Effects of current continuous and intermittent training strategies used for endurance development on cardio-vascular responses

The purpose of the present study was to examine the potentials of the endurance-related training methods based on central and peripheral components of maximal oxygen consumption level (VO2max). We analysed O2 consumption (VO2), cardiac output (Q), stroke volume (SV), heart rate (HR) and arteriovenous O2 difference (a-vO2diff) during 5 different regimes of high intensity training (HIT) loading and recovery periods for the aims. Eight well-trained male competitive cyclists take part in the study (age: 22.1±3.1 years; body mass: 66.2±8.5 kg; height: 175.4±5.2 cm; body fat: 7.2%±1.1%; V ̇O2max: 64±5.61 mL∙min-1∙kg-1). Following familiarization sessions, VO2max was determined, and then, maximal SV, HR, Q and a-vO2diff (SVmax), (HRmax), (Qmax), (a-vO2diff_max) were evaluated using exercise intensities corresponding to 40 to 110% of VO2max separately, by nitrous-oxide re-breathing method. Thereafter, training models; HIT1: 16 repetitions with power at ~110% of VO2maks (p@~ 110%VO2maks) for 45-sec with 1:1 work and recovery (w/r) ratio, intermittent model; HIT2: 4 repetitions with p@~93%VO2maks for 3-min with 1:1 w/r ratio, intermittent model; HIT3: 1-min with p@~VO2maks and 4-min with p@anaerobic threshold (AnT) × 5 repetitions alternating continuous model; HIT4: 25-min constant-load continuous model; HIT5: 6 repetitions of 30-sec at 7,5% body weight with 1:7 w/r ratio sprint interval specific HIT model were performed. Maximal session effort prescription was adopted for all exercise sessions. After the repeated-measures analyses, possible significant differences will be investigated by post-hoc LSD test or Wilcoxon test. Time spent (Tspent) above 95% of VO2max is higher in HIT2 session than other exercise modalities (p<0.05). Tspent at Qmaks is higher in HIT3 and HIT4 sessions than Short and Long HIT (p<0.05). Tspent at SVmaks was higher in Constant-Loading HIT session than HIT1, HIT2 and HIT5 sessions (p<0.05). Tspent at a-vO2diff_max were higher HIT1 and HIT2 sessions than HIT3 and HIT4 sessions. Maximal lactate and maximal post exercise fat oxidation were attained in HIT5 session (p<0.05). These results show that different exercise modalities reaching similar VO2max levels may be effective in the development of different components associated with VO2max. It may be said that continuous HIT modalities are more appropriate to improve central component of VO2max, while intermittent HIT modalities seems better for peripheral one.