Oxygen uptake during the last bouts of exercise incorporated into high-intensity intermittent cross-exercise exceeds the V˙ O2max of the same exercise mode.

Oxygen uptake (V˙ O2) was measured during a non-exhaustive high-intensity intermittent cross-exercise (HIICE) protocol consisting of four alternating bouts of 20 â€‹s running (R) and three bouts of bicycle exercise (BE) at ∼160% and ∼170% maximal oxygen uptake (V˙ O2max), respectively, with 10 â€‹s between-bout rests (sequence R-BE-R-BE-R-BE-R). The V˙ O2 during the last BE ([52.2 â€‹± â€‹5.0] mL·kg-1·min-1) was significantly higher than the V˙ O2max of the BE ([48.0 â€‹± â€‹5.4] mL·kg-1·min-1, n â€‹= â€‹30) and similar to that of running. For clarifying the underlying mechanisms, a corresponding HIICE-protocol with BE and arm cranking ergometer exercise (AC) was used (sequence AC-AC-BE-AC-BE-AC-AC-BE). In some experiments, thigh blood flow was occluded by a cuff around the upper thigh. Without occlusion, the V˙ O2 during the AC ([39.2 â€‹± â€‹7.1] mL·kg-1·min-1 [6th bout]) was significantly higher than the V˙ O2max of AC ([30.2 â€‹± â€‹4.4] mL·kg-1·min-1, n â€‹= â€‹7). With occlusion, the corresponding V˙ O2 ([29.8 â€‹± â€‹3.9] mL·kg-1·min-1) was reduced to that of the V˙ O2max of AC and significantly less than the V˙ O2 without occlusion. These findings suggest that during the last bouts of HIICE may exceed the of the specific exercise, probably because it is a summation of the V˙ O2 for the ongoing exercise plus excess post-oxygen consumption (EPOC) produced by the previous exercise with a higher V˙ O2max.

Effect of Exogenous Acute ß-Hydroxybutyrate Administration on Different Modalities of Exercise Performance in Healthy Rats.

PURPOSE: A ketone body (ß-hydroxybutyrate [ß-HB]) is used as an energy source in the peripheral tissues. However, the effects of acute ß-HB supplementation on different modalities of exercise performance remain unclear. This study aimed to assess the effects of acute ß-HB administration on the exercise performance of rats. METHODS: In study 1, Sprague-Dawley rats were randomly divided into six groups: endurance exercise (EE + PL and EE + KE), resistance exercise (RE + PL and RE + KE), and high-intensity intermittent exercise (HIIE + PL and HIIE + KE) with placebo (PL) or ß-HB salt (KE) administration. In study 2, metabolome analysis using capillary electrophoresis mass spectrometry was performed to profile the effects of ß-HB salt administration on HIIE-induced metabolic responses in the skeletal and heart muscles. RESULTS: The maximal carrying capacity (rest for 3 min after each ladder climb, while carrying heavy weights until the rats could not climb) in the RE + KE group was higher than that in the RE + PL group. The maximum number of HIIE sessions (a 20-s swimming session with a 10-s rest between sessions, while bearing a weight equivalent to 16% of body weight) in the HIIE + KE group was higher than that in the HIIE + PL group. However, there was no significant difference in the time to exhaustion at 30 m·min -1 between the EE + PL and the EE + KE groups. Metabolome analysis showed that the overall tricarboxylic acid cycle and creatine phosphate levels in the skeletal muscle were higher in the HIIE + KE group than those in the HIIE + PL group. CONCLUSIONS: These results indicate that acute ß-HB salt administration may accelerate HIIE and RE performance, and the changes in metabolic responses in the skeletal muscle after ß-HB salt administration may be involved in the enhancement of HIIE performance.

Effect of acute high-intensity intermittent exercise on serum brain-derived neurotrophic factor concentrations.

