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This scientific short report investigated how successful male coaches perceive gender differences in training characteristics and coaching practice among medal-winning endurance athletes. Ten male Norwegian coaches with a track record of coaching both female and male endurance world-class athletes (total of 269 Olympic, World and European Championship medals) participated in semi-structured interviews. Inductive thematic analysis revealed that all coaches mainly adjusted their key training and coaching principles to the individual athlete, rather than gender. A coach-driven and athlete-centered individualization process was essential to create trust, mutual understanding, and optimal training content. Potential gender/sex differences were perceived in four main themes: sport-specific competition demands, physiological, psychological and interpersonal factors (e.g., gender of the coach). In this context, all coaches described how training and coaching of female athletes differs from that of men, thus considering male athletes as the reference group and male physiology and psychology as the norm. Furthermore, societal factors such as a male-dominant sports culture and underlying gender stereotypes were suggested as amplifiers of gender differences. Accordingly, our report highlights the need for female perspectives in elite sports and invites further in-depth investigations of the identified gender/sex differences within the respective disciplines of training science, physiology, psychology and sociology. Key Words: Coaching, Endurance Training, Gender Differences, Sex Difference, Training Science

John F Moxnes,1 Øyvind Sandbakk,2 Kjell Hausken31Department for Protection, Norwegian Defence Research Establishment, Kjeller, Norway; 2Center for Elite Sports Research, Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway; 3Faculty of Social Sciences, University of Stavanger, Stavanger, NorwayAbstract: The current study adapts the power balance model to simulate cross-country skiing on varying terrain. We assumed that the skier’s locomotive power at a self-chosen pace is a function of speed, which is impacted by friction, incline, air drag, and mass. An elite male skier’s position along the track during ski skating was simulated and compared with his experimental data. As input values in the model, air drag and friction were estimated from the literature based on the skier's mass, snow conditions, and speed. We regard the fit as good, since the difference in racing time between simulations and measurements was 2 seconds of the 815 seconds racing time, with acceptable fit both in uphill and downhill terrain. Using this model, we estimated the influence of changes in various factors such as air drag, friction, and body mass on performance. In conclusion, the power balance model with locomotive power as a function of speed was found to be a valid tool for analyzing performance in cross-country skiing.Keywords: air drag, efficiency, friction coefficient, speed, locomotive power

John F Moxnes,1 Øyvind Sandbakk,2 Kjell Hausken31Department for Protection, Norwegian Defence Research Establishment, Kjeller, Norway; 2Human Movement Science Program, Norwegian University of Science and Technology, Trondheim, Norway; 3Faculty of Social Sciences, University of Stavanger, Stavanger, NorwayAbstract: The current study simulated cross-country skiing on varying terrain by using a power balance model. By applying the hypothetical inductive deductive method, we compared the simulated position along the track with actual skiing on snow, and calculated the theoretical effect of friction and air drag on skiing performance. As input values in the model, air drag and friction were estimated from the literature, whereas the model included relationships between heart rate, metabolic rate, and work rate based on the treadmill roller-ski testing of an elite cross-country skier. We verified this procedure by testing four models of metabolic rate against experimental data on the treadmill. The experimental data corresponded well with the simulations, with the best fit when work rate was increased on uphill and decreased on downhill terrain. The simulations predicted that skiing time increases by 3%–4% when either friction or air drag increases by 10%. In conclusion, the power balance model was found to be a useful tool for predicting how various factors influence racing performance in cross-country skiing.Keywords: skiing, power balance, metabolic rate, work rate, air drag, friction coefficient

In cross-country ski skating, both the G2 and G4 sub-techniques involve one pole push for every second ski push but are used at largely different speed-slope ranges. The aim of this study was to compare temporal and kinematic patterns between G2 and G4 at both identical and different speed-slope conditions. A mixed model was used to analyse spatio-temporal parameters, while a combination of dynamic time warping and statistical parametric mapping was used to compare time traces. Main spatio-temporal parameters, such as cycle time, ski contact time and swing time, differed between G2 and G4 (all p < 0.01). Moreover, two forward and more pronounced acceleration phases of the centre of mass (CoM) were visible in G4 while only one acceleration phase was present in G2. The more continuous propulsion in G2 allows for maintaining a more constant speed at steep slopes and low speeds where this sub-technique is preferred. In contrast, the achievement of high speeds while skiing on flatter terrain seem to require more dynamic motion with shorter, more explosive propulsion periods allowed for in G4. In conclusion, G2 and G4 are two unique movements as characterised by fundamentally different CoM motion and should be denoted as two different sub-techniques. [ABSTRACT FROM AUTHOR]

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Abstract The interaction of acute exercise and the central nervous system evokes increasing interest in interdisciplinary research fields of neuroscience. Novel approaches allow to monitor large-scale brain networks from mobile electroencephalography (EEG) applying graph theory, but it is yet uncertain whether brain graphs extracted after exercise are reliable. We therefore aimed to investigate brain graph reliability extracted from resting state EEG data before and after submaximal exercise twice within one week in male participants. To obtain graph measures, we extracted global small-world-index (SWI), clustering coefficient (CC) and characteristic path length (PL) based on weighted phase leg index (wPLI) and spectral coherence (Coh) calculation. For reliability analysis, Intraclass-Correlation-Coefficient (ICC) and Coefficient of Variation (CoV) were computed for graph measures before (REST) and after POST) exercise. Overall results revealed poor to excellent measures at PRE and good to excellent ICCs at POST in the theta, alpha-1 and alpha-2, beta-1 and beta-2 frequency band. Based on bootstrap-analysis, a positive effect of exercise on reliability of wPLI based measures was observed, while exercise induced a negative effect on reliability of Coh-based graph measures. Findings indicate that brain graphs are a reliable tool to analyze brain networks in exercise contexts, which might be related to the neuroregulating effect of exercise inducing functional connections within the connectome. Relative and absolute reliability demonstrated good to excellent reliability after exercise. Chosen graph measures may not only allow analysis of acute, but also longitudinal studies in exercise-scientific contexts.

