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Biomedical subjects

H M Toussaint

Publications and source records attributed to H M Toussaint.

At least 19 recordsLinked to original sources
PubMed2002

Effect of high-intensity hypoxic training on sea-level swimming performances.

The objective of this study was to test the hypothesis that high-intensity hypoxic training improves sea-level performances more than equivalent training in normoxia. Sixteen well-trained collegiate and Masters swimmers (10 women, 6 men) completed a 5-wk training program, consisting of three high-intensity training sessions in a flume and supplemental low- or moderate-intensity sessions in a pool each week. Subjects were matched for gender, performance level, and training history, and they were assigned to either hypoxic [Hypo; inspired O2 fraction (Fi(O(2))) = 15.3%, equivalent to a simulated altitude of 2,500 m] or normoxic (Norm; Fi(O(2)) = 20.9%) interval training in a randomized, double-blind, placebo-controlled design. All pool training occurred under Norm conditions. The primary performance measures were 100- and 400-m freestyle time trials. Laboratory outcomes included maximal O(2) uptake (Vo(2 max)), anaerobic capacity (accumulated O(2) deficit), and swimming economy. Significant (P = 0.02 and <0.001 for 100- and 400-m trials, respectively) improvements were found in performance on both the 100- [Norm: -0.7 s (95% confidence limits: +0.2 to -1.7 s), -1.2%; Hypo: -0.8 s (95% confidence limits: -0.1 to -1.5 s), -1.1%] and 400-m freestyle [Norm: -3.6 s (-1.8 to -5.5 s), -1.2%; Hypo: -5.3 s (-2.3 to -8.3 s), -1.7%]. There was no significant difference between groups for either distance (ANOVA interaction, P = 0.91 and 0.36 for 100- and 400-m trials, respectively). Vo(2 max) was improved significantly (Norm: 0.16 +/- 0.23 l/min, 6.4 +/-8.1%; Hypo: 0.11 +/- 0.18 l/min, 4.2 +/- 7.0%). There was no significant difference between groups (P = 0.58). We conclude that 5 wk of high-intensity training in a flume improves sea-level swimming performances and Vo(2 max) in well-trained swimmers, with no additive effect of hypoxic training.

Adult↗
PubMed2001

Within-subject variability in low back load in a repetitively performed, mildly constrained lifting task.

STUDY DESIGN: A repeated-measures in vivo experiment. OBJECTIVE: To describe within-subject variability of spinal compression in repetitive lifting. SUMMARY OF BACKGROUND DATA: Epidemiology and failure mechanics suggest that peak loads may be more predictive of injury than average loads. Nevertheless, biomechanical studies usually focus on the latter. METHODS: Ten healthy males performed 360 lifts in 1 hour of a 45-L crate, weighted with a stable 10-kg mass on 1 day and with an unstable mass (10 kg of water) on another day. The maximum compression force in each lift was estimated, using a simple inverse dynamics model and a single equivalent muscle model. RESULTS: The individual distributions of maximum compression force were slightly skewed to the right (average skewness 0.67). Median and 95th percentile values were used to characterize the distribution. The median (50th percentile) compression ranged from 3375 to 6125 N, and from 3632 to 6298 N in the stable and unstable load conditions, respectively. The within-subjects peak (95th percentile) compression forces were from 405 to 1767 N and from 526 to 2216 N, respectively, higher than the median values. The peak values differed significantly between conditions, whereas the difference in medians did not reach significance. Only a limited trendwise (fatigue-related) variance could be demonstrated. CONCLUSION: Peak spinal compression by far exceeds median compression in repetitive lifting and can be affected by task conditions independently from the median. Therefore, the variability of spinal loads needs to be taken into consideration when analyzing and redesigning tasks that can cause spinal injuries.

Adult↗
PubMed2001

An EMG technique for measuring spinal loading during asymmetric lifting.

