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PubMed1972

The relations between sarcomere length and characteristics of isometric twitch contractions of frog sartorius muscle.

1. Relations between sarcomere length, tension and time course of isometric twitches at 20 degrees C were determined for thirty-two sartorius muscles from Rana temporaria.2. The maximum isometric twitch tension per unit cross-sectional area of muscle ranged from 0.56 to 2.2 kg/cm(2) at 20 degrees C and initial sarcomere length about 2.1 mu. This variation was not correlated with the corresponding measure of tetanic tension.3. The maximum isometric twitch tension per unit cross-sectional area of muscle at 2.1 mu sarcomere length was directly correlated with twitch contraction time and inversely correlated with the cross-sectional area of the muscle.4. The isometric twitch contraction was potentiated with increase in initial sarcomere length from about 2.1 to about 2.8 mu at 20 degrees C, and the degree of potentiation was inversely correlated with the maximum isometric twitch tension per unit cross-sectional area of muscle at 2.1 mu sarcomere length.5. The sarcomere length: twitch tension relation is labile and may be altered by changes in temperature and the after-effects of repetitive stimulation.6. Variation in twitch contractions at different sarcomere lengths are discussed in connexion with excitation-contraction coupling and the degree of activation of muscle fibres during twitch contractions at 20 degrees C.

Animals↗

PubMed1975

Relation between length, isometric force, and O2 consumption rate in vascular smooth muscle.

The length-tension and length-oxygen consumption rate relationships were studied in bovine mesenteric vein at 37 degrees C. The absence of spontaneous mechanical activity permits straightforward interpretation in terms of active (smooth muscle) and passive components of the vein wall. Longitudinal loops, the predominant smooth muscle component being oriented in the longitudinal (axial) direction, were maximally stimulated using epinephrine (2-5 mug-ml-1). An optimum length for isometric tension development was exhibited at which the passive tension was 25% of the total tension. The population regression indicated that tension was developed at lengths which ranged from 0.33 to 1.41 times the length at which maximum tension was developed. Oxygen consumption was measured using a Clark-type polarographic electrode. Basal oxygen consumption was 0.432 plus or minus 0.014 (n equal to 121) mumol-min-1 (g dry wt)-1. The basal rate was found to be independent of the passive tension. Under conditions of maximal stimulation, the oxygen consumption rate at L-o, the resting length at which the tissue maintained 1 g-wt passive tension, was approximately twice the basal rate. The length dependence of the suprabasal oxygen consumption was parallel to that of the active isometric force. This parallel relation reflected a linear relation between active isometric force (deltaP-o) and suprabasal oxygen consumption rate (deltaJ-o2). The slope of the deltaJ-o2-deltaP-o linear regression was 0.142 plus or minus 0.013 nmol O2-MIN-1 (G-WT-CM)-1. DeltaJ-o2 at the minimum contracted length, at which no active force was developed, was 15-20% of the deltaJ-o2 measured when maximum isometric force was developed. This provides an upper bound to the rate of chemical energy utilization required for activation processes. The length dependence of active isometric force and chemical energy utilization is most simply interpreted in terms of a sliding-filament model.

Animals↗

PubMed1982

Measurement of airway response by isometric and nonisometric techniques in situ.

Because isometric systems differ substantially from methods of measuring airway smooth muscle tone that depend on airway diameter, we determined the sensitivity and significance of data derived from these different methods in 20 anesthetized dogs. The airway contractile response was measured directly from an isometric tracheal segment in situ and simultaneously as pulmonary resistance (RL) and dynamic compliance (Cdyn). The contractile response to intravenous (iv) methacholine (MC) (2.6 X 10(-11) to 2.6 X 10(-6) mol/kg) and norepinephrine (NE) (1.2 X 10(-11) to 1.2 X 10(-6) mol/kg) was measured in dose-response studies of beta-blocked and ganglion-blocked animals. A statistically significant change in isometric tracheal tension was first observed at 2.6 X 10(-10) mol/kg iv MC and 1.2 X 10(-9) mol/kg iv NE. Statistically significant changes in Cdyn and RL did not occur at doses less than 10(-8) mol/kg for either agonist. Substantial increase in isometric tracheal tension (greater than 10 g force/cm) occurred before any change in RL or Cdyn. These finding indicate that change in isometric tension reflects parallel changes in RL and Cdyn. For NE and MC, tracheal tension is a more sensitive and selective measurement of airway contraction than RL or Cdyn.

