Variability of unilateral and bilateral isometric muscle strength of lower extremities extensors in young females and males.

BACKGROUND: The muscle strength of the lower extremity extensors can be evaluated in the closed kinetic chain (CKC) during unilateral or bilateral conditions. Factors such as the mass and length of the muscle, joint angle, type of contraction, and gender influence the magnitude of the muscle strength. The aim of this study was to compare the isometric strength of lower extremity extensors between the different knee extension angles (KEs) as well as between bilateral and unilateral conditions. METHODS: Nineteen female students (age: 20.2 ± 0.6 years) and nineteen male students (age: 20.3 ± 0.7 years) participated in the study. The muscle strength was evaluated in CKC using the strain gauge dynamometer. The analysis included values of the maximum muscle strength normalized to body mass (MS/BM) for the six KEs of 80°, 70°, 60°, 50°, 40° and 30°. RESULTS: A significant main effect in the MS/BM values for the angle factor (p < 0.001) and condition factor (p < 0.001) was found. Moreover, there was a non-significant interaction effect between the angle factor and gender factor (p = 0.476) as well as between the condition factor and gender factor (p = 0.770). Comparisons showed significant differences in the MS/BM values between the six KEs (p < 0.001). Furthermore, significantly lower MS/BM values for bilateral conditions than unilateral conditions at the 30° KE were observed (p < 0.001). CONCLUSION: The decrease in KE by 10° significantly increased the muscle strength of the lower extremity extensors. Gender did not affect the change in MS/BM values with the change in KE and conditions. Findings also revealed significant bilateral deficit, i.e., significantly a lower summed muscle strength during bilateral conditions than unilateral conditions. The study emphasized the importance of selecting the 30° KE as the optimal angle to assess the maximum strength developed in CKC.

Is the Symmetry of Classical Ballet Positions Perfect?

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.

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.

Lower Extremities Strength Differences in Female Volleyball Players With Stage 1 Patellar Tendinopathy.

ABSTRACT: Kabacinski, J, Murawa, M, Fryzowicz, A, Gorwa, J, and Dworak, LB. Lower extremities strength differences in female volleyball players with stage 1 patellar tendinopathy. J Strength Cond Res 36(8): 2230-2235, 2022-The main purpose of the study was to compare the muscle strength between the involved knee (IK) and uninvolved knee (UK) in 12 female volleyball players with stage 1 chronic patellar tendinopathy. Evaluation included the isometric maximal strength to body mass (MS/BM) of the lower extremities extensors for unilateral and bilateral conditions, concentric isokinetic peak torque to body mass (PT/BM) of the hamstrings and quadriceps at 60°·s -1 and 180°·s -1 , IK to UK extensors maximal strength ratio (SR), IK to UK hamstrings (or quadriceps) peak torque ratio (TR), and hamstrings to quadriceps peak TR (H/Q). The results indicated a significantly lower unilateral and bilateral MS/BM of lower extremities extensors for IK than UK ( p < 0.001). However, there were no significant differences in SR variable between the unilateral condition and bilateral condition ( p = 0.448). Only at the 60°·s -1 velocity, significantly lower quadriceps PT/BM for IK compared with the UK ( p < 0.001) and the control group ( p < 0.001) were observed. Torque ratio related to the quadriceps group was significantly lower at 60°·s -1 than 180°·s -1 ( p = 0.004). Furthermore, significantly higher H/Q for IK compared with UK ( p < 0.001) and control group ( p = 0.008) only at 60°·s -1 was found. These findings show a significant isometric strength asymmetry for both unilateral and bilateral conditions and a significant concentric strength asymmetry at the low velocity. This study suggests strengthening the weaker quadriceps group and balancing the strength between hamstrings and quadriceps within the knee with patellar tendinopathy.

Comparison of isokinetic knee torque and bioelectrical activity for hamstrings, quadriceps and erector spinae muscles in elite rowers.

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.

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.

Muscle activation varies between high-bar and low-bar back squat.

BACKGROUND: Differences in the muscular activity between the high-bar back squat (HBBS) and the low-bar back squat (LBBS) on the same representative group of experienced powerlifters are still scarcely investigated. The main purpose of the study was to compare the normalized bioelectrical activity and maximal angles within single homogeneous group between the HBBS and LBBS for 60% one repetition maximum (1RM), 65% 1RM and 70% 1RM. METHODS: Twelve healthy men (age 24.3  ± 2.8 years, height 178.8  ± 5.6 cm, body mass 88.3  ± 11.5 kg), experienced in powerlifting performed HBBS and LBBS with comparable external loads equal 60% 1RM, 65% 1RM, and 70% 1RM. Electromyography (EMG) signals of muscle groups were synchronously recorded alongside kinematic data (joints angle) by means of a motion capture system. RESULTS: EMG activity during eccentric phase of squat motion were significantly higher during LBBS than in HBBS for all selected muscles (60% 1RM and 65% 1RM) (p < 0.05). All examined muscles were more activated during concentric phase of the squat cycle (p < 0.05). In the concentric phase, significant differences between the loads were generally not observed between just 5% 1RM change in load level for LBBS. CONCLUSIONS: Our results confirmed significant differences in muscles activation between both squat techniques. Muscle activity during eccentric phase of squat motion were significantly higher during LBBS than HBBS. The differences are crucial for posterior muscle chain during eccentric phase of squat cycle.

