Temporal Response of Angiogenesis and Hypertrophy to Resistance Training in Young Men.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 28846563 · doi:10.1249/MSS.0000000000001409
What was done
Thirty-six young men (mean age 22 ± 1 yr) participated in a double-blind, randomized controlled trial examining muscle adaptations to 12 weeks of resistance training with either protein supplementation or placebo. Muscle biopsies were collected at baseline and after 2, 4, 8, and 12 weeks of training. Immunohistochemistry evaluated fiber type-specific cross-sectional area and capillarization, while Western blot and RT-PCR measured molecular regulators of angiogenesis.
What was found
Resistance training increased Type I fiber cross-sectional area by 15% ± 4% (P < 0.01) and Type II fiber area by 28% ± 5% (P < 0.0001), with a trend for greater Type II hypertrophy with protein supplementation (P = 0.078). Capillary-to-fiber ratio increased in Type I (P = 0.001) and Type II (P = 0.015) fibers after 12 weeks, with increases evident by 2 weeks. Capillary-to-fiber perimeter exchange index increased only in Type I fibers (P = 0.054). Training reduced VEGF mRNA (P = 0.008), but increased VEGFR2 (P = 0.016), HIF-1α (P = 0.016), and eNOS (P = 0.01). HIF-1α protein was higher in the protein group (P = 0.02), and eNOS exhibited a divergent time-group interaction (P = 0.049).
Why it matters
This study shows that resistance training stimulates rapid skeletal muscle angiogenesis within two weeks, matching fiber hypertrophy and challenging the assumption that microvascular adaptations are exclusive to endurance training.
Limits
The sample was limited to 36 young, healthy men, precluding generalization to women, older adults, or clinical populations. There was no non-exercising control group to control for repeated biopsy effects.
Cited by
- supports Hypoxia-inducible factor (HIF) is hypothesized to increase the hypertrophic response to exercise.