David Ben-Sira | The Zinman College of Physical Education, Wingate Institute (original) (raw)

Papers by David Ben-Sira

Research paper thumbnail of Identification of feigned strength test of the knee extensors and flexors based on the shape of the isokinetic torque curve

Isokinetics and Exercise Science, 2001

The purpose of this study is to assess the ability of clinicians to identify false isokinetic str... more The purpose of this study is to assess the ability of clinicians to identify false isokinetic strength test of the knee flexors and extensors, based only on the shape of the torque curve. The concentric strength was measured bilaterally using an isokinetic dynamometer at 60 • /sec. Each subject performed two modes of testing: a) A Genuine strength test (GST) which consisted of five consecutive cycles of knee extension and flexion at maximal effort. b) A false strength test (FST) which consisted of five consecutive cycles of knee extensions and flexion attempting to feign pain. For each test, the torque curves were printed and presented to four judges to mark each of the tests as a GST or a FST based on the shape of the torque curves. The mean percentage of success in identifying a GST and a FST for the 4 judges was 91.9% (range = 87.5-97.5%) and 90.6% (range = 82.5-95%) respectively In conclusion, in spite of the constraints, which were imposed on the judges, the rate of correct classification was high.

Research paper thumbnail of Isokinetic moment curve abnormalities are associated with articular knee lesions

Biology of sport, 2018

The aim of this study was to test whether lesions of the medial meniscus (MM) and of the anterior... more The aim of this study was to test whether lesions of the medial meniscus (MM) and of the anterior cruciate ligament (ACL) are associated with specific abnormalities of isokinetic moment curves (IMCs). Fifty-four young adults (20 active healthy people, and 34 patients with unilateral knee injuries) were assessed through knee extensor and flexor isokinetic tests at 60°/s. Qualitative IMC analysis was performed using a novel classification system which identified three distinct abnormal shapes. The chi-squared (χ2) test was used to determine the inter-individual and intra-individual differences between the groups. Quantitative IMC inter-group comparisons were performed by a one-way analysis of variance (ANOVA). Knees with MM and ACL lesions were consistently associated with IMC shape irregularities (p<0.001) and with abnormal quantitative scores (p<0.001). More specifically, knees with isolated ACL lesions and knees with combined ACL and MM lesions presented similar distribution ...

Research paper thumbnail of Factors defining oxygen uptake at peak exercise in aged people

European Review of Aging and Physical Activity, 2010

Research paper thumbnail of A Simple Procedure for Event Marking when Filming with One or Two Cameras

Research Quarterly. American Alliance for Health, Physical Education and Recreation

ABSTRACT A researcher who has access to one motor-driven 16mm high speed camera containing intern... more ABSTRACT A researcher who has access to one motor-driven 16mm high speed camera containing internal timing lights may find circumstances when some part of an event cannot be in the camera&#39;s filming zone. When using devices such as a force platform, electrogoniometer, electromyograph, or other measurement tools the researcher must in some way identify the start and often the completion of an event synchronously with all devices and cameras. In an effort to resolve these problems, a series of experiments was conducted using one or two electronic flash units (operated either AC or by battery) to identify the event on film for the 16mm camera.

Research paper thumbnail of Muscle torques and landing kinematics are associated with maintenance of sports participation at five to ten years after ACL reconstruction

Orthopaedic Journal of Sports Medicine, 2020

Research paper thumbnail of A comparison of the mechnical characteristics of the instep kick between skilled soccer players and novices

Research paper thumbnail of Personalized multicomponent exercise programs using smartphone technology among older people: protocol for a randomized controlled trial

BMC Geriatrics, 2021

Background Optimal application of the recently updated World Health Organization (WHO) guidelines... more Background Optimal application of the recently updated World Health Organization (WHO) guidelines for exercise in advanced age necessitates an accurate adjustment for the age-related increasing variability in biological age and fitness levels, alongside detailed recommendations across a range of motor fitness components, including balance, strength, and flexibility. We previously developed and validated a novel tool, designed to both remotely assess these fitness components, and subsequently deliver a personalized exercise program via smartphone. We describe the design of a prospective randomized control trial, comparing the effectiveness of the remotely delivered personalized multicomponent exercise program to either WHO exercise guidelines or no intervention. Methods Participants (n = 300) are community dwelling, healthy, functionally independent, cognitively intact volunteers aged ≥65 at low risk for serious fall injuries, assigned using permuted block randomization (age/gender) ...

Research paper thumbnail of Direct vs. Indirect Blood Pressure Measurement at Peak Anaerobic Exercise

International Journal of Sports Medicine, 1999

The present study compared the direct intra-arterial method with the indirect conventional sphygm... more The present study compared the direct intra-arterial method with the indirect conventional sphygmomanometer during all-out anaerobic exercise, in young healthy subjects. Systolic and diastolic blood pressures were measured by intraarterial means and by auscultation. Fourteen young healthy males (23+/-2 yrs) were measured at rest and during all-out anaerobic exercise. Comparisons were made with simultaneously determined intra-arterial catheter and auscultation measurements. The data suggest that indirect systolic pressure is highly correlated with the direct method at rest (r = 0.684), with mean of 107+/-7 and 101+/-6 mmHg, respectively, and during all-out anaerobic exercise (r = 0.87), with mean of 197+/-11 and 191+/-9 mmHg, respectively. Indirect diastolic blood pressure correlates well with intra-arterial at rest (r = 0.62), with mean of 84+/-11 and 77+/-9 mmHg, respectively. However, during all-out anaerobic exercise, the correlation coefficient between the direct and the indirect methods was low (r = 0.36), with mean of 101+/-12 and 103+/-9 mmHg, respectively. These results suggest that when utilizing an all-out anaerobic exercise, the indirect method is not valid for assessment of diastolic pressure. In addition, although the anaerobic test is a dynamic type of exercise, its blood pressure responses for both direct and indirect methods were similar to those seen during isometric exercise.

