Phase-dependent modulation of corticospinal excitability during the observation of the initial phase of gait.

This study was undertaken to identify the temporal characteristics of corticospinal excitability of tibialis anterior muscle during the observation of the initial phase of gait. For this purpose, using transcranial magnetic stimulation, we recorded motor evoked potentials (MEPs) during the observation of the second step of an actor's first three steps of gait initiation with (complex gait) or without (normal gait) an obstacle and unstable surface. The results demonstrate that (1) MEPs during the observation of the initial phase of normal gait were significantly increased only at early swing phase, but not other phases (mid-swing, heel contact, mid-stance, and heel off) and (2) MEPs during the observation of the initial phase of complex gait were significantly increased at early swing and also at mid-swing and heel contact phases. These findings provide the first evidence that corticospinal excitability during the observation of gait, especially the initial phase, is modulated in phase- and motor-demanded-dependent manners.

Plasma oxidative stress is induced by single-sprint anaerobic exercise in young cigarette smokers.

Cigarette smoking increases oxidative stress, which is a risk factor for several diseases. Smoking has also been reported to enhance plasma oxidative stress during strenuous exercise. However, no prior study has examined the changes in plasma oxidative stress after single-sprint anaerobic exercise in cigarette smokers. The purpose of this study was to investigate these changes in young cigarette smokers by measuring reactive oxygen species generation and total antioxidant content. Participants were 15 male smokers (mean age: 25·9 ± 2·9 years) and 18 male non-smokers (mean age: 24·2 ± 4·3 years). Hydroperoxide concentration and biological antioxidant potential (BAP) in plasma were measured at baseline and after the Wingate anaerobic test. A significant interaction between group and time was observed for plasma hydroperoxide concentration (P = 0·037). Plasma hydroperoxide concentration was significantly increased after exercise in both smokers and non-smokers (P = 0·001 and <0·001, respectively). However, no significant interaction was observed between groups by time on plasma BAP (P = 0·574), and a main effect of time was observed (P<0·001). Plasma BAP was significantly increased after exercise in both groups (both, P<0·001). These findings indicate that plasma oxidative stress is higher in cigarette smokers than in non-smokers after single-sprint anaerobic exercise, which may increase the risk of oxidative damage.

Cigarette smoking decreases dynamic inspiratory capacity during maximal exercise in patients with type 2 diabetes.

To investigate the influence of cigarette smoking on exercise capacity, respiratory responses and dynamic changes in lung volume during exercise in patients with type 2 diabetes. Forty-one men with type, 2 diabetes without cardiopulmonary disease were recruited and divided into 28 non-current smokers and 13 current smokers. All subjects received lung function tests and cardiopulmonary exercise testing using tracings of the flow-volume loop. Exercise capacity was compared using the percentage of predicted oxygen uptake at maximal workload (%VO2max). Respiratory variables and inspiratory capacity (IC) were compared between the two groups at rest and at 20%, 40%, 60%, 80% and 100% of maximum workload. Although there was no significant difference in lung function tests between the two groups, venous carboxyhemoglobin (CO-Hb) levels were significantly higher in current smokers. %VO2max was inversely correlated with CO-Hb levels. Changing patterns in respiratory rate, respiratory equivalent and IC were significantly different between the two groups. Current smokers had rapid breathing, a greater respiratory equivalent and a limited increase in IC during exercise. Cigarette smoking diminishes the increase in dynamic IC in patients with type 2 diabetes. As this effect of smoking on dynamic changes in lung volume will exacerbate dynamic hyperinflation in cases complicated by chronic obstructive pulmonary disease, physicians should consider smoking habits and lung function when evaluating exercise capacity in patients with type 2 diabetes.

Pulmonary oxidative stress is induced by maximal exercise in young cigarette smokers.

INTRODUCTION: Oxidative stress is induced by both cigarette smoking and acute exercise. It has also been reported that exercise can induce plasma oxidative stress in young cigarette smokers. However, no previous report has demonstrated that exercise induces pulmonary oxidative stress in cigarette smokers. The aim of this study was to determine whether pulmonary oxidative stress is induced by maximal exercise in cigarette smokers as measured by reactive oxygen species generation and total antioxidant content. METHODS: Fifteen male smokers (mean age: 25.9 ± 2.9 years) and 18 male nonsmokers (mean age: 24.2 ± 4.3 years) participated in this study. Hydrogen peroxide (H(2)O(2)) concentration and biological antioxidant potential (BAP) in exhaled breath condensate (EBC) were measured at baseline and after maximal exercise in the Wingate anaerobic test. RESULTS: A significant interaction of group by time was observed for EBC H2O2 concentration (p = .015). After exercise, EBC H(2)O(2) concentrations were significantly increased in the smoking group (p = .030) but not in the nonsmoking group. There were no significant changes in EBC BAP in either group. CONCLUSIONS: These findings indicate that in cigarette smokers, maximal exercise induces pulmonary oxidative stress, which may lead to oxidative damage in the lungs.

The influence of lung function on exercise capacity in patients with type 2 diabetes.

