Maximal steady state versus state of conditioning

The origin of the maximal lactate steady state (MLSS)

The maximal lactate steady state, abbreviated as MLSS, is the maximal exercise intensity where the concentration of earlobe capillary or arterial blood lactate remains constant over time. In the late 1970s and early 1980s, we (i.e. Hermann Heck and co-workers) developed a direct test to determine the MLSS to investigate whether it occurred at a lactate concentration of 4 mmol.L- 1, as earlier predicted by Alois Mader and colleagues. The test consisted of each participant performing several constant-intensity running bouts of ≈ 30 min at intensities close to the estimated MLSS. During each run, we measured lactate every 5 min. Based on the results, we defined the MLSS as the "workload where the concentration of blood lactate does not increase more than 1 mmo.L- 1during the last 20 min of a constant load exercise". This MLSS protocol is impractical for performance testing as it requires too many exercise bouts, but it is a gold standard to determine the real MLSS. It is especially useful to validate indirect tests that seek to estimate the MLSS.

Comparação entre métodos invasivos e não invasivo de determinação da capacidade aeróbia em futebolistas profissionais

O Limiar Anaeróbio (Lan) pode ser determinado por protocolos que utilizam concentrações fixas de lactato sanguíneo como o OBLA (Onset of Blood Lactate Accumulation) e os que utilizam procedimentos mais individualizados, como o Lactato Mínimo (Lacmin). Independente do método, a mensuração da capacidade aeróbia através do Lan nesses casos exige a utilização de equipamentos sofisticados, além do elevado custo por atleta, o que torna sua aplicação limitada. Como alternativa, um dos testes não invasivos mais empregados no meio esportivo é o de 12 minutos proposto por Cooper. O objetivo principal do presente estudo foi comparar a intensidade de exercício obtida pelo teste de 12min com as intensidades correspondentes ao Lan obtido pelo protocolo adaptado ao de Tegtbur et al. (1993) (Lac minat) e pelo OBLA em futebolistas profissionais. Para tanto participaram 16 atletas pertencentes a uma equipe profissional filiada à série A3 do futebol paulista. Cada atleta foi avaliado nos três protocolos, com intervalo mínimo de 48 e máximo de 72 horas. Os resultados mostraram diferença (p < 0,05) entre as velocidades (km.h-1) obtidas pelo teste de Cooper (15,09 ± 0,94) e OBLA (14,28 ± 1,02); entretanto, esses testes apresentaram correlação significativa. Cooper e OBLA não apresentaram correlação com o Lac minat, mas as velocidades foram similares com esse protocolo. Dessa maneira, a partir da análise de regressão entre os valores de Cooper e OBLA foi possível determinar uma equação de correção que permita, através do teste de Cooper, a obtenção da intensidade correspondente ao Lan determinado pelo OBLA em futebolistas profissionais.

The concept of maximal lactate steady state: a bridge between biochemistry, physiology and sport science

The maximal lactate steady state (MLSS) is defined as the highest blood lactate concentration (MLSSc) and work load (MLSSw) that can be maintained over time without a continual blood lactate accumulation. A close relationship between endurance sport performance and MLSSw has been reported and the average velocity over a marathon is just below MLSSw. This work rate delineates the low- to high-intensity exercises at which carbohydrates contribute more than 50% of the total energy need and at which the fuel mix switches (crosses over) from predominantly fat to predominantly carbohydrate. The rate of metabolic adenosine triphosphate (ATP) turnover increases as a direct function of metabolic power output and the blood lactate at MLSS represents the highest point in the equilibrium between lactate appearance and disappearance both being equal to the lactate turnover. However, MLSSc has been reported to demonstrate a great variability between individuals (from 2-8 mmol/L) in capillary blood and not to be related to MLSSw. The fate of enhanced lactate clearance in trained individuals has been attributed primarily to oxidation in active muscle and gluconeogenesis in liver. The transport of lactate into and out of the cells is facilitated by monocarboxylate transporters (MCTs) which are transmembrane proteins and which are significantly improved by training. Endurance training increases the expression of MCT1 with intervariable effects on MCT4. The relationship between the concentration of the two MCTs and the performance parameters (i.e. the maximal distance run in 20 minutes) in elite athletes has not yet been reported. However, lactate exchange and removal indirectly estimated with velocity constants of the individual blood lactate recovery has been reported to be related to time to exhaustion at maximal oxygen uptake.

Anaerobic threshold: the concept and methods of measurement

The anaerobic threshold (AnT) is defined as the highest sustained intensity of exercise for which measurement of oxygen uptake can account for the entire energy requirement. At the AnT, the rate at which lactate appears in the blood will be equal to the rate of its disappearance. Although inadequate oxygen delivery may facilitate lactic acid production, there is no evidence that lactic acid production above the AnT results from inadequate oxygen delivery. There are many reasons for trying to quantify this intensity of exercise, including assessment of cardiovascular or pulmonary health, evaluation of training programs, and categorization of the intensity of exercise as mild, moderate, or intense. Several tests have been developed to determine the intensity of exercise associated with AnT: maximal lactate steady state, lactate minimum test, lactate threshold, OBLA, individual anaerobic threshold, and ventilatory threshold. Each approach permits an estimate of the intensity of exercise associated with AnT, but also has consistent and predictable error depending on protocol and the criteria used to identify the appropriate intensity of exercise. These tests are valuable, but when used to predict AnT, the term that describes the approach taken should be used to refer to the intensity that has been identified, rather than to refer to this intensity as the AnT.

