Low-volume High-intensity Interval versus Continuous Endurance Training: Effects on Hematological and Cardiorespiratory System Adaptations in Professional Canoe Polo Athletes
The aim of this study was to compare the effect of two paddling-based high-intensity interval training (HIIT) and continuous endurance training (CET) on hematological, immunological, and cardiorespiratory adaptations in professional canoe polo athletes. Twenty one male canoe polo athletes were randomly divided into one of three groups (N=7): 1) HIIT with variable intensity (VIHIIT) (6×60-second at 100,110,120,130,130, 130,120,110,100% vV[Combining Dot Above]O2peak from 1st to 9th session respectively, 1:3 work to recovery ratio); 2) HIIT with variable volume (VVHIIT) (6,7,8,9,9,9,8,7,6 repetitions/session from 1st to 9th session respectively)×60-second at lowest velocity that elicited V[Combining Dot Above]O2peak (vV[Combining Dot Above]O2peak), 1:3 work to recovery ratio); and 3) the CET group performed 3 times × 60 min paddling sessions (75% vV[Combining Dot Above]O2peak) per week for 3 weeks. Significant increases in V[Combining Dot Above]O2peak (ml·kg-1·min-1) (VIHIIT=7.6%, VVHIIT=6.7%), ventilation (V[Combining Dot Above]E) at V[Combining Dot Above]O2peak (VIHIIT=11.5%, VVHIIT=15.2%), respiratory frequency (Rf) at V[Combining Dot Above]O2peak (VVHIIT=21.1%), V[Combining Dot Above]O2 at ventilatory threshold (VT) (VIHIIT=10.5%, VVHIIT=25.1%), V[Combining Dot Above]E at VT (VIHIIT=12.4%, VVHIIT=34.0%), tidal volume at VT (VIHIIT=11.7%, VVHIIT=33.3%), Rf at VT (VIHIIT=9.7%), V[Combining Dot Above]E/V[Combining Dot Above]O2 at VT (VVHIIT=13.1%), V[Combining Dot Above]O2/HR at VT (VIHIIT=12.9%, VVHIIT=21.4%), and V[Combining Dot Above]E/HR at VT (VIHIIT=7.8%, VVHIIT=27.2%) were seen compared to pre-training. Training interventions resulted in significant increases in mean platelet volume (VIHIIT=2.7%, VVHIIT=1.9%), mean corpuscular hemoglobin concentration (CET=3.3%), and significant decrease in red blood cell distribution width (VVHIIT=−4.3), and cell numbers of lymphocyte (CET=−27.1) compared to pre-training. This study demonstrated that paddling-based HIIT enhances aerobic capacity and respiratory makers, without negatively affecting the immune system over 3 weeks.