Relative age effect in French alpine skiing: Problem and solution.

This study aims to identify the potential bias of the relative age effect (RAE) in French alpine skiers and to propose a mathematical correction adjustment for such a bias. All performances and birthdates of skiers on the national and international circuit were collected from the 2004 up to 2019. A goodness-of-fit chi-square test and the residuals were used to study the distribution of birth trimesters in youth competitors. A linear relationship between the distribution of performances and the months obtains a calibration coefficient allowing to rebalance the performance by considering the effect of RAE. Individuals born at the beginning of the year are over-represented in the elite young selections in all disciplines for both genders. A coefficient based on the relationship between month of birth and performance adjusts individual performance and cancels out the effect of RAE. The results show that RAE is present in French alpine skiing. We present a method allowing to consider the effect of the RAE in the performances realized in each gender and discipline. This method allows coaches to have a more objective opinion on performance and to reduce selection bias.

Lower limb force-production capacities in alpine skiing disciplines.

Specific force capacities might be a limiting factor for alpine skiing performance, yet there is little consensus on the capabilities in question, and whether they differ between disciplines. We aimed to test discipline (speed and technical) and performance (event-specific world standing) effects on lower limb force-production qualities. National-level skiers (N = 31) performed loaded squat jumps and isometric mid-thigh pulls to detect dynamic force output at extremely low and high velocities and maximum isometric force and rate of force development, respectively. Discipline differences were assessed via a general linear model including performance and allowing for interaction effects, with performance associations further characterized via distinct Pearson's correlations. Jump height did not differentiate disciplines, with absolute power slightly higher in speed athletes (F(1,27)  = 4.42, P = .045, ω2  = 0.10), and neither variables were related to performance. Speed athletes possessed greater dynamic force at low velocities (F0 ; F(1,27)  = 13.8, P < .001, ω2  = 0.17), and greater relative and absolute maximum isometric force (F(1,25)  = 11.19-20.70, ω2  = 0.16-0.22, P < .003). Overall, higher ranked athletes possessed more force-dominant profiles (F(1,27)  = 16.28, ω2  = 0.34; r = 0.60 to 0.67, P < .001) and increased rate of force development characteristics (average and maximum, r = -0.50 to -0.82, P < .048). Very robust associations existed between maximum isometric force and speed performance (r = -0.88, P < .001), but only a trend for higher absolute isometric force in technical athletes (r = -0.49, P = .052). Alpine skiers display a preponderance for dynamic force output at low velocities, and isometric force for speed athletes, which highlights the interest in specific assessment and conditioning practices for ski athletes.

The effect of countermovement on force production capacity depends on extension velocity: A study of alpine skiers and sprinters.

In jumping, countermovement increases net propulsive force and improves performance. We aimed to test whether this countermovement effect is velocity specific and examine the degree to which this varies between athletes, sports or performance levels. Force-velocity profiles were compiled in high-level skiers (N= 23) and sprinters (N= 30), with their performance represented in their overall world ranking and season-best 100 m time, respectively. Different ratios between force-velocity variables were computed from squat and countermovement jumps (smaller = less effect): jump height (CRh), maximum power (CRP), force (CRF), and velocity (CRv). Countermovement effect differed per velocity (inverse relationship between CRF and CRv, rs = -0.74, p< .001), and variation force-velocity profiles with countermovement. Skiers exhibited smaller CRF (rrb = -0.675, p< .001), sprinters smaller CRv (rrb = 0.426, p= .008), and "moderate" velocity conditions did not differentiate groups (CRP or CRh, p> .05). 33% of the variance in skiers' performance level was explained by greater maximum force and a lower CRF (i.e., high explosiveness at low-velocities without countermovement), without an association for sprinters. Countermovement effect appears specific to movement velocity, sport and athlete level. Consequently, we advise sports-specific assessment, and potentially training to reduce the countermovement effect per the relevant velocity.

Energy Demands in Well-Trained Alpine Ski Racers During Different Duration of Slalom and Giant Slalom Runs.

