ECSS Paris 2023: CP-BM08
INTRODUCTION: Alpine skiing requires strength, power, and neuromuscular control due to its complex biomechanics and intense eccentric muscle contractions, particularly in the lower body. Effective training is crucial for performance optimization and injury prevention. Iso-inertial, eccentric-overload resistance training, especially using YoYo devices, has been explored for its benefits in skiing. This study compares kinematics, kinetics, and muscle activation patterns between YoYo training and alpine skiing data from the literature, highlighting biomechanical similarities and potential applications for sport-specific training. METHODS: Six moderately trained subjects performed three 20-second trials, executing lower limb flexion-extension movements to simulate skiing. Trials took place on an inertial system (YoYo, Hance, Sweden) with ski bindings. Joint angles were estimated using an Xsens system (Movella). Forces exerted were measured via four load cells (Fyearfly, 200 kg) mounted between the ski bindings and YoYo, two per side-one front, one rear. EMG sensors (MiniWave, Cometa) recorded muscular activation of the Vastus Lateralis (VL), Biceps Femoris (BF), Gastrocnemius Medialis (GM), and Tibialis Anterior (TA) bilaterally. Data were processed, cycle-averaged based on minimum knee flexion, and compared with literature. Left and right side data were averaged due to movement symmetry. RESULTS: Trunk flexion ranged from 20° ± 20° to 53° ± 11°, hip flexion from 24° ± 11° to 86° ± 22°, knee flexion from 14° ± 4° to 53° ± 7°, and ankle dorsiflexion from 6° ± 2° to 18° ± 5°. Considering forces, the anterior force varied between 0.3 ± 0.08 BW and 1 ± 0.21 BW, the posterior force between 0.2 ± 0.08 BW and 0.6 ± 0.15 BW, while the total force ranged from 0.5 ± 0.05 BW to 1.6 ± 0.32 BW. VL showed a peak activation at around 52% of the cycle, BF at 76%, GM at 90%, and TA at 42%. CONCLUSION: Greater trunk flexion ROM was observed. Hip and knee flexion angles were lower than outdoor data, while ankle dorsiflexion was comparable [1]. Max vertical forces were slightly lower, while min vertical forces were higher than outdoor [2]. TA showed a similar activation pattern with a peak slightly earlier. BF showed peak activation only during knee extension. Since no VL and GM data were available, activation was compared with synergistic muscles. VL showed a similar pattern to VM, while GM was comparable to GL [3]. The exercise can be used in training as muscle activations resemble outdoor activities, and ground reaction forces are comparable. Proper technique is crucial, as there is a tendency for lower hip and knee angles and increased trunk flexion, which may raise injury concerns. Further investigations are ongoing to compare indoor and outdoor data using a similar setup. 1. D. Heinrich et al. Front. Bioeng. Biotechnol. (2022) 2. K. Nakazato et al. J Sports Sci. Med. (2011) 3. F. Panizzolo et al. Procedia Engineering (2010)
Read CV Isacco CostaECSS Paris 2023: CP-BM08
INTRODUCTION: Cross-country races feature a mix of steep ascents, where the cyclists must generate high power to tackle the slopes, and descents, where the cyclists’ performance depends on their riding skills. To optimize the cyclist’s efficiency, the bike fitting is performed with the aim of improving performance (1). Although bike fitting is often performed on a cycling simulator without simulating various slopes, they can influence the cyclist’s pedalling. The aim of this study was to evaluate the three-dimensional kinematics at different pedalling intensities and slopes in young competitive cyclists. METHODS: Eleven off-road cyclists were recruited. Each cyclist was assessed on own bike after a bike fitting. In the first test session, each cyclist performed an incremental test with a 15 W per minute increase until exhaustion. During the test, a gas analyzer (Cortex; MetaLyzer 3B) was used to assess the VO2max. In the second test session (48 h later), each cyclist performed 4 trials of 2 minutes at different intensities (65%, 75%, 85%, 95% of the VO2max) and the bike set at a 0° slope with a 3-minute rest between trials. Subsequently, the same 4 trials were repeated with a 10° slope. For the kinematic analysis, a 3D motion capture system composed of multiple cameras positioned around the cyclist (Cycling 