Sho Onodera

Effects of endurance training on resting and post-exercise cardiac autonomic control

PURPOSE Endurance training induces reductions in both resting and postexercise heart rate (HR). If adaptation in cardiac autonomic regulation is a contributing factor in these reductions, changes in cardiac autonomic nervous system (ANS) should correspond to those in HR during an endurance-training program. We investigated the changes in resting and postexercise HR variabilities (both in the time and frequency domain) over a 6-wk training program. METHODS HR variability was measured five times in an endurance-training group (N = 7) and four times in a control group (N = 5) during the course of study. RESULTS Endurance training decreased HR and increased indices of parasympathetic modulation measured both at rest and during postexercise recovery periods. Noteworthy is that no changes in either HR or indices of ANS modulation measured during postexercise recovery periods were detectable after the first 7 d of the study despite continued changes in resting HR and indices in ANS modulation measured between the 7th and 42nd days of the endurance-training program. CONCLUSIONS The study demonstrates that with endurance-training changes in cardiac ANS modulation partly contribute to a decrease in HR at rest and during postexercise recovery period, and that adaptation of the cardiac autonomic control occurs sooner in immediate postexercise periods than at rest.

Effects of endurance exercise on three-dimensional trabecular bone microarchitecture in young growing rats

Appropriate endurance exercise is capable of increasing bone mass and strength in both animals and humans. We examined the skeletal changes induced by treadmill running exercise in young growing rats with a particular emphasis on three-dimensional trabecular bone microarchitecture. Fourteen male Wistar rats were divided into sedentary (CON; n = 7) and exercised (RUN; n = 7) groups at the age of 4 weeks. The rats in the RUN group performed the treadmill running exercise of 30 m/min for 60 min, 5 times a week. After 10 weeks of exercise, bone mineral density (BMD), cortical geometry, diaphyseal breaking force, and trabecular bone microarchitecture in the femur were measured. Three-dimensional trabecular bone microarchitecture was evaluated at the distal femoral metaphysis using microcomputed tomography. The running exercise significantly increased BMD, bone volume, bone volume fraction, trabecular thickness, and trabecular number, whereas trabecular bone pattern factor, the parameter associated with decreased trabecular connectivity, was significantly lower in the RUN group than the CON group. On the other hand, no significant difference in the degree of anisotropy and structure model index was observed between the two groups. At the femoral diaphysis, running exercise significantly increased cortical bone area, width, and maximum load without affecting bending stress, implying that the material properties of bone had not changed in the exercised rats. These results suggest that the increase in bone strength induced by endurance exercise is mediated by changes in trabecular bone microarchitecture as well as density and cortical geometry.

Variations in carotid arterial compliance during the menstrual cycle in young women

The effect of menstrual cycle phase on arterial elasticity is controversial. In 10 healthy women (20.6 ± 1.5 years old, mean ±s.d.), we investigated the variations in central and peripheral arterial elasticity, blood pressure (carotid and brachial), carotid intima–media thickness (IMT), and serum oestradiol and progesterone concentrations at five points in the menstrual cycle (menstrual, M; follicular, F; ovulatory, O; early luteal, EL; and late luteal, LL). Carotid arterial compliance (simultaneous ultrasound and applanation tonometry) varied cyclically, with significant increases from the values seen in M (0.164 ± 0.036 mm2 mmHg−1) and F (0.171 ± 0.029 mm2 mmHg−1) to that seen in the O phase (0.184 ± 0.029 mm2 mmHg−1). Sharp declines were observed in the EL (0.150 ± 0.033 mm2 mmHg−1) and LL phases (0.147 ± 0.026 mm2 mmHg−1; F= 8.51, P < 0.05). Pulse wave velocity in the leg (i.e. peripheral arterial stiffness) did not exhibit any significant changes. Fluctuations in carotid arterial elasticity correlated with the balance between oestradiol and progesterone concentrations. No significant changes were found in carotid and brachial blood pressures, carotid artery lumen diameter, or IMT throughout the menstrual cycle. These data provide evidence that the elastic properties of central, but not peripheral, arteries fluctuate significantly with the phases of the menstrual cycle.

Attenuated Increases in Blood Pressure by Dynamic Resistance Exercise in Middle-Aged Men

The present study was performed to test the hypothesis that the blood pressure (BP) response to resistance exercise in middle-aged men with stiffening arteries is greater than that in young men with compliant arteries. The BP responses to acute dynamic resistance exercise (leg press) at individual relative (low, moderate and high) and absolute intensities were investigated in both young and middle-aged men. A total of 21 sedentary healthy normotensive men, 21−25 years of age (young) and 41−59 years of age (middle-aged), were included in the study. At rest, the arterial compliance (simultaneous ultrasound and applanation tonometry) and muscle strength (leg press) were lower, and indices of arterial stiffness and BP were higher in the middle-aged men than in the young men (p<0.05). There were no significant differences in height, body mass, or heart rate between the two groups. During exercise, the systolic BP of the middle-aged men at 80% one-repetition maximum (1RM) was significantly lower than that of the young men for the last half of the exercise period (p<0.05). The amounts of change in systolic and diastolic BP from baseline to the end of resistance exercise were lower in the middle-aged men than in the young men at individual relative intensities (p<0.05) and at individual absolute intensity. In contrast to our hypothesis, these findings indicated that the BP response during dynamic resistance exercise using large muscle groups may be attenuated in middle-aged men relative to young men.

