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PubMedDate not supplied

Primary stability of interference screw fixation. Influence of screw diameter and insertion torque.

Interference screw fixation is frequently used in anterior cruciate ligament reconstruction with the bone-patellar tendon-bone graft. There have been no data available about the influence of screw diameter and insertion torque on primary stability. We designed a cadaveric study using paired knees to analyze the comparative effectiveness of 20-mm long screws of different diameters (9 mm versus 7 mm) and the significance of torque during screw insertion. Testing to failure was performed in a tensiometer with a crosshead speed of 200 mm/min. After slippage of a bone peg in the 7-mm screw specimens, the experiment was repeated in each specimen with a 9-mm screw fixation. Maximum tensile force was greater at the femoral insertion than at the tibial site. Results of refixations with 9-mm screws were only slightly inferior to the original 9-mm screw fixation specimens. Our results further showed that the torque can be used as a predictor of the stability of the bone block but cannot be used as an indicator for the strength of the reconstruction. The 7-mm screws are not recommended for tibial fixation. Failed 7-mm screw fixations can be replaced by 9-mm screws and refixations were successful in our study model.

Adult↗
PubMedDate not supplied

Plyometric training in female athletes. Decreased impact forces and increased hamstring torques.

The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height. After training, peak landing forces from a volleyball block jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-to-quadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side, correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21% on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%. This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes.

Adolescent↗
PubMed2004

High-precision measurements of light-induced torque on absorbing microspheres.

Laser beams have been demonstrated to be capable of exerting torque as well as forces on microparticles. Using a custom magneto-optic manipulator, we directly measured the torque exerted by laser light on absorbing microspheres as a result of the transfer of spin angular momentum. A general method for measuring torque has been developed, and the experimental apparatus has shown a sensitivity of approximately 1 pN/nm.

Journal Article↗
PubMed1993

The relative effectiveness of three forms of visual knowledge of results on peak torque output.

Therapists often search for more efficient and effective ways to provide patients with information regarding their performance. The purpose of this study was to determine whether certain types of machine-based visual displays could be used as a source of error-correction information to facilitate the immediate and/or delayed performance of a maximal effort isokinetic movement of the knee. The relative effectiveness of the knowledge of results (KR) provided by visual displays that differed in degree of precision and presentation schedule were compared during a practice and retention test phase. Twenty-four healthy male subjects (mean age = 22 years) performed isokinetic extension and flexion of the knee at low (120 degrees/sec) and high (240 degrees/sec) exercise speeds. A no-KR maximal effort pretest was followed by two practice sessions during which three groups each received one form of visual KR and a fourth group practiced without KR. A no-KR maximal effort posttest was administered to all groups following a 1-day rest interval. Although visual KR did not result in any significant differences in mean peak torque output during practice, between-group comparisons of pretest to posttest changes in mean peak torque indicated that groups receiving visual KR in addition to practice demonstrated significantly greater (p < .03) improvements in mean peak torque in three of the four conditions tested when compared with the group that practiced without KR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1997

Peak passive resistive torque at maximum inversion range of motion in subjects with recurrent ankle inversion sprains.

Although a number of mechanical and neuromuscular processes have been identified, the primary mechanisms underlying residual functional instability of the ankle remain unclear. Understanding such mechanisms will help physical therapists identify where to focus treatment efforts, ultimately leading to more effective rehabilitation. In the present investigation, resistive torque at maximum ankle inversion was evaluated to determine if lateral ankle structures demonstrated mechanical laxity. Thirty subjects with a history of unilateral recurrent inversion sprains were tested bilaterally. A custom-made apparatus provided a stress to the lateral ankle in a method that was similar to the inversion stress test. Two measures of laxity were used: maximum passive inversion range of motion and peak passive resistive torque. Differences between the involved and uninvolved ankles were determined using analysis of covariance procedures. There were no significant differences between involved and uninvolved ankles for maximum inversion range of motion and for peak passive resistive torque. Post hoc testing confirmed adequate statistical power. The results support previous investigations, which suggest that functional instability can exist in the absence of mechanical lateral ankle laxity.

Adult↗
PubMed1995

Evaluation of the human vestibulo-ocular reflex at high frequencies with a helmet, driven by reactive torque.

