Constructing a Talent Identification Index System and Evaluation Model for Cross-Country Skiers.

A talent identification index system for male and female cross-country skiers in four age groups (11-12 years old, 13-14 years old, 15-16 years old, and 17-18 years old) was established. The system comprises five body shape indexes ( i =5): Leg-to-Body Ratio (LBR), body fat percentage, maturity status, spreaded brachia index, and upper extremity length. The physiological function indexes ( i =2) are VO2max and haemoglobin mass (Hb). The psychological indexes ( i =5) cover reaction time, perception speed, a quality-of-will scale, an attention test, and operational thinking. The physical fitness indexes ( i =11) comprise upper limb explosiveness, vertical jump, 3000-metre run, orthostatic forward flexion, closed-eyes single-leg stand, standing long jump, 20-metre sprint, pull-ups (males), flexed arm hang (females), hexagon jump, and a Functional Movement Screen (FMS) test. The athletic performance indexes ( i =3) comprise on-snow time trials for 1.2 km, 5 km, and 10 km. The talent identification evaluation model was created using automated evaluation software. The talent identification index system and evaluation standard table for cross-country skiers passed the P60 shortlist and P90 elite boundaries established using the percentile method. Thus, the results of this test profile verify that the evaluative model is objectively effective.

Influence of Chronic Nitrate-Rich Beetroot Juice Supplementation on the Endurance Performance of Active Winter Triathletes: A Randomized Controlled Trial.

OBJECTIVE: The impact of high-nitrate beetroot juice (BRJ) supplementation has seen a recent explosion of interest in sports science. This study examined the potential influence of 7-day BRJ supplementation on the endurance performance of winter triathletes. METHODS: Eighty young active winter triathletes (44 males, age = 21.50 ± 1.15 yrs; 36 females, age = 20.66 ± 1.45 yrs) participated in this study and were provided with either BRJ (6.5 mmol NO3-/70 mL) or a placebo (PL, 0.065 mmol NO3-/70 mL) for 7 days (a dose of ×3 per day) in a randomized, double-blind design. The athletes then completed a submaximal treadmill run, intraday cycling exhaustion testing, and a 10-km cross country (XC) skiing competition on the second day. RESULTS: There was a significant decrease in the oxygen uptake, respiratory exchange ratio, and blood lactic acid level (p < 0.05) between the BRJ and PL treatment groups during V3 speed running (males: 13.3 km·h-1, females: 11.6 km·h-1). BRJ treatment also remarkably increased the time to exhaustion (TTE) during cycling exhaustion testing (males: p = 0.02, females: p = 0.04). No significant differences were observed in medium- or low-speed submaximal treadmill runs and 10-km XC skiing performance. CONCLUSIONS: One week of daily nitrate-rich BRJ supplementation improved running economy at high speed during the submaximal treadmill running test and extended the TTE of athletes during cycling exhaustion testing. However, BRJ supplementation did not improve the performance in 10-km on-snow time trials in XC skiing. Regarding nutritional strategies to improve endurance performance in exercise training and competition, these results should be carefully considered owing to the different motor skill levels and competitive abilities of participants.

Dose-response relationship between training load and anaerobic performance in female short-track speed skaters: A prospective cohort study.

This study aimed to assess the dose-response relationship (DRR) between measures of training load (TL) and anaerobic performance in female short-track speed skaters. TL data from 22 female short-track speed skaters (mean ± SD; calendar age 20.7 ± 2.01 years, training length 4.18 ± 1.23 years, height 164.20 ± 5.53 cm, weight 52.00 ± 5.58 kg) was collected over a six week period. Participants completed two anaerobic capacity assessments (cycling parameters: total work, maximal anaerobic power [MAnP], power duration indices, maximal blood lactate, fatigue indices, and peak power output [PPO]) pre- and post-training, which included three tests (short-term, intermediate-term, and 120 s maximal anaerobic test). The mean weekly TL measures calculated were total distance, red zone (time spent > 85% of peak heart rate), Edwards training impulse (eTRIMP), Stagno training impulse (gTRIMP), Lucia training impulse, and session ratings of perceived exertion. The gTRIMP identified a curvilinear relationship and explained 79% and 63% of the variance in changes of MAnPi and PPO (R2 = 0.79, 95%CI = 0.64 to 1.00, turn point 621AU; R2 = 0.63, 95%CI = 0.27 to 1.00, turn point 633AU, respectively). Likewise, The eTRIMP identified a curvilinear relationship and explained 62% and 54% of the variance in changes of MAnPi and PPO (R2 = 0.62, 95%CI = 0.11 to 1.00, turn point 485AU; R2 = 0.54, 95%CI = 0.07 to 1.00, turn point 515AU, respectively). All other variables exhibited a DRR below moderate. This study investigated a TL strategy to improve the speed endurance of female short-track speed skaters and suggested the superiority of gTRIMP and eTRIMP methods of internal TL.

Effects of Pre-, Post- and Intra-Exercise Hyperbaric Oxygen Therapy on Performance and Recovery: A Systematic Review and Meta-Analysis.

Background: As a World Anti-doping Agency (WADA)-approved treatment, hyperbaric oxygen (HBO2) therapy has been used to improve exercise performance in sports practice. Objective: We aimed to investigate the effect of pre-, post-, and intra-exercise HBO2 therapy on performance and recovery. Methods: A literature search was conducted using EMBASE, CENTRAL, PubMed, Web of Science, and SPORTDiscus to obtain literature published until May 2021. A total of 1,712 studies that met the following criteria were identified: (1) enrolled healthy adults who were considered physically active; (2) evaluated HBO2 therapy; (3) included a control group exposed to normobaric normoxic (NN) conditions; (4) involved physical testing (isokinetic or dynamic strength exercise, maximal incremental treadmill/cycle exercise, etc.); and (5) included at least one exercise performance/recovery index as an outcome measure. The Cochrane risk of bias assessment tool was used to evaluate the included studies, and the heterogeneity of therapy effects was assessed using the I2 statistic by Review Manager 5.3. Results: Ten studies (166 participants) were included in the qualitative analysis, and six studies (69 participants) were included in the quantitative synthesis (meta-analysis). In comparisons between participants who underwent HBO2 therapy and NN conditions, the effects of pre-exercise HBO2 therapy on exercise performance were not statistically significant (P > 0.05), and the effects of post-exercise HBO2 therapy on recovery were not statistically significant either (P > 0.05). Although individual studies showed positive effects of intra-exercise HBO2 therapy on exercise performance, a meta-analysis could not be performed. Conclusion: Hyperbaric oxygen therapy before or after exercise had no significant effect on performance and recovery. However, hyperbaric oxygen therapy during exercise could improve muscle endurance performance, which needs to be confirmed by further empirical studies. At present, the practical relevance of these findings should be treated with caution.