Sport-specific balance tests account for youth alpine skiers’ ranking

Objective: Alpine skiing requires complex motor skills and fine adjustments to maintain balance in dynamic and challenging conditions. This study aimed to understand whether the balance ability in unspecific (UST) and sport-specific (SST) tasks could depend on the skiers’ ranking level. The balance performance of the dominant and non-dominant limbs in the SST was also investigated.Methods: Twenty-five skiers (14.96 ± 1.61 yrs; 1.69 ± 0.69 m; 59.9 ± 9.52 kg) were divided into high-ranking (position < 50) and low-ranking (position > 50) groups. Subjects performed three balance conditions: static (ST), dynamic UST, and dynamic SST. Subjects stood on an unstable board over a force platform during UST. During SST, subjects wore ski boots, grasped ski poles, and each foot was clipped to an unstable board over two force plates. From the center-of-pressure (CoP) trajectory the area of the 95th percentile ellipse and the CoP mean velocity were calculated. Angular displacements were recorded by a 12-camera system, to calculate the full balance (FB), fine (FiB), and gross (GB) balance in UST and SST.Results: Balance control was higher (p < 0.01) in high-ranking than low-ranking skiers only in the SST. Kinematic parameters (i.e., FB, FiB, and GB) showed a higher (p < 0.001) balance performance in SST than UST independently from the group. Dominant and non-dominant limbs motion was similar (Pearson correlation, r = 0.97) in SST independently from the skiers’ ranking.Conclusion: High-ranking skiers showed better balance control and performance than low-ranking skiers only when the task was sport-specific. Therefore, we suggest testing balance under sport-specific conditions to discriminate the youth skiers’ abilities

THE VALIDITY OF MEASURING SKIPPING CADENCE WITH A NOVEL WEARABLE SENSOR - SINTEC SMART PATCH

The aim of this study was to test the validity of running cadence assessed with a novel smart patch designed within a SINTEC Horizon 2020 project. Participants performed 3 consecutive 20-seconds skipping with increasing intensity (slow, medium, fast). Cadence was derived from raw data from a “SINTEC” smart patch, Dytran accelerometers, and HBM bilateral force plates. Data from all devices were compared using Bland-Altman analysis and Wilcoxon signed-rank test. The mean bias between cadence measured with Dytran accelerometer and force plates with ‘’SINTEC’’ smart patch was 0.08 and -0.17 steps/min, respectively. In addition, there were no statistically significant difference between the mean cadence determined with different sensors/devices. Therefore, we can conclude that the measurement of cadence using a novel SINTEC smart patch showed good validity

Karakterizacija človeške kože s kombinacijo fototermalne radiometrije in difuzne refleksijske spektroskopije

In this thesis I combine two optical techniques to enable assessment of structure and composition of human skin in vivo: Pulsed photothermal radiometry (PPTR), which involves measurements of transient dynamics in mid-infrared emission from sample surface after exposure to a light pulse, and diffuse reflectance spectroscopy (DRS) in visible part of the spectrum. The analysis involves simultaneous fitting of measured PPTR signals and DRS spectra with corresponding predictions of a Monte Carlo model of light-tissue interaction. By using a four-layer optical model of skin (epidermis, papillary dermis, reticular dermis and subcutis) I obtain a good match between the experimental and model data when scattering properties of the epidermis and dermis are also optimized on an individual basis. The assessed parameter values correlate well with literature data and demonstrate the expected trends in controlled tests involving temporary obstruction of peripheral blood circulation using a pressure cuff, and acute as well as seasonal sun tanning. The obtained epidermal thickness values were tested by coregistration with a multiphoton microscope. Moreover, I evaluate the potential of this approach for quantitative evaluation of tattoos during laser removal treatment. For this purpose, I apply a three-layer optical model of skin consisting of epidermis, upper dermis, and bottom dermis which includes the tattoo ink. However, the involved iterative optimization of 14 skin model parameters using a numerical forward model (i.e., inverse Monte Carlo - IMC) is computationally very expensive. In order to overcome this drawback, we have constructed a very fast predictive model (PM) based on machine learning. The PM involves random forests, trained on $sim$9,000 examples computed using my forward MC model.Cilj tega doktorskega dela je določitev strukture in sestave človeške kože in vivo. V ta namen sem združila dve optični tehniki: sunkovno fototermalno radiometrijo (SFTR), ki temelji na zaznavanju infrardečega sevanja lasersko segretega vzorca in difuzno refleksijsko spektroskopijo (DRS) v vidnem delu spektra. Pri analizi sem sočasno prilagajala izmerjene PPTR signale in DRS spektre z ustreznimi napovedmi Monte Carlo modela interakcije med svetlobo in tkivom. Z uporabo štiri-plastnega modela kože (vrhnjica, zgornja in spodnja usnjica ter maščevje), pri katerem sem individualno prilagajala tudi sipalne lastnosti vrhnjice in usnjice, sem dobila dobro ujemanje med eksperimentalnimi in modelskimi podatki. Dobljene vrednosti parametrov človeške kože so zelo dobro primerljive z vrednostmi, ki jih najdemo v literaturi. Pri kontroliranih testih, kot so začasni zastoj periferne krvi z uporabo manšete za merjenje krvnega tlaka in akutna ter kronična izpostavljenost sončnemu sevanju, so vrednosti parametrov prav tako pokazale pričakovane trende. Vrednosti za debelino vrhnjice sem primerjala z vrednostmi dobljenimi z večfotonskim mikroskopom. Zgoraj opisan pristop sem uporabila tudi za kvantitativno karakterizacijo tetovaže na človeški kože med procesom laserskega odstranjevanja le-te. Za ta namen sem uporabila tri-plastni model kože sestavljen iz vrhnjice, zgornje usnjice in spodnje usnjice, ki vsebuje barvilo. Iterativna optimizacija 14 modelskih parametrov z uporabo numeričnega modela (i.e., inverzni Monte Carlo) je računsko zelo zahtevna. Da bi izboljšala to pomanjkljivost našega pristopa, smo zgradili zelo hitri napovedni model (NM), ki temelji na strojnem učenju. NM vsebuje naključne gozdove naučene na približno 9,000 primerih

