This Investment Boom Gives the Economy Running Room

In our age of information superhighway,there is an invis-ible boom in communications investment owing to the highquality and low price of the communications equipment.Interms of the price,the government reports a rise of some 7 percent since t989.However,Business Week estimates that thetrue price declines by about 35 per cent.In terms of invest-

Metabolic cost of level,uphill,and downhill running in highly cushioned shoes with carbon-fiber plates

Background:Compared to conventional racing shoes,Nike Vaporfly 4% running shoes reduce the metabolic cost of level treadmill running by4%.The reduction is attributed to their lightweight,highly compliant,and resilient midsole foam and a midsole-embedded curved carbon-fiber plate.We investigated whether these shoes also could reduce the metabolic cost of moderate uphill(+3°) and downhill(-3°) grades.We tested the null hypothesis that,compared to conventional racing shoes,highly cushioned shoes with carbon-fiber plates would impart the same ~4%metabolic power(W/kg) savings during uphill and downhill running as they do during level running.Methods:After familiarization,16 competitive male runners performed six 5-min trials(2 shoes × 3 grades) in 2 Nike marathon racing-shoe models(Streak 6 and Vaporfly 4%) on a level,uphill(+3°),and downhill(-3°) treadmill at 13 km/h(3.61 m/s).We measured submaximal oxygen uptake and carbon dioxide production during Minutes 4-5 and calculated metabolic power(W/kg) for each shoe model and grade combination.Results:Compared to the conventional shoes(Streak 6),the metabolic power in the Vaporfly 4% shoes was 3.83%(level),2.82%(uphill),and2.70%(downhill)less(all p <0.001).The percent of change in metabolic power for uphill running was less compared to level running(p=0.04;effect size(ES)=0.561) but was not statistically different between downhill and level running(p=0.17;ES=0.356).Conclusion:On a running course with uphill and downhill sections,the metabolic savings and hence performance enhancement provided by Vaporfly 4% shoes would likely be slightly less overall,compared to the savings on a perfectly level race course.

Stride length-velocity relationship during running with body weight support

Background： Lower body positive pressure （LBPP） treadmills can be used in rehabilitation programs and/or to supplement tun mileage in healthy runners by reducing the effective body weight and impact associated with running. The purpose of this study is to determine if body weight support influences the stride length （SL）-velocity as well as leg impact acceleration relationship during running. Methods： Subjects （n = 10, 21.4 ± 2.0 years, 72.4 ± 10.3 kg, 1.76 ± 0.09 m） completed 16 run conditions consisting of specific body weight support and velocity combinations. Velocities tested were 100%, 110%, 120%, and 130% of the preferred velocity （2.75± 0.36 m/s）. Body weight support conditions consisted of 0, 60%,5, 70%, and 80% body weight support. SL and leg impact accelerations were determined using a light-weight accelerometer mounted on the surface of the anterior-distal aspect of the tibia. A 4 × 4 （velocity x body weight support） repeated measures ANOVA was used for each dependent variable （a = 0.05）. Results： Neither SL nor leg impact acceleration were influenced by the interaction of body weight support and velocity （p 〉 0.05）. SL was least during no body weight support （p 〈 0.05） but not different between 60%, 70%, and 80% support （p 〉 0.05）. Leg impact acceleration was greatest during no body weight support （p 〈 0.05） but not different between 60%, 70%, and 80% support （p 〉 0.05）. SL and leg impact accelerations increased with velocity regardless of support （p 〈 0.05）. Conclusion： The relationships between SL and leg impact accelerations with velocity were not influenced by body weight support.

Is changing footstrike pattern beneficial to runners?

Some researchers, running instructors, and coaches have suggested that the "optimal" footstrike pattern to improve performance and reduce running injuries is to land using a mid-or forefoot strike. Thus, it has been recommended that runners who use a rearfoot strike would benefit by changing their footstrike although there is little scientific evidence for suggesting such a change. The rearfoot strike is clearly more prevalent. The major reasons often given for changing to a mid-or forefoot strike are(1) it is more economical;(2) there is a reduction in the impact peak and loading rate of the vertical component of the ground reaction force; and(3) there is a reduction in the risk of a running-related injuries. In this paper,we critique these 3 suggestions and provide alternate explanations that may provide contradictory evidence for altering one's footstrike pattern.We have concluded, based on examining the research literature, that changing to a mid-or forefoot strike does not improve running economy, does not eliminate an impact at the foot-ground contact, and does not reduce the risk of running-related injuries.

The effect of flutamide on the physical working capacity and activity of some of the key enzymes for the energy supply in adult rats

The aim of the study was to assess the effects of androgen receptor antagonists on the physical working capacity and activity of some of the key muscle enzymes for the energy supply in rats. Young adult male Wistar rats were divided into two groups. One group received 15 mg kg-1 of flutamide daily for 6 days a week and the other group served as control for 8 weeks. At the beginning and at the end of the experiment, all rats were subjected to submaximal running endurance （SRE）, maximum time to exhaustion （MTE）, and maximal sprinting speed （MSS） tests. At the end of the trial, maximum oxygen consumption （VO2max） test was performed and the levels of testosterone, erythrocytes, hemoglobin as well as enzyme activity of succinate dehydrogenase （SDH）, lactate dehydrogenase （LDH）, and NAD.H2-cytochrome-c reductase （NAD.H2） of the gastrocnemius muscle were measured. Serum testosterone of the flutamide-treated rats was higher than that of the controls, which verifies the effectiveness of the dose chosen. MTE and SRE of the anti-androgen-treated group were lower compared with the initial values. Flutamide treatment decreased the activity of SDH and NAD.H2 compared with the controls. We found no effect of the anti-androgen treatment on MSS, VO2max, running economy, LDH activity, and hematological variables. Our findings indicate that the maintenance of the submaximal and maximal running endurance as well as the activity of some of the key enzymes associated with muscle oxidative capacity is connected with androgen effects mediated by androgen receptors.