european college of sport science

Thursday, June 25th, 2009
14:15 - 15:15
Poster presentations
PP-PH16 Physiology 16
IS BICARBONATE A PERFORMING ENHANCING DRUG?
ZINNER, C., WAHL, P., HAEGELE, M., BEHRINGER, M., SPERLICH, B., MESTER, J.
GERMAN SPORT UNIVERSITY COLOGNE
Introduction: During past years numerous studies analysed the effects of bicarbonate loading on performance. These studies postulate
different effects of bicarbonate on blood lactate concentrations and performance of exercise bouts of different durations. Purpose of the
present study was to determine the effects of bicarbonate on blood lactate accumulation, metabolism and performance. To visualize the
effects of HCO3 our aim was to exhaust the “normal” in-vitro buffer capacity by short all-out intervals.
Methods: 8 male athletes (27.4 ±6years, 182.3 ±8cm, 75.6 ±9kg, 67.9 ±4ml/kg/min) performed two seperated sessions each consiting of
four 30 sec lasting bike sprints on a cycle ergometer. Between the sprints subjects remained in a sedentary position on the cycle ergometer
for 5 min. The sessions started with a warming up of 10 minutes at an intensity of 1.5 Watt/kg. Subjects ingested either 0.3 g/kg of
sodium bicarbonate (NaHCO3) or 2 g of a Placebo (P) (calcium carbonate) diluted in 0.02 ml/kg of water over a 90 min resting period
before the warming up started. Arterialised capillary blood samples (115µl) were taken from the hyperemized earlobe before ingestion,
post ingestion, after the warm up and during the rest periods between each bout (30´´, 4´).
Results: Prior the ingestion, pH and [HCO3] did not differ between the two interventions ((NaHCO3) vs. (P), 7.39 ±0.02 vs. 7.39 ±0.01, 24.6
±0.8 mmol/l vs. 24.6 ±1.4 mmol/l). The pre exercise pH and [HCO3] (post warming up (WU)) were significantly increased after ingestion
((NaHCO3) vs. (P) 30.7 ±1.3mmol/l vs. 25.4 ±1.3mmol/l, 7.46 ±0.01 vs. 7.40 ±0.01). At the end of the trials the pH was significantly lower for
the P condition (7.09 ±0.04 vs. 7.16 ±0.02). At the end of the tests lactate values showed significant differences between P (16.3
±5.8mmol/l) and NaHCO3 (20.3 ±6.6mmol/l).
The mean power (MP) showed significant differences between both conditions. During the first and the second bout performance was
nearly identical (1st bout: (NaHCO3) 768 ±219W vs. (P) 769 ±250W, 2nd bout: 697 ±203W vs. 698 ±224W). The performance during the
third and the fourth bout were significantly lower in the P intervention (third bout: 632 ±197W vs. 581 ±213W, fourth bout: 606 ±209W vs.
536 ±184W).
Discussion: The results of our study show significantly higher MP values during the 3rd and the 4th test after bicarbonate supplementation.
Lactate is transported in a symport with H+ ions by monocarboxylate transporter proteins. Bicarbonate which does not enter the
muscle therefore increases the concentration gradient of H+ ions between the muscle and the blood causing a greater efflux of H+ ions
out of the muscle accompanied by lactate into the blood. The supplementation seems not to increase only the ’in vitro’ buffer capacity but
also the ’in vivo’ buffer capacity, which is the ability of a cell to regulate pH. It can be speculated that hence the muscle is capable of
maintaining performance for a longer period of time.
HEART RATE VARIABILITY IN OBESE ADOLESCENTS
STUCKEY, M.I., GUEUGNON, C., TORDI, N., MOUGIN-GUILLAUME, F., PETRELLA, R., REGNARD, J.
1. UNIVERSITY OF WESTERN ONTARIO, 2. UNIVERSITÉ DE FRANCHE-COMTÉ
Introduction: Obesity is an important risk factor for cardiovascular disease and obesity rates are increasing in all age categories including
adolescents. Autonomic dysfunction is common in obese adults and adolescents. Heart rate variability (HRV) is a popular means of
characterizing the autonomic nervous system since HRV values outside of the normal range are predictors of cardiovascular morbidity
and mortality. The purpose of this investigation was to test the hypothesis that lifestyle modification therapies would positively affect
frequency domain indices of HRV in obese adolescents. Methods: 34 Adolescents (aged 11-18) were recruited from an obesity rehabilitation
centre (Maison d’enfants la beline, Salins les Bains, France). Treatment at the centre included dietary and psychological counseling as
well as access to a variety of daily physical activities and medical intervention for co-morbidities. 17 adolescents followed this treatment
plan and 17 attended supervised cycle exercise sessions in addition to the normal treatment. Before and after 8 weeks of exercise (2
weeks familiarization, 6 weeks training) heart rate was collected during 5 minutes of quiet, seated rest. Results: Power spectral analysis
of RR intervals before and after the intervention period revealed that there were no significant changes in any frequency domain index of
HRV (p > 0.05). Conclusion: Contrary to our hypothesis treatment for obesity did not improve HRV in adolescents. This work was funded by
the Lawson Health Research Institute.
KINETICS OF O2 UPTAKE AND MUSCLE DEOXYGENATION DURING MODERATE AND SUPRA MAXIMAL INTENSITY
CYCLING EXERCISE IN HUMANS
ADAMI, A., DEROIA, G., POGLIAGHI, S., CAPELLI, C.
UNIVERSITY OF VERONA - SCHOOL OF SPORT AND EXERCISE SCIENCE
Introduction: It is not still clear whether V’O2 kinetics at the onset of square-wave supra maximal (SM) exercise is faster (Hebestreit et al.,
1998) or slower (Barstow and Molè, 1991, Hughson et al, 2000) than during moderate (M) intensity exercise. It has been also shown that
muscle capillary perfusion response may be substantially slower than that of pulmonary gas exchanges and cardiovascular O2 delivery
(Harper et al., 2006). As such, it may limit the V’O2 kinetics during exercise performed above peak O2 uptake. Therefore, the aim of this
study was to analyse in parallel V’O2 kinetics and muscular deoxygenation responses at the onset of M and SM square wave exercise in
humans.
Methods: 14 active male subjects (26 ± 5 yr; 175 ± 6 cm; 73 ± 5.7 Kg; V’O2max 4.13 ± 0.36 L min-1) were studied at the onset of squarewave
cycling exercise of M (80% of maximal aerobic work rate) and SM (120% of maximal aerobic work rate) intensities.
B-by-B V’O2 at the mouth and muscle oxygenation of the right vastus lateralis were continuously measured (NIRS).
OSLO/NORWAY, JUNE 24-27, 2009 213