bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Role of Proprioceptive Information during Arm Movements Using a Model of the Human Arm
Authors: Stroeve Sybert
Published: August 2016

Using a model for the neuromuscular control of human arm movements, the possible roles of different proprioceptive signals are analyzed. The control model is represented by a neural network and includes both feedback and feedforward control modes. After a learning process, the controller regulates a wide range of arm movements. Evaluation of the roles of different afferent signals shows that sensed muscle forces are important to achieve accurate control of fast movements. For a moderately high loop delay (50 ms), velocity feedback is not essential, but for small loop delays (0 and 25 ms) an increased performance is attained by feedback of velocity. Position sense is essential to prevent steady-state errors. The arm impedance is affected considerably by the delay in the control loop and by the configuration of the motor control system. The achieved relation between muscle length and force is similar to the invariant characteristics laying at the basis of the equilibrium-point (EP) hypothesis. However, control of fast movements on the basis of EP alone is not feasible, but requires feedforward control. During training in a velocity-dependent force field, the impedance of the arm increases at first, due to enhanced cocontraction. Subsequently, both impedance and movement errors decrease, indicating a successful representation of the changed inverse dynamics.
Approaching Grasping from Different Perspectives
Authors: Rosenbaum David A. , Meulenbroek Ruud J.G. , Vaughan Jonathan , Elsinger Catherine
Published: August 2016

The hypothesis introduced by Smeets and Brenner concerning the perpendicular approach of the thumb and index finger during grasping has heuristic value, but it also has limitations. Among the limitations are the following: (a) the approach parameter is not directly testable and it is unclear how the values of deceleration at contact and movement time are set theoretically; (b) it is questionable that motion of the thumb and index finger are independent; (c) reliance on the minimum-jerk account ignores critiques of that account; and (d) the model begs the question of how the effectors proximal to the index finger and thumb are controlled. We briefly review an alternative model that can handle these challenges.
Is It Pointing to Grasping or Grasping Pointing?
Authors: Savelsbergh Geert J.P. , Van der Kamp John
Published: August 2016

The Smeets and Brenner view on grasping is simple: grasping is in fact pointing. In our comments we examine the model beyond the reach-to-grasp task namely, by grasping (without reaching) of moving objects and eating. The model fits the data of both tasks. Although generalization of a model to different tasks usually strengthens its acceptance, in the present case it reveals its shortcomings, namely, both tasks include a clear grasping component that is hard to accept as pointing.
Neural Features of the Reach and Grasp
Authors: Robertson Edwin M.
Published: August 2016

The concept of canonical representations within the motor system has been both supported and refuted using a variety of behavioral studies. Here, based upon neurophysiological data, I discuss the relationship amongst those neuronal substrates of action and the behavioral components of a movement. A novel view of reaching and grasping has been proposed which predicts that movements with similar kinematic and dynamic properties have a similar representation within the nervous system (Smeets & Brenner, 1999). However this is broadly inconsistent with a variety of neurophysiological findings that emphasize the independence amongst representations of action.
Stability of Bimanual Coordination in Parkinson's Disease and Cognitive Modulation of Intention
Authors: Geuze Reint H.
Published: August 2016

The functional integrity of the bimanual neuromotor system of Parkinson's disease (PD) subjects (stage II) compared to controls (2 × n = 16) was evaluated by measures of coordination stability of tapping in in-phase. anti-phase. and 90°-phase. Recently, intentional influence was modeled as an additive attractor function on the intrinsic dynamics, resulting in predictions tested by Scholz and Kelso (1990). In this study, the intentional influence was modulated by attaching cognitive meaning to the rhythmical pattern, which was expected to enhance the stability of coordination and, if effective, might be profitable to PD patients. Half of the PD subjects significantly lacked stability. They were less stable than controls, lost coordination at lower frequencies, and needed more time to switch between phase patterns. The reduction of stability was reflected in the progression of the disease. Cognitive meaning reduced variability of the single hands but not of relative phase, and no effect on switching time was found. The results suggest a weaker coupling strength between the limbs in PD patients lacking stability.
An Evaluation of the Minimum-Jerk and Minimum Torque-Change Principles at the Path, Trajectory, and Movement-Cost Levels
Authors: Breteler Mary D. Klein , Meulenbroek Ruud G.J. , Gielen Stan C.A.M.
Published: August 2016

In the present study we evaluated the minimum-jerk and the minimum torque-change model at the path, trajectory, and movement-cost levels. To date, most evaluations of these models have mainly been restricted to path comparisons. Assessments of the time courses of realized jerk and torque changes are surprisingly lacking. Moreover, the extent to which the presumed optimized parameters change as a function of the duration and other temporal features of aiming movements has never been investigated, most probably because the models presuppose movement time. In order to till mis gap, we analyzed a subset of the data of an earlier experiment in which 12 participants performed leftward and rightward planar pointing movements. Hand displacements and joint excursions were recorded with a 3D motion-tracking system and subsequently evaluated by means of model-based analyses. The results show that despite a good agreement between observed paths and predicted paths, especially by the minimum torque-change model, the time courses of jerk and torque changes of observed and modeled movements differed considerably. These differences could mainly be attributed to asymmetrical properties of the time functions of slow movements. Variations of movement costs as a function of movement lime and skewness of tangential velocity profiles show that, especially at high movement speed, costs increase exponentially with departures of symmetry. It is concluded that trajectory-formation models have limited explanatory power in situations that require demanding information processing during the homing-in phase of goal-directed movements. However. for slow movements, deviations from the optimal timing profiles require little extra costs in terms of jerk or torque change.
Development of Force Control and Timing in a Finger-Tapping Sequence with an Attenuated-Force Tap
Authors: Inui Nobuyuki , Katsura Yumi
Published: August 2016

