Akemi Ota

Forced respiration during the deeper water immersion causes the greater inspiratory muscle fatigue in healthy young men.

[Purpose] The purpose of the present study was to evaluate the effect of water immersion at different water depths on respiratory function and the effect of inspiratory load breathing (ILB) during water immersion at different water depths on respiratory muscle strength evaluated by maximum inspiratory and expiratory pressures (PImax and PEmax, respectively). [Subjects] Eight healthy men participated randomly in three trials. [Methods] All sessions were conducted with the participants in a sitting position immersed in a water bath. We evaluated respiratory function, PImax and PEmax during submersion at three different levels of water depth (umbilicus; 4th-rib; or clavicle, CL) and after subsequent 15-min ILB. [Results] Decreases in vital capacity and expiratory reserve volume from baseline by water immersion were significantly greater in the CL trial than those in the other trials. In the CL trial, PImax was immediately reduced after ILB compared to that at baseline, and the reduction was significantly greater than those in the other trials. PEmax was not affected by ILB in any of the trials. [Conclusion] Forced respiration during deeper water immersion caused greater inspiratory muscle fatigue in healthy young men.

Inhibitory Effects of Intranasal Administration of Insulin on Fat Oxidation during Exercise Are Diminished in Young Overweight Individuals

It remains unknown whether the high insulin (INS) levels in the brain affect fat oxidation during exercise. We examined the effects of the intranasal administration of INS, which increases the INS concentration in the cerebrospinal fluid when peripheral effects are lacking, on the maximum fat oxidation rate (maxFOR) and its intensity (FATmax) during exercise in 15 young normal-weight (N group) and eight young overweight (O group) individuals. On two separate days, either INS or placebo (PL) was randomly administered intranasally before a graded exercise test. Indirect calorimetry was used to assess maxFOR and FATmax during exercise. Blood INS and glucose levels did not change after INS administration. In the N group, maxFOR and FATmax were significantly smaller in the INS trial than in the PL trial. MaxFOR was significantly smaller in the O group than in the N group and was not influenced by INS administration. Exercise-induced elevation in blood epinephrine levels tended to be reduced by INS administration only in the N group. Intranasal INS administration reduces fat oxidation during exercise without any peripheral effects, possibly by suppressing sympathetic nerve activity. This inhibitory effect is diminished in overweight subjects, suggesting that cerebral insulin effects are attenuated in this population.

Effects of 2-Year Cognitive–Motor Dual-Task Training on Cognitive Function and Motor Ability in Healthy Elderly People: A Pilot Study

We aimed to examine the effect of 2-year cognitive–motor dual-task (DT) training on cognitive functions and motor ability of healthy elderly people without marked cognitive impairment. From the 25 participants of our 12-week DT trial conducted in 2014, we recruited 8 subjects who voluntarily participated in a new DT training program once a week for 2 years (exercise (EX) group). Their cognitive functions were evaluated by the Modified Mini-Mental State (3MS) examination and the Trail Making Test, and results were compared with those of the 11 subjects who discontinued the training and did not perform any types of exercise for 2 years (non-exercise (NO) group). Subjects in the NO group showed deterioration in the 3MS examination results, especially in the cognitive domain of attention. Meanwhile, participation in DT training maintained the scores in almost all domains of cognitive function, as well as the total 3MS scores. However, both groups had impaired quadriceps muscle strength and motor ability after the 2-year observation period. These results suggest that participating in exercise program comprising DT training for 2 years may be beneficial for maintaining the broad domains of cognitive function in healthy elderly people, although further verification is needed.

Intranasal insulin administration does not modulate incretin secretion, gastric emptying, and appetite in healthy young adults

Intranasal insulin (INS) administration reduces food intake and body weight in humans. It remains unclear whether the intranasal delivery of INS to the brain affects incretin secretion via the brain–gut axis. In the present study, we examined the effect of intranasal INS administration on glucagon-like peptide-1 (GLP-1) secretion, gastric emptying, and appetite. Thirteen normal-weight, healthy, young volunteers (age 21.2 ± 2.9 (SD) years) participated in a randomized single-blind, crossover study. Sixteen puffs of regular INS (10 IU; total dose, 160 IU) or normal saline as a placebo (0.1 mL, with a total dose of 1.6 mL) were intranasally administered in a random order after an overnight fast. Afterward, a fixed meal test, including 1,500 mg paracetamol to measure gastric emptying, was performed in each participant. Blood glucose, INS, the active form of GLP-1, paracetamol, and postprandial satiety (measured using the visual analog scale) levels were evaluated during the 180-min meal test. Meal intake similarly induced the elevation of blood glucose, INS, and GLP-1 levels in both trials. The total increases in blood glucose, INS, and GLP-1 levels during the meal test evaluated by the area under the curve were not different between the trials. Gastric emptying velocity and postprandial satiety were not significantly different either. In conclusion, we could find no significant effect of intranasal delivery of INS to the brain on postprandial GLP-1 secretion, gastric emptying, or postprandial satiety in the present study with healthy young adults.