Isokinetic Knee Strength Research Articles

The Influence of Pronated Foot Posture on Knee Isokinetic Strength, Static and Dynamic Postural Stability in Healthy Young Individuals

Background: The foot is a complex body structure that plays an important role in static and dynamic situations. Previous studies have reported that altered foot posture might affect knee joint strength and postural stability, however their relationship still remains unclear. Objects: The purpose of this study was to identify whether pronated foot posture has an influence on knee isokinetic strength and static and dynamic postural stability. Methods: Forty healthy young males aged 18 to 26 years were included. Foot posture was evaluated using the Foot Posture Index-6 (FPI-6), and the subjects were divided into two groups according to their FPI-6 scores: a neutral foot group (n = 20, FPI-6 score 0 to +5) and a pronated foot group (n = 20, FPI-6 score +6 or more). Biodex Systems 3 isokinetic dynamometer was used to evaluate knee isokinetic strength and hamstring to quadriceps ratio at three angular velocities: 60°/sec, 90°/sec, and 180°/sec. The static and dynamic postural stability in a single-leg stance under the eyes-open and eyes-closed conditions were measured with a Biodex Balance System. Results: There were no significant differences between the groups in knee isokinetic strength and static postural stability (p > 0.05), but there was a significant difference in the medial– lateral stability index (MLSI) for dynamic postural stability under the eyes-closed condition (p = 0.022). The FPI-6 scores correlated significantly only with the dynamic overall stability index (OSI) and the MLSI (OSI: R = 0.344, p = 0.030; MLSI: R = 0.409, p = 0.009) under the eyesclosed condition. Conclusion: Participants with pronated foot had poorer medial–lateral dynamic stability under an eyes-closed condition than those without, and FPI-6 scores were moderately positively correlated with dynamic OSI and dynamic MLSI under the eyes-closed condition. These results suggest that pronated foot posture could induce a change in postural stability, but not in knee isokinetic strength.

Knee strength outcomes in adolescents by age and sex during late-stage rehabilitation after anterior cruciate ligament reconstruction

ObjectiveTo determine if knee strength differences exist according to age group and sex among adolescents during late-stage anterior cruciate ligament reconstruction (ACLR) rehabilitation. DesignRetrospective cohort study. MethodsConsecutive patients who had undergone ACLR with a hamstring autograft completed isokinetic knee strength assessment. Patients were categorized into early (ages 11–14 years) and middle (ages 15–17 years) adolescence. A two-way MANOVA was used to examine strength differences according to age group and sex. Results144 patients were included in the analysis (56.9% females, age = 15.3 ± 1.5 years; days since surgery = 228.2 ± 41.2). Differences in quadriceps peak torque were identified between age groups on the involved (p = 0.001) and uninvolved limbs (p < 0.001), however, no differences in quadriceps peak torque were found between age groups when normalized to body mass (p = 0.16–0.49). Differences between groups according to sex were identified for each strength outcome (p < 0.01), with decreased normalized quadriceps (12–13%) and hamstring (13–16%) peak torque for females. No interactions between age group and sex were noted, F(8, 133) = 1.48, p = 0.17. ConclusionEarly adolescents produced less quadriceps and hamstring peak torque compared to middle adolescents after ACLR. No differences were found between age groups when normalized to body mass.

