Relationship between Reactive Strength and Leg Stiffness at Submaximal Velocity: Effects of Age on Distance Runners

Background: Musculotendinous reactive strength is a key factor for the utilization of elastic energy in sporting activities such as running. AIM: To evaluate the relationship between musculotendinous reactive strength and lower-limb stiffness during running as well as to identify age-related differences in both variables. Methods: Fifty-nine amateur endurance runners performed three 20-cm drop jumps and a constant 3-min easy run on a motorized treadmill. Reactive strength index and dynamic lower-limb stiffness were calculated with a photoelectric cell system by jumping and running, respectively. Additionally, sit to stand difference in plantar arch height was assessed as a static lower-limb stiffness measure. The cluster analysis allows the comparison between younger and older runners. Results: No significant correlations were found between jumping reactive strength and running lower-limb stiffness. The younger group performed better at drop jumps (p = 0.023, ES = 0.82), whereas higher-but-no-significant results were found for reactive strength index and stiffness-related metrics. Conclusions: Musculotendinous vertical reactiveness may not be transferred to combined vertical and horizontal movements such as running

Strength training habits in amateur endurance runners in Spain: influence of athletic level

This study determined the strength training (ST) habits of amateur endurance runners in Spain regarding athletic level. A sixteen-item online questionnaire comprised of (i) demographic information, (ii) performance, and (iii) training contents was completed by 1179 athletes. Five group levels were determined according to the personal best times of the athletes in a 10-km trial (LG1: level group 1, 50–55 min; LG2: level group 2, 45–50 min; LG3: level group 3, 40–45 min; LG4: level group 4, 35–40 min; LG5: level group 5, 30–35 min). Most athletes (n = 735, 62.3%) perceived ST as being a key component in their training program. Resistance training (RT) was reported as a ST type used by 63.4% of the athletes, 66.9% reported using bodyweight exercises, 46.8% reported using plyometric training, 65.6% reported using uphill runs, and 17.8% reported using resisted runs. The prevalence of runners who excluded ST from their training programs decreased as the athletic performance level increased (18.2% in lower-level athletes vs. 3.0% in higher-level), while the inclusion of RT, bodyweight exercises, plyometric training, and uphill and resisted runs was more frequent within higher-level groups. Most athletes included ST using low-to-moderate loads and high a number of repetitions/sets comprised of RT, plyometric training, resisted runs, and core, respiratory, and foot muscles training

Análisis de las variables influyentes en el modelo Masa-Muelle aplicado a la carrera de larga distancia.

El estudio de las variables del modelo masa-muelle (spring mass model en su acepción inglesa) en la carrera han sido una gran fuente de información a la hora de conocer el comportamiento asociado a este modo de locomoción tanto de animales como de humanos. Los parámetros espacio-temporales han definido en gran medida el comportamiento del modelo con una gran capacidad de predicción y estimación de variables tanto cinemáticas como dinámicas. Aunque la bibliografía en este campo es amplia, todavía existe escaso conocimiento acerca de cuáles son todas las variables que predefinen el comportamiento del modelo masa-muelle en cada individuo. El objetivo principal de esta tesis ha sido conocer y ampliar el conocimiento de la implicación de diferentes variables (talla, masa, inclinación, velocidad, rigidez del pie, características neuromusculares de la extremidad inferior, nivel atlético) que influyen en dicho modelo y estudiar la posible implementación de herramientas para la aplicación del modelo de estudio en condiciones de campo. Para llevar a cabo este objetivo se realizaron una serie de estudios que culminaron en 6 artículos: i) Efecto de la variación de peso asistido por un tapiz rodante LBPP (lower body positive pressure o presión positiva en parte inferior del cuerpo) (ARTICULO I); ii) Efecto de la talla en los parámetros espacio-temporales y su variabilidad a diferentes velocidades (ARTICULO II); iii) Relación de la rigidez del arco longitudinal del pie en los parámetros espacio-temporales de carrera (ARTICULO III). iv) Estudio de la influencia de los parámetros de rendimiento muscular de extremidad inferior con la capacidad de salto y las adaptaciones de los parámetros espacio-temporales a diferentes velocidades (ARTICULO IV). v) Determinar el efecto de la inclinación del pavimento en los parámetros espacio-temporales y examinar el efecto del nivel atlético en la adaptación corriendo en inclinación positiva (ARTICULO V). vi) Determinar la fiabilidad absoluta y la validez concurrente de un sistema wearable de bajo coste y un sistema optoelectrónico basado en barreras fotoeléctricas (ARTICULO VI).Tesis Univ. Granada.Programa Oficial de Doctorado en Biomedicin

Relationship between Connective Tissue Morphology and Lower-Limb Stiffness in Endurance Runners. A Prospective Study

