Background: Pre-exhausting a synergist prior to a compound exercise has been shown to alter the firing patterns in the muscles during the exercise. Pre-exhausting a muscle is done by exercising a muscle group to fatigue with a single joint exercise prior to an exercise. Aim: The purpose of this study was to further investigate the effects of pre-exhausting the triceps brachii prior to performing a bench press, measuring the EMG activity in pectoralis major, triceps brachii and deltoid anterior. Methods: 30 participants, men (n=15) and women (n=15), performed two different protocols (T1 and T2) while the muscle activity was measured with surface EMG. Electrodes were placed on pectoralis major, triceps brachii and deltoid anterior. Maximum voluntary isometric contraction (MVIC) was performed prior to performing protocols in order to get reference values. Results: Pectoralis major and deltoid anterior activation was significantly higher when preexhausting triceps brachii before bench press compared to no PRE, but no significant increase was seen in triceps brachii (p=0.000, p=.0009 and p=0.405 respectively) MVIC expressed in percentages and mean values ± standard deviation during protocol T1 for pectoralis major 45.3(±12.4), triceps brachii 56.28(±15.9) and deltoid anterior 63.45(±31.4) and during protocol T2 pectoralis major 56.41(±18.4), triceps brachii 58.49(±20.07) and deltoid anterior 71.65(±42.7). Conclusion: These results suggest that pre-exhausting a synergist prior to a compound exercise may change the muscle activity in the involved muscles. This can be used in a practical sense to develop weak points in the muscles by changing the activation pattern in the muscles hence being able to target specific muscles better.

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Atherosclerotic cardiovascular disease is the leading cause of death worldwide. To decrease mortality and morbidity in cardiovascular disease, the development of accurate, non-invasive methods for early diagnosis of atherosclerotic cardiac and vascular engagement is of considerable clinical interest. Cardiovascular ultrasound imaging is today the cornerstone in the routine evaluation of cardiovascular function and recent development has resulted in two new techniques, tissue velocity imaging (TVI) and speckle tracking, which allow objective quantification of cardiovascular function. TVI and speckle tracking are the basis for three new approaches to cardiac and vascular monitoring presented in this thesis: wave intensity wall analysis (WIWA), two-dimensional strain imaging in the common carotid artery, and the state diagram of the heart.   WIWA uses longitudinal and radial strain rate as input for calculations of wave intensity in the arterial wall. In this thesis, WIWA was validated against a commercially available wave intensity system, showing that speckle tracking-derived strain variables can be useful in wave intensity analysis. WIWA was further tested in patients with end stage renal disease and documented high mortality in cardiovascular disease. The latter study evaluated the effects of a single session of hemodialysis using WIWA and TVI variables and showed improved systolic function after hemodialysis. The results also indicated that preload-adjusted early systolic wave intensity obtained by the WIWA system may contribute in the assessment of left ventricular contractility in this patient category. Two-dimensional strain imaging in the common carotid artery is a new approach showing great potential to detect age-dependent differences in mechanical properties of the common carotid artery. Among the measured strain variables, global circumferential strain had the best discriminating performance and appeared to be superior to conventional measures of arterial stiffness such as elastic modulus and β stiffness index. The state diagram is a visualisation tool that provides a quantitative overview of the temporal interrelationship of mechanical events in the left and right ventricles. Case examples and a small clinical study showed that state diagrams clearly visualize cardiac function and can be useful in the detection of non ST-elevation myocardial infarction (NSTEMI).   Even though WIWA, two-dimensional strain imaging in the common carotid artery and the state diagram show potential to be useful in the evaluation of cardiovascular function, there still remains a considerable amount of work to be done before they can be used in the daily clinical practice. / <p>QC 20100705</p>

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