Factors influencing inter-individual variability of responses to resistance training(RT) remain to be fully elucidated. We have proposed the importance of capillarization in skeletal muscle for the satellite cell (SC) response to RT-induced muscle hypertrophy, and hypothesized that aerobic conditioning (AC) would augment RT-induced adaptations. Fourteen healthy young (22 ± 2 years) men and women underwent AC via 6 weeks of unilateral cycling followed by 10 weeks of bilateral RT to investigate how AC alters SC content, activity, and muscle hypertrophy following RT. Muscle biopsies were taken at baseline (unilateral), post AC (bilateral), and post RT (bilateral) in the aerobically conditioned (AC + RT) and unconditioned (RT) legs. Immunofluorescence was used to determine muscle capillarization, fiber size, SC content, and activity. Type I and type II fiber cross-sectional area (CSA) increased following RT, and when legs were analyzed independently, AC + RT increased type I, type II, and mixed-fiber CSA, where the RT leg tended to increase type II (p = .05), but not type I or mixed-fiber CSA. SC content, activation, and differentiation increased with RT, where type I total and quiescent SC content was greater in AC + RT compared to the RT leg. Those with the greatest capillary-to-fiber perimeter exchange index before RT had the greatest change in CSA following RT and a significant relationship was observed between type II fiber capillarization and the change in type II-fiber CSA with RT (r = 0.35). This study demonstrates that AC prior to RT can augment RT-induced muscle adaptions and that these differences are associated with increases in capillarization.

Satellite cells (SC) and ribosomes are key determinants of the skeletal muscle adaptive response. Both are thought to increase acutely after resistance exercise and chronically with resistance training. However, the acute SC and ribosome exercise response with prior aerobic conditioning is unknown. Fourteen young men and women underwent 6 weeks of single-legged aerobic conditioning followed by an acute bout of 300 eccentric contractions. Muscle biopsies were taken from the vastus lateralis of the aerobically conditioned (AC) and the control (CTL) legs before (Pre), 24 (24h) and 48 (48h) hours post-contractions. SC pool expansion (PAX7+ cells/100 fibres) was greater in type-I (1.3-fold) and mixed-fibres (1.2-fold) in the AC leg compared to the CTL. Pax7 (1.2-fold) and MyoD1 (1.4-fold) mRNA expression was also greater in the AC leg compared to the CTL. AC had greater RNA concentration (1.2-fold) and mRNA expression of Ubf (1.2-fold) and Tif-1a (1.3-fold) compared to CTL. Only the AC leg increased (Pre-48h) c-Myc (3.0-fold), (Pre-24h) 45S pre-rRNA (2.6-fold), 5.8S ITS (2.1-fold) and 28S ITS (2.0-fold) following eccentric contractions. We discovered that aerobic conditioning augmented type-I SC pool expansion and ribosome content following an acute bout of eccentric contractions.

Samples of GI<-S-the familiar copolymer of butadiene and styrene-irere taken from a continuous emulsion-polymerization system a t conversions 32.0, 45.1, 61.2, and 73.4% respectively, and each, after careful drying, was carefully fractionated to give five or sin "top" fractions. For each of these fractions values of intrinsic viscosity [ r ] ] and of the viscosity slope "constants",L? and k' were determined. As with normal and cross-linked polystyrene, and.kf appear to be constant for all linear species, but to have higher 1,alues for branched species, the increase being a measure of the extent or degree of branching From the data obtained it is concluded that in GR-S there is little or no branching a t low con-~.ersions, that the degree of branching increases markedly with increasing con-\.emion, and that branching occurs to the greatest degree in the species of highest molecular weight.There seemed to be, for this polymer a t least, a molecular weight below which branching coilid not be detected, regardless of conversion, but above which branching increased with increasing molecular weight.

Samples of GR-S were taken from a continuous emulsion-polymerization system at conversions 32.0, 45.1, 61.2, and 73.4 per cent, respectively, and each, after careful drying, was carefully fractionated to give five or six top fractions. For each of these fractions, values of intrinsic viscosity [η] and of the viscosity slope constants, β and k′, were determined. As with normal and cross-linked polystyrene, β and k′ appear to be constant for all linear species, but to have higher values for branched species, the increase being a measure of the extent or degree of branching. From the data obtained it is concluded that in GR-S there is little or no branching at low conversions, that the degree of branching increases markedly with increasing conversion, and that branching occurs to the greatest degree in the species of highest molecular weight. There seemed to be, for this polymer at least, a molecular weight below which branching could not be detected, regardless of conversion, but above which branching increased with increasing molecular weight.