ECSS Paris 2023: CP-PN07
INTRODUCTION: The energetic cost of transport (CoT) follows a U-shaped curve during walking (where the lowest walking CoT defines the economical speed (ES), intersecting with a linear running CoT at the economical transition speed (EOTS). Muscle tissue saturation index (TSI), derived from near-infrared spectroscopy (NIRS), quantifies local oxygenation and may reflect different components of the oxygen transport chain. Environmental factors such as heat and hypoxia are known to influence CoT as well as muscular TSI. The aim of the study was a) to assess the relationship between CoT and muscle TSI during human locomotion under environmental stress and b) to assess the impacts of environmental stress on energetic markers of economy (ES and EOTS). METHODS: Thirteen participants completed four randomized trials in control (CON; FiO2 20.9%, 24 °C, 50% relative humidity [RH]), heat (HOT; FiO2 20.9%, 35 °C, 50% RH), moderate normobaric hypoxia (MH; FiO2 16.8%, simulating ~1800 m altitude, 24 °C, 50% RH), and severe hypoxia (SH; FiO2 13.3%, simulating ~3600 m altitude, 24 °C, 50% RH) conditions. Each trial included eight walking stages (from 2.4 to 7.3 km·h-1) and four running stages (from 7.3 to 9.4 km·h-1). A computerized breath-by-breath system (Quark, Cosmed, Rome, Italy) was used to measure Pulmonary oxygen uptake (VO2) and carbon dioxide output (VCO2) for CoT, while the TSI of the vastus lateralis was continuously recorded using a portable NIRS device (PortaMon, Artinis Medical Systems, Zetten, the Netherlands). RESULTS: Walking and running CoT increased significantly in SH (+8.8 ± 0.95%, P = 0.003 and +6.0 ± 0.6%, P = 0.005, respectively) and in MH (+7.4 ± 0.9%, P = 0.006 and +8.1 ± 0.6%, P = 0.0002, respectively) versus CON. HOT had no significant effect during walking (-1.9 ± 0.9%, P = 0.47), and running (-3.4 ±. 0.6%, P = 0.099) versus CON. TSI in SH significantly decreased during walking (-9.9 ± 10.7%, P = <0.00001) and running (-13.8 ± 12.5%, P = 0.0009), While in MH no difference was observed during walking (-1.5 ± 8.7%, P =0.39) or running (-1.0 ± 9.7%, P =0.75), compared to CON. No significant difference observed in HOT during walking (-0.9 ± 9.1%, P =0.61) and running (-4.1 ±1 1.7%, P =0.27) compared to CON. ES and EOTS did not significantly change under any condition. CONCLUSION: These results suggest that pulmonary gas exchange limitations under SH contribute substantially to increases in CoT and reductions in muscle TSI during locomotion. MH also increases CoT but without a significant impact on TSI, indicating possible compensatory mechanisms or insufficient environmental stress to observe effects. HOT appears not to have any significant impact on either CoT or TSI, possibly due to thermoregulatory adjusments such as increased cardiac output and blood flow redistribution. The lack of change in ES and EOTS suggests that other factors maintain gait transition parameters under environmental stress.
