Evaluation of mean power spectral frequency of EMG signal during 100 metre crawl

Abstract

The aim of our study was to compare mean frequency (MNF) decrease in some upper body muscles during a 100-metre allout crawl by using two different normalization methods: firstly, when MNF at the end of swimming (MNF Send ) was normalized with respect to its initial value at the beginning and expressed with a fatigue index (FI) labelled FI start , and secondly when MNF min was used to calculate FI min . MNF min presented the lowest MNF obtained during isometric contractions until exhaustion executed on land after swimming for each of three observed muscles Á triceps brachii (TB), latissimus dorsi (LD) and pectoralis major (PM). Eleven experienced swimmers participated in the study and surface electromyography (EMG) signals from TB, the upper and lower parts of LD (LD1 and LD2 respectively) and the upper and lower parts of PM (PM1 and PM2 respectively) were recorded during both swimming and isometric contractions. Results showed no differences in FI start ; however, when FI min values were compared differences between the muscles were found (P B 0.05). The triceps brachii (TB) and the upper part of the latissimus dorsi muscles (LD1) showed the lowest FI min (40.0915.7 and 40.7924.4 respectively), which implied that MNF Send obtained from these muscles most closely approached their respective MNF min values during swimming. This might suggest that these muscles fatigued more than other observed muscles. The use of a different type of muscle contraction for calculating FI min (isometric versus dynamic) might represent a drawback to our study, but this approach could be acceptable when between-muscle comparisons are made.

Surface EMG Analysis of Biceps Brachii Fatigue During Isometric Contraction: A Preliminary Study

“…The researchers measured mean power frequency following fatigue of the elbow flexors and reported that the mean frequency was 100 -105 Hz prior to the fatiguing exercise and declined to ~70 Hz after exercise. The discrepancy between the present study and previous studies [12,14] was possibly due to the fatigue process (60% MVIC load vs. 50% MVIC load) [12], different muscles (biceps brachii vs. triceps brachii) [14] and small sample size in the present study.…”

“…The mean power frequency was initially ~165 Hz and reduced to ~125Hz at the end of test. The results were similar but slightly greater compared to those reported in previous studies [12,14]. The researchers measured mean power frequency following fatigue of the elbow flexors and reported that the mean frequency was 100 -105 Hz prior to the fatiguing exercise and declined to ~70 Hz after exercise.…”

Improving Myoelectric Prosthetic Arm Proportional Control Under MUAP Envelope Colored Noise

“…The most widely used standard techniques developed for the MUAP envelope extraction employ the mean square value (MSV) criterion [4], waveform produced by the rectified signal [15], [16], and the Hilbert transform [17]. Since these methods do not completely remove artifacts and ripples, the output is sometimes smoothed that, however, may yield unacceptably large bias errors and does not prevent spikes [18], [19]. The envelope can be improved using the Savitsky-Golay smoother combined with a low-pass filter [20], but only if the time-delay-lag causing EMG is not an issue.…”

Sports Performance

“…Therefore, no in-depth biomechanical studies have been performed on swimmers, although a few studies have monitored arm muscle activity during the front crawl stroke (Conceicao et al 2010;Stirn et al 2011Stirn et al , 2013. However, detailed analyses of motion and muscle activity during swimming are difficult.…”