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

Effect of the Rotational Speed of a Long Jump Rope in a Person Turning the Rope on Heart Rate and Oxygen Uptake

The purpose of this study was to clarify the effect of different rotational speeds on the heart rate (HR) and oxygen uptake of a person turning a long jump rope. The subjects consisted of six healthy Japanese males who volunteered to participate in the study. They were asked to turn a long jump rope. The measurement was set at three rotational speed conditions: 70, 90 and 110 rpm. The measurement indexes were HR, oxygen uptake, rating of perceived exertion and blood pressure. The 90 and 110 rpm conditions demonstrated significant HR increases from the first to the third minute of the 3-minute exercise compared with the 70 rpm condition. The 110 rpm condition showed significant HR increases from the first to the third minute compared with the 90 rpm condition. The 90 and 110 rpm conditions demonstrated significant oxygen uptake increases from the first to the third minute compared with the 70 rpm condition. The 110 rpm condition showed significant oxygen uptake increases from the first to the third minute compared with the 90 rpm condition. The changes in the HR and oxygen uptake of the rope turner were dependent on the rotational speed of the long jump rope

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

Circadian variations in anaerobic threshold

This study aimed to determine whether certain respiratory and cardiovascular parameters associated with anaerobic threshold (AT), measured during graded exercise testing, occur at lower intensities in the morning than in the evening. Ten healthy Japanese men volunteered to participate in this study, which involved two conditions that were performed at different times of day: morning (M) exercise was performed between 9:00 and 10:00 a.m., and afternoon (A) exercise was performed between 4:00–6:00 p.m. After resting supine for 30 minutes, each subject performed graded cycle ergometer exercise testing comprising 90-second stages. Exercise intensity was initially 10 W and was increased by 10 W for each stage. Heart rate (HR), blood pressure (BP), absolute double product (DP), cardiac autonomic nervous system modulation, and ventilatory volume (VE) were measured during each exercise stage. Ventilatory threshold (VT), the double product breaking point (DPBP), and breaking point of the natural log of high frequency (ln HF) (HFBP) were reached at a lower exercise intensity in the M condition than in the A condition (p<.05). Values for VE at VT intensity, DP, HR, and systolic blood pressure (SBP) at DPBP were significantly lower in the M condition than in the A condition (p<.05). These data suggest that AT is reached at a lower intensity in the morning than in the afternoon, and that relative burden, as indicated by HR and SBP, is greater in the morning than in the afternoon. Exercise prescriptions that incorporate awareness of the circadian rhythms may prevent cardiac or cerebrovascular accidents during exercise

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