Research paper thumbnail of Changes in the muscles' strength ratio as a result of fatigue

Humanismo Y Nuevas Tecnologias En La Educacion Fisica Y El Deporte Aiesep Congreso Mundial Madrid 26 31 Julio De 1988 1990 Isbn 84 257 0033 7 Pags 321 324, 1990

Research paper thumbnail of Perceptual Responses to Exercise: The Effect of Load-Awareness on Physiological Responses During an Isometric Bout

International Journal of Sports Medicine, 1999

To evaluate the effect of awareness of load on cardiovascular and metabolic responses, thirty mal... more To evaluate the effect of awareness of load on cardiovascular and metabolic responses, thirty males were compared in three different loads during upright deadlift isometric exercise, at 25%, 30% and 35% of maximal voluntary contraction for 3 min. Significant differences (P &lt; 0.05) were found from rest to 25%, 30% and 35% for all physiological variables, heart rate (66.5+/-9.0, 104.0+/-12.0, 115.0+/-9.0, and 123.0+/-11.0 beats x min(-1), respectively), and for lactic acid (2.2+/-0.4, 4.6+/-0.7, 5.7+/-1.1, and 6.3+/-1.5 mM x l(-1), respectively). However, no significant differences were revealed between the various conditions when rate-perceived exertion data were analyzed, despite increased absolute loads. These data indicate that the psychological manipulation introduced in this study did not affect physiological responses during isometric exercise, in contrast to that seen during dynamic exercise.

Research paper thumbnail of What Maintains the Metabolic Cost at Maximal Exercise in Heart Transplant Recipients and Coronary Artery Disease Patients?

The Journal of Heart and Lung Transplantation, 2007

Background: In this study we assess the influence of disease status on hemodynamic and cardiac ou... more Background: In this study we assess the influence of disease status on hemodynamic and cardiac output values, as measured by oxygen utilization at peak aerobic exercise, in heart transplant recipients (HTRs) and coronary artery disease patients (CAD). Methods: Fifteen CAD patients and 13 HTRs (40.2 Ϯ 12.6 and 41.7 Ϯ 11.7 years, respectively) underwent a peak cardiopulmonary exercise test on bicycle ergometry. Arterial oxygen was defined on the basis of echocardiography and venous oxygen content. Results: At rest, except for cardiac output, oxygen uptake and lactate levels, all variables were significantly (p Ͻ 0.01) different between groups. At peak exercise, compared with HTRs, CAD patients had significantly (p Ͻ 0.0001) higher values for cardiac output (12.4 Ϯ 0.8 and 20.2 Ϯ 1.7 liters/min, respectively), stroke volume (87.3 Ϯ 5.4 and 129.3 Ϯ 9.7 ml, respectively) and oxygen uptake (22.7 Ϯ 3.6 and 29.7 Ϯ 2.7 ml/kg/min, respectively) (p Ͻ 0.01), whereas (a Ϫ v)O 2 was significantly lower (127.0 Ϯ 4.3 and 141.9 Ϯ 6.4 O 2 ml/liter, respectively; p Ͻ 0.0001). Conclusions: The differences in oxygen utilization at peak exercise may be attributed to differences in energy metabolism, namely higher oxygen extraction in HTRs, compensating for the dramatically reduced oxygen delivery. It is further suggested that CAD patients and HTRs respond to a greater extent to maximal aerobic testing by reducing their left ventricular systolic function despite increased after-load.

Research paper thumbnail of Left Ventricular Contractility in Response to Upright Isometric Exercise in Heart Transplant Recipients and Healthy Men

Journal of Cardiopulmonary Rehabilitation and Prevention, 2008

We evaluated left ventricular contractility during upright isometric exercise, in heart transplan... more We evaluated left ventricular contractility during upright isometric exercise, in heart transplant recipients (HTRs) and in healthy controls, using ejection fraction and end-systolic pressure/volume ratio indexes. Fifteen healthy men (40 +/- 13 years) and 10 HTRs (42 +/- 12 years) underwent dead lift (DL) test at 30% of maximal effort for 3 minutes. Echocardiographic variables were measured during the final 45 seconds. During DL test, HTRs were significantly different (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .01) from controls in all parameters except end-diastolic volume. DL test had lower mean values of ejection fraction (49.9% +/- 8.3% vs 67.0% +/- 4.3%, respectively) and left ventricular end-systolic pressure/volume ratio (3.5 +/- 0.7 vs 5.5 +/- 1.2, respectively) whereas higher values of end-systolic volume (51.0 +/- 9.4 mL vs 34.1 +/- 5.3 mL, respectively). Importantly, an intergroup effect was found in end-systolic pressure/volume ratio, further signifying differential response of HTRs. End-systolic pressure/volume ratio increased consistently (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001) in both groups, whereas the overall main effect of ejection fraction response was not significant. Left ventricular function during upright isometric exercise displays differential pattern of response in HTRs in comparison with healthy controls. However, cardiac contractility in HTRs remained stable at peak systolic blood pressure produced by the isometric DL exercise. Results suggest that both ejection fraction and end-systolic pressure/volume ratio indexes can be used for assessment of ventricular function in patients after heart transplantation.

Research paper thumbnail of Paraoxonase Activity Following Exercise-Based Cardiac Rehabilitation Program

Journal of Cardiopulmonary Rehabilitation and Prevention, 2007

The effect of gender on paraoxonase activity was determined in 37 ischemic heart disease patients... more The effect of gender on paraoxonase activity was determined in 37 ischemic heart disease patients who underwent a 12-week aerobic exercise training program. Paraoxonase activity was measured by its arylesterase activity (spectrophotometrically, at 250 degrees C, wavelength 270 nm). A 16.7% increase in paraoxonase activity was found following the 12-week exercise program. In addition, there was a significant gender effect with higher mean paraoxonase levels among women during both preexercise (20.8%) and postexercise (24.2%) testing. Aerobic exercise training was found to be an effective means in inducing plasma levels elevation of the antioxidative, antiatherogenic paraoxonase in patients with coronary artery disease, and particularly in female patients.