Bottollier, V, Coulmy, N, Le Quellec, L, and Prioux, J. Energy demands in well-trained alpine ski racers during different duration of slalom and giant slalom runs. J Strength Cond Res 34(8): 2156-2164, 2020-The purpose of this study was to investigate the energy demands of different duration slalom (SL) and giant slalom (GS) events in well-trained alpine ski racers. Eight well-trained alpine ski racers (age: 18.2 ± 0.8 years; stature: 1.72 ± 0.10 m; body mass: 65.8 ± 12.0 kg) performed an incremental laboratory test on cycle ergometer and 4 standardized alpine ski runs: short (ST) and long (LG) versions of SL and GS (SLST, SLLG, GSST, and GSLG). Oxygen uptake (V[Combining Dot Above]O2) and heart rate (HR) were recorded continuously in all conditions. Blood lactate ([La]) was determined immediately before run and 3 and 5 minutes after run ([La]peak). The contribution of aerobic, glycolytic, and phosphagen energy systems was estimated. The aerobic system was the primary energy system involved in GSST (43.9 ± 5.7%) and GSLG (48.5 ± 2.5%). No significant difference in the contribution of aerobic and glycolytic systems was observed in SLST and SLLG. [La]peak was higher in SLLG (11.10 ± 2.41 mmol·L) than in GSST (8.01 ± 2.01 mmol·L). There was no difference in oxygen uptake peak between GSST and GSLG. Energetic training goals should focus on the improvement of both aerobic, glycolytic, and phosphagen systems for alpine ski racers who perform SL and GS. Giant slalom specialists might benefit from emphasizing the improvement of the aerobic system, without neglecting other systems.

Live high-train low guided by daily heart rate variability in elite Nordic-skiers.

PURPOSE: To analyze if live high-train low (LHTL) effectiveness is improved when daily training is guided by heart rate variability (HRV). METHODS: Twenty-four elite Nordic skiers took part in a 15-day LHTL study and were randomized into a HRV-guided training hypoxic group (H-HRV, n = 9, sleeping in normobaric hypoxia, FiO2 = 15.0%) and two predefined training groups sleeping either in hypoxia (H, n = 9, FiO2 = 15.0%) or normoxia (N, n = 6). HRV and training loads (TL) were recorded daily. Prior (Pre), one (Post-1), and 21 days (Post-21) following LHTL, athletes performed a 10-km roller-ski test, and a treadmill test for determination of [Formula: see text] was performed at Pre and Post-1. RESULTS: Some HRV parameters measured in supine position were different between H-HRV and H: low and high (HF) frequency power in absolute (ms2) (16.0 ± 35.1 vs. 137.0 ± 54.9%, p = 0.05) and normalized units (- 3.8 ± 10.1 vs. 53.0 ± 19.5%, p = 0.02), HF(nu) (6.3 ± 6.8 vs. - 13.7 ± 8.0%, p = 0.03) as well as heart rate (3.7 ± 6.3 vs. 12.3 ± 4.1%, p = 0.008). At Post-1, [Formula: see text] was improved in H-HRV and H (3.8 ± 3.1%; p = 0.02 vs. 3.0 ± 4.4%; p = 0.08) but not in N (0.9 ± 5.1%; p = 0.7). Only H-HRV improved the roller-ski performance at Post-21 (- 2.7 ± 3.6%, p = 0.05). CONCLUSION: The daily individualization of TL reduced the decrease in autonomic nervous system parasympathetic activity commonly associated with LHTL. The improved performance and oxygen consumption in the two LHTL groups confirm the effectiveness of LHTL even in elite endurance athletes.

Influence of Training Load and Altitude on Heart Rate Variability Fatigue Patterns in Elite Nordic Skiers.

We aimed to analyse the relationship between training load/intensity and different heart rate variability (HRV) fatigue patterns in 57 elite Nordic-skiers. 1063 HRV tests were performed during 5 years. R-R intervals were recorded in resting supine (SU) and standing (ST) positions. Heart rate, low (LF), high (HF) frequency powers of HRV were determined. Training volume, training load (TL, a.u.) according to ventilatory threshold 1 (VT1) and VT2 were measured in zones I≤VT1; VT1VT2, IV for strength. TL was performed at 81.6±3.5% in zone I, 0.9±0.9% in zone II, 5.0±3.6% in zone III, 11.6±6.3% in zone IV. 172 HRV tests matched a fatigue state and four HRV fatigue patterns (F) were statistically characterized as F(HF-LF-)SU_ST for 121 tests, F(LF+SULF-ST) for 18 tests, F(HF-SUHF+ST) for 26 tests and F(HF+SU) for 7 tests. The occurrence of fatigue states increased substantially with the part of altitude training time (r2=0.52, p<0.001). This study evidenced that there is no causal relationship between training load/intensity and HRV fatigue patterns. Four fatigue-shifted HRV patterns were sorted. Altitude training periods appeared critical as they are likely to increase the overreaching risks.

Exploring the effect of the menstrual cycle or oral contraception on elite athletes' training responses when workload is not objectively quantifiable: the MILS approach and findings from female Olympians.

