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The aim of this study was to quantify the movement patterns of various playing positions during professional rugby union match-play, such that the relative importance of aerobic and anaerobic energy pathways to performance could be estimated. Video analysis was conducted of individual players (n=29) from the Otago Highlanders during six 'Super 12' representative fixtures. Each movement was coded as one of six speeds of locomotion (standing still, walking, jogging, cruising, sprinting, and utility), three states of non-running intensive exertion (rucking/mauling, tackling, and scrummaging), and three discrete activities (kicking, jumping, passing). The results indicated significant demands on all energy systems in all playing positions, yet implied a greater reliance on anaerobic glycolytic metabolism in forwards, due primarily to their regular involvement in non-running intense activities such as rucking, mauling, scrummaging, and tackling. Positional group comparisons indicated that while the greatest differences existed between forwards and backs, each positional group had its own unique demands. Front row forwards were mostly involved in activities involving gaining/retaining possession, back row forwards tended to play more of a pseudo back-line role, performing less rucking/mauling than front row forwards, yet being more involved in aspects of broken play such as sprinting and tackling. While outside backs tended to specialize in the running aspects of play, inside backs tended to show greater involvement in confrontational aspects of play such as rucking/mauling and tackling. These results suggest that rugby training and fitness testing should be tailored specifically to positional groups rather than simply differentiating between forwards and backs. [ABSTRACT FROM AUTHOR]

The physiological, perceptual, and functional effects of dehydration may depend on how it is incurred (e.g., intense exercise releases endogenous water via glycogenolysis) but this basic notion has rarely been examined. We investigated the effects of active (exercise) heat- vs. passive heat-induced dehydration, and the kinetics of ad libitum rehydration following each method. Twelve fit participants (five females and seven males) completed four trials in randomised order: DEHydration to -3% change in body mass (∆BM) under passive or active heat stress, and EUHydration to prevent ∆BM under passive or active heat stress. In all trials, participants then sat in a temperate-controlled environment, ate a standard snack and had free access to water and sports drink during their two-hour recovery. During mild dehydration (≤2% ∆BM), active and passive heating caused comparable increases in plasma osmolality (P osm : ~4 mOsmol/kg, interaction: p = 0.138) and reductions in plasma volume (PV: ~10%, interaction: p = 0.718), but heat stress per se was the main driver of hypovolaemia. Thirst in DEHydration was comparably stimulated by active than passive heat stress ( p < 0.161) and shared the same relation to P osm (r ≥ 0.744) and ∆BM (r ≥ 0.882). Following heat exposures, at 3% gross ∆BM, PV reduction was approximately twice as large from passive versus active heating ( p = 0.003), whereas P osm perturbations were approximately twice as large from EUHydration versus DEHydration ( p < 0.001). Rehydrating ad libitum resulted in a similar net fluid balance between passive versus active heat stress and restored PV despite the incomplete replacement of ∆BM. In conclusion, dehydrating by 2% ∆BM via passive heat stress generally did not cause larger changes to PV or P osm than via active heat stress. The heat stressors themselves caused a greater reduction in PV than dehydration did, whereas ingesting water to maintain euhydration produced large reductions in P osm in recovery and therefore appears to be of more physiological significance.

Purpose: This study assessed whether increasing sodium in a sports drink above that typical (~ 20 mmol L -1 ) affects plasma sodium and volume responses during prolonged exercise in the heat., Methods: Endurance trained males (N = 11, 36 ± 14 y, 75.36 ± 5.30 kg, [Formula: see text]O 2max 60 ± 3 mL min -1  kg -1 ) fulfilled requirements of the study including one 1-h exercise pre-trial, to estimate fluid losses (to prescribe fluid intake), and two, experimental trials (3-h or until tolerance), in random order, cycling (55% [Formula: see text]O 2max , 34 °C, 65% RH). Beverages contained 6% carbohydrate and either 21 mmol L -1 (Low Na + ) or 60 mmol L -1 sodium (High Na + ). Analyses included linear mixed models and t-tests., Results: Cycling time was similar 176 ± 9 min (Low Na + ); 176 ± 7 min (High Na + ). Fluid intake was 1.12 ± 0.19 L h -1 ; 1.14 ± 0.21 L h -1 , resp. Body mass change was - 0.53 ± 0.40%;  - 0.30 ± 0.45%, resp. Sodium intake was 69 ± 12 mmol; 201 ± 40 mmol, resp. Plasma sodium concentration was greater in High Na + than Low Na + (p < 0.001); decreasing in Low Na + (- 1.5 ± 2.2 mmol L -1 ), increasing in High Na + (0.8 ± 2.4 mmol L -1 ) (p = 0.048, 95% CI [- 4.52, - 0.02], d = 0.99). Plasma volume decreased in Low Na + (- 2 ± 2%) but remained unchanged in High Na + (0 ± 3%) (p = 0.01, 95% CI [- 3.2, - 0.5], d = 0.80)., Conclusions: When conducting prolonged exercise in the heat, those who fully hydrate would benefit by increased sodium content of the beverage by improved plasma volume and sodium maintenance. Australian New Zealand Clinical Trials Registry (ACTRN12616000239460) 22/02/16., (© 2022. The Author(s).)

The objective of this study was to compare acute effects of prolonged sitting, prolonged standing and sitting interrupted with regular activity breaks on vascular function and postprandial glucose metabolism. In a randomized cross-over trial, 18 adults completed: 1. Prolonged Sitting; 2. Prolonged Standing and 3. Sitting with 2-min walking (5 km/h, 10% incline) every 30 min (Regular Activity Breaks). Flow mediated dilation (FMD) was measured in the popliteal artery at baseline and 6 h. Popliteal artery hemodynamics, and postprandial plasma glucose and insulin were measured over 6 h. Neither raw nor allometrically-scaled FMD showed an intervention effect (p = 0.285 and 0.159 respectively). Compared to Prolonged Sitting, Regular Activity Breaks increased blood flow (overall effect of intervention p<0.001; difference = 80%; 95% CI 34 to 125%; p = 0.001) and net shear rate (overall effect of intervention p<0.001; difference = 72%; 95% CI 30 to 114%; p = 0.001) at 60 min. These differences were then maintained for the entire 6 h. Prolonged Standing increased blood flow at 60 min only (overall effect of intervention p<0.001; difference = 62%; 95% CI 28 to 97%; p = 0.001). Regular Activity Breaks decreased insulin incremental area under the curve (iAUC) when compared to both Prolonged Sitting (overall effect of intervention P = 0.001; difference = 28%; 95% CI 14 to 38%; p<0.01) and Prolonged Standing (difference = 19%; 95% CI 4 to 32%, p = 0.015). There was no intervention effect on glucose iAUC or total AUC (p = 0.254 and 0.450, respectively). In normal-weight participants, Regular Activity Breaks induce increases in blood flow, shear stress and improvements in postprandial metabolism that are associated with beneficial adaptations. Physical activity and sedentary behaviour messages should perhaps focus more on the importance of frequent movement rather than simply replacing sitting with standing., Competing Interests: The authors have declared that no competing interests exist.

