Introducing EL-FIT (Exercise and Liver FITness): A Smartphone App to Prehabilitate and Monitor Liver Transplant Candidates

Abstract

Preserved physical function is key for successful liver transplantation (LT); however, prehabilitation strategies are underdeveloped. We created a smartphone application (app), EL-FIT (Exercise and Liver FITness), to facilitate exercise training in end-stage liver disease (ESLD). In this feasibility study, we tested EL-FIT app usage and the accuracy of physical activity data transfer and obtained feedback from initial users. A total of 28 participants used the EL-FIT app and wore a physical activity tracker for 38 ± 12 days (age, 60 ± 8 years; 57% males; Model for End-Stage Liver Disease-sodium, 19 ± 5). There was fidelity in data transfer from the tracker to the EL-FIT app. Participants were sedentary (1957 [interquartile range, 873-4643] steps/day) at baseline. Level of training assigned by the EL-FIT app agreed with that from a physical therapist in 89% of cases. Participants interacted with all app features (videos, perceived exertion, and gamification/motivational features). We rearranged training data to generate heart rate-validated steps as a marker of performance and showed that 35% of the participants had significant increases in their physical performance. Participants emphasized their interest in having choices to better engage in exercise, and they appreciated the sense of community the EL-FIT app generated. We showed that patients with ESLD are able to use and interact with the EL-FIT app. This novel smartphone app has the potential of becoming an invaluable tool for home-based prehabilitation in LT candidates.

FIG. 1.

EL-FIT screenshots showing the main features of the app. Videos shows the Education and Strength & Mobility videos for patients who are frail. Profile displays the percentage of their day performing very light to vigorous activities and sleep time along with a bar chart with the total number of steps per day, statistics on the number of videos watched, and the number of badges received. Leaderboard demonstrates performance in average daily steps for 5 volunteers included in the Strength & Mobility training level; below each nickname, the corresponding LFI and MELD can be observed for each participant. Community/Feed is an automatic feed of achievements from each participant that allows EL-FIT members to congratulate and cheer for each other via emojis.

FIG. 2.

Exercise training levels allocated by stratification algorithm. The EL-FIT app considers the following 3 levels of training: (1) Strength & Mobility Training, which starts with exercises in a chair for patients who are frail and builds up physical challenges until patients can do basic standing exercises; (2) Low-Intensity Training, with various workouts that assume patients have gained full mobility; and (3) Moderate-Intensity Training, which includes more complex workouts for the physically robust with no limitations. The stratification algorithm considers liver and physical function data to allocate patients to 1 of these 3 training levels. Patients can graduate from 1 level and move on to the next level. A fourth section, Balance & Miscellaneous, includes workouts aiming to prevent falls, help with back pain, and a basic Tai Chi form favoring coordination. This fourth section is only made available to patients allocated to Low-Intensity Training or Moderate-Intensity Training.

FIG. 3.

Patterns of daily step performance while using the EL-FIT app. Changes in daily step count from baseline (week 1) to the week of best performance for all patients and for groups of patients showing a pattern of improvement from baseline (increase in more than 500 steps/day per week for 2 of up to 5 follow-up weeks), deterioration (decrease in more than 500 steps/day per week for 2 of up to 5 follow-up weeks), or stability (none of the above). Numbers in boxes represent median and interquartile range.