The modulation and strength of the human soleus short latency stretch reflex was investigated by mechanically perturbing the ankle during an unconstrained pedaling task. Eight subjects pedaled at 60 rpm against a preload of 10 Nm. A torque pulse was applied to the crank at various positions during the crank cycle, producing ankle dorsiflexion perturbations of similar trajectory. The stretch reflex was greatest during the power phase of the crank cycle and was decreased to the level of background EMG during recovery. Matched perturbations were induced under static conditions at the same crank angle and background soleus EMG as recorded during the power phase of active pedaling. The magnitude of the stretch reflex during the dynamic condition was not statistically different from that during the static condition throughout the power phase of the movement. The results of this study indicate that the stretch reflex is not depressed during active cycling as has been shown with the H-reflex. This lack of depression may reflect a decreased susceptibility of the stretch reflex to inhibition, possibly originating from presynaptic mechanisms.
Michael J. Grey, Charles W. Pierce, Theodore E. Milner and Thomas Sinkjaer
Takashi Kato, Yusaku Takeda, Toshio Tsuji and Tatsuya Kasai
The present study investigated the relative contribution of the cortical and spinal mechanisms for post-exercise excitability changes in human motoneurons. Seven healthy right-handed adults with no known neuromuscular disabilities performed an isometric voluntary wrist flexion at submaximum continuous exertion. After the subjects continued muscle contraction until volitional fatigue, the H-reflexes induced by an electric stimulation and motor evoked potentials (MEPs) induced by a transcranial magnetic stimulation (TMS) from a flexor carpi radialis (FCR) muscle were recorded 7 times every 20 s. The H-reflex was used to assess excitability changes at the spinal level, and the MEP was used to study excitability changes at the cortical level. H-reflexes showed a depression (30% of control value) soon after the cessation of wrist flexion and recovered with time thereafter. On the other hand, an early (short latency) MEP showed facilitation immediately after the cessation of wrist flexion (50% of control value) and thereafter decreased. A possible mechanism for the contradictory results of the 2 tests, in spite of focusing on the same motoneuron pool, might be the different test potential sizes between them. In addition, a late (long latency) MEP response appeared with increasing exercise. With regard to the occurrence of late MEP response, a central mechanism may be proposed to explain the origin—that is, neural pathways with a high threshold that do not participate under normal circumstances might respond to an emergency level of muscle exercise, probably reflecting central effects of fatigue.
Melissa Bopp, Sara Wilcox, Marilyn Laken, Steven P. Hooker, Deborah Parra-Medina, Ruth Saunders, Kimberly Butler, Elizabeth A. Fallon and Lottie McClorin
Physical activity (PA) participation offers many benefits especially among ethnic groups that experience health disparities. Partnering with faith-based organizations allows for a more culturally tailored approach to changing health behaviors.
8 Steps to Fitness was a faith-based behavior-change intervention promoting PA among members of African American churches. A quasi-experimental design was used to examine differences between the intervention group (n=72) and comparison group (n = 74). Health (resting blood pressure, body mass index, waist-hip ratio, fasting blood glucose), psycho-social (PA self-efficacy, social support, enjoyment, self-regulation, depression), and behavioral variables (PA, diet) were assessed at baseline, 3- and 6-months. Repeated measures ANCOVAs tested changes across time between groups.
At 3-months, the intervention group showed significantly more favorable changes in body mass index, waist circumference and social support than the control group. At 6-months, the intervention group showed significantly more favorable changes in hip circumference, waist to hip ratio, systolic blood pressure, and depressive symptoms. There was notable attrition from both the intervention (36%) and the comparison group (58%).
This study was conducted in a real-world setting, and provided insight into how to deliver a culturally-tailored PA intervention program for African Americans with a potential for dissemination.
Jennifer L. Etnier, William B. Karper, Jennifer I. Gapin, Lisa A. Barella, Yu Kai Chang and Karen J. Murphy
This pilot study was designed to test the efficacy of a physical activity program for improving psychological variables and fibromyalgia syndrome (FMS) symptoms and to provide preliminary evidence regarding the effects on perceived cognitive symptoms and objectively measured cognitive performance by FMS patients.
