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.

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.

Changes in joint, muscle, and tendon stiffness following repeated hopping exercise.

The purpose of this study was to elucidate the mechanisms of decline in joint stiffness after repeated stretch-shortening cycle exercises according to changes in both muscle-tendon properties and neuromuscular activities. Eleven males performed fatigue task (5 sets of 50 hopping). Ankle joint stiffness and electromyographic activities (mEMG) of plantar flexor and tibial anterior muscles during drop jump were measured before and after fatigue task.

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.

Effects of repeated eccentric and isometric contractions with relatively low loading dose on joint stiffness.

Background: The purpose of the present study was to compare changes in joint stiffness after repeated eccentric (ECC; leading to muscle fatigue) and isometric (ISO; leading to tendon fatigue) contractions and to elucidate the mechanisms responsible for decline in joint stiffness after repeated stretch-shortening cycle exercises reported previously.

Methods: Ankle joint stiffness (change in joint torque divided by change in joint angle during braking phase) and electromyographic activity (mEMG) of the plantar flexor muscles during drop jump using the ankle joint were measured before and after ECC, ISO, and control conditions.

Results: Peak ankle joint torque, range of motion, and joint stiffness during drop jump did not change after ECC or ISO.

Measurement of active muscle stiffness with and without the stretch reflex.

The purpose of the present study was to evaluate active muscle stiffness with the stretch reflex according to changes (in 110-ms period after stretching) in torque and fascicle length during slower angular velocity (peak angular velocity of 100 deg·s) in comparison with active muscle stiffness without the stretch reflex (in 60-ms period after stretching) during slower and faster (peak angular velocity of 250 deg·s) angular velocities. Active muscle stiffness in the medial gastrocnemius muscle was calculated according to changes in estimated muscle force and fascicle length with slower and faster stretching during submaximal isometric contractions (10-90% maximal voluntary contractions). Active muscle stiffness significantly increased for both angular velocities and analyzed periods as torque levels exerted became higher.

Effects of plyometric and isometric training on muscle and tendon stiffness in vivo.

The purpose of this study was to compare the effects of plyometric and isometric training on tendon properties during ramp and ballistic contractions and muscle stiffness under passive and active conditions. Eleven subjects completed 12 weeks (3 days/week) of a unilateral training program for the plantar flexors. They performed plyometric training on one side (PLY) and isometric training on the other side (ISO).

Quantification of collagen fiber orientation in human tendons with the coefficient of variation of echogenicity.

The grayscale distribution on the ultrasonic images of tendons may be reduced with alignment of collagen fibers, because ultrasound signal intensity changes with alterations in tendon collagen fiber orientation due to acoustic anisotropy in the tendons. The purpose of this study was to investigate changes in the coefficient of variation (CV) of echogenicity in the Achilles tendon during passive dorsiflexion (the angle task) and isometric plantar flexion (the contraction task). Achilles tendon transverse ultrasonic images were collected from 14 healthy individuals every 10° from 20° to -20° (positive values for plantar flexion) in the angle task and every 10% maximum voluntary contraction (MVC) from 0% to 70% MVC in the contraction task.

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.

Tendon properties and muscle architecture for knee extensors and plantar flexors in boys and men.

Background: The purpose of this study was to compare the elastic properties and size of tendinous structures and muscle architecture for knee extensors and plantar flexors in boys and men.

Methods: Twenty-two early pubescent boys (9.6-12.

Acute and chronic effects of hyperbaric oxygen therapy on blood circulation of human muscle and tendon in vivo.

This study aimed to investigate the acute and chronic effects of hyperbaric oxygen therapy on blood circulation of human muscle and tendon in vivo. Using near-infrared spectroscopy and red laser lights, we determined acute changes in blood volume (THb) and oxygen saturation (StO2) of the medial gastrocnemius muscle and Achilles tendon during 60 minutes of hyperbaric oxygen therapy (1.3 atm absolute and 50% O2, experiment 1).

Blood circulation of patellar and achilles tendons during contractions and heating.

Purpose: Recent studies using ultrasonography have demonstrated that training-induced changes in the mechanical properties of tendons in plantar flexors (i.e., Achilles tendon) are lower than those in knee extensors (i.

Changes in bone alkaline phosphatase and procollagen type-1 C-peptide after static and dynamic exercises.

We investigated the effects of two types of nonweight-bearing exercise on changes in bone-specific alkaline phosphatase (BAP) and procollagen type 1 C-peptide (PIP). BAP is a specific marker of bone synthesis, whereas P1P reflects synthesis of type 1 collagen in other organs as well as bone. Eight participants performed static and dynamic unilateral knee extensions.

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).

Relationship between muscle fiber type and tendon properties in young males.

The purpose of this study was to investigate the relationship between the estimated muscle fiber type and tendon properties in human knee extensors and plantar flexors (n = 50). Measurements included time-to-peak twitch torque (TPT) and tendon properties. TPT did not correlate significantly with the maximal elongation and stiffness of tendon.

A longitudinal assessment of running economy and tendon properties in long-distance runners.

The aim of this study was to investigate longitudinal changes in tendon properties and running economy of long-distance runners (LDRs) in the preparatory periods of track season (TS) and road season (RS). Eleven well-trained LDRs and 6 untrained subjects participated in the present study. In each period, muscle strength, neural activation level, and tendon elongation for both knee extensors and plantar flexors, jump performances, and oxygen consumption during submaximal running velocities were measured.

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.

Effects of acupuncture and heating on blood volume and oxygen saturation of human Achilles tendon in vivo.

The purpose of this study was to investigate the effects of acupuncture (dry needling) and heating (application of hot pack) treatments on the blood volume and oxygen saturation of the human Achilles tendon in vivo. Nine healthy males participated in this study. During the treatments (acupuncture and heating; both 10 min) and recovery period (30 min), the blood volume and oxygen saturation of the Achilles tendon were measured using red laser lights.

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 different duration contractions on elasticity, blood volume, and oxygen saturation of human tendon in vivo.

The present study aimed to investigate changes in elasticity, blood volume, and oxygen saturation of tendon caused by repeat contractions of different durations. Eight male subjects performed endurance tests, which consisted of isometric plantar flexion with two different durations: a shorter contraction (SC) and a longer contraction (LC). During endurance tests and a recovery period, we measured the total hemoglobin (THb) and oxygen saturation (StO(2)) of the medial gastrocnemius muscle and Achilles tendon using near infrared spectroscopy and red laser lights.