BACKGROUND: This study aimed to examine changes in serum brain-derived neurotrophic factor (BDNF) concentrations after exhaustive high-intensity intermittent exercise (HIIE) and non-exhaustive HIIE, and to compare the two conditions. METHODS: Eight healthy male college students (age: 22±1 year) participated in exhaustive (sets: 6-7) and non-exhaustive (sets: 5) HIIE. In both conditions, participants repeated sets of 20 seconds of exercise at 170% V̇O2max with 10 seconds of rest between sets. Serum BDNF was measured 8 times in each condition: 30 minutes after resting, 10 minutes after sitting, immediately after HIIE, and 5, 10, 30, 60, and 90 minutes after main exercise. Changes in serum BDNF concentrations over time and between measurement points in both conditions were measured using a two-way repeated measures ANOVA. RESULTS: Serum BDNF concentrations were measured, revealing significant interaction between two factors (conditions and measurement points) (F=3.482, P=0.027). In the exhaustive HIIE, there were significant increases at 5 minutes (P<0.01) and 10 minutes (P<0.01) after exercise compared to after resting. In the non-exhaustive HIIE, there was a significant increase immediately after (P<0.01) and 5 minutes after (P<0.01) exercise compared to resting. Comparison of the serum BDNF concentrations at each measurement point showed a significant difference at 10 minutes after exercise, with significantly higher values for the exhaustive HIIE condition (P<0.01, r=0.60). CONCLUSIONS: Exhaustive and non-exhaustive HIIE are time-efficient exercises that increase serum BDNF concentrations in healthy adults.

Effects of Prolonged Sitting with or without Elastic Garments on Limb Volume, Arterial Blood Flow, and Muscle Oxygenation.

PURPOSE: The physiological response induced by acute prolonged sitting is not fully understood. Therefore, we examined the effects of 8-h constant sitting on microcirculation and associated factors in the lower extremity among healthy males. We also evaluated the protective effects of lower-pressure thigh-length elastic compression garments on these parameters. METHODS: Nine healthy males (age, 22.6 ± 1.4 yr; body mass index, 22.4 ± 1.8 kg·m-2) completed the 8-h constant sitting experiment. Following baseline measurements, each subject was randomized to wear a lower-pressure elastic garment on the right or left leg from the inguinal region to the ankle joint, with the noncompressed contralateral leg as a control. Circumferences of the calf and malleolus, extracellular water contents, blood flow and shear rate of the dorsal metatarsal artery, and oxygen dynamics in the gastrocnemius muscles were measured in both extremities before and during 8-h constant sitting. RESULTS: Compared with baseline values, 8-h constant sitting caused enlargement of circumferences (calf, 2.4% ± 0.7%; malleolus, 2.7% ± 1.4%), retention of extracellular water in lower extremity muscles (10.1% ± 1.78%), deterioration of the blood flow (61.4% ± 16.2% of baseline) and shear rate of the dorsal metatarsal artery, and decrease in oxygenated hemoglobin and total hemoglobin levels in the gastrocnemius muscle (P < 0.05, respectively). When subjects wore the lower-pressure thigh-length compression garment, a significant reduction of these effects was observed (P < 0.05, for all). CONCLUSIONS: Prolonged sitting for 8 h induced edema, as well as deterioration of the arterial blood flow, shear rate, and microcirculation in lower limb muscles. Conversely, application of the lower-pressure elastic garment successfully prevented the pathophysiological deterioration associated with prolonged sitting.

Tabata training: one of the most energetically effective high-intensity intermittent training methods.

For decades, high-intensity interval/intermittent exercise training methods have been used by elite athletes to improve their performance in sports. One of the most effective training methods, i.e., 'Tabata training,' is reviewed herein from the viewpoint of the energetics of exercise. The prior research describing the metabolic profile and effects of Tabata training is also summarized, with some historical anecdotes.

Gene expression profile of muscle adaptation to high-intensity intermittent exercise training in young men.

High-intensity intermittent exercise training (HIIT) has been proposed as an effective approach for improving both, the aerobic and anaerobic exercise capacity. However, the detailed molecular response of the skeletal muscle to HIIT remains unknown. We examined the effects of the HIIT on the global gene expression in the human skeletal muscle. Eleven young healthy men participated in the study and completed a 6-week HIIT program involving exhaustive 6-7 sets of 20-s cycling periods with 10-s rests. In addition to determining the maximal oxygen uptake ([Formula: see text]), maximal accumulated oxygen deficit, and thigh muscle cross-sectional area (CSA), muscle biopsy samples were obtained from the vastus lateralis before and after the training to analyse the skeletal muscle transcriptome. The HIIT program significantly increased the [Formula: see text], maximal accumulated oxygen deficit, and thigh muscle CSA. The expression of 79 genes was significantly elevated (fold-change >1.2), and that of 73 genes was significantly reduced (fold-change <0.8) after HIIT. Gene ontology analysis of the up-regulated genes revealed that the significantly enriched categories were "glucose metabolism", "extracellular matrix", "angiogenesis", and "mitochondrial membrane". By providing information about a set of genes in the human skeletal muscle that responds to the HIIT, the study provided insight into the mechanism of skeletal muscle adaptation to HIIT.

