Masato Nishiwaki

Effects of resistance training under hypoxic conditions on muscle hypertrophy and strength

It has been reported that exercise under hypoxic conditions elevates acute growth hormone secretion after exercise compared with that under normoxic conditions. This study examined the influence of resistance training under moderate hypoxic conditions on muscle thickness, strength and hormonal responses. Thirteen healthy men were assigned into two groups matched for physical fitness level and then randomized into two groups that performed exercise under normoxic (FiO2 = 20·9%) or hypoxic (FiO2 = 12·7%) conditions. Three sets of elbow extensions with unilateral arm were performed to exhaustion at a workload of a 10 repetition maximum with 1‐minute intervals for 3 days per week for 8 weeks. The thickness of the biceps and triceps brachii was determined using B‐mode ultrasound before and after training. Blood sampling was carried out before and after exercise, as well as during the first and last training sessions. Increase in the thickness of the triceps brachii in trained arm was significantly greater in the hypoxic group than in the normoxic group. The 10 repetition maximum was significantly increased not only in the trained arm but also in the untrained arm in both groups. Serum growth hormone concentrations after exercise were significantly higher in the hypoxic group than in the normoxic group on both the first and last training sessions. These findings suggest that hypoxic resistance training elicits more muscle hypertrophy associated with a higher growth hormone secretion, but that the greater muscle hypertrophy did not necessarily contribute a greater gain of muscle strength.

Sex Differences in Flexibility-Arterial Stiffness Relationship and Its Application for Diagnosis of Arterial Stiffening: A Cross-Sectional Observational Study

Purpose Arterial stiffness might be related to trunk flexibility in middle-aged and older participants, but it is also affected by age, sex, and blood pressure. This cross-sectional observational study investigated whether trunk flexibility is related to arterial stiffness after considering the major confounding factors of age, sex, and blood pressure. We further investigated whether a simple diagnostic test of flexibility could be helpful to screen for increased arterial stiffening. Methods According to age and sex, we assigned 1150 adults (male, n = 536; female, n = 614; age, 18–89 y) to groups with either high- or poor-flexibility based on the sit-and-reach test. Arterial stiffness was assessed by cardio-ankle vascular index. Results In all categories of men and in older women, arterial stiffness was higher in poor-flexibility than in high-flexibility (P<0.05). This difference remained significant after normalizing arterial stiffness for confounding factors such as blood pressure, but it was not found among young and middle-aged women. Stepwise multiple-regression analysis also supported the notion of the sex differences in flexibility-arterial stiffness relationship. Receiver operating characteristic curve analysis revealed that cut-off values for sit-and-reach among men and women were 33.2 (area under the curve [AUC], 0.711; 95% confidence interval [CI], 0.666–0.756; sensitivity, 61.7%; specificity, 69.7%) and 39.2 (AUC, 0.639; 95% CI, 0.592–0.686; sensitivity, 61.1%; specificity, 62.0%) cm, respectively. Conclusion Our results indicate that flexibility-arterial stiffness relationship is not affected by BP, which is a major confounding factor. In addition, sex differences are observed in this relationship; poor trunk flexibility increases arterial stiffness in young, middle-aged, and older men, whereas the relationship in women is found only in the elderly. Also, the sit-and-reach test can offer a simple method of predicting arterial stiffness at home or elsewhere.

Reduction of V̇O2 slow component by priming exercise: novel mechanistic insights from time‐resolved near‐infrared spectroscopy

Novel time‐resolved near‐infrared spectroscopy (TR‐NIRS), with adipose tissue thickness correction, was used to test the hypotheses that heavy priming exercise reduces the V̇O2 slow component (V̇O2SC) (1) by elevating microvascular [Hb] volume at multiple sites within the quadriceps femoris (2) rather than reducing the heterogeneity of muscle deoxygenation kinetics. Twelve subjects completed two 6‐min bouts of heavy work rate exercise, separated by 6 min of unloaded cycling. Priming exercise induced faster overall V̇O2 kinetics consequent to a substantial reduction in the V̇O2SC (0.27 ± 0.12 vs. 0.11 ± 0.09 L·min−1, P < 0.05) with an unchanged primary V̇O2 time constant. An increased baseline for the primed bout [total (Hb + Mb)] (197.5 ± 21.6 vs. 210.7 ± 22.5 μmol L−1, P < 0.01), reflecting increased microvascular [Hb] volume, correlated significantly with the V̇O2SC reduction. At multiple sites within the quadriceps femoris, priming exercise reduced the baseline and slowed the increase in [deoxy (Hb + Mb)]. Changes in the intersite coefficient of variation in the time delay and time constant of [deoxy (Hb + Mb)] during the second bout were not correlated with the V̇O2SC reduction. These results support a mechanistic link between priming exercise‐induced increase in muscle [Hb] volume and the reduced V̇O2SC that serves to speed overall V̇O2 kinetics. However, reduction in the heterogeneity of muscle deoxygenation kinetics does not appear to be an obligatory feature of the priming response.

