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Background: High-intensity interval training (HIIT) remains a promising exercise mode in managing cardiometabolic health. Large-scale analyses are necessary to understand its magnitude of effect on important cardiometabolic risk factors and inform guideline recommendations. Objective: We aimed to perform a novel large-scale meta-analysis on the effects of HIIT on cardiometabolic health in the general population. Methods: PubMed (MEDLINE), the Cochrane library and Web of Science were systematically searched. Randomised controlled trials (RCTs) published between 1990 and March 2023 were eligible. Research trials reporting the effects of a HIIT intervention on at least one cardiometabolic health parameter with a non-intervention control group were considered. Results: This meta-analysis included 97 RCTs with a pooled sample size of 3399 participants. HIIT produced significant improvements in 14 clinically relevant cardiometabolic health parameters, including peak aerobic capacity (VO2) [weighted mean difference (WMD): 3.895 ml min−1 kg−1, P < 0.001), left ventricular ejection fraction (WMD: 3.505%, P < 0.001), systolic (WMD: − 3.203 mmHg, P < 0.001) and diastolic (WMD: − 2.409 mmHg, P < 0.001) blood pressure, resting heart rate (WMD: − 3.902 bpm, P < 0.001) and stroke volume (WMD: 9.516 mL, P < 0.001). Body composition also significantly improved through reductions in body mass index (WMD: − 0.565 kg m−2, P < 0.001), waist circumference (WMD: − 2.843 cm, P < 0.001) and percentage body fat (WMD: − 0.972%, P < 0.001). Furthermore, there were significant reductions in fasting insulin (WMD: − 13.684 pmol L−1, P = 0.004), high-sensitivity C-reactive protein (WMD: − 0.445 mg dL−1, P = 0.043), triglycerides (WMD: − 0.090 mmol L−1, P = 0.011) and low-density lipoprotein (WMD: − 0.063 mmol L−1, P = 0.050), concurrent to a significant increase in high-density lipoprotein (WMD: 0.036 mmol L−1, P = 0.046). Conclusion: These results provide further support for HIIT in the clinical management of important cardiometabolic health risk factors, which may have implications for physical activity guideline recommendations. [ABSTRACT FROM AUTHOR]

The regeneration niche is commonly partitioned along a gradient from shade-tolerant to shade-intolerant species to explain plant community assembly in forests. We examined the shade tolerance of tree seedlings in a subtropical coastal forest to determine whether the ecological filtering effect of a dominant, synchronously monocarpic herb ( Isoglossa woodii) selects for species at either end of the light response continuum during the herb's vegetative and reproductive phases. Photosynthetic characteristics of seedlings of 20 common tree species and the herb were measured. Seedlings were grown in the greenhouse at 12-14% irradiance, and their light compensation points measured using an open-flow gas exchange system. The light compensation points for the tree species were low, falling within a narrow range from 2.1 ± 0.8 μmol m s in Celtis africana to 6.4 ± 0.7 μmol m s in Allophylus natalensis, indicating general shade tolerance, consistent with a high and narrow range of apparent quantum yield among species (0.078 ± 0.002 mol CO mol photon). Rates of dark respiration were significantly lower in a generalist pioneer species ( Acacia karroo) than in a forest pioneer ( C. africana), or in late successional phase forest species. We argue that the general shade tolerance, and phenotypic clustering of shade tolerance, in many tree species from several families in this system, is a result of ecological filtering by the prevailing low light levels beneath the I. woodii understorey, which excludes most light-demanding species from the seedling community. [ABSTRACT FROM AUTHOR]