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

Detection of ventilatory threshold by an automatic parabolic model

This work aims at presenting a method for automatic detection of the ventilatory threshold by modeling ventilatory equivalent of oxygen by a parabolic function. Thirty healthy male subjects were submitted to a single maximal oxygen uptake test, being monitored the ventilatory gas exchange signals. Ventilatory threshold by visual inspection, automatic v-slope and parabolic function methods was compared. The automatic methods showed no significant differences with visual inspection, but the parabolic technique presented higher consistence than v-slope. Since the parabolic method have low computation cost and is a simple method, it can be recommended as an alternative choice to v-slope method.

Estimation of the lactate threshold using bioelectrical impedance spectroscopy: a new noninvasive method

Bioelectrical Impedance Spectroscopy (BIS) is a noninvasive technology with potential application to study exercise physiology as body composition and estimation of maximal oxygen uptake. The aim of the study was to compare the power at lactate threshold (WLT) obtained using blood lactate concentration (BLC) with the power at lactate threshold from BIS (WBT). Fifty physical education students, 35 men and 15 women (age: 24.1 +/- 5.5 years; height: 168.6 +/- 24.6 cm; weight: 70.1 +/- 9.8 kg), undergoing incremental cycle ergometer test (ICET) have participated of the study. Significant correlations (p<0.05) for Pearson coefficient were found between the two methods (r = 0.96) and standard error of estimate (SEE)=5.6 W. The mean value showed 66.7+/- 20.3 W and 66.7+/- 21.1 W between the invasive technique (WLT) and noninvasive technique (WBT), respectively. The results of this study suggest that BIS, when applied with the ICET, is a valid method to estimate the power at LT.

Maximal lactate steady state in running mice: effect of exercise training

1. Maximal lactate steady state (MLSS) corresponds to the highest blood lactate concentration (MLSSc) and workload (MLSSw) that can be maintained over time without continual blood lactate accumulation and is considered an important marker of endurance exercise capacity. The present study was undertaken to determine MLSSw and MLSSc in running mice. In addition, we provide an exercise training protocol for mice based on MLSSw. 2. Maximal lactate steady state was determined by blood sampling during multiple sessions of constant-load exercise varying from 9 to 21 m/min in adult male C57BL/6J mice. The constant-load test lasted at least 21 min. The blood lactate concentration was analysed at rest and then at 7 min intervals during exercise. 3. The MLSSw was found to be 15.1 +/- 0.7 m/min and corresponded to 60 +/- 2% of maximal speed achieved during the incremental exercise testing. Intra- and interobserver variability of MLSSc showed reproducible findings. Exercise training was performed at MLSSw over a period of 8 weeks for 1 h/day and 5 days/week. Exercise training led to resting bradycardia (21%) and increased running performance (28%). Of interest, the MLSSw of trained mice was significantly higher than that in sedentary littermates (19.0 +/- 0.5 vs 14.2 +/- 0.5 m/min; P = 0.05), whereas MLSSc remained unchanged (3.0 mmol/L). 4. Altogether, we provide a valid and reliable protocol to improve endurance exercise capacity in mice performed at highest workload with predominant aerobic metabolism based on MLSS assessment.

Relationships between exercise capacity and front hoof longitudinal balance in horses

To the authors' knowledge, the effect of hoof balance alteration on exercise capacity or performance has not been investigated. With the aim of evaluating the relationships between longitudinal front hoof balance and exercise capacity (lactate vs. speed relationship, run time and stride characteristics), two experiments were undertaken. In the first test the horses, left unshod, performed an incremental speed test in which parameters chosen to evaluate exercise capacity were related to hoof longitudinal balance. In the second part of the study the same group of horses had the length of the toe altered (decreased and increased) with the application of shoes, while the angle of the foot and the height of the foot from the ground remained the same. The relative change in exercise capacity due to the alteration of longitudinal balance was observed. In the unshod experiment, lactate level at the speed of 10 ms-1 (5.0±2.0 mmoll-1) was significantly associated with the angles DC° (angle described by the dorsal cortex with respect to the ground; 50.0±3.2°) and PC° (angle described by the palmar cortex with respect to the ground; 29.6 ± 2.9°), while run time (14.07 ± 1.44 min) was associated with breakover indices (Breakover index1 0.33±0.03; Breakover index2 0.30 ± 0.04 – all values mean ± standard deviation (SD)) (breakover indices were created to express the distance between the point of the toe and the point of the third phalanx relative to the length of the palmar cortex or relative to the distance between the point of the third phalanx and the centre of rotation of the distal interphalangeal joint). These associations have to be judged cautiously because the influence of hoof balance on exercise capacity could be biased by other physiological factors and because hoof balance parameters themselves could reflect the conformation of other anatomical structures far from the phalanges. The selective alteration of front hoof balance in the second part of the study produced a significant difference in blood lactate level only at 6 ms-1 (mean ± SD: La6?m?s-1 0.32 ± 0.39 mmoll-1), with this benefit in terms of lactate level being associated with an increase in stride length (mean ± SD: ΔSL6ms-1 0.01 ± 0.05 m; ΔSL10ms-1 0.112 ± 0.218 m). In conclusion, while higher exercise capacity seemed to be associated with lower DC°, PC° and breakover indices, decreasing the toe length without altering the foot angle was beneficial only in terms of lactate level at the speed of 6 ms-1 for horses with DC° greater than 45°; this benefit was accompanied by a slight lengthening of the stride at both 6 and 10 ms-1.

