european college of sport science

Thursday, June 25th, 2009
THE DEPLETION OF A FIXED ANAEROBIC ENERGY STORE DOES NOT EXPLAIN TASK FAILURE DURING HIGH-INTENSITY
EXERCISE
DE VRIJER, A., BISHOP, D.
UNIVERSITY OF VERONA
THE DEPLETION OF A FIXED ANAEROBIC ENERGY STORE DOES NOT EXPLAIN TASK FAILURE DURING HIGH-INTENSITY EXERCISE
Introduction: Exercise at intensities above VO2max can only be sustained for several minutes. As the energy required to exercise at such
intensities can, by definition, not be generated solely by the aerobic system, the cause of task-failure has often been attributed to the
exhaustion of anaerobic energy stores. This is the basis of the critical power (CP) model, which states that, when the required power
exceeds the maximum power of the aerobic system (the so-called CP), task failure will coincide with the depletion of a fixed anaerobic
energy store. The obvious corollary of this is that following task failure, subjects will not be able to continue exercising unless the power
output is decreased to below the CP. The purpose of the present study was to test this hypothesis.
Methods: Seven healthy males each performed an incremental test on a cycle ergometer to determine their power at VO2max (P100%),
followed by a familiarisation trial and 4 time-to-task failure (TTF) tests at 120% of VO2max (P120%). The first 3 TTF tests were identical and
used to determine TTF at P120% (TTF_120). To ensure that TTF_120 represented the maximum performance of the subjects at this intensity,
only the best TTF of the three tests was used. The last TTF test was similar to the first three, but the subjects were now instructed to continue
exercising until TTF_120, if possible, and at the moment they reached this time, power output was decreased to P105% and subjects
were asked to continue again as long as possible (TTF_105). Capillary blood was sampled before each test, at task failure, and after 5
min of recovery at 60W.
Results: All subjects were able to reach TTF_120 (186 ñ 32 s) during the final TTF test. Six of the subjects were able to continue exercising at
P105% for over 25 s (mean TTF_105 was an additional 61 ñ 48 s). There was no significant difference between the [BLa] of TTF_120 and
TFT_105 measured during rest (0.9 ñ 0.2 vs. 0.9 ñ 0.1 mmol/L) or at task failure (13.9 ñ 2.7 vs 14.9 ñ 3.2 mmol/L), but [BLa] was significantly
different after the 5 min of recovery (14.3 ñ 1.9 vs 15.6 ñ 2.1 mmol/l). Also the heart rate was significantly higher after TTF_105 (185 ñ 9 bpm)
than after TTF_120 (179 ñ 8 bpm). There was no significant difference between the VO2 after TTF_120 and TTF_105 (49.0 ñ 5.6 vs. 51.3 ñ 4.0
ml/kg/min).
Discussion/Conclusions
After cycling to task failure at P120%, six of the seven subjects were able to continue exercising at P105%. These results cannot be explained
by the critical power model, since this model predicts that the anaerobic work capacity must have been depleted at TTF_120,
making it impossible to continue exercising at any intensity above CP (i.e., requiring a further anaerobic contribution). Thus, our results
suggest that the depletion of a fixed anaerobic energy store does not explain task failure during high-intensity exercise.
HANDGRIP STRENGTH AND FOREARM VASCULAR FUNCTION IN PATIENTS WITH RHEUMATOID ARTHRITIS
KEEWAN, E., ALOMARI, M., ALAWNEH, K., IBRAHEEM, R., KHATIB, S.
JORDAN UNIVERSITY OF SCIENCE AND TECHNOLOGY
INTRODUCTION: Rheumatoid arthritis (RA) is associated with compromised arterial function (AF) attributed to endothelium-dependent and
independent structural and functional changes. Additionally, physical activities (PA) play a critical role in enhancing vasodilatory capacity
subsequent to improved fitness level (FL) in healthy and diseased populations. Despite the accumulating evidence describing the benefits
RA patients gain from participating in regular PA, the relationship between FL and AF in RA patients is not clear. Accordingly, the current
study examined the relationship between maximum handgrip strength (MHGS) and AF measures in RA patients.
METHODOLGY
Measures of AF and MHGS were examined in 22 RA patients (PT) and 13 healthy controls (CT) with age range (17-49). Dominant forearm
arterial inflow (BF), at rest (RBF) and after 5 minutes of upper arm occlusion (IBF), were obtained using strain gauge plethysmography.
Subsequently vascular resistances (VR) at rest (RVR) and after occlusion (IVR) were calculated with mean arterial pressure/BF. Average
MHGS was calculated after 3 consecutive allout gripping trials with hand dynamometer. Student t-tests were used to compare forearm
AF measures and MHGS between PT and CT groups whereas measures of forearm AF relationships with MHGS were evaluated using
Pearson correlation.
RESULTS: Forearm RBF (CT: 3.8 ± 0.8 vs. PT: 3.0 ± 1.2 ml/100ml/min; p=0.03), and IBF (CT: 31.7 ± 7.3 vs. PT:18.0 ± 5.9 ml/100ml/min;
p=0.0001) were greater in the CTs, whereas RVR (CT: 23.6 ± 3.9 vs. PT: 33.0 ± 15.4 U; p=0.01), and IVR (CT: 2.8 ± 0.5 vs. PT: 5.9 ± 3.9 U;
p=0.001) were less in the CTs. Similarly, MHGS in the CTs was greater than in the PTs (CT: 32.5 ± 13.4 vs. PT: 21.3 ± 11.3 Kg; p=0.02). Finally,
MHGS correlated positively with RBF (r=0.5; p=0.002), and IBF (r=0.7; p=0.0001) as well as negatively with RVR (r=- 0.3; p=0.07), and
IVR (r=- 0.4; p=0.04).
DISCUSSION: The results confirm previous studies indicating diminished AF and MHGS in RA PTs. However the relationships between
forearm AF and MHGS suggests that FL contribute to enhancing the vasculature in RA PTs. Additionally the association between forearm
AF measures and MHGS suggest that AF is locally controlled in RA PTs.
14:15 - 15:15
Poster presentations
PP-PH17 Physiology 17
MODULATION OF HOFFMANN REFLEX: THE ROLE OF GROUP III-IV MUSCLE AFFERENT FIBERS
LAURIN, J.
MOVEMENT SCIENCE INSTITUTE (UMR-CNRS 6233)
Introduction: The Hoffmann (H) reflex is frequently used to explore the spinal sensorimotor plasticity in response to physical exercise or to
training. However, neural mechanisms responsible of H-reflex modulation after exercise remain unclear. Numerous studies suggested
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