Kirsty J. Elliott-Sale

β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis.

Objective To conduct a systematic review and meta-analysis of the evidence on the effects of β-alanine supplementation on exercise capacity and performance. Design This study was designed in accordance with PRISMA guidelines. A 3-level mixed effects model was employed to model effect sizes and account for dependencies within data. Data sources 3 databases (PubMed, Google Scholar, Web of Science) were searched using a number of terms (‘β-alanine’ and ‘Beta-alanine’ combined with ‘supplementation’, ‘exercise’, ‘training’, ‘athlete’, ‘performance’ and ‘carnosine’). Eligibility criteria for selecting studies Inclusion/exclusion criteria limited articles to double-blinded, placebo-controlled studies investigating the effects of β-alanine supplementation on an exercise measure. All healthy participant populations were considered, while supplementation protocols were restricted to chronic ingestion. Cross-over designs were excluded due to the long washout period for skeletal muscle carnosine following supplementation. A single outcome measure was extracted for each exercise protocol and converted to effect sizes for meta-analyses. Results 40 individual studies employing 65 different exercise protocols and totalling 70 exercise measures in 1461 participants were included in the analyses. A significant overall effect size of 0.18 (95% CI 0.08 to 0.28) was shown. Meta-regression demonstrated that exercise duration significantly (p=0.004) moderated effect sizes. Subgroup analyses also identified the type of exercise as a significant (p=0.013) moderator of effect sizes within an exercise time frame of 0.5–10 min with greater effect sizes for exercise capacity (0.4998 (95% CI 0.246 to 0.753)) versus performance (0.1078 (95% CI −0.201 to 0.416)). There was no moderating effect of training status (p=0.559), intermittent or continuous exercise (p=0.436) or total amount of β-alanine ingested (p=0.438). Co-supplementation with sodium bicarbonate resulted in the largest effect size when compared with placebo (0.43 (95% CI 0.22 to 0.64)). Summary/conclusions β-alanine had a significant overall effect while subgroup analyses revealed a number of modifying factors. These data allow individuals to make informed decisions as to the likelihood of an ergogenic effect with β-alanine supplementation based on their chosen exercise modality.

Exercise interventions for weight management during pregnancy and up to 1 year postpartum among normal weight, overweight and obese women: a systematic review and meta-analysis

Background The prevalence of excessive gestation weight gain, extended postpartum weight retention and pregravid obese women is increasing and is associated with numerous adverse health outcomes. Objective To review the evidence from studies employing exercise-only interventions for weight management among pregnant and postpartum women. Search strategy Ten databases were searched for randomised controlled trials conducted during pregnancy or within the 12 months following childbirth and published between 1990 and 2013. Selection criteria There were no restrictions to the type, frequency, duration or intensity of exercise intervention. Interventions not specifically designed to target weight were excluded. The outcomes were a change in body weight (kg) or body mass index (BMI; kg/m2). Data collection and analysis All data were continuous and were reported as weighted mean differences (WMD), with 95% CIs. Data were analysed with a fixed-effect model and heterogeneity was determined using the I2 statistic. Results Five studies were included in this review. Exercise significantly reduced gestational weight gain (WMD=−2.22 kg, CI −3.14 to −1.3, p≤0.00001) and had no significant effect on postpartum weight loss (WMD=−1.74 kg, CI −3.59 to 0.10, p=0.06) or BMI during pregnancy (WMD=−2.8 kg/m2, CI −5.60 to 0.00, p=0.05) or postpartum (WMD=−0.54 kg/m2, CI −1.17 to 0.08, p=0.09). Conclusions There is currently limited evidence to suggest that exercise can be used to limit maternal gestational weight gain.

Examining the role of oral contraceptive users as an experimental and/or control group in athletic performance studies

BACKGROUND This study was conducted to examine the effect of oral contraceptives on endogenous reproductive hormone levels in order to assess the suitability of oral contraceptive users as experimental and/or control groups in human performance studies. STUDY DESIGN Ninety-five females who were taking a variety of oral contraceptives (2 types and 11 brands) were recruited. A single blood sample was analysed for endogenous concentrations of oestradiol and progesterone. RESULTS There were significant differences (p<.05) in circulating oestradiol and progesterone as a result of oral contraceptive type and brand. Overall, oral contraceptive use resulted in low levels of oestradiol and progesterone and large variation in hormone concentration when multiple brands were analysed together. CONCLUSION This study indicates that future studies should employ a single pill type and brand when using oral contraceptive users as either a control or experimental group and that comparison between oral contraceptive users as a control group and the early follicular phase of the menstrual cycle as an experimental group should be reconsidered.

