applied to it. These burns are uncomfortable. Healing typically occurs with just minor scars after two to three weeks. In contrast, deep partial-thickness burns affect the deeper reticular dermis. Blisters may remain intact on these burns, much like the superficial forms. Until the blisters are debrided, the underlying wound bed has a mottled appearance and gradually blanches when pressure is applied. The patient who has a partial thickness burn feels minimal pain only with deep compression. Though it can take longer and cause scars, these burns can heal with no surgery [17].
Patients were excluded if they had open wounds in or adjacent to the treatment areas, chemical or electrical burns, inhalation injuries, musculoskeletal conditions that would impact outcomes during exercises and testing, sight or hearing impairments, neurological, psychiatric, or cognitive disorders, or exhibited uncooperative behavior.
Sample size calculation
A sample size of 76 patients was estimated utilizing G*POWER statistical software (version 3.1.9.4; Franz Faul, Universität Kiel, Germany) to achieve adequate statistical power. The sample size was estimated based on handheld dynamometer (HHD) data from a previous study by Meenakshi et al. [18], which reported a significant effect of Pilates on lower limb muscle strength compared to closed kinetic chain exercises in subjects with knee osteoarthritis. Accordingly, the required sample size was determined to be 38 subjects per group. The calculations were based on a two-sided 5% significance level, an effect size of 0.7, and a power of 85%.
Randomization
Each participant was provided with information regarding the characteristics, objectives, and benefits of the research, as well as their right to withdraw or decline participation at any point. After signing the consent forms, demographic data were obtained. An independent researcher then assigned the 76 participants randomly and equally to either Group A or B using computer-generated random cards, enclosed in sealed and opaque envelopes. The envelopes were sealed and sequentially numbered to ensure the concealed allocation and participants were unaware of their group allocation. The participant flow is illustrated in Figure 1 following the CONSORT 2010 guidelines [19].
Fig. 1. CONSORT flow chart of the study
Outcomes measures
Measurements were taken both before and after the eight-week intervention.
Primary outcome measures
Lafayette Hand-held Dynamometer (HHD)
The hand-held dynamometer (HHD) is a practical device known for its reliability and validity in muscle strength assessment in clinical settings [20]. A Lafayette Manual Muscle Tester, Model # 01163, (Lafayette Instrument Inc., Lafayette, Indiana) was used in this study. The maximal isometric force of the knee extensor and flexor was determined using the isometric “make” test, in which each participant exerted maximum effort against a stationary HHD while maintaining a stable position. Each participant performed three 5s contractions with a 30s relaxation between trials and a five minute rest between muscle groups. The mean value for each muscle group across all these trials was calculated. Patients were motivated to exert their maximum efforts during the investigations. Measurements were taken while participants sat with their hips and knees bent at 90 degrees. The HHD was placed just above the ankle joint, on the front of the lower leg to evaluate the knee extensors and on the back of the lower leg to evaluate the knee flexors [21].
Berg Balance Scale (BBS)
The BBS is extensively utilized for evaluating balance and is recognized for its validity and reliability [22]. Balance was evaluated using the 14-item BBS. This assessment required 10 to 20 minutes for completion and measured the ability of the participant to maintain balance for set periods, both in static positions and during various functional activities. Each item is scored from 0 to 4, where 0 indicates an inability to perform the task and 4 signifies independent completion. The total score can range from 0 to 56. A score below 45 denotes a higher risk of falling, while a perfect score of 56 reflects good functional balance. The BBS assesses both static and dynamic balance components [23].
Secondary outcome measures
Lower extremity functional scale (LEFS)