The purpose of this study was to compare the effect of two different methods of organizing endurance training in elite cross-country skiers approaching the competition period. During the 5-week intervention period, one group performed block periodization ( BP; n = 10) with 5 and 3 high-intensity sessions ( HIT) during the first and third training week. One HIT was performed during the remaining weeks in BP, while the group performing traditional training organization ( TRAD, n = 9) performed two weekly HIT except during the third week where they performed three HIT. HIT were interspersed with low-intensity training ( LIT) and both groups performed similar total amount of both HIT and LIT during the intervention. BP achieved a larger relative increase in peak power output and power output at a blood lactate concentration of 4 mmol/L than TRAD (4 ± 4 vs −3 ± 6% and 11 ± 10 vs 2 ± 4%, respectively, both P < 0.01). BP also increased maximal oxygen uptake by 2 ± 2% ( P < 0.05), while no changes occurred in TRAD. The effect sizes of the relative improvement in these measurements revealed moderate effects of BP vs TRAD training. The present study suggests that block periodization of endurance training have superior effects on several endurance and performance indices compared with traditional organization. [ABSTRACT FROM AUTHOR]

Three dominant techniques are used for downhill turning in cross-country skiing. In this study, kinematic, kinetic, and temporal characteristics of these techniques are described and related to skier strength and power. Twelve elite female cross-country skiers performed six consecutive turns of standardized geometry while being monitored by a Global Navigation Satellite System. Overall time was used as an indicator of performance. Skiing and turning parameters were determined from skier trajectories; the proportional use of each technique was determined from video analysis. Leg strength and power were determined by isometric squats and countermovement jumps on a force plate. Snow plowing, parallel skidding, and step turning were utilized for all turns. Faster skiers employed less snow plowing and more step turning, more rapid deceleration and earlier initiation of step turning at higher speed ( r = 0.80-0.93; all P < 0.01). Better performance was significantly correlated to higher mean speed and shorter trajectory ( r = 0.99/0.65; both P < 0.05) and to countermovement jump characteristics of peak force, time to peak force, and rate of force development ( r = −0.71/0.78/−0.83; all P < 0.05). In conclusion, faster skiers used step turning to a greater extent and exhibited higher maximal leg power, which enabled them to combine high speeds with shorter trajectories during turns. [ABSTRACT FROM AUTHOR]

This investigation was designed to analyse the kinematics and kinetics of cross-country skiing at different velocities with the herringbone technique on a steep incline. Eleven elite male cross-country skiers performed this technique at maximal, high, and moderate velocities on a snow-covered 15° incline. They positioned their skis laterally (25 to 30°) with a slight inside tilt and planted their poles laterally (8 to 12°) with most leg thrust force exerted on the inside forefoot. Although 77% of the total propulsive force was generated by the legs, the ratio between propulsive and total force was approximately fourfold higher for the poles. The cycle rate increased with velocity (1.20 to 1.60 Hz), whereas the cycle length increased from moderate up to high velocity, but then remained the same at maximal velocity (2.0 to 2.3 m). In conclusion, with the herringbone technique, the skis were angled laterally without gliding, with the forces distributed mainly on the inside forefoot to enable grip for propulsion. The skiers utilized high cycle rates with major propulsion by the legs, highlighting the importance of high peak and rapid generation of leg forces. [ABSTRACT FROM AUTHOR]

Greater gender differences have been found in exercise modes where the upper body is involved. Therefore, the present study investigated the influence of poling on gender differences in endurance performance by elite cross-country skiers. Initially, the performance of eight male and eight female sprint skiers was compared during four different types of exercise involving different degrees of poling: double poling ( DP), G3 skating, and diagonal stride ( DIA) techniques during treadmill roller skiing, and treadmill running ( RUN). Thereafter, DP was examined for physiological and kinematic parameters. The relative gender differences associated with the DP, G3, DIA and RUN performances were approximately 20%, 17%, 14%, and 12%, respectively. Thus, the type of exercise exerted an overall effect on the relative gender differences ( P < 0.05). In connection with DP, the men achieved 63%, 16%, and 8% higher VO2peak than the women in absolute terms and with normalization for total and fat-free body mass (all P < 0.05). The DP VO2peak in percentage of VO2max in RUN was higher in men ( P < 0.05). The gender difference in DP peak cycle length was 23% ( P < 0.05). In conclusion, the present investigation demonstrates that the gender difference in performance by elite sprint skiers is enhanced when the contribution from poling increases. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to examine the effect of frequency on efficiency and performance during G3 roller ski skating. Eight well-trained male cross-country skiers performed three submaximal 5-min speeds (10, 13, and 16 km/h) and a time-to-exhaustion ( TTE) performance (at 20 km/h) using the G3 skating technique using freely chosen, high, and low frequency at all four speeds. All tests were done using roller skis on a large treadmill at 5% incline. Gross efficiency ( GE) was calculated as power divided by metabolic rate. Power was calculated as the sum of power against frictional forces and power against gravity. Metabolic rate was calculated from oxygen consumption and blood lactate concentration. Freely chosen frequency increased from 60 to 70 strokes/min as speed increased from 10 to 20 km/h. GE increased with power. At high power (20 km/h performance test), both efficiency and performance were significantly reduced by high frequency. In regard to choice of frequency during G3 roller ski skating, cross-country skiers seems to be self-optimized both in relation to energy saving (efficiency) and performance ( TTE). [ABSTRACT FROM AUTHOR]

This study looks at how emotions were associated with ski jumping competitions in world cup for four athletes representing the Norwegian national team in Nordic combined. The athletes documented their emotional experiences during competition rounds (trial-, and competition rounds) and non-competitive episodes (the period just after the competition round). The results in this study show that there is no clear relationship between emotions and performance between- and within the different episodes among the athletes. However, both hedonic emotions and eudaimonic emotions were experienced at high levels across all the measured episodes. Eudaimonic emotions were significantly higher during competing episodes (trial- and competition round) compared with non-competing episodes. Anger and sadness were higher after both trial jumps and competing jumps, whereas the opposite pattern was found for fear: more fear was experienced during jumps than after jumps. The results are discussed in regard of applied implications and possible future research. [ABSTRACT FROM AUTHOR]

This article looks at how emotions are associated with performance during cross-country skiing competitions among 10 senior Norwegian national level athletes. The results in this study show that there is a relatively similar emotional distribution pattern found among the athletes who are most satisfied with their performance compared to the less satisfied ones. However, the intensity in their emotions is different. The most satisfied athletes have higher intensity in their eudaimonic and hedonic emotions, while the negative emotions "sad" and "scared" are higher among the less satisfied athletes. The emotion "angry" is not significantly different between the two groups of athletes, and significantly higher in intensity compared to "sad" and "scared". The emotions in this study explain 53 % of the variance in subjective performance. The results are discussed in regard of applied implications and possible future research. [ABSTRACT FROM AUTHOR]

