Christian Marquardt - Academia.edu (original) (raw)

Papers by Christian Marquardt

In recent years, the analysis of movement patterns has increasingly focused on the individuality ... more In recent years, the analysis of movement patterns has increasingly focused on the individuality of movements. After long speculations about weak individuality, strong individuality is now accepted, and the first situation–dependent fine structures within it are already identified. Methodologically, however, only signals of the same movements have been compared so far. The goal of this work is to detect cross-movement commonalities of individual walking, running, and handwriting patterns using data augmentation. A total of 17 healthy adults (35.8 ± 11.1 years, eight women and nine men) each performed 627.9 ± 129.0 walking strides, 962.9 ± 182.0 running strides, and 59.25 ± 1.8 handwritings. Using the conditional cycle-consistent generative adversarial network (CycleGAN), conditioned on the participant’s class, a pairwise transformation between the vertical ground reaction force during walking and running and the vertical pen pressure during handwriting was learned in the first step....

The Open Sports Sciences Journal, 2020

Background: Female professional golf tours are gaining popularity around the world; there are key... more Background: Female professional golf tours are gaining popularity around the world; there are key performance factors that are related to high performance on the female professional tour, like “driving distance and accuracy” and “putting per round”. However, there is a lack of research on the putting kinematics of female golfers with a lack of understanding the differences between the skill levels of female golfers. Objective: This study aimed to assess the putting performance and kinematics across three skill levels of female golfers. Methods: A total of one hundred and forty-nine right-handed female golfers were divided into three groups based on their playing skill levels: 64 professional tour golfers, 46 national team level golfers, and 39 college level golfers. Each participant executed seven putts on a straight, three meter indoor artificial turf. The three-dimensional kinematic data of each putt were captured using a high-precision ultrasound system (70Hz*3) (SAM PuttLab, Sci...

Journal of Sport and Exercise Psychology, 2013

Attunement to visual information has been suggested to mediate the performance advantage associat... more Attunement to visual information has been suggested to mediate the performance advantage associated with adopting an external focus of attention (e.g., Al-Abood, Bennett, Moreno Hernandez, Ashford, & Davids, 2002; Magill, 1998). We tested this hypothesis by examining the extent to which online visual information underpins the external focus advantage. The study examined skilled golfers on a putting task under one of three attentional focus conditions: control (no instructions), irrelevant (tone counting), and external (movement effect focus), with either full or occluded vision. In addition to task performance, the effect of attentional focus and vision on between-trial movement variability was examined. We found a significant advantage for an external focus of attention in the absence of vision. The results of the movement variability analysis further indicated that external focus was not mediated by the online use of vision. We discuss these findings in the context of traditional ...

International Journal of Sports Science & Coaching, 2009

Data was collected using the SAM PuttLab from 264 amateur golfers who were measured during an ama... more Data was collected using the SAM PuttLab from 264 amateur golfers who were measured during an amateur tournament series in Germany. Each golfer had to hit seven straight putts on a regular putting green at a distance of four meters using their own putter. Findings include that Heavy-Yips golfers showed an impaired control of face rotation and face angle at impact. It is proposed that the Yips is a Contextual Movement Disorder and a number of specific factors seem to be involved in its development: Anxiety, overcontrol, interference, and awareness of the problem. These factors operate in a vicious circle and any of the factors could trigger the start of the Yips. A behavioural treatment approach can be used to interrupt this vicious circle, based on the premise that the putting movements can normally be executed without breakdown in a different context.

International Journal of Sports Science & Coaching, 2007

The portable SAM PuttLab uses innovative ultra-sound technology to measure all aspects of a putti... more The portable SAM PuttLab uses innovative ultra-sound technology to measure all aspects of a putting stroke with high precision. It is considered that in putting a lack of objective feedback will limit earning and performance. The PuttLab uncovers individual strengths and weaknesses and provides relevant feedback to tailor individual training programs. The PuttLab has been used to collect a reference data sample of 99 PGA Tour players. The data reveals a wide variety of different putting techniques and putting strategies. The common attribute between players is the high consistency of the individual performance. A framework for successful putting is discussed with learning being defined as the search for an optimal solution in the individual motor-workspace, trading off sound technique and high consistency of movement automation

Psychological Medicine, 1991

SYNOPSISA comparative study of diabetics with autonomic neuropathy (N = 13) as against non-neurop... more SYNOPSISA comparative study of diabetics with autonomic neuropathy (N = 13) as against non-neuropathic diabetics (N = 16) and healthy control persons (N = 20) was carried out with respect to heart rate both at rest and under stress, frequency of cardiac arrhythmias in a 24-h ECG and accuracy of heartbeat and arrhythmia perception. In the subjects with diabetic autonomic neuropathy, the spontaneous variability and stress-induced reactivity of the heart rate as well as the number of tachycardic episodes were reduced, whereas the frequency of ventricular extrasystoles was somewhat increased. Impaired heartbeat perception and a complete loss of perception of arrhythmias as a consequence of neuropathic deafferentation could be demonstrated. Cardiac perception disorders also play a vital role in other clinical problems, e.g. silent myocardial infarction and lack of awareness of hypoglycaemia in diabetes mellitus.

