Cardiac Power Output (CPO) has shown to effectively indentify declining cardiac performance in Heart Failure (HF) patients. We compared CPO to other commonly used hemodynamic parameters to establish its usefulness in determining when Mechanical Circulatory Support (MCS) is required. A retrospective study of 28 HF patients previously implanted with MCS were analyzed at 3 stages of pharmacological support. Studied subjects were separated into two categories (survived versus deceased) to compare contractile reserve differences in order to predict when complete cardiac dysfunction was met. CPO and Cardiac Power Index (CPI) were the two hemodynamic parameters that identified remaining contractile reserve in the declining heart (p < 0.05). Other commonly used hemodynamic parameters failed to provide information that can detect the need for MCS. Patients who decreased below 0.70 (Watts) had higher incidences of mortality and /or morbidity. Clinicians who cannot medically manage HF patients above 0.70 W may consider MCS as an alternative treatment to retain hemodynamic stability.

No description available.

Syftet med denna studie var att undersöka om vistelse på hög höjd påverkar den anaeroba arbetsförmågan. Sex aktiva universitetsstudenter, fyra män och två kvinnor, deltog frivilligt i studien. Expeditionen till Nepal varade i 40 dagar och under den perioden sov och vandrade försökspersonerna mellan 1400 och 5100 meter över havet. Före och efter expeditionen genomförde försökspersonerna ett anaerobt wingatetest där peak power, average power, minimum power and power drop uppmättes. Resultatet visade en signifikant sänkning av average power efter den genomförda expeditionen på hög höjd, med ett medelvärde på 8.44 ± 0,84 w/kg före expeditionen och 7.81 ± 0,87 w/kg efter expeditionen. Inga signifikanta förändringar sågs hos övriga uppmätta parametrar. Konklusionen är att average power försämras efter 40 dagars vistelse på hög höjd.

<p>Abstract 1.</p><p>The purpose of this study was to investigate the effects whole body vibrations on maximal strength, power output and neuromuscular activity in m. pectoralis major during bench press.</p><p>Participants consisted of 35 male and 9 female military high school students (m=23, 1 years). On the basis of initial maximal performances in bench press the participants was divided into two experiments groups and one control group. Intervention groups performed a specifically designed push up program on a vibrating plate respectively a step board during 12 weeks</p><p> </p><p>Initial load at 60 % of 1 RM showed an average of 46, 5 kg. All groups showed an average increase of 13 kg for each person after 12 weeks. Initial value for power output showed a mean of 265 watt, which also showed an increase with an average of 7 watt (with a load equivalent of 60 % of 1 RM at the current test occasion), respectively an increase of 41 watt (with the load performed during the first test occasion). A positive correlation existed between the load at 60 % of 1 RM and achieved power output. No significant differences between groups were exposed concerning estimated maximum strength or power output in bench press. </p><p>All participants showed an increase in strength development, indicating that vibration stimuli could be compared to traditional push ups training without vibrations. Vibrations seem to have more effects on the magnitude of recruited motor units, why vibrations training could be a good complement to established strength training.</p><p>Abstract 2. </p><p>The purpose of this study was to investigate the effects whole body vibrations on strength development, power output and neuromuscular activity in m. pectoralis major during bench press. The purpose was also to examine what roll self-efficacy plays in strength tasks. </p><p>Participants consisted of 35 male and 9 female military high school students (m=23, 1 years). On the basis of initial maximal performances in bench press the participants was divided into two experiments groups and one control group. Intervention groups performed a specifically designed push up program on a vibrating plate respectively a step board during 12 weeks. All participants answered a battery of questionnaires concerning backgrounds, motives for sport participation, self-efficacy and efficacy sources. </p><p>Initial load at 60 % of 1 RM showed an average of 46, 5 kg (sd = 13, 8). All groups showed an average increase of 13 kg for each person after 12 weeks. Initial value for power output showed a mean of 265 watt, which also showed an increase with an average of 7 watt (with a load equivalent of 60 % of 1 RM at the current test occasion), respectively an increase of 41 watt (with the load performed during the first test occasion). A positive correlation existed between the load at 60 % of 1 RM and achieved power output. No significant differences between groups were exposed concerning estimated maximum strength or power output in bench press. Gender differences showed that men lifted significantly heavier loads at 60 % of 1RM compared to women. </p><p>No significant differences could be seen between the groups concerning self efficacy. Gender differences were exposed concerning self-efficacy to push ups with a pat. The efficacy sources “performance accomplishments” was valuated to be the most influential to form self-efficacy expectations. A strong positive relationship between “performance accomplishments” and achieved self-efficacy to push ups with pats were shown. Self-efficacy to push ups with a pat also correlated positively with power output and performed 60 % of 1 RM in bench press. </p><p>All participants showed an increase in strength development, indicating that vibration stimuli could be compared to traditional push ups training without vibrations. Vibrations seem to have more effects on the magnitude of recruited motor units, why vibrations training could be a good complement to established strength training. Participants relatively high self-efficacy to strength tasks is probably a result of performance accomplishments in there own strength straining rather than the intervention training. Positive relationships between self-efficacy and power output as well as performed 60 % of 1 RM in bench press, indicating that high self-efficacy have a positive influence on strength performance. </p><p>Keywords: estimated maximal strength (1RM), neuromuscular activity, power output, self-efficacy.</p>

