The effect of core stabilization exercises on balance and functional performance in individuals with functional ankle instability: An open-label randomized controlled trial

INTRODUCTION

Ankle sprains are a commonly reported musculoskeletal disorder.^[1] It has been observed that lateral ankle sprain recurs more frequently, leading to chronic ankle instability (CAI).^[2] The common features seen in CAI include frequent sprains, a sense of giveaway, pain, reduced range of motion (ROM), muscle weakness, sensorimotor control deficits, and low self-reported function.^[3,4] Based on causal factors, there are two types of CAI – mechanical instability (due to damage to the ankle ligamentous structure) and functional ankle instability (FAI) (due to neuromuscular and proprioceptive deficits).^[5,6]

Repetitive ankle sprains commonly lead to FAI, with a reported prevalence rate of 32–47%.^[3] The common clinical features are impaired proprioception, delayed reflexes, muscle weakness, reduced postural stability, and impaired balance.^[7,8] It has been reported that FAI contributes to altered day-to-day function and quality of life with increased fear of falls.^[9,10]

Varied rehabilitation strategies focus on mobility, muscle strength, balance, and proprioception in FAI.^[11,12] Balance training and conventional exercises also improve postural control in patients with ankle instability.^[13] The biomechanics of the ankle complex and its injuries are linked to proximal control and core stability.^[14]

The lumbar spine, pelvis, and hip musculature form the core. This assists the function of the kinetic chain throughout the body.^[15] Core ensures maintenance of the spine’s stability within the neutral during the performance of movements. It creates a stable proximal control to ensure proper muscle recruitment and motor control during the distal upper and lower limb movements.^[16] Dastmanesh et al. reported improved postural control after eight weeks of core stability training in patients with CAI.^[17] Alizamani et al. showed that 8 weeks of core stabilization training improved ankle muscle strength, dorsiflexion range, and proprioception in athletes with CAI.^[18] This study aimed to investigate the effect of core stabilization exercises on balance and functional performance in FAI.

MATERIALS AND METHODS

Study procedure

After receiving approval from the Ethical Committee, the study was conducted on 30 patients with FAI. The purpose of the study was explained in detail to the participants.

A total of 158 participants were assessed for eligibility, of which 111 were excluded based on the selection criteria, 17 denied participation in the study, and 30 were recruited [Figure 1]. Randomization was done using computer-generated software. Allocation of participants into experimental and control groups was done using sequentially numbered opaque sealed envelopes with a ratio of 1:1. The experimental group (n = 15) received core stabilization exercises along with conventional exercises. In contrast, the control group (n = 15) received only conventional exercises. The intervention period was six weeks, three sessions per week. Pre- and post-assessment were performed before and after the intervention.

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Figure 1:

Consolidated standards of reporting trails (CONSORT) flow diagram.

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RESULTS

Most participants were female (n = 26, 86.7%), compared to males (n = 4, 13.3%). The median and interquartile range values of demographic characteristics such as age, height, weight, and body mass index are shown in Table 2.

Within-group analysis showed an improvement in the experimental and control groups for the single-leg stance test and all direction reach distances of mSEBT. However, no improvement was seen in the pre- and post-scores of the side hop test [Tables 3 and 4].

Between-group analysis revealed significant improvement in mSEBT and single-leg stance scores in the experimental group compared to the control group. However, no significant difference was seen in side hop test scores [Table 5].

DISCUSSION

The present study revealed that core stabilization exercises improved static and dynamic balance compared to mobility and strengthening exercises. However, there was no effect on the functional performance test or sidehop.

Core muscles act as a corset to provide stability while performing motion. It builds up inertia in response to any perturbation given to the body. It comprises abdominal muscles in front, vertebrae and gluteal muscles behind, diaphragm at the roof, and pelvic floor muscles from the floor. Intra-abdominal pressure increases on activation of the transverse abdominis muscle, which leads to an increase in the intra-abdominal pressure, which, further, causes tightening of the thoracolumbar fascia.^[15]

These contractions occur before initiating limb movement, allowing a stable base for lower limb movement.^[15] The rectus abdominis and oblique muscles provide postural stability as they are activated in a direction-specific pattern concerning limb movement. A precise cocontraction of the transversus abdominis and multifidus leads to an increase in muscle stiffness due to the feedforward nature of activation, thus utilizing primary muscles more efficiently and providing segmental stabilization.^[25]

The activation of core musculature is necessary to generate rotational torques, which assist in the production of motion in the extremities.^[15] During the performance of mSEBT, an individual needs to maintain balance on the stance leg and reach using the opposite leg in a specified direction. This leads to the firing of rectus abdominis and oblique muscles before limb movement. This helps to maintain balance. Furthermore, the multifidi and transverse abdominis muscles would help maintain dynamic balance during lower extremity movement by supporting the lumbar spine.^[26]

Kahle and Gribble reported that a six-week core stability program led to an improvement in dynamic balance. This study hypothesized that recruitment of the abdominal muscles provides a stable base of support for postural stability.^[27] Dastmanesh et al. reported improved postural control after eight weeks of core stability exercise training in patients with CAI. Core stability promoted an increase in the feedforward mechanism and improved neuromuscular control of the lower extremities.^[17] This agrees with the findings of our study.

The present study showed no effect of core stabilization on the functional performance – side hop test. Naderi et al. divided 36 athletes with FAI into three groups – core stability training group, neuromuscular training group, and control group.

Exercises were administered for six weeks in core stability training and neuromuscular training groups. The control group did not receive any treatment. There was an improvement in dynamic balance and physical function in athletes with FAI in the core stability training and neuromuscular training group compared to the control group. However, the core stability training and neuromuscular training groups were equally effective.^[28] Apart from core stability, a major requirement for the hop test was cardiorespiratory endurance, which was not very well trained and, hence, compromised in our study population. Furthermore, our study included the general population, which was not involved in any sports or high level of training and exercise, which could be the reason for the lack of significant improvements in the hop tests.^[29]

There are a few limitations in the study. The sample size was small, and the duration of the intervention was six weeks, which is relatively short, the inclusion of the general population who were not involved in sports, and the majority of participants were females.

CONCLUSION

The present study concludes that core stabilization exercises have an additional effect in improving static and dynamic balance compared to conventional exercises in individuals with FAI.

RECOMMENDATIONS

Studies with long-term effects of core stability training with larger cohorts that will help generalize the results can be conducted in the future. Incorporating a core stability program provides a comprehensive and holistic approach toward rehabilitation in individuals with FAI. Hence, it is highly recommended that core stability training be implemented to manage FAI.