Methods to determine aerobic endurance

Physiological testing of elite athletes requires the correct identification and assessment of sports-specific underlying factors. It is now recognised that performance in long-distance events is determined by maximal oxygen uptake (V(2 max)), energy cost of exercise and the maximal fractional utilisation of V(2 max) in any realised performance or as a corollary a set percentage of V(2 max) that could be endured as long as possible. This later ability is defined as endurance, and more precisely aerobic endurance, since V(2 max) sets the upper limit of aerobic pathway. It should be distinguished from endurance ability or endurance performance, which are synonymous with performance in long-distance events. The present review examines methods available in the literature to assess aerobic endurance. They are numerous and can be classified into two categories, namely direct and indirect methods. Direct methods bring together all indices that allow either a complete or a partial representation of the power-duration relationship, while indirect methods revolve around the determination of the so-called anaerobic threshold (AT). With regard to direct methods, performance in a series of tests provides a more complete and presumably more valid description of the power-duration relationship than performance in a single test, even if both approaches are well correlated with each other. However, the question remains open to determine which systems model should be employed among the several available in the literature, and how to use them in the prescription of training intensities. As for indirect methods, there is quantitative accumulation of data supporting the utilisation of the AT to assess aerobic endurance and to prescribe training intensities. However, it appears that: there is no unique intensity corresponding to the AT, since criteria available in the literature provide inconsistent results; and the non-invasive determination of the AT using ventilatory and heart rate data instead of blood lactate concentration ([La(-)](b)) is not valid. Added to the fact that the AT may not represent the optimal training intensity for elite athletes, it raises doubt on the usefulness of this theory without questioning, however, the usefulness of the whole [La(-)](b)-power curve to assess aerobic endurance and predict performance in long-distance events.

Exercise capacity of thoracotomy patients in the early postoperative period

OBJECTIVE

We investigated the mechanism involved with the initial drop and subsequent recovery of exercise capacity in the early postoperative period of thoracotomy patients.

METHODS

Sixteen patients (13 who had undergone lobectomy, 3 who had undergone pneumonectomy) underwent a routine pulmonary function test (PFT) and a cardiopulmonary exercise test preoperatively, within 14 postoperative days (POD; post-1; mean +/- SD, 9 +/- 2 POD), and after 14 POD (post-2; mean, 26 +/- 12 POD).

RESULTS

After surgery on post-1, PFT results of FVC, FEV(1), and maximum ventilatory volume (MVV) significantly decreased. Oxygen uptake (VO(2)) at a venous blood lactate level of 2.2 mmol/L (La-2. 2), which was adopted as the empirical anaerobic threshold, and maximum V O(2) (VO(2)max) decreased significantly to 88.2 +/- 7.9% and 73.1 +/- 15.4% of the preoperative values, respectively. La-2.2 min ventilation (VE)/ MVV and maximum VEmax)/MVV increased significantly from 0.36 +/- 0.08 to 0. 66 +/- 0.20 and from 0.58 +/- 0.14 to 0.80 +/- 0.09, respectively. On post-2, though La-2.2 VO(2) did not change, VO(2)max improved significantly to 81.5 +/- 19.7% of the preoperative values, in association with significant increases in maximal tidal volume and VEmax, which were produced by significant increases in the PFT results. La-2.2 VE/MVV also decreased significantly to 0.49 +/- 0.13, which indicated a sufficient recovery of respiratory reserve at submaximal exercise.

CONCLUSIONS

The initial drop of exercise capacity after lung resection seems to be derived from both circulatory and ventilatory limitations. Further, the subsequent recovery within 1 month seems to be produced by an improvement in ventilatory limitation, which was caused by the surgical injury to the chest wall.

Avaliação do fluxo arterial mesentérico em humanos durante o exercício

O aumento da atividade simpática durante o exercício dinâmico progressivo associa-se à resposta da concentração de lactato sangüíneo. Com o objetivo de testar a hipótese de que a diminuição do fluxo da artéria mesentérica superior também tenha relação com a lactiacidemia, oito indivíduos saudáveis (idade de 21-26 anos) foram submetidos a exercício com incremento progressivo de cargas ajustadas para os limiares de lactato, sendo o fluxo da artéria mesentérica superior medido pelo EcoDoppler. O fluxo na artéria mesentérica superior, calculado por medidas planimétricas das velocidades e medidas da área de secção, foi avaliado em repouso, após carga de 30 Watts, no primeiro e segundo limiares de lactato e esforço máximo, O fluxo (média ± EP) no repouso foi de 1.034 ± 112 ml/min, de 1.002 ± 124 na carga de 30 Watts, de 869 ± 122 ml/min no primeiro limiar de lactato, de 866 ± 127 ml/min no segundo limiar de lactato e de 689 ± 104 ml/min logo após o esforço máximo, Ocorreu uma redução linear, sendo a redução média na carga máxima de 34% do fluxo de repouso, não havendo correlação com os limiares de lactato. Portanto, a redução do fluxo da artéria mesentérica superior apresenta uma resposta linear ao exercício progressivo.