Distribution of Power Output During Cycling

We aim to summarise the impact and mechanisms of work-rate pacing during individual cycling time trials (TTs). Unlike time-to-exhaustion tests, a TT provides an externally valid model for examining how an initial work rate is chosen and maintained by an athlete during self-selected exercise. The selection and distribution of work rate is one of many factors that influence cycling speed. Mathematical models are available to predict the impact of factors such as gradient and wind velocity on cycling speed, but only a few researchers have examined the inter-relationships between these factors and work-rate distribution within a TT. When environmental conditions are relatively stable (e.g. in a velodrome) and the TT is >10 minutes, then an even distribution of work rate is optimal. For a shorter TT (< or = 10 minutes), work rate should be increased during the starting effort because this proportion of total race time is significant. For a very short TT (< or = 2 minutes), the starting effort should be maximal, since the time saved during the starting phase is predicted to outweigh any time lost during the final metres because of fatigue. A similar 'time saving' rationale underpins the advice that work rate should vary in parallel with any changes in gradient or wind speed during a road TT. Increasing work rate in headwind and uphill sections, and vice versa, decreases the variability in speed and, therefore, the total race time. It seems that even experienced cyclists naturally select a supraoptimal work rate at the start of a longer TT. Whether such a start can be 'blunted' through coaching or the monitoring of psychophysiological variables is unknown. Similarly, the extent to which cyclists can vary and monitor work rate during a TT is unclear. There is evidence that sub-elite cyclists can vary work rate by +/-5% the average for a TT lasting 25-60 minutes, but such variability might be difficult with high-performance cyclists whose average work rate during a TT is already extremely high (>350 watts). During a TT, pacing strategy is regulated in a complex anticipatory system that monitors afferent feedback from various physiological systems, and then regulates the work rate so that potentially limiting changes do not occur before the endpoint of exercise is reached. It is critical that the endpoint of exercise is known by the cyclist so that adjustments to exercise work rate can be made within the context of an estimated finish time. Pacing strategies are thus the consequence of complex regulation and serve a dual role: they are both the result of homeostatic regulation by the brain, as well as being the means by which such regulation is achieved. The pacing strategy 'algorithm' is sited in the brain and would need afferent input from interoceptors, such as heart rate and respiratory rate, as well as exteroceptors providing information on local environmental conditions. Such inputs have been shown to induce activity in the thalamus, hypothalamus and the parietal somatosensory cortex. Knowledge of time, modulated by the cerebellum, basal ganglia and primary somatosensory cortex, would also input to the pacing algorithm as would information stored in memory about previous similar exercise bouts. How all this information is assimilated by the different regions of the brain is not known at present.

Efeitos do consumo prévio de carboidratos sobre a resposta glicêmica e desempenho

INTRODUÇÃO E OBJETIVO: A nutrição é uma importante ferramenta dentro da prática desportiva. Dentre os nutrientes, os carboidratos destacam-se como uma fonte energética importante. Dessa forma, o objetivo deste trabalho foi verificar a influência da resposta glicêmica no desempenho de indivíduos saudáveis, após a ingestão de bebidas com diferentes tipos de carboidratos. MÉTODOS: Foram avaliados 10 voluntários, do sexo masculino, com idade de 23 ± 2,1 anos. Os voluntários preencheram recordatório alimentar de três dias e de atividade física. Foram realizadas avaliações antropométricas e teste de cargas progressivas em cicloergômetro para determinação do consumo máximo de oxigênio e limiares ventilatórios. Cada voluntário realizou três testes submáximos na intensidade do 2º limiar ventilatório. Trinta minutos antes de cada teste submáximo, foram ingeridos 250ml de uma das bebidas compostas por: maltodextrina (malto), glicose (glicose), ou suco dietético (placebo). Foram realizadas punções de sangue capilar para determinação dos níveis glicêmicos e lactato sanguíneo. RESULTADOS E CONCLUSÃO: Houve aumento significativo na glicemia após 30 minutos do consumo da bebida malto (87,4 ± 11,2 para 116,9 ± 19,6ml.dl¹). Aos 15 minutos do exercício, houve diminuição nos níveis glicêmicos após o consumo das bebidas malto (116,9 ± 19,6 para 77,6 ± 14,5ml.dl¹) e glicose (113,2 ± 23,5 para 81,8 ± 13,1ml.dl¹) em comparação com o placebo. A ingestão da bebida glicose provocou aumento significativo na freqüência cardíaca durante o exercício (167,7 ± 14,2 e 177,1 ± 10,4bpm). O consumo de bebidas com diferentes tipos de carboidratos e de alto índice glicêmico antes do exercício não foi capaz de alterar o desempenho dos voluntários; entretanto, ocasionou alterações na glicemia e na freqüência cardíaca durante o exercício. Embora se especule que oscilações na glicemia durante o exercício possam prejudicar o desempenho em exercícios de longa duração, esse fato não foi verificado em nosso estudo.

Effects of a 30-km race upon salivary lactate correlation with blood lactate

Blood lactate has been used to determine the aerobic capacity and long distance performance. Recently, a new methodology has been suggested to supplant the invasive blood lactate techniques. Salivary lactate has received attention because it shows high correlation to blood lactate in progressive overload test. We evaluated the correlation between salivary and blood lactate during a long distance run and assessed possible changes in salivary lactate concentration. Fifteen expert marathon racers ran 30 km as fast as possible. Saliva and 25 muL of blood were collected at rest and at each 6 km for lactate determination. Blood lactate concentration increased in the 6th km and then remained constant until the end of the race. Salivary lactate increased after 18 km in relation to basal. We found high correlations between blood and saliva absolute lactate (r=0.772, p<0.05) and the blood lactate relative concentration corrected by protein (r=0.718, p<0.05). The highest correlation found between absolute and relative salivary lactate was r=0.994 (p<0.001). Our results show that it is possible to use salivary lactate with absolute values or relative protein concentration. In addition, salivary lactate showed a high correlation with blood lactate in endurance events.

A Simplified Strategy for the Estimation of the Exercise Ventilatory Thresholds

PURPOSE

To analyze the limits of agreement between exercise ventilatory threshold values (VT1 and VT2) estimated from a combination of pulmonary gas exchange and ventilatory variables (cardiopulmonary exercise testing) and those derived from an alternative approach based on the ventilatory response only (V(E), ventilometry).

METHODS

Forty-two nontrained subjects (24 males, aged 18-48, peak VO(2) = 33.1 +/- 8.6 mL.min(-1).kg(-1)) performed a maximum incremental cardiopulmonary exercise testing on an electromagnetically braked cycle ergometer. The participants breathed through a Pitot tube (Cardio2 System, MGC) and a fixed-resistance ventilometer (Micromed, Brazil), which were connected in series. HR values at the estimated VT (VTHR1 and VTHR2) were obtained by the conventional method (ventilatory equivalents, end-expiratory pressures for O(2) and CO(2), and the V-slope procedure) and an experimental approach (V(E) vs time, V(E)/time vs time, and breathing frequency vs time).

