Isometric Exertions Research Articles

Quantification of Perceived Exertion During Isometric Force Production With the Borg Scale in Healthy Individuals and Patients With Chronic Stroke

Background: The Borg Rating of Perceived Exertion (RPE) scale is widely used for many patient populations, but the ability of patients to accurately report their RPE without visual feedback has not been studied. Objective: The objective was to determine whether the Borg scale could be used as a measure of perceived isometric exertion in healthy subjects and patients with stroke. Methods: In experiment 1, young healthy subjects (n = 15) were instructed to perform spontaneous pushes (ie, self-selected effort) without visual feedback and to produce and hold self-determined isometric finger flexion at 5 Borg levels without visual feedback. In experiment 2, subjects with chronic stroke (n = 10) were instructed to produce self-determined isometric elbow flexion at 4 perceptual levels on the impaired and nonimpaired sides. Results: In experiment 1, young healthy subjects, asked to self-select without visual feedback (spontaneous push), tended to exert at a “somewhat hard” level, about 12% of maximal voluntary contraction (MVC). Self-selection of forces ranged from 2% of MVC (ie, very light) to 39% of MVC (ie, very hard). In experiment 2, subjects with stroke were able to distinguish different levels of perceived exertion among light (19% MVC), somewhat hard (33% MVC), and hard (63% MVC) levels; this ability was not different for the impaired and nonimpaired limbs. Conclusion: Both healthy subjects and subjects with stroke are able to differentiate distinct levels of perceived exertion during isometric force when prompted with the Borg scale. Efforts at lower percentages of MVC are perceived by subjects with stroke as greater-than-normal Borg RPE levels.

EEG signatures of arm isometric exertions in preparation, planning and execution

The electroencephalographic (EEG) activity patterns in humans during motor behaviour provide insight into normal motor control processes and for diagnostic and rehabilitation applications. While the patterns preceding brisk voluntary movements, and especially movement execution, are well described, there are few EEG studies that address the cortical activation patterns seen in isometric exertions and their planning. In this paper, we report on time and time-frequency EEG signatures in experiments in normal subjects (n=8), using multichannel EEG during motor preparation, planning and execution of directional centre-out arm isometric exertions performed at the wrist in the horizontal plane, in response to instruction-delay visual cues. Our observations suggest that isometric force exertions are accompanied by transient and sustained event-related potentials (ERP) and event-related (de-)synchronisations (ERD/ERS), comparable to those of a movement task. Furthermore, the ERPs and ERD/ERS are also observed during preparation and planning of the isometric task. Comparison of ear-lobe-referenced and surface Laplacian ERPs indicates the contribution of superficial sources in supplementary and pre-motor (FCz), parietal (CPz) and primary motor cortical areas (C1 and FC1) to ERPs (primarily negative peaks in frontal and positive peaks in parietal areas), but contribution of deep sources to sustained time-domain potentials (negativity in planning and positivity in execution). Transient and sustained ERD patterns in μ and β frequency bands of ear-lobe-referenced and surface Laplacian EEG indicate the contribution of both superficial and deep sources to ERD/ERS. As no physical displacement happens during the task, we can infer that the underlying mechanisms of motor-related ERPs and ERD/ERS patterns do not only depend on change in limb coordinate or muscle-length-dependent ascending sensory information and are primary generated by motor preparation, direction-dependent planning and execution of isometric motor tasks. The results contribute to our understanding of the functions of different brain regions during voluntary motor tasks and their activity signatures in EEG can shed light on the relationships between large-scale recordings such as EEG and other recordings such as single unit activity and fMRI in this context.

