Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies.

Concerns that the phytoestrogens (isoflavones) in soy may feminize men continue to be raised. Several studies and case-reports describing feminizing effects including lowering testosterone levels and raising estrogen levels in men have been published. For this reason, the clinical data were meta-analyzed to determine whether soy or isoflavone intake affects total testosterone (TT), free testosterone (FT), estradiol (E2), estrone (E1), and sex hormone binding globulin (SHBG). PubMed and CAB Abstracts databases were searched between 2010 and April 2020, with use of controlled vocabulary specific to the databases. Peer-reviewed studies published in English were selected if (1) adult men consumed soyfoods, soy protein, or isoflavone extracts (from soy or red clover) and [2] circulating TT, FT, SHBG, E2 or E1 was assessed. Data were extracted by two independent reviewers. With one exception, studies included in a 2010 meta-analysis were included in the current analysis. A total of 41 studies were included in the analyses. TT and FT levels were measured in 1753 and 752 men, respectively; E2 and E1 levels were measured in 1000 and 239 men, respectively and SHBG was measured in 967 men. Regardless of the statistical model, no significant effects of soy protein or isoflavone intake on any of the outcomes measured were found. Sub-analysis of the data according to isoflavone dose and study duration also showed no effect. This updated and expanded meta-analysis indicates that regardless of dose and study duration, neither soy protein nor isoflavone exposure affects TT, FT, E2 or E1 levels in men.

Sodium Bicarbonate Ingestion Improves Time-to-Exhaustion Cycling Performance and Alters Estimated Energy System Contribution: A Dose-Response Investigation.

This study investigated the effects of two sodium bicarbonate (NaHCO3) doses on estimated energy system contribution and performance during an intermittent high-intensity cycling test (HICT), and time-to-exhaustion (TTE) exercise. Twelve healthy males (stature: 1.75 ± 0.08 m; body mass: 67.5 ± 6.3 kg; age: 21.0 ± 1.4 years; maximal oxygen consumption: 45.1 ± 7.0 ml.kg.min-1) attended four separate laboratory visits. Maximal aerobic power (MAP) was identified from an incremental exercise test. During the three experimental visits, participants ingested either 0.2 g.kg-1 BM NaHCO3 (SBC2), 0.3 g.kg-1 BM NaHCO3 (SBC3), or 0.07 g.kg-1 BM sodium chloride (placebo; PLA) at 60 min pre-exercise. The HICT involved 3 × 60 s cycling bouts (90, 95, 100% MAP) interspersed with 90 s recovery, followed by TTE cycling at 105% MAP. Blood lactate was measured after each cycling bout to calculate estimates for glycolytic contribution to exercise. Gastrointestinal (GI) upset was quantified at baseline, 30 and 60 min post-ingestion, and 5 min post-exercise. Cycling TTE increased for SBC2 (+20.2 s; p = 0.045) and SBC3 (+31.9 s; p = 0.004) compared to PLA. Glycolytic contribution increased, albeit non-significantly, during the TTE protocol for SBC2 (+7.77 kJ; p = 0.10) and SBC3 (+7.95 kJ; p = 0.07) compared to PLA. GI upset was exacerbated post-exercise after SBC3 for nausea compared to SBC2 and PLA (p < 0.05), whilst SBC2 was not significantly different to PLA for any symptom (p > 0.05). Both NaHCO3 doses enhanced cycling performance and glycolytic contribution, however, higher doses may maximize ergogenic benefits.

The effects of hyperoxia on repeated sprint cycling performance & muscle fatigue.

OBJECTIVES: Hyperoxia (>21% oxygen) can evoke performance improvements in aerobic and anaerobic exercise. The aims of the current study were to determine the effects of breathing hyperoxic gas (fraction of inspired oxygen [FiO2] 1.00) on repeated cycle performance, and to assess the nature and extent of fatigue after intermittent sprinting. DESIGN & METHODS: Testing (n=14 males) comprised two visits to the laboratory. Each session involved 10×15s repeated cycle sprints breathing FiO2 1.00 (hyperoxia) or FiO2 0.21 (normoxia). Muscle fatigue was measured pre and post sprints using Maximal Voluntary Contraction (MVC), voluntary activation (VA) and potentiated doublet twitch (PTF). Blood lactate (BLa) was taken between sprints. Paired samples t-tests were used to examine difference between conditions in power output (peak and mean Watts) and BLa. Two-way ANOVA was used to examine fatigue variables pre and post sprints according to condition. RESULTS: Mean power output was 4% greater in hyperoxia (p<0.01), with no difference in peak power (p>0.05). There was a significant increase in BLa in hyperoxia compared with normoxia (p<0.01) in sprints 4 and 8, as well as meaningful difference in sprints 4-10. There was no significant difference in fatigue factors (MVC, VA and PTF) (p>0.05) in response to the cycling, although a large drop in PTF occurred in both conditions. CONCLUSION: Hyperoxia can elicit improvements in mean cycling power, with no significant change in post exercise muscle fatigue. Hyperoxia as a training aid may provide performance enhancing effects during repeated sprint cycling by reducing concurrent muscle fatigue, primarily via peripheral factors.