Maximal aerobic velocity measured by the 5-min running field test on two different fitness level groups

The aim of the study was to verify the validity and the accuracy of the 5-min running field test (5RFT) relatively to the classical treadmill test. Two groups of subjects were tested, the first one being made of sub-elite runners (G1, n = 18) and the second one of athletes of other individual or collective disciplines (G2, n = 23). To check the field technique, maximal aerobic velocity (vamax) and an approached VO2max calculated from vamax during the 5RFT were compared with the corresponding values directly determined during a treadmill test. vamax obtained on treadmill (vamax(t)) or during a 5RFT (vamax(5)) were significantly higher in G1 than in G2 (+3.7 km.h-1 and +3.6 km.h-1 among the test). In each group, the difference between vamax(t) and vamax(5) was not significant (19.4 +/- 1.0 vs 19.5 +/- 0.9 km.h-1 in G1; 15.7 +/- 2.2 vs 15.9 +/- 1.2 km.h-1 in G2). A significant correlation was found between vamax(t) and vamax(5) (slope = 0.92; r = 0.86 in G1; slope = 0.71; r = 0.84 in G2). In each group, the approached VO2max(5) was significantly higher than VO2max(t) (respectively 67.8 +/- 2.9 vs 63.7 +/- 3.5 in G1; 54.8 +/- 3.9 vs 52.0 +/- 3.2 ml.min-1.kg-1 in G2. Weak but significant correlations were found between VO2(t) and vamax(5) (r = 0.69 and r = 0.56 respectively in G1 and G2). In conclusion, the 5RFT allows to measure vamax accurately whatever the physical fitness of the subjects but more closely in runners than in non-runners. The low correlation between VO2max(t) and vamax(5) for both groups indicates that a vamax running field test is specific and cannot evaluate VO2max with reasonable accuracy whatever the group, runners or non-runners.

Use of blood lactate measurements for prediction of exercise performance and for control of training. Recommendations for long-distance running

Time over a distance, i.e. speed, is the reference for performance for all events whose rules are based on locomotion in different mechanical constraints. A certain power output has to be maintained during a distance or over time. The energy requirements and metabolic support for optimal performance are functions of the length of the race and the intensity at which it is completed. However, despite the complexity of the regulation of lactate metabolism, blood lactate measurements can be used by coaches for prediction of exercise performance. The anaerobic threshold, commonly defined as the exercise intensity, speed or fraction of maximal oxygen uptake (VO2max) at a fixed blood lactate level or at a maximal lactate steady-state (MLSS), has been accepted as a measure of the endurance. The blood lactate threshold, expressed as a fraction of the velocity associated with VO2max, depends on the relationship between velocity and oxygen uptake (VO2). The measurement of the post-competition blood lactate in short events (lasting 1 to 2 minutes) has been found to be related to the performance in events (400 to 800m in running). Blood lactate levels can be used to assist with determining training exercise intensity. However, to interpret the training effect on the blood lactate profile, the athlete's nutritional state and exercise protocol have also to be controlled. Moreover, improvement of fractional utilisation of VO2max at the MLSS has to be considered among all discriminating factors of the performance, such as the velocity associated with VO2max.

A test to approach maximal lactate steady-state in 12-year old boys and girls

The purpose of this study was to measure the running velocity corresponding to the individual maximal lactate steady-state of a group of 12-year old boys and girls on a treadmill. This running velocity (v MLST) was compared with the maximal aerobic running velocity (v a max) at which maximal oxygen uptake (VO2 max) occurs. Thirteen pupils of the same school whose puberal maturation corresponded to the end of stage 2 and the beginning of stage 3 of Tanner: 6 boys (12.2 years old +/- 0.5, 38.4 +/- 2 kg, 150 +/- 4.8 cm: group 1) and 7 girls (12.3 years old +/- 0.5, 37.6 +/- 6 kg, 151.4 +/- 5.6 cm: group 2) carried out two tests at one week interval. The first test was a maximal incremental test for the determination of VO2 max with Douglas's bag method and v a max. The purpose of the second test was the determination of maximal lactate steadystate velocity (v MLST) With two stages of ten minutes at 60 +/- 5% and 74 +/- 4.5% v a max separated by 40 minutes of complete rest (Billat, 1992); VO2max and v a max were significantly different, equal to 49.4 +/- 7 ml.min-1.kg-1, 40.4 +/- 4.7 ml.min-1.kg-1 and 12.6 +/- 0.2 km.h-1, 11.2 +/- 1.2 km.h-1 for group 1 and 2 respectively (P < 0.05). Moreover, maximal lactate steady state velocity (v MLST) was respectively equal to 64.8 +/- 12.5% and 64.6% +/- 12.5% VO2 max respectively, representing 67.8 +/- 6.2% and 68.8% +/- 8.3% v a max and was not significantly different for group 1 and 2. In conclusion, this study shows that maximal lactate steady-state velocity is not significantly different between young boys and girls of 12 years old, when expressed in fraction of VO2 max or v a max. However, VO2 max and v a max were significantly higher in boys: +27.2 and +11.6% higher respectively.

Prediction of endurance running performance for middle-aged and older runners

The purpose of this study was to develop regression equations that would sufficiently predict the endurance running performance (ERP) of middle-aged and older runners (n = 55, 43-79 years). Among many independent variables which were selected as possible predictors of the ERP, oxygen uptake corresponding to the lactate threshold (VO2@LT), or age was found to be the single best predictor. Some variables representing training habits correlated significantly but only moderately with the ERP. Linear multiple regression equations developed in this study were: V5km = 4.203 + 0.054X1 - 0.028X2 (r = 0.87) V5km = 4.436 + 0.045X1 - 0.033X2 + 0.005X3 (r = 0.89) V10km = 4.252 + 0.042X1 - 0.026X2 (r = 0.79) V10km = 4.371 + 0.037X1 - 0.031X2 + 0.005X3 (r = 0.82) VM = 3.207 + 0.048X1 - 0.022X2 (r = 0.91) VM = 3.707 + 0.038X1 - 0.031X2 + 0.005X3 (r = 0.93) where V5km, V10km and VM are the mean running velocity at 5 km, 10 km and marathon races, respectively, and X1 = VO2@LT (ml kg-1 min-1), X2 = age (year), and X3 = average running duration per workout (min). We suggest that the ERP of middle-aged and older runners can be predicted from a linear combination of VO2@LT and age or a combination of these variables plus average running duration per workout.

