Article RETRACTED due to manipulation by the authors Effectiveness of high-intensity interval training versus moderate-intensity continuous training on peak oxygen uptake (vo2peak) a cardiorespiratory parameter for individuals aged 40 and above: a sy

Cardiorespiratory fitness (CRF) is a crucial indicator for assessing an individual's maximal oxygen uptake capacity. Although numerous studies have investigated the effects of exercise on CRF, comparisons between high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) in individuals aged 40 and above remain limited and fragmented. This research employs a Systematic Literature Review (SLR) and meta-analysis to evaluate the effectiveness of HIIT and MICT in improving VO2peak in individuals aged 40 and above. Data were collected from Scopus and WoS databases using the PRISMA method. Articles that met the inclusion criteria were analyzed using RevMan 5.4 and JASP 0.18.3. The analysis revealed that HIIT has a greater advantage in enhancing VO2peak compared to MICT in individuals aged 40 and above. Overall, HIIT increased VO2peak with a z-value of 5.59 (p-value < 0.00001) and a 95% confidence interval of 0.35 [0.23, 0.48]. Conversely, MICT showed a z-value of 1.84 (p-value = 0.07) and a 95% confidence interval of 0.11 [-0.01, 0.23]. Inter-study heterogeneity was low to moderate, with an I² value of 25% and τ² of 0.03 for HIIT, and an I² value of 0% for MICT. HIIT tends to be more effective than MICT in improving cardiorespiratory fitness in individuals aged 40 and above. However, the difference between the two methods is not statistically significant. Further research with more homogeneous designs and longer intervention durations is needed to confirm these findings and understand the underlying mechanisms of the differences in effectiveness between HIIT and MICT. Keywords: HIIT, MICT, VO2peak, CRF, exercise