Differences in functional performance of the shoulder musculature with obesity and aging

The workforce includes an increasing number of workers who are obese and/or older, which may lead to higher rates of workplace injuries. We examined the main and interactive effects of obesity and age on strength and functional performance during sustained isometric exertions involving shoulder flexion in two postures. Four groups of eight participants each (non-obese (18.5 < BMI < 25 kg/m2) young (18–25 years), non-obese older (50–65 years), obese (30 < BMI < 40 kg/m2) young, and obese older) completed static endurance tasks in each posture, at fixed target levels of shoulder moment. Shoulder strength was ∼25% higher with obesity and equivalent between age groups. Both obesity and age affected endurance time, with the obese and younger groups both having shorter endurance. Obesity and age did not have an interactive effect on endurance time and the results were inconclusive regarding acute fatigue effects for individuals who are older and obese. Further work is needed under more realistic task conditions, to explore the likely complex effects of these individual differences. Relevance to industryShoulder strength was increased with obesity, though obesity was associated with substantially reduced endurance times. Such a difference may have implications for determining work-rest schedules based on task demand and predicted endurance times. It remains unclear whether obesity and age interact to cause substantial functional decrements.

Comparison of exercises inducing maximum voluntary isometric contraction for the latissimus dorsi using surface electromyography

The aim of this study was to compare muscular activation during five different normalization techniques that induced maximal isometric contraction of the latissimus dorsi. Sixteen healthy men participated in the study. Each participant performed three repetitions each of five types of isometric exertion: (1) conventional shoulder extension in the prone position, (2) caudal shoulder depression in the prone position, (3) body lifting with shoulder depression in the seated position, (4) trunk bending to the right in the lateral decubitus position, and (5) downward bar pulling in the seated position. In most participants, maximal activation of the latissimus dorsi was observed during conventional shoulder extension in the prone position; the percentage of maximal voluntary contraction was significantly greater for this exercise than for all other normalization techniques except downward bar pulling in the seated position. Although differences in electrode placement among various electromyographic studies represent a limitation, normalization techniques for the latissimus dorsi are recommended to minimize error in assessing maximal muscular activation of the latissimus dorsi through the combined use of shoulder extension in the prone position and downward pulling.

The effect of bracing availability on one-hand isometric force exertion capability

Environmental obstructions that workers encounter can kinematically limit the postures that they can achieve. However, such obstructions can also provide an opportunity for additional support by bracing with the hand, thigh or other body part. The reaction forces on bracing surfaces, which are in addition to those acting at the feet and task hand, are hypothesised to improve force exertion capability, and become required inputs to biomechanical analysis of tasks with bracing. The effects of kinematic constraints and associated bracing opportunities on isometric hand force were quantified in a laboratory study of 22 men and women. Analyses of one-hand maximal push, pull and lift tasks demonstrated that bracing surfaces available at the thighs and non-task hand enabled participants to exert an average of 43% more force at the task hand. Task hand force direction deviated significantly from the nominal direction for exertions performed with bracing at both medium and low task hand locations. Practitioner summary: This study quantifies the effect of bracing on kinematically constrained force exertions. Knowledge that appropriate bracing surfaces can substantially increase hand force is critical to the evaluation of task-oriented strength capability. Force estimates may also involve large off-axis components, which have clear implications for ergonomic analyses of manual tasks.

Obesity-related differences in muscular capacity during sustained isometric exertions

Over one-third of the world adult population is overweight or obese, and the prevalence continues to increase. Obesity is a risk factor for injury, and the growing prevalence may be associated with increases in the future incidence and cost of injuries. In this study, we examined obesity-related differences in muscular capacity during sustained isometric exertions involving hand grip, shoulder flexion, and trunk extension. Thirty-six young individuals who were obese or not obese (aged 18–29) completed these exertions at fixed levels of absolute loads involving low-moderate levels of effort. Individuals who were obese had an overall ∼20% higher absolute strength, but ∼20% lower relative strength. These differences were most evident in the hand grip and shoulder exertions. Parameters of fitted exponential relationships between endurance time and task demands (as a percentage of strength) were similar in both groups. Perceptual and performance responses were also consistent between groups. Accordingly, we conclude that obesity may not substantially influence muscular capacity for these tasks.

