Free-living competitive racewalkers and runners with energy availability estimates of <35 kcal·kg fat-free mass-1·day-1 exhibit peak serum progesterone concentrations indicative of ovulatory disturbances: a pilot study.

Introduction: The release of luteinising hormone (LH) before ovulation is disrupted during a state of low energy availability (EA). However, it remains unknown whether a threshold EA exists in athletic populations to trigger ovulatory disturbances (anovulation and luteal phase deficiency) as indicated by peak/mid-luteal serum progesterone concentration (Pk-PRG) during the menstrual cycle. Methods: We assessed EA and Pk-PRG in 15 menstrual cycles to investigate the relationship between EA and Pk-PRG in free-living, competitive (trained-elite) Guatemalan racewalkers (n = 8) and runners (n = 7) [aged: 20 (14-41) years; post-menarche: 5 (2-26) years; height: 1.53 ± 0.09 m; mass: 49 ± 6 kg (41 ± 5 kg fat-free mass "FFM")]. EA was estimated over 7 consecutive days within the follicular phase using food, training, and physical activity diaries. A fasted blood sample was collected during the Pk-PRG period, 6-8 days after the LH peak, but before the final 2 days of each cycle. Serum progesterone concentration was quantified using electrochemiluminescence immunoassay. Results: Participants that reported an EA of <35 kcal·kg FFM-1·day-1 (n = 7) exhibited ovulatory disturbances (Pk-PRG ≤9.40 ng·mL-1). Athletes with EA ≥36 kcal·kg FFM-1·day-1 (n = 8) recorded "normal"/"potentially fertile" cycles (Pk-PRG >9.40 ng·mL-1), except for a single racewalker with the lowest reported protein intake (1.1 g·kg body mass-1·day-1). EA was positively associated with Pk-PRG [r(9) = 0.79, 95% confidence interval (CI): 0.37-0.94; p = 0.003; 1 - ß = 0.99] after excluding participants (n = 4) that likely under-reported/reduced their dietary intake. Conclusions: The result from the linear regression analysis suggests that an EA ≥ 36 kcal·kg FFM-1·day-1 is required to achieve "normal ovulation." The threshold EA associated with ovulatory disturbances in athletes and non-invasive means of monitoring the ovulatory status warrant further research.

Long-chain n-3 PUFA ingestion for the stimulation of muscle protein synthesis in healthy older adults.

This review aims to critically evaluate the efficacy of long-chain Õ¸-3 PUFA ingestion in modulating muscle protein synthesis (MPS), with application to maintaining skeletal muscle mass, strength and function into later life. Ageing is associated with a gradual decline in muscle mass, specifically atrophy of type II fibres, that is exacerbated by periods of (in)voluntary muscle disuse. At the metabolic level, in otherwise healthy older adults, muscle atrophy is underpinned by anabolic resistance which describes the impaired MPS response to non-pharmacological anabolic stimuli, namely, physical activity/exercise and amino acid provision. Accumulating evidence implicates a mechanistic role for n-3 PUFA in upregulating MPS under stimulated conditions (post-prandial state or following exercise) via incorporation of EPA and DHA into the skeletal muscle phospholipid membrane. In some instances, these changes in MPS with chronic Õ¸-3 PUFA ingestion have translated into clinically relevant improvements in muscle mass, strength and function; an observation evidently more prevalent in healthy older women than men. This apparent sexual dimorphism in the adaptive response of skeletal muscle metabolism to EPA and DHA ingestion may be related to a greater propensity for females to incorporate Õ¸-3 PUFA into human tissue and/or the larger dose of ingested Õ¸-3 PUFA when expressed relative to body mass or lean body mass. Future experimental studies are warranted to characterise the optimal dosing and duration of Õ¸-3 PUFA ingestion to prescribe tailored recommendations regarding n-3 PUFA nutrition for healthy musculoskeletal ageing into later life.

Effects of vitamin D supplementation on maximal strength and power in athletes: a systematic review and meta-analysis of randomized controlled trials.

