Concussion-Related Biomarker Variations in Retired Rugby Players and Implications for Neurodegenerative Disease Risk: The UK Rugby Health Study.

The health and well-being of retired rugby union and league players, particularly regarding the long-term effects of concussions, are of major concern. Concussion has been identified as a major risk factor for neurodegenerative diseases, such as Alzheimer's and Amyotrophic Lateral Sclerosis (ALS), in athletes engaged in contact sports. This study aimed to assess differences in specific biomarkers between UK-based retired rugby players with a history of concussion and a non-contact sports group, focusing on biomarkers associated with Alzheimer's, ALS, and CTE. We randomly selected a sample of male retired rugby or non-contact sport athletes (n = 56). The mean age was 41.84 ± 6.44, and the mean years since retirement from the sport was 7.76 ± 6.69 for participants with a history of substantial concussions (>5 concussions in their career) (n = 30). The mean age was 45.75 ± 11.52, and the mean years since retirement was 6.75 ± 4.64 for the healthy controls (n = 26). Serum biomarkers (t-tau, RBP-4, SAA, Nf-L, and retinol), plasma cytokines, and biomarkers associated with serum-derived exosomes (Aß42, p-tau181, p-tau217, and p-tau231) were analyzed using validated commercial ELISA assays. The results of the selected biomarkers were compared between the two groups. Biomarkers including t-tau and p-tau181 were significantly elevated in the history of the substantial concussion group compared to the non-contact sports group (t-tau: p < 0.01; p-tau181: p < 0.05). Although between-group differences in p-tau217, p-tau231, SAA, Nf-L, retinol, and Aß42 were not significantly different, there was a trend for higher levels of Aß42, p-tau217, and p-tau231 in the concussed group. Interestingly, the serum-derived exosome sizes were significantly larger (p < 0.01), and serum RBP-4 levels were significantly reduced (p < 0.05) in the highly concussed group. These findings indicate that retired athletes with a history of multiple concussions during their careers have altered serum measurements of exosome size, t-tau, p-tau181, and RBP-4. These biomarkers should be explored further for the prediction of future neurodegenerative outcomes, including ALS, in those with a history of concussion.

Blood-Based Biomarkers in the Diagnosis of Chronic Traumatic Encephalopathy: Research to Date and Future Directions.

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease consistently associated with repetitive traumatic brain injuries (TBIs), which makes multiple professions, such as contact sports athletes and the military, especially susceptible to its onset. There are currently no approved biomarkers to diagnose CTE, thus it can only be confirmed through a post-mortem brain autopsy. Several imaging and cerebrospinal fluid biomarkers have shown promise in the diagnosis. However, blood-based biomarkers can be more easily obtained and quantified, increasing their clinical feasibility and potential for prophylactic use. This article aimed to comprehensively review the studies into potential blood-based biomarkers of CTE, discussing common themes and limitations, as well as suggesting future research directions. While the interest in blood-based biomarkers of CTE has recently increased, the research is still in its early stages. The main issue for many proposed biomarkers is their lack of selectivity for CTE. However, several molecules, such as different phosphorylated tau isoforms, were able to discern CTE from different neurodegenerative diseases. Further, the results from studies on exosomal biomarkers suggest that exosomes are a promising source of biomarkers, reflective of the internal environment of the brain. Nonetheless, more longitudinal studies combining imaging, neurobehavioral, and biochemical approaches are warranted to establish robust biomarkers for CTE.

Accuracy, Linearity and Precision of Spine QCT vBMD Phantom Measurements for Different Brands of CT Scanner: A Multicentre Study.

