Objective: The 6-min walking test (6 MWT) is commonly used to assess obese patients’ aerobic fitness, but it has rarely been compared with a direct measurement of maximal aerobic capacities (VO_2max or VO_2peak) in obese adults. The aim of this study was to investigate the relationship between the distance covered during a 6 MWT with objectively measured VO_2peak and to propose a new equation to predict VO_2peak from this walking test in obese patients. Methods: One hundred and thirty-seven obese patients (45.6 ± 12.5 years) admitted to our hospital for a multidisciplinary rehabilitation program were enrolled. After assessment of their body composition, the participants were asked to perform a 6 MWT and their maximal aerobic capacities (VO_2peak) were measured. Result: There is a significant linear relation between VO_2peak and the distance covered during the 6 MWT (p < 0.001; r = 0.349). The determinant of VO_2peak was body mass index, waist-to-hip ratio, fat free mass, leading to the follow prediction equation VO_2peak such as VO_2peak (l/min) = (body mass index ×0.0150065) − (waist-to-hip-ratio × 0.8595088) + (fat-free-mass × 0.0295478) + (6-min walk test ×0.0020672) − 0.5853372. Conclusion: The 6-min walk test is a reliable method to reflect obese women’s aerobic capacities and the distance covered can be used to accurately estimate VO_2peak according to our newly proposed equation.

As ¾ of the global population either have excess or insufficient fat, it has become increasingly critical to understand the functions and dysfunctions of adipose tissue (AT). AT serves as a key organ in energy metabolism, and recently, attention has been focused on white AT, particularly its mitochondria, as the literature evidence links their functions to adiposity. This narrative review provides an overview of mitochondrial functionality in human white AT. Firstly, it is noteworthy that the two primary AT depots, subcutaneous AT (scAT) and visceral AT (vAT), exhibit differences in mitochondrial density and activity. Notably, vAT tends to have a higher mitochondrial activity compared to scAT. Subsequently, studies have unveiled a negative correlation between mitochondrial activity and body mass index (BMI), indicating that obesity is associated with a lower mitochondrial function. While the impact of exercise on AT mitochondria remains uncertain, dietary interventions have demonstrated varying effects on AT mitochondria. This variability holds promise for the modulation of AT mitochondrial activity. In summary, AT mitochondria exert a significant influence on health outcomes and can be influenced by factors such as obesity and dietary interventions. Understanding the mechanisms underlying these responses can offer potential insights into managing conditions related to AT and overall health.

Over the last decades, a growing interest in eccentric (ECC) exercise has emerged, but mitochondrial adaptations to ECC training remain poorly documented. Using an approach for manipulating mechanical and metabolic exercise power, we positioned that for same metabolic power, training using concentric (CON) or ECC contractions would induce similar skeletal muscle mitochondrial adaptations. Sixty adult rats were randomly assigned to a control (CTRL) or three treadmill training groups running at 15m·min⁻¹ for 45min, 5days weekly for 8 weeks at targeted upward or downward slopes. Animals from the CON (+15%) and ECC30 (-30%) groups trained at iso-metabolic power while CON and ECC15 (-15%) exercised at iso-mechanical power. Assessments were made of Vastus Intermedius mitochondrial respiration (oxygraphy), enzymatic activities (spectrophotometry) and real-time qPCR for mRNA transcripts. Maximal rates of mitochondrial respiration was 14-15% higher in CON and ECC30 compared to CTRL and ECC15. Apparent K_m for ADP for trained groups was 40-66% higher than CTRL, with statistical significance reached for CON and ECC30. Complex I and citrate synthase activities were 1.6 (ECC15) to 1.8 (ECC30 and CON) times values of CTRL. Complex IV activity was higher than CTRL (p<0.05) only for CON and ECC30. mRNA transcripts analyses showed higher TFAM, SLC25A4, CKMT2 and PPID in the ECC30 compared to CTRL. Findings confirm that training-induced skeletal muscle mitochondrial function adaptations are governed by the extent of metabolic overload irrespective of exercise modality. The distinctive ECC30 mRNA transcript pattern may reflect a cytoskeleton damage-repair or ECC adaptive cycle that differs from that of biogenesis.