Effects of β-hydroxy-β-methylbutyrate supplementation on muscle mass and strength in onabotulinumtoxin type-A-injected and contralateral quadriceps femoris in rabbits.

Objective: To determine the effects of the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) on strength, muscle mass, and contractile material in muscle wasting induced by onabotulinumtoxin type-A (BoNT-A) injection into the quadriceps femoris muscles of New Zealand white rabbits.

Methods: A total of 21, female rabbits were divided into 3 groups (n=7, each). Group 1 (Control) received intramuscular injection of saline.

Effect of a prebiotic supplement on knee joint function, gut microbiota, and inflammation in adults with co-morbid obesity and knee osteoarthritis: study protocol for a randomized controlled trial.

Background: Osteoarthritis (OA) is a chronic and painful condition where the articular cartilage surfaces progressively degenerate, resulting in loss of function and progressive disability. Obesity is a primary risk factor for the development and progression of knee OA, defined as the "metabolic OA" phenotype. Metabolic OA is associated with increased fat deposits that release inflammatory cytokines/adipokines, thereby resulting in systemic inflammation which can contribute to cartilage degeneration.

Force depression following a stretch-shortening cycle depends on the amount of residual force enhancement established in the initial stretch phase.

Studies on residual force enhancement (rFE) and residual force depression (rFD) of the muscle-tendon unit (MTU) have typically been conducted independent of each other, with little information available on how stretch-induced rFE affects the shortening phase and the steady-state MTU isometric force at the end of stretch-shortening cycles (SSCs). We showed previously that when rFE is kept constant, but the force at the end of the stretch is varied by changing the stretch speed, the steady-state forces at the end of SSCs were the same. These results led to the hypothesis that the amount of rFE of the MTU established in the initial stretch phase of SSCs determines the steady-state force following the shortening phase of SSCs.

Force depression following a stretch-shortening cycle is independent of stretch peak force and work performed during shortening.

The steady-state isometric force following active muscle shortening or lengthening is smaller (force depression; FD) or greater (residual force enhancement; RFE) than a purely isometric contraction at the corresponding length. The mechanisms behind these phenomena remain not fully understood, with few studies investigating the effects of FD and RFE in stretch-shortening cycles (SSC). The purpose of this study was to investigate the influence of RFE and peak force at the end of the stretch phase on the steady-state isometric force following shortening.

Messenger RNA profiling of rabbit quadriceps femoris after repeat injections of botulinum toxin: Evidence for a dynamic pattern without further structural alterations.

Introduction: Onabotulinum toxin type A (BoNT-A) is widely used clinically, but it may cause adverse effects. Earlier studies showed repeat BoNT-A injections did not cause progressive atrophy or function loss. The purpose of this study was to assess the influence of repeat BoNT-A injections into rabbit muscle on subsequent molecular alterations.

Shortening-induced force depression is modulated in a time- and speed-dependent manner following a stretch-shortening cycle.

The steady-state isometric force following active muscle shortening or lengthening is smaller (force depression, FD) or greater (residual force enhancement, RFE) than a purely isometric contraction at the corresponding length. The mechanism underlying these phenomena is not explained within the context of the cross-bridge theory, with few studies investigating the effects of FD and RFE in stretching-shortening cycle (SSC). The purpose of this study was to perform SSC, where the time between the end of stretch and the end of shortening was manipulated by (1) adding a pause between stretch and shortening (protocol 1) or (2) performing the shortening contraction at different speeds (protocol 2).

In vivo Sarcomere Lengths and Sarcomere Elongations Are Not Uniform across an Intact Muscle.

Sarcomere lengths have been a crucial outcome measure for understanding and explaining basic muscle properties and muscle function. Sarcomere lengths for a given muscle are typically measured at a single spot, often in the mid-belly of the muscle, and at a given muscle length. It is then assumed implicitly that the sarcomere length measured at this single spot represents the sarcomere lengths at other locations within the muscle, and force-length, force-velocity, and power-velocity properties of muscles are often implied based on these single sarcomere length measurements.

Residual force enhancement following shortening is speed-dependent.

The steady-state isometric force following active muscle shortening or lengthening is smaller (force depression; FD) or greater (residual force enhancement; RFE) than a purely isometric contraction at the corresponding length. The mechanisms underlying these phenomena are not explained within the context of the cross-bridge theory and are rarely studied in concert. Previous studies have shown RFE to be speed-independent.