We describe a multicenter study using the European Spine Phantom (ESP) to compare the accuracy, linearity and precision of QCT measurements of spine vBMD between different brands of scanner, different models of the same brand and identical units of the same model. Ten scans of the same ESP with repositioning were performed on forty CT scanners from five manufacturers in different hospitals across China, all calibrated with the Mindways QCT system. The three ESP vertebral bodies simulating low (L1), medium (L2) and high (L3) vBMD and their average (L1-3 vBMD) were compared with phantom values. Linearity was assessed using the standard error of the estimate derived from linear regression. Precision errors were expressed as the standard deviation of the ten measurements on each scanner. Median (IQR) vBMD over all forty CT scanners compared with phantom values were: L1: 52.2 (49.9-56.4) vs 51.0; L2: 104.4 (101.2-108.6) vs 102.2; L3: 201.4 (195.0-204.9) vs 200.4; L1-3: 119.3 (116.6-123.2) vs 117.9 mg/cm3. Statistically significant differences in L1-3 vBMD were found between different brands (p= 0.005) and between different models of the same brand and identical units of the same model (both p< 0.001). Cross-calibration using linear regression gave a good fit for all forty systems with a median standard error of the estimate of 1.7 mg/cm3. The median precision error for L1-3 vBMD was 0.61 mg/cm3. Statistically significant differences in spine vBMD measurements between different scanners reinforce the importance of cross-calibration in multi-center studies. Cross-calibration can be reliably performed using linear regression equations.

Lean Mass, Muscle Strength, and Muscle Quality in Retired Rugby Players: The UK Rugby Health Project.

Although athletes from sports such as rugby have greater lean mass and strength during their playing careers, little is known about these characteristics post-retirement. Therefore, this study investigated lean mass, strength, and muscle quality in retired elite and amateur rugby players and non-contact athletes. Retired elite male rugby players (n=42, 43.9±10.3 y; 101.1±13.4 kg; 1.82±0.09 m), amateur rugby players (n=46, 48.0±10.5 y; 98.9±16.6 kg; 1.79±0.07 m) and non-contact athletes (n=30, 51.3±12.5 y; 91.3±13.4 kg; 1.79±0.07 m) received one total body dual-energy X-ray absorptiometry assessment of appendicular lean mass (ALM) and ALM index (ALMI). Grip strength was measured, and muscle quality (grip strength/unit of arm lean mass) was calculated. Sarcopenia was identified as ALMI<7.23 kg/m2 and handgrip strength<37.2 kg. Total lean mass, ALM and grip strength were greater in the elite rugby compared to amateur rugby and non-contact groups (p<0.01). There were no significant differences in muscle quality or sarcopenia prevalence. Retired elite rugby players had greater lean mass and grip strength than amateur rugby and non-contact athletes, although muscle quality was similar. The greater lean mass and strength might reflect genetic influences or previous participation in a highly physical sport.

Vertebral Anomalies in Retired Rugby Players and the Impact on Bone Density Calculation of the Lumbar Spine.

Dual energy X-ray absorptiometry (DXA) lumbar spine bone mineral density (BMD) measurements are subject to artificial elevation in the presence of structural abnormalities that are more common with age and injury, including osteoarthritis, fracture and osteophytes. The aims of this study were to investigate the presence of vertebral abnormalities on DXA scans in retired rugby players and a nonrugby control group, and to explore the effect of vertebral exclusion on the BMD diagnostic outcome. Eigty-seven male retired rugby players and 51 non-rugby controls from the UK Rugby Health Project participated in the study. Lumbar spine, total hip and femoral neck BMD were measured by DXA and scans were analyzed pre and post exclusion of anomalous vertebrae. Data were analyzed by age group to enable application of T-scores (≥50 y) and Z-scores (<50 y). From 138 lumbar spine scans, 66 required adjustment. One hundred twenty-two vertebral exclusions were made, and 12 lumbar spine scans (10 in retired rugby athletes) were un-reportable (<2 evaluable vertebrae). Vertebral exclusion significantly lowered lumbar spine BMD across all groups (p<0.01) and lowered the overall lowest T/Z-score. This effect was more pronounced in rugby groups (age <50 y, p < 0.001; age ≥50 y, p = 0.031) than in the control groups (age <50y, p = 0.125; age ≥50 y, p = 0.250). Vertebral abnormalities detected on lumbar spine scans, were highly prevalent and impacted final the T/Z-score in this cohort of retired rugby players. Current guidelines recommend exclusion of abnormalities from lumbar spine scans in adults aged ≥50 years. Our findings suggest that vertebral exclusions should also be applied to lumbar spine scans performed in those aged <50 years, particularly in former contact sports athletes, given their high risk for vertebral deformity.

