Effect of glycerol-induced hyperhydration on thermoregulation and metabolism during exercise in the heat

This study examined the effect of glycerol ingestion on fluid homeostasis, thermoregulation, and metabolism during rest and exercise. Six endurance-trained men ingested either 1 g glycerol in 20 ml H₂O.kg^-1 body weight (bw) (GLY) or 20 ml H₂O.kg^-1bw (CON) in a randomized double-blind fashion, 120 min prior to undertaking 90 min of steady state cycle exercise (SS) at 98 % of lactate threshold in dry heat (35 degrees C, 30 % RH), with ingestion of CHO-electrolyte beverage (6 % CHO) at 15-min intervals. A 15-min cycle, where performance was quantified in kJ, followed (PC). Pre-exercise urine volume was lower in GLY than CON (1119 ± 97 vs. 1503 ± 146 ml· 120 min^-1; p < .05). Heart rate was lower (p < .05) throughout SS in GLY, while forearm blood flow was higher (17.1 ± 1.5 vs. 13.7 ± 3.0 ml.100 g tissue·min^-1; p < .05) and rectal  temperature lower (38.7 ± 0.1 vs. 39.1 ± 0.1 ° C; p < .05) in GLY late in SS. Despite these changes, skin and muscle temperatures and circulating catecholamines were not different between trials. Accordingly, no differences were observed in muscle glycogenolysis, lactate accumulation, adenine nucleotide, and phosphocreatine degradation or inosine 5'-monophosphate accumulation when comparing GLY with CON. Of note, the work performed during PC was 5 % greater in GLY (252 ± 10 vs. 240 ± 9 kJ; p < .05). These results demonstrate that glycerol, when ingested with a bolus of water 2 hours prior to exercise, results in fluid retention, which is capable of reducing cardiovascular strain and enhancing thermoregulation. Furthermore, this practice increases exercise performance in the heat by mechanisms other than alterations in muscle metabolism.

Effect of sodium bicarbonate on muscle metabolism during intense endurance cycling

Introduction: Sodium bicarbonate (NaHCO₃) ingestion has been shown to increase both muscle glycogenolysis and glycolysis during brief submaximal exercise. These changes may be detrimental to performance during more prolonged, exhaustive exercise. This study examined the effect of NaHCO₃ ingestion on muscle metabolism and performance during intense endurance exercise of ~60 min in seven endurance-trained men. Methods: Subjects ingested 0.3 g·kg^-1 body mass of either NaHCO₃ or CaCO₃ (CON) 2 h before performing 30 min of cycling exercise at 77 ± 1% [latin capital V with dot above]O_2peak followed by completion of 469 ± 21 kJ as quickly as possible (~30 min, ~80% [latin capital V with dot above]O_2peak). Results: Immediately before, and throughout exercise, arterialized-venous plasma HCO₃- concentrations were higher (P < 0.05) whereas plasma and muscle H⁺ concentrations were lower (P < 0.05) in NaHCO₃ compared with CON. Blood lactate concentrations were higher (P < 0.05) during exercise in NaHCO₃, but there was no difference between trials in muscle glycogen utilization or muscle lactate content during exercise. Reductions in PCr and ATP and increases in muscle Cr during exercise were also unaffected by NaHCO₃ ingestion. Accordingly, exercise performance time was not different between treatments. Conclusion: NaHCO₃ ingestion resulted in a small muscle alkalosis but had no effect on muscle metabolism or intense endurance exercise performance in well-trained men.

Carbohydrate ingestion reduces skeletal muscle acetylcarnitine availability but has no effect on substrate phosphorylation at the onset of exercise in man

