Publications by authors named "Takuma Arimitsu"

19 Publications

  • Page 1 of 1

Low caffeine dose improves intermittent sprint performance in hot and humid environments.

J Therm Biol 2020 Oct 26;93:102698. Epub 2020 Aug 26.

Department of Sports Research, Japan Institute of Sports Sciences (JISS), 3-15-1 Nishigaoka Kita-ku, Tokyo, 115-0056, Japan.

While the effects of caffeine have been evaluated in relation to endurance exercise, few studies have assessed the ergogenic effects of low caffeine doses on intermittent exercise performance in hot and humid environments. Thus, we aimed to determine the effects of low-dose caffeine supplementation on intermittent exercise performance under these conditions. Eight male soccer players (age, 19.9 ± 0.3 years; height, 173.7 ± 6.3 cm; body mass, 65.1 ± 5.5 kg; V˙Omax, 50.0 ± 3.1 mL ⋅ kg⋅ min) participated in this double-blind, randomized, cross-over study. Caffeine was orally administered at 60 min before exercise (dosage, 3 mg ⋅ kg). The participants completed a 90-min intermittent sprint cycling protocol under two conditions (after receiving caffeine and placebo) at 32 °C and at 70% relative humidity. A significant improvement in the total amount of work was observed in the caffeine condition compared to the placebo condition (155.0 ± 15.8 vs 150.8 ± 14.5 kJ, respectively; p < 0.05, d = 0.28). In contrast, the rectal temperature measured at the end of exercise showed no significant difference between the conditions (38.9 ± 0.4 °C and 38.7 ± 0.5 °C in the caffeine and placebo conditions, respectively; p > 0.05, d = 0.57). Other thermal responses, such as the mean skin temperature, heart rate, or sweat volume, were not significantly different between these conditions. These results suggested that a low caffeine dose improved the intermittent sprint performance and the reasons could be explained by the fact that a low caffeine dose ingestion did not affect the thermoregulatory responses compared to the placebo condition and, thus, did not attenuate its ergogenic effect on exercise in hot and humid environments.
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http://dx.doi.org/10.1016/j.jtherbio.2020.102698DOI Listing
October 2020

Body Composition and Physical Fitness Profiles of Elite Female Japanese Wrestlers Aged <12 Years until >20 Years.

Sports (Basel) 2020 May 31;8(6). Epub 2020 May 31.

Sports Design Lab, Minato, Tokyo 108-0023, Japan.

Studies evaluating the physical fitness levels of elite wrestlers during junior high school are limited. This study aimed to examine the body composition and physical fitness profiles of elite Japanese female wrestlers aged <12 years until >20 years. There were 114 elite female wrestlers enrolled. Measurements were conducted in the following age categories: <12 years (U-12), <15 years (U-15), <17 years (U-17: cadet), <20 years (U-20: junior), and >20 years (senior). Body composition variables consisted of body mass index (BMI), percent body fat, fat free mass, and fat free mass index (FFMI). Fitness measurements included grip strength, back strength, sit-up, rope-climbing, and endurance running tests. The wrestlers in this study demonstrated comparable or greater FFMI values (e.g., FFMI: 17.9 ± 0.4 kg/m for light and 19.8 ± 0.9 kg/m for heavy weight categories in U-20), when compared with young female wrestlers in previous studies, whereas stature, body mass, and BMI of the wrestlers in our study were unremarkable. Regarding the fitness assessment, a remarkable increase in back strength was observed after late puberty. An outstanding enhancement of muscle strength after late puberty, which is unlikely to occur in ordinary women, would be an important requirement to become the world's top female wrestler.
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http://dx.doi.org/10.3390/sports8060081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7353630PMC
May 2020

Evenly Distributed Protein Intake over 3 Meals Augments Resistance Exercise-Induced Muscle Hypertrophy in Healthy Young Men.

J Nutr 2020 07;150(7):1845-1851

Faculty of Sport and Health Science, Ritsumeikan University, Nojihigashi, Kusatsu, Shiga, Japan.