Ingesting a small amount of beer reduces arterial stiffness in healthy humans

Epidemiological studies reveal a J‐shaped association between alcohol consumption and arterial stiffness, with arterial stiffening lower among mild‐to‐moderate drinkers than heavy drinkers or nondrinkers. This study aimed to examine the effects of ingesting a small amount of beer, corresponding to the amount consumed per day by a mild drinker, on arterial stiffness. Eleven men (20–22 years) participated, in random order and on different days, in four separate trials. The participants each drank 200 or 350 mL of alcohol‐free beer (AFB200 and AFB350) or beer (B200 and B350), and were monitored for 90 min postingestion. There were no significant changes in arterial stiffness among trials that ingested AF200 or AF350. However, among trials ingesting B200 and B350, breath alcohol concentrations increased significantly, while indexes of arterial stiffness decreased significantly for approximately 60 min: carotid‐femoral pulse wave velocity (B200: −0.6 ± 0.2 m/sec; B350: −0.6 ± 0.2 m/sec); brachial‐ankle pulse wave velocity (B200: −53 ± 18 cm/sec; B350: −57 ± 19 cm/sec); and cardio‐ankle vascular index (B200: −0.4 ± 0.1 unit; B350: −0.3 ± 0.1 unit). Furthermore, AFB showed no effect on arterial stiffness, regardless of whether or not it contained sugar, and no significant difference in antioxidant capacity was found between AFB and B. This is the first study to demonstrate that acute ingestion of relatively small amounts of beer reduces arterial stiffness (for approximately 60 min). Our data also suggest that the reduction in arterial stiffness induced by ingestion of beer is largely attributable to the effects of alcohol.

Habitually increasing physical activity in daily life during 8-week intervention reduces arterial stiffness in older women: a community-based pilot study.

BACKGROUND The recent Japanese official physical activity (PA) guidelines for health promotion recommend increasing PA by 10 minutes per day (Plus 10), which generally corresponds to about 1000 steps per day. However, whether habitually increasing PA in daily life improves arterial stiffness in older people is unclear. The present study aimed to examine the effects of habitually increasing PA during an intervention on arterial stiffness in older women. METHODS Twenty-one older women (age, 76±1 years) participated in supervised group activity and seated exercise for 60 min per session, once each week during an 8-week intervention. The women wore an activity monitor for 1 week to determine baseline values and for the 8 weeks of intervention. Arterial stiffness was assessed before and after the intervention using the Cardio-Ankle Vascular Index (CAVI). RESULTS Based on changes in steps between baseline and the intervention, the participants were assigned to control (<1000 steps/day, N.=14) or PA-increased (≥1000 steps/day, N.=7) groups with changes of -138±198 steps/day and 2,047±580 steps/day, respectively. The CAVI was significantly reduced only in the PA-increased group (Pre, 9.2±0.2; Post, 9.0±0.2 units), and changes in CAVI were significantly inversely correlated with changes in step counts (rs=-0.62). CONCLUSIONS Habitually increasing PA in daily life during 8-week intervention can induce a small but significant reduction in arterial stiffness among older women.

A pilot lifestyle intervention study: Effects of an intervention using an activity monitor and Twitter on physical activity and body composition

BACKGROUND This pilot study aimed to examine the effects of a lifestyle intervention comprising an activity monitor and the concurrent use of Twitter, on physical activity (PA) and body composition. METHODS Seventeen healthy volunteers (36±3 years) were randomly assigned to normal (N, N.=8) or Twitter (T, N.=9) intervention groups for six weeks. Participants in both groups wore an activity monitor but those in the T group also tweeted daily about their PA. An observer read the tweets from each participant and provided feedback. Body composition was determined using bioelectrical impedance analysis before and after the intervention. RESULTS Significantly more daily steps and PA at an intensity of ≥3 metabolic equivalents (METs) were recorded by the T than the N during six weeks. The number of steps and PA did not significantly change over time in the N, but significantly increased in the T from weeks one to six (8170±1130 to 12,934±1400 steps/day and 2.6±0.5 to 5.0±0.8 METs·h/day). In addition, significantly more body fat was lost in the T, than in the N (-1.1±0.2 vs. -0.1±0.3 kg), and the changes in PA significantly correlated with the changes in body fat (r=-0.713). CONCLUSIONS Lifestyle intervention can increase daily PA and reduce body fat more effectively when using an activity monitor and Twitter than an activity monitor alone.