This article looks at how psychological variables such as passion, perceived performance, affect, worries and working alliance are associated with athlete burnout and illness and injuries among junior athletes in sport. A sample of 356 junior elite athletes from different sports such as cross country skiing, biathlon, Nordic combined, shooting, ice-hockey, ice-skating, ski jumping, alpine skiing, cycling, track and field, football, orienteering, handball, football and volleyball participated in the investigation. Our results show that harmonic passion, perceived performance, positive and negative affect, worry and working alliance are uniquely associated with athlete burnout, whereas sex, perceived performance and working alliance uniquely are associated with illness and injuries. The results are discussed in regard of applied implications and possible future research. [ABSTRACT FROM AUTHOR]

Background: Our scientific understanding of the mechanistic and practical connections between training session prescriptions, their execution by athletes, and adaptations over time in elite endurance sports remains limited. These connections are fundamental to the art and science of coaching., Objective: By using successful Norwegian endurance coaches as key informants, the aim of this study is to describe and compare best practice session models across different exercise intensities in Olympic endurance sports., Methods: Data collection was based on a four-step pragmatic qualitative study design, involving questionnaires, training logs from successful athletes, and in-depth and semi-structured interviews, followed by negotiation among researchers and coaches to assure our interpretations. Twelve successful and experienced male Norwegian coaches from biathlon, cross-country skiing, long-distance running, road cycling, rowing, speed skating, swimming, and triathlon were chosen as key informants. They had been responsible for the training of world-class endurance athletes who altogether have won > 370 medals in international championships., Results: The duration of low-intensity training (LIT) sessions ranges from 30 min to 7 h across sports, mainly due to modality-specific constraints and load tolerance considerations. Cross-training accounts for a considerable part of LIT sessions in several sports. Moderate (MIT)- and high-intensity training (HIT) sessions are mainly conducted as intervals in specific modalities, but competitions also account for a large proportion of annual HIT in most sports. Interval sessions are characterized by a high accumulated volume, a progressive increase in intensity throughout the session, and a controlled, rather than exhaustive, execution approach. A clear trend towards shorter intervals and lower work: rest ratio with increasing intensity was observed. Overall, the analyzed sports implement considerably more MIT than HIT sessions across the annual cycle., Conclusions: This study provides novel insights on quantitative and qualitative aspects of training session models across intensities employed by successful athletes in Olympic endurance sports. The interval training sessions revealed in this study are generally more voluminous, more controlled, and less exhaustive than most previous recommendations outlined in research literature., Competing Interests: Declarations Funding Open access funding provided by Kristiania University College. Competing Interests The authors declare that they have no conflicts of interest relevant to the content of this article. Availability of Data and Materials All data and materials support the published claims and comply with field standards. To protect the anonymity of the key informants, as well as their athletes, the transcribed interviews cannot be made publicly available. Ethics Approval The study followed the institutional requirements and was pre-approved by the Norwegian Centre for Research Data (reference #605672). Consent to Participate Prior to the study, the coaches provided a written informed consent to participate. Consent for Publication All respondents approved the submitted version of the manuscript for publication. Code Availability Not applicable. Author Contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Espen Tønnessen and Øyvind Sandbakk. The first draft of the manuscript was written by Thomas Haugen and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. As the authors of this study, we assert that our background provides a high level of expertise and experience in both scientific research and coaching practice arenas, enhancing the qualitative interpretation of these data. Our experience spans over 30 years, during which we have closely collaborated with world-class endurance coaches and athletes, both within the Norwegian Olympic Federation (Olympiatoppen) and various national sports federations. This hands-on involvement includes conducting training analyses alongside coaches, actively participating in training camps, and closely observing the day-to-day practices of top athletes. Additionally, many of us were involved in the development of Olympiatoppen's training diary, intensity scale, and test protocols – all crucial tools in athlete performance tracking. Moreover, we have published more than 150 articles in the field of endurance sports, demonstrating our in-depth understanding of the subject. We contend that this experience uniquely qualifies us to collect and interpret the data presented here., (© 2024. The Author(s).)

Research on world-class athletes in endurance events, such as cycling Grand Tours, has reported extreme levels of total energy expenditure. However, it has been argued that over extended periods, such as months, sustained energy expenditure is capped at approximately 2.5 times the basal metabolic rate. Triathlon is particularly notable for its high energetic demands due to its multimodal nature, requiring athletes to maintain high training volumes. In this case study, we analyzed the total energy expenditure of world-class triathlete Kristian Blummenfelt using doubly labelled water over two specific periods, along with three years of training data. Total energy expenditure ranged from 7,019-8,506 kcal/day. Reported energy intake ranged from 4,899 to 6,360 kcal/day. The annual training volumes for the years 2020-2022 were 1,480, 1,350 and 1,308 hours, respectively, following a pyramidal intensity distribution. Approximately 53% of the entire three-year period matched with the doubly labeled water measurement periods in terms of training volume, indicating that the recorded total energy expenditure is representative of the majority of the observed data. Hence, the greater part of the three-year period likely exceeds the proposed metabolic ceiling for sustained total energy expenditure. This not only questions the validity of the current metabolic limits but also suggests a new perspective on what is physiologically achievable in world-class athletes.

Purpose: To investigate the influence of menstrual-cycle (MC) phase on objective sleep and perceived recovery following high- (HIT) and low-intensity training (LIT) in endurance-trained women., Methods: Fifteen naturally menstruating, endurance-trained women completed standardized HIT and LIT sessions during the early follicular phase (EFP), ovulatory phase (OP), and midluteal phase (MLP) of 2 MCs. Overnight sleep was monitored using a Somnofy sleep monitor after each training session, and perceived recovery was assessed after 24 hours using self-report scales. MC phases were determined using the 3-step method, and noneumenorrheic MCs were retrospectively excluded from analysis., Results: MC phase had a main effect on wake after sleep onset (P ≤ .001), with higher values in MLP (33 [22] min) than EFP (22 [19] min, P = .043) and OP (14 [9] min, P = .001), sleep efficiency (P = .033), with lower values in MLP (87% [6%]) than OP (90% [8%], P = .047), and light sleep (P = .023) with higher values in MLP (59% [6%]) than EFP (54% [7%], P = .037). Session type had a main effect on perceived recovery (P < .018) and perceived muscle soreness (P = .007), indicating lower perceived recovery and higher perceived muscle soreness following HIT compared to LIT (P < .001, P = .018, respectively). No interactions were found between MC phase and session type for any of the measured variables., Conclusions: Objective sleep quality, but not perceived recovery, was influenced by MC phase, as indicated by small impairments to multiple indices of objective sleep during MLP. There were no interactions between MC phase and session type, indicating that the effect of MC on sleep and recovery is consistent regardless of session type.