This study investigated the effect of reduced acetylcarnitine availability on oxidative metabolism during the transition from rest to steady-state exercise. Eight male subjects completed two randomised exercise trials at 68 % of the peak rate of O2 uptake (V̇O2,peak). On one occasion subjects ingested 1 g (kg body mass)−1 glucose 75 min prior to exercise (CHO), whereas the other trial acted as a control (CON). Muscle samples were obtained pre- and 75 min post-ingestion, and following 1 and 10 min of exercise. Plasma glucose and insulin were elevated (P < 0.05), and plasma free fatty acids (FFA) were lower at the onset of exercise in CHO. Acetylcarnitine (CON, 4.8 ± 1.8; CHO, 1.5 ± 0.9 mmol (kg dry mass (d.m.))−1, P < 0.05) and acetyl CoA (CON, 13.2 ± 2.3; CHO, 6.3 ± 0.6 μmol (kg d.m.)−1, P < 0.05) were lower at rest, whereas pyruvate dehydrogenase activation (PDHa) was greater in CHO compared with CON (CON, 0.78 ± 0.07; CHO, 1.44 ± 0.19 mmol min−1 (kg wet mass (w.m.))−1). Respiratory exchange ratio (RER) was significantly elevated during exercise in CHO. The acetyl groups increased at similar rates at the onset of exercise (1 min) and there was no difference in substrate phosphorylation as determined from lactate accumulation and phosphocreatine degradation between trials. Subsequently, oxidative metabolism during the transition from rest to steady-state exercise was not affected by prior carbohydrate ingestion. Although exercise resulted in the rapid activation of PDH in both trials, PDHa was greater at 1 min in CHO (CON, 2.36 ± 0.22; CHO, 2.91 ± 0.18 mmol min−1 (kg w.m.)−1). No differences in muscle metabolite levels and PDHa were observed after 10 min of moderate exercise between trials. In summary, at rest, carbohydrate ingestion induced multiple metabolic changes which included decreased acetylcarnitine availability and small increases in PDHa. The prior changes in PDHa and acetylcarnitine availability had no effect on substrate phosphorylation and oxidative metabolism at the onset of exercise. These data suggest that acetylcarnitine availability is unlikely to be the site of metabolic inertia during the transition from rest to steady-state moderate intensity exercise.

Pregnancy and lactation have no long-term deleterious effect on measures of bone mineral in healthy women: a twin study

BACKGROUND: The long-term effects of pregnancy and lactation on measures of bone mineral in women remain unclear.

OBJECTIVE: We studied whether pregnancy or lactation has deleterious long-term effects on bone mineral in healthy women.

DESIGN: We measured bone mineral density (BMD; g/cm(2)) in women aged > or = 18 y. Analyses were performed on 3 data sets: study 1, 83 female twin pairs (21 monozygous and 62 dizygous) aged (x +/- SD) 42.2 +/- 15.5 y who were discordant for ever having been pregnant beyond 20 wk; study 2, 498 twin pairs aged 42.3 +/- 15.0 y; and study 3, 1354 individual twins, their siblings, and family members.

RESULTS: In study 1, there were no significant within-pair differences in unadjusted BMD or BMD adjusted for age, height, and fat mass at the lumbar spine or total-hip or in total-body bone mineral content (BMC; kg) (paired t tests). In study 2, there was no significant within-pair difference in measures of bone mineral or body composition related to the within-pair difference in number of pregnancies. In study 3, subjects with 1 or 2 (n = 455) and > or = 3 pregnancies (n = 473) had higher adjusted lumbar spine BMD (2.9% and 3.8%, respectively; P = 0.001) and total-body BMC (2.2% and 3.1%; P < 0.001) than did nulliparous women (n = 426). Parous women who breast-fed had higher adjusted total-body BMC (2.6%; P = 0.005), total-hip BMD (3.2%; P = 0.04), and lower fat mass (10.9%; P = 0.01) than did parous non-breast-feeders.

CONCLUSION: We found no long-term detrimental effect of pregnancy or breast-feeding on bone mineral measures.

Effects of creatine loading and prolonged creatine supplementation of body composition, fuel selection, sprint and endurance performance in humans

Most research on creatine has focused on short-term creatine loading and its effect on high-intensity performance capacity. Some studies have investigated the effect of prolonged creatine use during strength training. However, studies on the effects of prolonged creatine supplementation are lacking. In the present study, we have assessed the effects of both creatine loading and prolonged supplementation on muscle creatine content, body composition, muscle and whole-body oxidative capacity, substrate utilization during submaximal exercise, and on repeated supramaximal sprint, as well as endurance-type time-trial performance on a cycle ergometer. Twenty subjects ingested creatine or a placebo during a 5-day loading period (20g·day^-1) after which supplementation was continued for up to 6 weeks (2g·day^-1). Creatine loading increased muscle free creatine, creatine phosphate (CrP) and total creatine content (P<0.05). The subsequent use of a 2g·day^-1 maintenance dose, as suggested by an American College of Sports Medicine Roundtable, resulted in a decline in both the elevated CrP and total creatine content and maintenance of the free creatine concentration. Both short- and long-term creatine supplementation improved performance during repeated supramaximal sprints on a cycle ergometer. However, whole-body and muscle oxidative capacity, substrate utilization and time-trial performance were not affected. The increase in body mass following creatine loading was maintained after 6 weeks of continued supplementation and accounted for by a corresponding increase in fat-free mass. This study provides definite evidence that prolonged creatine supplementation in humans does not increase muscle or whole-body oxidative capacity and, as such, does not influence substrate utilization or performance during endurance cycling exercise. In addition, our findings suggest that prolonged creatine ingestion induces an increase in fat-free mass.

