Trampas Tenbroek

Medially posted insoles consistently influence foot pronation in runners with and without anterior knee pain

Anterior knee pain (AKP) is a common injury among runners and effectively treated with posted insoles and foot orthotics. While clinically effective, the underlying biomechanical mechanisms that bring about these improvements remain debatable. Several methodological factors contribute to the inconsistent biomechanical findings, including errors associated with removing and reattaching markers, inferring foot motion from markers placed externally on a shoe, and redefining segmental coordinate systems between conditions. Therefore, the purpose of this study was to evaluate the influence of medially posted insoles on lower extremity kinematics in runners with and without AKP while trying to limit the influence of these methodological factors. Kinematics of 16 asymptomatic and 17 runners with AKP were collected while running with and without insoles. Reflective markers were attached to the surface of the calcaneus and kept in place (as opposed to detached) between conditions, eliminating the error associated with reattaching markers and redefining segmental coordinate systems. Using these methods, no significant interactions between insole and injury and the main effect of injury were detected (p>0.05); therefore, means were pooled across injury. Insoles, on average, reduced peak eversion by 3.6° (95% confidence interval -2.9° to -4.3°), peak eversion velocity by 53.2°/s (95% confidence interval -32.9 to -73.4) and eversion range of motion by 1.33 (95% confidence interval -0.8 to -1.9). However, while insoles systematically reduced eversion variables, they had small influences on the transverse plane kinematics of the tibia or knee, indicating that they may bring about their clinical effect by influencing other variables.

LYAPUNOV EXPONENT ESTIMATION FOR HUMAN GAIT ACCELERATION SIGNALS

While it is not possible to analytically define the Lyapunov exponents for biological systems, estimating the spectrum of exponents or simply the largest exponent is possible. Two algorithms are often used for experimental data: the Wolf algorithm [1] and the Rosenstein algorithm [2]. Rosenstein’s algorithm was developed to address limitations inherent in the Wolf algorithm, including: reliability issues with small data sets, computational intensity, and sensitivity to noise. Wolf and Rosenstein both suggest a minimum of 10 data points for Lyapunov estimation, where d is the dimension of the attractor; however, Rosenstein et al. claim their algorithm performs well with smaller data sets. How well these algorithms perform on small biological data sets (<10) is of interest.

Effects of unknown footwear midsole thickness on running kinematics within the initial six minutes of running

Introduction: Research on minimal footwear hasn’t utilised runners who habitually wear typical training footwear and therefore what adjustments to running patterns are made and how quickly they occur is unknown. Purpose: The purposes of this study were: 1) to investigate how kinematic patterns are adjusted while running barefoot and in footwear with systematic changes in shock attenuating material; and 2) to determine the time it takes for adjustments to occur when little is known about the footwear condition before running commences. Methods: Ten male heel-toe runners performed treadmill runs of 6 minutes in thin, medium, and thick footwear and barefoot. Participants ran immediately after putting shoes on to limit information about each footwear condition. Standard kinematics and acceleration signals were captured. Repeated measures analysis of variance (ANOVA) was utilised (p < 0.05) to determine differences across footwear conditions and time. Results: The foot was flatter at touchdown (due to a more vertical leg segment and more plantar flexion), the knee had reduced excursion, and stance times, eversion and tibial rotation excursions were greater in the thin footwear or when barefoot. Several variables were adjusted from the initial steps to later in the run. Acceleration standard deviations had more variability during initial steps than immediately following. Discussion: Many kinematic adjustments agreed with previous works though participants did not adopt a midfoot or forefoot strike pattern. Experimental design and participant knowledge and experiences may be contributing to discrepancies in footstrike patterns. Runners sensitive to eversion and tibial internal rotation should use caution when barefoot or in minimal footwear. Finally, the greatest kinematic changes occurred within the first six to eight steps, however more subtle changes continued throughout the six minute run.

Evaluating runners with and without anterior knee pain using the time to contact the ankle joint complexes' range of motion boundary.

