directional symmetry index. As a symmetry index may be used in clinical decisions, it is vital that the measure is consistent. 7 One method of insuring a stable mean symmetry index (SMSI) is to collect a large number of strides, as exemplified by calculating an interlimb symmetry index from all strides
Search Results
Strides to Achieve a Stable Symmetry Index During Running
Shane P. Murphy, Zach B. Barrons, and Jeremy D. Smith
Stable and Unstable Load Carriage Effects on the Postural Control of Older Adults
Gregory S. Walsh, Daniel C. Low, and Marco Arkesteijn
can move the COM. Together these findings suggest that load carriage reduces postural stability, 5 which could have implications for fall risk in older adults. Unstable loads have different effects on postural control than stable loads, 3 suggesting the type of load can also impact postural control
Stable Coordination Variability in Overground Walking and Running at Preferred and Fixed Speeds
Hannah E. Wyatt, Gillian Weir, Carl Jewell, Richard E.A. van Emmerik, and Joseph Hamill
anticipated to contribute to the number of trials needed to reach a stable mean and suitably reflect group CV outcomes; these features include mode (walking or running), speed (preferred or fixed), and surface (treadmill or overground). Due to the systematic regulation of dynamic neuromuscular control that
Scapulothoracic Muscle Activation on Stable and Unstable Support Surfaces
Se-yeon Park, Won-gyu Yoo, Hun Kwon, Dong-hyun Kim, Si-eun Lee, and Mi-jin Park
Activation of the upper trapezius, lower trapezius, serratus anterior, and triceps brachii muscles was measured, while center of pressure excursion beneath the hands was simultaneously monitored, during the performance of a push-up exercise on both a stable and an unstable base of support. The activation levels of all muscles were significantly greater for the unstable support surface when compared to those for a stable support surface (p < 0.05). A negative correlation was found between activation of the serriatus anterior muscle and center of pressure excursion (r = -0.64, p < 0.05). Performance of the push-up exercise on an unstable support surface appears to elicit greater muscle activation than a standard push-up exercise performed on a stable support surface.
The Effect of Exercise Training on Total Daily Energy Expenditure and Body Composition in Weight-Stable Adults: A Randomized, Controlled Trial
Gregory A. Hand, Robin P. Shook, Daniel P. O’Connor, Madison M. Kindred, Sarah Schumacher, Clemens Drenowatz, Amanda E. Paluch, Stephanie Burgess, John E. Blundell, and Steven N. Blair
been prescribed for 3 or more months and stable • Internet access (home or other; agreement by participant that they will comply with the extent of Internet use required). We are experienced with using Internet interventions and are aware that we must be certain that participants have regular Internet
Nonstationarity of Stable States in Rhythmic Bimanual Coordination
Eric G. James
The HKB model and its variants characterize bimanual coordination with fixedpoint dynamics and predict stationarity of the mean and variance of relative phase in stable coordinative states. In the current study, participants performed in-phase and antiphase coordination modes in rhythmic bimanual finger and elbow flexionextension tasks. The results of runs tests revealed that discrete relative phase was nonstationary in 49.25%, 50.25%, and 54% of time-series in the 10, 20, and 30 box runs tests, respectively. In all individual Task conditions >38% of time-series were nonstationary. These findings contradicted model predictions that the mean and variance of relative phase are stationary in bimanual coordination and distinguish the concept of dynamical stability from statistical stationarity. The findings indicated that relative phase was not attracted to a stationary fixed-point and that fluctuations in relative phase are not Gaussian white noise as in existing models of bimanual coordination.
Shoulder Muscular Activity During Isometric Three-Point Kneeling Exercise on Stable and Unstable Surfaces
Rodrigo Cappato de Araújo, Rodrigo de Andrade, Helga Tatiana Tucci, Jaqueline Martins, and Anamaria Siriani de Oliveira
The purpose of this study was to determine if performing isometric 3-point kneeling exercises on a Swiss ball influenced the isometric force output and EMG activities of the shoulder muscles when compared with performing the same exercises on a stable base of support. Twenty healthy adults performed the isometric 3-point kneeling exercises with the hand placed either on a stable surface or on a Swiss ball. Surface EMG was recorded from the posterior deltoid, pectoralis major, biceps brachii, triceps brachii, upper trapezius, and serratus anterior muscles using surface differential electrodes. All EMG data were reported as percentages of the average root mean square (RMS) values obtained in maximum voluntary contractions for each muscle studied. The highest load value was obtained during exercise on a stable surface. A significant increase was observed in the activation of glenohumeral muscles during exercises on a Swiss ball. However, there were no differences in EMG activities of the scapulothoracic muscles. These results suggest that exercises performed on unstable surfaces may provide muscular activity levels similar to those performed on stable surfaces, without the need to apply greater external loads to the musculoskeletal system. Therefore, exercises on unstable surfaces may be useful during the process of tissue regeneration.