Background: Vitamin D is thought to be a powerful modulator of skeletal muscle physiology. However, available data on the effects of vitamin D supplementation on muscle function in athletes are limited and with mixed results. This meta-analysis therefore, aimed to quantitatively summarize the up-to-date literature assessing the effects of vitamin D supplementation on muscle strength and power in athletes. Methods: Sport Discus, PubMed, Cochrane Library and Web of Science were searched to identify randomized controlled trials (RCTs) that used one-repetition maximum (1RM) tests to assess maximal strength, and vertical jump to assess muscle power in athletes. The Cochrane Risk of Bias tool was used to evaluate the included RCTs for sources of bias. The standardized mean difference (SMD) was used as the effect size, interpreted together with its 95% confidence intervals (CI). The effect sizes were calculated on the changes from baseline between vitamin D and placebo groups for maximal strength results by upper body and lower body, and for power results. Results: Eleven RCTs involving 436 athletes were included. The results indicated that if baseline serum 25(OH)D concentration was < 75 nmol/L, the treatment had a small effect on upper body muscle strength [SMD 0.25, 95% CI: (-0.44, 0.95), p = 0.47] and on lower body muscle strength [SMD 0.26, 95% CI: (-0.13, 0.65), p = 0.19]; if the baseline serum 25(OH)D concentration was ≥ 75 nmol/L, the treatment had a trivial effect on muscle power [SMD 0.15, 95% CI: (-0.42, 0.72), p = 0.61]. Discussion: This meta-analysis demonstrated that there is not a statistically significant effect of vitamin D supplementation on improving maximum strength and power, but highlights that further research is required addressing the key limitations in previous studies before definitive conclusions can be made.

A randomised trial to assess fluid and electrolyte balance responses following ingestion of different beverages in young and older men.

BACKGROUND: Older adults are susceptible to dehydration and fluid overload due to a reduced ability to maintain homeostatic control of fluid and electrolyte balance. PURPOSE: To assess fluid and electrolyte balance responses in young and older men following ingestion of commonly consumed beverages differing in composition. METHODS: 12 young and 11 older men were recruited. Euhydrated body mass was recorded. Participants consumed 1L (250 ml every 15 min) of water, fruit juice, a sports drink or low-fat milk in a randomized cross-over design. Urine and blood samples were obtained before and after the drinking period and every hour thereafter for 3-h. Samples were used to determine osmolality, electrolytes (Na+ and K+), water clearance, and glomerular filtration rate. RESULTS: Free water clearance was significantly higher in Young than Older at 1 and 2 h after the ingestion of W and S (p < 0.05). Net Na+ and K+ balance were not different between Young and Older (p = 0.91 and p = 0.65) adults, respectively. At 3 h Na+ balance was negative after ingesting water and fruit juice, but neutral after sport drink and milk. Net K+ balance was neutral at 3 h after ingesting milk, but negative after water, fruit juice and sport drink. CONCLUSIONS: Milk was retained longer than other beverages in Young, but not in Older, despite similar net electrolyte balance responses. Older had higher fluid retention in the first 2 h after the ingestion of all beverages, except for milk when compared to Young, indicating an age-related loss of ability to regulate fluid balance under current study conditions.

Fish oil supplementation fails to modulate indices of muscle damage and muscle repair during acute recovery from eccentric exercise in trained young males.

We aimed to investigate the influence of 4-wk of fish oil (FO) supplementation on markers of muscle damage, inflammation, muscle soreness, and muscle function during acute recovery from eccentric exercise in moderately trained males. Sixteen moderately-trained males ingested 5 g/d of FO (n = 8) or soybean oil (placebo) capsules (n = 8) for 4-wk prior to- and 3-d following an acute eccentric exercise bout. Eccentric exercise consisted of 12 sets of isokinetic knee extension and knee flexion. Indices of muscle damage, soreness, function and inflammation were measured at baseline and during exercise recovery. Eccentric exercise elicited an increase in muscle soreness (p < 0.010) and thigh volume (p < 0.001), and reduced peak isometric torque by 31.7 ± 6.9%, (p < 0.05, 95% CI 10.6-52.8) during 3-d of recovery. Blood omega-3 polyunsaturated fatty acid concentration was 14.9 ± 2.4% higher in FO than PLA (p < 0.01, 95% CI 9.8-20.1). However, FO did not ameliorate the cumulative creatine kinase response (expressed as AUC; p = 0.368), inflammation (p = 0.400), muscle soreness (p > 0.140), or muscle function (p > 0.249) following eccentric exercise. FO supplementation confers no clear benefit in terms of ameliorating the degree of muscle damage, or facilitating the muscle repair process, during acute eccentric exercise recovery. These data suggest that FO supplementation does not provide an effective nutritional strategy to promote exercise recovery, at least in moderately-trained young men.Abbreviations: ANOVA: Analysis of variance; AUC: Area under curve; CI: Confidence interval; CK: Creatine kinase; CMJ: Countermovement jump; COX: Cyclooxygenase; CRP: C-reactive protein; DHA: Docosahexaenoic acid; DOMS: Delayed-onset muscle soreness; EIMD: Exercise-induced muscle damage; En%: Energy percent; EPA: Eicosapentaenoic acid; FO: Fish oil; IL-6: Interleukin-6; LDH: Lactate dehydrogenase; LOX: Lipoxygenase; Mb: Myoglobin; mTOR: Mechanistic target of rapamycin; PLA: Placebo; ROM: Range of motion; ROS: Reactive oxygen species; SD: Standard deviation; SEM: Standard error of the mean; TNF-α: Tumour necrosis factor alpha; VAS: Visual analogue scale; Ω3-PUFA: Omega-3 polyunsaturated fatty acids; Ω6-PUFA: Omega-6 polyunsaturated fatty acidsHighlightsThe anti-inflammatory properties of omega-3 polyunsaturated fatty acids, alongside their propensity to incorporate into the muscle phospholipid membrane underpins the idea that fish oil supplementation may attenuate muscle damage and promote muscle repair following eccentric-based exercise.Four weeks of high-dose (5 g/d) fish oil supplementation prior to eccentric exercise failed to attenuate the rise in creatine kinase concentration and muscle soreness during acute exercise recovery in physically-active young men.Future studies are warranted to investigate the efficacy of combining omega-3 polyunsaturated fatty acids with other nutrients (i.e. protein/amino acids) for the promotion of muscle recovery following eccentric-based damaging exercise.

