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PubMed1991

[Muscular isokinetic dynamometry].

In the past, muscular strength has primarily been measured using isometric, isotonic or tensiometric techniques. The advent of isokinetic dynamometers has supplied an objective method of measuring peak torque throughout a full range of motion at a predetermined speed of contraction. An isokinetic contraction is a refinement of the controlled motion concept. The isokinetic contraction is dynamic, but the speed of the motion is held constant by a special device. In this way, resistance is in direct ratio to the varying force applied through the full course of a natural movement. The purpose of this study was to determine the peak torque of quadriceps (Q), and hamstrings (H), and their biomechanical angle of production, H to Q ratio and bilateral comparisons of these variables for the first time in a Southamerican population. Twenty healthy and voluntary males (age: 21.9 +/- 3.1 years, height 193.2 +/- 6.5 cm, weight: 84.2 +/- 5.2 kgs.), were tested on the Cybex II Dynamometer and Cybex Data Reduction Computer (CDRC). Quadriceps and hamstrings peak torque (pkTQ), in Newton-meters, were obtained at angular velocities of 60, 180 and 240 degrees. sec-1. Also, the angle of the range of motion at which peak torque occurred in both directions, H and Q peak torque to body weight ratios, H to Q ratio were measured. Finally, CDRC provided the bilateral comparison of the different variables expressed in percentages. All measurements were automatically corrected for the effect of gravity. The absolute maximal pkTQ of dominant (D), and non-dominant (ND), quadriceps at 60 degrees/sec was DQ 297 +/- 25 Nwm and nDQ 303 +/- 13 Nwm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2000

Passive tensile stress and energy of the human hamstring muscles in vivo.

The present study measured passive resistance to stretch in the hamstring muscles during a standardized stretch maneuver to estimate tensile forces and energy of the individual hamstring muscles in 7 flexible and 6 inflexible persons defined according to joint range of motion. Using a dynamometer, knee joint moment was measured during slow passive knee extension to a maximal angle (dynamic phase) followed by a 90-s static phase. Cross-sectional areas (CSA) of the separate hamstring muscles were obtained with magnetic resonance (MR) imaging. Mathematical modeling was used to calculate instantaneous muscle length and joint moment arm for each muscle. Subsequently, passive muscle tension (N/cm2) was calculated based on moment arm lengths, knee joint moments, and CSA. Maximal tolerated joint angle was greater in flexible (delta1.30+/-0.06 rad) than inflexible (delta0.84+/-0.06 rad) subjects, P<0.01. The peak tension at maximal angle was greater in flexible (81.8+/-12.5 N/cm2) than inflexible subjects (29.3+/-4.1 N/ cm2), P<0.001. For the separate muscles the overall change in muscle length (delta cm) and moment arm (delta cm) differed between groups, P<0.01. Similarly, muscle stiffness (delta tension/delta muscle length) was greater in flexible than inflexible subjects in the final 3 cm, P<0.01, and in the final 20% of length change, P<0.01. Absorbed energy (mJ/cm2) was greater in flexible than inflexible subjects in the final 40% of length change, P<0.05. These data show that flexible persons can attain a greater angle of stretch with an accompanying greater tensile stress and energy than inflexible persons due to an apparent greater tolerance to the externally applied load, and larger change in moment arm. The obtained stress data appear to be in the toe region of a 'classical' stress-strain curve, and energy rather than stiffness may therefore be more appropriate to analyze during the stretch procedure.

Adult↗
PubMed2006

Effects of eccentric exercise on joint stiffness and muscle connectin (titin) isoform in the rat hindlimb.

We investigated the effects of repeated eccentric exercise for rat medial gastrocnemius muscle on ankle joint stiffness and muscle connectin (titin) isoform composition (longer form, alpha-connectin; shorter form, beta-connectin). Male Wistar rats were trained on a custom-made, isokinetic dynamometer (eccentric-exercise group, n = 6; sham-operated group, n = 6). The exercise session consisted of 20 eccentric contractions elicited by submaximal electric stimulations under anesthesia. The contracting muscle was forcibly lengthened by an isokinetic dorsi-flexion of the ankle joint (velocity, 30 degrees/s; range of motion, 45 degrees). Rats in the eccentric-exercise group were trained every two days for 20 days (10 sessions in total). The static passive resistive torque (PRT) of 45 degrees at the ankle joint was used as a measure of the joint stiffness, and was determined before and after the experimental period. After 10 sessions of eccentric exercise, the wet weight of medial gastrocnemius muscle significantly increased (P < 0.05), whereas the static PRT significantly decreased (P < 0.05) in the eccentric-exercise group, when compared to the sham-operated group. Myosin-ATPase staining showed a decrease in the number of type IIb/IId fibers (P < 0.001) and an increase in the number of type IIa fibers (P < 0.05). However, no significant difference was seen in the connectin (titin) isoform composition between the eccentric-exercise group and the sham-operated group, suggesting that the reduction in PRT was not due to change in resting mechanical properties of muscle fibers.