OBJECTIVES: To compare two methods of calibrating the erector spinae electromyographic signal against moment generation in order to predict extensor moments during asymmetric lifting tasks, and to compare the predicted moments with those obtained using a linked-segment model. METHODS: Eight men lifted loads of 6.7 and 15.7 kg at two speeds, in varying amounts of trunk rotation. For each lift, the following were recorded at 60 Hz; the rectified and averaged surface electromyographic signal, bilaterally at T10 and L3, lumbar curvature using the 3-Space Isotrak, movement of body segments using a 4-camera Vicon system, and ground reaction forces using a Kistler force-plate. Electromyographic (EMG) and Isotrak data were used to calculate lumbosacral extensor moments using the electromyographic model, whereas movement analysis data and ground reaction forces were used to estimate net moments using the linked-segment model. For the electromyographic technique, predictions of extensor moment were based on two different sets of EMG-extensor moment calibrations: one performed in pure sagittal flexion and the other in flexion combined with 45 degrees of trunk rotation. RESULTS: Extensor moments predicted by the electromyographic technique increased significantly with load and speed of lifting but were not influenced by the method of calibration. These moments were 7-40%greater than the net moments obtained with the linked-segment model, the difference increasing with load and speed. CONCLUSIONS: The calibration method does not influence extensor moments predicted by the electromyographic technique in asymmetric lifting, suggesting that simple, sagittal-plane calibrations are adequate for this purpose. Differences in predicted moments between the electromyographic technique and linked-segment model may be partly due to different anthropometric assumptions and different amounts of smoothing and filtering in the two models, and partly due to antagonistic muscle forces, the effects of which cannot be measured by linked-segment models. RelevanceAsymmetric lifting is a significant risk factor for occupationally-related low back pain. Improved techniques for measuring spinal loading during such complex lifting tasks may help to identify work practices which place the spine at risk of injury.

Adult↗
PubMed2001

Anticipatory postural adjustments in a bimanual, whole-body lifting task seem not only aimed at minimising anterior--posterior centre of mass displacements.

Anticipatory postural adjustments (APAs) were studied in a bimanual whole-body lifting task, using a mechanical analysis of the downward movement phase preceding loaded versus unloaded lifts. APAs in the backward ground reaction force were found to lead the perturbing forward box reaction with approximately 400 ms, thus inducing a backward centre of mass momentum. Both the APA onset and magnitude were scaled as a function of the load to be lifted. We conclude that, in this lifting task, the APAs served the generation of an appropriate extending moment of the ground reaction force after box pick-up, rather than the traditionally defined goal of minimising anterior-posterior centre of mass displacements.

Adaptation, Physiological↗
PubMed2001

Lumbar loading during lifting: a comparative study of three measurement techniques.

Low back loading during occupational lifting is thought to be an important causative factor in the development of low back pain. In order to regulate spinal loading in the workplace, it is necessary to measure it accurately. Various methods have been developed to do this, but each has its own limitations, and none can be considered a "gold standard". The purpose of the current study was to compare the results of three contrasting techniques in order to gain insight into possible sources of error to which each is susceptible. The three techniques were a linked segment model (LSM), an electromyographic (EMG)-based model, and a neural network (NN) that used both EMG and inertial sensing techniques. All three techniques were applied simultaneously to calculate spinal loading when eight volunteers performed a total of eight lifts in a laboratory setting. Averaged results showed that, in comparison with the LSM, the EMG technique calculated a 25.5+/-33.4% higher peak torque and the NN technique a 17.3+/-10.5% lower peak torque. Differences between the techniques varied with lifting speed and method of lifting, and could be attributed to differences in anthropometric assumptions, antagonistic muscle activity, damping of transient force peaks by body tissues, and, specific to the NN, underestimation of trunk flexion. The results of the current study urge to reconsider the validity of other models by independent comparisons.

Adult↗
PubMed2000

Lifting an unexpectedly heavy object: the effects on low-back loading and balance loss.

OBJECTIVE: This study evaluates the effects of lifting an unexpectedly heavy object on low-back loading and loss of balance. BACKGROUND: It is often suggested that lifting an unexpectedly heavy object may be a major risk factor for low-back pain. This may lead to an increase in muscle activation, stretch of ligaments and posterior disc, and loss of balance.METHODS. Nine healthy male subjects were asked to pick up and lift a box as quickly as possible. The weight of the box was unexpectedly increased by 5 or 10 kg. Kinematics and force data were recorded throughout the experiment. RESULTS: Lifting of an unexpectedly heavy box led to a decrease in maximum torque of the low back compared to lifting the same box mass with correct expectation. The maximum lumbar angle did not increase compared to the light box condition. Only the threat to balance appeared to be somewhat increased.CONCLUSIONS. The lifting of an unexpectedly heavier box appeared not to lead to an increased balance loss or a clearly increased stress of the structures of the low back, although a burst of abdominal muscle activity was found in one condition. These results do not fully clarify the assumed relation between lifting unexpectedly heavy objects and low-back injury. RelevanceA commonly cited cause of low-back pain is the lifting of an unexpectedly heavy object. A study of the responses to such perturbation is important to an understanding of spine mechanics and the etiology of low-back injury.

