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This case study aims to examine changes in the lower limb joint kinematic profile and performance stability induced by repeated ski runs in two world‐class alpine skiers. Two Olympic medallist alpine skiers were tested during their slalom training, with continuous recording of right knee and hip angles, along with turn time and run time. The eight runs of the training session were analysed with linear mixed models. Results showed no effect of runs repetition on performance (i.e., run and turn time; P ≥ 0.279). There was no global effect of runs repetition on minimal and maximal angles for either the knee or the hip (P > 0.151). There was an interaction between run and leg for the maximal angle of both the knee and hip (P ≤ 0.047), which increased across runs for the outside leg and decreased for the inside leg. The maximal angular velocity for both the knee and hip increased with runs repetition in extension (P ≤ 0.028). There were no overall changes in maximal angular velocity in flexion with runs repetition (P ≥ 0.264), but there was an interaction between run and leg for the knee (P < 0.001) due to faster eccentric velocities across runs for the outside leg and slower velocities for the inside leg. In conclusion, the observed joint kinematic alterations without concomitant performance impairment support the concept of multiple movement strategies in athletes to achieve similar performance, especially under fatigue conditions. [ABSTRACT FROM AUTHOR]

The purpose of the study was to assess the influence of a preceding mountain ultramarathon on the impact between the foot and the ground and the resulting soft tissue vibrations (STV). Two sessions of measurements were performed on 52 trail runners, before and just after mountain trail running races of various distances (from 40 to 171 km). Triaxial accelerometers were used to quantify the foot-ground impact (FGI) and STV of both gastrocnemius medialis (GAS) and vastus lateralis (VL) muscles during level treadmill running at 10 km·h−1. A continuous wavelet transform was used to analyze the acceleration signals in the time–frequency domain, and the maps of coefficients as well as the frequency and damping properties of STV were computed. Fatigue was assessed from isometric maximal voluntary contraction force loss of knee extensors (KE) and plantar flexors (PF) after each race. Statistical nonParametric Mapping and linear mixed models were used to compare the means between the data obtained before and after the races. FGI amplitude and GAS STV were not modified after the race, while VL STV amplitude, frequency and damping significantly decreased whatever the running distance. A significant force loss was observed for the PF (26 ± 14%) and KE (27 ± 16%), but this was not correlated to the changes observed in STV. These results might reveal a protection mechanism of the muscles, indicating that biomechanical and/or physiological adaptations may occur in mountain ultramarathons to limit STV and muscle damage of knee extensors. Trial registration: ClinicalTrials.gov identifier: NCT04025138.. Trail running races with distances from 40 to 171 km induced the same alterations of soft-tissue vibrations. Due to the hilly characteristics of trail running, only the vastus lateralis soft-tissue vibrations were affected by the races. Vastus lateralis vibration amplitude, frequency and damping coefficient were reduced after trail running races. These modifications can arise from a protection mechanism and/or modification in the muscle properties. Neuromuscular fatigue quantified with loss of maximal isometric force production is not predictive of soft-tissue vibration modifications. [ABSTRACT FROM AUTHOR]

Cyclists are exposed for a long period to continuous vibrations. When a muscle is exposed to vibration, its efficiency decreases, the onset of fatigue occurs sooner, and the comfort of the cyclist is reduced. This study characterised the vastus lateralis (VL) soft tissue vibrations for different input frequencies and different pedalling phases. Ten cyclists were recruited to pedal at 55, 70, 85, and 100 rpm on a vibrating cycle ergometer that induced vibrations at frequencies ranging from 14.4 Hz (55 rpm) to 26.3 Hz (100 rpm). The VL vibration amplitude was quantified with a continuous wavelet transform and expressed as a function of the crank angle. The pedalling cycle was split into four phases (downstroke, backstroke, upstroke, and overstroke) to express the mean vibration amplitude and frequency of each phase. Statistical analysis depicted that VL vibration frequency increased with the pedalling cadence and that the VL was exposed to up to 50% more vibration amplitudes during the downstroke phase at a slow cadence. The increase in the pedal vibration frequency, a higher vibration transmission due to greater normal force on the pedal, and strong activation of the VL during the downstroke phase were discussed to explain these results. [ABSTRACT FROM AUTHOR]

Self-myofascial release (SMR) is a popular method to potentially increase the compliance and extensibility of the fascia and reduce muscle stiffness. The purpose of this study was to examine the acute effects of posterior muscle chain SMR on flexibility, vertical jump performance and balance ability. Eighteen young participants volunteered to take part in this crossover design study. They performed two self-massage sessions in randomized order separated by at least one week. One session consisted of posterior muscle chain SMR whereas the other one was performed on the upper limbs as a control intervention (CON). Flexibility was measured with the Toe Touch Test (TTT), Weight-Bearing Lunge Test (WBLT), and Straight Leg Raise Test (SLR). Jump performance was evaluated during a squat jump, a counter movement jump and a stiffness jump. Dynamic balance ability was assessed through the Star Excursion Balance Test. All these variables were measured before and after each intervention. A significant increase in flexibility (+3.5 ± 1.8 cm, +1.6 ± 1.0°, and +7.7 ± 4.0° for the TTT, WLBT, and SLR, respectively, p < 0.003) and balance performance (4.8 ± 3.9 cm, p < 0.003) was observed following SMR intervention compared to CON. Conversely, jumping performance was unchanged in both groups. SMR improves joint flexibility and dynamic balance ability. [ABSTRACT FROM AUTHOR]

The present study aims to determine the test-retest reliability of the input signal (INPUT) of foot impact and soft tissue vibration (STV) of the lower limb muscles during treadmill running. Twenty-six recreational runners participated in three running trials at constant velocity (10 km/h) within two days. The INPUT and STV of gastrocnemius medialis (GAS) and vastus lateralis (VL) were extracted from 100 steps measured by three triaxial accelerometers. The Intraclass Correlation Coefficient (ICC) was calculated to determine the Intra-trial and Inter-day reliability of the different variables. Intra-trial reliability results indicated that most of the INPUT and GAS STV parameters, except for damping coefficient and setting time, have good to excellent reliability (0.75 < ICC < 0.9) from the beginning of the run (10 steps) to the end. In contrast, only 4 VL STV parameters showed good reliability. Furthermore, inter-trial reliability measured on day one showed that the number of reliable parameters reduced, especially for VL STV, and more steps were required (20 < steps < 80) to achieve good reliability. Inter-day reliability results showed that only one VL STV parameter reached good reliability. Therefore, the present results show that the measurement of the foot impact and the calf muscle vibrations present a good to excellent reliability measured on a single trial and two trials carried out on the same day. The reliability of these parameters remains good when comparing two days of experimentation. We recommend measuring impact and STV parameters during treadmill running in the same session. [ABSTRACT FROM AUTHOR]