Abstract 1. The purpose of this study was to investigate the effects whole body vibrations on maximal strength, power output and neuromuscular activity in m. pectoralis major during bench press. Participants consisted of 35 male and 9 female military high school students (m=23, 1 years). On the basis of initial maximal performances in bench press the participants was divided into two experiments groups and one control group. Intervention groups performed a specifically designed push up program on a vibrating plate respectively a step board during 12 weeks Initial load at 60 % of 1 RM showed an average of 46, 5 kg. All groups showed an average increase of 13 kg for each person after 12 weeks. Initial value for power output showed a mean of 265 watt, which also showed an increase with an average of 7 watt (with a load equivalent of 60 % of 1 RM at the current test occasion), respectively an increase of 41 watt (with the load performed during the first test occasion). A positive correlation existed between the load at 60 % of 1 RM and achieved power output. No significant differences between groups were exposed concerning estimated maximum strength or power output in bench press. All participants showed an increase in strength development, indicating that vibration stimuli could be compared to traditional push ups training without vibrations. Vibrations seem to have more effects on the magnitude of recruited motor units, why vibrations training could be a good complement to established strength training. Abstract 2. The purpose of this study was to investigate the effects whole body vibrations on strength development, power output and neuromuscular activity in m. pectoralis major during bench press. The purpose was also to examine what roll self-efficacy plays in strength tasks. Participants consisted of 35 male and 9 female military high school students (m=23, 1 years). On the basis of initial maximal performances in bench press the participants was divided into two experiments groups and one control group. Intervention groups performed a specifically designed push up program on a vibrating plate respectively a step board during 12 weeks. All participants answered a battery of questionnaires concerning backgrounds, motives for sport participation, self-efficacy and efficacy sources. Initial load at 60 % of 1 RM showed an average of 46, 5 kg (sd = 13, 8). All groups showed an average increase of 13 kg for each person after 12 weeks. Initial value for power output showed a mean of 265 watt, which also showed an increase with an average of 7 watt (with a load equivalent of 60 % of 1 RM at the current test occasion), respectively an increase of 41 watt (with the load performed during the first test occasion). A positive correlation existed between the load at 60 % of 1 RM and achieved power output. No significant differences between groups were exposed concerning estimated maximum strength or power output in bench press. Gender differences showed that men lifted significantly heavier loads at 60 % of 1RM compared to women. No significant differences could be seen between the groups concerning self efficacy. Gender differences were exposed concerning self-efficacy to push ups with a pat. The efficacy sources “performance accomplishments” was valuated to be the most influential to form self-efficacy expectations. A strong positive relationship between “performance accomplishments” and achieved self-efficacy to push ups with pats were shown. Self-efficacy to push ups with a pat also correlated positively with power output and performed 60 % of 1 RM in bench press. All participants showed an increase in strength development, indicating that vibration stimuli could be compared to traditional push ups training without vibrations. Vibrations seem to have more effects on the magnitude of recruited motor units, why vibrations training could be a good complement to established strength training. Participants relatively high self-efficacy to strength tasks is probably a result of performance accomplishments in there own strength straining rather than the intervention training. Positive relationships between self-efficacy and power output as well as performed 60 % of 1 RM in bench press, indicating that high self-efficacy have a positive influence on strength performance. Keywords: estimated maximal strength (1RM), neuromuscular activity, power output, self-efficacy.