Background: Perceived stress from schoolwork and perceived teacher care are shown to influence adolescents' life satisfaction. However, there is a need to further explore how levels of perceived school stress affect life satisfaction of Norwegian adolescents across gender and school levels using nationwide data, and whether this association is moderated by perceived teacher care. Hence, this paper sought to: (1) describe perceived school stress, perceived teacher care and satisfaction with life in Norwegian adolescents stratified by gender and school level, (2) examine the association between perceived school stress and satisfaction with life by testing perceived teacher care as a possible moderator and (3) explore the association between perceived teacher care and adolescents' satisfaction with life., Methods: We utilized cross-sectional data from the Norwegian Ungdata Survey from 2021, encompassing adolescents from lower and upper secondary school. Two-thirds of all Norwegian adolescents participated in the Ungdata Survey from 2021. All data is anonymous. The study variables are presented according to lower and upper secondary school as well as gender. Linear regressions were conducted and adjusted for socioeconomic status (SES) by using SPSS., Results: In total, 139,841 adolescents were included. Girls exhibited higher perceived school stress, lower perceived teacher care, and lower life satisfaction than boys in both lower and secondary school (all p < 0.01). Strong inverse associations on satisfaction with life were found in both genders in lower and upper secondary school among those who reported very frequent perceived school stress, with perceived teacher care moderating the relationship (B= -0.67; 95% CI [-0.70 to -0.65], P < 0.01]). Moreover, robust associations were unveiled between high and low levels of perceived teacher care and life satisfaction across gender and school level., Conclusions: Higher perceived school stress was strongly inversely associated with life satisfaction in Norwegian adolescents, in both girls and boys, and in both lower and secondary school. Teacher care was identified as a moderator and seems to play a crucial part in the everyday life of Norwegian adolescents. These implications extend to teacher education, practice, and policy, which should be aware of the pivotal role of perceived teacher care on Norwegian school-based adolescents' life satisfaction., (© 2024. The Author(s).)

Purpose: To investigate the effect of exercise intensity on standing shooting performance and related technical variables in elite biathletes performing roller skiing and live shooting outdoors., Methods: Nineteen male biathletes performed two 5-shot series in the following order of exercise intensity: rest, low (%heart rate max 73 ± 4; blood lactate 1.5 ± 0.3 mmol·L-1), moderate (84 ± 3; 2.4 ± 0.6), 'race-pace' (90 ± 2; 4.5 ± 0.8), and 'final-lap' (i.e., near-maximal effort: 93 ± 3; 8.7 ± 1.4). Except for rest, each shooting series was preceded by 1 km roller ski skating on a competition track. Rifle movements and triggering were determined from marker-based motion capture and accelerometer data. The primary variables were shooting outcome (hit/miss) and distance from center (dC), determined from an electronic target, and barrel velocity. Mediation analyses for shooting outcome and dC were conducted with barrel velocity (mean over last 0.25 s before triggering) as mediator and intensity as predictor., Results: Exercise intensity increased the likelihood of miss at 'race' (odds ratio (OR) 2.2, 95% CI 1.0-4.7) and 'final-lap' (OR 2.8, 95% CI 1.4-5.8) intensities compared to rest, with no meaningful differences between rest, low, and moderate intensities. Further, intensity affected dC (~32 ± 15 mm at rest, low, and moderate, 36 ± 20 mm at 'race', and 40 ± 23 mm at 'final-lap'; p < 0.001). Barrel velocity was a partial mediator of both shooting outcome and dC, explaining some, but not all, of the effect of intensity., Conclusions: Exercise intensity seems to have a clear negative effect on standing shooting performance in biathlon, which is partially explained by an increase in barrel velocity. Deteriorating effects were mainly seen at the two highest (race-like) intensities. Accordingly, for specificity reasons, more shooting practice should perhaps be performed at higher, competition-like exercise intensities than what is currently the norm., Competing Interests: Conflict of Interest and Funding Source: No conflicts of interest were declared for any of the authors. No funding was received for this research., (Copyright © 2024 by the American College of Sports Medicine.)

In recent years, many countries have significantly increased military spending, mainly due to geopolitical instability in several regions and the potential risk of armed conflicts spreading worldwide. In this context, understanding the nutritional needs of soldiers in different climates (warm, cold and high altitude) is important and directly impacts the performance and health of soldiers, especially in extreme environments. The amount of liquids, calories, and macro- and micronutrients contained in military rations must be determined considering the type of exercise, duration and environment. Military rations, in addition to being nutritionally adequate, must be practical, sustainable and easy to consume at any temperature and situation. Given these considerations, this study aimed to review scientific knowledge regarding the convenience, sensory attributes and nutritional components of military rations. Furthermore, this review studied the factors influencing soldiers' appetite, gut microbiota and nutritional needs during training or combat in extreme environments (warm, cold and high altitude). This exploration further advances our understanding of contemporary nutritional strategies for military personnel, contributing to future research and highlighting areas that must be developed.

Background and Purpose: Cross-country skiing, biathlon, and Nordic combined are Winter Olympics sports that involve cross-country skiing in undulating terrain, characterized by various subtechniques and repeated intensity fluctuations. The stochastic interval profile of these sports necessitates the continuous regulation of work and energy expenditure throughout training sessions and competitions, a concept known as pacing. With the advent of technological advancements that allow for the measurement of these features during training and competitions, scientific studies have broadened our understanding of the associated racing and pacing demands. We provide the current scientific overview of pacing demands in competitive cross-country skiing, biathlon, and Nordic combined and propose guidelines for how performance can be enhanced by adjusting pacing behavior., Conclusions and Practical Applications: The study of pacing in skiing has evolved from basic lap-to-lap, or segment, analyses to detailed insights into micropacing strategies. This includes analysis of speed, internal and external power, subtechnique distribution, and associated temporal patterns, combined with subjective ratings of effort. While several objective tools such as heart rate, blood lactate concentration, and speed measurements are widely used in practice, current understanding suggests that these measures should supplement, rather than replace, the use of perceived effort (eg, rating of perceived exertion) to regulate intensity during training and competition in undulating terrain. Therefore, the ability to self-regulate effort appears to be an important performance characteristic and should be developed in adolescents and systematically used to optimize and evaluate the training process and race performance throughout athletes' careers.

