Attention is the ability to extract task-relevant information and reject irrelevant information in order to avoid excessive information processing in the nervous system, and influences task performance in daily life including physical and sporting activities. Basic attentional phenomena at the behavioral and neural levels have recently been employed as measures of attentional functions to examine the effects of exercise training and motor learning in the real world. However, these basic phenomena have been demonstrated in strictly manipulated laboratory experiments; therefore, it currently remains unclear whether they may be applied to the examination of attentional functions in real-world conditions. We herein briefly review basic attentional theories derived from a number of dual-task experiments and discuss their applicability to a more realistic world.
Regeneration of muscle is undertaken by muscle stem cell populations named satellite cells which are normally quiescent or at the G0 phase of the cell cycle. However, upon signals from damaged muscle, satellite cells lose their quiescence, and enter the G1 cell cycle phase to expand the population of satellite cell progenies termed myogenic precursor cells (MPCs). Eventually, MPCs stop their cell cycle and undergo terminal differentiation to form skeletal muscle fibers. Some MPCs retract to quiescent satellite cells as a self-renewal process. Therefore, cell cycle regulation, consisting of satellite cell activation, proliferation, differentiation and self-renewal, is the key event of muscle regeneration. In this review, we summarize up-to-date progress on research about cell cycle regulation of myogenic progenitor cells and muscle stem cells during embryonic myogenesis and adult muscle regeneration, aging, exercise and muscle diseases including muscular dystrophy and muscle fiber atrophy, especially focusing on cyclin-dependent kinase inhibitors (CDKIs).
The hypothalamus controls glucose and lipid metabolism in peripheral tissues. Recent studies have revealed that the ventromedial hypothalamus (VMH) and arcuate nucleus (ARC) of the hypothalamus play an important role in the regulation of glucose and lipid metabolism in skeletal muscle and the liver. The fat-derived hormone leptin was thus shown to stimulate glucose uptake and fatty acid oxidation in red-type skeletal muscle by activating VMH neurons - likely mediated in part by augmentation of synaptic plasticity between leptin receptor and proopiomelanocortin (POMC)-expressing neurons in the ARC and melanocortin receptor (MCR)-expressing VMH neurons - and consequent activation of sympathetic nerves innervating the muscle tissue. The VMH - sympathetic nerve axis was also found to be activated by orexin-positive neurons in mediation of hedonic feeding-induced glucose uptake in red-type skeletal muscle. The effects of orexin and leptin on glucose metabolism in skeletal muscle are interconnected with those of insulin, with the action of VMH also being necessary for the beneficial effects of exercise on metabolism. Leptin ameliorates diabetic phenotypes in animals with uncontrolled insulin-deficient diabetes as well as in patients with or animal models of lipodystrophy through the central nervous system (CNS). Finally, a single injection of fibroblast growth factor 1 (FGF1) into the lateral ventricle was shown to induce sustained remission of hyperglycemia in several animal models of type 2 diabetes, at least in part by increasing glucose uptake in skeletal muscle. The CNS thus plays an important role in the control of glucose and lipid metabolism, with the VMH as well as POMC neurons being implicated as key regulators of such metabolism in skeletal muscle.
Satellite cells are resident muscle stem cells located between the basal lamina and the plasma membrane of myofibers. They play crucial roles in muscle growth during the postnatal stage and muscle regeneration following postnatal development. However, the roles of satellite cells in adult muscles - in muscle growth, function, and adaptation - are poorly understood. Recently, by studying genetically engineered mice with conditionally ablated satellite cells, it has been reported that satellite cells play important roles in muscle growth and maintenance of muscle spindles or neuromuscular junctions, and produce growth factors that affect other organs. Here, we review the recent studies using tamoxifen-inducible Pax7-DTA mice and describe the novel roles of satellite cells in the maintenance of skeletal muscle plasticity.
