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Offering large muscle benefits despite low metabolic demand, continuous eccentric exercise appears to be an interesting alternative to concentric exercise. Nevertheless, further knowledge is needed about prolonged eccentric exercise. This work sought to investigate the cardiovascular responses to prolonged constant-load eccentric compared to concentric cycling. Ten healthy males performed two 45-min exercise sessions of either concentric or eccentric cycling separated by a month and matched for heart rate during the first 5 min of exercise. Cardiorespiratory, autonomic nervous system and vascular responses were assessed at rest, and during exercise and recovery. During cycling, oxygen uptake, cardiac output and systolic blood pressure were similar but heart rate and diastolic blood pressure were greater whereas stroke volume was lower during eccentric than concentric cycling (118±21 vs. 104±10 bpm; 77±9 vs. 65±8 mmHg; 122±12 vs. 135±13 mL). Baroreflex and noradrenaline concentration were altered during eccentric cycling, and after eccentric exercise, vascular tone was greater than after concentric cycling. We observed increased cardiovascular strain and altered baroreflex activity during eccentric compared with concentric exercise, suggesting eccentric cycling triggers greater sympathetic activity., Competing Interests: The authors declare no conflict of interest., (© Georg Thieme Verlag KG Stuttgart · New York.)

Muscle deoxygenation responses provide information about the training impulse of an exercise session enabling adaptation to be predicted. Our aim was to investigate muscle oxygenation profiles during prolonged low-intensity eccentric and concentric cycling. Twelve healthy men performed two 45-min exercise sessions of concentric (CON) and eccentric (ECC) cycling, matched for the same heart rate at the start of each session. Mechanical power output during ECC was ~2.5 times that of CON (210±40 W vs. 82±16 W). Oxygen uptake, blood lactate, cardiac output and systolic arterial pressure responses did not differ between exercises. Heart rate was similar at 5 min of each exercise bout but progressively increased during ECC and was higher at 15, 30 and 45 min of ECC compared to CON (+10 bpm), with a trend for a lower stroke volume. Diastolic and mean blood pressures were higher during ECC. No significant differences were observed in muscle oxygenation profiles. Muscle oxygenation responses during prolonged low-intensity exercise were not affected by the type of muscle action at the same metabolic demand and cardiac output., Competing Interests: The authors have no conflict of interest to declare., (© Georg Thieme Verlag KG Stuttgart · New York.)

Endothelial function and microvesicle concentration changes after acute bouts of continuous eccentric exercise have not been assessed previously nor compared with concentric exercise at similar aerobic power outputs. This method of training may be useful among some clinical populations, but acute responses are not well described. As such, 12 healthy males completed 2 experimental sessions of either 45 min of eccentric or concentric cycling at a matched aerobic power output below the ventilatory threshold. Brachial artery vascular function was assessed throughout 5 min of forearm ischemia and 3 min thereafter, before and at 5 and 40 min of recovery following each exercise session [flow-mediated dilation (FMD)]. Venous blood samples were acquired before each vascular function assessment. FMD significantly decreased after eccentric cycling by 40 min of recovery ( P < 0.05), but was unaltered after concentric exercise. No differences in peak hyperemic blood flow velocity occurred neither between modalities nor at any time point ( P > 0.05). Platelet-derived microvesicles increased by ~20% after both exercise modalities ( P < 0.05) while endothelial-derived microvesicles were unchanged ( P > 0.05). Moderate relationships with cardiac output, a surrogate for shear stress, and norepinephrine were apparent ( P < 0.05), but there were no relationships with inflammatory or acute phase proteins. In summary, eccentric endurance exercise induced macrovascular endothelial dysfunction; however, endothelial activation determined by endothelial microvesicles did not occur suggesting that this modality may induce oxidative stress but no significant endothelial damage. In addition, the increase in platelet microvesicle concentrations may induce beneficial microvascular adaptations as suggested by previous research. NEW & NOTEWORTHY Continuous eccentric cycling exercise induces substantial skeletal muscle, tendon, and bone strain providing a potentially beneficial stimulus among clinical populations. This modality also induces temporary endothelial dysfunction but no apparent damage or activation of the endothelium indicated by microvesicle production, whereas proangiogenic platelet microvesicles are released similarly following both concentric and eccentric cycling and may relate to the shear stress and catecholamine response to exercise., (Copyright © 2017 the American Physiological Society.)

