Shi Zhou

Despite the functional importance of the human quadriceps femoris in movements such as running, jumping, lifting and climbing, and the known effects of muscle architecture on muscle function, no research has fully described the complex architecture of this muscle group. We used ultrasound imaging techniques to measure muscle thickness, fascicle angle and fascicle length at multiple regions of the four quadriceps muscles in vivo in 31 recreationally active, but non-strength-trained adult men and women. Our analyses revealed a reasonable similarity in the superficial quadriceps muscles, which is suggestive of functional similarity (at least during the uni-joint knee extension task) given that they act via a common tendon. The deep vastus intermedius (VI) is architecturally dissimilar and therefore probably serves a different function(s). Architecture varies significantly along the length of the superficial muscles, which has implications for the accuracy of models that assume a constant intramuscular architecture. It might also have consequences for the efficiency of intra- and intermuscular force transmission. Our results provide some evidence that subjects with a given architecture of one superficial muscle, relative to the rest of the subject sample, also have a similar architecture in other superficial muscles. However, this is not necessarily true for vastus lateralis (VL), and was not the case for VI. Therefore, the relative architecture of one muscle cannot confidently be used to estimate the relative architecture of another. To confirm this, we calculated a value of whole quadriceps architecture by four different methods. Regardless of the method used, we found that the absolute or relative architecture of one muscle could not be used as an indicator of whole quadriceps architecture, although vastus medialis, possibly in concert with VL and the anterior portion of VI, could be used to provide a useful snapshot. Importantly, our estimates of whole quadriceps architecture show a gender difference in whole quadriceps muscle thickness, and that muscle thickness is positively correlated with fascicle angle whereas fascicle length is negatively, although weakly, correlated with fascicle angle. These results are supportive of the validity of estimates of whole quadriceps architecture. These data are interpreted with respect to their implications for neural control strategies, region-specific adaptations in muscle size in response to training, and gender-dependent differences in the response to exercise training.

High prevalence of physical inactivity and obesity in children and adolescents has become a global problem. This systematic review aimed to examine the existing literature regarding the factors that influence participation in physical activity (PA) in children and adolescents with reference to the social ecological model (SEM) proposed by McLeroy et al. (1988). The SEM provides a framework under which the influencing factors are categorized into five levels: intrapersonal, interpersonal, organizational, community, and public policy. A systematic search of relevant literature published before July 2020 was conducted through Ebsco, ProQuest, PubMed Central, Scopus, and Web of Science. A total of fourteen studies met the inclusion criteria. The selected articles were all of high quality as assessed using the Mixed Methods Appraisal Tool (2018). The results indicated that gender, age, ethnicity, and self-concept were the most common influencing factors at the intrapersonal level. At the interpersonal and organization levels, supports from friends, parents, and teachers were positive predictors of students' PA participation. Accessibility of facilities and safe neighborhoods was a crucial factor that influenced children and adolescents' participation in PA at the community level. Future studies on the effective types of policies or practices that could successfully promote facilities' accessibility and improve neighborhood safety are required. The outcomes of this systematic review are expected to inform practice and support the development and implementation of sound policies for the promotion of PA participation in children or adolescents from a comprehensive social ecological viewpoint.

Cross education refers to the contralateral effect of chronic motor activity in one limb. The effect can enhance or diminish motor activity and is specific to the homologous muscles and the training task. The mechanisms underlying the phenomenon involve adaptations in the nervous system, probably at the level of the spinal cord.

This study compared the effect of prolonged moderate-intensity continuous training (MICT) on reducing abdominal visceral fat in obese young women with that of work-equivalent (300 kJ/training session) high-intensity interval training (HIIT). Forty-three participants received either HIIT (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mn fontstyle="italic">15</mml:mn></mml:math>), MICT (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mn fontstyle="italic">15</mml:mn></mml:math>), or no training (CON,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mi>n</mml:mi><mml:mo>=</mml:mo><mml:mn fontstyle="italic">13</mml:mn></mml:math>) for 12 weeks. The abdominal visceral fat area (AVFA) and abdominal subcutaneous fat area (ASFA) of the participants were measured through computed tomography scans preintervention and postintervention. Total fat mass and the fat mass of the android, gynoid, and trunk regions were assessed through dual-energy X-ray absorptiometry. Following HIIT and MICT, comparable reductions in AVFA (−9.1, −9.2 cm 2 ), ASFA (−35, −28.3 cm 2 ), and combined AVFA and ASFA (−44.7, −37.5 cm 2 ,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mi>p</mml:mi><mml:mo>&gt;</mml:mo><mml:mn fontstyle="italic">0</mml:mn><mml:mo>.</mml:mo><mml:mn fontstyle="italic">05</mml:mn></mml:math>) were observed. Similarly, reductions in fat percentage (−2.5%, −2.4%), total fat mass (−2.8, −2.8 kg), and fat mass of the android (−0.3, −0.3 kg), gynoid (−0.5, −0.7 kg), and trunk (−1.6, −1.2 kg,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mi>p</mml:mi><mml:mo>&gt;</mml:mo><mml:mn fontstyle="italic">0</mml:mn><mml:mo>.</mml:mo><mml:mn fontstyle="italic">05</mml:mn></mml:math>) regions did not differ between HIIT and MICT. No variable changed in CON. In conclusion, MICT consisting of prolonged sessions has no quantitative advantage, compared with that resulting from HIIT, in abdominal visceral fat reduction. HIIT appears to be the predominant strategy for controlling obesity because of its time efficiency.