Hypervolemia and cycling time trial performance

Luetkemeier, Maurie J.; Thomas, Evan L.

doi:10.1249/00005768-199404000-00016

Cited by 38 publications

(30 citation statements)

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“…A beneficial effect of PV expansion requires that the enhanced cardiac filling and elevated

{\overset{Q}{true}}_{\max}

outweigh the hemodilution (Warburton et al., ). The effect of acute PV expansion on

{\dot{normalV} O}_{2 max}

and TT performance is controversial with some studies reporting an effect (Luetkemeier & Thomas, ; Berger et al., ); however, this seems to level off with increasing PV expansion and training status (Hopper et al., ; Coyle et al., ; Warburton et al., ), indicating that the relative increase in cardiac output does not outweigh the hemodilution in situations with large PV expansion, or where the subjects already have a large blood volume. Therefore, although a small PV expansion might transfer to improved performance in cool conditions even in trained athletes (Lorenzo et al., ; Buchheit et al., ; Racinais et al., ), the benefit of a large PV expansion is probably countered by the hemodilution and did not result in improved

{\dot{normalV} O}_{2 max}

or TT performance in cool conditions in the present study.…”

Section: Discussionmentioning

confidence: 99%

Heat acclimatization does not improve VO_2max or cycling performance in a cool climate in trained cyclists

Karlsen

Racinais

Jensen

et al. 2015

Scandinavian Med Sci Sports

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This study investigated if well-trained cyclists improve VO 2max and performance in cool conditions following heat acclimatization through natural outdoor training in hot conditions. Eighteen trained male cyclists were tested for physiological adaptations, VO 2max , peak aerobic power output, exercise efficiency, and outdoor time trial (TT) performance (43.4 km in cool environment, ∼5-13°C) before and after 2 weeks of training in a cool (CON, n = 9) or hot (∼35°C, HA, n = 9) environment. After heat acclimatization, TT performance in the heat was improved by 16%; however, there was no change in the HA group in VO 2max (4.79 ± 0.21 L/min vs 4.82 ± 0.35 L/min), peak aerobic power output (417 ± 16 W vs 422 ± 17 W), and outdoor TT performance in cool conditions (300 ± 14 W/69 ± 3 min vs 302 ± 9 W/69 ± 4 min). The present study shows that 2 weeks of heat acclimatization was associated with marked improvements in TT performance in the heat. However, for the well-trained endurance athletes, this did not transfer to an improved aerobic exercise capacity or outdoor TT performance in cool conditions.

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“…A beneficial effect of PV expansion requires that the enhanced cardiac filling and elevated

{\overset{Q}{true}}_{\max}

outweigh the hemodilution (Warburton et al., ). The effect of acute PV expansion on

{\dot{normalV} O}_{2 max}

{\dot{normalV} O}_{2 max}

or TT performance in cool conditions in the present study.…”

Section: Discussionmentioning

confidence: 99%

Heat acclimatization does not improve VO_2max or cycling performance in a cool climate in trained cyclists

Karlsen

Racinais

Jensen

et al. 2015

Scandinavian Med Sci Sports

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“…Notably, blood doping also increases hematocrit and hence the oxygen carrying capacity of the blood, which is in contrast to the normal physiological training response where hematocrit is slightly lowered (170), and care should, therefore, be taken when extrapolating findings from these studies. Nevertheless, data from trained endurance athletes suggests that the increase in erythrocyte mass (208,385) and plasma and blood volume (266) are important training adaptations for endurance exercise performance.…”