Patients with type 2 diabetes have impaired exercise capacity. While numerous factors are known to contribute to impaired exercise capacity, the role of lung function remains unclear. We conducted the present study to investigate the influence of lung function on exercise capacity in patients with type 2 diabetes. Cardiopulmonary exercise testing was carried out in 31 male patients with type 2 diabetes without diabetic complications or cardiopulmonary diseases. Patients with abnormal spirometry results such as a percentage of predicted forced vital capacity (%FVC) < 80% and/or a ratio of forced expiratory volume in one second (FEV1) to FVC (FEV1/FVC) < 70% were excluded from the study. We used the percentage of predicted maximal oxygen uptake (%VO2max) as an index of exercise capacity. The correlations between %VO2max and lung function and other factors known to be associated with impaired exercise capacity were then assessed. Univariate analysis revealed %VO2max correlated significantly with percentage of predicted FEV1 (%FEV1), duration of type 2 diabetes, regular exercise habits, and systolic and diastolic blood pressures. In a multivariate analysis, %FEV1 and regular exercise habits were found to be independent determinants of %VO2max. A mild reduction in %FEV1, which may be a complication of diabetes, is associated with impaired exercise capacity in patients with type 2 diabetes. When evaluating spirometric values in patients with type 2 diabetes, a reduction in %FEV1 should be noted even when both %FVC and FEV1/FVC are within normal limits.

The neural influence on the occurrence of locomotor-respiratory coordination.

This study focused on the neurogenic mechanisms of coordination between locomotor and respiratory rhythms. The aim of the present study was to investigate the influence of peripheral neurogenic drive from moving limbs, and the level of consciousness, on locomotor-respiratory coordination. Subjects performed movement for 20 min in a supine position using a bicycle ergometer. The movement comprised three types of leg movements: active (loadless) movement, passive movement while awake and passive movement during sleep. We found no difference between active and passive movement in the degree of coordination. However, the degree of coordination during sleep was significantly lower than that while awake (p<0.05). We conclude that peripheral neurogenic drive from moving limbs is able to generate locomotor-respiratory coordination, and that the level of consciousness may influence the degree of coordination.

Determinants of the daily rhythm of blood fluidity.

BACKGROUND: Numerous processes in the living body exhibit daily rhythmicity. In this study, we characterized a daily rhythm of blood fluidity and identified its determinants. METHODS: The subjects were nine young males. We measured the physiological parameters and performed hematological and biochemical analyses. We repeated the measurements six times during the day at 7:30 (just after getting up and before breakfast), 10:00, 13:30 (after lunch), 16:30, 19:30 (after dinner), and 21:30. The subjects performed sedentary work all day, and the contents and time of the meals were uniform. Investigation of blood rheology was based on Kikuchi's microchannel method. RESULTS: Blood passage time varied significantly with time of day. Stepwise regression analysis was used to determine the significant factors affecting blood passage time. Body temperature, heartbeat, hematocrit, white blood cell and total cholesterol were significant determinants of blood passage time. CONCLUSION: We confirmed that blood fluidity has a daily rhythm. In addition, we found that the determinants of blood fluidity included physiological parameters such as body temperature and heartbeat, hematological parameters such as hematocrit, and white blood cell and total cholesterol.

Effect of aerobic exercise training on oxidative stress in patients with type 2 diabetes mellitus.

The purpose of this study was to determine whether moderate-intensity exercise training reduces oxidative stress in patients with type 2 diabetes mellitus over 12 months. The patients were divided into 3 groups: aerobic training combined with the use of a fitness center (group A, n = 43), aerobic training only (group B, n = 44), or controls (group C, n = 16). The subjects in groups A and B were instructed to exercise at 50% of peak oxygen uptake for more than 30 minutes on at least 3 days per week over a 12 month period. In addition, the subjects in group A were instructed to use a fitness center and were taught how to perform aerobic training in the indicated manner by certified fitness instructors. We measured the levels of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a parameter of oxidative stress. Serum glycated albumin levels were reduced significantly after 6 and 12 months in groups A and B and after 12 months in group C. Urinary 8-OHdG levels decreased after 12 months in groups A and B, but remained unchanged in group C. There was a significant positive linear association between percentage changes in urinary 8-OHdG and glycated albumin levels over the 12 months. In conclusion, aerobic exercise training improved glycemic control and reduced oxidative stress in patients with type 2 diabetes mellitus. Furthermore, improvement in glycemic control was associated with a reduction in oxidative stress.

Vastus lateralis oxygenation during prolonged cycling in healthy males.

This study examined the relationship between acute cardiorespiratory and muscle oxygenation and blood volume changes during prolonged exercise. Eight healthy male volunteers (mean maximum oxygen uptake VO(2max) = 41.6 +/- 2.4 mL/kg/min) performed 60 min submaximal cycling at 50% VO(2max). Oxygen uptake VO(2) was measured by indirect spirometry, cardiac output (CO) was estimated using a Portapre, and right vastus lateralis oxyhemoglobin/ myoglobin (oxyHb/Mb), deoxyhemoglobin/myoglobin (deoxyHb/Mb), and total hemoglobin/myoglobin (total Hb/Mb) were recorded using near-infrared spectroscopy (NIRS). After 40 min of exercise, there was a significant increase in VO(2) due to a significantly higher arteriovenous oxygen difference ((a - v)O(2diff). After 30 min of exercise CO remained unchanged, but there was a significant decrease in stroke volume and a proportionate increase in heart rate, thus indicating the occurrence of cardiovascular drift. During the first few minutes of exercise, there was a decline in oxyHb/Mb and total Hb/Mb, whereas deoxyHb/Mb remained unchanged. Thereafter, oxyHb/Mb and total Hb/Mb increased systematically until the termination of exercise while deoxyHb/Mb declined. After 40 min of exercise, these changes were significantly different from the baseline values. There were no significant correlations between the changes in the NIRS variables and systemic VO(2) or mixed (a - v)O(2)diff during exercise. These results suggest that factors other than localized changes in muscle oxygenation and blood volume account for the increased VO(2) during prolonged submaximal exercise.