Isokinetic quadriceps training in patients with patellofemoral pain syndrome

The aims of the present investigation were (a) to evaluate the effect of eccentric quadriceps training in patients with unilateral patellofemoral pain and (b) to compare the effect of eccentric and concentric quadriceps training in patients with bilateral patellofemoral pain. Fifteen patients (9 male and 6 female, aged 17–36 years with a mean of 27.5 years) participated in this study. Nine patients had unilateral pain and trained their painful leg eccentrically, while six had bilateral pain and trained one leg eccentrically and the other concentrically. Quadriceps muscle training was performed on a Kin-Com dynamometer at 90°/s and 120°/s angular velocity twice a week for 8 weeks. Before and after the treatment period the thigh muscle torques were measured on the Kin-Com dynamometer at 60°/s, 90°/s, 120°/s and 180°/s for quadriceps and at 60°/s and 180°/s for hamstrings. Nine controls, matched for gender and age with the group with unilateral pain, were tested in the same way on the Kin-Com dynamometer. For functional evaluation a knee score was calculated before training, after 8 weeks of training and at a mean of 3.4 years after completion of the training. After 8 weeks of training and at follow-up times of 1 and 3.4 years the patients were also questioned regarding whether or not they felt improvement from the training programme. To determine the degree of knee pain during the training Borg's pain scale was used. The results showed that, compared with the controls, the patients had a significantly lower knee extensor torque in their painful leg at all velocities measured. The greatest difference was found during eccentric actions. However, in comparison with the controls there were no significant differences in eccent ic and concentric knee flexor torques. After training there was a significant increase particularly in eccentric but also in concentric torque of the knee extensor in the painful leg of the eccentrically trained group. Of the six patients in the bilateral training group there were five who increased their concentric knee extensor torque and three who increased their eccentric torque. There were no significant differences in concentric and eccentric knee flexor torques before and after training in either of the legs in both training groups. The hamstring/quadriceps ratio was significantly higher in the patients' painful leg before training. However, due to increased quadriceps strength the hamstring/quadriceps ratio dropped after training. Patients in both groups reported no pain or mild pain during the training sessions. The eccentrically trained group was significantly improved both after 8 weeks of treatment and at follow-up 3.4 years later as evaluated using the knee score. The bilaterally trained group was significantly improved 3.4 years after completion of the training programme as evaluated using the knee score.     

Isometric and isokinetic knee joint performance in Japanese alpine ski racers.

Isometric and isokinetic (concentric and eccentric, strength of alpine skiers with different performance levels were measured. Nine national (elite, EG) and 10 collegiate (trained, TG) female alpine skiers (16 to 23 years of age) performed maximal voluntary knee extension and flexion. Peak torque was measured at an angular velocity of 30 deg.s-1. The cross-sectional area (CSA) of thigh muscles (quadriceps and hamstring muscles) was determined by an ultrasonic method. No significant differences in anthropometric variables and CSA were observed between EG and TG. EG had significantly greater (p < 0.01 for extensors and p < 0.05 for flexors) eccentric knee extensor and flexor strength than that of TG whereas no significant differences were noted in isometric and concentric strength. Eccentric strength/CSA ratio was also higher for EG than for TG. It was suggested that knee extension and flexion strength during eccentric muscle action might be related to the performance level of alpine skiers.     

Effect of leg extension training on concentric and eccentric strength of quadriceps femoris muscles

Ten healthy male subjects carried out bilateral concentric leg extension training twice a week for 8 weeks. Before and after the training, maximal voluntary isometric and isokinetic strength and cross-sectional areas of the quadriceps femoris were measured. Maximal bilateral leg extension power increased significantly after the training. Isometric and concentric unilateral strength did not change significantly before and after the training, while eccentric strength at 0.52 and 1.05 rad·s⁻¹ increased after the training with no changes in cross-sectional area. The correlations between strength and cross-sectional area increased significantly after the training. It was speculated that the increase in eccentric strength of knee extensors was due to modification of the neural inhibition during eccentric muscle actions.     