Increases in DXA-Derived Visceral Fat Across One Season in Professional Rugby Union Players: Importance of Visceral Fat Monitoring in Athlete Body Composition Assessment.

INTRODUCTION: In rugby, the average player body mass has increased by approximately 25% since 1955. Visceral adipose tissue (VAT) is associated with low grade inflammation, and chronic diseases, such as cardiovascular diseases. The purpose of this study was to investigate changes in VAT in relation to other indices of body composition, across 1 season in professional rugby. METHODOLOGY: One hundred and sixteen male rugby union players' (age: 26.2 ± 4.6 y, BMI: 29.40 ± 3.22 kg.m2) total body composition dual energy X-ray absorptiometry scans from 4 time points across the season (baseline, preseason, midseason, and postseason) were analyzed. Players were grouped by playing position, forwards (n = 65) and backs (n = 51). Players followed individually tailored diet plans. RESULTS: Mean baseline VAT was 404.67 ± 229.43 g (forwards: 469.36 ± 263.16 g, backs: 311.40 ± 121.15 g). Total mass, lean mass, body fat percentage (%BF), and VAT were greater in forwards than backs at all 4 timepoints. Meaningful increases in VAT across the season, were observed in 37.5% of backs and 53.6% of forwards. There was a positive linear relationship between lean mass and total mass, up to 116.04 kg total mass. Beyond this threshold, lean mass accumulation reduced and %BF and VAT mass increased. There were significant relationships between %BF, VAT, and BMI (p < 0.001), but no physiological relevant pattern was discerned. CONCLUSIONS: Despite regular high-intensive exercise and individually tailored dietary control across a professional rugby season, players from both playing positions demonstrated increases in VAT, although the cause remains unknown. Our findings indicate the importance of monitoring VAT in athletes alongside standard measures of body composition. Additionally, our findings suggest there may be an upper threshold of body mass beyond which lean mass may not increase further and instead %BF and VAT are more likely to accumulate. Further research is required to identify how increasing player size may impact long-term cardiometabolic health given the known links between VAT and cardiometabolic risk.

Body Mass and Body Composition Changes over 7 Years in a Male Professional Rugby Union Team.

The purpose of this study was to investigate longitudinal body mass and body composition changes in one professional rugby union team (n=123), (i) according to position [forwards (n=58) versus backs (n=65)], analysis of players with 6 consecutive seasons of DXA scans (n=21) and, (iii) to examine differences by playing status [academy and international], over 7 years. Players [mean age: 26.8 y, body mass index: 28.9+kg.m2] received DXA scans at fourtime points within each year. A modest (but non-significant) increase in mean total mass (0.8 kg) for professional players was reflected by increased lean mass and reduced body fat mass. At all-time points, forwards had a significantly greater total mass, lean mass and body fat percentage compared to backs (p<0.05). Academy players demonstrated increased total and lean mass and decreased body fat percentage over the first 3 years of senior rugby, although this was not significant. Senior and academy international players had greater lean mass and lower body fat percentage (p<0.05) than non-international counterparts. Despite modest increases in total mass; reflected by increased lean mass and reduced fat mass, no significant changes in body mass or body composition, irrespective of playing position were apparent over 7 years.

Short-Term Precision Error of Body Composition Assessment Methods in Resistance-Trained Male Athletes.

