Andrew W. Froehle

Climate variables as predictors of basal metabolic rate: new equations.

Estimation of basal metabolic rate (BMR) and daily energy expenditure (DEE) in living humans and in fossil hominins can be used to understand the way populations adapt to different environmental and nutritional circumstances. One variable that should be considered in such estimates is climate, which may influence between‐population variation in BMR. Overall, populations living in warmer climates tend to have lower BMR than those living in colder climates, even after controlling for body size and composition. Current methods of estimating BMR ignore climate, or deal with its effects in an insufficient manner. This may affect studies that use the factorial method to estimate DEE from BMR, when BMR is not measured but predicted using an equation. The present meta‐analysis of published BMR uses stepwise regression to investigate whether the inclusion of climate variables can produce a generally applicable model for human BMR. Regression results show that mean annual temperature and high heat index temperature have a significant effect on BMR, along with body size, age and sex. Based on the regression analysis, equations predicting BMR from body size and climate variables were derived and compared with existing equations. The new equations are generally more accurate and more consistent across climates than the older ones. Estimates of DEE in living and fossil humans using the new equations are compared with estimates using previously published equations, illustrating the utility of including climate variables in estimates of BMR. The new equations derived here may prove useful for future studies of human energy expenditure. Am. J. Hum. Biol., 2008.

Ontogenetic scaling of the human nose in a longitudinal sample: Implications for genus Homo facial evolution

Researchers have hypothesized that nasal morphology, both in archaic Homo and in recent humans, is influenced by body mass and associated oxygen consumption demands required for tissue maintenance. Similarly, recent studies of the adult human nasal region have documented key differences in nasal form between males and females that are potentially linked to sexual dimorphism in body size, composition, and energetics. To better understand this potential developmental and functional dynamic, we first assessed sexual dimorphism in the nasal cavity in recent humans to determine when during ontogeny male-female differences in nasal cavity size appear. Next, we assessed whether there are significant differences in nasal/body size scaling relationships in males and females during ontogeny. Using a mixed longitudinal sample we collected cephalometric and anthropometric measurements from n = 20 males and n = 18 females from 3.0 to 20.0+ years of age totaling n = 290 observations. We found that males and females exhibit similar nasal size values early in ontogeny and that sexual dimorphism in nasal size appears during adolescence. Moreover, when scaled to body size, males exhibit greater positive allometry in nasal size compared to females. This differs from patterns of sexual dimorphism in overall facial size, which are already present in our earliest age groups. Sexually dimorphic differences in nasal development and scaling mirror patterns of ontogenetic variation in variables associated with oxygen consumption and tissue maintenance. This underscores the importance of considering broader systemic factors in craniofacial development and may have important implications for the study of patters craniofacial evolution in the genus Homo.

Skeletal growth and the changing genetic landscape during childhood and adulthood

Growth, development, and decline of the human skeleton are of central importance to physical anthropology. All processes of skeletal growth (longitudinal growth as well as gains and losses of bone mass) are subjected to environmental and genetic influences. These influences, and their relative contributions to the phenotype, can be asserted at any stage of life. We present here the gross phenotypic and genetic landscapes of four skeletal traits, and show how they vary across the life span. Phenotypic sex differences are found in bone diameter and cortical index (a ratio of cortical thickness over bone diameter) at a very early age and continue throughout most of life. Sexual dimorphism in summed cortical thickness and bone length, however, is not evident until shortly after the pubertal growth spurt. Genetic contributions (heritability) to these skeletal phenotypes are generally moderate to high. Bone length and bone diameter (which both scale with body size) tend to have the highest heritability, with heritability of bone length fairly stable across ages (with a notable dip in early childhood) and that of bone diameter peaking in early childhood. The bone traits summed cortical thickness and cortical index that may better reflect bone mass, a more plastic phenomenon, have slightly lower genetic influences, on average. Results from our phenotypic and genetic landscapes serve three key purposes: 1) demonstration of the integrated nature of the genetic and environmental underpinnings of skeletal form, 2) identification of periods of bones relative sensitivity to genetic and environmental influences, 3) and stimulation of hypotheses predicting the effects of exposure to environmental variables on the skeleton, given variation in the underlying genetic architecture.

