Figure 1.

Hierarchy chart depicting the general steps for associating clinical assessments of fatigability with overall fatigue in individuals with MS. Self-reported measures of perceived fatigue do not consistently correspond to performance-based measures of fatigability. Valid functional measures of fatigue must be associated with accepted estimates of fatigability and viable for use in rehabilitation settings. Better understanding of the relationship between the performance-based criterion measures and the trait characteristic of fatigability may aid our approach to the assessment and treatment of those people with multiple sclerosis. Notes: *Examples of criterion measures include the duration of task sustainability, rate of change in force production, power, voluntary activation, reaction times, heart rate, mean arterial pressure, core temperature, and outcomes of muscle morphology. ^†Examples of functional performance tests include the Adult Myopathy Assessment Test (AMAT), Short Physical Performance Battery Protocol (SPPB), and Dalgas’ Functional Capacity Test (FCT). ^‡Examples of state variables include the exercise prescription, modality of exercise, and exercise environment. ^§Examples of intervention to manipulate a state variable: a progressive resistance exercise program or an aerobic endurance exercise program.