Predicting overstriding with wearable IMUs during treadmill and overground running.

Running injuries are prevalent, but their exact mechanisms remain unknown largely due to limited real-world biomechanical analysis. Reducing overstriding, the horizontal distance that the foot lands ahead of the body, may be relevant to reducing injury risk. Here, we leverage the geometric relationship between overstriding and lower extremity sagittal segment angles to demonstrate that wearable inertial measurement units (IMUs) can predict overstriding during treadmill and overground running in the laboratory. Ten recreational runners matched their strides to a metronome to systematically vary overstriding during constant-speed treadmill running and showed similar overstriding variation during comfortable-speed overground running. Linear mixed models were used to analyze repeated measures of overstriding and sagittal segment angles measured with motion capture and IMUs. Sagittal segment angles measured with IMUs explained 95% and 98% of the variance in overstriding during treadmill and overground running, respectively. We also found that sagittal segment angles measured with IMUs correlated with peak braking force and explained 88% and 80% of the variance during treadmill and overground running, respectively. This study highlights the potential for IMUs to provide insights into landing and loading patterns over time in real-world running environments, and motivates future research on feedback to modify form and prevent injury.

Using inertial measurement units to estimate spine joint kinematics and kinetics during walking and running.

Optical motion capture (OMC) is considered the best available method for measuring spine kinematics, yet inertial measurement units (IMU) have the potential to collect data outside the laboratory. When combined with musculoskeletal modeling, IMU technology may be used to estimate spinal loads in real-world settings. To date, IMUs have not been validated for estimates of spinal movement and loading during both walking and running. Using OpenSim Thoracolumbar Spine and Ribcage models, we compare IMU and OMC estimates of lumbosacral (L5/S1) and thoracolumbar (T12/L1) joint angles, moments, and reaction forces during gait across six speeds for five participants. For comparisons, time series are ensemble averaged over strides. Comparisons between IMU and OMC ensemble averages have low normalized root mean squared errors (< 0.3 for 81% of comparisons) and high, positive cross-correlations (> 0.5 for 91% of comparisons), suggesting signals are similar in magnitude and trend. As expected, joint moments and reaction forces are higher during running than walking for IMU and OMC. Relative to OMC, IMU overestimates joint moments and underestimates joint reaction forces by 20.9% and 15.7%, respectively. The results suggest using a combination of IMU technology and musculoskeletal modeling is a valid means for estimating spinal movement and loading.

Applying an evolutionary mismatch framework to understand disease susceptibility.

Noncommunicable diseases (NCDs) are on the rise worldwide. Obesity, cardiovascular disease, and type 2 diabetes are among a long list of "lifestyle" diseases that were rare throughout human history but are now common. The evolutionary mismatch hypothesis posits that humans evolved in environments that radically differ from those we currently experience; consequently, traits that were once advantageous may now be "mismatched" and disease causing. At the genetic level, this hypothesis predicts that loci with a history of selection will exhibit "genotype by environment" (GxE) interactions, with different health effects in "ancestral" versus "modern" environments. To identify such loci, we advocate for combining genomic tools in partnership with subsistence-level groups experiencing rapid lifestyle change. In these populations, comparisons of individuals falling on opposite extremes of the "matched" to "mismatched" spectrum are uniquely possible. More broadly, the work we propose will inform our understanding of environmental and genetic risk factors for NCDs across diverse ancestries and cultures.

Comparing measured dietary variation within and between tropical hunter-gatherer groups to the Paleo Diet.