Airway Resistance↗

PubMed1995

Lesser vagal withdrawal during isometric exercise with age.

The tachycardia that accompanies isometric exercise decreases with age in humans; however, the mechanism of this decline is unknown. To determine whether less cardiac vagal withdrawal is associated with the age-related decrease in this response, we assessed high-frequency R-R interval variability (0.15-0.40 Hz), an index of cardiac vagal tone, before (control) and during isometric exercise to exhaustion in healthy young (21-29 yr; n = 12) and older (61-72 yr; n = 11) men. During control, the two groups did not differ in respiratory rate, mean arterial pressure, or heart rate, although the older subjects had a lower high-frequency amplitude (12.2 +/- 1.1 vs. 29.4 +/- 4.6 ms/Hz; P < 0.05). During isometric exercise, the respiratory rate and arterial pressure responses did not differ; however, the older men had a lower absolute heart rate and a smaller increase in heart rate, and only the young men demonstrated a significant decline in high-frequency amplitude. The heart rate responses to exercise were correlated with the declines in high-frequency amplitude (initial, r = -0.808; midpoint, r = -0.714; peak, r = -0.632; all P < 0.005), which were, in turn, correlated with the control high-frequency amplitude (initial, r = -0.727; midpoint, r = -0.643; peak, r = -0.610; all P < 0.01). Thus smaller declines in high-frequency amplitude, related to lower baseline amplitude, corresponded to smaller increases in heart rate throughout isometric exercise. Therefore, we conclude that the smaller tachycardiac response to isometric exercise in older humans is associated with an inability to decrease cardiac vagal tone below an already reduced baseline level.

Adult↗

PubMed2003

Hindlimb unloading-induced muscle atrophy and loss of function: protective effect of isometric exercise.

The primary objective of this study was to determine the effectiveness of isometric exercise (IE) as a countermeasure to hindlimb unloading (HU)-induced atrophy of the slow (soleus) and fast (plantaris and gastrocnemius) muscles. Rats were assigned to either weight-bearing control, 7-day HU (H7), H7 plus IE (I7), 14-day HU (H14), or H14 plus IE (I14) groups. IE consisted of ten 5-s maximal isometric contractions separated by 90 s, administered three times daily. Contractile properties of the soleus and plantaris muscles were measured in situ. The IE attenuated the HU-induced decline in the mass and fiber diameter of the slow-twitch soleus muscle, whereas the gastrocnemius and plantaris mass were not protected. These results are consistent with the mean electromyograph recordings during IE that indicated preferential recruitment of the soleus over the gastrocnemius and plantaris muscles. Functionally, the IE significantly protected the soleus from the HU-induced decline in peak isometric force (I14, 1.49 +/- 0.12 vs. H14, 1.15 +/- 0.07 N) and peak power (I14, 163 +/- 17 vs. H14, 75 +/- 11 mN.fiber length.s-1). The exercise protocol showed protection of the plantaris peak isometric force at H7 but not H14. The IE also prevented the HU-induced decline in the soleus isometric contraction time, which allowed the muscle to produce greater tension at physiological motoneuron firing frequencies. In summary, IE resulted in greater protection from HU-induced atrophy in the slow soleus than in the fast gastrocnemius or plantaris.

Animals↗

PubMed1999

The comparison of intraocular pressure reductions after isometric and isokinetic exercises in normal individuals.