Effects of Different Exercise Modes on Arterial Stiffness and Nitric Oxide Synthesis.

PURPOSE: Aerobic training (AT) and high-intensity intermittent training (HIIT) reduce arterial stiffness, whereas resistance training (RT) induces deterioration of or no change in arterial stiffness. However, the molecular mechanism of these effects of different exercise modes remains unclear. This study aimed to clarify the difference of different exercise effects on endothelial nitric oxide synthase (eNOS) signaling pathway and arterial stiffness in rats and humans. METHODS: In the animal study, forty 10-wk-old male Sprague-Dawley rats were randomly divided into four groups: sedentary control (CON), AT (treadmill running, 60 min at 30 m·min, 5 d·wk for 8 wk), RT (ladder climbing, 8-10 sets per day, 3 d·wk for 8 wk), and HIIT (14 repeats of 20-s swimming session with 10-s pause between sessions, 4 d·wk for 6 wk from 12-wk-old) groups (n = 10 in each group). In the human study, we confirmed the effects of 6-wk HIIT and 8-wk AT interventions on central arterial stiffness and plasma nitrite/nitrate level in untrained healthy young men in randomized controlled trial (HIIT, AT, and CON; n = 7 in each group). RESULTS: In the animal study, the effect on aortic pulse wave velocity (PWV), as an index of central arterial stiffness, after HIIT was the same as the decrease in aortic PWV and increase in arterial eNOS/Akt phosphorylation after AT, which was not changed by RT. A negative correlation between aortic PWV and eNOS phosphorylation was observed (r = -0.38, P < 0.05). In the human study, HIIT- and AT-induced changes in carotid-femoral PWV (HIIT -115.3 ± 63.4 and AT -157.7 ± 45.7 vs CON 71.3 ± 61.1 m·s, each P < 0.05) decreased, and plasma nitrite/nitrate level increased compared with those in CON. CONCLUSIONS: HIIT may reduce central arterial stiffness via the increase in aortic nitric oxide bioavailability despite it being done in a short time and short term and has the same effects as AT.

Effects of short-lasting supramaximal-intensity exercise on diet-induced increase in oxygen uptake.

This study was undertaken to quantify the additional increase in diet-induced oxygen uptake after exhaustive high-intensity intermittent exercise (HIIE), consisting of 6-7 bouts of 20-sec bicycle exercise (intensity: 170% V˙O2max) with a 10-sec rest between bouts. Using a metabolic chamber, the oxygen uptake of ten men was measured from 10:30 am to 07:00 am the next day on two separate days with or without HIIE, with lunch (12:00) and supper (18:00) (Diet experiment). On two other days, the oxygen uptake of six different subjects was measured from 10:30 to 16:00 with or without HIIE, but without meals (Fasting experiment). Ten minutes of exercise at 50% V˙O2maxpreceded the HIIE in both experiments; EPOC (excess postexercise oxygen consumption) after HIIE was found to wear off before 12:00 in both experiments. In the Diet experiment, oxygen uptake during HIIE and EPOC were 123.4 ± 12.0 and 115.3 ± 32.3 mL·kg-1, respectively. Meals elevated resting oxygen uptake on both days, but those on the HIIE day were significantly higher than on the control day. This enhanced diet-induced oxygen uptake (difference in resting oxygen uptake from 12:00-23:00 between HIIE and control day: ΔDIT) was 146.1 ± 90.9 mL·kg-1, comparable to the oxygen uptake during the HIIE and EPOC The ΔDIT was correlated with subjects' V˙O2max(52.1 ± 6.6 mL·kg-1·min-1) (r = 0.76, n = 10, P < 0.05). We concluded that HIIE enhances diet-induced oxygen uptake significantly, and that it is related to the cardiorespiratory fitness.