We conducted an experiment to examine age-related differences in the control of force and timing in a finger-tapping sequence with an attenuated-force tap. Participants between 7 and 20 years old tapped on a load cell with feedback on practice trials. They were required to recall the force pattern (300 g, 300 g, 300 g, 100 g) and the intertap interval (400 ms) without feedback on test trials. Analysis indicated that the last attenuated tap affected the first three taps of the tapping sequence in adults and adolescents but not in children. Adults and adolescents appeared to respond with four taps as a chunk, resulting in a contextual effect on the timing of force control, but younger children had difficulty with such chunking. Further, adults and adolescents were able to more accurately produce individual force magnitudes to match target magnitudes than younger children. For the ratio of force in serial positions 1:4, 2:4, and 3:4, consequently, 7- to 8-year-old children had lower ratios than the other age groups. Although there was no difference among age groups for timing control of peak force to press duration as a control strategy of force, 7- to 8-year-old children spent more time to produce force than the other age groups. Peak force with a decreased force was more variable in the attenuated force serial position (4) than in the other serial positions in all five age groups. Peak force variability was particularly robust in younger children. These findings suggest that younger children have difficulty with both temporal and spatial (i.e., magnitude) components of force control.
Scaling the Components of Prehension
Authors: Cesari Paola , Newell Karl M.
Published: August 2016

The experiment reported examined: (a) the role of the geometrical body scaled informational invariant for the transition of human grip configurations; (b) whether the same invariant can be scaled considering also the force applied during the grasp phase; and (c) how the temporal duration of the grasp and displacement phases of prehension are scaled to the object properties of size and mass. Adult subjects performed a series of trials in reaching, grasping, and displacing spheres that varied in size and mass. The grip transitions were described by the body scaled relation:where Ls and Ms are, respectively, the diameter and the mass of the spheres grasped and Lh and Mh are the length and the mass of the hand. The impulse during the grasp phase was linearly related with the mass of the spheres within each density. The temporal durations of the grasp and displacement components were scaled coherently to the object properties. These findings provide support to the hypothesis that the grasp and displacement components of prehension are organized coherently within a single action.
Implications of Low Mechanical Impedance in Upper Limb Reaching Motion
Authors: Popescu Florin C. , Rymer W. Zev
Published: August 2016

The equilibrium point hypothesis (EPH), much discussed in recent years, is central in a class of theories that posits an important role for muscular mechanical and reflex properties in the control of voluntary movement. We review briefly the findings of our studies testing the idea of equifinality, a major tenet of the EPH, which predicts that terminal limb position will be achieved regardless of transient perturbations in initial position or during ongoing movement. Our observations do not support this prediction of equifinality. We also report our findings that joint viscosity and elastic stiffness estimated during ballistic motion are unexpectedly low, limiting their potential contributions to the regulation either of limb movement trajectory or of limb stability. Taken together, our results imply that neuromuscular mechanical properties are unlikely to be used for regulating voluntary motion and that other control strategies, most notably the use of feedforward controllers in which muscles act as force generators acting primarily on inertial loads, are more consistent with our observations.
Adaptations in Bilateral Mechanical Power Patterns during Obstacle Avoidance Reveal Distinct Control Strategies for Limb Elevation versus Limb Progression
Authors: Niang Assane E.S. , McFadyen Bradford J.
Published: August 2016

The present study investigated the adaptations of specific power bursts during the combined contexts of the proximity (lead vs. trail limb) and height of an obstruction in relation to limb elevation versus progression. Ten young, adult, male subjects walked at their natural speed during unobstructed walking and the bilateral avoidance of moderate and high obstacles. Hip flexor generation power was unaffected by obstacle height for the leading limb and always delayed for the trailing limb. The knee extensor absorption power burst at toe-off was also eliminated for the trailing limb and was found to reappear in mid-swing. Few differences were seen for ankle push-off power. The results suggest that the hip joint is dedicated to limb advancement only, while the knee joint is directly involved in limb elevation and the control of multiarticular effects.
Contextual Effects on Force Control and Timing in a Finger-Tapping Sequence with an Accentuated- or Attenuated-Force Tap
Authors: Inui Nobuyuki
Published: August 2016