Purpose: This study aimed to investigate the effect of the MC and endogenous sex hormone concentrations on performance-determining variables in three distinct MC phases in endurance-trained females., Methods: Twenty-one eumenorrheic trained/highly trained endurance athletes completed a standardized test battery during the early follicular phase (EFP), ovulatory phase (OP), and midluteal phase (MLP) for either one ( n = 7) or two test cycles ( n = 14). MC phases were determined using calendar-based counting, urinary ovulation testing, and verified with serum hormone analysis. MCs were retrospectively classified as eumenorrheic or disturbed. Disturbed MCs were excluded from analysis. The test battery consisted of 4-6 × 5-min submaximal stages with stepwise speed increases, a 30-s all-out double-poling ski ergometer test, and a maximal incremental treadmill running test., Results: At a group level, there was no effect of MC phase or the serum concentrations of estrogen and progesterone on peak oxygen uptake (V̇O 2peak ), oxygen uptake at 4 mmol·L -1 blood lactate concentration, time to exhaustion, running economy, or mean 30-s power output (MPO 30s ). Serum testosterone concentration was positively associated with MPO 30s ( P = 0.016). Changes in V̇O 2peak from EFP to MLP were inconsistent between individuals and across cycles., Conclusions: None of the measured performance-determining variables were influenced by MC phase or serum estrogen or progesterone concentrations. Although some individual patterns could be observed, there was no indication that any single MC phase is consistently associated with improved or impaired V̇O 2peak on a group level., (Copyright © 2024 by the American College of Sports Medicine.)

Purpose: To investigate the training and development process of a multiple-Grand-Slam finalist., Methods: A mixed-methods case-study design was used to capture the quantitative and qualitative aspects related to the training and successful development process. We used a 3-step data-collection process and pragmatic analyses of (1) training history based on logs, plans, and questionnaires; (2) in-depth semistructured interviews with the player's head coach/father, physical coach, and team administrator/mother; and (3) systematic quality assurance through negotiation among researchers and all key informants, including the player., Results: The player's exceptional performance level was achieved by a progressive, nonlinear increase in annual training load during childhood and early youth, stabilizing at 800 sessions and 1250 to 1300 hours per year at the age of 19. The annual tennis-specific training plateaued at ∼750 hours from the age of 15, and 60 to 80 matches were played in most of the analyzed years. Point-play accounted for approximately 50% of the total amount of specific tennis training, clearly ahead of ground strokes (∼30%), serve/return (∼15%), and smash/volley (∼5%). Physical-conditioning hours increased 5-fold from 12 to 19 years, before stabilizing at ∼500 hours at senior age. Key success factors included the athlete's multidimensional sports talent, discipline, and inner drive; a highly dedicated father and tennis-enthusiastic family; and strong support from a complementary and interdisciplinary performance team., Conclusion: This study provides novel information regarding the training and development process for a world-leading tennis player, providing a point of departure for the development of future talents.

Purpose: To compare designs of training sessions applied by world-class cross-country skiers during their most successful junior and senior season., Methods: Retrospective analysis of self-reported training characteristics (ie, training form, intensity, and exercise mode) among 8 male and 7 female world-class cross-country skiers was conducted., Results: Total number of sessions (441 [71] vs 519 [34], P < .001, large effect) and mean duration (1.5 [0.1] h vs 1.7 [0.1] h, P < .001, moderate effect) increased from junior to senior age. More double-session days were performed at senior age (124 [50] vs 197 [29] d, P < .001, large). The number (310 [64] vs 393 [64], P < .001, large effect) and duration (1.3 [0.1] h vs 1.5 [0.1] h, P < .001, moderate effect) of low-intensity training sessions increased from junior to senior age. Regarding intensive training, most emphasis was put on high-intensity training sessions lasting 20 to 39 minutes with <5-minute intervals at junior age, while 40 to 59 minutes of moderate-intensity training with 5- to 9-minute intervals was predominant at senior age. More MIXED (combined moderate- and high-intensity) sessions (9 [7] vs 14 [7], P = .023, moderate effect) and longer races (0.5 [0.1] h vs 0.6 [0.1] h, P = 0.29, moderate effect) compensated for fewer high-intensity training sessions at senior age (36 [17] vs 25 [10], P = .027, moderate effect). Duration of strength-training sessions increased significantly (0.6 [0.1] vs 0.8 [0.2] h, P = 0.30, moderate effect), while other training forms remained unchanged., Conclusions: World-class cross-country skiers increased their training volume from junior to senior age primarily by more and longer low-intensity training sessions and more often training twice per day. Concurrently, the most frequent intensive sessions were modified from high- to moderate-intensity training, lasted longer, and contained longer intervals.

Background: A robust association between physical activity (PA) and satisfaction with life (SWL) has been established, wherein self-efficacy has been identified as a mediator across different populations. However, there is a need to further examine the relationship between PA and SWL and whether self-efficacy act a as mediator within different levels of PA among Norwegian adolescents. Thus, the objective of this study was to explore the relationship between levels of PA and SWL by testing for self-efficacy as a possible mediator., Methods: Cross-sectional data from the 2022 Norwegian Ungdata Survey was utilized. Data included demographics and various health data that was collected anonymously. The electronic survey took place in classrooms and was administered by the respective teacher. Permission to access and use data was approved by the Norwegian Agency for Shared Services in Education and Research (SIKT). Statistical analyses were conducted using the PROCESS macro by Andrew Hayes for SPSS software., Results: Descriptive findings revealed that girls reported lower self-efficacy than boys (14.2 vs. 15.5, with a maximum of 20) and lower SWL (6.8 vs. 7.6, with a maximum of 10). About one out of five girls and one out of seven boys reported no days of weekly PA, whereas 4% of girls and 9.5% of boys adhered to the PA-recommendation of 60-min of daily exercise. Associations between PA levels and SWL was mediated by self-efficacy (all p  < 0.05), with the highest indirect effect (56.3%) revealed in the association between those adhering to the PA-recommendations and SWL., Conclusions: Norwegian girls reported more sedentary behavior, less PA, lower self-efficacy, and lower SWL than boys across all grade levels. Mediation analysis revealed that up to 56.3% of the enhancement in SWL among those adhering to 60-min of PA recommendations was explained by increased self-efficacy. Norwegian government and policymakers should promote initiatives and regulations focusing on higher levels of PA to foster a resilient adolescent population with higher individual beliefs and higher subjective wellbeing., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Grasaas, Ostojic and Sandbakk.)

