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.

Perception of muscular effort in multiple sclerosis.

BACKGROUND: Resistance exercise is effective in improving muscle strength and preventing muscle weakness in multiple sclerosis (MS) patients. Control of resistance training intensity based on perceived muscular effort is applicable to healthy individuals, yet there is no evidence of its utility for MS patients. OBJECTIVE: To compare perception of muscular effort in MS patients to healthy controls. METHODS: Based on their perception of muscular effort, twenty-five MS patients and twenty-eight controls adjusted static elbow extension tasks according to five levels on the OMNI-Resistance Exercise Scale. Elbow extension strength and muscle activity were measured via load cell dynamometer and surface electromyography (EMG) and related to each participant's maximal voluntary contraction (MVC) strength and muscle activity. Two-way analysis of variance was used to evaluate statistical significance. RESULTS: There were no statistically significant differences between MS patients and healthy controls, they produced similar relative torque values (F1 = 0.196; p > 0.05) and extensor muscle activities (F(2,617) = 1.556; p > 0.05) across all effort levels. CONCLUSION: No differences were found in the perception of muscular effort in MS patients and the age-matched control group. Future studies should explore, whether rating of perceived exertion is an effective instrument to control resistance training intensity in MS patients.