Athletic populations require high-precision body composition assessments to identify true change. Least significant change determines technical error via same-day consecutive tests but does not integrate biological variation, which is more relevant for longitudinal monitoring. The aim of this study was to assess biological variation using least significant change measures from body composition methods used on athletes, including surface anthropometry (SA), air displacement plethysmography (BOD POD), dual-energy X-ray absorptiometry (DXA), and bioelectrical impedance spectroscopy (BIS). Thirty-two athletic males (age = 31 ± 7 years; stature = 183 ± 7 cm; mass = 92 ± 10 kg) underwent three testing sessions over 2 days using four methods. Least significant change values were calculated from differences in Day 1 Test 1 versus Day 1 Test 2 (same-day precision), as well as Day 1 Test 1 versus Day 2 (consecutive-day precision). There was high agreement between same-day and consecutive-day fat mass and fat-free mass measurements for all methods. Consecutive-day precision error in comparison with the same-day precision error was 50% higher for fat mass estimates from BIS (3,607 vs. 2,331 g), 25% higher from BOD POD (1,943 vs. 1,448 g) and DXA (1,615 vs. 1,204 g), but negligible from SA (442 vs. 586 g). Consecutive-day precision error for fat-free mass was 50% higher from BIS (3,966 vs. 2,276 g) and SA (1,159 vs. 568 g) and 25% higher from BOD POD (1,894 vs. 1,450 g) and DXA (1,967 vs. 1,461 g) than the same-day precision error. Precision error in consecutive-day analysis considers both technical error and biological variation, enhancing the identification of small, yet significant changes in body composition of resistance-trained male athletes. Given that change in physique is likely to be small in this population, the use of DXA, BOD POD, or SA is recommended.

Age- and sex-specific reference intervals for visceral fat mass in adults.

BACKGROUND/OBJECTIVES: Dual-energy X-ray absorptiometry (DXA) is becoming a method of choice for the assessment of visceral adipose tissue (VAT) but the lack of robust reference ranges presents a challenge to the interpretation of VAT in clinical practice, research settings, and the athletic environment. The objective of this study was to develop age- and sex-specific reference intervals for DXA-derived VAT mass. SUBJECTS/METHODS: The reference group comprised 3219 adults (1886 general population, 42% women; 1333 athletes, 11% women) in the United Kingdom, aged 18-83 years. Total body scans were performed using a GE Lunar iDXA and VAT analyses were enabled through Corescan software (Encore version 15.0). Age-specific reference ranges were derived in samples stratified by sex and general population/ athlete status. We modelled the mean and SD of Box-Cox transformed VAT mass as a function of age with a generalised least squares method using fractional polynomials (Stata® -xrigls- program). Centile values were then back-transformed to provide reference intervals on the original scale. RESULTS: In general population samples, average VAT mass increases with age up until around 65-70 years, and then begins to decline at older ages, though data are relatively sparse at the upper end of the age range. In athletes, on average, VAT mass increases with advancing age in men and women. Both 95 and 98% reference ranges are presented in 5-year increments in all samples, and we provide equations to enable the calculation of any centile, for any age within the range. CONCLUSIONS: These reference data can aid the interpretation of VAT mass specific to an individual's sex, age, and athletic status, increasing the utility and applicability of DXA-derived VAT assessments. Additional research is needed in adults over 65 years and female athletes, with different DXA devices, across different ethnic groups and specific sports.

Bone Mineral Density Precision for Individual and Combined Vertebrae Configurations From Lumbar Spine Dual-Energy X-Ray Absorptiometry Scans.

The accurate interpretation of repeat DXA scan measurements and the understanding of what constitutes a true and meaningful change require knowledge of measurement error (precision) and least significant change. The interpretation of lumbar spine bone mineral density in particular can be confounded by artefacts and as such, the International Society for Clinical Densitometry (ISCD) recommends exclusion of individual vertebrae if they are affected by local structural change or an artefact. The aim of this study was to determine the precision of bone mineral density measures of individual and various configurations of vertebrae from PA lumbar spine scans. The study group comprised of 30 women (age 36.3 ± 6.5 years; height: 165.2 ± 5.7 cm; weight: 67.7 ± 12.6 kg) who each received 2 consecutive anterior-posterior lumbar spine scans (Lunar iDXA, GE Healthcare, Madison, WI), with repositioning. Precision errors varied by individual vertebrae and by different configurations of vertebrae but all were within the ISCD acceptable range of precision. For vertebrae configurations containing at least 2 vertebrae, precision error ranged from 0.005 to 0.008 RMS-SD (0.44%-0.70% CV). Of the individual vertebrae, the lowest precision error was observed at L4, and from the different configurations, for L2L3L4 and L1L2L3L4. In conclusion, this study group demonstrated excellent precision for BMD measurements of individual and various configurations of L1-L4 vertebrae using the GE Lunar iDXA densitometer.

