Biomechanics and Medicine in Swimming XI

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In addition, review of the scientific literature revealed that peak blood lactate levels are not significantly different between sexes, suggesting that the capacity to produce high lactate levels in the blood is probably acquired through training, rather than being sex related (Chatard et al. 1988; Jacobs et al.1983) The success in these tests seems to depend on the swimmer’s capacity to achieve higher velocities with lower blood lactate levels and/or utilizing a lower percentage of their VO2 max.(Ribeiro 1990). The purpose of the present study was to compare two specific tests for the determination of maximum accumulation of lactic acid in blood, based on two distances of 2x100m and 4x50m freestyle of maximum intensity and the same rest, comparing: a) the two tests and b) the two genders. Methods In the present study 8 swimmers of competitive level participated (4 males of 16.2±0.96 years, body mass 71.70±5.56kg and body stature 181.12±7.86cm and 4 females of 15.5±2.08 years, body mass 53.27±14.92kg and body stature 164.87±9.20cm). At the beginning, they swam 2x100 meters freestyle with maximum intensity and time performance and the blood lactate accumulation was measured. Five days later the same athletes were tested for 4x50 meters with 10 seconds rest between each effort of 50meters. In order to determine maximum concentration of lactic acid in the two different tests, capillary samples of blood were taken from the finger of 3rd, 5th, 7th and 10th minute of recovery time and analysed using the automatic analyzer Lactate Scout. For the comparison of mean values of blood lactate production in the two tests, the t - test for dependent samples was applied. Furthermore, the correlation coefficient was examined between the two tests. results The average time performance of swimmers in 2x100 meters freestyle was 120.79±5.67sec and 146.32±5.26sec while in 4x50m it was 120.43±5.96sec and 139.64±5.44sec in males and females respectively. Maximum accumulation of lactic acid in 2x100 meters freestyle was 11.3±2.6 and 10.3±2.1 mmol/l in males and females respectively. In relation to the test of 4x50 it was 12.1±2.3 and 12.5±3.9 mmol/l in males and females, respectively. Significant correlation was found between the two tests in lactic acid accumulation only among the females (r=0.871; p
BiomechanicsandmedicineinswimmingXi Can Blood Glucose Threshold be Determined in Swimmers Early in the Swimming Season? sengoku, Y. 1 , nakamura, K. 2 , takeda, t. 2 , nabekura, Y. 2 , tsubakimoto, s. 2 1 Heisei International University, Saitama, Japan 2 University of Tsukuba, Ibaraki, Japan The present study investigated whether blood glucose threshold (GT) could be determined in swimmers early in the swimming season. Seven university swimmers participated in this study and performed an incremental swimming test in a swimming flume. The test was conducted 4 – 5 weeks after the winter season commencement. Blood glucose (Glu) and blood lactate (Bla) were measured after each swimming incremental step, and the velocity corresponding to GT and blood lactate threshold (LT) was calculated. A LT was observed in all swimmers. However, Glu tended to decrease as the test started and then did not increase with swimming intensity. The low Glu observed during high intensities may be due to high glucose uptake by the working muscles or low endurance capacity in the early season. A GT could not be observed for all swimmers. Key words: endurance capacity, incremental swimming test, glucose metabolism IntroductIon Blood lactate concentration (Bla) is known to increase rapidly at high exercise intensity during an incremental test and the exercise intensity where Bla starts to rise is recognized as lactate threshold (LT). LT is observed when lactate production surpasses the lactate removal rate and thus this intensity is considered to demonstrate the boundary of aerobic and anaerobic energy supply and is utilized as an indicator of aerobic endurance performance (Hollman, 1985). Recently, Simões et al. (1999) reported that blood glucose (Glu) also increases during an incremental running test and a blood glucose threshold (GT) could be observed as for LT. It was reported that GT significantly correlates with LT, ventilation threshold (VT) and maximal lactate steady state (MLSS) (Simões et al., 1999; Simões et al., 2003; Sotero et al., 2009), thus GT may also be a good indicator for the aerobic-anaerobic transition. Simões et al. (1999) speculated that the increase of Glu when exercise became more intense was due to activated catecholamine and glucagon responses. It is considered that these hormonal activities will elevate when the exercise intensity rises above the anaerobic threshold (AT) and higher glucose production than glucose uptake by the skeletal muscle may lead to a Glu increment. For these reasons, it could be suggested that Glu reflects the shift of glucose metabolism and the GT could be a new index for energy metabolism during endurance exercise. However, observations of GT were reported only in running (Simões et al., 1999; Simões et al., 2003; Sotero et al., 2009) and cycling ( Júnior et al., 2001) and there is no study investigating GT in competitive swimmers whose endurance capacity is supposed to be important. As a previous study reported that Glu is lower in swimming than running after sub-maximal continuous exercise (Flynn et al., 1990), there are possibilities that different Glu response may occur even during incremental exercise. The purpose of the present study was to investigate Glu response during an incremental swimming test and verify whether GT could be determined as in running on land early in the swimming season. Methods Seven male university swimmers specialized in middle and long distance freestyle (n = 3) or individual medley (n = 4) participated in this study (20.1 ± 0.9 years of age, 173.1 ± 4.3 cm height, 65.2 ± 2.6 kg 224 body weight, 4:02.1 ± 5.8 for best 400 m freestyle). All swimmers were competing at national level championships. The measurement was conducted 4 – 5 weeks after the winter season commencement (Nov. 2009). The subjects were made fully aware of the risks, benefits and stresses of the study and their informed consent was obtained. All incremental swimming tests were conducted in a swimming flume at University of Tsukuba. The schematic representation of the testing is presented in Fig. 1. Swimming velocity of the incremental swimming test was individualized by each swimmer’s average swimming speed for their best 400 m freestyle (V400). After a 5 min warm up at 55% V400 and a 4 min rest, the participants completed an incremental swimming test consisting of a series of seven 3 min swimming steps with 2 min interval for blood sampling. The intensity of each step was increased from 55 % to 85% V400. W-up Time(min) 0 5 9 12 14 17 19 22 24 27 29 32 34 37 39 42 55%V400 55%V400 60%V400 65%V400 70%V400 75%V400 80%V400 85%V400 Bla ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ Glu ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑ Fig. 1 Schematic representation of the testing sequence Before the test and right after each incremental swimming step, blood samples were obtained from the finger tip and blood glucose (Glu; Glucocard, GT-1670, Arkray, Japan) and blood lactate (Bla; Lactate Pro, LT-1710, Arkray, Japan) were measured. The accuracy of the portable measurement devices are assessed in previous studies (Weitgasser et al., 1999; Tanner et al., 2010). Swimming velocity corresponding to GT (VGT) and LT (VLT) were analyzed utilizing Blood Lactate Endurance Marker Software (Lactate-E) (Newell et al., 2007). The subjects were instructed to refrain from strenuous physical activity and caffeine intake on the testing day and finish their last meal 3 h before testing. Only water ingestion was allowed after the final meal. All data are reported as mean ± SD. results Glu and Bla before the test were 5.5 ± 0.8 mmol·l -1 and 1.2 ± 0.4 mmol·l -1 respectively. Result of the Glu and Bla measurements during the incremental swimming test are presented in Fig. 2. LT was observed in all swimmers and the average VLT was 1.24 ± 0.05 m·sec -1 . Glu tended to decrease as the test started and did not increase at the higher swimming intensity steps. Consequently, a GT threshold could not be determined for all swimmers. Blood Lactate (mmol/l) Blood Glucose (mmol/l) 12.0 10.0 8.0 6.0 4.0 2.0 0.0 Bla Glu 55 60 65 70 75 80 85 %V 400 Fig. 2 Blood glucose and blood lactate responses during incremental swimming test
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Pahlen Norge AS Pahlen Norge AS Cha
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