An experiment was conducted to examine contextual effects of the magnitude of changes in force on force control in a finger-tapping sequence with an accentuated- (accentuated-force condition) or attenuated-force tap (attenuated-force condition). Participants were trained to produce a finger-tapping sequence with an intertap interval of 500 ms and four force patterns. During practice, visual force feedback pertaining to the two target forces in the tapping sequences was provided. After practice, the participants reproduced the learned tapping sequences in the absence of feedback. A main result was that the last accentuated-force tap affected the first three taps of the tapping sequence. For the accentuated-force conditions, the larger the difference between the first three target forces and the last target force, the larger the first three forces. This indicates the contextual effect of serial position for force control. This effect was not observed, however, under the attenuated-force conditions.
Developing an “Anchor” System to Enhance Postural Control
Authors: Mauerberg-deCastro Eliane
Published: August 2016

This article uses an anchor metaphor to explain the dynamic interplay between the human body's active uses of nonrigid tools to mediate information about its adjacent environment to enhance postural control. The author used an “anchor” system (e.g., ropes attached to varying weights resting on the floor) to test blindfolded adults who performed a restricted-balance task (30 s one-foot standing). Participants were tested while holding the anchors under a variety of weight conditions (125 g, 250 g, 500 g, and 1 kg) and again during a baseline condition (no anchors). When compared with the baseline condition, there was a significant reduction in the amount of body sway across the anchor conditions. The author found that mechanical support provided by the anchor system was secondary to its haptic exploratory function and that an individual can use the anchoring strategy with a dual purpose: for resting and for reorientation after intrinsic disruptions.
From Parallel Sequence Representations to Calligraphic Control: A Conspiracy of Neural Circuits
Authors: Bullock Daniel
Published: August 2016

Calligraphic writing presents many challenges for motor control, including: learning and recall of stroke sequences; critical timing of stroke onsets and durations; fine control of grip and contact forces; and letterform invariance under size scaling, which entails fine control of stroke directions and amplitudes during recruitment and derecruitment of musculoskeletal degrees of freedom. Experimental and computational studies in behavioral neuroscience have progressed toward explaining the learning, planning, and control exercised in tasks that share features with calligraphic writing and drawing. This article highlights component operations ranging from parallel sequence representations to fine force control. Treated in succession are: competitive queuing models of sequence representation, performance, learning, and recall; letter size scaling and motor equivalence; cursive handwriting models in which sensory-motor transformations are performed by circuits that learn inverse differential kinematic mappings; and fine-grained control of timing and transient forces by circuit models that learn to solve inverse dynamics problems.
Stability of Coordination Patterns in Handwriting: Effects of Speed and Hand
Authors: Sallagoïty Isabelle , Athènes Sylvie , Zanone Pier-Giorgio , Albaret Jean-Michel
Published: August 2016

Previous studies have shown the existence of preferred stroke directions and shapes in handwriting. Assuming that such a two-dimensional trajectory formation process relies on the nonlinear coordination between two abstract orthogonal oscillators, a recent study (Athènes et al., in press) investigated the relative stability and the temporal accuracy of such coordination patterns in performing various ellipsoids corresponding to different phase and amplitude relationships between the oscillators. Results showed that only a small subset of the patterns was stable and accurate. The present study tested and verified the assumption that more stable coordination patterns deteriorate less under a speed constraint. In addition, differences between the dominant and nondominant hands gave insights into various effects modulating the stability and accuracy of such preferred patterns. Evidence of preferred coordination patterns and the predictability of their deterioration corroborate the existence of dynamics underlying handwriting in terms of nonlinearly coupled oscillators.
Energy-Minimization Bias: Compensating for Intrinsic Influence of Energy-Minimization Mechanisms
Authors: Oliveira Flavio T.P. , Elliott Digby , Goodman David
Published: August 2016

Anecdotal and scientific evidence suggest humans tend to undershoot targets in rapid movements. We investigated whether this undershoot bias derives from energy minimization mechanisms. Participants performed 200 trials of two tasks: (1) a simple slider push to a target, and (2) a modified version of (1), designed so overshooting was less energy consuming than undershooting. Results support that the undershoot bias found in (1), as well as the overshoot bias found in (2), results from an energy minimization mechanism. Energy minimization might be inherent to biological systems. Movement biases were undesirable for maximal performance. Nonetheless, participants presented biases despite financial incentives to perform maximally. Participants did, however, appear sensitive to systematic errors produced by the attraction to less energy costly responses. We suggest that the motor system is constrained such that maximal performance trades off with energetic optimality although humans are able to learn and compensate for the energy minimization biases.
Muscle Synergies at the Elbow in Static and Oscillating Isometric Torque Tasks with Dual Degrees of Freedom
Authors: Ettema Gertjan J.C. , Taylor Emma , North J. David , Kippers Vaughan
Published: August 2016