Purpose: To compare acute physiological responses and perceived training stress between one long and two short time- and intensity-matched sessions of moderate-intensity training in endurance athletes., Methods: Fourteen male endurance athletes (VO 2max : 69.2 ± 4.2 mL·min -1 ·kg -1 ) performed one 6 × 10-min interval session (SINGLE) and two 3 × 10-min interval sessions interspersed with 6.5 h recovery (DOUBLE) of moderate-intensity training on two separate days, while running in the laboratory, using a counterbalanced cross-over trial. The two training days were separated into a first part/session (interval stage 1-3) and second part/session (interval stage 4-6). Respiratory variables, heart rate (HR), blood lactate concentrations (BLa), and rating of perceived exertion (RPE) were collected during sessions, whereas supine heart rate (HR) was assessed in a 60-min recovery period following sessions. Measures of perceived training stress (1-10) were assessed in the morning of the subsequent day., Results: HR, Bla, and RPE increased in the second compared to first part of SINGLE (168 ± 7 vs. 173 ± 7 bpm, 2.60 ± 0.75 vs. 3.01 ± 0.81 mmol·L -1 , and 13.4 ± 1.0 vs. 14.8 ± 1.1-point, respectively, all p < 0.05). HR and Bla decreased in the second compared to first session of DOUBLE (171 ± 9 vs. 166 ± 9 bpm and 2.72 ± 0.96 vs. 2.14 ± 0.65 mmol·L -1 , respectively, both p < 0.05). SINGLE revealed higher supine HR in the recovery period following sessions (65.4 ± 2.5 vs. 60.7 ± 2.5 bpm p < 0.05), session RPE (sRPE, 7.0 ± 1.0 vs. 6.0 ± 1.3-point, p = .001) and sRPE training load (929 ± 112 vs. 743 ± 98, p < 0.001) compared to DOUBLE. In the subsequent morning, increased levels of perceived fatigue and muscle soreness were observed following SINGLE compared to DOUBLE (7.0 ± 2.5 vs. 8.0 ± 1.0-point, p = .049 and 6.0 ± 2.5 vs. 7.0 ± 2.5-point, p = .002, respectively)., Conclusion: One long moderate-intensity training session was associated with a duration-dependent "drift" in physiological responses compared to two short time- and intensity-matched sessions, thereby suggesting a higher overall training stimulus. Simultaneously, the lower cost of the two shorter sessions indicates that such organization could allow more accumulated time at this intensity. Overall, these findings serve as a starting point to better understand the pros and cons of organizing moderate-intensity training as one long versus shorter sessions performed more frequently (e.g., as "double threshold training") in endurance athletes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Kjøsen Talsnes, Torvik, Skovereng and Sandbakk.)

Purpose: To describe how high-level European sprint coaches (from 100 to 400 m) work to improve important factors associated with the quality of the holistic training process and the quality of the specific training session., Methods: A descriptive analysis was conducted using questionnaires from 31 European elite sprint coaches (ie, training athletes defined as tiers 3, 4, and 5) who participated voluntarily., Results: The coaches used traditional periodization (45%) with a 10- to 15-day tapering phase (48%) that includes a reduction in volume, maintenance of intensity, and focus on correct technical execution. In the 3 mesophases, coaches prioritized the basic development of strength and sprint work in the first phases of the season and emphasized more sprint-specific work in the competitive phase. Before sessions, adjustments were made based on factors such as psychological (77%), technical (48%), and physical (39%) parameters. In-session load management relies on a combination of objective and subjective measures (55%), in which the dialogue with athletes (65%) was regarded as the main resource. Feedback during and after sessions covers technical (54%), psychological (48%), and physical (35%) aspects. Recovery protocols after sessions mainly involve rest and professional guidance (42%). For performance assessment and testing, coaches utilize countermovement jump (52%), force-velocity profile (45%), and 30-m flying (61%) as main tools., Conclusions: European sprint coaches demonstrated a comprehensive approach to planning and management, shedding light on the multifaceted nature of their training methodologies and the diverse tools employed for athlete testing and monitoring.

Recent methodological recommendations suggest the use of the "3-step method," consisting of calendar-based counting, urinary ovulation testing, and serum blood sampling, for the identification of subtle menstrual disturbances (SMDs). However, the use of the 3-step method is not always feasible, so a less demanding combination of calendar-based counting and urinary ovulation testing, that is, the 2-step method, may be a viable alternative., Purpose: To investigate the agreement between the 2- and 3-step methods for the detection of SMDs., Methods: Menstrual cycles (MCs, 98) of 59 athletes were assessed using the 2- and 3-step methods. Regular-length MCs (ie, ≥21 and ≤35 d) were classified as either having no SMD (luteal phase length ≥10 d, midluteal progesterone concentration ≥16 nmol·L-1, and being ovulatory) or having an SMD (eg, short luteal phase [<10 d], inadequate luteal phase [midluteal progesterone concentration <16 nmol·L-1], or being anovulatory). Method agreement was assessed using the McNemar test and Cohen kappa (κ)., Results: Substantial agreement was observed between methods (κ = .72; 95% CI, .53-.91), but the 2-step method did not detect all MCs with an SMD, resulting in evidence of systematic bias (χ2 = 5.14; P = .023). The 2-step method detected 61.1% of MCs that had an SMD ([51.4, 70.8]), as verified using the 3-step method, and correctly identified 100% of MCs without an SMD., Conclusions: MCs classified as being disturbed using the 2-step method could be considered valid evidence of SMDs. However, MCs classified without SMDs do not definitively confirm their absence, due to the proven underdetection via the 2-step method.

Background: In the last decade, a growing body of research has focused on the many aspects and challenges of combining parenthood with elite sport. Although the number of father-athletes is significantly higher than the number of mother-athletes, few studies to date have focused on male athletes' experiences in a parenting context., Aim: The aims of the present study were to explore how father-athlete challenges manifest among elite Nordic skiers in Norway, and to better understand how male athletes balance their priorities as they initiate, maintain, and/or discontinue their athletic career as a father-athlete., Methods: Qualitative data were collected through semi-structured interviews with 10 world-class male Nordic skiers in Norway (3 athletes without a child, 4 current father-athletes and 3 former father-athletes) and the content was analyzed using thematic analysis., Results: Four main stages were identified in the father-athlete transition: (a) Expecting incompatibility (b) Taking the step, (c), The first blow, and (d) Finding the optimal balance. Through these stages the informants expected/had experienced challenges such as performance decline, disturbed sleeping patterns, fear of sickness and role conflicts. To manage these challenges, the father-athletes had developed various strategies to balance their dual roles (e.g., adapting training and competition seasons). Among the benefits, the father-athletes mentioned that they had become more structured, time efficient and ruthless with their priorities, enhanced motivation to train and a better work-life balance., Conclusion: This study offers valuable insights into father-athlete challenges that can be used to support career longevity and work-life balance among male athletes., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Bergström, Solli, Sandbakk, McGawley and Sæther.)

