@article{Fonda2021,

title = {The medial‐lateral pedal force component correlates with q‐angle during steady‐state cycling at different workloads and cadences},

author = {Borut Fonda and Jan Babi\v{c} and Nejc \v{S}arabon},

doi = {10.3390/app11031004},

issn = {20763417},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {Applied Sciences (Switzerland)},

volume = {11},

number = {3},

pages = {1--8},

abstract = {Leg movement during cycling is constrained to the pedal/crank path and predominantly occurs in a sagittal plane. Medial‐lateral force (FML) applied to the pedals is considered as a waste and does not contribute to the pedaling. The aim of this study was to examine the changes in FML across different cadences and workloads, and to examine the correlation with lateral knee movement (Q‐angle). Twenty‐two cyclists completed six trials at three workloads (2, 2.5 and 3 W/kg) and three cadences (75, 85, 95 rpm). Forces were recorded from the force pedal mounted to the left side. Absolute and normalized (to the peak total force) FML were compared across conditions and crosscorrelation with Q‐angle was calculated. Absolute FML was significantly different across cadences and workloads (p \< 0.05) with higher absolute FML at higher cadence. There was no significant difference in normalized FML across the three cadences. There was a significant decrease in normalized FML ($sim$10 N) at higher workloads. Statistically significant correlations were found between the FML and Q‐angle (R = 0.70\textendash0.77). The results demonstrate the link between the FML and Q‐ angle in healthy pain‐free cyclists during stationary cycling. It has also been observed that smaller normalized magnitude of the FML is present when the force effectiveness is increased.},

keywords = {Ergonomy, Human Performance Augmentation, Sport},

pubstate = {published},

tppubtype = {article}

}

@article{Sever2021,

title = {Postural responses to sudden horizontal perturbations in tai chi practitioners},

author = {Jernej Sever and Jan Babi\v{c} and \v{Z}iga Kozinc and Nejc \v{S}arabon},

doi = {10.3390/ijerph18052692},

issn = {16604601},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {International Journal of Environmental Research and Public Health},

volume = {18},

number = {5},

pages = {1--12},

abstract = {Tai Chi has been shown to elicit numerous positive effects on health and well-being. In this study, we examined reactive postural control after sudden unloading horizontal perturbations, which resembled situations encountered during Tai Chi. The study involved 20 participants, 10 in the Tai Chi group (age: 37.4 ± 7.8 years), who had been regularly training the push-hand technique for at least 7 years, and 10 in the control group, consisting of healthy adults (age: 28.8 ± 5.0). Perturbations were applied at three different positions (hips, shoulders, and arms) via the load-release paradigm. Twenty measurements were carried out for each perturbation position. We measured peak vertical and horizontal forces on the ground (expressed percentage of body mass (%BM)), peak center of pressure displacement and peak horizontal and vertical velocities at the knee, hip and shoulder joints. The Tai Chi group exhibited smaller increases in vertical ground reaction forces when perturbations were applied at the hips (11.5 ± 2.1 vs. 19.6 ± 5.5 %BW; p = 0.002) and the arms (14.1 ± 4.2 vs. 23.2 ± 8.4 %BW; p = 0.005). They also responded with higher horizontal force increase after hip perturbation (16.2 ± 3.2 vs. 13.1 ± 2.5 %BW; p \< 0.001). Similar findings were found when observing various outcomes related to velocities of vertical movement. The Tai Chi group also showed lower speeds of backward movement of the knee (p = 0.005\textendash0.009) after hip (0.49 ± 0.13 vs. 0.85 ± 0.14 m/s; p = 0.005) and arm perturbations (0.97 ± 0.18 vs. 1.71 ± 0.29 m/s; p = 0.005). Center of pressure displacements were similar between groups. Our study demonstrated that engaging in Tai Chi could be beneficial to reactive postural responses after sudden perturbations in a horizontal direction; however, future interventional studies are needed to directly confirm this. Moreover, because of the age difference between the groups, some confounding effects of age cannot be ruled out.},

keywords = {Kinematics, Neuromusculoskeletal Modelling, Postural Balance, Sport},