The lowering effect of physical exercise on intraocular pressure (IOP) has been reported both in healthy people and those with glaucoma, but a comparison of the lowering effect of isometric and isokinetic exercises on IOP has not been conducted in any study. Our aims were to investigate the relationship between intensity of exercise and IOP, and whether a significant difference in IOP lowering effect existed between isometric and isokinetic exercises. Sixty-seven patients with an age range of 23-40 who had no ocular disease were randomly divided into two groups. While 31 patients in the first group, group A, performed isokinetic exercise with the Cybex 6000 dynamometer, 32 patients in the second group, group B, had isometric exercises with the same machine. IOP was measured in the right eye of patients with Shiotz tonometer just before and 10 min following exercise. Exercise intensity and total energy consumption were determined by the machine for each patient. While IOP values measured before exercise, the degree of exercise applied, and total energy consumption did not differ significantly between groups, both isometric and isotonic exercises lowered IOP significantly. As a result, isometric and isokinetic exercises lowered IOP in ophthalmologically normal subjects with direct relationship to exercise intensity and total energy consumption. Since the pressure lowering effect of isokinetic exercise was more significant, it might prove useful to glaucomatous patients.

Adult↗

PubMedDate not supplied

Patterns of diastolic abnormalities during isometric stress in patients with systemic hypertension.

This study was undertaken to determine the prevalence and distribution of diastolic function abnormalities at rest and during isometric exercise in patients with systemic hypertension using the recently introduced handgrip-apexcardiographic test (HAT). It has been shown that HAT reflects left ventricular pressure changes in early (relaxation) and late (compliance) diastole. A HAT was obtained in 132 patients with systemic hypertension (duration >1 year) without history of congestive heart failure. A healthy group (n = 186) served as control subjects. Diastolic abnormalities were present at rest in 53/132 (40%) and during isometric handgrip stress in 92/132 (70%) patients. At rest the most frequent diastolic abnormality was the prolongation of relaxation time (27%) whereas an isolated increase in A wave was rare (8%). During isometric exercise, however, an elevation of A wave was the predominant abnormality (38%) whereas an isolated prolongation of relaxation time was less frequent (14%). Alternatively, an 'ischemic' pattern (abnormal prolongation of resting normal relaxation time during handgrip and/or abnormal as well as more than double increase of resting normal relative A wave to total height during or after handgrip) was observed in 29%. In 89% of these patients with an ischemic pattern of diastolic changes, a typical angina and/or positive stress ECG and/or angiographically proved coronary artery disease were present. Using HAT data the present study demonstrates for the first time that in patients with systemic hypertension: (1) diastolic abnormalities occur significantly more frequently during isometric stress than at rest, (2) the most frequently observed diastolic abnormality at rest is the relaxation time prolongation whereas during isometric stress the A wave elevation, and (3) patients with an ischemic pattern of exercise-induced diastolic abnormalities show frequently clinical or angiographic evidence of demand ischemia. Thus, HAT can become a useful additional diagnostic tool for detecting latent diastolic dysfunction and myocardial ischemia in this clinical setting.

Adolescent↗

PubMed2003

Effects of isometric exercise on subfoveal choroidal blood flow in smokers and nonsmokers.

PURPOSE: Little is known about potential effects of smoking on ocular blood flow regulation. In the present study, the hypothesis was that choroidal blood flow (CBF) changes during an increase in ocular perfusion pressure induced by isometric exercise are altered in chronic smokers. METHODS: The study was performed in 24 (12 smokers and 12 nonsmokers) healthy male volunteers in an observer-masked, two-cohort study design. The difference in CBF regulation between smokers and nonsmokers was tested during isometric exercise over a period of 6 minutes. CBF was assessed with laser Doppler flowery (LDF), and ocular perfusion pressure (OPP) was calculated from mean arterial pressure (MAP) and intraocular pressure (IOP). RESULTS: Six minutes of isometric exercise induced a significant increase in MAP, pulse rate (PR), OPP, and CBF in smokers and nonsmokers (each P<0.001). The increase in CBF was significantly higher in the smoking group (P<0.001) than in the healthy control group, whereas a comparable increase in MAP (P=0.18), PR (P=0.18), and OPP (P=0.43) occurred in smokers and nonsmokers. IOP remained unchanged during isometric exercise in both groups. Moreover, in smokers, CBF started to increase at OPPs more than 49% above baseline, whereas CBF in nonsmokers remained stable until an increase in OPP of 74% over baseline. This difference between the two groups was significant (P<0.001). CONCLUSIONS: These data indicate abnormal CBF regulation in chronic smokers compared with age-matched nonsmoking subjects during isometric exercise. The pathways responsible for this abnormal blood flow response remain to be elucidated.

