Adam Czaplicki

Introduction. The primary objective of this study was to perform a wavelet analysis of the time-course of the vertical ground reaction force acting on the forefoot (vGRF_F) during the Romberg test. The secondary objective was to conduct a time-frequency energy analysis of this signal. Material and Methods. The study included 93 female volleyball players (age: 15.29 ± 0.49 years, body height: 174.14 ± 7.36 cm, body mass: 62.67 ± 9.41 kg). The participants performed the test on a treadmill (Noraxon FDM-T) equipped with a high-resolution pressure sensor matrix. A time-frequency analysis of the signal originating from the treadmill was conducted using the Morse wavelet. Results. The average percentage contribution of signal energy in three analyzed frequency bands and the inter-band energy flow were determined as a function of eye status (open vs. closed) during the Romberg test. Conclusions. Appropriately preprocessed, the vGRF_F signal can serve as a viable alternative to traditional stabilographic metrics. It possesses high discriminative capability, particularly within the low-frequency range of 0.05 to 1 Hz.

The primary aim of this study was to evaluate the postural stability control mechanisms of young female volleyball players using wavelet analysis. The practical objective of the study was also to validate the signal derived from a baroresistive platform. The study involved 93 young female volleyball players (age: 15 years; height: 174.1 cm; body mass: 62.7 kg) and 30 female university students (age: 20.3 ± 0.6 years; height: 168 ± 3.5 cm; body mass: 61.9 ± 5.4 kg). All participants performed a standard 30-second Romberg test on an instrumented treadmill (Noraxon FDM-T) under both eyes-open and eyes-closed conditions. A time–frequency analysis of the treadmill signal was conducted using the Morse wavelet. The obtained results revealed several aspects of postural stability control in young volleyball players that may be the consequence of long-term athletic training. The treadmill signal demonstrated discriminative properties within the frequency ranges associated with visual and vestibular control.

Purpose: This study analysed the relationship between haematological indices and near-infrared spectroscopy (NIRS) parameters, as they are rarely explored. Methods: Nineteen elite male speed skaters performed a 2-min cycling time trial (TT) during which muscle oxygen saturation (SmO ₂ ) and local haemoglobin concentration (tHb _muscle ) were continuously monitored using NIRS. Haematological parameters was evaluated through (1) total haemoglobin mass (tHb _mass ), plasma volume (PV), blood volume (BV), and red cell volume (RCV), using the carbon monoxide (CO) rebreathing method, and (2) complete blood count from venous blood samples. Exploratory correlation and regression analyses were conducted to investigate potential associations between the variables. Results: Baseline SmO ₂ was not associated with any parameters, whereas tHb _muscle was positively correlated with RCV, BV, and PV ( p < 0.05). SmO₂ values exhibited three distinct phases: a descent and plateau during the TT, followed by an ascent during recovery. None of the haematological variables explained SmO ₂ variability in the entire cohort. After dividing the participants based on the median of haematological variables into low and high groups, regression analyses showed that dichotomised tHb _mass ( p < 0.01), BV ( p < 0.01), and PV ( p < 0.05) explained the variability of SmO ₂ only in the linear part of the descent phase. During recovery, half-time of local muscle reoxygenation correlated negatively with relative values of PV, BV ( p < 0.05) and tHb _mass ( p < 0.06). Conclusions: Haematological status, irrespective of the assessment method, did not appear to influence either resting SmO ₂ or SmO₂ kinetics during the time trial. However, muscle reoxygenation dynamics may be associated with haematological parameters obtained via the CO rebreathing method.

Vitamin D, calcium, and iron are micronutrients crucial for bone health. However, their effect has been studied primarily in the cortical bone, with vitamin D status being assessed mainly from the total 25(OH)D serum fraction. The study aimed to investigate the impact of vitamin D (total and free fraction) and iron status (i.e., serum ferritin or soluble transferrin receptor) and calcium intake (ADOS-Ca questionnaire) on lumbar cortical and trabecular bone. In a cohort of 113 male subjects (76 athletes, 37 non-athletes) aged 15–19, the lumbar spine status (Z-score, bone mineral apparent density (BMAD), and trabecular bone score (TBS)) was determined using dual-energy X-ray absorptiometry (DXA). Relationships between the examined micronutrients and bone health parameters were observed only in athletes. Free 25(OH)D was significantly (p < 0.001) correlated with Z-score and BMAD, while total 25(OH)D (p < 0.001) and iron status (ferritin, Fe stores; p < 0.01) correlated solely with BMAD. Free 25(OH)D and ferritin concentrations were the best determinants of bone status (R² = 0.330; p < 0.001) and explained 25% and 7% of the BMAD variance, respectively. No relationships were found between the micronutrients and TBS. The results confirmed the positive influence of vitamin D and iron on cortical, but not trabecular, bone status solely in physically active subjects. In athletes, free 25(OH)D seems to be a superior indicator of bone health to a total 25(OH)D fraction.

