Guillain-Barré Syndrome (GBS) is an acute inflammatory demyelinating polyradiculoneuropathy or acute motor axonal neuropathy. It is an immune-mediated polymyopathy that affects sensory, motor, and autonomic nerves and is caused by an abnormal immune response to infection. Although peripheral nerve damage is the primary mechanism, the exact etiology remains unclear [1]. The incidence of this rare condition is 0.89-1.89 per 100,000 people, with men exhibiting a 1.78 times higher risk than women [2]. The primary clinical manifestations of GBS include rapid-onset paralysis and sensory deficits, which range from mild muscle weakness to complete paralysis [3].

Maximum muscle weakness typically occurs 2-4 weeks after symptom onset, with gradual improvement over subsequent weeks and months. Although most patients recover, some experience persistent physical dysfunction. Notably, approximately 10-20% of patients are unable to regain walking ability even six months after disease onset [3,4]. Treatment requires a multidisciplinary approach, combining immunomodulatory therapies such as plasma exchange and intravenous immunoglobulins with rehabilitation interventions [3,5]. Rehabilitation aims to prevent and minimize physical impairments [1]. Evidence suggests that physical rehabilitation strategies, including core stability exercises, combined exercise regimens, high-intensity resistance training, and gait training, can reduce disability and improve muscle strength, lung function, functional independence, and quality of life in patients with GBS [6-9].

Restoration of walking ability is a critical goal of rehabilitation in neurological disorders, including GBS. Achieving this requires targeted muscle strengthening and improvements in basal physical fitness through gait training. Robotic gait training (RGT) has emerged as a promising alternative approach, offering early initiation of walking therapy, prolonged and high-intensity sessions, reproducible gait patterns, and objective performance measurement [10]. Studies have demonstrated the efficacy of RGT in enhancing motor and cardiorespiratory functions in patients with stroke and spinal cord injury [11-13]. However, evidence on its application in GBS remains limited. Given the scarcity of robust evidence on the effectiveness of exercise interventions for GBS and the lack of standardized exercise protocols, further research is needed to assess the role of RGT in improving walking ability and physical fitness in this patient population.

Therefore, in this study, we aimed to evaluate changes in body composition, basal physical fitness, and quality of life in patients with GBS using end-effector-type robotic gait training devices. Additionally, the study sought to identify the potential benefits of RGT in GBS rehabilitation and contribute to the development of effective exercise rehabilitation protocols to enhance gait ability and overall physical function.

This study is the first to utilize a robotic gait device for interval-style training in patients with GBS. The maximum heart rate was maintained at 141 bpm, which likely increased the total fat oxidation rate. High-intensity interval training (HIIT) is known to effectively reduce visceral abdominal fat. This effect can be attributed to an increase in excess post-exercise oxygen consumption (EPOC) and the activation of fat-oxidizing enzymes following exercise [15]. Consequently, it is anticipated that RGT in this study similarly enhanced fat oxidation and improved the metabolic rate.

Muscle mass increased by 3.3% (27.5 kg vs. 28.4 kg). According to Petré et al. [16], HIIT may be more effective than continuous medium-intensity exercise in promoting muscle hypertrophy and strength. This is because HIIT elevates mechanical tension in the muscles, thereby activating the mTOR pathway. Activation of mTOR promotes the phosphorylation of p70S6K and 4E-BP1, enhancing muscle protein synthesis. Although the exercise was aerobic, high-intensity interval training over a relatively short period appears to have stimulated muscle protein synthesis. The isometric muscle strength measurements yielded encouraging results, with significant increases observed across all joints and items. Particularly, affected muscles demonstrated substantial gains in isometric strength, with the greatest improvement observed in hip flexion (HF_Affected), which increased by 69.4%. This finding suggests that interval training using a gait robot promotes neuromuscular adaptations. Yu et al. [17] reported that HIIT selectively mobilizes and induces hypertrophy of Type II muscle fibers by lowering the kinetic unit mobilization threshold, increasing firing frequency, and improving neuromuscular junction efficiency. Additionally, in patients with GBS, such training may promote peripheral nerve remyelination and accelerate axonal regeneration, as suggested by Fletcher et al. [18].

As shown in Figure 4, walking speed improved remarkably by 157.1% (from 0.7 km/h to 1.8 km/h), and the number of steps per minute increased by 133.3% (from 33.0 to 77.0). These improvements can be attributed to the principles of motor learning and neuroplasticity. A recent study demonstrated that repetitive and intensive training with a walking robot activates the central pattern generator (CPG) and induces corticospinal reorganization [19]. Robot-assisted gait training strengthens functional connectivity between the motor cortex and spinal cord, facilitating the relearning of gait patterns. Furthermore, during the high-intensity interval training phase, greater motor unit recruitment likely enhanced muscle strength and coordination, improving gait ability. A study by Shen et al. [20] using functional near-infrared spectroscopy (fNIRS) supported these findings, showing increased activation of movement-related brain regions during HIIT. A 7.1% improvement in the TUG test indicates better dynamic balance and functional mobility. Interval training may enhance vestibular and proprioceptive system integration. Naro et al. [21] demonstrated that repetitive gait training promotes motor learning in the cerebellum, increasing gait automatization and efficiency. Functional magnetic resonance imaging (fMRI) studies have shown enhanced cerebellar functional connectivity following gait training. Therefore, as demonstrated in this study, interval training using RGT could be beneficial for patients with neurological and muscular disorders.

ESE increased by 29.1%. This finding suggests that successful exercise stimulates the secretion of neurotransmitters such as dopamine and serotonin, creating a positive feedback loop. Numerous studies have reported that physical activity and exercise influence circulating levels of these neurotransmitters and serve as effective non-drug therapies for reducing anxiety and depression [22,23]. Martinez-Diaz et al. [24] reported significant increases in blood brain-derived neurotrophic factor (BDNF) levels and working memory capacity following HIIT (10 bouts × 1 min) in 25 male college students. This suggests that the acute stress of HIIT induces notable responses in BDNF and cortisol, enhancing working memory capacity. However, the relationship between cognitive and neurophysiological markers during high-intensity exercise requires further clarification. Additionally, a systematic review and meta-analysis by Wilke et al. [25] demonstrated that exercise-induced increases in BDNF promote neuroplasticity, enhance cognitive function, and improve overall quality of life. Notably, they emphasized that HIIT elicits greater BDNF release compared to continuous moderate-intensity exercise. Shah et al. [7] found that supervised strength, aerobic, and gait training over 12 weeks in patients with GBS improved gait, activities of daily living (Barthel Index), quality of life, and fatigue more effectively than unsupervised voluntary exercise at home. These findings suggest that supervised exercise is a more advantageous rehabilitation approach for patients with GBS compared to unsupervised exercise. However, further research on acute and chronic GBS is needed.

In summary, this case report suggests that 4 weeks of intensive robotic gait interval training may effectively restore physical function and enhance quality of life in patients with GBS. Significant improvements in lower limb muscle strength, gait ability, and ESE can be attributed to neuromuscular adaptation, motor learning, and neuroplasticity. However, as this is a single case study, the generalizability of the findings is limited. Future randomized controlled trials involving a larger cohort of patients with GBS, longterm follow-up assessments, and comparative studies of varying intervention durations and intensities are warranted.