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PubMed2002

Effects of a 4-month season on glenohumeral joint rotational strength and range of motion in female collegiate tennis players.

The purpose of this study was to examine the effects of a 4-month season of collegiate tennis on glenohumeral joint internal and external rotation strength and range of motion in female collegiate tennis players. Eleven female collegiate tennis players were isokinetically tested to assess glenohumeral joint internal and external rotation strength with 90 degrees of abduction on a Cybex 6000 isokinetic dynamometer. Subjects were also measured for internal and external rotation range of motion using a universal goniometer with 90 degrees of abduction. Measurements were taken before and immediately after a 4-month season of competitive collegiate tennis play. A repeated-measures analysis of variance showed no significant difference in internal or external rotation strength or range of motion between pre- and postseason measures. Results from this study show that, despite 4 months of competitive tennis play, changes in rotational strength and range of motion did not occur. These data have implications for clinicians as well as strength and conditioning professionals designing rehabilitation and preventative conditioning programs for athletes in this population.

Adaptation, Physiological↗
PubMed1997

Characterization of global synkineses during hand grip in hemiparetic patients.

OBJECTIVE: Global synkineses are defined as nonpurposive associated movements on the involved side of hemiparetic subjects that are triggered during a voluntary movement. The purpose of this study was to characterize the intensity and pattern of upper limb global synkineses in hemiparetic subjects with a static biarticular dynamometer and electromyography during maximal progressive hand grip on the unaffected side. DESIGN: Survey, convenience sample. SETTINGS: University secondary care rehabilitation center. DATA SET: Global synkineses (ie, torques and electromyographic activities) in patients with severe (n = 8) and moderate (n = 7) deficits in motor performance, as evaluated by the Fugl-Meyer assessment, were compared with those obtained in a group of healthy subjects (n = 11). Clinically the subjects from the severe deficit group were more spastic and showed less strength at the elbow than the subjects from the moderate deficit group. RESULTS: Results of analyses of variance showed significant increases of shoulder torque in flexion and internal rotation, and elbow torque in flexion, with increasing force exertion during contralateral hand grip in subjects with severe deficits (p < .05). Furthermore, in these subjects increases of electromyographic activity were also observed in biceps brachii, brachioradialis, and triceps brachii muscles with increasing hand grip force levels. In contrast, no significant torques or electromyographic increases were observed in subjects with moderate deficits and in control subjects during contralateral hand grip exertions. CONCLUSION: These results provide a quantitative assessment of the kinematic and electromyographic patterns of global synkineses and their correlates with clinical observations. Within the limits of the experimental results presented in this study, it is suggested that global synkineses result from contralateral overflow of the voluntary command to hyperexcitable motoneuron pools.

Adult↗
PubMed1996

Age, fat-free weight, and isokinetic peak torque in high school female gymnasts.

The purpose of this study was to examine the covariate influence of fat-free weight (FFW) on age-related increases in isokinetic peak torque for leg flexion and extension in high school female gymnasts. Seventy-two gymnasts (X age +/- SD = 15 7 +/- 1.2 yr) volunteered to be measured for isokinetic leg flexion and extension strength using a calibrated Cybex II dynamometer at 30, 180, and 300 degrees*s(-1) as well as for body composition from underwater weighing. The results indicated that there were significant (P < 0.05) zero-order correlations for age versus leg flexion (r = 0.36-0.47) and extension (r = 0.51-0.57) peak torque, as well as FFW versus leg flexion (r = 0.50-0.66) and extension (r = 0.620.73) peak torque. There were also significant (P < 0.05) first-order partial correlations between age and peak torque (covaried for FFW) for leg extension at 30 (r = 0.25), 180 (r = 0.36-0.39), and 300 degrees*s(-1) (r = 0.25-0.28) but not for leg flexion. These findings indicated that for the high school female gymnasts in the present study, there were age-related increases in strength that could not be accounted for by changes in FFW. It is possible that factors such as an increase in muscle mass per unit of FFW and/or neural maturation contribute to strength increases during adolescence in female athletes.

Adolescent↗
PubMed1998

Passive properties of human skeletal muscle during stretch maneuvers. A review.

