Cardiovascular changes with age and exercise

Various studies report a 0–22% per decade decline in circulatory function (VO_2max) with advancing age. Twelve exercising men (E) were followed for 28 years, mean age 43 and 71 years, initial to final measurement, while 12 dropouts (C) detrained for 21 years, with a mean age from first to last measurement of 48 and 69 years, respectively. VO₂ max in E changed from 45.9 to 39.4 ml · min⁻¹· kg⁻¹, 5% per decade, whereas C declined from 36.0 to 21.4 ml min⁻¹· kg⁻¹, 19% per decade. Resting blood pressure was unchanged in E, 119/75 mmHg, whereas C rose from 128/85 to 149/90 mmHg. The data suggest that regular aerobic exercise forestalls the usual loss of circulatory function with increasing age.     

Short‐term low‐intensity blood flow restricted interval training improves both aerobic fitness and muscle strength

The present study aimed to analyze and compare the effects of four different interval‐training protocols on aerobic fitness and muscle strength. Thirty‐seven subjects (23.8 ± 4 years; 171.7 ± 9.5 cm; 70 ± 11 kg) were assigned to one of four groups: low‐intensity interval training with (BFR, n = 10) or without (LOW, n = 7) blood flow restriction, high‐intensity interval training (HIT, n = 10), and combined HIT and BFR (BFR + HIT, n = 10, every session performed 50% as BFR and 50% as HIT). Before and after 4 weeks training (3 days a week), the maximal oxygen uptake (VO_2max), maximal power output (P_max), onset blood lactate accumulation (OBLA), and muscle strength were measured for all subjects. All training groups were able to improve OBLA (BFR, 16%; HIT, 25%; HIT + BFR, 22%; LOW, 6%), with no difference between groups. However, VO_2max and P_max improved only for BFR (6%, 12%), HIT (9%, 15%) and HIT + BFR (6%, 11%), with no difference between groups. Muscle strength gains were only observed after BFR training (11%). This study demonstrates the advantage of short‐term low‐intensity interval BFR training as the single mode of training able to simultaneously improve aerobic fitness and muscular strength.     

不同湿度高温环境下机体有氧运动能力相关指标比较

目的:探讨不同湿度高温环境对有氧运动能力的影响。方法:随机选取10名男性大学生为对象,设定环境温度为33℃,相对湿度分别为20%、40%、60%、80%作为模型,实验时间4周,两次测试之间间隔1周。测试时受试者进行递增负荷跑台运动,以8 km/h为起始速度,每分钟增加0.8 km/h到16 km/h为止,然后逐级加坡度,0.5%为起始坡度,每分钟递增0.5%直至受试者不能坚持,运动过程中监测心率、摄氧量、每分钟通气量(VE)以及主观用力感觉指数(RPE),测试前及结束后无名指采血测试血乳酸。结果:不同湿度高温环境下运动VE、最大心率(HRmax)、最大摄氧量(VO2max)无显著性差异,60%相对湿度下运动时VO2max(3831.7±313.16 ml/min)、VE(137.5±9.38 L/min)、HRmax(199.1±8.29 beat/min)均较其余相对湿度大。20%相对湿度组运动后3 min及5 min血乳酸较80%湿度组显著升高(P<0.05),60%相对湿度组运动后3 min血乳酸亦显著高于80%湿度组(P<0.05)。80%相对湿度组运动后1 min RPE仍显著高于40%相对湿度组(P<0.05),20%相对湿度组RPE值增加较缓慢,运动至第7和10 min时RPE值显著低于60%相对湿度组(P<0.05)。结论:与其余湿度相比,33℃高温环境下,80%相对湿度中机体有氧运动能力并未得到充分发挥。     

Effects of sprint interval training on VO2max and aerobic exercise performance: A systematic review and meta‐analysis

