Reliable assessments of maximal and rapid muscle strength are essential for evaluating neuromuscular performance and adaptations. This study examined the effects of verbal instruction and trial selection criteria on performance outcomes and intersession test-retest reliability during maximal isometric knee extensor testing. Twenty-three physically active, healthy adults completed three separate test sessions, performing isometric knee extensor contractions under three standardized verbal instructions: Hard and Fast (HF; "as hard and fast as possible"), Fast Only (FO; "as fast as possible"), and Hard Only (HO; "Gradual increase in force"). Rate of torque development (RTD) and impulse were calculated using three selection criteria: the trial with the highest peak torque (Max_Peak_Torque), the trial with the highest 200-ms impulse (Max_Impulse200), and the highest value for each time interval (Max_Composite_Interval). Both FO and HF instructions demonstrated good-to-excellent reliability, reflected by intraclass correlation coefficients (ICC) and within-subject coefficients of variation (CVw-s) for RTD and impulse (ICC = 0.75-0.93, CVw-s = 8%-15%), with improved reproducibility between sessions 2-3. Selection criteria strongly influenced test-retest reliability, with Max_Impulse200 and Max_Composite_Interval yielding higher ICCs and lower CVw-s compared with Max_Peak_Torque. FO instruction consistently produced higher RTD and impulse values than HF (p ≤ 0.05). Peak torque increased across sessions, yet reliability remained excellent for both HF and HO (ICC > 0.90, CVw-s < 7%). These findings indicate Fast Only instruction and selection of the Max_Impulse200 selection criterion may enhance reproducibility and magnitude of rapid knee extensor force assessments, especially after familiarization.
Elite performance in Olympic winter sports depends on the interplay among the athlete, equipment, and the snow or ice. This naturally evolves with temperature, humidity, wind, preparation, and contact between the equipment and its surface. Together, these factors continuously rebalance the forces of gravity, aerodynamic drag, and friction, requiring athletes, coaches, and organizers to adapt technique, equipment, and surface management, e.g., snow grooming and salting, ice resurfacing or pebbling, and rink climate control. This narrative review (SANRA-guided) synthesizes the scientific literature across four domains: (i) the evolution of equipment and athlete-surface interaction; (ii) the physics of resistive forces and targeted countermeasures; (iii) sensing and monitoring with robust, field-validated technologies and analytics; and (iv) the digitalization of coaching, officiating, and broadcasting. We integrate design and validation with sport regulations and governance. This includes the ban on fluorinated waxes, geometry and mass limits, and principles for data stewardship, model transparency, and fairness. A central component of this review is the assessment of quality aspects of technologies, including the assessment of ecological validity under field-specific conditions before their use in high-stakes coaching, medical, or officiating decisions. We conclude with actionable recommendations for Milano-Cortina 2026: (i) align equipment and surface preparation with expected regimes of drag and friction; (ii) deploy sensors and analytics with demonstrated accuracy, precision, and reliability; (iii) quantify uncertainty in key performance indicators; and (iv) treat federation rules as a priori design constraints. This approach enables innovation to deliver faster, safer, and more equitable outcomes in winter sport at Milano-Cortina 2026 and beyond.