Neurorehabilitation and Neural Repair, 2013

Background. No treatment for auditory neglect and no randomized controlled trial evaluating smoot... more Background. No treatment for auditory neglect and no randomized controlled trial evaluating smooth pursuit eye movement therapy (SPT) for multimodal neglect are available. Objective. To compare the effects of SPT and visual scanning therapy (VST) on auditory and visual neglect in chronic stroke patients with neglect. Methods. A randomized, prospective trial was conducted. Fifty patients with left auditory and visual neglect were randomly assigned. Twenty-four patients completed SPT therapy and 21 patients VST. Five patients (4 VST, 1 SPT) were lost. Each group received 1-hour sessions of neglect therapy for 5 consecutive days totaling 5 hours. Outcome measures in visual neglect (digit cancellation, visuoperceptual- and motor line bisection, paragraph reading) and auditory neglect (auditory midline) were assessed twice before therapy, thereafter, and at 2-week follow-up. The SPT group practiced smooth pursuit eye movements while tracking stimuli moving leftward. The VST group systema...

Neuropsychologia, 2012

Optokinetic stimulation (OKS) modulates many facets of the neglect syndrome. This sensory stimula... more Optokinetic stimulation (OKS) modulates many facets of the neglect syndrome. This sensory stimulation technique is known to activate multiple brain regions (temporo-parietal cortex, basal ganglia, brain stem, cerebellum) some of which are involved in auditory and visual space coding. Here, we evaluated whether OKS modulates auditory neglect transiently and induces a sustained effect (Study 1), and whether repetitive OKS permanently recovers auditory neglect (Study 2). In Study 1, 20 patients with visuospatial neglect and auditory neglect in an auditory midline task following rightsided stroke were randomly allocated to an experimental and a control group matched for neglect severity and socio-demographic factors. Both groups showed a stable, pathological shift of their auditory subjective median plane (ASMP) in front space to the right side. During leftward OKS the experimental group showed a complete normalization of the shift of the ASMP, which endured until 30 min poststimulation, and returned almost to baseline values 24h after OKS. In contrast, the control group who viewed the identical but static dot pattern, showed neither change in their ASMP during this condition, nor any significant change at 30 min or 24h poststimulation. In Study 2, we show in two samples of neglect patients (N = 3 each) that repetitive leftward OKS with smooth pursuit eye movements as a therapy induces lasting improvements in auditory (the ASMP) and visual neglect while visual scanning therapy yielded no measurable effects on auditory and significantly smaller effects on visual neglect. In conclusion, the experiments show that a single session of OKS induces rapid though transient recovery from auditory neglect including a sustained effect after termination of stimulation, while repetitive OKS therapy yields enduring and multimodal recovery from auditory and visual neglect. OKS therapy with pursuit eye movements therefore represents a multimodally effective and easily applicable technique for the treatment of auditory and visual neglect.

Experimental Brain Research, 2000

. When we move grasped objects, our grip force precisely anticipates gravitational and inertial... more . When we move grasped objects, our grip force precisely anticipates gravitational and inertial loads. We analysed the control of grip forces during very substantial load changes induced by parabolic flights. During these flight manoeuvres, the gravity varies between hypergravity associated with a doubling of normal terrestrial gravity and a 20-s period of microgravity. Accordingly, the contribution of the object&#x27;s weight to the load changed from being twice the normal value to being absent. Two subjects continuously performed vertical and horizontal movements of an object equipped with grip force and acceleration sensors. Whereas, during vertical movements performed under normal and hypergravity, a load force maximum occurred at the lower turning point and a minimum at the upper turning point, the load force pattern was completely changed under microgravity. In particular, the upper turning point was also associated with a load force maximum. Analysis of the grip forces produced by the two subjects revealed that the grip forces underwent the same characteristic changes as the load forces. Thus, subjects were able to adjust grip forces in anticipation of arm movement-induced fluctuations in load force under different and novel load conditions. Adaptation to changing levels of gravity was also obvious when the vertical and horizontal movements were compared: grip forces depended heavily on movement direction during normal and hypergravity but not during microgravity. The predictive coupling of grip force and load force was observed even during transitions between gravity levels, indicating rapid adaptation to changing load conditions. To account for the striking preservation of the normal characteristics of grip force control, we suggest that a highly automatized, extremely flexible sensorimotor mechanism firmly implemented within the central nervous system can cope with even massive changes in the environmental conditions.

