Strength and Dual-Task on Sarcopenia in People With Parkinson's Disease

Parkinson's disease (PD) and parkinsonian syndromes are neurodegenerative conditions characterized by progressive motor and non-motor impairments that can negatively affect functional independence and quality of life. In these populations, sarcopenia and reductions in muscle strength and physical performance may contribute to frailty, falls, disability, and loss of independence.

Progressive resistance training (PRT) represents a potentially relevant physiotherapy intervention for addressing muscle weakness and sarcopenia-related impairments in people with Parkinson's disease. Previous research has shown that resistance training can improve muscle strength and functional performance when appropriately prescribed and supervised. However, most available studies have focused primarily on idiopathic Parkinson's disease and have generally examined resistance training from a functional perspective rather than within a comprehensive sarcopenia framework integrating muscle strength, body composition, physical performance, nutritional status, and cognitive characteristics.

People with Parkinson's disease and parkinsonian syndromes may also experience difficulties when performing motor and cognitive tasks simultaneously. These dual-task difficulties can interfere with mobility and activities of daily living. Therefore, incorporating cognitive tasks into physical training may facilitate the assessment and training of cognitive-motor interaction within a functional context.

In addition, postural instability and impaired balance are clinically relevant features in Parkinson's disease and some parkinsonian syndromes. Resistance training performed with additional instability or postural control demands may provide a different stimulus from conventional progressive resistance training. Nevertheless, comparative evidence regarding progressive resistance training with and without instability remains limited.

Nutritional status may also influence sarcopenia and the response to exercise. For this reason, standardized nutritional education is incorporated into all three study groups, allowing the supervised exercise components to be compared while maintaining a common educational approach across interventions.

This study is designed as a prospective, parallel-group, three-arm randomized controlled trial involving adults with a clinical diagnosis of Parkinson's disease or parkinsonism confirmed by a neurologist. Participants must be aged 18 years or older, be classified within Hoehn and Yahr stages 1-3, have stable antiparkinsonian medication for at least four weeks, be able to ambulate independently with or without an assistive device, and be able to understand and follow basic safety instructions.

Participants with severe or uncontrolled additional pathology, other neurological diseases that interfere with assessment, recent fractures, severe dyskinesias or unpredictable motor fluctuations that compromise safety, or medical conditions contraindicating supervised physical exercise will be excluded.

Following the baseline assessment, eligible participants will be randomly assigned to one of three intervention groups:

Education Group: Participants will receive standardized nutritional education and general physical exercise recommendations according to usual clinical recommendations for people with Parkinson's disease. The intervention will include an initial face-to-face session in which structured educational materials will be explained and provided. A follow-up session will be conducted midway through the 12-week intervention period to answer questions, reinforce the recommendations included in the educational materials, and review adherence to the proposed nutritional and exercise guidelines. Participants in this group will not participate in structured strength training or supervised exercise sessions as part of the study.

Progressive Resistance Training (PRT) Group: Participants will receive standardized nutritional education and a supervised progressive resistance training program targeting the lower limbs, upper limbs, and trunk muscles. Exercises will use dumbbells, resistance bands, weights, body weight, and other appropriate therapeutic exercise resources. Training intensity will be individually adjusted and progressively increased toward approximately 60%-90% of one-repetition maximum (1-RM), according to each participant's functional status, exercise tolerance, and progression. Training load will be periodically adjusted by modifying the external resistance or exercise complexity. Cognitive dual tasks will be simultaneously incorporated into the exercise program to address cognitive-motor interference and promote functional transfer.

Progressive Resistance Training plus Instability (PRT + Instability) Group: Participants will receive the same standardized nutritional education, progressive resistance training, and cognitive dual-task components as the PRT Group. The relative training intensity and strength-training load will follow the same principles as those used in the PRT Group. In addition, instability and increased postural control demands will be incorporated through unstable surfaces and other postural challenges. Exercise intensity and complexity will be individually adapted according to each participant's functional and cognitive status, with safety and adherence prioritized throughout the intervention.