Background: Insulin-like growth factor-I (IGF-1) is an anabolic hormone that stimulates cell growth and division. The effects of IGF-1 may be beneficial (muscle growth/repair) or detrimental (increased risk of several types of cancer and mortality) for health. Dietary protein and physical activity are thought to be factors that modulate IGF-1., Objective: This study analysed the relationships dietary protein vs IGF-1 and physical activity vs IGF-1 independently with a large sample size, and determined if/how physical activity affected the association between dietary protein and IGF-1 in healthy adults., Methods: Regression models were used to assess the association between dietary protein and/or physical activity on serum IGF-1 in a cross-sectional sample of 60,677 healthy adults that were enrolled in the UK Biobank project., Results: Dietary protein was positively associated with IGF-1 (0.030 nmol/L;95%CI 0.027-0.033;p < 0.001). Individuals undertaking 10-50 excess MET h/week of physical activity had 0.129 nmol/L greater IGF-1 than participants completing less than 10 excess MET h/week (95%CI 0.028-0.230). The "high" category of physical activity (>50 excess MET h/week) was not correlated with IGF-1 (-0.055 nmol/L;95%CI -0.185-0.076). When dietary protein and physical activity were included in the same model, physical activity did not change the relationship between dietary protein and IGF-1, nor visa-versa., Conclusions: The positive association between dietary protein and IGF-1 was not influenced by physical activity. The former association was stronger than the latter. Thus, when seeking to adjust IGF-1 for possible health concerns, regulating dietary protein may be more pertinent than physical activity as a primary intervention., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Interrupting sedentary behaviour with regular activity breaks benefits glycaemic control; however, the influence of the energy utilised during these activity breaks on postprandial metabolic response is relatively unknown. Therefore, the aim of this study was to investigate whether the energy utilisation of regular (every 30 min) short (1 min 40 s or 2 min) activity breaks was associated with the lowering of postprandial glycaemia, insulinemia and lipidemia., Using separate data from two previously performed studies (ALPhA Study n = 65, age 25.7 (5.2) y, 40% male, BMI 23.6 (4.1) kg · m -2 . ABPA study n = 35, age 25.1 (3.7) y, 31% male, BMI 23.4 (3.2) kg · m -2 ) we investigated the association between energy utilisation (measured by indirect calorimetry) and postprandial glucose, insulin and triglycerides during prolonged sitting, and regular activity breaks.Results., Mixed effects regression models indicated that energy utilisation was not consistently associated with postprandial glucose, insulin or triglyceride responses (p > 0.05 for all). Additionally, there was some indication that energy utilisation was obscuring (mildly suppressing) the effects of regular activity breaks on glucose, insulin and triglyceride iAUC.Conclusions., If energy utilisation does not mediate the association between regular activity breaks and postprandial glycaemic response, it is possible that it is the frequency of the activity breaks that is beneficial.

Objective: To quantify energy drink consumption and influences affecting consumption in those who participate in or watch extreme sports., Methods: An online survey, informed by focus groups, was administered via Quadrics®. Advertisement was via social media, emailing extreme sport clubs, flyers at extreme sport locations, and word of mouth. Participation was limited to those >18 y who watched and/or participated in extreme sports. The study was conducted in New Zealand, with international online availability. Variables measured comprised age, sex, energy drink consumption, reasons for their use, extreme sport viewing, advertising, and sponsorship. Logistic regression models were utilised., Results: Amongst participants who completed the questionnaire ( n  = 247), the mean (SD) age was 26.2 (8.2) y, 40.5% were female, 57.9% consumed energy drinks, and 25.5% consumed >one per week. For every year older, odds of consuming energy drinks were 3.1% lower ( p =0.04). A 31% increase in energy drink consumption for every single increase of viewing extreme sport per week was observed ( p =0.009); however, reported viewing of advertising was not associated with increased consumption., Conclusions: A large proportion of extreme sport enthusiasts regularly consume energy drinks, especially younger adults. Extreme sport viewing, where energy drink sponsorship is common, appears to increase their consumption, even if not considered advertising by the viewers themselves., Competing Interests: The authors declare that there are no conflicts of interest regarding the publication of this paper., (Copyright © 2020 Conrad A. Goodhew et al.)

Insulin-like growth factor 1 (IGF-1) is a dichotomous hormone. While beneficial for growth/repair, and regulating muscle hypertrophy, high concentrations of IGF-1 are associated with increased risk of cancer and mortality. Factors thought to mediate IGF-1 include dietary protein and exercise. The purpose of this study was to analyze acute effects of dietary protein and/or exercise on plasma free IGF-1 and the time-course thereof to inform individuals who may benefit from increased IGF-1 (muscle growth/repair) or reduced IGF-1 (risk/diagnosis of cancer). Twenty-four participants (11 females, 24.9±4.6y) completed the three-way crossover study consisting of: (1)a high protein (42g) meal; (2)exercise (20min with four 30sec sprints); and (3)exercise followed by a high protein meal. Blood samples were collected fasted at rest, immediately after rest (or 5min after exercise), and at regular intervals throughout a 5h recovery. An additional fasted venipuncture was performed the morning following each condition (24h after baseline). Free IGF-1 was higher at immediately after exercise in the exercise condition (p=0.04). In the protein condition the 24h IGF-1 was 17.5% higher (p=0.02) than baseline. IGF-1 did not change over time in response to exercise with protein. The data gleaned from this study can enhance the knowledge of the time-course effects from protein and/or exercise on IGF-1. This study can provide a foundation for future research to investigate optimal timing and dosage to enhance muscle protein synthesis for athletes, as well as investigate whether consistent high protein meals may chronically elevate IGF-1 and increase the risk of deleterious health outcomes., Competing Interests: Conflict of Interest The authors declare no conflicts of interest arising from the conclusions of this work. Declaration of Interest Statement We, the authors, declare this manuscript is original, has not been published before and is not currently being considered for publication elsewhere. The manuscript and order of authors has been read/approved by all authors. There are no other personas who satisfied the authorship criteria. There are no impediments to publication. Our institutions intellectual property regulations have been followed. The involvement of human patients has met ethical approval (acknowledged in manuscript). We understand the Corresponding Author is the sole contact for the Editorial process and is responsible for communicating with the other authors.

The gut microbiota harvests energy from indigestible plant polysaccharides, forming short-chain fatty acids (SCFAs) that are absorbed from the bowel. SCFAs provide energy-presumably after easily digested food components have been absorbed from the small intestine. Infant night waking is believed by many parents to be due to hunger. Our objective was to determine whether faecal SCFAs are associated with longer uninterrupted sleep in infants. Infants (n = 57) provided faecal samples for determining SCFAs (7 months of age), and questionnaire data for determining infant sleep (7 and 8 months). Linear regression determined associations between SCFAs-faecal acetate, propionate and butyrate-and sleep. For each 1% higher propionate at 7 months of age, the longest night sleep was 6 (95% CI: 1, 10) minutes longer at both 7 and 8 months. A higher proportion of total faecal SCFA as propionate was associated with longer uninterrupted infant sleep.

Purpose: To examine the movement and physiological demands of rugby union officiating in elite competition., Methods: Movement demands of 9 elite officials across 12 Super Rugby matches were calculated, using global positioning system devices. Total distance (in m), relative distance (in m·min -1 ), and percentage time spent in various speed zones were calculated across a match. Heart-rate (HR) responses were also recorded throughout each match. Cohen d effect sizes were reported to examine the within-match variations., Results: The total distance covered was 8030 (506) m, with a relative distance of 83 (5) m·min -1 and with no differences observed between halves. Most game time was spent at lower movement speeds (76% [2%]; <2.0 m·s -1 ), with large effects for time spent >7.0 m·s -1 between halves (d = 2.85). Mean HR was 154 (10) beats·min -1 (83.8 [2.9]%HR max ), with no differences observed between the first and second halves. Most game time was spent between 81%HR max and 90%HR max (40.5% [7.5%]) with no observable differences between halves. Distances covered above 5.1 m·s -1 were highest during the first 10 min of a match, while distance at speeds 3.7 to 5 m·s -1 decreased during the final 10 min of play., Conclusions: These findings highlight the highly demanding and intermittent nature of rugby union officiating, with only some minor variations in physical and physiological demands across a match. These results have implications for the physical preparation of professional rugby union referees.

Salmon, DM, Handcock, PJ, Sullivan, SJ, Rehrer, NJ, and Niven, BE. Can neck strength be measured using a single maximal contraction in a simulated contact position? J Strength Cond Res 32(8): 2166-2173, 2018-Neck strengthening has been postulated to potentially reduce the incidence and severity of concussions and neck injuries in collision-based sports. A quick and reliable method to assess neck strength would permit identification of those at risk and tracking of progress after injury. The purpose of this study was to determine if neck strength could be reliably assessed in a simulated contact posture using a single maximal contraction. During a single session, 30 healthy male university students performed 3 maximal voluntary contractions of the neck musculature in each of the following directions: extension (Ext), flexion (Flx), left lateral flexion (LtFlx), and right lateral flexion (RtFlx). To evaluate the reliability of these measures, intraclass correlation coefficients (ICCs) were calculated. The findings revealed a significant effect for direction (p < 0.01), where Ext (234.8 N) tested stronger than Flx (141.0 N), LtFlx (134.5 N), and RtFlx (123.0 N). In addition, Flx tested stronger than RtFlx (p = 0.03). No other differences were observed between LtFlx and RtFlx. When the combined mean values of the trials (1: 151.6 N, 2: 160.0 N, 3: 163.5 N) and the interaction contrast were compared, these were not significant (p = 0.08-1.0), indicating no changes in peak force occurred over the 3 trials. The ICC values for Ext, RtFlx, and LtFlx were all "excellent" (0.91-0.94), whereas Flx demonstrated "good" reliability (0.86). In a simulated contact posture, a reliable measure of peak force was obtained using a single maximal contraction. This may have practical applications for the quick and reliable assessment of contact sport athletes in a position that has functional relevance to their sports.

