Electromyographic Fatigue Analysis In The Three Heads Of Triceps Brachii During Isometric And Isotonic Contractions

• Main Author: Hussain, Jawad
• Format: Thesis
• Language: English; English
• Published: 2020
• Subjects: Q Science (General); QP Physiology
• Online Access: http://eprints.utem.edu.my/id/eprint/25405/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=119776

Triceps brachii (TB), a three headed (lateral, long and medial) biarticular upper extremity skeletal muscle, is mainly responsible for elbow and shoulder extension and arm abduction. It is predominantly composed of type II muscle fibres, hence, easily susceptible to fatigue. The three heads have different anatomy, which suggest varying biomechanical functions. Previous studies investigated fatigue in TB from a single head only, which is not representative of the whole elbow extensor group. To investigate the manifestation of fatigue in the three heads, as well as whether they work in unison, 25 young and healthy male subjects performed 10 different exercises in 5 sessions. Surface electromyography (sEMG) data was recorded using a SHIMMER™ data acquisition system. Subjects performed isometric elbow extension exercise at three different intensities [30%, 45% and 60% maximum voluntary contraction (MVC)], isotonic elbow extension exercise at three different intensities [30%, 45% and 60% one repetition maximum (1RM)] and isotonic elbow extension exercise at three different speeds (slow, medium and fast at 45% 1RM), until task failure. Further, to investigate the effect of cognitive stress (CS) in TB, isotonic elbow extension exercise was performed at 45% 1RM with CS until task failure. Endurance time (ET), number of repetitions (NR) and rate of fatigue (ROF) were statistically investigated for each exercise and each head. In addition, root mean square (RMS), mean power frequency (MPF) and median frequency (MDF) under non-fatiguing (NF) and fatiguing (Fa) conditions were statistically compared. ROF was statistically insignificant among the three heads for all the isotonic exercises, while it was significantly different (P<0.05) at 30% and 45% MVC for isometric exercises. ROF was found consistent among intensities for all heads during isometric exercises, whereas it increases in tandem with exercise intensity and speed during isotonic exercises (P<0.05). For all the exercise intensities, MPF and MDF of all three heads tend to decrease with increase in the exercise intensity under NF condition but remained the same under Fa condition. ROF was found lower with CS when compared with non-cognitive stress (NCS). CS increases the ET (24.74%) and NR (27%) of the exercise. The three heads showed statistically significant (P<0.05) MPF and MDF with all the performed exercises under both conditions, whereas the RMS was significantly different only under Fa conditions for isotonic exercises. Post-hoc analysis reveals that long-medial head pair exhibit different behaviour then the lateral-long and lateral-medial head pairs. The behaviour of the spectral parameters indicate that the three heads do not work in unison under any of the conditions. Changes in the speed of triceps push-down exercise affect the lateral and long heads, but changes in the exercise intensity affected the attributes of all heads to a greater extent. In addition, the RMS was found to be better approximator of CS, whereas MPF and MDF were more resistant to the effects of CS. MPF and MDF were observed to be better predictors of peripheral muscle fatigue. These findings provide further understanding on the functioning of the TB and thus can potentially be used in clinical applications for prosthetic control or targeted sports training. Furthermore, the effects of CS on peripheral muscle fatigue can improve the understanding of the condition of an individual during training or rehabilitation.