Relationship between Isokinetic Knee Strength and Speed, Agility, and Explosive Power in Elite Soccer Players.

The aim of this study was to determine the relationship between the isokinetic characteristics of knee extensors and flexors with selected motor abilities: Speed, agility, and explosive power of lower extremities of professional football players in the preparation period of a yearly training cycle. Twenty-one players (age: 24.5 ± 3.9 years; body mass: 76.7 ± 4.7 kg and body height: 183.5 ± 5.5 cm) playing in the highest Polish soccer league participated in the study. The isokinetic concentric torque of the knee extensors and flexors was measured at 300°/s, 180°/s, and 60°/s velocities. Sprint performance was assessed in the 30 m sprint test (standing start). The forward, lateral, and backward movements were assessed using the T-Test of agility. Explosive power was quantified by performing the squat jump (SJ) and countermovement (CMJ), using the force platform. Due to sport-specific demands of soccer activities measured in this experiment, the relationships between peak torque (PT) and the 30 m sprint, T-Test of agility, and power of vertical jumps (SJ and CMJ) were low or medium at speeds of 60°/s and 300°/s. One of the main reasons for the lack of high dependence of the above-mentioned factors are that the measurements were performed during the initial training period where the level of individual abilities is at a low level. Additionally, this experiment may also indicate that the measurement of isokinetic knee flexion and extension peak is effective when performed at the correct angular velocity in relation to the evaluation of the intended motion structure.

Isokinetic and Isometric Assessment of the Knee Joint Extensors and Flexors of Professional Volleyball Players.

PURPOSE: The main objective of this study was to evaluate the level of muscle strength by using isokinetic and isometric measurements-more specifically, the force ratio between the knee flexors and extensors (values of the torques). METHODS: An experimental group of elite volleyball players (n = 14) were compared to a control group (n = 14) of healthy non-athletes of comparable ages. Torque measurements were obtained under three concentric conditions (angular velocities of 60 °/s, 180 °/s, and 300 °/s) and one static condition by utilizing the Biodex System 3. RESULTS: In all trials, the volleyball players achieved significantly higher peak torque (PT) values for both the extensors and flexors (p < 0.05) than those of the control group. However, the strength ratio of the flexors and extensors (H/Q) in the experimental group was only 83% of the standard reported in the literature. The most developed and dominating muscles in the knee joints of the volleyball players were the extensors, which accounted for the low strength ratio and dynamic instability of this joint. CONCLUSION: Based on a proper assessment of the strength ratio of the knee flexors and extensors, properly selected and implemented resistance training can improve the maximum strength and power production and reduce the incidence of injuries in volleyball.

Biomechanical evaluation of swing-through crutch gait in patients with lower extremity injury.

PURPOSE: The main purpose was to determine the values of spatio-temporal parameters and ground reaction forces during the swingthrough crutch gait. METHODS: Eighteen male patients with unilateral injury within the foot, ankle or shank (age: 25.4 ± 7.7 years, body height: 1.79 ± 0.06 m, body mass: 76.1 ± 11.5 kg) participated in the study. In the experiment, 6-camera optoelectronic motion capture system and force platform were used. The measurements of spatio-temporal parameters and ground reaction force (GRF) were performed for uninjured lower extremity (ULE), crutch on the ULE side (CrU) and crutch on the injured lower extremity side (CrI). RESULTS: Analysis demonstrated a significantly longer stance phase and a significantly shorter swing phase for ULE than crutches ( p < 0.05), and a significantly longer first, compared to the second, double support phase ( p < 0.05). Comparisons showed also significantly higher maximum values of the vertical GRF and extreme values of the horizontal antero-posterior GRF for ULE than crutches ( p < 0.05) as well as for CrI than CrU ( p < 0.05). CONCLUSIONS: The present study provides biomechanical data related to the spatio-temporal parameters and GRFs for the swing-through crutch gait in patients with the lower extremity injuries.

Reference values of spatiotemporal parameters, joint angles, ground reaction forces, and plantar pressure distribution during normal gait in young women.

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.

Dynamic parameters of three-point crutch gait in female patients after total hip arthroplasty.

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.

Dynamic load indicators for take-off-landing sequence in blocks and attacks of elite female volleyball players.

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.

A comparison of take-off dynamics during three different spikes, block and counter-movement jump in female volleyball players.