The geometry of the receiver and recuperator in a small-scale open and direct recuperative solar thermal Brayton cycle can be optimised in such a way that the system produces maximum net power output. The purpose of this work was to apply the second law of thermodynamics and entropy generation minimisation to optimise these geometries using an optimisation method. The dynamic trajectory optimisation method was used and off-the-shelf micro-turbines and a range of parabolic dish concentrator diameters were considered. A modified cavity receiver was used in the analysis with an assumed cavity wall construction method of either a circular tube or a rectangular channel. A maximum temperature constraint of 1 200 K was set for the receiver surface temperature. A counterflow plate-type recuperator was considered and the recuperator length was constrained to the length of the radius of the concentrator. Systems producing a steady-state net power output of 2 – 100 kW were analysed. The effect of various conditions, such as wind, receiver inclination and concentrator rim angle on the maximum net power output, and optimum geometry of the system were investigated. Forty-five different micro-turbines and seven concentrator diameters between 6 and 18 metres were considered. Results show the optimum geometries, optimum operating conditions and minimum entropy generation as a function of the system mass flow rate. The optimum receiver tube diameter was relatively large when compared with the receiver size. The optimum counterflow plate-type recuperator channel aspect ratio is a linear function of the optimum system mass flow rate for a constant recuperator height. The optimum recuperator length and optimum NTU are small at small system mass flow rates but increase as the system mass flow rate increases until the length constraint is reached. For the optimised systems with maximum net power output, the solar receiver is the main contributor to the total rate of minimum entropy generation. The contributions from the recuperator, compressor and turbine are next in line. Results show that the irreversibilities were spread throughout the system in such a way that the minimum internal irreversibility rate was almost three times the minimum external irreversibility rate for all optimum system geometries and for different concentrator diameters. For a specific environment and parameters, there exists an optimum receiver and recuperator geometry so that the system can produce maximum net power output. / Dissertation (MEng)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / unrestricted

No description available.

Modern power systems are characterized by an increasing penetration of renewable energy generating units. These aim to reduce the carbon emissions in the environment by replacing conventional energy generating units which rely on fossil fuels. In this new power systems composition, wind generators (WGs) dominate, being one of the largest and fastest-growing sources of renewable energy production. Nevertheless, their unpredictable and highly volatile power output hinders their efficient and secure large-scale deployment, and poses challenges for the transient stability of power systems. Given that, we identify two challenges in the operation of modern power systems: rendering WGs capable of reguating their power output while securing transient stabilization of conventional synchronous generators (SGs). This dissertation makes several contributions for effectively dealing with these major challenges by introducing new distributed control techniques for SGs, storage devices and state-of-the-art (SoA) WGs. Initially, this dissertation introduces a novel nonlinear control design which is able to coordinate a storage device and a SG to attain transient stabilization and concurrent voltage regulation on their terminal bus. Thereafter, it proposes control designs that SoA WGs can adopt to effectively regulate their power out- put to meet local or group objectives. In this context, the rst control design is a decentralized nonlinear energy-based control design, that can be employed by a wind double-fed induction generator (DFIG) with an incorporated energy storage device (namely a SoA WG) to regulate its power output by harnessing stored energy, with guaranteed performance for a wide-range of operating conditions. Recognizing that, today, albeit wind farms (WFs) are comprised of numerous WGs which are sparsely located in large geographical areas, they are required to respond rapidly and provide services to the grid in an efficient, reliable and timely fashion. To this end, this dissertation proposes distributed control methods for power output regulation of WFs comprised of SoA WGs. In particular, a novel distributed control design is proposed, which can be adopted by SoA WGs to continuously, dynamically and distributively self-organize and control their power outputs by leveraging limited peer-to-peer communication. By employing the proposed control design, WGs can exploit their storage devices in a fair load-sharing manner so that their total power output tracks a total power reference under highly dynamical conditions. Finally, this dissertation proposes a distributed control design for wind DFIGs without a storage device, the most common type of WGs deployed today. With this control design, wind DFIGs can dynamically, distributively and fairly self-dispatch and adjust the power they extract from the wind for the purpose of their total power tracking a dynamic reference. The effectiveness of the control designs proposed in this dissertation is illustrated through several case studies on a 3-bus power system and the IEEE 24-bus Reliability Test System.

