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Purpose: This study aimed to compare performance and pacing strategies between elite male and female cross-country skiers during a sprint competition on snow using the skating technique. Methods: Twenty male and 14 female skiers completed an individual time-trial prolog (TT) and three head-to-head races (quarter, semi, and final) on the same 1,572-m course, which was divided into flat, uphill and downhill sections. Section-specific speeds, choice of sub-technique (i.e., gear), cycle characteristics, heart rate and post-race blood lactate concentration were monitored. Power output was estimated for the different sections during the TT, while metabolic demand was estimated for two uphill camera sections and the final 50-m flat camera section. Results: Average speed during the four races was ∼12.5% faster for males than females (P < 0.001), while speeds on the flat, uphill and downhill sections were ∼11, 18, and 9% faster for the males than females (all P< 0.001 for terrain, sex, and interaction). Differences in uphill TT speed between the sexes were associated with different sub-technique preferences, with males using a higher gear more frequently than females (P < 0.05). The estimated metabolic demand relative to maximal oxygen uptake (V˙" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V˙V˙O2max) was similar for both sexes during the two uphill camera sections (∼129% of V˙" role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; ma

Purpose: This study aimed to investigate the physiological factors affected by rifle carriage during biathlon skiing performance, as well as the sex differences associated with rifle carriage. Methods: Seventeen national- and international-level biathletes (nine females and eight males; age 23.0 ± 3.3 years, V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2max 59.4 ± 7.6 mL.kg–1.min–1) performed a submaximal incremental test and a maximal time-trial (TT) using treadmill roller-skiing (gear 3, skating technique) on two occasions separated by at least 48 h. One condition involved carrying the rifle on the back (WR) and the other condition no rifle (NR) and the tests were randomized. Submaximal V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2, skiing speed at 4 mmol.L–1 of blood lactate (speed@4mmol), gross efficiency (GE), aerobic (MRae), and anaerobic (MRan) metabolic rates, and V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2max were determined. Results: Submaximal V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: norma

BACKGROUND: Whilst the ergogenic effects of carbohydrate intake during prolonged exercise are well-documented, few investigations have studied the effects of carbohydrate ingestion during cross-country skiing, a mode of exercise that presents unique metabolic demands on athletes due to the combined use of large upper- and lower-body muscle masses. Moreover, no previous studies have investigated exogenous carbohydrate oxidation rates during cross-country skiing. The current study investigated the effects of a 13C-enriched 18% multiple-transportable carbohydrate solution (1:0.8 maltodextrin:fructose) with additional gelling polysaccharides (CHO-HG) on substrate utilization and gastrointestinal symptoms during prolonged cross-country skiing exercise in the cold, and subsequent double-poling time-trial performance in ~ 20 °C. METHODS: Twelve elite cross-country ski athletes (6 females, 6 males) performed 120-min of submaximal roller-skiing (69.3 ± 2.9% of [Formula: see text]O2peak) in -5 °C while receiving either 2.2 g CHO-HG·min- 1 or a non-caloric placebo administered in a double-blind, randomized manner. Whole-body substrate utilization and exogenous carbohydrate oxidation was calculated for the last 60 min of the submaximal exercise. The maximal time-trial (2000 m for females, 2400 m for males) immediately followed the 120-min submaximal bout. Repeated-measures ANOVAs with univariate follow-ups were conducted, as well as independent and paired t-tests, and significance was set at P < 0.05. Data are presented as mean ± SD. RESULTS: Exogenous carbohydrate oxidation contributed 27.6 ± 6.6% to the total energy yield with CHO-HG and the peak exogenous carbohydrate oxidation rate reached 1.33 ± 0.27 g·min- 1. Compared to placebo, fat oxidation decreased by 9.5 ± 4.8% with CHO-HG, total carbohydrate oxidation increased by 9.5 ± 4.8% and endogenous carbohydrate utilization decreased by 18.1 ± 6.4% (all P < 0.05). No severe gastrointestinal symptoms were reported in ei

INTRODUCTION: Reaching an international level in any endurance sport requires a large volume of systematic training performed over time. While the annual training characteristics of senior, elite-level cross-country (XC) skiers are well documented (1), limited data exist regarding the long-term training of developing XC skiers. The current study aimed to describe the training undertaken by a group of highly-trained XC skiers throughout their transition from junior- to senior-level athletes. METHODS: In this retrospective cohort study, self-reported training data were obtained from 32 highly-trained female (n = 13) and male (n = 19) XC skiers for the season they turned 16 years old (y) until the season they turned 23 y. At the time of inclusion, 26 skiers (11 females and 15 males) had represented at least one of the Swedish national teams (senior, development or junior), and eight of these skiers (6 females and 2 males) had won at least one individual U23 or Junior World Championship medal. The remaining six skiers were part of a specialist ski university in Sweden, where selection is based on the potential to perform at a world-class level. Training data were organized by training form (endurance, strength, and speed), mode (e.g. on-snow skiing, roller skiing, running, and cycling), and intensity (using a 4-zone model), which were then divided into five annual training phases (transition, general preparation [GP], specific preparation [SP], competition [CP], regeneration). RESULTS: Data from 155 seasons, including 59 026 individual training sessions and 94 964 h of training, were analysed. From age 16 to 22 y the total volume of endurance training increased from 472 ± 70 to 721 ± 86 h/yr (p < 0.001). Low-intensity training (LIT, below the first lactate threshold, <85% HRmax) and high-intensity training (HIT, above the first lactate threshold, >85% HRmax) increased from 414 ± 61 to 656 ± 72 h/yr (p < 0.001) and 58 ± 33 to 65 ± 16 h/yr (p = 0.018), respect

