Description:
A paucity of research is available on the optimal pacing strategy for cycling events longer than 4 km. Anecdotal evidence suggests that an even pacing strategy is most suitable; however, controlled studies have only determined that a slow start is more suitable than a fast start pacing strategy. Currently, it is unclear which strategy is more effective for endurance cycling time trials. This study sought to identify differences in 30-km cycling time trial (TT30) performance related to pacing strategies by comparing individually chosen pacing strategy with time-to-exhaustion (TE) at the average power output achieved during TT30. Eight moderately trained male cyclists (Vo2max = 50.9 +/- 5.2 mlxkgxmin) performed 2 TT30 tests and 2 TE tests at the average power output of TT30 on a Velotron cycle ergometer at the same time of day, separated by at least 48 hours. During TT30, participants generally chose to use a 'fast start' pacing strategy, cycling at a speed relative to the TT average (TTAvg) of 103.1 +/- 2.2% during the first 5 km. There was no significant difference in performance time between the TE test and TT30. Starting pace (TT0-5) was significantly correlated with finishing pace (TT25-30) (r = -0.91; p < 0.01) and TE (r = 0.85; p < 0.01). Subjects cycling at a relative starting speed (RS0-5) >105% had a significantly longer TE than subjects cycling at <105%, whereas TT30 performance time was not different between the two groups. The present investigation provided indirect evidence that a fast start pacing strategy decreases finishing speed and overall performance in TT30, and increased TT performance can be achieved by selecting a starting pace no more than 5% above TTAvg.
Description:
A paucity of research is available on the optimal pacing strategy for cycling events longer than 4 km. Anecdotal evidence suggests that an even pacing strategy is most suitable; however, controlled studies have only determined that a slow start is more suitable than a fast start pacing strategy. Currently, it is unclear which strategy is more effective for endurance cycling time trials. This study sought to identify differences in 30-km cycling time trial (TT30) performance related to pacing strategies by comparing individually chosen pacing strategy with time-to-exhaustion (TE) at the average power output achieved during TT30. Eight moderately trained male cyclists (Vo2max = 50.9 +/- 5.2 mlxkgxmin) performed 2 TT30 tests and 2 TE tests at the average power output of TT30 on a Velotron cycle ergometer at the same time of day, separated by at least 48 hours. During TT30, participants generally chose to use a 'fast start' pacing strategy, cycling at a speed relative to the TT average (TTAvg) of 103.1 +/- 2.2% during the first 5 km. There was no significant difference in performance time between the TE test and TT30. Starting pace (TT0-5) was significantly correlated with finishing pace (TT25-30) (r = -0.91; p < 0.01) and TE (r = 0.85; p < 0.01). Subjects cycling at a relative starting speed (RS0-5) >105% had a significantly longer TE than subjects cycling at <105%, whereas TT30 performance time was not different between the two groups. The present investigation provided indirect evidence that a fast start pacing strategy decreases finishing speed and overall performance in TT30, and increased TT performance can be achieved by selecting a starting pace no more than 5% above TTAvg.
Description:
Free spans or suspended spans normally occur in subsea pipelines due to the irregularity of seabed and/or the scouring action of sea water. A problem of significance to the free spans of subsea pipeline is that currents or waves flowing across pipelines can shed vortices and induce vibration which may cause fatigue damage to the pipelines. Natural frequencies of free spans are required when solving vibration amplitude and cyclic stresses in the free span. The natural frequency is usually calculated with simplified equations, where factors such as boundary conditions and axial forces are not accurately taken into account. In this study, the influence of boundary conditions, mass of hydrocarbon products, axial force, and multiple spans on the natural frequencies of pipeline are investigated and corresponding suggestions are provided for frequency calculation.
