Long term bed rest with and without vibration exercise countermeasures: effects on human muscle protein dysregulation

The present investigation, the first in the field, was aimed at analyzing differentially, on individual samples, the effects of 55 days of horizontal bed rest, a model for microgravity, on myosin heavy and myosin light chain isoforms distribution (by SDS) and on the proteome (by 2-D DIGE and MS) in the vastus lateralis (VL), a mixed type II/I (～50:50%) head of the quadriceps and in the calf soleus (SOL), a predominantly slow (～35:65%) twitch muscle. Two separate studies were performed on six subjects without (BR) and six with resistive vibration exercise (RVE) countermeasures, respectively. Both VL and SOL underwent in BR decrements of ～15% in cross-sectional area and of ～22% in maximal torque that were prevented by RVE. Myosin heavy chain distribution showed increased type I and decreased type IIA in BR both in VL and in SOL, the opposite with RVE. A substantial downregulation of proteins involved in aerobic metabolism characterized both in SOL and VL in BR. RVE reversed the pattern more in VL than in SOL, whereas proteins involved in anaerobic glycolysis were upregulated. Proteins from the Z-disk region and from costamers were differently dysregulated during bed rest (both BR and RVE), particularly in VL.     

Energy metabolism in the tropical abalone, Haliotis asinina Linné: Comparisons with temperate abalone species

The abalone, Haliotis asinina, is a large, highly active tropical abalone that feeds at night on shallow coral reefs where oxygen levels of the water may be low and the animals can be exposed to air. It is capable of more prolonged and rapid exercise than has been reported for temperate abalone. These unusual behaviours raised the question of whether H. asinina possesses enhanced capacities for aerobic or anaerobic metabolism. The blood oxygen transport system of H. asinina resembles that of temperate abalone in terms of a large hemolymph volume, similar hemocyanin concentrations, and in most hemocyanin oxygen binding properties; however, absence of a Root effect appears confined to hemocyanin from H. asinina and may assist oxygen uptake when hemolymph pH falls during exercise or environmental hypoxia. During exposure to air, H. asinina reduces oxygen uptake by at least 20-fold relative to animals at rest in aerated seawater, and there is no significant ATP production from anaerobic glycolysis or phosphagen hydrolysis in the foot or adductor muscles. This slowing of metabolism may contribute to survival at lower water oxygen levels than normally encountered by most temperate abalone. While crawling speeds of H. asinina in water are not exceptionally high, an aerobic expansibility of 5.5-fold at speeds less than 20% of maximum is more than 2.7-fold greater than reported for several temperate abalone. The high aerobic expansibility also supports the enhanced frequency and duration of flipping behaviour without recourse to the additional inputs from anaerobic glycolysis required by other abalone. Metabolic profiles of foot and adductor muscles of H. asinina are similar to those of other abalone. Common features are low activities of enzymes unique to aerobic ATP production, relatively high activities of arginine kinase, tauropine and d-lactate dehydrogenase as the predominant pyruvate reductases, and low intracellular pH buffering capacities. It is concluded that the exceptional abilities of H. asinina for prolonged and rapid exercise are supported by higher rates of aerobic metabolism rather than any enhanced capacity for anaerobic muscle work. It is unexpected, and instructive, that the exceptional aerobic expansibility is not apparent in obvious adjustments of the blood oxygen delivery system or muscle properties associated with aerobic ATP production. The absence of a hemocyanin Root effect, and the extent to which both aerobic and anaerobic metabolism can be reduced may be special features that assist prolonged exercise and survival of H. asinina when environmental oxygen becomes limiting.     

The effect of muscularity on thermal responses,muscle performance,and dexterity during whole body exposure to 10 °C

1.

The study evaluated the effects of exposure to cold air (10 °C) on thermal responses, muscle performance and dexterity of muscular subjects and their matched lean counterparts.     