Influence of pistachios on force production, subjective ratings of pain, and oxidative stress following exercise-induced muscle damage in moderately trained athletes: A randomized, crossover trial.

Although previous studies have focused on the role of pistachios on metabolic health, the ergogenic effects of the nut must be elucidated. This study evaluated the impact of ingesting raw, shelled, unsalted pistachios on subjective pain ratings, force production, vertical jump, and biochemical indices of recovery from eccentrically biased exercise. Using a crossover design, 27 moderately trained, male athletes completed 3 trials in a randomized counterbalanced fashion. Control received water only, low dose (1.5 oz/d; PL) and high dose (3.0 oz/d; PH) consumed pistachios for 2 weeks with a 3-4-week washout between trials. PH had lower pain ratings in most muscles after 72 h of recovery (p < 0.05). PH prevented a decrease in force production at 120°/s of knee flexion (p > 0.05); whereas force was diminished in the other trials. Creatine kinase, myoglobin, and C-reactive protein increased over time following exercise (p < 0.05); however, there were no advantages following pistachio consumption. No significant changes in vertical jump or superoxide dismutase were elicited during any trial. This study demonstrates that 3.0 oz/d of pistachios can reduce delayed onset of muscle soreness and maintain muscle strength, potentially promoting exercise tolerance and training adaptations. ClinicalTrialsgov Identifier: NCT03698032.

A preliminary study of the reliability of soccer skill tests within a modified soccer match simulation protocol.

AIM: This study examined test-retest reliability of soccer-specific skills within a modified version of the soccer match simulation (SMS) protocol. METHODS: Ten professional youth academy soccer players (18 ± 1 years) from the United Kingdom completed 30 minutes of the modified SMS on two occasions under standardised conditions. During each trial, participants performed 20-m dribbling, short passing (4.2-m), long passing (7.9-m), shooting skills, and 15-m sprints within four blocks of soccer specific activity. RESULTS: Collapsed normative data (mean (SD)) for trial 1 and trial 2 for dribbling speed was 2.7 (0.2) m/s, for sprint speed 5.9 (0.4) m/s, for short pass speed 11.1 (0.5) km/h, for long pass speed was 12.2 (0.5) km/h, and for shooting speed was 13.3 (0.4) km/h. Mean results from trial 1 and trial 2 were not different for all measures evaluated (P > 0.05). Good to excellent reliability (ICC 0.76-0.99) was observed for long and short passing speed, shooting speed, sprint speed, and long pass accuracy, with CVs typically < 5-10%. Moderate reliability (ICC 0.50-0.75) was observed for dribbling speed. Poor reliability (ICC <0.50) was observed for dribbling accuracy and shooting accuracy. CONCLUSIONS: The reliability of the modified version of the SMS protocol is promising for most of the skills assessed, with the exception of dribbling and shooting accuracy in this group of professional youth soccer players. The modified protocol is easy to implement within professional clubs without specialist equipment, but due to the limited sample size the reliability requires further confirmation in a larger sample.

Impact of Physical Activity on Adiposity and Risk Markers for Cardiovascular and Metabolic Disease.