Research paper thumbnail of The Effect of Long-Term β-Adrenergic Receptor Blockade on the Oxygen Delivery and Extraction Relationship in Patients With Coronary Artery Disease

Journal of Cardiopulmonary Rehabilitation and Prevention, 2008

Research paper thumbnail of Left Ventricular Function at Peak All-Out Anaerobic Exercise in Older Men

Gerontology, 2005

All-out anaerobic exercise may be dangerous for the older population, due to hypoxia and inapprop... more All-out anaerobic exercise may be dangerous for the older population, due to hypoxia and inappropriate blood pressure response. This study compared and evaluated left ventricular function at peak all-out anaerobic effort in 12 well-trained older (58 +/- 1 years) and 12 young men (22 +/- 1 years). Subjects were studied by echocardiography at peak all-out anaerobic exercise, on a cycle ergometer. Seven older subjects experienced ECG abnormalities. Significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) differences between the older group and the young group, respectively, were noted for: cardiac output (9.8 +/- 0.9 and 15.8 +/- 0.9 l.min(-1)), left ventricular end-systolic pressure-volume ratio (4.7 +/- 0.8 and 4.4 +/- 4.9), left ventricular end-diastolic volume (104.8 +/- 6.9 and 125.7 +/- 6.2 ml), ejection fraction (67.1 +/- 6.0 and 59.8 +/- 5.5%), left ventricular end-systolic pressure volume ratio (4.4 +/- 0.4 and 4.8 +/- 0.3 ratio), and total peripheral resistance (966.0 +/- 84.0 and 660 +/- 82.8 dyn.s(-1).cm(-5)). Data suggest that during all-out anaerobic exercise, forces opposing ejection were not reduced enough to avoid left ventricular dysfunction and ECG abnormalities in the older subjects. This is attributed to functional changes with age in the myocardium and associated blood vessels, leading to impairment of left ventricular function and blunted inotropic and chronotropic responses to catecholamine. Therefore, an all-out anaerobic-type effort should not be given to an older subject due to the great hazardous potential.

Research paper thumbnail of Effects of Chronic Overload Training and Aging on Left Ventricular Systolic Function

Gerontology, 1997

To examine the effects of age and chronic overload training on left ventricular systolic function... more To examine the effects of age and chronic overload training on left ventricular systolic function during static exercise, Doppler echocardiography studies were performed in 14 young (28 +/- 6 years) and 10 older (51 +/- 3 years) weight lifters and also in 14 young (29 +/- 6 years) and 10 older (52 +/- 1.1 years) normal individuals during upright dead-lift isometric exercise, at 30% of maximal voluntary contraction for 3 min. At rest, older weight lifters demonstrated impaired left ventricular systolic function as compared with the other three groups. During exercise, peak and mean velocity values increased significantly (p &lt; 0.05) from resting values in the young groups, but remained unchanged in the older groups. Flow period and acceleration and deceleration times were significantly (p &lt; 0.05) lower in the younger subjects than those observed for the old ones, with the highest (p &lt; 0.05) values obtained by the old weight lifters. This study suggests that the differences between the groups are related to differences in impedance and not to fundamental changes in the properties of the myocardium.

Research paper thumbnail of Effect of Changes in Load Carriage while Walking on the Left Ventricular Function in Highly Trained Elderly Subjects

Gerontology, 2002

In previous studies, the effect of isometric stress on the dynamic performance of a graded exerci... more In previous studies, the effect of isometric stress on the dynamic performance of a graded exercise test in normal subjects augmented afterload and brought about changes in left ventricular function more often than did results from physical exercise. This study used the metabolic charts and echocardiography to examine the influence of two different types of load carriage during 30 min of treadmill walking on left ventricular function, hemodynamics, and cardiovascular responses. Fifteen elderly (age 66.1 +/- 3.5 years) aerobically well-trained male subjects (VO(2 peak) 44.2 +/- 5.0 ml x kg(-1) x min(-1)) volunteered in this study. The subjects walked on a treadmill (at a speed of 4.5 km x h(-1)), carrying a load of 20 kg during one session and a load of 30 kg during a second session. Following the 30-min exercise in each session, significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) differences were noted between the 20-kg and the 30-kg work loads with regard to cardiac output (6.8 +/- 0.5 and 7.8 +/- 0.4 l.min(-1)), heart rate (114.0 +/- 11.0 and 126.0 +/- 10.0 beats.min(-1)), diastolic blood pressure (79.4 +/- 5.0 and 84.3 +/- 5.0 mm Hg, mean arterial blood pressure (104.0 +/- 4.0 and 109.2 +/- 3.0 mm Hg), and left ventricular contractility ratio (3.3 +/- 0.4 and 3.6 +/- 0.3). No significant differences were noted between the work loads with regard to systolic blood pressure, cardiac output, left ventricular volumes, and ejection fraction. This study suggests that in the highly trained elderly, the influence of the autoregulation mechanism dominates during combined dynamic and isometric exercises, thus the opposing force to the left ventricular ejection is reduced which in turn does not change left ventricular global function.

Research paper thumbnail of What Maintains Energy Supply at Peak Aerobic Exercise in Trained and Untrained Older Men?

