Graded exercise testing for uphill walking studies

Pfl�gers Archiv European Journal of Physiology, 1994

2017

Purpose: To investigate a blood glucose profile and turn point during incremental exercise. Methods: Thirty-three national and international-level swimmers undertook a 7 × 200 m discontinuous, incremental, training set on a six-minute turnaround. Subjects were asked to be two hours post-absorptive, which resulted in a mean blood glucose level of 5.5 ± 0.57 mmol/l. After each 200 m-swim blood lactate, blood glucose, and heart rate were taken and values plotted against the velocity of each swim. A Glucose turn point (Gt) was observed and defined in this study as an upward deflection after which blood glucose continues to rise. The Dmax, Borch, and LogLog methods were used to calculate Anaerobic Threshold (AnT). Results: Significant differences were observed between Gt and all three methods of AnT for swim pace, heart rate, blood glucose, and lactate (P < 0.005). Conclusions: Blood glucose profiles and the identification of Gt are not linked to AnT. Gt may be an effective tool for t...

Lactate is an end product of glucose metabolism that is usually produced in a larger quantity during exercise. This increase in production during exercise has been understood to be the reason for fatigue. The aim of this study is to determine the responses of serum lactate to aerobic exercise among amateur athletes and non-athletes. 48 consenting males (24 amateur athletes and 24 non-athletes) participated in this comparative quasi-experimental design. Subjects cycled on a bicycle ergometer to attain moderate intensity exercise target heart rate (MIETHR) and maintained the MIETHR till exhaustion (15 on Borgs scale or volitional exertion) while the serum lactate was measured at intervals. Data were analyzed with descriptive statistics and inferential statistics of Analysis of variance (ANOVA). Alpha level was set at p < 0.05. The mean age of the participants was 26.08±2.28 and 28.13±1.51 for the athletes and non-athletes respectively. There was a significant difference p=0.001 Training induced adaptations include a lower serum lactate level, a point that should be noted in studying of metabolic adaptations.

British Journal of Sports Medicine, 2011

Objective This study analysed cardiopulmonary, metabolic and rating of perceived exertion (RPE) responses during exercise bouts performed below, at and above the second lactate threshold (LT2) intensity. Methods 10 healthy men performed constant workloads to exhaustion at the fi rst lactate threshold (LT1), LT2 and 25% of the difference between LT2 and maximal aerobic power output (TW 25% ) identifi ed during an incremental test. The time to exhaustion (TE) was 93.8 (18.0), 44.5 (16.0) and 22.8 (10.6) min at LT1, LT2 and TW 25% , respectively (p < 0.001). Metabolic and cardiopulmonary parameters and RPE data were time normalised to the exercise bout duration. The correlation between the slope of these variables and TE was calculated. Results Differences were found for respiratory exchange ratio (RER), RPE and potassium at LT1; RER, RPE, norepinephrine and potassium at LT2; and ventilation, respiratory rate (RR), RPE, lactate and potassium at TW 25% . Except for RR, no cardiopulmonary or metabolic parameter increased signifi cantly after 50% of the exercise duration, indicating a physiological steady state. VO 2 , heart rate and lactate at exhaustion in all exercise bouts were signifi cantly lower than values reached in the maximal incremental test. The slope of most metabolic variables was not correlated to TE in LT1, LT2 and TW 25% , whereas the slope of RPE was signifi cantly correlated to TE (r = −0.72 to −0.84; p < 0.05) for the three exercise intensities. Conclusion Contrary to traditional suggestions, exercise at LT1, LT2 and TW 25% intensities is performed and terminated in the presence of an overall physiological steady state.

Equine Veterinary Journal, 2010

In several species, physical conditioning (training) provokes a large shift in substrate utilisation during submaximal exercise. Few studies in horses have quantitatively examined these effects. Therefore, the effects of exercise training on plasma glucose kinetics during submaximal exercise were examined in 7 horses (5 Thoroughbred, 2 Standardbred; age 3-9 years) that had been paddock-rested for at least 6 months. Two days after determination of maximum aerobic capacity (VO 2max ), horses ran on a treadmill (4°incline) at 55% of VO 2max (UT) for 60 min or until fatigue and then completed 6 weeks of moderateintensity training on a treadmill (5 days/week). Following training and a second VO 2max test, the horses completed exercise trials at the same absolute (ABS) and relative (REL) workload in random order, with at least 3 days between tests. After training, VO 2max had increased (P<0.05) by 14.9% (mean ± s.e. pretraining 118.4 ± 7.4 ml/kg bwt/min; post-training 136.1 ± 7.8 ml/kg bwt/min). Mean exercise duration was longer (P<0.05) in the ABS trial (57 ± 1.9 min) than in the UT (46 ± 3.9 min) and REL (49 ± 4.6 min) trials. Plasma glucose concentration increased during exercise, and was lower (P<0.05) in ABS than in UT and REL at the end of exercise. Mean glucose rate of appearance (R a ) and disappearance (R d ) were 22 and 21% lower (P<0.05), respectively, in ABS than in UT, but mean glucose R a and R d did not differ between the UT and REL trials. Exerciseinduced changes in glucagon, epinephrine and norepinephrine were blunted (P<0.05) in ABS, but not REL, when compared to UT. It is concluded that 6 weeks of moderate-intensity training results in a decrease in glucose flux during submaximal exercise at the same absolute, but not relative, workload. The traininginduced decrease in glucose flux may, in part, be due to altered plasma concentrations of the major glucoregulatory hormones.

American Journal of Physiology-Endocrinology and Metabolism, 1999

We evaluated the hypotheses that alterations in glucose disposal rate (Rd) due to endurance training are the result of changed net glucose uptake by active muscle and that blood glucose is shunted to working muscle during exercise requiring high relative power output. We studied leg net glucose uptake during 1 h of cycle ergometry at two intensities before training [45 and 65% of peak rate of oxygen consumption (V˙o 2 peak)] and after training [65% pretrainingV˙o 2 peak, same absolute workload (ABT), and 65% posttrainingV˙o 2 peak, same relative workload (RLT)]. Nine male subjects (178.1 ± 2.5 cm, 81.8 ± 3.3 kg, 27.4 ± 2.0 yr) were tested before and after 9 wk of cycle ergometer training, five times a week at 75%V˙o 2 peak. The power output that elicited 66.0 ± 1.1% ofV˙o 2 peak before training elicited 54.0 ± 1.7% after training. Whole body glucose Rd decreased posttraining at ABT (5.45 ± 0.31 mg ⋅ kg−1 ⋅ min−1at 65% pretraining to 4.36 ± 0.44 mg ⋅ kg−1 ⋅ min−1) but not at RLT (5.9...

International Journal of Environmental Research and Public Health, 2020

During low-intensity exercise stages of the lactate threshold test, blood lactate concentrations gradually diminish due to the predominant utilization of total fat oxidation. However, it is unclear why blood glucose is also reduced in well-trained athletes who also exhibit decreased lactate concentrations. This review focuses on decreased glucose and lactate concentrations at low-exercise intensity performed in well-trained athletes. During low-intensity exercise, the accrued resting lactate may predominantly be transported via blood from the muscle cell to the liver/kidney. Accordingly, there is increased hepatic blood flow with relatively more hepatic glucose output than skeletal muscle glucose output. Hepatic lactate uptake and lactate output of skeletal muscle during recovery time remained similar which may support a predominant Cori cycle (re-synthesis). However, this pathway may be insufficient to produce the necessary glucose level because of the low concentration of lactate ...