Background: Neck strength has been reported to reduce the incidence of concussions and neck injuries. However, little is known about how neck strength changes over a playing season. The aim of this study was to understand the impact a 20-week rugby season has on neck strength, neck pain (NP) and neck stiffness (NS) in a cohort of rugby players, relative to a non-contact control group., Methods: This prospective cohort study employed a fixed-frame dynamometer to measure neck strength in a simulated contact posture in rugby players (N.=32) and controls (N.=15). During each assessment, participants performed a single maximal voluntary contraction in extension, flexion, left (LtFlx) and right lateral flexion (RtFlx). To quantify neck dysfunction, "current," "average," and "worst" NP and NS were measured using visual analogue scales., Results: Post-season improvements (35.3-59.1 N) in neck strength were observed for the forwards for all measured directions (P<0.01), and were significant when compared to controls. For the backs, improvements were seen in extension, flexion and LtFlx (P=0.01-0.05), with only extension (29.8 N) and flexion (35.14 N) remaining significant when contrasted against the controls. The controls' neck strength remained unchanged over the season. Despite improvements in peak force, NP increased (all three measures) for the forwards (P=0.01-0.04), while only current (P=0.03) and worst NP (P=0.04) increased for the backs. Unexpectedly, NS remained unchanged for the forwards, while backs reported increases for all three measures (P=0.01-0.02)., Conclusions: A season of rugby resulted in neck strength adaptations in the rugby players. Despite these improvements, increased levels of NP and NS were reported.

Aims: To quantify and compare energy utilization associated with prolonged sitting alone, or interrupted with regular activity breaks and/or an additional bout of continuous physical activity., Methods and Results: Thirty six adults (11 males, BMI 24.1 ± 4.6) completed four interventions: (1) prolonged sitting (SIT), (2) sitting with 2-min of walking every 30 min (RAB), (3) prolonged sitting with 30-min of continuous walking at the end of the day (SIT + PA), (4) a combination of the activities in (2) and (3) above (RAB + PA). All walking was at a speed and incline corresponding to 60% V̇O 2max . Energy utilization over 7 h for each intervention was estimated using indirect calorimetry. Compared to SIT, SIT + PA increased total energy utilization by 709 kJ (95% CI 485-933 kJ), RAB by 863 kJ (95% CI 638-1088 kJ), and RAB + PA by 1752 kJ (95% CI 1527-1927 kJ) (all p < 0.001). There was no difference in total energy utilization between SIT + PA and RAB, however, post-physical activity energy utilization in RAB was 632 kJ greater than SIT + PA (95% CI 561-704 kJ; p < 0.001)., Conclusions: Short frequent activity, results in greater accumulation of elevated post-physical activity energy utilization compared to a single bout of continuous activity; however the total energy utilization is similar. Combining activity breaks with a longer continuous bout of activity will further enhance energy utilization, and in the longer term, may positively affect weight management of a greater magnitude than either activity pattern performed alone., Trial Registration: ANZCTR12614000624684., (Copyright © 2018 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.)

Background: The cumulative effect of too much sedentary behavior may contribute to weight gain and obesity., Objective: The aim of this study was to conduct a systematic review and meta-analysis of prospective cohorts and randomized controlled studies to determine the association between sedentary behavior and body weight and obesity in adults., Data Sources and Study Selection: Relevant studies were identified from searches of the MEDLINE, Embase, AMED and PubMed databases up to May 2017, and by manual searches of in-text citations. Studies that evaluated the association in adults between sedentary behavior and body weight or obesity, while controlling for physical activity, were included. Overall, 31 publications met the eligibility criteria, including 23 prospective cohort studies with data that could be extracted for a quantitative meta-analysis, and a single randomized controlled trial., Results: There were no significant associations between sedentary behavior and any measure of body weight or obesity, with the exception of waist circumference. For the latter outcome, over a 5-year follow-up period, each 1 h per day increase-from baseline to follow-up-in sedentary behavior was associated with a 0.02 mm [95% confidence interval (CI) 0.01-0.04; p = 0.001) increase in waist circumference. The odds ratio of becoming overweight or obese was 1.33 (95% CI 1.11-1.60; p = 0.001) in the highest compared with lowest categories of sedentary behavior., Conclusions: Meta-analysis of data from prospective cohort studies showed small, inconsistent and non-significant associations between sedentary behavior and body weight.

Regular activity breaks increase energy expenditure; however, this may promote compensatory eating behaviour. The present study compared the effects of regular activity breaks and prolonged sitting on appetite. In a randomised, cross-over trial, 36 healthy adults (BMI (Body Mass Index) 23.9 kg/m² (S.D. = 3.9)) completed four, two-day interventions: two with prolonged sitting (SIT), and two with sitting and 2 min of walking every 30 min (RAB). Standardized meals were provided throughout the intervention, with an ad libitum meal at the end of Day 2. Appetite and satiety were assessed throughout both days of each intervention using five visual analogue scales. The five responses were combined into a single appetite response at each time point. The area under the appetite response curve (AUC) was calculated for each day. Intervention effects for appetite response AUC and ad libitum meal intake were tested using linear mixed models. Appetite AUC did not differ between interventions (standardised effect of RAB compared to SIT: Day 1: 0.11; 95% CI: -0.28, 0.06; p = 0.212; Day 2: 0.04; 95% CI: -0.15, 0.24; p = 0.648). There was no significant difference in energy consumed at the ad libitum lunch meal on Day 2 between RAB and SIT. Interrupting prolonged sitting with regular activity breaks does not acutely influence appetite or volume of food consumed, despite inferred increases in energy expenditure. Longer-term investigation into the effects of regular activity breaks on energy balance is warranted., Competing Interests: The authors declare no conflict of interest.

Heat is a major stressor during exercise, though its value in driving adaptation is not well understood. Muscle heating can upregulate pathways facilitating protein synthesis and could thereby enhance effects of exercise training, however, few studies have investigated this possibility. We examined whether heating active muscle during resistance training differentially affected physical and functional adaptations. Within a randomised contralateral-limb control study, ten healthy, resistance-untrained individuals (21 ± 3 y; 5 female) completed 30 sessions of progressive resistance training (12 weeks), performing 4 × 8 unilateral knee extensions at 70% of 1RM. One randomly-allocated thigh was heated during, and for 20 min after, each session using an electric pad eliciting muscle temperatures of >38 °C (HOT); the contralateral limb remained unheated (CON). Training intensity was progressed using 4-weekly strength assessments. Quadricep lean mass (measured using DXA) increased by 15 ± 7% in HOT ( p = 0.00) and 15 ± 6% in CON ( p = 0.00); the difference being trivial ( p = 0.94). Peak isokinetic torque at 90°.s -1 increased by 30 ± 25% (HOT; p = 0.00) and 34 ± 33% (CON; p = 0.01), with no difference ( p = 0.84) between limbs. Rate of torque development increased ∼40%, with no difference between limbs ( p = 0.73). The increase in 3-RM strength was also similar in HOT (75 ± 16%) and CON (71 ± 14%; p = 0.80 for difference). No differences in mass or strength changes were evident between sexes. In conclusion, supplemental heating of active muscle during and after each bout of resistance training showed no clear positive (or negative) effect on training-induced hypertrophy or function.