pubstate = {published},

tppubtype = {article}

}

@article{Trost2021,

title = {A system to measure the human body asymmetries using accelerometers},

author = {Andrej Tro\v{s}t and Marko Jam\v{s}ek and Nejc \v{S}arabon and Jan Babi\v{c}},

url = {https://ev.fe.uni-lj.si/5-2021/Trost.pdf},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {Elektrotehniski Vestnik/Electrotechnical Review},

volume = {88},

number = {5},

pages = {267--272},

abstract = {In sports, acute and chronic injuries of athletes are common despite the growing knowledge and interest in the preventive activity in the sports practice. One of the main causes of injuries in athletes are their body asymmetries, which can only be dealt with if properly quantified. Despite the availability of several measuring systems, the majority of them do not allow segmental measurements and those that do are not portable. To solve the issue, a portable measuring system to measure the body asymmetries of the lower part of the human body was designed and manufactured. It measures and stores the data acquired by six accelerometers attached at the foot, tibia and pelvis of the human both legs. The system is compact, lightweight, portable and allowing a local data storage on the measuring device itself and triggering external signal to start the data acquisition. The system is driven by a sophisticated microcontroller that ensures data sampling at a high sampling rate. Results of a preliminary experimental system evaluation and validation are positive and encouraging for its further development and enhancement.},

keywords = {Exoskeleton Design and Control, Sport},

pubstate = {published},

tppubtype = {article}

}

@article{Sarabon2019,

title = {Effect of rowing ergometer compliance on biomechanical and physiological indicators during simulated 2,000-metre race},

author = {Nejc \v{S}arabon and \v{Z}iga Kozinc and Jan Babi\v{c} and Goran Markovi\'{c}},

year  = {2019},

date = {2019-01-01},

urldate = {2019-01-01},

journal = {Journal of Sports Science and Medicine},

volume = {18},

pages = {264--270},

abstract = {This study compared biomechanical characteristics and physiological responses during rowing on three devices: (i) stable ergometer (STE), (ii) transversally compliant ergometer (TCE) and (iii) frontally compliant ergometer (FCE). Eleven young competitive rowers completed a 2000 meter simulated race under each of the ergometer conditions in a randomized order. Stroke rate, average force, power output, velocity and amplitude of the handle and stretcher or seat, heart rate and blood lactate were measured at 500 m intervals. Force and power at the stretcher were significantly lower (p \< 0.03) for TCE, while stroke rate and velocities of the handle and the seat were higher (p \< 0.01). No significant differences were observed between STE and FCE in biomechanical parameters. The lowest rowing performance was observed in FCE (p = 0.007), and was accompanied with the highest average heart rate (p = 0.031). Our findings indicate that in TCE, rowers modified their technique, but were able to maintain physiological strain and performance. In contrast, FCE had no effect on rowing biomechanics, but decreased rowing performance and increased physiological strain. It seems plausible that transversal, but not frontal compliance, elicited a biomechanical technique that might reduce the discrepancy between a rowing ergometer and on-water rowing.},

keywords = {Ergonomy, Neuromusculoskeletal Modelling, Sport},

pubstate = {published},

tppubtype = {article}

}

@article{Zorko2015a,

title = {The Waist Width of Skis Influences the Kinematics of the Knee Joint in Alpine Skiing.},

author = {Martin Zorko and Bojan Nemec and Jan Babi\v{c} and Bla\v{z} Le\v{s}nik and Matej Supej},

