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Background: Low back pain is a highly prevalent condition in the United States and has a staggeringly negative impact on society in terms of expenses and disability. It has previously been suggested that rehabilitation strategies for persons with recurrent low back pain should be directed to the medial back muscles as these muscles provide functional support of the lumbar region. However, many individuals with low back pain cannot safely and effectively induce trunk muscle adaptation using traditional high-load resistance exercise, and no viable low-load protocols to induce trunk extensor muscle adaptation exist. Herein, we present the study protocol for a randomized controlled trial that will investigate the "cross-transfer" of effects of a novel exercise modality, blood flow restricted exercise, on cross-sectional area (primary outcome), strength and endurance (secondary outcomes) of trunk extensor muscles, as well as the pain, disability, and rate of recurrence of low back pain (tertiary outcomes).Methods and Study Design: This is a single-blinded, single-site, randomized controlled trial. A minimum of 32 (and up to 40) subjects aged 18 to 50 years with recurrent low back pain and poor trunk extensor muscle endurance will be recruited, enrolled and randomized. After completion of baseline assessments, participants will be randomized in a 1:1 ratio to receive a 10-week resistance exercise training program with blood flow restriction (BFR exercise group) or without blood flow restriction (control exercise group). Repeat assessments will be taken immediately post intervention and at 12 weeks after the completion of the exercise program. Furthermore, once every 4 weeks during a 36-week follow-up period, participants will be asked to rate their perceived disability and back pain over the past 14 days.Discussion: This study will examine the potential for blood flow restricted exercise applied to appendicular muscles to result in a "cross-transfer" of therapeutic effect to the lumbar musculature in individuals with low back pain. The results of this study will provide important insights into the effectiveness of this novel exercise modality, which could potentially provide the foundation for a cost-effective and easy-to-implement rehabilitation strategy to induce muscle adaptation in the absence of high mechanical and compressive loading on the spine.Trial Registration: This trial is registered with ClinicalTrials.gov (registration number: NCT02308189, date of registration: 2 December 2014). [ABSTRACT FROM AUTHOR]

The purpose of the present study was to determine the effects of obesity and biological sex on myostatin expression in humans and to examine the direct effects of myostatin, SMAD2, and SMAD3 on insulin signaling in primary human skeletal muscle cells (HSkMCs). For cohort 1 , 15 lean [body mass index (BMI): 22.1 ± 0.5 kg/m 2 ; n = 8 males; n = 7 females] and 14 obese (BMI: 40.6 ± 1.4 kg/m 2 ; n = 7 males; n = 7 females) individuals underwent skeletal muscle biopsies and an oral glucose tolerance test. For cohort 2 , 14 young lean (BMI: 22.4 ± 1.9 kg/m 2 ; n = 6 males; n = 8 females) and 14 obese (BMI: 39.3 ± 7.9 kg/m 2 ; n = 6 males; n = 8 females) individuals underwent muscle biopsies for primary HSkMC experiments. Plasma mature myostatin ( P = 0.041), skeletal muscle precursor myostatin ( P = 0.048), and skeletal muscle SMAD3 ( P = 0.029) were elevated in obese females compared to lean females, and plasma mature myostatin ( r = 0.58, P = 0.029) and skeletal muscle SMAD3 ( r = 0.56, P = 0.037) were associated with insulin resistance in females but not males. Twenty-four hours of myostatin treatment impaired insulin signaling in primary HSkMCs derived from females ( P < 0.024) but not males. Overexpression of SMAD3, but not SMAD2, impaired insulin-stimulated AS160 phosphorylation in HSkMCs derived from lean females (-27%, P = 0.040), whereas silencing SMAD3 improved insulin-stimulated AS160 phosphorylation and insulin-stimulated glucose uptake (25%, P < 0.014) in HSkMCs derived from obese females. These results suggest for the first time that myostatin-induced impairments in skeletal muscle insulin signaling are sex specific and that increased body fat in females is associated with detrimental elevations in myostatin and SMAD3, which contribute to obesity-related insulin resistance. NEW & NOTEWORTHY Obesity is considered a main risk factor for the development of insulin resistance and type 2 diabetes. The present study utilizes in vivo and in vitro experiments in human skeletal muscle to demonstrate for the first time that females are inherently more susceptible to myostatin-induced insulin resistance, which is further enhanced with obesity due to increased myostatin and SMAD3 expression.

Background: Expanded insurance coverage will likely increase the demand for primary care physicians in the United States. Despite this demand, the number of medical students planning to specialize in primary care is decreasing., Objective: To explore premedical students' attitudes toward the primary care specialty., Methods: Students enrolled in premedicine at a large Midwestern university were invited to complete the Primary Care Attitudes Survey (Cronbach α=.76). This 25-item survey measures attitudes about primary care on a 5-point Likert scale, ranging from 1, "strongly disagree" to 5, "strongly agree." Basic sociodemographic characteristics were assessed using descriptive statistics, and frequencies of individual survey responses were calculated using SPSS statistical software version 21.0., Results: A total of 100 premedical students (mean [SD] age, 19.8 [1.5] years; 59 female, 82 white non-Hispanic, and 33 freshman) completed the survey. Of 100 students, 33 planned to pursue primary care; 66 thought that primary care physicians would always have a job; 25 thought that primary care may become obsolete as medicine becomes more specialized; 48 thought that physician assistants and nurse practitioners would take over many primary care duties in the future; 91 thought that primary care physicians make important contributions to medicine; and 84 agreed that primary care focuses on the whole patient., Conclusions: Premedical students held positive views about the importance of primary care; however, many expressed uncertainty about the stability of primary care careers in the future. Further, a substantial number of students believed common misconceptions about the scope and practice of primary care, such as primary care doctors are gatekeepers and mostly diagnose colds and ear infections.