Objectives: Develop the Markov Index Load State (MILS) model, based on hidden Markov chains, to assess athletes' workload responses and investigate the effects of menstrual cycle (MC)/oral contraception (OC), sex steroids hormones and wellness on elite athletes' training. Methods: On a 7-month longitudinal follow-up, daily training (volume and perceived effort, n=2200) and wellness (reported sleep quality and quantity, fitness, mood, menstrual symptoms, n=2509) data were collected from 24 female rowers and skiers preparing for the Olympics. 51 MC and 54 OC full cycles relying on 214 salivary hormone samples were analysed. MC/OC cycles were normalised, converted in % from 0% (first bleeding/pill withdrawal day) to 100% (end). Results: MILS identified three chronic workload response states: 'easy', 'moderate' and 'hard'. A cyclic training response linked to MC or OC (95% CI) was observed, primarily related to progesterone level (p=8.23e-03 and 5.72e-03 for the easy and hard state, respectively). MC athletes predominantly exhibited the 'easy' state during the cycle's first half (8%-53%), transitioning to the 'hard' state post-estimated ovulation (63%-96%). OC users had an increased 'hard' state (4%-32%) during pill withdrawal, transitioning to 'easy' (50%-60%) when on the pill. Wellness metrics influenced the training load response: better sleep quality (p=5.20e-04), mood (p=8.94e-06) and fitness (p=6.29e-03) increased the likelihood of the 'easy' state. Menstrual symptoms increased the 'hard' state probability (p=5.92e-02). Conclusion: The MILS model, leveraging hidden Markov chains, effectively analyses cumulative training load responses. The model identified cyclic training responses linked to MC/OC in elite female athletes.

Potential estimation model in French alpine skiing - Individual evolution curve and progression typology.

Estimating the potential of alpine skiers is an unresolved question, especially because of the complexity of sports performance. We developed a potential estimation model based solely on the evolution of performance as a function of age. A bayesian mixed model allowed to estimate the potential curve and the age at peak performance for the population (24.81 ± 0.2) and for each individual as the uncertainty around this curve. With Gaussian mixtures, we identified among all the estimates four types of curves, clustered according to the performance level and the progression per age. Relying on the uncertainty calculated on the progression curve the model created also allow to estimate a score and an uncertainty associated with each cluster for all individuals. The results allows to: i) describe and explain the relationship between age and performance in alpine skiing from a species point of view (at 0.87%) and ii) to provide to sport staffs the estimation of the potential of each individual and her/his typology of progression to better detect sports potential. The entire methodology is based on age and performance data, but the progression identified may depend on parameters specific to alpine skiing.

Reliability of Alpine Ski Racing-Specific Field Test: The 80s-Slide-Test.

PURPOSE: The purpose of this study was to determine the test-retest reliability of the 80s-slide-test in well-trained alpine ski racers. METHODS: The sample consisted of 8 well-trained alpine ski racers (age = 17.8 [0.7] y old; height = 1.80 [0.09] m; body mass = 72.1 [9.5] kg) who performed a lab-based maximal graded test on cycle ergometer and three 80s-slide-tests in 4 separate sessions. The 80s-slide-test consisting of maximal push-offs performed for 80s on a 8-ft slide board. Oxygen uptake (V˙O2) and heart rate (HR) were recorded continuously. Blood lactate ([La]b) was determined immediately prerun, followed by 3 minutes postrun. Three minutes after the completion of the session, the subjects were asked to indicate their rate of perceived exertion using Borg scale ranging from 6 to 20. Total and every 10s mean push-offs number were assessed by camera. Typical errors of measurement, intraclass correlation coefficients, and smallest worthwhile change were calculated. RESULTS: The 80s-slide-test showed strong reliability for total push-offs number, V˙O2peak, V˙O2mean, HRpeak, and HRmean. Δ[La]b, fatigue index, and the rate of perceived exertion were moderately reliable. CONCLUSION: The 80s-slide-test is a reliable test for well-trained alpine ski racers and can be used easily by trainers.

Force output in giant-slalom skiing: A practical model of force application effectiveness.