During gait, the temporal patterns of stride-to-stride fluctuations and muscle activation exhibit similar responses. This study examined if increasing task demands such as fatigued high intensity running affects this relationship. Eleven experienced runners completed two 400-m runs (R1, R2) with a 3-min break to induce fatigue. Stride Time Intervals (STI) were measured using inertial sensors (IMUs), while Inter-Muscle Peak Intervals (IMPI) were derived from the electromyographic (EMG) activity of the Vastus Lateralis and Gastrocnemius Medialis. We calculated the Hurst exponent and coefficient of variation (CV) for all time series. The association (matching) between STI and IMPI metrics was analyzed using Pearson's correlation. To assess fatigue status, we monitored muscle oxygen saturation (SmO2) and EMG frequency characteristics. Hurst exponent was estimated from the Hurst-Kolmogorov process which is proposed as suitable for short time series. Baseline SmO2 immediately prior to the second run was significantly lower for R2 (p < 0.001). This was supported by EMG fatigue signatures: median frequency decreased and root mean square increased in both muscles. Significantly higher Hurst values were observed for all time series, whereas CV increased significantly only for the STI and Vastus Lateralis IMPI in R2 (p < 0.05). The STI-IMPI correlations (for CV and Hurst) increased significantly in R2 for both VL and GM (r = 0.66 to 0.96). The changes in EMG characteristics indicate less flexible neuromuscular control and possibly provide a physiological explanation for the increased Hurst exponent (persistency). Fatigue strengthened the coupling between stride-to-stride fluctuations and muscle activation. This suggests high-intensity fatigue causes the locomotor system to reorganize into a more tightly coupled, less flexible state.
As the Milano Cortina 2026 Winter Olympic Games approach, a comprehensive understanding of performance determinants across Olympic snow sports is increasingly important to further evolve training and performance. However, the scientific literature remains unevenly distributed, with well-established knowledge in cross-country skiing, biathlon, and alpine skiing, and limited data in disciplines such as ski mountaineering, freestyle skiing, snowboarding, ski jumping, and Nordic combined. This narrative review synthesizes current evidence to (1) identify key performance-determining factors, (2) describe discipline-specific training characteristics, and (3) highlight critical knowledge gaps. Regarding performance determinants, Olympic snow sports can be broadly categorized into endurance-dominant disciplines (e.g., cross-country skiing, biathlon, ski mountaineering), which rely on high aerobic capacity and movement efficiency, and the gravity and technical disciplines (e.g., alpine skiing, freestyle skiing, snowboarding, ski jumping), which emphasize neuromuscular power and technical precision. Nordic combined represents a hybrid of these categories. In terms of training characteristics, elite athletes' training models reflect sport-specific demands through tailored combinations of endurance, strength-power, technical, tactical, and psychological preparation. Finally, regarding knowledge gaps, sex-specific analyses of physiological profiles, biomechanics, and training responses remain scarce, particularly in gravity and technical sports. Furthermore, standardized documentation of training structure, integration of on-snow monitoring technologies, and research on energy availability remain underdeveloped. Addressing these gaps through holistic, multidisciplinary research is essential to develop individualized, sex-informed, and evidence-based frameworks that support athlete development and performance optimization in the lead-up to Milano Cortina 2026 and future Olympic cycles.
Pacing is a critical determinant of performance in Olympic endurance winter sports such as cross-country skiing, biathlon, and speed skating. Although the physiological ("engine") and psychological ("operator") determinants of pacing have frequently been examined in isolation, growing evidence highlights the need for an integrated psychophysiological perspective. This structured narrative review first outlines the defining characteristics of Olympic winter sports and, within this context, synthesizes current knowledge on the psychophysiological mechanisms governing pacing to inform optimal preparation strategies. We describe how the physiological engine, encompassing energy systems, fatigue, and afferent feedback, and the psychological operator, involving self-regulation, expectations, and cognitive-affective processes, interact to shape pacing behavior. Moreover, the distinctive demands of winter endurance events necessitate consideration of environmental factors such as head-to-head racing formats, variable weather conditions, and undulating terrain. The affordance competition hypothesis is proposed as a unifying framework for understanding pacing as a continuous decision-making process driven by dynamic mind-muscle-environment interactions. Finally, practical recommendations for athletes and coaches preparing for the Milano-Cortina 2026 Winter Olympic Games are presented, advocating a phased training approach that integrates physiological and psychological development within ecologically valid environments. Future research should prioritize real-world competition settings, neurocognitive mechanisms, and underrepresented populations, including women and para-athletes. We conclude that Olympic success in modern endurance winter sports depends on mastering an integrated psychophysiological control system, where performance is determined by both physical capacity and its effective regulation under varying environmental conditions.
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