Background: Although daily protein intake (PI) has been reported to be essential for regulating muscle mass, the distribution of daily PI in individuals is typically the lowest at breakfast and skewed toward dinner. Skewed protein intake patterns and inadequate PI at breakfast were reported to be negative factors for muscle maintenance.

Objectives: This study examined whether a protein-enriched meal at breakfast is more effective for muscle accretion compared with the typical skewed PI pattern.

Methods: This 12-wk, parallel-group, randomized clinical trial included 26 men (means ± SEs; age: 20.8 ± 0.4 y; BMI: 21.8 ± 0.4 kg/m2). The "high breakfast" (HBR) group (n = 12) consumed a protein-enriched meal at breakfast providing a PI of 0.33 g/kg body weight (BW); their PI at lunch (0.46 g/kg BW) and dinner (0.48 g/kg BW) provided an adequate overall daily PI (1.30 g/kg BW/d). The "low breakfast" (LBR) group (n = 14) consumed 0.12 g protein/kg BW at breakfast; intakes at lunch (0.45 g/kg BW) and dinner (0.83 g/kg BW) yielded the same daily PI as in the HBR group. The participants performed supervised resistance training (RT) 3 times per week (75-80% 1-repetition maximum; 3 sets × 10 repetitions). DXA was used to measure the primary outcome variable, that is, total lean soft tissue mass (LTM).

Results: The total LTM at baseline did not differ between the HBR (52.4 ± 1.3 kg) and LBR (53.4 ± 1.2 kg) groups. After the intervention, increases in total LTM were significant in both groups, with that in the HBR group (2.5 ± 0.3 kg) tending to be greater than that in the LBR group (1.8 ± 0.3 kg) (P = 0.06), with a large effect size (Cohen d = 0.795).

Conclusions: For RT-induced muscle hypertrophy in healthy young men, consuming a protein-enriched meal at breakfast and less protein at dinner while achieving an adequate overall PI is more effective than consuming more protein at dinner.This study was registered at University hospital Medical Information Network (UMIN) Clinical Trials Registry as UMIN000037583 (https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000042763).
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http://dx.doi.org/10.1093/jn/nxaa101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7330467PMC
July 2020

Association of Protein Intake in Three Meals with Muscle Mass in Healthy Young Subjects: A Cross-Sectional Study.

Nutrients 2019 Mar 13;11(3). Epub 2019 Mar 13.

Faculty of Sport and Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan.

Protein intake of >0.24 g/kg of body weight (BW) at a single meal is necessary to maximize muscle protein synthesis in a young population. However, the association between the protein intake rate for three meals and muscle mass in the young population has not been evaluated. We hypothesized that a protein intake of >0.24 g/kg BW at all three meals is effective for maintaining muscle mass. Therefore, we cross-sectionally examined the association between protein intake at all three meals with muscle mass in 266 healthy young subjects (aged 21.4 ± 2.4 years). Subjects were divided into the AP group, which achieved protein intake >0.24 g/kg BW at all three meals; and the NP group, which did not. We calculated total fat-free mass (FFM) and appendicular fat-free mass (AppFFM) with dual-energy X-ray absorptiometry, and the percentage of total FFM (TotalFFM%) and appendicular FFM (AppFFM%) were calculated as the percentage of BW (%BW). We demonstrated that TotalFFM% (77.0 ± 0.5 vs. 75.2 ± 0.4%, = 0.008) and AppFFM% (34.7 ± 0.3 vs. 34.1 ± 0.2%, = 0.058) were higher in the AP than in the NP group. This finding suggests that achieving protein intake of >0.24 g/kg BW at all three meals is important for muscle mass maintenance in young populations.
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http://dx.doi.org/10.3390/nu11030612DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6471574PMC
March 2019

Skipping breakfast is associated with lower fat-free mass in healthy young subjects: a cross-sectional study.

Nutr Res 2018 12 19;60:26-32. Epub 2018 Sep 19.

