Effects of high-intensity interval exercise on muscle fatigue and SR function in rats: a comparison with moderate-intensity continuous exercise.

In this study, we compared muscle fatigue induced by high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE), with a focus on changes in the function of sarcoplasmic reticulum (SR) and myofibril. To achieve the aim of this study with mechanically skinned fibers with sealed transverse tubules and intact SR membrane, myofibrillar Ca sensitivity, depolarization-induced force, and action potential-induced force were evaluated. Rat gastrocnemius muscles were subjected to HIIE-mimicking or MICE-mimicking stimulation in situ.

Treatment with EUK-134 improves sarcoplasmic reticulum Ca release but not myofibrillar Ca sensitivity after fatiguing contraction of rat fast-twitch muscle.

Skeletal muscles undergoing vigorous activity can enter a state of prolonged low-frequency force depression (PLFFD). This study was conducted to examine whether antioxidant treatment is capable of accelerating the recovery from PLFFD, with a focus on the function of the sarcoplasmic reticulum (SR) and myofibril. One hour before fatiguing stimulation (FS) was administered, rats received an intraperitoneal injection of Eukarion (EUK-134), which mimics the activities of superoxide dismutase and catalase.

Ingestion of soy protein isolate attenuates eccentric contraction-induced force depression and muscle proteolysis via inhibition of calpain-1 activation in rat fast-twitch skeletal muscle.

Objective: Eccentric contraction (ECC) is a contraction in which skeletal muscles are stretched while contracting. The aim of this study was to determine how ingestion of soy protein isolate (SPI) or animal-based proteins affect force deficit, calpain activation, and proteolysis of calcium ion (Ca)-regulatory proteins in rat fast-twitch muscles subjected to ECC.

Methods: In the first experiment, male Wistar rats were randomly assigned to a control and an SPI group, which were fed a 20% casein and a 20% SPI diet, respectively, for 28 d before the ECC protocol.

Thermal pretreatment facilitates recovery from prolonged low-frequency force depression in rat fast-twitch muscle.

The aim of this study was to examine whether thermal pretreatment can accelerate recovery from prolonged low-frequency force depression. The hindlimbs of thermal treated (T-treated) rats were immersed in water heated to 42.0°C for 20 min (thermal pretreatment).

l-arginine ingestion inhibits eccentric contraction-induced proteolysis and force deficit via S-nitrosylation of calpain.

It has been shown that calpains are involved in the proteolysis of muscle proteins that occurs with eccentric contraction (ECC) and that exogenously applied nitric oxide decreases the calpain-mediated proteolysis. The aim of this study was to examine the effects of ingestion of l-arginine (ARG), a nitric oxide precursor, on ECC-related calpain activation. In the first and second experiments, male Wistar rats were given ARG in water for 7 days starting from 3 days before the ECC protocol (average ingestion, ~600 mg kg-body wt  day ).