LOWER QUARTER Y-BALANCE TEST SCORES ARE ASSOCIATED WITH ISOKINETIC KNEE STRENGTH

Background:Lower extremity asymmetry has been shown to be associated with increased risk of anterior cruciate ligament injury. Return-to-sport screens commonly involve assessing the restoration of symmetrical strength and balance. Therefore, it is important to understand how these measures are related.Hypothesis/Purpose:To determine if relationships exist between the Lower Quarter Y-Balance Test (LQ-YBT) component scores, composite scores, and isokinetic knee strength in healthy, female athletes.Methods:Female adolescent athletes completed the LQ-YBT and isokinetic knee strength as a part of a comprehensive evaluation in competitive level athletes (Tegner activity scale≥7). LQ-YBT anterior, posteromedial, and posterolateral component scores for the each leg were normalized to leg length, and composite scores for each leg were calculated for each participant. Knee flexion/extension strength was collected at 120°/second using a Biodex System 4. Peak torque was normalized by body weight, and paired t-tests were used to compare legs (α<0.05). Spearman correlation coefficients were calculated to test whether any LQ-YBT measures were associated to knee strength.Results:A total of 106 participants (age 13.8±2.4 years; BMI 20.2±3.0) were tested, and all were right leg dominant. No differences were found between LQ-YBT right and left component (Table 1), or composite scores (right 97.9 vs left 98.2, p=0.29). Flexion and extension strength were significantly increased on the right side (p=0.02, <0.01 respectively). There were significant, weak to moderate correlations between all LQ-YBT scores (components and composite) versus knee flexion strength (r=0.26 to 0.40) (Table 2). Left knee extension strength was weakly correlated to left anterior and posteromedial component scores (r=0.24, 0.34 respectively), as well as the left composite score (r=0.29). Right knee extension strength was only correlated to the right posteromedial component score (r=0.21) and the right composite score (r=0.22).Conclusion:Weak to moderate relationships exist between both component and composite LQ-YBT scores and knee strength. The strongest correlations were found between the LQ-YBT composite scores and knee flexion strength. LQ-YBT composite scores were relatively high, indicating a low chance of injury while differences were seen in knee strength between legs. Future injury prevention programs would benefit from utilizing both tools as the Y-Balance test evaluates motor control and isokinetic strength identifies muscular imbalance, both of which are important in reducing future injury risk.Tables/Figures:

HURDLE STEP COMPONENT SCORE FROM THE FUNCTIONAL MOVEMENT SCREEN IS ASSOCIATED WITH STRENGTH, SPEED, AND JUMP PERFORMANCE

Background:The Functional Movement Screen (FMS) is a tool designed to establish a baseline for fundamental movement capacity, highlight limitations and limb asymmetries, and identify potential injury risk. Previous research has shown that individual components of the screen are also indicative of injury risk, as well as potential predictors of athletic performance unlike the FMS composite scores. However, this literature is limited and lacks statistical power. Identifying which component scores are predictive of injury risk and athletic performance would provide a quick, powerful tool for coaches and trainers to evaluate athletes.Purpose:To determine if individual component scores of the FMS are associated with athletic performance in highly-active youth athletes.Methods:Youth athletes participated in the Specialized Athlete Functional Evaluation (SAFE) Program. Data collection was extensive, however, for the purpose of this abstract, only a selection of data was analyzed – age, BMI, years played, total number of past injuries, isokinetic knee strength, 10- and 20-meter sprint, single-leg hop (SLH) distance, and FMS scores. Seated knee flexion/extension strength was collected at 120°/second using a Biodex System 4, and peak torque was normalized by body weight. The maximum distance of three SLHs was recorded for each leg and normalized to leg length. FMS scores used for analysis included the total composite and component scores, including the deep squat, hurdle step, in-line lunge, shoulder mobility, active straight-leg raise, trunk stability push-up, and rotary stability. Wilcoxon Signed Ranks Tests were used to determine side-to-side differences, and Kruskal-Wallis tests were performed to determine differences in athletic performance based on FMS scores (α<0.05).Results:A total of 38 highly-active, youth athletes (26F; 15.4±2.6 years; BMI 21.0±5.3) were tested. Participants reported playing organized sports for 8.7±3.4 years, having 2.0±1.2 past sports-related injuries, and 74% reported specializing in a single sport. No side-to-side differences were found. While the composite FMS score significantly differed by number of past injuries (p=0.036), it was not associated with athletic performance. Alternatively, left knee strength, sprint speeds, and right hop distance significantly differed by the hurdle step component score (Table 1).Conclusion:While the composite FMS score was not an indicator of athletic performance, the hurdle step component score was associated with strength, speed, and jump performance. This individual task could be a beneficial tool for coaches and trainers when evaluating athletic ability and injury risk of athletes.Tables/Figures:

Swing Phase Mechanics of Maximal Velocity Sprints-Does Isokinetic Lower-Limb Muscle Strength Matter?

