. Adaptations in human muscle sarcoplasmic reticulum to prolonged submaximal training. J Appl Physiol 94: 2034-2042, 2003; 10.1152/japplphysiol.00244.2002.-In this study, we employed single-leg submaximal cycle training, conducted over a 10-wk period, to investigate adaptations in sarcoplasmic reticulum (SR) Ca 2ϩ -regulatory proteins and processes of the vastus lateralis. During the final weeks, the untrained volunteers (age 21.4 Ϯ 0.3 yr; means Ϯ SE, n ϭ 10) were exercising 5 times/wk and for 60 min/session. Analyses were performed on tissue extracted by needle biopsy ϳ4 days after the last training session. Compared with the control leg, the trained leg displayed a 19% reduction (P Ͻ 0.05) in homogenate maximal Ca 2ϩ -ATPase activity (192 Ϯ 11 vs. 156 Ϯ 18 mol ⅐ g protein Ϫ1 ⅐ min Ϫ1 ), a 4.3% increase (P Ͻ 0.05) in pCa 50, defined as the Ca 2ϩ concentration at half-maximal activity (6.01 Ϯ 0.05 vs. 6.26 Ϯ 0.07), and no change in the Hill coefficient (1.75 Ϯ 0.15 vs. 1.76 Ϯ 0.21). Western blot analysis using monoclonal antibodies (7E6 and A52) revealed a 13% lower (P Ͻ 0.05) sarco(endo)plasmic reticulum Ca 2ϩ -ATPase (SERCA) 1 in trained vs. control in the absence of differences in SERCA2a. Training also resulted in an 18% lower (P Ͻ 0.05) SR Ca 2ϩ uptake and a 26% lower (P Ͻ 0.05) Ca 2ϩ release. It is concluded that a downregulation in SR Ca 2ϩ cycling in vastus lateralis occurs with aerobic-based training, which at least in the case of Ca 2ϩ uptake can be explained by reduction in Ca 2ϩ -ATPase activity and SERCA1 protein levels. calcium homeostasis; Ca 2ϩ -ATPase; Ca 2ϩ uptake; Ca 2ϩ release; exercise REGULAR CONTRACTILE ACTIVITY is a potentially potent stimulus for altering the composition, structure, and function of the muscle cell. Nowhere is this more evident than with the chronic low-frequency electrical stimulation (CLFS) model in which contractile activity is characteristically induced for 12-24 h/day over several weeks. Induced patterns of submaximal contractions of this nature typically applied to muscles composed of a predominance of fast-twitch (type II) fibers result in extensive reorganization of both the excitation and contraction processes and the energy metabolic pathways involved in energy supply. Although the magnitude of the adaptations vary, qualitatively similar adaptations appear to occur between species (dog, rat, mouse, rabbit) (29).Despite the fact that the CLFS model has proved invaluable for studying the limits of phenotypic plasticity in skeletal muscle and the factors regulating the expression of a large number of proteins involved in fiber-type transformation, it is nonphysiological (30). In physiological models, voluntary activity is used to elicit training adaptations. Voluntary training typically involves a relatively brief session of exercise followed by a prolonged recovery period, which could last for 2-3 days depending on the training frequency. Moreover, it is not clear how the intracellular signals mediating altered protein expression in CLFS translate into different ...

We concluded that postexercise supplementation with PRO-CHO resulted in similar increases in strength after a resistance exercise training program as compared with CR-CHO. However, the greater gains in total mass for the CR-CHO group may have implications for sport-specific performance.

We examined the effects of androstenedione supplementation on the hormonal profile of 10 males and its interaction with resistance exercise. Baseline testosterone, luteinizing hormone, estradiol, and androstenedione concentrations were established by venous sampling at 3 hr intervals over 24 hr. Subjects ingested 200 mg of androstenedione daily for 2 days, with second and third day blood samples. Two weeks later, they ingested androstenedione or a placebo for 2 days, in a double-blind, cross-over design. On day 2, they performed heavy resistance exercise with blood sampled before, after, and 90 min post. The supplement elevated plasma androstenedione 2--3-fold and luteinizing hormone approximately 70% but did not alter testosterone concentration. Exercise elevated testosterone, with no difference between conditions. Exercise in the supplemented condition significantly elevated plasma estradiol by approximately 83% for 90 min. Androstenedione supplementation, thus, is unlikely to provide male athletes with any anabolic benefit and, with heavy resistance exercise, elevates estrogen.

Recent evidence from our laboratory and others have suggested that the mechanism for a decrease in resting blood pressure after an acute bout of exercise is a centrally mediated decrease in total peripheral resistance. This study examined the effect of the central serotonergic system on post exercise hypotension (PEH) in 11 borderline hypertensive individuals (nine male, two female) aged 24.5 ؎ 5.1 years. Each subject completed two, 30-min cycling bouts at 70% of V O 2 Peak while under placebo or a selective serotonin re-uptake inhibitor (SSRI) treatment. Blood pressure was recorded directly from the radial artery, and treatments were randomised, double blinded and separated by at least 14 days. Baseline blood pressure was 145/72 mm Hg for systolic (SBP) and diastolic (DBP) respectively. Peripheral measures of serotonin (5-HT) were lower under SSRI treatment, whereas the major 5-HT metabolite, 5-hydroxyindoleacetic acid, was not significantly changed,