Genetic influences on exercise participation in 37,051 twin pairs from seven countries

A Mendelian randomization study: physical activities and chronic kidney disease

Increasing evidence has shown that physical activity is related to a lower risk of chronic kidney disease (CKD), thus indicating a potential target for prevention. However, the causality is not clear; specifically, physical activity may protect against CKD, and CKD may lead to a reduction in physical activity. Our study examined the potential bidirectional relationship between physical activity and CKD by using a genetically informed method. Genome-wide association studies from the UK Biobank baseline data were used for physical activity phenotypes and included 460,376 participants. For kidney function (estimated Glomerular Filtration Rate (eGFR) and CKD, with eGFR < 60 mL/min/1.73 m2), CKDGen Consortium data were used, which included 480,698 CKD participants of European ancestry. Mendelian randomization (MR) analysis was used to determine the causal relationship between physical activities and kidney function. Two-sample MR genetically predicted that heavy DIY (do it yourself) (e.g., weeding, lawn mowing, carpentry, and digging) decreased the risk of CKD (odds ratio [OR] = 0.287, 95% CI = 0.117-0.705, p = 0.0065) and improved the level of eGFR (β = 0.036, 95% CI = 0.005-0.067, p = 0.021). The bidirectional MR showed no reverse causality. It is worth noting that other physical activities, such as walking for pleasure, strenuous sports, light DIY (e.g., pruning and watering the lawn), and other exercises (e.g., swimming, cycling, keeping fit, and bowling), were not significantly correlated with CKD and eGFR. This study used genetic data to provide reliable and robust causal evidence that heavy physical activity (e.g., weeding, lawn mowing, carpentry, and digging) can protect kidney function and further lower the risk of CKD.

Genome-Wide Genetic Analysis of Dropout in a Controlled Exercise Intervention in Sedentary Adults With Overweight or Obesity and Cardiometabolic Disease

BACKGROUND

Despite the benefits of exercise, many individuals are unable or unwilling to adopt an exercise intervention.

PURPOSE

The purpose of this analysis was to identify putative genetic variants associated with dropout from exercise training interventions among individuals in the STRRIDE trials.

METHODS

We used a genome-wide association study approach to identify genetic variants in 603 participants initiating a supervised exercise intervention. Exercise intervention dropout occurred when a subject withdrew from further participation in the study or was otherwise lost to follow-up.

RESULTS

Exercise intervention dropout was associated with a cluster of single-nucleotide polymorphisms with the top candidate being rs722069 (T/C, risk allele = C) (unadjusted p = 2.2 × 10-7, odds ratio = 2.23) contained within a linkage disequilibrium block on chromosome 16. In Genotype-Tissue Expression, rs722069 is an expression quantitative trait locus of the EARS2, COG7, and DCTN5 genes in skeletal muscle tissue. In subsets of the STRRIDE genetic cohort with available muscle gene expression (n = 37) and metabolic data (n = 82), at baseline the C allele was associated with lesser muscle expression of EARS2 (p < .002) and COG7 (p = .074) as well as lesser muscle concentrations of C2- and C3-acylcarnitines (p = .026).

CONCLUSIONS

Our observations imply that exercise intervention dropout is genetically moderated through alterations in gene expression and metabolic pathways in skeletal muscle. Individual genetic traits may allow the development of a biomarker-based approach for identifying individuals who may benefit from more intensive counseling and other interventions to optimize exercise intervention adoption.

CLINICAL TRIAL INFORMATION

STRRIDE I = NCT00200993; STRRIDE AT/RT = NCT00275145; STRRIDE-PD = NCT00962962.

The 'Behavioral Balance Model': A new perspective on the aetiology and therapy of obesity

Obesity is a debilitating disease of global proportions that necessitates refined, concept-driven therapeutic approaches. Policy makers, the public and even health care professionals, but also individuals with obesity harbour many misconceptions regarding this disease, which leads to prejudice, negative attitudes, stigmatization, discrimination, self-blame, and failure to provide and finance adequate medical care. Decades of intensive, successful scientific research on obesity have only had a very limited effect on this predicament. We propose a science-based, easy-to-understand conceptual model that synthesizes the complex pathogenesis of obesity including biological, psychological, social, economic and environmental aspects with the aim to explain and communicate better the nature of obesity and currently available therapeutic modalities. According to our integrative 'Behavioral Balance Model', 'top-down cognitive control' strategies are implemented (often with limited success) to counterbalance the increased 'bottom-up drive' to gain weight, which is triggered by biological, psycho-social and environmental mechanisms in people with obesity. Besides offering a deeper understanding of obesity, the model also highlights why there is a strong need for multimodal therapeutic approaches that may not only increase top-down control but also reduce a pathologically increased bottom-up drive.

Echocardiographic Parameters Associated With Cardiorespiratory Fitness and Physical Activity in Childhood Acute Lymphoblastic Leukemia Survivors

BACKGROUND

Children's exposure to chemotherapeutic agents causes several long-term adverse effects but physical activity has been evidenced to be an effective strategy to improve cardiac function. This cross-sectional study aimed to explore the association between physical activity levels, cardiorespiratory fitness, and cardiac parameters measured by echocardiography.

METHODS

Participants were 216n childhood acute lymphoblastic leukemia survivors who underwent a maximal cardiopulmonary exercise test and self-reported their daily minutes of moderate to vigorous physical activity. They underwent a complete transthoracic echocardiographic assessment. Systolic and diastolic function analysis and strain images analysis were performed. The associations were studied through the preventive fraction (examined with univariate crude and adjusted logistic regression models) of regular physical activity (≥150 min·wk-1) and adequate cardiorespiratory fitness levels (above the median ≥ 32.0 mL·kg-1·min-1) on cardiac parameters.