This study’s aim was to identify the effect of oscillation of torques in isometric tasks under identical mechanical conditions on the muscle synergies used. It was hypothesized that bi-functional muscles would play a lesser role in torque oscillation, because they would also generate an undesired oscillation. Thus, changes in muscle synergies were expected as a consequence of oscillation in torque generation. The effect of the trajectory of torque generation was investigated in dual-degrees-of-freedom submaximal isometric oscillation torque tasks at the elbow. The torques were flexion-extension and supination-pronation. Oscillation torques were compared with static torque generations at four torque positions during oscillation. Muscle activity was determined with surface electromyography. Compared with the static torque tasks, the oscillation tasks showed an overall increased muscle activity. The oscillation tasks, however, showed similar activity patterns and muscle synergies compared to the static composite tasks. It was found that the motor system is well able to control different orthogonal combinations of slow torque oscillations and constant torques by employing a single oscillating muscle synergy.
The Effect of Workspace on the Use of Motor Abundance
Authors: Tseng Ya-weng , Scholz John P.
Published: August 2016

The uncontrolled manifold approach was used to examine the effect of workspace location on the use of motor abundance to control the hand’s path during reaching. Participants pointed to targets located in the contralateral and ipsilateral workspaces at two different distances. When reaching to all parts of the workspace, the component of joint configuration variance consistent with an identical hand path across trials was significantly higher than the component of joint configuration variance leading to a variable hand path. The relative magnitude of this difference was affected primarily by target orientation and minimally by target distance. The control of hand-path direction when reaching ipsilaterally was associated with more selective use of motor abundance compared to reaching contralaterally. The control of hand-path extent was not affected by target orientation. Biomechanical factors are discussed as possible reasons that lead to the observed selective workspace effects.
Effects of Response Task on Reaction Time and the Detection of Affordances
Authors: Pepping Gert-Jan , Li François-Xavier
Published: August 2016

Studies on affordance perception commonly report systematic errors; a finding that is at odds with the observation that everyday motor behavior is accurate. The present study investigated whether the means by which perceptual performance is measured could explain the reported errors. Perception of overhead reachability and reaction time were measured using a verbal and an actual reaching response in a standing reach, and a reach-and-jump. Results show that participants accurately perceived their action boundaries for both tasks and in both response conditions. A simple reach, however, took less time to initiate (1,094 ms) than a reach-and jump (1,214 ms). Interestingly, the verbal response took considerably more time to initiate (1,424 ms) than the actual reach (1,154 ms). These results suggest that making verbal judgments about affordances is a different task than actually acting on them. It is therefore concluded that the use of conscious judgments to measure perceptual performance should be considered with care.
Coupling of Force Variability in Bimanual Tapping with Asymmetrical Force
Authors: Inui Nobuyuki
Published: August 2016

An experiment was conducted to examine the coupling of force variability in bimanual finger tapping sequences with asymmetrical forces. Right-handed participants were trained to produce bimanual finger tapping sequences consisted of an intertap interval of 500 ms and eight force conditions: two alternating force left high, two alternating force right high, two simultaneous force left high, and two simultaneous force right high conditions. During practice, visual force feedback was provided for both hands performing the bimanual tapping sequences. After practice, the participants produced the learned tapping sequences in the absence of feedback. Most importantly, whereas the peak force variability of the nondominant left hand was larger than that of the dominant right hand under the right high conditions, there was no left–right difference under the simultaneous left high conditions. This suggests that under the simultaneous left high conditions, both hemispheres were activated, resulting in overflow in the right hand, and bringing the two force variabilities closer together.
Assessment of Body Composition in Children
Authors: Lohman Timothy G.
Published: August 2016

The assessment of body composition in children has taken on greater significance because of the need to study the prevalence of obesity in children and youth, the need to better document the tracking and genetics of body fatness, the need to relate fat patterning in childhood and fat patterning in adults, and the need to assess changes in the prevalence in obesity over time in a given population. This paper reviews methods of estimating body composition in children and youth. The use of body mass index, anthropometry, body density, and bioelectric impedance methodologies is emphasized, as well as the need to use multicomponent models for validation studies of new methods. Also explored in this article is the relationship between body composition and health related fitness.
Plasma Somatomedin–C in 8- to 10-Year-Old Swimmers
Authors: Denison Barbara A. , Ben-Ezra Victor
Published: August 2016

Plasma somatomedin–C (SM-C), important for linear growth, is reduced under conditions of caloric deficit whether induced by diet or exercise. The purpose of this study was to determine the effect of diet and exercise on plasma SM-C levels in 37 8- to 10-year-old children, 18 swimmers (SWM) and 19 control children (CTL). All children kept a 3-day dietary record for 2 weeks prior to collection of a fasted, resting blood sample. Both groups showed RDA-normal total kcal intake (SWM = 2301 ± 664; CTL = 2072 ± 449) and twice the RDA for protein for this age group (SWM = 3.1 ± 2.3 g • kg−1; CTL = 3.0 ± 2.4 g • kg−1). Plasma SM-C levels for SWM (1.39 ± .84 U • ml−1) and CTL (.91 ± .33 U • ml−1) were significantly different (P<.01) but within the normal range for this age group. These data suggest that 8- to 10-year-old children who are training regularly, in combination with adequate energy and protein intake, show SM-C levels within the normal range expected for this age.
Utility of Exercise Testing to Assess Aortic Recoarctation
Authors: Zellers Thomas M. , Driscoll David J.
Published: August 2016

