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Normalization of the electromyography amplitude during a multiple-set resistance training protocol: Reliability and
Marcel B Lanza1, Lucas T Lacerda2, Marina Gurgel Simões3
1Department of Physical Therapy and Rehabilitation, School of Medicine, University of Maryland, Baltimore, United States.
Summary
Electromyography (EMG) normalization for quadriceps muscles during knee extensions depends on the specific EMG parameter and muscle. However, all tested EMG parameters demonstrated excellent reliability between days for muscle activity assessment.
Area of Science:
- Biomechanics
- Exercise Physiology
- Muscle Physiology
Background:
- Accurate electromyography (EMG) amplitude normalization is crucial for analyzing muscle activity during resistance exercises.
- Previous research has not consistently identified the optimal EMG parameters for normalizing superficial quadriceps femoris muscle activity.
- Understanding normalization methods is key for reliable muscle function assessment in sports science and rehabilitation.
Purpose of the Study:
- To investigate how different electromyography (EMG) parameters affect the normalization of superficial quadriceps femoris muscle amplitude during knee extension exercises.
- To assess the between-day reliability of EMG parameters used for normalization.
- To determine the influence of normalization methods on muscle activity analysis across different sets.
Main Methods:
- Eleven young males participated in a study involving one-repetition maximum tests, maximal voluntary isometric contractions, and resistance training until failure.
- Surface EMG was recorded from the rectus femoris, vastus lateralis, and vastus medialis muscles.
- Seven EMG parameters were used to normalize EMG amplitude during knee extensions, with analyses including repeated-measures two-way ANOVA and reliability metrics (ICC, CV, Bland-Altman plots).
Main Results:
- Normalized EMG amplitude of superficial quadriceps muscles during knee extensions was influenced by the chosen EMG parameter and varied between muscles.
- The rectus femoris and vastus lateralis showed one normalization parameter with consistent values, while the vastus medialis identified two such parameters.
- All EMG parameters exhibited excellent reliability and agreement between different testing days for all measured muscles.
Conclusions:
- The selection of EMG normalization parameters significantly impacts the analysis of quadriceps muscle activity during knee extensions, with muscle-specific differences observed.
- Despite parameter variability, the tested EMG normalization methods demonstrate high reliability and consistency for assessing muscle activation over time.
- These findings aid in refining EMG analysis protocols for resistance exercise research and clinical applications.
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