College of Sport and Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan. Electronic address:

Skipping breakfast has been reported to decrease daily energy and nutrient intake. We aimed to investigate whether habitual breakfast intake frequency is associated with fat-free mass (FFM) in healthy young subjects. We hypothesized that skipping breakfast and the subsequent negative energy balance may be risk factors for reduced muscle mass. This cross-sectional study included 270 healthy young subjects (152 men, 118 women). We collected information on habitual breakfast intake frequency, sleep quality according to the Pittsburgh Sleep Quality Index, circadian rhythm type using the Morningness-Eveningness Questionnaire, and physical activity using the International Physical Activity Questionnaire. According to the definition of National Health and Nutrition Examination Survey in Japan, the subjects were asked to report habitual breakfast intake frequency over the preceding month (excluding consumption of tablets, energy drinks, confectionary, fruits, dairy products, or sweetened beverages alone). FFM was assessed using dual-energy x-ray absorptiometry; then, appendicular FFM (AppFFM) was calculated. We also calculated appendicular skeletal muscle mass index (kg AppFFM/m) and %AppFFM (% body weight) to adjust body size between individuals. Multiple regression analysis showed that habitual breakfast intake frequency was positively associated with appendicular skeletal muscle mass index (β = .087, P = .031) and %AppFFM (β = .086, P = .045) after adjusting for age, sex, living conditions, Pittsburgh Sleep Quality Index, Morningness-Eveningness Questionnaire, and International Physical Activity Questionnaire scores as covariates. These findings suggest that skipping breakfast is a risk factor for lower muscle mass in healthy young subjects, irrespective of strong confounders, such as age, sex, and physical activity.
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http://dx.doi.org/10.1016/j.nutres.2018.09.006DOI Listing
December 2018

Ice slurry ingestion reduces human brain temperature measured using non-invasive magnetic resonance spectroscopy.

Sci Rep 2018 02 9;8(1):2757. Epub 2018 Feb 9.

Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, 739-8521, Japan.

We previously reported that ice slurry ingestion reduced forehead skin temperature, thereby potentially reducing brain temperature (T). Therefore, in the current study, we investigated the effect of ice slurry ingestion on T using proton magnetic resonance spectroscopy, which is a robust, non-invasive method. Eight male participants ingested 7.5 g/kg of either a thermoneutral drink (37 °C; CON) or ice slurry (-1 °C; ICE) for about 5 min following a 15-min baseline period. Then, participants remained at rest for 30 min. As physiological indices, T, rectal temperature (T), mean skin temperature, nude body mass, and urine specific gravity were measured. Subjective thermal sensation (TS) and thermal comfort (TC) were measured before and after the experiment. T and T significantly reduced after ingestion of ICE compared with after ingestion of CON, and there was a significant correlation between T and T. The other physiological indices were not significantly different between beverage conditions. TS and TC were significantly lower with ICE than with CON (p < 0.05). These results indicate that ice slurry ingestion can cool the brain, as well as the body's core.
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http://dx.doi.org/10.1038/s41598-018-21086-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5807509PMC
February 2018

The Effect of Ongoing Vitamin D and Low-Fat Milk Intake on Bone Metabolism in Female High-School Endurance Runners.

J Clin Med Res 2018 Jan 1;10(1):13-21. Epub 2017 Dec 1.

Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.

Background: Vitamin D and calcium are essential nutrients for bone health. In addition, vitamin D suppresses inflammatory cytokines and increases bone resorption. Therefore, improvements in bone health by calcium and vitamin D supplementation have the potential to not only improve calcium metabolism but also suppress inflammation associated with exercise training. The purpose of this study was to determine whether ongoing vitamin D supplementation and low-fat milk intake by female high-school endurance runners would improve bone metabolism by suppressing inflammatory cytokines and the parathyroid hormone (PTH).

Methods: Twenty female high-school runners were assigned to a vitamin D supplement and low-fat milk intake group (MKD) or a control group (CON). Participants in the MKD group consumed a vitamin D supplement (1,000 IU/day) and low-fat milk (Ca 315 mg/day) for 6 months. Bone mineral density measurements, blood samples, and questionnaires (regarding menses and diet) were carried out. The UMIN Clinical Trials Registry number is UMIN000027854.