Time to exhaustion at VO2max and lactate steady state velocity in sub elite long-distance runners

The aim of the present study was to estimate the importance of lactate steady state velocity (WCL) of the running velocity at maximal oxygen uptake (Va max) and its time to exhaustion (Tlim), in the performance of a half marathon stated by the velocity over 21.1 km sustained by the runners during 1 h 12 min +/- 2 min 27 s. The population consisting of ten sub-elite male long distance runners (32 +/- 4 years old) was homogeneous with regard to their velocities on 21 km (V21 = 17.5 +/- 0.88 km.h-1, coefficient of variation, CV = 5%) and their aerobic maximal speed (Va max) (21.6 +/- 1.2 km.h-1, CV 6%). The fractional utilization of VO2max on 21 km was calculated from their own running economy (oxygen consumed per kilo of body mass and kilometer run (194 +/- 74 ml.kg-1.km-1). V21 represented 83 +/- 5% VO2max (VO2max = 68.1 +/- 4.1 ml.kg-1.min-1) and 81 +/- 3.3% Va max. The velocity corresponding to lactate steady state and called "lactate steady state velocity" (WCL) was measured according to a protocol proposed by CHASSAIN (1986). The subjects ran twenty minutes at a constant velocity representing 70-75% and 85-90% VO2max. Lactatemia was measured at the fifth (Lact 5) and the twentieth minute (Lact 20). Lactate slope was measured for two running velocities in order to determine the velocity (WCL) corresponding to lactate steady state, i.e. the lactate slope is equal to zero.(ABSTRACT TRUNCATED AT 250 WORDS)

A method for determining the maximal steady state of blood lactate concentration from two levels of submaximal exercise

The aim of this study was to estimate the characteristic exercise intensity (WCL) which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults [maximal oxygen uptake (VO2max) 62 (SD 7) ml.min-1.kg-1] exercised for two 30-min periods on a cycle ergometer at 67% (test 1.1) and 82% of VO2max (test 1.2) separated by 40 min. They exercised 4 days later for 30 min at 82% of VO2max without prior exercise (test 2). Blood lactate was collected for determination of lactic acid concentration every 5 min and heart rate and O2 uptake (VO2) were measured every 30 s. There were no significant differences at the 5th, 10th, 15th, 20th, 25th, or 30th min between VO2, lactacidaemia, and heart rate during tests 1.2 and 2. Moreover, we compared the exercise intensities (WCL) which produced the MLSS obtained during tests 1.1 and 1.2 or during tests 1.1 and 2 calculated from differential values of lactic acid blood concentration ([la-]b) between the 30th and the 5th min or between the 20th and the 5th min. There was no significant difference between the different values of WCL [68 (SD 9), 71 (SD 7, 73 (SD 6), 71 (SD 11)% of VO2max] (ANOVA test, P < 0.05). Four subjects ran for 60 min at their WCL determined from periods performed on the same day (test 1.1 and 1.2) and the difference between the [la-]b at 5 min and at 20 min (delta ([la-]b)) was computed.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimation of maximum oxygen uptake from submaximal exercise on a Concept II rowing ergometer

The purpose of this study was to develop a submaximal test, on the Concept II rowing ergometer, to estimate the maximum oxygen uptake (VO2 max) of male rowers and non-rowers. Eleven rowers and 14 non-rowers completed a submaximal and a maximal rowing test. The submaximal test consisted of exercising for 6 min at five different incremental speeds with at least 6 min recovery between each speed. Speed, heart rate and oxygen uptake were monitored during the last minute of each increment. In the maximal test, the subjects were asked to row for 6 min at a speed calculated to elicit 105 degrees, of their predicted maximum heart rate (HRmax). The HRmax was predicted from 220 beats min-1-age. Actual HRmax was recorded and the highest value of oxygen uptake measured was regarded as the subject's VO2 max. An analysis of covariance revealed that the data collected for rowers and non-rowers had to be considered separately. The greatest differences were seen for the submaximal speed-VO2 relationship, which showed that the rowers were more efficient on the ergometer than the non-rowers. Measured HRmax was found to average 9 beats min-1 below the predicted HRmax. The measured VO2 max values for the whole group averaged 4.16 +/- 0.64 1 min-1 (mean +/- S.D.). A nomogram was developed to predict VO2 max. At an exercise intensity of 80-90% HRmax, the average estimated VO2 max, using predicted HRmax calculated from 220 beats min-1-age, was 4.34 +/- 0.7 1 min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen transport during incremental exercise load as a predictor of operative risk in lung cancer patients

To evaluate functional parameters related to the morbidity and mortality after thoracotomy, exercise loading was applied in 31 lung cancer patients under right heart catheterization. The routine pulmonary function and predicted postoperative pulmonary function (ppo) parameters were also evaluated. Patients were grouped according to postoperative complications: no complications (group 1, n = 17), nonfatal complications (group 2, n = 10), and fatal complications (group 3, n = 4). In all the patients %VCppo was above 40 percent and in patients undergoing pneumonectomy, pulmonary artery mean pressure during the unilateral pulmonary artery occlusion test was below 25 mm Hg. FEV1 percent and MVV/BSA were statistically significant between groups 1 and 2 but were not between groups 1 and 3 or groups 2 and 3. The %FEV1 ppo was statistically significant between groups 1 and 2 and groups 1 and 3 but was not between groups 2 and 3. Thus, the routine pulmonary function and predicted postoperative lung function tests, although they are mandatory for screening patients who are at risk, did not definitely discriminate between patients experiencing nonfatal and fatal complications after thoracotomy. VO2/BSALa20, CILa20, O2D/BSALa20, and TPVRILa20 were statistically significant between groups 1 and 3 and groups 2 and 3: in all the group 3 patients, as well as three patients of group 1 and one of group 2, VO2/BSALa20 was below 350 ml/min/m2. On the other hand, O2D/BSALa20 was below 500 ml/min/m2 in all the group 3 patients, while it was above 560 ml/min/m2 in all patients in groups 1 and 2. O2D/BSALa20 was the only parameter that definitely discriminated between experiencing nonfatal and fatal complications. We conclude that in addition to the generally accepted functional guidelines, VO2/BSALa20 should be above 400 ml/min/m2 and O2D/BSALa20 should be above 500 ml/min/m2 in patients who will undergo thoracotomy.