Introduction. Patellar instability in younger patients is a common injury (3.3% of all knee injury episodes) and the most frequent dislocation of the knee observed. The sensitivity and reliability of clinical diagnostic tests after medial patellofemoral ligament (MPFL) reconstruction remain unclear and biased. The primary aim of the present study was thus to detect, using wavelet analysis, differences in the rearfoot loading of the operated limb of patients after MPFL reconstruction. The authors hypothesised that applying this specific examination technique would allow for more accurate and less biased clinical results evaluation. Material and Methods. The study involved a group of 15 female subjects (age: 22.8 ± 6.3 years; weight: 58.5 ± 5.1 kg) after MPFL reconstruction and a control group of 29 healthy females (23.2 ± 2.8 years; 61.1 ± 7.7 kg). The subjects performed a 30-second classic Romberg test on a treadmill (Noraxon FDN-T) equipped with a matrix of baroresistive sensors to measure ground reaction forces. Time-frequency analysis of the signal originating from the treadmill was done using an analytic Morse wavelet. Results. The results indicate differences in visual control and vestibular stability in patients before and 3 months after a surgery. They are characterised by a deficit of energy attributed to visual control in favour of an excess of energy associated with vestibular control. Patellar instability patients show greater energy expenditure to maintain body balance for at least 6 months after MPFL reconstruction. Conclusions. Patellar instability patients have increased vestibular control while maintaining balance. Our results suggest an extended rehabilitation period for patients after MPFL reconstruction beyond 6 months.

A backward tucked somersault from the standing position is analyzed in this study. The used computations were based on a three-dimensional model of the human body defined in natural coordinates. The net torques and internal reactions occurring at the ankle, knee, hip, upper trunk-neck and neck-head joints were obtained by inverse dynamics. The achieved results confirmed the significant loads at the joints at the beginning of the landing phase and revealed the way the analyzed stunt was controlled. It was also shown that the natural coordinates provide a useful environment for modeling spatial biomechanical structures.

The primary aim of the current study was to determine the time curves of changes in the record scores in the snatch and its variations during a two-year training cycle in young weightlifters. This study also aimed at assessing the ratios between these scores and at predicting the snatch record scores at the end of the subsequent annual training macrocycle. The final purpose was to compare the record scores with the isometric peak torque values of the trunk and knee extensors. The study involved 16 weightlifters who were tested seven times at three-month intervals. The overall mean ratios of the record scores in the hang snatch to those in the snatch and the record scores in the hang power snatch to those in the snatch were approximately constant and amounted to 0.95 and 0.79, respectively. The overall mean ratio between the scores in the power snatch to those in the snatch was approximately 0.88. Statistically significant differences (p < 0.05) between the individual time trajectories of record scores in the snatch and its derivatives were identified in two consecutive annual training macrocycles. The error in predicting record results at the end of the following annual training macrocycle was 6.7 ± 4.7% or 8.1 ± 3.4% depending on the way the measurement data were modeled. The results of the study also indicate that the measurements of the isometric peak torque of the trunk extensors performed in laboratory conditions can be useful in diagnosing the strength capacity of young weightlifters.

The aim of this paper is to present the results of an assessment of internal loads in the joints of the lower limbs during the snatch performed by young weightlifters. A planar model of a weightlifter composed of 7 rigid segments (the lower trunk, thighs, lower legs and feet) connected by six hinge joints was used in the computations. The dynamic equations of the motion of the model were obtained using a projective technique. Kinematic data were recorded by a Vicon system with a sampling frequency of 200 Hz. The ground reactions were measured independently for the left and right limbs on two force platforms. The inverse dynamics problem was solved to assess the internal loads (the muscle forces and joint reactions) in the lower limbs. Relatively high differences in the reactions in the joints and muscle forces in the left and right lower extremities were identified. The obtained results also reveal that the snatch, a lift which tends to be geometrically symmetrical in the sagittal plane, is not necessarily characterized by symmetry of internal loads. Thus, this study has shown that a kinematics analysis of the lifter’s movement, which is commonly used to assess the technique of the snatch, is insufficient and should be supplemented with a dynamics analysis.

Purpose: The identification of activation, synchronization and work of individual muscles in the subsequent stages of lifting weights is interesting for researchers and trainers. Unfortunately, the existing methods of research do not provide such possibilities. Such information could be gathered from infrared measurements as they are non-invasive and can be carried out without the direct involvement of the weightlifter. The purpose of the study was to analyse temperature changes in the shoulder girdle in the first phase of the snatch in weightlifting. Methods: The study involved 11 weightlifters who competed in two weight categories, 94 and 105 kg, during the World University Championships in 2018. The performance of the snatch was recorded using a thermographic camera in three consecutive attempts. We analysed the temperature changes in the left and right shoulder girdles in the two initial stages of the snatch. Statistical analysis of empirical data was performed using linear mixed effects models. Results: Statistically significant temperature increases were found from the moment of gripping the barbell to the moment it was pulled. These effects were different in individual weightlifters, but did not depend on the attempt or the side of the body. Conclusions: Temperature increases in the initial phase of the snatch are most likely the result of activating successive motor units in order to perform the effort needed to pull the barbell and cause it to accelerate. The results obtained confirm that thermography is an effective method of monitoring muscle activity in weightlifting, which may be useful for coaches and athletes.