Results: The 25-hydroxyvitamin D (25(OH)D) concentration in MKD was sustained and PTH concentration was decreased regardless of the state of menses. The correlation coefficients of 25(OH)D or PTH concentrations and bone metabolism markers were analyzed by partial correlation coefficient via adjusting the model for frequency of menses. CTX and 25(OH)D concentration were significantly and inversely correlated at baseline (r = -0.61, P < 0.01), 3 months (r = -0.54, P = 0.02), and 6 months (r = -0.53, P = 0.02). CTX and PTH were significantly and positively correlated at 3 months (r = 0.63, P < 0.01) and 6 months (r = 0.52, P = 0.02). The bone alkaline phosphatase (BAP)/CTX ratio and 25(OH)D concentration were significantly and positively correlated at 3 months (r = 0.59, P = 0.01) and 6 months (r = 0.56, P = 0.01). The BAP/CTX ratio and PTH were significantly and inversely correlated at 3 months (r = -0.59, P = 0.01) and 6 months (r = -0.58, P < 0.01).

Conclusions: This study suggested that vitamin D and low-fat milk supplementation improves bone metabolism by sustaining the 25(OH)D concentration and decreasing the PTH concentration in female high-school endurance runners regardless of the state of menses.
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http://dx.doi.org/10.14740/jocmr3209wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5722040PMC
January 2018

Hypoxia affects tissue oxygenation differently in the thigh and calf muscles during incremental running.

Eur J Appl Physiol 2017 Oct 17;117(10):2057-2064. Epub 2017 Aug 17.

Department of Sports Science, Japan Institute of Sports Sciences, Tokyo, Japan.

Purpose: The present study was performed to determine the impact of hypoxia on working muscle oxygenation during incremental running, and to compare tissue oxygenation between the thigh and calf muscles.

Methods: Nine distance runners and triathletes performed incremental running tests to exhaustion under normoxic and hypoxic conditions (fraction of inspired oxygen = 0.15). Peak pulmonary oxygen uptake ([Formula: see text]) and tissue oxygen saturation (StO) were measured simultaneously in both the vastus lateralis and medial gastrocnemius.

Results: Hypoxia significantly decreased peak running speed and [Formula: see text] (p < 0.01). During incremental running, StO in the vastus lateralis decreased almost linearly, and the rate of decrease from warm-up (180 m min) to [Formula: see text] was significantly greater than in the medial gastrocnemius under both normoxic and hypoxic conditions (p < 0.01). StO in both muscles was significantly decreased under hypoxic compared with normoxic conditions at all running speeds (p < 0.01). The rate at which StO was decreased by hypoxia was greater in the vastus lateralis as the running speed increased, whereas it changed little in the medial gastrocnemius.

Conclusions: These results suggest that the thigh is more deoxygenated than the calf under hypoxic conditions, and that the effects of hypoxia on tissue oxygenation differ between these two muscles during incremental running.
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http://dx.doi.org/10.1007/s00421-017-3696-8DOI Listing
October 2017

Do Two Tissue Blood Volume Parameters Measured by Different Near-Infrared Spectroscopy Methods Show the Same Dynamics During Incremental Running?

Adv Exp Med Biol 2016 ;876:27-33

Department of Sports Science, Japan Institute of Sports Sciences, 3-15-1 Nishigaoka, Kita-ku, Tokyo, 115-0056, Japan.

Unlabelled: Both the change in total hemoglobin concentration (cHb), assessed by near-infrared continuous-wave spectroscopy (NIR-CWS), and the normalized tissue hemoglobin index (nTHI), assessed by NIR spatially resolved spectroscopy (NIR-SRS), were used to quantify changes in tissue blood volume. However, it is possible that these parameters may show different changes because of the different measurement systems. The present study aimed to compare changes in cHb and nTHI in working muscles, which were selected for measurement because the parameters changed dynamically.

Methods: After a standing rest, seven male runners (age 24±3 years, mean±S.D.) performed an incremental running exercise test on a treadmill (inclination=1%) from 180 to 300 m min(-1). During the tests, cHb and nTHI were monitored from the vastus lateralis (VL) and medial gastrocnemius (GM) muscles. These parameters were relatively evaluated from the minimal to maximal values through the test.

