Bjoern Braunstein

Footwear affects the gearing at the ankle and knee joints during running

The objective of the study was to investigate the adjustment of running mechanics by wearing five different types of running shoes on tartan compared to barefoot running on grass focusing on the gearing at the ankle and knee joints. The gear ratio, defined as the ratio of the moment arm of the ground reaction force (GRF) to the moment arm of the counteracting muscle tendon unit, is considered to be an indicator of joint loading and mechanical efficiency. Lower extremity kinematics and kinetics of 14 healthy volunteers were quantified three dimensionally and compared between running in shoes on tartan and barefoot on grass. Results showed no differences for the gear ratios and resultant joint moments for the ankle and knee joints across the five different shoes, but showed that wearing running shoes affects the gearing at the ankle and knee joints due to changes in the moment arm of the GRF. During barefoot running the ankle joint showed a higher gear ratio in early stance and a lower ratio in the late stance, while the gear ratio at the knee joint was lower during midstance compared to shod running. Because the moment arms of the counteracting muscle tendon units did not change, the determinants of the gear ratios were the moment arms of the GRFs. The results imply higher mechanical stress in shod running for the knee joint structures during midstance but also indicate an improved mechanical advantage in force generation for the ankle extensors during the push-off phase.

Effect of rocker shoe design features on forefoot plantar pressures in people with and without diabetes

BACKGROUND There is no consensus on the precise rocker shoe outsole design that will optimally reduce plantar pressure in people with diabetes. This study aimed to understand how peak plantar pressure is influenced by systematically varying three design features which characterise a curved rocker shoe: apex angle, apex position and rocker angle. METHODS A total of 12 different rocker shoe designs, spanning a range of each of the three design features, were tested in 24 people with diabetes and 24 healthy participants. Each subject also wore a flexible control shoe. Peak plantar pressure, in four anatomical regions, was recorded for each of the 13 shoes during walking at a controlled speed. FINDINGS There were a number of significant main effects for each of the three design features, however, the precise effect of each feature varied between the different regions. The results demonstrated maximum pressure reduction in the 2nd-4th metatarsal regions (39%) but that lower rocker angles (<20°) and anterior apex positions (>60% shoe length) should be avoided for this region. The effect of apex angle was most pronounced in the 1st metatarsophalangeal region with a clear decrease in pressure as the apex angle was increased to 100°. INTERPRETATION We suggest that an outsole design with a 95° apex angle, apex position at 60% of shoe length and 20° rocker angle may achieve an optimal balance for offloading different regions of the forefoot. However, future studies incorporating additional design feature combinations, on high risk patients, are required to make definitive recommendations.

Lower leg musculoskeletal geometry and sprint performance

The purpose of this study was to investigate whether sprint performance is related to lower leg musculoskeletal geometry within a homogeneous group of highly trained 100-m sprinters. Using a cluster analysis, eighteen male sprinters were divided into two groups based on their personal best (fast: N=11, 10.30±0.07s; slow: N=7, 10.70±0.08s). Calf muscular fascicle arrangement and Achilles tendon moment arms (calculated by the gradient of tendon excursion versus ankle joint angle) were analyzed for each athlete using ultrasonography. Achilles tendon moment arm, foot and ankle skeletal geometry, fascicle arrangement as well as the ratio of fascicle length to Achilles tendon moment arm showed no significant (p>0.05) correlation with sprint performance, nor were there any differences in the analyzed musculoskeletal parameters between the fast and slow sprinter group. Our findings provide evidence that differences in sprint ability in world-class athletes are not a result of differences in the geometrical design of the lower leg even when considering both skeletal and muscular components.

Is it possible to predict optimal rocker shoe design using barefoot gait parameters

Curved rocker shoes are routinely prescribed for people with diabetes in order reduce in-shoe plantar pressures. However, previous research has shown that different individuals may require different rocker outsole geometries in order to optimise pressure reduction [1, 2]. This has led some researchers to suggest that every individual should try a range of possible outsole designs to identify the design which maximises pressure reduction [1]. However, this process may not be feasible in a clinical setting. Given that plantar pressure has been shown to depend on specific gait variables [3], it may be possible to develop an algorithm which could predict an individual’s pressure response to a specific rocker outsole design using an input of gait data. Such an algorithm would remove the need to try on a large number of pairs of rocker shoes.

What is the best Rocker Shoe design

Background Rocker shoes are often prescribed to reduce in-shoe pressures in order to minimise the risk of ulceration in diabetic patients. However, the efficacy of the 3 principal design features of a rocker shoe (apex position, rocker angle and apex angle, see Figure 1) is unknown. Only one known study to date has systematically varied 2 of the 3 design features [1]. Therefore the aim of this study was to investigate the effect of the three principal design features, quantify inter subject variability and establish whether there is any difference in the response of the diabetic and the healthy cohort by recording in shoe plantar pressure.

Evaluating the effect of apex position and rocker in curved rocker shoes

Curved rocker shoes are designed with a contoured outsole which can be characteristics by three principle design features: rocker angle, apex angle and apex position. Although these shoes are routinely prescribed to reduce in-shoe pressure in patients with diabetes, there is only minimal scientific evidence to inform the choice of value for each of the three design features. Results from a previous study [1], suggested that a 95° apex angle may be the best compromise for offloading the different regions of the forefoot. The results of this study also suggested that higher rocker angle may lead to decrease pressure, however, this study did not quantify the precise effect of rocker angle and apex position in shoes with a 95° apex angle.

The gearing function of midsole longitudinal bending stiffness in running

Increasing the longitudinal bending stiffness (LBS) of running shoes (to an individual optimum level) has been shown to reduce energy absorption at the metatarsal phalangeal joint (MPJ) and has bee...