The main aim of the present study was to investigate the impact of physical activity (PA) on adiposity and for cardiovascular and metabolic disease risk markers (CMDRMs). In total, 55 adults (33 lean [L] and 22 overweight/obesity [O/O]) visited the laboratory on two occasions. During the first session, body composition and anthropometric measurements were taken as well as resting blood pressure (BP). Free-living PA intensity was monitored using an ActiGraph accelerometer, which the participants wore for a period of 6 days. During the second visit, blood samples for the analysis of disease risk markers were obtained from the participants in the morning after overnight fasting (≥10 hr). There was no significant difference between groups in the percentage of time spent in PA levels (54.5% ± 1.2% and 54.9% ± 2.1% for L and O/O, respectively). Although, the O/O group was within recommended PA level, they had higher leptin, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and high-sensitivity C-reactive protein (hsCRP) levels than the L group (all p < .01). The O/O group had higher levels of triglycerides, low-density lipoprotein (LDL), and very low-density lipoprotein (VLDL) and lower levels of high-density lipoprotein (HDL; all p < .01). Interestingly, vigorous activity was positively correlated with HDL (r = .30, p < .05) and negatively with LDL (r = -.26, p = .05) levels and the arachidonic acid to eicosapentaenoic acid (ARA/EPA) ratio (r = -.30, p < .05). Only the O/O group had elevated CMDRMs. However, vigorous activity may improve health-related blood lipids such as HDL, LDL, and ARA/EPA ratio. Regardless of body composition status, low active participants were more likely to have higher level of leptin and hsCRP. Further exploration of the beneficial effects of vigorous exercise on adiposity and CMDRMs is warranted.

Carbohydrate Intake Practices and Determinants of Food Choices During Training in Recreational, Amateur, and Professional Endurance Athletes: A Survey Analysis.

Carbohydrate (CHO) intake during exercise can optimize endurance performance. However, there is limited information regarding fueling practices of endurance athletes during training. Accordingly, an anonymous German-language online survey was circulated examining the determinants of CHO choices, and intake practices among runners, triathletes, and cyclists during training. Survey questions included predefined answers, and a Likert scale with response of CHO food choice intakes from 1 = never to 5 = always. 1,081 endurance participants (58.0% male, 68.6% aged 18-39 years) of varying competitive levels were included in the analysis. Overall, most participants consumed a combination of commercial sport nutrition products and everyday foods (67.4%, n = 729) with their primary reason that food-first was preferred, but in some exercise scenarios, commercial sport nutrition products were deemed more convenient (61.3%, n = 447). Participants consuming commercial sport nutrition products only (19.3%, n = 209) most often valued their ease of intake during exercise (85.2%, n = 178). Among those consuming everyday foods only (13.2%, n = 143), the most common reason was the perceived importance of eating wholesome foods/natural ingredients (84.6%, n = 121). Between the most frequently consumed CHO sources during training at low-to-moderate intensities (n = 1032), sports drinks (mean ± SD; 2.56 ± 1.33) were consumed significantly more often than bananas (2.27 ± 1.14, p < 0.001), with no significant difference in intake frequency between bananas and traditional muesli/fruit/energy bars (2.25 ± 1.14, p = 0.616). Whereas during high intensities (n = 1,077), sports drinks (3.31 ± 1.51) were significantly more often consumed than gels (2.79 ± 1.37), and gels significantly more often than energy bars (2.43 ± 1.28), all commercial sport nutrition products (all, p < 0.001). Overall, 95.1% (n = 1028) of all participants consumed CHO during training at all exercise intensities, with males (n = 602; 2.35 ± 0.70) consuming significantly more often commercial sport nutrition products than females (n = 424; 2.14 ± 0.79, p < 0.001); females consumed significantly more often everyday foods than males (1.66 ± 0.47 vs. 1.54 ± 0.42, p < 0.001). Most participants used mixed CHO forms during low-to-moderate (87.9%), and high exercise intensities (94.7%). 67.6% (n = 731) of all participants reported guiding their CHO intake rates during training by gut feeling. These large-scale survey findings suggest a preference of endurance participants' CHO intake during training in liquid form independent of exercise intensities and offer novel insights into CHO intake practices to guide sports nutrition strategies and education.

Fluid and electrolyte balance considerations for female athletes.