Biathlon is an endurance sport combining rifle shooting and intermittent cross-country skiing while carrying a rifle (minimum weight 3.5 kg). Previous studies have shown that the skiing component explains 60% of overall biathlon performance (1) and that rifle carriage affects different physiological responses such as blood lactate, oxygen uptake (VO2) and heart rate during skiing (2, 3). However, the effects of rifle carriage on skiing performance and variables such as maximal VO2 (VO2max), lactate threshold, efficiency of movement and anaerobic energy contribution have not yet been investigated.METHODS:Seventeen biathletes (9 females, 8 males; age 23.0 (3.3) years, VO2max 59.8 (7.3) mL/kg/min), competing at a national and/or international level, and completing approximately three biathlon training sessions/week with the rifle on the back, performed a submaximal incremental test and a 900–1000-m maximal time-trial (TT) using treadmill roller-skiing (gear 3 skating technique) on two occasions separated by at least 48 hours. One condition involved carrying the rifle on the back (WR) and the other no rifle (NR), with the order randomized. The VO2 and skiing speed at 4 mmol/L of blood lactate (VO2@4mmol and speed@4mmol, respectively), gross efficiency (GE), metabolic aerobic (MRae) and anaerobic (MRan) rates, and VO2max were determined. RESULTS:Submaximal VO2 at all levels and GE (16.7 (0.9) vs 16.5 (1.1) %, p<0.05) were higher for WR compared to NR, while speed@4mmol (11.3 (1.5) vs 11.7 (1.5) km/h, p<0.05) and MRan (27.3 (6.7) vs 30.5 (7.6) kJ/min, p<0.01) was lower. There were no differences in VO2@4mmol or MRae between the two conditions. The mean speed during the TT was higher for NR compared to WR (16.5 (1.5) vs 15.5 (1.4) km/h, p<0.001), but there was no difference in VO2max. Mean speed during the TT was correlated to speed@4mmol (WR: r=0.810, p<0.001; NR: r=0.659, p<0.01), GE (WR: r=0.691; NR r=0.529, both p<0.05) and VO2max (WR: r=0.514; NR

This study investigated whether commercially available compression garments (COMP) exerting a moderate level of pressureand/or neuromuscular electrical stimulation (NMES) accelerate recovery following a cross-country sprint skiing competitioncompared with a control group (CON) consisting of active recovery only. Twenty-one senior (12 males, 9 females) and 11junior (6 males, 5 females) Swedish national team skiers performed an outdoor sprint skiing competition involving foursprints lasting ∼3–4 min. Before the competition, skiers were matched by sex and skiing level (senior versus junior) andrandomly assigned to COMP (n = 11), NMES (n = 11) or CON (n = 10). Creatine kinase (CK), urea, countermovementjump (CMJ) height, and perceived muscle pain were measured before and 8, 20, 44 and 68 h after competition. NeitherCOMP nor NMES promoted the recovery of blood biomarkers, CMJ or perceived pain post-competition compared withCON (all P > .05). When grouping all 32 participants, urea and perceived muscle pain increased from baseline, peaking at8 h (standardised mean difference (SMD), [95% confidence intervals (CIs)]): 2.8 [2.3, 3.2]) and 44 h (odds ratio [95%CI]: 3.3 [2.1, 5.1]) post-competition, respectively. Additionally, CMJ was lower than baseline 44 and 68 h postcompetitionin both males and females (P < .05). CK increased from baseline in males, peaking at 44 h (SMD: 1.4 [−0.4,0.9]), but was decreased in females at 20 h post-competition (SMD: −0.8 [−1.4, −0.2]). In conclusion, cross-countrysprint skiing induced symptoms of exercise-induced muscle damage peaking 8–44 h post-competition. However, neitherCOMP nor NMES promoted physiological or perceptual recovery compared with CON.

Purpose: The present study aimed to compare four methods of estimating anaerobic energy production during supramaximal exercise. Methods: Twenty-one junior cross-country skiers competing at a national and/or international level were tested on a treadmill during uphill (7°) diagonal-stride (DS) roller-skiing. After a 4-minute warm-up, a 4 × 4-min continuous submaximal protocol was performed followed by a 600-m time trial (TT). For the maximal accumulated O2 deficit (MAOD) method the V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2-speed regression relationship was used to estimate the V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2 demand during the TT, either including (4+Y, method 1) or excluding (4-Y, method 2) a fixed Y-intercept for baseline V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; outline: 0px !important;">V.V.O2. The gross efficiency (GE) method (method 3) involved calculating metabolic rate during the TT by dividing power output by submaximal GE, which was then converted to a V." role="presentation" style="box-sizing: border-box; display: inline; line-height: normal; word-spacing: normal; word-wrap: nor