Exercise Interventions for Preventing and Treating Low Bone Mass in the Forearm: A Systematic Review and Meta-analysis.

OBJECTIVE: To examine the effectiveness of exercises for improving forearm bone mass. DATA SOURCES: MEDLINE, EMBASE, CINAHL, AMED, Web of Science, and Cochrane CENTRAL were searched from their inception until December 2018. STUDY SELECTION: Eligibility included adults undertaking upper limb exercise interventions (≥12wk) to improve bone mass. DATA EXTRACTION: Screening of titles, abstracts, and full texts and data extraction were undertaken independently by pairs of reviewers. Included studies were quality appraised using Cochrane risk of bias tool. DATA SYNTHESIS: Exercise interventions were classified into "resistance training" of high or low intensity (HIRT/LIRT, respectively) or "impact." Random-effects meta-analysis of the percentage change in forearm bone mass from baseline was conducted. Twenty-six studies were included in the review, of which 21 provided suitable data for meta-analysis. Methodological quality ranged from "low" to "unclear" risk of bias. Exercise generally led to increases (moderate-quality evidence) in forearm bone mass (standard mean difference [SMD], 1.27; 95% CI, 0.66-1.88; overall effect Z value=4.10; P<.001). HIRT (SMD, 1.00; 95% CI, 0.37-1.62; Z value=3.11; P=.002), and LIRT (SMD, 2.36; 95% CI, 0.37-4.36; Z value=2.33; P<.001) led to moderate increases in forearm bone mass. Improvements resulting from impact exercises (SMD, 1.12; 95% CI, -1.27 to 3.50; Z value=0.92; P=.36) were not statistically significant (low-quality evidence). CONCLUSIONS: There is moderate-quality evidence that exercise is effective for improving forearm bone mass. There is moderate-quality evidence that upper body resistance exercise (HIRT/LIRT) promotes forearm bone mass but low-quality evidence for impact exercise. Current evidence is equivocal regarding which exercise is most effective for improving forearm bone mass.

Same-Day Vs Consecutive-Day Precision Error of Dual-Energy X-Ray Absorptiometry for Interpreting Body Composition Change in Resistance-Trained Athletes.

The application of dual-energy X-ray absorptiometry (DXA) in sport science settings is gaining popularity due to its ability to assess body composition. The International Society for Clinical Densitometry (ISCD) recommends application of the least significant change (LSC) to interpret meaningful and true change. This is calculated from same-day consecutive scans, thus accounting for technical error. However, this approach does not capture biological variation, which is pertinent when interpreting longitudinal measurements, and could be captured from consecutive-day scans. The aims of this study were to investigate the impact short-term biological variation has on LSC measures, and establish if there is a difference in precision based on gender in a resistance-trained population. Twenty-one resistance-trained athletes (age: 30.6 ± 8.2 yr; stature: 174.2 ± 7.2 cm; mass: 74.3 ± 11.6 kg) with at least 12 mo consistent resistance training experience, underwent 2 consecutive DXA scans on 1 d of testing, and a third scan the day before or after. ISCD-recommended techniques were used to calculate same-day and consecutive-day precision error and LSC values. There was high association between whole body (R2 = 0.98-1.00) and regional measures (R2 = 0.95-0.99) for same-day (R2 = 0.98-1.00), and consecutive-day (R2 = 0.95-0.98) measurements. The consecutive-day precision error, in comparison to same-day precision error, was significantly different (p < 0.05), and almost twice as large for fat mass (1261 g vs 660 g), and over 3 times as large for lean mass (2083 g vs 617 g), yet still remained within the ISCD minimum acceptable limits for DXA precision error. No whole body differences in precision error were observed based on gender. When tracking changes in body composition, the use of precision error and LSC values calculated from consecutive-day analysis is advocated, given this takes into account both technical error and biological variation, thus providing a more accurate indication of true and meaningful change.

Muscle quality as a complementary prognostic tool in conjunction with sarcopenia assessment in younger and older individuals.