RESULTS

There were no significant between-method differences on VT(HR1), VT(HR2), VT(VE1), VT(VE2), and peak V(E) (P > 0.05). After certification of data normality, a Bland-Altman analysis revealed that the mean bias +/- 95% confidence interval of the between-method differences were lower for VT(HR2) than VT(HR1) (2 +/- 9 and 0 +/- 17 bpm, respectively). VT(HR2) according to ventilometry differed more than 10 bpm from the standard procedure in 3 out of 42 subjects (9%). Between-method differences were independent of the level of fitness, as estimated from peak VO(2) (P > 0.05).

CONCLUSIONS

: A simplified approach, based on the ventilatory response as a function of time, can provide acceptable estimates of the exercise ventilatory thresholds--especially VT2--during ramp-incremental cycle ergometry. This new strategy might prove to be useful for exercise training prescription in nontrained adults.

Running velocities and heart rates at fixed blood lactate concentrations in young soccer players

The purpose of this study was to examine the running velocities and heart rates at fixed lactate concentrations of young soccer players according to playing position and age. A total of 223 young male soccer players participated in this study. Each player performed incremental exercise tests on a treadmill. Running velocities and heart rates at 2 mmol/L-1, 2.5 mmol/L-1, 3 mmol/L-1, and 4 mmol/L-1 blood lactate concentrations were calculated with use of the spline function. Data were analyzed through analysis of variance to examine differences among various playing positions (ie, defenders, midfielders, and forwards) and 3 age groups (U17, under 17 y; U19, under 19 y; and U21, under 21 y). No significant differences were discerned between defenders, midfielders, and forwards in terms of running velocities and heart rates in accordance with specified lactate concentrations. Running velocities corresponding to all lactate concentrations showed no significant differences at all age groups, but heart rates in soccer players in the U21 and U19 age groups were significantly lower than in the U17 age group. Following a 3-y trial of 20 players, running velocities increased and heart rates decreased at all corresponding lactate concentrations. Results of this study suggest that (1) the endurance performance level of young soccer players is similar for all positions, and (2) heart rates are lowered with age and with training.

Interaction of carbohydrate metabolism and rat liquid gastric emptying in sustained running

BACKGROUND

Moderate to severe running usually leads to gastrointestinal dysmotility and critical energy exhaustion. It is unknown whether the carbohydrate metabolism of runners can influence gastric emptying (GE). Using a running rat model, the present study explored the impact of exercise/carbohydrate metabolism on liquid GE.

METHODS

Rats were put on the runways of a moving treadmill for 1 h. Trained rats underwent daily running 5 days a week for 4 weeks. Untrained rats were those put on a quiet treadmill to serve as sham exercise. On the motility study day, trained and untrained rats ran for 45 min. After orogastric feeding of radiochromium marker, they resumed running for an additional 15 min and were then killed in order to measure GE. Another group of trained and untrained rats received lactate infusion for 1 h in the quiet condition to measure their GE. The third group of rats received glucose infusion during running to measure GE.

RESULTS

Running of untrained (P < 0.05) and trained (P < 0.01) rats enhanced GE compared to sham exercise. Running for the untrained rats rather than the trained counterparts had diminished plasma glucose level (P < 0.05). Running also elevated plasma lactate levels for both untrained (P < 0.001) and trained rats (P < 0.01). Lactate infusion delayed GE in untrained (P < 0.01) and trained rats (P < 0.05). Glucose infusion of untrained rats during running was not only to correct hypoglycemia (P < 0.01) but also to restore their enhanced GE (P < 0.01).

CONCLUSIONS

Running-induced hypoglycemia, rather than lactate accumulation, is one of the essential factors leading to enhanced liquid GE in untrained rats.

Caracterização da curva do lactato sanguíneo e aplicabilidade do modelo Dmax durante protocolo progressivo em esteira rolante

PROPÓSITO: Caracterizar o comportamento do lactato sanguíneo ([La]), durante protocolo progressivo em esteira rolante, e investigar a aplicabilidade do modelo Dmax na detecção do limiar de lactato (LL) e rendimento esportivo. MÉTODOS: Vinte e sete homens atletas de nível regional executaram protocolo de Heck et al. (1985), com incrementos a cada três minutos. O rendimento esportivo foi obtido pela velocidade média da prova de 10km. O 1º e 2º LL foram determinados através de análise visual da curva das [La] (LLv1 e LLv2) e por interpolação na velocidade referente às concentrações de 2,0 e 3,5mmol.l¹ (LL2,0 e LL3,5). O modelo Dmax identificou o LL em valores medidos (DmaxMED) e preditos pelas funções polinomial (DmaxPOL), linear de dois segmentos (DmaxSEG) e exponencial contínua (DmaxEXP). A característica do lactato sanguíneo durante o teste incremental foi verificada pelos ajustes linear de dois segmentos e exponencial contínua. RESULTADOS: Não houve diferença significativa entre o somatório dos resíduos quadrados dos ajustes de curva, porém, houve tendência de melhor ajuste exponencial contínua em 70,4% da amostra. Enquanto não houve diferença significativa entre os DmaxMED, DmaxPOL, DmaxSEG e DmaxEXP, os métodos Dmax foram maiores do que LLv1, menores do que LL3,5 e não diferentes de LL2,0. Todos os critérios Dmax foram significativamente menores do que a velocidade média da prova de 10km. CONCLUSÕES: Enquanto as [La] tenderam a um aumento exponencial durante protocolos progressivos em esteira rolante, o modelo Dmax apresentou evidências da sua aplicabilidade para a detecção do LL, mas não do rendimento esportivo.

Specific incremental test in elite squash players

OBJECTIVES

To compare cardiorespiratory responses between incremental treadmill (non-specific) and field (sport specific) tests in elite squash players.

METHODS

Seven elite players (ranked 1 to 25 in their national federation including the World number 1) randomly performed an incremental treadmill test (TT) and a squash specific graded test (ST) to exhaustion. The ST consisted of repeated displacements replicating the game of squash, at increasing speed on the court. In both tests, ventilatory variables and heart rate were determined at the ventilatory threshold, respiratory compensation point, and maximal loads (max).

RESULTS

Heart rate and percentage maximal oxygen uptake (VO2MAX) at the ventilatory threshold and respiratory compensation point were not different between the ST and TT, whereas VO2MAX was higher in the ST than in the TT (63.6 (3.0) v 54.9 (2.5) ml/kg/min; p < 0.001). Time to exhaustion was not different between the ST and TT (1056 (180) v 962 (71) seconds) but correlated with the ranking of the players only in the ST (r = -0.96, p < 0.001).

