Are increases in skeletal muscle mass accompanied by changes to resting metabolic rate in rugby athletes over a pre-season training period?

Optimising dietary energy intake is essential for effective sports nutrition practice in rugby athletes. Effective dietary energy prescription requires careful consideration of athletes' daily energy expenditure with the accurate prediction of resting metabolic rate (RMR) important due to its influence on total energy expenditure and in turn, energy balance. This study aimed to (a) measure rugby athletes RMR and (b) report the change in RMR in developing elite rugby players over a rugby preseason subsequent to changes in body composition and (c) explore the accurate prediction of RMR in rugby athletes. Eighteen developing elite rugby union athletes (age 20.2 ± 1.7 years, body mass 101.2 ± 14.5 kg, stature 184.0 ± 8.4 cm) had RMR (indirect calorimetry) and body composition (dual energy x-ray absorptiometry) measured at the start and end of a rugby preseason ∼14 weeks later. There was no statistically significant difference in RMR over the preseason period (baseline 2389 ± 263 kcal·day^-1 post 2373 ± 270 kcal·day^-1) despite a significant increase in lean mass of +2.0 ± 1.6 kg (P < 0.01) and non-significant loss of fat mass. The change in RMR was non-significant and non-meaningful; thus, this study contradicts the commonly held anecdotal perception that an increase in skeletal muscle mass will result in a significant increase in metabolic rate and daily energy needs. Conventional prediction equations generally under-estimated rugby athletes' measured RMR, and may be problematic for identifying low energy availability, and thus updated population-specific prediction equations may be warranted to inform practice.

Allometry and performance: the evolution of skull form and function in felids

Allometric patterns of skull-shape variation can have significant impacts on cranial mechanics and feeding performance, but have received little attention in previous studies. Here, we examine the impacts of allometric skull-shape variation on feeding capabilities in the cat family (Felidae) with linear morphometrics and finite element analysis. Our results reveal that relative bite force diminishes slightly with increasing skull size, and that the skulls of the smallest species undergo the least strain during biting. However, larger felids are able to produce greater gapes for a given angle of jaw opening, and they have overall stronger skulls. The two large felids in this study achieved increased cranial strength by increasing skull bone volume relative to surface area. Allometry of skull geometry in large felids reflects a trade-off between the need to increase gape to access larger prey while maintaining the ability to resist unpredictable loading when taking large, struggling prey.

Validation of a skinfold based index for tracking proportional changes in lean mass

BACKGROUND

The lean mass index (LMI) is a new empirical measure that tracks within-subject proportional changes in body mass adjusted for changes in skinfold thickness.

OBJECTIVE

To compare the ability of the LMI and other skinfold derived measures of lean mass to monitor changes in lean mass.

METHODS

20 elite rugby union players undertook full anthropometric profiles on two occasions 10 weeks apart to calculate the LMI and five skinfold based measures of lean mass. Hydrodensitometry, deuterium dilution, and dual energy x ray absorptiometry provided a criterion choice, four compartment (4C) measure of lean mass for validation purposes. Regression based measures of validity, derived for within-subject proportional changes through log transformation, included correlation coefficients and standard errors of the estimate.

RESULTS

The correlation between change scores for the LMI and 4C lean mass was moderate (0.37, 90% confidence interval -0.01 to 0.66) and similar to the correlations for the other practical measures of lean mass (range 0.26 to 0.42). Standard errors of the estimate for the practical measures were in the range of 2.8-2.9%. The LMI correctly identified the direction of change in 4C lean mass for 14 of the 20 athletes, compared with 11 to 13 for the other practical measures of lean mass.

CONCLUSIONS

The LMI is probably as good as other skinfold based measures for tracking lean mass and is theoretically more appropriate. Given the impracticality of the 4C criterion measure for routine field use, the LMI may offer a convenient alternative for monitoring physique changes, provided its utility is established under various conditions.

Physique traits of lightweight rowers and their relationship to competitive success

OBJECTIVES

Physique traits and their relationship to competitive success were assessed amongst lightweight rowers competing at the 2003 Australian Rowing Championships.

METHODS

Full anthropometric profiles were collected from 107 lightweight rowers (n = 65 males, n = 45 females) competing in the Under 23 and Open age categories. Performance assessments were obtained for 66 of these rowers based on results in the single sculls events. The relationship between physique traits and competitive success was then determined.

