The effects of yogurt consumption on immune function in university male track and field athletes -A randomized, double-blind, placebo-controlled, parallel-group study- / 体力科学

This study aimed to evaluate the effects of ingesting yogurt fermented with Lactobacillus delbrueckii subsp. bulgaricus (OLL1073R-1) on the immune function of healthy university men track and field athletes. Study design Randomized, double-blind, placebo-controlled, parallel-group study. A total of 37 track and field athletes aged ≥18 years were randomly assigned into two groups. For 2 weeks, two bottles of yogurt fermented with OLL1073R-1 and Streptococcus thermophilus OLS3059 or placebo sour milk were ingested daily to the participants. During the intake period, a 1-week training camp was held and participants were subjected to strenuous exercise. Natural killer (NK) cell activity, which is the primary endpoint, was significantly lower in the placebo group after ingestion than that at baseline; however, it remained unchanged during the pre-exercise level of the yogurt group. The two-way repeated measures analysis of variance showed an interaction effect in the NK cell activity change (P=0.018) and a significant difference between the groups after the 2-week ingestion (P=0.015). Among the secondary endpoints, cytokines and chemokines levels involved in activating innate immunity maintained or enhanced only in the yogurt group. ALT, LDH, and CK significantly elevated only in the placebo group. Furthermore, amino acid levels were significantly lower in the placebo group after ingestion than that at baseline; however, it remained unchanged during the pre-exercise level in the yogurt group. Consuming yogurt fermented with OLL1073R-1 prevents the decline in immune function associated with strenuous exercise. Additionally, the yogurt may contribute to stable physical condition.

Effects of Resveratrol Supplementation on Oxidative Damage and Lipid Peroxidation Induced by Strenuous Exercise in Rats

The purpose of the present study was to investigate the effects of resveratrol supplementation on oxidative damage and lipid peroxidation induced by strenuous exercise in rats. The rats were randomly divided into five groups: a sedentary control group, an exercise control group, and three treatment exercise groups administered increasing doses of resveratrol (25, 50, and 100 mg/kg body weight). Resveratrol was administered by oral gavage once daily for four weeks. At the end of the four-week period, the rats performed a strenuous exercise on the treadmill, and the levels of lactate dehydrogenase (LDH), creatine kinase (CK), malondialdehyde (MDA), 4-hydroxy-2-nonenal (4-HNE), and 8-hydroxy-2\'-deoxyguanosine (8-OHdG) were measured. The results showed that resveratrol supplementation had protective effects against strenuous exercise-induced oxidative damage and lipid peroxidation by lowering the levels of LDH, CK, MDA, 4-HNE, and 8-OHdG in the serum or muscle of rats. These beneficial effects are probably owing to the inherent antioxidant activities of resveratrol.

Leukocytosis, muscle damage and increased lymphocyte proliferative response after an adventure sprint race

The effect of an adventure sprint race (ASR) on T-cell proliferation, leukocyte count and muscle damage was evaluated. Seven young male runners completed an ASR in the region of Serra do Espinhaço, Brazil. The race induced a strong leukocytosis (6.22±2.04×103 cells/mm3 before vs 14.81±3.53×103 cells/mm3 after the race), marked by a significant increase of neutrophils and monocytes (P<0.05), but not total lymphocytes, CD3+CD4+ or CD3+CD8+ cells. However, the T-cell proliferative response to mitogenic stimulation was increased (P=0.025) after the race, which contradicted our hypothesis that ASR, as a high-demand competition, would inhibit T-cell proliferation. A positive correlation (P=0.03, r=0.79) was observed between the proliferative response of lymphocytes after the race and the time to complete the race, suggesting that the proliferative response was dependent on exercise intensity. Muscle damage was evident after the race by increased serum levels of aspartate amino transferase (24.99±8.30 vs 50.61±15.76 U/L, P=0.003). The results suggest that humoral factors and substances released by damaged muscle may be responsible for lymphocyte activation, which may be involved in muscle recovery and repair.

