Biomedical subjects

A Usaj

Publications and source records attributed to A Usaj.

6 recordsLinked to original sources

PubMed2001

The endurance training effect on the oxygenation status of an isometrically contracted forearm muscle.

The aim of the study was to find the influence of training on the oxygenation status of a forearm muscle during submaximal isometric contraction. Six subjects performed a test of isometric contraction of a forearm muscle by continuous pressing of a handgrip dynamometer with a force of 15 kp, until exhaustion. The continuous measurements of oxygen saturation (%) (OXY), concentration of oxygenated haemoglobin (microM) (OXYHb), deoxygenated haemoglobin (microM) (DEOXYHb) and total haemoglobin (microM) (TOTHb) in blood, which passed through the muscle, were made by the near infrared spectroscope Oxymeter 96208 (ISS, USA). This test was repeated before and after the four weeks training period, which consisted of 5 continuous isometric contractions of 30 s at the beginning and of 1:15 min during the last week. Training did not significantly influence maximal isometric force (55.5 +/- 10 kp before, 60.2 +/- 9 kp after). On the other hand, the duration of isometric contraction increased from 271 +/- 117 s to 388 +/- 152 s (P < 0.05). Subjects were substantially different in duration of muscle contraction and also in oxygenation status during the contractions. Therefore, the relationship between these parameters and the training effect was calculated. The training effect was represented as the difference between the duration of muscle contraction before and after the training period., This parameter significantly correlated with relative oxygen saturation (r = -0.88; P < 0.05) and with relative concentration of deoxygenated haemoglobin (r = 0.87; P < 0.05). These results demonstrated the importance of individual training adaptations of forearm muscles. The increase of the duration of submaximal isometric contraction, as a training effect, can be dependent on larger muscle deoxygenation.

Adult↗

PubMed2000

Changes in blood pH, lactate concentration and pulmonary ventilation during incremental testing protocol on cycle ergometer.

We investigated mutual changes in the blood lactate concentration ([LA]), blood pH and pulmonary ventilation (VE) to obtain insight into the regulation of pH at different levels of the exercise intensity. For this purpose the ratio VE/[LA] (1/min/mmol/l) was determined at each particular pH corresponding to exercise intensity in seven healthy subjects on the cycle ergometer during incremental exercise test. Changes in VE/[LA] ratio were found to exhibit three phases. In the first phase, the ratio increased without significant changes in [LA] and pH until it reached certain individual peak value. In the second phase, VE/[LA] decreased because increases in [LA] were considerably bigger than those of VE. Decreases in blood pH followed those of VE/[LA], nevertheless differences existed among subjects depending on how successful individual subjects regulated their blood pH. In the third phase with the VE/[LA] values stabilized between 15 and 22 and pH values between 7.32 and 7.26, whereas differences between subjects became negligible. Similar trends to VE/[LA] were observed in case of the Onset of Blood Lactate Accumulation (OBLA) throughout the test at pH values below 7.32, as was manifested by the correlation coefficient. We conclude that blood pH regulation due to respiratory compensation of the lactate acidosis is more successful in subjects with better endurance (higher OBLA) but only when [LA] is slightly increased or at slight acidosis.

Adult↗

PubMed2000

The oxygen uptake threshold during incremental exercise test.

The linear relationship between oxygen consumption (VO2) and exercise intensity is a well established phenomenon observed during incremental exercise. Recently, a non-linear increase in VO2 has been reported by Zoladz et al., who used a relatively complicated method to describe the phenomenon. In this study, we tried to ascertain whether the same phenomenon, which we named the oxygen uptake threshold (OUT), could be described by a simple method, using the two best fitting lines adopted for the less and more steep parts of the VO2 increase. Our hypothesis was that the non-linear VO2 increase was the result of a continuous VO2 increase (oxygen drift) occurring during the more intense steps only. Therefore, we analysed the VO2 time course during each step. Six cyclists performed an incremental exercise test on a cyclo-ergometer. The lactate threshold (LT) was calculated by using the intersection point of the two best fitting lines in the diagram of log LA (lactate concentration) dependence on log P (Power). The time course of VO2 during each step was analysed by an exponential rise to the maximum model. The results showed that OUT could be determined in five of the six subjects, whereas LT could be determined in all six subjects. The power output determined by OUT (168 +/- 13 W) was similar to that determined by LT (180 +/- 25 W). The VO2 time course during each step showed steady values during low intensity exercise. At intensities above LT and OUT, however, VO2 increased continuously, showing oxygen drift. It may be concluded that OUT is a realistic phenomenon, which is based on oxygen drift.

Adult↗

PubMed1999

Endurance training increases fatty acid turnover, but not fat oxidation, in young men.