Participants allocated to the PRT and PRT + Instability groups will complete two supervised physiotherapy sessions per week for 12 weeks. Sessions will be supervised by a physiotherapist and individualized according to the participant's abilities, functional status, cognitive status, exercise tolerance, and clinical presentation.

Study assessments will be conducted at three time points: baseline before the intervention (T0), immediately following completion of the 12-week intervention (T1), and four weeks after completion of the intervention (T2). This design will allow the evaluation of within-group and between-group changes and the initial persistence of intervention effects following completion of supervised training.

Clinical and functional assessment will include the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS Parts I-IV), fall recording, the Short Physical Performance Battery (SPPB), and the Timed Up and Go (TUG). Neurological diagnosis, relevant clinical characteristics, dopaminergic medication, ON/OFF status, levodopa equivalent daily dose (LEDD), available neuroimaging, and relevant clinical history will be recorded at baseline and updated at subsequent assessments when clinically relevant changes occur.

Sarcopenia-related assessment will follow the conceptual framework of the European Working Group on Sarcopenia in Older People (EWGSOP2). Measures will include SARC-F, calf circumference, handgrip dynamometry, physical performance assessment, and body composition measured using bioelectrical impedance analysis.

Nutritional status will be assessed using the Mini Nutritional Assessment-Short Form (MNA-SF) and the Malnutrition Screening Tool (MST). The EAT-10 questionnaire will also be used to screen for self-reported swallowing difficulties.

Neurocognitive status will be classified according to DSM-5 criteria as normal cognition, mild neurocognitive disorder, or major neurocognitive disorder. Neurocognitive status will be considered as part of the multimodal characterization of participants and as a potential factor influencing treatment response and tolerance to cognitive-motor dual-task training. Neurocognitive reassessment will also be performed at post-intervention and follow-up assessments according to neuropsychological criteria.

The Charlson Comorbidity Index will be recorded as part of the baseline clinical characterization. When available from participants' medical records or routine clinical practice, analytical biomarkers including vitamin D, albumin/prealbumin, hemoglobin, hematocrit, total cholesterol, HDL cholesterol, and LDL cholesterol will also be recorded. No blood tests will be specifically performed for the purpose of obtaining these biomarkers for the study.

Available neuroimaging information, including DaTSCAN, PET-DOPA, and brain magnetic resonance imaging, will be recorded when available in the clinical record. New neuroimaging or analytical information arising during the study may be incorporated into subsequent assessments when clinically relevant. These medical examinations are not performed specifically as part of the study intervention.

The interventions are based on therapeutic exercise and strength-training procedures commonly used in clinical practice. Potential intervention-related risks are considered low and may include transient muscle discomfort, fatigue, dizziness, musculoskeletal pain, or imbalance during exercise. To minimize these risks, supervised sessions will be individually adapted and will follow principles of progressive loading, safety, and adequate recovery.

If an adverse event occurs during an intervention session, exercise will be stopped immediately and the participant will be assessed by the healthcare professional responsible for the intervention. Appropriate clinical follow-up will be provided according to the nature and severity of the event, including referral to medical or healthcare services when required. Adverse events will be recorded and documented, including their severity, evolution, and possible relationship with the intervention. Continued participation will be considered individually according to clinical safety criteria.

The main objective of the trial is to compare the effects of the three intervention approaches-education, progressive resistance training with cognitive dual tasks, and progressive resistance training with cognitive dual tasks plus instability-on sarcopenia-related parameters and physical function in people with Parkinson's disease and parkinsonian syndromes.

Secondary objectives include describing participants' neurocognitive and nutritional profiles and their sarcopenia and physical-function characteristics; analyzing changes in muscle strength, body composition, and functional performance associated with each intervention; evaluating the effects of incorporating instability on postural control and fall-related functional risk; and exploring the potential influence of neurocognitive and nutritional status on response to treatment.

By comparing these three clinically applicable intervention approaches, the study aims to provide further evidence regarding the role of progressive resistance training within a multimodal approach to sarcopenia and functional impairment in people with Parkinson's disease and parkinsonian syndromes, as well as the potential additional contribution of instability and postural control demands.