Despite limited scientific knowledge, stretching of human skeletal muscle to improve flexibility is a widespread practice among athletes. This article reviews recent findings regarding passive properties of the hamstring muscle group during stretch based on a model that was developed which could synchronously and continuously measure passive hamstring resistance and electromyographic activity, while the velocity and angle of stretch was controlled. Resistance to stretch was defined as passive torque (Nm) offered by the hamstring muscle group during passive knee extension using an isokinetic dynamometer with a modified thigh pad. To simulate a clinical static stretch, the knee was passively extended to a pre-determined final position (0.0875 rad/s, dynamic phase) where it remained stationary for 90 s (static phase). Alternatively, the knee was extended to the point of discomfort (stretch tolerance). From the torque-angle curve of the dynamic phase of the static stretch, and in the stretch tolerance protocol, passive energy and stiffness were calculated. Torque decline in the static phase was considered to represent viscoelastic stress relaxation. Using the model, studies were conducted which demonstrated that a single static stretch resulted in a 30% viscoelastic stress relaxation. With repeated stretches muscle stiffness declined, but returned to baseline values within 1 h. Long-term stretching (3 weeks) increased joint range of motion as a result of a change in stretch tolerance rather than in the passive properties. Strength training resulted in increased muscle stiffness, which was unaffected by daily stretching. The effectiveness of different stretching techniques was attributed to a change in stretch tolerance rather than passive properties. Inflexible and older subjects have increased muscle stiffness, but a lower stretch tolerance compared to subjects with normal flexibility and younger subjects, respectively. Although far from all questions regarding the passive properties of humans skeletal muscle have been answered in these studies, the measurement technique permitted some initial important examinations of vicoelastic behavior of human skeletal muscle.

Age Factors↗
PubMed1999

Effect of grip span on maximal grip force and fatigue of flexor digitorum superficialis.

The aim of this study was to investigate the effect of grip span on isometric grip force and fatigue of the flexor digitorum superficialis (FDS) muscle during sustained voluntary contractions at 60-65% of the maximal voluntary contraction (MVC). Eighteen subjects performed isometric, submaximal gripping contractions using a grip dynamometer at four different grip span settings while the pronated forearm rested on a horizontal surface. Maximal absolute grip force and median power frequency of FDS surface electromyography (EMG) during the submaximal trials were analyzed. Fatigue of FDS, as inferred from EMG frequency shifts, did not change as a function of grip size. However, middle grip sizes allowed for greater absolute forces than the small or large size. When contractions are at 60-65% MVC and the muscle is allowed to fatigue, however, grip size may be less influential than when maximal absolute force is required.

Adult↗
PubMed2001

Oral creatine supplementation facilitates the rehabilitation of disuse atrophy and alters the expression of muscle myogenic factors in humans.

1. We investigated the effect of oral creatine supplementation during leg immobilization and rehabilitation on muscle volume and function, and on myogenic transcription factor expression in human subjects. 2. A double-blind trial was performed in young healthy volunteers (n = 22). A cast was used to immobilize the right leg for 2 weeks. Thereafter the subjects participated in a knee-extension rehabilitation programme (3 sessions x week(-1), 10 weeks). Half of the subjects received creatine monohydrate (CR; from 20 g down to 5 g daily), whilst the others ingested placebo (P; maltodextrin). 3. Before and after immobilization, and after 3 and 10 weeks of rehabilitation training, the cross-sectional area (CSA) of the quadriceps muscle was assessed by NMR imaging. In addition, an isokinetic dynamometer was used to measure maximal knee-extension power (Wmax), and needle biopsy samples taken from the vastus lateralis muscle were examined to asses expression of the myogenic transcription factors MyoD, myogenin, Myf5, and MRF4, and muscle fibre diameters. 4. Immobilization decreased quadriceps muscle CSA (approximately 10 %) and Wmax (approximately 25 %) by the same magnitude in both groups. During rehabilitation, CSA and Wmax recovered at a faster rate in CR than in P (P < 0.05 for both parameters). Immobilization changed myogenic factor protein expression in neither P nor CR. However, after rehabilitation myogenin protein expression was increased in P but not in CR (P < 0.05), whilst MRF4 protein expression was increased in CR but not in P (P < 0.05). In addition, the change in MRF4 expression was correlated with the change in mean muscle fibre diameter (r = 0.73, P < 0.05). 5. It is concluded that oral creatine supplementation stimulates muscle hypertrophy during rehabilitative strength training. This effect may be mediated by a creatine-induced change in MRF4 and myogenin expression.

Adenosine Triphosphate↗
PubMed2002

Isokinetic leg strength of institutionalized older adults with mental retardation with and without Down's syndrome.