Section: Blood Volume Response To Exercise Trainingmentioning

confidence: 99%

Cardiovascular Adaptations to Exercise Training

Hellsten

Nyberg

2015

Comprehensive Physiology

209

185

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Aerobic exercise training leads to cardiovascular changes that markedly increase aerobic power and lead to improved endurance performance. The functionally most important adaptation is the improvement in maximal cardiac output which is the result of an enlargement in cardiac dimension, improved contractility, and an increase in blood volume, allowing for greater filling of the ventricles and a consequent larger stroke volume. In parallel with the greater maximal cardiac output, the perfusion capacity of the muscle is increased, permitting for greater oxygen delivery. To accommodate the higher aerobic demands and perfusion levels, arteries, arterioles, and capillaries adapt in structure and number. The diameters of the larger conduit and resistance arteries are increased minimizing resistance to flow as the cardiac output is distributed in the body and the wall thickness of the conduit and resistance arteries is reduced, a factor contributing to increased arterial compliance. Endurance training may also induce alterations in the vasodilator capacity, although such adaptations are more pronounced in individuals with reduced vascular function. The microvascular net increases in size within the muscle allowing for an improved capacity for oxygen extraction by the muscle through a greater area for diffusion, a shorter diffusion distance, and a longer mean transit time for the erythrocyte to pass through the smallest blood vessels. The present article addresses the effect of endurance training on systemic and peripheral cardiovascular adaptations with a focus on humans, but also covers animal data.

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“…Indeed an increase in plasma albumin has been shown to enhance the effective colloid osmotic pressure gradient between the fluid compartments, resulting in a net fluid movement into the vascular space to maintain plasma albumin concentration (Convertino et al 1980). Furthermore, Deschamps et al (1992) found that HR and core temperature responses were attenuated and Luetkemeier and Thomas (1994) reported that cycling performance was improved by more than 10% following acute plasma volume expansion with either saline or dextran infusions. Conversely though, others have failed to show any significant effect of plasma volume expansion on HR, core temperature, skin blood flow or even performance during exercise in the heat (Grant et al 1997).…”

Section: Or Negatively Affected (Toone and Bettsmentioning

confidence: 99%

Combined carbohydrate–protein supplementation improves competitive endurance exercise performance in the heat

et al. 2011

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Laboratory-based studies have demonstrated that adding protein (PRO) to a carbohydrate (CHO) supplement can improve thermoregulatory capacity, exercise performance and recovery. However, no study has investigated these effects in a competitive sporting context. This study assessed the effects of combined CHO-PRO supplementation on physiological responses and exercise performance during 8 days of strenuous competition in a hot environment. Twenty-eight cyclists participating in the TransAlp mountain bike race were randomly assigned to fitness-matched placebo (PLA 76 g L(-1) CHO) or CHO-PRO (18 g L(-1) PRO, 72 g L(-1) CHO) groups. Participants were given enough supplements to allow ad libitum consumption. Physiological and anthropometric variables were recorded pre- and post-exercise. Body mass decreased significantly from race stage 1 to 8 in the PLA group (-0.75 ± 0.22 kg, P = 0.01) but did not change in the CHO-PRO group (0.42 ± 0.42 kg, P = 0.35). Creatine kinase concentration and muscle soreness were substantially elevated during the race, but were not different between groups (P = 0.82, P = 0.44, respectively). Urine osmolality was significantly higher in the CHO-PRO versus the PLA group (P = 0.04) and the rise in tympanic temperature from pre- to post-exercise was significantly less in CHO-PRO versus PLA (P = 0.01). The CHO-PRO group also completed the 8 stages significantly quicker than the PLA group (2,277 ± 127 vs. 2,592 ± 68 min, respectively, P = 0.02). CHO-PRO supplementation therefore appears to prevent body mass loss, enhance thermoregulatory capacity and improve competitive exercise performance despite no effect on muscle damage.

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Hypervolemia and cycling time trial performance

Cited by 38 publications

References 0 publications

Heat acclimatization does not improve VO_2max or cycling performance in a cool climate in trained cyclists

Heat acclimatization does not improve VO_2max or cycling performance in a cool climate in trained cyclists

Cardiovascular Adaptations to Exercise Training

Combined carbohydrate–protein supplementation improves competitive endurance exercise performance in the heat

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Hypervolemia and cycling time trial performance

Cited by 38 publications

References 0 publications

Heat acclimatization does not improve VO2max or cycling performance in a cool climate in trained cyclists

Heat acclimatization does not improve VO2max or cycling performance in a cool climate in trained cyclists

Cardiovascular Adaptations to Exercise Training

Combined carbohydrate–protein supplementation improves competitive endurance exercise performance in the heat

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Heat acclimatization does not improve VO_2max or cycling performance in a cool climate in trained cyclists

Heat acclimatization does not improve VO_2max or cycling performance in a cool climate in trained cyclists