To question the relation between uni- and bipedal postural skills, 21 subjects were required to stand on a force platform through uni- and bipedal conditions. These two protocols are commonly used paradigms to assess the balance capacities of healthy and disabled patients. The recorded displacements of the center of pressure (CP) were decomposed along mediolateral and anteroposterior axes and assessed through variance positions and parameters obtained from fractional Brownian motion (fBm) modeling to determine the nature and the spatiotemporal organization of the successive controlling mechanisms. The variances underline the relative independence of the two tasks. Nevertheless, as highlighted by the fBm framework, postural correction is initiated for the unipedal stance after shorter time delays and longer covered distances. When compared to bipedal standing, one of the main characteristics of unipedal standing is to induce better-controlled CP trajectories, as deduced from the scaling regimes computed from the fBm modeling. Lastly, the control of the CP trajectories during the shortest time intervals along the anteroposterior axis appears identical for both uni- and bipedal conditions. Unipedal and bipedal standing controls should thus be viewed as two complementary tasks, each providing specific and complementary insights into the postural control organization.
Cyril Burdet and Patrice Rougier
W. Neil Widmeyer, Lawrence R. Brawley and Albert V. Carron
Although group size has been one of the most frequently examined small-group variables, it has rarely been studied in sport. In Study 1 the effects of number of team members on cohesion and performance were examined. Teams of 3, 6, and 9 members participated in a 3-on-3 basketball league. Discriminant function analyses indicated that team size was related to pre-and postseason task cohesion and postseason social cohesion. Study 2 determined effects of action-unit size (number from one team on the field of action) on enjoyment and cohesion. Relationships between these outcomes and five more immediate outcomes were also investigated. As predicted, enjoyment and cohesion decreased as size increased. This decrease was also observed for the more immediate outcomes of exercise/fatigue, influence/responsibility, and organization/strategy whereas feelings of crowding increased with size. The best predictor of enjoyment was exercise/fatigue in smaller units and reduced influence/responsibility in large units. Organization/strategy was the best predictor of cohesion for all action-unit sizes.
Katharina Diehl, Ansgar Thiel, Stephan Zipfel, Jochen Mayer, Alexia Schnell and Sven Schneider
The authors’ aim was to examine the prevalence of (daily) dietary-supplement (DS) use among elite adolescent athletes and to differentiate use by different types of DS according to their function. Data were analyzed for associations between users of these DS types, sociodemographic, sport-specific characteristics, and opinion on the need for DS. In addition, sources of supply and information were examined. In the framework of the GOAL Study, 1,138 German elite adolescent athletes (14–18 yr) answered questions about DS. The data were analyzed to identify groups at risk for using DS after a classification by supplemental function. Of the young athletes, 91.1% reported DS use during the previous month. (Daily) DS use was significantly associated with sex, kind of sport, and the weekly duration of sporting activity. Furthermore, some athletes were required to use DS by their sporting organization. DS use was more likely in these athletes than in those whose sporting organizations had no such requirement. Overall, DS with short- and long-term supplemental function were mostly associated with the use of magnesium. However, DS with medium-term muscle-building function played an important role among daily users. The main source of information about DS was coaches; main source of supply was parents. Professional education is urgently needed, as 9 out of 10 athletes used DS, and strong positive opinions toward the use of DS were present, particularly in the DS users.
Nicolas Fabre, Stéphane Perrey, Loïc Arbez and Jean-Denis Rouillon
This study aimed (1) to determine whether paced breathing (synchronization of the expiration phase with poling time) would reduce the metabolic rate and dictate a lower rate of perceived exertion (RPE) than does spontaneous breathing and (2) to analyze the effects of paced breathing on poling forces and stride-mechanics organization during roller-ski skating exercises.
Thirteen well-trained cross-country skiers performed 8 submaximal roller-skiing exercises on a motorized driven treadmill with 4 modes of skiing (2 skating techniques, V2 and V2A, at 2 exercise intensities) by using 2 patterns of breathing (unconscious vs conscious). Poling forces and stride-mechanics organization were measured with a transducer mounted in ski poles. Oxygen uptake (VO2) was continuously collected. After each bout of exercise RPE was assessed by the subject.
