Accumulating 10,000 steps: does this meet current physical activity guidelines?

The purpose of this study was to determine whether taking 10,000 steps in a day is equivalent to meeting the current minimum physical activity guidelines of accumulating at least 30 min of moderate physical activity (IMPA). Fifty-nine women ages 20-65 years wore a pedometer and accelerometer concurrently on their right hip for 1 day. There were no differences in the age, body mass index, or the amount of time the pedometers and accelerometers were worn between the 10K+ and the < 10K groups. The 10K+ group accumulated significantly more steps and minutes of MPA than the < 10K group (M = 13,084 steps, SD = 2,603 vs. M = 7,518 steps, SD = 1,956; and M = 62.1 min, SD = 27.7 vs. M = 38.8 min, SD = 18.9; p < .05). A 2 x 2 chi-square analysis demonstrated no difference between the proportions of 10K and < 10K participants who met the step goal, when all minutes of MPA accumulated throughout the day were considered (chi2 = 1.8, df = 1, p = .175). When only continuous bouts of MPA lasting > 5 min and > 10 min were considered, a significantly greater proportion of 10K participants met the current physical activity guidelines than the < 10K participants (chi2 = 11.5, df = 1, p = .001, and chi2 = 5.9, df = 1, p = .015, respectively). Our finding, suggest that individuals who accumulate 10,000 steps/day are more likely to meet the current physical activity guidelines by engaging in the length of bouts promoted by the Centers for Disease Control and Prevention and the American College of Sports Medicine (Pate et al., 1995) and the US Surgeon General (U.S. Department of Health and Human Services, 1996). However, the data also reveal that accumulating 10,000 steps/day does not guarantee meeting the guidelines in the bout lengths documented to confer the health benefits of physical activity.     

Zero dynamics and funnel control for linear electrical circuits

We consider electrical circuits containing linear resistances, capacitances and inductances. The circuits can be described by differential-algebraic input–output systems, where the input consists of voltages of voltage sources and currents of current sources and the output consists of currents of voltage sources and voltages of current sources. We generalize a characterization of asymptotic stability of the circuit and give sufficient topological criteria for its invariant zeros being located in the open left half-plane. We show that asymptotic stability of the zero dynamics can be characterized by means of the interconnectivity of the circuit and that it implies that the circuit is high-gain stabilizable with any positive high-gain factor. Thereafter we consider the output regulation problem for electrical circuits by funnel control. We show that for circuits with asymptotically stable zero dynamics, the funnel controller achieves tracking of a class of reference signals within a pre-specified funnel; this means in particular that the transient behavior of the output error can be prescribed and the funnel controller does neither incorporate any internal model for the reference signals nor any identification mechanism, it is simple in its design. The results are illustrated by a simulation of a discretized transmission line.     

Learning from Non-Reported Data: Interpreting Missing Body Mass Index Values in Young Children

The objective of this study was to examine the pattern of relations between missing weight and height (BMI) data and a range of demographic, physical activity, sedentary behavior, and academic measures in a young sample of elementary school children. A secondary analysis of a large cross-sectional study, PLAY-On, was conducted using self-reported data from a convenience sample of fifth- to eighth-grade students (9–14 years) attending 30 elementary schools in Ontario, Canada. Items assessed related to demographics (age, gender, and ethnicity), physical activity (energy expenditure, location, and sport participation), sedentary behavior (communication and screen-time), and academics. Of the 2,111 children who were included in the analyses, 960 (45.5%) were missing BMI data. Children without BMI data were more likely to be younger, female, of non-white ethnicity, have lower daily energy expenditure values, not participate in school sports, and have lower-rated academic standing than those children with BMI data. Overall, this study demonstrates characteristics of children who fail to self-report their height or weight. The trend for younger children to be more likely to fail to report BMI suggests that some children may be unmotivated non-responders. Meanwhile, the trend for girls to be more likely to fail to report weight than boys indicates that some girls may be motivated non-responders. Self-report BMI might include too much missing data to be effective for determining children's progress toward previously established targets for intervention and surveillance efforts.     

Effect of postural changes on 3D joint angular velocity during starting block phase

Abstract

Few studies have focused on the effect of posture during sprint start. The aim of this study was to measure the effect of the modification of horizontal distance between the blocks during sprint start on three dimensional (3D) joint angular velocity. Nine trained sprinters started using three different starting positions (bunched, medium and elongated). They were equipped with 63 passive reflective markers, and an opto-electronic Motion Analysis® system was used to collect the 3D marker trajectories. During the pushing phase on the blocks, norm of the joint angular velocity (NJAV), 3D Euler angular velocity (EAV) and pushing time on the blocks were calculated. The results demonstrated that the decrease of the block spacing induces an opposite effect on the angular velocity of joints of the lower and the upper limbs. The NJAV of the upper limbs is greater in the bunched start, whereas the NJAV of the lower limbs is smaller. The modifications of NJAV were due to a combination of the movement of the joints in the different degrees of freedom. The medium start seems to be the best compromise because it leads, in a short pushing time, to a combination of optimal joint velocities for upper and lower segments.     

Stress Reduction and Mood Enhancement in Four Exercise Modes: Swimming,Body Conditioning,Hatha Yoga,and Fencing

Abstract

The influence of exercise mode and practice qualities on the stress reduction benefits of exercise was examined. College students in swimming, body conditioning, hatha yoga, fencing, exercise, and lecture-control classes completed the Profile of Mood States and the State Anxiety Inventory before and after class on three occasions. Swimmers had unusually positive initial moods and reported less tension and confusion after swimming only on the first day of testing. Participants in yoga, an anaerobic activity that satisfied three of the four mode requirements, were significantly less anxious, tense, depressed, angry, fatigued, and confused after class than before on all three occasions. Supporting the importance of the four mode characteristics, participants in the exercise control activity of fencing reported improvements only in vigor. A possible influence of practice conditions was observed when members of the body conditioning class reported significant increases in fatigue, but no other mood changes. Results of this study supported the possibility that exercise mode and practice requirements in the proposed taxonomy moderate the stress reduction benefits.     

Adolescents‘ Self-Efficacy to Overcome Barriers to Physical Activity Scale

This paper describes a revised measure of self-efficacy to overcome barriers to moderate and vigorous physical activity in a sample of 484 high school students in Toronto, Ontario. The students had a mean age of 15.3 years. Principal axis factoring with oblique rotation yielded five factors: self-efficacy to overcome internal, harassment, physical environment, social environment, and responsibilities barriers. Two problematic items were removed, which resulted in a 22-item measure. Subsequent analyses were conducted on responses to this shortened measure. Confirmatory factor analysis supported the five-factor model and demonstrated age- and sexinvariance. The subscales had good internal consistency reliability. Structural regressions demonstrated a strong relationship between the resulting factors and a physical activity measure (energy expenditure), showing predictive validity.