Adult↗

PubMedDate not supplied

The relationship of the femoral attachment site to the isometric tracking of the anterior cruciate ligament graft.

The large number of reconstructive procedures in the treatment of ACL reflect a lack of consistent clinical success, thus creating the current controversy over the treatment of ACL injuries. The purpose of this study on the relationship of the femoral attachment site to the isometric tracking of the ACL graft was three-fold: 1) to develop a method for evaluating the femoral attachment site for the ideal isometric graft tracking pattern; 2) to develop a reference table comparing femoral attachment sites to graft excursion; and 3) to apply this information to the surgical procedure to allow for stepwise refinement of the attachment site for improved clinical results. To aid in graphic representation, the attachment sites were identified from radiographs by the sclerotic margin of the drill hole in the bone or the bone trough. These attachment sites were transferred to a trace diagram and compiled to form a composite diagram. Three distinct graft tracking patterns were identified. Group I represented the modified "over-the-top" technique with a deep cancellous bone trough and represented the most isometric tracking. Group II represented the modified over-the-top technique with a shallow or no cancellous bone trough and Group III the drill hole technique. Groups II and III were nonisometric. In surgery, palpation of the graft for excursion while performing a range of motion allows for review of isometric graft tracking. Stepwise intraoperative refinement of the femoral attachment site can result in isometric graft tracking.

Adolescent↗

PubMed2006

Oxygen cost of dynamic or isometric exercise relative to recruited muscle mass.

BACKGROUND: Oxygen cost of different muscle actions may be influenced by different recruitment and rate coding strategies. The purpose of this study was to account for these strategies by comparing the oxygen cost of dynamic and isometric muscle actions relative to the muscle mass recruited via surface electrical stimulation of the knee extensors. METHODS: Comparisons of whole body pulmonary delta VO2 were made in seven young healthy adults (1 female) during 3 minutes of dynamic or isometric knee extensions, both induced by surface electrical stimulation. Recruited mass was quantified in T2 weighted spin echo magnetic resonance images. RESULTS: The delta VO2 for dynamic muscle actions, 242 +/- 128 ml x min(-1) (mean +/- SD) was greater (p = 0.003) than that for isometric actions, 143 +/- 99 ml x min(-1). Recruited muscle mass was also greater (p = 0.004) for dynamic exercise, 0.716 +/- 282 versus 0.483 +/- 0.139 kg. The rate of oxygen consumption per unit of recruited muscle (VO2(RM)) was similar in dynamic and isometric exercise (346 +/- 162 versus 307 +/- 198 ml x kg(-1) x min(-1); p = 0.352), but the VO2(RM) calculated relative to initial knee extensor torque was significantly greater during dynamic exercise 5.1 +/- 1.5 versus 3.6 +/- 1.6 ml x kg(-1) x Nm(-1) x min(-1) (p = 0.019). CONCLUSION: These results are consistent with the view that oxygen cost of dynamic and isometric actions is determined by different circumstances of mechanical interaction between actin and myosin in the sarcomere, and that muscle recruitment has only a minor role.

Journal Article↗

PubMed1975

Myocardial ischemic effects of isometric, dynamic and combined exercise in coronary artery disease.

