A COMPARISON OF LOWER EXTREMITY FORCES, JOINT ANGLES, AND MUSCLE ACTIVITY DURING SHOD AND BAREFOOT RUNNING

INTRODUCTION: Knowledge of the characteristics of barefoot running may enhance understanding of the muscular and gait modifications induced by wearing shoes. METHOD: Nine male competitive heel strike runners ran naturally across a Kistler force platform, mounted beneath a polyflex track, with the right foot while running at a speed of 4.5ms-1 +7.5%. Joint angular data was determined from marker digitisation of 100 Hz cine filming performed perpendicular to the plane of motion. Radiotelemetry was used to record the activity of six leg muscles: vastus medialis (VM); vastus lateralis (VL); rectus femoris (RF); tibialis anterior (TA); medial gastrocnemius (MG); lateral gastrocnemius (LG). Subject characteristics (mean, SD) were: age 30.8 +10.6 years; height 1.77 +0.06m; mass 70.9 +9.0kg. RESULTS: For all subjects the mean respective speeds (mean, SD) of the eight shod and barefoot running were 4.64ms-1 and 4.53ms-1, and these were not significantly different (P>0.05). In barefoot running the mean peak vertical impact force with respect to body weight(BW) was significantly higher, and mean minimal vertical impact lower. Also, the time to peak mean vertical impact, mean peak braking force and the stance time were significantly less in barefoot running. [table] Joint angles were determined at the hip, knee, ankle and knee-ankle-heel angle 10ms prior to impact, at impact, sole of the foot/shoe flat, maximum knee flexion and heel off. Of the twenty comparisons only three were significant, the barefoot ankle angle was significantly lower at heel off (), the barefoot knee-ankleheel angle was significantly lower at maximum knee flexion () and the barefoot knee-ankle-heel angle was significantly lower at heel off (). Analysis of within subject muscle activity indicated that in barefoot running TA activity at impact was less than in shod running, and LG and/or MG activity often increased before impact. Increases in VL,VM, and RF activity were frequently observed during barefoot running. CONCLUSION: Leg muscular activity alterations at impact are generally evident between barefoot and shod running, but there are interindividual differences

SYMMETRY OF GROUND REACTION FORCE MEASURES IN SUCCESSIVE FOOTFALLS DURING RUNNING

Historically ground reaction forces have taken pl'ace using a single force platform during running. Dainty and Norman (1987) stated that force platforms must be designed to accommodate foot contact with a minimum necessity of targeting the platform. Such statements are verified by differences in ground reaction force variables when a subject has to alter their stride pattern on the approach to the plate. Differences have been primarily evident during the impact phase for both walking and running (Ohallis, 2001). The alteration of these kinetic variables was related to modification of lower limb angles at contact with the platform (Challis, 2001). It can be concluded that targeti ng of the force platform in gait analysis would produce kinetic measures that are not representational, or typical of subjects standard foot contact pattern. Many of the problems of targeting can be eliminated by sound experimental procedures, such as adequate approach and run-off distances, clear verbal instructions, and ensuring the subject maintains optical focus away from the platform surface. In addition, it is possible to measure footstrikes on more than one force platform. Providing the sUbject has no major biomechanical' deficit, or injury at the time of testing, measurement of successive footstrikes should not yield ground reaction force differences in normal walking or running (Dyson and Janaway, 2000). However, recent results in running (Smith et ai., 2004) revealed vertical impact loading rate and braking forces to be greater on the second of two successive footstrikes in soccer players. It was proposed this result could be attributed to increased muscular development on the SUbjects preferred r1imb. The aim of the current investigation is to assess the symmetry of successive footstrikes during running, with a secondary aim of investigating differences in force between the preferred and non-preferred limb

EFFECT OF FORCE PLATFORM SURFACE ON GROUND REACTION PEAK FORCE

Repeated running and walking at a preferred speed across the two alternative surface covers was the basis of a comparison of peak force measures. These were obtained using a polyflex surface mounted on two force platforms, within a polyflex track system, with those obtained with a metal surface interface. When both the first and second foot strikes were considered within a stride, measures of peak impact and peak propulsion were almost the same. Mean ±s.e. measures were 2.021±0.068 BW and of 2.620±0.033 BW respectively for the polyflex and 1.987±0.066 BW and 2.607±0.031 BW respectively for the metal cover at a running speed of 3.9±0.09ms-1. Peak braking forces did not differ significantly between the surface coves. In running, the 0.017m of polyflex on the 0.004m aluminium base plate did not significantly attenuate peak vertical forces or braking forces