Concentric hip and eccentric knee joint mechanics affect sprint performance. Although the biarticular hamstrings combine these capacities, empirical links between swing phase mechanics and corresponding isokinetic outcome parameters are deficient. This explorative study aimed (1)to explain the variance of sprint velocity, (2)to compare maximal sprints with isokinetic tests, (3)to associate swing phase mechanics with isokinetic parameters, and (4)to quantify the relation between knee and hip joint swing phase mechanics. A total of 22 sprinters (age = 22y, height = 1.81m, weight = 77kg) performed sprints and eccentric knee flexor and concentric knee extensor tests. All exercises were captured by 10 (sprints) and 4 (isokinetics) cameras. Lower-limb muscle balance was assessed by the dynamic control ratio at the equilibrium point. The sprint velocity (9.79 [0.49]m/s) was best predicted by the maximal knee extension velocity, hip mean power (both swing phase parameters), and isokinetic peak moment of concentric quadriceps exercise (R2 = 60%). The moment of the dynamic control ratio at the equilibrium point (R2 = 39%) was the isokinetic parameter with the highest predictive power itself. Knee and hip joint mechanics affected each other during sprinting. They were significantly associated with isokinetic parameters of eccentric hamstring tests, as well as moments and angles of the dynamic control ratio at the equilibrium point, but restrictedly with concentric quadriceps exercise. The maximal sprints imposed considerably higher loads than isokinetic tests (eg,13-fold eccentric knee joint peak power). Fast sprinters demonstrated distinctive knee and hip mechanics in the late swing phase, as well as strong eccentric hamstrings, with a clear association to the musculoarticular requirements of the swing phase in sprinting. The transferability of isokinetic knee strength data to sprinting is limited inter alia due to different hip joint configurations. However, isokinetic tests quantify specific sprint-related muscular prerequisites and constitute a useful diagnostic tool due to their predicting value to sprint performance.

Evaluation of Shoulder and Knee Isokinetic Strength Profile Among Elite Adolescent Badminton Players.

Badminton continues to be a highly competitive sport where training is introduced at an early age and load has intensified. This exposes players to a greater risk of injuries, in particular when assessing related training outcomes such as strength, agonist-antagonist ratio, and bilateral deficit among adolescents where age- and sex-associated growth and development should be considered. To evaluate strength profile of the upper and lower limbs among adolescent elite Malaysian badminton players. Cross-sectional study. Laboratory. Forty-eight asymptomatic athletes (24 males and 24 females) were grouped into early and late adolescence (13-14 y old and 15-17 y old, respectively). Strength (absolute and normalized) of the external/internal rotators of the shoulder and flexor/extensor of the knee and strength derivatives, conventional strength ratio (CSR), dynamic control ratio (DCR), and bilateral deficits were measured. Males showed greater strength in all strength indices (P < .05). The older group had greater strength compared to younger for most of the upper and lower limb indices (P < .05); these effects diminished when using normalized data. For females, there was no age group effect in the shoulder and knee strength. All players displayed lower shoulder and knee normative values for CSR and DCR. Dominant and non-dominant knee strength were comparable between sex and age groups. For males, growth and maturation had a greater contribution to strength gained compared to training, whereas for females, growth, maturation, and training did not improve strength. The normalized data indicated that training did not improve all indices measured apart from external rotator strength in females. All players also displayed lower normative values of CSR and DCR. These results suggest that training in elite adolescent Malaysian badminton players lacks consideration of strength gain and injury risk factors.

Correlation of bilateral and ipsilateral strength ratios with balance in female taekwondo athletes

This study aimed to analyze preferred leg (PLs) and non-preferred leg (NPLs) isokinetic knee strength, lateral asymmetry ratios and to examine their correlation with static balance. Sixteen female taekwondo (TKD) athletes voluntarily participated in the study. Knee isokinetic extension (Ex) and flexion (Flx) strength were measured in concentric / concentric (Con / Con) contractions at angular velocities of 60°/s, 180°/s, and 240°/s. Ipsilateral hamstring / quadriceps (H/Q) and bilateral (H/H and Q /Q) ratios were calculated. Static balances were determined by taking the center of body pressure in X (COPX) and Y (COPY) axis. Paired sample t-test and Pearson correlation tests were used in statistical analysis. When the isokinetic knee strength was examined, it was found that 60°/s angular velocity parameter was significantly different in Flx phase while 180°/s and 240°/s angular velocities were found to be significantly different in Ex phase in favor of PLs. There was no significance in bilateral and ipsilateral strength ratios of all angular velocities. There was a significant correlation between 240°/s HQ and COPX in terms of ipsilateral asymmetry ratios whereas a significant correlation was found between 60°/s HH and COPX in terms of bilateral asymmetry ratios. It was found that there were differences in strength between PL and NPLs, but no asymmetry was observed. There was no high level of correlation between lateral asymmetry ratios and balance in female TKD practitioners.

