This is a pilot trial to explore the cardiovascular of eight weeks of twice weekly high intensity interval training in people with progressive multiple sclerosis. A control group of people with progressive multiple sclerosis will undergo continuous moderate intensity exercise, twice weekly for 8 weeks.

This is a pilot trial to explore the cardiovascular of eight weeks of twice weekly high intensity interval training in people with progressive multiple sclerosis. A control group of people with progressive multiple sclerosis will undergo continuous moderate intensity exercise, twice weekly for 8 weeks.

The training program will entail 6x1.5 minute intervals working at 80-95% heart rate max on a cycle ergometer. Each interval will be interspersed with 1.5 minutes of working rest at a light resistance of the participant's choosing.

The continuous moderate intensity exercise program will entail 20 minutes on a cycle ergometer working at 60-70% heart rate max.

Inclusion Criteria:

• Diagnosed with a progressive form of MS
• Aged 18 years or older
• Known to members of staff of the MS service NHS Ayrshire & Arran
• Ability to attend Douglas Grant Rehabilitation centre twice a week for eight weeks
• EDSS 4-6.0
• Able to cycle on ergometer

Exclusion Criteria:

• A relapse of symptoms requiring treatment within the past three months.
• A respiratory condition that would be exacerbated by high intensity exercise including but not limited to: chronic obstructive pulmonary disorder, uncontrolled or poorly controlled asthma.
• Uncontrolled high pressure at screening (>190/100 mmHg)
• Cognitive impairment affecting ability to understand instructions as noted in patient's notes.
• Currently engaging in another research trial for their MS or that may affect their physiological or cardiovascular outcomes
• Weighing more than 110 kg (weight limit of ergometer)
• Any pathology or medical intervention that would preclude high intensity exercise, maximal exertion testing or could attenuate the cardiovascular effect of exercise including but not limited to: unstable angina; diabetes; peripheral vascular disease or intermittent claudication; having a pace maker or medicine pump; surgical clips; having another neurological condition other than MS; and pregnancy. To be established from patient's notes and at screening session.
• A serious cardiovascular event in the past year including but not limited to: transient ischaemic attack, cerebrovascular event and myocardial infarction.
• Taking any of the following medication: beta blockers; vasodilators; ACE inhibitors; diuretics or any other medication that could cause exercise induced hypotension; hypoglycaemic insulin; metformin or other oral insulin medicine.