BACKGROUND Little biomechanical evidence exists to support the association between excessive foot pronation and anterior knee pain (AKP). One issue could be the way excessive pronation has been defined. Recent evidence has suggested that evaluating pronation in the context of the joints available range of motion (ROM, anatomical threshold) provides greater insight on when pronation contributes to injury. Theoretically, quantifying the amount of time the joint has to respond before reaching end range (neuromuscular threshold) could provide additional insight. Therefore the purpose of this study was to use a neuromuscular threshold, the time to contact (TtC) the ankle joint complexs ROM boundary, to evaluate runners with and without AKP. METHODS Nineteen healthy and seventeen runners with AKP had their ROM and running biomechanics evaluated. The TtC was calculated using each individuals angular distance from end range (eversion buffer) and eversion velocity. Data were recorded over ten stance phases and evaluated using a one way analysis of variance and 95% confidence intervals. RESULTS Runners with AKP had significantly shorter TtC the joints ROM boundary when compared to healthy runners (64.0 ms vs. 35.6 ms, p=0.01). While not statistically significant, this shorter TtC was in large part due to having a smaller eversion buffer, however velocity was found to have a substantial influence on the TtC of select individuals. These results provide evidence that a link between pronation and AKP exists when using anatomical and neuromuscular based thresholds.

Midsole thickness affects running patterns in habitual rearfoot strikers during a sustained run.

The purpose of this study was to: (1) investigate how kinematic patterns are adjusted while running in footwear with THIN, MEDIUM, and THICK midsole thicknesses and (2) determine if these patterns are adjusted over time during a sustained run in footwear of different thicknesses. Ten male heel-toe runners performed treadmill runs in specially constructed footwear (THIN, MEDIUM, and THICK midsoles) on separate days. Standard lower extremity kinematics and acceleration at the tibia and head were captured. Time epochs were created using data from every 5 minutes of the run. Repeated-measures ANOVA was used (P < .05) to determine differences across footwear and time. At touchdown, kinematics were similar for the THIN and MEDIUM conditions distal to the knee, whereas only the THIN condition was isolated above the knee. No runners displayed midfoot or forefoot strike patterns in any condition. Peak accelerations were slightly increased with THIN and MEDIUM footwear as was eversion, as well as tibial and thigh internal rotation. It appears that participants may have been anticipating, very early in their run, a suitable kinematic pattern based on both the length of the run and the footwear condition.

Cushioning mode and magnitude affect treadmill running kinematics

Based on an injury definition of a 20 point change in VAS scores, 14 (37%) subjects experienced an injury. The incidence of injury was 20.1 injuries per 1000 athletic exposures. Participants in dance type classes reported significantly (p5 0.001) greater pain throughout the 8-week period compared to all other class categories (Figure 1). Of the 38 respondents in the study, 26 had experienced a previous injury. On average participants had been attending classes for 13 months, attending 2.4 classes per week. The average class length was 60minutes. The 3 most commonly worn shoe brands were Asics, Nike and Adidas worn by 25%, 22% and 16% of subjects, respectively. Eighty-six per cent of subjects wore a running shoe during their classes, only 3.8% wore a cross-trainer (Figure 2). Thirty-eight per cent responded that their shoes do not provide sufficient support during their class participation, and 67% agree that their shoes are comfortable enough without additional support. Thirty-one per cent wore an orthotic, more than half of which were custom made. Primary reasons for orthotic use were for foot support or to address an injury. Discussion and conclusion

Removing sources of variance from an analysis of barefoot vs. shod running

Barefoot vs. shod research suggests shock attenuation provided by footwear reduces the metabolic cost of running and offsets the cost of the additional mass (Frederick et al. 1983, Franz et al. 2012). Kinematic differences can also be anticipated when barefoot and shod running are compared (De Wit et al. 2000, TenBroek et al. 2013) and somewhat attributable to the lack of protection and shock attenuation. TenBroek et al. (2011) demonstrated when barefoot running on a foam treadmill many but not all kinematic differences were eliminated. The persisting differences indicate other footwear characteristics are influencing movement patterns. To further investigate, additional sources of variance must be removed.