Muscular Patterns Research Articles

Electromyographic Evaluation of Neuromuscular Coordination of Subject After Orthodontic Intervention

The aim of this work was to investigate the neuromuscular changes associated with the orthodontic post-treatment using surface electromyography. One hundred (100) young, healthy adults without signs and symptoms of temporomandibular dysfunction (TMD) were divided into two groups: 60 subjects who were undergoing orthodontic intervention (Ortho Group) and 40 subjects who had no orthodontic intervention (Control Group), aged 18-25 years. EMG activity of masseter and temporalis anterior muscle was recorded during two different tests: 1. maximum voluntary clench (MVC) with cotton rolls; and 2. MVC in intercuspal position. In all subjects, both tests were performed with symmetric muscular patterns (more than 85%) and with insignificant latero-deviating of the mandible (lower than 10%). There are no statistically significant differences between the subjects of both groups evaluated. Both groups showed medium index values calculated according to the normal standards established previously.

Measurements of the quadriceps femoris function after meniscus refixation at the stable athlete’s knee

The purpose of this study was to monitor the muscular changes regarding the isokinetic strength and torque pattern of the quadriceps femoris at the stable athlete's knee after meniscus tear refixation. Therefore 15 athletes (10 male, 5 female) performing recreational or competitional sports at least five times a week before injury were retrospectively examined in the average 2.5 years after isolated arthroscopic meniscus refixation using Inside Out technique. Next to function and sport activity focused scores the isokinetic peak torque (PT) and in the EMG have been analyzed compared to the uninjured knee. The mean age was 31.26 years. The time between injury and surgery was in the average 13.7 days. According to our first results the data suggest a complete recovery of functional and muscular pattern after meniscus refixation at the stable athlete's knee. No significant EMG changes for quadriceps femoris were detectable. The PT was fully recovered. The functional and sport activity score analysis (Lysholm and Tegner score) showed no changes in the postoperative long-term follow up compared to the preinjured status. Examining isokinetic PT and the EMG of the quadriceps femoris, these data show no side-to-side differences. Regarding the function and sports activity score system, the functionally high demand patients seem to profit by this procedure.

Electromyographic analysis of masticatory and neck muscles in subjects with natural dentition, teeth‐supported and implant‐supported prostheses

To compare the electromyographic (EMG) characteristics of masticatory and neck muscles in patients with natural dentition, teeth-supported prostheses and implant-supported prostheses. Twenty-five subjects aged 40-80 years were examined. Five patients had maxillary and mandibular implant-supported fixed prostheses; five patients had mandibular implant-supported fixed prosthesis and maxillary removable complete denture; seven patients had implant-supported fixed prosthesis (one arch) and natural dentition or full-arch tooth-fixed prosthesis (one arch); and eight control subjects had natural dentition or single tooth-fixed prostheses. Surface EMG of masseter, temporal and sternocleidomastoid muscles was performed during maximum teeth clenching and unilateral gum chewing. Interarch dental contacts were assessed with shim stocks. All groups had similar interarch dental contacts (P>0.05). During clenching, patients with maxillary and mandibular implant-supported fixed prostheses had unbalanced standardized masseter and temporalis anterior activities (74%), with significantly larger values found in the other patients and control subjects (all mean values larger than 86%, P=0.017). All patients chewed with significantly larger muscular potentials than control subjects (on average, 1434-2100 microV s vs. 980 microV s, P=0.04), and had altered muscular patterns (left side, P=0.021). The patients with one arch with natural dentition/tooth fixed prostheses had chewing muscular patterns similar to the control subjects. Clenching with the analyzed prostheses was performed with a relative increment of temporalis activity. Neuromuscular coordination during chewing was larger in patients who maintained their teeth or dental roots, independently from the number of dental contacts.

