ECSS Paris 2023: OP-BM03
INTRODUCTION: In competition, there are four main alpine skiing events: slalom (SL), giant slalom (GS), super giant slalom (SG), and downhill (DH). Each event differs in race duration, turn number, turn radii and speed reached (1). Therefore, the average turn-by-turn forces and impulses the skier applies vary across events (2). The off-snow lower-limb isometric force has been previously shown to be related to skiing event-specific performance (3). Nevertheless, despite evidence demonstrating the appearance of fatigue after repeated turns (4), this study only focused on free-fatigue maximal force capacities without considering strength endurance capacities The latter can be characterized by the critical force, i.e. the maximal force which can be sustained without inducing acute fatigability. Therefore, the present study aimed to test the relationship between skiing event-specific performance and maximal isometric force, rate of force development and critical force. METHODS: Nineteen skiers (27 to 100 FIS points) participated in this study. Maximal isometric force (Fmax), maximal rate of force development (RFDmax), and critical force (CF) were assessed using an isometric leg press ergometer within the same session. CF was determined using a Ramp Above Critical Level Endurance Test (5). Briefly, this test consisted of repeated submaximal isometric 2s contractions spaced by 2s of rest during a 300s-decreasing ramp test from 80% to 0% of Fmax. Every 28s, maximal isometric force was assessed. Based on the model of Bowen et al. (6), CF was computed as the targeted force at the instant when the maximal isometric force stopped to decrease and started to recover. Performance indexes in each skiing event (SL, GS, SG, and DH) were defined as the FIS points for the 2022/2023 season. Multiple linear regressions were used to understand whether interindividual variability in each physical capacity (Fmax, RFDmax, and CF) explains variability in event-specific performance. RESULTS: SL performance was only and positively associated with RFDmax (model R2 = 0.41, p = 0.004). GS performance was only and positively associated with CF (model R2 = 0.36, p = 0.008). SG performance was only and positively associated with CF (model R2 = 0.37, p = 0.008). DH performance was positively associated with CF and Fmax (model R2 = 0.89, p < 0.001). CONCLUSION: This study demonstrates specific associations between skiing performance and off-snow physical capacities. Performance is mainly explained by RFDmax in SL, CF in GS, CF in SG and both CF, and Fmax in DH. Physical capacities explained a higher part of skiing performance in DH compared to the other events. These results evidence the importance of strength endurance capacities in skiing performance and can help trainers and skiers in event-specific physical preparation.
Read CV Mickael CholletECSS Paris 2023: OP-BM03
INTRODUCTION: The Critical Power is the severe intensity domain boundary above which fatigue develops drastically and non-steady-state physiological responses occur (1). However, a given power can be developed using different combinations of torque and velocity. During maximal effort, velocity is known to influence the maximal torque or power, which is well described by linear force-velocity or polynomial power-velocity relationships. Although a vast literature has studied critical power, relatively few studies have focused on the effect of the velocity condition. In addition, only 2 velocity conditions were usually tested given the physical hardship and/or time-consuming aspects of assessing critical power using time to exhaustion or 3-min all-out methods (2). Thanks to the development of a new method for assessing critical power during a single 5-min submaximal exercise: the Ramp Above Critical Level Endurance Test (RACLET) (3), the study’s aim was to test the effect of the velocity condition on critical power (Pc) and torque (Tc) over a large spectrum in pedaling. METHODS: Based on Bowen model (4), which establishes the proportionality between work accumulation above the critical intensity (Wac) and fatigability during exercise in the severe domain, RACLET was used to determine Tc and Pc under different velocity conditions. Briefly, this test consisted of a 5-min isokinetic pedaling decreasing power ramp, where maximal power was assessed every 30 s from a 6-pedal-strokes sprints. The ramp is designed such that the target power starts above and decreases below Pc without leading to exhaustion. Thus, Pc