RESULTS

Lower body fat (heat time estimate -8.4 s kg(-1), p<0.01), greater total body mass (heat time estimate -4.4 s kg(-1), p = 0.03), and muscle mass (heat time estimate -10.2 s kg(-1), p<0.01) were associated with faster 2000 m heat times.

CONCLUSIONS

The more successful lightweight rowers were those who had lower body fat and greater total muscle mass.

Live high:train low increases muscle buffer capacity and submaximal cycling efficiency

This study investigated whether hypoxic exposure increased muscle buffer capacity (beta(m)) and mechanical efficiency during exercise in male athletes. A control (CON, n=7) and a live high:train low group (LHTL, n=6) trained at near sea level (600 m), with the LHTL group sleeping for 23 nights in simulated moderate altitude (3000 m). Whole body oxygen consumption (VO2) was measured under normoxia before, during and after 23 nights of sleeping in hypoxia, during cycle ergometry comprising 4 x 4-min submaximal stages, 2-min at 5.6 +/- 0.4 W kg(-1), and 2-min 'all-out' to determine total work and VO(2peak). A vastus lateralis muscle biopsy was taken at rest and after a standardized 2-min 5.6 +/- 0.4 W kg(-1) bout, before and after LHTL, and analysed for beta(m) and metabolites. After LHTL, beta(m) was increased (18%, P < 0.05). Although work was maintained, VO(2peak) fell after LHTL (7%, P < 0.05). Submaximal VO2 was reduced (4.4%, P < 0.05) and efficiency improved (0.8%, P < 0.05) after LHTL probably because of a shift in fuel utilization. This is the first study to show that hypoxic exposure, per se, increases muscle buffer capacity. Further, reduced VO2 during normoxic exercise after LHTL suggests that improved exercise efficiency is a fundamental adaptation to LHTL.

Beta-hydroxy-beta-methylbutyrate (HMB) supplementation and the promotion of muscle growth and strength

Beta-hydroxy beta-methylbutyrate (HMB), a metabolite of the essential amino acid leucine, is one of the latest dietary supplements promoted to enhance gains in strength and lean body mass associated with resistance training. Unlike anabolic hormones that induce muscle hypertrophy by increasing muscle protein synthesis, HMB is claimed to influence strength and lean body mass by acting as an anticatabolic agent, minimising protein breakdown and damage to cells that may occur with intense exercise. Research on HMB has recently tested this hypothesis, under the assumption that it may be the active compound associated with the anticatabolic effects of leucine and its metabolites. While much of the available literature is preliminary in nature and not without methodological concern, there is support for the claims made regarding HMB supplementation, at least in young, previously untrained individuals. A mechanism by which this may occur is unknown, but research undertaken to date suggests there may be a reduction in skeletal muscle damage, although this has not been assessed directly. The response of resistance trained and older individuals to HMB administration is less clear. While the results of research conducted to date appear encouraging, caution must be taken when interpreting outcomes as most manuscripts are presented in abstract form only, not having to withstand the rigors of peer review. Of the literature reviewed relating to HMB administration during resistance training, only 2 papers are full manuscripts appearing in peer reviewed journals. The remaining 8 papers are published as abstracts only, making it difficult to critically review the research. There is clearly a need for more tightly controlled, longer duration studies to verify if HMB enhances strength and muscular hypertrophy development associated with resistance training across a range of groups, including resistance trained individuals.

Beta-hydroxy beta-methylbutyrate (HMB) supplementation does not influence the urinary testosterone: epitestosterone ratio in healthy males

Six healthy, recreationally active, males undertook two weeks supplementation with beta-Hydroxy beta-Methylbutyrate (HMB). Supplementation was in capsule form with 3 g consumed each day in three even doses of 1 g at main meals. Mid stream urine samples were collected prior to, as well as, after one and two weeks of supplementation and subsequently analysed for testosterone and epitestosterone. The testosterone: epitestosterone ratio was not affected by 2 weeks of HMB supplementation (mean +/- SD baseline 1.02 +/- 0.68; week one 0.98 +/- 0.61; week two 0.92 +/- 0.62). Our results support the claim that supplementation with HMB at the doses recommended will not influence the urinary testosterone: epitestosterone ratio and thus not breach doping policies of the International Olympic Committee for exogenous testosterone or precursor administration.