PURPOSE: This pilot study investigated differences in lean tissue mass, muscle strength, muscle quality (strength per unit of muscle mass; MQ), and functional performance in healthy younger and older individuals. The most robust predictors of appendicular lean mass (ALM) were then determined in each group. METHODS: Fifty younger (18-45 years) and 50 older (60-80 years) participants completed tests of upper and lower body strength alongside body composition by dual-energy X-ray absorptiometry from which upper- and lower-body MQ were estimated. Available cut-points for older people were used to determine low upper-body MQ in both groups. Low lower-body MQ was determined as at least two standard deviations below the mean of the younger group. Functional performance was assessed by gait speed. Sarcopenia was identified using two established definitions. RESULTS: Upper and lower body strength, ALM, lower-body MQ and gait speed were significantly higher in the younger group (all p < 0.002). Sarcopenia was identified in 2-4% of the older group. Low upper-body MQ was evident in 32% and 42% of the younger and older group, respectively. Low lower-body MQ was observed in 4% of younger participants, and 50% of older participants. In both groups, the most robust predictors of ALM were upper and lower body strength (young R2 = 0.74, 0.82; older R2 = 0.68, 0.72). CONCLUSIONS: Low MQ despite low prevalence rates of sarcopenia in both groups suggests a need for age-specific MQ cut-points. Muscle quality assessments might be useful complementary prognostic tools alongside existing sarcopenia definitions.

Are changes in running economy associated with changes in performance in runners? A systematic review and meta-analysis.

Improvements in running economy (RE) are thought to lead to improvements in running performance (P). Multiple interventions have been designed with the aim of improving RE in middle and long-distance runners. The aim of this study was to assess the effect of interventions of at least 2-weeks' duration on RE and P and to determine whether there is a relationship between changes in RE (ΔRE) and changes in running performance (ΔP). A database search was carried out in Web of Science, Scopus and SPORTDiscus. In accordance with a PRISMA checklist 10 studies reporting 12 comparisons between interventions and controls were included in the review. There was no correlation between percentage ΔRE and percentage ΔP (r = 0.46, P = 0.936, 12 comparisons). There was a low risk of reporting bias but an unclear risk of bias for other items. Meta-analyses found no statistically significant differences between interventions and controls for RE (SMD (95% CI) = -0.37 (-1.43, 0.69), 204 participants, p = 0.49) or for P (SMD (95% CI) = -0.65 (-26.02, 24.72, 204 participants, p = 0.99). There is a need for studies of greater statistical power, methodological quality, duration and homogeneity of intervention and population. Standardised measures of performance and greater control over non-intervention training are also required.

High Prevalence and Magnitude of Rapid Weight Loss in Mixed Martial Arts Athletes.

The practice of rapid weight loss (RWL) in mixed martial arts (MMA) is an increasing concern but data remain scarce. The aim of this study was to investigate the prevalence, magnitude, methods, and influencers of RWL in professional and amateur MMA athletes. MMA athletes (N = 314; 287 men and 27 women) across nine weight categories (strawweight to heavyweight), completed a validated questionnaire adapted for this sport. Sex-specific data were analyzed, and subgroup comparisons were made between athletes competing at professional and amateur levels. Most athletes purposefully reduced body weight for competition (men: 97.2%; women: 100%). The magnitude of RWL in 1 week prior to weigh-in was significantly greater for professional athletes compared with those competing at amateur level (men: 5.9% vs. 4.2%; women: 5.0% vs. 2.1% of body weight; p < .05). In the 24 hr preceding weigh-in, the magnitude of RWL was greater at professional than amateur level in men (3.7% vs. 2.5% of body weight; p < .05). Most athletes "always" or "sometimes" used water loading (72.9%), restricting fluid intake (71.3%), and sweat suits (55.4%) for RWL. Coaches were cited as the primary source of influence on RWL practices (men: 29.3%; women: 48.1%). There is a high reported prevalence of RWL in MMA, at professional and amateur levels. Our findings, constituting the largest inquiry to date, call for urgent action from MMA organizations to safeguard the health and well-being of athletes competing in this sport.