Because it is not known how often and how uniformly exercise testing is used to “unmask” recurrent or persistent coarctation of the aorta, this study was designed to determine (a) the frequency with which exercise testing is used by the clinician to evaluate patients after coarctation repair, and (b) the hemodynamic measures obtained with exercise that are considered to be indicative of significant persistent or recurrent coarctation. Questionnaires were sent to 80 randomly selected pediatric cardiologists; 49 were returned completed. About half of the respondents performed exercise testing (ET) on all of their patients after coarctation repair and 75 % tested at least half. Those who supervised an exercise laboratory used ET for a significantly greater number of their patients. In descending order, rest arm-leg gradient (ALG), maximal exercise systolic blood pressure (MXBP), and postexercise ALG were considered the most important indicators of significant recoarctation. The majority of respondents made decisions based on data from the ET that were consistent with published guidelines.
Aquatic Experiences for Young Children: Evaluating Risks and Benefits
Authors: Langendorfer Stephen
Published: August 2016

Aquatic experiences including structured instructional programs for young children have become extremely popular over the past two decades despite opposition and controversy. Surprisingly, this popularity and controversy have not given rise to extensive or sustained research efforts by exercise scientists or aquatic professionals. Most information available for assessing risks and benefits of aquatic experiences for young children must be gleaned from ancillary sources in medical and educational literature. This paper reviews important issues and questions in the medical, developmental, and pedagogical areas of early childhood aquatics. The need for basic and applied research efforts by teams of exercise scientists from physiologic, psychologic, medical, and aquatic backgrounds is apparent.
Achievement of Plateau and Reliability of V̇O2max in Trained Adolescents Tested with Different Ergometers
Authors: Rivera-Brown Anita M. , Frontera Walter R.
Published: August 2016

This study examined the effect of different testing ergometers on V̇O2max, V̇O2max criteria achievement, and reliability of V̇O2max for V̇O2 plateau achievers and nonachievers. Twenty trained adolescents completed a treadmill, cycling, and rowing protocol twice. Of all subjects, 35%, 65%, and 45% did not achieve a plateau in either test (No P) during treadmill, cycling, and rowing, respectively. V̇O2max did not differ between tests for the total group or within the plateau and No P groups in any of the ergometers. A high reliability for V̇O2max was obtained in all ergometers. Our data suggest that Taylor’s criterion should not be a requisite for V̇O2max when testing trained adolescents.
Sex and Ethnic Differences in Children’s Physical Activity: Discrepancies between Self-Report and Objective Measures
Authors: Sallis James F. , McKenzie Thomas L. , Elder John P. , Hoy Patricia L. , Galati Todd , Berry Charles C. , Zive Michelle M. , Nader Philip R.
Published: August 2016

Previous studies have not used both self-report and objective measures to assess sex and ethnic differences in children’s physical activity. In the present study, 187 Mexican American and Anglo American children, aged 11 to 12 years, were assessed by two 7-day physical activity recall interviews and up to 8 days of accelerometer (Caltrac) monitoring over a 6-month period. Compared to Anglo American boys, accelerometer data showed Mexican American boys, Anglo American girls, and Mexican American girls to be 95,81, and 75% as active, respectively. Activity recall data showed that, compared to Anglo American boys, Mexican American boys, Anglo American girls, and Mexican American girls were 95,95, and 90% as active, respectively. The extent of sex and ethnic differences in children’s physical activity depend on the measure used.
Sport Participation and Perceived Academic Performance of School Children and Youth
Authors: Lindner Koenraad J.
Published: August 2016

School children and youth from Primary Grade 5 to Secondary Grade 7 (average age range, 9 to 18 years) in Hong Kong completed a sports participation questionnaire and rated their own academic performance (AP). Results of ANOVAs indicated that frequency and extent of participation tended to be significantly higher for students with high self-ratings than for students with less satisfactory self-reported performance, and that this trend was significantly stronger in females than males and present in all age groups. The correlations between participation and AP were generally significant but low. These results indicate that those who perceive themselves to be the better achievers in academic subjects are as a group the more frequent participants, with stronger motives for involvement in sport and physical activity. A prevalent fear among parents and teachers in Hong Kong, that regular sport participation could threaten academic achievement, appears unfounded.
Reliability of Isokinetic Concentric and Eccentric Strength in Circumpubertal Soccer Players
Authors: Kellis Eleftherios , Kellis Spiros , Gerodimos Vasilios , Manou Vasiliki
Published: August 2016

The reliable examination of isokinetic parameters in young athletes is important for the establishment of appropriate strength testing protocols. The purpose of this study was to examine the reliability of peak moments, non-preferred/preferred leg and reciprocal ratios during isokinetic knee efforts in young soccer players. Thirteen circumpubertal (age = 13.0 ± 0.4 years) soccer players performed maximum knee extension and flexion efforts at 30, 120 and 180°·s1 in two occasions, a week apart. The reliability of the peak moments was high, with reliability coefficients ranging from 0.71 to 0.98. The non-preferred/preferred leg and reciprocal ratios demonstrated moderate to high reliability (coefficients ranged from 0.42 to 0.87). The reliable examination of moments of force and ratio measurements during eccentric tests and at fast angular velocities in young soccer players requires extensive familiarization of the subjects prior to the main test.
Learning to Swim Using Buoyancy Aides
Authors: Parker Helen E. , Blanksby Brian A. , Quek Kian L.
Published: August 2016

