Effect of posture on high-intensity constant-load cycling performance in men and women

The time sustained during a graded cycle exercise is ~10% longer in an upright compared with a supine posture. However, during constant-load cycling this effect is unknown. Therefore, we tested the postural effect on the performance of high-intensity constant-load cycling. Twenty-two active subjects (11 men, 11 women) performed two graded tests (one upright, one supine), and of those 22, 10 subjects (5 men, 5 women) performed three high-intensity constant-load tests (one upright, two supine). To test the postural effect on performance at the same absolute intensity, during the upright and one of the supine constant-load tests subjects cycled at 80% of the peak power output achieved during the upright graded test. To test the postural effect on performance at the same relative intensities, during the second supine test subjects cycled at 80% of the peak power output achieved during the supine graded test. Exercise time on the graded and absolute intensity constant-load tests for all subjects was greater (P<0.05) in the upright compared with supine posture (17.9±3.5 vs. 16.1±3.1 min for graded; 13.2±8.7 vs. 5.2±1.9 min for constant-load). This postural effect at the same absolute intensity was larger in men (19.4±8.5 upright vs. 6.6±1.6 supine, P<0.001) than women (7.1±2 upright vs. 3.9±1.4 supine, P>0.05) and it was correlated (P<0.05) with both the difference in VO₂ between positions during the first minute of exercise (r=0.67) and the height of the subjects (r=0.72). In conclusion, there is a very large postural effect on performance during constant-load cycling exercise and this effect is significantly larger in men than women.

Effects of starting strategy on 5-min cycling time-trial performance

The importance of pacing for middle-distance performance is well recognized, yet previous research has produced equivocal results. Twenty-six trained male cyclists ( V O_2peak 62.8+5.9 ml ·kg^-1 · min^-1· maximal aerobic power output 340+43 W; mean+s) performed three cycling time-trials where the total external work (102.7+13.7 kJ) for each trial was identical to the best of two 5-min habituation trials. Markers of aerobic and anaerobic metabolism were assessed in 12 participants. Power output during the first quarter of the time-trials was fixed to control external mechanical work done (25.7+3.4 kJ) and induce fast-, even-, and slow-starting strategies (60, 75, and 90 s, respectively). Finishing times for the fast-start time-trial (4:53+0:11 min:s) were shorter than for the even-start (5:04+0:11 min:s; 95% CI=5 to 18 s, effect size=0.65, P 50.001) and slow-start time-trial (5:09+0:11 min:s; 95% CI=7 to 24 s, effect size=1.00, P 50.001). Mean VO₂ during the fast-start trials (4.31+0.51 litres · min^-1) was 0.18+0.19 litres · min^-1 (95% CI=0.07 to 0.30 litres · min^-1, effect size=0.94, P =0.003) higher than the even- and 0.18+0.20 litres · min^-1 (95% CI=0.5 to 0.30 litres · min^-1, effect size=0.86, P =0.007) higher than the slow-start time-trial. Oxygen deficit was greatest during the first quarter of the fast-start trial but was lower than the even- and slow-start trials during the second quarter of the trial. Blood lactate and pH were similar between the three trials. In conclusion, performance during a 5-min cycling time-trial was improved with the adoption of a fast- rather than an even- or slow-starting strategy.

Cycling performance of lithium metal polymer cells assembled with ionic liquid and poly(3-methyl thiophene)/carbon nanotube composite cathode

A poly(3-methylthiophene) (PMT)/multi-walled carbon nanotube (CNT) composite is synthesized by in situ chemical polymerization. The PMT/CNT composite is used as an active cathode material in lithium metal polymer cells assembled with ionic liquid (IL) electrolytes. The IL electrolyte consists of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and LiBF4. A small amount of vinylene carbonate is added to the IL electrolyte to prevent the reductive decomposition of the imidazolium cation in EMIBF4. A porous poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) film is used as a polymer membrane for assembling the cells. Electrochemical properties of the PMT/CNT composite electrode in the IL electrolyte are evaluated and the effect of vinylene carbonate on the cycling performance of the lithium metal polymer cells is investigated. The cells assembled with a non-flammable IL electrolyte and a PMT/CNT composite cathode are promising candidates for high-voltage–power sources with enhanced safety.

