The Effect of a Backpack Hip Strap on Energy Expenditure While Walking.

Objective To examine the effect of backpack hip strap use on walking energy expenditure while carrying a loaded backpack. Background Previous studies have demonstrated that energy cost increases as the mass of the load carried increases. However, few investigations have focused on backpack carriage design. Methods Fifteen young, healthy, male subjects walked at a self-selected pace for 10 minutes in two backpack loading conditions: with a hip strap (strapped) and without a hip strap (nonstrapped). Oxygen consumption (VO2), rating of perceived exertion (RPE), respiratory exchange ratio (RER), and heart rate (HR) were monitored throughout each 10-minute trial. Change scores from the 4th to 10th minute were calculated for each variable. A t test was used to evaluate the difference between conditions for each variable. Results The changes in VO2 (-0.62 ± 0.40 vs. 0.33 ± 0.23, p = .04) and RPE (1 ± 0.25 vs. 2 ± 0.21, p < .01) from the 4th to the 10th minute were different for the strapped versus nonstrapped condition. There was no difference in the change in RER (0.04 ± 0.01 vs. 0.03 ± 0.01, p > .05) or HR (3.53 ± 0.93 vs. 4.07 ± 1.39, p > .05) for the strapped versus unstrapped condition. Conclusions Wearing a hip strap reduced the energy expenditure and perceived exertion in as little as 10 minutes of walking compared to the nonstrapped condition. Future work should consider the effect of a hip strap on these variables while hiking for extended periods. Application Wearing a hip strap may increase the comfort and reduce the energy required of wearing a backpack. This is useful information for backpack designers, military personnel, and recreational hikers.

The impact of financial barriers on access to care, quality of care and vascular morbidity among patients with diabetes and coronary heart disease.

BACKGROUND: The prevalence and consequences of financial barriers to health care among patients with multiple chronic diseases are poorly understood. OBJECTIVE: We sought to assess the prevalence of self-reported financial barriers to health care among individuals with diabetes and coronary heart disease (CHD) and to determine their association with access to care, quality of care and clinical outcomes. DESIGN: The 2007 Centers for Disease Control Behavioral Risk Factor Surveillance Survey. PARTICIPANTS: Diabetic patients with CHD. MAIN MEASURES: Financial barriers to health care were defined by a self-reported time in the past 12 months when the respondent needed to see a doctor but could not because of cost. The primary clinical outcome was vascular morbidity­a composite of stroke, retinopathy, nonhealing foot sores or bilateral foot amputations. KEY RESULTS: Among the 11,274 diabetics with CHD, 1,541 (13.7 %) reported financial barriers to health care. Compared to individuals without financial barriers, those with financial barriers had significantly reduced rates of medical assessments within the past 2 years, hemoglobin (Hgb) A1C measurements in the past year, cholesterol measurements at any time, eye and foot examinations within the past year, diabetic education, antihypertensive treatment, aspirin use and a higher prevalence of vascular morbidity. In multivariable analyses, financial barriers to health care were independently associated with reduced odds of medical checkups (Odds Ratio [OR], 0.61; 95 % Confidence Intervals [CI], 0.55­0.67), Hgb A1C measurement (OR, 0.85; 95 % CI, 0.77­0.94), cholesterol measurement (OR, 0.76; 95 % CI, 0.67­0.86), eye (OR, 0.85; 95 % CI, 0.79­0.92) and foot (OR, 0.92; 95 % CI, 0.84­1.00) examinations, diabetic education (OR, 0.93; 95 % CI, 0.87­0.99), aspirin use (OR, 0.88; 95 % CI, 0.81­0.96) and increased odds of vascular morbidity (OR, 1.23; 95 % CI, 1.14­1.33). CONCLUSIONS: In diabetic adults with CHD, financial barriers to health care were associated with impaired access to medical care, inferior quality of care and greater vascular morbidity. Eliminating financial barriers and adherence to guideline-based recommendations may improve the health of individuals with multiple chronic diseases.

Ontogeny and the evolution of adult body size dimorphism in apes.

This analysis investigates the ontogeny of body size dimorphism in apes. The processes that lead to adult body size dimorphism are illustrated and described. Potential covariation between ontogenetic processes and socioecological variables is evaluated. Mixed-longitudinal growth data from 395 captive individuals (representing Hylobates lar [gibbon], Hylobates syndactylus [siamang], Pongo pygmaeus [orangutan], Gorilla gorilla [gorilla], Pan paniscus [pygmy chimpanzee], and Pan troglodytes ["common" chimpanzee]) form the basis of this study. Results illustrate heterogeneity in the growth processes that produce ape dimorphism. Hylobatids show no sexual differentiation in body weight growth. Adult body size dimorphism in Pongo can be largely attributed to indeterminate male growth. Dimorphism in African apes is produced by two different ontogenetic processes. Both pygmy chimpanzees (Pan paniscus) and gorillas (Gorilla gorilla) become dimorphic primarily through bimaturism (sex differences in duration of growth). In contrast, sex differences in rate of growth account for the majority of dimorphism in common chimpanzees (Pan troglodytes). Diversity in the ontogenetic pathways that produce adult body size dimorphism may be related to multiple evolutionary causes of dimorphism. The lack of sex differences in hylobatid growth is consistent with a monogamous social organization. Adult dimorphism in Pongo can be attributed to sexual selection for indeterminate male growth. Interpretation of dimorphism in African apes is complicated because factors that influence female ontogeny have a substantial effect on the resultant adult dimorphism. Sexual selection for prolonged male growth in gorillas may also increase bimaturism relative to common chimpanzees. Variation in female growth is hypothesized to covary with foraging adaptations and with differences in female competition that result from these foraging adaptations. Variation in male growth probably corresponds to variation in level of sexual selection. © 1995 Wiley-Liss, Inc.