Antagonist muscle coactivation during isokinetic knee extension

The aim of the present study was to quantify the amount of antagonist coactivation and the resultant moment of force generated by the hamstring muscles during maximal quadriceps contraction in slow isokinetic knee extension. The net joint moment at the knee joint and electromyographic (EMG) signals of the vastus medialis, vastus lateralis, rectus femoris muscles (quadriceps) and the biceps femoris caput longum and semitendinosus muscles (hamstrings) were obtained in 16 male subjects during maximal isokinetic knee joint extension (KinCom, ROM 90-10 degrees, 30 degrees x s(-1)). Two types of extension were performed: [1] maximal concentric quadriceps contractions and [2] maximal eccentric hamstring contractions Hamstring antagonist EMG in [1] were converted into antagonist moment based on the EMG-moment relationships determined in [2] and vice versa. Since antagonist muscle coactivation was present in both [1] and [2] a set of related equations was constructed to yield the moment/EMG relationships for the hamstring and quadriceps muscles, respectively. The equations were solved separately for every 0.05 degrees knee joint angle in the 90-10 degrees range of excursion (0 degrees = full extension) ensuring that the specificity of muscle length and internal muscle lever arms were incorporated into the moment/EMG relationships established. Substantial hamstring coactivation was observed during quadriceps agonist contraction. This resulted in a constant level of antagonist hamstring moment of about 30 Nm throughout the range of motion. In the range of 30-10 degrees from full knee extension this antagonist hamstring moment corresponded to 30-75% of the measured knee extensor moment. The level of antagonist coactivation was 3-fold higher for the lateral (Bfcl) compared to medial (ST) hamstring muscles The amount of EMG crosstalk between agonist-antagonist muscle pairs was negligible (Rxy2<0.02-0.06). The present data show that substantial antagonist coactivation of the hamstring muscles may be present during slow isokinetic knee extension. In consequence substantial antagonist flexor moments are generated. The antagonist hamstring moments potentially counteract the anterior tibial shear and excessive internal tibial rotation induced by the contractile forces of the quadriceps near full knee extension. In doing so the hamstring coactivation is suggested to assist the mechanical and neurosensory functions of the anterior cruciate ligament (ACL).     

A 10-week randomized trial comparing eccentric vs. concentric hamstring strength training in well-trained soccer players

PURPOSE: To compare the effects of a 10-week training program with two different exercises -- traditional hamstring curl (HC) and Nordic hamstrings (NH), a partner exercise focusing the eccentric phase -- on muscle strength among male soccer players. METHODS: Subjects were 21 well-trained players who were randomized to NH training (n = 11) or HC training (n = 10). The programs were similar, with a gradual increase in the number of repetitions from two sets of six reps to three sets of eight to 12 reps over 4 weeks, and then increasing load during the final 6 weeks of training. Strength was measured as maximal torque on a Cybex dynamometer before and after the training period. RESULTS: In the NH group, there was an 11% increase in eccentric hamstring torque measured at 60 degrees s(-1), as well as a 7% increase in isometric hamstring strength at 90 degrees, 60 degrees and 30 degrees of knee flexion. Since there was no effect on concentric quadriceps strength, there was a significant increase in the hamstrings:quadriceps ratio from 0.89 +/- 0.12 to 0.98 +/- 0.17 (11%) in the NH group. No changes were observed in the HC group. CONCLUSION: NH training for 10 weeks more effectively develops maximal eccentric hamstring strength in well-trained soccer players than a comparable program based on traditional HC.     