CONCLUSIONS

VO2MAX values derived from laboratory testing were not relevant for accurately estimating fitness in elite squash players. So the ST may be used as an additional test for determination of training intensity. Improved training advice for prescribing aerobic exercise or perfecting stroke technique may result from these results.

Maximal lactate steady state determination with a single incremental test exercise

The aim of this study was to determine whether the power output associated with a maximal lactate steady state (MLSS) (.W(MLSS)) can be assessed using a single incremental cycling test. Eleven recreational sportsmen (age: 22+/-1 years, height: 175+/-6 cm, weight: 71+/-5 kg) volunteered to participate in the study. For each subject the first and second ventilatory thresholds (VT(1) and VT(2), respectively) and the power output corresponding to (respiratory exchange ratio) RER=1.00 were determined during an incremental test to exhaustion. Thereafter, each subject performed several 30-min constant load tests to determine MLSS. The workload used in the first constant test was set to the .W(RER=1.00) determined during the incremental test. .W(VT1) (175+/-24 W) and .W(VT2) (265+/-31 W) were significantly different from .W(MLSS )(220+/-36 W). Whereas, .W(RER=1.00) (224+/-33 W) was similar to .W(MLSS). HR, RER and .VE were significantly different between the 10th and the 30th minutes when exercising at .W(RER=1.00) and at .W(MLSS). In contrast, .VO(2) and .VCO(2) were stable over those 30-min constant tests. Power output at VT(1), RER=1.00 and VT(2) were all correlated to .W(MLSS) but the relationship was stronger between RER=1.00 and MLSS (R (2)=0.95). The present study shows that the power output associated with a RER value equal to 1.00 during an incremental test does not differ from that determined for MLSS. Hence, the MLSS can be estimated with a single exercise test.

Running velocities and heart rates at fixed blood lactate concentrations in elite soccer players

This study was undertaken to examine the endurance performance of elite soccer players, according to age and playing position. A total of 197 male soccer players participated in this study. Each player performed exercise tests on the treadmill that included 3-minute runs and 30-second blood sampling intervals. During these tests, running speeds at the first and second stages were 10 km/hr -1 and 12 km/hr -1, respectively. When these tests were completed, running speed was increased by 1 km/hr every 3 minutes until the runner reached exhaustion. Blood samples were analyzed immediately by means of an automated lactate analyzer. Heart rate was monitored continuously at 5-second intervals. Running velocities and heart rates at 2-mmol/L -1, 2.5-mmol/L -1, 3-mmol/L -1, and 4-mmol/L -1 blood lactate concentrations were calculated with use of the spline function. Analysis of variance was used to analyze data to determine the differences between playing positions (goalkeepers, defenders, midfielders, and forwards) and age groups (older than 30 years of age, between 25 and 29 years old, between 20 and 24 years old, and 19 years old and younger). Statistical significance was set at P<.01. No significant differences were revealed between defenders, midfielders, and forwards regarding running velocities and heart rates and their correlation with specified lactate concentrations. Goalkeepers demonstrated lower endurance performance than players in the other playing positions (P<.001). Running velocities corresponding to all lactate concentrations showed no significant differences in all age groups, but heart rates in soccer players older than 30 years of age were significantly lower than those of players in other age groups (P<.01). Results of this study suggest that the endurance performance level of professional players is similar for players in all positions, except for goalkeepers, and that endurance performance is not adversely affected when a person's age increases beyond 30 years of age.

Comparação entre a utilização de saliva e sangue para determinação do lactato mínimo em cicloergômetro e ergômetro de braço em mesa-tenistas

O objetivo do estudo foi verificar a possibilidade de determinar o teste de lactato mínimo (TLM) com concentrações de sódio (Na+), potássio (K+) e lactato (LAC) na saliva em ergômetro de braço e cicloergômetro. Foram participantes deste estudo oito mesa-tenistas de nível internacional. Como estímulo anaeróbio no TLM em ambos os ergômetros foram utilizados testes máximos de 30 segundos. No ergômetro de braço isocinético (Cybex Ube 2432) foi aplicada a força máxima com rotação fixa em 102rpm e no cicloergômetro, aplicada a carga de 7,5% do peso corporal (Kp). Após o estímulo anaeróbio no ergômetro de braço, foi iniciado um teste incremental com rotações na manivela constante a 60rpm, iniciado a 49 watts com aumento de 16 watts a cada estágio de três minutos de exercício. A intensidade correspondente ao TLM foi determinado com amostras de sangue e saliva (LACmin braço; Na+min braço-saliva e K+min braço-saliva, respectivamente). Para o cicloergômetro, a carga inicial foi de 85 watts e aumento de 17 watts com rotação do pedal constante a 70rpm. Cada estágio de exercício também teve a duração de três minutos. O LACmin foi determinado utilizando amostras de sangue e saliva (LACmin ciclo; Na+min ciclo-saliva, K+min ciclo-saliva e LACmin ciclo-saliva, respectivamente). Em ambos os ergômetros, as intensidades obtidas no TLM foram correspondentes à derivada zero do ajuste polinomial entre metabólito versus intensidade. Foram utilizados, como procedimentos estatísticos, o teste ANOVA One Way, teste t de Student pareado e teste de correlação de Pearson com níveis de significância de 5%. Os LACmin determinados com amostras de sangue e de saliva, tanto para o ergômetro de braço (LACmin braço 91,71 ± 12,43; Na+min braço-saliva 71,99 ± 23,42; K+min braço-saliva 79,67 ± 17,72), quanto para cicloergômetro (LACmin ciclo 157,68 ± 13,48; LACmin ciclo-saliva 135,49 ± 33,2; Na+min ciclo-saliva 121,81 ± 51,31; K+min ciclo-saliva 135,49 ± 33,21), não foram diferentes significativamente. Contudo, essas intensidades não apresentaram correlações significativas. Pode-se então concluir que a utilização de metabólitos na saliva para determinação do TLM não parece ser possível para esse protocolo quando os ergômetros utilizados são o ergômetro de braço isocinético e o cicloergômetro.

