Factors influencing isometric exercise training-induced reductions in resting blood pressure.

Hypertension is a major health concern, and current recommendations for blood pressure management (lifestyle modifications and pharmacological intervention) have not been universally successful. For two decades, isometric exercise training (IET) has become established as effective at reducing in resting BP (RBP) in a short period (4-10 weeks). The most common IET modes have comprised isometric handgrip (IHG) or isometric bilateral leg (IBL) training and 4 × 2-min contractions at ∼20-50% maximal voluntary contraction with 1-5-min rest between. Although this type of exercise training could have important implications, for hypertensive patients and in preventing hypertension development, little is known about the mechanisms responsible for IET-induced RBP reductions. This uncertainty derives from a lack of understanding concerning the most effective IET programs for specific populations. Possible influential factors and mechanisms include age, sex, pre-existing disease and medication, and IET-induced adaptations in the exercising muscle and nervous system, which are discussed in this review. Designing effective IET programs may involve manipulation of exercise intensity, frequency, duration and mode, as well as consideration of yet discovered mechanisms for RBP reductions. We call for additional research designed to understand more about the mechanisms involved in IET-induced RBP reductions for maximum effectiveness.

Ajuga turkestanica increases Notch and Wnt signaling in aged skeletal muscle.

BACKGROUND: The declining myogenic potential of aged skeletal muscle is multifactorial. Insufficient satellite cell activity is one factor in this process. Notch and Wnt signaling are involved in various biological processes including orchestrating satellite cell activity within skeletal muscle. These pathways become dysfunctional during the aging process and may contribute to the poor skeletal muscle competency. Phytoecdysteroids are natural adaptogenic compounds with demonstrated benefit on skeletal muscle. AIM: To determine the extent to which a phytoecdysteroid enriched extract from Ajuga turkestanica (ATE) affects Notch and Wnt signaling in aged skeletal muscle. MATERIALS AND METHODS: Male C57BL/6 mice (20 months) were randomly assigned to Control (CT) or ATE treatment groups. Chow was supplemented with either vehicle (CT) or ATE (50 mg/kg/day) for 28 days. Following supplementation, the triceps brachii muscles were harvested and immunohistochemical analyses performed. Components of Notch or Wnt signaling were co-labelled with Pax7, a quiescent satellite cell marker. RESULTS: ATE supplementation significantly increased the percent of active Notch/Pax7+ nuclei (p = 0.005), Hes1/Pax7+ nuclei (p = 0.038), active B-catenin/Pax7+ nuclei (p = 0.011), and Lef1/Pax7+ nuclei (p = 0.022), compared to CT. ATE supplementation did not change the resting satellite cell number. CONCLUSIONS: ATE supplementation in aged mice increases Notch and Wnt signaling in triceps brachii muscle. If Notch and Wnt benefit skeletal muscle, then phytoecdysteroids may provide a protective effect and maintain the integrity of aged skeletal muscle.