Gerontology, 2007

Aging-related changes occur mainly in the cardiopulmonary system and skeletal muscles, bringing a... more Aging-related changes occur mainly in the cardiopulmonary system and skeletal muscles, bringing about a reduction in physical performance. Consequently, maximal oxygen uptake (VO(2)max) decreases. The current study investigated exercise oxygen utilization during maximal aerobic exercise in trained and untrained elderly. Fifteen trained (59.3 +/- 1.1 years) and 15 untrained (60.1 +/- 1.1 years) elderly underwent a peak cardiopulmonary exercise test on a bicycle ergometer. Arterial O(2 )was defined from echocardiograph and venous oxygen content. At rest, trained compared to untrained elderly had significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) higher values of end diastolic volume (108.1 +/- 5.8 and 100.7 +/- 6.2 ml, respectively) and stroke volume (68.1 +/- 4.3 and 57.3 +/- 6.5 ml, respectively), while heart rate (68.7 +/- 9.3 and 81.3 +/- 8.2 beats . min(-1), respectively), and mean arterial blood pressure (90.6 +/- 6.9 and 95.4 +/- 7.2 mm Hg, respectively) were significantly lower. At peak aerobic test, the trained elderly, compared to the untrained subjects, achieved significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) higher values of end diastolic volume (156.1 +/- 8.2 and 134.1 +/- 7.6 ml, respectively), stroke volume (123.0 +/- 7.9 and 96.0 +/- 4.8 ml, respectively), cardiac output (20.2 +/- 1.5 and 15.0 +/- 1.3 liters.min(-1), respectively) and oxygen uptake (42.1 +/- 2.1 and 31.1 +/- 2.4 ml.kg(-1).min(-1), respectively), while diastolic blood pressure (70.3 +/- 5.6 and 77.5 +/- 4.2 mm Hg, respectively) and total peripheral resistance [4.3 +/- 0.8 and 5.9 +/- 1.41 (dyn.s(-1).cm(-5)).10(-1), respectively], were significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) lower. The present study suggests that the differences between trained and untrained elderly in absolute oxygen uptake of the working muscles and peak power output at maximal exercise test are due to physical activity status. The higher aerobic capacity in the trained elderly is related to increased cardiovascular function and to a lesser extent to increased muscle mitochondria concentration and capillarity. Although untrained elderly have reduced maximal oxygen uptake at peak aerobic exercise, intrinsic regulation of mitochondrial function does not seem to be significantly altered because of aging associated physical inactivity. Therefore, untrained elderly can partially compensate for their lower cardiac output by increasing oxygen extraction to levels comparable with those of trained elderly.

Research paper thumbnail of Effects of gradient and load carried on human haemodynamic responses during treadmill walking

European Journal of Applied Physiology, 2000

This study examined the effects of different loads carried and gradients, on haemodynamic and car... more This study examined the effects of different loads carried and gradients, on haemodynamic and cardiovascular responses during 45 min of treadmill walking. A group of 20 male endurance-trained athletes [mean maximal oxygen uptake 61.4 (SD 4) ml x kg(-1) x min(-1)] volunteered for this study. The subjects took part in three separate trials. The first involved a backpack weighing 25 kg, the second a 35 kg backpack, and the third trial, unladen, while walking on a treadmill at a speed of 5 km x h(-1). The subjects began walking on the treadmill with the randomized load at 0% gradient. After 15 min, the gradient was increased by 5% every 15 min for a total of 45 min. The order of the loads carried was randomized among subjects. No significant differences were noted for all the variables measured attributable to loads between 25 kg and 35 kg. However, significant (P&lt;0.05) differences were seen for all variables each time the gradient was increased. Cardiac output increased from 11.4 (SD 0.6) 1 x min(-1) at 0% to 13.6 (SD 0.8) l x min(-1) at 5% and to 17.6 (SD 1.3) l x min(-1) at 10% carrying the 35 kg load. Similarly, lactic acid concentrations in the blood increased from 2.8 (SD 0.2) to 3.1 (SD 0.6) and to 5.3 (SD 1.3) mmol x l(-1), respectively. Similar changes were observed for all variables while carrying the 25 kg load. In addition, steady states in oxygen uptake and other physiological variables were obtained throughout the course of the tests. These data suggest that during isodynamic exercise, one of the main factors determining metabolic and haemodynamic responses will be the change in gradient and to a lesser extent, the mass of the load carried.

Research paper thumbnail of The effect of gender on left ventricular function immediately after the wingate test

European Journal of Applied Physiology, 1997

The eect of gender on left ventricular systolic function and exercise haemodynamics in healthy yo... more The eect of gender on left ventricular systolic function and exercise haemodynamics in healthy young subjects was studied during 30-s all-out sudden strenuous dynamic exercise. A group of 22 men [19.3 (SD 1) years] 20 women [19.1 (SD 1) years] volunteered to participate in this study. Two-dimensional direct Mmode and Doppler echocardiograph studies were performed with the subject in the sitting position. The Doppler examination of¯ow was located with continuous-wave, interrogating ascending aorta measurements. The subjects completed the study without showing any electrocardiograph abnormalities. An interaction eect with stroke volume (P < 0.05) was characterized by a decrease in the men and an increase of stroke volume in the women. Cardiac output rose signi®cantly (P < 0.05) up to 14.5 (SD 6) l á min)1) for the men and 12.1 (SD 4) l á min)1 for the women compared to the rest values [5.8 (SD 0.4) and 4.7 (SD 0.5) l á min)1 , respectively]. Flow velocity integral and acceleration time diered signi®cantly between the two groups at rest (P < 0.05). During exercise these dierences showed an interaction eect (P < 0.05). These results would indicate that normal men and women respond to sudden strenuous exercise by reducing their left ventricular systolic function, with a signi®cantly greater decrease in women (P < 0.05). The gender dierences in the haemodynamic responses during the present study, may, as suggested by others, be attributable to dierences in energy metabolism. In addition, changes in Doppler parameters of aortic¯ow, haemodynamics and blood pressure responses during sudden strenuous exercise diered markedly from those seen before with endurance exercise.

