Functional electrical stimulation-induced muscular fatigue: Effect of fiber composition and stimulation frequency on rate of fatigue development.

This investigation evaluated the progression towards fatigue in two muscles of differing fast- and slow-twitch fiber proportions (abductor pollicis brevis (APB) and vastus lateralis (VL)) when activated by functional electrical stimulation (FES) at three frequencies (10, 35, and 50 Hz). Fatigue was defined as a 50% drop from the initial FES-induced force of 25% maximal voluntary contraction (MVC). Ten healthy adults (mean age: 23.2 ±â€¯3.0 years) were recruited; participants signed an IRB approved consent form prior to participation. Protocols were developed to evaluate the effects of muscle size, fiber type and FES frequency on total time to fatigue. Results indicated that the predominantly fast-twitch VL fatigued more quickly than the slow-twitch APB at the higher frequencies (p < 0.05), but did not significantly differ with stimulation at 10 Hz. Overall, muscle size and FES frequencies showed some significant interactions when generating a defined force and during fatigue development. Furthermore, it appears that to reduce fatigue, FES treatments should not extend past ∼14-16 min for large and small muscle groups, respectively, when the muscle group's optimal stimulation frequency is applied.

Associations Among Work and Family Health Climate, Health Behaviors, Work Schedule, and Body Weight.

OBJECTIVES: Correctional employees exhibit elevated obesity rates. This study examines interrelations among health behaviors, health climate, body mass index (BMI), and work schedule. METHODS: Using survey results from correctional supervisors (n = 157), mediation and moderated-mediation analyses were performed to examine how health behaviors explain relationships between obesity, work health climate (WHC) and family health climate (FHC), and work schedule. RESULTS: Over 85% of the sample was overweight/obese (mean BMI = 30.20). Higher WHC and FHC were associated with lower BMI, mediated by nutrition, and physical activity. The interaction effect between health behavior and work schedule revealed a protective effect on BMI. Overtime shift work may share a relationship with BMI. CONCLUSIONS: Findings may have implications for reexamining organizational policies on maximum weekly overtime in corrections. They provide direction for targeted obesity interventions that encourage a supportive FHC and promote healthy behaviors among supervisors working overtime.

Perceived Self-Efficacy and Financial Incentives: Factors Affecting Health Behaviors and Weight Loss in a Workplace Weight Loss Intervention.

OBJECTIVE: To evaluate if self-efficacy (SE) and financial incentives (FI) mediate the effect of health behavior on weight loss in a group of overweight and obese nursing-home employees participating in a 16-week weight-loss intervention with 12-week follow-up. METHODS: Ninety nine overweight/obese (body mass index [BMI] > 25) employees from four nursing-homes participated, with a mean age of 46.98 years and BMI of 35.33. Nursing-homes were randomized to receiving an incentive-based intervention (n = 51) and no incentive (n = 48). Participants' health behaviors and eating and exercise self-efficacy (Ex-SE) were assessed at week 1, 16, and 28 using a self-reported questionnaire. Mediation and moderated mediation analysis assessed relationships among these variables. RESULTS: Eating self-efficacy (Eat-SE) and Ex-SE were significant mediators between health behaviors and weight loss (P < 0.05). Incentives significantly moderated the effects of self-efficacy (P = 0.00) on weight loss. CONCLUSIONS: Self-efficacy and FI may affect weight loss and play a role in weight-loss interventions.

Electrically and Hybrid-Induced Muscle Activations: Effects of Muscle Size and Fiber Type.

The effect of three electrical stimulation (ES) frequencies (10, 35, and 50 Hz) on two muscle groups with different proportions of fast and slow twitch fibers (abductor pollicis brevis (APB) and vastus lateralis (VL)) was explored. We evaluated the acute muscles' responses individually and during hybrid activations (ES superimposed by voluntary activations). Surface electromyography (sEMG) and force measurements were evaluated as outcomes. Ten healthy adults (mean age: 24.4 ± 2.5 years) participated after signing an informed consent form approved by the university Institutional Review Board. Protocols were developed to: 1) compare EMG activities during each frequency for each muscle when generating 25% Maximum Voluntary Contraction (MVC) force, and 2) compare EMG activities during each frequency when additional voluntary activation was superimposed over ES-induced 25% MVC to reach 50% and 75% MVC. Empirical mode decomposition (EMD) was utilized to separate ES artifacts from voluntary muscle activation. For both muscles, higher stimulation frequency (35 and 50Hz) induced higher electrical output detected at 25% of MVC, suggesting more recruitment with higher frequencies. Hybrid activation generated proportionally less electrical activity than ES alone. ES and voluntary activations appear to generate two different modes of muscle recruitment. ES may provoke muscle strength by activating more fatiguing fast acting fibers, but voluntary activation elicits more muscle coordination. Therefore, during the hybrid activation, less electrical activity may be detected due to recruitment of more fatigue-resistant deeper muscle fibers, not reachable by surface EMG.