BACKGROUND: Although human diets varied considerably before the spread of agriculture, public perceptions of preagricultural diets have been strongly influenced by the Paleo Diet, which prescribes percentage calorie ranges of 19-35% protein, 22-40% carbohydrate, and 28-47% fat, and prohibits foods with added sugar, dairy, grains, most starchy tubers, and legumes. However, the empirical basis for Paleolithic nutrition remains unclear, with some of its assumptions challenged by the archaeological record and theoretical first principles. OBJECTIVES: We assessed the variation in diets among tropical hunter-gatherers, including the effect of collection methods on implied macronutrient percentages. METHODS: We analyzed data on animal food, plant food, and honey consumption by weight and kcal from 15 high-quality published ethnographic studies representing 11 recent tropical hunter-gatherer groups. We used Bayesian analyses to perform inference and included data collection methods and environmental variables as predictors in our models. RESULTS: Our analyses reveal high levels of variation in animal versus plant foods consumed and in corresponding percentages of protein, fat, and carbohydrates. In addition, studies that weighed food items consumed in and out of camp and across seasons and years reported higher consumption of animal foods, which varied with annual mean temperature. CONCLUSIONS: The ethnographic evidence from tropical foragers refutes the concept of circumscribed macronutrient ranges modeling preagricultural diets.

Biomechanical Tradeoffs in Foot Function From Variations in Shoe Design.

There is debate and confusion over how to evaluate the biomechanical effects of running shoe design. Here, we use an evolutionary perspective to analyze how key design features of running shoes alter the evolved biomechanics of the foot, creating a range of tradeoffs in force production and transmission that may affect performance and vulnerability to injury.

Variation in human functional eccrine gland density and its implications for the evolution of human sweating.

OBJECTIVES: We aim to test three questions regarding human eccrine sweat gland density, which is highly derived yet poorly understood. First, is variation in functional eccrine gland density ("FED") explained by childhood climate, suggesting phenotypic plasticity? Second, is variation in FED explained by genetic similarity (a proxy for "geographic ancestry"), implying divergent evolutionary pathways in this trait of ancestral populations? Third, what is the relationship between FED and sweat production? MATERIALS AND METHODS: To test questions one and two, we measured FED in 68 volunteers aged 18-39 with varied childhood climate regimes and geographic ancestries. To test question three, we compared sweat production to FED in our n = 68 sample. In addition, we examined the relationship between FED and whole-body sweat loss during cycling in warm conditions using a sample of eight heat-acclimated endurance athletes. RESULTS: Interindividual variation in six-site FED was more than twofold, ranging from 60.9 to 132.7 glands/cm2 . Variation in FED was best explained by body surface area and limb circumferences (negative associations) and poorly explained by childhood climatic conditions and genetic similarity. Pilocarpine-induced sweat production was unrelated to FED while whole-body sweat loss during cycling was significantly, though modestly, associated with FED. DISCUSSION: We hypothesize that gland-level phenotypic plasticity, rather than changes in eccrine gland density, was sufficient to permit thermal adaptation to novel environments as humans colonized the globe. Future research should measure effects of FED in dehydrated states and the relationship between FED and salt loss, and control for effects of microclimate to rule out phenotypic plasticity effects.

Obesity and the risk of cardiometabolic diseases.

The prevalence of obesity has reached pandemic proportions, and now approximately 25% of adults in Westernized countries have obesity. Recognized as a major health concern, obesity is associated with multiple comorbidities, particularly cardiometabolic disorders. In this Review, we present obesity as an evolutionarily novel condition, summarize the epidemiological evidence on its detrimental cardiometabolic consequences and discuss the major mechanisms involved in the association between obesity and the risk of cardiometabolic diseases. We also examine the role of potential moderators of this association, with evidence for and against the so-called 'metabolically healthy obesity phenotype', the 'fatness but fitness' paradox or the 'obesity paradox'. Although maintenance of optimal cardiometabolic status should be a primary goal in individuals with obesity, losing body weight and, particularly, excess visceral adiposity seems to be necessary to minimize the risk of cardiometabolic diseases.

General Versus Regional Anesthesia in Sacrospinous Ligament Fixation for Pelvic Organ Prolapse: Assessment of a National Database.