No difference was observed for VO2 between spontaneous and paced breathing conditions, although RPE was lower with paced breathing (P < .05). Upper-limb cycle time and recovery time were significantly (P < .05) increased by paced breathing during V2A regardless of the exercise intensity, but no changes for poling time were observed. A slight trend of increased peak force with paced breathing was observed (P = .055).
The lack of a marked effect of paced breathing on VO2 and some biomechanical variables could be explained by the extensive experience of our subjects in cross-country skiing.
Gretchen Kerr, Anthony Battaglia and Ashley Stirling
, & DeSouza, 2012 ). Organizational polices, the ways that programs are designed and delivered, and the nature and quality of the interactions that youth athletes have with coaches, parents, and peers all influence the optimization of positive development outcomes in the sport domain ( Fraser-Thomas et
Jennifer L. Copeland
the population, and by the year 2050 there will be more than 2 billion older adults globally ( World Health Organization [WHO], 2015 ). Furthermore, they are more sedentary than any other age group ( Colley et al., 2011 ; Matthews et al., 2012 ). A systematic review of studies from 10 countries found
C. Jessie Jones and Janie Clark
Because of the recognized value of exercise for older adults, senior fitness programs have been developed in various facilities throughout the United States and in many other countries. However, there appears to be a shortage of professionally trained senior fitness specialists to develop and instruct such programs. A number of professional health and fitness organizations/associations and individual entrepreneurs have developed training programs leading to some type of certification. However, because there are no published curriculum standards to guide the development of these training programs, they often lack components essential for teaching students how to instruct safe and effective classes for senior participants. Curriculum Standards to Prepare Senior Fitness Instructors, developed by a national coalition, were presented at the 1995 International Conference on Aging and Physical Activity in Colorado. This project was undertaken not to promote national certification or licensing but, rather, to help educators plan training programs. Input from the conferees was synthesized into the standards, which are provided in this paper.
Sondra G. Siegel, T. Richard Nichols and Timothy C. Cope
Cutaneous reflexes have been described primarily according to their actions in the flexion/extension plane. It is shown here, by measuring electromyography and isometric force in decerebrate cats, that ankle muscles are activated in relation to their actions in the abduction/adduction plane during sural nerve (SNR) and crossed-extension (XER) reflexes. Ankle adductors (tibialis posterior, extensor digitorum longus, and flexors digitorum and hallucis longus) were active in XER, but not in SNR. Muscles producing ankle abduction (medial and lateral gastrocnemii and peroneus longus and brevis) were often activated in both reflexes, and medial gastrocnemius and peroneus longus were consistently more strongly activated in SNR than in XER. This differential pattern of muscle activation results in greater abduction torque at the ankle in SNR than in XER. These data demonstrate reflex organization in relation to the multidirectional torque generated by individual muscles.
John R. Biggan, Forest Melton, Michael A. Horvat, Mark Ricard, David Keller and Christopher T. Ray
The understanding of prefrail and nonfrail older adults’ postural control with and without increased environmental and cognitive stress is imperative to the development of targeted interventions to decrease fall risk within these populations. Thirty-eight individuals participated in this study. Postural control testing included the Sensory Organization Test (SOT) on a NeuroCom EquiTest. Cognitive and environmental load testing was performed during Condition 6 of the SOT. Though there were no group differences on composite equilibrium score (p = .06), the cognitive task (Stroop task) impaired equilibrium scores more than the auditory or visual distracter tasks (p < .05 and p < .01) for both groups. These results suggest that both prefrail and nonfrail older adults’ postural control is reduced in demanding environments. Given these findings, the need for multimodal exercise interventions to target both physical and cognitive factors is apparent.
Maureen Lucas and Cynthia J. Heiss
Protein recommendations by some professional organizations for young adults engaged in resistance training (RT) are higher than the recommended dietary allowance (RDA), but recommendations for resistance-training older adults (>50 years old) are not well characterized. Some argue that the current RDA is adequate, but others indicate increased protein needs. Although concerns have been raised about the consequences of high protein intake, protein intake above the RDA in older adults is associated with increased bone-mineral density when calcium intake is adequate and does not appear to compromise renal health in older individuals with normal renal function. Individual protein needs for older adults in RT are likely highly variable according to health and training regimen, but an intake of 1.0–1.3 g · kg−1 · day−1 should adequately and safely meet the needs of older adults engaged in RT, provided that their energy needs are met.