The Effect of Exercise on Muscle Dysfunction in Cystinosis

Overview

Classification of activity tolerance is of importance in chronic progressive myopathies, not only to better understand functional implications of the disease state itself, but also for purposes of exercise prescription for health maintenance. Maximal exercise testing has been considered as the gold standard of assessing maximal aerobic capacity, however testing in individuals with neuromuscular disease is often limited due to pain, activity intolerance, musculoskeletal impairments, fatigue and other such related variables. Often, submaximal exercise testing can overcome some of these obstacles, and as such, is used frequently in the clinical environment. Non-ambulatory exercise testing utilizing an arm ergometer specifically has not been studied as heavily, especially in those with progressive myopathies. For this study, we will use maximal aerobic capacity testing for individuals with Cystinosis Myopathy utilizing a bike ergometer to allow testing of individuals regardless of their ambulatory status.

High Intensity Interval Training (HIIT) has been frequently used and studied in normal populations. HIIT exercise shows improved exercise capacity with possible benefits to the neuroendocrine system and neurotransmitters associated with well-being. In this study, we plan to compare aerobic capacity changes during seated HIIT aerobic exercise of individuals with Cystinosis Myopathy. Additionally, we will assess peripheral fatigue using quantitative strength force production and slope decline before and after HIIT aerobic training. High Intensity interval training: HIIT is a type of interval training that alternates between intense efforts and less intense recovery periods. Benefits include improved aerobic capacity, anaerobic energy, oxygen transport, lactate clearance and neuromuscular coordination. In this study, participants will train at maximal intensities (90-95% of VO2 Max) to place less strain on the neuromuscular system. The goal is to work at longer time periods above the lactate threshold causing an increase in blood lactate concentrations and improve muscles ability to oxidize fats and carbohydrates . Other studies have shown cardiovascular benefits of improved heart volume, maximal mitochondrial capacity and cardiac efficiency. HIIT training compared to regular moderate intensity exercise shows no difference in safety risk for individuals who are sedentary, have heart disease or stroke. However, compared to continuous exercise, HIIT appears to have improved oxygen consumption, blood vessel function, and glucose metabolism in healthy individuals . Methods: Ten participants who consent to participate in this exercise study, with no history or evidence of cardiomyopathy or conduction abnormality, and pass screening assessment for ability to complete the training program will be included and provided with an activity monitor, lower/upper extremity ergometer and remote fitness application that the participant will follow for the in-home training. This study will be a HIIT based home exercise program where participants will perform the lower extremity ergometer based on a HIIT protocol 3x week for 20-30 minutes for a total of 8 weeks. Baseline and end of training assessments will include MRI, muscle biopsy, strength and functional assessments including VO2 Max exercise testing and Timed Up and Go (TUG) tests. Participants will be provided hands on training to use the exercise ergometer, activity monitor, heart rate monitor, and exercise plan. The activity monitor will be programmed so that the researchers have access to monitor the patient's activity to ensure adherence to the program and changes in activity level. Additionally, a HIIT based fitness application will be installed on the participant's phone. The fitness application will be used as a guided exercise program and also allow the researchers a secondary method to monitor exercise adherence. The researchers will have access to the participant's Fitbit and fitness application use to monitor compliance. Participants who miss one session will be contacted by researchers as a reminder to follow the exercise plan. Skype sessions will be used as needed based on participant adherence or as needed for safety.