Research paper thumbnail of Identification of feigned strength test of the knee extensors and flexors based on the shape of the isokinetic torque curve

Isokinetics and Exercise Science, 2001

The purpose of this study is to assess the ability of clinicians to identify false isokinetic str... more The purpose of this study is to assess the ability of clinicians to identify false isokinetic strength test of the knee flexors and extensors, based only on the shape of the torque curve. The concentric strength was measured bilaterally using an isokinetic dynamometer at 60 • /sec. Each subject performed two modes of testing: a) A Genuine strength test (GST) which consisted of five consecutive cycles of knee extension and flexion at maximal effort. b) A false strength test (FST) which consisted of five consecutive cycles of knee extensions and flexion attempting to feign pain. For each test, the torque curves were printed and presented to four judges to mark each of the tests as a GST or a FST based on the shape of the torque curves. The mean percentage of success in identifying a GST and a FST for the 4 judges was 91.9% (range = 87.5-97.5%) and 90.6% (range = 82.5-95%) respectively In conclusion, in spite of the constraints, which were imposed on the judges, the rate of correct classification was high.

Research paper thumbnail of Isokinetic moment curve abnormalities are associated with articular knee lesions

Biology of sport, 2018

The aim of this study was to test whether lesions of the medial meniscus (MM) and of the anterior... more The aim of this study was to test whether lesions of the medial meniscus (MM) and of the anterior cruciate ligament (ACL) are associated with specific abnormalities of isokinetic moment curves (IMCs). Fifty-four young adults (20 active healthy people, and 34 patients with unilateral knee injuries) were assessed through knee extensor and flexor isokinetic tests at 60°/s. Qualitative IMC analysis was performed using a novel classification system which identified three distinct abnormal shapes. The chi-squared (χ2) test was used to determine the inter-individual and intra-individual differences between the groups. Quantitative IMC inter-group comparisons were performed by a one-way analysis of variance (ANOVA). Knees with MM and ACL lesions were consistently associated with IMC shape irregularities (p<0.001) and with abnormal quantitative scores (p<0.001). More specifically, knees with isolated ACL lesions and knees with combined ACL and MM lesions presented similar distribution ...

Research paper thumbnail of Factors defining oxygen uptake at peak exercise in aged people

European Review of Aging and Physical Activity, 2010

Research paper thumbnail of A Simple Procedure for Event Marking when Filming with One or Two Cameras

Research Quarterly. American Alliance for Health, Physical Education and Recreation

ABSTRACT A researcher who has access to one motor-driven 16mm high speed camera containing intern... more ABSTRACT A researcher who has access to one motor-driven 16mm high speed camera containing internal timing lights may find circumstances when some part of an event cannot be in the camera&#39;s filming zone. When using devices such as a force platform, electrogoniometer, electromyograph, or other measurement tools the researcher must in some way identify the start and often the completion of an event synchronously with all devices and cameras. In an effort to resolve these problems, a series of experiments was conducted using one or two electronic flash units (operated either AC or by battery) to identify the event on film for the 16mm camera.

Research paper thumbnail of Muscle torques and landing kinematics are associated with maintenance of sports participation at five to ten years after ACL reconstruction

Orthopaedic Journal of Sports Medicine, 2020

Research paper thumbnail of A comparison of the mechnical characteristics of the instep kick between skilled soccer players and novices

Research paper thumbnail of Personalized multicomponent exercise programs using smartphone technology among older people: protocol for a randomized controlled trial

BMC Geriatrics, 2021

Background Optimal application of the recently updated World Health Organization (WHO) guidelines... more Background Optimal application of the recently updated World Health Organization (WHO) guidelines for exercise in advanced age necessitates an accurate adjustment for the age-related increasing variability in biological age and fitness levels, alongside detailed recommendations across a range of motor fitness components, including balance, strength, and flexibility. We previously developed and validated a novel tool, designed to both remotely assess these fitness components, and subsequently deliver a personalized exercise program via smartphone. We describe the design of a prospective randomized control trial, comparing the effectiveness of the remotely delivered personalized multicomponent exercise program to either WHO exercise guidelines or no intervention. Methods Participants (n = 300) are community dwelling, healthy, functionally independent, cognitively intact volunteers aged ≥65 at low risk for serious fall injuries, assigned using permuted block randomization (age/gender) ...

Research paper thumbnail of Direct vs. Indirect Blood Pressure Measurement at Peak Anaerobic Exercise

International Journal of Sports Medicine, 1999

The present study compared the direct intra-arterial method with the indirect conventional sphygm... more The present study compared the direct intra-arterial method with the indirect conventional sphygmomanometer during all-out anaerobic exercise, in young healthy subjects. Systolic and diastolic blood pressures were measured by intraarterial means and by auscultation. Fourteen young healthy males (23+/-2 yrs) were measured at rest and during all-out anaerobic exercise. Comparisons were made with simultaneously determined intra-arterial catheter and auscultation measurements. The data suggest that indirect systolic pressure is highly correlated with the direct method at rest (r = 0.684), with mean of 107+/-7 and 101+/-6 mmHg, respectively, and during all-out anaerobic exercise (r = 0.87), with mean of 197+/-11 and 191+/-9 mmHg, respectively. Indirect diastolic blood pressure correlates well with intra-arterial at rest (r = 0.62), with mean of 84+/-11 and 77+/-9 mmHg, respectively. However, during all-out anaerobic exercise, the correlation coefficient between the direct and the indirect methods was low (r = 0.36), with mean of 101+/-12 and 103+/-9 mmHg, respectively. These results suggest that when utilizing an all-out anaerobic exercise, the indirect method is not valid for assessment of diastolic pressure. In addition, although the anaerobic test is a dynamic type of exercise, its blood pressure responses for both direct and indirect methods were similar to those seen during isometric exercise.