Blood lactate in trained cyclists during cycle ergometry at critical power

The purposes of this investigation were to determine the validity of critical power (CP) as a measure of the work rate that can be maintained for a very long time without fatigue and to determine whether this corresponded with the maximal lactate steady-state (lass,max). Eight highly trained endurance cyclists (maximal oxygen uptake 74.1 ml.kg-1.min-1, SD 5.3) completed four cycle ergometer tests to exhaustion at pre-determined work rates (360, 425, 480 and 520 W). From these four co-ordinates of work and time to fatigue the regression of work limit on time limit was calculated for each individual (CP). The cyclists were then asked to exercise at their CP for 30 min. If CP could not be maintained, the resistance was reduced minimally to allow the subject to complete the test and maintain a blood lactate plateau. Capillary blood was sampled at 0,5,10,20 and 30 min into exercise for the analysis of lactate. Six of the eight cyclists were unable to maintain CP for 30 min without fatigue. In these subjects, the mean power attained was 6.4% below that estimated by CP. Mean blood lactates (n = 8) reached a steady-state (8.9 mmol.l-1 SD 1.6) during the last 20 min of exercise indicating that CP slightly overestimated lass,max, Individual blood lactates during the last 20 min of exercise were more closely related to the gamma-intercept of the CP curve (r = 0.78, P less than 0.05) than either CP (0.34, NS) or mean power output (r = 0.42, NS).

Cardiopulmonary exercise testing after single and double lung transplantation

The cardiopulmonary response to exercise was investigated in six single and six double lung transplant recipients using a three-minute incremental work rate protocol on a cycle ergometer. Maximum VO2 averaged 44.2 +/- 9.2 percent and 48.5 +/- 5.0 percent of predicted maximal VO2 in the single and double lung transplant groups, respectively. No evidence of ventilatory limitation to exercise was found in either group. Circulatory factors that may have limited exercise capacity included anemia and submaximal heart rates. There was a strong correlation between VO2/kg at venous blood lactate level of 2.2 mEq/L and vital capacity/body surface area in the single, but not in the double, lung recipients. Maximum VO2 in these lung transplant recipients was comparable to previously published values in heart-lung transplant recipients. The factors that limit maximum exercise capacity after lung transplantation deserve further study.

Critical determinants of endurance performance in middle-aged and elderly endurance runners with heterogeneous training habits

The current investigation was designed to determine which factor or what combination of factors would best account for distance running performance in middle-aged and elderly runners (mean age 57.5 years SD +/- 9.7) with heterogeneous training habits. Among 35 independent variables which were arbitrarily selected as possible prerequisites in the distance running performance of these runners, oxygen uptake (VO2) at lactate threshold (LT) (r = 0.781-0.889), maximal oxygen uptake (VO2 max) (r = 0.751 approximately 0.886), and chronological age (r = -0.736-(-)0.886) were found to be the 3 predictor variables showing the highest correlations with the mean running velocity at 5 km (V5km), 10 km (V10km), and marathon (VM). When all independent variables were used in a multiple regression analysis, any 3 or 4 variables selected from among VO2 at LT, chronological age, systolic blood pressure (SBP), atherogenic index (AI), and Katsura index (KI) were found to give the best explanation of V5km, V10km, or VM in a combined linear model. Linear multiple regression equations constructed for predicting the running performances were: V5km = 0.046X1-0.026X2-0.0056X3+5.17, V10km = 0.028X1-0.028X2-0.190X4-1.34X5+6.45, and VM = -0.0400X2-0.324X4-1.16X5+7.36, where X1 = VO2 at LT (ml.min-1.kg-1), X2 = chronological age, X3 = SBP, X4 = AI, and X5 = KI.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood lactate during constant-load exercise at aerobic and anaerobic thresholds

Venous blood lactate concentrations [1ab] were measured every 30 s in five athletes performing prolonged exercise at three constant intensities: the aerobic threshold (Thaer), the anaerobic threshold (Than) and at a work rate (IWR) intermediate between Thaer and Than. Measurements of oxygen consumption (VO2) and heart rate (HR) were made every min. Most of the subjects maintained constant intensity exercise for 45 min at Thaer and IWR, but at Than none could exercise for more than 30 min. Relationships between variations in [1ab] and concomitant changes in VO2 or HR were not statistically significant. Depending on the exercise intensity (Thaer, IWR, or Than) several different patterns of change in [1ab] have been identified. Subjects did not necessarily show the same pattern at comparable exercise intensities. Averaging [1ab] as a function of relative exercise intensity masked spatial and temporal characteristics of individual curves so that a common pattern could not be discerned at any of the three exercise levels studied. The differences among the subjects are better described on individual [1ab] curves when sampling has been made at time intervals sufficiently small to resolve individual characteristics.