This review explores the effects of oestrogen and progesterone fluctuations across the menstrual cycle on fluid and electrolyte balance. The review aims to provide information on this topic for the exercising female but also for researchers working in this field. Beginning with a basic introduction to fluid and electrolyte balance, the review goes on to describe how oestrogen and progesterone have independent and integrated roles to play in the regulation of fluid and electrolyte balance. Despite evidence that oestrogen can influence the osmotic threshold for arginine vasopressin release, and that progesterone can influence aldosterone production, these actions do not appear to influence fluid retention, plasma volume changes at rest and during exercise, or electrolyte losses. However, the large inter-individual variations in hormonal fluctuations throughout the menstrual cycle may mean that specific individuals with high fluctuations could experience disturbances in their fluid and electrolyte balance. During phases of oestrogen dominance (e.g. late-follicular phase) heat dissipation is promoted, while progesterone dominance (e.g. mid-luteal phase) promotes heat conservation with overall higher basal body temperature. However, these responses do not consistently lead to any change in observed sweat rates, heat-stress, or dehydration during exercise. Finally, the literature does not support any difference in fluid retention during post-exercise rehydration periods conducted at different menstrual cycle phases. Although these mean responses largely reveal no effects on fluid and electrolyte balance, further research is required particularly in those individuals who experience high hormonal fluctuations, and greater exploration of oestrogen to progesterone interactions is warranted.

Dietary Observations of Ultra-Endurance Runners in Preparation for and During a Continuous 24-h Event.

Carbohydrate (CHO) intake recommendations for events lasting longer than 3h indicate that athletes should ingest up to 90g.h.-1 of multiple transportable carbohydrates (MTC). We examined the dietary intake of amateur (males: n=11, females: n=7) ultra-endurance runners (mean age and mass 41.5±5.1years and 75.8±11.7kg) prior to, and during a 24-h ultra-endurance event. Heart rate and interstitial glucose concentration (indwelling sensor) were also tracked throughout the event. Pre-race diet (each 24 over 48h) was recorded via weighed intake and included the pre-race meal (1-4h pre-race). In-race diet (24h event) was recorded continuously, in-field, by the research team. Analysis revealed that runners did not meet the majority of CHO intake recommendations. CHO intake over 24-48h pre-race was lower than recommended (4.0±1.4g·kg-1; 42±9% of total energy), although pre-race meal CHO intake was within recommended levels (1.5±0.7g·kg-1). In-race CHO intake was only in the 30-60g·h-1 range (mean intake 33±12g·h-1) with suboptimal amounts of multiple transportable CHO consumed. Exercise intensity was low to moderate (mean 68%HRmax 45%VO2max) meaning that there would still be an absolute requirement for CHO to perform optimally in this ultra-event. Indeed, strong to moderate positive correlations were observed between distance covered and both CHO and energy intake in each of the three diet periods studied. Independent t-tests showed significantly different distances achieved by runners consuming ≥5 vs. <5g·kg-1 CHO in pre-race diet [98.5±18.7miles (158.5±30.1km) vs. 78.0±13.5miles (125.5±21.7km), p=0.04] and ≥40 vs. <40g·h-1 CHO in-race [92.2±13.9miles (148.4±22.4km) vs. 74.7±13.5miles (120.2±21.7km), p=0.02]. Pre-race CHO intake was positively associated with ultra-running experience, but no association was found between ultra-running experience and race distance. No association was observed between mean interstitial glucose and dietary intake, or with race distance. Further research should explore approaches to meeting pre-race dietary CHO intake as well as investigating strategies to boost in-race intake of multiple transportable CHO sources. In 24-h ultra-runners, studies examining the performance enhancing benefits of getting closer to meeting pre-race and in-race carbohydrate recommendations are required.

Associated Sociodemographic and Facility Patterning of Uptake, Attendance, and Session Count Within a Scottish Exercise Referral Scheme.

BACKGROUND: Exercise referral schemes (ERS) aim to tackle noncommunicable disease via increasing levels of physical activity. Health benefits are reliant on uptake and attending ERS sessions. Hence, it is important to understand which characteristics may influence these parameters to target interventions to improve uptake and attendance to those who need it most. METHOD: Secondary analysis of one ERS database was conducted to (1) profile participants' nonuptake of exercise referral; (2) describe any differences between nonattenders and attenders; and (3) report session count of attenders, exploring any relationship between attender demographics and session count. RESULTS: The study showed that (1) sociodemographic profile of nonattenders was very similar to that of those who attended; (2) there was a high, early withdrawal rate of attenders wherein 68% exited the scheme at 5 exercise sessions or less; and (3) session count did not appear to differ by demographic characteristics. CONCLUSIONS: Nonattendance and session count did not appear to differ by demographic characteristics. Attendance at ERS was low. Nonuptake and reduced attendance may limit any associated health benefits that may be achieved from ERS. Therefore, it is important to identify additional factors that may influence participants' choice to uptake and attend ERS.