The effect of calcium supplementation on bone density in premenarcheal females: a co-twin approach

The age and developmental stage at which calcium supplementation produces the greatest bone effects remain controversial. We tested the hypothesis that calcium supplementation may improve bone accrual in premenarcheal females. Fifty-one pairs of premenarcheal female twins (27 monozygotic and 24 dizygotic; mean ± SD age, 10.3 ± 1.5 yr) participated in a randomized, single-blind, placebo-controlled trial with one twin of each pair receiving a 1200-mg calcium carbonate (Caltrate) supplement. Areal bone mineral density (aBMD) was measured at baseline and 6, 12, 18 and 24 months. There were no within-pair differences in height, weight, or calcium intake at baseline. Calcium supplementation was associated (P < 0.05) with increased aBMD compared with placebo, adjusted for age, height, and weight at the following time points from baseline: total hip, 6 months (1.9%), 12 months (1.6%), and 18 months (2.4%); lumbar spine, 12 months (1.0%); femoral neck, 6 months (1.9%). Adjusted total body bone mineral content was higher in the calcium group at 6 months (2.0%), 12 months (2.5%), 18 months (4.6%), and 24 months (3.7%), respectively (all P < 0.001). Calcium supplementation was effective in increasing aBMD at regional sites over the first 12–18 months, but these gains were not maintained to 24 months.

Effect of accurate exercise on uncoupling protein3 is a fat metabolism-mediated effect

Human and rodent uncoupling protein (UCP)3 mRNA is upregulated after acute exercise. Moreover, exercise increases plasma levels of free fatty acid (FFA), which are also known to upregulate UCP3. We investigated whether the upregulation of UCP3 after exercise is an effect of exercise per se or an effect of FFA levels or substrate oxidation. Seven healthy untrained men [age: 22.7 ± 0.6 yr; body mass index: 23.8 ± 1.0 kg/m²; maximal O₂ uptake (VO_{2 max}): 3,852 ± 211 ml/min] exercised at 50% VO_{2 max} for 2 h and then rested for 4 h. Muscle biopsies and blood samples were taken before and immediately after 2 h of exercise and 1 and 4 h in the postexercise period. To modulate plasma FFA levels and fat/glucose oxidation, the experiment was performed two times, one time with glucose ingestion and one time while fasting. UCP3 mRNA and UCP3 protein were determined by RT-competitive PCR and Western blot. In the fasted state, plasma FFA levels significantly increased (P < 0.0001) during exercise (293 ± 25 vs. 1,050 ± 127 μmol/l), whereas they were unchanged after glucose ingestion (335 ± 54 vs. 392 ± 74 µmol/l). Also, fat oxidation was higher after fasting (P < 0.05), whereas glucose oxidation was higher after glucose ingestion (P < 0.05). In the fasted state, UCP3L mRNA expression was increased significantly (P < 0.05) 4 h after exercise (4.6 ± 1.2 vs. 9.6 ± 3.3 amol/µg RNA). This increase in UCP3L mRNA expression was prevented by glucose ingestion. Acute exercise had no effect on UCP3 protein levels. In conclusion, we found that acute exercise had no direct effect on UCP3 mRNA expression. Abolishing the commonly observed increase in plasma FFA levels and/or fatty acid oxidation during and after exercise prevents the upregulation of UCP3 after acute exercise. Therefore, the previously observed increase in UCP3 expression appears to be an effect of prolonged elevation of plasma FFA levels and/or increased fatty acid oxidation.