Sixteen women diagnosed with FMS were randomly assigned to an 18-week physical activity program or to a control condition. Psychological measures, FMS symptoms, perceived cognitive function, objective measures of cognition, and walking capacity were assessed at baseline and post-test.
At posttest, there were significant differences in fatigue (effect size, ES = 1.86), depression (ES = 1.27), FMS symptoms (ES = 1.56), self-reported cognitive symptoms (ES = 1.19), and delayed recall performance (ES = 1.16) between the physically active group and the control group, indicating that the FMS patients benefited from physical activity. Beneficial effects were also observed for 6 of the 7 objective measures of cognition and ranged from small to large (ESs = 0.26 to 1.06).
Given that all FMS patients do not respond well to conventional treatments, these beneficial effects of physical activity are important. Future studies with larger samples are warranted to test the reliability of the findings for the objective measures of cognition.
Ruth E. Taylor-Piliae, Joan M. Fair, William L. Haskell, Ann N. Varady, Carlos Iribarren, Mark A. Hlatky, Alan S. Go and Stephen P. Fortmann
This study examined the construct validity and reliability of the new 2-item Stanford Brief Activity Survey (SBAS).
Secondary analysis was conducted using data collected from the healthy older controls (n = 1023) enrolled in the Atherosclerotic Disease Vascular Function and Genetic Epidemiology (ADVANCE) study. Construct validity was examined by regression analyses to evaluate significant trends (P ≤ .05) across the SBAS activity categories for the selected psychological health factors measured at baseline and year 2, adjusted for gender, ethnicity and education level. Test-retest reliability was performed using Spearman’s rank correlation.
At baseline, subjects were 66 ± 2.8 years old, 38% female, 77% married, 61% retired, 24% college graduate, and 68% Caucasian. At baseline, lower self-reported stress, anxiety, depression, and cynical distrust, and higher self-reported mental and physical well-being were significantly associated with higher levels of physical activity (p trend ≤ 0.01). These associations held at year 2. The test-retest reliability of the SBAS was statistically significant (rs= 0.62, P < .001).
These results provide evidence of the construct validity and reliability of the SBAS in older adults. We also found a strong dose-response relationship between regular physical activity and psychological health in older adults, independent of gender, education level and ethnicity.
Cindy Lentino, Amanda J. Visek, Karen McDonnell and Loretta DiPietro
An innovative strategy for helping people achieve recommended levels of daily physical activity is dog walking. We assessed differences in physical activity and risk indicators between dog owners who 1) walk their dog (n = 399) and 2) do not walk their dog (n = 137) and compared them with adults who do not own dogs (n = 380).
Participants (39 ± 13 years) were recruited online and completed an electronic questionnaire. Healthy People 2010 risk indicators included physical activity, overweight status, tobacco use, nutrition behaviors, chronic conditions, depressive symptoms, and social support.
Compared with dog walkers, those who did not own or walk their dog reported less physical activity (MET-min·week−1) and a higher body mass index (P < .01). Moreover, after adjusting for age and moderate to high physical activity, those who did not own dogs had significantly greater odds of self-reported diabetes [OR = 2.53; 95%CI (1.17−5.48)], hypertension [OR = 1.71; 95%CI (1.03−2.83)], hypercholesterolemia [OR = 1.72; 95%CI (1.06−2.81)], and depression [OR = 1.49; 95%CI (1.09−2.05)] compared with participants who regularly walked their dogs.
Because of the health benefits associated with dog walking, this activity should be encouraged within communities as a method of promoting and sustaining a healthy lifestyle.
Jocelyn S. Carter, Sabrina Karczewski, Draycen D. DeCator and Alescia M. Hollowell
Children who engage in regular physical activity are protected from developing behavioral problems at home and school, but many children do not have the opportunity to participate in regular physical activity. The purpose of this study was to determine whether a noncurricular school-based physical activity program resulted in reductions in children’s psychological problems in 2 domains: internalizing (eg, depression) and externalizing (eg, aggression) and whether these effects varied according to ethnicity, gender, and baseline psychological symptoms.