Exercise Referral Instructors' Perspectives on Supporting and Motivating Participants to Uptake, Attend and Adhere to Exercise Prescription: A Qualitative Study.

Exercise referral schemes are designed to support people with non-communicable diseases to increase their levels of exercise to improve health. However, uptake and attendance are low. This exploratory qualitative study aims to understand uptake and attendance from the perspectives of exercise referral instructors using semi-structured interviews. Six exercise referral instructors from one exercise referral scheme across four exercise referral sites were interviewed. Four themes emerged: (i) the role that instructors perceive they have and approaches instructors take to motivate participants to take-up, attend exercise referral and adhere to their exercise prescription; (ii) instructors' use of different techniques, which could help elicit behaviour change; (iii) instructors' perceptions of participants' views of exercise referral schemes; and (iv) barriers towards providing an exercise referral scheme. Exercise referral instructors play an important, multifaceted role in the uptake, attendance and adherence to exercise referral. On-going education and peer support for instructors may be useful. Instructors' perspectives help us to further understand how health and leisure services can design successful exercise referral schemes.

Human skeletal muscle metabolic responses to 6 days of high-fat overfeeding are associated with dietary n-3PUFA content and muscle oxidative capacity.

Understanding human physiological responses to high-fat energy excess (HFEE) may help combat the development of metabolic disease. We aimed to investigate the impact of manipulating the n-3PUFA content of HFEE diets on whole-body and skeletal muscle markers of insulin sensitivity. Twenty healthy males were overfed (150% energy, 60% fat, 25% carbohydrate, 15% protein) for 6 d. One group (n = 10) received 10% of fat intake as n-3PUFA rich fish oil (HF-FO), and the other group consumed a mix of fats (HF-C). Oral glucose tolerance tests with stable isotope tracer infusions were conducted before, and following, HFEE, with muscle biopsies obtained in basal and insulin-stimulated states for measurement of membrane phospholipids, ceramides, mitochondrial enzyme activities, and PKB and AMPKα2 activity. Insulin sensitivity and glucose disposal did not change following HFEE, irrespective of group. Skeletal muscle ceramide content increased following HFEE (8.5 ± 1.2 to 12.1 ± 1.7 nmol/mg, p = .03), irrespective of group. No change in mitochondrial enzyme activity was observed following HFEE, but citrate synthase activity was inversely associated with the increase in the ceramide content (r=-0.52, p = .048). A time by group interaction was observed for PKB activity (p = .003), with increased activity following HFEE in HF-C (4.5 ± 13.0mU/mg) and decreased activity in HF-FO (-10.1 ± 20.7 mU/mg) following HFEE. Basal AMPKα2 activity increased in HF-FO (4.1 ± 0.6 to 5.3 ± 0.7mU/mg, p = .049), but did not change in HF-C (4.6 ± 0.7 to 3.8 ± 0.9mU/mg) following HFEE. We conclude that early skeletal muscle signaling responses to HFEE appear to be modified by dietary n-3PUFA content, but the potential impact on future development of metabolic disease needs exploring.

Development of an Anthropometric Prediction Model for Fat-Free Mass and Muscle Mass in Elite Athletes.

The monitoring of body composition is common in sports given the association with performance. Surface anthropometry is often preferred when monitoring changes for its convenience, practicality, and portability. However, anthropometry does not provide valid estimates of absolute lean tissue in elite athletes. The aim of this investigation was to develop anthropometric models for estimating fat-free mass (FFM) and skeletal muscle mass (SMM) using an accepted reference physique assessment technique. Sixty-four athletes across 18 sports underwent surface anthropometry and dual-energy X-ray absorptiometry (DXA) assessment. Anthropometric models for estimating FFM and SMM were developed using forward selection multiple linear regression analysis and contrasted against previously developed equations. Most anthropometric models under review performed poorly compared with DXA. However, models derived from athletic populations such as the Withers equation demonstrated a stronger correlation with DXA estimates of FFM (r = .98). Equations that incorporated skinfolds with limb girths were more effective at explaining the variance in DXA estimates of lean tissue (Sesbreno FFM [R2 = .94] and Lee SMM [R2 = .94] models). The Sesbreno equation could be useful for estimating absolute indices of lean tissue across a range of physiques if an accepted option like DXA is inaccessible. Future work should explore the validity of the Sesbreno model across a broader range of physiques common to athletic populations.

Addition of an Alginate Hydrogel to a Carbohydrate Beverage Enhances Gastric Emptying.