RESULTS

Crude analysis shows that regular physical activity was associated with a significant preventive fraction in mitral E/A ratio (56%; P = .013), while adjusted analyses highlighted a nonsignificant reduction of 74% to 37% in the prevalence of cardiac parameters associated with physical activity. Similar associations of adequate cardiorespiratory fitness on cardiac parameters were observed. Adjusted analyses revealed a nonsignificant reduction of 7% to 86% in the prevalence of cardiac parameters associated with cardiorespiratory fitness.

CONCLUSION

This study reports that regular physical activity and adequate cardiorespiratory fitness were associated with a higher preventive fraction. Thus, engaging in physical activity prevents childhood acute lymphoblastic leukemia survivors' cardiac dysfunctions. These findings are novel and clinically relevant in pediatric cardiooncology and provide additional evidence to strengthen the benefits of exercise as long-term care in childhood cancer survivors.

Relationships between personality traits, high school sports participation, and physical activity of college students in the United States

Objective: The study aimed to 1) examine relationships between contexts of PA, personality traits, and high school sports participation (sports) and 2) determine significant PA correlates in a college population. Participants: 237 undergraduates at a university in the United States between September 2020 and May 2021 participated. Methods: Participants completed a survey evaluating PA, personality traits, sports, and demographic variables. Pearson partial correlations assessed correlations between different PA domains, personality traits, and sports. Conscientiousness was positively associated with all PA measures (r = .14-.30), except for active transport PA. Sports were related to vigorous and leisure PA. Conscientiousness is related to PA measures and is a significant PA correlate. However, more research is necessary to understand if leisure time PA can enhance Conscientiousness.

Cardiorespiratory fitness, regular physical activity, and autonomic nervous system reactivity to laboratory and daily life stress

The cross-stressor adaptation hypothesis-which posits that adjustment to physical stress as a result of regular physical activity and its effects on fitness crosses over to psychological stress reactivity-has been around for over four decades. However, the literature has been plagued by heterogeneities preventing definitive conclusions. We address these heterogeneity issues in a combined laboratory and daily life study of 116 young adults (M = 22.48 SD = 3.56, 57.76% female). The exposure, i.e., the potential driver of adaptation, was defined in three ways. First, a submaximal test was performed to obtain aerobic fitness measured as the VO₂ max (kg/ml/min). Second, leisure time exercise behavior, and third, overall moderate-to-vigorous physical activity (MVPA), were obtained from a structured interview. Outcomes were autonomic nervous system (ANS) reactivity and affective responsiveness to stressors. ANS activity was measured continuously and expressed as inter-beat-interval (IBI), pre-ejection-period (PEP), respiratory sinus arrythmia (RSA), and non-specific Skin Conductance Responses (ns.SCR). Negative and positive affect were recorded after each experimental condition in the laboratory and hourly in daily life with a nine-item digital questionnaire. Linear regressions were performed between the three exposure measures as predictors and the various laboratory and daily life stress measurements as outcomes. Our results support the resting heart rate reducing effect of aerobic fitness and total MVPA in both the laboratory and daily life. We did not find evidence for the cross-stressor adaptation hypothesis, irrespective of ANS or affective outcome measure or whether the exposure was defined as exercise/MVPA or aerobic fitness.

Genetic Pathways Underlying Individual Differences in Regular Physical Activity

Twin and family studies show a strong contribution of genetic factors to physical activity (PA) assessed by either self-report or accelerometers. PA heritability is around 43% across the lifespan. Genome-wide association studies have implied biological pathways related to exercise ability and enjoyment. A polygenic score based on genetic variants influencing PA could help improve the success of intervention programs.

Exercise sustains the hallmarks of health

Exercise has long been known for its active role in improving physical fitness and sustaining health. Regular moderate-intensity exercise improves all aspects of human health and is widely accepted as a preventative and therapeutic strategy for various diseases. It is well-documented that exercise maintains and restores homeostasis at the organismal, tissue, cellular, and molecular levels to stimulate positive physiological adaptations that consequently protect against various pathological conditions. Here we mainly summarize how moderate-intensity exercise affects the major hallmarks of health, including the integrity of barriers, containment of local perturbations, recycling and turnover, integration of circuitries, rhythmic oscillations, homeostatic resilience, hormetic regulation, as well as repair and regeneration. Furthermore, we summarize the current understanding of the mechanisms responsible for beneficial adaptations in response to exercise. This review aimed at providing a comprehensive summary of the vital biological mechanisms through which moderate-intensity exercise maintains health and opens a window for its application in other health interventions. We hope that continuing investigation in this field will further increase our understanding of the processes involved in the positive role of moderate-intensity exercise and thus get us closer to the identification of new therapeutics that improve quality of life.

Genome-wide association analyses of physical activity and sedentary behavior provide insights into underlying mechanisms and roles in disease prevention

Although physical activity and sedentary behavior are moderately heritable, little is known about the mechanisms that influence these traits. Combining data for up to 703,901 individuals from 51 studies in a multi-ancestry meta-analysis of genome-wide association studies yields 99 loci that associate with self-reported moderate-to-vigorous intensity physical activity during leisure time (MVPA), leisure screen time (LST) and/or sedentary behavior at work. Loci associated with LST are enriched for genes whose expression in skeletal muscle is altered by resistance training. A missense variant in ACTN3 makes the alpha-actinin-3 filaments more flexible, resulting in lower maximal force in isolated type IIA muscle fibers, and possibly protection from exercise-induced muscle damage. Finally, Mendelian randomization analyses show that beneficial effects of lower LST and higher MVPA on several risk factors and diseases are mediated or confounded by body mass index (BMI). Our results provide insights into physical activity mechanisms and its role in disease prevention.