Recently, several studies have examined whether low‐volume sprint interval training (SIT) may improve aerobic and metabolic function. The objective of this study was to systematically review the existing literature regarding the aerobic and metabolic effects of SIT in healthy sedentary or recreationally active adults. A systematic literature search was performed (Bibliotek.dk, SPORTDiscus, Embase, PEDro, SveMed+, and Pubmed). Meta‐analytical procedures were applied evaluating effects on maximal oxygen consumption (VO_2max). Nineteen unique studies [four randomized controlled trials (RCTs), nine matched‐controlled trials and six noncontrolled studies] were identified, evaluating SIT interventions lasting 2–8 weeks. Strong evidence support improvements of aerobic exercise performance and VO_2max following SIT. A meta‐analysis across 13 studies evaluating effects of SIT on VO_2max showed a weighted mean effects size of g = 0.63 95% CI (0.39; 0.87) and VO_2max increases of 4.2–13.4%. Solid evidence support peripheral adaptations known to increase the oxidative potential of the muscle following SIT, whereas evidence regarding central adaptations was limited and equivocal. Some evidence indicated changes in substrate oxidation at rest and during exercise as well as improved glycemic control and insulin sensitivity following SIT. In conclusion, strong evidence support improvement of aerobic exercise performance and VO_2max following SIT, which coincides with peripheral muscular adaptations. Future RCTs on long‐term SIT and underlying mechanisms are warranted.     

Effects of endurance and high intensity training on ICAM-1 and VCAM-1 levels and arterial pressure in obese and normal weight adolescents

Objectives: Obesity prevalence has increased in Iranian adolescents in recent years. However, few studies have examined the impact of intervention programs on this health issue. The main objective of this study was to evaluate the effects of 8-week endurance training (ET) and high intensity interval training (HIIT) on intercellular adhesion molecule-1(ICAM-1) and vascular adhesion molecule-1(VCAM-1) levels among obese and normal-weight male adolescents.

Methods: Thirty obese and 30 normal-weight subjects were assigned to the ET, HIIT, or control group for eight weeks. Before and after the intervention, ICAM-1, VCAM-1, body weight, BMI, VO_2max, and blood pressures were measured. SPSS (Version 21) was used for data analysis, and the significance level was set at p < 0.05.

Results: Mixed design ANOVAs indicated that the obese participants had significantly (p < 0.05) lower ICAM-1 levels in the ET (from 509 ± 61 ng/ml to 387 ± 43 ng/ml) and HIIT (from 517 ± 72 ng/ml to 374 ± 50 ng/ml), but their VCAM-1 level was significantly (p < 0.05) reduced only after the HIIT (from 1689 ± 119 ng/ml to 1282 ± 63 ng/ml). Similarly, normal weight participants significantly (p < 0.05) lowered their ICAM-1 levels in the ET (from 296 ± 18 ng/ml to 216 ± 14 ng/ml) and HIIT (from 289 ± 22 ng/ml to 202 ± 12 ng/ml), but their VCAM-1 level was significantly (p < 0.05) reduced only after the HIIT (from 895 ± 50 ng/ml to 673 ± 142 ng/ml). Systolic blood pressure and diastolic blood pressures of all the participants were significantly (p < 0.01) decreased at the conclusion of the ET and HIIT.

Conclusion: While both the ET and HIIT were useful in lowering the SBP and DBP of the participants, HIIT was more effective than ET in reducing ICAM-1 and VCAM-1 content in normal and obese adolescents.     

Effects of leg muscle fatigue on gait in patients with Parkinson's disease and controls with high and low levels of daily physical activity