PURPOSE: This study aimed to examine the effect of altering osmolality or adding sodium alginate and pectin to a concentrated carbohydrate (CHO) beverage on gastric-emptying (GE) rate. METHODS: Boluses (500 mL) of three drinks were instilled double blind in eight healthy men while seated, GE was measured using the double sampling method for 90 min, and blood samples were collected regularly. Drinks consisted of glucose and fructose (MON; 1392 mOsmol·kg), maltodextrin and fructose (POLY; 727 mOsmol·kg), and maltodextrin, fructose, sodium alginate, and pectin (ENCAP; 732 mOsmol·kg) with each providing 180 g·L CHO (CHO ratio of 1:0.7 maltodextrin or glucose/fructose). RESULTS: Time to empty half of the ingested bolus was faster for ENCAP (21 ± 9 min) than for POLY (37 ± 8 min); both were faster than MON (51 ± 15 min). There were main effects for time and drink in addition to an interaction effect for the volume of test drink remaining in the stomach over the 90 min period, but there were no differences between MON and POLY at any time point. ENCAP had a smaller volume of the test drink in the stomach than MON at 30 min (193 ± 62 vs 323 ± 54 mL), which remained less up to 60 min (93 ± 37 vs 210 ± 88 mL). There was a smaller volume of the drink remaining in the stomach in ENCAP compared with POLY 20 min (242 ± 73 vs 318 ± 47 mL) and 30 min (193 ± 62 vs 304 ± 40 mL) after ingestion. Although there was a main effect of time, there was no effect of drink or an interaction effect on serum glucose, insulin or nonesterified fatty acid concentrations. CONCLUSION: The addition of sodium alginate and pectin to a CHO beverage enhances early GE rate but did not affect serum glucose, insulin, or nonesterified fatty acid concentration at rest.

Effect of Drinking Rate on the Retention of Water or Milk Following Exercise-Induced Dehydration.

This study investigated the effect of drinking rate on fluid retention of milk and water following exercise-induced dehydration. In Part A, 12 male participants lost 1.9% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water or low-fat milk equal to the volume of sweat lost during exercise was provided. Beverages were ingested over 30 or 90 min, resulting in four beverage treatments: water 30 min, water 90 min, milk 30 min, and milk 90 min. In Part B, 12 participants (nine males and three females) lost 2.0% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water equal to the volume of sweat lost during exercise was provided. Water was ingested over 15 min (DR15), 45 min (DR45), or 90 min (DR90), with either DR15 or DR45 repeated. In both trials, nude body mass, urine volume, urine specific gravity and osmolality, plasma osmolality, and subjective ratings of gastrointestinal symptoms were obtained preexercise and every hour for 3 hr after the onset of drinking. In Part A, no effect of drinking rate was observed on the proportion of fluid retained, but milk retention was greater (p < .01) than water (water 30 min: 57% ± 16%, water 90 min: 60% ± 20%, milk 30 min: 83% ± 6%, and milk 90 min: 85% ± 7%). In Part B, fluid retention was greater in DR90 (57% ± 13%) than DR15 (50% ± 11%, p < .05), but this was within test-retest variation determined from the repeated trials (coefficient of variation: 17%). Within the range of drinking rates investigated the nutrient composition of a beverage has a more pronounced impact on fluid retention than the ingestion rate.

Influence of Peak Menstrual Cycle Hormonal Changes on Restoration of Fluid Balance After Induced Dehydration.

The present study examined the impact of hormonal differences between late follicular (LF) and midluteal (ML) phases on restoration of fluid balance following dehydration. Ten eumenorrheic female participants were dehydrated by 2% of their body mass through overnight fluid restriction followed by exercise-heat stress. Trials were undertaken during the LF (between Days 10 and 13 of the menstrual cycle) and ML phases (between Days 18 and 23 of the menstrual cycle) with one phase repeated to assess reliability of observations. Following dehydration, participants ingested a volume equivalent to 100% of mass loss of a commercially available sports drink in four equal volumes over 30 min. Mean serum values for steroid hormones during the ML (estradiol [E2]: 92 ± 11 pg/ml, progesterone: 19 ± 4 ng/ml) and LF (estradiol [E2]: 232 ± 64 pg/ml, progesterone: 3 ± 2 ng/ml) were significantly different between phases. Urine tests confirmed no luteinizing hormone surge evident during LF trials. There was no effect of menstrual cycle phase on cumulative urine volume during the 3-hr rehydration period (ML: 630 [197-935] ml, LF: 649 [180-845] ml) with percentage of fluid retained being 47% (33-85)% on ML and 46% (37-89)% on LF (p = .29). There was no association between the progesterone:estradiol ratio and fluid retained in either phase. Net fluid balance, urine osmolality, and thirst intensity were not different between phases. No differences in sodium (ML: -61 [-36 to -131] mmol, LF: -73 [-5 to -118] mmol; p = .45) or potassium (ML: -36 [-11 to -80] mmol, LF: -30 [-19 to -89] mmol; p = .96) balance were observed. Fluid replacement after dehydration does not appear to be affected by normal hormonal fluctuations during the menstrual cycle in eumenorrheic young women.