Training induced physiological and metabolic changes associated with improvements in running performance

The purpose of the present study was to examine the relationship between improvements in running performance and some of the prominent physiological and metabolic adaptations to endurance exercise training. Twelve male undergraduates agreed to participate in this study (trial group), aged matched physical education students provided a control group. Running performance, assessed as a five km time trial, improved from 19.69 +/- 2.24 to 19.22 +/- 2.03 min in the trial group (P less than 0.01) after training. Maximal oxygen uptake values increased from 56.0 +/- 6.1 to 60.7 +/- 5.4 ml.kg-1.min-1, the running speed equivalent to a blood lactate reference concentration of 4 mmol.l-1 (V-4 mM) increased from 3.79 +/- 0.77 to 4.04 +/- 0.71 m.s-1, and the rate of oxygen consumption at 3.58 m.s-1 (running economy) increased from 43.3 +/- 3.2 to 45.0 +/- 3.4 ml.kg-1.min-1 (P less than 0.01). The control group did not show any significant changes. The improved five km times in the trial group were significantly correlated (r = -0.71; P less than 0.01) with changes in the running economy rather than changes in the VO2 max (r = -0.07; ns), or V-4 mM (r = -0.13; ns) suggesting the increased rate of oxygen utilization reflected a greater oxidative degradation of metabolic substrates together with a slower rate of lactate production.

Aerobic fitness and running performance of male and female recreational runners

The purpose of the present study was to assess fitness and running performance in a group of recreational runners (men, n = 18; women, n = 13). 'Fitness' was determined on the basis of their physiological and metabolic responses during maximal and submaximal exercise. There were strong correlations between VO2 max and treadmill running speeds equivalent to blood lactate concentrations of 2 mmol l-1 (V-2 mM) or 4 mmol l-1 (V-4 mM), 'relative running economy' and 5 km times (r = -0.84), but modest and non-significant correlations between muscle fibre composition and running performance. The results of the submaximal exercise tests suggested that the female runners were as well trained as the male runners. However, the men still recorded faster 5 km times (19.20 +/- 1.97 min vs 20.97 +/- 1.70 min; P less than 0.05). Therefore the of the present study suggest that the faster performance times recorded by the men were best explained by their higher VO2 max values, rather than their training status per se.

The evolving role of exercise testing prior to lung resection

Exercise testing prior to lung resection has long and honored tradition. It began as a test of tolerance using simple techniques such as stair climbing. This was followed by aggressive and invasive protocols using right cardiac catheterization in the search for pulmonary hypertension. More recently, measurement of VO2 with exercise has been reported to predict both postoperative mortality and survivable morbidity. Exercise testing holds promise as a noninvasive test to predict the physiologic outcome from lung resection. Significant questions remain concerning the pathophysiologic mechanisms responsible for an abnormal result and who should be denied thoracotomy based on these results.

A progressive shuttle run test to estimate maximal oxygen uptake

The purpose of the present study was to examine the validity of using a 20 m progressive shuttle run test to estimate maximal oxygen uptake. Running ability was described as the final level attained on the shuttle run test and as time on a 5 km run. Maximal oxygen uptake (VO2 max) was determined directly for seventy-four volunteers (36 men, 38 women) who also completed the shuttle run test. Maximal oxygen uptake values were 58.5 +/- 7.0 and 47.4 +/- 6.1 ml.kg-1.min-1 for the men and women respectively (mean +/- SD, P less than 0.01). The levels attained on the shuttle run test were 12.6 +/- 1.5 (men) and 9.6 +/- 1.8 (women; P less than 0.01). The correlation between VO2 max and shuttle level was 0.92. The correlation between VO2 max and the 5 km run was -0.94 and the correlation between both field tests was -0.96. The results of this study suggest that a progressive shuttle run test provides a valid estimate of VO2 max and indicates 5 km running potential in active men and women.

Comparison of incremental and steady state tests of endurance training

To compare the results obtained by incremental or constant work load exercises in the evaluation of endurance conditioning, a 20-week training programme was performed by 9 healthy human subjects on the bicycle ergometer for 1 h a day, 4 days a week, at 70-80% VO2max. Before and at the end of the training programme, (1) the blood lactate response to a progressive incremental exercise (18 W increments every 2nd min until exhaustion) was used to determine the aerobic and anaerobic thresholds (AeT and AnT respectively). On a different day, (2) blood lactate concentrations were measured during two sessions of constant work load exercises of 20 min duration corresponding to the relative intensities of AeT (1st session) and AnT (2nd session) levels obtained before training. A muscle biopsy was obtained from vastus lateralis at the end of these sessions to determine muscle lactate. AeT and AnT, when expressed as % VO2max, increased with training by 17% (p less than 0.01) and 9% (p less than 0.05) respectively. Constant workload exercise performed at AeT intensity was linked before training (60% VO2max) to a blood lactate steady state (4.8 +/- 1.4 mmol.l-1) whereas, after training, AeT intensity (73% VO2max) led to a blood lactate accumulation of up to 6.6 +/- 1.7 mmol.l-1 without significant modification of muscle lactate (7.6 +/- 3.1 and 8.2 +/- 2.8 mmol.kg-1 wet weight respectively). It is concluded that increase in AeT with training may reflect transient changes linked to lower early blood lactate accumulation during incremental exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of lung resection on blood lactate threshold in lung cancer patients