The weight loss blogosphere: an online survey of weight loss bloggers.

Blogging is a form of online journaling that has been increasingly used to document an attempt in weight loss. Despite the prevalence of weight loss bloggers, few studies have examined this population. We examined characteristics of weight loss bloggers and their blogs, including blogging habits, reasons for blogging, like and dislikes of blogging, and associations between blogging activity and weight loss. Participants (N = 194, 92.3 % female, mean age = 35) were recruited from Twitter and Facebook to complete an online survey. Participants reported an average weight loss of 42.3 pounds since starting to blog about their weight loss attempt. Blogging duration significantly predicted greater weight loss during blogging (ß = -3.65, t(185) = -2.97, p = .003). Findings suggest that bloggers are generally successful with their weight loss attempt. Future research should explore what determines weight loss success/failure in bloggers and whether individuals desiring to lose weight would benefit from blogging.

Work Characteristics as Predictors of Correctional Supervisors' Health Outcomes.

OBJECTIVE: This study examined associations among health behaviors, psychosocial work factors, and health status. METHODS: Correctional supervisors (n = 157) completed a survey that assessed interpersonal and organizational views on health. Chi-square and logistic regressions were used to examine relationships among variables. RESULTS: Respondents had a higher prevalence of obesity and comorbidities compared with the general US adult population. Burnout was significantly associated with nutrition, physical activity, sleep duration, sleep quality, diabetes, and anxiety/depression. Job meaning, job satisfaction, and workplace social support may predict health behaviors and outcomes. CONCLUSIONS: Correctional supervisors are understudied and have poor overall health status. Improving health behaviors of middle-management employees may have a beneficial effect on the health of the entire workforce. This paper demonstrates the importance of psychosocial work factors that may contribute to health behaviors and outcomes.

Demographic, health-related, and work-related factors associated with body mass index and body fat percentage among workers at six Connecticut manufacturing companies across different age groups: a cohort study.

BACKGROUND: Effective workplace interventions that consider the multifactorial nature of obesity are needed to reduce and prevent obesity among adults. Furthermore, the factors associated with obesity may differ for workers across age groups. Therefore, the objective of this study was to identify demographic, health-related, and work-related factors associated with baseline and changes in body mass index (BMI) and body fat percentage (BFP) and among Connecticut manufacturing workers acrossage groups. METHODS: BMI and BFPof 758 workers from six Connecticut manufacturing companies were objectively measuredat two time points approximately 36 months apart. Demographic, health-related, and work-related factors wereassessed via questionnaire. All variables were included in linear regression models to identify factors associated with baseline and changes in BMI and BFP for workers in 3 age groups: <45 years (35 %), 45-55 years (37 %), >55 years (28 %). RESULTS: There were differences in baseline and changes in BMI and BFP among manufacturing workers across age groups. Being interested in changing weight was significantly (p < 0.01) associated with higher baseline BMI and BFP across all age categories. Other factors associated with higher baseline BMI and BFP differed by age group and included: male gender (BMI p = 0.04), female gender (BFP p < 0.01), not having a college education (BMI p = 0.01, BFP p = 0.04), having childcare responsibilities (BMI p = 0.04), and working less overtime (p = 0.02) among workers in the <45 year age category, male gender (BMI p = 0.02), female gender (BFP p < 0.01) and reporting higher stress in general (BMI p = 0.04) among workers in the 45-55 year age category, and female gender (BFP p < 0.01) and job tenure (BFP p = 0.03) among workers in the >55 year age category. Few factors were associated with change in BMI or BFP across any age category. CONCLUSIONS: Among manufacturing workers, we identified associations between individual, health-related, and work-related factors and baseline BMIand BFP that differed by age. Such results support the use of strategies tailored to the challenges faced by workers in specific age groups rather than adopting a one size fits all approach. Effective interventions should consider a full range of individual, health-related, and work-related factors. More work must be done to identify factors or strategies associated with changes in obesity over time.