Impact of Patellar Tendinopathy on Isokinetic Knee Strength and Jumps in Professional Basketball Players.

Patellar tendinopathy is characterized by tendon pain which may reduce the level of performance. This study’s main aim was to compare isokinetic knee strength and jump performances at the start of the sport season between players with patellar tendinopathy and those without. Secondary aims were to assess the relationship between knee strength and jump function. Sixty-two professional basketball players were enrolled (mean age: 25.0 ± 4.0). All players performed knee isokinetic measurements, single leg countermovement jumps, and one leg hop tests. Correlations between knee strength and jump performances were examined. Twenty-four players declared a patellar tendinopathy and were compared to the 38 players without tendinopathy. The isokinetic quadriceps strength was lower in cases of patellar tendinopathy, and a camel’s back curve was observed in 58% of the cases of patellar tendinopathy. However, jump performances were preserved. No link was found between quadriceps and hamstring limb symmetry indexes at 60 and 180°/s with jumps. This preseason screening enabled us to identify the absence of consequences of patellar tendinopathy in professional basketball players. Jump performances were not altered, possibly due to compensatory strategies.

Effects of Hip Flexion on Knee Extension and Flexion Isokinetic Angle-Specific Torques and HQ-Ratios

Background and MethodsDuring isokinetic knee strength testing, the knee flexion angles that correspond to the measured torque values are rarely considered. Additionally, the hip flexion angle during seated testing diverges from that in the majority of daily life and sporting activities. Limited information concerning the influence of hip angle, muscle contraction mode, and velocity on the isokinetic knee strength over the entire range of motion (ROM) is available.Twenty recreational athletes (10 females, 10 males; 23.3 ± 3.2 years; 72.1 ± 16.5 kg; 1.78 ± 0.07 m) were tested for isokinetic knee flexion and extension at 10° and 90° hip flexion with the following conditions: (i) concentric at 60°/s, (ii) concentric at 180°/s, and (iii) eccentric at 60°/s. The effects of hip angle, contraction mode, and velocity on angle-specific torques and HQ-ratios as well as conventional parameters (peak torques, angles at peak torque, and HQ-ratios) were analyzed using statistical parametric mapping and parametric ANOVAs, respectively.ResultsGenerally, the angle-specific and conventional torques and HQ-ratios were lower in the extended hip compared to a flexed hip joint. Thereby, in comparison to the knee extension, the torque values decreased to a greater extent during knee flexion but not consistent over the entire ROM. The torque values were greater at the lower velocity and eccentric mode, but the influence of the velocity and contraction mode were lower at shorter and greater muscle lengths, respectively.ConclusionsIsokinetic knee strength is influenced by the hip flexion angle. Therefore, a seated position during testing and training is questionable, because the hip joint is rarely flexed at 90° during daily life and sporting activities. Maximum knee strength is lower in supine position, which should be considered for training and testing. The angle-specific effects cannot be mirrored by the conventional parameters. Therefore, angle-specific analyses are recommended to obtain supplemental information and consequently to improve knee strength testing.

The relevance of whole or segmental body bioelectrical impedance phase angle and physical performance in adolescent athletes

Objective. The physical condition of athletes can be assessed easily and quantitatively using objective indicators. Bioelectrical impedance measures the phase angle (PA), representing hydration and cell function, and is a potential clinical indicator of physical condition. This study aimed to investigate the association between PA and physical performance in adolescent athletes. Approach. Overall, 170 adolescent athletes underwent a sports medical check-up, including body composition measurements and physical performance tests. Whole-body and segmental PAs (arm and leg) were determined based on body composition values. Isometric grip power and knee isokinetic muscle strength were measured as parameters of muscle strength. Counter movement jump height and squat jump height were measured as jump parameters. Associations between PA and each muscle strength or jump parameters were analysed using Pearson product-moment correlation coefficient or Spearman’s rank correlation coefficient. Main results. Whole-body and upper limb PAs were highly correlated with grip power (r = 0.70–0.80). Whole-body and lower limb PAs were correlated with knee isokinetic muscle strength (r = 0.43–0.59). Whole and all segmental PAs were correlated with counter movement jump height (r = 0.46–0.57) and squat jump height (r = 0.42–0.52). Significance. PA can be used to monitor physical condition and sports performance in adolescent athletes. Segmental PAs can help assess the condition of the corresponding body part.