Conditioned taste avoidance induced by forced and voluntary wheel running in rats

Voluntary exercise by rats running in a freely rotating wheel (free wheel) produces conditioned taste avoidance (CTA) of a flavored solution consumed before running [e.g., Lett, B.T., Grant, V.L., 1996. Wheel running induces conditioned taste aversion in rats trained while hungry and thirsty. Physiol. Behav. 59, 699-702]. Forced exercise, swimming or running, also produces CTA in rats [e.g., Masaki, T., Nakajima, S., 2006. Taste aversion induced by forced swimming, voluntary running, forced running, and lithium chloride injection treatments. Physiol. Behav. 88, 411-416]. Energy expenditure may be the critical factor in producing such CTA. If so, forced running in a motorized running wheel should produce CTA equivalent to that produced by a similar amount of voluntary running. In two experiments, we compared forced running in a motorized wheel with voluntary running in a free wheel. Mean distance run over 30 min was equated as closely as possible in the two apparatuses. Both types of exercise produced CTA relative to sedentary, locked-wheel controls. However, voluntary running produced greater CTA than forced running. We consider differences between running in the free and motorized wheels that may account for the differences in strength of CTA.     

Effects of 28 days of beta-alanine and creatine monohydrate supplementation on aerobic power,ventilatory and lactate thresholds,and time to exhaustion

Summary. The effect of beta-alanine (β-Ala) alone or in combination with creatine monohydrate (Cr) on aerobic exercise performance is unknown. The purpose of this study was to examine the effects of 4 weeks of β-Ala and Cr supplementation on indices of endurance performance. Fifty-five men (24.5 ± 5.3 yrs) participated in a double-blind, placebo-controlled study and randomly assigned to one of 4 groups; placebo (PL, n = 13), creatine (Cr, n = 12), beta-alanine (β-Ala, n = 14), or beta-alanine plus creatine (CrBA, n = 16). Prior to and following supplementation, participants performed a graded exercise test on a cycle ergometer to determine VO_2peak, time to exhaustion (TTE), and power output, VO₂, and percent VO_2peak associated with VT and LT. No significant group effects were found. However, within groups, a significant time effect was observed for CrBa on 5 of the 8 parameters measured. These data suggest that CrBA may potentially enhance endurance performance.     

Alpine skiing is associated with higher femoral neck bone mineral density

Objective:

To evaluate the influence of elite-level alpine skiing on athletes’ skeleton.

Methods:

Thirteen professional alpine skiers (9 males and 4 females with mean age of 22.6 years) and their age- and height matched control subjects were measured with dual energy X-ray absorptiometry (total body, lumbar spine, proximal femur, forearm) and quantitative ultrasound (hand).

Results:

After adjusting for sex, age, weight and height, between-group differences were 15% (p=0.012) for the lumbar spine, 14% (p=0.022) for the femoral neck, 10% (p=0.051) for the total hip, and 11% (p=0.001) for the total body favoring the alpine skiers. However, after controlling for total body lean mass (~muscle mass), the group-differences lost their statistical significance, the borderline 10% difference (p=0.051) in femoral neck BMD excluded.

Conclusion:

Factors contributing to the alpine skiers’ higher BMD may not only include the greater muscle mass (~stronger muscles) of these athletes but also a large number of impacts and possibly other high-frequency features in external loading generated by the high-speed skiing performance.     

Acute metabolic,hormonal, and psychological responses to strength training with superimposed EMS at the beginning and the end of a 6 week training period

Objectives:The aim was to determine metabolic and hormonal responses to strength training with or without superimposed electromyostimulation (EMS) at the beginning and the end of a 6 week training period.Methods:20 strength trained subjects were randomly assigned to two groups. The first group (S) performed 4 sets of back squats with a constantly adjusted additional load of their individual 10 repetition maximum (10 RM) twice a week over 6 weeks. The second group (S+E) did the same training program with superimposed EMS on leg and trunk muscles. Physiological responses were determined before and after the first (TS 1) and the last training session (TS 12).Results:No significant differences of hormonal responses could be observed between groups and TSs. However, small to large effects on metabolism occurred between groups and TSs. Delayed onset muscle soreness (DOMS) was significantly higher 48h after TS 1 for S+E.Conclusions:Despite a higher DOMS after S+E, there is no acute effect of superimposed EMS on hormonal response to exhaustive resistance exercise. We suggest that, because of the high resistance during 10 RM bouts, most of the muscle fibers are already activated and superimposed EMS only activates few additional muscle fibers.     