No Difference Between the Effects of Supplementing With Soy Protein Versus Animal Protein on Gains in Muscle Mass and Strength in Response to Resistance Exercise.

Much attention has been given to determining the influence of total protein intake and protein source on gains in lean body mass (LBM) and strength in response to resistance exercise training (RET). Acute studies indicate that whey protein, likely related to its higher leucine content, stimulates muscle protein synthesis to a greater extent than proteins such as soy and casein. Less clear is the extent to which the type of protein supplemented impacts strength and LBM in long-term studies (≥6 weeks). Therefore, a meta-analysis was conducted to compare the effect of supplementation with soy protein to animal protein supplementation on strength and LBM in response to RET. Nine studies involving 266 participants suitable for inclusion in the meta-analysis were identified. Five studies compared whey with soy protein, and four studies compared soy protein with other proteins (beef, milk, or dairy protein). Meta-analysis showed that supplementing RET with whey or soy protein resulted in significant increases in strength but found no difference between groups (bench press: χ2 = 0.02, p = .90; squat: χ2 = 0.22, p = .64). There was no significant effect of whey or soy alone (n = 5) on LBM change and no differences between groups (χ2 = 0.00, p = .96). Strength and LBM both increased significantly in the "other protein" and the soy groups (n = 9), but there were no between-group differences (bench: χ2 = 0.02, p = .88; squat: χ2 = 0.78, p = .38; and LBM: χ2 = 0.06, p = .80). The results of this meta-analysis indicate that soy protein supplementation produces similar gains in strength and LBM in response to RET as whey protein.

The effects of lower-body compression garments on walking performance and perceived exertion in adults with CVD risk factors.

OBJECTIVES: Compression garments are used by athletes in attempts to enhance performance and recovery, although evidence to support their use is equivocal. Reducing the exertion experienced during exercise may encourage sedentary individuals to increase physical activity. The aim of this study was to assess the effect of compression garments on walking performance (self-paced and enforced pace) and rate of perceived exertion (RPE) in adults who presented with two or more CVD risk factors. Participants (n=15, 10 female, 58.9±11.5 years, BMI 27.5±4.5kgm2) were recruited. DESIGN: A repeated measures design. METHODS: Participants were randomised to Modified Bruce Protocol (enforced pace), or the 6min walk test (self-paced), and completed the test wearing compression garments or normal exercise clothes (Control). Outcome measures included stage completed, gross efficiency (%) and RPE in Modified Bruce Protocol, and distance walked (m) and RPE in 6 min walk test. RESULTS: In the Modified Bruce Protcol participants had a higher RPE (15.5±2.5 vs 14.3±2.2) and a lower efficiency (19.1±5.9 vs 21.1±6.7) in the compression garment condition compared with control, p<0.05. In the 6 min walk test participants walked 9% less in the compression garment condition (p<0.05) but did not have a lower RPE. CONCLUSIONS: Compared with previous studies reporting enhanced or no effects of compression garments on performance or RPE, this study shows adverse effects of such clothing in untrained individuals with CVD risk factors. The mechanisms underlying this negative effect require further exploration. Use of garments designed for the athletic individuals may not be suitable for the wider population.

Action Schools! BC: a school-based physical activity intervention designed to decrease cardiovascular disease risk factors in children.

OBJECTIVE: Our primary objective was to determine whether a novel 'active school' model--Action Schools! BC--improved the cardiovascular disease (CVD) risk profile in elementary-school children. Our secondary objective was to determine the percentage of children with elevated CVD risk factors. METHODS: We undertook a cluster-randomized controlled school-based trial with 8 elementary schools across 1 school year, in British Columbia, Canada, beginning in 2003. Boys and girls (n=268, age 9-11 years) were randomly assigned (by school) to usual practice (UP, 2 schools) or intervention (INT, 6 schools) groups. We assessed change between groups in cardiovascular fitness (20-m Shuttle Run), blood pressure (BP), and body mass index (BMI, wt/ht(2)). We evaluated total cholesterol (TC), total:high-density cholesterol (TC:HDL-C), low-density lipoprotein, apolipoprotein B, C-reactive protein and fibrinogen on a subset of volunteers (n=77). RESULTS: INT children had a 20% greater increase in fitness and a 5.7% smaller increase in BP compared with children attending UP schools (P<0.05). Forty five percent of children had at least one elevated risk factor (fitness, BP or BMI) at baseline. There were no significant differences between groups for change in BMI or in any of the blood variables. CONCLUSION: Action Schools! BC was an effective school-based physical activity model for improving the CVD risk profile of elementary-school children. Our multi-component intervention exposed children to fitness enhancing physical activity. It may be important for education stakeholders to adequately resource the delivery of the active school models if cardiovascular health benefits are to be achieved on a population basis.