The ontogeny of nasal shape: An analysis of sexual dimorphism in a longitudinal sample.

OBJECTIVES Potential integration between the nasal region and noncranial components of the respiratory system has significant implications for understanding determinants of craniofacial variation. There is increasing evidence that sexual dimorphism in body size and associated male-female differences in energetically relevant variables influence the development of the nasal region. To better understand this relationship, we examined the ontogeny of sexual dimorphism in nasal shape using a longitudinal series of lateral cephalograms. METHODS We collected a series of two dimensional coordinate landmark data from n = 20 males and n = 18 females from 3.0 to 20.0+ years of age totaling n = 290 observations across nine age groups. First, we tested whether there are sex differences in the nasal shape related to ontogenetic increases in body size (i.e., sitting height). Additionally, we examined whether there are male-female differences in patterns of nonallometric variation in nasal shape. Next, we tested whether there are sex differences in the strength of integration between the nasal region and other aspects of the facial skeleton. RESULTS Our results indicate that there are a number of similarities in patterns of morphological variation in the nasal region between males and females. However, as sitting height increases males exhibit a disproportionate increase in nasal region height that is not present in the female sample. Moreover, the male nasal region is less integrated with the surrounding facial skeleton when compared to the female sample. CONCLUSIONS These results are consistent with the hypothesis that sex differences in nasal development are associated with male-female differences in energetically relevant variables.

Relationships Between Age at Menarche, Walking Gait Base of Support, and Stance Phase Frontal Plane Knee Biomechanics in Adolescent Girls.

Age at menarche impacts patterns of pubertal growth and skeletal development. These effects may carry over into variation in biomechanical profiles involved in sports‐related traumatic and overuse knee injuries. The present study investigated whether age at menarche is a potential indicator of knee injury risk through its influence on knee biomechanics during normal walking.

Moderate to high levels of exercise are associated with higher resting energy expenditure in community-dwelling postmenopausal women.

Postmenopausal women experience an age-related decline in resting energy expenditure (REE), which is a risk factor for energy imbalance and metabolic disease. Exercise, because of its association with greater lean tissue mass and other factors, has the potential to mediate REE decline, but the relation between exercise and REE in postmenopausal women is not well characterized. This study tests the hypothesis that exercise energy expenditure (EEE) is positively associated with REE and can counter the effects of age and menopause. It involves a cross-sectional sample of 31 healthy postmenopausal women (aged 49-72 years) with habitual exercise volumes at or above levels consistent with current clinical recommendations. Subjects kept exercise diaries for 4 weeks that quantified exercise activity and were measured for body composition, maximal oxygen uptake, and REE. Multiple regression analysis was used to test for associations between EEE, age, body composition, and REE. There was a significant positive relation between EEE and lean tissue mass (fat-free mass and fat-free mass index). The relation between REE and EEE remained significant even after controlling for lean tissue mass. These results support the hypothesis that exercise is positively associated with REE and can counter the negative effects of age and menopause. They also indicate a continuous relation between exercise and REE across ranges of exercise, from moderate to high. Exercise at levels that are at or above current clinical guidelines might, in part, ameliorate the risk for energy imbalance and metabolic disease because of its positive relation with REE.

Improved Early Postoperative Range of Motion in Total Knee Arthroplasty Using Tranexamic Acid: A Retrospective Analysis

Abstract The use of tranexamic acid (TXA) in total knee arthroplasty (TKA) has become common practice. Recent literature has demonstrated a reduction in postoperative knee swelling and drain output while using TXA. Our purpose is to analyze the range of motion (ROM) following TKA in patients who received TXA compared with a control group. We hypothesize that patients treated with TXA will have improved early postoperative ROM when compared with controls. A retrospective chart review was performed for patients who underwent TKA from 2010 to 2012 performed by a single orthopaedic surgeon. Patients were stratified into three cohorts by route of TXA administration including intravenous (IV), topical, and a control group. Dependent variables analyzed included extension, flexion, and total arc ROM on each postoperative day (POD), average ROM across all three postoperative days, as well as pre‐to‐postoperative differences in ROM. Demographic data were recorded for each patient. A total of 174 patients were included for analysis, 75 controls and 99 receiving TXA. A significant difference was found between the treatment groups and the control for all variables (for each, p ≤ 0.002). There were no significant differences in ROM between the IV and topical TXA treatment groups (for each, p ≥ 0.558). A multivariate analysis demonstrated no significant difference between the groups in complication rate or demographic variables. The use of TXA may improve early postoperative ROM following TKA.