Patients with Parkinson's disease (PD) are more susceptible to muscle fatigue, which can damage their gait. Physical activity can improve muscle condition, which is an important aspect during walking. The aim of this study was to analyze the effects of lower limb muscle fatigue on gait in patients with PD and healthy individuals, grouped according to physical activity level. Twenty Patients with PD (PD group) and 20 matched individuals (control group) were distributed according to physical activity level into four subgroups of ten individuals (active and inactive). Participants performed three walking trials before and after lower limb muscle fatigue, induced by a repeated sit-to-stand task on a chair. Kinematic (stride length, width, duration, velocity and percentage of time in double support) and kinetic (propulsive and breaking anterior–posterior and medio-lateral impulse) gait parameters were analyzed. In both groups, participants increased stride length and velocity and decreased stride duration and braking vertical impulse after lower limb muscle fatigue. The PD groups presented higher step width and percentage of double time support than the control groups before muscle fatigue. The control groups increased step width and decreased percentage of time in double support, while the PD groups did not change these parameters. For physical activity level, active individuals presented longer stride length, greater stride velocity, higher braking and propulsive anterior–posterior impulse and shorter step width than inactive individuals. Groups sought more balance and safety after lower limb muscle fatigue. Physical activity level does not appear to modify the effects of lower limb muscle fatigue during unobstructed walking in individuals with PD or controls.     

高气压暴露对大鼠血浆内皮素-1含量、血清一氧化氮含量、一氧化氮合酶活性的影响

目的 探讨高气压暴露对大鼠血浆内皮素-1(endothelin-1,ET-1)含量、血清一氧化氮(nitric oxide,NO)含量、一氧化氮合酶(nitric oxide synthase,NOS)活性的影响.方法 40只SD大鼠随机分为5组.A组为对照组,B组0.7 MPa空气暴露后缓慢减压,C组0.7 MPa空气暴露后快速减压,D组0.147 MPa纯氧暴露后减压,E组0.250 MPa纯氧暴露后减压.各组暴露时间均为60 min.采用放射免疫方法测定血浆ET-1含量,硝酸还原酶法测定血清NO含量,比色法测定血清NOS活性.结果 与对照组相比,安全减压组和高压氧组的血浆ET-1含量明显升高(P<0.05),原因可能与高分压氧有关(PO2=0.147 MPa/0.250 MPa);快速减压组血清NO含量、NOS活性明显升高(P<0.05),与血浆ET-1含量升高的3个组相比,血清NO、NOS升高得更为显著(P<0.01).结论 NO与ET-1在机体对高气压暴露的反应中呈拮抗关系.高气压与高压氧暴露导致血浆ET-1的释放增加,但快速减压刺激血管内皮细胞产生更多的NO,这种机制可能是通过提高血浆中的NOS活性实现的,这个现象可能是血管内皮系统对血管内气泡产生的应激性反应之一.     

Effects of intense aerobic exercise and/or antihypertensive medication in individuals with metabolic syndrome

We studied the blood pressure lowering effects of a bout of exercise and/or antihypertensive medicine with the goal of studying if exercise could substitute or enhance pharmacologic hypertension treatment. Twenty‐three hypertensive metabolic syndrome patients chronically medicated with angiotensin II receptor 1 blockade antihypertensive medicine underwent 24‐hr monitoring in four separated days in a randomized order; (a) after taking their habitual dose of antihypertensive medicine (AHM trial), (b) substituting their medicine by placebo medicine (PLAC trial), (c) placebo medicine with a morning bout of intense aerobic exercise (PLAC +EXER trial) and (d) combining the exercise and antihypertensive medicine (AHM +EXER trial). We found that in trials with AHM subjects had lower plasma aldosterone/renin activity ratio evidencing treatment compliance. Before exercise, the trials with AHM displayed lower systolic (130 ± 16 vs 133 ± 15 mm Hg; P  = .018) and mean blood pressures (94 ± 11 vs 96 ± 10 mm Hg; P  = .036) than trials with placebo medication. Acutely (ie, 30 min after treatments) combining AHM +EXER lowered systolic blood pressure (SBP ) below the effects of PLAC +EXER (−8.1 ± 1.6 vs −4.9 ± 1.5 mm Hg; P  = .015). Twenty‐four hour monitoring revealed no differences among trials in body motion. However, PLAC +EXER and AHM lowered SBP below PLAC during the first 10 hours, time at which PLAC +EXER effects faded out (ie, at 19 PM ). Adding exercise to medication (ie, AHM +EXER ) resulted in longer reductions in SBP than with exercise alone (PLAC +EXER ). In summary, one bout of intense aerobic exercise in the morning cannot substitute the long‐lasting effects of antihypertensive medicine in lowering blood pressure, but their combination is superior to exercise alone.     