Pancreatic enhancement and pulse sequence analysis using low-dose mangafodipir trisodium

OBJECTIVE

The purpose of this study was to evaluate pancreatic enhancement with low-dose mangafodipir trisodium (5 mumol/kg) using three different T1-weighted pulse sequences.

SUBJECTS AND METHODS

Fifteen patients, six of whom had proven focal pancreatic tumors, underwent T1-weighted gradient-recalled echo imaging, spin-echo imaging, and fat-suppressed spin-echo imaging before and 30 min after injection of 5 mumol/kg of mangafodipir trisodium. Region-of-interest measurements were obtained in the pancreas before and after contrast enhancement. Signal-to-noise ratios were calculated in all 15 patients. Contrast-to-noise ratios were calculated in the six patients with pancreatic tumors.

RESULTS

The signal-to-noise ratios of the pancreas increased after injection of mangafodipir trisodium on all three T1-weighted pulse sequences (p < .001). Enhanced fat-suppressed sequences (29 +/- 7.7) and gradient-recalled echo sequences (29 +/- 9.6) had the highest signal-to-noise ratios. Contrast-to-noise ratios between normal pancreatic tissue and pancreatic tumor also increased after contrast administration (p < .05) and were highest on the fat-suppressed (-9.6 +/- 4.0) pulse sequence.

CONCLUSION

Mangafodipir trisodium produced marked pancreatic enhancement at a dose of 5 mumol/kg for all three T1-weighted pulse sequences. The enhanced T1-weighted spin-echo fat-suppressed sequence showed the highest signal-to-noise and contrast-to-noise ratios.

MR imaging of pelvic lymph nodes in primary pelvic carcinoma with ultrasmall superparamagnetic iron oxide (Combidex): preliminary observations

The potential of ultrasmall superparamagnetic iron oxide (Combidex)-enhanced MRI of pelvic lymph nodes in patients with primary pelvic carcinoma is evaluated. Fifteen histologically classified lymph nodes in six patients with known primary pelvic cancer (four prostate; one rectum; one uterus) were evaluated with T2-weighted fast spin-echo (FSE) and T2*-weighted gradient-echo (GRE) MRI at 1.5T 12 to 48 hours after intravenous administration of Combidex at a dose of 1.7 mg Fe/kg. Quantitative image evaluation was performed by comparing signal intensity of individual nodes on pre- and postcontrast images. All patients proceeded to pelvic lymph-node biopsy or surgical dissection, where six were found to be benign and nine were malignant. Of the 15 lymph nodes, four nodes showed a decrease in signal intensity. Of these, three, in which signal loss was homogenous were benign, and one, in which the signal-intensity decrease was heterogeneous, was malignant (micrometastases). No signal change was noted in 11 of 15 lymph nodes of which three were benign (inflammatory) and eight were malignant. Combidex is a promising MR contrast agent for evaluating pelvic lymph nodes. Our preliminary observations suggest that the agent is most useful for classifying normal lymph nodes.

Mn-DPDP enhanced MR imaging of the liver: analysis of pulse sequence performance

AIM

To compare liver enhancement and lesion-liver contrast on T1-weighted (T1W) gradient recalled echo (GRE), spin-echo (SE) and fat-suppressed SE (FS-SE) pulse sequences at Manganese-DPDP (Mn-DPDP) enhanced magnetic resonance (MR) imaging of the liver. PATIENTS AND METHODS. Twenty-one patients with known liver lesions were administered 5 mumol/kg of Mn-DPDP. TIW GRE (78/2.3/80 degrees), SE and F-SE (300/12) images were obtained before and 15 min after Mn-DPDP. Signal/noise ratio (SNR) and lesion-liver contrast/noise ratio (CNR) were calculated for each pulse sequence.

RESULTS

Liver SNR (n = 21) and lesion-liver CNR (n = 10) increased significantly after Mn-DPDP on all three pulse sequences (P < 0.0001). Liver SNR was highest on the FS-SE and GRE pulse sequences (FS-SE = 43.8, GRE = 38.4, SE = 29.2). Lesion-liver CNR was highest on the FS-SE pulse sequence (FS-SE = -29.3, SE = -23.2, GRE = -19.8), which was significantly higher than the GRE pulse sequence (P < 0.05).