The electrocardiographic effects isometric (handgrip) and combined isometric-dynamic (treadmill-plus-brief-case) exercise were evaluated and compared to a submaximal treadmill stress test in 140 patients with known or suspected coronary artery disease. Only 3 of 90 patients developed ischemic ST changes during handgrip, as opposed to 25 positive treadmill tests (p less than 0.01). Of 19 of 50 patients who were positive during the standard treadmill test, only 17 showed positive findings during the combined treadmill-briefcase test. Analysis of hemodynamic responses showed significant (p less than 0.01) differences between the handgrip and treadmill tests in terms of heart rate response (control 83 plus or minus beats/minute, handgrip 105 plus or minus 4, treadmill 151 plus or minus 6), diastolic blood pressure (control 80 plus or minus 2 mm Hg, isometric 93 plus or minus 3, treadmill 81 plus or minus 3) and heart rate-systolic pressure product (control 9940 plus or minus 564 units, handgrip 15022 plus or minus 779, treadmill 22270 plus or minus 1147). In comparing treadmill and combined treadmill-briefcase tests, significant differences were seen in systolic blood pressure (control 114 plus or minus 2 mm Hg, treadmill 143 plus or minus 3, briefcase 155 plus or minus 3), diastolic blood pressure (control 83 plus or minus 2 mm Hg, treadmill 82 plus or minus 2, briefcase 89 plus or minus 2) and rate-pressure product (control 10134 plus or minus 373, treadmill 19624 plus or minus 777, briefcase 21201 plus or minus 798). Isometric exercise alone is much less likely to produce myocardial ischemia than vigorous dynamic exercise. Higher arterial diastolic (coronary perfusion) pressure may retard the development of myocardial ischemia during isometric or combined isometricdynamic exercise in coronary patients.

Angina Pectoris↗

PubMedDate not supplied

Phase I design and evaluation of an isometric muscle reeducation device for knee osteoarthritis rehabilitation.

Our long-term goal is to improve adherence to a home-based isometric program for rehabilitation of knee osteoarthritis (OA) using a force-biofeedback device (Isopad). Our goal for Phase I was to design and evaluate an Isopad-based program in a supervised clinical setting. Our subjects were five patients with knee OA of Kellgren stage II or greater. A capacitive force sensor was tested for accuracy, repeatability, and durability. An Arthritis Foundation home-based isometric program inspired the Isopad design. The Isopad provided visual and auditory feedback instantaneously and continuously about force generated between the ankles. The five subjects completed a supervised 8-week progressive isometric program using the Isopad. Absolute isolated quadriceps and hamstring torques were quantified with a dynamometer, and patients completed a self-assessment of symptoms (Western Ontario and McMaster Universities Osteoarthritis Index). The capacitive sensor accuracy error averaged 10% and repeatability 4%. Cognitively intact subjects used the Isopad successfully for isometric progressive resistance training. Quadriceps and hamstrings absolute torques increased an average of 30%. Patients reported decreased functional complaints (Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index). All changes were trends. The Isopad helped subjects with knee OA adhere to a supervised isometric program and meet progressive strength targets. The next-generation Isopad will be employed in a home-based program.

Electromyography↗

PubMed1976

Effect of beta-adrenoreceptor blockers on heart rate and blood pressure in dynamic and isometric exercise.

Previous studies on the effects on heart rate and blood pressure in normals and hypertensive patients during dynamic exercise (ergometer bicycling or treadmill walking) and isometric exercise (sustained handgrip) are reviewed. In one study utilising sub-maximal bicycle exercise in hypertensives, there was a 43% increase in heart rate for a 33% increase in systolic pressure and 5% fall in diastolic pressure. Beta-adrenoreceptor blockade decreased the heart rate level by 18 to 19% for a decrease of systolic blood pressure level by 4 to 11%, whereas the diastolic pressure level was unaffected. A protocol is described utilising a blind indirect blood pressure recording machine ("Auto-Manometer") with which cuff inflation and deflation are automatic and constant, and blood pressure values stored at suitable Korotkov sound phases. The machine also records heart rate. By this method, isometric exercise at 50% of maximal voluntary contraction (sustained handgrip) has been studied in normals and hypertensives off and on different treatments. Both in normals and established hypertensives, there was about a 25% increase in systolic blood pressure during isometric exercise for about a 22% increase in diastolic blood pressure, and 26% increase in heart rate. Normotensive women had the lowest rise in blood pressure and the highest rise in heart rate. Beta-Adrenoreceptor blocking agents lowered heart rate during isometric exercise by 15 to 20% but did not affect the blood pressure level. Since resting blood pressure levels were decreased, the percentage rise in pressure was enhanced following beta-blockers. A combination of a beta-blocker, clonidine and/or a vasodilator produced a reduction in both systolic (24%) and diastolic (12%) pressure, as well as in heart rate (18%), during isometric exercise.

