Perception of Muscular Effort During Dynamic Elbow Extension in Multiple Sclerosis

Objective: To investigate the perception of muscular effort in individuals with multiple sclerosis (MS) and healthy controls during dynamic contractions.

Design: Case-control study.

Setting: MS day care center.

Participants: Individuals with MS (n=28) and controls (n=28) (N=56).

Interventions: Not applicable.

Main outcome measures: Perceived muscular effort during dynamic elbow extensions was rated at 9 different weight intensities (10%-90% of 1-repetition maximum) in a single-blind, randomized order using the OMNI-Resistance Exercise Scale. Muscle activity of the triceps brachii muscle (lateral head) was measured via surface electromyography and normalized to maximal voluntary excitation.

Results: According to OMNI-level ratings, significant main effects were found for the diagnostic condition (F=27.33, P<.001, η(2)=.11), indicating 0.7 (95% confidence interval [CI], 0.3-1.1) lower mean OMNI-level ratings for MS, and for the intensity level (F=46.81, P<.001, η(2)=.46), showing increased OMNI-level ratings for increased intensity levels for both groups. Furthermore, significant main effects were found for the diagnostic condition (F=16.52, P<.001, η(2)=.07), indicating 7.1% (95% CI, -8.6 to 22.8) higher maximal voluntary excitation values for MS, and for the intensity level (F=33.09, P<.001, η(2)=.36), showing higher relative muscle activities for increasing intensity levels in both groups.

Conclusions: Similar to controls, individuals with MS were able to differentiate between different intensities of weight during dynamic elbow extensions when provided in a single-blind, randomized order. Therefore, perceived muscular effort might be considered to control resistance training intensities in individuals with MS. However, training intensity for individuals with MS should be chosen at approximately 1 OMNI level lower than recommended, at least for dynamic elbow extension exercises.