Description:
Introduction Many disability prevention strategies are focused on acute injuries and brief illness episodes, but there will be growing challenges for employers to manage circumstances of recurrent, chronic, or fluctuating symptoms in an aging workforce. The goal of this article is to summarize existing peer-review research in this area, compare this with employer discourse in the grey literature, and recommend future research priorities. Methods The authors participated in a year-long sponsored collaboration that ultimately led to an invited 3-day conference, “Improving Research of Employer Practices to Prevent Disability”, held October 14–16, 2015, in Hopkinton, Massachusetts, USA. The collaboration included a topical review of the scientific and industry literature, group discussion to identify key areas and challenges, drafting of initial documents, and feedback from peer researchers and a special panel of experts with employer experience. Results Cancer and mental illness were chosen as examples of chronic or recurring conditions that might challenge conventional workplace return-to-work practices. Workplace problems identified in the literature included fatigue, emotional exhaustion, poor supervisor and co-worker support, stigma, discrimination, and difficulties finding appropriate accommodations. Workplace intervention research is generally lacking, but there is preliminary support for improving workplace self-management strategies, collaborative problem-solving, and providing checklists and other tools for job accommodation, ideas echoed in the literature directed toward employers. Research might be improved by following workers from an earlier stage of developing workplace concerns. Conclusions Future research of work disability should focus on earlier identification of at-risk workers with chronic conditions, the use of more innovative and flexible accommodation strategies matched to specific functional losses, stronger integration of the workplace into on-going rehabilitation efforts, and a better understanding of stigma and other social factors at work.
Description:
Cracked cross-beam connections made of thin-walled rectangular hollow sections (RHS) are repaired with carbon fiber-reinforced polymer (CFRP) sheets. Constant amplitude fatigue experiments are conducted on the repaired specimens. A pilot test is conducted on a T-connection of square hollow sections (SHS) to explore the effective method of applying CFRP. Due to the peeling effect at the corner region of the SHS-to-SHS connection, early debonding happens in the pilot test that only results in a slight extension in fatigue life. In the following experiments of repairing RHS-to-RHS cross-beam connections, circumferential or transverse restraining CFRP patches are applied in the corner region that prevents early debonding successfully and leads to significant increase in fatigue life. Finally, an improvement is made with the addition of steel strengthening plates that increase both the flexural stiffness and fatigue life of the cracked specimens significantly. The proposed retrofitting method may be useful for repairing other similar fatigue-cracked welded tubular connections.
Description:
Aims. Levels of fatigue as experienced by people with end stage renal disease (ESRD), were assessed using the Fatigue Severity Scale (FSS). Background. Fatigue, a common symptom reported by people with ESRD, is a multifaceted, subjective experience, which is readily understood by individuals but difficult to measure. There is limited understanding of the level of fatigue experienced by people with ESRD, with research currently limited to people treated with haemodialysis. Method. The FSS was completed by 92 people with ESRD who were patients of a renal service in far North Queensland, Australia. Demographic and renal health history data were also collected with the self-report survey. Results. Comparisons were preformed between overall fatigue levels and different renal disorders, genders, ethnicity and renal replacement therapy (RRT). Participants in this study were more fatigued than the general population; there was no difference in levels of fatigue between gender and ethnicity. Participants with diabetic nephropathy and those who were predialysis were the most fatigued. A significant difference between mean fatigue scores was found for type of RRT [F(3,88) = 2.4, p < 0.05], with participants using peritoneal dialysis reporting the most fatigue. Additionally, participants categorized according to type of RRT, erythropoietin replacement therapy and current haemoglobin levels revealed significant mean differences on fatigue levels [F(3,88) = 2.74, p < 0.05]. Relevance to clinical practice. People with ESRD experience considerable fatigue; it is particularly important for nurses to understand this level of fatigue impacts on the daily life of patients. These findings provide the preliminary evidence to support the development of renal nursing practice guidelines related to symptom recognition and management of fatigue.
Description:
Aims and objectives: To examine the impact of fatigue on the daily activity levels of people with chronic kidney disease, compare whether being predialysis or receiving different renal replacement therapies had any effect on fatigue and activity and identify whether any items in the fatigue severity scale were more predictive of daily activity levels. Background: Chronic kidney disease is a complex and long-term disease where people commonly experience fatigue and reduced levels of fitness; both of which impact on an individual's ability to carry out routine activities of daily life. Design: A descriptive cross-sectional design. Methods: A convenience sample of 112 people completed the fatigue severity scale and Human Activity Profile. Participants differed in their renal history and were either predialysis or receiving renal replacement therapy. Results: Women or older participants were significantly more fatigued and less active than men or younger participants. A significant difference between mean fatigue and activity scores was found for type of renal replacement therapy, with participants receiving peritoneal dialysis being the most fatigued and the least active. Additionally, lower levels of albumin were significantly correlated with greater levels of fatigue and the ability to engage in fewer activities. Conclusion: People with chronic kidney disease regardless of whether they are predialysis or receiving either peritoneal or haemodialysis experience high levels of fatigue and are able to engage in fewer daily activities. The fatigue severity scale and the Human Activity Profile are useful indicators of fatigue and physical activities which can be used in routine assessment practices. Relevance to clinical practice: Renal nurses are ideally positioned to engage in early identification and regular monitoring of both fatigue and activity levels in people with chronic kidney disease. Individual care plans can be developed to incorporate supportive rehabilitative strategies which aim to reduce fatigue and maximise activity levels.