Results: When the exercise began, cHb and nTHI quickly decreased and then gradually increased during running. In comparison with both VL and GM, there was significant interaction between cHb and nTHI.

Conclusions: The present results suggest that cHb and nTHI in working muscles are not always synchronized, particularly at the onset of exercise and at high intensities. Although cHb was previously used as the change of tissue blood volume, it is implied that tissue blood volume assessed by cHb is overestimated.
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http://dx.doi.org/10.1007/978-1-4939-3023-4_3DOI Listing
May 2016

Effects of Five Nights under Normobaric Hypoxia on Sleep Quality.

Med Sci Sports Exerc 2015 Jul;47(7):1512-8

1Department of Sports Sciences, Japan Institute of Sports Sciences, Nishigaoka, Kita-ku, Tokyo, JAPAN; 2Faculty of Sport Sciences, Waseda University, Mitakajima, Tokorozawa, Saitama, JAPAN; 3Director General, Japan Institute of Sports Sciences, Nishigaoka, Kita-ku, Tokyo, JAPAN.

Purpose: The purpose of this study was to evaluate the effects of five nights' sleep under normobaric hypoxia on ventilatory acclimatization and sleep quality.

Methods: Seven men initially slept for six nights under normoxia and then for five nights under normobaric hypoxia equivalent to a 2000-m altitude. Nocturnal polysomnograms (PSGs), arterial blood oxygen saturation (SpO2), and respiratory events were recorded on the first and fifth nights under both conditions.

Results: The hypoxic ventilatory response (HVR), hypercapnic ventilatory response (HCVR), and resting end-tidal CO2 (resting PETCO2) were measured three times during the experimental period. The duration of slow-wave sleep (SWS: stage N3) and the whole-night delta (1-3 Hz) power of nonrapid eye movement (NREM) sleep EEG decreased on the first night under hypoxia. This hypoxia-induced sleep quality deterioration on the first night was accompanied by a lower mean and minimum SpO2, a longer time spent with SpO2 below 90% (<90% SpO2 time), and more episodes of respiratory disturbance. On the fifth night, the SWS duration and whole-night delta power did not differ between the conditions. Although the mean SpO2 under hypoxia was still lower than under normoxia, the minimum SpO2 increased, and the <90% SpO2 time and number of episodes of respiratory disturbance decreased during the five nights under hypoxia. The HVR increased and resting PETCO2 decreased after five nights under hypoxia.

Conclusions: The results suggest that five nights under hypoxia improves the sleep quality. This may be derived from improvements of respiratory disturbances, the minimum SpO2, and <90% SpO2 time.
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http://dx.doi.org/10.1249/MSS.0000000000000569DOI Listing
July 2015

Relationship between effort sense and ventilatory response to intense exercise performed with reduced muscle glycogen.

Eur J Appl Physiol 2012 Jun 1;112(6):2149-62. Epub 2011 Oct 1.

Graduate School of Education, Hokkaido University, Kita-11, Nishi-7, Kita-ku, Sapporo 060-0811, Japan.

The purpose of the present study was to examine the effects of muscle glycogen reduction on surface electromyogram (EMG) activity and effort sense and ventilatory responses to intense exercise (IE). Eight subjects performed an IE test in which IE [100-105% of peak O(2) uptake ([Formula: see text]), 2 min] was repeated three times (IE(1st), IE(2nd) and IE(3rd)) at 100-120-min intervals. Each interval consisted of 20-min passive recovery, 40-min submaximal exercise at ventilatory threshold intensity (51.5 ± 2.7% of [Formula: see text]), and a further resting recovery for 40-60 min. Blood pH during IE and subsequent 20-min recovery was significantly higher in the IE(3rd) than in the IE(1st) (P < 0.05). Effort sense of legs during IE was significantly higher in the IE(3rd) than in the IE(1st) and IE(2nd). Integrated EMG (IEMG) measured in the vastus lateralis during IE was significantly lower in the IE(3rd) than in the IE(1st). In contrast, mean power frequency of the EMG was significantly higher in the IE(2nd) and the IE(3rd) than in the IE(1st). Ventilation ([Formula: see text]) in the IE(3rd) was significantly higher than that in the IE(1st) during IE and the first 60 s after the end of IE. These results suggest that ventilatory response to IE is independent of metabolic acidosis and at least partly associated with effort sense elicited by recruitment of type II fibers.
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http://dx.doi.org/10.1007/s00421-011-2190-yDOI Listing
June 2012

Ventilatory response to moderate incremental exercise performed 24 h after resistance exercise with concentric and eccentric contractions.