A Mechanism Underlying Preventive Effect of High-Intensity Training on Colon Cancer.

INTRODUCTION: We examined effects of high-intensity training on chemically induced aberrant crypt foci (ACF) in rat colon. We also investigated mechanisms that may underlie the results obtained, with a focus on secreted protein acidic and rich in cysteine (SPARC), which has been proposed as an exercise-related factor of colon cancer prevention. METHODS: After an administration of 1,2-dimethylhydrazine, F344 rats executed high-intensity intermittent swimming training (HIIST) (twelve 20-s swimming with a weight [16% body weight] with 10-s pauses between the bouts) 5 d·wk for 4 wk. The acute and chronic effects of the HIIST on SPARC were evaluated in rats. We evaluated the in vitro and in vivo effects of 5' AMP-activated protein kinase (AMPK) activator on SPARC in rat serum and epitrochlearis muscle. In human subjects, we determined serum SPARC after exhaustive bicycling consisting of six to seven bouts of exercise at 170% V˙O2max with 10-s rests between the bouts (high-intensity intermittent bicycling [HIIB]). The SPARC mRNA in human vastus lateralis was measured before and after the HIIB for 4 d·wk for 6 wk (HIIB-training [HIIBT]). RESULTS: The numbers of ACF were lower in the HIIST (47 ± 22) compared with the control (122 ± 47) rats (P < 0.05). SPARC in epitrochlearis and serum after HIIS of the trained rat was higher than that in the control resting rats. In vitro and vivo AMPK stimulation increased mRNA and SPARC protein in rat epitrochlearis, respectively. The human serum SPARC after the HIIB was elevated. SPARC mRNA in human muscle was elevated after the HIIBT. CONCLUSIONS: The results demonstrated that HIIST inhibits 1,2-dimethylhydrazine-induced colon ACF development. This effect may be explained by SPARC induction by the exercise intensity-related factor AMPK, potentially explaining the preventive effects of high-intensity intermittent exercise training against colon cancer.

High-intensity intermittent exercise training with chlorella intake accelerates exercise performance and muscle glycolytic and oxidative capacity in rats.

The purpose of this study was to investigate the effect of chronic chlorella intake alone or in combination with high-intensity intermittent exercise (HIIE) training on exercise performance and muscle glycolytic and oxidative metabolism in rats. Forty male Sprague-Dawley rats were randomly assigned to the four groups: sedentary control, chlorella intake (0.5% chlorella powder in normal feed), HIIE training, and combination of HIIE training and chlorella intake for 6 wk (n = 10 each group). HIIE training comprised 14 repeats of a 20-s swimming session with a 10-s pause between sessions, while bearing a weight equivalent to 16% of body weight, 4 days/week. Exercise performance was tested after the interventions by measuring the maximal number of HIIE sessions that could be completed. Chlorella intake and HIIE training significantly increased the maximal number of HIIE sessions and enhanced the expression of monocarboxylate transporter (MCT)1, MCT4, and peroxisome proliferator-activated receptor γ coactivator-1α concomitantly with the activities of lactate dehydrogenase (LDH), phosphofructokinase, citrate synthase (CS), and cytochrome-c oxidase (COX) in the red region of the gastrocnemius muscle. Furthermore, the combination further augmented the increased exercise performance and the enhanced expressions and activities. By contrast, in the white region of the muscle, MCT1 expression and LDH, CS, and COX activities did not change. These results showed that compared with only chlorella intake and only HIIE training, chlorella intake combined with HIIE training has a more pronounced effect on exercise performance and muscle glycolytic and oxidative metabolism, in particular, lactate metabolism.

Endurance training-induced increase in circulating irisin levels is associated with reduction of abdominal visceral fat in middle-aged and older adults.

