Reliability of a laboratory-based long sprint cycling test: applications of the smallest worthwhile changes in performance forrepeated measures designs / Confiabilidade de um teste em laboratório de sprint longo no ciclismo: aplicações da menor mudança significativa em desempenho para desenhos de medidas repetidas

Abstract The aims of the present study were to assess the reliability of long sprint cycling performance in a group of recreationally trained cyclists and to provide thresholds for changes in performance for this particular group of subjects in repeated measures designs through a scale of magnitudes. Repeatability of mean power output during a 1-min cycling time trial was assessed in a group of 15 recreationally trained cyclists (26 ± 5, years, 176 ± 5 cm, 78 ± 8 kg). They were tested on separate days, approximately one week apart. The test and retest values for the whole group of cyclists were 7.0 ± 0.5 W/kg and 6.9 ± 0.6 W/kg (systematic change and 90% confidence limits of -1.0% ± 1.1%). Our results indicated good test-retest reproducibility (typical error of 1.8%, 90% confidence limits of 1.4% to 2.6%; intraclass correlation coefficient of 0.96, confidence limits of 0.91 to 0.99), but suggested a reduction of mean power for the "slower" subjects on retest (-2.0%, 90% confidence limits of ±1.8%). If not monitored, this systematic decrease could interfere in results of studies utilizing groups with similar performance levels, particularly investigating strategies to improve performance in sprint cycling exercises around 1 min. The thresholds for moderate, large, very large and extremely large effects for mean power output on long sprint cycling performance are about 0.4%, 1.3%, 2.3%, 3.6%, and 5.8%, respectively.

Resumo Os objetivos do presente estudo foram avaliar a confiabilidade do desempenho de sprint longo no ciclismo em um grupo de ciclistas recreacionais e fornecer limiares para mudanças no desempenho para este grupo de sujeitos em delineamentos de medidas repetidas, através de uma escala de magnitudes. A reprodutibilidade da potência média durante um contrarrelógio de 1-min foi avaliada em um grupo de 15 ciclistas recreativamente treinados (26 ± 5 anos, 176 ± 5 cm, 78 ± 8 kg). Eles foram avaliados em dias separados, com aproximadamente uma semana de intervalo. Os valores de teste-reteste no contrarrelógio de 1-min para o grupo inteiro foram 7,0 ± 0,5 W/kg and 6,9 ± 0,6 W/kg (mudança sistemática e limite de confiança de 90% de -1,0% ± 1,2%). Nossos resultados indicam boa reprodutibilidade teste-reteste (erro típico de 1,8%, limite de confiança de 90% de 1,4% para 2,6%; coeficiente de correlação intraclasse de 0,96, limite de confiança de 90% de 0,91 para 0,99), mas sugeriu uma redução da média de potência para os sujeitos "mais lentos" no reteste (-2,0%, limite de confiança de 90% de ±1,8%). Se não monitorada, esta queda sistemática na potência pode interferir nos resultados de estudos utilizando grupos com níveis similares de desempenho, particularmente investigando estratégias para melhorar o desempenho em sprints com duração próxima a 1 min. Os limiares para efeitos moderado, grande, muito grande e extremamente grande para média da potência em sprint longo no ciclismo são aproximadamente 0,4%, 1,3%, 2,3%, 3,6% e 5,8%, respectivamente.

A influência de variáveis aeróbias e anaeróbias no teste de "sprints" repetidos / Influence of aerobic and anaerobic variables on repeated sprint tests

Resumo O objetivo deste estudo foi determinar o modo e o grau com que variáveis aeróbias e anaeróbias influenciam o desempenho e a fadiga em "sprints" repetidos (RS) na corrida. Para este fim, participaram do estudo 24 homens, sendo oito corredores velocistas, oito corredores fundistas e oito sujeitos ativos. Em uma pista sintética de atletismo estes sujeitos foram submetidos aos seguintes testes: 1) teste incremental para determinação do VO2max e da velocidade aeróbia máxima (VAM); 2) teste de velocidade constante realizado a 110%VAM para determinar a cinética do VO2 durante exercício e o máximo déficit acumulado de oxigênio (MAOD); 3) teste de "sprints" repetidos (10 "sprints" de 35 m, intercalados com 20 s de recuperação) para determinar o tempo total dos "sprints" (TT), tempo do melhor sprint (TM) e a queda do desempenho em percentual (Sdec). Para analisar a diferença entre os grupos e as relações entre as variáveis foram utilizadas a análise de variância ANOVA "one-way", complementada pelo teste de Tukey, e a correlação de Pearson, respectivamente. O TT em RS foi diferente significativamente entre todos os grupos (velocistas, 49,5 ± 0,8 s; fundistas, 52,6 ± 3,1 s; ativos, 55,5 ± 2,6 s) e Sdec foi significativamente inferior em fundistas comparado aos outros grupos (velocistas, 8,9 ± 2,1%; fundistas, 4,0 ± 2,0%; ativos, 8,4 ± 4,4%). O TT foi correlacionado significativamente com o TM (r = 0,85, p < 0,01) e com o MAOD (r = - 0,54, p < 0,01). Além disso, Sdec foi correlacionado significativamente com variáveis aeróbias (VO2max, r = - 0,58, < 0,01; VAM, r = - 0,59, p < 0,01; constante de tempo "tau", r = 0,45, p = 0,03). Portanto, conclui-se que apesar de índices aeróbios influenciarem na redução da fadiga em RS, o desempenho em RS é principalmente influenciado por características anaeróbias.(AU)

