A Preclinical Model of Sepsis-Induced Myopathy with Disuse in Mice.

Sepsis is a major cause of in-hospital deaths. Improvements in treatment result in a greater number of sepsis survivors. Approximately 75% of the survivors develop muscle weakness and atrophy, increasing the incidence of hospital readmissions and mortality. However, the available preclinical models of sepsis do not address skeletal muscle disuse, a key component for the development of sepsis-induced myopathy. Our objective in this protocol is to provide a step-by-step guideline for a mouse model that reproduces the clinical setting experienced by a bedridden septic patient. Male C57Bl/6 mice were used to develop this model. Mice underwent cecal ligation and puncture (CLP) to induce sepsis. Four days post-CLP, mice were subjected to hindlimb suspension (HLS) for seven days. Results were compared with sham-matched surgeries and/or animals with normal ambulation (NA). Muscles were dissected for in vitro muscle mechanics and morphological assessments. The model results in marked muscle atrophy and weakness, a similar phenotype observed in septic patients. The model represents a platform for testing potential therapeutic strategies for the mitigation of sepsis-induced myopathy.

Interindividual variability of adaptations following either traditional strength or power training combined to endurance training in older men: A secondary analysis of a randomized clinical trial.

This study aimed to investigate the interindividual responses following two different concurrent training (CT) regimens in neuromuscular, cardiorespiratory and functional outcomes of older men. Thirty-five older men (65.8 ± 3.9 years) were randomly allocated into one of two CT groups: power training (PT) + high-intensity interval training (HIIT) (n = 17); or traditional strength training (TST) + HIIT (n = 18). Maximal dynamic strength (one-repetition maximum, 1RM), rate of force development at 100 milliseconds (RDF100), countermovement jump power (CMJ), quadriceps femoris muscle thickness (QF MT), functional tests (sit-to-stand, timed-up-and-go, and stair climbing), and peak oxygen consumption (VO2peak) were assessed pre-, post-8 and post-16 weeks of training. The Chi-squared test was used for assessing differences in the prevalence of responders (Rs), non-responders (NRs), and adverse responders (ARs). Similar prevalence of individual responses (Rs, NRs and ARs) between groups were observed after intervention in almost all outcomes: 1RM; power at CMJ; QF MT, and functional tests (P > 0.05). However, a significant difference in the distribution of Rs, NRs and ARs between groups was observed in the RFD100 after 16 weeks (p = 0.003), with PT + HIIT group presenting high prevalence of Rs than TST + HIIT (100 % vs. 50 %). The inclusion of explosive-type of contractions in a concurrent training regime induces greater responsiveness in the RFD100 in older men, while no differences compared to traditional strength training are observed in maximal strength, muscle size, VO2peak, and functional performance.

Muscle quality and functionality in older women improve similarly with muscle power training using one or three sets.

The present study compared the effects of 12 weeks of muscle power training performing one or three sets on muscle quality assessed by echo intensity (MQEI) and index (MQindex), muscle power-related outcomes, and functional capacity in older women. Participants were randomly assigned into two groups: 1SET (n = 13) and 3SET (n = 13). Lower limb muscle power and vertical jump height were measured during a countermovement jump, maximal rate of torque development (MRTD), and root mean square (RMS) of electromyography signals and rate of rise (RER) of quadriceps maximal electromyography activation during unilateral knee extension at 0-50 and 0-200 ms, MQEI, MQindex (absolute muscle power/MQEI, and MRTD/MQEI) and functionally in both groups using timed-up-and-go were evaluated before and after training. There were significant and similar (p < 0.05) increases in muscle power, vertical jump height, MQEI, MQindex, and functionally (p ≤ 0.0001) in both groups. In contrast, MRTD increased only in 1SET (p ≤ 0.001), and the RMS0-200 and RER0-50 increased for 3SET only (p ≤ 0.05), with no difference between groups (p > 0.05). In conclusion, similar neuromuscular adaptations and improvements in the functional performance occurred in both groups.

Higher muscle power training volume is not determinant for the magnitude of neuromuscular improvements in elderly women.

The aim of this study was to compare the effects of 12 weeks of muscle power training using one- and three-sets on neuromuscular adaptations in elderly women. Twenty six healthy elderly women were randomly assigned into two groups: one-set (n = 13) and three-sets (n = 13). Maximal dynamic and isometric strength, rapid force assessed as absolute and normalized rate of force development (RTD) and contractile impulse during unilateral leg knee extension at 0-50 and 0-200 ms, overall quadriceps muscle thickness, muscle power during a countermovement jump (CMJ), and functional performance using time-up-and-go and the timed stair climb tests were evaluated before and after training. After 12 weeks, one-set and three-sets groups exhibited significant (p ≤ 0.05) and comparable increases in dynamic and isometric strength, absolute RTD and contractile impulse at 0-50 and at 0-200 ms and in the performance of both functional tests. No significant differences between groups were evident for any measured parameters (p > 0.05). Furthermore, the normalized RTD did not increase for any group (p > 0.05). Over 12 weeks, the muscle power training performing one- or three-sets induced alike improvements in muscle function, mass and functionally. These evidences suggest that a low training volume is able to induce significant improvements in age-related neuromuscular changes.