Cold air breathing during isometric handgrip: effect of healthy aging on coronary blood flow

Cold air inhalation and isometric exertion both trigger symptoms of angina, but the underlying causes are unknown. The current echocardiography‐based study sought to determine the effect of healthy aging on coronary blood flow velocity during a combined handgrip and cold air inhalation protocol (COLD+GRIP). Fifteen young (25±1 years) and eleven older (63±1 years) healthy subjects underwent a 2‐minute bout of isometric handgrip (30% MVC) while inspiring cold air (−15°C) through a custom system. Transthoracic echocardiography was used to measure coronary blood flow velocity in the LAD artery. Finometer‐derived mean arterial pressure (MAP), heart rate (HR), air temperature, and grip workload were monitored continuously. Unpaired t‐tests were used to assess group differences. Height, weight, BMI, grip workload, and resting HR were not different between groups. The change in HR during COLD+GRIP was significantly blunted in the older subjects (Δ=7±2 bpm) compared to younger subjects (Δ=20±3 bpm) while the change in MAP was not different between groups (OLD Δ=23±3 vs. YOUNG Δ=24±2 mmHg). The change in coronary blood flow velocity was also not different between groups (OLD Δ=5.3±1.1 vs. YOUNG Δ=6.8±2.1 cm/sec). In conclusion, healthy aging blunts the HR response to COLD+GRIP, which may act to prevent ischemia.This study supported by Wilderness Medical Society Grant (MDM), P01 HL096570 (LIS) and UL1 RR033184 (LIS)

The utility of an empirically derived co-activation ratio for muscle force prediction through optimization

Biomechanical optimization models that apply efficiency-based objective functions often underestimate or negate antagonist co-activation. Co-activation assists movement control, joint stabilization and limb stiffness and should be carefully incorporated into models. The purposes of this study were to mathematically describe co-activation relationships between elbow flexors and extensors during isometric exertions at varying intensity levels and postures, and secondly, to apply these co-activation relationships as constraints in an optimization muscle force prediction model of the elbow and assess changes in predictions made while including these constraints. Sixteen individuals performed 72 isometric exertions while holding a load in their right hand. Surface EMG was recorded from elbow flexors and extensors. A co-activation index provided a relative measure of flexor contribution to total activation about the elbow. Parsimonious models of co-activation during flexion and extension exertions were developed and added as constraints to a muscle force prediction model to enforce co-activation. Three different PCSA data sets were used. Elbow co-activation was sensitive to changes in posture and load. During flexion exertions the elbow flexors were activated about 75% MVC (this amount varied according to elbow angle, shoulder flexion and abduction angles, and load). During extension exertions the elbow flexors were activated about 11% MVC (this amount varied according to elbow angle, shoulder flexion angle and load). The larger PCSA values appeared to be more representative of the subject pool. Inclusion of these co-activation constraints improved the model predictions, bringing them closer to the empirically measured activation levels.

Time to Task Failure of Trunk Extensor Muscles Differs With Load Type

ABSTRACT Time to task failure of trunk extensor muscles during seated submaximal isometric exertions was assessed in 18 healthy participants using 2 different load types. One required supporting an inertial load (position-matching task) whereas the 2nd required maintaining an equivalent torque against a rigid restraint (force-matching task). Time to task failure was significantly longer for position-matching tasks compared to the force-matching tasks. This finding is opposite to that reported for the appendicular muscles. A subset of 4 individuals completed a 2nd experiment to test the time to task failure of the elbow flexors in the position- and force-matching tasks. Time to task failure of the elbow flexors was significantly longer for the force-matching tasks compared to position matching. Thus, the same population shows that the effects of load type on time to task failure are opposite for the appendicular and axial muscles. This could be an important issue in understanding the mechanisms of task failure, and the endurance capacity of the trunk extensor muscles.