Der Nervenarzt, 2009

Visually based reading disorders are frequently encountered in patients with acquired brain damag... more Visually based reading disorders are frequently encountered in patients with acquired brain damage. Homonymous visual field defects, impaired elementary visual capacities (acuity, contrast sensitivity, convergent fusion, ocular motor disorders), visual neglect or Balint-Holmes syndrome are the most frequent causes of such reading disorders. Reading is not only an important prerequisite for vocational and private life, but is also indispensable for subsequent cognitive abilities such as verbal working memory and long-term memory. Despite this importance no comprehensive system exists for the standardised assessment and treatment of visually based reading capacities in the German-speaking area. Here, we describe the basic properties of such a system (READ). After a short survey of the main causes of visually based reading disorders after brain damage, the anamnesis, diagnostic facilities, normative data as well as a variety of treatment techniques of the novel system are described. Selected results from ongoing clinical group studies as well as case examples highlight the diagnostic sensitivity and therapeutic efficiency of the new system for better management of visually based reading disorders after brain damage.

Behavioural Brain Research, 2009

When we manipulate familiar objects in our daily life, our grip force anticipates the physical de... more When we manipulate familiar objects in our daily life, our grip force anticipates the physical demands right from the moment of contact with the object, indicating the existence of a memory for relevant object properties. This study explores the formation and consolidation of the memory processes that associate either familiar (size) or arbitrary object features (color) with object weight. In the general task, participants repetitively lifted two differently weighted objects (580 and 280 g) in a pseudo-random order. Forty young healthy adults participated in this study and were randomly distributed into four groups: Color Cue Single task (CCS, blue and red, 9.8 3 cm 3), Color Cue Dual task (CCD), No Cue (NC) and Size Cue (SC, 9.8 3 and 6 3 cm 3) group. All groups performed a repetitive precision grasp-lift task and were retested with the same protocol after a 5-min pause. The CCD group was also required to simultaneously perform a memory task during each lift of differently weighted objects coded by color. The results show that groups lifting objects with arbitrary or familiar features successfully formed the association between object weight and manipulated object features and incorporated this into grip force programming, as observed in the different scaling of grip force and grip force rate for different object weights. An arbitrary feature, i.e., color, can be sufficiently associated with object weight, however with less strength than the familiar feature of size. The simultaneous memory task impaired anticipatory force scaling during repetitive object lifting but did not jeopardize the learning process and the consolidation of the associative memory.

Behaviour Research and Therapy, 1991

In panic disorder bodily sensations appear to play an important role as a trigger for anxiety. In... more In panic disorder bodily sensations appear to play an important role as a trigger for anxiety. In our psychophysiological model of panic attacks we postulate the following vicious circle: individuals with panic attacks perceive even quite small increases in heart rate and interpret these changes as being catastrophic. This elicits anxiety and a further increase in heart rate. To evaluate this model we conducted a field study of 28 subjects with panic attacks and 20 healthy controls. A 24 hr ambulatory ECG was recorded and the subjects were instructed to report any cardiac perceptions during this period and to rate the anxiety elicited by these perceptions. The incidence of cardiac perceptions was about the same in both groups, but only subjects with panic attacks reported anxiety associated with such perceptions. Analysis of the ECGs revealed that in both groups heart rate accelerations preceded cardiac perceptions. Following cardiac perceptions, the healthy controls showed a heart rate deceleration, whereas the subjects with panic attacks had a further acceleration. This heart rate increase after cardiac perceptions was positively related to the level of anxiety elicited by the perceptions. These results provide clear evidence in support of the vicious circle model of panic attacks.

from the World Scientific Congress of Golf 2016 in St. Andrews, Scotland Purpose Typically Yips i... more from the World Scientific Congress of Golf 2016 in St. Andrews, Scotland Purpose Typically Yips is assigned to the occurrence of involuntary movement jerks, spasms or freezing while putting. Between 20% and 30% of golfers seem to be affected by Yips (Smith et al., 2003, Klämpfl et al., 2013). Yips has been described as an organic problem (dystonia), a psychological problem (choking), or a continuum between both (Smith et al. 2003). The co-contractions found in Yips resemble to taskspecific dystonia (Adler et al. 2005). Marquardt (2009) suggested that Yips is the consequence of exaggerated self-perception and conscious control. This paper also points out, that the putting data collected with SAM PuttLab shows Yips symptoms also in beginners and high handicap golfers. It is speculated that these novices might bring in the movement problem from other racket sports such as tennis. In the two studies we present here we now investigated Yips symptoms in explicit golf novices who never pla...

