Recovery and Fatigue Behavior of Forearm Muscles during a Repetitive Power Grip Gesture in Racing Motorcycle Riders

Despite a reduction in the maximal voluntary isometric contraction (MVCisom) observed systematically in intermittent fatigue protocols (IFP), decrements of the median frequency, assessed by surface electromyography (sEMG), has not been consistently verified. This study aimed to determine whether recovery periods of 60 s were too long to induce a reduction in the normalized median frequency (MFEMG) of the flexor digitorum superficialis and carpi radialis muscles. Twenty-one road racing motorcycle riders performed an IFP that simulated the posture and braking gesture on a motorcycle. The MVCisom was reduced by 53% (p < 0.001). A positive and significant relationship (p < 0.005) was found between MFEMG and duration of the fatiguing task when 5 s contractions at 30% MVCisom were interspersed by 5 s recovery in both muscles. In contrast, no relationship was found (p > 0.133) when 10 s contractions at 50% MVC were interspersed by 1 min recovery. Comparative analysis of variance (ANOVA) confirmed a decrement of MFEMG in the IFP at 30% MVCisom including short recovery periods with a duty cycle of 100% (5 s/5 s = 1), whereas no differences were observed in the IFP at 50% MVCisom and longer recovery periods, with a duty cycle of 16%. These findings show that recovery periods during IFP are more relevant than the intensity of MVCisom. Thus, we recommend the use of short recovery periods between 5 and 10 s after submaximal muscle contractions for specific forearm muscle training and testing purposes in motorcycle riders.

The structure design and performance analysis of a racing welded steering knuckle

Steering knuckle as an important safety components of automobiles, in the process of lightweight design, if not taking into account the structure, process and other factors, will inevitably cause the steering knuckle strength and stiffness and other performance reduction, forming a major safety hazard. Based on a four-wheel drive off-road racing car, this paper performs strength analysis and modal analysis of the steering joint after weld analysis, uses multi-body dynamics to break down the hard spot load on the steering joint, and uses the test site test analysis and verification, so as to obtain a good performance steering knuckle.

Sportsman’s authority in the perspective of man’s weakness

Background: History of glory and fall of the cyclist Lance Armstrong refers to the issues from the borderline of sociology, psychology, pharmacology and qualified sport. It stirs many emotions and extreme opinions in which human attitudes are focused on phenomena impossible to be interpreted unequivocally. The purpose of this research was to learn opinions on the life path of Lance Armstrong, regarding his struggle both with cancer and his rivals in the peloton, but at the same time marked with forbidden doping. Material and methods: The research was carried out using the survey method, which asked one question about the ethics of behaviour of the former professional road racing cyclist. Results: People participating in the research had their own oncological experience and pursued the passion of sport-recreational activity. That means that in both areas their life refers to the path of one of the most recognizable sportsmen of the turn of centuries. In most cases, they find understanding for his behaviour. Conclusions: The main conclusion coming from the assessment of Armstrong concerns recognition that among people who have a similar history of life, most of them are able to indicate his numerous contributions to humanity, minimizing and sometimes even undervaluing shameful reputation, which disgraced professional sport.

Modelling the effect of curves on distance running performance

Background Although straight ahead running appears to be faster, distance running races are predominately contested on tracks or roads that involve curves. How much faster could world records be run on straight courses? Methods Here,we propose a model to explain the slower times observed for races involving curves compared to straight running. For a given running velocity, on a curve, the average axial leg force (${\overline{F}}_{a}$) of a runner is increased due to the need to exert centripetal force. The increased ${\overline{F}}_{a}$ presumably requires a greater rate of metabolic energy expenditure than straight running at the same velocity. We assumed that distance runners maintain a constant metabolic rate and thus slow down on curves accordingly. We combined published equations to estimate the change in the rate of gross metabolic energy expenditure as a function of ${\overline{F}}_{a}$, where ${\overline{F}}_{a}$ depends on curve radius and velocity, with an equation for the gross rate of oxygen uptake as a function of velocity. We compared performances between straight courses and courses with different curve radii and geometries. Results The differences between our model predictions and the actual indoor world records, are between 0.45% in 3,000 m and 1.78% in the 1,500 m for males, and 0.59% in the 5,000 m and 1.76% in the 3,000 m for females. We estimate that a 2:01:39 marathon on a 400 m track, corresponds to 2:01:32 on a straight path and to 2:02:00 on a 200 m track. Conclusion Our model predicts that compared to straight racecourses, the increased time due to curves, is notable for smaller curve radii and for faster velocities. But, for larger radii and slower speeds, the time increase is negligible and the general perception of the magnitude of the effects of curves on road racing performance is not supported by our calculations.

Regulating Off-Road: The California Desert and Collaborative Environmentalism

Historians often understand the 1970s and 1980s in terms of a declining New Deal order, in which an antistatist right as well as a conflicted relationship between public interest movements and administrative authorities undermined the notion of an effective federal government. Nowhere was the erosion of federal administration seemingly more apparent than in the West. An examination of the regulation of off-road racing in the California desert, focusing on everyday administration rather than on elections and lawsuits, reveals how federal agencies actually worked more collaboratively and productively with different interest groups than familiar narratives about these polarized decades would suggest. Contrary to depictions of federal agencies as administrating from afar, and of environmental organizations as overly litigious and out of touch, regulatory work in the California desert happened locally and through relationships shaped by new laws such as the National Environmental Policy Act.

Modelling the effect of curves on distance running performance

Background On a curve, the average axial leg force (Fa) of a runner is increased due to the need to exert centripetal force. The increased Fa presumably requires a greater rate of metabolic energy expenditure than straight running at the same velocity. We propose a model that explains the velocity reduction on curves, compared to straight running, assuming that runners maintain a constant metabolic rate. Methods We combined published equations to estimate the change in the rate of gross metabolic energy expenditure as a function of Fa, where Fa depends on curve radius and velocity, with an equation for the gross rate of oxygen uptake as a function of velocity. We compared performances between straight courses and courses with different curve radii and geometries. Results The differences between our model predictions and the actual indoor world records, are between 0.45 % in 3000 m and 1.78 % in the 1500 m for males, and 0.59 % in the 5000 m and 1.76 % in the 3000 m for females. We estimate thata 2:01:39 marathon on a 400 m track, corresponds to 2:01:32 on a straight path and to 2:02:00 on a 200 m track. Conclusion Our model predicts that compared to straight racecourses, the increased time due to curves, is notable for smaller curve radii and for faster velocities. But, for larger radii and slower speeds, the time increase is negligible and the general perception of the magnitude of the effects of curves on road racing performance is not supported by our calculations.