Mechanical properties of muscles and tendon structures in middle-aged and young men.

The purpose of this study was to compare the mechanical properties of muscles and tendon structures for plantar flexor muscles at various strain rates and jump performances using single joint between middle-aged and young men in order to clarify the mechanisms of age-related decline in power output during vertical jump of middle-aged people previously reported. Passive muscle stiffness of the medial gastrocnemius muscle was determined based on passive muscle force and fascicle length during passive stretching at four angular velocities. Active muscle stiffness was calculated based on changes in muscle force and fascicle length during stretching at five angular velocities after submaximal isometric contractions.

Effects of plyometric training on muscle-tendon mechanical properties and behavior of fascicles during jumping.

The purpose of this study was to investigate the effects of plyometric training on the muscle-tendon mechanical properties and behavior of fascicles during jumping in order to elucidate the mechanisms of improved jump performance due to plyometric training. Eleven subjects completed a 12-week unilateral training program for plantar flexors. Active muscle stiffness with (100°·s ) and without (250°·s ) stretch reflex were calculated according to changes in muscle force and fascicle length during fast stretching after submaximal isometric contractions.

Mechanical properties of muscle and tendon at high strain rate in sprinters.

The aim of the present study was to compare the mechanical properties of muscles and tendons at high strain rates between sprinters and untrained men. Fifteen sprinters and 18 untrained men participated in this study. Active muscle stiffness of the medial gastrocnemius muscle was calculated according to changes in the estimated muscle force and fascicle length during fast stretching at five different angular velocities (100, 200, 300, 500, and 600 deg·s ) after submaximal isometric contractions.

Effect of angular velocity on active muscle stiffness in vivo.

We previously reported that active muscle stiffness could be evaluated in vivo. However, we were not able to investigate active muscle stiffness as more than 250 deg·s due to the limitation of the torque motor of dynamometer. The aim of the present study was to investigate the effect of angular velocities (including higher angular velocities of more than 250 deg·s) on active muscle stiffness.

Effects of 4, 8, and 12 Repetition Maximum Resistance Training Protocols on Muscle Volume and Strength.

Kubo, K, Ikebukuro, T, and Yata, H. Effects of 4, 8, and 12 repetition maximum resistance training protocols on muscle volume and strength. J Strength Cond Res 35(4): 879-885, 2021-The purpose of this study was to determine skeletal muscle adaptations (strength and hypertrophy) in response to volume-equated resistance training with divergent repetition strategies.

Effects of the strain rate on mechanical properties of tendon structures in knee extensors and plantar flexors .

The purpose of present study was to investigate site differences in the effects of strain rate on tendon properties between knee extensors and plantar flexors. Elongation of tendon structures (L) in vastus lateralis and medial gastrocnemius muscles was measured by ultrasonography while participants performed ramp and ballistic contractions to their voluntary maximum, followed by ramp and sudden relaxation. The relationship between muscle force (Fm) and L was fit to linear regression, the slope of which was defined as stiffness of tendon structures.

Effects of squat training with different depths on lower limb muscle volumes.

Purpose: The purpose of this study was to compare the effects of squat training with different depths on lower limb muscle volumes.

Methods: Seventeen males were randomly assigned to a full squat training group (FST, n = 8) or half squat training group (HST, n = 9). They completed 10 weeks (2 days per week) of squat training.

Is the stiffness of human muscle and tendon structures related to muscle fiber composition in vivo?

Background: The aim of the present study was to investigate the relationship between estimated muscle fiber composition (time-to-peak twitch torque; TPT) and muscle stiffness under passive and active conditions as well as stiffness of tendon structures in human plantar flexors.

Methods: TPT was assessed using supramaximal electrical stimulation. Active muscle stiffness in the medial gastrocnemius muscle was calculated based on changes in estimated muscle force and fascicle length during fast stretching after 50% maximal isometric contractions.

Effects of Concentric and Eccentric Training on the Stiffness and Blood Circulation of the Patellar Tendon.

The aim of the present study was to investigate the effects of concentric (CON) and eccentric (ECC) training on stiffness and blood circulation of the tendon, and clarify whether relative changes in tendon stiffness are related to those in tendon blood circulation. 17 subjects were assigned to training (n=9) and control (n=8) groups. Training group completed 12 weeks of unilateral training program for knee extensors.

Active muscle and tendon stiffness of plantar flexors in sprinters.

