The primary goal of this interventional study is to objectively examine the prevalence of walking-related performance fatigability, together with the psychometric properties of its measuring parameters. The secondary aim is to investigate the relation of other clinical symptoms to walking-related performance fatigability.

The following three research questions will be addressed:

1. How prevalent is walking-related performance fatigability and what are the psychometric properties of fatigability formulas in preparation of use as experimental outcome measure?
2. What are associated symptoms of walking-related motor fatigability and how long does this manifest?
3. What is the relationship between cognitive fatigability and walking-related performance fatigability?

participants perform two six-minute walking test (6MWT), with 3-5 days in between. Before and after the 6MWT, three screenings test (spasticity, muscle strength, balance) are executed and the participants have to indicate the severity of eleven possible symptoms (= symptom inventory, SI) on a VAS scale. These screening tests and SI are continued every 10 minutes for half an hour. During a third test session, participants perform a 6-minute vigilance alphabet test in rest and while doing a 6MWT to investigate the relationship between cognitive and motor fatigability.

Inclusion Criteria:

• Age between 18 - 70 years
• Confirmed diagnosis according to the McDonald criteria
• Performed a 6MWT before, to ensure familiarization
• Able to walk independently or with unilateral support for 6 minutes without rest
• Signed the informed consent

Exclusion Criteria:

• Exacerbation or relapse within last 3 months before study
• Other neurological diagnosis, such as stroke and Parkinson
• MS-like syndromes, such as neuromyelitis optica
• Other medical condition interfering with walking ability (e.g. cardiac or respiratory diseases, arthritis and fibromyalgia)