url = {https://www.jssm.org/hfabst.php?id=jssm-14-606.xml},

issn = {1303-2968},

year  = {2015},

date = {2015-01-01},

journal = {Journal of sports science \& medicine},

volume = {14},

number = {3},

pages = {606--19},

abstract = {Recently alpine skis with a wider waist width, which medially shifts the contact between the ski edge and the snow while turning, have appeared on the market. The aim of this study was to determine the knee joint kinematics during turning while using skis of different waist widths (65mm, 88mm, 110mm). Six highly skilled skiers performed ten turns on a predefined course (similar to a giant slalom course). The relation of femur and tibia in the sagital, frontal and coronal planes was captured by using an inertial motion capture suit, and Global Navigation Satellite System was used to determine the skiers' trajectories. With respect of the outer ski the knee joint flexion, internal rotation and abduction significantly decreased with the increase of the ski waist width for the greatest part of the ski turn. The greatest abduction with the narrow ski and the greatest external rotation (lowest internal rotation) with the wide ski are probably the reflection of two different strategies of coping the biomechanical requirements in the ski turn. These changes in knee kinematics were most probably due to an active adaptation of the skier to the changed biomechanical conditions using wider skis. The results indicated that using skis with large waist widths on hard, frozen surfaces could bring the knee joint unfavorably closer to the end of the range of motion in transversal and frontal planes as well as potentially increasing the risk of degenerative knee injuries. Key pointsThe change in the skis' waist width caused a change in the knee joint movement strategies, which had a tendency to adapt the skier to different biomechanical conditions.The use of wider skis or, in particular, skis with a large waist width, on a hard or frozen surface, could unfavourably bring the knee joint closer to the end of range of motion in transversal and frontal planes as well as may potentially increase the risk of degenerative knee injuries.The overall results of the abduction and internal rotation in respect to turn radii and ground reaction forces indicated that the knee joint movements are likely one of the key points in alpine skiing techniques. However, the skiing equipment used can still significantly influence the movement strategy.},

keywords = {Human Motor Control, Sport},

pubstate = {published},

tppubtype = {article}

}

@article{Gorjanc2015,

title = {Koro\v{s}ka 8000: digit responses to cold stress following himalayan expedition to broadpeak, Pakistan (8051 m)},

author = {Jurij Gorjanc and Shawnda Morrison and Adam McDonnell and Jan Babi\v{c} and Igor B Mekjavi\'{c}},

url = {http://extremephysiolmed.biomedcentral.com/articles/10.1186/2046-7648-4-S1-A43},

doi = {10.1186/2046-7648-4-S1-A43},

issn = {2046-7648},

year  = {2015},

date = {2015-01-01},

journal = {Extreme Physiology \& Medicine},

volume = {4},

number = {Suppl 1},

pages = {A43},

abstract = {We investigated the effects chronic hypobaric hypoxia exposure would have on alpinists' physiological adapta- tions, including: aerobic fitness, body composition, haema- tological variables and digit perfusion responses to cold stress, performed before and immediately after a 35 day high altitude climbing expedition.},

keywords = {Sport},

pubstate = {published},

tppubtype = {article}

}

@article{Nemec2014,

title = {Estimation of Alpine Skier Posture Using Machine Learning Techniques},

author = {Bojan Nemec and Tadej Petri\v{c} and Jan Babi\v{c} and Matej Supej},

url = {https://www.mdpi.com/1424-8220/14/10/18898},

doi = {10.3390/s141018898},

issn = {1424-8220},

year  = {2014},

date = {2014-10-01},

journal = {Sensors},

volume = {14},

number = {10},

pages = {18898--18914},

abstract = {High precision Global Navigation Satellite System (GNSS) measurements are becoming more and more popular in alpine skiing due to the relatively undemanding setup and excellent performance. However, GNSS provides only single-point measurements that are defined with the antenna placed typically behind the skier's neck. A key issue is how to estimate other more relevant parameters of the skier's body, like the center of mass (COM) and ski trajectories. Previously, these parameters were estimated by modeling the skier's body with an inverted-pendulum model that oversimplified the skier's body. In this study, we propose two machine learning methods that overcome this shortcoming and estimate COM and skis trajectories based on a more faithful approximation of the skier's body with nine degrees-of-freedom. The first method utilizes a well-established approach of artificial neural networks, while the second method is based on a state-of-the-art statistical generalization method. Both methods were evaluated using the reference measurements obtained on a typical giant slalom course and compared with the inverted-pendulum method. Our results outperform the results of commonly used inverted-pendulum methods and demonstrate the applicability of machine learning techniques in biomechanical measurements of alpine skiing.},

keywords = {Machine Learning, Postural Balance, Sport},

pubstate = {published},

tppubtype = {article}

}