We studied the effect of a decrease in vital capacity (VC) on the blood lactate threshold detected during exercise in 16 preoperative (PRE) and 10 postoperative (POST) lung cancer patients who had undergone lobectomy or pneumonectomy. The PRE patients were selected on the basis of having normal preoperative pulmonary function. The POST patients were selected on the basis of having normal preoperative pulmonary function and a postoperative VC of less than 80%. The oxygen consumption/body surface area at a 2.2 m.mol.l-1 arterial lactate concentration (VO2/BSA at La-2.2) was adopted as the blood lactate threshold. VC/BSA in the POST group significantly correlated with VO2/BSA at La-2.2 (r = 0.85, P less than 0.01), but not in the PRE group. SaO2 at La-2.2 was 95.4 +/- 1.5% in the PRE group and 95.2 +/- 1.3% in the POST group. SaO2 at La-2.2 did not correlated with VC/BSA in either group. The hemoglobin concentration (Hb) in the arterial blood correlated significantly with VC/BSA in the POST group (r = 0.65, P less than 0.05) but not in the PRE group. These results indicate that VO2/BSA at La-2.2 was restricted by VC in patients with restrictive pulmonary function disorder. Of the three elements of oxygen delivery, Hb was a limiting factor for VO2/BSA at La-2.2 but SaO2 was not. Cardiac output, which was not measured in our study, was speculated to be another limiting factor for VO2/BSA at La-2.2.

Exercise tolerance test in lung cancer patients: the relationship between exercise capacity and postthoracotomy hospital mortality

To evaluate the significance of the blood lactate threshold as a predictor of postthoracotomy hospital mortality resulting from pulmonary complications, a 3-minute incremental exercise test was administered to 33 lung cancer patients who underwent thoracotomy between October, 1981, and May, 1984. The oxygen consumption/body surface area at an arterial lactate level of 20 mg/dl (VO2/BSA at La-20) was adopted as the blood lactate threshold. Age and pulmonary function parameters such as forced expiratory volume in one second (FEV1)/body surface area (BSA), FEV1/forced vital capacity, diffusing capacity for the carbon monoxide/lung volume, and maximum ventilatory volume/BSA revealed significant differences between patients with postthoracotomy pulmonary complications and those without such complications. However, there was no difference in pulmonary function test results between the surviving and deceased patients. In contrast, although VO2/BSA at La-20 did not differ between the patients with and without pulmonary complications, it differed significantly between the surviving and deceased patients. We concluded that postthoracotomy pulmonary complications depended on the severity of preoperatively associated pulmonary function disorders and that the blood lactate threshold expressed by VO2/BSA at La-20 was an important indicator of the risk of hospital mortality.

The effects of maximum steady state pace training on running performance

Maximum aerobic power (VO2 max), maximum anaerobic power (AP max), submaximal exercise heart rate (HRsub), and performance times for distances of 15m, 600 m, 3.22 km, and 10 km were evaluated in 12 male runners prior to and after 7 weeks of a running programme at each individual's maximum steady-state (MSS) pace. MSS pace, a running speed at which blood lactate is believed to equal 2.2 mmol . l-1, was calculated from weekly 3.22 km runs utilising the regression equation of LaFontaine et al (1981). During the training period, the mean MSS pace increased 11.3% from 3.76 to 4.19 m.s.-1. Body weight and maximal exercise heart rate were unaffected by MSS training. However, MSS training was associated with increases (p less than 0.05) in absolute VO2 max (8.9%) and VO2 max relative to body weight (8.1%), absolute AP max (3.7%) and AP max, relative to body weight (4.3%); decreases in resting HR (5.4%) and HRsub (6.9%); and decreases in performance times for runs of 15m (1.8%), 600 m (4.4%), 3.22 km (9.6%), and 10 km (12.1%). MSS paces determined prior to the pre- and post-training 10 km races were significantly related to the pre-training (r = 0.98) and post-training 10 km (r = 0.95) performance paces. Pretraining MSS pace, maximal aerobic power, and performance times for the 3.22 km and 10 km distances were highly related to improvements in MSS pace and performance times for the 3.22 km and 10 km runs. Our findings indicate that training at MSS pace is an effective method to increase maximal aerobic and anaerobic power, and decrease performance times for short- and middle-distance running events. Pre-training running performance may predict the magnitude of improvement due to MSS pace training.

A critical review of the literature on ratings scales for perceived exertion

The study of human performance and perceived exertion during physical activity has been an area of considerable interest and research for over 50 years. This review considers the evidence of many investigators who have been researching the physiological basis as well as non-physiological basis for the ratings of perceived exertion. During low levels of activity, physical perception in the working muscles appears to be the primary stimulus for effort perception. When work intensity exceeds the lactate threshold, incremental elevations in blood lactate complement peripheral input from the neuromuscular mechanisms. Once a critical absolute ventilatory threshold is reached, central input also contributes to effort perception. In most instances, peripheral input predominates over central cues, although it has been shown that pronounced central cues may dominate the perception of effort. Central (heart rate, VE, VO2) or local (muscle and blood lactate, adenosine triphosphate, creatine phosphokinase, glycogen) cues highlighted in these studies demonstrate both the complexity of effort perception, and the need for better understanding of the physiological components upon which it is based. Athletes have been shown to have a greater tendency to reduce perceptual ratings than their non-active counterparts. In view of these observations, it is apparent that a theoretical framework based upon physiological and psychological considerations may exist to support the concept of training-induced alterations in perceived exertion. This appears to be particularly true in higher ranges of exercise intensity. Part of the problem in reaching a conclusion on the issue of perceptual ratings trainability centres upon the agreement on what should be recognised as a significant decrement in perceived exertion. It is concluded that there is considerable variation in the findings of the literature and that any reported variations in performance may well be greatly influenced by intersubject variability, the type of exercise, and nutritional status of subject. Further research is required to understand this issue better.

