Posture Induced Changes in the Maximal M-wave and the H-reflex Amplitude

The purpose of this study was to investigate posture induced changes in the H-reflex and maximal M-wave (M_max) amplitude in soleus muscle (SOL). The hypothesis of the present study is that both H-reflex amplitude and M_max amplitude change with posture. Nine healthy males were tested under two randomly administered conditions; prone and standing position. The ankle joint angle was set at the same angle in each postural condition by monitoring the electrical goniometer. H-reflex was elicited in the SOL from the right leg every 5 seconds using electrical stimulation to the tibial nerve in the popliteal fossa. Surface electromyography (EMG) was recorded from the middle surface of the SOL and the tibialis anterior muscle (TA) using silver bipolar electrodes. Absolute values of H_max, M_max amplitude and H_max/M_max ratio in each postural condition obtained from the H-M recruitment curve were compared. All H_max/M_max ratios, H_max amplitudes and M_max amplitudes were significantly lower in the standing position. The hypothesis of the present study was verified, and M_max amplitude in the SOL was inhibited by the standing posture. There is a possibility that M_max amplitude is changed in conjunction with the posture induced physiological response

The Relationship between Inferior Vena Cava Distensibility and Arterial Blood Pressure

The purpose of this study was to clarify the relationship between the inferior vena cava distensibility and blood pressure. Six Japanese healthy males volunteered to participate in this study. We measured the cross-sectional area of inferior vena cava (CSAivc) and blood pressure at rest and during passive leg raising in supine position. We calculated the change rates of each parameter, based on the value at rest in supine position. We observed a negative correlation between the change rate of CSAivc and systolic blood pressure (P<0.05). These results suggest that the inferior vena cava distensibility affects partially systolic blood pressure

Effects of Eating or Skipping Breakfast on Heart Rate and Oxygen Uptake

The purpose of this study was to compare changes in heart rate, oxygen uptake, blood pressure and oral temperature between subjects eating breakfast and subjects skipping breakfast when they exercise each day at 11:00 AM and 2:00 PM. The study design included two different groups, a breakfast group and a skipping group. Subjects rested for five minutes, and they exercised on a pendulum ergometer for twenty minutes. After exercising, the resistance was returned to zero for a one minute cool down followed by five more minutes of complete rest(recovery phase). Oral temperatures of the skipping group were lower than those of the breakfast group at 11:00 AM. Diet induced thermogenesis (DIT), which increases core body temperature, is generated by eating breakfast. In the skipping group, the resting heart rates at 11:00 AM were lower than at 2:00 PM. A significant difference in heart rate after the first minute of exercise was seen between 11:00 AM and 2:00 PM in the skipping group. These results suggested that when skipping breakfast, the heart rate response immediately after beginning exercise is slow in the morning. Although all subjects did cooling down for one minute after exercising, oxygen uptake during the recovery phase in the skipping group at 11:00 AM was significantly higher than at rest. These results suggest that eating breakfast has a physiological influence on both heart rate and oxygen uptake

Day-to-Day Variation in the Hoffmann Reflex in Females

The present study aimed to investigate changes in the Hoffmann reflex (H-reflex) at the same time on different days and to compare the findings between genders. Four males and five females in healthy subjects agreed to participate in the study and provided informed consent. All subjects were nonsmokers, and none of the females were consuming any oral contraceptives. The H-reflex was elicited in the right soleus muscle by constant current stimulation of the tibial nerve in the popliteal fossa with the subjects in the prone position. As a reference, the maximal amplitude of the H-wave relative to that of the M-wave (Hmax/Mmax) was measured to determine changes in α-motoneuron excitability. Hmax/Mmax of 6 to 9 trials and was represented by the coefficient of variation (CV). The CV of Hmax/Mmax in females was significantly higher than that in males. The level of Hmax/Mmax for males was highly reproducible, suggesting that fewer factors alter α-motoneuron excitability in males compared with those in females. Several female subjects experienced symptoms of depression and suffered from body and menstrual pain. Variations in Hmax/Mmax values were considerably greater for females than for males, suggesting that the α-motoneuron might be influenced by the menstrual cycle phase as well as by individual differences

Effect of Environmental Change while Climbing Mt. Daisen on Forced Vital Capacity and Forced Expiratory Volume % in Young Women

The aim of the present study was to clarify the effects of environmental change while climbing Mt. Daisen on forced vital capacity and forced expiratory volume % in young women in summer. Seven healthy Japanese women (age: 22.6 ± 4.2 years) volunteered to climb Mt. Daisen (1,709m), located in Tottori prefecture, in August. Participants\u27 expiratory forced vital capacity (FVC), forced expiratory volume % (FEV_%) and arterial oxygen saturation (SpO_2) were measured at 4 points (Ground: 10m, Rest point: 780m, Summit: 1,709m, Goal point: 780m). The measurements were conducted soon after the subjects\u27 arrival at each point. The degree of dyspnea sensation was measured at Ground, Rest point, Goal point and at each station. There were no significant changes in FVC. FEV_% at the summit was significantly lower than at the Ground and Rest point. No significant differences were found in SpO_2 at each measuring point. The degree of dyspnea sensation at each station soon after the subjects\u27 arrival was significantly higher than those at the Rest point. The results of this study indicated mild airway contraction induced by stresses on the respiratory system from increasing exercise intensity during an ascent of Mt. Daisen

Relationship between Protection against Cold and the Physiological Index during a Cold Environment

A snow cave is a bivouac shelter used in mountain climbing that is widely used as a shelter against the cold during winter. In the outdoors, wind velocity and air temperature have an influence on temperature change. It could stabilize body temperature if it can control the convection of ambient air. This paper could develop a theory focusing on the relation between physiological indexes and the protection against the cold while staying in a snow cave. For example, protection against the cold could be thermal insulation underwear, thermal insulation gloves, thermal insulation socks, a steam warmed temperature sheet and a rescue sheet. Measurement items were heart rate, blood pressure, rectal temperature, score of a subjective thermal sensation and the activity of the parasympathetic nervous system. It was clarified that the protection against the cold could be effective for the decrease of the physiological index. These field studies suggest that they would enable the adaptation in the adjustment range of the autonomic nervous system given these protections against the cold