Relationship between perceived fatigue and performance fatigability in people with multiple sclerosis: A systematic review and meta-analysis

Adjustments in Torque Steadiness During Fatiguing Contractions Are Inversely Correlated With IQ in Persons With Multiple Sclerosis

Fatigue is one of the most debilitating symptoms of multiple sclerosis (MS), and the underlying mechanisms are poorly understood. When exposed to a physical or cognitive challenge, individuals with MS tend to exhibit greater declines in task performance (performance fatigability) and increased levels of self-reported fatigue (perceived fatigability), but these effects may be attenuated by greater intellectual capacity. The purpose of our study was to examine the influence of intelligence on fatigability in persons with MS. We hypothesized that greater intellectual capacity confers some protection against heightened levels of fatigue and fatigability associated with MS. Twelve adults with relapsing-remitting MS were compared with 12 control (CO) subjects who were matched for age, sex, and premorbid intellectual capacity. Performance fatigability was measured as the decline in maximal voluntary contraction (MVC) torque after 60 isometric contractions (10 s contraction at 25% MVC, 5 s rest) performed with the knee extensor muscles. Perceived fatigability was assessed with the modified fatigue impact scale (MFIS) questionnaire (trait fatigability) and the Borg rating of perceived exertion (RPE, state fatigability). Persons with MS reported greater MFIS scores (MS: 43 ± 14; CO: 11 ± 8, P ≤ 0.001). Initial MVC torque for the knee extensors did not differ between the groups (MS: 112 ± 38 N⋅m; CO: 107 ± 44 N⋅m) and the decline (performance fatigability) was similar for both groups (MS: -16 ± 19 N⋅m; CO: -13 ± 16 N⋅m). RPE increased during the fatiguing contraction for both groups (P < 0.001) but was significantly greater in magnitude (main effect for group, P = 0.03) and increased more for the MS group (group × time interaction, P = 0.05). Torque steadiness declined during the fatiguing contractions (main effect for time, P = 0.05) and was less steady for the MS group (main effect for group, P = 0.02). Performance and full-4 IQ was correlated with the decline in torque steadiness for the MS group (r = -0.63, P < 0.05; r = -0.64, P < 0.05). Intellectual capacity was not associated with fatigability in persons with MS but was associated with adjustments in muscle activation during the fatiguing contractions.

Increases in fatigue do not change spasticity scores in persons with multiple sclerosis

AIM

Fatigue is a common finding in multiple sclerosis (MS) which may result in worsening of gait, function and other MS symptoms, like spasticity. Although the worsening of spasticity with fatigue has been reported by persons with MS, the effect of fatigue on spasticity has not been measured.

PURPOSE

The purpose of this study was to compare lower extremity Modified Ashworth Scale (MAS) scores of persons with mild-to-moderate MS symptoms before and after fatigued and unfatigued conditions.

METHODS

Using a randomized crossover design, MS subjects underwent 6-min walk to induce fatigue and 6-min supine rests, with lower extremity spasticity measured before and after each condition. Friedman tests gave paired comparisons of MAS before and after each condition.

RESULTS

16 subjects with mild-to-moderate MS completed the study (mean age = 56; standard deviation = 11.7). Friedman tests showed a significant decrease in mean rank for overall average MAS for both lower extremities (p = 0.031) when comparing fatigued to unfatigued conditions. This appeared to be driven by the right lower extremity average MAS (p = 0.002) and, more specifically, in post hoc pre to post-test comparisons for right knee flexor (p = 0.002 fatigued; p = 0.059 unfatigued) and right knee extensor (p = 0.001 fatigued; p = 0.020 unfatigued) MAS mean rank differences. Fatigue did not result in increased spasticity.

CONCLUSION

Spasticity in these subjects with MS was not worsened by fatigue suggesting that worsening of gait with fatigue may be due to causes other than spasticity.