This study investigated the physiological responses and effects of exercise training under hypoxic conditions at the skeletal muscle level induced by reducing muscle temperature in cold water environment. Participants were divided into two intervention groups, cooling and control conditions, according to the water temperature of 15°C and 33°C where the training were conducted in. Eight participants in each group performed submaximal cycling exercise in the water for 30 minutes at the lactate threshold (LT) intensity, three times a week for four weeks (12 sessions). LT intensity was assessed at pre- and post-intervention in a 33°C water temperature environment. A progressive load cycling test was performed on land to assess maximal oxygen uptake (VO2max) and Wingate test was conducted to measure anaerobic power. In the cooling group, working muscle deoxygenation increased during submaximal and maximal exercise, suggesting an improvement in the muscle oxygen extraction capacity. However, no effects on aerobic capacity such as VO2max or LT intensity were observed. The improvement in mean power and time to peak during the Wingate test in the cooling group indicated that LT intensity exercise training in a cold water environment would increase anaerobic power.

This study aimed to elucidate the effects of exercise intensity on stretch-shortening cycle (SSC) function of the lower limbs after cycling. Ten male triathletes performed a cycling graded test to determine the ventilatory threshold (VT) and two hopping-cycling (30 min of cycling at 90 or 110% VT)-hopping tests. The two hopping-cycling-hopping tests performed in random order. Power output (PO), heart rate (HR) and rate of perceived exertion (RPE) were monitored throughout the 30-min cycling. Blood lactate concentrations (BLa) were measured in order to assess metabolic stress. The SSC function was calculated as the ratio of the jump height to the time spent in contact with the ground (reactive strength index [RSI]). PO, HR and RPE values during cycling at 110%VT was higher than at 90%VT (p < 0.01). BLa value after the cycling at 110%VT was higher than at 90%VT (90%VT: 2.4±1.0 vs. 110%VT: 5.9±2.8 mmol/L, p < 0.01). Regardless of the cycling exercise intensity, the RSI significantly decreased after the cycling exercise (p < 0.01). The RSI remained decreased at 15 min after the cycling exercise (p < 0.05). These results demonstrated that the SSC function decreased after cycling. Exercise intensity during cycling is likely to have no effect on the decrease in SSC function.

Blood lactate kinetics is an important physiological determinant of endurance exercise performance. Recently, some studies reported that the blood glucose transition point can also be observed (blood glucose threshold; GT) and the GT is consistent with the lactate threshold (LT). However, we have recently reported that blood glucose kinetics and blood lactate kinetics were different during two sets of incremental running tests in the same day. This result suggested that influence of low glycogen storage on GT and LT are different. This study was intended to clarify the effect of low glycogen storage on the blood glucose and the blood lactate kinetics during incremental running test performed two successive days. Eight male endurance runners participated in incremental running test performed two successive days. The main finding was that the blood glucose was significantly lower in the second day than the first day during incremental test, although blood glucose was not different at rest in both days. However, blood lactate was not different form rest to fifth stages in both days, significantly lower only at the final stage in the second day than the first day. Respiratory exchange ration were lower in the second day compared to the first day. GT was significantly higher in the second day than the first day, but LT was not different in both days. We concluded that low glycogen storage effected blood glucose kinetics more than blood lactate kinetics, and resulted in only the change of GT.