Exercise-associated hyponatremia can be life-threatening. Excessive hypotonic fluid ingestion is the primary etiological factor but does not explain all variability. Possible effects of chronic sodium intake are unknown. The aim of this study was to determine whether dietary sodium affects plasma sodium concentration [Na + ] during exercise in the heat, when water intake nearly matches mass loss. Endurance-trained men (n = 9) participated in this crossover experiment. Each followed a low-sodium (lowNa) or high-sodium (highNa) diet for 9 days with 24-h fluid intakes and urine outputs measured before experimental trials (day 10). The trials were ≥2 week apart. Trials comprised 3 h (or if not possible to complete, to exhaustion) cycling (55% VO 2max ; 34 °C, 65% RH) with water intake approximating mass loss. Plasma [Na + ], hematocrit, sweat and urine [Na + ], heart rate, core temperature, and subjective perceptions were monitored. Urine [Na + ] was lower on lowNa 24 h prior to (31 ± 24, 76 ± 30 mmol/L, P = 0.027) and during trials (10 ± 10, 52 ± 32 mmol/L, P = 0.004). Body mass was lower on lowNa (79.6 ± 8.5, 80.5 ± 8.9, P = 0.03). Plasma [Na + ] was lower on lowNa before (137 ± 2, 140 ± 3, P = 0.007) and throughout exercise (P = 0.001). Sweat [Na + ] was unaffected by diet (54.5 ± 40, 54.5 ± 23 mmol/L, P = 0.99). Heart rate and core temperature were higher on lowNa (P ≤ 0.001). Despite decreased urinary sodium losses, plasma sodium was lower on lowNa, with decreased mass indicating (extracellular) water may have been less, explaining greater heart rate and core temperature. General population health recommendations to lower salt intake may not be appropriate for endurance athletes, particularly those training in the heat., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Compared with prolonged sitting, regular activity breaks immediately lower postprandial glucose and insulin, but not triglyceride responses. Postprandial triglycerides can be lowered by physical activity but the effect is often delayed by ∼12 to 24 hours., Objective: The objective of the study was to determine whether regular activity breaks affect postprandial triglyceride response in a delayed manner similar to physical activity., Methods: In a randomized crossover trial, 36 adults (body mass index 23.9 kg/m 2 [standard deviation 3.9]) completed four 2-day interventions: (1) prolonged sitting (SIT); (2) prolonged sitting with 30 minutes of continuous walking (60% VO 2max ), at the end of Day 1 (SIT + PA D1 ); (3) Sitting with 2 minutes of walking (60% VO 2max ) every 30 minutes (RAB); (4) A combination of the continuous walking and regular activity breaks in 2 and 3 above (RAB + PA D1 ). Postprandial plasma triglyceride, nonesterified fatty acids, glucose, and insulin responses were measured in venous blood over 5 hours on Day 2., Results: Compared with SIT, both RAB (difference: -43.61 mg/dL·5 hours; 95% confidence interval [CI] -83.66 to -2.67; P = .035) and RAB + PA D1 (-65.86 mg/dL·5 hours; 95% CI -112.14 to -19.58; P = .005) attenuated triglyceride total area under the curve (tAUC). RAB + PA D1 produced the greatest reductions in insulin tAUC (-23%; 95% CI -12% to -31%; P < .001), whereas RAB resulted in the largest increase in nonesterified fatty acids (tAUC, 10.08 mg/dL·5 hours; 95% CI 5.60-14.84; P < .001). There was no effect on glucose tAUC (P = .290)., Conclusions: Postprandial triglyceride response is attenuated by regular activity breaks, when measured ∼24 hours after breaks begin. Combining regular activity breaks with 30 minutes of continuous walking further improves insulinemic and lipidemic responses., (Copyright © 2017 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Purpose: To compare energy use and substrate partitioning arising from repeated lower- versus upper-body sprints, or endurance exercise, across a 24-h period., Methods: Twelve untrained males (24±4 y) completed three trials in randomized order: (1) repeated sprints (five 30-s Wingate, 4.5-min recovery) on a cycle ergometer (SIT Legs ); (2) 50-min continuous cycling at 65% V̇O 2 max (END); (3) repeated sprints on an arm-crank ergometer (SIT Arms ). Respiratory gas exchange was assessed before and during exercise, and at eight points across 22h of recovery., Results: Metabolic rate was elevated to greater extent in the first 8h after SIT Legs than SIT Arms (by 0.8±1.1kJ/min, p=0.03), and tended to be greater than END (by 0.7±1.3kJ/min, p=0.08). Total 24-h energy use (exercise+recovery) was equivalent between SIT Legs and END (p = 0.55), and SIT Legs and SIT Arms (p=0.13), but 24-h fat use was higher with SIT Legs than END (by 26±38g, p=0.04) and SIT Arms (by 27±43g, p=0.05), whereas carbohydrate use was higher with SIT Arms than SIT Legs (by 32±51g, p=0.05). Plasma volume-corrected post-exercise and fasting glucose and lipid concentrations were unchanged., Conclusion: Despite much lower energy use during five sprints than 50-min continuous exercise, 24-h energy use was not reliably different. However, (i) fat metabolism was greater after sprints, and (ii) carbohydrate metabolism was greater in the hours after sprints with arms than legs, while 24-h energy usage was comparable. Thus, sprints using arms or legs may be an important adjunct exercise mode for metabolic health., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: To determine whether a facilitated recovery via cold-water immersion (CWI) after simulated rugby sevens would influence parasympathetic reactivation and repeated-sprint (RS) performance across 6 matches in a 2-d tournament., Methods: Ten male team-sport athletes completed 6 rugby sevens match simulations over 2 d with either postmatch passive recovery (PAS) or CWI in a randomized crossover design. Parasympathetic reactivation was determined via the natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent R-R intervals (ln rMSSD). RS performance was calculated as time taken (s) to complete 6 × 30-m sprints within the first half of each match., Results: There were large increases in postintervention ln rMSSD between CWI and PAS after all matches (ES 90% CL: +1.13; ±0.21). Average heart rate (HR) during the RS performance task (HRAverage RS) was impaired from baseline from match 3 onward for both conditions. However, HRAverage RS was higher with CWI than with PAS (ES 90% CL: 0.58; ±0.58). Peak HR during the RS performance task (HRPeak RS) was similarly impaired from baseline for match 3 onward during PAS and for match 4 onward with CWI. HRPeak RS was very likely higher with CWI than with PAS (ES 90% CL: +0.80; ±0.56). No effects of match or condition were observed for RS performance, although there were moderate correlations between the changes in HRAverage RS (r 90% CL: -0.33; ±0.14), HRPeak RS (r 90% CL: -0.38; ±0.13), and RS performance., Conclusion: CWI facilitated cardiac parasympathetic reactivation after a simulated rugby sevens match. The decline in average and peak HR across matches was partially attenuated by CWI. This decline was moderately correlated with a reduction in RS performance.

The purpose of this study was to examine the reliability of repeated isometric measurements of neck strength and endurance in a simulated rugby contact posture. Data were collected from healthy active university students (n = 20) over 3 sessions. Each session consisted of a single maximal voluntary contraction (MVC) and endurance trial for extension and flexion. The endurance trials were analyzed to determine the area under the force curve (%AUC) and the time to fatigue (TTF). Reliability was calculated using the SEM and minimal detectable change (MDC). The results revealed that the MVC values for extension were nonsignificant for session (p = 0.21), whereas some session differences were seen for flexion (p = 0.01), where session 1, 115.3 N was less than session 3, 126.4 N (p = 0.03). For %AUC, flexion values (%AUC 86.0) were greater than extension (%AUC 59.4) (p = 0.02). A similar effect was observed for TTF with flexion (125.0 seconds) having significantly greater TTF than extension (86.1 seconds). For peak force, the greatest SEM and MDC were achieved for extension (15.3 and 42.3 N), while flexion produced lower values (11.3 and 31.2 N). In contrast, for the endurance trials, SEM and MDC were greater in flexion than in extension. The findings from this study indicate that the neck musculature can be reliably assessed in a simulated contact posture. For peak force, extension provided more consistent measures across time as there seems to be a learning effect for flexion. Additionally, the SEM and MDC scores provide a useful tool for future assessment of neck strength and endurance.

