ECSS Paris 2023: CP-PN20
INTRODUCTION: Physiological and anthropometric adaptations to training have been well documented in elite senior cross-country skiers. In contrast, comparatively little is known about physiological profiles and seasonal adaptations in youth and junior skiers (XC), whose development is influenced by training exposure, biological maturation, and ongoing growth. Additionally, it remains unclear whether performance level influences adaptation during adolescence. Consequently, the aim of this study was to compare physiological and morphological profiles, as well as preparatory-period changes, between highly ranked junior and lower-ranked youth XC METHODS: Physiological and anthropometric profiles of 18 adolescent XC (14–18 years) were assessed at the beginning (May) and end (October) of the preparatory period following an extensive summer training program including roller skiing, running, bounding, strength training, and plyometrics. Group classification was based on results from the preceding winter season. Top performers (n = 7; 16.3 ± 1.1 years) placed within the top 5 at the Moscow Championships in the U16–U18 categories, whereas lower performers (n = 11; 14.3 ± 0.5 years) placed within the top 100 in the U14–U16 categories. Laboratory testing comprised three domains: (1) Structural – seven anthropometric parameters; (2) Neuromuscular power – eleven strength and power variables; and (3) Metabolic – eleven upper- and full-body endurance parameters and three cardiovascular variables. Both absolute and relative values were analyzed to account for differences in body size and biological maturation. Differences within each domain were evaluated using mixed factorial MANOVAs. RESULTS: A significant main effect of time was observed, with most parameters improving in both groups (p < .05–.001). No significant time × group interactions were detected in any category, indicating similar adaptation patterns between groups. Large effect sizes were observed for strength and power (Ŋp2 = .911), endurance (Ŋp2= .363-.392),. body composition (Ŋp2 = .421), and morphology (Ŋp2 = .293). Significant main effects of group were identified for upper- and full-body endurance parameters, indicating superior performance in top-ranked juniors. CONCLUSION: Top-performing junior and lower-performing youth XC differed in absolute physiological and morphological levels, but not in their adaptive trajectories during the preparatory period. These differences were attenuated when expressed relative to body mass or body surface area. The greatest between-group differences in relative parameters were observed for lower- and upper-body peak power, cardiac output index, VO₂max, and VO₂peak. Importantly, the absence of time × group interactions indicates similar short-term adaptations between groups at this developmental stage. Because top performers were, on average, approximately two years older, the observed differences likely reflect a combination of training history, biological maturation, and performance level.
Read CV Victor FeofilaktovECSS Paris 2023: CP-PN20
INTRODUCTION: Repeated sprint training in hypoxia (RSH) is used to enhance repeated-sprint ability, yet athletes may show heterogeneous adaptations. This study investigated (1) whether inter-individual variability exists in training effects of RSH intervention, and (2) which training parameters (SpO₂, training load, mechanical work) are associated with that variability. METHODS: Sixteen male highly-trained sprint runners completed a 2-week RSH intervention in normobaric hypoxia (FiO₂ = 0.15): 6 sessions (3/week), each comprising 2 sets of 5 × 10-s all-out cycling sprints (30-s recovery; 5-min between sets). Repeated sprint performance was assessed pre/post in normoxia (FiO₂ = 0.21) using 10 × 10-s all-out cycling sprints with 30-s recovery. Mean power output (MPO), sprint decrement score (Sdec), SpO₂, blood lactate concentration, TRIMP, and mechanical load was assessed. Inter-individual variability was estimated using test–retest data to account for random noise, and responder proportion was derived relative to the smallest worthwhile change. RESULTS: MPO increased by +3.8% after the intervention (P = 0.001), and Sdec improved (P = 0.047), while heart rate and blood lactate did not meaningfully change. Inter-individual variability existed with 81.3% classified as responders (~20% non-responders). Average SpO₂ during training correlated with relative total work (r = 0.435, P = 0.008), and relative total work strongly correlated with %MPO improvement (r = 0.833, P < 0.001). TRIMP showed no significant association with SpO₂, relative total work, or performance improvement. CONCLUSION: Despite a clear group-mean improvement following RSH intervention, inter-individual variability exists, with a notable proportion of non-responders (~20%). Variability in arterial oxygen desaturation (SpO₂) appears to influence the mechanical work achieved during hypoxic training, which in turn is strongly linked to performance gains. Monitoring SpO₂ together with mechanical output (work performed) may help individualize RSH prescription to maximize training benefits.
Read CV Naoya TakeiECSS Paris 2023: CP-PN20
INTRODUCTION: Marathon competitions are frequently held in hot environments (e.g., Summer Olympics, World Athletics Championships); consequently, performance is significantly impaired compared to that in thermoneutral environments. It has been suggested that higher environmental temperatures reduce oxygen saturation in the vastus lateralis [1]. The increase in respiratory workload associated with hyperventilation is thought to induce respiratory muscle fatigue, and respiratory muscle fatigue is one of the factors that limit oxygen delivery to locomotor muscles [2]. However, the effects of higher environmental temperature and humidity on the oxygenation of both “locomotor” and “respiratory” muscles during actual running remain unclear. The purpose of this study was to investigate the effects of different environmental temperatures and humidities on locomotor and respiratory muscle oxygenation during prolonged running. METHODS: Six male runners (age, 32.8 ± 3.6 years; height, 171.7 ± 1.9 cm; weight, 59.0 ± 1.2 kg) completed prolonged running (60 min of treadmill running at 75% of maximal oxygen uptake) under three environmental conditions that were close to actual races (Olympic Games, World Athletics Championships, World Marathon Majors): (1) 32℃ condition (70% relative humidity), (2) 20℃ condition (60%RH), and (3) 10°C condition (50%RH), in a single-blind, randomized crossover design. All trials were performed in a climate-controlled chamber. Muscle oxygenation changes in the vastus lateralis and intercostal muscle were evaluated using near-infrared spectroscopy. Respiratory gases, heart rate, cardiac output, and core temperature were measured continuously during running, and skin blood flow was evaluated before and after running. RESULTS: Muscle oxygen saturation in the intercostal muscle was significantly lower at 32℃ compared with both 20℃ and 10℃ (ΔStO2; 32℃: -24.8±4.3%, 20℃: -15.7±3.7%, 10℃: -12.8±3.3%, p < 0.05). In contrast, muscle oxygen saturation in the vastus lateralis did not differ significantly among all conditions (ΔStO2; 32℃: -13.5±1.1%, 20℃: -14.4±2.4%, 10℃: -10.2±1.7%, p > 0.05). Peak core temperature was significantly higher at 32℃ compared with both 20℃ and 10℃ (32℃: 39.8±0.2 degrees, 20℃: 38.7±0.2 degrees, 10℃: 38.3±0.1 degrees, p < 0.05). Minute ventilation and respiratory rate were also significantly higher at 32℃ compared with both 20℃ and 10℃ (p < 0.05). Furthermore, five out of six subjects failed to complete the 60-min run at 32℃. CONCLUSION: Prolonged running in the heat induces hyperventilation for thermoregulation, resulting in a significant decrease in oxygen saturation in the intercostal muscle. Surprisingly, oxygen saturation in the vastus lateralis was similarly maintained under all environmental conditions. These findings suggest that respiratory muscle function may be a critical limiting factor and potential target for heat strategies in marathon races. [1] Periard et al. (2013) / [2] Harms et al. (1997)
Read CV Ayano ImaiECSS Paris 2023: CP-PN20