Effect of linear polarized near-infrared light irradiation on the recovery of isokinetic muscle exertion after strenuous exercise / 体力科学

This study aimed to examine the effect of linear polarized near-infrared light (PL) irradiation on the recovery of isokinetic muscle exertion and subjective fatigue sensation in muscles after strenuous exercise. Eighteen healthy college students participated in the experiment for all conditions of meridian point irradiation (MPI), femurs muscles irradiation (FMI), and no irradiation (NI) . They all took isokinetic knee extension and flexion tests (IK test) before and after strenuous exercise up to exhaustion. Each subject was irradiated at the meridian point or in femurs muscles after the second IK test. The third IK test was carried out after ten-minutes rest.<BR>The effects of PL irradiation were confirmed on the recovery rate of muscle fatigue in knee extension motion with high load intensity (PT 60 d/s and TW 60 d/s : MPI, FMI> NI, p<0.05 16.2%, 13.4%>8.5%, and 16.1%, 14.1%>8.3%, respectively) . Also, in flexion motion, significant differences in the recovery-degree for each condition were found, and the effect of PL irradiation was suggested. There was no difference between the effect of MPI and FMI. In addition, subjective fatigue sensation in muscles after rest decreased significantly in MPI as compared with NI (MPI: 52.1%>NI : 36.6%, p<0.05) . From the above, it was suggested that PL irradiation is effective on recovery in muscle fatigue after strenuous exercise regardless of irradiation conditions, MPI or FMI.

Changes in serum mineral levels in athletes before and after a triathlon competition. Comparison between young and middle-aged groups / 体力科学

Using atomic absorption spectrophotometry, we measured serum mineral (Fe, Cu, Z n, Mg, Ca, K, Na) concentrations in blood of male athletes participating in a triathlon competition held at Nakajima, Ehime in 1989. The athletes were divided into a young group (n=9, 24.2±3.6 yr) and a middle-aged group (n=9, 49.3±4.4 yr) . Blood samples were taken on the day before the competition, at the finish, on the following day and for eight days after.<BR>Immediately after the race, the concentrations of iron, calcium and potassium were increased significantly in sera taken from both groups, and those of copper and zinc were found to be increased only in the young group. In the middle-aged group, serum magnesium and sodium concentrations were decreased significantly. On the day after the race, most of the serum mineral concentrations had returned to values similar to those measured before the race, although the serum sodium concentration in the middle-aged group was still below the previous value, and this low level persisted for eight days after the race in both groups.<BR>Noticeable differences between the young and middle-aged groups were that recovery of increased iron concentration in serum tended to be prolonged in the middle-aged group, and the concentrations of serum copper and zinc were higher than those in the young group throughout the measurement period, with only small changes evident before and after the race. By contrast, serum potassium concentration in the middle-aged group was lower than in the young group throughout the measurement period.

Circulatory responses to sudden strenuous exercise. A study by mechanocardiographic method / 体力科学

A study was conducted for further investigation of the mechanism of notch formation of heart rate (HR) in sudden strenuous exercise (SSE), and rapid increase in stroke volume (SV) right after SSE which were the questions arised in the prior experiment.<BR>Six healthy male students volunteered for the study. A bicycle ergometer was prepared for SSE. The intensity and duration of SSE were 100%VO<SUB>2</SUB>max and 1 min, respectively. Warming-up consisting of 80%VO<SUB>2</SUB>max for 5 min, preceeded SSE. The interval between SSE and warming-up varied from 5 to 30 min. A control experiment was also conducted without warming-up.<BR>The main results obtained were as follows :<BR>1) Diastolic time (DT) temporarily elongated when a notch of HR was formed at the early stage of SSE. Warming-up prevented this formation. No notch was observed throughout total electromechanical systolic time (QS<SUB>2</SUB>), left ventricular ejection time (LVET) or preejection time (PEP) .<BR>2) DT was prolonged immediately after SSE, while LVET, PEPi (PEP index, Weissler's equation) were shortened. PEP/LVET did not change in the initial stage of the recovery period, while electrical systolic time (QT) and QS<SUB>2</SUB> shortend and QT/QS<SUB>2</SUB> increased temporarily.<BR>These results suggest the following conclusions :<BR>1) Notch formation observed in heart rate is due to the temporary extension of DT at the early stage of SSE.<BR>2) Decrease in afterload may be the main cause for the rapid increase in stroke volume after SSE, though other factors such as increase in preload, myocardial contractility and sympathetic tone should also be considered.