The use of buoyancy and propulsion aides in teaching young swimmers is contentious. Some believe that such aides provide an artificial crutch that retards learning of independent swimming. Others believe they provide valuable learning cues for progress. This study investigated the progress made by 7 year olds learning to swim with and without buoyancy and propulsion aides. A single primary class was divided into 2 matched-ability groups: aides (n = 10) and self-support (n = 9). Each group attended 10 daily, 40-min lessons prior to the school day. Unsupported stroking and kicking actions were videotaped in the last 10 min of each lesson and scored using the MERS-F scale. As a whole, significant improvements were revealed by the third lesson (p < .05), although no significant differences existed between groups. Case studies of the most rudimentary swimmers in each group confirmed that teaching frontcrawl to beginner swimmers using multiple buoyancy aides failed to enhance skills beyond those gained by using a kickboard only in 10 lessons.
Validity of a Submaximal 1-Mile Track Jog Test in Predicting VO2max in Fit Teenagers
Authors: Hunt Brian R. , George James D. , Vehrs Pat R. , Fisher A. Garth , Fellingham Gilbert W.
Published: August 2016

The purpose of this study was to validate the ability of the 1-mile jog test to predict VO2max in fit teenagers. Forty-one males and 42 females performed the steady-state, submaximal jogging test on an indoor track, along with a maximal graded exercise test (GXT) on a treadmill. Open circuit calorimetry was used during the GXT to measure maximal oxygen consumption (VO2max). We generated the following age-specific prediction equation applicable to boys and girls 13–17 years old (n = 83, Radj = .88, SEE = 3.26 ml · kg−1 · min−1): VO2max = 92.91 + 6.50 × gender (0 = female, 1 = male) − 0.141 × body mass (kg) − 1.562 × jog time (min) − 0.125 × heart rate (bpm). Cross-validation results were acceptable (SEEpress = 3.44 ml · kg−1 · min−1). As a field test, the submaximal 1-mile jogging test may alleviate problems associated with pacing, motivation, discouragement, injury, and fatigue that are sometimes associated with maximal effort timed or distance run tests.
Development of Anaerobic Function during Childhood and Adolescence
Authors: Van Praagh Emmanuel
Published: August 2016

This review summarizes the research relating anaerobic function to growth among children and adolescents. Pediatric practitioners and scientists are always struck by the impressive accumulation of results relating to the cardiopulmonary system. However, anaerobic fitness has received much less research attention. This is surprising, considering that high-intensity exercises lasting only a few seconds is a more “natural” pattern during growth than prolonged low-intensity exercises. In anaerobic tasks or sport events such as sprint running, sprint swimming, sprint cycling, jumping, or throwing, the child’s performance is distinctly lower than that of the adult. This partly reflects the child’s lesser ability to generate mechanical energy from chemical energy sources during short-term intensive work or exercise. Because both intramuscular high energy phosphate kinetics and muscle cross-section vary during growth and maturation, this review examines some developmental aspects of energetic- and mechanical factors involved in anaerobic performance. Anaerobic muscle function and performance are quantitative traits influenced by several determinants such as genetic factors, age and gender, muscle fiber characteristics, hormonal and training factors. Because of ethical and methodological constraints when investigating healthy children, this review also includes fundamental work done on some animal models.
Evaluation of the Canadian Aerobic Fitness Test with 10- to 15-Year-Old Children
Authors: Garcia Anne W. , Zakrajsek Jennifer S.
Published: August 2016

The objective of this study was to evaluate the utility of the Canadian Aerobic Fitness Test (CAFT), a field measure of cardiovascular fitness. After providing anthropometric measures, 31 subjects, ages 10 to 15, completed a maximal treadmill test and the CAFT, a 3-stage step test. Multiple regression analyses were conducted where maximal oxygen consumption from the treadmill test was estimated based on the oxygen cost of stepping, age and various combinations of body composition. For the total sample, the best model (R = 0.79, SEE = 6.7), obtained from the sum of 4 skinfolds, was the body composition estimate. This model was slightly more accurate for males (R = 0.83, SEE = 6.0) than for females (R = 0.77, SEE = 7.0). When the regression equation incorporated less time consuming indicators of body composition, the predictive power, albeit lower, was still satisfactory. It appears that the CAFT can be a useful option for measuring cardiovascular fitness for youth, with the decision dependent on the purpose of the test, the testing resources, the setting, and the motivation of the subjects.
A Cross-Sectional Survey Assessing Physical Fitness of 9- to 19-Year-Old Girls and Boys in Switzerland
Authors: Cauderay Michel , Narring Françoise , Michaud Pierre-André
Published: August 2016