Genome-wide Association Study of Liking for Several Types of Physical Activity in the UK Biobank and Two Replication Cohorts

INTRODUCTION

A lack of physical activity (PA) is one of the most pressing health issues today. Our individual propensity for PA is influenced by genetic factors. Stated liking of different PA types may help capture additional and informative dimensions of PA behavior genetics.

METHODS

In over 157,000 individuals from the UK Biobank, we performed genome-wide association studies of five items assessing the liking of different PA types, plus an additional derived trait of overall PA-liking. We attempted to replicate significant associations in the Netherlands Twin Register (NTR) and TwinsUK. Additionally, polygenic scores (PGS) were trained in the UK Biobank for each PA-liking item and for self-reported PA behavior, and tested for association with PA in the NTR.

RESULTS

We identified a total of 19 unique significant loci across all five PA-liking items and the overall PA-liking trait, and these showed strong directional consistency in the replication cohorts. Four of these loci were previously identified for PA behavior, including CADM2 , which was associated with three PA-liking items. The PA-liking items were genetically correlated with self-reported ( rg = 0.38-0.80) and accelerometer ( rg = 0.26-0.49) PA measures, and with a wide range of health-related traits. Each PA-liking PGS significantly predicted the same PA-liking item in NTR. The PGS of liking for going to the gym predicted PA behavior in the NTR ( r2 = 0.40%) nearly as well as a PGS based on self-reported PA behavior ( r2 = 0.42%). Combining the two PGS into a single model increased the r2 to 0.59%, suggesting that PA-liking captures distinct and relevant dimensions of PA behavior.

CONCLUSIONS

We have identified the first loci associated with PA-liking and extended our understanding of the genetic basis of PA behavior.

Restlessness and an Increased Urge to Move (Drive for Activity) in Anorexia Nervosa May Strengthen Personal Motivation to Maintain Caloric Restriction and May Augment Body Awareness and Proprioception: A Lesson From Leptin Administration in Anorexia Nervosa

Anorexia nervosa (AN), a disorder of voluntary food restriction leading to severe weight loss in female adolescents, remains an enigma. In particular, the appropriation of the starved thin body into the self-concept in AN is a process insufficiently researched and still poorly understood. Healthy humans undergoing starvation experience a slowing of movements and avoid voluntary exercise. By contrast, AN tends to be not infrequently associated with voluntary, sometimes excessive and/or compulsive exercise. Such deliberate exercise, not reported in starvation, seems to be facilitated by an increased urge for movement and physical restlessness, particular to AN. The increased urge to move would reflect spontaneous daily activity, the energy expended for everything that is not sleeping, eating, or voluntary exercise. Our hypothesis is that the starvation-induced increased urge to move and restlessness may promote the development of AN. Reversal of the fasting state, by either high caloric food or by leptin administration, would be expected to reduce restlessness and the increased urge to move along with improvement in other symptoms in AN. This review explores the idea that such restless activation in AN, in itself and through accelerating body weight loss, might foster the integration of the starving body into the self-concept by (1) enhancing the person’s sense of self-control and sense of achievement and (2) through invigorating proprioception and through intensifying the perception of the changing body shape. (3) Tentative evidence from studies piloting leptin administration in chronic AN patients which support this hypothesis is reviewed. The findings show that short term administration of high doses of leptin indeed mitigated depressive feelings, inner tension, intrusive thoughts of food, and the increased urge to be physically active, easing the way to recovery, yet had little influence on the patients’ personal commitment to remain at a low weight. Full recovery then requires resolution of the individuals’ personal unresolved psychological conflicts through psychotherapy and frequently needs specialized treatment approaches to address psychiatric co-morbidities. AN might be conceptualized as a hereditary form of starvation resistance, facilitated by the effects of starvation on fitness allowing for an exceptionally intense personal commitment to perpetuate food restriction.

Affective response to physical activity as a deep phenotype in a non-randomized pilot study

Large-scale genomic studies are beginning to identify genetic predictors of physical activity (PA). For those genetically predisposed to engage in low PA, a behavioral intervention may target a malleable factor that mediates genetic predisposition to low PA (i.e., intermediate phenotype) to mitigate the genetic influences. In a non-randomized exercise promotion pilot study, we test the feasibility of examining affective response to PA (how one feels during PA) as an intermediate phenotype between genetic variation and PA adherence. We hypothesized that three single nucleotide polymorphisms (SNPs; rs8044769 and rs3751812 in FTO; rs6265 in BDNF), identified from a prior systematic review, would be predictive of affective response to PA, and that affective response to PA would mediate the SNP-PA link. Forty five healthy, low-active adults received a 12-week print-based PA promotion program. Baseline affective response to PA was assessed using the Feeling Scale, a single-item measure of affective valence. Moderate to vigorous PA (MVPA) was assessed using accelerometers pre- and post-intervention. We examined the three SNPs in a weighted genetic score. Age, sex, body mass index, race, and neighborhood walkability were potential covariates. Affective response to PA and MVPA at follow-up (minutes/day over 4-7 days) were regressed on variation in SNPs, controlling for covariates. One unit increase in genetic score was associated with a 0.14 higher mean Feeling Scale, though was not statistically significant (p = 0.13). Among individual SNPs, having an additional FTO rs8044769 C allele was associated with a mean Feeling Scale score of 0.53 units higher (p = 0.015), which was statistically significant after applying the corrected p-value of 0.016. The genetic score or individual SNPs were not predictive of MVPA 12 weeks later, thereby mediation analyses were not performed. The preliminary findings demonstrate the promise of the intermediate phenotype approach.