Fluctuations in carotid arterial distensibility during the menstrual cycle do not influence cardiovagal baroreflex sensitivity

Aim:  Fluctuations in autonomic nervous functions throughout the menstrual cycle and the underlying mechanism concerning them are not well known. This study was designed to test the hypothesis that fluctuations in cardiovagal baroreflex sensitivity (BRS) throughout the menstrual cycles of young women are due to fluctuations in carotid arterial distensibility.

Effect of aging on carotid artery stiffness and baroreflex sensitivity during head-out water immersion in man

To examine the possible age-related blood pressure (BP) deregulation in response to central hypervolemia, we measured spontaneous baroreflex sensitivity (SBRS), carotid arterial compliance (CC), and R-R interval coefficient of variation (RRICV) during basal and thermoneutral resting head-out-of-water immersion (HOWI) in 7 young (YG = 24.0 +/- 0.8 years) and 6 middle-aged/older (OL = 59.3 +/- 1.3 years) healthy men. Compared with basal conditions (YG = 19.6 +/- 4.0 vs OL = 6.1 +/- 1.5 ms/mmHg, P < 0.05), SBRS remained higher in YG than OL during rest HOWI (YG = 23.6 +/- 6.6 vs OL = 9.3 +/- 2.1 ms/mmHg, P < 0.05). The RRICV was significantly different between groups (YG = 6.5 +/- 1.4 vs OL = 2.8 +/- 0.4%, P < 0.05) under HOWI. The OL group had no increase in CC, but a significant increase in systolic BP (basal = 115.3 +/- 4.4 vs water = 129.3 +/- 5.3 mmHg, P < 0.05) under HOWI. In contrast, the YG group had a significant increase in CC (basal = 0.16 +/- 0.01 vs water = 0.17 +/- 0.02 mm(2)/mmHg, P < 0.05) with no changes in systolic BP. SBRS was positively related to CC (r = 0.58, P < 0.05 for basal vs r = 0.62, P < 0.05 for water). Our data suggest that age-related vagal dysfunction and reduced CC may be associated with SBRS differences between YG and OL groups, and with BP elevation during HOWI in healthy older men.

Exhaustive exercise increases the TNF-α production in response to flagellin via the upregulation of toll-like receptor 5 in the large intestine in mice

Although intense exercise may induce temporary immune depression, it is unclear whether exercise stimulates tumor necrosis factor-alpha (TNF-α) production in response to flagella protein flagellin (FG), which binds to toll-like receptor 5 (TLR5) and induces the production of pro-inflammatory cytokines. Male C3H/HeN mice were administered FG (1mg/kg, i.v.) after exhaustive exercise (EX), and the plasma TNF-α concentrations were examined. The production of TNF-α and the TLR5 expression in both RAW264 and Caco2 cells were measured under FG conditions in vitro. Although the plasma TNF-α concentrations were observed to significantly increase in both the EX and non-EX (N-EX) mice (p<0.01, respectively) following FG injection, the TNF-α levels in the EX mice were significantly higher than those observed in the N-EX mice (p<0.01). Epinephrine (Ep) treatment accelerated the FG-induced TNF-α production and TLR5 expression on the Caco2, but not RAW264 cells. Interestingly, a high Ep-induced TLR5 expression was observed on the Caco2 cell surface, which was inhibited by an inhibitor of phosphoinositide3-kinase (PI3K), Ly294002, as well as a β-adrenergic blocker, propranolol. In addition, the EX-induced TNF-α production observed in response to FG was also attenuated by pretreatment with propranolol. Our findings suggest that exhaustive exercise upregulates the production of TNF-α in response to FG via a high expression of TLR5 on the intestinal cell surface following the stimulation of β-adrenergic receptors with exercise.

Effects of Low-Intensity Exercise in the Morning on Physiological Responses During Unsteady Workload Exercise in the Evening.

Abstract Nishimura, K, Nagasaki, K, Yamaguchi, H, Yoshioka, A, Onodera, S, and Takamoto, N. Effects of low-intensity exercise in the morning on physiological responses during unsteady workload exercise in the evening. J Strength Cond Res 30(6): 1735–1742, 2016—This study examined the effects of low-intensity morning exercise (ME) on physiological response during unsteady workload evening exercise. Nine healthy men participated in the following 2 experimental conditions: 15 minutes of bicycle exercise at 40% maximum oxygen consumption (V[Combining Dot Above]O2max) in the morning (the ME condition) and rest (control [C] condition). Heart rate (HR), blood pressure (BP), temperature, oxygen uptake, and natural logarithm of high frequency, an index of cardiac parasympathetic modulation, were measured before evening exercises, which were performed for 32 minutes in 2 parts: The steady-state exercise test included three 4-min bouts of exercise at 20, 60, and 40% V[Combining Dot Above]O2max. The unsteady exercise test consisted of 4-min bouts of exercise with gradual increases and decreases in workload at 20 and 60% V[Combining Dot Above]O2max. Heart rate, BP, and oxygen uptake were measured in both experiments. Maximal and minimal values, amplitude, and phase lags were measured with each cycle of unsteady workload exercise. With steady-state exercise, HR and systolic BP at 60 and 40% V[Combining Dot Above]O2max were significantly lower in the ME condition than in the C condition. However, oxygen uptake was not significantly different between the 2 conditions. With unsteady exercise, the HR and oxygen uptake phase lags were significantly shorter and the amplitude of oxygen intake was significantly larger in the ME condition than in the C condition. There were no significant differences in physiological parameters between the conditions at rest or during recovery. The physiological response during evening exercise is enhanced by low-intensity ME, which might be an effective conditioning method on a sporting event day.