Influence of high and low plasma insulin levels on the uptake of fluorine-18 fluorodeoxyglucose in myocardium and femoral muscle,assessed by planar imaging

The aim of this study was to optimize the metabolic conditions for planar myocardial fluorine-l8 fluorodeoxyglucose (FDG) imaging. The effects of high and low insulin levels during euglycaemic clamping on myocardial and femoral muscle FDG uptake were compared since insulin plays a major role in glucose metabolism. FDG uptake in 11 patients was studied using planar scintigraphy. Patients were studied twice: in the low-dose insulin protocol (LDI), insulin was infused at a rate of 20 mU/kg per hour, starting 1 h before FDG administration, while in the high-dose insulin protocol (HDI) it was infused at a rate of 100 mU/kg per hour. Glucose infusion rate was adjusted according to frequently determined blood glucose levels. Somatostatin was infused to block endogenous insulin release. Planar images were obtained from the thorax region and femoral muscles. Regions of interest were drawn over normal and abnormal myocardial areas (based on angiographic and thallium-201 data) and over lung, liver and muscle areas. After clamping, insulin levels during LDI and HDI att=60 were 30.6±13.3 and 129.6±30.5 mU/1 respectively (P<0.0001). Femoral muscle uptake was significantly higher during HDI (P<0.001). Uptake in normal and abnormal myocardial areas did not differ between the two protocols. Heart/lung ratios (NS) and heart/liver ratios (P<0.05) increased during HDI. It may be concluded that planar FDG imaging is influenced by plasma insulin levels. The euglycaemic hyperinsulinaemic clamp technique, although more demanding, gives an adjustable metabolic steady state without significantly altering the FDG uptake patterns in normal and abnormal myocardial regions. The image quality of planar FDG images improves due to lower background uptake of FDG during clamping with high plasma insulin levels.This study was presented in part at the 40th annual meeting of the Society of Nuclear Medicine, 8–11 June 1993, Toronto, Canada     

Effects of acute and 2‐week administration of oral salbutamol on exercise performance and muscle strength in athletes

Our objective was to investigate effects of acute and 2‐week administration of oral salbutamol on repeated sprint ability, exercise performance, and muscle strength in elite endurance athletes. Twenty male elite athletes [VO_2max: 69.4 ± 1.8 (Mean ± SE) mL/min/kg], aged 25.9 ± 1.4 years, were included in a randomized, double‐blinded and placebo‐controlled parallel study. At baseline, after acute administration, and again after 2‐week administration of the study drugs (8 mg salbutamol or placebo), subjects' maximal voluntary contraction (MVC) of m. quadriceps and isometric endurance of m. deltoideus were measured, followed by three repeated Wingate tests. Exercise performance at 110% of VO_2max was determined on a bike ergometer. Acute administration of salbutamol increased peak power during first Wingate test by 4.1 ± 1.7% (P < 0.05). Two‐week administration of salbutamol increased (P < 0.05) peak power during first and second Wingate test by 6.4 ± 2.0 and 4.2 ± 1.0%. Neither acute nor 2‐week administration of salbutamol had any effect on MVC, exercise performance at 110% of VO_2max or on isometric endurance. No differences were observed in the placebo group. In conclusion, salbutamol benefits athletes' sprint ability. Thus, the present study supports the restriction of oral salbutamol in competitive sports.     

Role of CaMKII and sarcolipin in muscle adaptations to strength training with different levels of fatigue in the set

