Following inclusion, baseline measurements (PRE) will be performed in MS patients (n=80). First, static(isometric) muscle strength (dynamometry), exercise capacity (maximal graded exercise test) and body composition (DEXA) will be evaluated. After 4 days of recovery, m. vastus lateralis muscle samples (Bergström procedure) will be taken. Hereafter, MS patients will be randomly allocated to one of four intervention groups following either 12 weeks of 'classical' moderate intensity cardiovascular exercise therapy (n=40) or periodized exercise therapy (n=40), with (MSβclassic, n=20; MSβperiod, n=20) or without (MSclassic, n=20; MSperiod, n=20) β-alanine supplementation. Groups not receiving β-alanine supplements, will receive placebo tablets that will be identical in taste and appearance. To evaluate post training fatigue, perceived exertion will be recorded following each training session (6-20 BORG scale). Following 12 weeks of classic or periodized training POST intervention measurements will be performed similar to baseline.