Eur J Appl Physiol 2011 Aug 9;111(8):1769-75. Epub 2011 Jan 9.

Department of Human Developmental Sciences, Faculty of Education, Hokkaido University, Kita-11, Nishi-7, Kita-ku, Sapporo, 060-0811, Japan.

In order to test our hypothesis that muscle condition has an effect on the cognition of self-motion and consequently on the ventilatory response during exercise, six healthy subjects performed a moderate incremental exercise test (IET) on a cycle ergometer under two conditions [resistance exercise condition (REC) and control condition (CC)]. In the REC, resistance exercise (30 incline leg presses) was conducted during two sessions scheduled at 48 and then 24 h prior to the IET. For the CC, the subjects were instructed to refrain from participating in strenuous exercise for a period of 2 days prior to the IET. In the IET, the workload was increased from 78 to 118 watts in steps of 8 watts every 3 min. Although the ventilatory response during the IET was significantly higher in the REC than in the CC, there were no significant differences in cognitive indexes (RPE and awareness of change in workload) between the two conditions. In addition, the magnitude of muscle soreness was significantly higher in the REC than in the CC. However, the level of soreness in the REC was very low, and there were no significant differences in blood lactate concentration and integrated EMG between the two conditions. These results suggest that a change in peripheral neural reflex is the primary cause of increased ventilatory response to moderate exercise after resistance exercise, although the role of a cognitive element cannot be absolutely excluded.
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http://dx.doi.org/10.1007/s00421-010-1801-3DOI Listing
August 2011

Effect of blood volume in resting muscle on heart rate upward drift during moderately prolonged exercise.

J Physiol Anthropol 2010 ;29(6):205-10

Laboratory of Exercise Physiology, Graduate School of Education, Hokkaido University, Sapporo, Japan.

The aim of this study was to determine whether the increase in blood volume in resting muscle during moderately prolonged exercise is related to heart rate (HR) upward drift. Eight healthy men completed both arm-cranking moderately prolonged exercise (APE) and leg-pedaling moderately prolonged exercise (LPE) for 30 min. Exercise intensity was 120 bpm of HR that was determined by ramp incremental exercise. During both APE and LPE, HR significantly increased from 3 to 30 min (from 108±9.3 to 119±12 bpm and from 112±8.9 to 122±11 bpm, respectively). However, there was no significant difference between HR in APE and that in LPE. Oxygen uptake was maintained throughout the two exercises. Skin blood flow, deep temperature, and total Hb (blood volume) in resting muscle continuously increased for 30 min of exercise during both APE and LPE. During both APE and LPE, there was a significant positive correlation between total Hb and deep temperature in all subjects. Moreover, there was a significant positive correlation between HR and total Hb (in seven out of eight subjects) during LPE. However, during APE, there was no positive correlation between HR and total Hb (r=0.391). These findings suggest that an increase of blood pooling in resting muscle could be proposed as one of the mechanisms underlying HR upward drift during moderately prolonged exercise.
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http://dx.doi.org/10.2114/jpa2.29.205DOI Listing
March 2011

Effects of sodium bicarbonate ingestion on EMG, effort sense and ventilatory response during intense exercise and subsequent active recovery.

Eur J Appl Physiol 2011 May 10;111(5):851-8. Epub 2010 Nov 10.

Graduate School of Education, Hokkaido University, Kita-11, Nishi-7, Kita-ku, Sapporo, 060-0811, Japan.