Strength training promotes a IIX‐to‐IIA shift in myosin heavy chain (MHC) composition, likely due to changes in sarcoplasmic [Ca²⁺] which are sensed by CaMKII. Sarcoplasmic [Ca²⁺] is in part regulated by sarcolipin (SLN), a small protein that when overexpressed in rodents stimulates mitochondrial biogenesis and a fast‐to‐slow fiber type shift. The purpose of this study was to determine whether CaMKII and SLN are involved in muscle phenotype and performance changes elicited by strength training. Twenty‐two men followed an 8‐week velocity‐based resistance training program using the full squat exercise while monitoring repetition velocity. Subjects were randomly assigned to two resistance training programs differing in the repetition velocity loss allowed in each set: 20% (VL20) vs 40% (VL40). Strength training caused muscle hypertrophy, improved 1RM and increased total CaMKII protein expression, particularly of the δ_D isoform. Phospho‐Thr²⁸⁷‐CaMKII δ_D expression increased only in VL40 (+89%), which experienced greater muscle hypertrophy, and a reduction in MHC‐IIX percentage. SLN expression was increased in VL20 (+33%) remaining unaltered in VL40. The changes in phospho‐Thr²⁸⁷‐CaMKII δ_D were positively associated with muscle hypertrophy and the number of repetitions during training, and negatively with the changes in MHC‐IIX and SLN. Most OXPHOS proteins remained unchanged, except for NDUFB8 (Complex I), which was reduced after training (?22%) in both groups. The amount of fatigue allowed in each set critically influences muscle CaMKII and SLN responses and determines muscle phenotype changes. With lower intra‐set fatigue, the IIX‐to‐IIA MHC shift is attenuated.     

紫外线照射充氧自血回输对兔急性梭曼中毒血清一氧化氮及一氧化氮合酶水平的影响

目的:探讨紫外线照射充氧自血回输(UB IO)治疗梭曼急性中毒的机理。方法:建立兔急性梭曼中毒模型。100只家兔随机分为正常对照组、中毒组、常规治疗组、UB IO治疗组及UB IO加常规治疗(复合治疗)组。观察14 d,检测兔血清一氧化氮(NO)及一氧化氮合酶(NOS)水平的变化。结果:正常对照组中兔血清NO及NOS水平分别为(8.38±3.40)μmol/L及(19.25±2.11)U/m l,中毒组中兔血清NO及NOS水平分别为(6.81±1.57)μmol/L及(17.46±1.12)U/m l,两组间有显著性差异(P<0.05)。经UB IO和复合治疗后,NO浓度分别为(7.88±2.05)及(8.03±2.46)μmol/L,NOS水平分别为(19.23±2.67)及(18.73±2.51)U/m l,与中毒组比较有显著差异(P<0.05)。结论:梭曼急性中毒后可使血清NO及NOS水平发生改变,此改变可能参与梭曼中毒的损伤,UB IO治疗对NO、NOS有极为有益的调节作用,能有效地治疗梭曼急性中毒。     

严重多发伤患者血浆F1+2、D-二聚体水平的变化及与弥散性血管内凝血的关系

目的 探讨严重多发伤患者血浆凝血酶原片段(F1+2)、D一二聚体水平变化及与创伤后弥散性血管内凝血(DIC)之间的关系. 方法 将66例多发伤患者分为轻伤组(ISS＜16分)21例和重伤组(ISS≥16分)45例,再把重伤患者分为并发DIC组(12例)与未并发DIC组(33例).另10例健康人设为正常对照组.正常对照组采外周静脉血1次,其余组分别于伤后1、3、7d空腹采集外周静脉血,应用ELISA方法测定血浆F1+2浓度,全自动乳胶微粒增强免疫比浊分析方法测定血浆D一二聚体浓度. 结果 轻伤与重伤组血浆F1+2、D-二聚体水平伤后均明显高于正常对照组,且重伤组又明显高于轻伤组.非DIC组伤后F1+2、D-二聚体水平逐渐降低,DIC组F1+2、D-二聚体水平持续升高并显著高于非DIC组.血浆F1+2、D-二:聚体水平在伤后1、3、7 d均呈明显的正相关. 结论 创伤后急性期F1+2、D-二聚体水平的升高程度不仅与创伤严重程度有关,而且与创伤后DIC的发生密切相关.因此,测定严重多发伤患者急性期外周血浆F1+2、D-二聚体水平变化对早期预测创伤后DIC的发生具有一定价值.     