A new technique was developed to test the VOR in humans. A tightly but comfortably fitting helmet was provided with an electronically controlled torque motor that rotated a mass around a vertical axis. Acceleration of the motor caused reactive torque of the helmet in the opposite direction which was transmitted to the (freely movable) head. Sinusoidal head oscillations in the frequency range 2-20 Hz (peak-to-peak amplitudes about 10 degrees and 0.1 degrees respectively) were easily achieved, as well as step displacements of the head with accelerations on the order of 1000 degrees/s2. Limitation of the maximum torque and lack of any rigid attachment of the head to a fixed structure made the technique safe and comfortable. Eye and head rotations were recorded, independently of head translations, with eye and head search coils in a homogeneous a.c. magnetic field. In normal subjects, gain was near unity at 2 Hz: above 8 Hz, gain increased progressively toward 1.1-1.3 at 20 Hz. Phase lag increased from a few degrees at 2 Hz to about 45 degrees at 20 Hz. Above 2 Hz, these results were unaffected by visual conditions; lower gains and increased phase lags were found in subjects with bilateral or unilateral vestibular loss. For step displacements, gain (measured in the first 100 ms) was near unity for normals, near zero after bilateral vestibular loss and strongly asymmetrical after unilateral vestibular loss. Thus, the technique seems highly effective in testing vestibular function with minimal contamination by other systems.

Acceleration↗
PubMed1989

Comparison of rotational speeds and torque properties between air-bearing and ball-bearing air-turbine handpieces.

We examined the effects of air pressure on the free-running speed of air-bearing and torque-type ball-bearing air-turbine handpieces. The air pressure for the former should be kept at a certain high level to maintain the stable super-thin air-bearing film and to provide the quasi-constant speed of around 420,000 to 480,000 rpm. On the other hand, the air pressure for the latter could be adjusted to provide some varieties of speeds, ranging from about 150,000 to 320,000 rpm. Subsequently, to compare torque properties and cutting effectiveness between these two handpieces, weight-load cutting tests were conducted, using a glass-ceramic workpiece and a commercial diamond point. It was confirmed that the air-bearing handpiece had the lower torque power but exhibited better cutting effectiveness, compared with its counterpart.

Air Pressure↗
PubMed1992

Eccentric and concentric torques of knee and elbow extension in young and older men.

The purpose of this study was to compare the strength of knee extensors and elbow extensors in young and older men under conditions of eccentric loading and concentric contractions. Twelve men ages 23 to 32 years and 12 ages 60 to 75 years were tested at two angular velocities of movement, 90 and 180 degrees.s-1, on a KinCom isokinetic dynamometer. Compared to young men, older men had lower concentric peak torque values for elbow (31%) and knee (32%) extensors (p less than 0.05). The older group showed lower eccentric peak torques on all elbow comparisons (21% lower), and for knee extension at the slower velocity (20%). At the faster velocity, knee extension eccentric peak torque did not differ from that of younger men. Differences between the age groups were significantly less for the eccentric muscle action than for the concentric one. The observation of maintained eccentric strength in older men, particularly at fast velocity, warrants research in defining the mechanism.

Adult↗
PubMed1992

Torque-velocity relation and muscle fibre characteristics of foot dorsiflexors after long-term overuse of residual muscle fibres due to prior polio or L5 root lesion.

Isokinetic foot dorsiflexion strength and muscle biopsy data from eight patients with overuse of tibialis anterior muscle (TA) fibres due to weakness after prior polio or L5 root lesion were compared to data from age and sex matched, healthy subjects. Concentric peak torque at an angular velocity of 30 degrees/s was 6-24 Nm in the patients and 15-34 Nm in the controls (p < 0.01). Muscle biopsies from TA showed a significantly higher proportion of type 1 fibres in the patients as compared to the controls (p < 0.005). The type 1 fibres in the patients had a significantly larger cross-sectional area than in the controls (p < 0.005). The type 1 fibre proportion and relative area were inversely correlated to the relative concentric torque produced at 180 degrees/s (p < 0.05) and 240 degrees/s (p < 0.05) compared to that produced at 30 degrees/s in the controls but not in the patients. However, the relative concentric torque produced at 180 degrees/s and 240 degrees/s compared to that produced at 30 degrees/s was not significantly different in the patients and the controls. This indicates that the contractile properties of the overused muscle fibres do not change in parallel with the histochemical fibre type.