The Link between Musculoskeletal Pain, Lifestyle Behaviors, Exercise Self-Efficacy, and Quality of Life in Overweight and Obese Individuals.

OBJECTIVE: To determine the extent musculoskeletal (MS) pain in the low back and knee (weight-bearing (WB) joints), shoulder and wrist (non-weight bearing joints), and exercise self-efficacy mediates associations between overweight and obesity levels based on BMI (4 levels: overweight, obese class I, II, or III), physical function, emotional role, social interference, and physical activity (PA) levels. DESIGN: Cross-sectional study. SETTING: Four long-term nursing home facilities in the Northeast U.S. PARTICIPANTS: 99 overweight or obese (BMI > 25) nursing home employees. INTERVENTIONS: Self-reported survey administered to employees who met inclusion and exclusion criteria. MAIN OUTCOME MEASURES: General health status, physical function, emotional role, Exercise Self-Efficacy Scale (ESE), physical activity (PA), and frequency of pain at each joint. RESULTS: Reported pain frequency were 66.3%, 54.4%, 42.2%, and 24.1% for lower back, knee, shoulder, and wrist, respectively. Higher obesity levels were associated with lower physical function (r=-0.109, p=0.284). PA decreased with higher obesity levels (r=-0.248, p<0.05), particularly in moderate PA (r=-0.293, p<0.05). Obesity was associated with a lower ESE (r=-0.239, p<0.05). Wrist pain significantly mediated the effect of obesity on moderate physical function, emotional role, and ESE. ESE was a significant mediator between obesity and moderate and vigorous PA. CONCLUSIONS: Overweight and obese nursing home employees are at higher risk for developing musculoskeletal disorders due to high demand, low control jobs, and the associated biomedical compromises while working. To increase the effectiveness of weight loss interventions for this population, the mediating effects of MS pain with higher levels of obesity should be considered.

Psychological Health and Overweight and Obesity Among High Stressed Work Environments.

Correctional employees are recognized to underreport stress and stress symptoms and are known to have a culture that discourages appearing "weak" and seeking psychiatric help. This study assesses underreporting of stress and emotions. Additionally, it evaluates the relationships between stress and emotions on health behaviors. Correctional employees (n=317) completed physical assessments to measure body mass index (BMI), and surveys to assess perceived stress, emotions, and health behavior (diet, exercise, and sleep quality). Stress and emotion survey items were evaluated for under-reporting via skewness, kurtosis, and visual assessment of histograms. Structural equation modeling evaluated relationships between stress/emotion and health behaviors. Responses to stress and negatively worded emotions were non-normally distributed whereas responses to positively-worded emotions were normally distributed. Emotion predicted diet, exercise, and sleep quality whereas stress predicted only sleep quality. As stress was a poor predictor of health behaviors and responses to stress and negatively worded emotions were non-normally distributed it may suggests correctional employees are under-reporting stress and negative emotions.

Lower-extremity joint kinematics and muscle activations during semi-reclined cycling at different workloads in healthy individuals.

BACKGROUND: A better understanding of lower-extremity muscles' activation patterns and joint kinematics during different workloads could help rehabilitation professionals with prescribing more effective exercise regimen for elderly and those with compromised muscles. We examined the relative contribution, as well as activation and co-activation patterns, of lower-extremity muscles during semi-reclined cycling at different workloads during a constant cadence. METHODS: Fifteen healthy novice cyclists participated at three 90-second cycling trials with randomly assigned workloads of 0, 50, and 100 W, at a constant cadence of 60 rpm. During all trials, electromyograms were recorded from four lower-extremity muscles: rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GT). Joint kinematics were also recorded and synchronized with the EMG data. Muscle burst onset, offset, duration of activity, peak magnitude, and peak timing, as well as mean joint angles and mean ranges of motion were extracted from the recorded data and compared across workloads. RESULTS: As workload increased, BF and TA displayed earlier activations and delayed deactivations in each cycle that resulted in a significantly (p < 0.05) longer duration of activity at higher workloads. RF showed a significantly longer duration of activity between 0 and 50 W as well as 0 and 100 W (p < 0.05); however, the activity duration of GT was not appeared to be affected significantly by workload. EMG peak-magnitude of RF, BF, and TA changed significantly (p < 0.05) as workload increased, but no changes were observed in the EMG peak-timing across workloads. Durations of co-activation in the RF-BF pair as well as the RF-TA pair increased significantly with workload, while the RF-TA and TA-GT pairs were only significantly different (p < 0.05) between the 0 and 100 W workload levels. Increased workload did not lead to any significant changes in the joint kinematics. CONCLUSIONS: Muscles' activity patterns as well as co-activation patterns are significantly affected by changes in cycling workloads in healthy individuals. These variations should be considered during cycling, especially in the elderly and those with compromised musculoskeletal systems. Future research should evaluate such changes specific to these populations.