IMPORTANCE: Sacrospinous ligament fixation is a prolapse repair surgical procedure that can be performed under general or regional anesthesia. Little is known about the impact of anesthesia on postoperative outcomes. OBJECTIVES: The primary objective of this study was to compare 30-day complication rates for patients undergoing sacrospinous ligament fixation by anesthesia type. Secondary objectives were to assess factors associated with type of anesthesia selected. STUDY DESIGN: This was a retrospective cohort analysis of the American College of Surgeons National Surgical Quality Improvement Program for the years of 2015 to 2020. Cases were selected based on procedural codes for sacrospinous ligament fixation and diagnostic codes for prolapse. Complications, readmissions, and reoperations were compared between general versus regional anesthesia cohorts. RESULTS: A total of 2,984 cases were included with 2,742 (91.9%) performed under general and 242 (8.1%) performed under regional anesthesia. The regional anesthesia cohort was older (69.2 vs 65.4 years old; P < 0.001) with no differences in medical history variables. Fewer patients in the regional anesthesia cohort were Hispanic (0.4% in regional vs 10.8% in general cohorts, P < 0.001). More superficial surgical site infections (2.5% vs 0.8%, P = 0.026) and cardiac complications (0.8% vs 0.1%, P = 0.035) were noted in the regional anesthesia cohort. However, multivariable regression analysis showed that anesthesia type was not associated with increased rates of minor or major complications. CONCLUSIONS: Mode of anesthesia was not a significant predictor of minor or major complications. Racial and ethnic differences in mode of anesthesia warrant further investigation to reduce racial disparities.

Evolutionary mismatch and the role of GxE interactions in human disease.

Globally, we are witnessing the rise of complex, non-communicable diseases (NCDs) related to changes in our daily environments. Obesity, asthma, cardiovascular disease, and type 2 diabetes are part of a long list of "lifestyle" diseases that were rare throughout human history but are now common. A key idea from anthropology and evolutionary biology-the evolutionary mismatch hypothesis-seeks to explain this phenomenon. It posits that humans evolved in environments that radically differ from the ones experienced by most people today, and thus traits that were advantageous in past environments may now be "mismatched" and disease-causing. This hypothesis is, at its core, a genetic one: it predicts that loci with a history of selection will exhibit "genotype by environment" (GxE) interactions and have differential health effects in ancestral versus modern environments. Here, we discuss how this concept could be leveraged to uncover the genetic architecture of NCDs in a principled way. Specifically, we advocate for partnering with small-scale, subsistence-level groups that are currently transitioning from environments that are arguably more "matched" with their recent evolutionary history to those that are more "mismatched". These populations provide diverse genetic backgrounds as well as the needed levels and types of environmental variation necessary for mapping GxE interactions in an explicit mismatch framework. Such work would make important contributions to our understanding of environmental and genetic risk factors for NCDs across diverse ancestries and sociocultural contexts.

The effect of vertical load placement on metabolic rate during loaded walking in humans.

We examined the effects of vertical load placement on the metabolic cost of walking. Twelve healthy participants walked on a treadmill with 13.8 and 23.4 kg loads in both high and low vertical positions. Metabolic rate was measured using respirometry. While load position had no effect on the net metabolic rate for the 13.8 kg load, the net metabolic rate with the 23.4 kg load was significantly reduced by 4.3% in the high vertical load position compared to the low vertical load position. Loads carried higher on the trunk were also associated with increased forward trunk lean that reduced the load gravitational moment arm in the sagittal plane suggesting that reduction of fore-aft upper body torques is an energy-saving mechanism during loaded walking. Practitioner Summary: Load placement within a backpack affects the biomechanics of load carriage. We experimentally tested the metabolic cost of high and low load placement during walking and found the high position to be less costly with large loads. Loading high may be the optimal technique for carrying heavy backpacks.

Characteristics and Future Direction of Tibialis Posterior Tendinopathy Research: A Scoping Review.