Does exercise prevent major non-communicable diseases and premature mortality? A critical review based on results from randomized controlled trials

Observational studies show that physical activity is strongly associated with a reduced risk of premature mortality and major non-communicable diseases. We reviewed to which extent these associations have been confirmed in randomized controlled trials (RCTs) for the outcomes of mortality, cardiovascular disease (CVD), type 2 diabetes (T2D), and fracture. The results show that exercise does not reduce all-cause mortality and incident CVD in older adults or in people with chronic conditions, based on RCTs comprising ∼50,000 participants. The results also indicate a lack of effect on cardiovascular mortality in people with chronic conditions, based on RCTs comprising ∼11,000 participants. Furthermore, there is inconsistent evidence regarding the effect of exercise on fractures in older adults, based on RCTs comprising ∼40,000 participants. Finally, based on RCTs comprising ∼17,000 participants, exercise reduces T2D incidence in people with prediabetes when combined with dietary modification, although evidence for the individual effect of exercise is lacking. Identified shortcomings of the current evidence include risks of publication bias, lack of high-quality studies in certain high-risk populations, and inconstant evidence with respect to some outcomes. Thus, additional large trials would be of value, especially with fracture as the primary outcome. In conclusion, according to current RCT evidence, exercise can prevent T2D assuming it is combined with dietary intervention. However, the current evidence shows that exercise does not prevent premature mortality or CVD, with inconsistent evidence for fractures.

Changes in leisure-time physical activity during the adult life span and relations to cardiovascular risk factors-Results from multiple Swedish studies

OBJECTIVE

To evaluate how self-reported leisure-time physical activity (PA) changes during the adult life span, and to study how PA is related to cardiovascular risk factors using longitudinal studies.

METHODS

Several Swedish population-based longitudinal studies were used in the present study (PIVUS, ULSAM, SHE, and SHM, ranging from hundreds to 30,000 participants) to represent information across the adult life span in both sexes. Also, two cross-sectional studies were used as comparison (EpiHealth, LifeGene). PA was assessed by questionnaires on a four or five-level scale.

RESULTS

Taking results from several samples into account, an increase in PA from middle-age up to 70 years was found in males, but not in females. Following age 70, a decline in PA was seen. Young adults reported both a higher proportion of sedentary behavior and a higher proportion high PA than the elderly. Females generally reported a lower PA at all ages. PA was mainly associated with serum triglycerides and HDL-cholesterol, but also weaker relationships with fasting glucose, blood pressure and BMI were found. These relationships were generally less strong in elderly subjects.

CONCLUSION

Using data from multiple longitudinal samples the development of PA over the adult life span could be described in detail and the relationships between PA and cardiovascular risk factors were portrayed. In general, a higher or increased physical activity over time was associated with a more beneficial cardiovascular risk factor profile, especially lipid levels.

The Moderating Effects of Genetic Variations on Changes in Physical Activity Level and Cardiorespiratory Fitness in Response to a Life-Style Intervention: A Randomized Controlled Trial

OBJECTIVE

Prior studies identified single nucleotide polymorphisms (SNPs) associated with physical activity (PA) level in a natural environment and intervention study: rs978656-DNAPTP6, rs10887741-PAPSS2, rs7279064-C18orf2, and rs6265-BDNF. Using the four SNPs' polygenic score (PGS), we examined whether PGS moderates a life-style intervention's effect on changes in PA level and cardiorespiratory fitness (CRF).

METHODS

This is a secondary analysis of Look AHEAD, a multicenter randomized controlled trial designed to test the health benefits of a life-style intervention among 2675 participants with overweight/obesity and type 2 diabetes (ages, 45-76 years). Using linear mixed-effects models, level of PA (Paffenbarger PA questionnaire) and treadmill-assessed CRF were each regressed on four SNPs' PGS, study time (baseline, year 1, and year 4), intervention arm, and interactions between the three. Models adjusted for age, sex, body mass index, ancestry principal components (population stratification), and study sites, with Bonferroni corrections for multiple testing (α < .005). Effect modification by age was examined.

RESULTS

PGS was not predictive of change in CRF or PA level in response to intervention. In analyses without PGS by intervention by time, the relationships between PGS and PA phenotypes were modified by age (p interaction = .048 for CRF and .058 for PA), such that a 1-unit increase in PGS was associated with 24 kcal · wk-1 more in moderate-intensity PA and 0.004 MET higher CRF only among older groups (age >55 years for CRF, >60 years for PA level).

CONCLUSIONS

The effects of the intervention on PA and CRF were not moderated by the four SNPs. Future studies with extended SNP list should confirm the findings on effect modification by age.