Investigating the role of the shoulder musculature during maximum unilateral isometric exertions

The extent to which specific muscles may limit maximum isometric force production is largely unknown. This study investigated shoulder muscle activity in six muscles and maximum force generation at the hand in three directions, while in eight different working positions. Ten right hand dominant, university-aged female participants completed twenty-four maximal isometric force hand exertions against a handle positioned by a robot arm within a 3-dimensional simulated workspace. A multivariate, full factorial ANOVA indicated a reach distance main effect where 11% greater force production occurred at the lesser reach distance. A target handle elevation and force direction interaction effect on maximum force production also existed. These findings add to normative static strength data for hand locations typical of an operating work envelope. Although hand force was significantly influenced by position in each direction (p &lt; 0.05), muscle EMG was not influenced in any of the six muscles measured. No muscle achieved 100% MVE in any of the tested conditions, with the highest total muscle activity recorded at 86% MVE for the Pectoralis Major – sternal origin. Collectively, these data better demonstrate that the location and direction of work presentation influences force outputs more than specific muscle demands (of those measured), and should be considered in evaluating workstations.

Computational model of the lumbar spine musculature: Implications of spinal surgery

Background The development of a comprehensive and detailed model of the musculature of the lumbar region is required if biomechanical models are to accurately predict the forces and moments experienced by the lumbar spine. Methods A new anatomical model representing the nine major muscles of the lumbar spine and the thoracolumbar fascia is presented. These nine muscles are modeled as numerous fascicles, each with its own force producing potential based on size and line of action. The simulated spine is fully deformable, allowing rotation in any direction, while respecting the physical constraints imposed by the skeletal structure. Maximal moments were predicted by implementing the model using a pseudo force distribution algorithm. Three types of surgery that affect the spinal musculature were simulated: posterior spinal surgery, anterior surgery, and total hip replacement. Findings Predicted moments matched published data from maximum isometric exertions in male volunteers. The biomechanical changes for the three different types of surgery demonstrated several common features: decreased spinal compression and production of asymmetric moments during symmetric tasks. Interpretation This type of analysis provides new opportunities to explore the effect of different patterns of muscle activity including muscle injury on the biomechanics of the spine.

Force distribution at the hand/handle interface for grip and pull tasks

The purpose of this experiment was to investigate how surface pressure distribution at the hand/handle interface changes during gripping and pulling and to enhance understanding of coupling between hands and grasped objects. Two pressure-sensing arrays were wrapped around a 3.18 cm diameter cylindrical handle which was fixed to a six-axis load cell. Six male subjects grasped the fixed overhead instrumented handle and performed two exertion types: downward pull exertions of 30, 60, and 90 percent of their measured grip strength and a maximal isometric grip exertion. Consistent with previous studies, the greatest pressure was exerted on the distal segments of the phalanges and at the base of the thumb and palm during maximum isometric gripping. However, when pulling, pressure on the palm (underside of the handle) was negligible. Most pull pressure was distributed over the fingers unevenly in a bimodal distribution, with the greatest pressures occurring on the proximal side of the hand followed by the fingertips. This supports the hypothesis that friction acts through the soft tissues of the fingers and creates an increased normal force in the direction of proximal segments (i.e. “belt friction”). When the surface of the handle is lumped into 5 equal zones, the observed bimodal trend is lost, with the greatest average pressure observed at the top of the handle corresponding to the pull direction. This discrepancy highlights the importance of resolution when making conclusions about applied hand forces. Future research is needed to investigate pressures on handles of different size and surface friction to develop comprehensive models of hand/object coupling.

Effect of bilateral versus unilateral exertion tests on maximum voluntary activity and within-participant reproducibility in the shoulder

Normalized surface EMG requires known muscle activity from a well defined reference contraction, often a maximum voluntary isometric exertion (MVIE). One factor that may impact the activity obtained during a MVIE is the use of a bilateral or unilateral version of the test. The objective of this work was to investigate how performing MVIE tests unilaterally or bilaterally affects maximum voluntary electrical activity (MVE) for selected shoulder muscles. Further, we examined if within-participant reproducibility could be improved with the use of bilateral or unilateral MVIE tests. Sixteen participants completed five repetitions of a palm press, empty can, and external rotation MVIE tests both bilaterally and unilaterally. Muscle activity was recorded from seven muscles acting at the glenohumeral joint during the performance of each test. Repeated measures ANOVAs were used to determine within-participant differences on muscle specific MVEs and hand force measures between the two versions of the test. Gender was compared as a between participants factor. Within-participant reproducibility in muscle activity between bilateral and unilateral MVIEs was compared using coefficients of variation. Performing a bilateral empty can MVIE test elicited significantly higher MVEs for the upper trapezius (14%) and supraspinatus muscles (15%) than a unilateral test in this study population. MVEs during the palm press and external rotation were not affected by performing the tests bilaterally or unilaterally. Reliability was similar between unilateral and bilateral exertions across MVIE tests. Hence, we recommend that the empty can MVIE test be performed bilaterally, while either bilateral or unilateral configurations are equivalent during the palm press and external rotation MVIE tests.