High‐density electromyography activity in various hamstring exercises

Proximal‐distal differences in muscle activity are rarely considered when defining the activity level of hamstring muscles. The aim of this study was to determine the inter‐muscular and proximal‐distal electromyography (EMG) activity patterns of hamstring muscles during common hamstring exercises. Nineteen amateur athletes without a history of hamstring injury performed 9 exercises, while EMG activity was recorded along the biceps femoris long head (BFlh) and semitendinosus (ST) muscles using 15‐channel high‐density electromyography (HD‐EMG) electrodes. EMG activity levels normalized to those of a maximal voluntary isometric contraction (%MVIC) were determined for the eccentric and concentric phase of each exercise and compared between different muscles and regions (proximal, middle, distal) within each muscle. Straight‐knee bridge, upright hip extension, and leg curls exhibited the highest hamstrings activity in both the eccentric (40%‐54%MVIC) and concentric phases (69%‐85%MVIC). Hip extension was the only BF‐dominant exercise (Cohen's d = 0.28 (eccentric) and 0.33 (concentric)). Within ST, lower distal than middle/proximal activity was found in the bent‐knee bridge and leg curl exercises (d range = 0.53‐1.20), which was not evident in other exercises. BFlh also displayed large regional differences across exercises (d range = 0.00‐1.28). This study demonstrates that inter‐muscular and proximal‐distal activity patterns are exercise‐dependent, and in some exercises are affected by the contraction mode. Knowledge of activity levels and relative activity of hamstring muscles in different exercises may assist exercise selection in hamstring injury management.     

Acute effects of static and dynamic stretching on leg flexor and extensor isokinetic strength in elite women athletes

The aim of this study was to explore the effects of static and dynamic stretching of the leg flexors and extensors on concentric and eccentric peak torque (PT) and electromyography (EMG) amplitude of the leg extensors and flexors in women athletes. Ten elite women athletes completed the following intervention protocol in a randomized order on separate days: (a) non‐stretching (control), (b) static stretching, and (c) dynamic stretching. Stretched muscles were the quadriceps and hamstring muscles. Before and after the stretching or control intervention, concentric and eccentric isokinetic PT and EMG activity of the leg extensors and flexors were measured at 60 and 180°/s. Concentric and eccentric quadriceps and hamstring muscle strength at both test speeds displayed a significant decrease following static stretching (P<0.01–0.001). In contrast, a significant increase was observed after dynamic stretching for these strength parameters (P<0.05–0.001). Parallel to this, normalized EMG amplitude parameters exhibited significant decreases following static (P<0.05–0.001) and significant increases following dynamic stretching (P<0.05–0.001) during quadriceps and hamstring muscle actions at both concentric and eccentric testing modes. Our findings suggest that dynamic stretching, as opposed to static or no stretching, may be an effective technique for enhancing muscle performance during the pre‐competition warm‐up routine in elite women athletes.     

Alterations of the in vivo torque-velocity relationship of human skeletal muscle following 30 days exposure to simulated microgravity

The purpose of this study was to examine the effect of 30 d of 6 degrees headdown bedrest (BR) on the in vivo strength of skeletal muscle. Peak angle specific (0.78 rad below horizontal) torque of the knee extensor (KE) and flexor (KF) muscle groups of both limbs was assessed during unilateral efforts at four speeds (0.52, 1.74, 2.97 and 4.19 rad.s-1) during concentric and at three speeds (0.52, 1.74 and 2.97 rad.s-1) during eccentric actions. The average decrease (p less than 0.05) of peak angle specific torque directly post-BR for the KE across speeds of concentric and eccentric actions was about 19% (n = 7). Recovery for 30 d following BR markedly improved strength to about 92% (p greater than 0.05) of "normal." Strength of the KF was not altered (p greater than 0.05) by BR (about a 6% decrease independent of speed and type of muscle action). Changes of strength were not affected by the type or speed of muscle action. The results indicate that strength of extensor more than of flexor muscle groups of the lower limb is decreased by 30 d of bedrest and that this response does not alter the nature of the in vivo torque-velocity relation.     