Abstract This study aimed to determine the manner and degree to which aerobic and anaerobic variables influence repeated running sprint performance and ability. Twenty four males (sprinters = 8, endurance runners = 8 and physical active subjects = 8) performed in a synthetic track the following tests: 1) incremental test to determine the VO2max and the maximum aerobic velocity (MAV); 2) constant velocity test performed at 110% of MAV to determine the VO2 kinetics and the maximum accumulated oxygen deficit (MAOD); 3) repeated sprint test (10 sprints of 35-m interspersed by 20s) to determine sprint total time (TT), best sprint time (BT) and score decrement (Sdec). Between-groups comparisons and the correlations between variables were analyzed by one-way ANOVA with a Tukey post-hoc tests and Pearson correlation, respectively. TT was significantly different among all groups (sprinters = 49.5 ± 0.8 s; endurance = 52.6 ± 3.1 s; active = 55.5 ± 2.6 s) and Sdec was significantly lower in endurance runners as compared with sprinters and physical active subjects (sprinters = 8.9 ± 2.1%; endurance = 4.0 ± 2.0%; active = 8.4 ± 4.4%). TT correlated significantly with BT (r = 0.85, p < 0.01) and MAOD (r = - 0.54, p < 0.01). Moreover, Sdec was significantly correlated with aerobic parameters (VO2max, r = - 0.58, p < 0.01; MAV, r = - 0.59, p < 0.01; time constant tau, r = 0.45, p = 0.03). In conclusion, although the aerobic parameters have an important contribution to RS ability, RS performance is mainly influenced by anaerobic parameters.(AU)

Effects of ischemic preconditioning on short-duration cycling performance.

It has been demonstrated that ischemic preconditioning (IPC) improves endurance performance. However, the potential benefits during anaerobic events and the mechanism(s) underlying these benefits remain unclear. Fifteen recreational cyclists were assessed to evaluate the effects of IPC of the upper thighs on anaerobic performance, skeletal muscle activation, and metabolic responses during a 60-s sprint performance. After an incremental test and a familiarization visit, subjects were randomly submitted in visits 3 and 4 to a performance protocol preceded by intermittent bilateral cuff inflation (4 × (5 min of blood flow restriction + 5 min reperfusion)) at either 220 mm Hg (IPC) or 20 mm Hg (control). To increase data reliability, each intervention was replicated, which was also in a random manner. In addition to the mean power output, the pulmonary oxygen uptake, blood lactate kinetics, and quadriceps electromyograms (EMGs) were analyzed during performance and throughout 45 min of passive recovery. After IPC, performance was improved by 2.1% compared with control (95% confidence intervals of 0.8% to 3.3%, P = 0.001), followed by increases in (i) the accumulated oxygen deficit, (ii) the amplitude of blood lactate kinetics, (iii) the total amount of oxygen consumed during recovery, and (iv) the overall EMG amplitude (P < 0.05). In addition, the ratio between EMG and power output was higher during the final third of performance after IPC (P < 0.05). These results suggest an increased skeletal muscle activation and a higher anaerobic contribution as the ultimate responses of IPC on short-term exercise performance.

Interval training in the boundaries of severe domain: effects on aerobic parameters.