Aim: The purpose of this study was to examine the changes in tissue oxygen saturation (StO2) with calf compression sleeves, before, during and after a cycling exercise., Methods: Eleven athletes came to the laboratory two times, to complete the same session with or without calf compression sleeves, in a randomized order. The session included a 15-min incremental cycling exercise: 3 min at each intensity - 40, 80, 120, 160 and 200 W, preceded (baseline) and followed (recovery) by a 10-min period at rest in seated position. Calf StO2 was recorded using near infrared spectroscopy during the three last min of the baseline period, during the cycling exercise and during the recovery period., Results: Baseline StO2 was significantly increased with the compression sleeves (P<0.001; +24.8±3.5%). During the cycling exercise, StO2 was significantly increased with the compression sleeves only at 40 W (P<0.05; +8.2±3.7%) and 80 W (P<0.05; +7.9±3.7%). At 120 W (P=0.23; +5.0±4.0%), 160 W (P=0.38; +3.9±4.1%) and 200 W (P=0.81; -0.1±4.9%), no significant difference was found with compression sleeves. During the recovery period, StO2 was significantly increased with the compression sleeves (1 to 10 min: P<0.001; +10.5±1.3%)., Conclusion: This study shows that wearing calf compression sleeves increases StO2 at rest (before and after an exercise) and at low intensities in cycling (40 W and 80 W). At high intensities (120 W and more), compression sleeves is not useful to increase StO2.

Introduction: Prolonged and strenuous exercise (PSE) induces transient left ventricular (LV) dysfunction. Although a consensus exists regarding the decrease in diastolic function, the existence of a decrease in systolic function by a PSE remains controversial, probably due to the transient tachycardia and changes in loading conditions observed upon the completion of exercise. Therefore, the objective was to evaluate LV systolic function before and after a PSE using two-dimensional speckle tracking echocardiography not only at rest but also during incremental tests to adjust heart rates (HR)., Methods and Results: Sixteen healthy young men (23 ± 3 yr old) performed a 3-h period of intensity-controlled upright cycling. LV strain (S), systolic strain rate (SR), rotation, and systolic rotational rate were evaluated by two-dimensional speckle tracking echocardiography before and after a 3-h period of PSE at rest and during incremental tests. Posttest evaluation was performed once the HR had returned to the pretest value. Under resting conditions, parameters of systolic function were either unchanged or increased after the PSE. However, during the incremental test, all LV systolic SR and apical rotational rates were decreased after PSE (radial SR at workload 3 (W3): 2.21 ± 0.12.s(-1) vs 1.87 ± 0.10.s(-1), P < 0.01 and apical rotational rate at W3: 128 ± 28 deg.s(-1) vs 105 ± 26 deg.s(-1), P < 0.05). Regression analyses between LV systolic SR and HR showed lower y-intercepts without differences in slopes, suggesting a decrease of both global and regional systolic functions irrespective of HR after the PSE., Conclusion: Our findings based on LV S and SR data during incremental tests demonstrate that the 3-h period of PSE induces LV systolic dysfunction.

Objective: To assess the safety and acute effects of a procedure using perceived exertion during a prior submaximal concentric (CON) test to individualize eccentric (ECC) cycling exercise intensity., Design: Prospective, monocentric open study., Setting: Technological investigation platform at a physical medicine and rehabilitation department in a university hospital., Participants: Healthy subjects (N=18; 15 men, 3 women) aged between 22 and 37 years., Interventions: The subjects performed 3 cycling exercises: (1) incremental CON test to determine the comfortable pedaling power (CPP) corresponding to a Borg scale rating of 12 (rate of perceived exertion); (2) steady-state CON exercise at the CPP workload to determine the corresponding plantar pressure; and (3) steady-state ECC exercise with an imposed resistance corresponding to the CPP plantar pressure., Main Outcome Measures: Rate of perceived exertion on Borg scale, oxygen uptake (V˙o2), heart rate, cardiac output, and stroke volume using inert gas rebreathing techniques were measured during steady-state CON and ECC exercises. Muscle soreness was rated on a visual analog scale immediately, 24, and 48 hours after the tests., Results: No adverse effects were reported. V˙o2 was about 5 times the resting value during CON exercise, while it was twice that during ECC exercise. Cardiac output was lower during ECC exercise (P<.05). This moderate increase of cardiac output was exclusively linked to a greater increase in stroke volume during ECC exercise than during CON exercise (P<.05)., Conclusions: Moderate-intensity ECC cycling exercise tailored according to perceived exertion during a prior CON test is well tolerated. It corresponds to a limited muscular use of oxygen and to an isolated increase in stroke volume. It appears to be a feasible procedure for preconditioning before ECC training., (Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.)