This study compared isokinetic leg strength of aged individuals with mental retardation (MR) with and without Down's syndrome (DS). Nine subjects with MR and DS (mean age = 61) and 16 subjects with MR but without DS (mean age = 63) performed a leg strength test on a Biodex dynamometer. Parameters measured were peak torque, peak torque percent body weight (ratio displayed as a percentage of the maximum torque production to the subject's body weight), and average power percent body weight. In addition, anthropometric measurements (height, weight, skinfolds, and body mass index) and intelligence quotient (IQ) were also analyzed and compared. The results indicate a significant increase of scores for isokinetic knee extension and flexion in the group with MR but without DS over the subjects in the group with MR and DS. As a group, the individuals with MR and DS tended to be smaller and fatter. No significant difference in IQ was observed between the 2 groups with MR. It was concluded that the strength of individuals with MR but without DS is greater than the group of subjects with MR and DS. When comparing their results to aged individuals without MR, a significant decline in muscle strength can be observed among people with MR.

Age Factors↗
PubMed2006

Validity and reliability of measurements of elbow flexion strength obtained from older adults using elastic bands.

PURPOSE: This study determined the validity and reliability of measurements of elbow flexion strength obtained from older adults using elastic bands. METHODS: Forty-eight community-dwelling older adults with documented functional limitations completed 3 assessments of elbow flexion strength: a 30-second test using elastic bands to generate resistance, a similar test using dumbbells, and a test using an isokinetic dynamometer. One week later, subjects repeated the 30-second elbow flexion test using elastic bands. RESULTS: The 30-second elbow flexion test using elastic bands was significantly correlated with both the 30-second elbow flexion test using dumbbells (r = 0.62, P < 0.01 ) and the maximum isokinetic torque of the elbow flexors (r = 0.46, P < 0.01 ). The 30-second elbow flexion test using elastic bands demonstrated a high degree of test-retest reliability (intraclass correlation coefficient = 0.89, P < 0.01 ). CONCLUSION: The validity and reliability elbow flexion strength measured with elastic bands supports its use among functionally limited elders.

Aged↗
PubMed2000

Isokinetic torque deficit of the knee extensor muscles after arthroscopic partial meniscectomy.

Isokinetic torque deficit of the knee extensor muscles in the operated leg was measured in 21 male patients (mean age 26.4 +/- 1.9 years) who had undergone arthroscopic partial medial meniscectomy. The isokinetic torque testing was performed 1, 3, and 6 months postoperatively using the Cybex II dynamometer according to standard technique. Isokinetic knee extension peak torque (PT) at angular velocities of 60 degrees and 180 degrees/s was determined in both legs, and the proportional PT deficit in the operated leg was compared with that in the nonoperated leg. A significant (P<0.001) isokinetic PT deficit in the operated leg in testing with angular velocity of 60 degrees and 80 degrees/s was observed at 1 month (28.6% and 31.0%, respectively) and 3 months (19.8% and 15.8%, respectively) postoperatively. At 6 months postoperatively a significant (P<0.001) isokinetic PT deficit (18.2%) of the knee extensor muscles in the operated leg was observed only in testing with angular velocity of 60 degrees/s; no significant differences (P>0.05) in isokinetic PT between the operated and nonoperated leg in testing with angular velocity of 180 degrees/s was found 6 months postoperatively. Thus in patients with arthroscopic partial meniscectomy the postoperative recovery of isokinetic strength of the knee extensor muscles in the injured leg is closely related to testing velocity, while it is more delayed at low than intermediate angular velocities.

Adult↗
PubMed2006

Mechanical properties of the triceps surae tendon and aponeurosis in relation to intensity of sport activity.

The purpose of the present study was to investigate whether the mechanical properties (i.e. force strain relationship) of the triceps surae tendon and aponeurosis relate to the performed sport activity in an intensity-dependent manner. This was done by comparing sprinters with endurance runners and subjects not active in sports. Sixty-six young male subjects (26+/-5 yr; 183+/-6 cm; 77.6+/-6.7 kg) participated in the study. Ten of these subjects were adults not active in sports, 28 were endurance runners and 28 sprinters. All subjects performed isometric maximal voluntary plantar flexion contractions (MVC) on a dynamometer. The distal aponeuroses of the gastrocnemius medialis (GM) was visualised by ultrasound during the MVC. The results showed that only the sprinters had higher normalised stiffness (relationship between tendon force and tendon strain) of the triceps surae tendon and aponeurosis and maximal calculated tendon forces than the endurance runners and the subjects not active in sports. Furthermore, including the data of all 66 examined participants tendon stiffness correlated significantly (r=0.817, P<0.001) with the maximal tendon force achieved during the MVC. It has been concluded that the mechanical properties of the triceps surae tendon and aponeurosis do not show a graded response to the intensity of the performed sport activity but rather remain at control level in a wide range of applied strains and that strain amplitude and/or frequency should exceed a given threshold in order to trigger additional adaptation effects. The results further indicate that subjects with higher muscle strength possibly increase the margin of tolerated mechanical loading of the tendon due to the greater stiffness of their triceps surae tendon and aponeurosis.