Adult↗
PubMed2000

Oxygen uptake in one-legged and two-legged exercise.

PURPOSE: The purpose of this study was to determine the primary factors causing the differential oxygen uptake (VO2) response at submaximal intensities between one-legged and two-legged exercise, and whether peak oxygen uptake (VO2peak) increases in proportion to the increase in active muscle mass. METHODS: Two different types of exercise were used for this experiment, each requiring a different movement, a different method of stabilizing posture, and, finally, a different limiting VO2peak. In experiment 1, nine male subjects performed one-legged cycling (OLC) and two-legged cycling exercise (TLC) at a pedaling rate of 80 rpm. The exercise intensity was first set at 80 W and was increased by 40 W every 3 min until exhaustion. In experiment 2, six healthy male subjects performed one-legged knee-extension (OKE) and two-legged knee-extension (TKE) exercise at a rate of 50 contractions per minute. The knee-extension exercise was done at constant work rates for a 3-min session in OKE or a 4-min session in TKE. The exercise bouts were performed intermittently at four to seven different submaximal intensities and VO2 was determined at each intensity in all exercises. RESULTS: At submaximal intensities, VO2 in relation to work rate of one-legged exercise was more steep than those of two-legged exercise, and the mean values of VO2 were significantly higher in one-legged exercise than those in two-legged exercise in both knee extension and cycling exercise. Mean values of VO2peak for two-legged exercise were significantly higher than that for one-legged exercise (P < 0.01); however, it was much lower than two times of that for one-legged exercise even in knee extension exercise where the VO2peak would be limited peripherally. CONCLUSION: The findings of this study suggest that the differential VO2 response between one-legged and two-legged exercise would be attributed not only to the difference in force application throughout the exercise movement and to the effect of a postural component but also to the inhibited circulatory response caused by the multiple limb exercise. In addition, it was supposed that VO2peak does not increase in proportion to the exercising muscle mass even during smaller muscle activity where the cardiac pumping capacity has not reached its upper limit.

Adult↗
PubMed1999

Dynamic forces acting on the lumbar spine during manual handling. Can they be estimated using electromyographic techniques alone?

STUDY DESIGN: Compressive loading of the lumbar spine was analyzed using electromyographic, movement analysis, and force-plate techniques. OBJECTIVES: To evaluate the inertial forces that cannot be detected by electromyographic techniques alone. SUMMARY OF BACKGROUND DATA: Links between back pain and manual labor have stimulated attempts to measure spine compressive loading. However, direct measurements of intradiscal pressure are too invasive, and force plates too cumbersome for use in the workplace. Electromyographic techniques are noninvasive and portable, but ignore certain inertial forces. METHODS: Eight men lifted boxes weighing 6.7 and 15.7 kg from the ground, while joint moments acting about L5-S1 were quantified 1) by using a linked-segment model to analyze data from Kistler force plates and a Vicon movement-analysis system, and 2) by measuring the electromyographic activity of the erector spinae muscles, correcting it for contraction speed and comparing it to moment generation during static contractions. The linked-segment model was used to calculate the "axial thrust," defined as the component of the L5-S1 reaction force that acts along the axis of the spine and that is unrelated to trunk muscle activity or static body weight. RESULTS: Peak extensor moments predicted by the two techniques were similar and equivalent to spinal compressive forces of 2.9-4.8 kN. The axial thrust "hidden" from the electromyographic technique was negligible during slow lifts, and remained below 4% of peak spinal compression even during fast heavy lifts. Peak axial thrust was proportional to the peak vertical ground reaction (R2 = 0.74). CONCLUSIONS: Electromyographic techniques can measure dynamic spinal loading, but additional force-plate data would improve accuracy slightly during lifts requiring a vigorous upward thrust from the legs.

Adult↗
PubMed1999

Adaptation of center of mass control under microgravity in a whole-body lifting task.