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.

Background: The crucial role of physical activity (PA) in promoting well-being and overall health of adolescents is widely acknowledged. Previous global studies have consistently revealed low adherence to PA recommendations among adolescents, emphasizing potential links between PA engagement and self-efficacy in school-based populations. However, there is a need for further exploration of this relationship, in particularly gender differences and taking into account the potential influences of the COVID-19 pandemic. The objective of this study is to provide a comprehensive description of adherence to PA recommendations and its associations with self-efficacy in Norwegian school-based adolescents over the period from 2017 to 2021., Methods: Cross-sectional data on physical activity (PA) levels and self-efficacy among 13-19-year-old Norwegian adolescents were collected from the Norwegian Ungdata Survey during the period 2017 to 2021. The survey, conducted in Norwegian lower- and upper-secondary schools, was administered electronically during school hours. All data collected is anonymous and has received approval from the Norwegian Agency for Shared Services in Education and Research (SIKT). Statistical analyses were performed using SPSS software., Results: Girls consistently exhibited lower adherence to PA recommendations (17.6-19.8%) compared to boys (27.7-31.1%) each year from 2017 to 2021 (all p  < 0.01). Similarly, girls reported lower self-efficacy (14.1 to 14.8 out of 20) than boys (15.5 to 15.9) during the same period (all p  < 0.01). Regression analyses highlighted robust positive associations between PA and self-efficacy in those adhering to PA recommendations (i.e., physically active at least 5 times a week) and strong inverse associations for those reporting inactivity (never active) in both girls and boys from 2017 to 2021., Conclusion: Adolescents in Norway report PA adherence ranging from 15 to 30%, with girls consistently exhibiting lower adherence to PA recommendations and reporting lower self-efficacy than boys. Notably, there are substantial associations between self-efficacy and both adherence to PA recommendations and inactivity over time. These findings underscore the significance of promoting adherence to PA recommendations during adolescence, especially among girls. Policymakers in Norway should focus on initiatives to increase PA levels among adolescents in both lower and upper secondary schools., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Grasaas and Sandbakk.)

In 2023, for the first time in history, the international ski and snowboard federation (FIS) arranged an official ski flying competition where the 15 highest ranked women were allowed to participate. This study investigated jump-to-jump performance development in female ski flying, with men's results used as reference data. Official FIS data from all six jumps of women were evaluated together with the eight jumps by men. Performance was evaluated by a score, where the distance points compensated by wind were divided by take-off speed, enabling performance to be evaluated across jumps and sexes. Women improved performance by 96% from the first to the sixth jump, with two major leaps; from the first to the second jump and from the first to the second day. In contrast, men mainly improved from training to competition. The best women had performance scores equivalent to the 10-20 best ranked men and the sex-difference between the top 3 athletes was 26.2%. This difference was thereafter compared to similar results in the normal and large hill World championship in Planica 2023, in which sex-differences between the top 3 were 8.6% and 14.6% in normal and large hill. This historical competition showed the importance of gaining practical experience with ski flying on performance, exemplified by the large improvement of female athletes. This, together with the enlarge sex-differences in large compared to normal hills, indicates that female ski jumpers have a particularly large improvement-potential in ski flying and must gain specific experience on this through traning and competitions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Elfmark, Sandbakk, Brevig and Ettema.)

Purpose: Advanced insight in energy requirements of Paralympic athletes is imperative for optimizing their nutritional counseling. Given the lack of accurate data on total daily energy expenditure (TDEE) of Paralympic athletes, this study aimed to assess energy expenditure and nutritional intake of a large cohort of Paralympic athletes, across different sports and disabilities., Methods: In this cross-sectional study, 48 Dutch and Norwegian Paralympic athletes (19 male/29 female) with various disabilities, competing in Para cycling, wheelchair tennis, wheelchair basketball, Para Nordic skiing, and alpine skiing participated. TDEE was assessed by the gold standard doubly labeled water method over a 14-d period, resting metabolic rate by ventilated hood indirect calorimetry, energy intake by three unannounced 24-h dietary recalls, body composition by dual-energy x-ray absorptiometry, and exercise training duration by a training log., Results: Mean TDEE was 2908 ± 797 kcal·d -1 , ranging from 2322 ± 340 kcal·d -1 for wheelchair basketball players to 3607 ± 1001 kcal·d -1 for Para cyclists. Regression analysis identified fat-free mass, exercise duration, and the presence of a spinal cord disorder as the primary predictors of TDEE, explaining up to 73% of the variance in TDEE. Athletes' energy intake (2363 ± 905 kcal·d -1 ) was below their TDEE, whereas their body mass remained constant, indicating underreporting. Carbohydrate intake (4.1 ± 1.9 g·kg -1 body mass) was low, even when considering underreporting, whereas protein intake (1.8 ± 0.6 g·kg -1 body mass) was relatively high., Conclusions: Paralympic athletes display moderate- to high-energy expenditure, varying across sports and individuals. Much of the variation in TDEE can be attributed to individual differences in fat-free mass and exercise duration. This study establishes the benchmarks for energy requirements of Paralympic athletes, serving as the foundation for future dietary guidelines within this population., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine.)

The aim of this study was to investigate relationships between changes in training practices and human development index (HDI) levels, and identify strategies employed by athletes who consistently maintained their training quantity during the first 100 days of the COVID-19 pandemic. A total of 10,074 athletes (5290 amateur and 4787 professional athletes from 121 countries) completed an online survey between 17 May to 5 July 2020. We explored their training practices, including specific questions on training frequency, duration and quantity before and during lockdown (March-June 2020), stratified according to the human development index (HDI): low-medium, high, or very high HDI. During the COVID-19 lockdown, athletes in low-medium HDI countries focused on innovative training. Nevertheless, women and amateur athletes experienced a substantial reduction in training activity. Performance-driven athletes and athletes from higher HDI indexed countries, were likely to have more opportunities to diversify training activities during lockdowns, facilitated by the flexibility to perform training away from home. Factors such as lockdown rules, socioeconomic environment, and training education limited training diversification and approaches, particularly in low-medium and high HDI countries. Athletes (amateurs and professionals) who maintained the quantity of training during lockdown appeared to prioritize basic cardiovascular and strength training, irrespective of HDI level. Modifying training and fitness programs may help mitigate the decrease in training activities during lockdowns. Customized training prescriptions based on gender, performance, and HDI level will assist individuals to effectively perform and maintain training activities during lockdowns, or other challenging (lockdown-like) situations., (© 2024. The Author(s).)