Effects of intermittent hypobaric hypoxic exercise for four weeks on cardiovascular responses

The present study examined the effects of intermittent hypobaric hypoxic exercise over a period of four weeks on cardiovascular adaptations. Twenty-four healthy male adults (age, 24 ± 3 yrs) who were matched for physical fitness levels were randomized into two groups, and was adjusted to be either normobaric normoxic (N; n = 12) or hypobaric hypoxic (H; n = 12). Both groups performed aquatic activities at an intensity of about 50% VO_2max for 30min/session, four days per week for four weeks in a pool within a chamber where the atmospheric pressure can be regulated. The H group exercised under hypobaric conditions corresponding to 2,000m above sea level, and were exposed for a total of 2.5h/session. Before and after experimental period, VO_2max and cardiovascular responses such as heart rate (HR), stroke volume (SV), cardiac output (CO), as well as systolic (SBP), diastolic (DBP), and mean blood pressure (MBP) were measured during cycling on an ergometer at an intensity of 50% VO_2max. Flowmediated vasodilation (FMD) was also evaluated by measuring changes in the diameter of the popliteal artery between rest and during reactive hyperemia. The VO_2max was not significantly changed after the four-week exercise period in both groups and changes in cardiovascular responses during moderate exercise were not evident in the N group. On the other hand, SV and CO were significantly increased (P＜0.05) in the H group, whereas DBP and MBP as well as the calculated TPR (MBP/CO) were significantly decreased (P＜0.05 for all). The FMD was significantly increased only in the H group (P＜0.05). These findings indicated that exercise under hypobaric hypoxic conditions could induce more beneficial cardiovascular adaptations in healthy male adults such as reductions in TPR and BP with an increase in FMD compared with exercise under normal conditions.

The effects of regular high-cocoa chocolate intake on arterial stiffness and metabolic characteristics during exercise

OBJECTIVE The aim of this study was to examine the effects of regular high-cocoa chocolate consumption on arterial stiffness and fat oxidation during light- to moderate-intensity exercise. METHODS This randomized, controlled, parallel-group intervention study included 32 Japanese college students (mean age, 20.7 ± 0.3 y; men, n = 24; women, n = 8) who were assigned to either control or intervention groups (n = 16 each). The control group did not alter their habitual diet or physical activity throughout the study period. The intervention group consumed 20 g/d (508 mg of cacao polyphenol) of high-cocoa chocolate for 4 wk. Blood pressure, heart-ankle pulse wave velocity, cardio-ankle vascular index, body composition, and metabolic characteristics during exercise at 50% maximal oxygen uptake level were assessed before and after the intervention. RESULTS Four weeks of high-cocoa chocolate ingestion significantly reduced heart-ankle pulse wave velocity and cardio-ankle vascular index (%change, intervention versus control: -2.3 ± 0.9% versus 0.9 ± 0.9%, and -4.8 ± 1.8% versus 0.7 ± 1.3%, respectively; both P < 0.05). However, blood pressure, weight, body mass index, body fat, waist circumference, and metabolic characteristics during exercise such as respiratory exchange ratio did not significantly change in either group. CONCLUSIONS Four weeks of regular high-cocoa chocolate consumption reduced arterial stiffness after considering blood pressure in healthy young men and women. However, the habitual consumption of high-cocoa chocolate for 4 wk did not affect metabolic characteristics during light- to moderate-intensity exercise and body composition.

Combined effect of coffee ingestion and repeated bouts of low-intensity exercise on fat oxidation.

We investigated the effect of the combination of coffee ingestion and repeated bouts of low‐intensity exercise on fat oxidation. Subjects were seven young, healthy male adults. They performed four trials: a single 30‐min bout of exercise following ingestion of plain hot water (WS) or coffee (CS); a trial with three 10‐min bouts of exercise separated by 10‐min periods of rest following ingestion of plain hot water (WR) or coffee (CR). The coffee contained 5 mg kg−1 of caffeine. All trials were performed on a cycle ergometer at 40% maximal oxygen uptake for each subject an hour after beverage ingestion. Oxygen uptake in the CS and CR trials was higher compared with the WS and WR trials at 90 min after exercise (P<0·05). Respiratory exchange ratio (RER) in the CS and CR trials was decreased during the whole recovery period compared with baseline (P<0·05), whereas no significant decreases were observed in either the WS or WR trials. Moreover, RER was significantly lower at 30 min after exercise in the CR trial than in either the WS or WR trials (P<0·05 each). Similarly, it is notable that fat oxidation rate in the CR trial was significantly higher at 30 min after exercise compared to that in the WS and WR trials (P<0·05). These results suggest that the combination of coffee intake and repeated bouts of low‐intensity exercise enhances fat oxidation in the period after exercise.

The effects of exercise training under mild hypoxic conditions on body composition and circulating adiponectin in postmenopausal women

This study aimed to examine the effects of exercise training under mild hypoxic conditions on body composition and circulating adiponectin levels in postmenopausal women.