To elucidate the effects of endurance training on circulating irisin levels in young and middle-aged/older adults, and to determine the association between endurance training-induced alteration of irisin and reduction in body fat. Twenty-five healthy young (age 21 ± 1 years; 16 men, 9 women) and 28 healthy middle-aged/older adults (age 67 ± 8 years; 12 men, 16 women) participated in the study. Each age cohort was divided into two groups: the endurance-training group (14 young, 14 middle-aged/older) and the control group. Subjects in the training groups completed an 8-week endurance-training program (cycling at 60-70% peak oxygen uptake [V̇O2peak] for 45 min, 3 days/week). Before and after the intervention, we evaluated serum irisin level, V̇O2peak, and body composition. The increase in V̇O2peak in the young and middle-aged/older training groups after the intervention period was significantly greater than those in the young and middle-aged/older control groups (P < 0.05). Serum irisin level was significantly increased in the middle-aged/older training group after the intervention period (P < 0.01), but not in the young training group. Furthermore, in the middle-aged/older training group, the endurance training-induced reduction in visceral adipose tissue area was negatively correlated with the change in serum irisin level (r = -0.54, P < 0.05). These results suggest a possible role for secreted irisin in the exercise-induced alteration of abdominal visceral fat in middle-aged and older adults.

Calf circumference as a surrogate marker of muscle mass for diagnosing sarcopenia in Japanese men and women.

AIM: To examine the relationship between calf circumference and muscle mass, and to evaluate the suitability of calf circumference as a surrogate marker of muscle mass for the diagnosis of sarcopenia among middle-aged and older Japanese men and women. METHODS: A total of 526 adults aged 40-89 years participated in the present cross-sectional study. The maximum calf circumference was measured in a standing position. Appendicular skeletal muscle mass was measured using dual-energy X-ray absorptiometry, and the skeletal muscle index was calculated as appendicular skeletal muscle mass divided by the square of the height (kg/m(2)). The cut-off values for sarcopenia were defined as a skeletal muscle index of less than -2 standard deviations of the mean value for Japanese young adults, as defined previously. RESULTS: Calf circumference was positively correlated with appendicular skeletal muscle (r = 0.81 in men, r = 0.73 in women) and skeletal muscle index (r = 0.80 in men, r = 0.69 in women). In receiver operating characteristic analysis, the optimal calf circumference cut-off values for predicting sarcopenia were 34 cm (sensitivity 88%, specificity 91%) in men and 33 cm (sensitivity 76%, specificity 73%) in women. CONCLUSIONS: Calf circumference was positively correlated with appendicular skeletal muscle mass and skeletal muscle index, and could be used as a surrogate marker of muscle mass for diagnosing sarcopenia. The suggested cut-off values of calf circumference for predicting low muscle mass are <34 cm in men and <33 cm in women.

Associations between the Serum 25(OH)D Concentration and Lipid Profiles in Japanese Men.

AIM: Low circulating 25-hydroxyvitamin D [25(OH)D] concentration has been linked to a high prevalence of cardiovascular disease. One explanation for this phenomenon is that there is an association between the serum 25(OH)D level and lipid profiles. However, studies examining this relationship are limited and have yielded inconsistent results. We thus aimed to evaluate the association between the serum 25(OH)D concentration and lipid profiles in Japanese men taking into consideration confounding factors, including the visceral fat area (VFA) and cardiorespiratory fitness. METHODS: A total of 136 men (age range: 20-79 years) participated in our study. Fasting blood samples were analyzed to determine the 25(OH)D, oxidized low-density lipoprotein (oxLDL), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), apolipoprotein (Apo)A-1 and ApoB levels. The VFA was evaluated on magnetic resonance imaging (MRI), and cardiorespiratory fitness was assessed by measuring the peak oxygen uptake (VO2 peak). RESULTS: The median 25(OH)D concentration was 35.6 nmol/L, and the prevalence of 25(OH)D deficiency was 78.7%. A multiple linear regression analysis revealed that the serum 25(OH)D concentration was inversely related to the LDL-C/HDL-C, TG, ApoB and ApoB/ApoA-1 values, even after adjusting for age, season, smoking status, alcohol consumption, medication use, vitamin D intake, calcium intake, VFA and cardiorespiratory fitness. CONCLUSIONS: Serum 25(OH)D level is inversely correlated with the LDL-C/HDL-C, TG, ApoB and ApoB/ApoA-1 values in Japanese men, independent of the VFA and cardiorespiratory fitness.

Circulating leptin levels are associated with physical activity or physical fitness in Japanese.