PURPOSE: Although time spent at VO2max (t@VO2max) has been suggested as an optimal stimulus for the promotion of greater VO2max improvements, scientific findings supporting this notion are surprisingly still lacking. To investigate this, the present study described t@VO2max in two different severe-intensity interval training regimens and compared its effects on aerobic indexes after a 4-week intervention. METHODS: Twenty-one recreational cyclists performed an incremental exercise test and six time-to-exhaustion tests on four different days to determine VO2max, lactate threshold (LT), critical power (CP) and the highest intensity (IHIGH) and lowest exercise duration (TLOW) at which VO2max was attained. Subjects were assigned to the lower (LO, n = 11, 4 × 5 min at 105% CP, 1 min recovery) or the upper severe-intensity training groups (UP, n = 10, 8 × 60% TLOW at 100% IHIGH, 1:2 work:recovery ratio). t@VO2max was measured during the first and last training sessions. RESULTS: A significantly higher t@VO2max was elicited in the UP during training sessions in comparison with the LO group (P < 0.05), and superior improvements were observed in VO2max (change in measure ± 95% confidence interval) (6.3 ± 1.9 vs. 3.3 ± 1.8%, P = 0.034 for interaction terms) and LT (54.8 ± 11.8 vs. 27.9 ± 11.3%, P = 0.023 for interaction terms). The other aerobic indexes were similarly improved between the groups. CONCLUSION: The present results demonstrated that UP training produced superior gains in VO2max and LT in comparison with LO training, which may be associated with the higher t@VO2max.

Effects of ischemic preconditioning on maximal constant-load cycling performance.

This study investigated the effects of ischemic preconditioning (IPC) on the ratings of perceived exertion (RPE), surface electromyography, and pulmonary oxygen uptake (V̇o2) onset kinetics during cycling until exhaustion at the peak power output attained during an incremental test. A group of 12 recreationally trained cyclists volunteered for this study. After determination of peak power output during an incremental test, they were randomly subjected on different days to a performance protocol preceded by intermittent bilateral cuff pressure inflation to 220 mmHg (IPC) or 20 mmHg (control). To increase data reliability, the performance visits were replicated, also in a random manner. There was an 8.0% improvement in performance after IPC (control: 303 s, IPC 327 s, factor SDs of ×/÷1.13, P = 0.01). This change was followed by a 2.9% increase in peak V̇o2 (control: 3.95 l/min, IPC: 4.06 l/min, factor SDs of ×/÷1.15, P = 0.04), owing to a higher amplitude of the slow component of the V̇o2 kinetics (control: 0.45 l/min, IPC: 0.63 l/min, factor SDs of ×/÷2.21, P = 0.05). There was also an attenuation in the rate of increase in RPE (P = 0.01) and a progressive increase in the myoelectrical activity of the vastus lateralis muscle (P = 0.04). Furthermore, the changes in peak V̇o2 (r = 0.73, P = 0.007) and the amplitude of the slow component (r = 0.79, P = 0.002) largely correlated with performance improvement. These findings provide a link between improved aerobic metabolism and enhanced severe-intensity cycling performance after IPC. Furthermore, the delayed exhaustion after IPC under lower RPE and higher skeletal muscle activation suggest they have a role on the ergogenic effects of IPC on endurance performance.

The Effects of Different Training Backgrounds on VO2 Responses to All-Out and Supramaximal Constant-Velocity Running Bouts.

To investigate the impact of different training backgrounds on pulmonary oxygen uptake (V̇O2) responses during all-out and supramaximal constant-velocity running exercises, nine sprinters (SPRs) and eight endurance runners (ENDs) performed an incremental test for maximal aerobic velocity (MAV) assessment and two supramaximal running exercises (1-min all-out test and constant-velocity exercise). The V̇O2 responses were continuously determined during the tests (K4b2, Cosmed, Italy). A mono-exponential function was used to describe the V̇O2 onset kinetics during constant-velocity test at 110%MAV, while during 1-min all-out test the peak of V̇O2 (V̇O2peak), the time to achieve the V̇O2peak (tV̇O2peak) and the V̇O2 decrease at last of the test was determined to characterize the V̇O2 response. During constant-velocity exercise, ENDs had a faster V̇O2 kinetics than SPRs (12.7 ± 3.0 vs. 19.3 ± 5.6 s; p < 0.001). During the 1-min all-out test, ENDs presented slower tV̇O2peak than SPRs (40.6 ± 6.8 and 28.8 ± 6.4 s, respectively; p = 0.002) and had a similar V̇O2peak relative to the V̇O2max (88 ± 8 and 83 ± 6%, respectively; p = 0.157). Finally, SPRs was the only group that presented a V̇O2 decrease in the last half of the test (-1.8 ± 2.3 and 3.5 ± 2.3 ml.kg-1.min-1, respectively; p < 0.001). In summary, SPRs have a faster V̇O2 response when maximum intensity is required and a high maximum intensity during all-out running exercise seems to lead to a higher decrease in V̇O2 in the last part of the exercise.

