Raw Data Trial 1Trial 2 Dave Megan Jeremiah Dianna Ogechi Ambar Difference scores of raw data Trial Trial 2-1 Change in mean Lower conf limit67.23 Upper conf limit Typical error52.09 Lower conf limit35.01 Upper conf limit Total error Limits of agreement Pearson r0.981 Intraclass r0.958 Can you directly compare EMG amp between subjects?

Reproducibility of surface EMG variables and peak torque during three sets of ten dynamic contractions Barbro Larsson Barbro Larsson, Bjarne Månsson, Christian Karlberg, Peter Syvertsson, Jessica Elert and Björn Gerdle Bjarne Månsson Christian Karlberg Peter Syvertsson Jessica Elert Björn Gerdle Barbro Larsson Bjarne Månsson Christian Karlberg Peter Syvertsson Jessica Elert Björn Gerdle

Introduction Isokinetic dynamometers are commonly used for assessment of dynamic muscle strength, endurance and fatigue. Isokinetic dynamometers are commonly used for assessment of dynamic muscle strength, endurance and fatigue. For measurement of reproducibility, intra- class correlation (ICC) is preferred. For measurement of reproducibility, intra- class correlation (ICC) is preferred.

Fatigue and EMG Peripheral muscle fatigue during sustained static contractions is generally characterized by increases in signal energy (RMS or iEMG) and shifts in the EMG spectrum towards lower frequencies (spectral shift). Peripheral muscle fatigue during sustained static contractions is generally characterized by increases in signal energy (RMS or iEMG) and shifts in the EMG spectrum towards lower frequencies (spectral shift). Fatigue increases amplitude Fatigue increases amplitude Fatigue decreases frequency Fatigue decreases frequency

Problems with Dynamic Contractions and EMG The interpretation of the EMG from dynamic contractions might be difficult—especially for frequency spectrum variables—because the movement per se introduces additional factors that might affect its characteristics The interpretation of the EMG from dynamic contractions might be difficult—especially for frequency spectrum variables—because the movement per se introduces additional factors that might affect its characteristics changes in force throughout the range of motion changes in force throughout the range of motion changes in fiber and muscle length changes in fiber and muscle length movement of the neuromuscular junction with relation to the electrodes position movement of the neuromuscular junction with relation to the electrodes position problems with non-stationary of the signal (recruitment and de-recruitment of MUs problems with non-stationary of the signal (recruitment and de-recruitment of MUs

Methods -- Isokinetic 3 sets of 10 isokinetic contractions at 90 d/s 3 sets of 10 isokinetic contractions at 90 d/s One hour between sets One hour between sets The electrodes were NOT REMOVED The electrodes were NOT REMOVED ROM was constrained to 90 – 15 deg ext. ROM was constrained to 90 – 15 deg ext. Subjects relaxed during knee flexion and the immediately performed extension. Subjects relaxed during knee flexion and the immediately performed extension.

Methods -- EMG Surface EMG from VL, VM & RF Surface EMG from VL, VM & RF 20 mm interelectrode distance on center of muscle in line with muscle fibers. 20 mm interelectrode distance on center of muscle in line with muscle fibers. Sampled at 2KHz with 12 bit A/D Sampled at 2KHz with 12 bit A/D EMG band pass filtered at Hz EMG band pass filtered at Hz Torque & Position low pass filtered at 40 Hz Torque & Position low pass filtered at 40 Hz

EMG Processing & Statistics FFT with Hamming window (2 Hz resolution) FFT with Hamming window (2 Hz resolution) RMS used for amplitude RMS used for amplitude Signal-amplitude ratio (SAR) of relaxation (flexion phase) to contraction (extension phase). Signal-amplitude ratio (SAR) of relaxation (flexion phase) to contraction (extension phase). ICC (3,1) Shrout & Fleiss ICC (3,1) Shrout & Fleiss One-way ANOVA was used to test for differences between sets. One-way ANOVA was used to test for differences between sets.

Results No significant differences between the three sets. No significant differences between the three sets. Peak torque had high reproducibility (0.99) Peak torque had high reproducibility (0.99) Rectus femoris generally had lower ICC than the two other muscles Rectus femoris generally had lower ICC than the two other muscles RMS generally had somewhat higher ICC than the MNF RMS generally had somewhat higher ICC than the MNF

Discussion High ICC may be due to limited ROM which may control movement effects. High ICC may be due to limited ROM which may control movement effects. Previous studies have reported good reproducibility for during and between day static contractions. Previous studies have reported good reproducibility for during and between day static contractions. Not REMOVING ELECTRODES may have contributed to high ICC Not REMOVING ELECTRODES may have contributed to high ICC

Discussion -- Cont We have reported that the MNF correspond to physiological properties during dynamic contractions We have reported that the MNF correspond to physiological properties during dynamic contractions Positive significant correlations have been reported between the proportion of Type-II muscle fibers and MNF during single dynamic (non-fatiguing) contractions Positive significant correlations have been reported between the proportion of Type-II muscle fibers and MNF during single dynamic (non-fatiguing) contractions