Animals↗
PubMed2003

The effect of eccentric training at different velocities on cross-education.

The purpose of this study was to determine whether cross-education, defined as the increase in strength of an untrained limb after training of the contralateral homologous limb, is specific to low and high velocity eccentric training. Twenty-six subjects were randomized into two groups ( n=13 each) that performed unilateral eccentric training of the elbow flexors on an isokinetic dynamometer at velocities of either 30 degrees s(-1) (0.52 rad s(-1)) or 180 degrees s(-1) (3.14 rad s(-1 )). Subjects trained three times per week for 8 weeks. Ten subjects served as controls and did not train. Subjects were tested before and after training for peak torque of the elbow flexors during eccentric and concentric contractions at 30 degrees s(-1) and 180 degrees s(-1). Eccentric peak torque at the velocity of 180 degrees s(-1) in the untrained arm increased only for the group that trained at that velocity (P<0.05). There were no other changes in untrained arms for any of the groups at velocities of 30 degrees s(-1) or 180 degrees s(-1). For the trained arm, the increase in eccentric torque (pooled over velocities) was greatest for the group training at 180 degrees s(-1), whereas the increase in concentric torque was similar for the groups training at 30 degrees s(-1) and 180 degrees s(-1). For the trained arm, there was no specificity for velocity or contraction type. We conclude that cross-education was specific to contraction type and velocity when fast (but not slow) eccentric contractions were used during training; whereas there was no specificity of training in the trained arm.

Adaptation, Physiological↗
PubMed1998

Effects of the type of meniscal lesion on knee function.

The relationship between the type of meniscal lesion (bucket-handle, flap or degenerative tears) and preoperative knee function (5.1 +/- 6.2 days before arthroscopic meniscectomy) was studied in 35 patients. Patients with bucket-handle tears (group B, n = 12) had large knee extension work deficits during maximal voluntary contractions at 30 degrees and 180 degrees/s (Kin-Com dynamometer). These work deficits were accompanied by proportional decreases in the prime mover or agonist-EMG levels (VM: vastus medialis and/or VL: vastus lateralis). These patients had smaller deficits during flexion movements at 30 degrees/s. Moreover, a larger number of negative clinical signs and symptoms (pain at rest and during tests, locking, thigh atrophy, extension and flexion movement deficits larger than 10 degrees) were found with an equal or a higher prevalence in group B than in the other groups. Patients with flap tears (group F, n = 15) had deficits in work and agonist-EMG activity (VM and VL) only during the extension tests. In contrast, patients with degenerative tears (group D, n = 8) had a work deficit and a concomitant decrease in the EMG level of the medial gastrocnemius (MG), only during the flexion test at 30 degrees/s. Comparable mean knee function scores, as measured by the Lysholm and Gillquist questionnaire [35], were obtained for the three groups of patients, suggesting that this measure was not sensitive enough to discern functional differences related to types of meniscal tears. The results of this study have demonstrated a link between the type of meniscal lesion and the consequent preoperative knee joint disability profile as defined by comparison with the sound leg. These results emphasize the need to consider meniscal lesion type and an individual's preoperative strength deficit when group comparisons of patients are made or the effects of therapy (arthroscopic surgery and rehabilitation) are evaluated.

Adult↗
PubMed2005

Influence of 90-day simulated microgravity on human tendon mechanical properties and the effect of resistive countermeasures.

While microgravity exposure is known to cause deterioration of skeletal muscle performance, little is known regarding its effect on tendon structure and function. Hence, the aims of this study were to investigate the effects of simulated microgravity on the mechanical properties of human tendon and to assess the effectiveness of resistive countermeasures in preventing any detrimental effects. Eighteen men (aged 25-45 yr) underwent 90 days of bed rest: nine performed resistive exercise during this period (BREx group), and nine underwent bed rest only (BR group). Calf-raise and leg-press exercises were performed every third day using a gravity-independent flywheel device. Isometric plantar flexion contractions were performed by using a custom-built dynamometer, and ultrasound imaging was used to determine the tensile deformation of the gastrocnemius tendon during contraction. In the BR group, tendon stiffness estimated from the gradient of the tendon force-deformation relation decreased by 58% (preintervention: 124 +/- 67 N/mm; postintervention: 52 +/- 28 N/mm; P < 0.01), and the tendon Young's modulus decreased by 57% postintervention (P < 0.01). In the BREx group, tendon stiffness decreased by 37% (preintervention: 136 +/- 66 N/mm; postintervention: 86 +/- 47 N/mm; P < 0.01), and the tendon Young's modulus decreased by 38% postintervention (P < 0.01). The relative decline in tendon stiffness and Young's modulus was significantly (P < 0.01) greater in the BR group compared with the BREx group. Unloading decreased gastrocnemius tendon stiffness due to a change in tendon material properties, and, although the exercise countermeasures did attenuate these effects, they did not completely prevent them. It is suggested that the total loading volume was not sufficient to completely prevent alterations in tendon mechanical properties.