The Roles of CPG Phase Modulation and Reflexive Muscular Patterns in Balance Recovery During Walking—A Simulation Study

Most walking assist systems reported are not available for real world environments where frequent perturbations are caused by slips, uneven terrain, slopes and obstacles. It is evident that humans are able to cope with such perturbations with reflexes that cause unconscious, relatively fixed muscular response patterns to perturbations within a short period of time. In our previous study, we showed that artificial reflexes could improve the perturbation resistance for simulated walkers, though the roles of different reflexive mechanisms were not quantitatively clarified. In this study, we focused on the different roles of reflexive muscle responses and the CPG phase modulation mechanism. By proposing and evaluating two stability criteria through a series of simulation experiments, we revealed different roles for two mechanisms in the simulated walkers. These will not only further increase the possibility of realising artificial reflexes for paralysed individuals, but also bring new insights into the field of motor control.

Penile erection and micturition events triggered by electrical stimulation of the mesopontine tegmental area

The cholinergic neurons in the laterodorsal tegmental nucleus (LDT) play a crucial role in the regulation of rapid eye movement (REM) sleep. Because penile erection occurs during REM sleep, the involvement of the LDT in penile erection was examined in unanesthetized head-restrained rats. To detect penile erection, corpus spongiosum of the penis (CSP) pressure was measured through a telemetric device with simultaneous bulbospongiosum (BS) muscle EMG recording through stainless wires. Electrical stimulation in and around the LDT induced the following three CSP pressure patterns: 1) a full erection pattern indistinguishable from the nonevoked or spontaneous erection, characterized by a slow increase in CSP pressure with additional sharp CSP peaks associated with BS muscle bursts, 2) a muscular pattern characterized by sharp CSP pressure peaks but in the absence of a vascular component, i.e., without an increase in baseline CSP pressure, and 3) a mixed-type response characterized by high-frequency CSP pressure peaks followed by a full erection response. Full erections were evoked in and around the LDT, including more medially and ventrally. The sites for inducing mixed-type events were intermingled with the sites that triggered full erections in the anterior half of the LDT, whereas they were separated in the posterior half. The sites for muscular responses were lateral to the sites for full erections. Finally, a CSP pressure response identical to micturition was evoked in and around the Barrington's nucleus and in the dorsal raphe nucleus. These results suggest that the LDT and surrounding region are involved in the regulation of penile erection. Moreover, different anatomical areas in the mesopontine tegmentum may have specific roles in the regulation of penile erection and micturition.

Coherence analysis of muscle activity during quiet stance

Studies of muscle activation during perturbed standing have demonstrated that the typical patterns of coordination ("ankle strategy" and "hip strategy") are controlled through multiple muscles activated in a distal-to-proximal or proximal-to-distal temporal pattern. In contrast, quiet stance is thought to be maintained primarily through the ankle musculature. Recently, spectral analysis of inter-segment body motion revealed the coexistence of both ankle and hip patterns of coordination during quiet stance, with the predominating pattern dependent on the frequency of body sway. Here we use frequency domain techniques to determine if these patterns are associated with the same muscular patterns as observed during perturbed stance. Six of the seven muscles measured showed a linear relationship to the sway of at least one body segment, all being leg muscles. Muscle-segment phases were consistent with that required to resist gravity at low frequencies, with increasing phase lag as frequency increased. Visual information had effects only at frequencies below 0.5 Hz, where the shift from in-phase to anti-phase trunk-leg co-phase was observed. These results indicate that co-existence of the ankle and hip pattern during quiet stance involves only leg musculature. Anti-phase movement of the trunk relative to the legs at higher frequencies arises from indirect biomechanical control from posterior leg muscles.