Preseason Body Composition Adaptations in Elite White and Polynesian Rugby Union Athletes.

During preseason training, rugby union (RU) athletes endeavor to enhance physical performance characteristics that are aligned with on-field success. Specific physique traits are associated with performance; therefore body composition assessment is routinely undertaken in elite environments. This study aimed to quantify preseason physique changes in elite RU athletes with unique morphology and divergent ethnicity. Twenty-two White and Polynesian professional RU athletes received dual-energy X-ray absorptiometry assessments at the beginning and conclusion of an 11-week preseason. Interactions between on-field playing position and ethnicity in body composition adaptations were explored, and the least significant change model was used to evaluate variations at the individual level. There were no combined interaction effects with the variables position and ethnicity and any body composition measure. After accounting for baseline body composition, Whites gained more lean mass during the preseason than Polynesians (2,425 ± 1,303 g vs. 1,115 ± 1,169 g; F = 5.4, p = .03). Significant main effects of time were found for whole body and all regional measures with fat mass decreasing (F = 31.1-52.0, p < .01), and lean mass increasing (F = 12.0-40.4, p < .01). Seventeen athletes (nine White and eight Polynesian) had a reduction in fat mass, and eight athletes (six White and two Polynesian) increased lean mass. This study describes significant and meaningful physique changes in elite RU athletes during a preseason period. Given the individualized approach applied to athletes in regard to nutrition and conditioning interventions, a similar approach to that used in this study is recommended to assess physique changes in this population.

Effect of Hand Positioning on DXA Total and Regional Bone and Body Composition Parameters, Precision Error, and Least Significant Change.

Dual-energy X-ray absorptiometry (DXA) body composition measurements are performed in both clinical and research settings for estimations of total and regional fat mass, lean tissue mass, and bone mineral content. Subject positioning influences precision and positioning instructions vary between manufacturers. The aim of the study was to determine the effect of hand position and scan mode on regional and total body bone and body composition parameters and determine protocol-specific body composition precision errors. Thirty-eight healthy subjects (men; mean age: 27.1 ± 12.1 yr) received 4 consecutive total body GE-Lunar iDXA (enCORE v 15.0) scans with re-positioning, and scan mode was dependent on body size. Twenty-three subjects received scans in standard mode and 15 received scans in thick scan modes. Two scans per subject were conducted with subject hands prone and 2 with hands mid-prone. The precision error (root mean squared standard deviation; percentage coefficient of variation) and least significant change for each protocol were determined using the International Society for Clinical Densitometry calculator. Hands placed in the mid-prone position increased arm bone mineral density (BMD) (standard mode: 0.185 g*cm-2, thick mode: 0.265 g*cm-2; p < 0.05), total body BMD (standard mode: 0.051 g*cm-2, thick mode: 0.069 g*cm-2; p < 0.001), and total body BMD Z-score (standard mode: 0.5. thick mode: 0.7; p < 0.001). This was due to reductions in bone area and bone mineral content. In standard mode, hands mid-prone reduced fat mass (0.05 kg, p < 0.05) and increased lean mass (0.11 kg, p < 0.05). There were no differences in body composition for thick mode scans. Hands mid-prone reduced lean mass precision error at the arms, trunk, and total body (p < 0.01). DXA clinical and research centers are advised to maintain consistency in their hand positioning and scan mode protocols, and consideration should be given to the hand positioning used for reference data. As a best practice recommendation, published DXA-based studies and reports for clinic-based total body assessments should ensure that subject positioning is fully described.

Cross Calibration of the GE Prodigy and iDXA for the Measurement of Total and Regional Body Composition in Adults.