Aerobic and anaerobic performance of the upper body (UB) and lower body (LB) were assessed by arm cranking and treadmill tests respectively in a comparison of national (N) and international (I) male gymnasts. Force velocity and Wingate tests were performed using cycle ergometers for both arms and legs. In spite of a significant difference in training volume (4–12 vs. 27–34 h·wk−1 for N and I, respectively), there was no significant difference between N and I in aerobic and anaerobic performance. Upper body and LB maximal oxygen uptake (JOURNAL/jscr/04.02/00124278-200611000-00029/ENTITY_OV0312/v/2017-07-20T235327Z/r/image-pngO2max) values were 34.44 ± 4.62 and 48.64 ± 4.63 ml·kg−1·min−1 vs. 33.39 ± 4.77 and 49.49 ± 5.47 ml·kg−1·min−1, respectively, for N and I. Both N and I had a high lactic threshold (LT), at 76 and 82% of JOURNAL/jscr/04.02/00124278-200611000-00029/ENTITY_OV0312/v/2017-07-20T235327Z/r/image-pngO2max, respectively. Values for UB and LB force velocity (9.75 ± 1.12 and 15.07 ± 4.25 vs. 10.63 ± 0.95 and 15.87 ± 1.25 W·kg−1) and Wingate power output (10.43 ± 0.74 and 10.98 ± 3.06 vs. 9.58 ± 0.60 and 13.46 ± 1.34 W·kg−1) were also consistent for N and I. These findings confirm the consistency of JOURNAL/jscr/04.02/00124278-200611000-00029/ENTITY_OV0312/v/2017-07-20T235327Z/r/image-pngO2max values presented for gymnasts in the last 4 decades, together with an increase in peak power values. Consistent values for aerobic and anaerobic performance suggest that the significant difference in training volume is related to other aspects of perfomance that distinguish N from I gymnasts. Modern gymnastics training at N and I levels is characterized by a focus on relative strength and peak power. In the present study, the high LT is a reflection of the importance of strength training, which is consistent with research for sports such as wrestling. Aerobic and anaerobic performance of the upper body (UB) and lower body (LB) were assessed by arm cranking and treadmill tests respectively in a comparison of national (N) and international (I) male gymnasts. Force velocity and Wingate tests were performed using cycle ergometers for both arms and legs. In spite of a significant difference in training volume (4–12 vs. 27–34 h·wk−1 for N and I, respectively), there was no significant difference between N and I in aerobic and anaerobic performance. Upper body and LB maximal oxygen uptake (JOURNAL/jscr/04.02/00124278-200611000-00029/ENTITY_OV0312/v/2017-07-20T235327Z/r/image-pngO2max) values were 34.44 ± 4.62 and 48.64 ± 4.63 ml·kg−1·min−1 vs. 33.39 ± 4.77 and 49.49 ± 5.47 ml·kg−1·min−1, respectively, for N and I. Both N and I had a high lactic threshold (LT), at 76 and 82% of JOURNAL/jscr/04.02/00124278-200611000-00029/ENTITY_OV0312/v/2017-07-20T235327Z/r/image-pngO2max, respectively. Values for UB and LB force velocity (9.75 ± 1.12 and 15.07 ± 4.25 vs. 10.63 ± 0.95 and 15.87 ± 1.25 W·kg−1) and Wingate power output (10.43 ± 0.74 and 10.98 ± 3.06 vs. 9.58 ± 0.60 and 13.46 ± 1.34 W·kg−1) were also consistent for N and I. These findings confirm the consistency of JOURNAL/jscr/04.02/00124278-200611000-00029/ENTITY_OV0312/v/2017-07-20T235327Z/r/image-pngO2max values presented for gymnasts in the last 4 decades, together with an increase in peak power values. Consistent values for aerobic and anaerobic performance suggest that the significant difference in training volume is related to other aspects of perfomance that distinguish N from I gymnasts. Modern gymnastics training at N and I levels is characterized by a focus on relative strength and peak power. In the present study, the high LT is a reflection of the importance of strength training, which is consistent with research for sports such as wrestling.