Aged↗
PubMed1992

Effect of external load on isokinetic torque production by the knee in anterior cruciate ligament deficient patients.

The purpose of this study was to examine the effect of an external load on the isokinetic torque production of the knee directly from the anterior cruciate ligament (ACL) of deficient patients. Ten surgically proven ACL deficient patients were included in this study. Each patient was preoperatively studied using a Biodex isokinetic dynamometer. Isokinetic contraction of the quadriceps muscle and hamstring muscles were performed in five repetitions with an angular velocity of 45 degrees per second with proximal and distal pad placement, respectively. The results demonstrated that the ratio of torque production of the ACL deficient knee to the contralateral normal knee was greater in proximal pad placement than in distal placement and that the ratio of torque production of the knee in proximal pad placement to that of the knee in distal pad placement was greater in the ACL deficient knee than in the contralateral normal knee. Similar results were found for both extension and flexion of the knee. The results showed that ACL deficient patients felt more confident doing isokinetic contractions of the knee with proximal pad placement.

Adult↗
PubMed1992

Concentric versus combined concentric-eccentric isokinetic training programs: effect on peak torque of human quadriceps femoris muscle.

To determine the effects of isokinetic resistance training of the quadriceps, 25 male volunteers were randomly assigned to five training groups: Concentric Slow (CS), Concentric Fast (CF), Concentric-Eccentric Slow (MS), Concentric-Eccentric Fast (MF), and Control (C). In training, subjects performed 20 contractions of each quadriceps using either 60 degrees/sec or 180 degrees/sec, for both sides, five days per week for 12 weeks. Testing consisted of measurement of peak torque, at intervals of 60 degrees/sec across a spectrum of velocities ranging from plus to minus 240 degrees/sec, at 0, 4, 8, and 12 weeks. Repeated MANOVA using planned comparisons showed that all trained subjects made significant peak torque gains (p < .05), but that the gains made by MS and MF were greater. These findings suggest that the addition of an eccentric training component to a concentric isokinetic training program may allow greater peak torque gains regardless of the velocity.

Adult↗
PubMed1990

Concentric and eccentric quadriceps torque in pre-adolescent males.

The purpose of this study was to evaluate the applicability of using the Kin Com (Chattecx Corp., Chattanooga, TN) isokinetic machine to measure concentric and eccentric quadriceps torque in a group of 12 healthy male volunteers aged 10-12 years. Each individual was tested by an experienced physiotherapist using a 60 degree per second velocity mode according to our standardized protocol. Average and peak torque values for concentric and eccentric contractions of the quadriceps were recorded; based upon the best of three maximum effort trials on each lower extremity. Retesting was performed on a randomly selected sub-group in an identical manner two weeks later. Our results showed no statistically significant difference between the original and retest values using the method error of repeated measurements and paired t-test analyses. Eccentric peak torque was greater on average than concentric. This was significant with p-values of 0.01 for the non-dominant quadriceps and 0.002 for the dominant side (paired t-test). There was no significant difference between the dominant and non-dominant sides. In conclusion, eccentric muscle testing has been reliably quantitated for the first time in children. This study has shown a practical and reproducible method of quantitative muscle strength assessment.

Child↗
PubMed1990

Correlation of knee extensor muscle torque and spasticity with gait speed in patients with stroke.

The purpose of this investigation was to determine in 17 stroke patients the correlation between two independent variables (knee extensor muscle torque [KET] and spasticity on the paretic side) and one dependent variable (gait speed). The patients had a mean age of 59 years; time since onset of first stroke was 51 days. Each variable was measured twice on each of two consecutive days. Both KET and spasticity were measured on a Cybex II dynamometer. Peak torque was measured during five-second maximal voluntary isometric knee extension efforts. Spasticity was defined by the relative angle of reversal (RAR) of the Cybex electrogoniometer curve obtained during pendulum tests. Gait speed was measured as patients walked 8.0 meters at their most comfortable speed while using their usual devices. The average of each day's KETs, RARs, and gait speeds was used in the calculation of Pearson product moment correlations. The correlations between KET and gait speed were significant (p less than .05) and were .574 (day 1) and .571 (day 2). The correlations between the RAR and gait speed were not significant (-.204 day 1 and -.262 day 2). All measurements had intraday and/or interday reliability coefficients (ICC 3,1) exceeding .930. The results of this study confirm that gait performance is correlated with measures of KET but not spasticity in stroke patients. Thus, at the knee, extensor muscle torque, unlike spasticity, appears to be justified as a practical and objective clinical measure.