BACKGROUND: The purpose of the study was to compare the take-off dynamics in counter-movement jump (CMJ), volleyball block and spikes. METHODS: Twelve professional female players, representing the highest volleyball league in Poland, participated in the laboratory tests. A force platform was used to record ground reaction force (GRF) during take-off phase in CMJ test, block from a run-up and spikes: front row attack, slide attack, back row attack. Vertical (v) GRF (peak: Rmax and integral mean: ), impulse of vGRF (J) and mechanical power (peak: Pmax and integral mean:

) were analyzed. RESULTS: Significant differences (P<0.05) of values of the dynamic parameters (Rmax, , J, Pmax, and

) were found between CMJ, block from a run-up and three different technique spikes. The highest values were recorded during take-off in the back row attack: peak vGRF (2.93±0.05 BW), integral mean vGRF (1.90±0.08 BW), impulse of vGRF (354±40 Ns), peak power (5320±918 W) and integral mean power (3604±683 W). Peak power (2608±217 W) and integral mean power (1417±94 W) were determined in CMJ test to evaluate the force-velocity capabilities of the players. CONCLUSIONS: In terms of GRF and the mechanical power, high level of dynamics in take-off influences positively the jumping height and significantly increases the effectiveness of attacks during spike of the ball over the block of the opponent.

Three point crutch gait from the perspective of biomechanics and kinesiology. State of knowledge and idea behind the research.

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.

[Analysis of knee joint injuries of competitive volleyball players in selected sports clubs of Poznan city--biomechanical context. Synthesis--proposal for the usage of physiotherapy methods in the prevention of the discussed injuries]. / Analiza urazów stawu kolanowego u trenujacych wyczynowo pilke siatkowa w wybranych klubach poznanskich--kontekst biomechaniczny. Synteza problemu--propozycja wykorzystania metod fizjoterapeutycznych w profilaktyce omawianych urazów.

INTRODUCTION: Volleyball is a source of direct injuries and chronic overloads of the joints, which indirectly results in traumas and permanent dysfunctions. This applies particularly to: knee joints, ankle joints, shoulder joints and small joints of the hand, as well as the joints of the lower spine regions. Each league team should employ a physiotherapist who would be responsible for the implementation of an injury prevention program as well as for choosing the right training loads. PURPOSE: The purpose of this study is to analyze the frequency and the type of knee joint injuries occurring in people practicing Volleyball at competitive level as well as to propose the usage of elements of modern physiotherapy in order to prevent these injuries. MATERIAL AND METHODS: The tests were performed over a group of 19 volleyball players from Poznan. In order to propose measures that would prevent injuries, the authors carried out a review of modern physiotherapy methods and suggested the implementation of certain therapeutic techniques for the region of the knee joint. RESULT ANALYSIS AND DISCUSSION: As much as 79% of the subjects reported having chronic pain and knee joint injuries in the past. All of them, due to their conditions, declared having used various forms of physiotherapy treatment. It seems that in a professional sports club not only the presence of a massage therapist but first of all a qualified physiotherapist is indispensable.

[Swing-through gait from the perspective of biomechanics and kinesiology. Critical analysis of the current state of knowledge and the idea behind the research]. / Chód kangurowy z perspektywy biomechaniki i kinezjologii. Krytyczna analiza stanu wiedzy i koncepcja badan.

The study defines the idea behind the research project which analyzes the swing-through gait from the biomechanical and kinesiological perspective. In the preliminary phase, the authors performed a synthetic analysis of the state of knowledge, created a description of the general kinematic structure of the swing-through gait as a form of locomotion with the use of crutches, proposed definitions. The problem was described with the use of time characteristics of vertical and horizontal anterior-posterior as well as lateral components of ground reaction forces, measured from under the supporting limb and the crutches. Presenting the idea behind the research project, the authors defined in detail the purpose of the study, the assumptions, research methodology--including a description of methods used and the measurement channels which consisted of: 2 AMTI force platforms integrated into a measurement walkway, a set of 6 optoelectronic cameras of the BTS System as well as a multichannel kinesiologic electromyography performed with the use of the NORAXON System. All phases of the research were characterized, presenting the research protocol in its entirety. The research will be conducted in the Laboratory of the Department of Biomechanics of USPS in Poznan, which possesses the ISO 9001:2008 quality management system certificate.