Dynamometric Strength Profile of Hip Muscles in Youth Soccer Players.

BACKGROUND: Soccer is the most widely practiced sport in the world, demanding high-speed activities such as jumps, sprints and changes of direction. Therefore, having optimal levels of muscle strength improves performance and reduces the injury rate. OBJECTIVES: The objectives of our study were (i) to determine the dynamometric profile of hip muscle strength in young soccer players by position, evaluated at different isokinetic speeds, (ii) to describe the conventional and functional unilateral muscle strength ratios, (iii) to analyze the bilateral balance. METHODS: Thirty-seven male soccer players (age 17.02 ± 0.92 years) participated in the study. Strength assessment was performed with a functional electromechanical dynamometer, and concentric and eccentric strength of abductors, adductors, extensors and hip flexors were measured bilaterally at 0.5 m/s and 1 m/s. RESULTS: For eccentric right hip abduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.013) and stronger than forwards (p = 0.140). For eccentric right hip adduction at 0.5 m/s, defenders are significantly stronger than midfielders (p = 0.005) and stronger than forwards (p = 0.253), as for eccentric right hip adduction at 1 m/s, defenders are significantly stronger than midfielders (p = 0.014) and stronger than forwards (p = 0.084). There is a significant effect for the conventional strength ratio of left abduction/adduction at 1 m/s. The conventional strength ratio of forwards is significantly higher than that of defenders (p = 0.045) and higher than that of midfielders (p = 0.152). CONCLUSIONS: Concentric and eccentric hip strength values differ according to playing position.

Efectos del autoinjerto hueso-tendón patelar-hueso sobre la posición articular y la fuerza en pacientes con reconstrucción del ligamento cruzado anterior / Effects of bone-patellar tendon-bone autograft on joint position and strength in patients with anterior cruciate ligament reconstruction

RESUMEN: El objetivo del estudio fue comparar el déficit propioceptivo a través del Joint position sense (JPS) y Force steadiness en pacientes con reconstrucción del ligamento cruzado anterior (LCA) injerto hueso-tendón patelar-hueso (HTH) 6 a 12 meses postcirugía. Participaron 15 pacientes (13 hombres y 2 mujeres, 25,5 ± 1,3 años) con reconstrucción de LCA con autoinjerto HTH y 20 personas sin lesión del LCA (19 hombres y 1 mujer, 24,1 ± 0,8 años). Para evaluar la sensación de posición de la articulación de la rodilla se midió la Joint position sense (JPS) en tres rangos: 0°-30°, 31°-60° y 61°-90° y la sensación de fuerza del cuádriceps fue evaluada con la prueba Force steadiness (FS) al 15 % de la contracción voluntaria máxima (CVM), ambas pruebas realizadas 6 a 12 meses post cirugía. Los resultados mostraron que no hubo diferencias estadísticamente significativas en la sensación de la posición articular (JPS 0°-30°) (p=0.564) y 31°-60° (p=0.681), mientras que en el rango 61°-90° (p=0.003) existieron diferencias estadísticamente significativas. En las mediciones de sensación de fuerza del cuádriceps (FS al 15 % CVM) entre los pacientes operados de LCA técnica HTH y el grupo control no hubo diferencias estadísticas (p= 0.987) La sensación de la fuerza del cuádriceps medida con la prueba FS al 15 % CVM no presentaría déficit entre los 6 a 12 meses en pacientes post operados de LCA al ser comparados con sujetos sin lesión ni cirugía de este ligamento. Se concluye que la sensación de la posición articular medida con la prueba JPS en en tres rangos articulares de pacientes con reconstrucción de LCA injerto HTH 6 a 12 meses post cirugía sólo mostró alteraciones en el rango de 61°- 90° al ser comparado con el grupo control, lo cual indica que la sensación de la posición articular presenta un déficit en este rango específico.

SUMMARY: The aim of the study was to compare the proprioceptive deficit through the Joint position sense (JPS) and Force steadiness in patients with anterior cruciate ligament (ACL) bone-patellar tendon-bone graft (PTH) reconstruction 6 to 12 months post-surgery. Fifteen patients (13 men and 2 women, 25.5 ± 1.3 years) with ACL reconstruction with HTH autograft and 20 persons without ACL injury (19 men and 1 woman, 24.1 ± 0.8 years) participated. To assess knee joint position sensation, Joint position sense (JPS) was measured in three ranges: 0°-30°, 31°- 60° and 61°-90° and quadriceps strength sensation was assessed with the Force steadiness (FS) test at 15 % of maximal voluntary contraction (MVC), both tests performed 6 to 12 months post surgery. The results showed that there were no statistically significant differences in joint position sensation (JPS 0°-30°) (p=0.564) and 31°-60° (p=0.681), while in the range 61°-90° (p=0.003) there were statistically significant differences. In the quadriceps strength sensation measurements (FS at 15 % CVM) between the patients operated on ACL HTH technique and the control group there were no statistical differences (p= 0.987). The quadriceps strength sensation measured with the FS test at 15 % CVM would not present a deficit between 6 to 12 months in post- operated ACL patients when compared to subjects without injury or surgery of this ligament. It is concluded that the joint position sensation measured with the JPS test in three joint ranges of patients with ACL reconstruction HTH graft 6 to 12 months post surgery only showed alterations in the range of 61°- 90° when compared to the control group, indicating that the joint position sensation presents a deficit in this specific range.

Low abundance of Mfn2 protein correlates with reduced mitochondria-SR juxtaposition and mitochondrial cristae density in human men skeletal muscle: Examining organelle measurements from TEM images.

The role of mitofusin 2 (Mfn2) in the regulation of skeletal muscle (SM) mitochondria-sarcoplasmic (SR) juxtaposition, mitochondrial morphology, mitochondrial cristae density (MCD), and SM quality has not been studied in humans. In in vitro studies, whether Mfn2 increases or decreases mitochondria-SR juxtaposition remains controversial. Transmission electron microscopy (TEM) images are commonly used to measure the organelle juxtaposition, but the measurements are performed "by-hand," thus potentially leading to between-rater differences. The purposes of this study were to: (1) examine the repeatability and reproducibility of mitochondrial-SR juxtaposition measurement from TEM images of human SM between three raters with different experience and (2) compare the mitochondrial-SR juxtaposition, mitochondrial morphology, MCD (stereological-method), and SM quality (cross-sectional area [CSA] and the maximum voluntary contraction [MVC]) between subjects with high abundance (Mfn2-HA; n = 6) and low abundance (Mfn2-LA; n = 6) of Mfn2 protein. The mitochondria-SR juxtaposition had moderate repeatability and reproducibility, with the most experienced raters showing the best values. There were no differences between Mfn2-HA and Mfn2-LA groups in mitochondrial size, distance from mitochondria to SR, CSA, or MVC. Nevertheless, the Mfn2-LA group showed lower mitochondria-SR interaction, MCD, and VO2max . In conclusion, mitochondrial-SR juxtaposition measurement depends on the experience of the rater, and Mfn2 protein seems to play a role in the metabolic control of human men SM, by regulating the mitochondria-SR interaction.