TY - JOUR
T1 - The effects of exercise intensity vs. Metabolic state on the variability and magnitude of left ventricular twist mechanics during exercise
AU - Armstrong, Craig
AU - Samuel, Jake
AU - Yarlett, Andrew
AU - Cooper, Stephen Mark
AU - Stembridge, Mike
AU - Stöhr, Eric J.
N1 - Publisher Copyright:
© 2016 Armstrong et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
PY - 2016/4/21
Y1 - 2016/4/21
N2 - 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, VO2peak: 45.5 ± 6.9 ml·kg-1·min-1, range of individual anaerobic threshold (IAT): 32-69% of VO2peak) 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 (F247 = 2.08, P < 0.05) during 40%peak compared with IAT(3.0 vs. 4.1 degrees). Despite the same workload and similar LV volumes, hypoxia increased LV twist and untwisting rate (P < 0.05), but the mean margin of error remained similar to that during 40%peak (3.2 degrees, 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.
AB - 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, VO2peak: 45.5 ± 6.9 ml·kg-1·min-1, range of individual anaerobic threshold (IAT): 32-69% of VO2peak) 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 (F247 = 2.08, P < 0.05) during 40%peak compared with IAT(3.0 vs. 4.1 degrees). Despite the same workload and similar LV volumes, hypoxia increased LV twist and untwisting rate (P < 0.05), but the mean margin of error remained similar to that during 40%peak (3.2 degrees, 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.
UR - http://www.scopus.com/inward/record.url?scp=84964681277&partnerID=8YFLogxK
U2 - 10.1371/journal.pone.0154065
DO - 10.1371/journal.pone.0154065
M3 - Article
C2 - 27100099
AN - SCOPUS:84964681277
SN - 1932-6203
VL - 11
JO - PLoS ONE
JF - PLoS ONE
IS - 4
M1 - e0154065
ER -