Arthrogenic muscle inhibition and return to sport after arthrofibrosis complicating anterior cruciate ligament surgery

ABSTRACT Arthrofibrosis is a devastating complication after Anterior Cruciate Ligament reconstruction (ACLr) characterized by a muscle weakness secondary to an arthrogenic muscle inhibition process. The loss of knee isokinetic strength due to arthrogenic muscle inhibition may be more important after arthrofibrosis, compared to an ACLr population with no complication. The isokinetic strength deficit [Limb Symmetry Index (LSI) at 60 and 180°/s of angular speed] was measured at 4, 7 and 12 post-operative months. Knee function, return to running and return to sport were evaluated. A comparison of the Quadriceps and the Hamstring LSI between patients with arthrofibrosis and those without post-operative complication was performed according to time and taking into consideration the type of surgical procedure. 539 primary ACLr patients were assessed. The arthrofibrosis group presented at 4, 7 and 12 post-operative months a Quadriceps LSI significantly lower compared to the control group, without influence of the graft procedure (LSI: 38, 53, 68% vs 63, 73, 85% at 60°/s, respectively). The Hamstring LSI was significantly lower at 4 and 7 post-operative months, but comparable at 12 months with an influence of the Hamstring procedure. Knee function was significantly lower at 4 and 7 post-operative months. Few arthrofibrosis ACLr patients returned to running at 7 post-operative months (6.8% vs 69.9%; p < .0001). An important and durable Quadriceps muscle weakness occurred after arthrofibrosis, whatever the type of graft procedure. This is explained by an Arthrogenic muscle inhibition which compromised the return to sport at the same level until 12 post-operative months. Highlights An important and durable quadriceps muscle weakness occurred after arthrofibrosis. The arthrogenic muscle inhibition was significant on the operated side independently of the type of the graft procedure. Arthrogenic muscle inhibition compromised the return to sport at the same level until 12 post-operative months.

Isokinetic knee strength deficit in patients with moderate haemophilia.

Knee joint bleedings are responsible for quadriceps atrophy and strength deficit in patients with severe haemophilia. Little is known about patients with moderate haemophilia (PWMH). To evaluate isokinetic quadriceps and hamstrings strength in PWMH and to assess correlation with radiological and clinical parameter. 18 PWMH aged 37.1±11.4 and 18 healthy age-, weight- and height-matched controls performed a knee isokinetic test at 180°/s to assess quadriceps and hamstrings strength. In the PWMH group, knee Pettersson's score was pursued and Haemophilia Joint Health Score 2.1 (HJHS) was performed to determine unaffected knees (knee HJHS=0) and affected ones (knee HJHS >0). Affected knees had a decrease of quadriceps strength compared to controls, 1.26±0.47 vs 1.64±0.27Nm/kg and a decrease of hamstring strength, 0.60±0.29 vs 1.03±0.21Nm/kg, (P<0.001). Unaffected knees also had a decrease of quadriceps strength compared to controls, 1.36±0.31 vs 1.64±0.27Nm/kg and a decrease of hamstring strength, 0.69±0.18 vs 1.03±0.21Nm/kg, (P<0.001). The conventional hamstring-to-quadriceps ratio was significantly decreased in affected knees compared to controls, 0.46±0.15 vs 0.64±0.13 (P<0.001) but also in unaffected knees, 0.53±0.16 vs 0.64±0.13 (P=0.02).No correlation was found between strength and HJHS or Pettersson's score. PWMH have a significant knee strength deficit, both on the quadriceps and the hamstrings, which is responsible for an important muscle imbalance.

AN EVALUATION OF VERTICAL JUMP HEIGHT AND ISOKINETIC KNEE STRENGTH OF ACTIVE VOLLEYBALL AND BASKETBALL PLAYERS

Study is to evaluate the relation between vertical jump performance and isokinetic knee strength in active volleyball and basketball players. Healthy 42 players volunteered for this study. Wilcoxon Test was used to evaluate the difference between isokinetic peak torque values, for dominant and non-dominant extremities at each angular velocity, of the groups that we identified as male basketball, male volleyball, female basketball and female volleyball. The Mann-Whitney U test was used to compare the quantitative values between the two groups. It was observed that H/Q ratio of dominant extremity was lower than non-dominant extremity (p<0.05). There was no significant difference in terms of sports type in both types of jumping, but the basketball players had statistically significant high values in the measurement formulas. Muscle strength is a significant factor in both sports due to the fact that isokinetic peak torque values of quadriceps and hamstring decrease and H/Q ratio increases gradually from lower angular velocity, is indicator of maximal force to high angular velocity, is indicator of endurance. In addition, when evaluating the athlete's jump performance, not only the jump distance but also the person's height and weight should be taken into account.

