Does exercise intensity versus metabolic state affect the variability and magnitude of left ventricular twist mechanics during exercise in healthy males?
During exercise, the intra-individual variability of LV twist mechanics is smaller at the same relative exercise intensity compared with IAT, and the absolute magnitude is associated with the prevailing rate pressure product.
Increased left ventricular (LV) twist and untwisting rate (LV twist mechanics) are essential responses of the heart to exercise. However, previously a large variability in LV twist mechanics during exercise has been observed, which complicates the interpretation of results. This study aimed to determine some of the physiological sources of variability in LV twist mechanics during exercise. Sixteen healthy males (age: 22 ± 4 years, Formula: see textO2peak: 45.5 ± 6.9 ml∙kg-1∙min-1, range of individual anaerobic threshold (IAT): 32-69% of Formula: see textO2peak) were assessed at rest and during exercise at: i) the same relative exercise intensity, 40%peak, ii) at 2% above IAT, and, iii) at 40%peak with hypoxia (40%peak+HYP). LV volumes were not significantly different between exercise conditions (P > 0.05). However, the mean margin of error of LV twist was significantly lower (F2,47 = 2.08, P 0.05). Overall, LV twist mechanics were linearly related to rate pressure product. During exercise, the intra-individual variability of LV twist mechanics is smaller at the same relative exercise intensity compared with IAT. However, the absolute magnitude (degrees) of LV twist mechanics appears to be associated with the prevailing rate pressure product. Exercise tests that evaluate LV twist mechanics should be standardised by relative exercise intensity and rate pressure product be taken into account when interpreting results.
Armstrong et al. (Thu,) studied this question.
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