FORCES AT THE FRONT AND REAR BLOCKS DURING THE SPRINT START

Five male sprinters (mean ± SO: age 21.0 ± 0.5 years; height 1.80 ± 0.07 m; body weight 763 ± 29 N) started a sprint using different combinations of front and rear block angles. The vertical and horizontal forces at the front block were significantly greater with the 300 block than with the 400 or 500 blocks, and sprint speed using the 300 front block was significantly higher over 10m and 5m than with 400 or 500 (

Bacterial fitness shapes the population dynamics of antibiotic-resistant and -susceptible bacteria in a model of combined antibiotic and anti-virulence treatment

Bacterial resistance to antibiotic treatment is a huge concern: introduction of any new antibiotic is shortly followed by the emergence of resistant bacterial isolates in the clinic. This issue is compounded by a severe lack of new antibiotics reaching the market. The significant rise in clinical resistance to antibiotics is especially problematic in nosocomial infections, where already vulnerable patients may fail to respond to treatment, causing even greater health concern. A recent focus has been on the development of anti-virulence drugs as a second line of defence in the treatment of antibiotic-resistant infections. This treatment, which weakens bacteria by reducing their virulence rather than killing them, should allow infections to be cleared through the body's natural defence mechanisms. In this way there should be little to no selective pressure exerted on the organism and, as such, a predominantly resistant population would be unlikely to emerge. However, much controversy surrounds this approach with many believing it would not be powerful enough to clear existing infections, restricting its potential application to prophylaxis. We have developed a mathematical model that provides a theoretical framework to reveal the circumstances under which anti-virulence drugs may or may not be successful. We demonstrate that by harnessing and combining the advantages of antibiotics with those provided by anti-virulence drugs, given infection-specific parameters, it is possible to identify treatment strategies that would efficiently clear bacterial infections, while preventing the emergence of resistant subpopulations. Our findings strongly support the continuation of research into anti-virulence drugs and demonstrate that their applicability may reach beyond infection prevention.Comment: Pre-review manuscript. Submitted to Journal of Theoretical Biology, July 21st 201

KINETIC ANALYSIS OF A UNILATERAL SNATCH MOVEMENT

The vertical ground reaction force (VGRF) of 7 weightlifters performing one-handed dumbbell power snatches with loads of 80%, 90% and 100% of 1RM were recorded at 500 Hz from 2 Kistler force platforms. There were no significant load or side effects for the pull phase peak VGRF or catch loading rates (P>0.05), although with the exception of the catch loading rate for the heaviest loads, non-lifting side values tended to be larger than those of the lifting side. In addition to this, lifting side pull phase duration was significantly longer than the non-lifting side (

FOOT ALIGNMENT AND UNIPODAL POSTURAL STABILITY OF DANCERS TRAINED IN CLASSICAL BALLET.

Eight female dancers (mean ± SD age 21.6 ± 3.0 years; body mass 55.4 ± 4.4 Kg) and eight female physically active non-dancer controls (age 20.5 ± 1.8 years; body mass 66.5 ± 8.6 N) participated. Dancers had 15.6 years of classical ballet training and currently performed 3.5 hours of ballet per week. In walking gait the dancers right foot progression angle (mean ± SE) was greater at 9.7 ± 1.30 than that of the left foot 7.2 ± 1.20 (

INFLUENCES OF GOLF CLUB SELECTION ON GROUND REACTION FORCES ON A NATURAL GRASS SURFACE

Ground reaction forces were measured on natural turf at both feet during the golf swing using a driver and a 3-iron. Sixteen male golfers, with handicaps 0-14, performed 5 shots with each club while wearing a golf shoe with an alternative spike design. The front foot forces were greater than the back foot forces in all three orthogonal planes. At the front foot the maximum vertical force (Fz) generated was much greater when using the 3 iron by approximately 50%. The mean Fz range was greater when using the 3 iron of approximately 1.2 BW compared to 0.79 BW when using the driver. The back foot mean maximal Fz force generated was again greater for the 3 iron by 59% and mean Fz range approximately twice as great as compared to when using the driver. The Fx medial lateral force generated at the back foot was 60% greater when using the 3 iron

THE INFLUENCE OF WEARING A LUMBAR SUPPORT BELT UPON JAVELIN THROWING PERFORMANCE

Six male javelin throwers (mean ±SD age 25 ± 4 years: height 1.82 ± 0.06 m; weight 891 ± 105 N) were filmed at 150 Hz throwing an 800g javelin from a polyflex athletic track with and without a lumbar support belt, to allow three- dimensional kinematic analysis. Two typical throws at similar run up velocities were analysed. Wearing the belt was associated with significantly greater peak velocity at the shoulder relative to the hip when the hyperextended torso flexed forwards to release the javelin (P=0.046). With the belt there was not a significant increase in the velocity of the arm segments or javelin release velocity, attitude angle, release height, though an insignificant increase of 1.45m in mean distance occurred (P>0.05) possibly due to javelin aerodynamic factors