Background: The lower limb behaves like a spring compressing and decompressing during running, where lower-limb stiffness is one of the most influential factors. This prospective observational study is aimed at examining the relationship between the connective tissue morphology and lower-limb stiffness and investigating whether the barefoot/shod condition influences on such relationship. Methods: 14 male amateur runners (10-km time trial <500 ) were included. Data were recorded over one session, where participants ran 2 trials (i.e., barefoot and shod conditions) of 3 minutes at 12 km/h, where running spatiotemporal parameters and vertical (Kvert) and leg stiffness (Kleg) were obtained. Prior to testing trials, thickness and cross-sectional area (CSA) were recorded for Achilles (AT) and patellar tendons (PT) and plantar fascia (PF) with ultrasound. Results: Under barefoot condition, a positive correlation was found between Kleg and AT-thickness and CSA and PF-thickness; and between Kvert and AT-thickness and PF thickness. Under shod condition, a positive correlation was found between Kleg and PT-CSA and PT-thickness, and between Kvert and PT-CSA and PT-thickness. Conclusions: The results reveal a specificity of the relationship between the lower-limb stiffness and the morphology of the connective tissue. Greater tendon shows higher lower-limb stiffness when that tendon is specially demanded by the function

Do age and sex influence on functional movement in school-age children?

Abstract. The aim of this study was to determine the influence of age and sex on the functional movement in Spanish primary school children. A group of 172, 6–11 years old children (83 girls and 89 boys), participated in this study. The main outcome measures were the Functional Movement ScreenTM (FMS), sex and chronological age of children. The ANCOVA (BMI as a covariate) revealed significant differences between age groups (p=0.003) but no between-sex differences (p≥0.05) in FMS total score. As for individual FMS tests, significant differences between age groups (p<0.05) were found in the in-line lunge and the shoulder mobility tests; whereas, according to sex, significant differences (p<0.05) were found in the in-line lunge test (under 10 years old group) and the push-up test (under 12 group). The stepwise linear regression analysis revealed BMI as a primary predictor of FMS total score in school age children, but with a significant additional contribution from age (R2= 0.206, p<0.001), whereas the sex was excluded from this model (p=0.097). In conclusion, the results reported in this study suggest that age is a moderate determinant of FMS scores, whereas sex is not a determinant in this battery test in school age children (6-11 years old). This study also highlights that BMI is the primary predictor of FMS total score in school age children, but with a significant additional contribution from age, whereas the sex was excluded from this model.El objetivo de este estudio fue determinar la influencia de la edad y el sexo en la funcionalidad del movimiento de niños españoles en edad escolar. Un grupo de 172, 6-11 años (83 niñas y 89 niños), participaron en este estudio. Las variables medidas en el estudio fueron el rendimiento en el Functional Movement ScreenTM (FMS), el sexo y la edad cronológica de los niños. Un ANCOVA (BMI como covariable) reveló diferencias significativas en la puntuación total obtenida en el FMS entre grupos de edad (p=0.003) pero no entre sexos (p≥0.05). En cuanto a los tests individuales incluidos en la batería, se hallaron diferencias entre grupos de edad en el test de lunge en línea y movilidad de hombro; mientras en relación al sexo, se hallaron diferencias significativas (p<0.05) se encontraron en el lunge en línea (en el grupo sub-10 años) y en el test de push-up (sub-12). El análisis de regresión lineal señaló al BMI como el principal predictor del rendimiento en FMS en escolares, con una significativa contribución de la variable edad (R2= 0.206, p<0.001), y la variable sexo excluida del modelo (p=0.097). En conclusión, los resultados reportados en este estudio sugieren que la edad es un predictor moderado del rendimiento total en FMS en niños en edad escolar, el sexo no parece determinar el rendimiento, mientras que el BMI resulta predictor primario de la puntuación total en el FMS en escolares españoles (6-11 años)

Reference Values of Spatial and Temporal Gait Parameters in a Contemporary Sample of Spanish Preschool Children: A Cross-Sectional Study

The aim of this study was to analyze the influence of age and sex on kinematic gait parameters in preschool children, and derive reference values for this population. A total of 383 preschool children (age 3&ndash;5 years; 207 girls, 176 boys) participated in this study. We used the OptoGait system to assess the kinematics of gait at a comfortable and self-determined speed. No significant differences between the sexes were found for the main gait parameters. Among the participants, there was a significant increase in double support, reductions in absolute cadence and the coefficient of variation (CV) of cadence, an increase in absolute step length (SL), and an increase in the walk ratio (WR) from 3 to 5 years of age. However, the normalized SL and normalized WR displayed a significant reduction in both sexes. Partial correlation indicated a significant association of age with SL and normalized SL, and WR. Additionally, WR showed a significant correlation with the CV of cadence. To summarize, no relevant differences in gait performance were found according to sex; however, age was found to influence gait maturation. The normative values established for Spanish preschool children can be used to monitor healthy gait development