Comparison of computerized methods for detecting the ventilatory thresholds

The aim of this study was to compare computerized automatic methods to detect the ventilatory threshold (VT). Thirty apparently healthy and physically active volunteers [22.5 (6.5) years; 1.72 (0.08) m; 71.9 (8.5) kg] were submitted to a progressive and maximal cycle exercise. The gas exchange was monitored breath-by-breath with a fast gas analyser. The VT and respiratory compensation (RC) were automatically detected based on the respiratory exchange ratio, the ventilatory equivalent for O2 and the ventilatory equivalent for CO2, pulmonary ventilation, end-tidal PO2 and PCO2, and v-slope. In addition, VT and RC were also determined independently by visual inspection by two experienced investigators, and the results were compared with those of the automatic procedures. The automatic VT averaged 77% of the maximal VO2 and the RC 88%. The agreement between the experienced observers was very close [mean difference: 44.4 (16.1) ml, r = 0.94, not significant]. Data were expressed as the mean value together with the standard deviation in each case. The automatic and visual inspection procedures did not present significant differences, resulting in 29.6 (29.6) ml with a reliability of r = 0.86. All methods were significantly correlated for VT and RC (r = 0.93 on average, P < 0.01). ANOVA did not show differences between either the VT methods (P = 0.131) or the RC methods (P = 0.41). In conclusion, the present study has compared several simultaneous breath-by-breath ergospirometric methods that are used to describe the anaerobic threshold, showing high confidence when compared to visual inspection. No statistical differences were found between the VT and RC techniques for physically active subjects indicating that these methods may be equally effectively employed.

Science and cycling: current knowledge and future directions for research

In this holistic review of cycling science, the objectives are: (1) to identify the various human and environmental factors that influence cycling power output and velocity; (2) to discuss, with the aid of a schematic model, the often complex interrelationships between these factors; and (3) to suggest future directions for research to help clarify how cycling performance can be optimized, given different race disciplines, environments and riders. Most successful cyclists, irrespective of the race discipline, have a high maximal aerobic power output measured from an incremental test, and an ability to work at relatively high power outputs for long periods. The relationship between these characteristics and inherent physiological factors such as muscle capilliarization and muscle fibre type is complicated by inter-individual differences in selecting cadence for different race conditions. More research is needed on high-class professional riders, since they probably represent the pinnacle of natural selection for, and physiological adaptation to, endurance exercise. Recent advances in mathematical modelling and bicycle-mounted strain gauges, which can measure power directly in races, are starting to help unravel the interrelationships between the various resistive forces on the bicycle (e.g. air and rolling resistance, gravity). Interventions on rider position to optimize aerodynamics should also consider the impact on power output of the rider. All-terrain bicycle (ATB) racing is a neglected discipline in terms of the characterization of power outputs in race conditions and the modelling of the effects of the different design of bicycle frame and components on the magnitude of resistive forces. A direct application of mathematical models of cycling velocity has been in identifying optimal pacing strategies for different race conditions. Such data should, nevertheless, be considered alongside physiological optimization of power output in a race. An even distribution of power output is both physiologically and biophysically optimal for longer ( > 4 km) time-trials held in conditions of unvarying wind and gradient. For shorter races (e.g. a 1 km time-trial), an 'all out' effort from the start is advised to 'save' time during the initial phase that contributes most to total race time and to optimize the contribution of kinetic energy to race velocity. From a biophysical standpoint, the optimum pacing strategy for road time-trials may involve increasing power in headwinds and uphill sections and decreasing power in tailwinds and when travelling downhill. More research, using models and direct power measurement, is needed to elucidate fully how much such a pacing strategy might save time in a real race and how much a variable power output can be tolerated by a rider. The cyclist's diet is a multifactorial issue in itself and many researchers have tried to examine aspects of cycling nutrition (e.g. timing, amount, composition) in isolation. Only recently have researchers attempted to analyse interrelationships between dietary factors (e.g. the link between pre-race and in-race dietary effects on performance). The thermal environment is a mediating factor in choice of diet, since there may be competing interests of replacing lost fluid and depleted glycogen during and after a race. Given the prevalence of stage racing in professional cycling, more research into the influence of nutrition on repeated bouts of exercise performance and training is required.

Homocysteine increases during endurance exercise

Hyperhomocysteinemia is a risk factor for cardiovascular and other diseases. Recently many endogenous and exogenous modulators of homocysteine (Hcy) have become known, e.g., B-vitamins. However, little is known about the effect of exercise on Hcy. The purpose of this study was to investigate the effect of three different types of acute endurance exercise on serum Hcy. We measured Hcy in 100 recreational athletes (87 males, 13 females) who participated in a marathon race (n = 46), a 100 km run (100 km; n = 12) or a 120 km mountain bike race (n = 42). Blood samples were taken before, 15 min and 3 h after the race. In athletes with pre-race Hcy > 12 micromol/l we also determined folate and vitamin B12. Marathon running induced a Hcy increase of 64%, while mountain biking and 100 km running had no significant effect on Hcy. Pre-race Hcy (25th-75th percentile) overall; marathon race; 100 km; mountain bike race was 9.7 (7.1-11.5) micromol/l; 9.8 (7.4-11.1) micromol/l; 10.2 (6.6-13.2) micromol/l; 9.1 (6.9-13.5) micromol/l, respectively. At 15 min and 3 h post-race, Hcy was 11.9 (8.4-16.4) micromol/l; 16.1 (12.7-20.4) micromol/l; 9.5 (7.8-15.9) micromol/l; 8.8 (7.1-11.2) micromol/l, respectively, and 11.5 (8.9-15.7) micromol/l; 14.9 (11.5-20.0) micromol/l; 10.0 (8.1-11.8) micromol/l; 9.4 (7.4-12.1) micromol/l, respectively. The change in Hcy correlated negatively with the running time. Twenty-three athletes had pre-race Hcy levels > 12 micromol/l, which were associated with relatively low folate (14.3 (11.6-18.9) nmol/l) and vitamin B12 levels (231 (183-261) pmol/l). Endurance exercise may induce a considerable Hcy increase, which varies between different disciplines and is most probably determined by the duration and intensity of exercise. Furthermore, about 25% of recreational endurance athletes exhibited hyperhomocysteinemia in association with low vitamin B12 and folate levels.

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.