Fatigue and recovery at long and short muscle lengths after eccentric training

PURPOSE: To determine the effects of high-speed eccentric training of rat plantar flexor muscles on: 1) maximum (120 Hz) force at 90 degrees ankle position; 2) fatigue (40 concentric muscle actions, ROM 50 degrees) and recovery (6 concentric muscle actions) tested at short or long muscle lengths; and 3) low-frequency fatigue. METHODS: Training consisted of eccentric muscle actions from ankle positions of 140 degrees to 40 degrees (velocity approximately 400 degrees x s(-1)) followed by unresisted concentric muscle actions (5 x 10 repetitions, 5 d x wk(-1) for 6 wk). Fatigue was induced by concentric muscle actions with a rest of 12.5 s between muscle actions, and recovery consisted of equivalent concentric muscle actions performed every 5 min for 30 min. Low-frequency fatigue was measured 35 min after testing at 90 degrees ankle position by using the ratio of isometric force produced by 20- and 100-Hz stimulation frequencies. RESULTS: Eccentric training increased maximal isometric force per muscle weight by 22% whereas muscle weights were unchanged. In control muscles (C), isometric force immediately preceding each concentric muscle action decreased more at long lengths than at short lengths during the fatigue protocol; this length-dependent difference disappeared after 30 min of recovery. At short lengths, isometric force decreased less in trained muscles (T) (C: 78.4 +/- 3.6%; T: 59.6 +/- 4.4%) and recovered more during the following 30-min period (C: 84.7 +/- 2.5%; T: 95.4 +/- 2.8% of initial values). Changes in F20/F100 were smaller for trained muscles (C: 35.4 +/- 2.0%; T: 22.0 +/- 1.4%). CONCLUSIONS: High-speed eccentric training (5 d x wk(-1) for 6 wk) reduced fatigability and enhanced recovery mainly at long muscle lengths. It also reduced low-frequency fatigue, which may be attributed to alterations in intracellular calcium handling.     

Effects of hamstring‐emphasized neuromuscular training on strength and sprinting mechanics in football players

The objective of this study was to examine the effects of a neuromuscular training program combining eccentric hamstring muscle strength, plyometrics, and free/resisted sprinting exercises on knee extensor/flexor muscle strength, sprinting performance, and horizontal mechanical properties of sprint running in football (soccer) players. Sixty footballers were randomly assigned to an experimental group (EG) or a control group (CG). Twenty‐seven players completed the EG and 24 players the CG. Both groups performed regular football training while the EG performed also a neuromuscular training during a 7‐week period. The EG showed a small increases in concentric quadriceps strength (ES = 0.38/0.58), a moderate to large increase in concentric (ES = 0.70/0.74) and eccentric (ES = 0.66/0.87) hamstring strength, and a small improvement in 5‐m sprint performance (ES = 0.32). By contrast, the CG presented lower magnitude changes in quadriceps (ES = 0.04/0.29) and hamstring (ES = 0.27/0.34) concentric muscle strength and no changes in hamstring eccentric muscle strength (ES = ?0.02/0.11). Thus, in contrast to the CG (ES = ?0.27/0.14), the EG showed an almost certain increase in the hamstring/quadriceps strength functional ratio (ES = 0.32/0.75). Moreover, the CG showed small magnitude impairments in sprinting performance (ES = ?0.35/?0.11). Horizontal mechanical properties of sprint running remained typically unchanged in both groups. These results indicate that a neuromuscular training program can induce positive hamstring strength and maintain sprinting performance, which might help in preventing hamstring strains in football players.     

Acute effects of static stretching on peak torque and the hamstrings‐to‐quadriceps conventional and functional ratios

Recent evidence has shown acute static stretching may decrease hamstring‐to‐quadriceps (H:Q) ratios. However, the effects of static stretching on the functional H:Q ratio, which uses eccentric hamstrings muscle actions, have not been investigated. This study examined the acute effects of hamstrings and quadriceps static stretching on leg extensor and flexor concentric peak torque (PT), leg flexor eccentric PT, and the conventional and functional H:Q ratios. Twenty‐two women (mean ± SD age=20.6 ± 1.9 years; body mass=64.6 ± 9.1 kg; height=164.5 ± 6.4 cm) performed three maximal voluntary unilateral isokinetic leg extension, flexion, and eccentric hamstring muscle actions at the angular velocities of 60 and 180°/s before and after a bout of hamstrings, quadriceps, and combined hamstrings and quadriceps static stretching, and a control condition. Two‐way repeated measures ANOVAs (time × condition) were used to analyze the leg extension, flexion, and eccentric PT as well as the conventional and functional H:Q ratios. Results indicated that when collapsed across velocity, hamstrings‐only stretching decreased the conventional ratios (P<0.05). Quadriceps‐only and hamstrings and quadriceps stretching decreased the functional ratios (P<0.05). These findings suggested that stretching may adversely affect the conventional and functional H:Q ratios.     