INTRODUCTION: The aim of this study was to compare the pacing strategies, choice of sub-technique (i.e., gear) and overall performance between elite male and female cross-country (XC) skiers during a ski-skating sprint time-trial (TT) on snow. METHODS: Thirty-four elite XC skiers (20 males and 14 females: age, 23 ± 4 and 21 ± 3 yr; body mass, 76 ± 8 and 64 ± 5 kg; height, 183 ± 7 and 171 ± 5 cm; sprint FIS points, 86 ± 42 and 90 ± 54) performed a 1.6 km TT, which was 56% flat (or undulating), 21% uphill and 22% downhill. The sprint course was measured with a differential global navigation satellite system and divided into four flat, three uphill and two downhill sections. Race time was measured with the EMIT timing system (Emit AS, Oslo, Norway) and one 25-m uphill (4°) section was filmed continuously with a fixed camcorder (50 Hz). All skiers used a similar stone-grind and all skis were glide-waxed similarly. The air temperature was +1°C (fresh snow at ±0°C), relative humidity was 90% and the friction coefficient between ski and snow was estimated to 0.045 (i.e., very slow). RESULTS: Average speed during the TT was 25 ± 1 and 22 ± 1 km/h (TT time: 227 ± 11 and 254 ± 10 s) for males and females, respectively (P < 0.001, Cohen’s d effect size [ES] = 2.6). Average relative power output (PO) was estimated to 3.9 ± 0.3 and 3.3 ± 0.2 W/kg for males and females, respectively (P < 0.001, ES = 2.5). Average heart rate was 95 ± 2% and 96 ± 1% of maximum for males and females (P = 0.51), with a 2-min post-race blood lactate concentration of 10 ± 2 mmol/L for both sexes (P = 0.64). Within-athlete coefficient of variation in speed between sections was 20 ± 2% for males and 24 ± 1% for females (P < 0.001, ES = 2.6). Speeds on the flat, uphill and downhill sections were 26 ± 1, 19 ± 1 and 32 ± 1 km/h for males and 23 ± 1, 16 ± 1 and 30 ± 1 km/h for females (main effects for terrain, sex and interaction, all P < 0.01) corresponding to 9%, 16% and 8% slower speeds on fl

Background: Dietary supplements such as caffeine and beetroot juice are used byathletes in an attempt to optimize performance and therefore gain an advantagein competition. Aim: To investigatethe individual and combined effects of caffeine and beetroot-juicesupplementation during submaximal and maximal treadmill running. Methods: Seven males (VO2max:59.0 ± 2.9 mL/kg/min) and two females (VO2max: 53.1 ± 11.4 mL/kg/min)performed a preliminary trial followed by four experimental test sessions,which consisted of two, 5-min submaximal running bouts (at ~ 70% and 80% of VO2max) and a maximal 1-km time-trial (TT) in a laboratory. Participants ingested a 70-ml dose of concentrated beetroot juice containing either 7.3 mmol of nitrate (BR) or no nitrate (PBR) 2.5 hours prior to each test session, theneither 4.8 ± 0.4 (4.3–5.6) mg/kg caffeine (C) or a caffeine placebo (PC)45 minutes before each test session. The four test sessions (BR-C, BR-PC,PBR-C and PBR-PC) were presented in a counter-balancedand double-blind manner. Results: Nosignificant differences were identified between the four interventionsregarding relative VO2, running economy, RER, heart rate (HR) or RPEat the two submaximal intensities (P > 0.05). Moreover, there were nosignificant differences in performance, maximum HR, peak blood lactateconcentration or RPE during the maximal TT when comparing the interventions (P> 0.05). Conclusion: No beneficialeffects of supplementing with typical doses of caffeine, beetroot juice or acombination of the two were observed for physiological, perceptual orperformance responses during submaximal or maximal treadmill running exercise.

Exposure to altitude results in multiple physiological consequences. These include, but are not limited to, a reduced maximal oxygen consumption, drop in arterial oxygen saturation, and increase in muscle metabolic perturbations at a fixed sub-maximal work rate. Exercise capacity during fixed work rate or incremental exercise and time-trial performance are also impaired at altitude relative to sea level. Recently, dietary nitrate (NO3-) supplementation has attracted considerable interest as a nutritional aid during altitude exposure. In this review, we summarise and critically evaluate the physiological and performance effects of dietary NO3- supplementation during exposure to simulated and terrestrial altitude. Previous investigations at simulated altitude indicate that NO3- supplementation may reduce the oxygen cost of exercise, elevate arterial and tissue oxygen saturation, improve muscle metabolic function, and enhance exercise capacity/performance. Conversely, current evidence suggests that NO3- supplementation does not augment the training response at simulated altitude. Few studies have evaluated the effects of NO3- at terrestrial altitude. Current evidence indicates potential improvements in endothelial function at terrestrial altitude following NO3- supplementation. No effects of NO3- supplementation have been observed on oxygen consumption or arterial oxygen saturation at terrestrial altitude, although further research is warranted. Limitations of the present body of literature are discussed, and directions for future research are provided.

Introduction: Traditional graded-exercise tests to volitional exhaustion (GXTs) are limited by the need to establish starting workloads, stage durations, and step increments. Short-duration time-trials (TTs) may be easier to implement and more ecologically valid in terms of real-world athletic events. The purpose of the current study was to assess the reliability and validity of maximal oxygen uptake (VO2max) and performance measured during a traditional GXT (STEP) and a four-minute running time-trial (RunTT). Methods: Ten recreational runners (age: 32 ± 7 years; body mass: 69 ± 10 kg) completed five STEP tests with a verification phase (VER) and five self-paced RunTTs on a treadmill. The order of the STEP/VER and RunTT trials was alternated and counter-balanced. Performance was measured as time to exhaustion (TTE) for STEP and VER and distance covered for RunTT. Results: The coefficient of variation (CV) for VO2max was similar between STEP, VER, and RunTT (1.9 ± 1.0, 2.2 ± 1.1, and 1.8 ± 0.8%, respectively), but varied for performance between the three types of test (4.5 ± 1.9, 9.7 ± 3.5, and 1.8 ± 0.7% for STEP, VER, and RunTT, respectively). Bland-Altman limits of agreement (bias ± 95%) showed VO2max to be 1.6 ± 3.6 mL·kg-1·min-1 higher for STEP vs. RunTT. Peak HR was also significantly higher during STEP compared with RunTT (P = 0.019). Conclusion: A four-minute running time-trial appears to provide more reliable performance data in comparison to an incremental test to exhaustion, but may underestimate VO2max.