The International Olympic Committee (IOC) recently published a framework on fairness, inclusion, and nondiscrimination on the basis of gender identity and sex variations. Although we appreciate the IOC's recognition of the role of sports science and medicine in policy development, we disagree with the assertion that the IOC framework is consistent with existing scientific and medical evidence and question its recommendations for implementation. Testosterone exposure during male development results in physical differences between male and female bodies; this process underpins male athletic advantage in muscle mass, strength and power, and endurance and aerobic capacity. The IOC's "no presumption of advantage" principle disregards this reality. Studies show that transgender women (male-born individuals who identify as women) with suppressed testosterone retain muscle mass, strength, and other physical advantages compared to females; male performance advantage cannot be eliminated with testosterone suppression. The IOC's concept of "meaningful competition" is flawed because fairness of category does not hinge on closely matched performances. The female category ensures fair competition for female athletes by excluding male advantages. Case-by-case testing for transgender women may lead to stigmatization and cannot be robustly managed in practice. We argue that eligibility criteria for female competition must consider male development rather than relying on current testosterone levels. Female athletes should be recognized as the key stakeholders in the consultation and decision-making processes. We urge the IOC to reevaluate the recommendations of their Framework to include a comprehensive understanding of the biological advantages of male development to ensure fairness and safety in female sports., (© 2024 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd.)

The rise of artificial intelligence (AI) applications in healthcare provides new possibilities for personalized health management. AI-based fitness applications are becoming more common, facilitating the opportunity for individualised exercise prescription. However, the use of AI carries the risk of inadequate expert supervision, and the efficacy and validity of such applications have not been thoroughly investigated, particularly in the context of diverse health conditions. The aim of the study was to critically assess the efficacy of exercise prescriptions generated by OpenAI's Generative Pre-Trained Transformer 4 (GPT-4) model for five example patient profiles with diverse health conditions and fitness goals. Our focus was to assess the model's ability to generate exercise prescriptions based on a singular, initial interaction, akin to a typical user experience. The evaluation was conducted by leading experts in the field of exercise prescription. Five distinct scenarios were formulated, each representing a hypothetical individual with a specific health condition and fitness objective. Upon receiving details of each individual, the GPT-4 model was tasked with generating a 30-day exercise program. These AI-derived exercise programs were subsequently subjected to a thorough evaluation by experts in exercise prescription. The evaluation encompassed adherence to established principles of frequency, intensity, time, and exercise type; integration of perceived exertion levels; consideration for medication intake and the respective medical condition; and the extent of program individualization tailored to each hypothetical profile. The AI model could create general safety-conscious exercise programs for various scenarios. However, the AI-generated exercise prescriptions lacked precision in addressing individual health conditions and goals, often prioritizing excessive safety over the effectiveness of training. The AI-based approach aimed to ensure patient improvement through gradual increases in training load and intensity, but the model's potential to fine-tune its recommendations through ongoing interaction was not fully satisfying. AI technologies, in their current state, can serve as supplemental tools in exercise prescription, particularly in enhancing accessibility for individuals unable to access, often costly, professional advice. However, AI technologies are not yet recommended as a substitute for personalized, progressive, and health condition-specific prescriptions provided by healthcare and fitness professionals. Further research is needed to explore more interactive use of AI models and integration of real-time physiological feedback., Competing Interests: The authors declare no conflict of interest. The authors wish to affirm that this research was executed with complete academic integrity, free of any commercial or financial biases. Specifically, while we employed the paid version of ChatGPT 4.0 for its advanced capabilities in exercise prescription, this was not done with any intention to promote or encourage its use. Our choice of this platform was strictly to assess its potential in the realm of exercise prescription, without any sponsorship or incentives from the developers or associated entities of ChatGPT. No author has affiliations with OpenAI or any other commercial entities related to the content of the manuscript. Our sole commitment remains to transparent, unbiased evaluations that serve to advance the intersection of sports medicine and artificial intelligence., (Copyright © Biology of Sport 2024.)

Purpose: To investigate performance, physiological, and perceptual responses of an entire sprint cross-country skiing competition in the skating style., Methods: Eighteen national-level male junior skiers participated in a simulated competition comprising an individual time trial (TT), followed by three heats (quarterfinals [QF], semifinals [SF], and final [F]). Participants' heart rate (HR) was continuously monitored while perceived readiness (RED, 1-10), rating of perceived exertion (RPE, 6-20), and blood lactate [La-] were assessed at standardized time points., Results: The total duration and distance covered were 03:30 ± 00:06 h and 25.2 ± 2.9 km, respectively. The participants spent 02:19 ± 00:27 h > 60% of their maximal HR (HR max ) and 00:16 ± 00:04 h > 85% of HR max . Average HR decreased from TT to F (89.3 ± 2.0% vs. 86.9 ± 3.0% of HR max , P < 0.01). [La-] levels were highest before (4.6 ± 2.0 vs. 2.9 ± 1.2, 3.2 ± 2.0 and 2.5 ± 1.3 mmol·L -1 , all P < 0.01) and after (10.8 ± 1.4 vs. 9.8 ± 1.6, 9.1 ± 1.8 and 8.7 ± 1.7 mmol·L -1 , all P < 0.05) F compared to TT, QF, and SF, respectively. RED was lowest before F compared to TT, QF, and SF (6.6 ± 1.4 vs. 7.9 ± 1.1, 7.6 ± 1.1, and 7.4 ± 1.4, respectively, all P < 0.05) while RPE was highest after TT compared to QF, SF, and F (17.8 ± 0.9 vs. 15.1 ± 2.0, 16.5 ± 1.2 and 16.6 ± 1.8, respectively, all P < 0.01). The six best-performing skiers demonstrated higher RED before F (7.2 ± 0.9 vs. 5.3 ± 1.2, P < 0.05) and higher [La-] after F (11.2 ± 0.2 vs. 10.2 ± 0.3, mmol·L -1 , P < 0.05) than lower-performing competitors., Conclusion: This study provides novel insights into physiological demands of an entire sprint cross-country skiing competition, which involves repeated 3-min high-intensity efforts interspersed with > 2 h (25 km) of low- to moderate-intensity exercise., (© 2023. The Author(s).)