The Arabic version of the lower extremity functional scale (LEFS) was utilized to evaluate lower extremity functional status. The LEFS is a useful patient-reported outcome measure used in both clinical and research settings to determine the degree of activity limitation. It has been found to be valid, reliable, and responsive for musculoskeletal problems. It comprises 20 items, with each scored on a 0–4 Likert scale. The overall score is calculated by summing the scores for all items, with the total ranging from 0 and 80: a higher score indicates a greater functional ability. To improve its use in all Arabic-speaking nations, the LEFS has been translated into classical Arabic [24].
Intervention
In this research, patients were randomly distributed to two groups, each comprising 38 participants: Group A (the study group) underwent Pilates exercises in combination with a traditional physiotherapy program, which included stretching, ROM, and strengthening exercises. Group B (the control group) underwent only the traditional physiotherapy program. Both groups followed a treatment regimen of 24 sessions over eight weeks, with three sessions per week.
Pilates exercises
Before the commencement of Pilates training, an instructional session was conducted to inform the patients about the principles of Pilates (breathing, concentration, centering, control, precision, and rhythm) and to instruct them to apply these principles throughout the training program [25].
Each Pilates session lasted 60 minutes, beginning with a 10-minute warm-up consisting of joint mobility in the form of hip rolls and arm circles and breathing exercises, followed by 40 minutes mat Pilates exercises, and ending with a 10-minute cool-down involving stretching exercises [26]. The selected Pilates exercises in this study included the following: hundred, spine stretch forward, roll up and down, single leg stretch, double leg stretch, clams, single leg kicks, side leg kicks, shoulder bridge, criss cross, one leg circle, hip twist, swimming, standing footwork, and squatting. These exercises were executed three times per week over eight weeks, with each exercise consisting of three sets of ten repetitions. Table 1 illustrates the progression of the Pilates exercises used in the training [3,27].
Tab. 1. Progression of the Pilates exercises
Traditional physiotherapy program
Over the eight week programme, all participants also received three sessions per week of traditional physiotherapy. This program consisted of 45-minute supervised and personalized exercises, beginning with calf and hamstring stretches (each held for 45 s and repeated three times), followed by ROM and strengthening exercises for the lower limb muscles. Free weights were utilized for strengthening exercises. The weight load began at 50% to 60% of the three-repetition maximum (3RM) during the first week. From the second to the sixth week, the intensity was raised to 70%–75% of the 3RM. In the seventh and eighth weeks, the intensity was further increased to 80%–85% of the 3RM, with a 5 s hold at the end of each range of motion. Each strengthening exercise consisted of three sets of ten repetitions.
Deep friction massage was applied for 15–20 minutes each visit for scar management. Deep circular movement was performed using thumb balls, with shear force and drag applied in sufficient amounts to mobilize the tissue tension. The skin was lifted and rolled after the tissue became more pliable. Additionally, a refabricated pressure garment consisting of an elastic tubular bandage was used to fit the entire scar. In areas where optimal pressure cannot be achieved, e.g. at body concavities, different insert materials such as silicone gel and silicone elastomers were used with pressure between 25 and 40mmHg; these were worn the whole day except during hygiene or exercises [28].
Statistical analysis
An unpaired t-test was utilized to compare subject characteristics across groups, while the sex distribution was compared using a chi-squared test. The Shapiro-Wilk test was applied to determine if the data were normally distributed. To test the homogeneity of variance across groups, Levene’s test was utilized. A mixed MANOVA was employed to study the impacts of the intervention on knee flexor and extensor strength, BBS, and LEFS. When significant results were achieved by the MANOVA, each outcome measure was subjected to follow-up univariate ANOVAs with Bonferroni correction to protect against type I error. All statistical tests were set at a significance level of p <0.05. The analysis was performed using SPSS version 25 for Windows (IBM SPSS, Chicago, IL, USA). There were no withdrawals from this study, and all individuals completed the treatment program.

