Comparison of sweating components during endurance exercise under the same load in a hot environment and in a neutral thermal environment / 体力科学

Sweat contains electrolytes (minerals), therefore, it is necessary to consider its loss through sweat in the fluid replacement strategy in sports. The purpose of this study was to compare the concentration of components in sweat, such as electrolytes (minerals), when endurance exercise is performed in hot and neutral thermal environments. Eight men cycled for 60 min at 55% VO2peak under two envitonment conditions: a hot environment (WetBulb Globe Temperature (WBGT): 29.0±0.2℃; Heat) and a neutral thermal environment (WBGT: 20.5±0.2℃; Con). During exercise, sweat loss, core temperature, and heart rate (HR) were measured, and sweat from the chest, back, and thigh was collected. The core temperature, sweat loss, and HR increased significantly in Heat. The sweat electrolyte concentration was significantly higher in Heat than in Con only for Na. Regarding the amount of electrolyte loss from sweat, Na and K showed a significantly higher value than Con in Heat in comparison of each region, and the total loss amount of three regions in Cu also had a significantly higher value than Con in Heat. In addition, there was no difference in the concentration of Ca and Cu between the regions, but there was a significant difference in the amount of loss. It was concluded that even if there was no difference in the electrolyte concentration in sweat, the amount of electrolyte loss increased in K and Cu in a hot environment, and that there was a site difference in the amount of loss in Ca and Cu.

Relationships between running performance and the cross–sectional area of the psoas major, and peak oxygen uptake in elite junior long–distance runners / 体力科学

The purpose of this study was to examine the relationships between running performance and the cross–sectional area of the psoas major, peak oxygen uptake, and running economy in male junior long–distance runners. The subjects were 37 male junior athletes who achieved good records in interscholastic athletic competition during 5 years (2011–2015). Their seasonal best times in a 5,000 m race (5,000m–SB) were 14:04.11 ± 0:07.25 (13:53.64–14:16.15). In a multiple regression analysis, 5,000m–SB was statistical significantly correlated with the cross–sectional area of psoas major (16.0 ± 1.7 cm²) measured on magnetic resonance imaging and peak oxygen uptake (4.25 ± 0.36 l min^-1 [76.9 ± 5.8 ml min^-1 kg^-1]) during a lactate curve test comprising five stages. However, 5,000m–SB was not related to oxygen uptake at the work–load which was less than the load at the lactate threshold estimated by using the lactate curve test results. These results suggest that a high volume of the psoas major, the largest hip–flexor muscle, and peak oxygen uptake are among the important factors for junior long–distance runner performance.

PHYSIOLOGIC EFFECTS OF 1, 300 METERS ALTITUDE ON SWIMMING TRAINING / 体力科学

To investigate effects of 1, 300 meters altitude on swimming training, several physiologic parameters were examined in eight female high school swimmers before, during and after living and training for six days at 1, 300 meters altitude.<BR>Variables included peak heart rate (peakHR), rate of perceived exhaustion (RPE) and blood lactate concentration (BLa) associated with 200m swimming at submaximal and maximal speeds were measured 2-3 days before, during and 1-2 days after altitude exposure. Blood samples were collected before, during and after altitude exposure.<BR>On day 1 of altitude exposure, peakHR and RPE at submaximal speeds increased from pre-altitude values while BLa didn't change. At maximal speed, swimming speed and BLa decreased, RPE increased, and peakHR didn't change from pre-altitude.<BR>During altitude exposure, for the first three days of altiude exposure for peakHR and for all six days for RPE, the same submaximal speeds elicited greater values than pre-altitude.<BR>Post-altitude BLa at submaximal speeds was reduced compared to pre-altitude. Maximal heart rate, RPE, and BLa at maximal speed didn't change pre- to post-altitude. However, mean values of them decreased from pre-altitude.<BR>Erythropoietin was elevated above pre-altitude on day 2, and reticulocytes increased post-altitude significantly from pre-altitude.<BR>These results indicate that the relative workload increased during the training at 1, 300 meters. There also appeared to be some stimulation for erythropoiesis.<BR>In summary, this study found that 1, 300 meters altitude increased the difficulty of swimming training and six days at 1, 300 meters produced mild stimulation of erythropoiesis in these female swimmers