Differences in heart rate variability between Asian and Caucasian children living in the same Canadian community.

Heart rate variability (HRV) is an umbrella term for a variety of measures that assess autonomic influence on the heart. Reduced beat-to-beat variability is found in individuals with a variety of cardiac abnormalities. A reduced HRV positively correlates with obesity, poor aerobic fitness, and increasing age. Racial (black-white) differences are apparent in adults and adolescents. We aimed to evaluate (i) Asian-Caucasian differences in HRV and (ii) differences in HRV between girls and boys. Sixty-two children (30 male (15 Caucasian, 15 Asian) and 32 female (15 Caucasian, 17 Asians)) with a mean age of 10.3 +/- 0.6 y underwent 5 min resting HRV recording, fitness testing (Leger's 20 m shuttle), and self-assessed maturity. Outcome HRV measures were a ratio of low to high frequency power (LF:HF), standard deviation of R-R intervals (SDRR) and root mean square of successive R-R intervals (RMSSD). Data were compared between groups using analysis of covariance (ANCOVA). There were no race or sex differences for time domain variables, mean R-R, body mass index, or blood pressure. Compared with Caucasian children, Asian children displayed a higher adjusted (fitness, R-R interval) LF:HF ratio (72.9 +/- 59.4 vs. 120.6 +/- 85.3, p < 0.05). Girls demonstrated a higher adjusted LF:HF power than boys (117.2 +/- 85.1 vs. 76.6 +/- 62.4, p = < 0.05). In conclusion, Asian and Caucasian children display different frequency domain components of heart rate variability.

Action Schools! BC: a socioecological approach to modifying chronic disease risk factors in elementary school children.

BACKGROUND: Childhood physical inactivity and obesity are serious public health threats. Socioecological approaches to addressing these threats have been proposed. The school is a critical environment for promoting children's health and provides the opportunity to explore the impact of a socioecological approach. CONTEXT: Thirty percent of children in British Columbia, Canada, are overweight or obese, and 50% of youths are not physically active enough to yield health benefits. METHODS: Action Schools! BC, a socioecological model, was developed to create 1) an elementary school environment where students are provided with more opportunities to make healthy choices and 2) a supportive community and provincial environment to facilitate change at the school and individual levels. CONSEQUENCES: The environment in British Columbia for school- and provincial-level action on health behaviors improved. Focus group and project tracking results indicated that the Action Schools! BC model enhanced the conceptual use of knowledge and was an influencing factor. Political will and public interest were also cited as influential factors. INTERPRETATION: The Action Schools! BC model required substantial and demanding changes in the approach of the researchers, policy makers, and support team toward health promotion. Despite challenges, Action Schools! BC provides a good example of how to enhance knowledge exchange and multilevel intersectoral action in chronic disease prevention.

Arterial compliance in young children: the role of aerobic fitness.

BACKGROUND: Reduced arterial compliance is reflective of vascular dysfunction, which promotes the atherosclerotic process, and is therefore an important predictor of vascular disease. In adults, obesity, age, aerobic fitness, oestrogens and race influence arterial compliance. Although stature and blood pressure are known to influence compliance in children, other determinants are less established. This investigation sought to determine the predictors of arterial compliance in children, assess the extent to which aerobic fitness is related to compliance, and compare compliance between girls and boys. METHODS: Participants (99 children aged 9-11 years, 55 boys) were assessed for aerobic fitness, physical activity level, blood pressure, body mass, percentage fat mass, height, maturity and arterial compliance (large and small). Predictors of compliance were determined using stepwise regression. Second, children were divided into quartiles according to fitness, and arterial compliance was compared using analysis of covariance (ANCOVA). Finally, differences in compliance between girls and boys were assessed using ANCOVA. RESULTS: We found that fitness, blood pressure and height accounted for 37% of the variance in large artery compliance. Mass, fitness, maturity and blood pressure accounted for 44% of the variance in small artery compliance. Children in the highest fitness quartile had greater compliance than children in the two lowest quartiles, by as much as 34%. There were no differences in compliance between girls and boys after adjusting for covariates. DISCUSSION: These data show that aerobic fitness is associated with arterial compliance in 9-11-year-old children, supporting the concept that physical fitness may exert a protective effect on the cardiovascular system.