Purpose: To investigate whether compression garments (CG) and neuromuscular electrical stimulation (NMES) augment post-race recovery compared with a passive control group (CON) following a cross-country sprint skiing competition. Methods: Twenty-one senior (12 males, 9 females) and 11 junior (6 males, 5 females) Swedish national team skiers performed a sprint skiing competition involving four, ~3-4 min sprints. After the race, skiers were matched by sex and skiing level (senior versus junior) and randomly assigned to a CON (n = 10), CG (n = 11) or NMES group (n = 11). Creatine kinase (CK) and urea, countermovement jump height (CMJ) and perceived sleep duration, sleep quality and muscle pain were measured before and 8, 20, 44 and 68 h after the race to assess the efficacy of each recovery intervention. Results: Neither CG nor NMES promoted the recovery of blood biomarkers, perceived wellness nor CMJ post-race compared with the passive control group (all P < 0.05). When grouping all 32 participants, CK, urea and muscle pain increased from pre-race values, peaking 20-44 h post-race (P < 0.05). CMJ was lower than pre-race values 44 and 60 h post-race in males and females (both P < 0.05). Sleep duration increased from pre-race to post-race (P < 0.05), whereas sleep quality was unchanged (P > 0.05). Conclusion: A cross-country sprint skiing competition induced symptoms of exercise-induced muscle damage peaking 20-44 h post-race. However, CG and NMES did not augment the recovery of physiological, perceptual or performance parameters compared with a passive control group after the sprint skiing competition.

Introduction: Habitual nutritional intakes in cross-country skiers have previously been reported (Fogelholm et al., 1992), however in elite cross-country skiers there is limited knowledge about race-specific nutritional practices, or the prevalence of dehydration and persistent low energy availability (EA). This study aimed to investigate, in the context of a simulated sprint race, energy intake, macronutrient intake, hydration status and the risk of persistent low EA in elite cross-country skiers. Methods: Thirty-two male (n = 18) and female (n = 14) elite Swedish cross-country skiers completed weighed food records the day prior to (day 1) and the day of a simulated sprint race (day 2); the food records were analysed for energy (kcal/kg), macronutrient (g/kg) and fluid intake (L). Urine specific gravity (USG) was also measured on day 1 and day 2. The risk for persistent low EA was assessed in the female skiers using the Low Energy Availability in Females Questionnaire (LEAF-Q; Melin et al., 2014). Results were analysed using a three-way mixed ANOVA. Statistical significance was set to a level of p ≤ 0.05. Results: Males had a higher energy intake (65±9 kcal/kg) on day 1, (pre-race) compared with day 2 (simulated sprint race; 58±9kcal/kg; p = 0.002). Females consumed 57±10 kcal/kg on day 1, which was similar to their day 2 energy intake (54±6 kcal on day 2; p > 0.05). Males consumed less carbohydrate (8.2±2.3g/kg) on day 1 compared with day 2 (8.9±2.3g/kg) (p = 0.026), as did females, consuming 7.0±1.5g/kg on day 1, and 8.4±1.7g/kg on day 2 (p = 0.003). There were similar fluid intakes across the two days for males (p > 0.05) and females (p > 0.05). Nine of the 18 males and 6 of the 14 females were dehydrated (USG > 1.020) on day 1, and 9 males and 5 females were dehydrated on day 2. Five of the 14 females were classified as being at risk of persistent low EA. Discussion: This study provides an initial insight into nutritional competition habits in elite

Introduction Two frequently used approaches for estimating anaerobic energy production during supramaximal exercise are the maximal accumulated oxygen (O2) deficit (MAOD) method and the gross efficiency (GE) method (Noordhof et al., 2011). Despite clear computational differences between the two methods, only one direct comparison has been performed (Noordhof et al., 2011). In cross-country roller-skiing, both the MAOD and the GE methods have been employed (Andersson et al., 2016). Therefore, this study aimed to compare the O2 deficits attained with these methods. Methods Eleven male and ten female cross-country skiers were tested on a treadmill employing uphill (7°) diagonal-stride roller-skiing. After collecting a 1-min baseline VO2, participants performed a 4 × 4-min continuous submaximal protocol (~ 60-90% of VO2max) followed by, a self-paced 600-m time-trial (TT). Speed and VO2 were measured continuously during the TT. For the MAOD method, the linear relationship between treadmill velocity and VO2 during the final 30 seconds of each 4 × 4-min submaximal stage was derived with the baseline VO2 as a Y-intercept included (4+Y) in or excluded (4-Y) from the model. The two regression equations were then used to estimate the VO2 demand during the TT. For the GE method, the metabolic rate during the TT was calculated by taking the average power output divided by the GE (an average of the four submaximal stages) and converted to a VO2 demand. Results The VO2 demand was significantly higher for the GE (68.9 ± 8.5 mL/kg/min) and 4-Y (68.4 ± 8.7 mL/kg/min) procedures compared with the 4+Y (64.3 ± 7.6 mL/kg/min) procedure (P < 0.05). The corresponding O2 deficits for the GE, 4-Y and, 4+Y procedures were 63.7 ± 9.7, 62.3 ± 10.4 and, 50.2 ± 9.6 mL/kg, respectively (P < 0.05 for GE and 4-Y vs. 4+Y). The mean difference between the O2 deficits estimated from the 4-Y and GE procedure -1.4 ± 3.9 mL/kg, and between the 4+Y and GE procedures was -13.5 ± 2.5 mL/kg. Correspon

