Expiratory Muscle Training and Trunk Flexion in Parkinson's Disease

Effect of Expiratory Muscle Strength Training on Forward Trunk Flexion in Parkinson's Disease

Postural abnormalities involving the trunk are prevalent in over 20% of patients with Parkinson's disease (PD). Pathological forward trunk flexion (FTF) is a drug-refractory complication in patients with PD leading to imbalance, pain and fall-related injuries. Deep abdominal muscle training is a key rehabilitation strategy for FTF, as muscles like the transversus abdominis and multifidus are crucial for lumbar stabilization. This training has been shown to improve body position and lumbar proprioception.

Abdominal muscles are also responsible for forced expiration. Expiratory muscle strength training (EMST) utilizing forced expiration through expiratory trainer has emerged as a beneficial intervention in the non-pharmacological management of PD, positively impacting clinical aspects such as dysphagia, dystussia, hypokinetic dysarthria, and drooling. EMG study showed large abdominal muscles activity, particularly the transversus abdominis and internus obliquus abdominis during EMST. Therefore, EMST might also be effective in improving lumbar stabilization.

Given the established role of abdominal muscles in trunk stabilization, it is plausible that activation of deep abdominal muscles during EMST with the right level of resistance might improve FTF in PD patients. No studies have yet examined the effect of EMST on posture in PD.

The primary aim of this study will be to evaluate the effect of EMST on forward trunk flexion in patients with Parkinson's disease.

The secondary aim will be to assess the potential duration of the EMST effect on postural abnormalities and its impact on patient stability.

Inclusion Criteria:

• Diagnosis of Parkinson's Disease
• Age ≥ 18 years
• MoCA (Montreal Cognitive Assessment) score ≥19
• Pathological forward trunk flexion defined as thoracic (≥25°) or lumbar (>15°) flexion during standing and walking, which completely disappears in the supine position.

Exclusion Criteria:

• Severe dyskinesia or "on-off" fluctuations
• Change in the PD medication in the last 3 months prior to enrollment
• History of major spinal surgery or musculoskeletal spinal disorders
• Need for assistive devices when rising from a chair or bed
• Other neurological, orthopedic, or cardiovascular comorbidities that could affect postural control
• Inadequate lip seal.