Caffeine Affects Time to Exhaustion and Substrate Oxidation during Cycling at Maximal Lactate Steady State.

This study analyzed the effects of caffeine intake on whole-body substrate metabolism and exercise tolerance during cycling by using a more individualized intensity for merging the subjects into homogeneous metabolic responses (the workload associated with the maximal lactate steady state-MLSS). MLSS was firstly determined in eight active males (25 ± 4 years, 176 ± 7 cm, 77 ± 11 kg) using from two to four constant-load tests of 30 min. On two following occasions, participants performed a test until exhaustion at the MLSS workload 1 h after taking either 6 mg/kg of body mass of caffeine or placebo (dextrose), in a randomized, double-blinded manner. Respiratory exchange ratio was calculated from gas exchange measurements. There was an improvement of 22.7% in time to exhaustion at MLSS workload following caffeine ingestion (95% confidence limits of ±10.3%, p = 0.002), which was accompanied by decrease in respiratory exchange ratio (p = 0.001). These results reinforce findings indicating that sparing of the endogenous carbohydrate stores could be one of the several physiological effects of caffeine during submaximal performance around 1 h.

The highest velocity and the shortest duration permitting attainment of VO2 max during running / A maior velocidade e o menor tempo de exercício em que o VO2max é alcançado na corrida

Abstract The severe-intensity domain has important applications for the prescription of running training and the elaboration of experimental designs. The objectives of this study were: 1) to investigate the validity of a previously proposed model to estimate the shortest exercise duration (TLOW) and the highest velocity (VHIGH) at which VO2 max is reached during running, and 2) to evaluate the effects of aerobic training status on these variables. Eight runners and eight physically active subjects performed several treadmill running exercise tests to exhaustion in order to mathematically estimate and to experimentally determine TLOW and VHIGH. The relationship between the time to achieve VO2 max and time to exhaustion (Tlim) was used to estimate TLOW. VHIGH was estimated using the critical velocity model. VHIGH was assumed to be the highest velocity at which VO2 was equal to or higher than the average VO2 max minus one standard deviation. TLOW was defined as Tlim associated with VHIGH. Runners presented better aerobic fitness and higher VHIGH (22.2 ± 1.9 km.h-1) than active subjects (20.0 ± 2.1 km.h-1). However, TLOW did not differ between groups (runners: 101 ± 39 s; active subjects: 100 ± 35 s). TLOW and VHIGH were not well estimated by the model proposed, with high coefficients of variation (> 6%) and a low correlation coefficient (r<0.70), a fact reducing the validity of the model. It was concluded that aerobic training status positively affected only VHIGH. Furthermore, the model proposed presented low validity to estimate the upper boundary of the severe-intensity domain (i.e., VHIGH), irrespective of the subjects' training status.

Resumo O domínio severo tem importantes aplicações para a prescrição do treinamento de corrida e elaboração de delineamentos experimentais. O estudo teve como objetivos: 1) investigar a validade de um modelo proposto previamente para estimativa do menor tempo de exercício (TINF) e maior velocidade (VSUP) em que o VO2max é alcançado na corrida; e 2) comparar os efeitos do estado de treinamento nestes parâmetros. Oito corredores e oito indivíduos fisicamente ativos realizaram uma série de testes até a exaustão em esteira rolante para estimar matematicamente e determinar experimentalmente o TINF e VSUP. A relação entre tempo para atingir o VO2 max e tempo de exaustão (Tlim) foi usado para estimar o TINF. A VSUP foi estimada pelo modelo de Velocidade Crítica. VSUP foi assumida como a maior velocidade em que o VO2 ± 2,1 km.h-1. Entretanto, TINF não foi diferente entre grupos (Corredores 101 ± 39; Ativos: 100 ± 35 s). VSUP e TINF não foram bem estimados pelo modelo proposto e apresentaram altos coeficientes de variação (> 6%) e baixa correlação (r < 0,70), o que diminuiu a sua validade. Pode-se concluir que o estado de treinamento aeróbio afetou positivamente apenas a VSUP. Além disso, o modelo proposto apresentou baixa validade para predição do limite superior do domínio severo (VSUP) independentemente do estado de treinamento dos indivíduos.

A fast-start pacing strategy speeds pulmonary oxygen uptake kinetics and improves supramaximal running performance.

