Reliability of SEMG spike parameters during concentric contractions

Area of Science:

• Biomechanics
• Neuroscience
• Exercise Physiology

Background:

• Surface electromyography (SEMG) is crucial for assessing muscle activation.
• Understanding the reliability of SEMG parameters is vital for accurate interpretation of muscle activity patterns.
• Concentric (isotonic) contractions are common in functional movements and rehabilitation.

Purpose of the Study:

• To evaluate the reliability of four SEMG spike parameters during repeated concentric contractions.
• To determine if a "warm-up" effect influences SEMG measurement stability and consistency.
• To assess the impact of repetitive dynamic contractions on motor unit recruitment patterns.

Main Methods:

• Eighteen subjects performed rapid elbow flexion with biceps brachii SEMG monitoring.
• Four SEMG spike parameters were analyzed: mean spike amplitude, frequency, slope, and peaks per spike.
• Reliability was assessed across four sessions using the first and last five trials to account for potential warm-up effects.

Main Results:

• All SEMG parameters showed significant increases across test days (p < 0.01).
• Intraclass correlation coefficients for early trials (1-5) ranged from 0.76 to 0.83, indicating good reliability.
• Later trials (96-100) demonstrated improved stability and consistency, with coefficients ranging from 0.85 to 0.93.

Conclusions:

• The four studied SEMG spike parameters are reliable for assessing muscle activity changes.
• Repetitive dynamic contractions appear to enhance the recruitment of fast-twitch motor units.
• SEMG reliability improves with practice, suggesting adaptations in muscle activation strategies over time.