Effects of protein versus mixed macronutrient supplementation on total energy intake (TEI) and protein intake during an ad libitum diet were examined. Trained males undertook two, 2-week dietary interventions which were randomized, double blinded, and separated by 2 weeks. These were high-protein supplementation (HP: 1034.5 kJ energy, 29.6 g protein, 8.7 g fat and 12.3 g CHO) and standard meal supplementation (SM: 1039 kJ energy, 9.9 g protein, 9.5 g fat, and 29.4 g CHO) consumed daily following a week of baseline measures. Eighteen participants finished both interventions and one only completed HP. TEI (mean ± SD) was not different between baseline (11148 ± 3347 kJ) and HP (10705 ± 3143 kJ) nor between baseline and SM (12381 ± 3877 kJ), however, TEI was greater with SM than HP (923 ± 4015 kJ p = .043). Protein intake (%TEI) was greater with HP (22.4 ± 6.2%) than baseline (19.4 ± 5.4%; p = .008) but not SM (20.0 ± 5.0%). No differences in absolute daily protein intake were found. Absolute CHO intake was greater with SM than HP (52.0 ± 89.5 g, p = .006). No differences in fat intake were found. Body mass did not change between baseline (82.7 ± 11.2 kg) and either HP (83.1 ± 11.7 kg) or SM (82.9 ± 11.0 kg). Protein supplementation increases the relative proportion of protein in the diet, but doesn't increase the absolute amount of total protein or energy consumed. Thus some compensation by a reduction in other foods occurs. This is in contrast to a mixed nutrient supplement, which does not alter the proportion of protein consumed but does increase TEI.

Unlabelled: Most heat acclimation data are from regimes longer than 1 week, and acclimation advice is to prevent dehydration., Objectives: We hypothesized that (i) short-term (5-day) heat acclimation would substantially improve physiological strain and exercise tolerance under heat stress, and (ii) dehydration would provide a thermally independent stimulus for adaptation., Methods: Nine aerobically fit males heat acclimated using controlled-hyperthermia (rectal temperature 38.5°C) for 90 min on 5 days; once euhydrated (EUH) and once dehydrated (DEH) during acclimation bouts. Exercising heat stress tests (HSTs) were completed before and after acclimations (90-min cycling in Ta 35°C, 60% RH)., Results: During acclimation bouts, [aldosterone]plasma rose more across DEH than EUH (95%CI for difference between regimes: 40-411 pg ml(-1); P = 0.03; n = 5) and was positively related to plasma volume expansion (r = 0.65; P = 0.05), which tended to be larger in DEH (CI: -1 to 10%; P = 0.06; n = 9). In HSTs, resting forearm perfusion increased more in DEH (by 5.9 ml 100 tissue ml(-1) min(-1): -11.5 to -1.0; P = 0.04) and end-exercise cardiac frequency fell to a greater extent (by 11 b min(-1): -1 to 22; P = 0.05). Hydration-related effects on other endocrine, cardiovascular, and psychophysical responses to HSTs were unclear. Rectal temperature was unchanged at rest but was 0.3°C lower at end exercise (P < 0.01; interaction: P = 0.52)., Conclusions: Short-term (5-day) heat acclimation induced effective adaptations, some of which were more pronounced after fluid-regulatory strain from permissive dehydration, and not attributable to dehydration effects on body temperature., (Copyright © 2014 Wiley Periodicals, Inc.)

We investigated the effect of added load and intense exercise on jump and landing performance and ground reaction force (GRF) during landings where attentional demand was varied. Fifty-two males (37 ± 9.2 years, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, maximal aerobic fitness (VO(₂max)) 50 ± 8.5 ml (.) kg(-1 .) min(-1), BMI 27.6 ± 3.1, mean ± s) completed a VO(₂max) test. Experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing body armour and appointments (loaded) and one without load (unloaded). A vertical jump, a drop landing concentrating on safe touchdown, a drop jump and a drop landing with an attentional distraction were performed. These were repeated 1 min after a 5-min treadmill run. Mean jump height decreased by 12% (P < 0.001) with loading and a further by 6% following the running task. Peak GRFs were increased by 13-19% with loading (P < 0.001) depending on the landing task demands and a further by 4-9% following intense exercise. The distracted drop landing had significantly higher GRFs compared to all other landings. Results demonstrate that added load impacts on jumping and landing performance, an effect that is amplified by prior intense exercise, and distraction during landing. Such increases in GRF apply to police officer performance in their duties and may increase the risk of injury.

Body armour is used widely by law enforcement and other agencies but has received mixed reviews. This study examined the influence of stab resistant body armour (SRBA) and mandated accessories on physiological responses to, and the performance of, simulated mobility tasks. Fifty-two males (37 ± 9.2 yr, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, VO2max 50 ± 8.5 ml kg(-1) min(-1), BMI 27.6 ± 3.1, mean ± SD) completed a running VO2max test and task familiarisation. Two experimental sessions were completed (≥4 days in between) in a randomised counterbalanced order, one while wearing SRBA and appointments (loaded) and one without additional load (unloaded). During each session participants performed five mobility tasks: a balance task, an acceleration task that simulated exiting a vehicle, chin-ups, a grappling task, and a manoeuvrability task. A 5-min treadmill run (zero-incline at 13 km·h(-1), running start) was then completed. One min after the run the five mobility tasks were repeated. There was a significant decrease in performance during all tasks with loading (p < 0.001). Participants were off-balance longer; slower to complete the acceleration, grapple and mobility tasks; completed fewer chin-ups; and had greater physiological cost (↑ %HRmax, ↑ %VO2max, ↑ RER) and perceptual effort (↑ RPE) during the 5-min run. Mean performance decreases ranged from 13 to 42% while loaded, with further decreases of 6-16% noted after the 5-min run. Unloaded task performance was no different between phases. Wearing SRBA and appointments significantly reduced mobility during key task elements and resulted in greater physiological effort. These findings could have consequences for optimal function in the working environment and therefore officer and public safety., (Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.)

Background: Sedentary behavior is a risk factor for cardiometabolic disease. Regularly interrupting sedentary behavior with activity breaks may lower this risk., Objective: We compared the effects of prolonged sitting, continuous physical activity combined with prolonged sitting, and regular activity breaks on postprandial metabolism., Design: Seventy adults participated in a randomized crossover study. The prolonged sitting intervention involved sitting for 9 h, the physical activity intervention involved walking for 30 min and then sitting, and the regular-activity-break intervention involved walking for 1 min 40 s every 30 min. Participants consumed a meal-replacement beverage at 60, 240, and 420 min., Results: The plasma incremental area under the curve (iAUC) for insulin differed between interventions (overall P < 0.001). Regular activity breaks lowered values by 866.7 IU · L(-1) · 9 h(-1) (95% CI: 506.0, 1227.5 IU · L(-1) · 9 h(-1); P < 0.001) when compared with prolonged sitting and by 542.0 IU · L(-1) · 9 h(-1) (95% CI: 179.9, 904.2 IU · L(-1) · 9 h(-1); P = 0.003) when compared with physical activity. Plasma glucose iAUC also differed between interventions (overall P < 0.001). Regular activity breaks lowered values by 18.9 mmol · L(-1) · 9 h(-1) (95% CI: 10.0, 28.0 mmol · L(-1) · 9 h(-1); P < 0.001) when compared with prolonged sitting and by 17.4 mmol · L(-1) · 9 h(-1) (95% CI: 8.4, 26.3 mmol · L(-1) · 9 h(-1); P < 0.001) when compared with physical activity. Plasma triglyceride iAUC differed between interventions (overall P = 0.023). Physical activity lowered values by 6.3 mmol · L(-1) · 9 h(-1) (95% CI: 1.8, 10.7 mmol · L(-1) · 9 h(-1); P = 0.006) when compared with regular activity breaks., Conclusion: Regular activity breaks were more effective than continuous physical activity at decreasing postprandial glycemia and insulinemia in healthy, normal-weight adults. This trial was registered with the Australian New Zealand Clinical Trials registry as ACTRN12610000953033.