To determine whether post-exercise ventilation is related to decrease in blood pH and also whether post-exercise ventilation, associated or not with decreased blood pH, involves an increase in central motor command during exercise, we examined the effects of NaHCO(3) ingestion on the ventilatory response ([Formula: see text]E), integrated electromyogram (iEMG) and effort sense of legs (ESL) during intense exercise (IE) and subsequent active recovery. Subjects performed two IE tests (105-110% of maximal work rate, 2 min) after ingestion of NaHCO(3) or CaCO(3). Subjects performed light load exercise (20 W) before and after IE for 6 min and 30 min, respectively. Although there was a significant difference in blood pH between the two conditions during and after IE, [Formula: see text]E, iEMG and ESL were similar. iEMG returned to the pre-IE level immediately after the end of IE, while ESL showed slow recovery. [Formula: see text]E decreased rapidly until about 50 s after the end of IE (fast phase) and then showed a slow recovery kinetics (slow phase). The ventilatory responses during the fast phase and during the slow phase were correlated with ESL at the end of IE and from 3 min after the end of IE, respectively. Moreover, there was no significant difference in the slopes and intercepts of regression lines between [Formula: see text]E and ESL under the two conditions in both phases. These results suggest that the ventilatory response after IE is associated with effort sense indirectly-elicited by central motor command, but the effort sense-mediated response is not affected by blood pH.
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http://dx.doi.org/10.1007/s00421-010-1715-0DOI Listing
May 2011

Effects of awareness of change in load on ventilatory response during moderate exercise.

Respir Physiol Neurobiol 2009 Oct 22;169(1):69-73. Epub 2009 Aug 22.

Department of Human Developmental Sciences, Faculty of Education, Hokkaido University, Kita-11, Nishi-7, Kita-ku, Sapporo 060-0811, Japan.

This study was designed to determine whether awareness of change in load alters ventilatory response during moderate exercise. Subjects performed two incremental exercise protocols on a cycle ergometer. The load was increased from 1.0 to 1.5kp in steps of 0.1kp every 3min. Subjects were provided true information about the load in the control protocol and untrue information that the load would remain constant in the deception protocol. Slope of ventilation against CO2 output was significantly lower in the deception protocol than control protocol. Integrated EMG (iEMG) and ratings of perceived exertion (RPE) were similar between the two protocols, but awareness of change in load was significantly attenuated by the deception protocol. However, there was no temporal coincidence between awareness and actual change in load. These results suggest that ventilatory response during moderate exercise depends not so much on RPE but mainly on awareness or attention that is closely connected to information detection.
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http://dx.doi.org/10.1016/j.resp.2009.08.009DOI Listing
October 2009

Examination of oxygen uptake kinetics in decremental load exercise by a numerical computation model.

J Physiol Anthropol 2008 Sep;27(5):247-54

Laboratory of Exercise Physiology, Health and Sport Education, Graduate School of Education, Hokkaido University.

The purpose of this study was to establish a numerical computation model for estimation of oxygen uptake (V(.)O2) kinetics in decremental load exercise (DLE) starting from a work rate (WR) above the ventilatory threshold (>VT). In the model, WR in DLE were separated into several steps (constant load exercise, CLE) of which the durations increased step by step. V(.)O2 kinetics in each step was estimated using an exponential equation, and the sum of VO2 values from all steps at a given time was regarded as simulated V(.)O2 in DLE. In the model, the time constants were set symmetrically in a step VT at onset and offset (tau(off)) of exercise. As a result, simulated V(.)O2 qualitatively, but not quantitatively, approximated measured V(.)O2. Consequently, we incorporated a new model in which a step >VT was subdivided into several parts. Although there was a slight difference quantitatively, the interval of subdivision of 3.0 min and tau(off) of 2.8 min allowed for qualitative approximation. The numerical computation model adopted in this study is useful for estimation of V(.)O2 kinetics during DLE starting from high intensity (>VT).
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http://dx.doi.org/10.2114/jpa2.27.247DOI Listing
September 2008

Effect of oral administration of sodium bicarbonate on surface EMG activity during repeated cycling sprints.

Eur J Appl Physiol 2007 Nov 13;101(4):409-17. Epub 2007 Jul 13.