Evidence for shared genetics between physical activity, sedentary behaviour and adiposity-related traits

Observational, cross-sectional and longitudinal studies showed that physical activity and sedentary behaviour are associated with adiposity-related traits, apparently in a bidirectional manner. Physical activity is also suggested to suppress the genetic risk of adiposity. Since phenotypic associations with genetic variants are not subject to reverse causation or confounding, they may be used as tools to shed light on cause and effect in this complex interdependency. We review the evidence for shared genetics of physical activity and adiposity-related traits and for gene-by-physical activity interactions on adiposity-related traits in human studies. We outline limitations, challenges and opportunities in studying and understanding of these relationships. In summary, physical activity and sedentary behaviour are genetically correlated with body mass index and fat percentage but may not be correlated with lean body mass. Mendelian randomisation analyses show that physical activity and sedentary behaviour have bidirectional relationships with adiposity. Several studies suggest that physical activity suppresses genetic risk of adiposity. No studies have yet tested whether adiposity enhances genetic predisposition to sedentariness. The complexity of the comprehensive causal model makes the assessment of the single or combined components challenging. Substantial progress in this field may need long-term intervention studies.

Drawing development of identical and non-identical twins: A case study of triplets

Differences in drawing development are conditioned by genetics, environment and individuality of children. Therefore, it is exciting to observe the drawing development in children, who are raised in the same environment and have a similar genetic basis, that is in twins, triplets, and so forth. In the study, we were interested in the similarities and differences in the drawing development of the triplets, two of which were identical twins (B1 and B2) and one was non-identical (A), and whether the characteristics of the drawing appear more congruently between B1 and B2 than with A. We proposed two hypotheses: H1: There are more similarities in drawings between identical twins (B1 vs B2) than between identical and non-identical one (A vs B1 and A vs B2); H2: The differences between non-identical and identical triplets are less pronounced at the beginning of the drawing development (in doodle phase) and become more distinctive in later development, in drawing of figure and space. We analysed 123 drawings that the triplets (41 drawings of each triplet) drew from 1 to 12 years of age at the same time and on the same topic. The results of our research have shown that both hypotheses can be confirmed. On the general level, there are more similarities in drawing between identical twins compared to non-identical ones; and the differences and similarities become more distinctive throughout the development, especially in figure drawing and in the depiction of space.

Genetic and Environmental Influences on Vigorous Exercise in South Korean Adolescent and Young Adult Twins

Twin studies of physical exercise for Asian twins are sparse. This study aimed to examine genetic and environmental influences on frequency of vigorous exercise (FVE) in South Korean twins, with a special emphasis on sex effects. Telephone interviews on FVE were administered to 1757 twins (mean age = 19.05 years, SD = 3.01 years). Tetrachoric correlations were significantly different between monozygotic (MZ) and dizygotic (DZ) twins in males (.40 vs. .12), but they were similar in females (.44 vs. .45), suggesting the importance of genetic factors in FVE in males and that of common environmental factors in females. A scalar sex-limitation model incorporating age as a modifier was applied to data. The results revealed that genetic, common and individual environmental influences did not vary significantly with age, but differed across two sexes, confirming twin correlational analyses. In the best-fitting model, additive genetic and individual environmental influences on FVE were, respectively, .35 (95% CI [.26, .39]) and .65 (95% CI [.61, .74]) in males, and common and individual environmental influences were, respectively, .45 (95% CI [.35, .53]) and .55 (95% CI [.47, .65]) in females. These results contrasted starkly with recent findings from a large sample of Chinese adult twins (age >18 years), in which most variance (≥95%) of vigorous physical activity was attributable to common environmental influences in both sexes. Replications in other Asian samples are clearly needed.

The fit-active profile to better reflect the benefits of a lifelong vigorous physical activity participation: mini-review of literature and population data

Physical activity is favourably considered for its effect on metabolic fitness and body composition. This observation is generally supported by observational studies and is concordant with endurance-trained individuals' metabolic and morphological profiles. However, in some contexts, the measurement of physical activity habits may not provide an adequate representation of its benefits. In this paper, we review relevant literature on the respective effects of fitness and physical activity on anthropometric and metabolic variables and the informative potential of a classification based on aerobic fitness and activity indicators. The relevance to defining a profile based on both fitness and activity is reinforced by data from the Quebec Family Study showing that, in both men and women, "fit-active" individuals displayed a much more favourable morphological and metabolic profile than "unfit-inactive" individuals. Moreover, these benefits seemed to be more related to variations in fitness than in physical activity. In summary, evidence suggests that a profile combining information on aerobic fitness and physical activity may better reflect the lifelong impact of physical activity on body composition and health. Novelty: The fit-active profile better reflects the long-term benefits of vigorous physical activity participation on health. The reported benefits seem to be more related to variations in aerobic fitness than to those in physical activity.

Affective response to physical activity as an intermediate phenotype

Over the past seventy years, biomedical and epidemiological research has shown that regular physical activity (PA) is critical for physical and mental health. Despite this knowledge, physical inactivity is the fourth leading risk factor for global mortality, accounting for 9% (5.3 million) of premature deaths annually. We suggest this mismatch between knowing about the risks of PA and engaging in regular PA can be reconciled by focusing less on expected health benefits of PA and more on how people feel during PA. Specifically, in this position paper, we argue that affective response (feeling good versus bad) to PA is an intermediate phenotype that can explain significant variance in PA behavior and is, in turn, a function of genetic variability. In making this argument, we first review empirical evidence showing that affective response to PA predicts future physical activity behavior. Second, we systematically review research on single nucleotide morphisms (SNPs) that are associated with affective response to PA. Investigating affective response to PA as an intermediate phenotype will allow future researchers to move beyond asking "What SNPs are associated with PA?", and begin asking "How do these SNPs influence PA?", thus ultimately optimizing the translation of knowledge gained from genomic data to intervention development.

Polygenic Risk Scores and Physical Activity

Supplemental digital content is available in the text.