Steadiness training with light loads in the knee extensors of elderly adults

PURPOSE: This study was conducted to determine the effect of steadiness training with light loads in the knee extensors of elderly adults. METHODS: Twenty-one elderly adults (72 +/- 4.6 yr) performed 16 wk of closely supervised knee extensor training that consisted of lifting and lowering 30% of the one-repetition maximum (1-RM) load as steadily as possible (10 reps per set, three sets per session, three sessions per week). Nine subjects served in a control group. Unilateral and bilateral maximal voluntary contraction (MVC) force; 1-RM load; force fluctuations during submaximal isometric, concentric, and eccentric contractions; timed functional performance (gait, chair rise, stair ascent and descent); muscle volume via magnetic resonance imaging (MRI); and the electromyogram (EMG) were measured. RESULTS: The training group exhibited modest average gains in MVC force and 1-RM load; muscle volume and EMG were unaltered. Although isometric steadiness was unchanged on average, training elicited the greatest improvements in the least steady subjects. Force fluctuations during concentric and eccentric contractions were significantly reduced. Of 21 subjects, 14 responded to training with gains in 1-RM load greater than the typical change (6%) in the control group. Before training, these responders exhibited greater force during bilateral compared with unilateral contractions. The small changes in physical functional performance were similar for the training and control groups. The training group could lift the pretraining 1-RM load 4.6 times after training (5.6 times for responders). CONCLUSIONS: Steadiness training with the knee extensors thus produced neural adaptations that increased strength in elderly adults who exhibited bilateral facilitation, improved isometric steadiness in unsteady subjects, improved steadiness during concentric and eccentric contractions, and enhanced the ability to lift heavy loads repeatedly.     

Eccentric muscle action increases site-specific osteogenic response.

PURPOSE: Strain magnitude is known to be a primary determinant of the osteogenic response to loading. However, whether bone adaptation to muscle loading is determined primarily by load magnitude is unclear. The purpose of this study was to determine the contribution of load magnitude from muscle action on the site-specific osteogenic response. METHODS: Twenty young women (12 exercise, 8 control) served as subjects. Bone mineral density (BMD) of the whole body and mid-femur segment and body composition were determined by dual-energy x-ray absorptiometry. Knee extension and flexion strengths were determined on a KinCom dynamometer, with surface electromyography of the vastus lateralis muscle. Exercise subjects trained three times weekly for 18 wk on a KinCom. One leg trained using eccentric knee extension and flexion, and the opposite leg trained using concentric knee extension and flexion. RESULTS: Eccentric exercise demonstrated greater force production with lower integrated electromyographic signal (IEMG) compared with concentric exercise. Significant increases in muscle strength occurred in both exercised legs (P < 0.05), which were of similar relative change. However, only the eccentric trained leg significantly increased mid-femur segment BMD (+3.9%, P < 0.05) and mid-thigh segment lean mass (+5.2%, P < 0.05). CONCLUSIONS: These results suggest that eccentric muscle training is more osteogenic than concentric muscle training and that eccentric training is more efficient by attaining higher force production with lower IEMG.     

Effect of activation force on knee extensor torques

The purpose of this study was to determine whether the magnitude of the activation force, defined as the force that must be applied to the load cell in order to activate the resistance arm of an isokinetic dynamometer, affected knee extensor torques. Twenty-four healthy female subjects performed resisted knee extension through the range of 95 degrees to 5 degrees knee flexion, with a 5-s rest between concentric and eccentric muscle actions. Six exercise sets, composed of the combinations of activation force (20,50, and 100 N) and angular velocity (45 and 135 degrees.s-1), were randomly assigned on each of two occasions, completed within a 10-d period. Although peak torques were not affected by the activation force, average torques, eccentric torques at mid-range (50 degrees knee flexion), and torques during the initial portion of each muscle action (80 degrees knee flexion during concentric muscle actions and 20 degrees flexion during eccentric actions) increased as the activation force increased. The effect of the activation force tended to be more pronounced during eccentric than during concentric muscle actions, and at the faster angular velocity. Comparisons of torques should be based on similar test protocols, including activation force.     