Background and Objectives: Tibialis posterior tendon pathologies have been traditionally categorized into different stages of posterior tibial tendon dysfunction (PTTD), or adult acquired flatfoot deformity (AAFD), and more recently to progressive collapsing foot deformity (PCFD). The purpose of this scoping review is to synthesize and characterize literature on early stages of PTTD (previously known as Stage I and II), which we will describe as tibialis posterior tendinopathy (TPT). We aim to identify what is known about TPT, identify gaps in knowledge on the topics of TPT, and propose future research direction. Materials and Methods: We included 44 studies and categorized them into epidemiology, diagnosis, evaluation, biomechanics outcome measure, imaging, and nonsurgical treatment. Results: A majority of studies (86.4%, 38 of 44 studies) recruited patients with mean or median ages greater than 40. For studies that reported body mass index (BMI) of the patients, 81.5% had mean or median BMI meeting criteria for being overweight. All but two papers described study populations as predominantly or entirely female gender. Biomechanical studies characterized findings associated with TPT to include increased forefoot abduction and rearfoot eversion during gait cycle, weak hip and ankle performance, and poor balance. Research on non-surgical treatment focused on orthotics with evidence mostly limited to observational studies. The optimal exercise regimen for the management of TPT remains unclear due to the limited number of high-quality studies. Conclusions: More epidemiological studies from diverse patient populations are necessary to better understand prevalence, incidence, and risk factors for TPT. The lack of high-quality studies investigating nonsurgical treatment options is concerning because, regardless of coexisting foot deformity, the initial treatment for TPT is typically conservative. Additional studies comparing various exercise programs may help identify optimal exercise therapy, and investigation into further nonsurgical treatments is needed to optimize the management for TPT.

Cultural variation in running techniques among non-industrial societies.

Research among non-industrial societies suggests that body kinematics adopted during running vary between groups according to the cultural importance of running. Among groups in which running is common and an important part of cultural identity, runners tend to adopt what exercise scientists and coaches consider to be good technique for avoiding injury and maximising performance. In contrast, among groups in which running is not particularly culturally important, people tend to adopt suboptimal technique. This paper begins by describing key elements of good running technique, including landing with a forefoot or midfoot strike pattern and leg oriented roughly vertically. Next, we review evidence from non-industrial societies that cultural attitudes about running associate with variation in running techniques. Then, we present new data from Tsimane forager-horticulturalists in Bolivia. Our findings suggest that running is neither a common activity among the Tsimane nor is it considered an important part of cultural identity. We also demonstrate that when Tsimane do run, they tend to use suboptimal technique, specifically landing with a rearfoot strike pattern and leg protracted ahead of the knee (called overstriding). Finally, we discuss processes by which culture might influence variation in running techniques among non-industrial societies, including self-optimisation and social learning.

The evolution of human step counts and its association with the risk of chronic disease.

Walking - humans' most fundamental form of moderate intensity physical activity - is associated with reduced risks of morbidity and mortality. Evolutionary perspectives have contributed much to understanding the effects of walking and other physical activities on health; however, we know comparatively little about how step counts (steps taken per day) changed over the course of human evolution, potentially affecting how selection operated on physiological responses to moderate intensity physical activity that influence morbidity and mortality. Here, we compare step counts across humans and our closest living relatives, the great apes. Compiling data from epidemiology and comparative physiology, we show how step counts more than tripled during human evolution, potentially linking higher levels of moderate intensity physical activity with reduced morbidity and mortality, and we highlight how recent decreases in step counts are an evolutionary mismatch. We raise the hypothesis that the dose-response relationship between moderate intensity physical activity and health was shifted in humans to require more steps per day to promote extended healthspan and lifespan.

Does plantar skin abrasion affect cutaneous mechanosensation?

In humans, plantar cutaneous mechanoreceptors provide critical input signals for postural control during walking and running. Because these receptors are located within the dermis, the mechanical properties of the overlying epidermis likely affect the transmission of external stimuli. Epidermal layers are highly adaptable and can form hard and thick protective calluses, but their effects on plantar sensitivity are currently disputed. Some research has shown no effect of epidermal properties on sensitivity to vibrations, whereas other research suggests that vibration and touch sensitivity diminishes with a thicker and harder epidermis. To address this conflict, we conducted an intervention study where 26 participants underwent a callus abrasion while an age-matched control group (n = 16) received no treatment. Skin hardness and thickness as well as vibration perception thresholds and touch sensitivity thresholds were collected before and after the intervention. The Callus abrasion significantly decreased skin properties. The intervention group exhibited no change in vibration sensitivity but had significantly better touch sensitivity. We argue that touch sensitivity was impeded by calluses because hard skin disperses the monofilament's standardized pressure used to stimulate the mechanoreceptors over a larger area, decreasing indentation depth and therefore stimulus intensity. However, vibration sensitivity was unaffected because the vibrating probe was adjusted to reach specific indentation depths, and thus stimulus intensity was not affected by skin properties. Since objects underfoot necessarily indent plantar skin during weight-bearing, calluses should not affect mechanosensation during standing, walking, or running.