Introduction: Supplementation with beetroot juice (BR), which is rich in inorganic nitrate (NO3-), has received considerable attention due to its beneficial effects on several physiological functions. For example, BR has led to lowered resting blood pressure (BP) and a reduced oxygen (O2) cost during moderate-intensity exercise in healthy individuals, as well as improved maximal performance (1). Similar beneficial effects in athletes are less clear (2). The anaerobic reduction of NO3- to nitrite (NO2-) in the oral cavity increases the bioavailability of nitric oxide (NO), which is thought to explain the ergogenic effect of BR. Since NO is generally produced endogenously using O2 and multiple cofactors (3), any reduction in O2 availability would attenuate this NO-pathway. Therefore, BR supplementation is believed to have a more pronounced effect in hypoxia (H). The aim of the present study was to investigate the effects of BR supplementation in competitive cross-country skiers exercising in normoxia (N) and H. Methods: Using a randomised crossover design, eight competitive cross-country skiers (5 males: age 22 +/- 3 y, body mass 74 +/- 8 kg, VO2max 5.2 +/- 0.4 L/min; 3 females: age 21 +/- 1 y, body mass 63 +/- 6 kg, VO2max 3.7 +/- 0.5 L/min;) supplemented with a single dose of NO3- (ca 13 mmol) or placebo (PL) performed two, 6-min submaximal exercise bouts and a 1000-m time-trial (TT) in N and H (16.8% O2). All tests were conducted on roller skis at a 6-degree incline using the diagonal-stride technique. Resting BP, blood O2 saturation (SpO2), VO2, respiratory exchange ratio (RER), heart rate (HR), rating of perceived exertion (RPE), blood lactate (La-) and time to complete the 1000-m TT (TTtime) were measured. Results: Plasma NO3- and NO2- levels were significantly higher following BR compared to PL (p < 0.001). However, resting BP, submaximal exercise variables and TTtime were unaffected by supplementation (p > 0.05). The VO2max obtained during the TT was

Caffeine appears to have a stimulating effect on the central nervous system and as such, is commonly used by athletes to improve performance(1). Nitrate-rich beetroot juice is also used as an ergogenic aid, demonstrating positive effects on both cycling economy and time-trial performance(2). While previous research has shown no additional benefits of combining caffeine and beetroot juice on cycling performance(3), no studies have compared the effects of individual and combined supplementation during running exercise. Therefore, the aim of the current study was to investigate the effects of caffeine and beetroot-juice supplementation during sub-maximal and maximal running. Nine recreational runners (seven males, VO2max 59.0 ± 2.9 l/min; two females, VO2max 53.1 ± 11.4 l/min) performed four laboratory-based test sessions in a crossover-design study. Each test session consisted of two, 5-minute sub-maximal running bouts at ~ 70% and 80% of VO2max followed by a maximal 1-km time trial (TT). The participants were given a 70-ml dose of concentrated beetroot juice containing either 4 mmol of nitrate (BJ) or no nitrate (placebo, P) 2.5 hours before warming up for each test. Participants were also given either 4-6 mg/kg body weight of caffeine (C) or a non-caffeine-containing placebo (P) 45 minutes before warming up. The four trials (BJ+C, BJ, C and P) were double-blinded and presented in a randomised order. Data were analysed using one-way ANOVAs with repeated measures. There were no significant differences between the four interventions for running economy, respiratory exchange ratio (RER), heart rate (HR) or rating of perceived exertion (RPE) at either of the sub-maximal running intensities (p > 0.05). Neither were there any significant differences in maximal HR or RPE, peak blood lactate concentration or 1-km TT performance between the four interventions (p > 0.05). This study has shown no beneficial effects of combining caffeine and beetroot juice on sub-maximal

This study investigated carbohydrate ingestion of varied doses and frequencies during a simulated cross-country skiing time trial. Ten men and three women (age: 30±7years; VO2max: 59.6±5.7 mL/kg/min) completed four, 30-km classic technique roller skiing time trials on a treadmill. A 1:1 maltodextrin-fructose carbohydrate solution was provided at high (2.4 g/min; HC) and moderate (1.2 g/min; MC) ingestion rates, each at high (six feeds;HF) and low (two feeds; LF) frequencies. In the LF trials, blood glucose was elevated following carbohydrate ingestion (at 4 and 19 km) but was reduced at 14 and 29 km compared with HF strategies (P≤0.05). Gastrointestinal discomfort was higher in HC-LF compared with all other trials (P≤0.05). Whole-body lipid oxidation was lowerand carbohydrate oxidation was higher in LF compared with HF trials (P≤0.05). While performance time was not significantly different between trials (140:11±15:31,140:43±17:40, 139:12±15:32 and 140:33±17:46 min:sin HC-HF, HC-LF, MC-HF, and MC-LF, respectively;P>0.05), it was improved with trial order (P<0.001). There was no effect of order on any other variable (P>0.05). Altering carbohydrate dose or frequency does not affect cross-country ski performance. However, low-frequency carbohydrate ingestion resulted in poorer maintenance of euglycemia, reduced lipid oxidation, and increased gastrointestinal discomfort., Published online 27th Aug 2015.

