The Influence of Footwear Longitudinal Bending Stiffness on Running Economy and Biomechanics in Older Runners.

Purpose: This study assessed the effects of footwear longitudinal bending stiffness on running economy and biomechanics of rearfoot striking older runners. Methods: Nine runners over 60 years of age completed two running bouts at their preferred running pace in each of three footwear conditions: low (4.4 ± 1.8 N·m-1), moderate (5.7 ± 1.7 N·m-1), and high (6.4 ± 1.6 N·m-1) bending stiffness. Testing order was randomized and a mirror protocol was used (i.e., A,B,C,C,B,A). Expired gases, lower limb kinematics, and ground reaction forces were collected simultaneously and lower limb joint kinetics, running economy (i.e., VO2), leg stiffness, and spatio-temporal variables were calculated. Results: Running economy was not different among stiffness conditions (p = 0.60, p = 0.53 [mass adjusted]). Greater footwear stiffness reduced step length (p = 0.046) and increased peak vertical ground reaction force (p = 0.019) but did not change peak ankle plantarflexor torque (p = 0.65), peak positive ankle power (p = 0.48), ankle positive work (p = 0.86), propulsive force (p = 0.081), and leg stiffness (p = 0.46). Moderate footwear stiffness yielded greater peak negative knee power compared to low (p = 0.04) and high (p = 0.03) stiffness. Conclusions: These novel findings demonstrate that increasing footwear longitudinal bending stiffness using flat carbon fiber inserts does not improve running economy and generally does not alter lower limb joint mechanics of rearfoot strike runners over 60 years. Future studies should investigate how other footwear characteristics (e.g., midsole material, plate location, and sole curvature) influence economy and biomechanics in this population.

Obtención de un colorante a partir de corteza de maracuyá con el uso de técnicas convencionales de extracción / Obtaining a dye from passion fruit cortex with the use of conventional extraction techniques

RESUMEN El maracuyá es un fruto tropical que se cultiva primordialmente para la obtención de pulpa, siendo la corteza su principal subproducto que carece, en la actualidad, de interés industrial; sin embargo, con el fin de diversificar los derivados provenientes de la producción de maracuyá, se ha demostrado que la corteza contiene carotenoides, dentro de los que se destaca el β-caroteno y la luteína, que podrían ser utilizados en alimentos, debido a su poder antioxidante e, incluso, como colorante natural alternativo. Por lo anterior, el objetivo de este trabajo fue obtener un extracto rico en carotenoides a partir de su corteza; para ello, se evaluó la extracción con etanol, mediante tres técnicas: inmersión, baño termostático y soxhlet. El mayor rendimiento, se obtuvo con el método soxhlet; para esta técnica, se estudió el efecto de la concentración de etanol (entre 80% y 90% v/v), la proporción solvente-materia prima (con relaciones entre 40:1 y 50:1) y el tiempo (definido entre 90 y 150 minutos). Los resultados, se analizaron mediante modelo de superficie de respuesta, obteniendo el mayor rendimiento con etanol al 90%, utilizando 50mL/g corteza y 150 minutos de operación. A estas condiciones, el rendimiento de extracción fue de 2208,53µg β-caroteno/100g muestra. Por último, se determinó la diferencia de color entre el extracto óptimo y una solución de tartrazina, evidenciando una diferencia de color de 3,07 unidades cieLAB, lo cual, muestra que el producto de lixiviación de la corteza de maracuyá tiene potencial para su uso como aditivo alimentario, reemplazando colorantes sintéticos, como la tartrazina.

ABSTRACT Passion fruit is a tropical fruit that is usually cultivated to obtain pulp, being the cortex its main not exploited by-product, because of the actual absence of industrial interest. However, with the aim of diversifying the derivates from the production of passion fruit products, it has been demonstrated that the cortex contains carotenoids, such as β-carotene and lutein; which could be used in food due to its antioxidant capacity, or even like a food colorant. Therefore, the objective of this work was to obtain a carotenoid-rich extract from its cortex; for this, three techniques of extraction with ethanol were evaluated, by immersion, thermostatic bath and Soxhlet. Being the last technique that one with which the best yield was obtained. With the highest yield technique, the following factors were evaluated: ethanol concentration on 80% and 90% v/v, solvent-raw material ratio on 40:1 and 50:1 and time on 90 and 150min. The best yield was obtaining to 90% ethanol, 50mL solvent/g raw material and 150min, for an extraction yield of 2208.53µg β-caroten/100 g sample. Finally, the color difference between the optimal extract and a tartrazine solution was determined, evidencing a color difference of 3.07cieLAB units; this shows that the passion fruit leaching product has the potential to be used as a food additive, replacing synthetic dyes such as tartrazine.