MUSCULAR RECRUITMENT PATTERNS DURING ACTIVE HIP EXTENSION EXERCISES

INTRODUCTION Deficiencies in movement patterns and motor regulation play a major role in the development of musculoskeletal dysfunctions, especially in the peripheral locomotive system [1]. Studies suggested that low back disorders are associated with muscle imbalance [2-4] and currently, emphasis has been placed on the importance of achieving coordinated activity between all muscles within a balanced muscular system for the prevention and treatment of low back pain [3]. Changes in activation patterns of hip extensors and pelvic stabilizing muscles are recognized as factors that cause low back disorders. These disturbances could have an impact on physiological loading and alter the direction and magnitude of joint reaction forces [4]. Therefore, the aim of this study was to investigate muscular recruitment patterns of the gluteus maximus, semitendinosus and erector spinae muscles with healthy young individuals during four different modalities of therapeutic exercises.

Monday July 3, 2006 12:00-13:30 Hall 5A Platform Session Adult Epileptology I

Abstract 1 E. Gardella, 1 F. Rondelli, 1 M. Stanzani Maserati, 1 G. Rubboli, 2 S. Francione, 2 L. Tassi, 3 R. Caterina, 3 M. Costa, 2 G. Lo Russo, 3 P. Ricci Bitti, and 1 C. Tassinari ( 1 Dept. of Neuroscience, Bellaria Hospital, University of Bologna, Italy , 2 Center of Epilepsy Surgery “C. Munari,” Niguarda Hospital, Milan, Italy , 3 Dept. of Psychology, University of Bologna, Italy ) Purpose: To investigate the emergence of emotional display during temporal versus frontal lobe seizures (TLS, FLS). Method: Three independent observers reviewed presurgical video-EEG recordings of 477 seizures, in 84 patients with drug-resistant epilepsy (45 temporal/39 frontal), analysing the topography of the ictal discharge and the ictal modifications of facial expression, suggesting emotions (FEE). The pattern of facial activation underwent FACS (facial action coding system) analysis. The presence of coherent emotional motor/acoustic behaviour and of a subjective feeling has been also investigated. Results: All the six fundamental emotions were observed, with the same muscular pattern of facial activation during FLS and TLS. Negative emotions, particularly fear, were most represented. The prevalence of FEE was similar in FLS (68%) versus TLS (67%); right-sided ictal discharge was observed more frequently (59%). Association of FEE with emotional motor/acoustic behaviours occurred in 21% of seizures and in 13% an emotional experience was referred. Despite the similar prevalence of ictal FEE in both genders, there was male predominance in facial display of rage and a female predominance in referring a subjective emotional feeling and/or in manifesting coherent motor behaviours related to FEE, especially in case of ictal fear. Conclusion: A coherent pattern of FEE and emotional behaviour can equally emerge during FLS and TLS, with a slight right prevalence of the ictal discharge, confirming the hemispheric right specialisation for emotion. Gender dimorphism expressing and/or referring fear and rage, could reflect either inborn or socio-behavioural differences.

Interlimb postural coordination in the standing cat

The dorsal-side-up body posture in standing quadrupeds is maintained by coordinated activity of four limbs. We studied this coordination in the cat standing on the platform periodically tilted in the frontal plane. By suspending different body parts, we unloaded one, two, or three limbs. The activity of selected extensor muscles and the contact forces under the limbs were recorded. With all four limbs on the platform, extensors of the fore- and hindlimbs increased their activity in parallel during ipsilateral downward tilt. With two forelimbs on the platform, this muscular pattern persisted in the forelimbs and in the suspended hindlimbs. With two hindlimbs on the platform, the muscular pattern persisted only in the hindlimbs, but not in the suspended forelimbs. These results suggest that coordination between the two girdles is based primarily on the influences of the forelimbs upon the hindlimbs. However, these influences do not necessarily determine the responses to tilt in the hindlimbs. This was demonstrated by antiphase tilting of the fore- and hindquarters. Under these conditions, the extensors of the fore- and hindlimbs appeared uncoupled and modulated in antiphase, suggesting an independent control of posture in the fore- and hindquarters. With only one limb supporting the shoulder or hip girdle, a muscular pattern with normal phasing was observed in both limbs of that girdle. This finding suggests that reflex mechanisms of an individual limb generate only a part of postural corrections; another part is produced on the basis of crossed influences.