Effect of body tilt angle on fatigue and EMG activities in lower limbs during cycling

This study compared the rate of fatigue and lower limb EMG activities during high-intensity constantload cycling in upright and supine postures. Eleven active males performed seven cycling exercise tests: one upright graded test, four fatigue tests (two upright, two supine) and two EMG tests (one upright, one supine). During the fatigue tests participants initially performed a 10 s all-out effort followed by a constant-load test with 10 s all-out bouts interspersed every minute. The load for the initial two fatigue tests was 80% of the peak power (PP) achieved during the graded test and these continued until failure. The remaining two fatigue tests were performed at 20% PP and were limited to the times achieved during the 80% PP tests. During the EMG tests subjects performed a 10 s all-out effort followed by a constant-load test to failure at 80% PP. Normalised EMG activities (% maximum, NEMG) were assessed in five lower limb muscles. Maximum power and maximum EMG activity prior to each fatigue and EMG test were unaffected by posture. The rate of fatigue at 80% PP was significantly higher during supine compared with upright posture (-68 ± 14 vs. -26 ± 6 W min-1, respectively, P\0.05) and the divergence of the fatigue responses occurred by the second minute of exercise. NEMG responses were significantly higher in the supine posture by 1–4 min of exercise. Results show that fatigue is significantly greater during supine compared with upright high-intensity cycling and this effect is accompanied by a reduced activation of musculature that is active during cycling.

Sprint cycling performance is maintained with short-term contrast water immersion

Purpose: Given the widespread use of water immersion during recovery from exercise, we aimed to investigate the effect of contrast water immersion on recovery of sprint cycling performance, HR and, blood lactate.

Methods: Two groups completed high-intensity sprint exercise before and after a 30-min randomized recovery. The Wingate group (n = 8) performed 3 x 30-s Wingate tests (4-min rest periods). The repeated intermittent sprint group (n = 8) cycled for alternating 30-s periods at 40% of predetermined maximum power and 120% maximum power, until exhaustion. Both groups completed three trials using a different recovery treatment for each trial (balanced randomized application). Recovery treatments were passive rest, 1:1 contrast water immersion (2.5 min of cold (8-C) to 2.5 min of hot (40-C)), and 1:4 contrast water immersion (1 min of cold to 4 min of hot). Blood lactate and HR were recorded throughout, and peak power and total work for pre- and postrecovery Wingate performance and exercise time and total work for repeated sprinting were recorded.

Results: Recovery of Wingate peak power was 8% greater after 1:4 contrast water immersion than after passive rest, whereas both contrast water immersion ratios provided a greater recovery of exercise time (È10%) and total work (È14%) for repeated sprinting than for passive rest. Blood lactate was similar between trials. Compared with passive rest, HR initially declined more slowly during contrast water immersion but increased with each transition to a cold immersion phase.

Conclusions: These data support contrast water immersion being effective in maintaining performance during a short-term recovery from sprint exercise. This effect needs further investigation but is likely explained by cardiovascular mechanisms, shown here by an elevation in HR upon each cold immersion.

The Tablet PC: A Complete Teaching Studio

The Tablet PC is a flexible teaching tool. It can be used to increase the lecturer’s productivity in note taking and in assignment marking. It can be used in the lecture room with increased interaction. With a few minor accessories it can be used to record all aspects of a lecture or presentation. It can also be used to record short topic segments that can be used as references or summaries by students. Containing the abilities of both a tablet device with multi touch, a pen interface for accurate drawing and handwriting and with the power of a full PC, it is a complete teaching studio.

The effect of environmental conditions on performance in timed cycling events

Air temperature, pressure and humidity are environmental factors that affect air density and therefore the relationship between a cyclist’s power output and their velocity. These environmental factors are changeable and are routinely quite different at elite cycling competitions conducted around the world, which means that they have a variable effect on performance in timed events. The present work describes a method of calculating the effect of these environmental factors on timed cycling events and illustrates the magnitude and significance of these effects in a case study. Formulas are provided to allow the calculation of the effect of environmental conditions on performance in a time trial cycling event. The effect of environmental factors on time trial performance can be in the order of 1.5%, which is significant given that the margins between ranked performances is often less than this. Environmental factors may enhance or hinder performance depending upon the conditions and the comparison conditions. To permit the fair comparison of performances conducted in different environmental conditions, it is recommended that performance times are corrected to the time that would be achieved in standard environmental conditions, such as 20 oC, 760 mmHg (1013.25 hPa) and 50% RH.

