Search

The correct assessment of the vertical jump height depends on an accurate and reliable measurement tool. This study aimed to determine the concurrent validity and reliability of the My Jump 2 app used for estimating the maximum height (MH) of the counter-movement jump (CMJ). Twenty-one male adults participated in this study. The MH of the CMJ was estimated based on the displacement of the jumper's center of mass (force platform), the displacement time of the reflective marker placed on the jumper's sacrum (smartphone, My Jump 2-DT) and the flight time of the jumper (smartphone, My Jump 2-FT). The assessment of the concurrent validity showed a poor agreement (ICC = 0.362; Bland–Altman bias = 12.4 cm) between the My Jump 2-FT and force platform (p < 0.001), and a good agreement (ICC = 0.858; Bland–Altman bias = −0.2 cm) between the My Jump 2-DT and force platform (p < 0.001). The ICC values for internal consistency (>0.9) indicated the excellent reliability of all measurement tools (p < 0.001). The findings revealed the high accuracy and good reliability of the My Jump 2 app for the new method of MH estimation for the CMJ, including the displacement time of the marker placed on the jumper's sacrum. [ABSTRACT FROM AUTHOR]

In sweep rowers, the lower extremities muscle strength translates into the driving force of the boat. Therefore, isokinetic assessment of muscle torque is used by coaches as an indicator of the level of athletes' preparation for competitions. A total of 22 elite sweep rowers performed an isokinetic test of knee joint flexors and extensors, and a test on an asymmetric ergometer with the electromyography measures. Significantly higher quadriceps peak torque was shown during the beginning than the end of the preparatory period (p < 0.05). However, there was no significant knee peak torque difference between the lower extremities (p = 0.398). In the case of the electromyography test of quadriceps, hamstrings and lumbar erector spinae, analysis demonstrated significant bioelectrical activity differences between the sides (p < 0.05). Lower values of quadriceps peak torque at the end of the preparatory period may result from a decrease in the number of power training units during the entire preparatory period. A similar muscle strength between both lower extremities seems to be the correct result in the context of injury prevention. In turn, significant bioelectrical activity differences between the sides possibly are associated with the asymmetric movement pattern in sweep rowers. [ABSTRACT FROM AUTHOR]

Introduction. The peak values of the vertical ground reaction force in the landing phase of attacks suggest a external loads of volleyball player. The high dynamic loads during landing in volleyball jumps may cause lower extremity injuries. Aim of Study. The main purpose of this study was to compare the impact forces between three different volleyball attack techniques. Material and Methods. Twelve female volleyball players (mean±standard deviation: age 22.3±4.2 years, body height 183.0±8.7 cm, body mass 74.4±10.9 kg) participated in the laboratory tests. A force platform was used to measure the ground reaction forces (GRFs) during landing in volleyball spikes. The vertical (v) component of GRF and horizontal (h) components (resultant) of GRFs, buildup index of these forces (vBIF, hBIF) and time to peak GRF (Tv, Th) were analyzed. Results. No significant differences in Tv and Th (from 0.05±0.01 s to 0.06±0.01 s) between the three volleyball jumps were demonstrated (p<0.05). Significant differences in the peak vGRF, hGRF, vBIF and hBIF between the back row attack and front row attack (23.7%, 18.2%, 38.2% and 29.7%, respectively), and between the back row attack and slide attack (21.1%, 27.3%, 28.7% and 26.4%, respectively) were found (p<0.05). The highest values of peak vGRF (3.8±0.3 BW⋅m-1), peak hGRF (1.1±0.2 BW⋅m-1), vBIF (79.4±14.6 BW⋅m-1⋅ s-1) and hBIF (21.2±7.2 BW⋅m-1⋅s-1) were obtained during landing in the back row attack (p<0.05). Conclusions. The peak vGRF and vBIF during landing in volleyball spikes ranged: from approximately 3 to 4 BW⋅m-1 (vGRF) and from approximately 50 to 80 BW⋅m-1⋅s-1 (vBIF), and were several times higher than hGRF and hBIF. Increased impact forces in spikes indicate higher external loads during landings and a greater risk of lower extremity injuries in female volleyball players. [ABSTRACT FROM AUTHOR]

Objective: It is expected that in classical ballet dancers would be able to execute all the techniques symmetrically from the right as well as from the left side of the body. This study aimed to evaluate the symmetry of kinematic parameters of hip joints, knee joints, and foot progression angle of the left and right lower extremities (LE) in five classical ballet positions, as well as the symmetry of active and passive turnout and range of passive hip external rotation., Methods: The experimental testing involved 12 female pre-professional ballet dancers. Three measurements of range of motion, made using a standard goniometer, were carried out to characterize the study group. Kinematic data of left and right LE in the five classical ballet positions were recorded using a motion capture system., Results: The comparisons revealed significantly lower (p < 0.01) hip external rotation values by 9.8% (1st position), 5.4% (2nd position), and 8.5-11.8% (3rd position) for the right LE than the left LE. Moreover for 3rd, 4th and 5th positions, there was significantly higher (p < 0.05) hip external rotation values by 7.0%-27.2% in the back LE than the front LE. In 4th position there was asymmetry in foot progression angle with significantly lower values (p < 0.01) by 5.3% in the front LE (left) than the back LE (right). In case of goniometric measurements, the results showed significantly higher (p < 0.05) passive hip external rotation values by 10.8% for the right LE than the left LE., Conclusion: The perfect ballet symmetry pursued by dancers is not in fact so ideal. The most astonishing result was the existence of statistically significant differences in hip external rotation in the case of the 1st and 2nd positions.