Human balance in stance is usually defined as the preservation of the vertical projection of the center of mass (COM) on the support area formed by the feet. Under microgravity conditions, the control of equilibrium seems to be no longer required. However, several reports indicate preservation of COM control in tasks such as arm or leg raising, tiptoe standing, or trunk bending. It is still unclear whether COM control is also maintained in complex multijoint movements during short term exposure to microgravity. In the current study, the dynamics of equilibrium control were studied in four subjects performing two series of seven whole-body lifting movements under microgravity during parabolic flights. The aims of the study were to examine whether the trajectory of horizontal COM motion during lifting movements changes in short-term exposure to microgravity and whether there is any sign of recovery after several lifting movements. It was found that, compared with control movements under normal gravity, the horizontal position of the COM was shifted backward during the entire lifting movement in all subjects. In the second series of lifting movements under microgravity, a partial recovery of the COM trajectory toward the normal gravity situation was found. Under microgravity, angles of the ankle, knee, hip, and lumbar joints differed significantly from the angles found under normal gravity. Recovery of joint angular trajectories in the second series of lifting movements mainly occurred for those angles that could contribute to a reduction of the backward COM shift. It is to be pointed out that COM control under microgravity is not redundant but functional. Persisting COM control under microgravity may be required for pure mechanical reasons, since rotational movements of the body are dependent on adequate control of the COM position with respect to external forces. It is shown that, from a mechanical perspective, subjects can benefit from a backward displacement of the COM in the downward as well as the upward phase of the lifting movement under microgravity.

Adaptation, Physiological↗
PubMed1999

Stoop or squat: a review of biomechanical studies on lifting technique.

OBJECTIVE: To assess the biomechanical evidence in support of advocating the squat lifting technique as an administrative control to prevent low back pain. BACKGROUND: Instruction with respect to lifting technique is commonly employed to prevent low back pain. The squat technique is the most widely advised lifting technique. Intervention studies failed to show health effects of this approach and consequently the rationale behind the advised lifting techniques has been questioned. METHODS: Biomechanical studies comparing the stoop and squat technique were systematically reviewed. The dependent variables used in these studies and the methods by which these were measured or estimated were ranked for validity as indicators of low back load. RESULTS: Spinal compression as indicated by intra-discal pressure and spinal shrinkage appeared not significantly different between both lifting techniques. Net moments and compression forces based on model estimates were found to be equal or somewhat higher in squat than in stoop lifting. Only when the load could be lifted from a position in between the feet did squat lifting cause lower net moments, although the studies reporting this finding had a marginal validity. Shear force and bending moments acting on the spine appeared lower in squat lifting. Net moments and compression forces during lifting reach magnitudes, that can probably cause injury, whereas shear forces and bending moments remained below injury threshold in both techniques. CONCLUSION: The biomechanical literature does not provide support for advocating the squat technique as a means of preventing low back pain. RELEVANCE: Training in lifting technique is widely used in primary and secondary prevention of low back pain, though health effects have not been proven. The present review assesses the biomechanical evidence supporting the most widely advocated lifting technique.

Biomechanical Phenomena↗
PubMed1999

Fractures of the lumbar vertebral endplate in the etiology of low back pain: a hypothesis on the causative role of spinal compression in aspecific low back pain.

It is hypothesized that, in a large number of cases of aspecific low back pain, the primary cause of the pain is a fracture of the vertebral endplate caused by compression forces. Clinical studies have shown that, in many low back pain patients, damage of the vertebral bodies and or the intervertebral disc is present. In vitro studies reveal that the most likely type of failure of this anterior part of the spine is a fracture of the endplate as a result of compression. The high incidence of aspecific low back pain concurs with the likeliness of compression fractures of the endplate to occur in everyday life. Furthermore, epidemiological findings and the natural history of low back pain appear to be in line with the proposed hypothesis.

Disease Progression↗
PubMed1999

Biomechanical analysis of posture in patients with spinal kyphosis due to ankylosing spondylitis: a pilot study.