The focus of the present study was to investigate the effects of a fast-start pacing strategy on running performance and pulmonary oxygen uptake (VO2) kinetics at the upper boundary of the severe-intensity domain. Eleven active male participants (28±10 years, 70±5 kg, 176±6 cm, 57±4 mL/kg/min) visited the laboratory for a series of tests that were performed until exhaustion: 1) an incremental test; 2) three laboratory test sessions performed at 95, 100 and 110% of the maximal aerobic speed; 3) two to four constant speed tests for the determination of the highest constant speed (HS) that still allowed achieving maximal oxygen uptake; and 4) an exercise based on the HS using a higher initial speed followed by a subsequent decrease. To predict equalized performance values for the constant pace, the relationship between time and distance/speed through log-log modelling was used. When a fast-start was utilized, subjects were able to cover a greater distance in a performance of similar duration in comparison with a constant-pace performance (constant pace: 670 m±22%; fast-start: 683 m±22%; P = 0.029); subjects also demonstrated a higher exercise tolerance at a similar average speed when compared with constant-pace performance (constant pace: 114 s±30%; fast-start: 125 s±26%; P = 0.037). Moreover, the mean VO2 response time was reduced after a fast start (constant pace: 22.2 s±28%; fast-start: 19.3 s±29%; P = 0.025). In conclusion, middle-distance running performances with a duration of 2-3 min are improved and VO2 response time is faster when a fast-start is adopted.

Efeito da ingestão de cafeína no desempenho em corrida de 200 metros rasos / Effect of caffeine ingestion on 200 meter running performance

O objetivo do estudo foi analisar a influência da cafeína no desempenho dos 200 metros rasos (200 m). Dezessete indivíduos fisicamente ativos (21,5 ± 2,15 anos; 175,9 ± 5,5 cm; 74,1 ± 10,04 kg) executaram em dias diferentes duas performances de 200m. Uma hora antes do teste foi ingerido de modo duplo-cego e randomizado cápsula gelatinosa contendo cafeína (6mg.kg-1) ou placebo. Foram analisados o tempo final dos 200 m rasos e o lactato sanguíneo ([La]; repouso, pré-aquecimento e pós-teste). A ingestão de cafeína diminuiu significantemente o tempo no desempenho dos 200m em relação ao placebo (27,398 ± 1,626 vs. 27,596 ± 1,714 s, respectivamente) e aumentou as [La] pré-aquecimento (1,236 ± 0,497 vs 1,064 ± 0,330 mM) sem modificações na [La] pico. Assim, podemos concluir que a ingestão de cafeína exerceu efeito ergogênico no desempenho com característica anaeróbia, nos indivíduos ativos avaliados neste estudo. Contudo a ausência de modificação na [La] pico indica que essa melhora não parece estar relacionada a um maior fluxo glicolítico.

The aim of this study was to investigate the influence of caffeine ingestion on 200 meters performance (200 m). Seventeen physical education students (21.5 ± 2.15 years; 175.9 ± 5.5 cm; 74.1 ± 10.04 kg) performed on two different days two performances of 200 m. One hour before the performance the participants ingested a gelatin capsule containing either caffeine (6 mg.kg-1) or placebo in a randomized double-blinded manner. Were analyzed the end time of the 200 m race and blood lactate ([La]; rest, pre-warm-up and post-test) Caffeine intake decreased the time to overcome 200 m race compared to placebo intake (27.398 ± 1.626 and 27.596 ± 1.714 s, respectively) and increased blood lactate concentration [La] pre-warm-up (1.236 ± 0.497; 1.064 ± 0.330 mM, respectively) without modification in [La] peak. Thus, we conclude that caffeine intake exert an ergogenic effect on anaerobic performance, however analyzing the [La] peak, this improvement does not seem to be related to increased glycolytic flux.

Intracellular shuttle: the lactate aerobic metabolism.

Lactate is a highly dynamic metabolite that can be used as a fuel by several cells of the human body, particularly during physical exercise. Traditionally, it has been believed that the first step of lactate oxidation occurs in cytosol; however, this idea was recently challenged. A new hypothesis has been presented based on the fact that lactate-to-pyruvate conversion cannot occur in cytosol, because the LDH enzyme characteristics and cytosolic environment do not allow the reaction in this way. Instead, the Intracellular Lactate Shuttle hypothesis states that lactate first enters in mitochondria and only then is metabolized. In several tissues of the human body this idea is well accepted but is quite resistant in skeletal muscle. In this paper, we will present not only the studies which are protagonists in this discussion, but the potential mechanism by which this oxidation occurs and also a link between lactate and mitochondrial proliferation. This new perspective brings some implications and comes to change our understanding of the interaction between the energy systems, because the product of one serves as a substrate for the other.