Research paper thumbnail of Changes in the muscles' strength ratio as a result of fatigue

Humanismo Y Nuevas Tecnologias En La Educacion Fisica Y El Deporte Aiesep Congreso Mundial Madrid 26 31 Julio De 1988 1990 Isbn 84 257 0033 7 Pags 321 324, 1990

Research paper thumbnail of Perceptual Responses to Exercise: The Effect of Load-Awareness on Physiological Responses During an Isometric Bout

International Journal of Sports Medicine, 1999

To evaluate the effect of awareness of load on cardiovascular and metabolic responses, thirty mal... more To evaluate the effect of awareness of load on cardiovascular and metabolic responses, thirty males were compared in three different loads during upright deadlift isometric exercise, at 25%, 30% and 35% of maximal voluntary contraction for 3 min. Significant differences (P &lt; 0.05) were found from rest to 25%, 30% and 35% for all physiological variables, heart rate (66.5+/-9.0, 104.0+/-12.0, 115.0+/-9.0, and 123.0+/-11.0 beats x min(-1), respectively), and for lactic acid (2.2+/-0.4, 4.6+/-0.7, 5.7+/-1.1, and 6.3+/-1.5 mM x l(-1), respectively). However, no significant differences were revealed between the various conditions when rate-perceived exertion data were analyzed, despite increased absolute loads. These data indicate that the psychological manipulation introduced in this study did not affect physiological responses during isometric exercise, in contrast to that seen during dynamic exercise.

Research paper thumbnail of What Maintains the Metabolic Cost at Maximal Exercise in Heart Transplant Recipients and Coronary Artery Disease Patients?

The Journal of Heart and Lung Transplantation, 2007

Background: In this study we assess the influence of disease status on hemodynamic and cardiac ou... more Background: In this study we assess the influence of disease status on hemodynamic and cardiac output values, as measured by oxygen utilization at peak aerobic exercise, in heart transplant recipients (HTRs) and coronary artery disease patients (CAD). Methods: Fifteen CAD patients and 13 HTRs (40.2 Ϯ 12.6 and 41.7 Ϯ 11.7 years, respectively) underwent a peak cardiopulmonary exercise test on bicycle ergometry. Arterial oxygen was defined on the basis of echocardiography and venous oxygen content. Results: At rest, except for cardiac output, oxygen uptake and lactate levels, all variables were significantly (p Ͻ 0.01) different between groups. At peak exercise, compared with HTRs, CAD patients had significantly (p Ͻ 0.0001) higher values for cardiac output (12.4 Ϯ 0.8 and 20.2 Ϯ 1.7 liters/min, respectively), stroke volume (87.3 Ϯ 5.4 and 129.3 Ϯ 9.7 ml, respectively) and oxygen uptake (22.7 Ϯ 3.6 and 29.7 Ϯ 2.7 ml/kg/min, respectively) (p Ͻ 0.01), whereas (a Ϫ v)O 2 was significantly lower (127.0 Ϯ 4.3 and 141.9 Ϯ 6.4 O 2 ml/liter, respectively; p Ͻ 0.0001). Conclusions: The differences in oxygen utilization at peak exercise may be attributed to differences in energy metabolism, namely higher oxygen extraction in HTRs, compensating for the dramatically reduced oxygen delivery. It is further suggested that CAD patients and HTRs respond to a greater extent to maximal aerobic testing by reducing their left ventricular systolic function despite increased after-load.

Research paper thumbnail of Left Ventricular Contractility in Response to Upright Isometric Exercise in Heart Transplant Recipients and Healthy Men

Journal of Cardiopulmonary Rehabilitation and Prevention, 2008

We evaluated left ventricular contractility during upright isometric exercise, in heart transplan... more We evaluated left ventricular contractility during upright isometric exercise, in heart transplant recipients (HTRs) and in healthy controls, using ejection fraction and end-systolic pressure/volume ratio indexes. Fifteen healthy men (40 +/- 13 years) and 10 HTRs (42 +/- 12 years) underwent dead lift (DL) test at 30% of maximal effort for 3 minutes. Echocardiographic variables were measured during the final 45 seconds. During DL test, HTRs were significantly different (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .01) from controls in all parameters except end-diastolic volume. DL test had lower mean values of ejection fraction (49.9% +/- 8.3% vs 67.0% +/- 4.3%, respectively) and left ventricular end-systolic pressure/volume ratio (3.5 +/- 0.7 vs 5.5 +/- 1.2, respectively) whereas higher values of end-systolic volume (51.0 +/- 9.4 mL vs 34.1 +/- 5.3 mL, respectively). Importantly, an intergroup effect was found in end-systolic pressure/volume ratio, further signifying differential response of HTRs. End-systolic pressure/volume ratio increased consistently (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001) in both groups, whereas the overall main effect of ejection fraction response was not significant. Left ventricular function during upright isometric exercise displays differential pattern of response in HTRs in comparison with healthy controls. However, cardiac contractility in HTRs remained stable at peak systolic blood pressure produced by the isometric DL exercise. Results suggest that both ejection fraction and end-systolic pressure/volume ratio indexes can be used for assessment of ventricular function in patients after heart transplantation.

Research paper thumbnail of Paraoxonase Activity Following Exercise-Based Cardiac Rehabilitation Program

Journal of Cardiopulmonary Rehabilitation and Prevention, 2007

The effect of gender on paraoxonase activity was determined in 37 ischemic heart disease patients... more The effect of gender on paraoxonase activity was determined in 37 ischemic heart disease patients who underwent a 12-week aerobic exercise training program. Paraoxonase activity was measured by its arylesterase activity (spectrophotometrically, at 250 degrees C, wavelength 270 nm). A 16.7% increase in paraoxonase activity was found following the 12-week exercise program. In addition, there was a significant gender effect with higher mean paraoxonase levels among women during both preexercise (20.8%) and postexercise (24.2%) testing. Aerobic exercise training was found to be an effective means in inducing plasma levels elevation of the antioxidative, antiatherogenic paraoxonase in patients with coronary artery disease, and particularly in female patients.