OBJECTIVES: Patients with ankylosing spondylitis may experience a progressive spinal kyphosis, which induces a forward and downward displacement of the centre of mass (COM) of the trunk. In this pilot study, the possible mechanisms used to compensate for the displacement of the trunk COM were analysed. METHODS: Joint angles of hip, knee and ankle were determined in four patients with ankylosing spondylitis and compared to data of 18 healthy subjects. Each patient stood on a force platform and had to adopt several predefined postures, which were recorded by a video camera. RESULTS: In three patients, the hips were flexed when standing relaxed, and in all patients hip extension was limited. The knee angles of three patients were smaller and in two patients the angle of the ankles was larger compared to healthy subjects. CONCLUSIONS: The results suggest that the hip joints are at least no longer involved in balance control. This may imply that conservative therapy should focus on the prevention of restriction of the hip joints.

Adult↗
PubMed1998

Scaling anticipatory postural adjustments dependent on confidence of load estimation in a bi-manual whole-body lifting task.

Anticipatory control of motor output enables fast and fluent execution of movement. This applies also to motor tasks in which the performance of movement brings about a disturbance to balance that is not completely predictable. For example, in bi-manual lifting the pick-up of a load causes a forward shift of the centre of mass with consequent disturbance of posture. Anticipatory postural adjustments are scaled to the expected magnitude of the perturbation and are initiated well before the availability of sensory information characterising the full nature of the postural disturbance. However, when the postural disturbance unexpectedly changes, the anticipatory adjustment of joint torques is not equilibrated and may result in a disturbance to balance. In a previous study, it was demonstrated that apart from anticipatory postural adjustments, corrective responses after load pick-up are used to further compensate the postural disturbance. In this study it was examined whether the central nervous system (CNS) assembles a strategy that incorporates both anticipatory control and corrective responses, in which the magnitude of the anticipatory postural adjustments depends on the perceived level of predictability of the postural disturbance. Subjects performed series of lifts in which the magnitude of the load was never revealed to the subject. Two boxes equal in size and colour, but different in mass (6 and 16 kg), were used. Differences in expectation were created by several lifts with the 16-kg load before the 6-kg box was presented. It was observed that the number of strong corrective responses (stepping) varied with the number of 16-kg trials that formed the prior experience when the final 6-kg trial was presented. The follow-up question was whether control relied more on anticipation in the stepping trials, compared with trials in which such gross signs of imbalance were absent. In this study it was shown that subjects when stepping (i) exhibited differential anticipatory postural adjustments in comparison with 6-kg trials in which expectation was not shaped by preceding 16-kg trials, and (ii) scaled the anticipatory postural adjustments similar to those preceding lift-off of the 16-kg trial preceding it. These findings emphasise the programmed nature of the anticipatory postural adjustments and the ability of the CNS to selectively tune the anticipatory postural adjustments to stored information gained during the previous lift(s).

Adaptation, Physiological↗
PubMed1998

Accuracy of the sagittal vertical axis in a standing lateral radiograph as a measurement of balance in spinal deformities.

Sagittal balance of the spine is becoming an important issue in the assessment of the degree of spinal deformity. On a standing lateral full-length radiograph of the spine, the plumb line, or sagittal vertical axis (SVA), can be used to determine the spinal sagittal balance. In this procedure patients have to adopt a habitual standing position with the knees extended during radiographic examination, though it is not known whether small changes in the position of the lower extremities affects the location of the SVA. The purpose of the present study was to investigate the effect of postural change on shifts of the SVA, and to evaluate whether the SVA as measured on a standing full-length lateral radiograph can be used as an accurate measurement of spinal balance in clinical practice. Sagittal balance was analyzed using a patient with ankylosis of the entire spine due to ankylosing spondylitis, to eliminate segmental movement of the spine. A virtual SVA was constructed for seven different standing postures by cross-referring the coordinate systems from a standing full-length lateral radiograph of the spine with video analysis. The horizontal distance between the SVA and the anterior superior corner of the sacrum was measured for each posture. Small changes in the joint angles of the lower extremities affected the SVA significantly, and resulted in the horizontal distance between the SVA and the anterior superior corner of the sacrum varying from -4.5 to +14.9 cm. High correlations were found between this distance and the joint angle of the hip (r = -0.959), knee (r = -0.936), and ankle (r = 0.755) (P < 0.01). The results of the study showed that SVA translations during standing radiographic analysis in a patient with a fixed spine depend on small changes in the hip, knee, and ankle joints. Thus, sagittal spinal (im)balance in ankylosing spondylitis can not be measured from the SVA on a standing lateral full-length radiograph of the spine unless strict procedures are developed to control for the angle of the hip, knee, and ankle joints. The accuracy of the SVA as a measurement of sagittal spinal balance in other spinal deformities, with possible additional segmental movements, therefore remains questionable.

