Systems Physiology: Cardiovascular THRESHOLD CHANGES IN BLOOD LACTATE, BEAT-TO-CARDIOVASCULAR FUNCTION, AND BREATH-BY-BREATH VO 2 DURING INCREMENTAL EXERCISE
Year: 2002
Type: article
Abstract: The relationships between the systolic blood pressure threshold (ST), heart rate (HR) threshold (HT), rate pressure product threshold (RT), lactate threshold (LT) and ventilatory threshold (VT) were studied in 14 subjects (10 males, 4 females). All subjects performed an incremental cycle ergometer test to volitional exhaustion. HR data was collected via ECG. SBP was determined beat by beat by tonometry. The LT and VT were determined through standard methods. The threshold or breakpoint for SBP, HR and RPP, as a function of VO 2, was determined as the deviation from linearity when the data were analyzed with non-linear regression analysis. When the pre and post threshold slopes for SBP, HR and RPP were analyzed it was found that most subjects demonstrated either an increased or decreased response post-threshold. The threshold responses were analyzed using two-way ANOVA. For SBP, it was found there was no significant difference in pre and post-threshold SBP in subjects that demonstrated an increase in SBP slope post-threshold (p=0.36). In contrast, there was a significant difference between the pre and post-threshold slopes for the subjects that exhibited a decreased post-threshold SBP response (p=0.000). The analysis of the HR data pre and post HT revealed differences in pre and post-threshold slopes for those subjects that demonstrated an increase HR response post-threshold (p=0.003) and those that exhibited a decreased post-threshold HR response (p=0.001). There was no significant difference in the pre and post-threshold RPP responses for either the group that demonstrated an increased post-threshold response or the group that demonstrated a decreased RPP response post-threshold. Two-way ANOVA revealed significant differences between the VO2 at the RT (2.17±0.26 L/min) and LT (1.84±0.13 L/min) (p=0.011) and the RT and VT (1.87±0.11 L/min) (p=0.011). There were also significant differences between HT (2.24±0.14 L/min) and LT (p=0.0019) and HT and VT (p=0.0025), indicating that the RT occurs at a significantly different VO2 than either the LT or VT. In summary, differences were noted in the pre and post threshold responses for SBP and HR. The RPP slopes were inconsistent between subjects due to both positive and negative changes in the SBP and HR curves after the threshold. The intensities at the HT and RT did not coincide with either the LT or VT.
Language: English
Subfield: Physiology (medical)
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2183819172