A more conservative test of sex differences in the treatment and outcome of in-hospital cardiac arrest.

BACKGROUND: Studies investigating sex disparities related to treatment and outcome of in-hospital cardiac arrest (IHCA) have produced divergent findings and have typically been unable to adjust for outstanding confounding variables. OBJECTIVES: The aim was to examine sex differences in treatment and survival following IHCA, using a comprehensive set of control variables including e.g., age, comorbidity, and patient-level socioeconomic status. METHODS: This retrospective study was based on data from the Swedish Register of Cardiopulmonary Resuscitation and Statistics Sweden. In the primary analyses, logistic regression models and ordinary least square regressions were estimated. RESULTS: The study included 24,217 patients and the majority (70.4%) were men. In the unadjusted analyses, women had a lower chance of survival after cardiopulmonary resuscitation (CPR) attempt, at hospital discharge (with good neurological function) and at 30 days (p<0.01). In the adjusted regression models, female sex was associated with a higher chance of survival after the CPR attempt (B = 1.09, p<0.01) and at 30-days (B = 1.09, p<0.05). In contrast, there was no significant association between sex and survival to discharge with good neurological outcome. Except for treatment duration (B=-0.07, p<0.01), no significant associations between sex and treatment were identified. CONCLUSIONS: No signs of treatment disparities or discrimination related to sex were identified. However, women had a better chance of surviving IHCA compared to men. The finding that women went from having a survival disadvantage (unadjusted analysis) to a survival advantage (adjusted analysis) attests to the importance of including a comprehensive set of control variables, when examining sex differences.

The Modern Double-Poling Technique Is Not More Energy Efficient Than the Old-Fashioned Double-Poling Technique at a Submaximal Work Intensity.

The purpose of the study was to investigate whether there are energy-efficiency differences between the execution of the old-fashioned double-poling technique (DPOLD) and the modern double-poling technique (DPMOD) at a submaximal work intensity among elite male cross-country skiers. Fifteen elite male cross-country skiers completed two 4-min tests at a constant mechanical work rate (MWR) using the DPMOD and DPOLD. During the last minute of each test, the mean oxygen uptake (VO2) and respiratory exchange ratio (RER) were analyzed, from which the metabolic rate (MR) and gross efficiency (GE) were calculated. In addition, the difference between pretest and posttest blood-lactate concentrations (BLadiff) was determined. For each technique, skiers' joint angles (i.e., heel, ankle, knee, hip, shoulder, and elbow) were analyzed at the highest and lowest positions during the double-poling cycle. Paired-samples t-tests were used to investigate differences between DPMOD and DPOLD outcomes. There were no significant differences in either VO2mean, MR, GE, or BLadiff (all P > 0.05) between the DPMOD and DPOLD tests. DPMOD execution was associated with a higher RER (P < 0.05). Significant technique-specific differences were found in either the highest and/or the lowest position for all six analyzed joint angles (all P < 0.001). Hence, despite decades of double-poling technique development, which is reflected in the significant biomechanical differences between DPOLD and DPMOD execution, at submaximal work intensity, the modern technique is not more energy efficient than the old-fashioned technique.

Treatment and survival following in-hospital cardiac arrest: does patient ethnicity matter?

AIMS: Previous research on racial/ethnic disparities in relation to cardiac arrest has mainly focused on black vs. white disparities in the USA. The great majority of these studies concerns out-of-hospital cardiac arrest (OHCA). The current nationwide registry study aims to explore whether there are ethnic differences in treatment and survival following in-hospital cardiac arrest (IHCA), examining possible disparities towards Middle Eastern and African minorities in a European context. METHODS AND RESULTS: In this retrospective registry study, 24 217 patients from the IHCA part of the Swedish Registry of Cardiopulmonary Resuscitation were included. Data on patient ethnicity were obtained from Statistics Sweden. Regression analysis was performed to assess the impact of ethnicity on cardiopulmonary resuscitation (CPR) delay, CPR duration, survival immediately after CPR, and the medical team's reported satisfaction with the treatment. Middle Eastern and African patients were not treated significantly different compared to Nordic patients when controlling for hospital, year, age, sex, socioeconomic status, comorbidity, aetiology, and initial heart rhythm. Interestingly, we find that Middle Eastern patients were more likely to survive than Nordic patients (odds ratio = 1.52). CONCLUSION: Overall, hospital staff do not appear to treat IHCA patients differently based on their ethnicity. Nevertheless, Middle Eastern patients are more likely to survive IHCA.

Effect of sub-technique transitions on energy expenditure and physiological load in the classical-style technique among elite male cross-country skiers.

PURPOSE: To investigate whether sub-technique transitions in the classical-style technique are associated with increased energy expenditure and/or metabolic stress among elite male cross-country skiers. METHODS: Fifteen elite male skiers completed three 10-min treadmill roller-skiing tests, each of which consisted of 5 min using the diagonal-stride technique (DS) and 5 min using the double-poling technique (DP), combined in three various modes all ensuring comparable mechanical workload, at an inclination of 2.5° and a speed of 13 km/h. In the first and third tests, the participants used 5 min continuous DS followed by 5 min continuous DP, or vice versa (no transition (NT) test), whereas in the second test, they made transitions between DS and DP every 6 s (repeated transition (RT) test). The last 3 min of each 5-min stage was used to calculate the mean values of oxygen uptake ([Formula: see text]), respiratory exchange ratio (RER), metabolic rate (MR), mechanical work rate (MWR), and gross efficiency (GE). In addition, the pre-post-difference in blood lactate concentration (Ladiff) was determined for each test. Paired-samples t tests were used to investigate differences between tests. RESULTS: There were no significant differences between NT and RT tests regarding V̇O2, MR, MWR, or GE. Conversely, significant differences were found in RER and Ladiff, where the NT test was associated with higher RER and Ladiff values. CONCLUSIONS: Roller skiing with repeated sub-technique transitions is not associated with an additional aerobic energy contribution; instead, the anaerobic energy contribution was lower compared to that under continuous use of DS and DP.

Production of functional human fetal hemoglobin in Nicotiana benthamiana for development of hemoglobin-based oxygen carriers.

Hemoglobin-based oxygen carriers have long been pursued to meet clinical needs by using native hemoglobin (Hb) from human or animal blood, or recombinantly produced Hb, but the development has been impeded by safety and toxicity issues. Herewith we report the successful production of human fetal hemoglobin (HbF) in Nicotiana benthamiana through Agrobacterium tumefaciens-mediated transient expression. HbF is a heterotetrameric protein composed of two identical α- and two identical γ-subunits, held together by hydrophobic interactions, hydrogen bonds, and salt bridges. In our study, the α- and γ-subunits of HbF were fused in order to stabilize the α-subunits and facilitate balanced expression of α- and γ-subunits in N. benthamiana. Efficient extraction and purification methods enabled production of the recombinantly fused endotoxin-free HbF (rfHbF) in high quantity and quality. The transiently expressed rfHbF protein was identified by SDS-PAGE, Western blot and liquid chromatography-tandem mass spectrometry analyses. The purified rfHbF possessed structural and functional properties similar to native HbF, which were confirmed by biophysical, biochemical, and in vivo animal studies. The results demonstrate a high potential of plant expression systems in producing Hb products for use as blood substitutes.

Differences in nitric oxide airway diffusion after maximum oxygen uptake test in asthmatic and nonasthmatic elite junior cross-country skiers.

Asthma is common in cross-country skiers and is often treated with ß2-agonists and inhaled corticosteroids (ICS). Exhaled nitric oxide (NO) is often used to guide ICS treatment in asthma. This study investigated the change in pulmonary NO dynamics before and after a maximum oxygen uptake (V'O2 max) test. An extended NO analysis was performed among Swedish elite junior cross-country skiers (n=25), with and without declared asthma, before and after a V'O2 max test using roller skis. Asthma was declared by six boys and two girls among whom five occasionally used ICSs. There were no differences in baseline NO parameters between those with and without declared asthma. The median (interquartile range) diffusion capacity over airway wall (D awNO) was 21 (17-25) mL·s-1, which is much increased for this age group. After the V'O2 max test, there were statistically significant differences from the baseline fraction of exhaled NO (F ENO50 ), NO flux from airways, D awNO and alveolar NO values; but not in the NO content in airway wall (C awNO) for all subjects together as one group. However, in the asthma group, differences were only seen in F ENO50 and C awNO. Interestingly, a majority of the subjects had an increase in the D awNO. An increase in D awNO has been found with allergic asthma together with elevated C awNO. The skiers did not have elevated C awNO, which indicates an absence of inflammation in the airway wall. Modelling of lung NO production clearly shows that the asthma among our skiers is distinct from the allergic asthma in nonathletes.

Discriminatory cardiac arrest care? Patients with low socioeconomic status receive delayed cardiopulmonary resuscitation and are less likely to survive an in-hospital cardiac arrest.

AIMS: Individuals with low socioeconomic status (SES) face widespread prejudice in society. Whether SES disparities exist in treatment and survival following in-hospital cardiac arrest (IHCA) is unclear. The aim of the current retrospective registry study was to examine SES disparities in IHCA treatment and survival, assessing SES at the patient level, and adjusting for major demographic, clinical, and contextual factors. METHODS AND RESULTS: In total, 24 217 IHCAs from the Swedish Register of Cardiopulmonary Resuscitation were analysed. Education and income constituted SES proxies. Controlling for age, gender, ethnicity, comorbidity, heart rhythm, aetiology, hospital, and year, primary analyses showed that high (vs. low) SES patients were significantly less likely to receive delayed cardiopulmonary resuscitation (CPR) (highly educated: OR = 0.89, and high income: OR = 0.98). Furthermore, patients with high SES were significantly more likely to survive CPR (high income: OR = 1.02), to survive to hospital discharge with good neurological outcome (highly educated: OR = 1.27; high income: OR = 1.06), and to survive to 30 days (highly educated: OR = 1.21; and high income: OR = 1.05). Secondary analyses showed that patients with high SES were also significantly more likely to receive prophylactic heart rhythm monitoring (highly educated: OR = 1.16; high income: OR = 1.02), and this seems to partially explain the observed SES differences in CPR delay. CONCLUSION: There are clear SES differences in IHCA treatment and survival, even when controlling for major sociodemographic, clinical, and contextual factors. This suggests that patients with low SES could be subject to discrimination when suffering IHCA.

Expression, Purification and Initial Characterization of Functional α1-Microglobulin (A1M) in Nicotiana benthamiana.

α1-Microglobulin (A1M) is a small glycoprotein that belongs to the lipocalin protein family. A major biological role of A1M is to protect cells and tissues against oxidative damage by clearing free heme and reactive oxygen species. Because of this, the protein has attracted great interest as a potential pharmaceutical candidate for treatment of acute kidney injury and preeclampsia. The aim of this study was to explore the possibility of expressing human A1M in plants through transient gene expression, as an alternative or complement to other expression systems. E. coli, insect and mammalian cell culture have previously been used for recombinant A1M (rA1M) or A1M production, but these systems have various drawbacks, including additional complication and expense in refolding for E. coli, while insect produced rA1M is heavily modified with chromophores and mammalian cell culture has been used only in analytical scale. For that purpose, we have used a viral vector (pJL-TRBO) delivered by Agrobacterium for expression of three modified A1M gene variants in the leaves of N. benthamiana. The results showed that these modified rA1M protein variants, A1M-NB1, A1M-NB2 and A1M-NB3, targeted to the cytosol, ER and extracellular space, respectively, were successfully expressed in the leaves, which was confirmed by SDS-PAGE and Western blot analysis. The cytosol accumulated A1M-NB1 was selected for further analysis, as it appeared to have a higher yield than the other variants, and was purified with a yield of ca. 50 mg/kg leaf. The purified protein had the expected structural and functional properties, displaying heme-binding capacity and capacity of protecting red blood cells against stress-induced cell death. The protein also carried bound chromophores, a characteristic feature of A1M and an indicator of a capacity to bind small molecules. The study showed that expression of the functional protein in N. benthamiana may be an attractive alternative for production of rA1M for pharmaceutical purposes and a basis for future research on A1M structure and function.

Gross and delta efficiencies during uphill running and cycling among elite triathletes.

PURPOSE: To investigate the gross efficiency (GE) and delta efficiency (DE) during cycling and running in elite triathletes. METHODS: Five male and five female elite triathletes completed two incremental treadmill tests with an inclination of 2.5° to determine their GE and DE during cycling and running. The speed increments between the 5-min stages were 2.4 and 0.6 km h-1 during the cycling and running tests, respectively. For each test, GE was calculated as the ratio between the mechanical work rate (MWR) and the metabolic rate (MR) at an intensity corresponding to a net increase in blood-lactate concentration of 1 mmol l-1. DE was calculated by dividing the delta increase in MWR by the delta increase in MR for each test. Pearson correlations and paired-sample t tests were used to investigate the relationships and differences, respectively. RESULTS: There was a correlation between GEcycle and GErun (r = 0.66; P = 0.038; R2 = 0.44), but the correlation between DEcycle and DErun was not statistically significant (r = - 0.045; P = 0.90; R2 = 0.0020). There were differences between GEcycle and GErun (t = 80.8; P < 0.001) as well as between DEcycle and DErun (t = 27.8; P < 0.001). CONCLUSIONS: Elite triathletes with high GE during running also have high GE during cycling, when exercising at a treadmill inclination of 2.5°. For a moderate uphill incline, elite triathletes are more energy efficient during cycling than during running, independent of work rate.

Plant based production of myoglobin - a novel source of the muscle heme-protein.

Myoglobin is a heme-protein in the muscle of vertebrates with important functions in the oxygenation of tissues and as a regulator in nitric oxide signaling. Myoglobin from many species is also an important nutritional source of bioavailable iron. In this study, we have successfully produced human myoglobin in the leaves of Nicotiana benthamiana by transient expression using a viral vector delivered by Agrobacterium tumefaciens. Analyses confirmed that heme was incorporated and the protein was functional, with observed properties consistent with those of native myoglobins. A relatively high degree of purity could be achieved with low cost methods. The results show the high potential of plants as a production platform for heme proteins, a group of proteins of interest for iron nutrition applications and possible future pharmaceutical development.

The acute effects of a short technique-intense training period on side-foot kick performance among elite female soccer players.

BACKGROUND: Previously, it was shown that elite soccer teams were 24% more likely to win matches if their passing effectiveness were increased by 1%. However, research interventions aiming to improve passing performance are scarce. The current study aimed to investigate the effect of a short technique-intense training period on side-foot kick performance among elite female soccer players. METHODS: Four side-foot kick tests were completed before and after a training period: kicking a stationary ball using match-relevant (SBRS) and maximal ball speed (SBMS), passing the ball on the move using match-relevant ball speed (RBRS), and repeated side-foot kicks onto a rebound-box with continuously increasing passing distance (RRB). The players were assigned to either the intervention group or the control group. The training intervention consisted of six 55-min training sessions with five side-foot kick exercises. Within-group and between-group differences were investigated using paired-samples t-test and Mann-Whitney U test, respectively. RESULTS: The intervention group improved the performance in the RBRS and RRB tests (both P<0.05), but no differences were found for the SBRS and SBMS tests (both P>0.05). No improvements were found for the control group independent of test condition (all P>0.05). Significant between-group differences were found for the RBRS and RRB tests (both P<0.05), whereas no differences were found for the SBRS and SBMS tests (both P>0.05). CONCLUSIONS: The fundamental soccer skill of passing a moving ball was improved in elite female soccer players by a short technique-intense training period.

The Influence of Task Conditions on Side Foot-Kick Accuracy among Swedish First League Women's Soccer Players.

The purpose of this study was to investigate the influence of the task conditions on 20-m side foot-kick accuracy among Swedish first league women's soccer players. Twenty-three players performed three side foot-kick tests under different task conditions: stationary ball using match-relevant ball speed (SBRS) and maximal ball speed (SBMS) and a 5-m run with the ball from different approach angles (0°, 30°, and 60°) to a predetermined position, where passing of the ball on the move was executed using match-relevant ball speed (RBRS). With each test, the players performed 30 side-foot kicks, alternating between kicking legs with the aim of hitting a target stick. The accuracy was determined using video analysis. The side foot-kick accuracy was significantly greater for SBRS, compared to RBRS and SBMS. For all three test variables, the preferred leg displayed greater accuracy. The preferred leg's accuracy was greater for the approach angle of 30° compared to both 0° and 60°. A significant deviation from the target stick was found for the straight-ahead approach, in which the right-foot and left-foot kicks deviated to respectively the left and right of the stick; in contrast, for the approach angle of 60°, the deviation from the target stick was on the opposite side of the approach side for both legs.

The effects of strength training versus ski-ergometer training on double-poling capacity of elite junior cross-country skiers.

PURPOSE: To compare the effects of strength training versus ski-ergometer training on double-poling gross efficiency (GE), maximal speed (V max), peak oxygen uptake ([Formula: see text]) for elite male and female junior cross-country skiers. METHODS: Thirty-three elite junior cross-country skiers completed a 6-week training-intervention period with two additional 40-min training sessions per week. The participants were matched in pairs and within each pair randomly assigned to either a strength-training group (STR) or a ski-ergometer-training group (ERG). Before and after the intervention, the participants completed three treadmill roller-skiing tests to determine GE, V max, and [Formula: see text]. Mixed between-within subjects analysis of variance (ANOVA) was conducted to evaluate differences between and within groups. Paired samples t tests were used as post hoc tests to investigate within-group differences. RESULTS: Both groups improved their V max and [Formula: see text] expressed absolutely (all P < 0.01). For the gender-specific sub-groups, it was found that the female skiers in both groups improved both V max and [Formula: see text] expressed absolutely (all P < 0.05), whereas the only within-group differences found for the men were improvements of V max in the STR group. No between-group differences were found for any of the investigated variables. CONCLUSIONS: Physiological and performance-related variables of importance for skiers were improved for both training regimes. The results demonstrate that the female skiers' physiological adaptations to training, in general, were greater than those of the men. The magnitude of the physiological adaptations was similar for both training regimes.

Aerobic power and lean mass are indicators of competitive sprint performance among elite female cross-country skiers.

The purpose of this study was to establish the optimal allometric models to predict International Ski Federation's ski-ranking points for sprint competitions (FISsprint) among elite female cross-country skiers based on maximal oxygen uptake ( [Formula: see text]) and lean mass (LM). Ten elite female cross-country skiers (age: 24.5±2.8 years [mean ± SD]) completed a treadmill roller-skiing test to determine [Formula: see text] (ie, aerobic power) using the diagonal stride technique, whereas LM (ie, a surrogate indicator of anaerobic capacity) was determined by dual-emission X-ray anthropometry. The subjects' FISsprint were used as competitive performance measures. Power function modeling was used to predict the skiers' FISsprint based on [Formula: see text], LM, and body mass. The subjects' test and performance data were as follows: [Formula: see text], 4.0±0.3 L min-1; LM, 48.9±4.4 kg; body mass, 64.0±5.2 kg; and FISsprint, 116.4±59.6 points. The following power function models were established for the prediction of FISsprint: [Formula: see text] and 6.95 × 1010 · LM-5.25; these models explained 66% (P=0.0043) and 52% (P=0.019), respectively, of the variance in the FISsprint. Body mass failed to contribute to both models; hence, the models are based on [Formula: see text] and LM expressed absolutely. The results demonstrate that the physiological variables that reflect aerobic power and anaerobic capacity are important indicators of competitive sprint performance among elite female skiers. To accurately indicate performance capability among elite female skiers, the presented power function models should be used. Skiers whose [Formula: see text] differs by 1% will differ in their FISsprint by 5.8%, whereas the corresponding 1% difference in LM is related to an FISsprint difference of 5.1%, where both differences are in favor of the skier with higher [Formula: see text] or LM. It is recommended that coaches use the absolute expression of these variables to monitor skiers' performance-related training adaptations linked to changes in aerobic power and anaerobic capacity.

The influence of sex, age, and race experience on pacing profiles during the 90 km Vasaloppet ski race.

The purpose of this study was to investigate pacing-profile differences during the 90 km Vasaloppet ski race related to the categories of sex, age, and race experience. Skiing times from eight sections (S1 to S8) were analyzed. For each of the three categories, 400 pairs of skiers were matched to have a finish time within 60 seconds, the same start group, and an assignment to the same group for the other two categories. Paired-samples Student's t-tests were used to investigate sectional pacing-profile differences between the subgroups. Results showed that males skied faster in S2 (P=0.0042), S3 (P=0.0049), S4 (P=0.010), and S1-S4 (P<0.001), whereas females skied faster in S6 (P<0.001), S7 (P<0.001), S8 (P=0.0088), and S5-S8 (P<0.001). For the age category, old subjects (40 to 59 years) skied faster than young subjects (19 to 39 years) in S3 (P=0.0029), and for the other sections, there were no differences. Experienced subjects (≥4 Vasaloppet ski race completions) skied faster in S1 (P<0.001) and S1-S4 (P=0.0054); inexperienced skiers (<4 Vasaloppet ski race completions) had a shorter mean skiing time in S5-S8 (P=0.0063). In conclusion, females had a more even pacing profile than that of males with the same finish time, start group, age, and race experience. No clear age-related pacing-profile difference was identified for the matched subgroups. Moreover, experienced skiers skied faster in the first half whereas inexperienced skiers had higher skiing speeds during the second half of the race.

Physiological Demands of Competitive Sprint and Distance Performance in Elite Female Cross-Country Skiing.

Carlsson, M, Carlsson, T, Wedholm, L, Nilsson, M, Malm, C, and Tonkonogi, M. Physiological demands of competitive sprint and distance performance in elite female cross-country skiing. J Strength Cond Res 30(8): 2138-2144, 2016-The purpose was to investigate the relationship between elite females' competitive performance capability in sprint and distance cross-country skiing and the variables of gross efficiency (GE), work rate at the onset of blood-lactate accumulation (OBLA4mmol), maximal oxygen uptake (V[Combining Dot Above]O2max), maximal speed (Vmax), and peak upper-body oxygen uptake (V[Combining Dot Above]O2peak). Ten elite female cross-country skiers (age 24.5 ± 2.8 years) completed treadmill roller-skiing tests to determine GE, OBLA4mmol, and V[Combining Dot Above]O2max using the diagonal-stride technique as well as Vmax and V[Combining Dot Above]O2peak using the double-poling technique. International Ski Federations ranking points for sprint (FISsprint) and distance (FISdist) races were used as competitive performance data. There were correlations between the FISsprint and the V[Combining Dot Above]O2max expressed absolutely (p = 0.0040), Vmax (p = 0.012), and V[Combining Dot Above]O2peak expressed absolutely (p < 0.001) and as a simple ratio-standard (p = 0.049). The FISdist were correlated with OBLA4mmol (p = 0.048), V[Combining Dot Above]O2max expressed absolutely (L·min) (p = 0.015) and as a simple ratio-standard (p = 0.046), and V[Combining Dot Above]O2peak expressed absolutely (p = 0.036) and as a simple ratio-standard (ml·min·kg) (p = 0.040). The results demonstrate that the physiological abilities reflected by V[Combining Dot Above]O2max and V[Combining Dot Above]O2peak are indicators of competitive sprint and distance performance in elite female cross-country skiing. In addition, the ability to generate a high Vmax indicates the performance in sprint races, whereas the skier's OBLA4mmol reflects the performance capability in distance races. Based on the results, when evaluating the performance capacity of elite female cross-country skiers, it is recommended to use physiological variables that reflect competitive performance.

Effects of UV-C and Vacuum-UV TiO2 Advanced Oxidation Processes on the Acute Mortality of Microalgae.

Advanced oxidation processes/technologies (AOT) that combine a semiconductor, such as titanium dioxide (TiO2 ), with a UV source have been used to eliminate microorganisms in various water treatment applications. To facilitate the applicability of this technique, the gain in efficiency from the semiconductor compared to the UV source alone with respect to different target organisms requires evaluation. The primary objective of this study was to determine the effects of TiO2 and UV wavelength on a freshwater alga, Pseudokirchneriella subcapitata and a marine alga, Tetraselmis suecica. For each species, dose-response experiments were conducted to determine the median lethal dose (LC50 ) of the following treatments: UV light emitted with a peak of 254 nm, UV light emitted with a peak of 254 nm in the presence of TiO2 and UV light emitted with a peak of 254 and 185 nm in the presence of TiO2 . In both species, the presence of TiO2 significantly increased mortality. Across all three treatments, P. subcapitata was more sensitive than T. suecica; moreover, the addition of the 185 nm wavelength significantly increased cell mortality in P. subcapitata but not in T. suecica.

Optimal [Formula: see text] ratio for predicting 15 km performance among elite male cross-country skiers.

The aim of this study was 1) to validate the 0.5 body-mass exponent for maximal. oxygen uptake [Formula: see text] as the optimal predictor of performance in a 15 km classical-technique skiing competition among elite male cross-country skiers and 2) to evaluate the influence of distance covered on the body-mass exponent for [Formula: see text] among elite male skiers. Twenty-four elite male skiers (age: 21.4±3.3 years [mean ± standard deviation]) completed an incremental treadmill roller-skiing test to determine their [Formula: see text]. Performance data were collected from a 15 km classical-technique cross-country skiing competition performed on a 5 km course. Power-function modeling (ie, an allometric scaling approach) was used to establish the optimal body-mass exponent for [Formula: see text] to predict the skiing performance. The optimal power-function models were found to be [Formula: see text] and [Formula: see text], which explained 69% and 81% of the variance in skiing speed, respectively. All the variables contributed to the models. Based on the validation results, it may be recommended that [Formula: see text] divided by the square root of body mass (mL · min(-1) · kg(-0.5)) should be used when elite male skiers' performance capability in 15 km classical-technique races is evaluated. Moreover, the body-mass exponent for [Formula: see text] was demonstrated to be influenced by the distance covered, indicating that heavier skiers have a more pronounced positive pacing profile (ie, race speed gradually decreasing throughout the race) compared to that of lighter skiers.

Oxygen uptake at different intensities and sub-techniques predicts sprint performance in elite male cross-country skiers.

PURPOSE: To investigate the relationship between sprint-prologue performance (using the classical technique) and the oxygen uptake at the lactate threshold (VO2obla), maximal oxygen uptake (VO2max), and mean oxygen uptake during double poling (VO2dp). METHODS: Eight elite male cross-country skiers [age 24.8 ± 4.8 years, (mean ± SD)] completed two treadmill roller-skiing tests using the diagonal-stride technique and a 60 s double-poling test on a ski-ergometer to determine their VO2obla, VO2max, and VO2dp. Performance data were generated from a 1.25 km sprint prologue. Power-function modelling was used to predict the skiers' race speeds based on the oxygen-uptake variables and body mass. RESULTS: There were correlations between the race speed and the absolute expression of the VO2obla (r = 0.79, P = 0.021), VO2max (r = 0.86, P = 0.0069), and VO2dp (r = 0.94, P = 0.00062). The following power-function models were established for race-speed prediction: 1.09 · VO2obla(0.21), 1.05 · VO2max(0.21), and 1.19 · VO2dp(0.20); these models explained 60% (P = 0.024), 73% (P = 0.0073), and 87% (P = 0.00073), respectively, of the variance in the race speed. However, body mass did not contribute to any of the models (P = 0.97, 0.88, and 0.21, respectively). CONCLUSIONS: Oxygen uptake at different intensities and sub-techniques is an indicator of elite male sprint-prologue performance. The absolute expression of the investigated oxygen-uptake variables should be used when evaluating elite male sprint-prologue performances; if skiers oxygen uptake differs by 1%, their performances will likely differ by 0.2% in favour of the skier with higher oxygen uptake.

Prediction of race performance of elite cross-country skiers by lean mass.

PURPOSE: To investigate the relationship between race performance and lean mass (LM) variables, as well as to examine sex differences in body composition in elite-standard cross-country skiers. METHODS: Thirty-four elite cross-country skiers (18 men and 16 women) underwent a dual-emission X-ray-absorptiometry body-composition test to determine LM, fat mass, and bone mineral content. For both sexes, performance data were collected from a sprint prologue and a distance race. RESULTS: The absolute expression of LM variables (whole-body [LMWB], upper body [LMUB], and lower body [LMLB]) was significantly correlated with finishing time in the sprint prologue independent of sex. Distance-race performance was significantly related to LMWB, LMUB, and LMLB in women; however, no correlation was found in men. Men had a significantly higher LM and lower fat mass, independent of expression (absolute or relative), for the whole body, arms, trunk, and legs, except for the absolute fat mass in the trunk. CONCLUSIONS: The absolute expressions of LMWB, LMUB, and LMLB were significant predictors of sprint-prologue performance in both sexes, as well as of distance-race performance in women only. Compared with women, male skiers have a higher LM in the body segments that are major contributors to propelling forces. These results suggest that muscle mass in the lower and upper body is equally important for race performance; thus, more focus of elite skiers' training should be directed to increasing whole-body muscle mass to improve their competitive performance capability.