Speed and surface steepness affect internal tibial loading during running

Background:Internal tibial loading is influenced by modifiable factors with implications for the risk of stress injury.Runners encounter varied surface steepness(gradients)when running outdoors and may adapt their speed according to the gradient.This study aimed to quantify tibial bending moments and stress at the anterior and posterior peripheries when running at different speeds on surfaces of different gradients.Methods:Twenty recreational runners ran on a treadmill at 3 different speeds(2.5 m/s,3.0 m/s,and 3.5 m/s)and gradients(level:0%;uphill:+5%,+10%,and+15%;downhill:-5%,-10%,and-15%).Force and marker data were collected synchronously throughout.Bending moments were estimated at the distal third centroid of the tibia about the medial-lateral axis by ensuring static equilibrium at each 1%of stance.Stress was derived from bending moments at the anterior and posterior peripheries by modeling the tibia as a hollow ellipse.Two-way repeated-measures analysis of variance were conducted using both functional and discrete statistical analyses.Results:There were significant main effects for running speed and gradient on peak bending moments and peak anterior and posterior stress.Higher running speeds resulted in greater tibial loading.Running uphill at+10%and+15%resulted in greater tibial loading than level running.Running downhill at-10%and-15%resulted in reduced tibial loading compared to level running.There was no difference between+5%or-5%and level running.Conclusion:Running at faster speeds and uphill on gradients≥+10%increased internal tibial loading,whereas slower running and downhill running on gradients≥-10%reduced internal loading.Adapting running speed according to the gradient could be a protective mechanism,providing runners with a strategy to minimize the risk of tibial stress injuries.

The Road to the Beijing Winter Olympics and Beyond: Opinions and Perspectives on Physiology and Innovation in Winter Sport

Beijing will host the 2022 Winter Olympics,and China strengthens research on various aspects to allow their athletes to compete successfully in winter sport.Simultaneously,Government-directed initiatives aim to increase public participation in recreational winter sport.These parallel developments allow research to advance knowledge and understanding of the physiological determinants of performance and health related to winter sport.Winter sport athletes often conduct a substan-tial amount of training with high volumes of low-to-moderate exercise intensity and lower volumes of high-intensity work.Moreover,much of the training occur at low ambient temperatures and winter sport athletes have high risk of developing asthma or asthma-related conditions,such as exercise-induced bronchoconstriction.The high training volumes require optimal nutrition with increased energy and dietary protein requirement to stimulate muscle protein synthesis response in the post-exercise period.Whether higher protein intake is required in the cold should be investigated.Cross-country ski-ing is performed mostly in Northern hemisphere with a strong cultural heritage and sporting tradition.It is expected that innovative initiatives on recruitment and training during the next few years will target to enhance performance of Chinese athletes in classical endurance-based winter sport.The innovation potential coupled with resourcing and population may be substantial with the potential for China to become a significant winter sport nation.This paper discusses the physiological aspects of endurance training and performance in winter sport highlighting areas where innovation may advance in athletic performance in cold environments.In addition,to ensure sustainable development of snow sport,a quality ski patrol and rescue system is recommended for the safety of increasing mass participation.

Caffeine Increases VerticalJumping Height in Young Trained Males Before But Not After a Maximal Effort Strength Training Session

The aim of the present study was to investigate the effect of caffeine on vertical jumping height in rested condition and after a heavy strength training session.Six well-trained young males with experience in jump and strength training were included in this double-blinded,randomised study with cross-over design.Caffeine(3 mg/kg body weight)or placebo were ingested 45 min prior to the jump tests.Jumping was performed on a force platform and vertical jumping height was calculated.After a standardized warm up,participants performed jumping series consisting of three maximal jumps with 30 s rest between jumps followed by five maximal jumps with 7 s rest between jumps.The participants performed a heavy strength training of the leg muscles(leg press:3×15 reps)and the jumping series was repeated immediately after(30 s),and after 5 min and 15 min recovery.Caffeine increased the maximal vertical counter movement jump height(P≤0.05)and mean value of the 5-jump sequence prior to the strength training.Caffeine increased jump height by 2.2 cm±0.5 cm at the first jump.Blood lactate after the strength training increased to 6.97±1.20 and 7.77±0.54 mmol/L in PLA and CAF,respectively(P=0.19).The jump height was reduced by 8 cm after the strength training.There were no differences in jump height after ingestion of caffeine or placebo immediately after the strength training session or in the recovery period,but blood lactate in the recovery period was higher in CAF compared to PLA(ANOVA;P<0.05).Conclusion:Caffeine increased the vertical jump height in the resting state.However,after a maximal effort strength training session the positive effect of caffeine was no longer significant.