Comparing high versus low-altitude populations to test human adaptations for increased ventilation during sustained aerobic activity.

Despite aerobic activity requiring up to tenfold increases in air intake, human populations in high-altitude hypoxic environments can sustain high levels of endurance physical activity. While these populations generally have relatively larger chest and lung volumes, how thoracic motions actively increase ventilation is unknown. Here we show that rib movements, in conjunction with chest shape, contribute to ventilation by assessing how adulthood acclimatization, developmental adaptation, and population-level adaptation to high-altitude affect sustained aerobic activity. We measured tidal volume, heart rate, and rib-motion during walking and running in lowland individuals from Boston (~ 35 m) and in Quechua populations born and living at sea-level (~ 150 m) and at high altitude (> 4000 m) in Peru. We found that Quechua participants, regardless of birth or testing altitudes, increase thoracic volume 2.0-2.2 times more than lowland participants (p < 0.05). Further, Quechua individuals from hypoxic environments have deeper chests resulting in 1.3 times greater increases in thoracic ventilation compared to age-matched, sea-level Quechua (p < 0.05). Thus, increased thoracic ventilation derives from a combination of acclimatization, developmental adaptation, and population-level adaptation to aerobic demand in different oxygen environments, demonstrating that ventilatory demand due to environment and activity has helped shape the form and function of the human thorax.

Testing delivery of components of cognitive behavioral therapy for insomnia to breast cancer survivors by smart speaker: a study protocol.

BACKGROUND: Insomnia is common in breast cancer survivors (BCS), affecting an estimated 30-50% of the 3.8 million BCS in the US. Insomnia is associated with health consequences for cardiometabolic and immune systems, neurobehavioral function, depression, fatigue, and quality of life and may put BCS at particular risk. While pharmacotherapy for insomnia may address symptoms in the short-term, cognitive behavioral therapy for insomnia (CBT-I) is considered the gold standard insomnia treatment. We describe our protocol to determine the efficacy of voice-activated delivery of CBT-I components on insomnia symptoms compared to a sleep education control among BCS. METHODS: We will conduct a 6-week, randomized controlled trial with two arms. Intervention arm participants will receive a smart speaker device and will be asked to engage with the program daily, using a voice-activated speaker with an accompanying smart-phone app. Control participants will have access to a website with basic information about CBT-I, sleep, and breast cancer survivorship and will be asked to engage with the website as desired. DISCUSSION: Our primary outcome is the Insomnia Severity Index total score. Secondary outcomes include sleep diary outcomes (sleep efficiency, wake after sleep onset, sleep onset latency, total sleep time, and sleep quality). This study will provide evidence on a promising modality to deliver elements of CBT-I for BCS experiencing insomnia. Trial Registration ClinicalTrials.gov NCT05233800 Released 3/25/2022.

The evolution of human fatigue resistance.

Humans differ from African great apes in numerous respects, but the chief initial difference setting hominins on their unique evolutionary trajectory was habitual bipedalism. The two most widely supported selective forces for this adaptation are increased efficiency of locomotion and improved ability to feed in upright contexts. By 4 million years ago, hominins had evolved the ability to walk long distances but extreme selection for endurance capabilities likely occurred later in the genus Homo to help them forage, power scavenge and persistence hunt in hot, arid conditions. In this review we explore the hypothesis that to be effective long-distance walkers and especially runners, there would also have been a strong selective benefit among Homo to resist fatigue. Our hypothesis is that since fatigue is an important factor that limits the ability to perform endurance-based activities, fatigue resistance was likely an important target for selection during human evolution for improved endurance capabilities. We review the trade-offs between strength, power, and stamina in apes and Homo and discuss three biological systems that we hypothesize humans evolved adaptations for fatigue resistance: neurological, metabolic and thermoregulatory. We conclude that the evolution of endurance at the cost of strength and power likely also involved the evolution of mechanisms to resist fatigue.