The aim of the present study was to investigate and compare muscle and tendon stiffness under active conditions in sprinters and untrained participants. In total, 14 sprinters and 24 untrained men participated in this study. Active muscle stiffness in the medial gastrocnemius muscle was calculated based on changes in estimated muscle force and fascicle length during fast stretching after submaximal isometric contractions.

Passive and active muscle stiffness in plantar flexors of long distance runners.

The aim of the present study was to compare passive and active muscle stiffness and tendon stiffness between long distance runners and untrained men. Twenty long distance runners and 24 untrained men participated in this study. Active muscle stiffness in the medial gastrocnemius muscle was calculated according to changes in estimated muscle force and fascicle length during fast stretching after submaximal isometric contractions.

Effect of gene polymorphisms on the mechanical properties of human tendon structures.

Recent studies showed that polymorphisms in alpha 1 chains of types I (COL1A1) and V (COL5A1) collagen, growth and differentiation factor 5 (GDF5), and matrix metalloproteinase 3 (MMP3) genes were associated with injuries in tendons and ligaments (e.g., September et al.

Time course of changes in the human Achilles tendon properties and metabolism during training and detraining in vivo.

The purpose of this study was to investigate the time course of changes in human tendon properties and metabolism during resistance training and detraining. Nine men (21-27 years) completed 3 months of isometric plantar flexion training and another 3 months of detraining. At the beginning and on every 1 month of training and detraining periods, the stiffness, blood circulation (blood volume and oxygen saturation), serum procollagen type 1 C-peptide (P1P; reflects synthesis of type 1 collagen), echointensity (reflects collagen content), and MRI signal intensity (reflects collagen structure) of the Achilles tendon were measured.

Morphological and mechanical properties of muscle and tendon in highly trained sprinters.

The purpose of this study was to investigate muscle and tendon properties in highly trained sprinters and their relations to running performance. Fifteen sprinters and 15 untrained subjects participated in this study. Muscle thickness and tendon stiffness of knee extensors and plantar flexors were measured.

Effects of training on muscle and tendon in knee extensors and plantar flexors in vivo.

The purpose of this study was to compare the effects of resistance training on muscle and tendon properties between knee extensors and plantar flexors in vivo. Twenty healthy young men voluntarily participated in this study. The subjects were randomly divided into two training groups: knee extension group (n=10) and plantar flexion group (n=10).

Effects of mechanical properties of muscle and tendon on performance in long distance runners.

The purpose of this study was to investigate the mechanical properties of muscle and tendon in long distance runners and their relations to running performance. Fifteen long distance runners (LDR) and 21 untrained subjects (CON) participated in this study. Muscle strength and activation level of knee extensors and plantar flexors were measured.

Time course of changes in muscle and tendon properties during strength training and detraining.

The purpose of this study was to investigate the time course of changes in mechanical and morphological properties of muscle and tendon during isometric training and detraining. Eight subjects completed 3 months of isometric knee extension training and detraining for another 3 months. At beginning and on every 1 month of training and detraining periods, muscle strength, neural activation level, muscle and tendon cross-sectional areas (CSA), and tendon stiffness were measured.

Effects of static and dynamic training on the stiffness and blood volume of tendon in vivo.

The purpose of this study was to investigate the effects of static and dynamic training on the stiffness and blood volume of the human tendon in vivo. Ten subjects completed 12 wk (4 days/wk) of a unilateral training program for knee extensors. They performed static training on one side [ST; 70% of maximum voluntary contraction (MVC)] and dynamic training on the other side (DT; 80% of one repetition maximum).

Effects of plyometric and weight training on muscle-tendon complex and jump performance.

Purpose: The purpose of this study was to investigate the effects of plyometric and weight training protocols on the mechanical properties of muscle-tendon complex and muscle activities and performances during jumping.

Methods: Ten subjects completed 12 wk (4 d.wk(-1)) of a unilateral training program for plantar flexors.

Effects of isometric squat training on the tendon stiffness and jump performance.

The present study aimed to investigate the effect of isometric squat training on human tendon stiffness and jump performances. Eight subjects completed 12 weeks (4 days/week) of isometric squat training, which consisted of bilateral leg extension at 70% of maximum voluntary contraction (MVC) for 15 s per set (10 sets/day). Before and after training, the elongations of the tendon-aponeurosis complex in the vastus lateralis muscle and patella tendon were directly measured using ultrasonography while the subjects performed ramp isometric knee extension up to MVC.