Purpose

Polygenic risk scores (PRS) summarize genome-wide genotype data into a single variable that produces an individual-level risk score for genetic liability. PRS has been used for prediction of chronic diseases and some risk factors. As PRS has been studied less for physical activity (PA), we constructed PRS for PA and studied how much variation in PA can be explained by this PRS in independent population samples.

Methods

We calculated PRS for self-reported and objectively measured PA using UK Biobank genome-wide association study summary statistics, and analyzed how much of the variation in self-reported (MET-hours per day) and measured (steps and moderate-to-vigorous PA minutes per day) PA could be accounted for by the PRS in the Finnish Twin Cohorts (FTC; N = 759–11,528) and the Northern Finland Birth Cohort 1966 (NFBC1966; N = 3263–4061). Objective measurement of PA was done with wrist-worn accelerometer in UK Biobank and NFBC1966 studies, and with hip-worn accelerometer in the FTC.

Results

The PRS accounted from 0.07% to 1.44% of the variation (R²) in the self-reported and objectively measured PA volumes (P value range = 0.023 to <0.0001) in the FTC and NFBC1966. For both self-reported and objectively measured PA, individuals in the highest PRS deciles had significantly (11%–28%) higher PA volumes compared with the lowest PRS deciles (P value range = 0.017 to <0.0001).

Conclusions

PA is a multifactorial phenotype, and the PRS constructed based on UK Biobank results accounted for statistically significant but overall small proportion of the variation in PA in the Finnish cohorts. Using identical methods to assess PA and including less common and rare variants in the construction of PRS may increase the proportion of PA explained by the PRS.

Spexin as an indicator of beneficial effects of exercise in human obesity and diabetes

Spexin is a novel neuropeptide playing an emerging role in metabolic diseases such as obesity and diabetes via involvement in energy homeostasis and food intake. The present study investigated the effects of obesity and type 2 diabetes (T2D) on circulating levels of spexin and its modulation by physical exercise. Normal-weight (n = 50) and obese adults with and without T2D (n = 69 and n = 66, respectively) were enrolled in the study. A subgroup of obese participants (n = 47) underwent a supervised 3-month exercise programme. Plasma spexin levels were measured by ELISA and correlated with various markers. Plasma spexin levels decreased in obese participants with or without T2D compared with those of normal-weight participants (0.43 ± 0.11, 0.44 ± 0.12 and 0.61 ± 0.23 ng/ml, respectively; P < 0.001). Spexin levels negatively correlated with adiposity markers and blood pressure in the whole study population (P < 0.05). Multiple regression analysis revealed blood pressure was the greatest predictive determinant of plasma spexin levels, which significantly increased in response to physical exercise in obese participants without and with T2D (P < 0.05). Spexin levels significantly increased only in responders to exercise (those with increased oxygen consumption, VO₂ max) with a concomitant improvement in metabolic profile. In conclusion, plasma spexin levels may be an indicator of response to physical exercise.

Longitudinal association between body mass index and physical activity among adolescents with different parental risk: a parallel latent growth curve modeling approach

Background

Data available on the association between physical activity (PA) and body mass index (BMI) in different periods of life is controversial. Using a parallel latent growth curve modeling (LGCM) approach, the current study aimed to investigate the influence of daily PA on adolescents’ BMI over a 12 year follow-up, taking into account their parental risk.

Method

Participants comprised 1323 adolescents (53.5% girls), aged 12–18 years who had participated in the baseline phase of Tehran Lipid and Glucose Study (TLGS) (2001–2003), and were followed for an average period of 12 years. Physical activity, including leisure time and occupational activities, was assessed using the reliable and validated Iranian version of the Modifiable Activity Questionnaire (MAQ). Weight and height were objectively measured in order to calculateBMI.Atwo-step cluster analysis was conducted to classify parents into two high- and low-risk clusters. Parallel LGCM was fitted to estimate cross-sectional, prospective and parallel associations, which assessed the longitudinal association between simultaneous changes in PA and BMI during the study period. Analyses were stratified by gender and parental clusters.

Results

A rising trend of BMI per 3 years was observed in boys 1.39 kg.m²(95% CI; 1.32, 1.48) and girls 0.9 kg.m²(95% CI; 0.82, 0.98), as well as in the low risk 1.11 kg.m²(95% CI; 1.03, 1.18) and high-risk 1.12 kg.m²(95% CI; 1.03, 1.22) clusters. Moreover, a positive prospective association between PA at baseline and BMI change over the 12 year follow-up, was observed in adolescents in the low-risk parental cluster 0.27(95% CI; 0.14, 0.41) indicating that higher levels of PA at baseline may lead to greater BMI in adolescents over time. However, examining longitudinal parallel association between simultaneous changes of PA and BMI per 3 years revealed adverse associations for adolescents in the low-risk parental cluster − 0.07 (95% CI; − 0.13, − 0.01) and in boys − 0.06 (95% CI; − 0.11, − 0.01).

Conclusion

Despite a positive prospective association between BMI and PA at baseline, there was a weak inverse parallel association between these variables over time, particularly in boys and adolescents with low parental risk. These findings imply the potential role of other influential factors indetermining adolescents’ weight status which need to be considered in the future plannings.