Biometric status, cardiovascular endurance, strength, speed, flexibility, and coordination were assessed in a cross-sectional survey involving 3,540 Swiss boys and girls, aged 9 to 19. Strength and endurance were better among boys, whereas girls displayed better flexibility. Most of the performances among girls did not change from 14 years onwards, while boys exhibited better performances after 15–16 years. The coefficients of correlation between the tests varied from as low as .16 (NS) to .63 (p < .01). Multiple regression analyses showed that height, weight, and chronological and biological age altogether were independently related to the performance on most of the tests. Fitness is a multidimensional concept that not only evolves with chronological age but also depends on biometrical characteristics such as pubertal stage, height, and weight.
Autonomic Characteristics Following Surgical Repair of Tetralogy of Fallot Using Heart Rate and Blood Pressure Variability
Authors: Perrault Hélène , Tzovanis Maria , Johnson Dominique , Davignon André , Chartrand Claude , Mokrane Abdelkader , Nadeau Réginald A.
Published: August 2016

This study compares the autonomic responses of 9 adolescents (mean ± SEM: 17±1 years) successfully operated for tetralogy of Fallot (TOF) in early childhood and 8 age-matched healthy controls (CTRL) using R-R and blood pressure variability. Continuous ECG and BP recordings were obtained during spontaneous and controlled respiration (CR) at 0.20 Hz as well as after an 85° head-up tilt (HUT) and during steady-state cycling at heart rates of 100 and 120 bpm, selected to reflect partial and complete cardiac vagal withdrawal. TOF exhibited total R-R variance and HF power (ms2) lower than CTRL under both spontaneous (938 ± 322 vs. 1,714 ± 296) and CR (1,541 ± 527 vs. 4,725 ± 1,207; p < .05), which may be indicative of a lower cardiac vagal activity. HUT decreased the R-R HF component, which remained lower in TOF than CTRL and increased the diastolic BP LF component in TOF but not in CTRL. Exercise decreased the R-R HF power more in TOF than CTRL. The exaggerated diastolic BP and limited heart rate responses to tilting and the more marked vagal withdrawal at Ex120 in TOF may be suggestive of a disturbance in the cardiac sympathetic response. Further studies are needed to confirm these observations on larger groups of young adults successfully operated for TOF.
Feasibility of Using the Tritrac Motion Sensor Over a 7-Day Trial with Older Children
Authors: Crocker Peter R.E. , Holowachuk Darryl R. , Kowalski Kent C.
Published: August 2016

This study assessed the feasibility of the Tritrac-R3D motion sensor over a 7-day period with 79 children in Grades 4–8. Eight sets of data were lost due to instrument breakdown or data downloading software problems. Despite daily telephone reminders and school visits, most participants reported problems with wearing the motion sensors, including forgetting to put the sensor on, physical discomfort, involvement in aquatics, public embarrassment, and not being allowed to wear the sensors during organized sport. The results also showed that the Tritrac scores were strongly correlated with Caltrac scores (r = .86) but were not significantly correlated to a 7-day interview recall (PAR) and a 7-day self-report of activity (PAQ-C). The two self-report measures were moderately related. These findings question the viability of the Tritrac to assess typical physical activity over extended periods in this population.
The Prevalence of Selected Modifiable Coronary Heart Disease Risk Factors in 12-Year-Old Greek Boys and Girls
Authors: Bouziotas Constantin , Koutedakis Yiannis , Shiner Ruth , Pananakakis Yiannis , Fotopoulou Vasiliki , Gara Styliani
Published: August 2016

The prevalence of 14 selected modifiable coronary heart disease (CHD) risk factors was determined in randomly selected adolescent boys (n = 117) and girls (n = 93) from provincial Greece. Based on published criteria thresholds for CHD, 45% of boys and 50% of girls exhibited three or more risk factors with time spent on “vigorous” activities, low cardiorespiratory fitness and fatness being among the most frequent in both sexes. Stronger associations were found between cardiorespiratory fitness and time spent on “vigorous” rather than “moderate-to-vigorous” activities in both boys and girls. Regression analysis indicated that energy expenditure (P < .01) in boys and energy expenditure (P < .05) and energy intake (P < .01) in girls could alone explain about 60% of the body-fat related findings in either group. Broadly based primary prevention strategies aimed at children should concentrate on reducing the overall energy intake and increasing the time spent on “vigorous” activities if future Greek adult CHD mortality is to be reduced.
Morphology and Hydrodynamic Resistance in Young Swimmers
Authors: Benjanuvatra Nataphoom , Blanksby Brian A. , Elliott Bruce C.
Published: August 2016

Six 9-, 11-, and 13-year-old, anthropometrically matched males and females were towed on the water surface via a mechanical winch at 1.3 to 2.5 ms−1 in increments of 0.3 ms−1 during a prone streamlined glide. Passive drag force of the 13-year age group was significantly larger than that of the 9-year age group at 1.9, 2.2, and 2.5 ms−1, but not at 1.3-1.6 ms−1. While anthropometry did not feature in any regression equation at any age for passive drag at velocities of 1.3 and 1.6 ms−1, body mass was the best predictor of drag at 1.9 and 2.5 ms−1.
New Standards for the Bruce Treadmill Protocol in Children and Adolescents
Authors: Wessel Hans U. , Strasburger Janette F. , Mitchell Brett M.
Published: August 2016