Description:
Objective: To compare the effects of anodal trans-cranial direct current stimulation (a-tDCS) over primary motor and dorsolateral prefrontal cortices on Fatigue Severity Scale and its lasting effect on fatigue reduction and improvement in quality of life in patients with multiple sclerosis. Design: A randomized, double-blinded, sham-controlled parallel clinical trial study. Setting: Neurological physiotherapy clinics. Subjects: Thirty-nine participants were randomly assigned to three groups: dorsolateral prefrontal cortex a-tDCS, primary motor a-tDCS (experimental groups) and sham a-tDCS. Finally, 36 participants completed the whole study (n = 12 in each group). Interventions: Participants in the experimental groups received six-session a-tDCS (1.5 mA, 20 minutes) during two weeks (three sessions per week). The sham group received six sessions of 20-minute sham stimulation. Main measures: The Fatigue Severity Scale and quality of life were assessed before, immediately and four weeks after the intervention. Results: Findings indicated a significant reduction in the Fatigue Severity Scale and a significant increase in the quality of life in both experimental groups, immediately after the intervention (P < 0.001), while Fatigue Severity Scale and quality of life changes were not significant in the sham a-tDCS group (P > 0.05). In addition, improvement of the variables remained four weeks after the intervention in dorsolateral prefrontal cortex a-tDCS (mean differences (95% confidence interval): 0.03 (−0.63 to 0.68) as compared to primary motor (−0.62 (−0.11 to −1.14) and sham a-tDCS groups (−0.47 (−1.37 to 0.43)). Conclusion: Both primary motor and dorsolateral prefrontal cortex a-tDCS as compared to sham intervention can immediately improve fatigue and quality of life. However, the effects last up to four weeks only by the dorsolateral prefrontal cortex a-tDCS.
Description:
Weld defects and severe variation of shape near the welds cause high stress concentration at weld toes or weld roots. This high stress concentration reduces fatigue lives of welded structures. A stress intensity factor (SIF) which includes this effect increases the accuracy of fatigue lives prediction. A magnification factor is commonly used to multiply the SIF of semi-elliptical surface cracks to account for the stress concentration effect in welded connections. Yamada and Hirt model is one of these methods. Comparison between Yamada & Hirt SIF equations and Newman & Raju SIF equations are applied to SIF of semi-elliptical surface cracks. The results suggest that Yamada & Hirt SIF equations are valid when the crack aspect ratio is less than 0.6. New empirical SIF equations are developed based on Yamada & Hirt SIF equations. The newly derived SIF equations are verified by comparing with experimental data.
Description:
The present study examined the agreement between peak power output during a standard Wingate anaerobic test (WAnT) and a six second 'all-out' test on a Wattbike Pro. Nine males (40.7 +/- 19.4 yrs, 1.76 +/- 0.03 cm, 82.11 +/- 8.9 kg) underwent three testing protocols on separate days. The protocols consisted 30 second WAnT (WAnT30), a modified WAnT over 6 seconds (WAnT6) and a 6 second peak power test (PPT6). PPT6 was correlated with WAnT30 (r = 0.9; p < 0.001) with a mean bias of 105 W. PPT6 correlated with WAnT6 (r = 0.95; p < 0.001) with a mean bias of 74 W. WAnT6 correlated with WAnT30 (r = 0.99; p < 0.001) with a mean bias of 31 W. There was no difference in time to peak power between any trial. PPT6 resulted in significantly greater power outputs than in WAnT30 and WAnT6 (p < 0.001). We conclude that PPT6 and WAnT6 are valid measures of peak power output compared with WAnT30. This identifies that PPT6 and WAnT6 as short duration 'all-out' tests that have practical applications for researchers and coaches who wish to assess peak power output without the fatiguing effects associated with a standard WAnT.