Effect of Sodium Bicarbonate Supplementation on 2000-m Rowing Performance

UNLABELLED The ability to buffer H+ could be vital to exercise performance, as high concentrations of H+ contribute to the development of fatigue. PURPOSE The authors examined the effect of sodium bicarbonate (SB) supplementation on 2000-m rowing-ergometer performance. METHODS Twenty male rowers (age 23 ± 4 y, height 1.85 ± 0.08 m, mass 82.5 ± 8.9 kg, 2000-m personal-best time 409 ± 16 s) completed two 2000-m rowing-ergometer time trials, separated by 48 h. Participants were supplemented before exercise with 0.3 g/kg body mass of SB or a placebo (maltodextrin; PLA). The trials were conducted using a double-blinded, randomized, counterbalanced crossover study design. Time to complete the 2000-m and time taken for each 500-m split were recorded. Blood lactate, bicarbonate, pH, and base excess were determined preexercise, immediately postexercise, and 5 min postexercise. Performance data were analyzed using paired t tests, as well as magnitude-based inferences; hematological data were analyzed using a repeated-measures ANOVA. RESULTS Using paired t tests, there was no benefit of SB over PLA (P = .095). However, using magnitude-based inferences there was a likely beneficial effect of SB compared with PLA (PLA 412.0 ± 15.1 s, SB 410.7 ± 14.9 s). Furthermore, SB was 0.5 ± 1.2 s faster than PLA in the third 500 m (P = .035; possibly beneficial) and 1.1 ± 1.7 s faster in the fourth 500 m (P = .004; very likely beneficial). All hematological data were different between SB and PLA and were different from preexercise to postexercise. CONCLUSION SB supplementation is likely to be beneficial to the performance of those competing in 2000-m rowing events, particularly in the second half of the event.

Reduced energy availability: implications for bone health in physically active populations

PurposeThe present review critically evaluates existing literature on the effects of short- and long-term low energy availability (EA) on bone metabolism and health in physically active individuals.MethodsWe reviewed the literature on the short-term effects of low EA on markers of bone metabolism and the long-term effects of low EA on outcomes relating to bone health (bone mass, microarchitecture and strength, bone metabolic markers and stress fracture injury risk) in physically active individuals.ResultsAvailable evidence indicates that short-term low EA may increase markers of bone resorption and decrease markers of bone formation in physically active women. Bone metabolic marker responses to low EA are less well known in physically active men. Cross-sectional studies investigating the effects of long-term low EA suggest that physically active individuals who have low EA present with lower bone mass, altered bone metabolism (favouring bone resorption), reduced bone strength and increased risk for stress fracture injuries.ConclusionsReduced EA has a negative influence on bone in both the short- and long-term, and every effort should be made to reduce its occurrence in physically active individuals. Future interventions are needed to explore the effects of long-term reduced EA on bone health outcomes, while short-term low EA studies are also required to give insight into the pathophysiology of bone alterations.

Antenatal weight management: Diet, physical activity, and gestational weight gain in early pregnancy