Influence of pacing on reliability of middle-distance cycling performance

The purpose of the present study was to examine the reliability of middle distance cycling time trials using fast-, even-, and slow-starts. Eighteen endurance-trained male cyclists [mean ± standard deviation; VO2peak 63.1 ± 6.1 mL⋅kg-1⋅min-1] performed nine cycling time trials where the total external work (96.5 ± 11.2 kJ) was identical to the better of two, 5-minute habituation time trials. Power output during the first quarter of the time-trials (24.1 ± 2.8 kJ) was fixed to induce fast-, even- or slow-starting strategies (60, 75 and 90 s, respectively). In consecutive sessions, participants performed three trials of each pacing condition although the order of these pacing conditions was counterbalanced. Average power output and performance time were unaffected by trial number in the fast- (P = 0.60), even- (P = 0.18) and slow-start (P = 0.53) trials. In all three pacing conditions, average power output was highly reliable and similar between trial 1 to 2 and trial 2 to 3 in fast- (standard error of measurement; SEM=8.3 and 8.2W), even (coefficient of variation; CV=2.8 and 2.4%) and slow-start (CV=2.4 and 1.5%) trials. In conclusion, the reproducibility of 5-min cycling time trials is unaffected by starting strategy and is acceptable following two selfpaced habituation trials. Research examining the influence of pacing strategies may therefore be conducted without the need for familiarisation trials using each individual pacing condition.

Máxima fase estável de lactato sanguíneo e potência crítica em ciclistas bem treinados

O principal objetivo deste estudo foi comparar a intensidade correspondente à máxima fase estável de lactato (MLSS) e a potência crítica (PC) durante o ciclismo em indivíduos bem treinados. Seis ciclistas do sexo masculino (25,5 ± 4,4 anos, 68,8 ± 3,0kg, 173,0 ± 4,0cm) realizaram em diferentes dias os seguintes testes: exercício incremental até a exaustão para a determinação do pico de consumo de oxigênio (VO2pico) e sua respectiva intensidade (IVO2pico); cinco a sete testes de carga constante para a determinação da MLSS e da PC; e um exercício até a exaustão na PC. A MLSS foi considerada com a maior intensidade de exercício onde a concentração de lactato não aumentou mais do que 1mM entre o 10º e o 30º min de exercício. Os valores individuais de potência (95, 100 e 110% IVO2pico) e seu respectivo tempo máximo de exercício (Tlim) foram ajustados a partir do modelo hiperbólico de dois parâmetros para a determinação da PC. Embora altamente correlacionadas (r = 0,99; p = 0,0001), a PC (313,5 ± 32,3W) foi significantemente maior do que a MLLS (287,0 ± 37,8W) (p = 0,0002). A diferença percentual da PC em relação à MLSS foi de 9,5 ± 3,1%. No exercício realizado na PC, embora tenha existido componente lento do VO2 (CL = 400,8 ± 267,0 ml.min-1), o VO2pico não foi alcançado (91,1 ± 3,3 %). Com base nesses resultados pode-se concluir que a PC e a MLSS identificam diferentes intensidades de exercício, mesmo em atletas com elevada aptidão aeróbia. Entretanto, o percentual da diferença entre a MLLS e PC (9%) indica que relação entre esses dois índices pode depender da aptidão aeróbia. Durante o exercício realizado até a exaustão na PC, o CL que é desenvolvido não permite que o VO2pico seja alcançado.

Effect of aerobic training status on both maximal lactate steady state and critical power

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

PHYSIOLOGICAL and PERCEIVED EXERTION RESPONSES AT INTERMITTENT CRITICAL POWER and INTERMITTENT MAXIMAL LACTATE STEADY STATE

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

There is no anaerobic work capacity replenishment at critical power intensity: An indirect evidence

Aim. - This study aimed to test if investigate whether the anaerobic work capacity is replenished while exercising at critical power intensity. Then, a known exercise duration, which demands high anaerobic energy contribution, was compared to intermittent exercise duration with passive and active (cycling at critical power intensity) rest periods.Methods. - Nine participants performed five sessions of testing. From the 1st to the 3rd sessions, individuals cycled continuously at different workloads (P-high, P-intermediate and P-low) in order to estimate the critical power and the anaerobic work capacity. The 4th and 5th sessions were performed in order to determine the influence of anaerobic work capacity replenishment oil exercise duration. They consisted of manipulating the resting type (passive or active) between two cycling efforts. The total exercise duration was determined by the sum of the two cycling efforts duration.Results. - The exercise duration under passive resting condition (408.0 +/- 42.0 s) was longer (p<0.05) than known exercise duration at P-intermediate (T-intermediate = 305.8 +/- 30.5 s) and than exercise duration performed under active resting conditions (T-active = 304.4 +/- 30.7s). However, there was no significant difference between T-intermediate and T-active.Conclusion. - These results demonstrated indirect evidence that the anaerobic work capacity is not replenished while exercising at critical power intensity. (C) 2008 Elsevier Masson SAS. All rights reserved.

