Effects of polarised, sprint interval, high-intensity interval, and low-intensity training programs on aerobic fitness and cardiovascular health markers in active individuals

Purpose: This study aimed to assess the impact of four distinct training programs on maximal oxygen uptake (VO2max) and cardiovascular health markers. The programs included: 1) a polarised training program (POL) incorporating sprint interval training (SIT), high-intensity interval training (HIIT) with long intervals, and low-intensity training (LIT); 2) a program focused solely on SIT training; 3) a program focused solely on long interval HIIT training; and 4) a program focused solely on LIT. The outcomes of interest were VO2max, lectin-like oxidised low-density lipoprotein receptor-1 (LOX-1) expression, and serum concentration of oxidised low-density lipoprotein (ox-LDL). Methods: This study enrolled 40 physically active individuals, categorised into four groups. Group POL (n = 10) engaged in a comprehensive POL training program, while group SIT (n = 10), group HIIT (n = 10), and group LIT (n = 10) participated in dedicated SIT, HIIT, and LIT training programs, respectively. SIT included 30-second all-out repetitions, HIIT included 3-minute high-intensity repetitions, LIT performed with intensity at the first ventilatory threshold. Throughout five weeks, participants in all groups underwent three weekly training sessions. Preceding and following the experiment, participants underwent an incremental test and a VO2max verification test. Additionally, serum concentrations of lectin-like oxidised lowdensity lipoprotein receptor-1 (LOX-1) and oxidised low-density lipoprotein (ox-LDL) were measured before the incremental test. Results: Following the conclusion of the experiment, notable mixed effects were observed. Specifically, statistically significant increases were identified in VO2max, with a 14.2% enhancement in the POL group and a 9.5% improvement in the HIIT group. Moreover, there were substantial reductions in LOX-1 levels, demonstrating a 51.5% decrease in the POL group and a 61.1% decrease in the HIIT group. Conclusions: The findings led to the conclusion that both the POL and long interval HIIT programs were effective in enhancing VO2max and lowering serum levels of LOX-1 among physically active individuals.