The effects of whole body vibration on mobility and balance in children with cerebral palsy: a systematic review with meta-analysis

Objective:

We performed a meta-analysis to evaluate the effects of whole-body vibration on physiologic and functional measurements in children with cerebral palsy.

Design and methods:

We searched MEDLINE, Cochrane Controlled Trials Register, EMBASE, Scielo, CINAHL (from the earliest date available to November 2014) for randomized controlled trials, that aimed to investigate the effects of whole-body vibration versus exercise and/or versus control on physiologic and functional measurements in children with cerebral palsy. Two reviewers independently selected the studies. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated.

Results:

Six studies with 176 patients comparing whole-body vibration to exercise and/or control were included. Whole-body vibration resulted in improvement in: gait speed WMDs (0.13 95% CI:0.05 to 0.20); gross motor function dimension E WMDs (2.97 95% CI:0.07 to 5.86) and femur bone density (1.32 95% CI:0.28 to 2.36). The meta-analysis also showed a nonsignificant difference in muscle strength and gross motor function dimension D for participants in the whole-body vibration compared with control group. No serious adverse events were reported.

Conclusions:

Whole-body vibration may improve gait speed and standing function in children with cerebral palsy and could be considered for inclusion in rehabilitation programs.     

Voluntary exercise delays monogenetic obesity and overcomes reproductive dysfunction of the melanocortin-4 receptor knockout mouse

The melanocortin system is involved in hypothalamic regulation of energy homeostasis. The melanocortin-4 receptor (MC4R) has been linked to both obesity and reproductive dysfunction. Deletion of the MC4R from the mouse genome has resulted in phenotypes including adult onset obesity, hyperphagia, and difficulty in reproducing when homozygote parents are bred. Additionally, polymorphisms of the human MC4R have been identified in morbidly obese children and adults. Herein, we have identified that voluntary exercise, provided via the presence of a running wheel, impedes the monogenetic obesity (at 20 weeks of age running wheel housed body weight=31+/-1.8 g versus conventionally housed body weight=41+/-2.3 g, a 25% decrease in body weight p<0.01), hyperphagia (average cumulative food intake is not statistically different than wild type mice housed in running wheel cages), and reproductive dysfunction phenotypes associated with the MC4R knockout mice housed by conventional means. These data demonstrate the novel finding that voluntary exercise at a young age may hinder genetically induced obesity.     

N-Acetyl-L-cysteine prevents exercise-induced intestinal lymphocyte apoptosis by maintaining intracellular glutathione levels and reducing mitochondrial membrane depolarization

Intense exercise leads to post-exercise lymphocytopenia and immunosuppression, possibly by triggering lymphocyte apoptosis. To test the role of oxidative stress on exercise-induced lymphocyte apoptosis, we administered the antioxidant N-acetyl--cysteine (NAC) and measured apoptosis in intestinal lymphocytes (IL) from exhaustively exercised animals. Eighty-seven female C57BL/6 mice were randomly assigned to receive NAC (1 g/kg) or saline 30 min prior to treadmill exercise for 90 min at 2degrees slope (30 min at 22 m min(-1), 30 min at 25 m min(-1), and 30 min at 28 m min(-1)) and sacrificed immediately (Imm) or 24 hours (24 h) after cessation of exercise. Control mice (nonexercised) were exposed to treadmill noise and vibration without running. Exercise increased IL phosphatidylserine externalization (p<0.001), mitochondrial membrane depolarization (p<0.05), and decreased intracellular glutathione concentrations (p<0.05) immediately following exercise in saline relative to nonexercised mice. At 24 h post-exercise, saline injected mice had fewer total (p<0.001) and CD3+ (p<0.005) IL compared to nonexercised animals. NAC injection in mice maintained intracellular glutathione levels, prevented phosphatidylserine externalization, mitochondrial membrane depolarization, and loss of IL immediately and 24 h after exercise. These data suggest that lymphocyte apoptosis precedes post-exercise lymphocytopenia and may be due to oxidative stress.