OBJECTIVE to investigate womens physical activity levels, diet and gestational weight gain, and their experiences and motivations of behavior change. DESIGN analysis of cross-sectional data collected during a longitudinal, cohort study examining physiological, psychological, sociodemographic, and self-reported behavioural measures relating to bodyweight. SETTING women recruited from routine antenatal clinics at the Nottingham University Hospitals NHS Trust. PARTICIPANTS 193 women ≤27 weeks gestation and aged 18 years or over. MEASUREMENTS & FINDINGS: measurements included weight and height, the Dietary Instrument for Nutrition Education (Brief Version), the International Physical Activity Questionnaire (Short Form), and open questions of perceptions of behaviour change. 50.3% (n=97) were overweight/obese, and women gained 0.26kg/wk (IQR 0.34kg/wk) since conception. The majority consumed low levels of fat (n=121; 63.4%), high levels of unsaturated fat (n=103; 53.9%), and used a dietary supplement (n=166; 86.5%). However, 41% (n=76) were inactive, 74.8% (n=143) did not consume high levels of fibre, and 90.0% (n=171) consumed less than 5 portions of fruit and vegetables a day. Body mass index category was not associated with diet, physical activity levels, or gestational weight gain. Themes generated from open-questions relating to behaviour change were: (1) Risk management, (2) Coping with symptoms, (3) Self-control, (4) Deviation from norm, (5) Nature knows best. CONCLUSIONS early pregnancy is a period of significant and heterogeneous behaviour change, influenced by perceptions of risk and womens lived experience. Behaviour was influenced not only by perceptions of immediate risk to the fetus, but also by the womens lived experience of being pregnant. IMPLICATIONS FOR PRACTICE There are exciting opportunities to constructively reframe health promotion advice relating to physical activity and diet in light of womens priorities. The need for individualized advice is highlighted, and women across all body mass index categories would benefit from improved diet and physical activity levels.

The Effect of Postexercise Carbohydrate and Protein Ingestion on Bone Metabolism

Purpose This study aimed to investigate the effect of feeding carbohydrate and protein (CHO + PRO), immediately or 2 h after an exhaustive run, on the bone turnover response in endurance runners. Methods Ten men (age = 28 ± 5 yr, height = 1.74 ± 0.05 m, body mass [BM] = 69.7 ± 6.3 kg) performed treadmill running at 75% V˙O2max, until exhaustion, on three occasions. Blood was collected before and immediately, 1, 2, 3, 4, and 24 h postexercise, for measurement of &bgr;-CTX, P1NP, parathyroid hormone, PO4, ACa, and Ca2+. This was a randomized, counterbalanced, placebo-controlled, and single-blinded crossover study. The three trials were (i) placebo (PLA), where the PLA solution was ingested immediately and 2 h postexercise; (ii) immediate feeding (IF), where CHO + PRO (1.5 g·kg−1 BM dextrose and 0.5 g·kg−1 BM whey) was ingested immediately postexercise and PLA 2 h postexercise; and (iii) delayed feeding (DF), where PLA was ingested immediately postexercise and CHO + PRO solution 2 h postexercise. Data were analyzed using repeated-measures ANOVA and Tukeys HSD post hoc test. Results At 1 and 2 h postexercise, &bgr;-CTX concentrations were lower in the IF trial compared with the DF and PLA trials (P ⩽ 0.001). At 3 h postexercise, &bgr;-CTX concentrations were higher in the PLA trial compared with the IF (P ⩽ 0.001) and DF trials (P = 0.026). At 4 h postexercise, &bgr;-CTX concentrations were lower in the DF trial compared with the IF (P = 0.003) and PLA trials (P ⩽ 0.001). At 4 h postexercise, P1NP was higher in the IF trial compared with the DF (P = 0.026) and PLA trials (P = 0.001). At 3 h postexercise, parathyroid hormone was higher in the IF trial compared with the DF trial (P ⩽ 0.001). Conclusions After exhaustive running, immediate ingestion of CHO + PRO may be beneficial, as it decreases bone resorption marker concentrations and increases bone formation marker concentrations, creating a more positive bone turnover balance.