The Effect of Exertion Level on Activation Patterns and Variability of Trunk Muscles During Multidirectional Isometric Activities in Upright Posture

An experimental design to investigate activation patterns of trunk muscles during multidirectional exertions. To evaluate trunk muscle activation patterns in varying directions and moment magnitudes during an isometric task, and to investigate the effects of angle and level of isometric exertion on the electromyography (EMG) variability of trunk muscles in upright posture. Few studies have investigated trunk muscle activation patterns in multidirectional exertions with different moment magnitudes. A total of 12 asymptomatic male subjects were participated in the study. The EMG activity of 10 selected trunk muscles was collected in the 3 seconds end point matching tasks in 8 angles and 3 magnitudes of exertion. Trunk muscle activation patterns were examined using EMG tuning curves and measuring preferred direction (mean vector direction) and the index of spatial focus. The effect of exertion level on these measures was investigated by Rao test. The effects of angle and level of exertion on the EMG variability of trunk muscles were tested by analysis of variance with repeated measures design. No significant difference in EMG tuning curves, preferred direction, and the index of spatial focus was found for each muscle studied across exertion levels (P > 0.05). The index of spatial focus of most muscles studied was not changed with increasing moment magnitude. EMG variability of trunk muscles was significantly affected by angle and level of exertion and their interaction effect (P < 0.001). Consistent activation patterns of trunk muscles were found within and among subjects in different moment magnitudes. The index of spatial focus indicated that probably no shift to a higher co-contraction strategy has been adapted with increasing moment magnitude. The results suggested that increased EMG variability of trunk muscles in asymmetric exertions may be associated with lower trunk controllability during combined exertions.

How does the central nervous system address the kinetic redundancy in the lumbar spine? Three-dimensional isometric exertions with 18 Hill-model-based muscle fascicles at the L4—L5 level

The human motor system is organized for execution of various motor tasks in a different and flexible manner. The kinetic redundancy in the human musculoskeletal system is a significant property by which the central nervous system achieves many complementary goals. An equilibrium-based biomechanical model of isometric three-dimensional exertions of trunk muscles has been developed. Following the definition and role of the uncontrolled manifold, the kinetic redundancy concept is explored in mathematical terms. The null space of the kinetically redundant system when a certain joint moment and/or stiffness are needed is derived and discussed. The aforementioned concepts have been illustrated, using a three-dimensional three-degrees-of-freedom biomechanical model of the spine with 18 anatomically oriented Hill-type-model muscle fascicles. The considerations of stability and its consequence on the internal loading of the spine and coactivation consequences are discussed in both general and specific cases. The results can shed light on the interaction mechanisms in muscle activation patterns seen in various tasks and exertions and can provide a significant understanding for future research studies and clinical practices related to low-back disorders. Alteration of recruitment patterns in low-back-pain patients has been explained on the basis of this biomechanical analysis. The higher coactivation results in higher internal loading while providing higher joint stiffness that enhances spinal stability, which guards against spinal deformation in the presence of any perturbations.