A biomechanical cadaver comparison of suture button fixation to plate fixation for pubic symphysis diastasis

OBJECTIVES To determine whether suture button fixation of the pubic symphysis is biomechanically similar to plate fixation in the treatment of partially stable pelvic ring injuries. METHODS Twelve pelvis specimens were harvested from fresh frozen cadavers. Dual-x-ray-absorptiometry (DXA) scans were obtained for all specimens. The pubic symphysis of each specimen was sectioned to simulate a partially stable pelvic ring injury. Six of the pelvises were instrumented using a 6 hole, 3.5 mm low profile pelvis plate and six of the pelvises were instrumented with two suture button devices. Biomechanical testing was performed on a pneumatic testing apparatus in a manner that simulates vertical stance. Displacement measurements of the superior, middle, and inferior pubic symphysis were obtained prior to loading, after an initial 440 N load, and after 30,000 and 60,000 rounds of cyclic loading. Statistical analysis was performed using Wilcoxon-Mann-Whitney tests, Fishers exact test, and Cohens d to calculate effect size. Significance was set at p < 0.05. RESULTS There was no difference between groups for DXA T scores (p = 0.749). Between group differences in clinical load to failure (p = 0.65) and ultimate load to failure (p = 0.52) were not statistically significant. For symphysis displacement, the change in fixation strength and displacement with progressive cyclic loading was not significant when comparing fixation types (superior: p = 0.174; middle: p = 0.382; inferior: p = 0.120). CONCLUSION Suture button fixation of the pubic symphysis is biomechanically similar to plate fixation in the management of partially stable pelvic ring injuries.

Validating a commercial device for continuous activity measurement in the older adult population for dementia management

With the introduction of the large number of fitness devices on the market, there are numerous possibilities for their use in managing chronic diseases in older adults. For example, monitoring people with dementia using commercially available devices that measure heart rate, breathing rate, lung volume, step count, and activity level could be used to predict episodic behavioral and psychological symptoms before they become distressing or disruptive. However, since these devices are designed primarily for fitness assessment, validation of the sensors in a controlled environment with the target cohort population is needed. In this study, we present validation results using a commercial fitness tracker, the Hexoskin sensor vest, with thirty-one participants aged 65 and older. Estimated physiological measures investigated in this study are heart rate, breathing rate, lung volume, step count, and activity level of the participants. Findings indicate that while the processed step count, heart rate, and breathing rate show strong correlations to the clinically accepted gold standard values, lung volume and activity level do not. This indicates the need to proceed cautiously when making clinical decisions using such sensors, and suggests that users should focus on the three strongly correlated parameters for further analysis, at least in the older population. The use of physiological measurement devices such as the Hexoskin may eventually become a non-intrusive way to continuously assess physiological measures in older adults with dementia who are at risk for distressing behavioral and psychological symptoms.

Gait Patterns After Bariatric Surgery

Compared to normal walking, obesity is associated with a slower, stiffer, more careful gait, posing a major challenge to mobility and physical function. Obese gait also contributes to knee osteoarthritis onset and progression, further limiting mobility and generating an obesity–immobility feedback loop that diminishes health-related quality-of-life and can lead to significant disability. Restoration of normal gait reduces functional disability among patients and is central to physical activity for postsurgical weight maintenance, and should therefore be considered a critical outcome of bariatric surgery. Six studies of postsurgical walking gait all show significant recovery of gait and function over postsurgical time periods ranging from 3 months to 5 years. Despite these promising outcomes, much work remains to be done to gain a better understanding of variation in the functional outcomes of bariatric surgery, and how best to improve gait rehabilitation for individual patients.