INTRODUCTION: Incremental tests to volitional exhaustion are widely used to assess VO2max. However, the need to establish starting workloads, stage durations, and step increments make administration problematic. Moreover, the validity of such tests has been questioned (Beltrami et al., 2012, Br J Sports Med, 46:23-29; Mauger & Sculthorpe, 2012, Br J Sports Med, 46:59-63). Short time trials represent a simpler and more ecologically valid alternative to assess VO2max and performance across exercise modes (Crouter et al., 2001, Med Sci Sports Exerc, 33:644-647; Ansley et al., 2004, Med Sci Sports Exerc, 36:1819-1825; McGawley & Holmberg, 2014, Int J Sports Physiol Perform 9:32-40). The aim of the current study was to assess the reliability and validity of a treadmill running time trial (RunTT) for the assessment of VO2max and performance. METHODS: Ten recreational athletes (5 males, 5 females; 32 ± 7 y) completed five incremental tests to exhaustion (INC) including a verification phase (VER) on a treadmill and five, 4-min RunTTs. The order of INC+VER and RunTT trials was alternated and counter-balanced. The INC and VER protocols were externally controlled, with incline increasing by 1% every minute during the INC. By contrast, the RunTT protocol was athlete controlled, with running speed self-adjusted via a laser system fitted to the treadmill (and incline fixed at 1%). Performance was measured as time to exhaustion for INC and VER and distance covered for RunTT. Heart rate (HR) was monitored continuously throughout each protocol. RPE and lactate were assessed immediately post-exercise and at 1-min intervals for four minutes post-exercise, respectively. RESULTS: The CV for VO2max was not significantly different between INC, VER and RunTT (1.9, 2.2 and 1.7%, respectively) but for performance was significantly different between all types of test (4.5, 9.7 and 1.8% for INC, VER and RunTT, respectively; P<0.005). VO2max was significantly higher for INC compa

Introduction Long-distance cross-country ski races typically last more than 2 h, depleting muscle glycogen stores in the legs and, to an even greater extent, the arms (Bergström et al. 1973). While carbohydrate (CHO) supplementation demonstrates clear performance-enhancing effects, particularly when ingested during exercise lasting > 1 h and in multiple forms (Jeukendrup 2004), there is limited information regarding the use of CHO during cross-country skiing. Therefore, the aim of the current study was to examine the effect of ingesting two different CHO solutions on 30-km cross-country skiing performance. Methods 10 male and 3 female trained cross-country skiers (age: 30±7 yr; body mass: 74±9 kg; VO2max: 60±6 mL/kg/min) completed 4 x 30-km classic roller-skiing time-trial efforts (consisting of 6 x 5-km loops) on separate days in a randomised, counter-balanced order on a treadmill. Two trials used a high rate of CHO ingestion (2.4 g/min, HC) and two trials used a lower rate of CHO ingestion (1.2 g/min, LC). In addition, two trials used a high frequency of CHO feeds (6 feeds, HF) and two trials used a low frequency of CHO feeds (2 feeds, LF). The CHO was a 1:1 mix of maltodextrin and fructose and the drinks were provided at 24% and 12% concentrations for HC and LC, respectively. Results There were no significant differences in performance over the four trials (140±16, 139±16, 141±18 and 141±18 min for HC-HF, LC-HF, HC-LF and LC-LF, respectively) and when matched for frequency of feeds, there were no significant performance differences between the paired comparisons (i.e., HC-HF vs LC-HF and HC-LF vs LC-LF). Moreover, there were no significant differences in blood glucose concentrations at 5-km intervals when comparing HC-HF with LC-HF (p>0.05) or HC-LF with LC-LF (p>0.05). However, an order effect was detected for performance (143±17, 140±16, 140±17 and 138±15 min for trials 1-4, respectively) with significant improvements from trials 1-2 (p=0.02) and 3-4 (

Introduction While carbohydrate ingestion can improve endurance performance, relatively little is known about the effect of frequency of carbohydrate ingestion. This may be of particular importance in cross-country skiing, where upper-body propulsion is inevitably decreased during drinking periods. Therefore, the study aim was to examine the effect of ingesting carbohydrate at two different frequencies on 30-km cross-country skiing performance. Methods Thirteen participants completed four, 30-km classic roller-skiing time-trials on a simulated treadmill course. A 1:1 maltodextrin-fructose solution was provided at high (6 feeds; HF) and low (2 feeds; LF) frequencies and high (2.4 g∙min-1, 24%;HC) and low (1.2 g∙min-1, 12%; LC) rates. Gastrointestinal discomfort was measured using an adapted 6-20 Borg scale. Results There were no differences in performance between the four trials (140±16, 139±16, 141±18 and 141±18 min for HF-HC, HF-LC, LF-HC and LF-LC, respectively), although LF-LC was likely harmful compared to HF-LC. However, an order effect was apparent (143±17, 140±16, 140±17 and 138±15 min for trials 1-4, respectively). There was a significant rate x frequency interaction for gastrointestinal discomfort, with greater discomfort in LF-HC (10.3±2.7) compared with HF-HC (8.5±3.1) and HF-LC (8.4±2.7). LF-LC (9.0±2.3) was not significantly different to any other trial. Discussion These data suggest there is no significant effect of ingestion frequency on 30-km simulated cross-country ski performance. However, there may be a practically relevant detrimental effect of low frequency ingestion at low rates. Further, LF carbohydrate ingestion increases gastrointestinal discomfort when ingested as HC.