Purpose: Effects of resistance training and detraining on glucose and insulin responses to an oral glucose load, muscle fiber type, and muscular performance in the offspring of those with type 2 diabetes (familial insulin resistant (FIR)) were investigated., Methods: Six FIR participants and 10 controls (C) completed 9 wk of resistance training and 9 wk of detraining. Measures of strength and power, an oral glucose tolerance test, and a muscle biopsy to determine myosin heavy chain (MHC) fiber composition were taken at baseline (T1), after training (T2), and after detraining (T3)., Results: Three-repetition maximum increased (P ≤ 0.001) similarly in both groups in all strength measures, e.g., leg press (FIR T1, T2: 121 ± 34 kg, 186 ± 50 kg; C T1, T2: 137 ± 42 kg, 206 ± 64 kg, respectively (means ± SD)). Wingate peak power increased (FIR T1, T2: 505 ± 137 W, 523 ± 143 W; C T1, T2: 636 ± 211 W, 672 ± 223 W, respectively; P ≤ 0.005 (means ± SD)). Training reduced insulin area under the curve more (P = 0.050) in FIR (T1, T2: 1219 ± 734 pmol·L, 837 ± 284 pmol·L, respectively (means ± SD)) than that in C (T1, T2: 647 ± 268 pmol·L, 635 ± 258 pmol·L, respectively (means ± SD)). MHC distribution did not change with training. Strength (three-repetition maximum measures) decreased with detraining (P ≤ 0.001) although Wingate power did not. Detraining increased insulin area under the curve (P = 0.018) in FIR (T2, T3: 837 ± 285 pmol·L, 1040 ± 194 pmol·L, respectively (means ± SD)) but not in C (T2, T3: 635 ± 258 pmol·L, 625 ± 213 pmol·L, respectively (means ± SD)). MHC IIX fibers increased with detraining (P = 0.026)., Conclusion: FIR appears to have exaggerated responses to resistance training and detraining, with a greater reduction in insulin release with glucose ingestion after training and increase when training ceases. Resistance training has a significant effect on insulin responses and may reduce future risk of type 2 diabetes mellitus among FIR.

Effectiveness of short-term acclimation has generally been undertaken using untrained and moderately-trained participants. The purpose of this study was to determine the impact of short-term (5-day) heat acclimation on highly trained athletes. Eight males (mean ± SD age 21.8 ± 2.1 years, mass 75.2 ± 4.6 kg, VO(2peak) 4.9 ± 0.2 L min(-1) and power output 400 ± 27 W) were heat acclimated under controlled hyperthermia (rectal temperature 38.5 °C), for 90-min on five consecutive days (T(a) = 39.5 °C, 60% relative humidity). Acclimation was undertaken with dehydration (no fluid-intake) during daily bouts. Participants completed a rowing-specific, heat stress test (HST) 1 day before and after acclimation (T(a) = 35 °C, 60% relative humidity). HST consisted 10-min rowing at 30% peak power output (PPO), 10 min at 60% PPO and 5-min rest before a 2-km performance test, without feedback cues. Participants received 250 mL fluid (4% carbohydrate; osmolality 240-270 mmol kg(-1)) before the HST. Body mass loss during acclimation bouts was 1.6 ± 0.3 kg (2.1%) on day 1 and 2.3 ± 0.4 kg (3.0%) on day 5. In contrast, resting plasma volume increased by 4.5 ± 4.5% from day 1 to 5 (estimated from [Hb] & Hct). Plasma aldosterone increased at rest (52.6 pg mL(-1); p = 0.03) and end-exercise (162.4 pg mL(-1); p = 0.00) from day 1 to 5 acclimation. During the HST T(re) and f(c) were lowered 0.3 °C (p = 0.00) and 14 b min(-1) (p = 0.00) after 20-min exercise. The 2-km performance time (6.52.7 min) improved by 4 s (p = 0.00). Meaningful physiological and performance improvements occurred for highly trained athletes using a short-term (5-day) heat acclimation under hyperthermia control, with dehydration.

Historically, the link between elevated cholesterol and increased risk of cardiovascular disease has been based on fasting measurements. This is appropriate for total, low-density lipoprotein and high-density lipoprotein cholesterol. However, triglyceride concentrations vary considerably throughout the day in response to the regular consumption of food and drink. Recent findings indicate that postprandial triglyceride concentrations independently predict future cardiovascular risk. Potential modulators of postprandial lipidemia include meal composition and physical activity. Early cross sectional studies indicated that physically active individuals had a lower postprandial lipidemic response compared to inactive individuals. However, the effect of physical activity on postprandial lipidemia is an acute phenomenon, which dissipates within 60 h of a single bout of exercise. Total exercise induced energy expenditure, rather than duration or intensity of the physical activity is commonly reported to be a potent modulator of postprandial lipidemia. However, the pooled results of studies in this area suggest that energy expenditure exerts most of its influence on fasting triglyceride concentrations rather than on the incremental change in triglyceride concentrations seen following meal consumption. It seems more likely that energy expenditure is one component of a multifactorial list of mediators that may include local muscle contractile activity, and other yet to be elucidated mechanisms., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

A rethinking of current heat-acclimation strategies is required as most research and advice for improving physiological strain in the heat includes maintaining hydration using long-term acclimation protocols (>10 days). Furthermore, these strategies have tended to use untrained and moderately trained participants. Therefore, the aims of this review were to (i) investigate the effectiveness of short-term heat acclimation (STHA) with moderately and highly trained athletes; (ii) determine the importance of fluid regulatory strain, which has a thermally independent role in heat adaptation; (iii) assess the impact of STHA on a marker of thermotolerance (inducible heat-shock protein 70 [HSP70]); and (iv) provide further information on the decay of acclimation to heat. The review suggests that 5-day STHA is effective, and adaptations may be more pronounced after fluid regulatory strain from a dehydration-acclimation regimen. Furthermore, highly trained athletes may have similar physiological gains to those who are less trained using STHA. However, research has tended to focus on untrained or moderately trained participants and more information is required for highly trained populations. HSP70 response is upregulated across STHA. This indicates increased thermotolerance and protective adaptive change that may indicate HSP70 response as a useful marker of heat acclimation. Physiological adaptations after heat acclimation are relatively short term and may vanish only a few days or weeks after removal from heat exposure. From a practical perspective 5-day STHA may be the preferred acclimation regimen for moderately and highly trained athletes as it has been shown to be effective, less expensive and less likely to disrupt the tapering for competition in elite performers. Furthermore, updated information on the time course of acclimation decay may allow a reliable estimate of how long individuals can be free from heat exposure before reacclimation is required. This is particularly pertinent in present times as many athletes, civilians and military personnel increasingly have to relocate to different climates of the world, often within a short period of time.

Introduction: A decrease in physical activity amongst adolescents has been observed and it is well documented that low levels of activity are associated with poor health. In an attempt to understand factors that influence physical activity (PA) in young people research was undertaken with high school students in New Zealand to identify preferred places for PA and establish factors that they felt influenced levels of PA., Methods: One hundred males and 73 females in year nine (aged 12-13) in health and physical education classes completed mapping exercises in which they delineated favourite and least favourite places for PA, where they went on a particular Sunday, how they got there and what they did, and chosen after-school activities and how they got there., Results: Open public spaces were the most favoured places for PA with a nearby beach and park most frequently cited. Specific physical activities, having fun, and having friends to do an activity with were the most frequently cited reasons for liking these places. An industrial harbour area, other schools, and cemeteries were the least favoured places. Less than 2% biked somewhere on the Sunday surveyed and only 23% walked somewhere. The majority were driven to activities by car and a similar reliance on cars was observed for after-school activities., Conclusions: A combination of environmental and social factors is important in both encouraging and discouraging PA and should be taken into account when seeking to enhance PA of young people.

Energy intake (EI) and energy expenditure (EE) are relatively easy to measure accurately over short periods in a laboratory setting, but less so during a multi-day competition. Our goal was to measure EI and EE as accurately as possible during a 6-day, 10-stage cycling race. We prepared all meals and supplements, assessed EI (weighed diet-records) and macrontrient intake, total EE (doubly labelled water), resting metabolic rate (respiratory gas exchange), exercise EE (power meters), and body mass. Body composition was measured several days before and after racing (dual x-ray absorptiometry). Body mass remained stable over the course of the race. The mean EI (27.3+/-3.8 MJ/day) nearly matched EE (27.4+/-2.0 MJ/day). The majority (62%) of EE was exercise EE. Macronutrient intake was within or exceeded the recommendations. Lean body mass increased and fat mass decreased in most of our participants. Our study indicates that EI can match high EE with adequate macronutrient intake during multi-day cycle racing and may be facilitated by appropriate foods being available at appropriate times. This optimization of nutritional provision supports positive changes in body composition.