We have developed normal standards for the Bruce exercise (EX) protocol since a review of 875 studies in patients with congenital or acquired heart disease showed that only 5.1% achieved the predicted 50th percentile for EX time of the standards reported by Cumming, Everatt, and Hastman (Am. J Cardiol 41:69, 1978). Our data are based on 160 males and 103 females, age 4–18 years who met the following criteria: trivial or no heart disease, maximal effort, maximal EX heart rate (HR) > 180 beats/min, and normal resting and EX ECG without arrhythmia. The ECG was monitored continuously and HR computed from the ECG and the end of each minute of EX. Comparison with the predicted data of Cumming et al. for each age group by stage showed essentially identical submaximal EX heart rates but slightly lower maximal HR (–2%), which averaged 197 beats per minute in males and females. EX times were on average 15% lower than the predicted 50th percentile for most age groups in males and females. We developed regression equations, which predict exercise time from age and body size or age, body size and 2nd stage exercise heart rate. They better reflect the capabilities of untrained, asymptomatic children and adolescents seen in our laboratory in the 1990s than the Canadian data of 1978.
Correlates of Time Spent in Physical Activity and Television Viewing in a Multi-Racial Sample of Adolescents
Authors: McGuire Maureen T. , Neumark-Sztainer Dianne R. , Story Mary
Published: August 2016

This study assessed whether the correlates related to physical activity and television viewing differed across gender, grade, and racial groups. Adolescents (n = 4746) from 31 junior and senior high schools completed a self-administered survey. Adolescents’ physical activity was related to their families’ and friends’ fitness concerns. Adolescents’ physical activity was also related to their own fitness and health concerns. Few correlates of physical activity differed by gender, age, or race. Television viewing was negatively related to the family’s fitness concerns and health concerns; however, these factors accounted for a small amount of the variance in adolescents’ television viewing. None of the factors related to television viewing differed by age or race groups. Future studies will need to identify the factors related to physical activity and television viewing among adolescents who are at greatest risk for inactivity.
Children’s and Adolescents’ Physical Self-Perceptions as Related to Moderate to Vigorous Physical Activity and Physical Fitness
Authors: Raudsepp Lennart , Liblik Raino , Hannus Aave
Published: August 2016

The aim of this study was to determine the relationship between physical self-perceptions, moderate to vigorous physical activity and physical fitness in Estonian school children and adolescents aged 11–14 years. The sample consisted of 134 boys and 119 girls. Self-perception of body appearance, physical conditioning, sport/athletic competence, strength and general physical self-worth were measured by the Children’s Physical Self-Perception Profile (C-PSPP). Moderate to vigorous physical activity was assessed using 7-day physical activity recall and physical fitness using 20 meter endurance shuttle run. All C-PSPP scales were significantly moderately related with physical activity and fitness in both boys and girls. Boys’ perceptions of strenght competence, physical condition and general self-worth were higher and they participated more in moderate to vigorous activities compared to girls. Multiple regression analysis results indicated the best predictors of moderate to vigorous physical activity and physical fitness were perceived sport/athletic competence, physical self-worth, and perceived strength competence Our results demonstrate that physical self-perceptions are significant correlates of physical activity and fitness in children and adolescents.
Assessment of Critical Power with Children
Authors: Fawkner Samantha G. , Armstrong Neil
Published: August 2016

The purpose of this study was to examine methods of assessing Critical Power (CP) with children. Eight boys and 9 girls (10.3 – 0.4 yrs) completed 3 cycle tests in one day, each at a different constant power output predicted to induce fatigue in 2 to 15 min. Time to exhaustion was recorded, and order of the tests was randomized, with 3 hours recovery between tests. The children repeated these tests and 2 additional tests with at least 24 hr recovery between each test. CP was determined using least squares linear regression analysis of the power — t−1 relationship, for the single day (CP1), the 5 tests from different days (CP2), and the repeated 3 tests from different days (CP3). The 95% limits of agreement (range of percentage differences) were −15.4 to 13.1% (CP1 v CP2), −16.8 to 13.5% (CP1 v CP3), and −8.4 to 6.7% (CP2 v CP3). CP is a robust measure even when only 3 tests are completed in a single day and may be used to provide a simple and useful parameter of exercise intensity for constant load exercise with children.
Sex, Ethnic and Socio-Economic Differences in Children’s Physical Activity
Authors: Woodfield Lorayne , Duncan Michael , Al-Nakeeb Yahya , Nevill Alan , Jenkins Charles
Published: August 2016

The present study examines the relationship of sex, ethnicity, and socio-economic status to physical activity levels of young people. Participants were 301 males and females (12.9 – 0.81 years). Physical activity was measured using the four by one-day physical activity recall questionnaire. ANOVA revealed that high socio-economic status children reported greater average daily energy expenditure levels than low socio-economic status children (p < .01). The daily energy expenditure of white-Caucasian children was significantly higher than black or Asian children. White boys were significantly more active than white girls, but no such sex differences were observed among black and Asian children. Although activity was always greater at weekends, a decline in activity by school year was observed on Saturdays and Sundays but with no such decline observed on weekdays.