INTRODUCTION: Short periods of intensified training elicit symptoms of overreaching within only 7 days (Halson et al. 2002). Despite this, block periodization of high-intensity interval training (HIT) has led to superior aerobic responses compared with traditional endurance training among trained alpine skiers and cyclists (Breil et al. 2010; Rønnestad et al. 2012). METHODS: 21 highly-trained junior cross-country skiers (10 males, 11 females; age 16-20 y) completed 2 x 3-week training blocks in a randomized crossover design, whereby the training sessions in each 3-week block were identical but the distribution of HIT and low-intensity training (LIT) was different. In traditional periodization (TP), 3 HIT sessions (5 x 4-min at >90% HRmax) were completed each week, with LIT sessions evenly distributed over the 3-week period. In block periodization (BP) the same 9 HIT sessions were completed in week 2 and only LIT sessions were completed in weeks 1 and 3. REST-Q data was collected after each training week while resting saliva sampling (for determination of IgA and cortisol), incremental tests and performance trials were completed pre and post each 3-week period. RESULTS: Although the overall training load (P=0.651) and total amount of work performed during HIT sessions (P=0.224) did not differ between TP and BP, the session RPE was higher and perceived recovery was lower in connection with the HIT sessions during BP (P<0.001). In addition, sport-specific stress REST-Q scores were higher following the BP-HIT week compared with all other weeks (P<0.008), whereas the global recovery-stress state was similar between all TP and BP weeks (P>0.05). Pre to post changes in salivary IgA and cortisol were also similar for TP and BP (P>0.05), although there was a tendency for IgA and cortisol to increase after TP (ES: 0.75 and 0.37) and decrease after BP (ES: 0.23 and 0.12, respectively). The change in VO2max was greater following TP versus BP (2±4% vs -1±3%; P=0.0

Despite the wealth of evidence regarding physical training strategies in soccer, there is little information regarding soccer-specific concurrent training and the effects of training order. The current study aimed to: i) quantify the effects of concurrent high-intensity run-based training (HIT) and strength- and power-based training (STR) on soccer-specific performance, and ii) investigate the order effect of completing HIT and STR either first or second within training sessions. Eighteen semi- and fully-professional players completed a battery of field- and gym-based tests before and after a 5-week pre-season training intervention. Players were pair-matched and completed 3 sessions per week of HIT followed by STR (n=9) or STR followed by HIT (n=9). ANCOVA tests revealed no differences between groups for changes in any of the measures (p>0.05). However, a training effect was observed for all measures (p<0.05), with 10-m sprint, 6×30-m repeated sprint, 40-m agility and Yo-Yo test performances improving by 1.8±2.6%, 1.3±1.8%, 1.0±1.5% and 19.4±23.4%, respectively (n=18). In conclusion, there was a positive effect of the concurrent training approach on key measures of soccer performance, but the order of completing HIT and STR appears inconsequential to performance adaptations., Published online 22nd May 2013.

The well-established ergogenic benefit of ingesting carbohydrates during single-discipline endurance sports has only been tested once within an Olympic-distance (OD) triathlon. The aim of the present study was to compare the effect of ingesting a 2:1 maltodextrin/fructose solution with a placebo on simulated OD triathlon performance. Six male and 4 female amateur triathletes (age, 25 ± 7 years; body mass, 66.8 ± 9.2 kg; peak oxygen uptake, 4.2 ± 0.6 L·min–1) completed a 1500-m swim time-trial and an incremental cycle test to determine peak oxygen uptake before performing 2 simulated OD triathlons. The swim and cycle sections of the main trials were of fixed intensities, while the run section was completed as a time-trial. Two minutes prior to completing every quarter of the cycle participants consumed 202 ± 20 mL of either a solution containing 1.2 g·min–1 of maltodextrin plus 0.6 g·min–1 of fructose at 14.4% concentration (CHO) or a sugar-free, fruit-flavored drink (PLA). The time-trial was 4.0% ± 1.3% faster during the CHO versus PLA trial, with run times of 38:43 ± 1:10 min:s and 40:22 ± 1:18 min:s, respectively (p = 0.010). Blood glucose concentrations were higher in the CHO versus PLA trial (p < 0.001), while perceived stomach upset did not differ between trials (p = 0.555). The current findings show that a 2:1 maltodextrin/fructose solution (1.8 g·min–1 at 14.4%) ingested throughout the cycle section of a simulated OD triathlon enhances subsequent 10-km run performance in triathletes.