Results

Participant characteristics
Table 2 shows the participant characteristics for both groups. No significant differences were found between the groups with regard to age, BMI, TBSA, TBSA LL, or sex distribution (p > 0.05).
Tab. 2. Comparing the characteristics of participants between both groups
Effects of the intervention on knee flexor and extensor strength, BBS, and LEFS
Mixed MANOVA demonstrated significant interaction effects between treatment and time (F= 99.74, p = 0.001, partial eta squared = 0.98), as well as significant main effects of treatment (F= 69.81, p = 0.001, partial eta squared = 0.79), and time (F = 1189.65, p = 0.001, partial eta squared = 0.82).
Within-group comparisons
Both groups A and B exhibited significant improvements in knee flexor and extensor strength, BBS, and LEFS over the course of treatment; the mean differences were -8.4, -10.2, -21.29 and -23.95, respectively, in Group A and -4.18, -6.17, -12.82 and -11.45, respectively, in Group B (p > 0.001). The percentage changes in knee flexor and extensor strength, BBS, and LEFS in Group A were 45.14%, 51.23%, 75.04%, and 45.69%, respectively, compared to 22.14%, 30.41%, 44.33%, and 21.74%, respectively, in Group B (Tables 3 and 4, Figure 2).
Between-group comparisons
No significant differences were found between groups before treatment (p > 0.05). However, post-treatment, significant improvements in knee flexor (effect size = 2.58) and extensor (effect size = 2.17) strength, BBS (effect size = 3.54), and LEFS (effect size = 6.67) were noted in Group A compared to Group B (p > 0.001) (Tables 3,4).
Tab. 3. Mean knee flexor and extensor strength before and after treatment, both groups
Tab. 4. Mean BBS and LEFS before and after treatment, both groups
Fig. 2. Estimated marginal means in both groups for (a) knee flexor strength (b) knee extensor strength (c)BBS score (d)LEFS score