Effects of rest interval on isokinetic strength and functional performance after short-term high intensity training.

OBJECTIVES: The ability to maximally generate active muscle tension during resistance training has been established to be a primary determinant for strength development. The influence of intrasession rest intervals may have a profound effect on strength gains subsequent to short-term high intensity training. The purpose of this study was to examine the effects of rest interval on strength and functional performance after four weeks of isokinetic training. METHODS: Fifteen healthy college aged individuals were randomly assigned to either a short rest interval group (group 1, n = 8) or a long rest interval group (group 2, n = 7). Subjects were evaluated for quadriceps and hamstring isokinetic strength at 60 (five repetitions) and 180 (30 repetitions) degrees/second and functional performance with the single leg hop for distance test. One leg of each subject was randomly assigned to a four week, three days/week isokinetic strength training programme for concentric knee extension and flexion performed at 90 degrees/second. Subjects in group 1 received a 40 second rest interval in between exercise sets, whereas subjects in group 2 received a 160 second rest period. RESULTS: A two factor analysis of variance for the pre-test--post-test gain scores (%) showed significantly greater improvements for isokinetic hamstring total work and average power at 180 degrees/second for the trained limb of subjects in group 2 than their contralateral non-trained limb and the subjects in group 1. Significantly greater improvements for the single leg hop for distance were also found for the trained limbs of subjects in both groups as compared with the non-trained limbs. CONCLUSIONS: The findings indicate that a relatively longer intrasession rest period resulted in a greater improvement in hamstring muscle strength during short term high intensity training.     

Muscle control in elite alpine skiing.

PURPOSE: The purpose of this study was to determine whether muscle control may be influenced by accelerative forces brought about by the downhill displacement of body mass in combination with the sharp turns during alpine skiing. METHODS: Sixteen elite skiers performed either super G (SG), giant slalom (GS), slalom (SL), or freestyle mogul (FM) skiing. Knee and hip joint angles and electromyographic (EMG) activity of the knee extensors were recorded. RESULTS: During the course of a turn, the minimum (deepest stance position) knee angle of the outside (main load-bearing) leg ranged from 60 degrees to 100 degrees, where the smallest angle was obtained in the FM event. Among the traditional alpine disciplines, smaller knee angles were obtained in the high-speed events (i.e., knee angle: SG相似文献   

Re-examination of training effects by electrostimulation in the human elbow musculoskeletal system

This study examines the effects of a 7 weeks sub-maximal training period of electrostimulation on the maximal isometric, concentric, eccentric voluntary torque and muscle contractile properties of the elbow flexor muscles of nine subjects. The daily program consisted of five series of six 6-s isometric actions (60 to 70% of maximal isometric voluntary action) at an elbow angle of 90 . After training the maximal voluntary isometric flexion torque increased significantly whereas the maximal voluntary isometric extension torque decreased significantly. Increases in isometric flexion torque were linked to an increase of the myoelectrical activity of the biceps brachii muscle. Under dynamic conditions flexion torque was significantly increased throughout the whole spectrum of angular velocities. These changes were accompanied by an increase in the myoelectrical activity of the agonist muscle under eccentric conditions and at two fast concentric angular velocities, without modifications of the myoelectrical activity of the antagonist muscle. The analysis of the electrical and mechanical twitches indicated that modifications of the muscle membrane electrical activity were also present at the muscle level. These results indicate that torque gains were attributed to neural adaptations and/or to a modification of the relative part of agonist and antagonist muscles in elbow flexion torque production.     