The effects of interval training on oxygen pulse and performance in supra-threshold runs

The aim of this study was to examine (i) the effects of a severe interval training period on oxygen pulse kinetics (O2-p, the ratio between VO2 and heart rate), and (ii) to study the consequences of these effects on the variation of performance (time to exhaustion) during severe runs. Seven athletes were tested before and after an eight-weeks period of a specific intermittent training at v Delta 50, i.e., the intermediate velocity between the lactate threshold (vLT) and the velocity associated with VO2max (vVO2max ). During the test sessions, athletes performed an incremental test and an all-out test at the pretraining v Delta 50. After the training period they also completed an additional all-out test at the posttraining v Delta 50 (v Delta 50bis). Results showed that after training there was i) an increase in the O2-p maximal value during the incremental test (22.7 +/- 1.5 mlO2.b-1 vs. 20.6 +/- 1.5 mlO2.b-1; p < 0.04), ii) a decrease in the time to reach the O2-p steady state (TRO2-p ) at the same absolute v Delta 50 (33 +/- 7 s vs. 60 +/- 27 s; p < 0.04) and iii) an increase in the O2-p steady state duration (TSSO2-p) at the same absolute v Delta 50 (552 +/- 201 s vs. 407 +/- 106 s; p < 0.04). However, there was no relationship between the improvement of these two O 2 -p kinetics parameters (TRO2-p and TSS O2-p) and those of the performance. This study found that after an individualised interval-training program conducted at the same absolute velocity, the O2-p kinetics reached a steady state quicker and for a longer duration than before training. This is however not related with the improvement of performance.

Whichever the initial training status, any increase in velocity at lactate threshold appears as a major factor in improved time to exhaustion at the same severe velocity after training

The first purpose of this study was to assess the eventual training adaptations in the time to exhaustion at the same severe velocity occurring after severe interval-training programs in few- and well-trained subjects. In the event of such training adaptations, the second purpose was to identify the discriminant factors of performance improvement according to the initial training status. Seven few- and six well-trained subjects performed: firstly, an incremental test to determine the maximal oxygen consumption (VO2max), the energy cost of running (ECR), the velocity associated with the achievement of VO2max (vVO2max) and the lactate threshold (LT expressed in VO2, km x h(-1), % vVO2max); secondly, an all-out test at the velocity corresponding to the midway between vLT and vVO2max (vdelta50) to determine the time to exhaustion (tmax); such tests were carried out before and after 4- and 8-week severe interval-training programs. In the few-trained subjects, all factors of performance (i.e., VO2max, ECR, vVO2max, LT expressed in VO2, km x h(-1), % vVO2max) and tmax at the pre-training vdelta50 were improved after training (+8, -8, +7, +9, +14, +6% and +79%, respectively); only the increase in vLT was related to the one in tmax (r = 0.714, p < or = 0.05, n = 7). In the well-trained subjects, only vVO2max was improved (+3%) due to the decrease in ECR (-3%), tmax at the pre-training vdelta50 did not vary after training; only the three subjects (over six) who improved their vLT (+0.5, +0.5, +0.8 km x h(-1), respectively) improved their tmax (+10, +24, +101%, respectively) (r = 0.895, p < or = 0.01, n = 6). So, whichever the initial training status, any training-induced adaptation in vLT appeared as a major factor of performance improvement especially at supra-LT velocities.

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.

Physiological correlates with endurance running performance in trained adolescents

PURPOSE

To examine the relationship between competitive 800-m and 1500-m performance times and a number of physiological variables in a group of endurance-trained, adolescent runners.

METHODS

Twenty-three boys and 17 girls volunteered to participate in the study. Track-based, running performance times were available for 18 boys and 14 girls for the 800 m, and 16 boys and 13 girls for the 1500 m. The relationships between these times and the following physiological variables were determined: peak VO(2) running economy (RE), estimated running speed at peak vV0(2peak), peak and mean anaerobic power, and fixed [BLa ] at 2.0, 2.5, and 4.0 mmol.L.

RESULTS

RE and vV0(2peak) were significant independent variables for the boys' 800 m (r = 0.62 and -0.62, < 0.01). For the girls, once chronological age was partialled out, none of the measured variables were significantly related to 800-m performance. For the 1500-m event, peak V0(2), vV0(2peak), and the running speed at 2.5 mmol.L (v2.5) were significant independent variables in the boys (r = -0.43, -0.39, and -0.53, < 0.05) and girls (r = -0.50, -0.61, and -0.54, < 0.05). In addition, the V0(2) at 2.5 mmol.L V0(2) (2.5) was related to the 1500-m time in the girls (r = -0.54, < 0.05).

CONCLUSION

The physiological variables that were most strongly correlated with middle-distance running performance were v2.5 and the vV0(2peak). To a lesser extent peak V02 may also play a role although it is understood that its contribution may be accounted by vV0(2 peak).

Method of lactate elevation does not affect the determination of the lactate minimum

PURPOSE

The aim of the study was to examine the effects of different lactate elevation protocols on the determination of the lactate minimum (Lac(min)) point.

METHODS

Eight highly trained racing cyclists each completed four continuous ramp lactate minimum tests using the following blood lactate elevation protocols: 1) continuous ramp maximal aerobic power (RMP(max)) assessment, 2) 30-s maximal sprint, 3) 40-s maximal sprint, and 4) two 20-s maximal sprints separated by a 1-min recovery. Each blood lactate elevation protocol was followed by a 5-min active recovery leading into a continuous ramp test commencing at a power of 60% of RMP(max), using a 6 W x min ramp rate, lasting 15 min.

RESULTS

Peak [La](b) values were significantly higher (P > 0.05) after the RMP(max) compared with all other protocols and higher in the 40-s versus 30-s sprint. However, by the start of Lac(min) ramp, [La](b) after the RMP(max) was no longer higher than the 40-s sprint, but Lac(min) [La](b) was similar for all protocols. This resulted in no differences in the total decline of [La](b) measured as a percentage from the highest to the lowest value. At Lac(min) point, there were no significant differences in power (P > 0.05), but heart rate was higher in the RMP versus 2 x 20 s and VO(2) was significantly higher after the 40 s compared with the 2 x 20 s protocol.

CONCLUSION

This study demonstrated that the determination of lactate minimum power in cycling is not dependent upon the lactate elevation protocol.

