Multiple sclerosis (MS) is a primary disorder of the central nervous system that may affect motor pathways and cause muscle weakness. Respiratory complications due to respiratory muscle weakness are common in the terminal stages of MS and contribute to mortality in these patients. Respiratory muscle weakness may also impair the performance of coughing and aspiration, pneumonia, or even acute ventilatory failure may ensue. Functional magnetic stimulation (FMS) is a non-invasive method that promotes the contraction of muscles through nerve activation. Over the last few years, the study investigators have demonstrated efficacy of FMS technology for stimulating respiratory muscles in animal models, able-bodied subjects [3] and spinal cord injured (SCI) patients [4]. In this study, the researchers will investigate the efficacy of using FMS technique for respiratory muscle conditioning in patients with MS. Furthermore, the investigators will also compare expiration related outcomes of FMS technique with resistive expiratory muscle training (REMT) methodology.

Hypotheses

1. FMS conditioning of the expiratory muscles can generate significant expiratory flows and pressures in patients with MS.
2. FMS conditioning of expiratory muscles is more effective compared to resistive expiratory muscle training (REMT) in patients with MS.

Optimal respiratory function depends on intact neural circuitry which orchestrates the interplay between respiratory muscles and intrinsic pulmonary function to maintain adequate ventilation. In the absence of respiratory muscle activation, pressure gradients cannot be developed and air exchange at the alveolar surface cannot occur. Thus, any impairment in respiratory muscle performance can lead to pulmonary dysfunction, respiratory distress and even death. Multiple sclerosis (MS) is a primary disorder of the central nervous system that often affects motor pathways, causing diminished muscle strength and endurance throughout the body including the ventilatory muscles. Respiratory complications are recognized as the major cause of morbidity and mortality in individuals with advanced MS. The investigators' research team has over 15 years of experience using Functional Magnetic Stimulation (FMS) for stimulating nerves and muscles below the level of injury in patients with chronic SCI; and has also demonstrated significant benefit for improving respiratory muscles, bladder and bowel functions. In this study, the investigators will investigate the efficacy of using FMS technique for respiratory muscle conditioning in patients with multiple sclerosis; and will compare the results of the expired functions (volume, pressure, and flow) generated by using the FMS technique with data obtained from using the resistive expiratory muscle training (REMT) methodology.

Inclusion Criteria:

• Multiple Sclerosis diagnosis
• Baseline maximal expiratory pressure (MEP) values between 50% and 70% of predicted values
• Patients must also be in stable condition and free of active brain disease or cardiovascular disorders (history of myocardial infarction, congestive heart disease, or uncontrolled hypertension).

Exclusion Criteria:

• Cardiac pacemakers, ferromagnetic metal implants, uncontrolled high blood pressure, active pulmonary conditions such as chronic obstructive pulmonary disease, bronchiectasis, asthma, and diaphragmatic paralysis.
• Patients who are ventilator dependent, with significant scoliosis, other chest wall deformity, obesity, severe diabetes mellitus, as well as pregnant women will be excluded from participating in the study.
• Patients with substance abuse or mental incompetence will also be excluded.