Effect of Absolute and Relative Loading on Muscle Activity During Stable and Unstable Squatting
Jeffrey M. McBride, Tony R. Larkin, Andrea M. Dayne, Tracie L. Haines, and Tyler J. Kirby
Purpose:
The purpose of this investigation was to determine the effect of stable and unstable conditions on one repetition maximum strength and muscle activity during dynamic squatting using absolute and relative loading.
Methods:
Ten recreationally weight-trained males participated in this study (age = 24.1 ± 2.0 y, height = 178.0 ± 5.6 cm, body mass = 83.7 ± 13.4 kg, 1RM/body mass = 1.53 ± 0.31), which involved two laboratory sessions separated by 1 wk. Linear position transducers were used to track bar displacement while subjects stood on a force plate for all trials. Vastus lateralis (VL), biceps femoris (BF) and erector spinae (L1) muscle activity (average integrated EMG [IEMG]) was also recorded during all trials. During the frst session subjects complete a one repetition maximum test in a stable dynamic squat (S1RM = 128.0 ± 31.4 kg) and an unstable dynamic squat (U1RM = 83.8 ± 17.3 kg) in a randomized order with a 30-min rest period between conditions. The second session consisted of the performance of three trials each for 12 different conditions (unstable and stable squats using three different absolute loads [six conditions] and unstable and stable squats using three different relative loads [six conditions]).
Results:
Results revealed a statistically significant difference between S1RM and U1RM values (P < .05). The stable trials resulted in the same or a significantly higher value for VL, BF and L1 muscle activity in comparison with the unstable trials for all twelve conditions.
Conclusions:
Unstable squatting is of equal or less (depending on the loading condition) benefit to improving or maximizing muscle activity during resistance exercise.
Application of Stable Isotope Tracers in the Study of Exercise Metabolism in Children: A Primer
Anthony D. Mahon and Brian W. Timmons
Exercise metabolism in children has traditionally been assessed using the respiratory exchange ratio (RER) to determine the contributions of fat and carbohydrate to the exercise energy demands. Although easily measured, RER measurements have limitations. Other methods to assess metabolism such as the obtainment of a muscle biopsy and the use of nuclear magnetic resonance spectroscopy carry ethical and feasibility concerns, respectively, which limit their use in studies involving children. Stable isotopes, used routinely in studies involving adults, can also be applied in studies involving children in an ethical and feasible manner. Two common stable isotopes used in metabolic studies involving children include carbon-13 (13C) and nitrogen-15 (15N). 13C-glucose can be used to study carbohydrate metabolism and 15N-glycine can be used to assess protein metabolism. This article reviews the use of 13C-glucose and 15N-glycine to study exercise metabolism in children, considers some of the associated ethical aspects, explains the general methodology involved in administering these isotopes and the resources required, and describes studies involving children utilizing these methods. Finally, suggestions for future research are provided to encourage further use of these techniques.
Recreational Physical Activity in Postmenopausal Women Is Stable Over 8 Years of Follow-Up
Huong Q. Nguyen, Jerald R. Herting, Ruth Kohen, Cynthia K. Perry, Andrea LaCroix, Lucile Lauren Adams-Campbell, Shirley A.A. Beresford, Charles B. Eaton, and Lesley Tinker
Background:
The goals of this study were to examine 1) longitudinal trajectories of energy expenditure from recreational physical activity (PA) in postmenopausal women, 2) whether women who belong to different PA trajectories engage in different types of PA, and 3) whether baseline sociodemographic, health, psychosocial, and lifestyle characteristics predict membership in PA trajectories.
Methods:
Women from the Women’s Health Initiative Observational Study with baseline PA data (n = 92,629) were included. Physical activity, measured via self-report 6 times over 8 years, was converted to MET hr/wk for analysis. Latent growth curve mixture models and latent profile models were used to analyze longitudinal PA trajectories and cross-sectional PA composition, respectively.
Results:
Three distinct, stable PA trajectories (highly, moderately, and minimally active) were identified with nearly 75% of the women classified as minimally active (≤ 8 MET-hr/wk). The majority of women who were at least moderately active engaged in a balanced combination of walking, moderate, and vigorous PA. Sociodemographic characteristics such as income, education, and past vigorous PA were predictive of PA trajectory, as were some health status indicators (eg, body mass index), but not health related quality of life.
Conclusions:
Self-reported PA is largely stable across nearly a decade of follow-up in postmenopausal women.
