The aim of our study was to investigate fiber type distribution and contractile characteristics of Latissimus Dorsi muscle (LDM). Samples were collected from 18 young healthy subjects (9 males and 9 females) through percutaneous fine needle muscle biopsy. The results showed a predominance of fast myosin heavy chain isoforms (MyHC) with 42% of MyHC 2A and 25% of MyHC 2X, while MyHC 1 represented only 33%. The unbalance toward fast isoforms was even greater in males (71%) than in females (64%). Fiber type distribution partially reflected MyHC isoform distribution with 28% type 1/slow fibers and 5% hybrid 1/2A fibers, while fast fibers were divided into 30% type 2A, 31% type A/X, 4% type X, and 2% type 1/2X. Type 1/slow fibers were not only less abundant but also smaller in cross-sectional area than fast fibers. During maximal isometric contraction, type 1/slow fibers developed force and tension significantly lower than the two major groups of fast fibers. In conclusion, the predominance of fast fibers and their greater size and strength compared to slow fibers reveal that LDM is a muscle specialized mainly in phasic and powerful activity. Importantly, such specialization is more pronounced in males than in females.
Different social norms influence the type and amount of information transmitted to palliative care patients. In Italy disclosure rate is low and medical decisions are often mediated by the family since communication of diagnosis and prognosis is viewed as harmful and brutal. Aims of our study were to assess palliative care patients knowledge about their diagnosis and prognosis and expectations; and to evaluate possible differences between palliative care patients with and without cancer.
The aim of the present study was to define the chronic effects of neuromuscular electrical stimulation (NMES) on the neuromuscular properties of human skeletal muscle. Eight young healthy male subjects were subjected to 25 sessions of isometric NMES of the quadriceps muscle over an 8-wk period. Needle biopsies were taken from the vastus lateralis muscle before and after training. The training status, myosin heavy chain (MHC) isoform distribution, and global protein pattern, as assessed by proteomic analysis, widely varied among subjects at baseline and prompted the identification of two subgroups: an "active" (ACT) group, which performed regular exercise and had a slower MHC profile, and a sedentary (SED) group, which did not perform any exercise and had a faster MHC profile. Maximum voluntary force and neural activation significantly increased after NMES in both groups (+?30% and +?10%, respectively). Both type 1 and 2 fibers showed significant muscle hypertrophy. After NMES, both groups showed a significant shift from MHC-2X toward MHC-2A and MHC-1, i.e., a fast-to-slow transition. Proteomic maps showing ?500 spots were obtained before and after training in both groups. Differentially expressed proteins were identified and grouped into functional categories. The most relevant changes regarded 1) myofibrillar proteins, whose changes were consistent with a fast-to-slow phenotype shift and with a strengthening of the cytoskeleton; 2) energy production systems, whose changes indicated a glycolytic-to-oxidative shift in the metabolic profile; and 3) antioxidant defense systems, whose changes indicated an enhancement of intracellular defenses against reactive oxygen species. The adaptations in the protein pattern of the ACT and SED groups were different but were, in both groups, typical of both resistance (i.e., strength gains and hypertrophy) and endurance (i.e., a fast-to-slow shift in MHC and metabolic profile) training. These training-induced adaptations can be ascribed to the peculiar motor unit recruitment pattern associated with NMES.
The muscle biopsy based on the Bergström needle has been widely used for more than 40 y for diagnosis and experimental studies on muscle. More recently, thinner needles and tru-cut needles have also been introduced. Such techniques have been largely tested on various muscles, including the quadriceps, with few studies on upper limb muscles like deltoid, and no studies on latissimus dorsi muscle (LDM). In this study, we implemented and validated a protocol to collect samples of LDM for experimental purposes, causing minimal discomfort to volunteers. Two main problems were considered: the anatomical localization of the biopsy site and the selection of an appropriate needle.
The aim of the present study was to clarify the impact of long term (1 year) resistance training (RT) on structure and function of single muscle fibres of vastus lateralis in young female subjects. Five young women (age: 25.4+/-6.2 year) performed exercise sessions at 60% of single subject own repetition maximum (1 RM) 1h twice a week. Maximum voluntary force was determined pre- and post-RT and was found to significantly increase post-RT ensuring a successful impact of RT on muscle performance in vivo. Needle muscle biopsy samples were obtained both pre- and post-RT and the following determinations were performed: myosin heavy chain isoform (MHC) distribution of the whole muscle samples by SDS-PAGE; cross sectional area (CSA), specific force (Po/CSA) and maximum shortening velocity (Vo) of a large population (n=358) of single skinned muscle fibres classified on the basis of MHC isoform composition by SDS-PAGE. The results suggest that the long duration of RT can determine a significant increase in specific force (Po/CSA) and unloaded shortening velocity (Vo) of single muscle fibres in female subjects, whereas no muscle fibre hypertrophy and no shift in MHC isoform content was observed.
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