OBJECTIVE: The aim of this study was to evaluate the link between circulating leptin levels and physical activity and/or physical fitness in apparently healthy Japanese. METHODS: A total of 85 men and 111 women who were not taking any medication were enrolled in this cross-sectional study. Circulating leptin levels, physical activity measured by tri-axial accelerometers and peak oxygen uptake were evaluated. We also assessed anthropometric data, blood pressure, blood examinations and energy intake. RESULTS: Circulating leptin levels were 3.2 ± 2.3 ng/mL in men and 5.9 ± 3.8 ng/mL in women. Circulating leptin levels were significantly and positively correlated with body weight, body mass index, abdominal circumference, insulin and the homeostasis model assessment index, and significantly and negatively correlated with peak oxygen uptake in both sexes. Stepwise multiple regression showed that peak oxygen uptake in men and physical activity evaluated by Σ[metabolic equivalents h per week(METs h/w)]. in women were determinant factors for circulating leptin levels after adjusting for confounding factors.

Circulating adiponectin levels are associated with peak oxygen uptake in Japanese.

OBJECTIVE: The aim of this study was to investigate the link between circulating adiponectin levels and peak oxygen uptake and/or physical activity in Japanese. METHODS: A total of 528 subjects (188 men and 340 women) were enrolled in this cross-sectional study. Circulating adiponectin levels, physical activity measured by tri-axial accelerometers, peak oxygen uptake and metabolic risk parameters were evaluated. We also assessed anthropometric factors, blood pressure, blood examinations and energy intake. RESULTS: Circulating adiponectin levels were 6.7 ± 3.0 µg/mL in men and 11.0 ± 4.9 µg/mL in women. Circulating adiponectin levels were positively correlated with physical fitness after adjusting for age, physical activity evaluated by Σ [metabolic equivalents × h per week (METs h/w)], cigarette smoking habit and energy intake in both sexes. However, these associations were attenuated further after adjusting for body mass index including other confounding factors, especially in men. However, circulating adiponectin levels were not associated with physical activity in either sex. CONCLUSION: Circulating adiponectin levels were associated with peak oxygen uptake rather than physical activity.

Association between serum 25-hydroxyvitamin D and inflammatory cytokines in healthy adults.

Here, we aimed to examine the associations between levels of serum 25-hydroxyvitamin D [25(OH)D] and inflammatory cytokines in healthy Japanese adults. A total of 95 healthy adults (61 women; age range 21-69 years) participated in our study. Fasting blood samples were analyzed for 25(OH)D, 1,25-dihydroxyvitamin D [1,25(OH)2D], interferon-γ (IFN-γ), interleukin-6 (IL-6), and interleukin-17 (IL-17) levels using enzyme-linked immunosorbent assays kits. Total percent body fat was determined by dual energy X-ray absorptiometry (DXA). Moderate to vigorous physical activity (MVPA) was assessed objectively using an activity monitor for 7 days. The mean 25(OH)D concentration was 34.7 nmol/L, and 83 subjects had 25(OH)D concentrations less than 50 nmol/L. Multiple linear regression analysis revealed that serum 25(OH)D level was positively related to plasma IL-17 level (ß=0.26, p=0.025), after adjustment for gender, age, vitamin D intake, alcohol consumption, smoking status, and percent body fat. This relationship remained statistically significant (ß=0.28, p=0.019) even after additional adjustment for MVPA. However, no significant association was found between serum 25(OH)D level and plasma IFN-γ or IL-6 levels. In conclusion, this study identified a high prevalence of vitamin D deficiency in healthy Japanese adults. Serum 25(OH)D level was positively related to IL-17 level, independent of physical activity.

Serum vaspin levels are associated with physical activity or physical fitness in Japanese: a pilot study.

AIM: To investigate the link between serum vaspin levels and physical activity and/or physical fitness in Japanese. METHODS: A total of 156 subjects (81 men and 75 women) was enrolled in this cross-sectional study. Serum vaspin levels, physical activity by uniaxial accelerometers, peak oxygen uptake, and metabolic risk parameters were evaluated. We also assessed anthropometric and body composition parameters. RESULTS: Serum vaspin levels were over the level of 10 ng/mL in 15 subjects (9.6 %: Vaspin High group). In Vaspin Low group (<5 ng/mL: 74 men and 67 women), serum vaspin levels were 0.12 ± 0.18 ng/mL in men and 0.39 ± 0.70 ng/mL in women. Peak oxygen uptake was significantly and positively correlated with serum vaspin levels even after adjusting for age, physical activity evaluated by Σ[metabolic equivalents × h per week (METs[Symbol: see text]h/w)], BMI, and other confounding factors in men. In turn, physical activity was significantly and positively correlated with serum vaspin levels even after adjusting for confounding factors in women. CONCLUSION: Serum vaspin levels were closely associated with physical fitness in men and physical activity in women independent of body composition in this Japanese cohort.