Cyclic time course of motor excitability modulation during the observation of a cyclic hand movement

The observation of a sinusoidal flexion–extension of the wrist was utilized to determine the continuous time course and phase relation between observed movement and its effects on the observer's motor pathways. While observing movements performed by others, the observers' cortical motor areas and spinal circuits were activated, reflecting the specific temporal and muscular pattern of the actual movement (motor resonance). H-reflexes and motor-evoked potentials (MEPs) were elicited, respectively, by electrical stimulation of the median nerve and magnetic stimulation of the appropriate cortical area, in the right forearm muscle Flexor Carpi Radialis (FCR) of subjects who were observing a 1-Hz cyclic oscillation of the right prone hand executed by a different person. Observation elicited a parallel cyclic excitability modulation of the observer's H-reflex and MEP responses with identical period as the observed movement. Modulation was phase advanced, as is muscle activation with respect to the real movement. The same results were obtained when the observed hand oscillation was executed with different frequency (1.6 Hz) and when the hands of mover and observer were supine. No motor resonance was elicited by observing the oscillation of a metal platform. The excitability modulation of MEPs simultaneously monitored in both antagonists of the observer's forearm (FCR and Extensor Carpi Radialis, ECR) was in almost perfect phase opposition, reflecting their natural reciprocal activation during the execution of a hand oscillation. These findings suggest that during observation, motor pathways are modulated subliminally reproducing with high temporal fidelity the motor commands needed to execute the observed movement.

Muscular Patterns and Activation Levels of Auxiliary Breathing Muscles and Thorax Movement in Classical Singing

The aim of this paper is to present an overview of the findings in seven studies exploring muscular patterns and muscle activation levels in selected muscles by classical singers. In addition, the relationship of these muscles to thorax (TX) movement was investigated. Loading levels and respiratory phasing of upper trapezius (TR), sternocleidomastoideus (STM) and the scalenes (SC) were investigated in vocalization tasks with variation in vocal loudness and pitch. Further, muscle activity in the posterior neck (PN) was investigated in inhalation and phonation and, finally, TR, intercostal (INT), lateral abdominal (OBL) and anterior abdominal (RC) muscle loading in student and professional singers was examined. Muscle activity was recorded by use of an ambulatory four-channel monitoring system (Physiometer PHY 400, Premed, Norway). TX movement was traced with two strain gauge sensors (RES-117) placed around the upper TX and lower TX. A phasing of upper TR activity to INT and OBL activity was discovered, all muscles supporting the expiration phase. During phonation, TR contributes in the compression of the upper TX, thus serving as an accessory muscle of expiration. TR activity is reduced with short breathing cycles and is mostly inactive in simplified speaking tasks. During phonation, professional opera singers activate the expiratory-phased TR, INT, OBL and RC muscles to higher levels than student singers do. STM and SC show correlated activity patterns during inhalation and phonation by classical singers. During demanding singing, expiratory-phased STM and SC activity peaks produce a counterforce to the compression of upper TX at high pitches. As breathing demands are lowered, STM and SC activity are reduced and attain inspiratory phasing. Substantial muscle activity is observed in PN during inhalation and phonation. EMG biofeedback performed on TR and STM have a secondary effect of lowering EMG activity in PN.

Evaluation of muscular activity, local muscular fatigue, and muscular rest patterns among dentists

In a previous study, dentists reported very high scores for perceived physical workload, but only low to moderate scores for the musculoskeletal system. This is difficult to explain when other occupational groups in the dental services are compared, and is the main reason why the present study was performed. To measure muscular activity, a surface electromyography (sEMG) study was done, and included the subjects who reported neck and shoulder complaints in the previous study. A portable sEMG system (MyoGuard) was used to collect a myoelectric signal on-line and analysis of the myoelectric signal in a computer. sEMG was recorded from both trapezius muscles for approximately 4 h during an ordinary working day. Twenty-seven dentists participated in the study. The results show accumulated rest% fairly close to that of female cashiers and supermarket employees and increased average rectified value percent (ARV%) during work that could contribute to the very high workload perceived by dentists.

