This study investigates a new training method designed to help older adults preserve their muscle strength during hospitalization. When older adults are admitted to the hospital and spend long periods in bed, their muscles can weaken very quickly. This condition is known as hospital-associated disability (HAD), and it can lead to longer hospital stays, reduced independence, and an increased risk of complications or even death. Conventional strength training with heavy weights is often too demanding or unsafe for frail patients, especially just after surgery or illness. As a safer alternative, this study combines light muscle exercises with a medically validated technique called blood flow restriction (BFR), which gently reduces blood flow to the leg to boost the effects of light exercises.

To make training more engaging and personalized, the GHOSTLY+ system was developed. This system consists of a game played on a tablet that responds to muscle activity through sensors placed on the skin. While playing, patients perform isometric muscle contractions (exercises where the muscles tighten without moving the joint) that help to maintain and rebuild strength. The system was carefully designed in collaboration with patients and therapists, and it has already been tested in a smaller pilot study at UZ Brussel.

The current study is a multicenter randomized controlled trial, taking place at UZ Brussel, UZ Antwerpen, and UZ Leuven. A total of 120 patients aged 65 or older will be recruited, all of whom are hospitalized and are unable to bear weight or transfer (e.g., from lying to seated position). Participants will be randomly assigned to one of two groups. One group receives standard physiotherapy. The other group receives standard therapy plus the GHOSTLY+ training program.

Those in the GHOSTLY+ group will train at least five times per week for two weeks, or until discharge from the hospital. Each training session lasts approximately 30 minutes and involves three sets of 12 muscle contractions, guided by the game. The difficulty is adapted to the individual's muscle strength, which is measured at the beginning of the training using a built-in calibration protocol. During the session, a smart cuff is applied to the upper leg to partially restrict blood flow - a technique shown to safely enhance muscle adaptation. The cuff is inflated to 50% of the individual's arterial occlusion pressure and deflated after the session ends. Before beginning, participants receive a short training session with a physiotherapist. Our pilot study (Debeuf et al., 2025) shows that most patients can use the system independently after about one hour of instruction.

Measurements and evaluations take place at three timepoints: before starting the training, after one week, and again at discharge. The main goal is to assess leg muscle strength, which will be measured using a handheld device called a dynamometer. In addition, researchers will collect information on:

• Muscle mass, via ultrasound of the thigh muscle
• Functional capacity, using a 30-second sit-to-stand test and a walking scale (Functional Ambulation Category)
• An index of independence in activities of daily living (Katz scale)
• Cognitive functioning, using the Mini-Mental State Examination (MMSE)
• Time spent bedridden and total length of hospital stay
• Therapy adherence and user experience, via usage data and questionnaires
• Muscle activity signals, such as fatigue, recorded during gameplay
• Implementation outcomes (collected via surveys, interview, site logbooks)

The study will also assess how easily the GHOSTLY+ system can be implemented in real hospital environments. This includes evaluations of user satisfaction, therapist feedback, and how consistently the system is used across hospital settings. Information will be gathered through structured interviews, surveys, and data logs from the app. These insights are crucial to understanding whether GHOSTLY+ can be broadly adopted in other hospitals in the future.

Blood flow restriction training is considered very safe when applied correctly and is already used in rehabilitation clinics and sports medicine worldwide. Over 300,000 sessions have been conducted internationally, with a very low rate of complications. Minor discomfort, such as temporary tightness or muscle fatigue, may occur, but the risk of serious side effects is extremely small.

By participating in this study, patients may benefit from improved muscle strength, reduced time spent in bed, and greater physical independence at discharge. The study also contributes to the development of more effective and enjoyable rehabilitation methods for older adults in hospitals.

Hospitalization places older adults at significant risk for hospital-associated disability (HAD), a condition marked by a rapid and often severe decline in muscle strength and function due to immobility. Research has shown that adults aged 65 and older can lose up to 15% of their lower-limb strength within a single week of bed rest, and as much as 5% of muscle mass per day. These declines not only prolong the length of hospital stay but also increase dependence, impair mobility, and elevate the risk of mortality. While high-load resistance training is considered the gold standard for preventing muscle loss, it is often contraindicated or simply unfeasible for frail or post-surgical patients. This creates an urgent need for effective, low-impact alternatives to preserve physical function during hospitalization.

Blood flow restriction (BFR) training has emerged as one such alternative. It works by partially occluding arterial blood flow and fully restricting venous return in a limb using a pressure cuff, thereby enhancing the effects of low-load exercise. BFR has been demonstrated to stimulate muscle hypertrophy and strength gains in various populations, including older adults, and has been shown to be safe in over 300,000 reported clinical sessions. In addition to physical limitations, another major challenge in hospital rehabilitation is poor adherence. Many patients fail to complete unsupervised therapy exercises, largely due to low motivation. Serious games - interactive applications designed with a therapeutic goal - have shown promise in improving engagement, but most are not designed specifically for clinical use or individualized for the needs of hospitalized older adults.

To address these challenges, the GHOSTLY+ system was developed. GHOSTLY+ is a mobile rehabilitation solution combining gamified muscle training with BFR, designed to be used during non-therapy time in hospitalized older adults. The system is based on a serious game app that transforms muscle contractions, measured via surface electromyography (EMG), into in-game actions. By engaging patients in a playful yet physiologically grounded environment, the system aims to increase motivation and ensure proper exercise intensity, even without the use of weights or active movement. GHOSTLY+ includes automated difficulty adjustment based on real-time EMG input and follows evidence-based parameters for strength training: isometric contractions at approximately 75% of each patient's maximum voluntary contraction (MVC), performed three times per session with 12 repetitions each set.