The increased work of breathing associated with intense cycling has been identified as a factor that may negatively affect cycling performance. The aerodynamic position, abnormal respiratory mechanics either at rest or during exercise, and the development of a tachypnoeic breathing pattern are factors known to increase the work of breathing. Breathing pattern retraining aims to decrease the work of breathing by delaying the onset of dynamic hyperinflation and the recruitment of accessory breathing muscles. To date no studies have investigated the performance, physiological and perceptual consequences of manipulating breathing pattern in trained cyclists. Purpose: The aim of the present study was to investigate the effect of breathing pattern retraining on 20-km time trial performance and respiratory and metabolic measures in competitive cyclists. Method: Twenty-four competitive male cyclists (age 37.7 ± 8.6 years, mean ± SD; peak 4.34 ± 0.47 L·min-1) were match paired on 20-km time trial performance and assigned at random to either an intervention group (breathing pattern retraining; N = 12) or control group (N = 12). 20-km time trial performance, pulmonary function and the physiological and perceptual response during a maximal incremental cycle step test were assessed pre- and post-intervention. The intervention group underwent four weeks of specific breathing pattern retraining using exercises designed to reduce dynamic hyperinflation and optimise respiratory mechanics. The control group attended the laboratory once a week during this period and performed a 10 minute sub-maximal ride wearing a biofeedback breathing harness. The control group was led to believe the purpose for their participation was to investigate the effect that maximal exercise had on breathing pattern, and to test the reliability of the breathing harness. There was no attempt to modify the breathing pattern of the control group. Data were analysed using an MS Excel spreadsheet designed for statistical analysis. The uncertainty in the effect was expressed as 90% confidence limits and a smallest worthwhile effect of 1.0% was assumed. Results: The intervention group showed substantial improvements in 20-km time trial performance (-1.5 ± 1.1%) and incremental power (3.2 ± 3%). Additionally, breathing frequency (-13.2 ± 8.9%; -9.5 ± 8.4%), tidal volume (10.6 ± 8.5%; 9.4 ± 7.6%), inspiratory time (10.1 ± 8%; 9.4 ± 7.7%), breathing RPE (-30 ± 33.9%; -24.7 ± 28.1%) and leg RPE (-27.9 ± 38.5%; -24.7 ± 28.2%) were all positively affected at lactate threshold and lactate turn point. No positive changes were observed in the control group for 20-km time trial performance (0.0 ± 1.0%), incremental power (-1.4 ± 3.5%), breathing frequency (-1.6 ± 8.0%; -2.0 ± 7.9%), tidal volume (0.9 ± 7.2%; 2.9 ± 9.4%), breathing RPE (16.1 ± 50.2%, 24.8 ± 43%) or leg RPE (13.4 ± 39.6%; 19.9 ± 43.2%) . Conclusion: These results provide evidence of the performance enhancing effect of four weeks of breathing pattern retraining in cyclists. Furthermore, they suggest breathing pattern can be retrained to exhibit a controlled pattern, without a tachypnoeic shift, during high intensity cycling. Additionally, these results indicate breathing pattern retraining attenuates the respiratory and peripheral perceived effort during incremental exercise. Key words: Breathing pattern disorders, retraining, blood stealing, cycling, performance, power output, respiratory mechanics, perceived exertion, 20km-TT