Influence of Fish Oil-Derived n-3 Fatty Acid Supplementation on Changes in Body Composition and Muscle Strength During Short-Term Weight Loss in Resistance-Trained Men.

Background: A detrimental consequence of diet-induced weight loss, common in athletes who participate in weight cutting sports, is muscle loss. Dietary omega-3 polyunsaturated fatty acids (n-3PUFA) exhibit a protective effect on the loss of muscle tissue during catabolic situations such as injury-simulated leg immobilization. This study aimed to investigate the influence of dietary n-3PUFA supplementation on changes in body composition and muscle strength following short-term diet-induced weight loss in resistance-trained men. Methods: Twenty resistance-trained young (23 ± 1 years) men were randomly assigned to a fish oil group that supplemented their diet with 4 g n-3PUFA, 18 g carbohydrate, and 5 g protein (FO) or placebo group containing an equivalent carbohydrate and protein content (CON) over a 6 week period. During weeks 1-3, participants continued their habitual diet. During week 4, participants received all food items to control energy balance and a macronutrient composition of 50% carbohydrate, 35% fat, and 15% protein. During weeks 5 and 6, participants were fed an energy-restricted diet equivalent to 60% habitual energy intake. Body composition and strength were measured during weeks 1, 4, and 6. Results: The decline in total body mass (FO = -3.0 ± 0.3 kg, CON = -2.6 ± 0.3 kg), fat free mass (FO = -1.4 ± 0.3 kg, CON = -1.2 ± 0.3 kg) and fat mass (FO = -1.4 ± 0.2 kg, CON = -1.3 ± 0.3 kg) following energy restriction was similar between groups (all p > 0.05; d: 0.16-0.39). Non-dominant leg extension 1 RM increased (6.1 ± 3.4%) following energy restriction in FO (p < 0.05, d = 0.29), with no changes observed in CON (p > 0.05, d = 0.05). Dominant leg extension 1 RM tended to increase following energy restriction in FO (p = 0.09, d = 0.29), with no changes in CON (p > 0.05, d = 0.06). Changes in leg press 1 RM, maximum voluntary contraction and muscular endurance following energy restriction were similar between groups (p > 0.05, d = 0.05). Conclusion: Any possible improvements in muscle strength during short-term weight loss with n-3PUFA supplementation are not related to the modulation of FFM in resistance-trained men.

Mussel Consumption as a "Food First" Approach to Improve Omega-3 Status.

Numerous United Kingdom and European Union expert panels recommend that the general adult population consumes ~250 mg of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) per day through the consumption of one portion of oily fish per week. The long-chain omega-3 fatty acids EPA and DHA are only found in appreciable amounts in marine organisms. Increasing oily fish consumption conflicts with sustaining fisheries, so alternative dietary sources of EPA and DHA must be explored. Mussels are high in omega-3 polyunsaturated fatty acids (PUFAs) and a good source of essential amino acids. Therefore, we aimed to investigate the impact of introducing mussels as a protein source in the lunchtime meal three times per week for two weeks on the omega-3 status of free-living participants. Following an initial two-week monitoring period, 12 participants (eight male and four female) attended the nutrition laboratory three times per week for two weeks. Each participant received a personalised lunch constituting one-third of their typical daily calorie consumption with ~20% of the calories supplied as cooked mussels. A portion of cooked mussels from each feeding occasion was tested for total omega-3 content. The mean ± SD mussel EPA + DHA content was 518.9 ± 155.7 mg/100 g cooked weight, meaning that each participant received on average 709.2 ± 252.6 mg of EPA + DHA per meal or 304.0 ± 108.2 mg of EPA + DHA per day. Blood spot analysis revealed a significant increase in the omega-3 index (week 1 = 4.27 ± 0.81; week 4 = 5.07 ± 1.00) and whole blood EPA content during the study (%EPA week 1 = 0.70 ± 0.0.35; %EPA week 4 = 0.98 ± 0.35). Consuming mussels three times per week for two weeks as the protein source in a personalised lunchtime meal is sufficient to moderately improve the omega-3 index and whole blood DHA + EPA content in young healthy adults.