The clinical study described here is a multicenter, randomized controlled trial (RCT) using a Hybrid Type 1 design. The trial will be conducted at three hospitals in Belgium (UZ Brussel, UZ Antwerpen, and UZ Leuven) and will enroll 120 older adults aged 65 years or above who are hospitalized, unable to bear weight or transfer independently, are expected to remain hospitalized for approximately 14 days, and are at high risk of muscle strength loss due to prolonged immobility. Participants will be randomly assigned to one of two groups. The control group will receive standard physiotherapy as prescribed in the hospital. The intervention group will receive standard care supplemented with the GHOSTLY+ system. Participants will use GHOSTLY+ for at least five sessions per week, over two weeks or until discharge, depending on their hospital stay duration.

Each GHOSTLY+ session begins with the application of a smart BFR cuff to the upper thigh of the target leg. The cuff automatically measures the arterial occlusion pressure (AOP) and inflates to 50% of this value, a level known to be effective while minimizing discomfort. Participants are then guided through an in-app calibration process in which they perform three maximal isometric contractions. Based on these readings, the system determines the individual's MVC and sets the game difficulty to 75% of that value. During gameplay, patients must complete three levels per session, with each level representing a set of twelve muscle contractions. Rest periods of two minutes are provided between sets. Based on a previous proof-of-concept study conducted at UZ Brussel (Debeuf et al., 2025), most patients are able to use the system independently after one hour of training. Physiotherapists at each site will be trained to guide this initial setup until patients are independently capable of setting up the GHOSTLY+ system.

The primary outcome of this study is lower-limb muscle strength at hospital discharge, assessed using a handheld MicroFet dynamometer. Secondary outcomes include muscle mass measured via ultrasound imaging of the rectus femoris, functional performance assessed through the 30-second sit-to-stand test and the Functional Ambulation Category, independence in activities of daily living using the Katz scale, time spent bedridden, total length of hospital stay, and patient-reported outcomes related to satisfaction and usability of the intervention. Cognitive status will be assessed using the Mini-Mental State Examination (MMSE), and additional analysis will be performed on EMG data to extract neuromuscular parameters such as signal amplitude and fatigue index. In addition to clinical and physiological data, patients and therapists will participate in implementation data collection via surveys, interviews, and site logbooks, in line with the Consolidated Framework for Implementation Research (CFIR).

Data will be collected at three time points: before the intervention (baseline), at the end of the first week, at the end of two weeks, or at hospital discharge if earlier. Randomization will be performed using a web-based system, with assessors blinded to group allocation to reduce bias. Participants will receive a study-specific ID and will be instructed not to disclose their group assignment to those collecting outcome measures.

Beyond evaluating clinical efficacy, the trial incorporates a robust implementation evaluation. Using the Consolidated Framework for Implementation Research (CFIR) and Proctor's framework, the study will examine key real-world indicators such as acceptability, adoption, fidelity, feasibility, penetration, and sustainability. Data will be gathered through staff surveys, administrative records, structured interviews, app usage data, and focus groups with healthcare professionals and patients. The qualitative data will be analyzed using content analysis and reflexive thematic analysis to identify implementation facilitators and barriers.

The study is powered to detect a 15% difference in lower-limb strength preservation between the intervention and control groups. Analysis will include repeated measures ANOVA, regression modeling, and subgroup analysis to explore the impact of baseline mobility status or cognitive performance. All data will be monitored for quality and completeness, and any serious adverse events will be reported to the competent authorities following the applicable safety guidance under the EU Medical Device Regulation.

Following trial completion, the research team will prepare an implementation package, including an e-learning training module for clinical staff, a Grol & Wensing-based implementation guideline, and a business case for broader adoption. Results will be disseminated through academic publications, clinician workshops, hospital presentations, and patient information campaigns.

In summary, this trial evaluates GHOSTLY+, a novel rehabilitation system combining blood flow restriction and EMG-guided gamified strength training for hospitalized older adults. It is designed to preserve muscle strength, reduce physical decline during bedrest, and boost adherence to therapy using interactive digital technology. By embedding implementation science into its structure, the study aims to not only prove the effectiveness of GHOSTLY+ but also support its sustainable integration into routine hospital care.

PATIENTS

Inclusion Criteria:

• Hospitalized, and expected to remain hospitalized for approximately 14 days
• 65+ yrs
• Unable to bear weight or transfer independently and at high risk of muscle strength loss due to prolonged immobility

Exclusion Criteria:

• Contraindications for physical exercise as assessed by the treating physician using the risk assessment tool proposed by Kacin et al. (2015) (can be overruled by the physician)
• Contraindications for blood flow restriction as assessed by the treating physician (can be overruled by the physician)
• Cognitive impairment (MMSE score < 19)
• Any condition that renders the patient unable to understand instructions or safely interact with the GHOSTLY+ system

THERAPISTS

Inclusion Criteria:

Therapists will be included if

• They are licensed physiotherapists employed at one of the three participating clinical sites
• They are involved in the daily rehabilitation of hospitalized older adults.

Exclusion Criteria:

Therapists will be excluded from participation if

• They are unable or unwilling to complete the GHOSTLY+ training
• They are not directly involved in the care of eligible patients during the study period
• They express any conflict of interest or ethical concern that may compromise the integrity of the study