Physiologic effects of 1,300 meters altitude on swimming training / 体力科学

To investigate effects of 1, 300 meters altitude on swimming training, several physiologic parameters were examined in eight female high school swimmers before, during and after living and training for six days at 1, 300 meters altitude.<BR>Variables included peak heart rate (peakHR), rate of perceived exhaustion (RPE) and blood lactate concentration (BLa) associated with 200m swimming at submaximal and maximal speeds were measured 2-3 days before, during and 1-2 days after altitude exposure. Blood samples were collected before, during and after altitude exposure.<BR>On day 1 of altitude exposure, peakHR and RPE at submaximal speeds increased from pre-altitude values while BLa didn't change. At maximal speed, swimming speed and BLa decreased, RPE increased, and peakHR didn't change from pre-altitude.<BR>During altitude exposure, for the first three days of altiude exposure for peakHR and for all six days for RPE, the same submaximal speeds elicited greater values than pre-altitude.<BR>Post-altitude BLa at submaximal speeds was reduced compared to pre-altitude. Maximal heart rate, RPE, and BLa at maximal speed didn't change pre- to post-altitude. However, mean values of them decreased from pre-altitude.<BR>Erythropoietin was elevated above pre-altitude on day 2, and reticulocytes increased post-altitude significantly from pre-altitude.<BR>These results indicate that the relative workload increased during the training at 1, 300 meters. There also appeared to be some stimulation for erythropoiesis.<BR>In summary, this study found that 1, 300 meters altitude increased the difficulty of swimming training and six days at 1, 300 meters produced mild stimulation of erythropoiesis in these female swimmers

Evaluation of torque-velocity curve and maximal power output of knee extensor under isokinetic contraction / 体力科学

In recent years, the knee extensor forces of athletes have usually been evaluated by measuring isokinetic output torque. The purpose of this study was to confirm the usefulness of normalizing the torque (force) -velocity curve and calculating the maximal power of knee extensor under isokinetic contraction.<BR>Seventy two (46 elite, 26 non-elite) Japanese male sprinters were chosen as the subjects in this study. The peak torque of the dominant side of knee extensor was measured by using the isokinetic dynamometer (Cybex II<SUP>+</SUP>) in three different angular velocities of 60, 180, 300 deg/sec. Moreover, the isometric torque (0 deg/sec) was measured in 39 athletes, 120 and 240 deg/sec of contraction were performed in 12 out of 39 athletes.<BR>The exponent equation (<I>F = F<SUB>o</SUB>× e<SUP>av</SUP>- kv</I> : Fenn 1935) was applied to normalize the torquevelocity curve without including the coefficient of viscosity (<I>k</I>) . The maximal power and its optimal velocity was presumed from this torque-velocity curve. The average of measured torque at 0 deg/sec contraction (<I>F<SUB>0</SUB></I>) was lower than that of 60 deg/sec, therefore<I>F<SUB>0</SUB></I>was presumed as the same as the maximal power. Those parameters were not significantly different when calculated from 3 velocities (60, 180, 300 deg/sec) and 5 velocities (plus 120, 240 deg/sec) in 12 athletes. For this reason, each parameter was calculated from 3 velocities.<BR>The maximal torque (<I>F<SUB>0</SUB></I>/BW) was the same between elite and non-elite group (4.0 Nm/kg) . Nevertheless, the coefficient of torque loss (<I>a</I>), maximal power and its optimal velocity were significantly different (-0.1586 : -0.1908, 9.6 : 7.8 watt/kg, 373: 309 deg/sec, respectively. P<0.01 Student-t) . It was said that to normalize the torque-velocity curve or to presume the maximal knee extension power and its optimal velocity were useful to assess the muscle function or the performance of athletes under isokinetic contraction.