Adult↗
PubMed1998

Asymmetric low back loading in asymmetric lifting movements is not prevented by pelvic twist.

Asymmetric lifting is associated with an increased risk of low back disorders. Especially in lifting movements, characterized by a small amount of asymmetry, it is still the question if asymmetric lumbosacral torques occur, or if subjects try to avoid asymmetric back loading by twisting their pelvis with respect to the feet. An increase of the lifting speed or the box weight might amplify the lumbar torques but might also result in an attempt to limit further increase of asymmetric torques by increasing pelvic twist. In the current study, asymmetrical lifting movements were analyzed with the aid of a 3D linked segment model, using cuffs mounted to the body segments. Eight subjects performed lifting movements with five different asymmetry conditions, ranging from 0 to 90 degrees lifting asymmetry with respect to the sagittal plane, using two lifting speeds and two box weights. A significant increase in lateral flexing and twisting low back torque was found for each increase in asymmetry of the lifting movement. Pelvic twist accounted more or less constantly for about 25% of the lifting asymmetry and was hardly influenced by lifting speed or box weight. Even for 10 or 30 degrees of lifting asymmetry, subjects did not twist their pelvis far enough to avoid asymmetric loading of the low back. Assuming that asymmetric loading of the low back is more strenuous to the spine than symmetric loading, the current results indicate that even small deviations of a lifting movement from the sagittal plane can explain an increased risk of low back disorders.

Back↗
PubMed1998

When is a lifting movement too asymmetric to identify low-back loading by 2-D analysis?

In ergonomics research, two-dimensional (2-D) biomechanical models are often used to study the mechanical loading of the low back in lifting movements. When lifting movements are asymmetric, errors of unknown size may be introduced in a 2-D analysis. In the current study, an estimation of these errors was made by comparing the outcome of a 2-D analysis to the results of a recently developed and validated 3-D model. Four subjects made two repetitions of five lifting movements, differing in the amount of asymmetry. The results showed a significant underestimation of the peak torque by 20, 36 and 61% when the initial position of a box was rotated 30, 60 and 90 degrees with respect to the sagittal plane of the subject. The main cause of this underestimation was a pelvic twist, resulting in an erroneous projection of a pelvic marker on to the sagittal plane due to pelvic twist. It is suggested that from 30 degrees box rotation a 2-D analysis may easily lead to wrong conclusions when it is used to study asymmetric lifting.

Adult↗
PubMed1998

Simulated front crawl swimming performance related to critical speed and critical power.

PURPOSE: Competitive pool swimming events range in distance from 50 to 1500 m. Given the difference in performance times (+/- 23-1000 s), the contribution of the aerobic and anaerobic energy systems changes considerably with race distance. In training practice the regression line between swimming distance and time (Distance = critical velocity x time + anaerobic swimming capacity) is used to determine the individual capacity of the aerobic and anaerobic metabolic pathways. Although there is confidence that critical velocity and anaerobic swimming capacity are fitness measures that separate aerobic and anaerobic components, a firm theoretical basis for the interpretation of these results does not exist. The purpose of this study was to evaluate the critical power concept and anaerobic swimming capacity as measures of the aerobic and anaerobic capacity using a modeling approach. METHODS: A systems model was developed that relates the mechanics and energetics involved in front crawl swimming performance. From actual swimming flume measurements, the time dependent aerobic and anaerobic energy release was modeled. Data derived from the literature were used to relate the energy cost of front crawl swimming to swimming velocity. A balance should exist between the energy cost to swim a distance in a certain time and the concomitant aerobic and anaerobic energy release. The ensuing model was used to predict performance times over a range of distances (50-1500 m) and to calculate the regression line between swimming distance and time. RESULTS AND CONCLUSIONS: Using a sensitivity analysis, it was demonstrated that the critical velocity is indicative for the capacity of the aerobic energy system. Estimates of the anaerobic swimming capacity, however, were influenced by variations in both anaerobic and aerobic energy release. Therefore, it was concluded that the anaerobic swimming capacity does not provide a reliable estimate of the anaerobic capacity.

Adolescent↗