Dual-energy X-ray absorptiometry (DXA) body composition measurements are widely performed in both clinical and research settings, and enable the rapid and noninvasive estimation of total and regional fat and lean mass tissues. DXA upgrading can occur during longitudinal monitoring or study; therefore, cross calibration of old and new absorptiometers is required. We compared soft tissue estimations from the GE Prodigy (GE Healthcare, Madison, WI) with the more recent iDXA (GE Healthcare) and developed translational equations to enable Prodigy values to be converted to iDXA values. Eighty-three males and females aged 20.1-63.3 yr and with a body mass index range of 17.0-34.4 kg/m2 were recruited for the study. Fifty-nine participants (41 females and 18 males) comprised the cross-calibration group and 24 (14 females and 10 males) comprised the validation group. Total body Prodigy and iDXA scans were performed on each subject within 24 h. Predictive equations for total and regional soft tissue parameters were derived from linear regression of the data. Measures of lean and fat tissues were highly correlated (R2 = 0.95-0.99), but significant differences and variability between machines were identified. Bland-Altman analysis revealed significant biases for most measures, particularly for arm, android, and gynoid fat mass (12.3%-22.7%). The derived translational equations reduced biases and differences for most parameters, although limits of agreement exceeded iDXA least significant change. In conclusion, variability in soft tissue estimates between the Prodigy and iDXA were detected, supporting the need for translational equations in longitudinal monitoring. The derived equations are suitable for group analysis but not individual analysis.

Interpretation of Dual-Energy X-Ray Absorptiometry-Derived Body Composition Change in Athletes: A Review and Recommendations for Best Practice.

Dual-energy X-ray absorptiometry (DXA) is a medical imaging device which has become the method of choice for the measurement of body composition in athletes. The objectives of this review were to evaluate published longitudinal DXA body composition studies in athletic populations for interpretation of "meaningful" change, and to propose a best practice measurement protocol. An online search of PubMed and CINAHL via EBSCO Host and Web of Science enabled the identification of studies published until November 2016. Those that met the inclusion criteria were reviewed independently by 2 authors according to their methodological quality and interpretation of body composition change. Twenty-five studies published between 1996 and November 2016 were reviewed (male athletes: 13, female athletes: 3, mixed: 9) and sample sizes ranged from n = 1 to 212. The same number of eligible studies was published between 2013 and 2016, as over the 16 yr prior (between 1996 and 2012). Seven did not include precision error, and fewer than half provided athlete-specific precision error. There were shortfalls in the sample sizes on which precision estimates were based and inconsistencies in the level of pre-scan standardization, with some reporting full standardization protocols and others reporting only single (e.g., overnight fast) or no control measures. There is a need for standardized practice and reporting in athletic populations for the longitudinal measurement of body composition using DXA. Based on this review and those of others, plus the official position of the International Society for Clinical Densitometry, our recommendations and protocol are proposed as a guide to support best practice.

Bone Density and Cross-sectional Geometry of the Proximal Femur Are Bilaterally Elevated in Elite Cricket Fast Bowlers.

The skeleton of a cricket fast bowler is exposed to a unique combination of gravitational and torsional loading in the form of substantial ground reaction forces delivered through the front landing foot, and anterior-posterior shear forces mediated by regional muscle contractions across the lumbo-pelvic region. The objectives of this study were to compare the hip structural characteristics of elite fast bowlers with recreationally active age-matched controls, and to examine unilateral bone properties in fast bowlers. Dual-energy X-ray absorptiometry of the proximal femur was performed in 26 elite male fast bowlers and 26 normally active controls. Hip structural analysis (GE Lunar; enCORE version 15.0) determined areal bone mineral density (BMD) of the proximal femur, and cross-sectional area, section modulus (Z), cross-sectional moment of inertia, and femoral strength index at the narrow region of the femoral neck. Mean femoral neck and trochanter BMD were greater in fast bowlers than in controls (p <0.001). All bone geometry properties, except for cross-sectional moment of inertia, were superior in fast bowlers (p <0.05) following adjustment for height and lean mass. There were no asymmetries in BMD or bone geometry when considering leg dominance of the fast bowlers (p > 0.05). Elite fast bowlers have superior bone characteristics of the proximal femur, with results inferring enhanced resistance to axial compression (cross-sectional area), and bending (Z) forces, and enhanced strength to withstand a fall impact as indicated by their higher femoral strength index. No asymmetries in hip bone properties were identified, suggesting that both torsional and gravitational loading offer significant osteogenic potential.