One hundred and eleven third-grade students (mean age = 8.47; 55% African American, 42% Latino) from 4 schools participated in the study. Children in 2 schools received the Work to Play physical activity intervention during the study (intervention condition) and children in the other 2 schools did not receive the program until after the study was complete (waitlist control condition). Teachers and parents reported on children’s psychological symptoms at baseline and at follow-up approximately 9 months later.
Regression analyses showed that children who participated in the program had fewer internalizing symptoms at follow-up. Ethnicity moderated intervention effects with significant decreases in internalizing symptoms for African American, but not Hispanic participants. Neither gender nor baseline psychological symptoms moderated the program’s effectiveness.
The Work-to-Play intervention program appeared to be effective in reducing internalizing symptoms for ethnic minority participants who are at the greatest risk for psychological problems.
Andres E. Carrillo, René J. L. Murphy and Stephen S. Cheung
Prolonged physical exertion and environmental heat stress may elicit postexercise depression of immune cell function, increasing upper respiratory tract infection (URTI) susceptibility. We investigated the effects of acute and short-term vitamin C (VC) compared with placebo (PL) supplementation on URTI susceptibility, salivary immunoglobulin A (s-IgA), and cortisol responses in healthy individuals following prolonged exercise-heat stress.
Twelve participants were randomized into the VC or PL group in a double-blind design. For 12 days, participants consumed 3 × 500 mg tablets of VC or PL per day, with testing completed at baseline, then following acute (1 d) and short-term (8 d) supplementation. Participants performed 120.1 ± 49.6 min of cycling at 54 ± 6% VO2max in a hot (34.8 ± 1.0°C and 13 ± 3% relative humidity) environment, with saliva samples collected at pre-, post-, and 72 h postexercise. Health logs specifying URTI symptoms were completed for 7 days postexercise.
A 2 × 3 × 3 mixed ANOVA with a post hoc Bonferroni correction factor revealed a significant linear trend in postexercise cortisol attenuation in the VC group, 21.7 ± 15.1 nmol/L (mean ± SD) at baseline, to 13.5 ± 10.0 at acute, to 7.6 ± 4.2 after short term (P = .032). No differences were detected in ratio of s-IgA to protein or URTI symptoms between groups.
These data suggest that vitamin C supplementation can decrease postexercise cortisol in individuals performing exercise similar to that of a half-marathon or marathon in hot conditions. However, no changes in s-IgA and URTI were evident, possibly due to previous moderate training and reduced physical and psychological stress compared with athletes participating in ultramarathons.
Rebecca A. Schlaff, Meghan Baruth, Faith C. LaFramboise and Samantha J. Deere
diagnosed postpartum depression vary depending on sociodemographic factors and assessment type and time point; however, worldwide, the prevalence of postpartum depression is typically estimated between 4% and 20%, 1 with a recent study reporting a global pooled estimate of 17.7%. 4 Previous research has
Vaithehy Shanmugam, Sophia Jowett and Caroline Meyer
In the current study, we had two aims. First, we investigated the associations between eating psychopathology, situational interpersonal difficulties, and dispositional interpersonal difficulties among athletes and nonathletes. Second, we examined the mediating role of self-critical perfectionism, self-esteem, and depression in these associations. A total of 152 athletes and 147 nonathletes completed self-report instruments pertaining to relationship quality with significant others, as well as social anxiety, loneliness, self-critical perfectionism, self-esteem, depression, and eating psychopathology. Social anxiety and loneliness were found to be the only significant independent predictors of eating psychopathology among both athletes and nonathletes. However, such associations were indirectly mediated through depression for athletes and through self-critical perfectionism, self-esteem, and depression for nonathletes. The findings of this study suggest that the psychosocial mechanisms involved in the eating psychopathology of athletes are relatively similar to that of nonathletes. Thus, it can be tentatively proposed that treatments and interventions that target reducing interpersonal conflicts currently available for the general population should also be offered to athletes.