Sampling rate effects on surface EMG timing and amplitude measures

Area of Science:

• Biomechanics
• Human Movement Science
• Neuroscience

Background:

• Growing trend of oversampling surface electromyography (SEMG) signals beyond the Nyquist rate.
• Limited evidence exists to support the necessity or benefits of SEMG oversampling.
• The optimal sampling rate for accurate SEMG analysis remains unclear.

Purpose of the Study:

• To evaluate the benefits of oversampling surface electromyography (SEMG) signals.
• To assess the impact of various sampling rates on common SEMG timing and amplitude measures.
• To determine if higher sampling rates improve the analysis of kinesiological data.

Main Methods:

• A within-subjects design with 8 participants analyzed SEMG from the triceps brachii.
• Signals were recorded during maximal, submaximal, fatiguing, and dynamic contractions.
• Analog signals (20 Hz–2 kHz) were oversampled at 6 kHz, then resampled to 3 kHz, 1 kHz, 500 Hz, and 250 Hz without anti-aliasing filters.

Main Results:

• Oversampling did not significantly alter timing or amplitude measures of rectified or smoothed SEMG signals.
• For smoothed SEMG, sampling at half the Nyquist rate sufficiently captured most timing and signal strength metrics.
• No significant improvements in data analysis were observed with higher sampling rates.

Conclusions:

• Oversampling is not required for typical amplitude and timing analysis of SEMG.
• Sampling SEMG below half the Nyquist rate can lead to inaccurate temporal and amplitude representations.
• Researchers can avoid expending excessive computational resources on oversampling SEMG without compromising typical data analysis.