Alpine ski racers require diverse physical capabilities. While enhanced force production is considered key to high-level skiing, its relevance is convoluted. The aims of this study were to i) clarify the association between performance path length and velocity, ii) test the importance of radial force, and iii) explore the contribution of force magnitude and orientation to turn performance. Ski athletes (N = 15) were equipped with ski-mounted force plates and a global navigation satellite system to compute the following variables over 14 turns: path length (L), velocity normalized energy dissipation [Δemech/vin], radial force [Fr], total force (both limbs [Ftot], the outside limb, and the difference between limbs), and a ratio of force application (RF = Fr/Ftot). Data were course-averaged or separated into sectional turn groupings, averaged, and entered into stepped correlation and regression models. Our results support Δemech/vin as a discriminative performance factor (R2 = 0.50-0.74, p < .003), except in flat sections. Lower course times and better Δemech/vin were associated with greater Fr (R2 = 0.34-0.69 and 0.31-0.52, respectively, p < .032), which was related to both Ftot and RF (ß = 0.92-1.00 and 0.63-0.81, respectively, p < .001) which varied in predictive order throughout the sections. Ftot was associated with increased outside limb force and a more balanced contribution of each limb (ß = 1.04-1.18 and -0.65- -0.92, respectively, p < .001). Fr can be improved by either increasing total force output or by increasing technical effectiveness (i.e., proportionally more force radially) which should increase the trajectories available to the skier on the ski course.

Effects of Different Training Intensity Distributions Between Elite Cross-Country Skiers and Nordic-Combined Athletes During Live High-Train Low.

Purpose: To analyze the effects of different training strategies (i.e., mainly intensity distribution) during living high - training low (LHTL) between elite cross-country skiers and Nordic-combined athletes. Methods: 12 cross-country skiers (XC) (7 men, 5 women), and 8 male Nordic combined (NC) of the French national teams were monitored during 15 days of LHTL. The distribution of training at low-intensity (LIT), below the first ventilatory threshold (VT1), was 80% and 55% in XC and NC respectively. Daily, they filled a questionnaire of fatigue, and performed a heart rate variability (HRV) test. Prior (Pre) and immediately after (Post), athletes performed a treadmill incremental running test for determination of V˙ O2max and V˙ O2 at the second ventilatory threshold ( V˙ O2V T2), a field roller-skiing test with blood lactate ([La-]) assessment. Results: The training volume was in XC and NC, respectively: at LIT: 45.9 ± 6.4 vs. 23.9 ± 2.8 h (p < 0.001), at moderate intensity: 1.9 ± 0.5 vs. 3.0 ± 0.4 h, (p < 0.001), at high intensity: 1.2 ± 0.9 vs. 1.4 ± 02 h (p = 0.05), in strength (and jump in NC): 7.1 ± 1.5 vs. 18.4 ± 2.7 h, (p < 0.001). Field roller-skiing performance was improved (-2.9 ± 1.6%, p < 0.001) in XC but decreased (4.1 ± 2.6%, p < 0.01) in NC. [La-] was unchanged (-4.1 ± 14.2%, p = 0.3) in XC but decreased (-27.0 ± 11.1%, p < 0.001) in NC. Changes in field roller-skiing performance and in [La-] were correlated (r = -0.77, p < 0.001). V˙ O2max increased in both XC and NC (3.7 ± 4.2%, p = 0.01 vs. 3.7 ± 2.2%, p = 0.002) but V˙ O2V T2 increased only in XC (7.3 ± 5.8%, p = 0.002). HRV analysis showed differences between XC and NC mainly in high spectral frequency in the supine position (HFSU). All NC skiers showed some signs of overreaching at Post. Conclusion: During LHTL, despite a higher training volume, XC improved specific performance and aerobic capacities, while NC did not. All NC skiers showed fatigue states. These findings suggest that a large amount of LIT with a moderate volume of strength and speed training is required during LHTL in endurance athletes.

Influence of slope steepness, foot position and turn phase on plantar pressure distribution during giant slalom alpine ski racing.

The purpose of this study was to investigate the evolution of ground reaction force during alpine skiing turns. Specifically, this study investigated how turn phases and slope steepness affected the whole foot normal GRF pattern while performing giant slalom turns in a race-like setting. Moreover, the outside foot was divided into different plantar regions to see whether those parameters affected the plantar pressure distribution. Eleven skiers performed one giant slalom course at race intensity. Runs were recorded synchronously using a video camera in the frontal plane and pressure insoles under both feet's plantar surface. Turns were divided according to kinematic criteria into four consecutive phases: initiation, steering1, steering2 and completion; both steering phases being separated by the gate passage. Component of the averaged Ground Reaction Force normal to the ski's surface([Formula: see text], /BW), and Pressure Time Integral relative to the entire foot surface (relPTI, %) parameters were calculated for each turn phases based on plantar pressure data. Results indicated that [Formula: see text] under the total foot surface differed significantly depending on the slope (higher in steep sections vs. flat sections), and the turn phase (higher during steering2 vs. three other phases), although such modifications were observable only on the outside foot. Moreover, [Formula: see text] under the outside foot was significantly greater than under the inside foot.RelPTI under different foot regions of the outside foot revealed a global shift from forefoot loading during initiation phase, toward heel loading during steering2 phase, but this was dependent on the slope studied. These results suggest a differentiated role played by each foot in alpine skiing turns: the outside foot has an active role in the turning process, while the inside foot may only play a role in stability.