This study was intended to clarify 1) the difference of the exercise intensity at blood lactate threshold (LT) and blood glucose threshold (GT), 2) the effect of exercise duration on the LT and GT during two sets of incremental running test. Ten male runners (age 25.0±3.2 yr, height 171.2±5.5 cm, body mass 57.9±4.0 kg, VO_2max 64.6±3.0 ml/kg/min) completed two sets of incremental running test (each set was set to run ten stages at 60-90% VO_2max). Second set was repeated after 8 min recovery. LT and GT speed were investigated at the first set. Lactate minimum (LM) and glucose minimum (GM) speed were selected where the blood lactate and glucose concentration were at the lowest during the second set. Using the indirect calorimetry (VO₂, VCO₂), fat and carbohydrate oxidation rates were calculated. GT was observed in all runners. VO₂ and energy expenditure were similar between the two incremental running tests, however, fat oxidation was significantly higher and carbohydrate oxidation was significantly lower during the first half of the second set. This change was regarded as the influence of the exercise duration in the first set. Furthermore, GM speed was significantly lower than GT speed, but LM speed and LT speed were not different. It was considered that the shift of GT was affected by the substrate utilization change during prolonged exercise.

The purpose of this study was to determine the difference in the attainment rate of maximal oxygen uptake in cycling and running (%cycVO_2max). Seven healthy male subjects (22.9±1.3 yrs, 171.9±4.7 cm, 61.0±5.2 kg) participated in a maximal incremental exercise test for running and cycling. During the exercise testing, oxygen uptake, carbon dioxide output, respiratory exchange rate, minute ventilation, tidal volume, respiratory rate, and heart rate were measured. Attainment rates of each physiological measurement for cycling and running were shown as %cycVO_2max, %cycVCO_2max, %cycRER_max, %cycVE_max, %cycVt, %cycRR and %cycHR_max. Transverse relaxation time (T2)-weighted spin echo images were acquired before and after the exercise periods. Exercise-induced T2 values of each muscle and muscle-group are indices of muscular activity level, so the difference between the T2 value of cycling and running in each muscle or muscle group was shown as ΔT2_%. VO_2max in cycling was 92.2% of VO_2max in running. Significant correlations were observed between %cycVO_2max and %cycVCO_2max, %cycVO_2max and %cycRR. Furthermore, significant correlations were recognized between %cycVO_2max and ΔT2_% of the m. quadriceps femoris, %cycVCO_2max and ΔT2_% of the m. quadriceps femoris, %cycVCO_2max and the m. triceps surae, as well. These results show that the higher muscular activity level of the thigh in cycling increases the uptake of oxygen in the muscle. The T2 value shows that the uptake or redistribution of fluid within muscle is driven by the accumulation of lactate and inorganic phosphate. Therefore, the T2 value of maximal incremental exercise would reflect the anaerobic capacity of the muscle. Judging from the significant correlations between %cycVO_2max and %cycVCO_2max or %cycRR, the anaerobic capacity of each subject would also affect the difference between the maximal oxygen uptake of cycling and running.

The present study was conducted to obtain basic information about blood glucose fluctuation and relation with race performance during 100 km marathon. Subcutaneous glucose of one well-trained runner was measured by continuous glucose monitoring system (CGMS) at 5 min interval and blood samples for biochemical analysis were drawn at pre, middle and post of the race. Energy balance during one week prior to the 100 km race was recorded, and the whole energy and fluid intake during the race was analyzed. Blood glucose fluctuated reflecting duration of exercise and energy supply during the race. During the latter part of the race (65–70 km), abrupt declines in blood glucose level, which reflected insufficient carbohydrate intake before the race (119 g), were accompanied by decrease in running speed. The present report suggests that continuous glucose monitoring supplemented with standard nutritional and physiological measurement provides precise and valuable information on runner’s energy state during the ultra-endurance race, and that athletes need to reassess their preparation for the race and planning of energy intake during the race.