Effect of 2 weeks of endurance training on uncoupling protein3 content in untrained human subjects

Aim: The mitochondrial uncoupling protein-3 (UCP3) is able to lower the proton gradient across the inner mitochondrial membrane, thereby uncoupling substrate oxidation from ATP production and dissipating energy as heat. What the effect of endurance training on UCP3 is, is still  controversial. Endurance-trained athletes are characterized by lower levels of UCP3, but longitudinal studies in rodents reported no effect of endurance training on muscular UCP3 levels. Here, we examined the effect of a 2-week training programme on skeletal muscle UCP3 protein content in untrained human subjects, and hypothesized that UCP3 will be reduced after the training programme. Methods: Nine untrained men [age: 23.3±3.2 years; BMI: 22.6±2.6 kg m^-2; maximal power output (^Wmax): 3.8±0.6 W kg^-1 body weight] trained for 2 weeks. Before and at least 72 h after the training period, muscle biopsies were taken for determination of UCP3 protein content. Results: UCP3 protein content tended to be lower after the training programme [95±10 vs. 109±12 arbitrary units (AU), P= 0.08]. Cytochrome c content tended to increase with 33% in response to endurance training (52± 6 vs. 39± 6 AU, P = 0.08). The ratio UCP3 relative to cytochrome c tended to decrease significantly upon endurance training (2.0±0.4 vs. 3.2±0.6 AU, P = 0.01). Conclusion: A short-term (2-week) endurance training programme decreased UCP3 protein levels and significantly reduced the ratio of UCP3 to cytochrome c.

Body weight, body image, and eating behaviours : relationships with ethnicity and acculturation in a community sample of young Australian women

A study was conducted to investigate associations between ethnicity and acculturation status and risk factors for eating disorders among young adult women. A community sample of 14,779 women aged 18–23 completed a comprehensive mail-out survey, which incorporated questions on country of birth, length of time spent in Australia, body weight, weight dissatisfaction, dieting, binge eating, and compensatory disordered eating behaviours. Results showed that risk factors for eating disorders were present across a range of ethnic groups. Further, a strong acculturation effect was observed, such that the longer the time spent in Australia, the more women reported weight-related values and behaviours similar to those of Australian-born women. Results challenge claims that risk factors for disordered eating are restricted to Caucasian females in Western societies. Implications for understanding ethnic and sociocultural influences on body weight, dieting, and disordered eating are considered.

Communication outside the humanities in media 'effect' research

This paper draws on the case study of a recent review of research literature on the influences (harms and benefits) on children and families of electronic media content and usage, undertaken on behalf of a Federal regulatory body (Australian Communications and Media Authority) by a multidisciplinary research team. Recent critiques of psychological studies of children and media have challenged the positivist social sciences to look outside of their own disciplinary warrants and to fully answer cultural studies critiques of ‘media effects’ research. Making connections outside the humanities in this case study involved making the rationales of communications and cultural studies methodologies available to those policy makers who normally may not consider such findings to be evidence-based or policy relevant. But it also involved providing a historical and institutional contextualization of positivist social and medical science findings, a contextualization not enabled by the underlying warrants and discourses of these disciplines. This paper focuses on those sections of the case study project concerned with psychological research on the effects of violent media and epidemiological and public health research on childhood obesity.

Apatite-inducing ability of titanium oxide layer on titanium surface : the effect of surface energy

In the present study, pure titanium (Ti) plates were firstly treated to form various types of oxide layers on the surface and then were immersed into simulated body fluid (SBF) to evaluate the apatite-forming ability. The surface morphology and roughness of the different oxide layers were measured by atomic force microscopy (AFM), and the surface energies were determined based on the Owens–Wendt (OW) methods. It was found that Ti samples after alkali heat (AH) treatment achieved the best apatite formation after soaking in SBF for three weeks, compared with those without treatment, thermal or H₂O₂ oxidation. Furthermore, contact angle measurement revealed that the oxide layer on the alkali heat treated Ti samples possessed the highest surface energy. The results indicate that the apatite-inducing ability of a titanium oxide layer links to its surface energy. Apatite nucleation is easier on a surface with a higher surface energy.

Effect of heat-treatment atmosphere on the bond strength of apatite layer on Ti substrate

Objectives
The purpose of this study was to investigate the bond strength of apatite layer on titanium (Ti) substrate coated by biomimetic method and to improve the bonding of apatite layer to Ti substrate by optimizing the alkali heat-treatment process.

Methods
Ti plates pre-treated with an alkali solution of 10 M sodium hydroxide (NaOH) were heat-treated at 600 °C for 1 h at different atmospheres: in air and in vacuum. A dense apatite layer formed on top of the sodium titanate layer after soaking the alkali and heat-treated Ti samples in simulated body fluid (SBF) for up to 3 weeks. The bond strengths of the sodium titanate layer on Ti substrate, and apatite layer on the sodium titanate layer, were measured, respectively, by applying a tensile load. The fracture sites were observed with a scanning electron microscope (SEM).