Description:
Purpose: To determine the effects of prolonged simulated tennis on performance and the ergogenic potential of caffeine, carbohydrates, and cooling. Methods: Twelve highly trained male tennis players (age 18.3 ± 3.0 y, height 178.8 ± 8.5 cm, body mass 73.95 ± 12.30 kg, mean ± SD) performed 4 simulated matches (2 h 40 min) against a ball machine on an indoor hard court. The counterbalanced experimental trials involved caffeine supplementation (3 mg/kg), carbohydrate supplementation (6% solution), precooling and intermittent cooling, and placebo control. Physiological markers (core temperature, heart rate, blood lactate, and blood glucose), subjective responses (ratings of perceived exertion and thermal sensation), stroke velocity and accuracy, serve kinematics, and tennis-specific perceptual skill quantified the efficacy of interventions. Results: Significant effects of time (P < .01) reflected increased physiological demand, reduced serve velocity and ground-stroke velocity and accuracy, and a slowing of the serve racket-arm acceleration phase. Caffeine increased serve velocity (165 ± 15 km/h) in the final set of the match (P = .014) compared with placebo (159 ± 15 km/h, P = .008) and carbohydrate (158 ± 13 km/h, P = .001) conditions. Carbohydrate and cooling conditions afforded physiological advantage (increased blood glucose, P < .01, and reduced preexercise thermal sensation, P < .01) but did not affect performance relative to the placebo condition. Conclusions: Prolonged simulated tennis induced significant decrements in tennis skills. Caffeine supplementation partly attenuated the effects of fatigue and increased serve velocity. In contrast, carbohydrate and cooling strategies had little ergogenic effect on tennis performance.
Description:
Purpose: To determine the effects of prolonged simulated tennis on performance and the ergogenic potential of caffeine, carbohydrates, and cooling. Methods: Twelve highly trained male tennis players (age 18.3 ± 3.0 y, height 178.8 ± 8.5 cm, body mass 73.95 ± 12.30 kg, mean ± SD) performed 4 simulated matches (2 h 40 min) against a ball machine on an indoor hard court. The counterbalanced experimental trials involved caffeine supplementation (3 mg/kg), carbohydrate supplementation (6% solution), precooling and intermittent cooling, and placebo control. Physiological markers (core temperature, heart rate, blood lactate, and blood glucose), subjective responses (ratings of perceived exertion and thermal sensation), stroke velocity and accuracy, serve kinematics, and tennis-specific perceptual skill quantified the efficacy of interventions. Results: Significant effects of time (P < .01) reflected increased physiological demand, reduced serve velocity and ground-stroke velocity and accuracy, and a slowing of the serve racket-arm acceleration phase. Caffeine increased serve velocity (165 ± 15 km/h) in the final set of the match (P = .014) compared with placebo (159 ± 15 km/h, P = .008) and carbohydrate (158 ± 13 km/h, P = .001) conditions. Carbohydrate and cooling conditions afforded physiological advantage (increased blood glucose, P < .01, and reduced preexercise thermal sensation, P < .01) but did not affect performance relative to the placebo condition. Conclusions: Prolonged simulated tennis induced significant decrements in tennis skills. Caffeine supplementation partly attenuated the effects of fatigue and increased serve velocity. In contrast, carbohydrate and cooling strategies had little ergogenic effect on tennis performance.
Description:
Fatigue is common among mothers of infants and young children and associated with a range of negative parenting outcomes. Little is understood, however, about the mechanisms by which fatigue may impact on parenting, particularly among mothers beyond 12 months post-partum. This study investigated the relationship between maternal fatigue and overreactive discipline, and whether parenting self-efficacy mediates this relationship. Methods: Participants were 252 Australian mothers of 1-4 years old children. Levels of fatigue, parenting self-efficacy, and overreactive discipline were recorded via a self-report questionnaire. Results: A simple mediation model analysis provided support for the direct effect of fatigue on overreactive discipline, as well as the mediation of this relationship by parenting self-efficacy. Conclusions: These findings suggest fatigue may contribute to overreactive discipline in mothers of young children via two pathways: directly, and indirectly via parenting self-efficacy. Interventions that support mothers to manage fatigue and maintain a sense of parenting self-efficacy while facing ongoing exhaustion may promote the use of more effective and less adverse discipline responses with children.