Movimento toracoabdominal e exercicios respiratorios: revisao da literatura

The chest wall is composed of the rib cage and the abdominal compartments, which move in synchrony during the breathing act. This movement reflects the participation of the inspiratory muscles that change the pulmonary volumes. The technological evolution and the concept of muscular participation during the phases of the breathing cycle and the thoracic and abdominal movement behavior was modified. Nowadays, we are aware that it is possible to estimate pulmonary flowing volume throughthoracoabdominal displacement, which determines the pattern and the activity of different muscles. It is well established that, during breathing, subjects displaced predominantly the abdomen when in supine, and the thoracic cage when in upright position. Chest physiotherapy has a great variety of techniques that interfere in the ventilatory pump behavior. In particular, breathing exercises that modify the involvement of muscles, improve pulmonary ventilation. Breathing exercises studies that deal with diaphragmatic and intercostal exercises have been basically analyzed in three aspects: 1) normalization of the thoracoabdominal movement, 2) ventilation distribution, 3) modification of the pattern and gaseous exchange, which relieves dyspnea. In the 80's, Cuello introduced a new scheme of breathing exercises denominated respiratory muscular pattern. He also studied the effects of these exercises in the ventilation distribution as well as their clinical results. Although, breathing exercises are widely used as a physiotherapeutic resource, they have been seldom studied. The study of the thoracoabdominal movement in association with breathing exercises as well as the investigation of the impact of these techniques in muscular action and pulmonary volumes generation may lead to a better understanding of chest physiotherapy.

Gait Training with a Driven Gait Orthosis – Comparison between Lokomat and Treadmill Therapy

Rehabilitation approaches for impairments in motor function of neurologically impaired patients like stroke victims rely heavily on physiotherapy. After the introduction of treadmill training for paraplegia, there has grown a body of experience in the use of treadmill training for hemiplegia as well. Since exercising with stroke patients or paraplegic patients on the treadmill is a very demanding task for therapists, new robotic devices have been developed to assist and even increase the effect of training sessions. We report our experience and results of first recordings with the Lokomat, a PC-controlled and driven orthosis, developed to enable completely paralyzed patients to walk on a treadmill without the physical help of therapists. The patients are supported with a suspension of the body weight by a harness, when walking in a driven gait orthosis, with actuators at hip and knee joints of either side inducing cyclic gait patterns. During treadmill training periodic excitation of muscular and cutaneous receptors is supposed to stimulate neural circuits in the spinal cord to facilitate or even induce cyclic gait patterns as put forward by the concept of central pattern generators. We measured EMG activity in 4 muscles of each leg during walking on a regular treadmill as well as on a treadmill with assistance of the Lokomat. Subjects were healthy controls and 9 hemiplegic stroke patients. Our results support the hypothesis that the use of an extrinsically given cyclic leg movement will induce typical muscular walking patterns, however reduced on the paralyzed side. Faster velocities would lead to higher EMG amplitudes. Treadmill training without the Lokomat induced less pronounced muscular patterns. Gait symmetry can almost perfectly be induced by Lokomat training. In addition, patients were able to use faster velocities on the Lokomat compared to the regular treadmill, leading to a higher number of repetitive gait cycles. Since the exercise is less strenuous for patients and therapists, the duration of training can be increased producing still augmented exercise. Our data show that Lokomat training is a highly effective gait exercise for severely disabled hemiplegic patients. First results indicate that it is at least as effective as typical physiotherapeutic gait training.