The scientific basis for high-intensity interval training: optimising training programmes and maximising performance in highly trained endurance athletes

While the physiological adaptations that occur following endurance training in previously sedentary and recreationally active individuals are relatively well understood, the adaptations to training in already highly trained endurance athletes remain unclear. While significant improvements in endurance performance and corresponding physiological markers are evident following submaximal endurance training in sedentary and recreationally active groups, an additional increase in submaximal training (i.e. volume) in highly trained individuals does not appear to further enhance either endurance performance or associated physiological variables [e.g. peak oxygen uptake (VO2peak), oxidative enzyme activity]. It seems that, for athletes who are already trained, improvements in endurance performance can be achieved only through high-intensity interval training (HIT). The limited research which has examined changes in muscle enzyme activity in highly trained athletes, following HIT, has revealed no change in oxidative or glycolytic enzyme activity, despite significant improvements in endurance performance (p < 0.05). Instead, an increase in skeletal muscle buffering capacity may be one mechanism responsible for an improvement in endurance performance. Changes in plasma volume, stroke volume, as well as muscle cation pumps, myoglobin, capillary density and fibre type characteristics have yet to be investigated in response to HIT with the highly trained athlete. Information relating to HIT programme optimisation in endurance athletes is also very sparse. Preliminary work using the velocity at which VO2max is achieved (V(max)) as the interval intensity, and fractions (50 to 75%) of the time to exhaustion at V(max) (T(max)) as the interval duration has been successful in eliciting improvements in performance in long-distance runners. However, V(max) and T(max) have not been used with cyclists. Instead, HIT programme optimisation research in cyclists has revealed that repeated supramaximal sprinting may be equally effective as more traditional HIT programmes for eliciting improvements in endurance performance. Further examination of the biochemical and physiological adaptations which accompany different HIT programmes, as well as investigation into the optimal HIT programme for eliciting performance enhancements in highly trained athletes is required.

Effect of an acute beta-adrenergic blockade on the blood glucose response during lactate minimum test

The aim of this study was to determine the relationship between blood lactate and glucose during an incremental test after exercise induced lactic acidosis, under normal and acute beta-adrenergic blockade. Eight fit males (cyclists or triathletes) performed a protocol to determine the intensity corresponding to the individual equilibrium point between lactate entry and removal from the blood (incremental test after exercise induced lactic acidosis), determined from the blood lactate (Lacmin) and glucose (Glucmin) response. This protocol was performed twice in a double-blind randomized order by ingesting either propranolol (80 mg) or a placebo (dextrose), 120 min prior to the test. The blood lactate and glucose concentration obtained 7 minutes after anaerobic exercise (Wingate test) was significantly lower (p < 0.01) with the acute beta-adrenergic blockade (9.1 +/- 1.5 mM; 3.9 +/- 0.1 mM), respectively than in the placebo condition (12.4 +/- 1.8 mM; 5.0 +/- 0.1 mM). There was no difference (p > 0.05) between the exercise intensity determined by Lacmin (212.1 +/- 17.4 W) and Glucmin (218.2 +/- 22.1 W) during exercise performed without acute beta-adrenergic blockade. The exercise intensity at Lacmin was lowered (p < 0.05) from 212.1 +/- 17.4 to 181.0 +/- 15.6 W and heart rate at Lacmin was reduced (p < 0 .01) from 161.2 +/- 8.4 to 129.3 +/- 6.2 beats min(-1) as a result of the blockade. It was not possible to determine the exercise intensity corresponding to Glucmin with beta-adrenergic blockade, since the blood glucose concentration presented a continuous decrease during the incremental test. We concluded that the similar pattern response of blood lactate and glucose during an incremental test after exercise induced lactic acidosis, is not present during beta-adrenergic blockade suggesting that, at least in part, this behavior depends upon adrenergic stimulation.

Interval training for performance: a scientific and empirical practice. Special recommendations for middle- and long-distance running. Part I: aerobic interval training

This article traces the history of scientific and empirical interval training. Scientific research has shed some light on the choice of intensity, work duration and rest periods in so-called 'interval training'. Interval training involves repeated short to long bouts of rather high intensity exercise (equal or superior to maximal lactate steady-state velocity) interspersed with recovery periods (light exercise or rest). Interval training was first described by Reindell and Roskamm and was popularised in the 1950s by the Olympic champion, Emil Zatopek. Since then middle- and long- distance runners have used this technique to train at velocities close to their own specific competition velocity. In fact, trainers have used specific velocities from 800 to 5000m to calibrate interval training without taking into account physiological markers. However, outside of the competition season it seems better to refer to the velocities associated with particular physiological responses in the range from maximal lactate steady state to the absolute maximal velocity. The range of velocities used in a race must be taken into consideration, since even world records are not run at a constant pace.

Decrease of O(2) deficit is a potential factor in increased time to exhaustion after specific endurance training

The main purpose of this study was to investigate the effects of an 8-wk severe interval training program on the parameters of oxygen uptake kinetics, such as the oxygen deficit and the slow component, and their potential consequences on the time until exhaustion in a severe run performed at the same absolute velocity before and after training. Six endurance-trained runners performed, on a 400-m synthetic track, an incremental test and an all-out test, at 93% of the velocity at maximal oxygen consumption, to assess the time until exhaustion. These tests were carried out before and after 8 wk of a severe interval training program, which was composed of two sessions of interval training at 93% of the velocity at maximal oxygen consumption and three recovery sessions of continuous training at 60--70% of the velocity at maximal oxygen consumption per week. Neither the oxygen deficit nor the slow component were correlated with the time until exhaustion (r = -0.300, P = 0.24, n = 18 vs. r = -0.420, P = 0.09, n = 18, respectively). After training, the oxygen deficit significantly decreased (P = 0.02), and the slow component did not change (P = 0.44). Only three subjects greatly improved their time until exhaustion (by 10, 24, and 101%). The changes of oxygen deficit were significantly correlated with the changes of time until exhaustion (r = -0.911, P = 0.01, n = 6). It was concluded that the decrease of oxygen deficit was a potential factor for the increase of time until exhaustion in a severe run performed after a specific endurance-training program.