Purpose: The aim of this study was to establish the reference values of spatiotemporal parameters, joint angles, ground reaction forces and plantar pressure distribution collected simultaneously on the same measurement path during normal gait in a homogenous group of young, healthy women., Methods: The studied group consisted of 28 healthy women aged 21 years on average. The motion capture system BTS Smart-D, 2 AMTI force platforms and Footscan pedobarographic platform were used in this research. The 14-metre measurement path and the 6-metre distance that examined women had to walk through before entering the measurement area ensured that a natural gait pattern was recorded. Statistical analysis was performed to evaluate differences between right and left lower extremities., Results: The applied method enabled collecting several parameters regarding normal female gait biomechanics such as: spatiotemporal parameters, angle-time characteristics as well as range of motion of pelvis, hip, knee and ankle joints in gait cycle, force-time characteristics and peaks of ground reaction force components in stance phase, peak pressure and time of loading of defined foot regions in stance phase., Conclusions: The results may be used by clinicians, physiotherapists or researchers as a reference in diagnosing gait disorders or evaluating patient's walking pattern. In recent literature there are some disparities in gait parameters reference values even regarding similar research groups. These differences may arise from distinct method, slower or faster gait, other laboratory environment etc. This should be considered and more than one source of normative values should be checked when searching for reference data.

Purpose: Patient recovery after a surgical procedure depends, among other factors, on the amount of the body weight with which patient loads lower limb. Research studies report different results of the degree of body weight with which lower limb is loaded during three-point crutch gait. The aim of this study was to evaluate the level of the ground reaction forces (GRF) during crutch gait used by patients after total hip arthroplasty (THA) in the first week after discharge from the orthopaedic units., Methods: Ten female patients diagnosed with primary unilateral coxarthrosis participated in a single measurement session. In order to record kinematic and dynamic variables of this gait pattern motion analysis system was used together with two force plates. The static test of body weight distribution between lower limbs was performed on a dual-top stabilometric plate., Results: The average peak values of loading on the operated (O) limb during mid stance and terminal stance of three-point crutch gait were 64.6% and 64.3% of body weight (BW), respectively, whereas in the case of the nonoperated (NO) limb 103.5%BW and 108.8%BW, respectively. The maximum loads on the crutches were significantly higher (by 9%BW) on the NO side as compared to the O side ( p < 0.05). During the static test, average values of body weight distribution on the O and NO limb were 36%BW and 64%BW, respectively., Conclusions: The patients showed surprisingly similar level of loading on the O limb. The weight bearing on the O limb was lower during static trial than during three-point crutch gait.

Purpose: Dynamic loads during landings determined by the ground reaction forces (GRFs) may elaborate internal loads and increase the risk of overload knee injuries as a result of performing volleyball jumps many times. The study dealt with a biomechanical assessment of dynamic load indicators in female volleyball players for the motion sequence of take-off-landing in blocks and attacks., Methods: Twelve professional female volleyball players participated in the study. Blocks and attacks were filmed by two cameras. GRFs vs. time graphs were recorded with the use of a force platform. Values of dynamic load indicators in terms of the relations of peak of vertical component of GRF, build-up index of this force (BIF), and power output (P) during landing to the vGRF, BIF and P during take-off (L/T) were calculated., Results: The statistically significant ( p < 0.05) highest values of L/T indicators were found for back row attack spikes: 2.4 (vGRF), 12.2 (BIF) and 3.1 (P). In the case of blocks, slide attack spikes and attack line spikes, results of these variables were in range: 1.8÷2.1, 5.9÷7.6 and 2.1÷2.9, respectively., Conclusions: The reduction of GRFs during landings contributes to decreasing the level of the load indicators L/T which should minimize the incidence of anterior cruciate ligament and patellar tendon injuries in female volleyball players.

The study characterizes the idea behind the research project which consists in biomechanical and kinesiological analysis of three point crutch gait. The structure of the study is in part similar to an earlier publication of the authors [1], which discussed swing through gait. By defining the three point crutch gait and describing its general kinematic structure as well as synthetically analyzing the state of knowledge, the authors formulated the purpose of the study, the adopted research model - including the description of the modern and integrated measurement systems that were used and which consisted of: 2 AMTI force plates integrated into a measurement walkway, a set of 6 optoelectronic cameras of the BTS System as well as a multichannel kinesiological electromyography performed with the use of the NORAXON System. All phases of the research were characterized, presenting the adopted research protocol in its entirety.