Effects of reduced energy availability on bone metabolism in women and men

BACKGROUND The short-term effects of low energy availability (EA) on bone metabolism in physically active women and men are currently unknown. PURPOSE We evaluated the effects of low EA on bone turnover markers (BTMs) in a cohort of women and a cohort of men, and compared effects between sexes. METHODS These studies were performed using a randomised, counterbalanced, crossover design. Eleven eumenorrheic women and eleven men completed two 5-day protocols of controlled (CON; 45kcal·kgLBM-1·d-1) and restricted (RES; 15kcal·kgLBM-1·d-1) EAs. Participants ran daily on a treadmill at 70% of their peak aerobic capacity (VO2 peak) resulting in an exercise energy expenditure of 15kcal·kgLBM-1·d-1 and consumed diets providing 60 and 30kcal·kgLBM-1·d-1. Blood was analysed for BTMs [β-carboxyl-terminal cross-linked telopeptide of type I collagen (β-CTX) and amino-terminal propeptide of type 1 procollagen (P1NP)], markers of calcium metabolism [parathyroid hormone (PTH), albumin-adjusted calcium (ACa), magnesium (Mg) and phosphate (PO4)] and regulatory hormones [sclerostin, insulin-like growth factor 1 (IGF-1), triiodothyronine (T3), insulin, leptin, glucagon-like-peptide-2 (GLP-2)]. RESULTS In women, β-CTX AUC was significantly higher (P=0.03) and P1NP AUC was significantly lower (P=0.01) in RES compared to CON. In men, neither β-CTX (P=0.46) nor P1NP (P=0.12) AUCs were significantly different between CON and RES. There were no significant differences between sexes for any BTM AUCs (all P values>0.05). Insulin and leptin AUCs were significantly lower following RES in women only (for both P=0.01). There were no differences in any AUCs of regulatory hormones or markers of calcium metabolism between men and women following RES (all P values>0.05). CONCLUSIONS When comparing within groups, five days of low EA (15kcal·kgLBM-1·d-1) decreased bone formation and increased bone resorption in women, but not in men, and no sex specific differences were detected.

Exercise and bone health across the lifespan

With ageing, bone tissue undergoes significant compositional, architectural and metabolic alterations potentially leading to osteoporosis. Osteoporosis is the most prevalent bone disorder, which is characterised by progressive bone weakening and an increased risk of fragility fractures. Although this metabolic disease is conventionally associated with ageing and menopause, the predisposing factors are thought to be established during childhood and adolescence. In light of this, exercise interventions implemented during maturation are likely to be highly beneficial as part of a long-term strategy to maximise peak bone mass and hence delay the onset of age- or menopause-related osteoporosis. This notion is supported by data on exercise interventions implemented during childhood and adolescence, which confirmed that weight-bearing activity, particularly if undertaken during peripubertal development, is capable of generating a significant osteogenic response leading to bone anabolism. Recent work on human ageing and epigenetics suggests that undertaking exercise after the fourth decade of life is still important, given the anti-ageing effect and health benefits provided, potentially occurring via a delay in telomere shortening and modification of DNA methylation patterns associated with ageing. Exercise is among the primary modifiable factors capable of influencing bone health by preserving bone mass and strength, preventing the death of bone cells and anti-ageing action provided.

Parathyroid Hormone Secretion Is Controlled by Both Ionized Calcium and Phosphate During Exercise and Recovery in Men

CONTEXT The mechanism by which PTH is controlled during and after exercise is poorly understood due to insufficient temporal frequency of measurements. OBJECTIVE The objective of the study was to examine the temporal pattern of PTH, PO4, albumin-adjusted calcium, and Ca(2+) during and after exercise. DESIGN AND SETTING This was a laboratory-based study with a crossover design, comparing 30 minutes of running at 55%, 65%, and 75% maximal oxygen consumption, followed by 2.5 hours of recovery. Blood was obtained at baseline, after 2.5, 5, 7.5, 10, 15, 20, 25, and 30 minutes of exercise, and after 2.5, 5, 7.5, 10, 15, 20, 25, 30, 60, 90, and 150 minutes of recovery. PARTICIPANTS Ten men (aged 23 ± 1 y, height 1.82 ± 0.07 m, body mass 77.0 ± 7.5 kg) participated. MAIN OUTCOME MEASURES PTH, PO4, albumin-adjusted calcium, and Ca(2+) were measured. RESULTS Independent of intensity, PTH concentrations decreased with the onset of exercise (-21% to -33%; P ≤ .001), increased thereafter, and were higher than baseline by the end of exercise at 75% maximal oxygen consumption (+52%; P ≤ .001). PTH peaked transiently after 5-7.5 minutes of recovery (+73% to +110%; P ≤ .001). PO4 followed a similar temporal pattern to PTH, and Ca(2+) followed a similar but inverse pattern to PTH. PTH was negatively correlated with Ca(2+) across all intensities (r = -0.739 to -0.790; P ≤ .001). When PTH was increasing, the strongest cross-correlation was with Ca(2+) at 0 lags (3.5 min) (r = -0.902 to -0.950); during recovery, the strongest cross-correlation was with PO4 at 0 lags (8 min) (r = 0.987-0.995). CONCLUSIONS PTH secretion during exercise and recovery is controlled by a combination of changes in Ca(2+) and PO4 in men.