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Double product response is accelerated above the blood lactate threshold
H Tanaka1, A Kiyonaga, Y Terao
1Laboratories of Exercise Physiology, School of Physical Education, Fukuoka University, Japan.
Medicine and Science in Sports and Exercise
|April 1, 1997
Summary
The double product (DP) steeply increases above the blood lactate threshold (LT). This finding suggests the DP breakpoint is a reliable marker for identifying the LT during exercise.
Area of Science:
- Exercise Physiology
- Cardiovascular Physiology
Background:
- Catecholamine levels rise significantly with increased work rates above the blood lactate threshold (LT).
- This suggests a potential physiological marker shift at exercise intensities exceeding the LT.
Purpose of the Study:
- To investigate if the double product (DP), a measure of cardiac workload, also increases abruptly above the LT.
- To determine if the DP breakpoint (DPBP) can serve as a valid indicator of the LT.
Main Methods:
- Ninety healthy students underwent a graded exercise test on a cycle ergometer.
- Heart rate (HR), systolic blood pressure (SBP), and DP were measured, and regression slopes above and below the LT were compared.
- DPBP determination protocol was assessed for reliability and correlation with LT.
Main Results:
- The slope of the DP regression line was significantly steeper above the LT compared to below it for all subjects.
- While HR and SBP slopes varied, the DP showed a consistent steeper increase above the LT.
- The DPBP demonstrated good test-retest reliability (r=0.951) and strong correlation with LT (r=0.900).
Conclusions:
- The double product exhibits a distinct increase in its rate of rise above the blood lactate threshold.
- The DP breakpoint (DPBP) is a valid and reliable non-invasive marker for identifying the exercise-induced lactate threshold.