was determined to be the power target when the maximal capacities stopped decreasing and began to recover. Twenty participants realized five RACLET under different pedaling rate conditions: from 40 to 120, every 20 RPM. From each RACLET, the model was fitted to the maximum power data to obtain the initial power (Pi) & Pc parameters for each cadence. The cadence effect on Tc, Pc, and Wac was modeled and tested using ANOV RESULTS: The model’s goodness of fit on the RACLET experimental data (changes in the maximal power over time) was excellent (mean adjusted R²=0.89, RMSE=5%Pi). Tc decreased significantly with the increase in cadence (p<0.001; from 37.3±4.5 to 18.0±4.2 %Ti for 40 to 120 rpm). Furthermore, the Tc as a function of velocity was well described by curved function (median R² = 0.92). The optimal velocity that allows to maximize the Pc was 67.2 ± 19.3 RPM CONCLUSION: The results show that it is possible to determine the individual model parameters Tc & Pc, at several velocities using a newly validated submaximal not-to-exhaustion test (RACLET). This allowed us to demonstrate that the critical power was affected by the velocity conditions. The maximum critical power was produced under individual optimum cadence conditions. The velocity condition is crucial when considering and testing the critical power. 1)Burnley. EJAP, 2022 2)Dekerle, JSMS, 2014 3)Bowen, ECSS, 2023 4)Bowen, JTB, 2024
Read CV Maximilien BowenECSS Paris 2023: OP-BM03
INTRODUCTION: Critical power is an important fatigue threshold in exercise physiology, separating moderate to severe intensity domains. When muscle effort is performed above the critical force (Fc), acute muscle fatigue drastically occurs. This critical threshold has great potential application in optimizing athletic training programs and performance as well as improving the life quality for chronic disease (e.g. chronic obstructive pulmonary disease (COPD)) patients (1). Historically, Fc has been provided by the asymptotic force-time relationship, obtained during multiple time-to-exhaustion or all-out test. The difficulty of these tests prevents them from being used routinely in clinical context. Based on Bowen et al. (2) model, we proposed an innovative non-exhaustive test to determine the Fc: the Ramp Above Critical Level Endurance Test (RACLET). The aims of this study were to i) test the validity of the RACLET and ii) its feasibility with COPD patients. METHODS: Sixteen healthy participants and ten COPD patients completed a RACLET on an isometric knee extension ergometer. The test consists in a 5-min decreasing ramp, from severe to moderate intensity domains, composed of intermittent contraction (3s on, 2s off) and brief maximal voluntary contraction (MVC) every 30s. RACLET started at 60% of the initial maximal force (Fi) and gradually decreased to reach 0 N after 5 min. Visual feedback enabled the participant to follow the target force. Healthy participants also performed, on a separated day, a 5-min all-out isometric test. Forces reached during all-out or MVCs performed during RACLET were modelled using derived equations based on: Fmax(t) = –(1/Tau)*int(F(t)-Fc)dt+Fi, where F is the target force and Tau is a time constant (2). The validity of the RACLET was assessed by examining the correlation and the root-mean-square error (RMSE) compared to the gold standard method being the 5-min all-out. RESULTS: The model’s goodness of the fit on RACLET and all-out test experimental data was excellent (median r2 = 0.96 and 0.97, respectively). Fi, Fc and Tau obtained from RACLET (656 ± 152 N, 283 ± 80 N and 64 ± 33 s, respectively) and from all-out test were highly correlated (r2 = 0.94, 0.92, 0.83, respectively, all p<0.001, RMSE = 6.4, 5.9, 20.8%). All COPD patients were able to complete the RACLET, the goodness of fit being excellent (median r2 = 0.95). The Fc expressed relatively to initial capacity was significantly lower than healthy participants (33 ± 11 vs 41 ± 7 %Fi respectively, p<0.05). CONCLUSION: Compared to the gold standard all-out method, the RACLET is valid to assess Fc in isometric knee extension. This innovative test does not lead to exhaustion. Thus, it has demonstrated to be feasible to determine Fc in COPD patients (stage 1 to 3). The RACLET could thus be a useful tool for determining a muscle intensity threshold (i.e. Fc) to tailor intervention or evaluate the effect of patient rehabilitation. REFERENCES: 1. Poole et al., MMSE, 2016 2. Bowen et al., JTB, 2023
Read CV Hervé Di DomenicoECSS Paris 2023: OP-BM03