Calcium-Sensing Receptor Gene Polymorphisms (CASRV1 and CASRV2) and the Physical Activity Level of Men in Lower Silesia, Poland

Calcium-sensing receptors (CASR) are a dimeric family of C-class G-protein-coupled receptors that play a crucial role in bone and mineral metabolism by regulating parathyroid hormone (PTH) secretion, skeletal development, and urinary Ca²⁺ excretion. Genetic factors mainly impact bone mineral density (BMD). However, many variable factors may affect bone health, including physical activity. The aim of our study was to investigate the potential associations between calcium-sensing receptor gene polymorphisms (CASRV1 and CASRV2) and the level of physical activity in adult males from Lower Silesia, a region in the south of Poland. A total of 428 adult male inhabitants of Lower Silesia were included in the study. Their physical activity was evaluated using the International Physical Activity Questionnaire. The CASRV1 (rs 1801725, G>T, A986S) and CASRV2 (rs 761486, T>G, non-coding region) polymorphisms were determined using polymerase chain reaction (PCR) and mini-sequencing. The polymorphisms were identified with GeneScan software ver. 3.1.2. We did not observe any statistically significant differences between the total energy expenditure (total MET) and the CASRV1 and CASRV2 polymorphisms. We did not find any association between the level of physical activity and the frequency of genotypes at the polymorphic locus of the calcium-sensing receptor genes CASRV1 and CASRV2. We found that the number of hours the subjects spent in a sitting position was unrelated to the genotypes at the polymorphic locus of the calcium-sensing receptor gene CASRV1. Based on our studies, we concluded that there were no associations between CASR and physical activity in the men inhabiting Lower Silesia in Poland. Our results do not suggest any influence of the assessed genetic factors in the population variability of the level of physical activity of adults.

Twin studies on the association of physical activity with cognitive and cerebral outcomes

Regular physical activity (PA) offers positive effects on the human body. However, the effects of PA on cognition and in the brain are less clear. In this paper, we narratively review the relationship of PA with cognition and dementia, first from general perspective and then through genetically informed studies on the topic. Then we move on to imaging studies on exercise and brain anatomy first by presenting an overall picture of the topic and then discussing brain imaging studies addressing PA and brain structure in twins in more detailed way. Regarding PA and cognition or dementia, genetically informed studies are uncommon, even though the relationship between PA and cognitive ageing has been extensively studied. It is challenging to find twin pairs discordant for PA and dementia. Concerning brain imaging studies, among PA discordant young adult twin pairs, the more active co-twins showed larger gray matter volumes in striatal, prefrontal, and hippocampal regions and in electrophysiological studies automatic deviance-detection processes differed in brain regions involved with sensorimotor, visual and memory functions.

Genetic Networks Underlying Natural Variation in Basal and Induced Activity Levels in Drosophila melanogaster

Exercise is recommended by health professionals across the globe as part of a healthy lifestyle to prevent and/or treat the consequences of obesity. While overall, the health benefits of exercise and an active lifestyle are well understood, very little is known about how genetics impacts an individual's inclination for and response to exercise. To address this knowledge gap, we investigated the genetic architecture underlying natural variation in activity levels in the model system Drosophila melanogaster Activity levels were assayed in the Drosophila Genetics Reference Panel fly strains at baseline and in response to a gentle exercise treatment using the Rotational Exercise Quantification System. We found significant, sex-dependent variation in both activity measures and identified over 100 genes that contribute to basal and induced exercise activity levels. This gene set was enriched for genes with functions in the central nervous system and in neuromuscular junctions and included several candidate genes with known activity phenotypes such as flightlessness or uncoordinated movement. Interestingly, there were also several chromatin proteins among the candidate genes, two of which were validated and shown to impact activity levels. Thus, the study described here reveals the complex genetic architecture controlling basal and exercise-induced activity levels in D. melanogaster and provides a resource for exercise biologists.

Heritability of objectively assessed and self-reported sedentary behavior

Understanding the sources of the large individual differences in sedentary behavior is of great importance as this behavior is associated with pre-mature mortality and non-communicable diseases. Here, we report on the contribution of genetic and environmental factors to the variation in objectively assessed (accelerometer) sedentary behavior and self-reported sitting and their shared genetic basis. In addition, the overlap of the genetic risk factors influencing sedentary time and moderate-to-vigorous physical activity (MVPA) was estimated. A sample of 800 individuals (twins and their siblings) was equipped with an Actigraph accelerometer for 7 days and reported on their sitting time and time spent on MVPA on those days using the IPAQ-SF. Genetic factors explained 56% (CI: 44%, 65%) of the individual differences in objective sedentary behavior (Actigraph) and 26% (CI: 0%, 51%) of the individual differences in self-reported sedentary behavior (IPAQ-SF). A modest correlation (0.33) was found between these measures, which was for 45% accounted for by genetic influences. The genetic correlation was 0.49 reflecting a partly overlapping set of genes that influenced both measurements. A modest correlation (-0.27) between Actigraph-derived sedentary time and MVPA was found, which was 13% accounted for by genetic effects. The genetic correlation was -0.31, indicating that there are overlapping genetic variants that increase sedentary time and decrease MVPA or vice versa. To conclude, more than half of the individual differences in objective sedentary time could be attributed to genetic differences, while for self-reported sitting this was much lower. In addition, using objective measurements, this study confirms that sedentary time is not simply the inverse of MVPA. Future studies are needed to understand the pathways translating genomic variation into variation in these behaviors and how this knowledge might feed into the development of health promotion interventions.