Adaptation, Physiological↗
PubMed1994

The relation between isometric lifting strength and muscular fitness measures.

The purpose of this study was to construct an isometric lift dynamometer and relate isometric lifting strength to dynamic measures of muscular fitness, leg and back strength and muscular power output. Thirty-one male subjects, aged 19-24 years, performed a standing broad jump (for distance), a vertical jump (for flight time), 3 maximal pulls (for peak power) on a rowing ergometer and maximal isometric leg and back extensions on a conventional dynamometer. The results of these tests were correlated with the maximum isometric lifting strength (MILS) obtained on the lift dynamometer using cluster correlation and multiple regression. Significant correlations (p < 0.001) were found between isometric lifting strength and back strength (BS) (r = 0.59), and leg strength (LS) (r = 0.74). A significant correlation was also noted between isometric lifting strength and both standing broad jump (SBJ) (r = 0.58, p < 0.001) and power output (PO) (r = 0.38, (p < 0.05). Multiple regression analysis was used to predict lifting performance from a battery of standard fitness tests. The prediction equation for maximal isometric lifting strength included the terms LS, BS, SBJ and PO (r = 0.80). The relation between isometric lifting strength and other muscular fitness variables suggest that the method used provides an acceptable measure of strength and an indication of the involvement of back and leg musculature in squat lifting.

Adult↗
PubMed1994

Functional asymmetry in the motor performances of women: neuropsychological effects of depression.

The influence of depression on the cerebral hemispheric motor functioning of 40 right-handed women, half of whom had been classified as depressed, the other half as nondepressed, was examined. The depressed women were also characterized by elevated state and trait anxiety, suggestive of an anxious-depressive state with heightened arousal. A hand dynamometer was used as a standardized measure of hemispheric motor functioning such as hand-grip strength, perseveration, and fatigue. Primary findings indicated that depressed women displayed significantly less perseveration at the left hand than did nondepressed women, but a nonsignificant trend only was noted for less perseveration at the right hand. These results suggest possible differential arousal of the left and right cerebral hemispheres in this sample of anxious-depressed women and are discussed in terms of arousal theory.

Adolescent↗
PubMed1993

Evaluation of isokinetic hip strength after rotational acetabular osteotomy.

Fifty-four patients with dysplastic hip and secondary degenerative arthrosis (58 hips) underwent rotational acetabular osteotomy (RAO) using a conventional anterior-posterior method or a new technique involving detachment of the greater trochanter. Pre- and postoperative hip abductor strength (HAS) and knee extensor strength (KES) were evaluated using an isokinetic dynamometer. Postoperative HAS in patients treated by detachment of the greater trochanter reached preoperative levels 16 weeks postoperatively. Comparison of the postoperative HAS based on the two different surgical approaches showed that RAO by detachment of the greater trochanter was superior to the conventional method. Pre- and postoperative HAS showed a good correlation. Postoperative improvements in HAS over presurgical values were not significant in patients with advanced-stage arthrosis and severely dysplastic hips. Preoperative HAS should serve as an index for determining whether RAO is undertaken using detachment of the greater trochanter.

Acetabulum↗
PubMedDate not supplied

Shoulder strength following acromioclavicular injury.

The acromioclavicular (AC) joint enjoys the dubious distinction of being one of the few joints in the body whose total dislocation is routinely treated by simply leaving the joint dislocated. Adherents of both conservative and operative treatment have presented reasons for their viewpoints. Residual shoulder weakness has been offered as a sequela of untreated acromioclavicular injury and a reason for repairing the joint. An objective evaluation of shoulder strength would be valuable in determining the optimum treatment for this injury. The purpose of our study was to quantitate, using the Cybex II, the residual shoulder weakness following various modes of treatment. Seventeen patients with Grade III AC separations and eight patients with Grade II AC sprains were reviewed. Nine of the Grade III injuries were treated and eight nonoperatively. All Grade II injuries were treated nonsurgically. All patients were tested on the Cybex II isokinetic dynamometer at both slow and fast speeds through various ranges of motion. Grade III injuries treated nonoperatively showed no significant strength deficits. Surgically treated Grade III injuries had a significant strength deficit in vertical abduction at fast speeds (19.8%) when compared to the uninjured shoulder. Interestingly, the Grade II injuries led to a significant weakness in horizontal abduction (24.3%) at fast velocity. Evaluation of subjective results showed that Grade III injuries treated conservatively had the most pain and stiffness, despite their strong shoulders. Patients with Grade III injuries treated operatively rated their overall outcome below that of those treated conservatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromioclavicular Joint↗
PubMed2003

Effect of strength and proprioception training on eversion to inversion strength ratios in subjects with unilateral functional ankle instability.