The falling of a metal sphere in a liquid in a graduated cylinder

In the diploma thesis we study the dependance of the terminal velocity of a metal spherical ball that is falling in a liquid in a graduated cylinder on the diameter of the ball. When we are doing experiments in school we assume that the liquid is unconstrained. In the thesis we experimentally study under what conditions (in particular for what ratios between the diameter of the ball and the inner diameter of the cylinder) the liquid may be considered as unconstrained. We also test, if for the liquids with different viscosity the wall effect is more or less important. Experimental part of this thesis is done with steel balls of different diameters, 4 different graduated cylinders and a high-speed video camera. The experiment is done with two liquids, the first is water and the second is glycerine. The data is processed in an open source software called Tracker and for the visualisation programs Excel and Graph are used

Noninvasive monitoring of dynamical processes in bruised human skin using diffuse reflectance spectroscopy and pulsed photothermal radiometry

We have augmented a recently introduced method for noninvasive analysis of skin structure and composition and applied it to monitoring of dynamical processes in traumatic bruises. The approach combines diffuse reflectance spectroscopy in visible spectral range and pulsed photothermal radiometry. Data from both techniques are analyzed simultaneously using a numerical model of light and heat transport in a four-layer model of human skin. Compared to the earlier presented approach, the newly introduced elements include two additional chromophores (β-carotene and bilirubin), individually adjusted thickness of the papillary dermal layer, and analysis of the bruised site using baseline values assessed from intact skin in its vicinity. Analyses of traumatic bruises in three volunteers over a period of 16 days clearly indicate a gradual, yet substantial increase of the dermal blood content and reduction of its oxygenation level in the first days after injury. This is followed by the emergence of bilirubin and relaxation of all model parameters towards the values characteristic for healthy skin approximately two weeks after the injury. The assessed parameter values and time dependences are consistent with existing literature. Thus, the presented methodology offers a viable approach for objective characterization of the bruise healing process

The Validity of a Three-Dimensional Motion Capture System and the Garmin Running Dynamics Pod in Connection with an Assessment of Ground Contact Time While Running in Place

A three-dimensional motion capture system (MoCap) and the Garmin Running Dynamics Pod can be utilised to monitor a variety of dynamic parameters during running. The present investigation was designed to examine the validity of these two systems for determining ground contact times while running in place by comparing the values obtained with those provided by the bilateral force plate (gold standard). Eleven subjects completed three 20-s runs in place at self-selected rates, starting slowly, continuing at an intermediate pace, and finishing rapidly. The ground contact times obtained with both systems differed significantly from the gold standard at all three rates, as well as for all the rates combined (p &lt; 0.001 in all cases), with the smallest mean bias at the fastest step rate for both (11.5 ± 14.4 ms for MoCap and −81.5 ± 18.4 ms for Garmin). This algorithm was developed for the determination of ground contact times during normal running and was adapted here for the assessment of running in place by the MoCap, which could be one explanation for its lack of validity. In conclusion, the wearables developed for monitoring normal running cannot be assumed to be suitable for determining ground contact times while running in place.Validerad;2023;Nivå 2;2023-09-07 (joosat);Funder: Slovenian Research Agency (grant number P5-0147)CC BY 4.0 License</p

Objective monitoring of laser tattoo removal in human volunteers using an innovative optical technique

Objectives: Assess the suitability of the technique for objective monitoring of laser tattoo removal by an extended treatment protocol. Materials and Methods: One half of the tattoo in the first volunteer was treated with nanosecond and the other half with picosecond laser pulses at 1064 nm. In the second subject, four test areas were treated repeatedly using different radiant exposures from 1.5 to 6 J/cm$^2$. Measurements of diffuse reflectance spectra and photothermal radiometric transients were performed 4–20 weeks after each treatment session. Inverse Monte Carlo analysis based on a three‐layer model of tattooed skin was applied to assess the tattoo characteristics and analyze their changes. Results: The results clearly indicate a gradual reduction of the ink content and an increase of the subsurface depth of the tattoo layer with all treatments at a radiant exposure of 3 J/cm$^2$ or higher. The observed dependences on laser pulse duration, radiant exposure, and a number of treatments are in excellent agreement with visual fading of the tattoo. Conclusions: The presented methodology enables noninvasive characterization of tattoos in human skin and objective monitoring of the laser removal treatment