Adult↗
PubMed1990

Peak torque values for antagonist muscle groups and concentric and eccentric contraction types for elite sprinters.

The purpose of this study was to provide descriptive strength estimates of the major muscle groups of the lower limbs for a group of elite sprinters by comparing both the eccentric and concentric and the agonist and antagonist peak torques. The peak torque values of the flexor and extensor muscle groups of the hip, knee, and ankle joints of the lower extremities were tested in a group of elite male and female sprinters. These values were measured both eccentrically and concentrically for each of the joint movements tested, using a Kin/Com isokinetic dynamometer. The peak torque values for the knee joint were found to be substantially larger than those reported for nonathletes, and comparable to those for other athletic populations. No comparable scores were located for the results of the hip and ankle scores. The flexion and extension ratios for the knee joint, at approximately .60, were similar to others reported, whereas the ratios for the hip joint were larger at .76. The concentric and eccentric ratios varied, depending on the speed of testing and the joint tested.

Adolescent↗
PubMed1990

The relationship between peak torque and work of the quadriceps and hamstrings after knee injury.

The purpose of the present study was to assess the relationship between the isometric and isokinetic peak torques (speed of movement 0, 60, 180 deg/sec) and the total work output of multiple contractions (180 deg/sec) of the quadriceps and hamstrings in 68 patients having seven years earlier a hemarthrotic knee injury. At every test speed the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the peak torque and the total work were highly significant (p less than 0.001) for the quadriceps and hamstrings in the uninjured (r = 0.74-0.92, rs = 0.75-0.93) as well as in the injured (r = 0.83-0.93, rs = 0.84-0.92) knees. All correlation coefficients were higher at the highest speed (180 deg/sec) of the isokinetic test (r = 0.90-0.93, rs = 0.91-0.93) than at the other speeds (0 and 60 deg/sec) (r = 0.74-0.88, rs = 0.75-0.89) obviously since the total work was registered at that speed. In conclusion, in injured or healthy knees the isokinetic total work analysis offers little additional information to that attained by more simple measurements, the peak torque recordings.

Adolescent↗
PubMed1989

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.

Adult↗
PubMed1989

Early changes in gait and maximum knee torque following knee arthroplasty.

Fourteen knees in 11 individuals were studied before knee arthroplasty and at three and six months following surgery. Eleven of these knees were further evaluated at 12 months following surgery. At each evaluation, kinematic, electromyographic, and force plate data were gathered during level walking. Maximum knee extension and flexion torques were also determined. The greatest improvement in gait was noted in the first three postoperative months when velocity increased 13% and stride length increased 14%. After six months gait changes were negligible. Maximum knee torques in the osteoarthritic population were decreased at three months, then returned to preoperative levels at six months. In the rheumatoid population, maximum knee torques steadily increased up to six months following surgery. Gait abnormalities that persist at six months and beyond following knee arthroplasty appear to be most related to the presence of arthritis in joints other than in the operated knee(s).

Aged↗
PubMed1989

Isokinetic peak torque and work relationship in the laterally unstable knee.

The purpose of this investigation was to assess the relationship between the isometric and isokinetic peak torque (speed of movement 0 degrees, 60 degrees, and 180 degrees/s) and the total work output of multiple contractions (180 degrees/s) of the quadriceps and hamstrings in subjects suffering from a chronic insufficiency of the lateral ligament compartment (LAT) of the knee. At every test speed the Pearson product moment (r) and the Spearman rank (rs) correlation coefficients between the peak torque and total work were highly significant for both muscle groups in the uninjured (r = .87-.97, rs = .86-.93) as well as in the laterally unstable (r = .65-.90, rs = .71-.90) knees. In both knees and in both muscle groups the correlation coefficients increased towards the highest speed of the isokinetic movement, obviously since the total work was registered at that speed. In conclusion, concerning laterally unstable knees the total work analysis may offer little additional information to that attained by more simple measurement, the peak torque analysis.

Adult↗