Discussion

Our main findings indicate that combining Pilates exercises with traditional physiotherapy yielded statistically significant improvements in lower extremity muscle strength, balance, and function compared to the traditional physiotherapy program alone in patients with healed lower limb burns. Post-treatment comparisons showed significantly greater improvements in knee flexor and extensor strength, BBS, and LEFS for Group A compared to Group B (p < 0.001). Knee flexor and extensor strength increased by 45.14% and 51.23% in Group A and 22.14% and 30.41% in Group B.
The positive effect of the Pilates approach, as indicated by HHD, can be attributed to several mechanisms. Pilates is an exercise method that combines stretching, strengthening, and core-focused exercises to enhance lower limb strength, core stability, flexibility, and coordination. It also promotes mental well-being by reducing stress and improving focus, contributing to overall physical fitness, posture, and balance [29]. Pilates incorporates synergistic movement patterns with isometric, eccentric, and concentric muscle contractions, which are directly applicable to functional activities [30]. In addition, Pilates mat exercises utilize body weight for resistance, contributing to increased muscle strength, improved balance, and enhanced functional performance [31].
This aligns with the outcomes by Azab et al. [27], who report significant decreases in pain intensity and improvements in hip abductor, external rotator and knee extensor strength, functional performance, and QoL in patients with patellofemoral pain syndrome following Pilates exercises integrated with the conventional program. Also, Preeti et al. [32] found Pilates exercises to yield significant improvements in lower extremity strength, flexibility, dynamic balance, and coordination in young men. Additionally, Bertoli et al. [33] reported that mat Pilates exercises improved multiple isokinetic torque parameters, including knee flexors and extensors, and hip flexors and extensors, in elderly women.
The percentage change in BBS was 75.04% in Group A, and 44.33% in Group B. These positive findings can be attributed to spinal and supraspinal neural adaptation process rather than increased lower limb muscle strength [14,34]. The stability of the vertebral column is achieved by both passive and active components, with muscle strength and endurance playing the most significant role in maintaining spinal stability. The primary muscles supporting the spine are the diaphragm, pelvic, abdominal, and back muscles, and contracting these muscles increases intra-abdominal pressure and vertebrate stability. Hence, strengthening these muscles improves spinal column stability [35].
Pilates training provides various inputs associated with proprioception and muscle stimulation, which enhance muscle strength; it also increases upright body alignment by engaging trunk muscles to counteract gravity and promoting the growth of sarcomeres and muscle fibers essential for contraction. Moreover, visual and auditory stimuli send impulses to the cerebellum and cerebral cortex, stimulating the agonist and antagonist muscles synergistically, especially the trunk stabilization muscles. These muscles respond to vestibular system activation, facilitating muscle response and system adaptations to maintain balance. Visual input and head control influence balance, so correct alignment needs to be maintained during Pilates exercises [36].
When doing Pilates exercises, it is important to concentrate on following the exercise sequence while breathing normally. The activation of supraspinal control enhances the synchronization of movements. Thus, by shortening weak muscles and activating supraspinal control, the principal mechanisms of directional preferences in Pilates exercises enhance motor control and improve pain and function clinical results [37].
Additionally, Pilates enhances trunk muscle strength, core stability, kinesthetic awareness, and the ability to correct faulty movement patterns, thus improving motor coordination of limbs, which subsequently enhances overall motor control and performance [38-39]. It also enhances mechanoreceptor sensitivity and proprioception around the knee joint, leading to improved muscle contraction, restoration of normal position sense, better movement control, and enhanced joint awareness [40].
This is in line with Guclu-Gunduz et al. [41], who found that an eight-week Pilates program significantly enhanced postural balance, strength, and mobility in multiple sclerosis patients. This research indicated that incorporating Pilates into physical therapy programs could address the imbalance and strength loss experienced by patients with multiple sclerosis, as it incorporates both strengthening and balance training. Additionally, Valenza et al. [42] reported that an eight-week Pilates exercise program led to a significant improvement in dysfunction, pain perception reduction, flexibility enhancement, and balance improvement in patients with chronic non-specific LBP.
In the present study, the functional status, assessed by LEFS, improved by 45.69% in Group A and by 21.74% in Group B. Improved functional status arises from enhanced balance and muscle strength [43]. These findings agree with those of Çoban et al. [44], who found that an eight-week Pilates program significantly improved balance, functional performance, movement skills, lower-limb strength, and reduced fall risks in Parkinson's patients. Additionally, Safyeldeen et al. [45] found that the Pilates approach resulted in significantly greater improvements in pain, functional impairment, and QoL for treating postnatal LBP compared to progressive muscle relaxation exercises. Meenakshi et al. [18], also found greater significant enhancements in pain relief, muscle strength, and function among knee osteoarthritis patients following Pilates training compared with closed kinetic chain exercises.
Clinical relevance
Our findings indicate significant improvements for all measured variables, highlighting the positive impact of Pilates exercises on patients with second-degree thermal burns. These findings imply that Pilates can improve recovery results for this particular population when included in a rehabilitation program.
Strengths and limitations
This study demonstrates the value of Pilates exercises, which were found to be effective while lacking adverse effects. It also supports their integration as a crucial part of rehabilitation for patients with lower extremity burns. However, the study has its limitations, including a lack of follow-up, a short treatment duration, and limited generalizability due to the small sample size and the specific population participating in this study (e.g., patients with TBSA of 30% to 40% and only second-degree thermal burns); the response to treatment also varied between individual patients.
To strengthen the evidence for Pilates in burn rehabilitation, further studies should include longer treatment durations, larger sample sizes, and follow-up assessments. Longer studies in more diverse populations will also be necessary to build on these findings. Additionally, future studies are suggested to assess the cost-effectiveness of Pilates compared to traditional rehabilitation methods is essential for understanding its economic viability and potential benefits. There is also a need for additional trials involving a larger patient population to investigate how treatment effects vary based on age and BMI. Additionally, it is important to create subgroups that reflect different age ranges BMI and TBSA categories.

Conclusion

Pilates exercises appear to effectively enhance lower limb muscle strength, balance, and functional status in adult patients undergoing rehabilitation for second-degree thermal burns, specifically in cases where TBSA ranges from 30% to 40%. This suggests that integrating Pilates into rehabilitation programs can significantly contribute to recovery outcomes for this patient population.

Acknowledgment

The authors greatly appreciate the patients who participated in this study.

Funding

This research received no external funding.

Conflicts of interest

The authors declare no conflict of interest.

References