Light-intensity physical activity is associated with insulin resistance in elderly Japanese women independent of moderate-to vigorous-intensity physical activity.

BACKGROUND: It is unclear whether light physical activity is beneficially associated with insulin resistance, similar to moderate and/or vigorous physical activity. This cross-sectional study was performed to determine the relationship between the amount of light physical activity, as determined with a triaxial accelerometer, and insulin resistance. METHODS: A total of 807 healthy men and women participated in this study. Physical activity was measured using a triaxial accelerometer worn for 28 days and summarized as light intensity (1.1-2.9 METs) or moderate to vigorous intensity (≥ 3.0 METs). Insulin resistance was evaluated by HOMA_R (FPG [mg/dL] × IRI [µU/mL]/405). RESULTS: The daily time spent in light physical activity was inversely associated with HOMA_R (r = -0.173, P < 0.05). After adjustment for confounders, the association between light physical activity and HOMA_R remained statistically significant (ß = -0.119, P < .05). Light physical activity remained significantly associated with HOMA_R following further adjustment for moderate to vigorous intensity activity (ß = -0.125, P < .05). Similar results were observed when light physical activity was modeled as quartiles, especially in elderly women. CONCLUSIONS: These cross-sectional data suggest that light-intensity physical activity is beneficially associated with insulin resistance in elderly Japanese women.

The relationship of body composition to daily physical activity in free-living Japanese adult men.

The objective of the present study was to investigate whether a previously reported apparent negative relationship between fat mass and daily physical activity in Japanese adult women would also be observed in Japanese adult men. The subjects were grouped into quartiles of BMI and body fat percentage (%BF). The number of steps walked each day and the duration of light- to vigorous-intensity physical activity were assessed by an accelerometer over the same period of time as for the doubly labelled water experiment. The results showed that BMI negatively correlated with the number of steps and time spent in moderate-intensity physical activity, whereas %BF showed a negative relationship with physical activity-related energy expenditure (PAEE)/body weight (BW) and physical activity level. The analysis of data using %BF quartiles revealed that PAEE/BW decreased from the second quartile in which the BMI was < 25 kg/m2. These observations are similar to those reported in our previous study in Japanese adult women. These cross-sectional studies cannot prove causality, and that obesity causes physical inactivity may be the case. However, the results of the present study provide information regarding which physical activity variables should be used in longitudinal studies.

Steps per day required for meeting physical activity guidelines in Japanese adults.

BACKGROUND: This study aimed to determine the optimal number of steps per day needed to meet the current physical activity guidelines in a large population sample of Japanese adults. METHODS: An accelerometer-based activity monitor (Kenz Lifecorder) was used to simultaneously measure moderate-to-vigorous intensity physical activity (MVPA) and step counts in 940 Japanese adults (480 women) aged 20 to 69 years. The step count per day equivalents to 2 different physical activity recommendations (23 MET-h/wk and 150 min/wk of MVPA) were derived using linear regression analysis and receiver operating characteristic (ROC) methodology. RESULTS: Linear regression analysis showed that daily step counts correlated with weekly PAEE (r = .83) and daily minutes of MVPA (r = .83). Linear regression analysis also showed that 23 MET-h/wk of MVPA is equivalent to 11,160 steps/d, and 150 min/wk of MVPA is equivalent to 7716 steps/d. ROC analysis yielded similar findings: 10,225 steps/d are required to accumulate ≥ 23 MET-h/wk of MVPA and 7857 steps/d are needed to meet the recommendation of ≥ 150 min/wk of MVPA. CONCLUSIONS: The findings suggest that 10,000 to 11,000 and 7700 to 8000 steps/d represent the optimal thresholds for accumulating ≥ 23 MET-h/wk of MVPA and ≥ 150 min/wk of MVPA, respectively, for Japanese adults.