Isoacceleration: a new concept of resistive exercise

This study presents the concept of constant (iso-) accelerative and decelerative exercise and compares concentric and eccentric torque output during isoaccelerative and isodecelerative movements with that during comparable constant velocity (isokinetic) conditions. Twelve men (19-42 yr) performed maximal voluntary concentric and eccentric knee extensions at velocities of 120 and 240 degrees.s-1 (isokinetic) and at accelerations of 180 and 720 degrees.s-2 (both isoaccelerative and isodecelerative) between 10 degrees and 90 degrees knee angles. At 50 degrees, the 180 and 720 degrees.s-2 tests had velocities of 120 and 240 degrees.s-1, respectively, and thus torque comparisons could be made at a corresponding position and velocity. No difference was seen among the isoaccelerative, isodecelerative, or isokinetic angle- and velocity-specific torques for either the concentric or eccentric tests (P greater than 0.05). The results demonstrated that, under conditions of maximal voluntary effort, movement speed as such (within the range studied) was the essential determinant of muscle force--not whether this speed was attained during accelerative, decelerative, or constant velocity movements. As a testing and training modality, the controlled acceleration technique, particularly eccentric deceleration and concentric accleration, appears to offer advantages as compared with existing methods, since it more faithfully reflects the contraction conditions during natural strength-requiring movements.     

Strength training and neuromuscular function in elderly people with total knee endoprosthesis

The effects of 1 year of intensive strength training on neuromuscular function were studied in elderly people operated for total endoprosthesis ( n =30) divided into 3 groups: training pup 1 (TG1, n =11), training pup 2 (TG2, n =10) and control group (CG, n =9). After the operation, TG1 and TG2 trained every second day and the training was controlled by training diaries, and CG performed only conventional exercises by themselves. The overall volume of training in TG2 was 30% greater than in TG1. Neuromuscular function was examined by measuring maximal electromyography (EMG) and maximum voluntary isometric and dynamic strength of the knee extensor and flexor muscles. The range of motion of the knee joint and the cross-sectional area (CSA) of the knee extensor muscles were also measured. After the preoperative tests, the same measurements were repeated 3, 6, 12, 24 and 52 weeks postoperatively. After the dramatic decreases in maximal isometric torque and EMG-activity during the first postoperative weeks in all groups, TG2 showed the most remarkable improvement in neuromuscular function. For instance, the maximum isometric extension torque measured at 90° knee angle increased between the 24th and 52nd weeks. The increase in the EMG-activity of the rectus femoris muscle was Significant between the 12th and 24th weeks. The CEA of the knee extensor muscles in TG2 was greater 1 year after the operation compared with the preoperative value. The intra- and extra-articular swelling of the knee joint may have irritated the free nerve endings, leading to reflex inhibition with a concomitant decrease in EMG and strength of the knee extensor muscles. Because TG2 demonstrated the most remarkable improvement in neuromuscular function after the first postoperative weeks, intensive training programs can be successfully used in rehabilitation after a major knee operation, even in elderly people.     

Bilateral isokinetic peak torque of quadriceps and hamstring muscles in professional soccer players with dominance on one or both two sides

AIM: Dominance of one leg may cause asymmetry between the contralateral muscle groups and develop predisposition for injury to the leg with the weaker muscle strength. The purpose of this study was to examine the strength balance in the extensor and flexor muscle groups, as well as the hamstring to quadriceps (H/Q) ratios of both legs in professional soccer players with dominance on one or both legs. METHODS: Forty-two professional soccer players of the first Greek division participated in this study. Participants were divided into 3 groups according to their leg use during training sessions and matches. Fifteen players comprised the first group with dominance to the right leg, 12 players formed the second group with dominance to the left leg, and 15 players consisted the third group with dominance to both the right and left legs. Maximum voluntary concentric torque of the hamstring and quadriceps muscles of both legs was assessed using a Norm isokinetic dynamometer at angular velocities of 12 degrees, 60 degrees, 180 degrees and 300 degrees/s. RESULTS: No significant differences in the strength balance found between the groups. The isokinetic variables comparing the right and left body side in each group, with dominance on one or both legs, did not differ. No differences were recorded in the H/Q between the right and left legs for any of the subject groups. CONCLUSIONS: There is no evidence of muscle imbalances in extensor and flexor muscle groups and H/Q ratios between the right and left legs in professional soccer players with dominance on one or both legs. The training sessions and matches appear to have imposed strength balance for the right and left body sides of professional soccer players.