The purpose of this study was to determine whether glycemic index (GI) is influenced by training state. Participants were tested in a randomized order: twice with a reference solution containing 50 g glucose and once each with 2 commercially available snack bars (Griffin's Fruitli bar and Peak Fuel's Summit bar) containing 50 g available carbohydrate. Eleven of the participants (6 men and 5 women, M + or - SD age 20.8 + or - 2.0 yr) were endurance trained (ET; VO(2max) 57.5 + or - 8.4 ml x kg(-1) x min(-1) ), and 9 participants (2 men and 7 women, M + or - SD age 22.4 + or - 1.8 yr) were sedentary (SE; VO(2max) 43.7 + or - 9.1 ml x kg(-1) x min(-1) ). After an overnight fast, participants consumed either the glucose solution or snack bar, with blood samples taken before eating and at 15, 30, 45, 60, 90, and 120 min after eating began. The mean incremental area under the curve (IAUC) of the glucose reference was 31% lower (95% CI 3-52%, p = .03), and the Fruitli bar 38% lower (95% CI 0-61%, p = .05) in ET than in SE participants. There was a trend for the IAUC for the Summit bar to be 35% lower in ET than in SE participants (95% CI -7% to 61% p = .09). There was no significant interaction between training state and test food. The GIs of the Fruitli and Summit bars was not significantly different between ET and SE participants (p = .65 and .54, respectively). ET participants had a lower glycemic response than SE participants; however, training state did not influence GI.

The purpose of this work was to investigate adaptation and decay from short-term (5-day) heat acclimation (STHA). Ten moderately trained males (mean +/- SD age 28 +/- 7 years; body mass 74.6 +/- 4.4 kg; VO2peak 4.26 +/- 0.37 l min(-1)) underwent heat acclimation (Acc) for 90-min on 5-days consecutively (T (a) = 39.5 degrees C, 60% RH), under controlled hyperthermia (rectal temperature 38.5 degrees C). Participants completed a heat stress test (HST) 1 week before acclimation (Acc), then on the 2nd and 8th day (1 week) following Acc (T (a) = 35 degrees C, 60% RH). Seven participants completed HSTs 2 and 3 weeks after Acc. HST consisted of 90-min cycling at 40% peak power output before an incremental performance test. Rectal temperature at rest (37.1 +/- 0.4 degrees C) was not lowered by Acc (95% CI -0.3 to 0.2 degrees C), after 90-min exercise (38.6 +/- 0.5 degrees C) it reduced 0.3 degrees C (-0.5 to -0.1 degrees C) and remained at this level 1 week later (-0.5 to -0.1 degrees C), but not two (0.1 degrees C -0.4 to 0.5 degrees C; n = 7) or 3 weeks. Similarly, heart rate after 90-min exercise (146 +/- 21 b min(-1)) was reduced (-13: -6 to -20 b min(-1)) and remained at this level after 1 week (-13: -6 to -20 b min(-1)) but not two (-9: 6 to -23 b min(-1); n = 7) or 3 weeks. Performance (746 s) increased 106 s: 59 to 152 s after Acc and remained higher after one (76 s: 31 to 122) but not two (15 s: -88 to 142 s; n = 7) or 3 weeks. Therefore, STHA (5-day) induced adaptations permitting increased heat loss and this persisted 1 week but not 2 weeks following Acc.

Unlabelled: In recent years, sports facilities have formed part of Norwegian public health policies to increase physical activity among children and adolescents. Despite large sums of public money being spent on such facilities, information on usage is limited., Aims: Our aim was to study the effects of gender, age and relative activity level on young people's use of sports facilities., Methods: We explored 662 young people's (age 6-16 years) usage of 19 different kinds of sports facilities. A questionnaire was administered to students and teachers, and situation plots of students at recess were made., Results: The findings indicate that sports facilities in general were less used by girls, adolescents (14-16 years) and the least active (physically active < or = 1 times/week outside school) than by boys, children (6-13 years) and the most active (physically active > or = 4 times/ week outside school). More general, multifunctional facilities were used to a greater extent than specialized facilities, particularly by the least active. Distance to facility was important for the use of common facilities., Conclusions: These results raise the question of whether sports facilities significantly increase physical activity among "all'' young people, which is the government's stated goal. More research on sports facilities use and physical activity levels among males and females of all ages is warranted.

This study was conducted to investigate effects of an acute sodium load on resting plasma volume (PV) and renal mechanisms across the menstrual cycle of endurance-trained women with natural (NAT) or oral contraceptive pill (OCP) controlled cycles. Twelve women were assigned to one of two groups, according to their usage status: 1) OCP [n = 6, 29 yr (SD 6), 59.4 kg (SD 3.2)], or 2) NAT [n = 6, 24 yr (SD 5), 61.3 kg (SD 3.6)]. The sodium load was administered as a concentrated sodium chloride/citrate beverage (164 mmol Na(+)/l, 253 mosmol/kgH(2)O, 10 ml/kg body mass) during the last high-hormone week of the OCP cycle (OCP(high)) or late luteal phase of the NAT cycle (NAT(high)) and during the low-hormone sugar pill week of OCP (OCP(low)) or early follicular phase of the NAT cycle (NAT(low)). The beverage ( approximately 628 ml) was ingested in seven portions across 60 min. Over the next 4 h, PV expanded more in the low-hormone phase for both groups (time-averaged change): OCP(low) 6.1% (SD 1.1) and NAT(low) 5.4% (SD 1.2) vs. OCP(high) 3.9% (SD 0.9) and NAT(high) 3.5% (SD 0.8) (P = 0.02). The arginine vasopressin increased less in the low-hormone phase [1.63 (SD 0.2) and 1.30 pg/ml (SD 0.2) vs. 1.82 (SD 0.3) and 1.57 pg/ml (SD 0.5), P = 0.0001], as did plasma aldosterone concentration ( approximately 64% lower, P = 0.0001). Thus PV increased more and renal hormone sensitivity was decreased in the low-hormone menstrual phase following sodium/fluid ingestion, irrespective of OCP usage.

Aim: Regular endurance exercise stimulates muscle metabolic capacity, but effects of very prolonged endurance exercise are largely unknown. This study examined muscle substrate availability and utilization during prolonged endurance exercise, and associated metabolic genes., Methods: Data were obtained from 11 competitors of a 4- to 5-day, almost continuous ultraendurance race (seven males, four females; age: 36 +/- 11 years; cycling Vo(2peak): males 57.4 +/- 5.9, females 48.1 +/- 4.0 mL kg(-1) min(-1)). Before and after the race muscle biopsies were obtained from vastus lateralis, respiratory gases were sampled during cycling at 25 and 50% peak aerobic power output, venous samples were obtained, and fat mass was estimated by bioimpedance under standardized conditions., Results: After the race fat mass was decreased by 1.6 +/- 0.4 kg (11%; P < 0.01). Respiratory exchange ratio at the 25 and 50% workloads decreased (P < 0.01) from 0.83 +/- 0.06 and 0.93 +/- 0.03 before, to 0.71 +/- 0.01 and 0.85 +/- 0.02, respectively, after the race. Plasma fatty acids were 3.5 times higher (from 298 +/- 74 to 1407 +/- 118 micromol L(-1); P < 0.01). Muscle glycogen content fell 50% (from 554 +/- 28 to 270 +/- 25 nmol kg(-1) d.w.; n = 7, P < 0.01), whereas the decline in muscle triacylglycerol (from 32 +/- 5 to 22 +/- 3 mmol kg(-1) d.w.; P = 0.14) was not statistically significant. After the race, muscle mRNA content of lipoprotein lipase and glycogen synthase increased (P < 0.05) 3.9- and 1.7-fold, respectively, while forkhead homolog in rhabdomyosarcoma, pyruvate dehydrogenase kinase 4 and vascular endothelial growth factor mRNA tended (P < 0.10) to be higher, whereas muscle peroxisome proliferator-activated receptor gamma co-activator-1beta mRNA tended to be lower (P = 0.06)., Conclusion: Very prolonged exercise markedly increases plasma fatty acid availability and fat utilization during exercise. Exercise-induced regulation of genes encoding proteins involved in fatty acid recruitment and oxidation may contribute to these changes.

