european college of sport science

PP-PH16 Physiology 16
V’O2 kinetics at the onset of exercise was described by using two- or three-component exponential model, whereas that of the deoxygenated
hemoglobin concentration ([HHb]) was described by using mono- or two-component models (DeLorey et al., 2003). This allowed
calculating the mean response time (MRT) of the responses (McDonald et al., 1997).
Results: Steady state V’O2 during M corresponded to 67.8% of V’O2max; at the end of SM it equalled 95.4 % of V’O2max.
MRT of V’O2 kinetics during M was not significantly different (38.6 ± 10 s) from that found in SM (MRT 36.9 ± 9.5 s). MRTs of [HHb] kinetics
were not significantly different between the two exercise conditions: M = 17.6 s ± 5.7; SM = 19.7 s ± 14.8.
Discussion: V’O2 kinetics did not differ in the two exercise modalities. These findings partially agree with of Hebestreit et al. (1998) who
observed a faster V’O2 kinetics during SM exercise. However, the fitting procedure may have yielded a spuriously fast V’O2 response of
SM exercise (Hughson et al, 2000). [HHb] response was similar to those described during M and severe intensity exercises (DeLorey et al.,
2003, Grassi et al,, 2003). The low MRT values of [HHb] kinetics are compatible with a slow adaptation of muscular capillary blood flow at
the onset of exercise (Harper et al., 2006). Nevertheless, this phenomenon, coupled with the large O2 request, did not seem to limit O2
uptake kinetics during SM exercise.
References
Barstow TJ, Molè PA. (1991). J Appl Physiol 71: 2099 - 2106.
Grassi B, Pogliaghi S, Rampichini S, Quaresima V, Ferrari M, Marconi C , Cerretelli P. (2003) J Appl Physiol 95: 149-158
Harper AJ, Ferriera LF, Lutjemeier BJ, Townsend DK, Barstow TJ (2006) Exp Physiol 91: 661 - 671.
Hebestreit H, Kriemler S, Hughson RL, Bar-Or O. (1998) J Appl Physiol 85: 1833 - 1841.
MacDonald M, Pedersen PK, Hughson RL. (1997) J Appl Physiol 83: 1318 - 1325.
DeLorey DS, Kowalchuk JM, Paterson DH. (2003) J Appl Physiol 95: 113-120.
A COMPARATIVE STUDY OF SKIN BLOOD FLOW AND SWEATING RESPONSES IN CYCLISTS OF DIFFERENT AGES DUR-
ING UPRIGHT AND SUPINE CYCLING.
BEST, S., THOMPSON, M.W., TAMMAM, A.
THE UNIVERSITY OF SYDNEY
Introduction: Age related impairment in thermoregulation has been reported to be a result of a diminished capacity and/or sensitivity of
the sweating response. There is evidence to suggest skin blood flow (SBF) is restricted in older adults through decreased vasodilation and
splanchnic vasoconstriction. During exercise in the older trained cyclist, a diminished SBF response may be compensated for by an
increased reliance on sweating. This is somewhat analogous to the onset of exercise when vasodilation is delayed and the increase in
body temperature stimulates a compensatory increase in sweating. Comparing SBF and sweat responses during upright exercise and
supine exercise, where SBF has been shown to increase 1, may potentially identify the relative contribution of SBF and sweating to thermoregulation
in young and older trained cyclists.
Method: An older (50-70yrs, n=4) and younger (age 20-35yrs, n=4) group of highly trained male cyclists were recruited to the study.
Testing was performed on an electromagnetically braked cycle ergometer modified to be used in the upright and supine positions. Each
subject completed a VO2max test in the upright and supine positions, before 3 cycling sessions of 60mins in the same hot environmental
conditions (35oC, 40%RH). The 3 heat tests varied in cycling position and intensity: 1) Cycling upright (U) at 70% Upright VO2max, 2) Cycling
supine (SU) at 70% Upright VO2max, 3) Cycling Supine (SS) at 70% Supine VO2max. Rectal temperature (Trec), skin temperature (Tsk),
Whole body sweat rate (Swb), Local sweat rate (Swl) and skin blood flow (SBF) were measured throughout each of the 3 exercise heat
tests.
Results: All subjects completed the 60mins in the upright position but 5 could not complete the SU test (Y=4, O=1) and 2 could not complete
the SS test (Y=2). Final Trec, Tsk and SBF values in the U, SU and SS heat tests were similar between the 2 age groups. Final Swl was
similar in the U (1.56 ±0.24 mg.min-1.cm2, 1.65 ±0.42 mg.min-1.cm2), SU (1.39 ±0.19 mg.min-1.cm2, 1.39 ±0.26 mg.min-1.cm2) and the SS
test (1.37 ±0.29 mg.min-1.cm2, 1.31 ±0.33 mg.min-1.cm2) for the young and older groups respectively. Swb was greater in the younger
than the older group respectively for the U (1.91 ±0.29 L.hr-1, 1.62 ±0.19L.hr-1), SU (2.16 ±0.48L.hr-1, 1.68 ±0.13L.hr-1) and SS (2.09
±0.39L.hr-1, 1.59 ±0.20L.hr-1) heat tests. Tsk and SBF values were higher and Swl lower for both age groups during the supine tests when
compared to the upright test. No difference in Swb was observed between upright and supine tests.
Discussion:
Preliminary results suggest no observable differences in skin blood flow or sweating response in highly trained older and younger cyclists,
in either upright or supine cycling positions. If age related differences do exist they may need a protocol that exposes cardiovascular
limitations such as the decline in VO2max as a consequence of sedentary living or an inherent outcome of ageing.
USING META-ANALYTICAL AND EXPERIMENTAL APPROACHES TO EXPLORE WHETHER BLOOD PRESSURE STATUS
REALLY IS THE MOST IMPORTANT DETERMINANT OF POST-EXERCISE HYPOTENSION
TAYLOR, C., CABLE, T., JONES, H., HADCROFT, J., ZAREGARIZI, M., ATKINSON, G.
LIVERPOOL JOHN MOORES UNIVERSITY, AND LIVERPOOL HEART AND CHEST HOSPITAL
Introduction: It has been maintained, both at the individual (Pescatello et al., 2004a) and whole-study (Pescatello and Kulikowich, 2001)
levels, that blood pressure (BP) status is the most important determinant of post-exercise hypotension. This claim is incorporated into the
ACSM position on hypertension (Pescatello et al, 2004b) and is based on reports that exercise-mediated changes in BP are correlated to
BP measured pre-exercise (PRE). Recently, this analysis has been questioned on the basis of potential regression-to-the-mean (RTM)
effects (Atkinson et al., 2005). Past syntheses of study results have also not involved standard meta-analytical weighting. The present aim
is to examine the degree to which BP status moderates post-exercise hypotension, via a novel combination of formal meta-analytical
and experimental approaches, while controlling for RTM.
Methods: As part of a systematic review of 67 studies (n=1155 participants), the reported exercise-mediated changes in daytime and
nocturnal BP were meta-regressed against PRE, and against the mean of pre- and post-exercise BP, which is an index of BP status not
prone to RTM. In a related experiment, 32 participants cycled for 30 min at 70% peak oxygen uptake (VO2peak). Systolic and diastolic BP,
and mean arterial pressure (MAP) were measured (Portapress) at baseline and for 20 min following exercise. Relations between BP
change, BP status and other potential moderators were described with regression analyses. Data are described as mean (95% confidence
limits).
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ANNUAL CONGRESS OF THE EUROPEAN COLLEGE OF SPORT SCIENCE