Introduction: The purpose of the present study was to examine the effects of two hydrotherapy techniques, cold water immersion (CWI) and contrast-water therapy (CWT), on the recovery of team-sport-specific exercise tests following muscle-damaging exercise. Methods: Seven male, team-sport players (mean±SD age: 21±2 y, body mass:76.8±7.2 kg) completed a preliminary familiarisation trial for three team-sport-specific exercise tests (TESTS), which included an all-out 30-m sprint test, two agility T-tests (left and right) and a vertical jump test. Three experimental trials were subsequently carried out, each separated by one week, using a counter-balanced cross-over design. On each visit a resting fingertip blood sample and a rating of perceived muscle soreness (PMS) was collected. Participants then performed the TESTS, followed by a 5-min rest period. A repeated sprint exercise (RSE) protocol was then performed to induce muscle damage, which comprised of 15 × 30-m sprints with a 10-m deceleration zone. Sprints were separated by 1 min. A second fingertip blood sample and PMS score was collected immediately after the RSE and a second set of TESTS were performed 10 min after the RSE. Participants then received either CWI, CWT or no water immersion (CON). The next day (24–28 h later) a final fingertip blood sample and PMS score was collected and a final set of TESTS were completed. Results and conclusion: There were no changes in plasma CK over time and no significant interaction effects between the three intervention groups (P > 0.05). The PMS increased from baseline to 24–28 h in the CON group (P < 0.05), but was not different from baseline at 24–28 h for the CWI or CWT groups (P > 0.05). The PMS was significantly higher for CON compared with CWT after 24–28 h (P < 0.05), but no other differences were found between groups (P > 0.05). There were no significant differences in performance during the TESTS between the three intervention groups across any of the

Introduction: The purpose of the present study was to investigate whether short-term sprint-interval training (SIT) would enhance repeated-sprint ability (RSA) via improvements in power output, work decrement and oxygen uptake in recovery. Methods: Eight male, recreational team-sport players (mean±SD age: 21±2 y, body mass: 78.1±4.3 kg) completed a repeated-sprint test (RST) and a graded cycle test to exhaustion for the evaluation of VO2max before and after two weeks of SIT. The RST consisted of 7×5-s cycle sprints interspersed with 25 s of passive recovery. Peak power output (PP), mean power output (MP), decrement in MP (MPdec) and total work done (TWD) were recorded. In addition, VO2 was measured during the 25-s passive recovery periods between each sprint. The SIT involved six sessions (three sessions per week) of 4, 5 or 6 × 30-s, all-out sprints interspersed with 4.5 min of light recovery. The number of sprint repetitions increased by one after every two training sessions. Results and conclusion: Although there was no change in PP for any of the 7×5-s sprints following SIT (P > 0.05) there were significant increases in MP for each of the 7×5-s sprints (P < 0.05) and in TWD during the RST (mean±SD: 7.6±3.0 versus 29.4±2.6 kJ from pre- to post-training; P < 0.05). The MPdec decreased from 12.4 ±6.8 to 7.4±2.9% from pre- to post-training (P < 0.05) but VO2 between sprints was unchanged (P > 0.05). Furthermore, VO2max was not different following training (45.7±7.7 versus 45.0±5.4 mLkg-1 min-1 from pre- to post-training; P > 0.05). These findings suggest that short-term SIT may be an effective intervention for improving RSA within team-sport athletes via increases in work done during each sprint and reductions in the decrement in work done over a series of sprints. This does not appear to be due to greater oxygen uptake during the 25-s recovery periods between sprints or improvements in peak power. Other metabolic adaptations to SIT that maintain m

Introduction: The purpose of the present study was to examine the effects of carbohydrate ingestion during the cycle leg of a simulated Olympic-distance triathlon (1500-m swim, 40-km cycle, 10-km run) on subsequent running performance. Methods: Five well-trained triathletes (4 male, 1 female) volunteered to participate (mean±SD age: 23.6±4.2 y, body mass: 63.0±7.6 kg and VO2max: 64.0±9.0 ml kg-1 min-1). Participants attended three separate testing sessions separated by at least five days. The first session involved a 1500-m swim time-trial (STT) followed approximately 30 min later by a graded cycle test to exhaustio nfor the evaluation of maximal aerobic power (MAP). The two subsequent sessions required participants to complete a simulated Olympic-distance triathlon involving a 1500-m pool swim to within 5% of the STT, a 40-km stationary cycle at 75% of MAP and a 10-km running time trial. Participants randomly consumed either a 14.4% carbohydrate drink containing 1.2 g min-1 of glucose and 0.6 g min-1 of fructose (CHO) or a fruit squash placebo (PLA) throughout the cycle leg of the triathlon. Fingertip blood samples were collected after every 5 km of the cycle leg and at the end of the run and were subsequently analysed for blood glucose (GLU) and lactate (LAC) concentrations. Rating of perceived exertion (RPE) and perceived stomach upset (PSU) were also measured after each 5-km cycle period and at the end of the run. Heart rate (HR) was measured throughout the cycle leg only. Results and conclusion: The 10-km run time was 4.2% faster following CHO (38 min 08 s ± 2 min 46 s) compared with PLA (39 min 44 s ±3 min 13 s; P < 0.05). The improved run timewas associated with increased GLU and LAC concentrations in the CHO compared with the PLA trial (P < 0.05), no difference in HR or PSU between trials (P > 0.05) and significantly lower RPE scores in the CHO compared with the PLA trial (P < 0.05). These results show that a 10-km run at the end of an Olympic-di

Aim. – The aim of this review was to state the use of critical power concept at different populations and to summarize studies reported data inorder to highlight its interest for the aerobic abilities assessement. Conclusion. – The critical power determination is based on times to exhaustion at different exercise intensities. The synthesis of several studiesshowed that this concept allows to discriminate populations relatively to their aerobic abilities. This is confirmed by its correlation to maximaloxygen uptake and ventilatory threshold in age and fitness different populations., This publication is in French.