This study was conducted during the high-hormone phase of both natural and oral contraceptive pill (OCP)-mediated menstrual cycles to determine whether preexercise ingestion of a concentrated sodium beverage would increase plasma volume (PV), reduce physiological strain, and aid endurance of moderately trained women cycling in warm conditions. Thirteen trained cyclists [peak O(2) uptake 52 ml x kg(-1) x min(-1) (SD 2), age 26 yr (SD 6), weight 60.8 kg (SD 5)] who were oral contraceptive users (n = 6) or not (n = 7) completed this double-blind, crossover experiment. Cyclists ingested a concentrated-sodium (High Na(+): 164 mmol Na(+)/l) or low-sodium (Low Na(+): 10 mmol Na(+)/l) beverage (10 ml/kg) before cycling to exhaustion at 70% Peak O(2) uptake in warm conditions (32 degrees C, 50% relative humidity, air velocity 4.5 m/s). Beverage (approximately 628 ml) was ingested in seven portions across 60 min beginning 105 min before exercise, with no additional fluid given until the end of the trial. Trials were separated by one to two menstrual cycles. High Na(+) increased PV (calculated from hematocrit and hemoglobin concentration) before exercise, whereas Low Na(+) did not [-4.4 (SD 1.1) vs. -1.9% (SD 1.3); 95% confidence interval: for the difference 5.20, 6.92; P < 0.0001], and it involved greater time to exhaustion [98.8 (SD 25.6) vs. 78.7 (SD 24.6) min; 95% confidence interval: 13.3, 26.8; P < 0.0001]. Core temperature rose more quickly with Low Na(+) [1.6 degrees C/h (SD 0.2)] than High Na(+) [1.2 degrees C/h (SD 0.2); P = 0.04]. Plasma [AVP], [Na(+)] concentration, and osmolality, and urine volume, [Na(+)], and osmolality decreased with sodium loading (P < 0.05) independent of pill usage. Thus preexercise ingestion of a concentrated sodium beverage increased PV, reduced thermoregulatory strain, and increased exercise capacity for women in the high-hormone phase of natural and oral contraceptive pill-mediated menstrual cycles, in warm conditions.

Plasma glucose and muscle glycogen oxidation during prolonged exercise [75-min at 48 and 76% maximal O(2) uptake (Vo(2 max))] were measured in eight well-trained male subjects [Vo(2 max) = 4.50 l/min (SD 0.63)] using a simplified tracer technique in which a small amount of glucose highly enriched in (13)C was ingested: plasma glucose oxidation was computed from (13)C/(12)C in plasma glucose (which was stable beginning at minute 30 and minute 15 during exercise at 48 and 76% Vo(2 max), respectively) and (13)CO(2) production, and muscle glycogen oxidation was estimated by subtracting plasma glucose oxidation from total carbohydrate oxidation. Consistent data from the literature suggest that this small dose of exogenous glucose does not modify muscle glycogen oxidation and has little effect, if any, on plasma glucose oxidation. The percent contributions of plasma glucose and muscle glycogen oxidation to the energy yield at 48% Vo(2 max) [15.1% (SD 3.8) and 45.9% (SD 5.8)] and at 76% Vo(2 max) [15.4% (SD 3.6) and 59.8% (SD 9.2)] were well in line with data previously reported for similar work loads and exercise durations using conventional tracer techniques. The significant reduction in glycogen concentration measured from pre- and postexercise vastus lateralis muscle biopsies paralleled muscle glycogen oxidation calculated using the tracer technique and was larger at 76% than at 48% Vo(2 max). However, the correlation coefficients between these two estimates of muscle glycogen utilization were not different from zero at each of the two work loads. The simplified tracer technique used in the present experiment appears to be a valid alternative approach to the traditional tracer techniques for computing plasma glucose and muscle glycogen oxidation during prolonged exercise.

This study compared 3 d of carbohydrate loading (CHOL; 8.4 g x kg(-1) x d(-1) carbohydrate) in female eumenorrheic athletes with 3 d of an isoenergetic normal diet (NORM; 5.2 g x kg(-1) x d(-1) carbohydrate) and examined the effect of menstrual-cycle phase on performance, muscle-glycogen concentration [glyc], and substrate utilization. Nine moderately trained eumenorrheic women cycled in an intermittent protocol varying in intensity from 45% to 75% VO2max for 75 min, followed by a 16-km time trial at the midfollicular (MF) and midluteal (ML) phases of the menstrual cycle on NORM and CHOL. Time-trial performance was not affected by diet (CHOL 26.10 +/- 1.04 min, NORM 26.16 +/- 1.35 min; P = 0.494) or menstrual-cycle phase (MF 26.05 +/- 1.10 min, ML 26.23 +/- 1.33 min; P = 0.370). Resting [glyc] was lowest in the MF phase after NORM (575 +/- 145 mmol x kg(-1) x dw(-1)), compared with the MF phase after CHOL (728 mmol x kg(-1) x dw(-1)) and the ML phase after CHOL and NORM (756 and 771 mmol x kg(-1) x dw(-1), respectively). No effect of phase on substrate utilization during exercise was observed. These data support previous observations of greater resting [glyc] in the ML than the MF phase of the menstrual cycle and suggest that lower glycogen storage in the MF phase can be overcome by carbohydrate loading.

Purpose: This study was conducted to determine whether preexercise ingestion of a highly concentrated sodium beverage would increase plasma volume (PV) and reduce the physiological strain of moderately trained males running in the heat., Methods: Eight endurance-trained (.VO2max: 58 mL.kg(-1).min(-1) (SD 5); 36 yr (SD 11)) runners completed this double-blind, crossover experiment. Runners ingested a high-sodium (High Na+: 164 mmol Na+.L(-1)) or low-sodium (Low Na+: 10 mmol Na+.L(-1)) beverage (10 mL.kg(-1)) before running to exhaustion at 70% .VO2max in warm conditions (32 degrees C, 50% RH, V(a) approximately equal to 1.5 m.s(-1)). Beverages (approximately 757 mL) were ingested in seven portions across 60 min beginning 105 min before exercise. Trials were separated by 1-3 wk. Heart rate and core and skin temperatures were measured throughout exercise. Urine and venous blood were sampled before and after drinking and exercise., Results: High Na+ increased PV before exercise (4.5% (SD 3.7)), calculated from Hct and [Hb]), whereas Low Na+ did not (0.0% (SD 0.5); P = 0.04), and involved greater time to exercise termination in the six who stopped because of an ethical end point (core temperature 39.5 degrees C: 57.9 min (SD 6) vs 46.4 min (SD 4); P = 0.04) and those who were exhausted (96.1 min (SD 22) vs 75.3 min (SD 21); P = 0.03; High Na+ vs Low Na+, respectively). At equivalent times before exercise termination, High Na+ also resulted in lower core temperature (38.9 vs 39.3 degrees C; P = 0.00) and perceived exertion (P = 0.01) and a tendency for lower heart rate (164 vs 174 bpm; P = 0.08)., Conclusions: Preexercise ingestion of a high-sodium beverage increased plasma volume before exercise and involved less thermoregulatory and perceived strain during exercise and increased exercise capacity in warm conditions.

Effects of feeding glucose on substrate metabolism during cycling were studied. Trained (60.0 +/- 1.9 mL x kg(-1) x min(-1)) males (N = 5) completed two 75 min, 80% VO(2max) trials: 125 g 13(C)-glucose CHO); 13(C)-glucose tracer, 10 g (C). During warm-up (30 min 30% VO2max) 2 . 2 g 13(C)-glucose was given as bicarbonate pool primer. Breath samples and blood glucose were analyzed for 13(C/12)C with IRMS. Protein oxidation was estimated from urine and sweat urea. Indirect calorimetry (protein corrected) and 13(C/12)C enrichment in expired CO(2)and blood glucose allowed exogenous (Gexo), endogenous (Gendo), muscle (Gmuscle), and liver glucose oxidation calculations. During exercise (75 min) in CHO versus C (respectively): protein oxidation was lower (6.8 +/- 2.7, 18.8 +/- 5.9 g; P = 0.01); Gendo was reduced (71.2 +/- 3.8, 80.7 +/- 5.7% P = 0.01); Gmuscle was reduced (55.3 +/- 6.1, 65.9 +/- 6.0%; P = 0.01) compensated by increased Gexo(58.3 +/- 2.1, 3.87 +/- 0.85 g; P = 0.000002). Glucose ingestion during exercise can spare endogenous protein and carbohydrate, in fed cyclists, without glycogen depletion.