Effectiveness of Financial Incentives in a Worksite Diabetes Prevention Program.

PURPOSE: To evaluate the effect of financial incentive in a diabetes prevention weight loss program at worksites. DESIGN: Group-level randomized intervention study. SETTING: Four long-term care facilities, randomly assigned to "incentive-IG" or "non incentive-NIG" groups. PARTICIPANTS: Ninety-nine employees, all overweight or obese (BMI= mean 34.8±7.4 kg/m2) and at risk for type 2 diabetes. INTERVENTION: A 16 week weight loss program (diabetes prevention program) with a 3 month follow up. IG could either choose a "standard incentive" to receive cash award when achieving the projected weight loss or to participate in a "standard plus deposit incentive" to get additional money matched with their deposit for projected weight loss. All of the participants received a one-hour consultation for a healthy weight loss at the beginning. MEASURES: Weight-loss, diabetes risk score (DRS), and cardiovascular risk outcomes. ANALYSES: Linear and logistic regressions for completed cases with adjustments for clustering effect at group level. RESULTS: IG lost on average more pounds (p=0.027), reduced BMI (p=0.04), and reduced in DRS (p=0.011) compared to NIG at week 16. At the 12-week follow-up period, those in IG plus deposit subgroup had twice the odds (OR=2.2, p=0.042) and those in the standard IG had three times the odds of achieving weight loss goals than NIG; those in the IG plus deposit group reduced DRS by 0.4 (p=0.045). CONCLUSION: Monetary incentives appear to be effective in reducing weight and diabetes risk.

Workplace-based participatory approach to weight loss for correctional employees.

OBJECTIVE: To evaluate the effectiveness of a participatory approach using an employee design team for a 12-week weight-loss program with an 8-week follow-up. METHODS: Twenty-four employees with mean [standard error (SE)] for weight 233.24 lb [8.16], body mass index 33.29 kg/cm [0.82], and age 42.7 years [1.5] participated in the study, among whom 75% were men and 25% women. RESULTS: Significant reductions in weight, body mass index, and waist circumference (among men) were observed before and after intervention (P < 0.05). About 73% and 68% of the variation in weight change (P < 0.01) and waist circumference (P < 0.01), respectively, were explained by Nutrition Knowledge and Exercise Confidence scores after controlling for gender and age. CONCLUSIONS: A participatory program with employee involvement resulted in positive outcomes. Increasing participants' knowledge and providing skills to manage their weight seem to change their attitudes, resulting in better outcomes.

Cost-effectiveness of a workplace-based incentivized weight loss program.

OBJECTIVE: To evaluate the cost-effectiveness ratios of a nursing home-based incentivized Behavioral Weight Management Program (BWMP) from the employer's perspective. METHODS: Seventy-two overweight and obese health care workers completed the BWMP (n = 35 incentivized; n = 37 nonincentivized). Weight change outcomes were compared for the pre- (0) and postintervention (28 weeks) follow-up periods within and between sites. Comprehensive estimates of BWMP direct program costs and avoided costs of absenteeism and productivity improvements were estimated to evaluate a business case. RESULTS: There was a significant difference (P = 0.01) between the average per-participant weight change between incentivized sites (-7.4 lb) and nonincentivized sites (-2.2 lb). The cost-effectiveness ratios per pound of weight loss were $25.5 and $58.1, respectively. CONCLUSIONS: In general, incentivized BWMPs were more cost effective. To generate a business case, enhancement in productivity becomes a critical factor and future research needs to investigate it further.

Assessment of a Worksite Health Promotion Readiness Checklist.