Exercise training improves arterial compliance due to increases in blood flow to skeletal muscle during repeated bouts of daily exercise. The effect of resuming training on arterial stiffness in previously well-trained subjects is poorly documented. Hence, the purpose of this study was to determine the vascular effects induced by return to exercise in highly trained cyclists. Pulse wave velocity (PWV), an index of arterial stiffness, was assessed at rest and during constant moderate-intensity cycle exercises before and after 16 weeks of endurance training. The impact of daily exercise on the concentration of nitric oxide (NO) measured as nitrate in plasma was examined at rest and during maximal exercise before and after the training period. At rest, PWV was significantly lower in the subjects after a training session (6.4 +/- 0.4 vs. 8.1 +/- 0.4 m x s(-1), p < 0.05). During constant exercise, PWV was significantly and positively correlated with increases in blood pressure. The increased PWV induced by exercise was, however, significantly lower after training (9.8 +/- 0.6 vs. 11.4 +/- 0.6 m x s(-1), p < 0.05). After the training program, nitrate plasma levels at rest were higher. During the maximal test, the plasma nitrate concentration was increased in the subjects studied before the training period, but not after. These results show that resumption of chronic endurance training rapidly induces adaptive changes in arterial stiffness and NO release that may contribute to improved physical fitness in athletes.

Aim: The purpose of this study was to examine the effects of a cycle competition on the large arteries stiffness, 24-hours after the end of the effort., Methods: Two males elite cyclists were studied before and after performing a stage-race. Their heart rate (HR) was measured continuously during the two competition days. The impact of the competition on their vascular system was determined using the measure of pulse wave velocity (PWV), an index of regional arterial stiffness. HR and blood pressure were also measured before and 24-hours postexercise., Results: During the race, mean cyclists HR were relatively similar. Changes in PWV and HR were found after competition: these measures increased for the offensive subject and decreased for the other., Conclusions: Despite their involvement in the same cycling competition, we suggest that the long-term effects induced by effort on arterial stiffness were inverted according to the subject's comportment during the race. This study should be completed by others measures in order to precise our results and to precise the possible link between arteries stiffness and the recovery kinetic process, both depending on the cardiovascular autonomic nervous system control.

The purpose of this study was to evaluate different efficiency indices, i.e., gross (GE: no baseline correction), net (NE: resting metabolism as baseline correction), and work (WE: unloaded exercise as baseline correction), to reveal the effect of endurance training on mechanical efficiency. Nine healthy sedentary women undertook an incremental test and submaximal cycling exercise, at an intensity corresponding to 50% of the pretraining peak oxygen uptake, before and after 6 weeks of endurance training (18 sessions of 45 min). The training effects on efficiency indices were tested by comparisons based on GE, NE, and WE as well as by the differences between the percentage changes of all indices (%GE, %NE, %WE). Endurance training resulted in significantly higher GE (+11.1%; p < 0.001) and NE (+9.1%; p < 0.01). Only minor significant improvement (+2.4%; p < 0.05) was observed with the WE index because the value used for baseline subtraction was significantly reduced by the training sessions, due perhaps to improvement in pedaling skill. As a consequence, %WE was significantly lower than %GE (p < 0.01) and %NE (p < 0.05), while %GE and %NE were not significantly different. We conclude that mechanical efficiency of cycling increases with training in women previously unfamiliar with cycling, and that the WE index is less sensitive to this training effect than GE and NE indices.

We tested the hypothesis that O(2) uptake (Vo(2)) kinetics at the onset of heavy exercise would be altered in a state of muscle fatigue and prior metabolic acidosis. Eight well-trained cyclists completed two identical bouts of 6-min cycling exercise at >85% of peak Vo(2) separated by three successive bouts of 30 s of sprint cycling. Not only was baseline Vo(2) elevated after prior sprint exercises but also the time constant of phase II Vo(2) kinetics was faster (28.9 +/- 2.4 vs. 22.2 +/- 1.7 s; P < 0.05). CO(2) output (Vco(2)) was significantly reduced throughout the second exercise bout. Subsequently Vo(2) was greater at 3 min and increased less after this after prior sprint exercise. Cardiac output, estimated by impedance cardiography, was significantly higher in the first 2 min of the second heavy exercise bout. Normalized integrated surface electromyography of four leg muscles and normalized mean power frequency were not different between exercise bouts. Vo(2) and Vco(2) kinetic responses to heavy exercise were markedly altered by prior multiple sprint exercises.