Research paper thumbnail of The Effect of Long-Term β-Adrenergic Receptor Blockade on the Oxygen Delivery and Extraction Relationship in Patients With Coronary Artery Disease

Journal of Cardiopulmonary Rehabilitation and Prevention, 2008

Research paper thumbnail of Left Ventricular Function at Peak All-Out Anaerobic Exercise in Older Men

Gerontology, 2005

All-out anaerobic exercise may be dangerous for the older population, due to hypoxia and inapprop... more All-out anaerobic exercise may be dangerous for the older population, due to hypoxia and inappropriate blood pressure response. This study compared and evaluated left ventricular function at peak all-out anaerobic effort in 12 well-trained older (58 +/- 1 years) and 12 young men (22 +/- 1 years). Subjects were studied by echocardiography at peak all-out anaerobic exercise, on a cycle ergometer. Seven older subjects experienced ECG abnormalities. Significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) differences between the older group and the young group, respectively, were noted for: cardiac output (9.8 +/- 0.9 and 15.8 +/- 0.9 l.min(-1)), left ventricular end-systolic pressure-volume ratio (4.7 +/- 0.8 and 4.4 +/- 4.9), left ventricular end-diastolic volume (104.8 +/- 6.9 and 125.7 +/- 6.2 ml), ejection fraction (67.1 +/- 6.0 and 59.8 +/- 5.5%), left ventricular end-systolic pressure volume ratio (4.4 +/- 0.4 and 4.8 +/- 0.3 ratio), and total peripheral resistance (966.0 +/- 84.0 and 660 +/- 82.8 dyn.s(-1).cm(-5)). Data suggest that during all-out anaerobic exercise, forces opposing ejection were not reduced enough to avoid left ventricular dysfunction and ECG abnormalities in the older subjects. This is attributed to functional changes with age in the myocardium and associated blood vessels, leading to impairment of left ventricular function and blunted inotropic and chronotropic responses to catecholamine. Therefore, an all-out anaerobic-type effort should not be given to an older subject due to the great hazardous potential.

Research paper thumbnail of Effects of Chronic Overload Training and Aging on Left Ventricular Systolic Function

Gerontology, 1997

To examine the effects of age and chronic overload training on left ventricular systolic function... more To examine the effects of age and chronic overload training on left ventricular systolic function during static exercise, Doppler echocardiography studies were performed in 14 young (28 +/- 6 years) and 10 older (51 +/- 3 years) weight lifters and also in 14 young (29 +/- 6 years) and 10 older (52 +/- 1.1 years) normal individuals during upright dead-lift isometric exercise, at 30% of maximal voluntary contraction for 3 min. At rest, older weight lifters demonstrated impaired left ventricular systolic function as compared with the other three groups. During exercise, peak and mean velocity values increased significantly (p &lt; 0.05) from resting values in the young groups, but remained unchanged in the older groups. Flow period and acceleration and deceleration times were significantly (p &lt; 0.05) lower in the younger subjects than those observed for the old ones, with the highest (p &lt; 0.05) values obtained by the old weight lifters. This study suggests that the differences between the groups are related to differences in impedance and not to fundamental changes in the properties of the myocardium.

Research paper thumbnail of Effect of Changes in Load Carriage while Walking on the Left Ventricular Function in Highly Trained Elderly Subjects

Gerontology, 2002

In previous studies, the effect of isometric stress on the dynamic performance of a graded exerci... more In previous studies, the effect of isometric stress on the dynamic performance of a graded exercise test in normal subjects augmented afterload and brought about changes in left ventricular function more often than did results from physical exercise. This study used the metabolic charts and echocardiography to examine the influence of two different types of load carriage during 30 min of treadmill walking on left ventricular function, hemodynamics, and cardiovascular responses. Fifteen elderly (age 66.1 +/- 3.5 years) aerobically well-trained male subjects (VO(2 peak) 44.2 +/- 5.0 ml x kg(-1) x min(-1)) volunteered in this study. The subjects walked on a treadmill (at a speed of 4.5 km x h(-1)), carrying a load of 20 kg during one session and a load of 30 kg during a second session. Following the 30-min exercise in each session, significant (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) differences were noted between the 20-kg and the 30-kg work loads with regard to cardiac output (6.8 +/- 0.5 and 7.8 +/- 0.4 l.min(-1)), heart rate (114.0 +/- 11.0 and 126.0 +/- 10.0 beats.min(-1)), diastolic blood pressure (79.4 +/- 5.0 and 84.3 +/- 5.0 mm Hg, mean arterial blood pressure (104.0 +/- 4.0 and 109.2 +/- 3.0 mm Hg), and left ventricular contractility ratio (3.3 +/- 0.4 and 3.6 +/- 0.3). No significant differences were noted between the work loads with regard to systolic blood pressure, cardiac output, left ventricular volumes, and ejection fraction. This study suggests that in the highly trained elderly, the influence of the autoregulation mechanism dominates during combined dynamic and isometric exercises, thus the opposing force to the left ventricular ejection is reduced which in turn does not change left ventricular global function.

Research paper thumbnail of What Maintains Energy Supply at Peak Aerobic Exercise in Trained and Untrained Older Men?