CONCLUSION

The T1-weighted fat-suppressed SE (FS-SE) pulse sequence provides highest liver enhancement and lesion-liver contrast and is recommended for Mn-DPDP enhanced MR imaging.

Endoscopic retrograde pancreatography: imaging findings

Endoscopic retrograde pancreatography (ERP) is commonly used in the diagnosis and management of pancreatic disorders. The aim of this pictorial essay is to provide an overview of the common appearances of normal anatomy, anatomic variants, and pancreatic diseases at ERP.

Blood-pool MR contrast material for detection and characterization of focal hepatic lesions: initial clinical experience with ultrasmall superparamagnetic iron oxide (AMI-227)

OBJECTIVE

AMI-227 is an ultrasmall superparamagnetic iron oxide colloid known to enhance tissue T1 and T2 relaxation rates. Animal studies show that AMI-227 has an estimated blood half-life of more than 200 min. In this study, we evaluated the clinical utility of AMI-227 as an MR contrast agent for detection and characterization of focal hepatic lesions, with MR imaging done while the contrast agent is in the intravascular space (blood-pool phase).

SUBJECTS AND METHODS

Twenty-two patients with known or suspected focal hepatic masses underwent T1- and T2-weighted MR imaging of the liver at 1.5 T before and immediately after drip infusion of AMI-227 at doses of 0.8, 1.1, or 1.7 mg Fe/kg. Unenhanced and contrast-enhanced images were analyzed qualitatively (lesion detection and tissue characterization) and quantitatively (lesion-liver contrast-to-noise ratio).

RESULTS

AMI-227 enhanced signal in normal liver and blood vessels on T1-weighted images and decreased signal in these tissues on T2-weighted images. Qualitatively and quantitatively, lesion-liver contrast was increased for solid tumors (non-cyst and nonhemangioma) at all three doses (p < .02) on both T1- and T2-weighted images. Differentiation between blood vessels and small lesions was easier on contrast-enhanced images, which allowed increased confidence in excluding lesions. Unique enhancement patterns were noted for hemangiomas, solid tumors, and cysts.

CONCLUSION

Initial clinical experience suggests that AMI-227 is a useful contrast agent for detection and characterization of focal hepatic lesions.

Free fibular bone grafting for femoral neck fractures: precise graft placement using a 'cannulated screw' technique

Use of the fibula as a free bone graft has been advocated in the treatment of femoral neck fractures, either fresh or where there is established non-union. There is debate about the best surgical technique; we present ours, which is simple and trouble-free.

Antibacterial activity of ciprofloxacin in conventional tests and in a model of bacterial cystitis

In conventional in vitro tests and an experimental bladder model ciprofloxacin proved very active against 103 strains of enterobacteria isolated from infected urine. Nalidixic acid-resistant strains were less susceptible to ciprofloxacin than nalidixic acid-sensitive strains, and the activity of the drug was reduced under acid conditions. Nevertheless, all strains were inhibited by 4 mg/l of ciprofloxacin at pH 5.5. Streptococcus spp., Staphylococcus aureus, Pseudomonas aeruginosa and Bacteroides spp. were less susceptible than enterobacteria, although most strains were inhibited by a therapeutically achievable concentration of 2 mg/l. Under conditions simulating the treatment of bacterial cystitis, changing concentrations of ciprofloxacin well within levels achievable in urine inhibited dense bacterial cultures for periods exceeding 24 hours, and surviving bacteria did not exhibit any reduction in susceptibility.

Detection of penicillin tolerance in streptococci

"Tolerance" to penicillin in streptococci was investigated by two different techniques. Of 70 strains examined, 35 appeared tolerant in conventional titrations and 31 appeared tolerant when tested by a recently-described disc method. There was 88% agreement between the two methods, but the disc test failed to detect tolerance shown by titrations in six strains of streptococci, including three beta-haemolytic strains belonging to Lancefield's group D. A significant relationship was observed between tolerance and Eagle's optimum dosage effect: 71% of tolerant strains examined displayed the Eagle effect, whereas only 17% of non-tolerant strains exhibited the effect.