OBJECTIVES: To examine the effect of six weeks of strength and proprioception training on eversion to inversion isokinetic strength ratios (E/I ratios) in subjects with unilateral functional ankle instability. METHODS: Thirty eight subjects were randomly assigned to one of four treatment groups: strength training (S); proprioception training (P); strength + proprioception training (B); control (C). Isokinetic strength was tested before and after training using a Kin Com 125 automatic positioning isokinetic dynamometer. Subtalar joint eversion and inversion motions were tested both concentrically and eccentrically through a range of motion involving 40 degrees. All peak torque and average torque values were normalised for body mass. E/I ratios were calculated from average torque and peak torque measures by taking the concentric eversion value and combining it with the eccentric inversion value. Data were analysed using a mixed model analysis of variance with repeated measures on the test factor. Average torque and peak torque E/I ratios at 30 and 120 degrees/s were analysed separately. RESULTS: There were no significant differences in average torque and peak torque E/I ratios of the functionally unstable ankle for any of the groups after training compared with before. CONCLUSIONS: Six weeks of strength and proprioception training (either alone or combined) had no effect on isokinetic measures of strength in subjects with self reported unilateral functional instability. Further studies examining this agonist (concentric) to antagonist (eccentric) muscle group strength ratio are needed.

Adult↗
PubMed1989

Arm function after stroke. An evaluation of grip strength as a measure of recovery and a prognostic indicator.

The value of strength of voluntary grip as an indicator of recovery of arm function was assessed by testing 38 recent stroke patients using a sensitive electronic dynamometer, and comparing the results with those from five other arm movement and function tests (Motricity Index, Motor Club Assessment, Nine Hole Peg Test, and Frenchay Arm Test). This procedure allowed measurement of grip in a large proportion of patients, and strength correlated highly with performance on the other tests. Measuring grip over a six month follow up period was a sensitive method of charting intrinsic neurological recovery. The presence of voluntary grip at one month indicates that there will be some functional recovery at six months.

Adult↗
PubMed2005

The magnitude of muscle damage induced by downhill backward walking.

While various models for exercise-induced muscle damage (EIMD) have been introduced, many of them use maximal voluntary contractions of the elbow flexors and knee extensors performed on isokinetic dynamometers. Few studies have used exercise protocols that attempt to replicate submaximal eccentric muscle actions that commonly occur during daily activities. Downhill backwards walking has been used previously as an EIMD model. However, the common markers of muscle damage have not been systematically examined for this model. The purpose of this study was to determine the magnitude of muscle damage induced by downhill backward walking with regard to changes in commonly-used indirect markers of EIMD. Twenty subjects aged between 19 y and 42 y completed a bout of 60 min of downhill (-15%) backward walking in which a single limb performed submaximal eccentric actions at a stepping rate of 30 - 35 strides per min. A repeated measures ANOVA revealed significant (p < 0.05) increases from baseline for soreness (24 hr- 96 hr), tenderness (24 hr - 96 hr), and plasma creatine kinase activity (0.5 hr - 96 hr), and significant decreases (p < 0.05) in maximal voluntary isometric (approximately 25%) and isokinetic (-15%) strength (0.5 hr - 96 hr) post-walk for the exercised limb. The time course of observed changes in these markers was similar to that reported for EIMD models of the elbow flexors and knee extensors. However, the magnitude of muscle damage appeared more consistent with that demonstrated following submaximal eccentric exercise.

Adult↗
PubMedDate not supplied

The relationship between two power-grip testing devices and their utility in physical capacity evaluations.

This study compared two isometric-grip testing devices and considered the efficacy of combining data from the two as a means of identifying both functional status and consistency of effort for physical capacity evaluations (PCEs). Two groups (26 healthy subjects and 40 patients who had upper-extremity impairments) were used to establish the reliability of applying force on a jamar dynamometer, and on an Isometric Strength Testing Unit (ISTU). Many of the patients had been referred because of inconsistencies between subjective complaint and medical presentation. The results indicate that power-grip force outputs are highly related across the two test devices, which validates their utility as part of a PCE for wrist-hand involvement. A simple index (2-ratio) of functional status and consistency was developed by combining test data from the two devices. The sensitivity of the 2-ratio, in combination with other indices of consistency, is discussed.

Analysis of Variance↗