Return to Sport Among French Alpine Skiers After an Anterior Cruciate Ligament Rupture: Results From 1980 to 2013.

BACKGROUND: There is little known about return to sport and performance after anterior cruciate ligament (ACL) tear in high-level alpine skiers. PURPOSE: To analyze the parameters that influence the return to sport and performance after an ACL tear in French alpine skiers from 1980 to 2013. STUDY DESIGN: Descriptive epidemiology study. METHODS: The study population included 239 male and 238 female skiers who competed on the national French alpine ski team for at least 1 season between 1980 and 2013 in the speed (downhill and super-G) and technical disciplines (giant slalom and slalom). Two groups were formed: group 1 (G1) included athletes who had sustained an ACL rupture, and group 2 (G2) included athletes who had never sustained an ACL rupture. Three performance indicators were selected: International Ski Federation (FIS) points calculation, FIS ranking, and podium finishes in the World Cup, World Championships, and Olympic Games. RESULTS: The first-decile FIS points and international FIS ranking showed that G1 skiers obtained better performance than did G2 skiers. The mean ± SD career length of G1 skiers (men, 7.9 ± 4.7 years; women, 7.1 ± 4.1 years) was longer than that of G2 skiers (men, 4.5 ± 3.3 years; women, 4.2 ± 3.5 years). In addition, 12.8% (61 of 477) of the skiers achieved at least a podium finish during their careers: 23.0% (34 of 148) in G1 and 8.3% (27 of 329) in G2. The mean age at ACL rupture was 22.6 ± 4.1 years for men and 19.9 ± 3.5 years for women. In G1, 55 podiums were achieved before ACL rupture and 176 after in all competitions. Skiers who improved their performances after ACL rupture were significantly younger (men, 22.2 ± 3.0 years; women, 18.7 ± 2.2 years; P < .0001) at the time of injury than those showing a performance deterioration after ACL rupture (men, 25.3 ± 4.2 years; women, 22.4 ± 4.0 years). All skiers who had ACL tears continued their competitive careers after the injury. CONCLUSION: The overall results showed that it is possible to return to preinjury or even higher levels of performance after an ACL rupture and that age is the main element that guides postsurgical recovery.

Fatigue shifts and scatters heart rate variability in elite endurance athletes.

PURPOSE: This longitudinal study aimed at comparing heart rate variability (HRV) in elite athletes identified either in 'fatigue' or in 'no-fatigue' state in 'real life' conditions. METHODS: 57 elite Nordic-skiers were surveyed over 4 years. R-R intervals were recorded supine (SU) and standing (ST). A fatigue state was quoted with a validated questionnaire. A multilevel linear regression model was used to analyze relationships between heart rate (HR) and HRV descriptors [total spectral power (TP), power in low (LF) and high frequency (HF) ranges expressed in ms(2) and normalized units (nu)] and the status without and with fatigue. The variables not distributed normally were transformed by taking their common logarithm (log10). RESULTS: 172 trials were identified as in a 'fatigue' and 891 as in 'no-fatigue' state. All supine HR and HRV parameters (Beta±SE) were significantly different (P<0.0001) between 'fatigue' and 'no-fatigue': HRSU (+6.27±0.61 bpm), logTPSU (-0.36±0.04), logLFSU (-0.27±0.04), logHFSU (-0.46±0.05), logLF/HFSU (+0.19±0.03), HFSU(nu) (-9.55±1.33). Differences were also significant (P<0.0001) in standing: HRST (+8.83±0.89), logTPST (-0.28±0.03), logLFST (-0.29±0.03), logHFST (-0.32±0.04). Also, intra-individual variance of HRV parameters was larger (P<0.05) in the 'fatigue' state (logTPSU: 0.26 vs. 0.07, logLFSU: 0.28 vs. 0.11, logHFSU: 0.32 vs. 0.08, logTPST: 0.13 vs. 0.07, logLFST: 0.16 vs. 0.07, logHFST: 0.25 vs. 0.14). CONCLUSION: HRV was significantly lower in 'fatigue' vs. 'no-fatigue' but accompanied with larger intra-individual variance of HRV parameters in 'fatigue'. The broader intra-individual variance of HRV parameters might encompass different changes from no-fatigue state, possibly reflecting different fatigue-induced alterations of HRV pattern.