european college of sport science

Wednesday, June 24th, 2009
THE EFFECT OF BICARBONATE INFUSION IN CEREBRAL METABOLISM DURING MAXIMAL EXERCISE
VOLIANITIS, S., RASMUSSEN, P., SEIFERT, T., SECHER, N.H.
AALBORG UNIVERSITY
Exercise lowers the cerebral metabolic ratio of O2 to carbohydrates (glucose + ½ lactate). Metabolic acidosis increases cerebral lactate
uptake and exacerbates the cerebral metabolic ratio in vitro. However, the influence of pH on cerebral lactate uptake and the cerebral
metabolic ratio during exercise in humans is not known.
PURPOSE: To evaluate the influence of pH on cerebral metabolism during maximal exercise. METHODS: Sodium bicarbonate (Bic, 1 M;
350-500 ml) or an equal volume of saline (Sal; 1 M) was infused intravenously at a constant rate during a ’2,000-m’ maximal ergometer
row in six male oarsmen (23 ± 2 yrs). Comparisons between the two conditions were made using two-way ANOVA with repeated measures.
RESULTS: During the Sal trial, pH decreased from 7.41 ± 0.01 at rest to 7.02 ± 0.02 but only to 7.36 ± 0.02 (P < 0.05) during the Bic
trial. Arterial lactate increased to 21.4 ± 0.8 mM (mean ± SEM) and 32.7 ± 2.3 mM during the Sal and Bic trials, respectively. The arterialjugular
venous (a-v) lactate difference increased from -0.03 ± 0.01 mM at rest to 3.2 ± 0.9 mM (P < 0.05) and 3.4 ± 1.4 mM (P < 0.05)
following the Sal and Bic trials, respectively. The cerebral metabolic ratio decreased equally during the Sal and Bic trials from 5.8 ± 0.6 at
rest to 1.7 ± 0.1 and 1.8 ± 0.2, respectively.
CONCLUSION: The enlarged blood-buffering capacity after infusion of Bic attenuated the metabolic acidosis but did not affect the cerebral
lactate uptake or the cerebral metabolic ratio during maximal exercise.
EFFECTS OF PRIOR EXHAUSTIVE LEG OR ARM EXERCISE ON SUBSEQUENT PERFORMANCE, POWER AND EMG ACTIVITY
IN A DIFFERENT MUSCLE GROUP
GABE BELTRAMI, F., DE GROOT, R., RAUCH, L., TUCKER, R., RAE, D.E., NOAKES, T.D.
UNIVERSITY OF CAPETOWN
Introduction: A prior bout of exhaustive exercise is known to result in early exhaustion being reached during a subsequent bout of maximal
exercise. Much of the research to date has examined peripheral factors for this phenomenon. Therefore, the aim of this study was to
investigate the contribution of central regulation on the performance of maximal exercise preceded by a bout of exhaustive exercise
using a different muscle group.
Methods: Ten healthy men (5 well-trained cyclists and 5 well-trained canoeists) were recruited for this study and all completed two exercise
trials. In trial 1, subjects performed an incremental leg ergometry test to exhaustion (LEG A), followed 15 minutes later by an incremental
arm ergometry test to exhaustion (ARM B). In trial 2, the order was reversed (ARM A followed 15 minutes later by LEG B). The two
trials were separated by at least 3 days and the order in which the subjects performed the trials was randomised. Time to exhaustion (TE),
power output (PO), heart rate (HR), rating of perceived exertion (RPE), oxygen consumption (VO2), ventilation rate (VE), plasma lactate (LA)
and electromyography (EMG) of two lower (rectus femoris and vastus lateralis) and two upper limb (triceps and biceps) muscles were
measured during all trials.
Results: During the A trials, subjects reached exhaustion faster and at a higher PO during legs compared to arms. While HR and RPE
were similar in the leg and arm tests at exhaustion, VO2 (p = 0.018) and VE (p = 0.008) were lower in the arm test. Performance during
ARM B was unaffected by prior LEG A. However, prior ARM A significantly reduced TE (p = 0.011) and peak PO (p = 0.011) during subsequent
LEG B. There were no changes in maximal VO2, HR, RPE, VE and LA between trials A and B of each muscle group. LA was higher at
the beginning of LEG B (p < 0.001) and ARM B (p = 0.001) exercise compared to their respective A trials. Prior LEG A affected subsequent
ARM B HR for the first 40% of the trial. During LEG B, however, HR differed only at the start and 20% of the test. EMG increased linearly
during all the trials and maximal EMG activity measured during the tests was only 55% of previous MVC. RPE rose linearly during all tests,
regardless of different levels of LA and HR. None of the measured physiological/neuromuscular variables measured showed a plateau at
exhaustion.
Conclusion: Prior arm exercise reduced peak power output during a subsequent bout of exhaustive leg exercise without altering the
physiological or EMG variables measured in this study. In contrast, prior leg exercise did not alter peak power output during subsequent
arm exercise. These results suggest that during the tests RPE was set in anticipation, being independent of the amount of muscle mass
activated, HR or LA. These data are difficult to interpret according to traditional peripheral models of exercise fatigue and deserves further
investigations.
IMPACT OF TRAINING STATUS ON MAXIMAL OXYGEN UPTAKE CRITERIA ATTAINMENT DURING CYCLING
CHRISTIE, C.
RHODES UNIVERSITY
Objectives: The aims of this study were to assess whether training status influenced maximal physiological and perceptual responses
and whether certain maximal criteria were more sensitive for individuals with different levels of training. Methods: Females who were
either trained (N = 10) or untrained (N = 10) underwent a maximal cycle ergometer test to assess whether the criteria to indicate VO2 max
were training-specific. Results: Expectedly, VO2 max was significantly higher in the trained (50.09 mlO2.kg-1.min-1) compared to the
untrained group (35.21 mlO2.kg-1.min-1) while the oxygen uptake plateau criterion was met by only 40% of the participants. Peak workload
(W) was significantly higher (234 W compared to 174 W) and total test time significantly longer (7 minutes compared to 5 minutes) in
the trained group. Peak lactate values did not reach maximal criteria and on completion of the test were not significantly different between
the groups (7.8 mmol.L-1 in the trained group and 8.1 mmol.L-1 in the untrained group). Likewise, maximal heart rates, respiratory
exchange ratio (RER) values and ratings of perceived effort were not different between the groups. Noteworthy is that none of the subjects
achieved all of the criteria indicating a maximal effort. The criteria most achieved in both samples were RPEmax and RERmax with the
latter being the most attained in the untrained group and RPEmax being mostly attained by the trained group. Conclusions: The criteria
used to indicate attainment of VO2 max may be limited and may differ when comparing a heterogeneous training sample. Although
VO2 max was significantly higher in the trained group, all the other responses were similar. However, the number of trained and untrained
subjects reaching particular criteria was different suggesting that certain criteria may be more sensitive for individuals with different
levels of training.
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