Results
The apatite layer on the substrate after alkali heat-treatment in air achieved higher bond strength than that on the substrate after alkali heat-treatment in vacuum. It was found that the interfacial structure between the sodium titanate and Ti substrate has a significant influence on the bond strength of the apatite layer.

Significance
It is advised that titanium implants can achieve better osseointegration under load-bearing conditions by depositing an apatite layer in vivo on a Ti surface subjected to alkali and heat-treated in air.

Appearance-based comments, body dissatisfaction and drive for muscularity in males

This study examined the role of positive and negative appearance-based comments on body dissatisfaction and drive for muscularity among young adult males. The direct and moderating effect of self-esteem were also investigated; and BMI, age, and social desirability were included as covariates. The participants were 214 males aged between 18 and 30 years. More frequent negative comments were associated with higher body dissatisfaction whilst more frequent positive comments were associated with lower body dissatisfaction. However, both frequent negative and positive commentary were associated with higher drive for muscularity. Self-esteem was also associated with both body dissatisfaction and the drive for muscularity, but it did not moderate that influence of either positive or negative messages. Longitudinal research is now needed to determine the directionality of these relationships. Further research is required to establish the contexts in which positive and negative messages are associated with body dissatisfaction and the drive for muscularity.

The effect of active support training on engagement, opportunities for choice, challenging behaviour and support needs

Background: The aim of this study was to evaluate active support (AS) training and to investigate changes to perceived engagement in domestic tasks, opportunities for choice, frequency of challenging behaviour, and level of support needs.

Method: Participants were 12 adults with ID aged 27–57 years (M = 37 years) residing in three group homes, and their support workers. The support workers completed assessments on three occasions (at baseline, post-training, and at follow-up).

Results: Residents' engagement in domestic tasks increased over time, and overall choice increased, although perceived choice in two life domains initially increased, but decreased to baseline levels at follow-up. Residents exhibited an overall decrease in anxiety, self-absorbed behaviour, disruptive behaviour, and problem behaviour in general. There was also an overall decrease in perceived support needs for five activity domains, with no change for one domain.

Conclusions: The results contribute to a growing body of evidence demonstrating favourable outcomes of AS in terms of engagement and challenging behaviour in people with ID. Surprising results are presented for choice and perceived support needs, warranting further investigation.

Undernutrition during suckling in rats elevates plasma adiponectin and its receptor in skeletal muscle regardless of diet composition : a protective effect?

Objective:
Nutrition during critical periods in early life may increase the subsequent risk of obesity, hypertension and metabolic diseases in adulthood. Few studies have focused on the long-term consequences of poor nutrition during the suckling period on the susceptibility to developing obesity when exposed to a palatable cafeteria-style high-fat diet (CD) after weaning.

Design:
This study examined the impact of early undernutrition, followed by CD exposure, on blood pressure, hormones and genes important for insulin sensitivity and metabolism and skeletal muscle mRNA expression of adiponectin receptor 1 (AdipoR1), carnitine palmitoyl-transferase I (CPT-1), cytochrome c oxidase 4 (COX4) and peroxisome proliferator-activated receptor alpha (PPARalpha). Following normal gestation, Sprague–Dawley rat litters were adjusted to 18 (undernourished) or 12 (control) pups. Rats were weaned (day 21) onto either palatable CD or standard chow.

Results:
Early undernourished rats were significantly lighter than control by 17 days, persisting into adulthood only when animals were fed chow after weaning. Regardless of litter size, rats fed CD had doubled fat mass at 15 weeks of age, and significant elevations in plasma leptin, insulin and adiponectin. Importantly, undernutrition confined to the suckling period, elevated circulating adiponectin regardless of post-weaning diet. Blood pressure was reduced in early undernourished rats fed chow, and increased by CD. Early undernutrition was associated with long-term elevations in the expression of AdipoR1, CPT-1, COX4 and PPARalpha in skeletal muscle.

Conclusion:
This study demonstrates the important role of early nutrition on body weight and metabolism, suggesting early undernourishment enhances insulin sensitivity and fatty-acid oxidation. The long-term potential benefit of limiting nutrition in the early postnatal period warrants further investigation.