Threshold for muscle lactate accumulation during progressive exercise.
ABSTRACT The purpose of this study was to investigate the relationship between muscle and blood lactate concentrations during progressive exercise. Seven endurance-trained male college students performed three incremental bicycle ergometer exercise tests. The first two tests (tests I and II) were identical and consisted of 3-min stage durations with 2-min rest intervals and increased by 50-W increments until exhaustion. During these tests, blood was sampled from a hyperemized earlobe for lactate and pH measurement (and from an antecubital vein during test I), and the exercise intensities corresponding to the lactate threshold (LT), individual anaerobic threshold (IAT), and onset of blood lactate accumulation (OBLA) were determined. The test III was performed at predetermined work loads (50 W below OBLA, at OBLA, and 50 W above OBLA), with the same stage and rest interval durations of tests I and II. Muscle biopsies for lactate and pH determination were taken at rest and immediately after the completion of the three exercise intensities. Blood samples were drawn simultaneously with each biopsy. Muscle lactate concentrations increased abruptly at exercise intensities greater than the "below-OBLA" stage [50.5% maximal O2 uptake (VO2 max)] and resembled a threshold. An increase in blood lactate and [H+] also occurred at the below-OBLA stage; however, no significant change in muscle [H+] was observed. Muscle lactate concentrations were highly correlated to blood lactate (r = 0.91), and muscle-to-blood lactate ratios at below-OBLA, at-OBLA, and above-OBLA stages were 0.74, 0.63, 0.96, and 0.95, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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ABSTRACT: The aim of this study was to establish the degree of similarity of exercise intensity values at the anaerobic threshold (AT) provided by five methods of lactate curve analysis, i.e., LTAT, LTloglog, 1 mmol AT, 4 mmol AT, and D-max. The pattern of similarities and differences was sought in athletes with varying levels of experience and sports skills, representing two disciplines with different prevailing types of power output during competition: on-road cycling (aerobic metabolism) and ice-hockey (anaerobic metabolism). All groups of athletes tested [Group 1: on-road cyclists (n = 19) at international sporting level (participants of the Olympic Games and World Championships); Group 2: on-road cyclists (n = 20) at national sporting level; Group 3: ice-hockey players (n = 24) at international sporting level (Polish National Team); and Group 4: ice-hockey players (n = 22) at international sporting level (Polish National Team U-20)] performed an incremental exercise. The greatest power values at the anaerobic threshold (PAT) were provided by the LTAT (221.93 ± 34.5 W) and 4 mmol AT (226.38 ± 32.33 W) methods, whereas the lowest were provided by the LTloglog (190.71 ± 25.92 W) method. The PAT produced by the LTloglog method was statistically significantly lower (p ≤ 0.001) than the values provided by LTAT, 4 mmol AT, and Dmax. The PAT levels were found to be statistically significantly different for power values determined using the 4 mmol AT and those produced by the 1 mmol AT (p ≤ 0.001) and D-max (p ≤ 0.01) methods. As shown by the analyses, PAT values vary in the international-level on-road cyclists depending on the method of lactate curve analysis applied.Journal of exercise science and fitness (JESF) 06/2013; 11(1):12-18. · 0.27 Impact Factor
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ABSTRACT: Exercise prescribed according to relative intensity is a routine feature in the exercise science literature and is intended to produce an approximately equivalent exercise stress in individuals with different absolute exercise capacities. The traditional approach has been to prescribe exercise intensity as a percentage of maximal oxygen uptake (VO2max) or maximum heart rate (HRmax) and these methods remain common in the literature. However, exercise intensity prescribed at a %VO2max or %HRmax does not necessarily place individuals at an equivalent intensity above resting levels. Furthermore, some individuals may be above and others below metabolic thresholds such as the aerobic threshold (AerT) or anaerobic threshold (AnT) at the same %VO2max or %HRmax. For these reasons, some authors have recommended that exercise intensity be prescribed relative to oxygen consumption reserve (VO2R), heart rate reserve (HRR), the AerT, or the AnT rather than relative to VO2max or HRmax. The aim of this review was to compare the physiological and practical implications of using each of these methods of relative exercise intensity prescription for research trials or training sessions. It is well established that an exercise bout at a fixed %VO2max or %HRmax may produce interindividual variation in blood lactate accumulation and a similar effect has been shown when relating exercise intensity to VO2R or HRR. Although individual variation in other markers of metabolic stress have seldom been reported, it is assumed that these responses would be similarly heterogeneous at a %VO2max, %HRmax, %VO2R, or %HRR of moderate-to-high intensity. In contrast, exercise prescribed relative to the AerT or AnT would be expected to produce less individual variation in metabolic responses and less individual variation in time to exhaustion at a constant exercise intensity. Furthermore, it would be expected that training prescribed relative to the AerT or AnT would provide a more homogenous training stimulus than training prescribed as a %VO2max. However, many of these theoretical advantages of threshold-related exercise prescription have yet to be directly demonstrated. On a practical level, the use of threshold-related exercise prescription has distinct disadvantages compared to the use of %VO2max or %HRmax. Thresholds determined from single incremental tests cannot be assumed to be accurate in all individuals without verification trials. Verification trials would involve two or three additional laboratory visits and would add considerably to the testing burden on both the participant and researcher. Threshold determination and verification would also involve blood lactate sampling, which is aversive to some participants and has a number of intrinsic and extrinsic sources of variation. Threshold measurements also tend to show higher day-to-day variation than VO2max or HRmax. In summary, each method of prescribing relative exercise intensity has both advantages and disadvantages when both theoretical and practical considerations are taken into account. It follows that the most appropriate method of relative exercise intensity prescription may vary with factors such as exercise intensity, number of participants, and participant characteristics. Considering a method's limitations as well as advantages and increased reporting of individual exercise responses will facilitate accurate interpretation of findings and help to identify areas for further study.Sports Medicine 04/2013; · 5.32 Impact Factor
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ABSTRACT: Garcia-Tabar I, Sánchez-Medina L, Aramendi JF, Ruesta M, Ibañez J, Gorostiaga EM. Heart Rate Variability Thresholds Predict Lactate Thresholds in Professional World-Class Road Cyclists. JEPonline 2013;16(5):38-50. This study aimed to predict widely used aerobic threshold (AeT) and anaerobic lactate thresholds (AnTs) and other cycling performance variables from mathematically determined heart rate variability thresholds (HRVTs). Twelve male professional world-class road cyclists performed a continuous maximal graded cycling test. Blood lactate concentration ([La-]), heart rate (HR), and RR intervals were monitored. Four different LTs (one AeT and three AnTs) were determined. HRVTs were determined from the standard deviation of the instantaneous beat-to-beat RR intervals (SD1). The AeT and one of the HRVT were not statistically different. Significant relationships (P<0.05) were found between the lactate thresholds and the HRVTs (r = 0.65-0.88). HRVTs strongly correlated with percentages of peak aerobic power (r = 0.94-0.97; P<0.001) and percentages of peak HR (r = 0.87-0.95; P<0.001) at which these thresholds occurred. The results indicate that lactate thresholds and percentages of peak aerobic power and peak HR at the HRVTs can be accurately predicted from SD1 values during a submaximal or maximal, non-invasive, low-cost, incremental exercise test in world-class road cyclists. The AeT might be coincidental with the vagal withdrawal of the heart.Journal of Exercise Physiology Online 10/2013; 16(5):38-50.