A review of the concept of the heart rate deflection point

The heart rate deflection point (HRDP) is a downward or upward change from the linear HR-work relationship evinced during progressive incremental exercise testing. The HRDP is reported to be coincident with the anaerobic threshold. In 1982, Conconi and colleagues suggested that this phenomenon could be used as a noninvasive method to assess the anaerobic threshold. These researchers developed a field test to assess the HRDP, which has become popularised as the 'Conconi test'. Concepts used to define and assess the anaerobic threshold as well as methodological procedures used to determine the HRDP are diverse in the literature and have contributed to controversy surrounding the HRDP concept. Although the HRDP may be assessed in either field or laboratory settings, the degree of HR deflection is highly dependent upon the type of protocol used. The validity of HRDP to assess the anaerobic threshold is uncertain, although a high degree of relationship exists between HRDP and the second lactate turnpoint. The HRDP appears to be reliable when a positive identification is made; however, not all studies report 100% reproducibility. Although the physiological mechanisms explaining the HRDP are unresolved, a relationship exists between the degree and direction of HRDP and left ventricular function. The HRDP has potential to be used for training regulation purposes. Clinically, it may be incorporated to set exercise intensity parameters for cardiac rehabilitation.

Effects of competition and its outcome on serum testosterone, cortisol and prolactin

In various species, competitive encounters influence hormonal responses in a different way depending on their outcome, victory or defeat. This study aimed to investigate the effects of sports competition and its outcome on hormonal response, comparing it with those displayed in situations involving non-effort and non-competitive effort. To this end, serum testosterone (T), cortisol (C) and prolactin (PRL) were measured in 26 judoists who participated in three sessions (control, judo fight and ergometry). The relationship between hormonal changes and psychological variables before and after the fight were also analysed. Our results showed a hormonal response to competition, which was especially characterized by an anticipatory rise of T and C. Depending on outcome, significant higher C levels were found in winners in comparison to losers through all the competition but not in T or PRL, both groups expending a similar physical effort. Furthermore, similar hormonal responses to the fight and to a non-competitive effort with the same caloric cost were found, other than with PRL. Winners showed a higher appraisal of their performance and satisfaction with the outcome, and perceived themselves as having more ability to win than losers, although there were no significant differences in motivation to win. Finally, the relationships found between T changes in competition and motivation to win, as well as between C response and self-efficacy suggest that in humans hormonal response to competition is not a direct consequence of winning and losing but rather is mediated by complex psychological processes.

Stability of the blood lactate-heart rate relationship in competitive athletes

INTRODUCTION

The identification of the HR (or RPE) associated with blood lactate concentrations of 2.5 mmol x L(-1)(aerobic threshold) (AerT) and 4.0 mmol x L(-1)(anaerobic threshold) (AnT) is a common method for defining training intensities. It is often assumed that the HR at AerT and AnT changes with changes in fitness, much as the power output (Watts: W) associated with AerT and AnT is known to change.

METHODS

We studied speed skaters (N = 13, 7 male, 6 female) during spring (deconditioned) and fall (conditioned) evaluations, using cycle ergometry (stage duration = 5 min) to determine W, HR, and RPE at AerT, AnT, and at maximal exercise (3000 (female) and 5000 (male) m cycle time trials).

RESULTS

In the spring vs. fall evaluations, the power output at AerT was 127+/-12 vs 162+/-9 W (P<0.05), at AnT was 216+/-14 vs. 230+/-13 W (P<0.05), and at maximal exercise was 341+/-15 vs. 364+/-19 W (P<0.05); HR at AerT was 129+/-6 vs. 130+/-7 bpm (P>0.05), at AnT was 162+/-7 vs. 164+/-7 bpm (P>0.05), and at maximal exercise was 196+/-6 vs. 198+/-5 bpm (P>0.05); RPE at AerT was 2.7+/-0.9 vs. 2.6+/-0.8 (P>0.05), at AnT was 5.3+/-1.0 vs. 5.3+/-0.9 (P>0.05).

CONCLUSIONS

These data suggest that although power output at AerT, AnT, and maximal exercise changes significantly with conditioning, there is no systematic change in the associated values for HR and/or RPE used as practical markers of training intensity. Accordingly, a single well-conducted evaluation may allow evaluation of appropriate training markers that may be longitudinally stable.

Interval training at VO2max: effects on aerobic performance and overtraining markers

PURPOSE

Between inefficient training and overtraining, an appropriate training stimulus (in terms of intensity and duration) has to be determined in accordance with individual capacities. Interval training at the minimal velocity associated with VO2max (vVO2max) allows an athlete to run for as long as possible at VO2max. Nevertheless, we don't know the influence of a defined increase in training volume at vVO2max on aerobic performance, noradrenaline, and heart rate.

METHODS

Eight subjects performed 4 wk of normal training (NT) with one session per week at vVO2max, i.e., five repetitions run at 50% of the time limit at vVO2max, with recovery of the same duration at 60% vVO2max. They then performed 4 wk of overload training (OT) with three interval training sessions at vVO2max.

RESULTS

Normal training significantly improved their velocity associated with VO2max (20.5+/-0.7 vs 21.1+/-0.8 km x h(-1), P = 0.02). As a result of improved running economy (50.6+/-3.5 vs 47.5+/-2.4 mL x min(-1) x kg(-1), P = 0.02), VO2max was not significantly different (71.6+/-4.8 vs 72.7+/-4.8 mL x min(-1) x kg(-1)). Time to exhaustion at vVO2max was not significantly different (301+/-56 vs 283+/-41 s) as was performance (i.e., distance limit run at vVO2max: 2052.2+/-331 vs 1986.2+/-252.9 m). Heart rate at 14 km x h(-1) decreased significantly after NT (162+/-16 vs 155+/-18 bpm, P < 0.01). Lactate threshold remained the same after normal training (84.1+/-4.8% vVO2max). Overload training changed neither the performance nor the factors concerning performance. However, the submaximal heart rate measured at 14 km x h(-1) decreased after overload training (155+/-18 vs 150+/-15 bpm). The maximal heart rate was not significantly different after NT and OT (199+/-9.5, 198+/-11, 194+/-10.4, P = 0.1). Resting plasma norepinephrine (veinous blood sample measured by high pressure liquid chromatography), was unchanged (2.6 vs 2.4 nm x L(-1), P = 0.8). However, plasma norepinephrine measured at the end of the vVO2max test increased significantly (11.1 vs 26.0 nm x L(-1), P = 0.002).

CONCLUSION

Performance and aerobic factors associated with the performance were not altered by the 4 wk of intensive training at vVO2max despite the increase of plasma noradrenaline.