Exercise appears to have overall benefit in pulmonary arterial hypertension (PAH); however, studies to date indicate little effect on the elevated pulmonary pressure or RV hypertrophy (RVH) and dysfunction associated with the disease. High intensity interval training (HIIT) is reported to be superior to the more customary prolonged continuous exercise training (CExT) protocol for chronic heart failure but has not been tested for PAH. Therefore, we investigated impact of a 6 wk HIIT vs. CExT treadmill program in a monocrotaline rat model of mild PAH (MCT, 40 mg/kg) on indicators of disease progression.
Methods:
Treadmill training was performed 5x/wk in male Sprague-Dawley MCT rats (250-300g), following a protocol of either HIIT (5 cycles of 2 min at ~90% VO
2
reserve [VO
2
R] + 3 min at 30% VO
2
R; n=8), or low intensity CExT (60 min at 50% VO
2
R; n=7). Statistical analysis was performed by one-way ANOVA.
Results:
MCT-induced decrements in VO
2
max were ameliorated by both HIIT and CExT (p
<
0.01 vs. sedentary MCT rats, MCT-SED, n=6), and were similar to healthy controls (CON, n=6). Most importantly, RV systolic pressure (RVSP, in mmHg; via Millar catheter) and RVH (ratio of RV to LV+S mass) were lowered (p<0.05) only by HIIT (28.7±2, and 0.32±0.02) and not by CExT (44.1±3, and 0.43±0.01) vs. MCT-SED (40.2±3.2, and 0.41±0.02). Cardiac output (Δ from baseline in μl, via RV echocardiography) was also improved by HIIT (117±28) vs. MCT-SED (6±42, p=0.04). Additional hemodynamic recordings
during
running, via novel implantable telemetry (DSI), were obtained serially at pre- and 2, 4, 6, and 8 wks post-MCT, and revealed ‘surges’ in RVSP during HIIT, vs. a steady RVSP pattern during CExT. Pulmonary eNOS (per immunoblotting) was increased (p<0.05) with HIIT, consistent with greater endothelial stimulation. Conclusions: HIIT is superior to CExT for improving hemodynamics and RV remodeling and dysfunction in MCT rats and warrants further investigation in other models and in patients. More favorable outcomes may be explained by greater sheer-stress mediated vascular endothelial adaptation to HIIT stimulus, or lower cumulative training-induced RV wall stress with the briefer HIIT session duration.
Enjoyment In Low Intensity Continuous Training Versus High Intensity Interval Training In An Iso-caloric Design