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.

On the track of the ideal turnout: Electromyographic and kinematic analysis of the five classical ballet positions.

The turnout of the lower extremities is the major component of the classical ballet positions (CPs) and correctly is initiated in the hips. The aim of this research was to determine the differences in the electromyographic and kinematic variables in the five CPs in ballet students with greater and lesser amount of passive hip external rotation (HER). A group of 14 female pre-professional ballet dancers 11-16 years of age participated in the study. Based on the amount of passive HER, participants with higher values made up greater rotation group (n = 7) whereas those with lesser values formed lesser rotation group (n = 7). Electromyographic activity of 14 muscles from right side of the trunk and right lower extremity was recorded with the surface electrodes while subjects were standing in all five CPs (CP1-CP5). The external rotation of the hips, knees and feet were recorded with the motion capture system. The kinematic differences between the groups were revealed in asymmetric positions CP4 and CP5 where foot progression angle was significantly lesser in forward than backward setting only in lesser rotation group. In lesser rotation group the ankle and back muscles were more engaged in CPs while abdominal and hip muscles less when compared with greater rotation group. This finding suggests that in the group with lesser passive HER the mechanism of forced turnout was employed. The most remarkable finding in our work was that various electromyographic patterns can be observed between groups in all CPs, while kinematic differences may be marked only in asymmetric positions.

Which of the five classical ballet positions is the most demanding for the dancer's body? An electromyography-based study to determine muscular activity.

PURPOSE: The study aimed to determine which of the five classical ballet positions is the most demanding regarding muscular activity, values of external rotation in the hip joints, angular values of foot progression as well as the inclination (tilt) of the pelvis in the sagittal plane. METHODS: In this cross-sectional study, 14 female pre-professional ballet dancers (aged 11-16) participated. Participants were tasked with the sequential adoption of five classical ballet positions (CP1-CP5). The electromyographic activity of the muscles of the trunk and the lower limb was recorded with surface electrodes. Kinematic data including hip and knee external rotation, foot progression angle and pelvic tilt were collected using a motion capture system. RESULTS: Symmetric positions CP1 and CP2 were not as demanding as asymmetric CP3-CP5. Higher values of hip and foot external rotation without greater muscular effort in CP2 than CP1 was noticed. Considering asymmetric positions, CP3 did not trigger a greater activity of hip or foot muscular groups than CP4 and CP5. CP4 was characterised by the greatest pelvic anterior tilt and the lowest activity of GM in the forward lower limb. In CP5, forward lower limb entailed a higher activity of muscles supporting the foot than in the remaining positions. CONCLUSION: In terms of biomechanics, the most demanding classical ballet position in pre-professional dancers is CP4, followed by CP5, CP3, CP1 and CP2. This finding can be applied in educational methodology of dancers, figure skaters, synchronized swimmers, acrobatic gymnasts, rhythmic gymnasts or cheerleaders.

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.

Knee strength ratios in competitive female athletes.

Knee strength ratios are related to the movement patterns, sport-specific training and knee injuries in athletes. The purpose of this study was to determine the ratios in the concentric isokinetic strength of the hamstrings and quadriceps and the isometric strength of the knee extensors. In female basketball players (n = 14) and female volleyball players (n = 12) were evaluated: the hamstrings to quadriceps peak torque ratio (H/Q) and side-to-side peak torque ratio (TR) for hamstrings and quadriceps; the ratio of the maximal bilateral strength to the summed maximal unilateral strength (B/U) and side-to-side maximal strength ratio (SR) for knee extensors. For the H/Q values, a 2 × 2 × 3 mixed-factorial analysis of variance and Bonferroni post hoc test were computed. The H/Q values increased from 48.0 (3.9)% at 60°/s to 70.4 (7.9)% at 300°/s. Furthermore, there were significant differences in the H/Q values between 300°/s and 180°/s, 300°/s and 60°/s in basketball and volleyball athletes, and between 180°/s and 60°/s only in basketball athletes (p < .05). Significantly higher H/Q results at 60°/s demonstrated basketball players than volleyball players (p < .05). Differences in the TR and SR mean values ranged from 4.4% to 8.6% and indicated no significant side-to-side strength deficits (p > .05). In both groups, greater isometric strength developed bilaterally was found (B/U > 100%). The findings revealed the magnitude of knee strength ratios in female athletes determined by sport-specific movements in basketball and volleyball. This study highlighted the importance of the bilateral strength deficit and muscular balance between the hamstrings and quadriceps in basketball and volleyball athletes in activities related to their movement patterns and specific training.

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.

[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.