Effects of Physical and Mental Demands on Muscle Activity of the Upper Extremity

Workplace tasks that involve multidimensional demands, such as physical and cognitive workloads, may increase the injury risks posed on workers. To aid in designing ergonomic guidelines for workplace safety, it is thus important to understand the interactive nature of these combined demands. The goal of this study was to investigate the effects of said multidimensional demands on the muscles of the upper extremity. Seventeen healthy participants performed isometric upper extremity exertions at five levels of physical intensities (5%, 25%, 45%, 65%, and 75% maximum voluntary contraction (MVC)) in the presence and absence of a mental task. Mean shoulder muscle activity and co-contraction indices (CCI) of the upper extremity were measured using electromyographic signals. Force fluctuations were measured using a force transducer to evaluate joint steadiness. In general, shoulder muscle activity (mean activity and CCIs) increased with increasing levels of physical exertions. A decrease in mean anterior and posterior deltoid muscle activity and CCI of the shoulder was observed in the presence of the mental task. However, these changes were more prominent at higher levels of physical workload compared to the lower levels. Force fluctuations were lowest at 25% MVC, and highest at 85% MVC. Mental workload significantly increased force fluctuations at 85% MVC, which may have been a result of decreased muscle output to maintain the loads in a steady posture. Overall, results from this study suggest that certain task demands are more susceptible to interference by mental workload than others. It will provide a better understanding of combined exposure levels in occupational settings and serve as a guideline to determine task demands for different occupational settings.

The Effect of Angle and Level of Exertion on Trunk Neuromuscular Performance During Multidirectional Isometric Activities

To quantify trunk muscle capability and controllability in different angles and levels of isometric exertion using a torque tracking system. To investigate the effect of biaxial isometric exertions on the maximum capability of trunk and to examine the effect of angle and level of isometric exertion on trunk controllability during the tracking task in upright posture. Combined motions of trunk at varying exertion levels occur in most daily and occupational activities and are important risk factors of low back pain. Few studies have investigated trunk capability and controllability during multidirectional activities with different exertion levels. Eighteen asymptomatic young male subjects performed isometric contractions of trunk muscles in 8 angles and 3 levels of exertion. The tracking system included a target, which was a thick line with a round endpoint. Subjects were asked to track the target line (path) and match the endpoint while maintaining torque for 3 seconds by exerting isometric contraction against B200 Isostation. The initial part of the tracking task was named path tracking phase and the final part, endpoint matching phase. Trunk capability was determined by measuring peak torque values obtained during maximal voluntary exertions. Trunk controllability was determined by measuring constant error and variable error during tracking tasks. Analysis of variance with repeated measures design was used to test the effects of angle and level of exertion on trunk capability and controllability. Trunk capability was significantly decreased during biaxial exertions (P < 0.001). Constant error and variable error were significantly affected by angle (P < 0.001) and level (P < 0.001) of exertion during both phases of the tracking task. Trunk capability and controllability were significantly decreased during biaxial exertions. Higher exertion levels had a major negative impact on trunk controllability in both uniaxial and biaxial exertions. The results suggested that combined exertions and more strenuous efforts may impair trunk neuromuscular control, increasing the risk of low back pain.

Changes in the EMG of Low Back Muscles during Static Lumbar Flexion

Prolonged and/or frequent lumbar flexion posture in industry has been known to contribute to the development of work-related low back pain or disorders but the specific biomechanics of this link has not been fully developed. In this study the effects of static lumbar flexion on back extensor muscles were evaluated by quantifying the changes in the flexion-relaxation onset angle, muscle activity level and the development of muscle fatigue associated with static lumbar flexion. Twenty healthy subjects performed submaximal isometric trunk extension exertions and isokinetic trunk flexion before and immediately after a 5 min continuous lumbar flexion posture while the trunk sagittal flexion angle and the myoelectric activities (EMG) of erector spinae muscles and latissimus dorsi muscles were recorded simultaneously. Results show an increase in the flexion-relaxation onset angle, normalized EMG of isometric extension, and decrease in the median power frequency of EMG as a consequence of the static lumbar flexion. It is suggested that back extensor muscles produce sustained low level contraction during static lumbar flexion, leading to muscular fatigue development. Together with creep deformed passive tissues of the low back and resultant spinal instability, the muscle fatigue of back extensors in static lumbar flexion may play a role in the development of low back pain or disorders.