Effects of warming-up on circulatory responses to sudden strenuous exercise / 体力科学

A study was conducted to elucidate the changes in circulatory responses to sudden strenuous exercise (SSE) using beat-by-beat analysis of heart rate (HR), stroke volume (SV) and blood pressure (BP) . The effects of warming-up on these responses were also studied.<BR>Six healthy male students volunteered for the study. A bicycle ergometer was prepared for SSE. The intensity and duration of SSE were 100% VO<SUB>2</SUB>max and 1 min, respectively. Warming-up of 80% VO<SUB>2</SUB>max for 5 min followed by SSE. The interval between SSE and warming-up varied from 5 to 30 min. A control experiment was also performed without warming-up.<BR>The main results obtained were as follows :<BR>1) BP decreased in the initial stage of SSE, followed by a steep increase. This temporary drop in BP was prevented by warming-up. This might contribute to the prevention of myocardial ischemia which is occasionally observed in the initial stage of SSE without warming-up.<BR>2) Time constants of HR and SV during SSE were shortened by warming-up with long intervals, while the time constant of BP was shortened when the interval was short.<BR>3) The recovery response of each parameter was accelerated by warming-up, but the effect of warming-up had almost disappeared after a 30 min interval.<BR>These results suggest the following conclusions :<BR>Warming-up accelerates the up-stroke and recovery of circulatory responses to SSE, but these effects of warming-up are strongly influenced by interval time. In particular, the effect of recovery acceleration is almost abolished by a 30 min interval.

Lactate oxidation in rats after strenuous exercise / 体力科学

Oxidation of lactate at rest (RE, n=4), or after short strenuous exercise (EX, n=6) was investigated in rats. Food and water were given ad libitum before experiment. In EX, rats ran to exhaustion at the speed of 80-100 m·min<SUP>-1</SUP>. Immediately after exercise, 4 μCi of (U-<SUP>14</SUP>C) lactate was injected into aorta through an indwelling catheter. In RE, (U-<SUP>14</SUP>C) lactate was injected into the rats at rest. Expired gas was collected by a Brooks type bottomless chamber on treadmill belt for 120 min. In EX, exercise duration was 109±18 sec (mean±SE), and maximum blood lactate concentration after the exercise was 23.7±2.1 mM (mean±SE) . Cumulative percent recovery of <SUP>14</SUP>C as <SUP>14</SUP>CO<SUB>2</SUB> for 120 min was 48.5±2.8% for EX and 61.7±0.9% for RE (mean±SE) . Significant difference was found between these two rates (p<0.01) . After 50 min of recovery, mean volume of <SUP>14</SUP>CO<SUB>2</SUB> expired per min in RE was significantly greater than that in EX (p<0.01) . Mean volume of <SUP>14</SUP>CO<SUB>2</SUB> expired per min per VCO<SUB>2</SUB> in RE was always greater than that in EX, and significant difference was found at 7.5 min of recovery (p<0.01) . It is concluded that although the rate of recovery of <SUP>14</SUP>C as <SUP>14</SUP>CO<SUB>2 </SUB>after exercise is lower than that at rest, the major pathway of lactate metabolism after short strenuous exercise is oxidation.