H-reflex and physiologic measures of ejaculation in men with spinal cord injury

Courtois F, Geoffrion R, Landry E, Bélanger M. H-reflex and physiologic measures of ejaculation in men with spinal cord injury. Arch Phys Med Rehabil 2004;85:910–8. Objective To investigate the various physiologic parameters characterizing and predicting ejaculation. Design Single case-control study. Setting A referred care center and university setting. Participants Two men with spinal cord injury (SCI) and 2 control subjects. Intervention Subjects were asked to self-stimulate with a Ferticare vibrator to induce ejaculation over 5 to 8 independent sessions. Main outcome measures Penile tumescence, blood pressure, heart rate, electromyographic activity of the bulbocavernosus muscles, abdominal muscles, soleus H-reflex, and occurrence of ejaculation. Results Changes on all measures were observed, with penile tumescence being more stable in control subjects. Blood pressure increased in both groups, whereas tachycardia was observed in controls and bradycardia in subjects with SCI. H-reflex dropped slightly in controls but increased in subjects with SCI. Muscular patterns differed on ejaculatory success or failure. Conclusions Physiologic changes on all measures can be observed in men with SCI as a function of ejaculation. Changes include hypertension and bradycardia, characteristic of hyperreflexia, and tachycardia in controls. The neural mechanisms underlying these patterns are discussed. H-reflex showed increased spinal cord excitability in subjects with SCI after ejaculation, which suggests spasticity. The results support investigation of the H-reflex to predict ejaculatory success or failure in men with SCI, along with specific analysis of muscular patterns.

사이클 운동시 페달 샤프트 너비에 따른 근육 활동 비교

본 연구의 목적은 사이클 운동 시, 3가지 다른 길이의 페달 샤프트 (표준형, 5.08 cm, 10.16 cm)가 근육활동에 미치는 영향을 근전도 측정을 통해 비교 분석하는데 있다. 사이클링을 활동적으로 하는 여학생 5명을 피험자로 선택하여 대퇴지근(RF), 외측광근(VL), 내측광근(VM) 대퇴이두근(BF)을 표면전극을 사용하여 관찰하였다. 자료 분석을 위해 두 대의 S-VHS 카메라 (Panasonic Digital 5000)를 사용하여 사이클링 동작을 촬영하였다. 연구의 목적을 위해 각 조건에 대한 표준화된 평균 및 최대 근전도치가 계산되어졌다. 각각의 변인에 대해 페달 샤프트의 길이에 따른 근전도치의 차이점을 분석하기 위해 반복측정에 의한 일원변량분석을 사용하였으며, 통계적 유의성이 있을 경우 Newman-Keuls 사후검증을 실시하였다. 일반적으로 5.08 cm 길이의 페달 샤프트를 사용했을 경우 표준형의 페달 샤프트와는 다르게 모든 하지근의 적분 근전도치가 줄어드는 것으로 나타났다. 페달 샤프트의 길이가 길어짐에 따라 외측광근의 적분 근전도치가 통계적으로 유의하게 낮게 나타났고, 5.08 cm 길이에서 대퇴이두근의 적분 근전도치가 통계적으로 유의하게 낮게 나타났다. 페달 샤프트 길이에 따른 최대 근전도치의 통계적 유의성을 찾을 수 없었지만, 일반적으로 5.08 cm 길이의 페달 샤프트를 사용할 때 최대 근전도치가 가장 낮게 나타났다. 본 연구의 결과, 페달 샤프트의 길이가 하지근의 활동정도와 형태를 변화시킨다는 것을 알 수 있었으며, 하지관절의 부하에 영향을 미치는 것으로 사료되어진다. 이에 따라, 개인의 해부 구조학적인 면을 고려한 페달 샤프트의 길이 조절은 효율적이며 안정적인 사이클링 동작을 수행하는데 많은 도움이 될 수 있을 것이다.