Applied physiology of marathon running

Performance in marathon running is influenced by a variety of factors, most of which are of a physiological nature. Accordingly, the marathon runner must rely to a large extent on a high aerobic capacity. But great variations in maximal oxygen uptake (VO2 max) have been observed among runners with a similar performance capacity, indicating complementary factors are of importance for performance. The oxygen cost of running or the running economy (expressed, e.g. as VO2 15 at 15 km/h) as well as the fractional utilisation of VO2 max at marathon race pace (%VO2 Ma X VO2 max-1) [where Ma = mean marathon velocity] are additional factors which are known to affect the performance capacity. Together VO2 max, VO2 15 and %VO2 Ma X VO2 max-1 can almost entirely explain the variation in marathon performance. To a similar degree, these variables have also been found to explain the variations in the 'anaerobic threshold'. This factor, which is closely related to the metabolic response to increasing exercise intensities, is the single variable that has the highest predictive power for marathon performance. But a major limiting factor to marathon performance is probably the choice of fuels for the exercising muscles, which factor is related to the %VO2 Ma X VO2 max-1. Present indications are that marathon runners, compared with normal individuals, have a higher turnover rate in fat metabolism at given high exercise intensities expressed both in absolute (m/sec) and relative (%VO2 max) terms. The selection of fat for oxidation by the muscles is important since the stores of the most efficient fuel, the carbohydrates, are limited. The large amount of endurance training done by marathon runners is probably responsible for similar metabolic adaptations, which contribute to a delayed onset of fatigue and raise the VO2 Ma X VO2max-1. There is probably an upper limit in training kilometrage above which there are no improvements in the fractional utilisation of VO2 max at the marathon race pace. The influence of training on VO2 max and, to some extent, on the running economy appears, however, to be limited by genetic factors.

Effects of previous exercise on the ventilatory determination of the aerobic threshold

To study the effects of previous submaximal exercise on the ventilatory determination of the Aerobic Threshold (AeT), 16 men were subjected to three maximal exercise tests (standard test = ST, retest = RT, and test with previous exercise = TPE ) on a cycle ergometer. The protocol for the three tests consisted of 3 min pedalling against 25 W, followed by increments of 25 W every minute until volitional fatigue. TPE was preceded by 10 min cycling at a power output corresponding to the AeT as determined in ST, followed by a recovery period pedalling against 25 W until VO2 returned to values consistent with the initial VO2 response to 25 W. AeT was determined from the gas exchange curves (ventilatory equivalent for O2, fraction of expired O2, excess of VCO2, ventilation, and respiratory gas exchange ratio) printed every 30 s. The results showed good ST X RT reliability (r = 0.89). TPE showed significantly higher AeT values (2.548 +/- 0.44 1 X min-1) when compared with ST (2.049 +/- 0.331 X min-1) and RT (2.083 +/- 0.30 1 X min-1). There were no significant differences for the sub-threshold respiratory gas exchange ratios among the trials. The sub-threshold VO2 response showed significantly higher values for TPE at power outputs above 50 W. It was concluded that the performance of previous exercise can increase the value for the ventilatory determination of the AeT due to a faster sub-threshold VO2 response.

Relationships of the anaerobic threshold with the 5 km, 10 km, and 10 mile races

The purpose of present study was to assess the relationship between anaerobic threshold (AT) and performances in three different distance races (i.e., 5 km, 10 km, and 10 mile). AT, VO2 max, and related parameters for 17 young endurance runners aged 16--18 years tested on a treadmill with a discontinuous method. The determination of AT was based upon both gas exchange and blood lactate methods. Performances in the distance races were measured within nearly the same month as the time of experiment. Mean AT-VO2 was 51.0 ml . kg-1 . min-1 (2.837 l . min-1), while VO2 max averaged 64.1 ml . kg-1 . min-1 (3.568 l . min-1). AT-HR and %AT (AT-VO2/VO2 max) were 174.7 beats . min-1 and 79.6%, respectively. The correlations between VO2 max (ml . kg-1 . min-1) and performances in the three distance races were not high (r = -0.645, r = -0.674, r = -0.574), while those between AT-VO2 and performances was r = -0.945, r = -0.839, and r = -0.835, respectively. The latter results indicate that AT-VO2 alone would account for 83.9%, 70.4%, and 69.7% of the variance in the 5 km, 10 km, and 10 mile performances, respectively. Since r = -0.945 (5 km versus AT-VO2) is significantly different from r = -0.645 (5 km versus VO2 max), the 5 km performance appears to be more related to AT-VO2 than VO2 max. It is concluded that individual variance in the middle and long distance races (particularly the 5 km race) is better accounted for by the variance in AT-VO2 expressed as milliliters of oxygen per kilogram of body weight than by differences in VO2 max.

The significance of the aerobic-anaerobic transition for the determination of work load intensities during endurance training

Anaerobic and aerobic-anaerobic threshold (4 mmol/l lactate), as well as maximal capacity, were determined in seven cross country skiers of national level. All of them ran in a treadmill exercise for at least 30 min at constant heart rates as well as at constant running speed, both as previously determined for the aerobic-anaerobic threshold. During the exercise performed with a constant speed, lactate concentration initially rose to values of nearly 4 mmol/l and then remained essentially constant during the rest of the exercise. Heart rate displayed a slight but permanent increase and was on the average above 170 beats/min. A new arrangement of concepts for the anaerobic and aerobic-anaerobic threshold (as derived from energy metabolism) is suggested, that will make possible the determination of optimal work load intensities during endurance training by regulating heart rate.