Key result
Six weeks of high-intensity interval training in previously inactive overweight women increased capillary contacts per fiber in type I fibers from 4.38 to 5.17 (P<0.05).
Why the study?
Does high-intensity interval training improve markers of microvascular density and oxidative capacity in skeletal muscle fibers of sedentary overweight women?
Does high-intensity interval training improve markers of microvascular density and oxidative capacity in skeletal muscle fibers of sedentary overweight women?
Absolute Event Rate: 5.17% vs 4.38%
p-value: p=< 0.05
Six weeks of high-intensity interval training increases markers of capillary density and mitochondrial content similarly in type I and type II skeletal muscle fibers in sedentary overweight women.
This is the authors' abstract. We don't add key points for this paper.
High-intensity interval training (HIIT) enhances skeletal muscle oxygen delivery and utilization but data are limited regarding fiber-specific adaptations in humans. We examined the effect of 18 sessions of HIIT (10 × 60-sec cycling intervals at ~90% HRmax, interspersed by 60-sec of recovery) over 6 weeks on markers of microvascular density and oxidative capacity in type I and II fibers in healthy but sedentary young women (Age: 26 ± 7 years; BMI: 30 ± 4 kg·m−2; VO2peak: 2.16 ± 0.45 L·m−1). Immunohistochemical analyses of muscle cross sections revealed a training-induced increase in capillary contacts per fiber in type I fibers (PRE: 4.38 ± 0.37 vs. POST: 5.17 ± 0.80; main effect, P < 0.05) and type II fibers (PRE: 4.24 ± 0.55 vs. POST: 4.92 ± 0.54; main effect, P < 0.05). The capillary-to-fiber ratio also increased after training in type I fibers (PRE: 1.53 ± 1.44 vs. POST: 1.88 ± 0.38; main effect, P < 0.05) and type II fibers (PRE: 1.45 ± 0.19 vs. POST: 1.76 ± 0.27; main effect, P < 0.05). Muscle oxidative capacity as reflected by the protein content of cytochrome oxidase IV also increased after training in type I fibers (PRE: 3500 ± 858 vs. POST: 4442 ± 1377 arbitrary units; main effect, P < 0.01) and type II fibers (PRE: 2632 ± 629 vs. POST: 3863 ± 1307 arbitrary units; main effect, P < 0.01). We conclude that short-term HIIT in previously inactive women similarly increases markers of capillary density and mitochondrial content in type I and type II fibers.
HIIT increased capillary and mitochondrial markers similarly in type I/II fibers; leaves open translation to clinical outcomes or other populations.
No takes yet. Share an insight, caveat, or question.
Tan et al. (2018) studied Overweight and sedentary. High-intensity interval training (HIIT) vs. Pre-training baseline was evaluated on Capillary contacts per fiber in type I fibers (p=< 0.05). Six weeks of high-intensity interval training in previously inactive overweight women increased capillary contacts per fiber in type I fibers from 4.38 to 5.17 (P<0.05).
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: