Sex Differences in Self-Reported Causes, Symptoms, and Recovery Strategies Associated With Underperformance in Endurance Athletes.

PURPOSE: This study investigated sex differences in self-reported causes, symptoms, and recovery strategies associated with underperformance in endurance athletes. METHODS: A total of 82 athletes (40 women) meeting the inclusion criteria (performance level ≥tier 3, used training diaries, and experienced 1 or more periods of underperformance during their career) completed an online questionnaire. The questionnaire encompassed inquiries regarding load monitoring and experiences with underperformance, focusing on causes, symptoms, and recovery strategies. RESULTS: The most frequently reported symptoms associated with underperformance included psychological (31%), physiological (23%), and health-related (12%) symptoms. Notably, female athletes were more likely to report psychological symptoms associated with underperformance (38% vs 25%, P = .01) compared with male athletes. The leading causes of underperformance comprised illness (21%), mental/emotional challenges (20%), training errors (12%), lack of recovery (10%), and nutritional challenges (5%). Female athletes reported nutritional challenges more frequently as the cause of underperformance compared with males (9% vs 1%, P = .01), whereas male athletes more often attributed underperformance to training errors (15% vs 9%, P = .03). Overall, 67% of athletes reported recovering from underperformance, with a tendency for more male than female athletes to recover (76% vs 58%, P = .07). Furthermore, a higher proportion of male than female athletes reported implementing changes in the training process as a recovery strategy (62% vs 35%, P = .02). CONCLUSIONS: This study offers valuable insights into sex differences in experiences with underperformance in endurance athletes. The findings could inform coaches and athletes in both the prevention and treatment of such incidents.

From juniors to seniors: changes in training characteristics and aerobic power in 17 world-class cross-country skiers.

Purpose: To compare training characteristics and aerobic power (VO2max) between the most successful junior and senior seasons of world-class cross-country (XC) skiers and to identify differences between sexes and among sprint and distance skiers. Methods: Retrospective analysis was conducted on self-reported training and VO2max tests of ten male and seven female world-class XC-skiers, collectively holding 38 Olympic medals. Training was categorized by form (endurance, strength, speed, other) and mode (specific, unspecific) and was divided into low- (LIT), moderate- (MIT), and high-intensity training (HIT). Results: Total training increased by 203 ± 130 h (35% ± 31%, p < .001, large effect) and 78 ± 69 sessions (21% ± 24%, p < .001, very large effect). Junior training volume (658 ± 107 h) did not correlate with senior volume (861 ± 74 h) but correlated negatively with changes in volume (r = -.822, p < .001). No sex differences were observed related to total volume, but distance skiers increased their total volume more than sprint skiers (p = .037, large effect). Endurance training increased by 197 ± 117 h (p < .001; large effect) tied to increased low-intensity training (186 ± 115 h, p < .001; large effect) and moderate-intensity training (13 ± 7 h, p < .001; large effect). Training intensity distribution (% LIT/MIT/HIT) was 91/3/6 in junior and 92/4/4 in senior season. Women demonstrated greater increase of unspecific modes (100 ± 58 vs. 37 ± 44 h, p = .022; large effect) and strength training (25 ± 23 vs. -3 ± 17 h, p = .010, large effect). Men improved absolute (8% ± 5%; p = .009; large effect) and relative VO2max (6% ± 4%; p = .016; large effect) from junior to senior, while women only increased relative VO2max (7% ± 5%, p = .012; large effect). Conclusion: This study provides novel information regarding changes in training characteristics and aerobic power from junior to senior age in world-class XC-skiers. Overall, the enhanced training volume during this transition was primarily driven by increased LIT and MIT and the exceptionally high relative VO2max at junior age further increased in both sexes.

Long-term development of performance, physiological, and training characteristics in a world-class female biathlete.

Purpose: The purpose of this study is to investigate the long-term development of performance, physiological, and training characteristics in a world-class female biathlete, with emphasis on differences between junior and senior athlete seasons. Methods: The participant is a highly decorated female biathlete with 22 (10 gold) medals from international championships and 28 individual World Cup wins. Performance development (ages 17-33), physiological tests (ages 22-33), and day-to-day physical and shooting training (ages 17-33) were analyzed. Training data were systemized by endurance [low-intensity training (LIT), moderate-intensity training (MIT), and high-intensity training (HIT)], exercise mode, and strength training. Shooting training recorded for each session included the number of shots fired during rest, LIT, MIT, HIT, or competitions and time spent on dry fire training. Results: The annual volume of physical training (409-792 h·season-1) and number of shots fired (1,163-17,328 shots·season-1) increased from the age of 17 to 28 followed by a subsequent reduction in physical training (range 657-763 h·season-1) and shots fired (13,275-15,355 shots·season-1) during the seasons of peak performance at ages 31-33. Maximal oxygen uptake in roller ski skating increased by 10% (62.9-69.2 ml·kg-1·min-1) from the age of 22 to 27. The physical training volume was 48% higher (694 ± 60 vs. 468 ± 23 h·season-1, P = .030), with 175% more shots fired (14,537 ± 1,109 vs. 5,295 ± 3,425 shots·season-1, P = .016) as a senior athlete than a junior athlete. In the physical training, these differences were mainly explained by higher volumes of LIT (602 ± 56 vs. 392 ± 22 h·season-1, P = .032) and MIT (34 ± 1 vs. 7 ± 2 h·season-1, P = .001) but less HIT (27 ± 1 vs. 42 ± 3 h·season-1, P = .006) as a senior than a junior. In line with this, shooting training as a senior included more shots fired both at rest (5,035 ± 321 vs. 1,197 ± 518 shots·season-1, P = .011) and during LIT (7,440 ± 619 vs. 2,663 ± 1,975 shots·season-1, P = .031), while a smaller insignificant difference was observed in the number of shots fired in connection with MIT, HIT, and competitions (2,061 ± 174 vs. 1,435 ± 893 shots·season-1, P = .149). Conclusions: This study provides unique insights into the long-term development of physical and shooting training from junior to senior in a world-class female biathlete. The major differences in training characteristics between junior and senior athlete seasons were higher sport-specific volumes of LIT and MIT and less HIT. These differences were accompanied by more shooting training, particularly at rest, and in connection with LIT.

The Evolution of World-Class Endurance Training: The Scientist's View on Current and Future Trends.

BACKGROUND: Elite sport is continuously evolving. World records keep falling and athletes from a longer list of countries are involved. PURPOSE: This commentary was designed to provide insights into present and future trends associated with world-class endurance training based on the perspectives, experience, and knowledge of an expert panel of 25 applied sport scientists. RESULTS: The key drivers of development observed in the past 10-15 years were related to (1) more accessible scientific knowledge for coaches and athletes combined with (2) better integration of practical and scientific exchange across multidisciplinary perspectives within professionalized elite athlete support structures, as well as (3) utilization of new technological advances. Based on these perspectives, we discerned and exemplified the main trends in the practice of endurance sports into the following categories: better understanding of sport-specific demands; improved competition execution; larger, more specific, and more precise training loads; improved training quality; and a more professional and healthier lifestyle. The main areas expected to drive future improvements were associated with more extensive use of advanced technology for monitoring and prescribing training and recovery, more precise use of environmental and nutritional interventions, better understanding of athlete-equipment interactions, and greater emphasis on preventing injuries and illnesses. CONCLUSIONS: These expert insights can serve as a platform and inspiration to develop new hypotheses and ideas, encourage future collaboration between researchers and sport practitioners, and, perhaps most important, stimulate curiosity and further collaborative studies about the training, physiology, and performance of endurance athletes.

Place of residence and coach-athlete relationship predict drop-out from competitive cross-country skiing.

The current study investigated whether factors such as living residence, the coach-athlete working alliance, goal orientation, and intrinsic motivation could explain drop-out, and whether these factors differed between athletes included in the elite- vs. general sport programs during high school years. In total 257 cross-country skiers, graduated from three different Norwegian Top Sport schools during the period from 2015 to 2019, were recruited to retrospectively investigate their experiences related to the time period when they participated in programs for cross-country skiing at high school. In total 116 of these athletes completed an online survey including validated and standardized instruments for the assessment of the coach-athlete working alliance (CAWAI), goal orientation (GO), perceived satisfaction with their performances (PAP) and intrinsic motivation (IM). The results showed that 84% of the athletes had dropped out from cross-country skiing, while 16% were still active. The highest ranked fixed statements of causes for drop-out was "a natural choice" (3.79 ± 1.11), "priority of education or work" (3.61 ± 1.30), "lack of motivation" (3.49 ± 1.28), "negative performance development" (3.46 ± 1.18), and "challenges with health" (3.25 ± 1.54). There were significant differences between active and drop-out in scores for reciprocity between the coaches' and the athletes' perceptions of goals (CAWAI-goal; 5.87 ± .98 vs. 5.07 ± 1.15; p = .004), the coach-athlete relationship bond (CAWAI-bond; 6.08 ± .91 vs. 5.07 ± 1.38; p = .001), and tasks chosen to reach the defined goals (CAWAI-task; 5.61 ± .92 vs. 4.90 ± 1.09; p = .006). Furthermore, active athletes had higher mastery orientation (22.11 ± 2.88 vs. 20.00 ± 3.74; p = .010). A hierarchical binary logistic regression analysis showed that place of residence and the coach-athlete working alliance were significant predictors of drop-out while mastery and performance goal orientation or intrinsic motivation were not significant. All five predictors explained 23% of the variability in drop out from cross-country skiing. Overall, 58% and 42% of the athletes participated in the elite and general programs for cross-country skiing during high school, respectively. The athletes that took part in the elite programs reported significantly stronger coach-athlete working alliances (CAWAI-sum; 14.46±3.10 vs. 14.28±3.37; p = .000), higher mastery orientation (21.19±3.50 vs. 19.36±3.66; p = .008), and performance satisfaction (PAP; 19.17±5.98 vs. 15.69±5.19; p = .001) compared to the athletes attending general programs. The results are discussed in terms of existing knowledge on how place of residence, the coach-athlete working alliance, goal orientation, performances, and motivation might impact drop-out in cross-country skiing.

Long-Term Development of Training Characteristics and Performance-Determining Factors in Elite/International and World-Class Endurance Athletes: A Scoping Review.

OBJECTIVE: In this scoping review, we aimed to 1) identify and evaluate existing research that describes the long-term development of training characteristics and performance-determining factors in male and female endurance athletes reaching an elite/international (Tier 4) or world-class level (Tier 5), 2) summarize the available evidence and 3) point out existing knowledge gaps and provide methodological guidelines for future research in this field. METHODS: This review was conducted following the Joanna Briggs Institute methodology for scoping reviews. RESULTS: Out of 16772 screened items across a 22-year period (1990-2022), a total of 17 peer-reviewed journal articles met the inclusion criteria and were considered for further analysis. These 17 studies described athletes from seven different sports and seven different countries, with 11 (69%) of the studies being published during the last decade. Of the 109 athletes included in this scoping review, one quarter were women (27%), and three quarters were men (73%). Ten studies included information about the long-term development of training volume and training intensity distribution. A non-linear, year-to-year increase in training volume was found for most athletes, resulting in a subsequent plateau. Furthermore, 11 studies described the development of performance determining factors. Here, most of the studies showed improvements in submaximal variables (e.g., lactate/anaerobic threshold and work economy/efficiency) and maximal performance-indices (e.g., peak speed/watt during performance testing). Conversely, the development of VO2max was inconsistent across studies. No evidence was found regarding possible sex differences in development of training or performance-determining factors among endurance athletes. CONCLUSION: Overall, a low number of studies describing the long-term development of training and performance-determining factors is available. This suggests that existing talent development practices in endurance sports are built upon limited scientific evidence. Overall, there is an urgent need for additional long-term studies based on systematic monitoring of athletes from a young age utilizing high-precision, reproducible measurements of training and performance-determining factors.

Training Quality-What Is It and How Can We Improve It?

PURPOSE: The concept of training quality reflects that the effect of training is dependent on more than the mere product of training load (eg, duration, intensity, frequency). The aims of this commentary are to (1) propose a practice-oriented framework to describe training quality and its general and context-dependent characteristics and (2) discuss how athletes and coaches can work to improve training quality. CONCLUSIONS: Training quality can be viewed from different perspectives. The holistic dimension includes the entire training process (goal setting, gap analysis, application of training principles and methods, etc), while a narrower dimension encompasses the specific training sessions and how they are executed in relation to the intended purpose. To capture the varying contexts, we define training quality as the degree of excellence related to how the training process or training sessions are executed to optimize adaptations and, thereby, improve overall performance. Although training quality is challenging to quantify, we argue that identification and assessment of quality indicators will increase our scientific understanding and consequently help coaches and athletes to improve training quality. We propose that the physical, technical, and psychological factors of training quality can be improved through an individualized learning process of systematic planning, execution, and debriefing. However, assessment tools should be identified and scientifically validated across different training sessions and sports. We encourage further interventions to improve training quality.

Performance Effects of Video- and Sensor-Based Feedback for Implementing a Terrain-Specific Micropacing Strategy in Cross-Country Skiing.

PURPOSE: To investigate the performance effects of video- and sensor-based feedback for implementing a terrain-specific micropacing strategy in cross-country (XC) skiing. METHODS: Following a simulated 10-km skating time trial (Race1) on snow, 26 national-level male XC skiers were randomly allocated into an intervention (n = 14) or control group (n = 12), before repeating the race (Race2) 2 days later. Between races, intervention received video- and sensor-based feedback through a theoretical lecture and a practical training session aiming to implement a terrain-specific micropacing strategy focusing on active power production over designated hilltops to save time in the subsequent downhill. The control group only received their overall results and performed a training session with matched training load. RESULTS: From Race1 to Race2, the intervention group increased the total variation of chest acceleration on all hilltops (P < .001) and reduced time compared with the control group in a specifically targeted downhill segment (mean group difference: -0.55 s; 95% confidence interval [CI], -0.9 to -0.19 s; P = .003), as well as in overall time spent in downhill (-14.4 s; 95% CI, -21.4 to -7.4 s; P < .001) and flat terrain (-6.5 s; 95% CI, -11.0 to -1.9 s; P = .006). No between-groups differences were found for either overall uphill terrain (-9.3 s; 95% CI, -31.2 to 13.2 s; P = .426) or total race time (-32.2 s; 95% CI, -100.2 to 35.9 s; P = .339). CONCLUSION: Targeted training combined with video- and sensor-based feedback led to a successful implementation of a terrain-specific micropacing strategy in XC skiing, which reduced the time spent in downhill and flat terrain for intervention compared with a control group. However, no change in overall performance was observed between the 2 groups of XC skiers.

Offered Support and Knowledge about the Menstrual Cycle in the Athletic Community: A Cross-Sectional Study of 1086 Female Athletes.

Many female athletes perceive that symptoms related to the menstrual cycle such as dysmenorrhea, premenstrual symptoms, amenorrhea or side-effects of hormonal contraceptives negatively impact their training, performance, and general well-being. Knowledge and communication about female athletes' health is therefore important in the sport community. The aims of this study were to explore the level of knowledge and communication about menstrual cycle issues and use of hormonal contraceptives in the athletic community and to describe the kinds of medical support offered to female athletes. A total of 1086 Swedish and Norwegian athletes from 57 different sports responded to a web-based questionnaire. Of these, 58% (n = 627) practiced team sports and 42% (n = 459) individual sports. Twenty-six percent (n = 278) of the athletes perceived their knowledge about female athlete health to be poor/very poor and the knowledge was most often acquired from medical staff. Fifty-three percent (n = 572) of the athletes perceived the knowledge acquired of their coaches as poor/very poor, even though a significantly (p < 0.001) higher proportion of athletes with a female coach (30%, n = 31) rated their coach's knowledge as very good/good, compared to athletes with a male coach (5%, n = 31). Only 11% (n = 116) of the athletes discussed female health issues with their coach. The majority (81%, n = 842) of the athletes partly to strongly agreed that female athlete health is considered a taboo topic in the athletic community. Forty-seven percent (n = 510) of the athletes had access to a physiotherapist, while only three percent (n = 29) had access to a gynecologist. Low perceived knowledge, lack of communication and support demonstrate the need for a multi-professional medical team and enhanced educational efforts focused on female athlete health in the athletic community.

Perceived impact of the menstrual cycle and hormonal contraceptives on physical exercise and performance in 1,086 athletes from 57 sports.

Female athletes train and compete under the potential influence of hormonal fluctuations during the menstrual cycle or during use of various hormonal contraceptives. Dysmenorrhea and premenstrual symptoms are common in the general population, as well as side effects of hormonal contraceptives. More detailed knowledge concerning prevalence and perceived impact of these symptoms on training and performance in different sports is required. The aim of the study was to 1) characterize perceptions of training and performance during the menstrual cycle phases and by hormonal contraceptive use in a large population of female athletes; 2) explore whether symptoms experienced are related to perceived performance; and 3) examine potential differences in these factors between athletes at different levels of performance. The study was based on self-reported data from 1,086 athletes from 57 sports at different performance levels via a web-based questionnaire. Thirty-seven percent (n = 407) of the athletes did not use hormonal contraceptives. In this group, menstrual cycle related symptoms were common across all athlete levels, particularly dysmenorrhea (74%, n = 300) and premenstrual symptoms (78%, n = 318), which also influenced perceived performance of aerobic fitness, muscle strength, mental sharpness, balance, and sleep quality. Sixty-three percent (n = 679) of the athletes used various hormonal contraceptives and 40% (n = 272) perceived a variety of side-effects. Physical performance was experienced equally independent of time-point of the pill-chart except for the period of inactive pills, which was associated with more negative impact. Nonetheless, only 18% (n = 191) of the athletes considered menstrual cycle or hormonal contraceptive issues when planning their training or competitions. These results indicate that greater focus is needed to identify and effectively treat different menstrual cycle and hormonal contraceptive related symptoms on an individual level.

One Long Versus 2 Short Sessions? Physiological and Perceptual Responses to Low-Intensity Training at Self-Selected Speeds in Cross-Country Skiers.

PURPOSE: To compare self-selected speeds and corresponding physiological responses and perceived training stress between 1 long session versus 2 shorter sessions of low-intensity training (LIT) in 1 day among cross-country skiers. METHODS: Thirteen national-level skiers performed 2 different LIT types during classical roller-skiing matched for the same distance in a counterbalanced order. The training consisted of either 1 long (approximately 3 h) session (1LIT) or 2 shorter (approximately 1.5 h each) sessions (2LIT) with 7 hours of recovery in between. Speed, heart rate, rating of perceived exertion, and blood lactate concentrations were measured, and perceived training stress (1-10) was assessed after sessions. RESULTS: 2LIT was performed at mean (SD) 1.9% (2.0%) higher speeds versus 1LIT (P ≤ .01). Higher speeds were also found in the second versus first session of 2LIT and the second versus first part of 1LIT (1.9% [3.2%] and 3.2% [3.6%], respectively, both P ≤ .01). There were no significant differences between LIT types in heart rate, although rating of perceived exertion increased in the second versus first part of 1LIT (0.9 [0.8] point, P ≤ .01). Blood lactate concentration was reduced in the second versus first session/part of both LIT types (approximately 0.16 [0.20] mmol·L-1, P ≤ .05). There were no differences in perceived training stress between LIT types 7 and 23 hours after training, although higher perceived muscular exertion (2.0 [1.1] points, P ≤ .01) was found directly after 1LIT. CONCLUSIONS: Compared with a distance-matched long session, skiers perform 2LIT at slightly higher self-selected speeds with the same physiological responses elicited, although minor differences in perceived training stress were observed.

Performance-Related Physiological and Haematological Changes During Pregnancy and Postpartum in a Well-Trained Cyclist Performing Endurance Training.

Purpose: To describe the performance-related physiological and haematological changes in a well-trained cyclist (peak oxygen uptake, VO2peak: 54.9 ml min-1·kg-1) performing endurance training during pregnancy and postpartum. Methods: Training data was systemized by training form (endurance and resistance), intensity (low- (LIT), moderate-, and high-intensity training), and modality (cycling, running, hiking, XC-skiing, strength training and other). Power output at 4 mmol L-1 [BLa-] (L4), maximal aerobic power (Wmax), and VO2peak as well as haemoglobin mass, blood volume, plasma volume and red blood cell volume (RBCV) were measured at different time points during pregnancy and 12 weeks postpartum. Results: L4 and Wmax increased by 3% while absolute VO2peak was unaltered from gestational wk 2 to 14, despite 12 and 14% increases in RBCV and BV. After delivery, BV was reduced by 7% but RBCV was maintained 5% above start-pregnancy levels, while VO2peak almost returned to (-1%), and Wmax increased by 5% above start-pregnancy levels 12 weeks postpartum. Conclusion: This case-study illustrates a disassociation between increases in haematological values and VO2peak during pregnancy. Furthermore, a quick resumption of LIT and a gradually increasing intensity of training in the 12 weeks following delivery ensured a return to start-pregnancy levels of VO2peak and corresponding improvements in Wmax. Although general recommendations cannot be given on the basis of these data, this study provides a framework for investigating pregnant endurance athletes and contributes to the generation of new hypotheses in this field.

Laboratory- and field-based performance-predictions in cross-country skiing and roller-skiing.

The purpose of the present study was to investigate how various laboratory- and field-based tests predict on-snow cross-country (XC) skiing and roller-skiing performance. Thirty-three national-level male XC skiers (19.0±2.5 years, maximal oxygen uptake [VO2max] 70.8±4.7 mL·min-1·kg-1) performed a 13.6-km roller-ski skating competition tracked by a global positioning system (GPS), which together with individual distance International Ski Federation (FIS) points was used to assess their performance level. On separate days, time in a 6.4-km uphill running time-trial (RUN-TT) and 1.3-km uphill roller-ski double-poling time-trial (DP-TT) was measured in the field and performance indices determined while running and roller-ski skating in the laboratory. The mean finishing times for the RUN-TT and the DP-TT showed moderate to large correlations with distance FIS points and performance in the roller-ski skating competition (r = 0.56-0.72; all p<0.05). RUN-TT was more strongly correlated with distance FIS points than DP-TT (r = 0.72 versus 0.56; p<0.05). Performance indices and VO2max in incremental running and roller-ski skating in the laboratory showed large to very large correlations with distance FIS points and roller-skiing performance (r = 0.50-0.90; all p<0.05). Performance indices and VO2max in running tended to be more strongly correlated with roller-skiing performance than corresponding values obtained while roller-ski skating (all p<0.10). The present findings suggest that both laboratory performance indices and field-based performance tests provide valid predictions of XC skiing and roller-skiing performance in a heterogeneous group of male XC skiers, with test values obtained in running tending to be more strongly correlated with XC skiing performance than those found for technique-specific modalities on roller skis. However, more sophisticated and mode-specific testing might be required for more homogenous groups of elite XC skiers.

Body Composition, Energy Availability, Training, and Menstrual Status in Female Runners.

PURPOSE: To determine body composition, energy availability, training load, and menstrual status in young elite endurance running athletes (ATH) over 1 year, and in a secondary analysis, to investigate how these factors differ between nonrunning controls (CON), and amenorrheic (AME) and eumenorrheic (EUM) ATH. Correlations to injury, illness, and performance were also examined. METHODS: Altogether 13 ATH and 8 CON completed the Low Energy Availability in Females Questionnaire. Anthropometric, energy intake, and peak oxygen uptake assessments were made at 4 time points throughout the year: at baseline post competition season, post general preparation, post specific preparation, and post competition season the following year. Logs of physical activity, menstrual cycle, illness, and injury were kept by all participants. Performance was defined using the highest International Association of Athletics Federations points prior to and after the study. RESULTS: ATH had significantly lower body mass (P < .008), fat percentage (P < .001), and body mass index (P < .027) compared with CON, while energy availability did not differ between ATH and CON. The Low Energy Availability in Females Questionnaire score was higher in ATH than in CON (P < .028), and 8 ATH (vs zero CON) were AME. The AME had significantly more injury days (P < .041) and ran less (P < .046) than EUM, while total annual running distance was positively related to changes in performance in ATH (r < .62, P < .043, n < 11). CONCLUSIONS: More than half of this group of runners was AME, and they were injured more and ran less than their EUM counterparts. Furthermore, only the EUM runners increased their performance over the course of the year.

The Training Characteristics of World-Class Male Long-Distance Cross-Country Skiers.

Purpose: To investigate the training characteristics of world-class long-distance cross-country skiers. Methods: Twelve world-class male long-distance cross-country skiing specialists reported training from their best season, through a questionnaire and follow-up interviews. Training data were systemized by training form (endurance, strength, and speed), intensity [low- (LIT), moderate- (MIT), and high-intensity training (HIT)], and exercise mode, followed by a division into different periodization phases. Specific sessions utilized in the various periodization phases were also analyzed. Results: The annual training volume was 861 ± 90 h, consisting of 795 ± 88 h (92%) of endurance training, 53 ± 17 h (6%) of strength training, and 13 ± 14 h (2%) of speed training. A pyramidal (asymptotic) endurance training distribution was employed (i.e., 88.7% LIT, 6.4% MIT, and 4.8% HIT). Out of this, 50-60% of the endurance training was performed with double poling (DP), typically in the form of a daily 3- to 5-h session. A relatively evenly distributed week-to-week periodization of training load was commonly used in the general preparation period, whereas skiers varied between high-load training weeks and competition weeks, with half the training volume and a reduced amount of DP during the competition period. Conclusions: To match the specific demands of long-distance cross-country skiing, specialized long-distance skiers perform relatively long but few training sessions and use a pyramidal intensity distribution pattern and a large amount of training spent using the DP technique.

Influence of Menstrual Cycle or Hormonal Contraceptive Phase on Physiological Variables Monitored During Treadmill Testing.

Purpose: To examine the influence of menstrual cycle (MC) and hormonal contraceptive (HC) cycle phases on physiological variables monitored during incremental treadmill testing in physically active women (eumenorrheic, EUM = 16 and monophasic HC-users, CHC = 12). Methods: Four running tests to exhaustion were performed at bleeding, mid follicular (mid FOL)/active 1, ovulation/active 2, and mid luteal (mid LUT)/inactive. HC and MC phases were confirmed from serum hormones. Heart rate (HR), blood lactate (Bla), and V ˙ O2 were monitored, while aerobic (AerT) and anaerobic (AnaT) thresholds were determined. V ˙ O2peak, maximal running speed (RUNpeak), and total running time (RUNtotal) were recorded. Results: No significant changes were observed in V ˙ O2 or Bla at AerT or AnaT across phases in either group. At maximal effort, absolute and relative V ˙ O2peak, RUNpeak, and RUNtotal remained stable across phases in both groups. No significant fluctuations in HRmax were observed across phases, but HR at both AerT and AnaT tended to be lower in EUM than in CHC across phases. Conclusion: Hormonal fluctuations over the MC and HC do not systematically influence physiological variables monitored during incremental treadmill testing. Between group differences in HR at AerT and AnaT underline why HR-based training should be prescribed individually, while recording of MC or HC use when testing should be encouraged as phase may explain minor, but possibly meaningful, changes in, e.g., Bla concentrations or differences in HR response.

Preparing for the Nordic Skiing Events at the Beijing Olympics in 2022: Evidence-Based Recommendations and Unanswered Questions.

At the 2022 Winter Olympics in Beijing, the XC skiing, biathlon and nordic combined events will be held at altitudes of ~ 1700 m above sea level, possibly in cold environmental conditions and while requiring adjustment to several time zones. However, the ongoing COVID-19 pandemic may lead to sub-optimal preparations. The current commentary provides the following evidence-based recommendations for the Olympic preparations: make sure to have extensive experience of training (> 60 days annually) and competition at or above the altitude of competition (~ 1700 m), to optimize and individualize your strategies for acclimatization and competition. In preparing for the Olympics, 10-14 days at ~ 1700 m seems to optimize performance at this altitude effectively. An alternative strategy involves two-three weeks of training at > 2000 m, followed by 7-10 days of tapering off at ~ 1700 m. During each of the last 3 or 4 days prior to departure, shift your sleeping and eating schedule by 0.5-1 h towards the time zone in Beijing. In addition, we recommend that you arrive in Beijing one day earlier for each hour change in time zone, followed by appropriate timing of exposure to daylight, meals, social contacts, and naps, in combination with a gradual increase in training load. Optimize your own individual procedures for warming-up, as well as for maintaining body temperature during the period between the warm-up and competition, effective treatment of asthma (if necessary) and pacing at ~ 1700 m with cold ambient temperatures. Although we hope that these recommendations will be helpful in preparing for the Beijing Olympics in 2022, there is a clear need for more solid evidence gained through new sophisticated experiments and observational studies.

Intensity Control During Block-Periodized High-Intensity Training: Heart Rate and Lactate Concentration During Three Annual Seasons in World-Class Cross-Country Skiers.

Purpose: To describe heart rate (HR) and blood lactate (Bla-) responses during high-intensity interval training (HIT) in a long-term block-periodized HIT regimen in world-class cross-country (XC) skiers. Methods: Data were collected in 14 world-class female XC skiers (aged 25 ± 5 years; body mass, 60.4 ± 6.5 kg; and maximal HR, 194 ± 8 beats · min-1) throughout three entire seasons. The HR and Bla- values were determined at the end of 572 intervals performed during 63 sessions and 17 HIT blocks utilizing different exercise modes: running, running with poles, and skiing (on-snow and roller ski) with classic and skating techniques. Results: The mean HR was 91 ± 3% of HRmax with a corresponding Bla- of 7.3 ± 2.1 mmol · L-1. The average HR and Bla- values were relatively similar across the different exercise modes, except for a lower HR (~90 vs. 92% of HRmax) for on-snow and roller ski classical skiing and lower Bla- values (5.9 vs. 7.0-7.8 mmol · L-1) for on-snow classical skiing compared to the other modes, both P < 0.05. An increase in HR and Bla- was observed from interval working periods 1 to 3 (90-92% of HRmax and 6.5-7.7 mmol · L-1) and further from 3 to 5 (92-93% of HRmax and 7.7-9.0 mmol · L-1), all P < 0.05. Conclusions: We describe long-term use of HIT-block periodization among world-class XC skiers who achieved target HR and Bla- levels in all six exercise modes employed. According to athletes and coaches, the key to successful blocks was intensity control to allow for high-quality HIT sessions throughout the entire HIT block.

Comparison of a Traditional Graded Exercise Protocol With a Self-Paced 1-km Test to Assess Maximal Oxygen Consumption.

PURPOSE: To compare the assessment of the maximal oxygen consumption (VO2max) in a traditional graded exercise test (GXT) with a 1-km self-paced running test on a nonmotorized treadmill in men and women. METHODS: A total of 24 sport-science students (12 women: age 23.7 [7.7] y, body height 1.68 [0.02] m, body mass 66.6 [4.3] kg; 12 men: 22.1 [3.1] y, body height 1.82 [0.06] m, body mass 75.6 [11.0] kg) performed a traditional GXT on a motorized treadmill and a 1-km self-paced running test on a nonmotorized treadmill. VO2max, blood lactate, heart rate, and rating of perceived exertion, together with running velocity and duration at each test, were measured. RESULTS: The main findings of the study were that the 1-km test produced significantly higher VO2max values (53.2 [9.9] vs 51.8 [8.8] mL/kg/min ) and blood lactate concentrations (11.9 [1.8] vs 11.1 [2.2] mmol/L) than the GXT (F ≥ 4.8, P ≤ .04, η2 ≥ .18). However, after controlling for sex, these differences were only present in men (60.6 [8.1] vs 58.1 [8.0] mL/kg/min , P = .027). Peak running velocity was higher in the GXT than in the 1-km test (15.7 [2.7] vs 13.0 [2.8] km/h). Men had higher VO2max values and running velocities than women in both tests. However, men and women used approximately similar pacing strategies during the 1-km test. CONCLUSIONS: Higher VO2max values were observed in a 1-km self-paced test than in the GXT. This indicates that a 1-km running test performed on a nonmotorized treadmill could serve as a simple and sport-specific alternative for the assessment of VO2max.

The Effects of a Short Specific Versus a Long Traditional Warm-Up on Time-Trial Performance in Cross-Country Skiing Sprint.

PURPOSE: To compare the effects of a short specific and a long traditional warm-up on time-trial performance in cross-country skiing sprint using the skating style, as well as related differences in pacing strategy and physiological responses. METHODS: In total, 14 (8 men and 6 women) national-level Norwegian cross-country skiers (age 20.4 [3.1] y; VO2max 65.9 [5.7] mL/kg/min) performed 2 types of warm-up (short, 8 × 100 m with gradual increase from 60% to 95% of maximal speed with a 1-min rest between sprints, and long, ∼35 min at low intensity, including 5 min at moderate and 3 min at high intensity) in a randomized order with 1 hour and 40 minutes of rest between tests. Each warm-up was followed by a 1.3-km sprint time trial, with continuous measurements of speed and heart rate. RESULTS: No difference in total time for the time trial between the short and long warm-ups (199 [17] vs 200 [16] s; P = .952), or average speed and heart rate for the total course, or in the 6 terrain sections (all P < .41, η2 < .06) was found. There was an effect of order, with total time-trial time being shorter during test 2 than test 1 (197 [16] vs 202 [16] s; P = .004). No significant difference in blood lactate and rating of perceived exertion was found between the short versus long warm-ups or between test 1 and test 2 at any of the measurement points during the test day (P < .58, η2 > .01). CONCLUSIONS: This study indicates that a short specific warm-up could be as effective as a long traditional warm-up during a sprint time trial in cross-country skiing.