Gerontology, 2007

Aging-related changes occur mainly in the cardiopulmonary system and skeletal muscles, bringing a... more Aging-related changes occur mainly in the cardiopulmonary system and skeletal muscles, bringing about a reduction in physical performance. Consequently, maximal oxygen uptake (VO(2)max) decreases. The current study investigated exercise oxygen utilization during maximal aerobic exercise in trained and untrained elderly. Fifteen trained (59.3 +/- 1.1 years) and 15 untrained (60.1 +/- 1.1 years) elderly underwent a peak cardiopulmonary exercise test on a bicycle ergometer. Arterial O(2 )was defined from echocardiograph and venous oxygen content. At rest, trained compared to untrained elderly had significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) higher values of end diastolic volume (108.1 +/- 5.8 and 100.7 +/- 6.2 ml, respectively) and stroke volume (68.1 +/- 4.3 and 57.3 +/- 6.5 ml, respectively), while heart rate (68.7 +/- 9.3 and 81.3 +/- 8.2 beats . min(-1), respectively), and mean arterial blood pressure (90.6 +/- 6.9 and 95.4 +/- 7.2 mm Hg, respectively) were significantly lower. At peak aerobic test, the trained elderly, compared to the untrained subjects, achieved significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) higher values of end diastolic volume (156.1 +/- 8.2 and 134.1 +/- 7.6 ml, respectively), stroke volume (123.0 +/- 7.9 and 96.0 +/- 4.8 ml, respectively), cardiac output (20.2 +/- 1.5 and 15.0 +/- 1.3 liters.min(-1), respectively) and oxygen uptake (42.1 +/- 2.1 and 31.1 +/- 2.4 ml.kg(-1).min(-1), respectively), while diastolic blood pressure (70.3 +/- 5.6 and 77.5 +/- 4.2 mm Hg, respectively) and total peripheral resistance [4.3 +/- 0.8 and 5.9 +/- 1.41 (dyn.s(-1).cm(-5)).10(-1), respectively], were significantly (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) lower. The present study suggests that the differences between trained and untrained elderly in absolute oxygen uptake of the working muscles and peak power output at maximal exercise test are due to physical activity status. The higher aerobic capacity in the trained elderly is related to increased cardiovascular function and to a lesser extent to increased muscle mitochondria concentration and capillarity. Although untrained elderly have reduced maximal oxygen uptake at peak aerobic exercise, intrinsic regulation of mitochondrial function does not seem to be significantly altered because of aging associated physical inactivity. Therefore, untrained elderly can partially compensate for their lower cardiac output by increasing oxygen extraction to levels comparable with those of trained elderly.

Research paper thumbnail of Effects of gradient and load carried on human haemodynamic responses during treadmill walking

European Journal of Applied Physiology, 2000

This study examined the effects of different loads carried and gradients, on haemodynamic and car... more This study examined the effects of different loads carried and gradients, on haemodynamic and cardiovascular responses during 45 min of treadmill walking. A group of 20 male endurance-trained athletes [mean maximal oxygen uptake 61.4 (SD 4) ml x kg(-1) x min(-1)] volunteered for this study. The subjects took part in three separate trials. The first involved a backpack weighing 25 kg, the second a 35 kg backpack, and the third trial, unladen, while walking on a treadmill at a speed of 5 km x h(-1). The subjects began walking on the treadmill with the randomized load at 0% gradient. After 15 min, the gradient was increased by 5% every 15 min for a total of 45 min. The order of the loads carried was randomized among subjects. No significant differences were noted for all the variables measured attributable to loads between 25 kg and 35 kg. However, significant (P&lt;0.05) differences were seen for all variables each time the gradient was increased. Cardiac output increased from 11.4 (SD 0.6) 1 x min(-1) at 0% to 13.6 (SD 0.8) l x min(-1) at 5% and to 17.6 (SD 1.3) l x min(-1) at 10% carrying the 35 kg load. Similarly, lactic acid concentrations in the blood increased from 2.8 (SD 0.2) to 3.1 (SD 0.6) and to 5.3 (SD 1.3) mmol x l(-1), respectively. Similar changes were observed for all variables while carrying the 25 kg load. In addition, steady states in oxygen uptake and other physiological variables were obtained throughout the course of the tests. These data suggest that during isodynamic exercise, one of the main factors determining metabolic and haemodynamic responses will be the change in gradient and to a lesser extent, the mass of the load carried.

Research paper thumbnail of The effect of gender on left ventricular function immediately after the wingate test

European Journal of Applied Physiology, 1997

The eect of gender on left ventricular systolic function and exercise haemodynamics in healthy yo... more The eect of gender on left ventricular systolic function and exercise haemodynamics in healthy young subjects was studied during 30-s all-out sudden strenuous dynamic exercise. A group of 22 men [19.3 (SD 1) years] 20 women [19.1 (SD 1) years] volunteered to participate in this study. Two-dimensional direct Mmode and Doppler echocardiograph studies were performed with the subject in the sitting position. The Doppler examination of¯ow was located with continuous-wave, interrogating ascending aorta measurements. The subjects completed the study without showing any electrocardiograph abnormalities. An interaction eect with stroke volume (P < 0.05) was characterized by a decrease in the men and an increase of stroke volume in the women. Cardiac output rose signi®cantly (P < 0.05) up to 14.5 (SD 6) l á min)1) for the men and 12.1 (SD 4) l á min)1 for the women compared to the rest values [5.8 (SD 0.4) and 4.7 (SD 0.5) l á min)1 , respectively]. Flow velocity integral and acceleration time diered signi®cantly between the two groups at rest (P < 0.05). During exercise these dierences showed an interaction eect (P < 0.05). These results would indicate that normal men and women respond to sudden strenuous exercise by reducing their left ventricular systolic function, with a signi®cantly greater decrease in women (P < 0.05). The gender dierences in the haemodynamic responses during the present study, may, as suggested by others, be attributable to dierences in energy metabolism. In addition, changes in Doppler parameters of aortic¯ow, haemodynamics and blood pressure responses during sudden strenuous exercise diered markedly from those seen before with endurance exercise.