The purposes of this study were to investigate the characteristics of physiological responses during flat-water kayaking events, and to quantify the contribution of aerobic and anaerobic energy systems. Eight male kayak paddlers participated in the study. The subjects performed an incremental test and five all-out tests (20, 40, 120, 240 and 600 sec) on a kayak ergometer. Peak oxygen uptake (VO₂peak ; 3790 ml · min^-1) in the incremental test was significantly lower than maximal oxygen uptake (VO₂max ; 3944 ml · min^-1) in the all-out test. In contrast, power at VO₂peak (154.0 W) was significantly higher than power at VO₂max (144.1 W). The contributions of energy systems were calculated by measurements of the accumulated oxygen uptake and accumulated oxygen deficit. The relative anaerobic energy system contributions for 200 m(40 sec), 500 m (120 sec), and1000 m (240 sec) averaged 71%, 43%, and 26%, respectively. These higher relative anaerobic energy system contributions, due to higher anaerobic capacity in kayak athletes, and the smaller muscle mass involved in kayak paddling limit oxygen uptake when exercise intensity is high. Furthermore, slower exercise cadence in kayak paddling leads to higher muscular tension, and thus may enhance the limiting of oxygen uptake.

The present study was conducted to obtain basic information about blood glucose fluctuation and relation with race performance during 100 km marathon. Subcutaneous glucose of one well-trained runner was measured by continuous glucose monitoring system (CGMS) at 5 min interval and blood samples for biochemical analysis were drawn at pre, middle and post of the race. Energy balance during one week prior to the 100 km race was recorded, and the whole energy and fluid intake during the race was analyzed. Blood glucose fluctuated reflecting duration of exercise and energy supply during the race. During the latter part of the race (65–70 km), abrupt declines in blood glucose level, which reflected insufficient carbohydrate intake before the race (119 g), were accompanied by decrease in running speed. The present report suggests that continuous glucose monitoring supplemented with standard nutritional and physiological measurement provides precise and valuable information on runner’s energy state during the ultra-endurance race, and that athletes need to reassess their preparation for the race and planning of energy intake during the race.

The purpose of this study was to investigate the relationship between 2-min kayak ergometer performance (KEP) and energy supply capacity. Seventeen (male : 9, female : 8) kayak paddlers completed a maximal incremental test to determine aerobic capacity{maximal oxygen uptake (VO_2max) and lactate threshold (LT)}, and a 2-min all-out test to measure performance and anaerobic capacity{maximal accumulated oxygen deficit (MAOD)}. In addition, total energy supply capacity was estimated by these variables [{(T-score of VO_2max+T-score of LT)/2+T-score of MAOD}/2]. Oxygen uptake and blood lactate concentrations were continuously measured during the incremental test and at the completion of both tests. These tests were conducted on an air-braked kayak ergometer. Unlike the previous research, no significant relationships were found between KEP and VO_2max and LT in either male or female. MAOD correlated with KEP in female (r=0.75, p<0.05), but not in male. On the other hand, there was a significant correlation between KEP and total energy supply capacity (r=0.89, p<0.05, both male and female). In conclusion, total energy supply capacity accounted for a large part of KEP. These results indicate that flat-water kayak paddlers need to develop both aerobic and anaerobic capacities.

A double blind randomized control trial was performed to clarify the effects of acupuncture using a press needle on muscle pain, serum creatine kinase (CK) activity and muscle stiffness that resulted from running a marathon race. Sham press needles (placebo needles), which have the same package but without a needle tip, were developed by the acupuncture study authors. The subjects were 15 university students who participated in a marathon for the first time. Subjects were randomly assigned to two groups: the real acupuncture group and the placebo acupuncture group.
Both the real and the sham needles were applied to eight traditional Chinese acupoints in the lower limbs. They were applied before the start of the race and removed five days after the race.
Physical and biochemical examinations to determine the degree of muscle pain, CK activity, LDH isozyme, body flexion in standing position and muscle hardness were evaluated three times-before the start, after the finish, and five days after the finish.
Result: 1) The real acupuncture group showed less muscle pain than the placebo acupuncture group. 2) CK activity and LDH4-5 showed higher levels after the finish than before the start, but no significant difference was obtained among the groups. 3) No significant difference in time course change of the body flexion was obtained among the groups. 4) Hardness of vastus lateralis and vastus medialis showed higher levels after the finish than before the start, but no significant difference was obtained among the groups.