Journal of Hand Therapy, 2009

Pre-post, single-group. Writer&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;am... more Pre-post, single-group. Writer&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s cramp (WC) is a focal dystonia causing impairments in daily life. Behavioral treatment approaches have been shown to improve handwriting performance, though outcomes remain sub-optimal. To examine the effects of the handwriting training and auditory grip force feedback in seven patients with WC. Handwriting performance was examined before and after treatment. Writing frequency, fluency, and pressure were recorded with a digitizing tablet and grip forces during handwriting were recorded. Subjective writing performance and pain were rated on visual analog scales. The treatment resulted in significant reductions in writing pressure and pain, while writing performance was significantly improved. Patients in this study with WC, who exhibit grip force and pressure problems, benefit from feedback-supported handwriting training.

Journal of Electromyography and Kinesiology, 1999

Tests of diadochokinesia are an inherent part of a neurological examination. Various quantifying ... more Tests of diadochokinesia are an inherent part of a neurological examination. Various quantifying methods have been proposed to increase the objectivity, sensitivity, and reliability of such examinations. The methods used and analyses performed, however, differ substantially between tasks. We used a three-dimensional, ultrasound-based recording device to continuously record joint angles during three diadochokinetic movements, avoiding any external constraints of the movements. Alternate pronation and supination of the forearm, tapping with the whole hand and with the index finger in isolation were analyzed in a sample of 63 healthy control subjects. The most sensitive measure for capturing effects of gender, sex, and active hand was frequency. The right hand was faster than the left in all tasks, tapping performance declined with increasing age, and male subjects were faster than females in forearm diadochokinesia. Other measures that characterize speed of movement such as maximum angular velocities and accelerations did not yield comparable sensitivity in detecting the same statistical effects. However, angular velocity achieved the highest test-retest reliability for forearm diadochokinesia, while frequency was reproduced in the tapping tasks. Additional measures characterizing symmetry of the angular velocity profiles and intraindividual variability were shown to be largely independent of movement speed. Examples in neurological patients showed that the data define a valuable standard against which pathological performance can be precisely evaluated. In addition, the different measures captured dissociable aspects of motor performance that may further help to characterize the deficit and adjust therapy.

Klinische Neurophysiologie - KLIN NEUROPHYSIOL, 2007

Human Movement Science, 2011

Muscular hyperactivity during handwriting, irregular and jerky scripts, as well as awkward and sl... more Muscular hyperactivity during handwriting, irregular and jerky scripts, as well as awkward and slowed pen movements are the cardinal symptoms of writer's cramp. Accordingly, impaired kinematics and increased force have been reported in writer's cramp. However, the relationship between these symptoms has rarely been investigated. In addition, measurements of finger forces have been restricted to the vertical pen pressure. In the present study, the pen of a graphic tablet was equipped with a force sensor matrix to measure also the grip force produced against the pen barrel despite highly variable pen grips of the patients. Kinematics of writing movements, vertical pen pressure, and grip force were compared in 27 patients with writer's cramp and normal control writers during writing of a test sentence. As expected, all measures revealed a significantly worse writing performance in the patients compared to the control subjects. Exaggerated forces were more frequent than abnormal kinematics, and evidenced by prolonged movement times and reduced writing frequencies. Correlations were found neither between kinematics and force measures nor between the two forces. Interestingly, patients relaxed the grip force during short periods of non-writing by the same relative amount as control subjects. The finding of a large heterogeneity of performances patterns in writer's cramp may reflect the variability of dystonic symptoms as well as the highly variable compensatory strategies of individual patients. Measurements of finger force and in particular of the grip force are valuable and important descriptors of 0167-9457/$ -see front matter Ó

Human Movement Science, 2006

Writer's Cramp (WC) is a focal, action-related dystonia, which induces hypertonic co-contractions... more Writer's Cramp (WC) is a focal, action-related dystonia, which induces hypertonic co-contractions and severely impairs handwriting. One behavioral treatment approach is the handwriting training developed by . Schreibtraining in der neurologischen Rehabilitation. In EKN-Materialien für die Rehabilitation. Dortmund: Borgmann] which includes among various motor exercises the use of a modiWed pen grip (stabilized between index and middle Wnger). This pen grip has proven particularly successful in clinical practice. The current study aims at elucidating the immediate eVects of the modiWed pen grip on writing in 23 WC patients and 11 healthy controls. All participants wrote a sentence with their usual and also with the modiWed pen grip. Movement and pressure were recorded with a digitizing tablet. Pressure, movement time for the whole sentence, script size and writing Xuency were analyzed. When writing with their usual pen grip, pressure in the WC patients was elevated, and writing speed was decreased compared to healthy controls. Changing over to the modiWed pen grip reduced the pressure signiWcantly in WC patients and controls, but left other aspects of their writing unaVected. This shows that the use of the modiWed pen grip is an eVective way to normalize pen pressure in WC patients, thereby providing the best conditions for the training of speed and Xuency.