The highest intensity and the shortest duration permitting attainment of maximal oxygen uptake during cycling: effects of different methods and aerobic fitness level

The aims of this study were: (1) to verify the validity of previous proposed models to estimate the lowest exercise duration (T (LOW)) and the highest intensity (I (HIGH)) at which VO(2)max is reached (2) to test the hypothesis that parameters involved in these models, and hence the validity of these models are affected by aerobic training status. Thirteen cyclists (EC), eleven runners (ER) and ten untrained (U) subjects performed several cycle-ergometer exercise tests to fatigue in order to determine and estimate T (LOW) (ET (LOW)) and I (HIGH) (EI (HIGH)). The relationship between the time to achieved VO(2)max and time to exhaustion (T (lim)) was used to estimate ET (LOW). EI (HIGH) was estimated using the critical power model. I (HIGH) was assumed as the highest intensity at which VO2 was equal or higher than the average of VO(2)max values minus one typical error. T (LOW) was considered T (lim) associated with I (HIGH). No differences were found in T (LOW) between ER (170 +/- 31 s) and U (209 +/- 29 s), however, both showed higher values than EC (117 +/- 29 s). I (HIGH) was similar between U (269 +/- 73 W) and ER (319 +/- 50 W), and both were lower than EC (451 +/- 33 W). EI (HIGH) was similar and significantly correlated with I-HIGH only in U (r = 0.87) and ER (r = 0.62). ET (LOW) and T (LOW) were different only for U and not significantly correlated in all groups. These data suggest that the aerobic training status affects the validity of the proposed models for estimating I (HIGH).

EFFECTS of PREFERRED and NONPREFERRED MUSIC on CONTINUOUS CYCLING EXERCISE PERFORMANCE

The aim of this study was to investigate the effects of preferred and nonpreferred music on exercise distance, Heart Rate (HR), and Rating of Perceived Exertion (RPE) during continuous cycling exercise performed at high intensity Fifteen participants performed five test sessions During two sessions, they cycled with fixed workload on ergometer to determine the Critical Power (Cl') intensity Then, they performed three more sessions cycling at CP intensity listening to Preferred Music, listening to Nonpreferred Music, and No Music The HR responses in the exercise sessions did not differ among all conditions However, the RPE was higher for Nonpreferred Music than in the other conditions The performance under Preferred Music (9 8 +/- 4 6km) was greater than under Nonpreferred Music (7 1 +/- 3 5km) conditions Therefore, listening to Preferred Music during continuous cycling exercise at high intensity can Increase the exercise distance, and individuals listening to Nonpreferred Music can perceive more discomfort caused by the exercise

Indexes of power and aerobic capacity obtained in cycle ergometry and treadmill running: comparisons between sedentary, runners, cyclists and triathletes

The objectives of this study were: a) to determine, in a cross-sectional manner, the effect of aerobic training on the peak oxygen uptake, the intensity at O2peak and the anaerobic threshold (AnT) during running and cycling; and b) to verify if the transference of the training effects are dependent on the analized type of exercise or physiological index. Eleven untrained males (UN), nine endurance cyclists (EC), seven endurance runners (ER), and nine triathletes (TR) were submitted, on separate days, to incremental tests until voluntary exhaustion on a mechanical braked cycle ergometer and on a treadmill. The values of O2peak (ml.kg-1.min-1) obtained in running and cycle ergometer (ER = 68.8 ± 6.3 and 62.0 ± 5.0; EC = 60.5 ± 8.0 and 67.6 ± 7.6; TR = 64.5 ± 4.8 and 61.0 ± 4.1; UN = 43.5 ± 7.0 and 36.7 ± 5.6; respectively) were higher in the group that presented specific training in the modality. The UN group presented the lower values of O2peak, regardless of the type of exercise. This same behavior was observed for the AnT (ml.kg-1.min-1) determined in running and cycle ergometer (ER = 56.8 ± 6.9 and 44.8 ± 5.7; EC = 51.2 ± 5.2 and 57.6 ± 7.1; TR = 56.5 ± 5.1 and 49.0 ± 4.8; UN = 33.2 ± 4.2 and 22.6 ± 3.7; respectively). It can be concluded that the transference of the training effects seems to be only partial, independently of the index (O2peak, IO2peak or AnT) or exercise type (running or cycling). In relation to the indices, the specificity of training seems to be less present in the O2peak than in the IO2peak and the AnT.