Description:
Recent studies on the application of carbon fibre reinforced polymer (CFRP) materials to defected steel structures have demonstrated the potential for significant reduction of stress intensity factor (SIF) values at crack tips leading to extended fatigue lives. However, most of the previous research relied on experimental and numerical methods, which were either expensive or time-consuming. In this paper, the SIF values at crack tips of steel plates strengthened with bonded composite materials were evaluated using linear elastic fracture mechanics. The analysis was based on the classical solution of SIF values of plain steel plates, considering load share effect and geometry correction factor change resulted from the overlay patch. The effect of different parameters were demonstrated and compared with experimental results, including initial damage degrees of specimens, geometric and mechanical properties of retrofitting materials and bond locations. Good agreement with the experimental data indicated that this approach could conservatively predict the SIF values with reasonable accuracy. A parametric study on variables including the CFRP modulus, the bond width and bond length was conducted based on this method to further investigate their effect on the SIF values.
Description:
Cracked thin-walled rectangular hollow section (RHS)-to-RHS cross-beam connections are repaired with carbon fibre reinforced polymer (CFRP) composites and constant amplitude fatigue experiments are conducted on them. A pilot test is first conducted on a square hollow section (SHS)-to-SHS T-connection to explore an effective method of applying CFRP. Due to the “peel off” effect at the corner region of the SHS-to-SHS specimen, early debonding appears in the pilot test which only results in a small increase in fatigue life. Circumferential or transverse restraining CFRP patches are added in the RHS-to-RHS cross-beam specimens which prevent early debonding successfully and lead to significant increase in fatigue life.
Description:
Previous studies have demonstrated that fatigue is a risk factor for depressive symptoms in mothers of young children. The aim of the present study was to investigate whether the five facets of mindfulness moderated the relationship between fatigue and depressive symptoms in mothers of young children. A sample of 723 mothers of children aged 1–5 years completed the Fatigue Assessment Scale, the Centre for Epidemiologic Studies Depression Scale, and the Five Facet Mindfulness Questionnaire-Short Form. Results showed that four out of the five mindfulness facets (non-judging of inner experience, non-reactivity to inner experience, acting with awareness, and describing) weakened the relationship between fatigue and depressive symptoms. Interaction effects were found to be small. Further investigation of the unique roles of the five mindfulness facets as well as other possible protective factors and interventions that may weaken the fatigue-depressive symptom relationship in mothers of young children is warranted.
Description:
A forward head and rounded shoulder posture is a poor posture that is widely seen in everyday life. It is known that sitting in such a poor posture with long hours will bring health issues such as muscle pain. However, it is not known whether sitting in this poor posture for a short period of time will affect human activities. This paper investigates the effects of a short-duration poor posture before some typical physical activities such as push-ups. The experiments are set up as follows. Fourteen male subjects are asked to do push-ups until fatigue with two surface electromyography (sEMG) at the upper limb. Two days later, they are asked to sit in this poor posture for 15 min with eight sEMG sensors located at given back muscles. Then they do the push-ups after the short-duration poor posture. The observations from the median frequency of sEMG signals at the upper limb indicate that the short-duration poor posture does affect the fatigue procedure of push-ups. A significant decreasing trend of the performance of push-ups is obtained after sitting in this poor posture. Such effects indicate that some parts of the back muscles indeed get fatigued with only 15 min sitting in this poor posture. By further investigating the time-frequency components of sEMG of back muscles, it is observed that the low and middle frequencies of sEMG signals from the infraspinatus muscle of the dominant side are demonstrated to be more prone to fatigue with the poor posture. Although this study focuses only on push-ups, similar experiments can be arranged for other physical exercises as well. This study provides new insights into the effect of a short-duration poor posture before physical activities. These insights can be used to guide athletes to pay attention to postures before physical activities to improve performance and reduce the risk of injury.
Description:
Management of maritime military platform life is a real challenge for operators and maintainers. One of the major problems is how to capture cost effective information about the hull defect and predict the remaining life? This paper will focus on the automation process for calculation of the failure rate and prediction from collated hull defects information. This data is assessed for accuracy, sensitivity and correctness of defect location and failure modes. An outline of the automation techniques investigated to determine the hull failures rates is discussed. Five major failure modes are analysed and a high level approach for integrating failure data collation is presented. The paper then discusses some of the issues and challenges with obtaining reliable maintenance data and opportunities for further research in finding a better solution.