The Influence of Pain-Related Fear on Peak Muscle Activity and Force Generation During Maximal Isometric Trunk Exertions

A cross-sectional study of peak activation of trunk muscles in 20 participants with chronic low back pain. To determine how pain-related fear influences peak activation of abdominal and trunk extensor muscles during maximal isometric trunk exertions. The pain adaptation model and the pain-spasm-pain model have been proposed to explain differences in trunk muscle activation between healthy participants and those with chronic low back pain. However, there is no clear consensus in the literature in support of either model, and there are no studies that have examined the role of pain-related fear on muscle activity in the context of these 2 models. Participants with chronic low back pain performed a series of maximal isometric exertions into extension, flexion, rotation right and left, and side-bend right and left from a tall kneeling position with the spine in a neutral posture. A doubly multivariate MANCOVA was conducted with a between subject factor of group (high pain-related fear, low pain-related fear), a within subject factor of direction (extension, flexion, rotation left and right, side bend left and right), McGill Pain Questionnaire ratings entered as covariates, and peak EMG for all 10 trunk muscles entered as dependent variables. Averaged across all pull directions and all 10 trunk muscles assessed, participants with high pain-related fear had peak EMG that was only 49.5% of participants with low fear. Additionally, we found significantly smaller peak force for isometric exertions in flexion, side-bend right, and side-bend left directions. Pain-related fear is associated with increased disability, in theory, because of avoidance behavior and disuse. Our data suggest that participants high in pain-related fear specifically avoid activation of the abdominal muscles during maximal isometric trunk exertions.

Left Ventricular Diastolic Function in Trained Male Weightlifters at Rest and During Isometric Exercise

Individuals involved in intense resistance training present with increased absolute left ventricular (LV) wall thickness and mass and show good systolic responses to isometric exercise. There is no consensus regarding diastolic features and no available information regarding diastolic function in athletes during isometric exertion itself. Therefore, the main aim of this study was to assess diastolic LV function at baseline and during exercise in athletes. The population consisted of 96 men (mean age 29 +/- 7 years): 48 weight lifters who trained for 15 to 20 hours/week and 48 sedentary men. All weight lifters had been active for >6 years, including the 6 months before the study. Ultrasound was performed using a commercially available Doppler echocardiographic system. Isometric exercise was performed in the supine position using a standard 2-hand bar dynamometer. The man end-diastolic volumes at rest were 97 +/- 6 ml in sedentary subjects and 101 +/- 5 ml in weight lifters, increasing to 100 +/- 6 and 118 +/- 11 ml during exercise (p = 0.06 and p <0.01, respectively). End-systolic volumes at rest were similar in the 2 groups, showing significantly greater reductions during exercise in the weight lifters. The mean absolute LV mass was 167 +/- 30 g in sedentary subjects and 202 +/- 32 g in weight lifters (p <0.0001). The mean stroke volume increased from 65 +/- 7 to 86 +/- 7 ml in sedentary subjects and from 70 +/- 6 to 107 +/- 11 ml in weight lifters (intergroup significance p = 0.05 and p <0.01, respectively). A similar pattern of response was documented for the ejection fraction (i.e., significantly greater increases during exercise in weight lifters). Regarding diastolic indexes, in the weight lifters, the mean peak early velocity at rest was 68 +/- 7 cm/s, the mean acceleration rate was 1,242 +/- 176 cm/s/s, and the mean deceleration rate was 414 +/- 44 cm/s/s. All these values were significantly higher than in sedentary subjects, with further increases during exercise (p <0.0001). In weight lifters, the mean peak atrial velocity at rest was 37 +/- 6 cm/s, the mean acceleration time was 55 +/- 4 ms, the mean isovolumic relaxation time was 63 +/- 3 ms, and the mean deceleration time was 164 +/- 4 ms; these values were lower than in sedentary subjects (p <0.0001 for all). In conclusion, intense resistance training leads to enhanced LV diastolic function at rest and during isometric exercise despite the markedly increased LV mass.