Adrenergic beta-Antagonists↗

PubMed1991

Isometric and isokinetic torque curves at the knee joint.

Isometric and isokinetic torques of bilateral quadriceps and hamstrings were measured with Isokinetic Rehabilitation and Testing System (Model No. Cybex 340) on 40 normal untrained subjects, 20 males and 20 females, ranging between the ages of 23 and 35 years. The mean peak isometric and isokinetic torque values of both muscle groups showed no significant differences between dominant (right) and nondominant (left) limbs in both sexes; however there were significant differences between the male and the female. As the angular velocity increased, the peak torque significantly decreased, and the point of peak torque output occurred significantly later in the range of motion for quadriceps and hamstrings (p less than 0.01). There were no significant changes in the hamstrings to quadriceps (H/Q) ratios as the angular velocity increased. However, there were significant differences of mean H/Q ratio between male and female (p less than 0.01). Height had significant positive correlation with peak isometric and isokinetic torques for both quadriceps and hamstrings (p less than 0.01). Weight was found to correlate significantly with peak isometric and isokinetic torques (p less than 0.01). The mean isometric torques were significantly higher than the mean isokinetic torques for any joint angles in both sexes (p less than .01).

Adult↗

PubMed2003

Age-related differences in knee extension rate of isometric force development and vertical jumping performance in women.

AIM: The purpose of this study was to compare knee extension rate of isometric force development and vertical jumping performance characteristics in young, middle-aged and elderly women. METHODS: Unilateral knee extension maximal rate of isometric force development (RFD) was measured by a dynamometer. Maximal squat (SJ) and counter-movement jumps (CMJ) were performed on a force platform. Twelve young (21- to 24-year-old), 12 middle-aged (50- to 58-year-old) and 13 elderly (70- to 76-year-old) women participated. RESULTS: Young women had greater (p<0.05) maximal isometric RFD as compared to older groups. No significant differences in maximal isometric RFD between middle-aged and elderly women have been found. The jumping height in SJ and CMJ was greater in young women as compared to older groups, and in middle-aged women greater as compared to elderly women. Absolute and body mass-related values of CMJ height was greater as compared to SJ height only in young women. Young women had greater jumping height relative to body mass in SJ and CMJ than the other groups. CONCLUSION: The ability to develop isometric force of the knee extensor muscles rapidly did not differ significantly in middle-aged and elderly women. Middle-aged and elderly women had a reduced ability to use the potentiating effect of stretch-shortening cycle to vertical jumping performance during CMJ.

Adult↗

PubMed1992

[Hypertensive cardiopathy. Functional evaluation during isometric effort after regression of left ventricular hypertrophy].

OBJECTIVE: Echocardiographic evaluation of the response to isometric exercise of hypertensive patients with and without left ventricular hypertrophy. PARTICIPANTS: 28 patients with severe arterial hypertension on long-term follow-up with or without regression of left ventricular hypertrophy on medical therapy; a control group of 10 healthy volunteers. METHODS: Two groups were considered: Group A persistent left ventricular hypertrophy and group B normalization of the left ventricular wall thickness and mass index. The arterial blood pressure and heart rate were evaluated and an echocardiographic record was obtained both at rest and after isometric exercise (maximal effort for 1 to 1.5 minutes). The following echocardiographic data were obtained: left ventricular diameters and thickness of septum and posterior wall during systole and diastole. Volumes, shortening and ejection fractions, cardiac output and index, mass index, end-systolic stress, contractility index and periferal resistance were calculated as usual. RESULTS: During isometric exercise there was a rise in systolic, diastolic and mean arterial pressures and heart rate. Systolic function was normal in all groups at rest. The shortening fraction was not altered in normotensive individuals with isometric exercise. Hypertensive patients showed a significant reduction within normal limits, however. End-systolic stress increased significantly in all groups although the rise was greater in hypertensive patients. The cardiac index rose significantly only in normotensives and hypertensive patients without left ventricular hypertrophy (group B). On the contrary the periferal resistance rose significantly only in hypertensive patients with left ventricular hypertrophy (group A). The contractility index (end-systolic stress/end-systolic volume index) increased significantly only in normotensive and hypertensive patients without left ventricular hypertrophy. CONCLUSIONS: There are functional alterations in hypertensive heart disease which although not evident at rest, can be revealed by isometric exercise. The regression of left ventricular hypertrophy back to normal, sets a trend for normalization of function and cardiac inotropic reserve, suggesting the importance of a complete regression of ventricular hypertrophy.