We examined the effects of exercise intensity and a 10-wk cycle ergometer training program [5 days/wk, 1 h, 75% peak oxygen consumption (VO2 peak)] on plasma free fatty acid (FFA) flux, total fat oxidation, and whole body lipolysis in healthy male subjects (n = 10; age = 25.6 +/- 1.0 yr). Two pretraining trials (45 and 65% of VO2 peak) and two posttraining trials (same absolute workload, 65% of old VO2 peak; and same relative workload, 65% of new VO2 peak) were performed by using an infusion of [1-13C]palmitate and [1,1,2,3, 3-2H]glycerol. An additional nine subjects (age 25.4 +/- 0.8 yr) were treated similarly but were infused with [1,1,2,3,3-2H]glycerol and not [1-13C]palmitate. Subjects were studied postabsorptive for 90 min of rest and 1 h of cycling exercise. After training, subjects increased VO2 peak by 9.4 +/- 1.4%. Pretraining, plasma FFA kinetics were inversely related to exercise intensity with rates of appearance (Ra) and disappearance (Rd) being significantly higher at 45 than at 65% VO2 peak (Ra: 8.14 +/- 1.28 vs. 6.64 +/- 0.46, Rd: 8. 03 +/- 1.28 vs. 6.42 +/- 0.41 mol. kg-1. min-1) (P </= 0.05). After training, when measured at the same absolute and relative intensities, FFA Ra increased to 8.84 +/- 1.1, 8.44 +/- 1.1 and Rd to 8.82 +/- 1.1, 8.35 +/- 1.1 mol. kg-1. min-1, respectively (P </= 0.05). Total fat oxidation determined from respiratory exchange ratio was elevated during exercise compared with rest, but did not differ among the four conditions. Glycerol Ra was elevated during exercise compared with rest but did not demonstrate significant intensity or training effects during exercise. Thus, in young men, plasma FFA flux is increased during exercise after endurance training, but total fat oxidation and whole-body lipolysis are unaffected when measured at the same absolute or relative exercise intensities.

Adolescent↗

PubMed1996

The increase of duration of isometric contraction may not relate to change of relative oxygenation of forearm muscle.

The aim of this study is to ascertain, how an increase in duration of isometric contraction influences tissue oxygenation of forearm muscles, undergoing physical training. Four subjects underwent 6 weeks of training of the left forearm muscles by performing isometric contractions. Subjects repeated 10 s contractions, 10-15 times in the first, and 20 s contractions in the second 3 week period. Relative oxygenation of forearm muscles was measured by using. Near Infrared Spectroscopy (CWS2000, NIM Incorporated, Philadelphia). The training increased the duration of isometric contraction at 20 kp of experimental forearm muscles by 41 +/- 25 s, which was more (P < 0.05) than in control forearm (8 +/- 4 s). This increase was not reflected in changes of maximum relative deoxygenation of experimental muscles, which decreased by only -6.9 +/- 14.4%. The results show that an increase in duration of isometric contraction may not depend on the oxygenation of muscle tissue at fixed force of 20 kp.

Exercise↗

PubMed1996

Blood pH and lactate kinetics in the assessment of running endurance.

To study how two types of testing protocols for the determination of the [LA] and blood pH kinetics during running match each other, a group of nine runners participated in two testing protocols. The first protocol consisted of a sequences of 8 x 2000 m runs at constant speed, which was increased on different testing days. The first protocol was used for the determination of running speed (v), [LA], pH and heart rate (HR) corresponding to the Lactate Threshold (LT) and the Threshold of Acidosis (TA), both occurring at similar running speeds (4.21 +/- 0.44 and 4.22 +/- 0.40 m/s) (mean +/- SD) and HR (159 +/- 7 and 160 +/- 9 1/min), [LA] = 2.0 +/- 0.6 mmol/l and pH = 7.411 +/- 0.018. Maximal steady values for [LA] (maxLAss) and minimal steady values for pH (minpHss) obtained by the second protocol were higher (p < 0.01) according to running speed (4.62 +/- 0.38 and 4.66 +/- 0.38 m/s), HR (172 +/- 7 and 174 +/- 8 1/min) and [LA] (5.7 +/- 1.3 mmol/l) and lower according to pH (7.364 +/- 0.021), respectively. Unlike similar running speeds determined by LT and TA, the minimal steady pH level occurred at a slightly higher speed than the speed at maxLAss. Additionally, we found a drift of pH towards a resting level, when [LA] fluctuated around a steady level. Furthermore, the parameters of pH kinetics correlated better with the running speed of the 4000 m run that was taken as the parameter of short endurance performance, than those of [LA] kinetics. We conclude that these differences in [LA] and pH kinetics could serve to predict the capabilities of runners with respect to the two endurance performance types: long and short.

Adult↗