Background:
Persons with Multiple Sclerosis (pwMS) experience increased fatigue and have a higher energetic demand during walking, compared to healthy persons. It is argued that changes in spatiotemporal parameters during the six minute walking test (6mwt) contribute to increased energetic cost of walking (Cw) and levels of fatigue.

Aim:
The aim of this study is to assess the energetic cost and spatiotemporal parameters of walking at fast speed in pwMS during the 6mwt.

Method:
Seven pwMS performed a 6mwt on the Computer Assisted Rehabilitation ENvironment. Oxygen consumption (VO2) and carbon dioxide production were measured continuously via indirect calorimetry. Steady state net Cw was calculated as VO2 during walking - resting VO2, expressed in milliliter VO2 per kilograms bodyweight per distance walked (net ml O2/kg/m). During walking, spatiotemporal parameters (walking speed, cadence, step length, step width) were collected and correlated with Cw, using Spearman correlation. Spatiotemporal parameters of seven healthy controls walking at high speeds was used as a reference. Six-minute walking distance (6mwd) was compared to normative values of healthy controls considering anthropometrics and heart rate(HR) as described by Casanova et. al (2011), expressed as percentage difference.

Results:
Persons with MS walked slower (1.35±0.44 vs. 1.48±0.16 m/s) and with higher Cw (0.14±0.05 vs 0.10±0.02 net mlO2/kg/m), compared to healthy controls. 6mwd for pwMS was 485±160m. Only cadence (123±15 vs. 121±6 steps/min) strongly correlated with Cw in both pwMS and HC (r=0.82, p=.02 vs. r=0.77, p=.04). 6mwd in pwMS was 21% higher, compared to normative values.

Discussion:
The higher Cw in PwMS may be explained by the increased cadence, compared to HC. Additionally, increased cadence and decrease step length can imply on impaired balance as frequently seen in pwMS. Our further research will investigate the relation between metabolic and mechanical energy demand during walking, aiming to explain the increased Cw.