Short-term aerobic conditioning prior to resistance training augments muscle hypertrophy and satellite cell content in healthy young men and women.
Level 3 - non-randomized controlled study
Controlled within-subject trial without explicit mention of randomization in the abstract
PubMed 35971745 · doi:10.1096/fj.202200398RR
What was done
Fourteen healthy young adults (age 22 ± 2 years) completed 6 weeks of unilateral cycling aerobic conditioning (AC) followed by 10 weeks of bilateral resistance training (RT). Muscle biopsies were taken at baseline, post-AC, and post-RT from both the conditioned (AC + RT) and unconditioned (RT alone) legs to measure muscle capillarization, fiber cross-sectional area (CSA), and satellite cell (SC) content and activation via immunofluorescence.
What was found
Both type I and type II fiber CSA increased after RT. When legs were analyzed independently, AC + RT increased type I, type II, and mixed-fiber CSA, whereas the RT leg only tended to increase type II CSA (p = .05) without significant changes in type I or mixed-fiber CSA. Type I total and quiescent SC content was higher in AC + RT than in RT alone. Pre-RT capillary-to-fiber perimeter exchange index correlated with post-RT CSA gains, with a significant correlation between type II fiber capillarization and change in type II CSA (r = 0.35). Absolute numerical values and confidence intervals were not reported in the abstract.
Why it matters
This paper demonstrates that building aerobic capillarization prior to resistance training may enhance muscle hypertrophy and satellite cell responsiveness, providing a mechanistic basis for periodized conditioning.
Limits
The sample size was small (n = 14) and limited to healthy young individuals. The abstract does not specify whether limb assignment was randomized, and unilateral exercise can produce systemic physiological cross-over effects that may confound contralateral control comparisons.
Cited by
- supports Endurance exercise promotes capillarization in skeletal muscle, enhancing blood flow and nutrient delivery, and activates satellite cells to donate nuclei that support hypertrophy from resistance exercise.