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Purpose: We evaluated whether repeated high-intensity interval exercise (HIIE) influences plasma oxytocin (OT) concentration in healthy men, and, given that OT is mainly synthesized in the hypothalamus, we assessed the concentration difference between the arterial (OT ART ) versus the internal jugular venous OT concentration (OT IJV ). Additionally, we hypothesized that an increase in cerebral OT release and the circulating concentration would be augmented by repeated HIIE., Methods: Fourteen healthy men (age = 24 ± 2 yr; mean ± SD) performed two identical bouts of HIIE. These HIIE bouts included a warm-up at 50%-60% maximal workload ( Wmax ) for 5 min followed by four bouts of exercise at 80%-90% Wmax for 4 min interspersed by exercise at 50%-60% Wmax for 3 min. The HIIE bouts were separated by 60 min of rest. OT was evaluated in blood through radial artery and internal jugular vein catheterization., Results: Both HIIE bouts increased both OT ART (median [IQR], from 3.9 [3.4-5.4] to 5.3 [4.4-6.3] ng·mL -1 in the first HIIE, P < 0.01) and OT IJV (from 4.6 [3.4-4.8] to 5.9 [4.3-8.2] ng·mL -1 , P < 0.01), but OT ART-IJV was unaffected (from -0.24 [-1.16 to 1.08] to 0.04 [-0.88 to 0.78] ng·mL -1 , P = 1.00). The increased OT levels were similar in the first and second HIIE bouts (OT ARTP = 0.25, OT IJVP = 0.36)., Conclusions: Despite no change in the cerebral OT release via the internal jugular vein, circulating OT increases during HIIE regardless of the accumulated exercise volume, indicating that OT may play role as one of the exerkines., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine.)

Purpose: No study has assessed the acute effect of caffeine supplementation on 100-m sprint running in athletics and caffeine's net ergogenicity on 100-m sprint running remains unclear. We investigated the acute effects of caffeine supplementation on 100-m sprint running performance in a field test., Methods: Thirteen male collegiate sprinters were subjected to 100-m sprint running time trials (TT) after the ingestion of 6 mg·kg -1 body weight caffeine or placebo supplementation in a double-blind, counterbalanced, randomized, and crossover design. Sprint velocity was measured with a laser system, and sprint time was calculated from the data in which the effects of environmental factors that would act as confounding factors on sprint time during TT were eliminated., Results: The corrected 100-m sprint time was significantly shortened by 0.14 s with caffeine supplementation compared with placebo (placebo: 11.40 ± 0.39 s, caffeine: 11.26 ± 0.33 s; P = 0.007, g = -0.33). The corrected sprint time up to 60 m during TT was also significantly shorter with caffeine supplementation than with placebo ( P = 0.002). Furthermore, the mean sprint velocity for splits of 0-10 and 10-20 m was significantly increased by caffeine supplementation (all P < 0.05)., Conclusions: Acute caffeine supplementation enhanced the corrected 100-m sprint time by improving the sprint performance in the first 60 m after more explosive acceleration in the early stage of the acceleration phase. Thus, for the first time, we directly demonstrated caffeine's ergogenicity on 100-m sprint performance in athletics., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine.)

Purpose: Blood flow restriction (BFR) walking is recognized as a beneficial strategy for increasing skeletal muscle mass and strength. No study has examined the effect of BFR exercise on cognitive functions, including executive function (EF). In this study, we examined the effect of BFR walking on EF., Methods: We performed two studies, at rest and exercise, with BFR or non-BFR (NBFR) in a crossover design. Sitting rest was performed for 15 min (study 1, n = 8). Exercise was programmed at five sets of 2-min walking at 5 km·h with 1-min rest intervals (study 2, n = 16). The BFR condition was achieved using 200 mm Hg pressure cuffs placed around the proximal region of the thighs. The NBFR condition involved no pressure cuffs. EF was assessed using the color-word Stroop task before and after each condition., Results: In study 1, there were no significant effects on EF parameters for both BFR and NBFR conditions, suggesting that BFR alone does not improve EF. In study 2, incongruent reaction time shortened after BFR walking compared with that before walking (P = 0.001). Furthermore, the reverse Stroop interference score decreased after BFR walking compared with that before walking (P < 0.001)., Conclusion: These findings suggest that, even with a mild exercise, BFR walking improves EF independently of the effect of BFR alone or walking alone.

Introduction: High-intensity interval exercise (HIIE) is more effective at increasing metabolic and cardiovascular health compared with moderate-intensity continuous exercise for patients with cardiovascular disease, but exhaustive high-intensity continuous exercise attenuates dynamic cerebral autoregulation (CA). This study assessed the effect of HIIE on dynamic CA., Methods: Nine healthy men (age, 24 ± 3 yr; mean ± SD) warmed up at 50%-60% maximal workload (Wmax) for 5 min before HIIE including four 4-min bouts of exercise at 80%-90% Wmax interspaced by four 3-min bouts at 50% to 60% Wmax. Transcranial Doppler determined middle cerebral artery mean blood velocity (MCA Vmean), and brachial artery catheterization determined mean arterial pressure (MAP). Dynamic CA was evaluated by transfer function analysis of changes in MAP and MCA Vmean., Results: The HIIE increased MAP (from 92 ± 9 to 104 ± 10 mm Hg; P < 0.0125), whereas MCA Vmean did not change. Transfer function phase increased and coherence decreased during HIIE (P < 0.0125 vs rest, respectively), whereas gain was unchanged., Conclusions: The results suggest that dynamic CA is unaffected during HIIE, indicating that the brain is protected from fluctuations in MAP. Thus, we propose that HIIE may be beneficial for brain-related health as maintenance of cerebral perfusion in contrast to high-intensity continuous exercise.

Purpose: The effect of exercise volume represented by exercise intensity and duration on postexercise executive function (EF) improvement remains unclear. In the present study, involving two volume-controlled evaluations, we aimed to compare acute exercise protocols with differing intensities and durations to establish an effective exercise protocol for improving EF., Methods: In study 1, 12 healthy male subjects performed cycle ergometer exercise, based on a low-intensity (LI) protocol for 20 min (LI20), moderate-intensity (MI) protocol for 20 min (MI20), and MI20 volume-matched LI protocol for 40 min (LI40). The exercise intensities for the LI and MI were set at 30% and 60% of peak oxygen consumption, respectively. In study 2, 15 healthy male subjects performed MI exercise for 10 min (MI10), MI20, and 40 min (MI40). To evaluate the EF, the color-word Stroop task was administrated before exercise, immediately after exercise, and during the 30-min postexercise recovery., Results: In study 1, postexercise EF improvement was sustained for a longer duration after MI20 than after LI40 and was sustained for a longer duration after LI40 than after LI20. In study 2, although there was no significant difference in post-MI exercise EF improvement, the magnitude of difference in the EF between preexercise and 30-min postexercise recovery period was moderately larger in MI40, but not in MI10 and MI20, indicating that the EF improvement during postexercise recovery could be sustained after MI40., Conclusion: The present findings showed that postexercise EF improvement could be prolonged after MI exercise with a moderate duration compared with volume-matched LI exercise with a longer duration. In addition, MI exercise with a relatively long duration may slightly prolong the postexercise EF improvement.