The Association Between Sprint Speed Test and Isokinetic Knee Strength in Healthy Male Volleyball Players

Background: Volleyball is a sport with technical elements and explosive power. Objectives: This study investigates the relationship between sprint speed and isokinetic knee strength applied at different angular velocities in male volleyball players. Methods: This study was conducted on 15 volunteer male volleyball players (age; 17 - 25 years, height; 1.75 + 0.12 m). Isomedx 2002 isokinetic dynamometer is employed to measure the isokinetic strength, and a 20 m sprint test is conducted to measure the speed. In measuring knee flexion and isokinetic extension strength, quadriceps and hamstring concentric/eccocentric are measured separately on both legs at 60°/sec angular velocity for three repetitions, at 180°/sec for six repetitions, and at 300°/sec for nine repetitions. For statistical analysis, the Spearman’s correlation test was performed using SPSS 18.0 (SPSS Inc., USA) software. Results: The highest torque value in subjects was recorded on both sides at 60°/sec angular velocity, 180 and 300 degrees, respectively, were lower. There was no significant relationship between speed and isokinetic strength at different angular velocities. Conclusions: Based on our results, the highest peak torque in volleyball players was found to be at 60°/sec angular velocity while no significant correlation was found between isokinetic strength of the knee at different angular velocities and speed of volleyball players.

INFLUENCE OF CORE STRENGTH TRAINING ON PEAK MUSCLE TORQUE OF QUADRICEPS AND HAMSTRING IN YOUNG SOCCER PLAYERS

The purpose of the present study was to investigate the effect of eight week core strength training (CST) on quadriceps and hamstring muscle strength and H/Q ratio. The study included a total of 20 young soccer players, 10 in the experimental group (EG) and 10 in the control group (CG). Isokinetic knee strength measurements at angular velocities of 60°sec−1 , 180°sec−1 and 240°sec−1 were performed on the subjects. Independent sample t-test and 2x2 ANOVA test were used for statistical analysis. No significance was found between the pre-test results of both EG and CG (p&gt;0.05). In post-test results, a difference was found in favour of EG group in RPM 60o EX value (p&lt;0.05). When the pre-test and posttest results of the groups were compared separately, a significant difference was found in RPM 60o EX, LPM 180o EX and LPM 240o EX parameters in EG (p&lt;0.05). A significant progress was found in LPM 180o EX, LPM 180o FLX and LPM 240o FLX values in CG (p&lt;0.05). It was found that CST applied on young soccer players affected knee isokinetic strength in different velocity and this effect caused significance especially in different angular speeds of EX phase. In addition, although significant progress was not observed in all parameters in EG after CST, it was found that there weren’t decreases in any parameters and at least strength was maintained.

Electromyographic responses of knee isokinetic and single-leg hop tests in athletes :dominant vs. non-dominant sides

ABSTRACT The purpose of the study is to perform the electromyographic (EMG) analysis of isokinetic and single-leg hop tests (SLHTs). We included 20 healthy male athletes (age: 23.18 years, height: 178.82 cm, weight: 73.76 kg and BMI: 47 kg/m2) voluntarily. Isokinetic knee strength tests at at 60°sec−1, 180°sec−1, 240°sec−1 velocities and different SLHTs; Single leg (SL), Triple leg (THD) and Crossover (CHD) hop for distance tests, 6 m timed-hop test (6 m THT), Single leg vertical jump test (VJ) were measured. Muscle activations of quadriceps (Q); vastus medialis (VM), vastus lateralis (VL), rectus femoris (RF) and hamstring (H); biceps femoris (BF) were obtained. There were significant differences in SL, THD, CHD and VJ in DS (p < 0.05).VJ revealed a statistical significance in NDS (p = 0.003). The comparison of the activations produced by the same muscles in different tests showed statistically significant differences in all the muscles for both sides (p < 0.05). In conclusion, we determined that the muscles produce similar activations in the isokinetic tests for both the DS and NDS, whereas there are differences in some of the SLHTs. The most active muscles were VM and RF (medial muscles) in isokinetic tests, and VL (lateral muscle) in SLHTs.g

Measure of efficiency and knee isokinetic strength in bike messengers and non-cyclist athletes.