Appendicular and mid-thigh lean mass are associated with muscle strength,physical performance,and dynamic balance in older persons at high risk of falls

BackgroundFalls in older persons are associated with muscle mass and strength alterations, which may also affect balance parameters. However, the most appropriate combined approach to assess muscle and balance components that predict falls in older persons is still lacking.Research questionWe hypothesized that appendicular lean and/or mid-thigh mass and muscle strength and performance are positively associated with balance indices and fall risk in older persons.MethodsCross-sectional analyses of retrospective data from 260 participants with risk and/or history of falls examined at a Falls and Fracture Clinic. Assessments included a comprehensive clinical exam, bone densitometry and body composition by DXA, grip strength, gait speed, posturography, timed up and go (TUG) and four-square step (FSST) tests. Retrospective falls and fracture history was collected. Associations between appendicular and mid-thigh lean mass and muscle strength/performance vs balance indicators were determined before and after adjusting for age and gender.ResultsMean age of participants was 78 ± 6.7 (65−96) years. Both appendicular and mid-thigh lean masses corrected for BMI (but not for height²), and muscle strength and performance measures are associated with better dynamic balance. Conversely, static balance indicators showed less consistent associations with lean mass. Only TUG and sit to stand time consistently showed significant associations with most static balance indicators.SignificanceCombined with strength and performance parameters, ALM and mid-thigh estimates adjusted by BMI strongly correlate with dynamic balance parameters and could become practical elements of falls risk assessment as well as markers of therapeutic response to falls prevention interventions.     

Effects of resistance training with moderate vs heavy loads on muscle mass and strength in the elderly: A meta‐analysis

The purpose of the present study was to perform a meta‐analysis to compare the efficacy of heavy (～80% of one repetition maximum, 1RM) vs light‐moderate load (～45% 1RM) resistance training (RT) programs in inducing strength gains and skeletal muscle hypertrophy in elderly people. To assess the role of training volumes, studies in which training protocols were matched for mechanical work were independently analyzed. In all 15 studies included (448 subjects, age 67.8 years), when comparing heavy with light‐moderate loads, strength gains tended to be larger following RT with higher intensities of load, with the resulting total population effect being μ = 0.430 (P = 0.060). Effect sizes were substantially smaller in “work‐matched” studies (μ = 0.297, P = 0.003). Training with higher loads also provoked marginally larger gains in muscle size, although the degree of training‐induced muscle hypertrophy was generally small (0.056 < μ < 0.136). To conclude, provided a sufficient number of repetitions is performed, RT at lower than traditionally recommended intensities of load may suffice to induce substantial gains in muscle strength in elderly cohorts.     

GBP影响Ⅱ型糖尿病大鼠空腹血糖及胰岛素的Meta分析

目的研究糖尿病胃转流手术（gastric bypass,GBP）对Ⅱ型糖尿病大鼠空腹血糖（FBG）和空腹胰岛素（FINS）调控的效果。方法计算机检索中文期刊全文数据库、维普中文科技期刊数据库、万方数据库收录的1979年1月～2010年12月发表的关于GBP降低Ⅱ型糖尿病大鼠血糖和胰岛素相关的对照研究,并辅以手工检索,对照纳入标准筛选文献。对符合纳入标准的研究的质量进行评价,用RevMan5．1软件进行Meta分析。结果共收集到相关文献37篇,其中符合纳入标准的有14篇,总的有效量合并RR值为0．79[95％CI（0．66,0．94）]。其中符合术后1、2、4W空腹血糖研究纳入标准的有9篇,其空腹血糖浓度合并RR值0．81[95％CI（0．76—0．86）],WMD为-0．21mmol／L[95％CI（-0．37～-0．04）];符合空腹胰岛素研究纳入标准的有6篇,术后2w空腹胰岛素合并RR值0．93[95％CI（0．84～1．02）],WMD为-0．083mmol／L[95％CI（-0．266～0．099）]。发表偏倚估计t=0．332,P〉0．05。结论GBP手术对降低Ⅱ型糖尿病大鼠空腹血糖和空腹胰岛素有显著的效果,并且具有一定的长效性。