Several methods, both invasive and non – invasive, have been used for estimating
the anaerobic threshold, and there is no consensus about what is the best procedure.
The aim of this study was the determination of anaerobic threshold by %SPO2
(percent saturation of Hb with O2) changes, and comparison of three common
methods in evaluation of anaerobic threshold by pulmonary gas exchanges. 15 active
men volunteered to participate in this study and did three incremental tests, at least
with 48h interval. Respiratory parameters were measured breath by breath, heart
rate was measured continuously every five seconds, and blood samples were collected
every third minutes. Finally %SPO2 changes were measured continuously throughout
the gas analysis test every ten second using pulse oximeter. Anaerobic threshold was
determined based on:1. Blood lactate concentration (lactate threshold), 2. respiratory
exchange ratio (RER threshold), 3. V-Slope method (v-slope threshold), 4. %SPO2
changes (spo2 threshold), 5. Ventilatoty equivalent for O2 (ve / ve2 threshold).
Equivalent of each factor including oxygen, heart rate, lactate and speed, for
anaerobic threshold, was calculated in each test. The correlations among variables
were made by pearson correlation coeficience test and regression analysis was
performed to determine the ability of prediction. The difference among variables was
determined by paired t – test. Significant correlation was found between RER
threshold and lactate threshold (r = 0.784, p<01), ve / vo2 threshold and lactate
threshold (r = 0.731, p< 01), v – slope threshold and lactate threshold (r = 0.59,
P<05), Spo2 threshold and lactate threshold (r = 0.61, P< .05).The results indicated
that determination of anaerobic threshold well correlates with the blood lactate –
based anaerobic threshold and in the present study, it seemed to be the best
respiratory index for estimation of anaerobic threshold. An other finding was that it is
possible to estimate the lactate threshold heart rate with 95% confidence considering
the heart rate of the RER threshold.
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