We investigated the associations between the DRD2/ANKK1 genotype (rs1800497, C > T) and both physical activity (PA) level and exercise habit. A total of 648 Japanese men and women aged 26 – 82 years were included in this cross-sectional study. The PA level was evaluated using a triaxial accelerometer. Exercise habits in the past year and in the period from childhood to adolescence were assessed using a questionnaire. There were no significant differences in PA level or exercise habit in the past year among the DRD2/ANKK1 genotypes. On the other hand, there was a significant association between the DRD2/ANKK1 genotype and exercise habit in the period from childhood to adolescence. Regular exercisers (Ex) showed a lower proportion of the CC genotype than non-exercisers (Non-Ex) (P < 0.05). Logistic regression analysis for exercise habit in the period from childhood to adolescence, controlling for gender and age in an additive genetic model, indicated significant associations with increased likelihood of exercisers (Ex) carrying the T allele, OR = 1.38 (95% CI: 1.06 – 1.80, P < 0.05). In conclusion, it was suggested that the DRD2/ANKK1 genotype is associated with exercise habit in the period from childhood to adolescence, but not current PA and exercise habit in the past year.
High-intensity interval training (HIIT) has recently received much attention as a new option for aerobic training. Despite its smaller time requirement, HIIT has been reported to have a greater effect than continuous moderate-intensity training on fat loss, especially a decrease in truncal adiposity. We therefore examined whether long-term HIIT preferentially modulates truncal adiposity rather than peripheral adiposity, especially thigh adiposity, where local muscle energy consumption increased profoundly during HIIT. We also examined the association between changes in adipose tissue distribution and serum adiponectin level. Twelve healthy male participants (28-48 years old) were assigned to a group that performed HIIT using only a leg ergometer (L-HIIT, n = 7) or to a group that performed HIIT using both leg and arm ergometers (LA-HIIT, n = 5) twice weekly for 16 weeks. The training programs consisted of 8 to 12 sets of >90% VO2 peak for 1 min, with 1 min of very light active recovery. Body composition analyses as well as aerobic fitness and measurements of serum adiponectin were performed at baseline and after intervention. A linear improvement in aerobic fitness was observed along with a decrease in leg fat (5.4 ± 1.7 vs. 5.1 ± 1.7 kg, p < 0.05) near the main working muscles during HIIT in the combined (L+LA-HIIT) group. Moreover, there was an association of decrease in leg fat or thigh adiposity with improvement in aerobic fitness in the combined group (ρ = -0.59, p < 0.05; and ρ = -0.71, p < 0.05, respectively). Visceral adiposity was decreased in L-HIIT (115 ± 45 vs. 100 ± 47 cm2, p < 0.05), however no decrease was observed in total fat or truncal fat in either group. No change was observed in serum adiponectin concentration in either group. Changes in serum adiponectin were associated with changes in visceral adiposity in the combined group (ρ = -0.72, p < 0.01). Regional rather than whole-body fat loss was observed after a 16-week HIIT program.
Exercise-induced changes in executive function affect the control of action in a dynamic environment. This study aimed to examine the effect of sustained high-intensity exercise on executive function. Nine healthy male and female participants (age, 21-28 years) completed an exercise session with 65-min treadmill running at 75% VO2max. Executive function was assessed before and after exercise with the Stroop Color and Word Test that included congruent and incongruent conditions. The reaction time and response accuracy of the test were measured, and the task difficulty was controlled by adjusting the stimulus duration so that each participant could maintain at least 80% response accuracy to exclude the effect of a speed–accuracy trade-off. The levels of plasma norepinephrine and adrenocorticotropic hormone were examined. A significant interaction with the reaction time was found (condition × time, P = 0.024), in which the reaction time significantly increased after exercise only in the incongruent condition (P = 0.019). The response accuracy was not significantly different between before and after exercise in both conditions, which indicated that the response accuracy was controlled as intended. The levels of plasma norepinephrine and adrenocorticotropic hormone were significantly increased after exercise (P < 0.05). These results demonstrated that the reaction time in the incongruent condition increased after sustained high-intensity exercise with a cognitive function test with the response accuracy controlled, indicating a decline in executive function. Increased levels of plasma norepinephrine and adrenocorticotropic hormone may contribute, at least in part, to such decline in executive function.