OBJECTIVE: To assess the utility of a Worksite Health Promotion Readiness Checklist (WRCL) designed to evaluate the worksite's readiness for implementing health promotion and health protection programs. METHODS: The WRCL was pilot tested in worksites with (WHPy) and without (WHPn) health promotion programs. The two parts of WRCL scores (observational and administrative) for WHPy and WHPn sites were compared within and between the worksites to establish WRCL utility and sensitivity. RESULTS: Observational WRCL (completed by two observers per site) demonstrated high interrater reliability (P < 0.05) for most items. Administrative WRCL (completed by three administrators per site) showed some discrepant responses between administrators. Overall, both sections of WRCL produced higher scores for WHPy sites. CONCLUSIONS: WRCL could be a valid and reliable instrument to measure readiness of a worksite toward health promotion and health protection programs.

The role of tailored consultation following health-risk appraisals in employees' health behavior.

OBJECTIVES: This study evaluates employees' health and lifestyle changes following health risk appraisal only and health risk appraisal with a consultation (HRAC) based on the constructs of Transtheoretical model (TTM). METHODS: Sixty employees self-selected to an HRAC or health risk appraisal only, implemented in 6-month interval. Demographics, lifestyle behavior, and stage of change (SOC) assessments based on TTM along with weight, height, body mass index, blood pressure, blood glucose, and cholesterol were measured. RESULTS: Second health risk appraisal showed improvements in nutrition, fitness, and overall health in both groups (P < 0.05). Significant improvements were found between HRAC group and their SOC for exercise, nutrition, and overall lifestyle. Also, group differences in SOC for exercise, amount of snack food, fruits and vegetables consumed, and physical activity (P < 0.05) were significant. CONCLUSION: HRAC based on TTM constructs is effective in promoting behavior change in high-risk employees.

Leg joint power output during progressive resistance FES-LCE cycling in SCI subjects: developing an index of fatigue.

BACKGROUND: The purpose of this study was to investigate the biomechanics of the hip, knee and ankle during a progressive resistance cycling protocol in an effort to detect and measure the presence of muscle fatigue. It was hypothesized that knee power output can be used as an indicator of fatigue in order to assess the cycling performance of SCI subjects. METHODS: Six spinal cord injured subjects (2 incomplete, 4 complete) between the ages of twenty and fifty years old and possessing either a complete or incomplete spinal cord injury at or below the fourth cervical vertebra participated in this study. Kinematic data and pedal forces were recorded during cycling at increasing levels of resistance. Ankle, knee and hip power outputs and resultant pedal force were calculated. Ergometer cadence and muscle stimulation intensity were also recorded. RESULTS: The main findings of this study were: (a) ankle and knee power outputs decreased, whereas hip power output increased with increasing resistance, (b) cadence, stimulation intensity and resultant pedal force in that combined order were significant predictors of knee power output and (c) knowing the value of these combined predictors at 10 rpm, an index of fatigue can be developed, quantitatively expressing the power capacity of the knee joint with respect to a baseline power level defined as fatigue. CONCLUSION: An index of fatigue was successfully developed, proportionalizing knee power capacity during cycling to a predetermined value of fatigue. The fatigue index value at 0/8th kp, measured 90 seconds into active, unassisted pedaling was 1.6. This indicates initial power capacity at the knee to be 1.6 times greater than fatigue. The fatigue index decreased to 1.1 at 2/8th kp, representing approximately a 30% decrease in the knee's power capacity within a 4 minute timespan. These findings suggest that the present cycling protocol is not sufficient for a rider to gain the benefits of FES and thus raises speculation as to whether or not progressive resistance cycling is an appropriate protocol for SCI subjects.

E-technology and pedometer walking program to increase physical activity at work.

This study examined the application of the transtheoretical model (TTM) as a means to increase physical activity at the worksite through the introduction of a 10-week pedometer walking program combined with internet-based motivational messages. Participants (N = 206) were employees of two worksites who completed a health history questionnaire and assessment based on the TTM. There were significant improvements in the number of steps per week, level of physical activity, movement through stage of change and other health related indicators (p < 0.05). The worksite pedometer walking program and e-technology may be effective interventions in improving the lifestyle of employees who might be at risk for developing chronic diseases. Editors' Strategic Implications: Because walking is an inexpensive, easy, and convenient form of physical activity for many adults, implementation of this type of workplace program--with the important element of increasing individuals' awareness of risks--could be an effective approach to reduce cardiovascular risk factors and manage overweight and obesity in sedentary adults. Future research should compare this simple model with more individualized (but often more expensive) programs.