3DMA, STT Systems), who wore markers in certain anatomical points, was used (2). For statistical analysis, the following parameters were considered: mean ankle flexion angle at 90° (AFA), mean knee flexion angle at 180° (KFA), mean hip flexion angle (HFA), vertical hip oscillations (VHO), mean shoulder flexion angle (SFA). RESULTS: At 90°, AFA decreased between: the trials at 65% and 95% and at 0°slope (p=0.001), the trials at 65% and 95% at 10°slope (p<0.001). At 180°, KFA increased between: the trials at 65% and 75% and at a 0°slope (p=0.049), the trials at 65% and 75% at 10°slope (p=0.029). Additionally, there was a significant decrease between the trial at 65% at 0°slope and the trial at 65% at 10°slope (p=0.035). There were no VHO in the flat trials, but between the slope trials from 65% to 85% (p=0.025). A significant decrease in SFA was observed both on flat trial (between 65% and 95%, p=0.003) and on slopes (p=0.001), with no differences between flat and slope conditions. CONCLUSION: Since slope influences the pedalling kinematics and considering that cyclists generate power during ascents in cross-country races, we suggest that coaches and cycling biomechanics perform bike fitting using slopes that simulate at least a 10° slope to best reproduce racing conditions. Reference 1. Holliday W, Theo R, Fisher J, Swart J. Cycling: joint kinematics and muscle activity during differing intensities. Sports Biomech. 2023;22(5):660-74. 2. Millour G, Velásquez AT, Domingue F. A literature overview of modern biomechanical-based technologies for bike-fitting professionals and coaches. International Journal of Sports Science & Coaching. 2023;18(1):292-303.
Read CV Domenico Savio Salvatore VicariECSS Paris 2023: CP-BM08
INTRODUCTION: PURPOSE: While it is known that the electric motor provides some power, reducing the overall effort required by the cyclist [1-2], and the cadence affects the oxygen uptake in the common muscular bike [3], it is not known if, using an e-bike, the oxygen uptake is influenced by assistance, the RPMs and their interaction. This study aimed to evaluate the effects of different levels of assistance at different pedaling cadences (RPM) on oxygen uptake while riding a city e-bike. METHODS: Fourteen (8 male, 6 female) active subjects (age 27±3.4 years), were tested at three different RPMs (60 – 90 and free choice: FCC), and three different levels of assistance (no assistance A0, the lowest A1 and the highest A3) in random order. The tests were performed using a city e-bike on a bike trainer, where an external power corresponding to the anaerobic threshold previously determined for each subject (4 mmol/L: 2.6 ± 0.5 W/kg) was set. Averaged oxygen uptake (VO2) values of the last 30” of each 5-minute trial were analyzed using a two-way ANOVA followed by a post hoc test (Bonferroni). RESULTS: VO2 is influenced both by the cadence (P< 0.01) and the level of assistance (P< 0.01), but not by their interaction (P>0.05). As expected, A3 shows lower values compared with A1 and A0, with a difference of 10 ml/min/kg and 23 ml/min/kg respectively. The cadence shows higher VO2 values at 90RPMs compared with 60RPMs and FCC with a difference of 5.98 ml/min/kg (P=0.02) and 4.78 ml/min/kg (P= 0.03) respectively. Interestingly, there are no significant differences in VO2 between FCC (80 ± 10 RPMs) and 60 RPMs (P=1.00). CONCLUSION: in this study, as expected, we can see the effect of motor assistance on VO2 uptake with lower consumption at the highest assistance. Moreover, we observe that the behavior of VO2 relative to cadence is similar to that studied on a conventional muscular bike: the higher the cadence at the same power output, the greater the oxygen consumption [3]. Last, as we didn’t expect, the VO2 at FCC is very close to VO2 at 60 RPMS. Therefore, we can assume that the cadence chosen by the subjects is probably the optimal balance that combines the metabolic and muscular efforts as in the conventional bike. However, in this case, the effect of RPM on oxygen consumption may also be influenced by the properties of the electric motor of the bike, which was found to provide more power at lower RPMs. From a practical point of view, we could, therefore, suggest developing engines based on FCC cadences to ensure also the best efficiency.
Read CV Beatrice TodescoECSS Paris 2023: CP-BM08