Adaptation, Physiological↗
PubMed2001

Stretching at the ankle joint: viscoelastic responses to holds and continuous passive motion.

PURPOSE: To compare the effect of static holds and continuous passive motion on stiffness and force relaxation of the soft tissue structures resisting ankle joint dorsiflexion. METHODS: This study used a randomized repeated measures trial design. Twenty-four asymptomatic subjects (15 males and 8 females) with a mean age of 26 yr participated. A Kin-Com dynamometer was used to measure the stiffness and force relaxation response of tissues about the ankle joint in response to a plantar flexor stretch. A comparison was made of the response for a 1 x 60-s hold, 2 x 30-s holds, 4 x 15-s holds, and continuous passive motion for 60 s. All subjects undertook all conditions. The main outcome measures were 1) stiffness at the ankle joint as it moved to 80% of the maximum range of dorsiflexion, and 2) the decrease in force at 80% of the maximum range of motion of the ankle joint. RESULTS: Stiffness was decreased significantly (P < 0.05) for the continuous passive motion condition only. The mean magnitude of the decrease in stiffness was 16%. Across hold times, force decreased significantly (P < 0.05). Bonferonni contrasts indicated that there was a significant difference (P < 0.05) between the continuous passive motion condition and all other hold conditions. There were no significant differences (P > 0.05) between the 4 x 15-s, 2 x 30-s, and 1 x 60-s holds. The magnitude of the decline in force was 10.5%, 21.5%, 21.7%, and 19% for the 0-, 15-, 30-, and 60-s holds, respectively. The greatest decreases in tension were achieved in the first 20 s of a hold. CONCLUSION: If decreasing stiffness is a key aim of a stretching program, the findings indicate that continuous motion is more effective than holds. In contrast, if relaxation of peak tension is the main aim, then holds are most effective.

Adult↗
PubMed1996

[Kienböck's disease treated by shortening osteotomy of the radius. Analysis of the results apropos of 13 cases].

A series of 13 cases of Kienbock's disease, treated by shortening of the radius, operated between 1975 and 1995, is presented. This series consisted of 7 males and 6 females with a mean age of 27.5 years (range: 17 to 37 years). The dominant hand was affected in 12 cases. 6 men and 5 women performed heavy work. The mean period between the first symptoms and the operation was 18 months (range: 3 months to 6 years). In 10 cases, pain was severe and limited activities; in 3 cases, pain was moderate with partial limitation of activity. 8 cases had a mobility greater than 75% compared to the healthy side. 5 cases had a mobility of approximately 50%. None of the cases had a mobility less than 25%. Strength was not measured preoperatively with the JAMAR dynamometer. The standard radiographic assessment included an AP palm-plate film (raised palm) and a true profile on a small board. This radiographic assessment established, for each case: the Decoulx and Lichtmann classification, the radioulnar index, the angle of the radial slope and the lunate fossa, collapse of the carpus according to Youm and McMurtry. There were two stage 1, three stage 2, eight stage 3 (six stage 3A, and two stage 3B) and no stage 4. The radioulnar index was negative in 10 cases, zero in 1 case, and positive in 2 cases. The mean angle of the radial slope was 23 degrees, the mean angle of the lunate fossa was 10.8 degrees, the mean height of the carpus was 0.476. The incision was anterior in 7 cases, and posterolateral in 6 cases. The mean shortening was 5 mm (range: 4 to 6 mm). Patients were reviewed with a mean follow-up of 5 years (range: 10 months to 12 years). The analysis according to Michon's criteria revealed 3 excellent results, 9 good results, 1 moderate result and no poor results. All patients were able to resume their previous occupation. Five no longer had any pain, 6 had moderate and rare pain, 2 patients presented pain limiting activity. 10 patients presented a mobility greater than 75% compared to the healthy side. In 2 cases, the mobility was greater than 50%. In 9 cases, the strength was greater than 75% compared to the healthy side, and in 4 cases, it was greater than 50%. Radiological assessment, all stages combined, showed 4 improvements, 7 stabilizations, 2 deteriorations. There was no correlation between the height of the carpus (which varied only very slightly postoperatively) and the clinical or radiological course. In this series of 13 patients; shortening osteotomy gave results on all stages of the disease. There was no correlation between the clinical and radiological course of the lunate, and the following factors: age, preoperative radiographic stage, instability of the carpus, position of the plate. On the basis of the results of our series, it appears important to increase the angle of the lunate fossa and to obtain an angulation greater than 12 degrees 5 and to maintain a negative radioulnar index. The 2 cases of radiological deteriorations corresponded to a positive postoperative radioulnar index, while the index remained negative in the 4 cases of improvement; all cases in which the angulation of the lunate fossa was greater than 12 degrees stabilized or improved radiologically, regardless of the preoperative stage. Despite contradictory theories, we believe, in the light of our series, that an angulation of the lunate fossa greater than 12 degrees and that a negative radioulnar index appear to be decisive criteria in the course of Kienböck's disease treated by shortening of the radius.

Adolescent↗