Adult↗

PubMed1991

[Influence of isometric exercise on left ventricular diastolic function in the normal subjects and in patients with hypertension and coronary heart disease].

To evaluate the influence of isometric exercise on left ventricular (LV) diastolic function, transmittal flow velocity was measured by pulsed Doppler echocardiography before and after handgrip in 15 normal subjects and the patients with hypertension as well as 18 patients with coronary heart disease (CHD). Statistically significant differences in peak velocity of early rapid filling (Ev), the ratios of peak early to late diastolic velocity (Ev/Av) and early to late velocity-time integral (Ei/Ai) between normal subjects and both the patients with hypertension and CHD were noted at rest. After isometric exercise, significant increase in Av (0.70 +/- 0.13 vs 0.76 +/- 0.14, P less than 0.01) and Ai/total VTi (0.35 +/- 0.07 vs 0.42 +/- 0.08, P less than 0.05) were showed in the hypertension group. In CHD, multiple Doppler parameters changed after isometric exercise with increase in Av (0.70 +/- 0.16 vs 0.85 +/- 0.18, P less than 0.01) and Ai/total VTi (0.36 +/- 0.08 vs 0.42 +/- 0.08, P less than 0.01) as well as decrease in Ev/Av (0.95 +/- 0.22 vs 0.82 +/- 0.15, P less than 0.05) and Ei/Ai (1.64 +/- 0.51 vs 1.35 +/- 0.34, P less than 0.05). However, there was no significant difference in any Doppler indices of LV diastolic function in the present normal subjects after isometric exercise. Thus, isometric exercise further enhanced late LV diastolic filling in the patients with impaired LV diastolic function in resting states greater than normal subjects, and myocardial ischemia induced by handgrip may play partial role in more changes in Doppler indices of LV diastolic function in CHD than the patients with hypertension.

Aged↗

PubMed1988

Isometric and isokinetic hip abductor strength in persons with above-knee amputations.

Recently introduced prosthetic socket designs for the above-knee amputee (AKA) feature a narrow medial-lateral dimension and emphasize maintenance of the residual limb in full physiologic adduction. Quantitative data on the effect of frontal plane limb position on the isometric hip abductor strength of ten otherwise healthy AKAs were obtained in the standing position. Residual limb isometric and isokinetic abductor strength was also measured and compared with that of the intact limb and with that of ten healthy age-, sex-, and height-matched control subjects using an identical technique. The testing hardware consisted of a modified Cybex II Isokinetic Dynamometer with a custom-made pelvis and trunk stabilizing device. Anthropometric measurements were taken. Results showed an essentially linear increase in residual limb abduction strength with progressive adduction from 30 degrees abduction to 16 degrees adduction. The average increase in abduction torque was .97% (range .29 to 1.5) of the peak neutral position strength per degree of change in femur angle when corrected for the effect of gravity. Similar strength increases with adduction of the femur were found for intact and control limbs. Mean residual limb isometric abduction torque measured 30% less than the intact limb value (p = .0018). The difference between the intact and the control limb mean isometric abduction torques was less than 1%. Isokinetic testing was technically more difficult than isometric testing but revealed similar weakness of the residual limb abductors when compared to the intact and control limbs.

Adult↗