A clinically relevant BTX-A injection protocol leads to persistent weakness, contractile material loss, and an altered mRNA expression phenotype in rabbit quadriceps muscles.

Botulinum toxin type-A (BTX-A) injections have become a common treatment modality for patients suffering from muscle spasticity. Despite its benefits, BTX-A treatments have been associated with adverse effects on target muscles. Currently, application of BTX-A is largely based on clinical experience, and research quantifying muscle structure following BTX-A treatment has not been performed systematically.

Tibiofemoral loss of contact area but no changes in peak pressures after meniscectomy in a Lapine in vivo quadriceps force transfer model.

Purpose: The menisci are thought to modulate load transfer and to absorb shocks in the knee joint. No study has experimentally measured the meniscal functions in the intact, in vivo joint loaded by physiologically relevant muscular contractions.

Methods: Right knee joints of seven New Zealand white rabbits were loaded using isometric contractions of the quadriceps femoris muscles controlled by femoral nerve stimulation.

Do skeletal muscle properties recover following repeat onabotulinum toxin A injections?

Onabotulinum toxin A (BTX-A) is a frequently used treatment modality to relax spastic muscles by preventing acetylcholine release at the motor nerve endings. Although considered safe, previous studies have shown that BTX-A injections cause muscle atrophy and deterioration in target and non-target muscles. Ideally, muscles should fully recover following BTX-A treatments, so that muscle strength and performance are not affected in the long-term.

Long-term repetitive mechanical loading of the knee joint by in vivo muscle stimulation accelerates cartilage degeneration and increases chondrocyte death in a rabbit model.

Background: Excessive chronic loading is thought to be one factor responsible for the onset of osteoarthritis. For example, studies using treadmill running have shown an increased risk for osteoarthritis, thereby suggesting that muscle-induced joint loading may play a role in osteoarthritis onset and progression. However, in these studies, muscle-induced loading was not carefully quantified.

Dynamic in-vivo force transfer in the lapine knee loaded by quadriceps muscle contraction.

Background: The rabbit knee is a frequently used model for experimental osteoarthritis (OA). Despite the acknowledged importance of joint loading in the onset and progression of OA, the load transfer in the three compartments of the intact rabbit knee remains unknown. Therefore, this study was aimed at determining load transfer in the three compartments for isometric, concentric, and eccentric knee extensor contractions.

The effects of electrical stimulation exercise on muscles injected with botulinum toxin type-A (botox).

Botulinum toxin type A (BTX-A) is a frequently used treatment modality for a variety of neuromuscular disorders. It acts by preventing acetylcholine release at the motor nerve endings, inducing muscle paralysis. Although considered safe, studies suggest that BTX-A injections create adverse effects on target and non-target muscles.

Effects of Russian current and low-frequency pulsed current on discomfort level and current amplitude at 10% maximal knee extensor torque.

Background: Low-frequency pulsed current (LFPC) and Russian current (RC), a type of kilohertz-frequency alternating current, have been frequently used for muscle strengthening in rehabilitation programs. Despite the popularity of these current types, it is unclear which is most effectively able to generate a similar submaximal torque with minimal discomfort and current amplitude.

Objective: To compare discomfort and current amplitude between LFPC and RC to achieve a knee extensor torque of 10% of the maximal isometric voluntary contraction (MIVC).

Catchlike property in human adductor pollicis muscle.

The "catchlike" property is defined as the dramatic force increase in skeletal muscles when a single pulse is added at the onset of a sub-tetanic low-frequency stimulation train. This property has been observed in single motor units, whole animal and human muscles. It is an inherent property of muscle fibres and is not related to an increase in motor unit recruitment.

The influence of cyclic concentric and eccentric submaximal muscle loading on cell viability in the rabbit knee joint.

Background: Cartilage loading is associated with the onset and progression of osteoarthritis and cell death may play an important role in these processes. Although much is known about cell death in joint impact loading, there is no information on joints loaded by muscular contractions. The aim of this study was to evaluate the influence of muscle generated eccentric and concentric submaximal joint loading on chondrocyte viability.

Changes in contractile properties of muscles receiving repeat injections of botulinum toxin (Botox).

Botulinum toxin type A (BTX-A) is a frequently used therapeutic tool to denervate muscles in the treatment of neuromuscular disorders. Although considered safe by the US Food and Drug Administration, BTX-A can produce adverse effects in target and non-target muscles. With an increased use of BTX-A for neuromuscular disorders, the effects of repeat injections of BTX-A on strength, muscle mass and structure need to be known.