Laboratory of Exercise Physiology, Graduate School of Education, Hokkaido University, Kita-11, Nishi-7, Kita-ku, Sapporo, 060-0811, Japan.

The purpose of this study was to determine the effect of oral administration of sodium bicarbonate (NaHCO3) on surface electromyogram (SEMG) activity from the vastus lateralis (VL) during repeated cycling sprints (RCS). Subjects performed two RCS tests (ten 10-s sprints) interspersed with both 30-s and 360-s recovery periods 1 h after oral administration of either NaHCO3 (RCSAlk) or CaCO3 (RCSPla) in a random counterbalanced order. Recovery periods of 360 s were set before the 5th and 9th sprints. The rate of decrease in plasma HCO3- concentration during RCS was significantly greater in RCSAlk than in RCSPla, but the rates of decline in blood pH during the two RCS tests were similar. There was no difference between change in plasma lactate concentration in RCSAlk and that in RCSPla. Performance during RCSAlk was similar to that during RCSPla. There were no differences in oxygen uptake immediately before each cycling sprint (preVO2) and in SEMG activity between RCSAlk and RCSPla. In conclusion, oral administration of NaHCO3 did not affect SEMG activity from the VL. This suggests that the muscle recruitment strategy during RCS is not determined by only intramuscular pH.
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http://dx.doi.org/10.1007/s00421-007-0512-xDOI Listing
November 2007

A 350-S recovery period does not necessarily allow complete recovery of peak power output during repeated cycling sprints.

J Physiol Anthropol 2007 Mar;26(2):51-7

Laboratory of Exercise Physiology, Graduate School of Education, Hokkaido University, Sapporo, Japan.

The aim of this study was to determine whether a 350-s recovery period allows recovery of peak power output (PPO) to its initial value under the condition of a blood lactate (La) concentration higher than 10 mmol.L-1 during repeated cycling sprints (RCS). RCS (10x10-s cycling sprints) were performed under two conditions. Under one condition, the recovery period of RCS was fixed at 35 s (RCS35), and under the other condition, a 350-s recovery period was set before the 5th and 9th sets, and a 35-s recovery period was set before the other sets (RCScomb). In RCScomb, PPO in the 5th set recovered to that in the 1st set, but PPO in the 9th set did not. Under both conditions, blood La concentration progressively increased and reached approximately 14 mmol.L-1 at the end of the RCS. In RCScomb, VO2 immediately before the 5th set was not significantly different from that immediately before the 9th set. Mean power frequency (MPF) values estimated by a surface electromyogram from the vastus lateralis in the 5th and 9th sets were significantly higher in RCScomb than in RCS35. In conclusion, a 350-s recovery period does not allow recovery of PPO to its initial value under the condition of a blood La concentration of 14 mmol.L-1 during RCS.
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http://dx.doi.org/10.2114/jpa2.26.51DOI Listing
March 2007

Effect of blood lactate concentration and the level of oxygen uptake immediately before a cycling sprint on neuromuscular activation during repeated cycling sprints.

J Physiol Anthropol 2006 Jul;25(4):267-73

Laboratory of Exercise Physiology, Graduate School of Education, Hokkaido University, Sapporo, Japan.

The purpose of this study was to determine whether neuromuscular activation is affected by blood lactate concentration (La) and the level of oxygen uptake immediately before a cycling sprint (preVO(2)). The tests consisted of ten repeated cycling sprints for 10 sec with 35-sec (RCS(35)) and 350-sec recovery periods (RCS(350)). Peak power output (PPO) was not significantly changed despite an increase in La concentration up to 12 mmol/L in RCS(350). Mean power frequency (MPF) of the power spectrum calculated from a surface electromyogram on the vastus lateralis showed a significantly higher level in RCS(350). In RCS(35), preVO(2) level and La were higher than those in RCS(350) in the initial stage of the RCS and in the last half of the RCS, respectively. Thus, neuromuscular activation during exercise with maximal effort is affected by blood lactate concentration and the level of oxygen uptake immediately before exercise, suggesting a cyclic system between muscle recruitment pattern and muscle metabolites.
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http://dx.doi.org/10.2114/jpa2.25.267DOI Listing
July 2006
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