Accelerometry and heart rate as a measure of physical fitness: cross-validation

PURPOSE: We recently reported on a new method to assess physical fitness, based on the combined use of accelerometry and heart rate (HR) registration. This study tested the validity of the prediction formula in a group of healthy young adults. METHODS: Twenty-six healthy subjects performed a maximal incremental test on a bicycle ergometer to determine VO2max. A triaxial accelerometer and a HR monitor were worn for 7 d under free-living conditions. The prediction formula developed in a previous experimental group (EXP) was applied on the cross-validation group (CV). RESULTS: No difference was found in subjects' characteristics between the EXP and CV groups except for accelerometer output (activity counts). Although measured VO2max could be predicted for 80% (P < 0.0001), a paired t-test showed a significant difference between measured and predicted VO2max (178 mL.min(-1); P = 0.015). Because of the difference in activity between the EXP and the CV groups, all data were combined and sorted according to activity counts, then two new groups were formed. As a result, EXP and CV groups were created that did not significantly differ in activity or any other parameters. The formula developed in the new experimental group (R2 = 0.74; P < 0.0001) explained 72% (P < 0.0001) of the variation in VO2max in the cross-validation group, a paired t-test showed no difference between measured and predicted VO2max, and Bland-Altman plotting showed no systematic bias. CONCLUSION: Although a good correlation was seen between measured and predicted VO2max in the cross-validation group, care should be taken in applying the prediction formula on groups that differ in physical activity from the current study population

Determinants of stunting and overweight among young children and adolescents in sub-Saharan Africa

BACKGROUND: Stunting and overweight are nutritional problems affecting most of sub-Saharan Africa. The region now has the world's highest rate of stunting among children (43%), while overweight and obesity are becoming a global epidemic, and Africa is not spared. The past two decades have seen a dramatic increase in obesity in sub-Saharan Africa. OBJECTIVE: The purpose of this systematic review is to explore the determinants of stunting and overweight in sub-Saharan Africa. METHODS: A literature search was conducted in PubMed using the key words stunting, overweight, obesity, Africa, sub-Saharan Africa, determinants, and prevalence. Limits were set to include articles published between 1990 and 2012. The systematic review resulted in 38 studies, and after selection based on title, content, and country of the study, 18 studies were eligible for this review. Data were analyzed by the chi-square test. RESULTS: The prevalence rates of stunting and overweight were dependent on socioeconomic, demographic, and environmental factors. Many studies indicate that male children and those living in a rural setting are more likely to be stunted, whereas overweight among children depends more on age, household composition, occupation of the mother, and the mother's body mass index. Stunting occurred together with overweight among both boys and girls from 1 to 5 years of age. Stunting was more prevalent among boys than among girls. Indicators of socioeconomic status, such as mother's education, mother's occupation, and household income, were some of the determinants directly linked to stunting, whereas environmental factors, such as rural or urban setting and sanitation, influenced both stunting and overweight. Concurrent stunting and overweight is influenced by maternal and household factors, such as maternal height, age, and education, large household size, and lower socioeconomic status. CONCLUSIONS: Although socioeconomic, demographic, and environmental factors were significant in determining stunting and overweight, other factors, such as nutrition and lifestyle, were important risk factors. Stunting in childhood is a risk factor that may result in overweight and obesity later in adolescence and adulthood, indicating the need to screen children below 1 year of age to identify stunting early in life. Promoting exclusive breastfeeding is reported to be important in preventing both stunting and overweight among children. More research is needed to explore the relationship between stunting and overweight and to explore policy guidelines to address the phenomenon

Cardiorespiratory fitness estimation using wearable sensors: laboratory and free-living analysis of context-specific submaximal heart rates

In this work, we propose to use pattern recognition methods to determine submaximal heart rate (HR) during specific contexts, such as walking at a certain speed, using wearable sensors in free-living, and use context-specific HR to estimate cardiorespiratory fitness (CRF). CRF of 51 participants was assessed by a maximal exertion test (VO2max). Participants wore a combined accelerometer and HR monitor during a laboratory based simulation of activities of daily living and for two weeks in free-living. Anthropometrics, HR while lying down and walking at predefined speeds in laboratory settings were used to estimate CRF. Explained variance (R2) was 0.64 for anthropometrics, and increased up to 0.74 for context-specific HR (0.73 to 0.78 when including fat-free mass). Then, we developed activity recognition and walking speed estimation algorithms to determine the same contexts (i.e. lying down and walking) in free-living. Context-specific HR in free-living was highly correlated with laboratory measurements (Pearson's r = 0.71-0.75). R2 for CRF estimation was 0.65 when anthropometrics were used as predictors, and increased up to 0.77 when including free-living context-specific HR (i.e. HR while walking at 5.5 km/h). R2 varied between 0.73 and 0.80 when including fat-free mass among the predictors. RMSE was reduced from 354.7 ml/min to 281.0 ml/min by the inclusion of context-specific HR parameters (21% error reduction). We conclude that pattern recognition techniques can be used to contextualize HR in free-living and estimated CRF with accuracy comparable to what can be obtained with laboratory measurements of HR response to walking

Social role participation questionnaire for patients with ankylosing spondylitis: Translation into Dutch, reliability and construct validity

Objective: The Social Role Participation Questionnaire (SRPQ) assesses the influence of health on participation in 11 specific and one general participation role across 4 participation dimensions: 'importance', 'satisfaction with time', 'satisfaction with performance' and 'physical difficulty'. This study aimed to translate the SRPQ into Dutch, and assess the clinimetric properties and aspects of its validity among patients with ankylosing spondylitis (AS). Methods: Translation was performed using the dual panel approach. For each participation dimension, internal consistency, test-retest reliability (n=31), and construct validity were assessed in 246 patients with AS. Results: The translation required only minor adaptations. Cronbach αs were α≥0.7. A strong correlation was present between satisfaction with 'time' and 'performance'(r=0.85). Test-retest reliability was satisfactory (κ=0.79-0.95). Correlations with participation domains of the Short- Form Health Survey 36 (SF-36), the WHO Disease Assessment Score II, and generic as well as disease-specific health outcomes (Physical and Mental component scale of the SF-36, Satisfaction With Life Scale, Bath Ankylosing Spondy