Isokinetic Muscle Performance Research Articles

Isokinetic Trunk Muscle Performance Characteristics of Classical Ballet Dancers

Presented at the Sports Physical Therapy Section Team Concept Meeting, December 1991, New Orleans, LA. Recent availability of trunk isokinetic dynamometers has created a need for documented normative data. The purpose of this initial investigation was to determine isokinetic norms for trunk flexion and extension in classical ballet dancers. Strength levels were determined by peak torque. A fatigue index was derived from 20 reciprocal contractions. Twenty-three dancers were tested - 17 females (F) and six males (M). Female dancers were further divided into professional (FP) and semiprofessional (FSP) groups. A questionnaire regarding dance background, training habits, and back pain was administered. Means and ranges for peak torque and fatigue were calculated for each group. T-tests were performed on peak torque and fatigue data grouped by gender and dance status. Peak torque analysis indicated trends of M > F and FP > FSP. A statistically significant (p < 0.05) difference existed for trunk extension between FP and FSP dancers, a possible sport-specific adaptation. Fatigue levels were lower than expected, and possible explanations are considered. J Orthop Sports Phys Ther 1992;15(2):99-106.

Isokinetic Limb and Trunk Muscle Performance Testing: Short-Term Reliability

This work was supported, in part, by grants from the National Institutes of Health (AR37562), the National Aeronautics and Space Administration (NAS9-343), Sandoz Pharmaceuticals, Squibb Mark Pharmaceuticals, and Cybex, Inc. There is a lack of information on the reliability of devices used to test trunk flexor and extensor strength. In this study, the short-term reliability of two isokinetic muscle performance testing devices was assessed. Measurements of knee flexion/extension and trunk flexion/extension were made in 15 normal subjects (mean age, 29.9 years). Determinations of peak torque and best work, as a percentage of body weight, were made 24 hours apart. Speeds used for the knee were 90, 180, and 240 degrees /sec, while speeds used for the trunk were 60, 90, and 120 degrees /sec. Correlation ranged from r = 0.82 to r = 0.96, showing strong associations between first and second measurements at either site for both performance parameters and for all speeds. Reliability (imprecision) was estimated as the average coefficient of variation (CV) for paired measurements. Coefficients of variation ranged from 4.4 to 8.7 percent for the knee parameters and from 2.9 to 12.1 percent for the trunk parameters. Using this range of imprecision, the minimum absolute changes in muscle performance needed to be significant at the five percent level were calculated for both the individual subject as well as for groups of subjects. At a three percent imprecision for the individual subject, muscle performance changes would have to be greater than 8.32 percent to be detected with 95 percent confidence. This estimate increases to approximately 33 percent at a imprecision level of 12 percent. However, muscle performance changes that can be detected with statistical confidence are three-fold less if a group of 10 subjects, for example, are examined. These findings have important implications where interventions to improve muscular performance may be of short duration and observed gains are relatively small. J Orthop Sports Phys Ther 1991;14(5):220-224.

Reliability of Isokinetic Measurements of Trunk Muscle Performance

The purpose of this investigation was to assess the reliability of isokinetic trunk muscle performance. Sixty-one volunteers participated (29 men, 32 women; age range, 20-60 years). All subjects were without low-back symptoms at the time of testing. All testing was performed with the subject initially standing, using speeds of 60, 120, and 180 degrees per second. Ten repetitions of flexion and extension were performed reciprocally at each speed, with a 3-minute rest period between speeds. Test-retest intervals were 1 and 3 weeks from the initial test. Peak torque-to-body-weight ratios, extension-to-flexion ratios, and average work per repetition were calculated for each speed for flexion and extension. Data were analyzed with analysis of variance, intraclass correlation coefficients, and Pearson correlation coefficients. Intraclass correlation coefficient values ranged from .74 to .88 for measurements derived from peak torque, and from .88-.93 for measurements derived from work (with the exception of .69 for men at 180 degrees/sec). Standard error of measurements ranged from 8 to 32 ft-lb, with a tendency to increase with increasing speeds. It was concluded that, when using this protocol, isokinetic measurements of muscle function offer the clinician sensitive and reliable measurements of trunk muscle performance and that incorporating increased practice with women and longer rest periods with men may further decrease error associated with these isokinetic trunk strength measurements.

Peak torque-to-body weight ratios in the trunk: a critical analysis.

The purpose of this study was to document the relationships between body weight and isokinetic extension and flexion peak torque produced by the trunk musculature. Using a dynamometer, we collected isokinetic measurements during trunk flexion and extension at speeds of 60 degrees and 120 degrees/sec on 61 healthy subjects (29 men, 32 women; 20-60 years old) while standing. Extension and flexion peak torque measurements were calculated for each subject at each speed. Male and female subjects' data were analyzed separately. Each subject's body weight was paired with peak torque at each speed, and Pearson product-moment correlation coefficients (r) were calculated. The correlation coefficients ranged from .27 to .39 for extension and from .66 to .70 for flexion, establishing a positive linear relationship between body weight and each of the isokinetic measurements. Body weight accounted for very small proportions of the variance (as low as 7%-15% in extension isokinetic measurements). In attempting to use a client's body weight to predict isokinetic peak torque measurements, the clinician should be aware that a great deal of unaccounted for variance exists. We recommend that clinicians use other variables (eg, activity level, age) in addition to body weight to control for individual differences among healthy subjects when measuring isokinetic trunk extension muscle performance.

Combined anterior cruciate-ligament reconstruction using semitendinosus tendon and iliotibial tract.

We are reporting the results of a reconstructive procedure designed to decrease anterior tibial subluxation due to disruption of the anterior cruciate ligament. The operation combines both intra-articular and extra-articular methods. The semitendinosus tendon and the iliotibial tract are both routed from opposite directions over the top of the lateral femoral condyle and through the same oblique drill-hole in the proximal part of the tibia: the semitendinosus tendon is passed up through the tibial drill-hole, across the knee joint, over the top of the lateral femoral condyle, and deep to the fibular collateral ligament, and the iliotibial tract is passed deep to the fibular collateral ligament, over the top of the lateral femoral condyle, across the knee joint, and down through the drill-hole. Both grafts are simultaneously pulled tight while the semitendinosus tendon is sutured to the iliotibial tract laterally and the iliotibial tract is sutured to the semitendinosus tendon medially below the drill-hole. The posteromedial and lateral parts of the capsule are advanced to tighten the secondary restraints. One hundred of the first 106 consecutive patients with chronic instability who had this procedure were evaluated using subjective and objective criteria at three to seven and one-half years after surgery. The positive anterior-drawer sign tested at 25 degrees of flexion was eliminated or reduced to 1+ in eighty knees, and the positive pivot shift was reduced to zero or 1+ in ninety-one knees. The objective assessment of isokinetic muscle performance and passive tibial rotation showed significant improvements in strength and normalization of tibial rotation.