Gross efficiency in cycling (GE) seems correlated with lower-body strength. This study investigated GE at four different pedaling rates and its relationship with an isokinetic strength test in bike messengers (BM) and experienced athletes non-bike messengers (NBM). Eight BM and eight NBM completed a maximal incremental test to determine maximal aerobic power (MAP) and maximal oxygen consumption (V̇O<inf>2max</inf>). GE, V̇O<inf>2</inf>, heart rate (HR) and blood lactate concentration (BLC) were measured at different cadences (60, 70, 90 and 100 rpm) during an efficiency test at 50% of MAP and participants then performed an isokinetic test of the right knee. A difference in GE (except at 90 rpm), BLC and MAP/kg was found in favor of BM. The most efficient cadence was 60 rpm in both groups. Increased cadence resulted in decreased GE and increased HR and V̇O<inf>2</inf> in both groups. BLC only increased in the NBM. We found no relationships between GE at different cadence, peak torque relative to bodyweight and muscle fatigability. This study is the first investigating performance and efficiency among BM. At equivalent power output, BM show a better GE than NBM. Those results are in line with previously described analysis in cyclists and explained by better aerobic capacity and training status. Isokinetic knee maximal strength and fatigability were not linked with GE, and thus does not appear appropriate for evaluating GE in cycling.

스피드스케이팅 남녀 선수들의 경기력 수준별 무산소성 파워 및 슬관절 등속성 근기능 특성 비교

스피드스케이팅 남녀 선수들의 경기력 수준별 무산소성 파워 및 슬관절 등속성 근기능 특성 비교

RELATIONSHIP OF ISOKINETIC LEG STRENGTH AND 2 KM TIME TRIAL ON STATIONARY ROWING ERGOMETER AMONG MALAYSIAN MALE NATIONAL ROWERS

Background: Strength of leg musculature is crucial to generate propulsive force during rowing. The purpose of this study was to determine the relationship of isokinetic dominant leg strength and 2 km time trial on stationary rowing ergometer among male national rowers. Methods: Seventeen male national rowers were recruited for the study. Their hip and knee isokinetic strength were determined in the sagittal plane at 60°/s angular velocity. The relationship between the hip and knee strength, and 2 km time trial performance were evaluated using Pearson correlation. Results: The national rowers completed the 2 km time trial duration in 7.20±0.39 minutes. The hamstring to quadriceps ratio (H:Q) was significantly correlated to 2 km time trial performance (r=-0.491, p=0.045). No other significant relationships between hip and knee isokinetic strength and 2 km time trial performance were observed. Conclusion: Increased isokinetic knee strength ratio (H:Q) may enhance 2 km time trial performance among male national rowers. Other isokinetic variables of hip and knee isokinetic strength were not significantly related to 2 km time trial.

The Relationship between Isokinetic Trunk, Leg Strength and Isometric Mid-Thigh Pull Test, Counter Movement Jump in National Rowing Athletes

OBJECTIVES The purpose of this study was to analyze the relationship between isokinetic leg strength and maximum Isometric Med-Thigh Pull Test(IMTP) and maximum height of Counter Movement Jump (CMJ) in Korean national rowers.METHODS Each eight male and female athletes were participated in the study. Isometric IMTP, CMJ, and isokinetic trunk, hip, and knee strength were measured to analyze the relationship between the IMTP, CMJ and isokinetic strength. The correlation between variables was analyzed by the step-wise method of multiple regression analysis after analyzing the correlation between dependent and independent variables.RESULTS Knee, Hip and trunk isokinetic flexion and extension strength showed high correlation with maximum IMTP with the all participants. Knee extension and trunk flexion isokinetic strength showed higher correlation with IMTP. Knee extension isokinetic strength showed high correlation with CMJ.CONCLUSIONS For strengthening exercise of National rowers, ipsilateral strength balance and agonistantagonist strength balance of leg and trunk should be considered to improve performance efficiently.