Author(s): BETZ, M., MONSEGUE, A.P., AUSSIEKER, T., HOUBEN, A.J.H.M., VERDIJK, L.B., VAN LOON, L.J.C., SNIJDERS, T., Institution: MAASTRICHT UNIVERSITY, Country: NETHERLANDS, Abstract-ID: 1318

INTRODUCTION:
Resistance exercise training is an effective treatment strategy to counteract the age-related loss of muscle mass and strength in older adults. However, there is a large inter-individual variation in muscle fiber hypertrophy following resistance exercise training in older adults. It has been hypothesized that an increase in muscle fiber capillarization and perfusion capacity are prerequisite to maximize muscle hypertrophy during resistance exercise training in older adults. We assessed whether 8 weeks of aerobic exercise preconditioning, to improve muscle fiber capillarization and perfusion capacity, augments the gains in muscle mass and strength during subsequent resistance exercise training in older adults.
METHODS:
In a randomized parallel design, thirty-four healthy older adults (71±5 y) participated in 12 weeks of progressive resistance exercise training, preceded by either 8 weeks of aerobic preconditioning (AER) or no exercise control (CON). Muscle strength (1RM), aerobic capacity (VO2peak test), and muscle fiber characteristics (immunohistochemistry) were assessed at baseline, following 8 weeks of AER or CON, and after subsequent 12 weeks of resistance exercise training. Femoral artery blood flow and vastus lateralis muscle microvascular perfusion kinetics were assessed at baseline and following 8 weeks of AER or CON intervention. Thigh muscle volume (MRI-scan) was assessed before and after 12 weeks of resistance exercise training. Data were analyzed by two-way repeated-measures ANOVA. A statistical level of P<0.05 was accepted. All data are expressed as mean±SD.
RESULTS:
Aerobic exercise preconditioning increased type I (C/Fi :+19±19%, P<0.05) and type II (C/Fi: +35±37%, P<0.05) muscle fiber capillarization, with no changes in the CON group (C/Fi Type I: +0±17% Type II: -3±26%). Whereas femoral artery blood flow remained unchanged, the vastus lateralis muscle microvascular perfusion capacity tended (interaction effect, P=0.051) to be lower during post-exercise recovery following aerobic exercise preconditioning, with no changes in the CON group. Subsequent resistance exercise training increased 1RM leg press (+16±10% vs +12±8%, respectively, P<0.001) and thigh muscle volume (+0.42±0.69 vs +0.31±0.62 L, respectively, P<0.001), with no differences between AER and CON group (interaction effects, P>0.4). No differences were observed in type I and type II muscle fiber hypertrophy in response to the entire intervention program between groups (interaction effect, P>0.5).
CONCLUSION:
Aerobic exercise preconditioning increases in type I and type II muscle fiber capillarization in healthy older adults. Aerobic exercise preconditioning does not further increase muscle hypertrophy during subsequent resistance exercise training in healthy older adults. Both structural and functional microvascular characteristics do not seem to restrict the skeletal muscle adaptive response to resistance type exercise training in healthy older adults.