Neuromuscular coordination of masticatory muscles in subjects with two types of implant‐supported prostheses

To compare the electromyographic (EMG) characteristics of masticatory muscles in patients with fixed implant-supported prostheses and implant overdentures. Nineteen subjects aged 45-79 years were examined. Fourteen were edentulous and had been successfully rehabilitated with (a) maxillary and mandibular implant-supported fixed prostheses (seven patients); (b) mandibular implant overdentures and maxillary complete dentures (seven patients). Five control subjects had natural dentition or single/partial (no more than two teeth) tooth or implant fixed dentures. Surface EMG of the masseter and temporal muscles was performed during unilateral gum chewing and during maximum teeth clenching. To reduce biological and instrumental noise, all values were standardized as percentage of a maximum clenching on cotton rolls. During clenching, temporal muscle symmetry was larger in control subjects and fixed implant-supported prosthesis patients than in overdenture patients (analysis of variance, P=0.005). No differences were found in masseter muscle symmetry or in muscular torque. Muscle activities (integrated areas of the EMG potentials over time) were significantly larger in control subjects than in implant-supported prosthesis patients (P=0.014). In both patient groups, a poor neuromuscular coordination during chewing, with altered muscular patterns, and a smaller left-right symmetry than in control subjects were found (P=0.05). No differences in masticatory frequency were found. Surface EMG analysis of clenching and chewing showed that fixed implant-supported prostheses and implant overdentures were functionally equivalent. Neuromuscular coordination during chewing was inferior to that found in subjects with natural dentition.

Musculature of an illoricate predatory rotifer Asplanchnopus multiceps as revealed by phalloidin fluorescence and confocal microscopy

The pattern of muscles in the actively swimming predatory rotifer Asplanchnopus multiceps is revealed by staining with tetramethyl-rhodamine isothiocyanate (TRITC)-labelled phalloidin and confocal scanning laser microscopy (CSLM). The major components of the musculature are: prominent semicircular muscles of the corona; paired lateral, dorsal and ventral retractors in the trunk; a network of six seemingly complete circular muscles and anastomosing longitudinal muscles in the trunk; two short foot retractors, originating from a transverse muscle in the lower third of the trunk. The sphincter of the corona marks the boundary between the head and the trunk. The muscular patterns in rotifers with different lifestyles differ clearly, therefore, the muscular patterns seem to be determined by the mode of locomotion and feeding behaviour.

The physiology of channel swimmers. 1955.

This paper presents the results of three years’ study of some of the factors concerned in the ability to endure immersion in cold water. People showing unusual tolerance of cold have been compared with people showing unusual intolerance. In 1951 there was a swimming-race across the English Channel in which eighteen of twenty competitors swam from France to England in times ranging from 12 to 20 hours in water at 15.5C (60F). This is of great interest because records of shipwreck survivors show that persons immersed in the sea at 60F usually live only about 5 hours, and seldom more than 6 hours, death being due to hypothermia (Molnar 1946). The swimmers in the 1951 race all conformed to a certain physical type, very different from that of athletes who cover long distances on land by running, cycling, skiing, or mountain climbing. Some of the swimmers were frankly obese; others were of stocky build and had well-rounded contours concealing the muscular pattern.

Information Processing and Movement Optimization During Development: Kinematics of Cyclical Pointing in 5- to 11-Year-Old Children

The authors studied the development of movement control in speed-accuracy tradeoff conditions in children aged 5–11 years and in adults performing cyclical pointings. Twelve difficulty levels (IDs), ranging from 2 to 6.58 bits, were defined (P. M. Fitts, 1954). Peak and time to peak velocity, acceleration, and deceleration, and acceleration profiles as a function of hand position (Hooke's portraits) were analyzed. Movement time decreased with age and was less affected by ID. Peak velocity and acceleration increased, acceleration and deceleration were decreasingly time consuming, and movement profiles turned to increased harmonicity with age and task easiness. Nevertheless, the developmental trends differed between parameters. Gain in velocity seemed chiefly dependent on improved muscular cooperation patterns before 7 years of age and on improved information processing from age 7 onward; achievement of an optimized strategy in the speed-accuracy tradeoff occurred at age 11 years.