Read CV Hubert WoronieckiECSS Paris 2023: CP-PN07
INTRODUCTION: Altitude training is widely used to enhance oxygen transport capacity; however, most supporting evidence derives from adult athletes exposed to >=2000 m. In contrast, youth training camps are frequently conducted at substantially lower elevations (~1250 m), where the hypoxic stimulus may be insufficient to induce meaningful erythropoietic adaptation. Whether short-term exposure at this altitude elicits measurable hematological responses during adolescence remains unclear. This study examined hematological responses to a 3-week training camp at 1250 m and evaluated whether performance level influenced adaptation. METHODS: Sixty-six adolescent athletes (15-17 years) were classified as first-class (n = 34) or elite-level (n = 32). Blood samples were collected during week 2 and week 3 of exposure. RBC, HGB, HCT, MCV, MCH, and MCHC were assessed. CK and BUN were measured to reflect accumulated training stress. Repeated-measures analyses and effect sizes were calculated. RESULTS: RBC (+1.9%) and HCT (+2.7%) showed modest upward trends; however, changes were not statistically significant and effect sizes were trivial-to-small. HGB remained stable. MCHC decreased slightly (-1.7%, p = 0.034), though the magnitude was physiologically limited. Elite athletes exhibited higher baseline oxygen transport indices (p < 0.05), yet no time x performance-level interactions were observed. Despite accumulated training stress (CK: 115.3 +/- 41.1 U/L), hematological adaptation was modest. CONCLUSION: Short-term exposure to 1250 m appears to provide a limited erythropoietic stimulus in adolescent athletes. The modest upward trends observed may reflect an early adaptive phase; however, the hypoxic dose was likely below the threshold required for substantial hematological remodeling. These findings underscore the importance of hypoxic dose considerations when designing altitude strategies for youth populatio These findings suggest that altitude presence alone does not guarantee hematological adaptation in youth populations. Rather, the magnitude and duration of hypoxic exposure appear to be critical determinants of response. Careful consideration of hypoxic dose may therefore be essential when designing altitude strategies for developing athletes.
Read CV YANG YEECSS Paris 2023: CP-PN07
INTRODUCTION: High-altitude environments cause changes to body composition, water-electrolyte levels and several physiological systems [1]. Therefore, nutritional and homeostatic assessment is vital for high-altitude expeditions to prevent risks, preserve performance, and speed recovery. This Himalayan trek study aimed to address these issues. METHODS: A total of 21 participants (12 m and 9 f, aged 43 ± 15 years and with a BMI of 24.2 ± 3.70 kg/m²) took part in the expedition. The uphill trek to the Pyramid Laboratory, during which participants took a 250 mg pill of acetazolamide once daily, took place over six days, interspersed with a day of rest. The descent trek after a five-day stay in the Pyramid took place in four days. Urine and blood samples were collected prior to the trek, in Kathmandu (LA, 1400 m a.s.l.), during the high-altitude phase at Pyramid (HA, 5000 m a.s.l.), and upon return in Kathmandu (LApost). Blood samples were also collected in Italy before and after the expedition. The food diaries were recorded on three separate days during the trek and further analysed through the FOODCONS software. Comparisons were made with the use of either the random effects analysis of variance (RM-ANOVA) or the mixed-effects RESULTS: In almost all participants, the mean daily energy intake was found to be considerably lower than the estimated total daily energy expenditure. The intake of water and protein was lower than recommended during the expedition. A lower body mass index was observed once back in Kathmandu (p=0.036, F(0.79, 14.2)=5.79). With regard to the urinary analyses, osmolality was higher at LApost, and pH at HA (p=0.063, F(2, 36)=2.99; p=0.012, F(2, 40)=4.93). With regard to the blood analysis, the levels of iron, ferritin and thyrotropin were lower at HA (p<0.001, F(2.47, 37.1)=10.9; p=0.011, F(1.83, 27.5)=5.55; p=0.003, F(2.05, 30.7)=7.09). Conversely, transferrin and free triiodothyronine levels were higher at HA (p=0.007, F(3.20, 56.8)=4.37; p=0.021, F(2.85, 42.7)=3.68). Creatinine levels did demonstrate a non-significant increase at HA (p=0.065, F(2.34, 37.4)=2.82). The alterations in blood urea nitrogen levels exhibited heterogeneity among the study participants. CONCLUSION: An overall negative energy balance during the course of the expedition emerged. The HA-induced renal compensation for balancing pH (a process further supported by acetazolamide) and mobilisation of iron reserves were in evidence. The increase in urinary osmolality upon returning to Kathmandu indicated a potential dehydration. The thyroid axis was activated at HA, followed by subsequent inhibition of the pituitary gland. During HA expeditions, in addition to medical examinations and pre-expedition advice [2], specific dietary strategies are strongly encouraged to support adequate physiological responses. REFERENCES: [1] Santangelo et al. (2024), Appl. Physiol. Nutr. Metab. [2] Burtscher et al. (2025), Minerva Med.
Read CV Danilo BondiECSS Paris 2023: CP-PN07