The effects of dopamine receptor genes on the trajectories of sport participation from adolescence through young adulthood

Background: Although previous studies suggest that dopamine receptor genes partially affect physical activity-related behaviours, all of these studies were cross-sectional studies that examined the effects of dopamine receptor genes on physical activity-related behaviours at some point in time. Therefore, the nature and extent of this relationship across the lifespan are even more uncertain.Aim: The purpose of this study is to examine the effects of dopamine receptor genes (i.e. DRD2, DRD4 and DRD5) on sport participation trajectories from adolescence to young adulthood.Subjects and methods: This study used the National Longitudinal Study of Adolescent Health data (wave 1-4). Group-based trajectory modelling was used to investigate the effect of dopamine receptor genes on the probability of being in each sport participation trajectory group.Results: A three-group model was the best fitting model for men whereas a two-group model was the best fitting model for women. The more participants possess the A1 allele of the DRD2, the less likely they are to be in the "high-decreasing group" rather than the "low-stable group" in both men and women. In male participants, the more participants carry the A1 allele of the DRD2, the more likely they are to be in the "high-stable group" rather than the "high-decreasing group" (coefficient = 0.206, p<.05).Conclusions: These results can contribute to the literature by providing important information on the effects of dopamine receptor genes on sport participation trajectories from adolescence through young adulthood.

Distribution of allele frequencies for genes associated with physical activity and/or physical capacity in a homogenous Norwegian cohort- a cross-sectional study

BACKGROUND

There are large individual differences in physical activity (PA) behavior as well as trainability of physical capacity. Heritability studies have shown that genes may have as much impact on exercise participation behavior as environmental factors. Genes that favor both trainability and participation may increase the levels of PA. The present study aimed to assess the allele frequencies in genes associated with PA and/or physical capacity, and to see if there is any association between these polymorphisms and self-reported PA levels in a cohort of middle-aged Norwegians of Scandinavian descent (n = 831; mean age mean age (± SD) 55.5 ± 3.8 years).

RESULTS

The genotype distributions of the ACTN3 R577X, ACE I/D and MAOA uVNTR polymorphisms were similar to other populations of European descent. When comparing the genotype distribution between the low/medium level PA group (LMPA) and high level PA groups (HPA), a significant difference in ACTN3 577X allele distribution was found. The X allele frequency was 10% lower in the HPA level group (P = 0.006). There were no differences in the genotype distribution of the ACE I/D or MAOA uVNTR polymorphism. Education and previous participation in sports or outdoor activities was positively associated with the self-reported PA levels (P ≤ 0.001).

CONCLUSIONS

To the best of our knowledge, this is the first study to report association between ACTN3 R577X genotype and PA level in middle-aged Scandinavians. Nevertheless, the contribution of a single polymorphism to a complex trait, like PA level, is likely small. Socioeconomic variables, as education and previous participation in sports or outdoor activities, are positively associated with the self-reported PA levels.

Omics and the molecular exercise physiology

Exercise is a well-known non-pharmacologic agent used to prevent and treat a wide range of pathologic conditions such as metabolic and cardiovascular disease. In this sense, the classic field of exercise physiology has determined the main theoretical and practical bases of physiologic adaptations in response to exercise. However, the last decades were marked by significant advances in analytical laboratory techniques, where the field of biochemistry, genetics and molecular biology promoted exercise science to enter a new era. Regardless of its application, whether in the field of disease prevention or performance, the association of molecular biology with exercise physiology has been fundamental for unveiling knowledge of the molecular mechanisms related to the adaptation to exercise. This chapter will address the natural evolution of exercise physiology toward genetics and molecular biology, emphasizing the collection of integrated analytical approaches that composes the OMICS and their contribution to the field of molecular exercise physiology.

Fat oxidation at rest and during exercise in male monozygotic twins

PURPOSE

We aimed to investigate if hereditary factors, leisure-time physical activity (LTPA) and metabolic health interact with resting fat oxidation (RFO) and peak fat oxidation (PFO) during ergometer cycling.

METHODS

We recruited 23 male monozygotic twin pairs (aged 32-37 years) and determined their RFO and PFO with indirect calorimetry for 21 and 19 twin pairs and for 43 and 41 twin individuals, respectively. Using physical activity interviews and the Baecke questionnaire, we identified 10 twin pairs as LTPA discordant for the past 3 years. Of the twin pairs, 8 pairs participated in both RFO and PFO measurements, and 2 pairs participated in either of the measurements. We quantified the participants' metabolic health with a 2-h oral glucose tolerance test.

RESULTS

Fat oxidation within co-twins was correlated at rest [intraclass correlation coefficient (ICC) = 0.54, 95% confidence interval (CI) 0.15-0.78] and during exercise (ICC = 0.67, 95% CI 0.33-0.86). The LTPA-discordant pairs had no pairwise differences in RFO or PFO. In the twin individual-based analysis, PFO was positively correlated with the past 12-month LTPA (r = 0.26, p = 0.034) and the Baecke score (r = 0.40, p = 0.022) and negatively correlated with the area under the curve of insulin (r = - 0.42, p = 0.015) and glucose (r = - 0.31, p = 0.050) during the oral glucose tolerance test.

CONCLUSIONS

Hereditary factors were more important than LTPA for determining fat oxidation at rest and during exercise. Additionally, PFO, but not RFO, was associated with better metabolic health.

Genetic variation in health insurance coverage

We provide the first investigation into whether and how much genes explain having health insurance coverage or not and possible mechanisms for genetic variation. Using a twin-design that compares identical and non-identical twins from a national sample of US twins from the National Survey of Midlife Development in the United States, we find that genetic effects explain over 40% of the variation in whether a person has any health coverage versus not, and nearly 50% of the variation in whether individuals younger than 65 have private coverage versus whether they have no coverage at all. Nearly one third of the genetic variation in being uninsured versus having private coverage is explained by employment industry, self-employment status, and income, and together with education, they explain over 40% of the genetic influence. Marital status, number of children, and available measures of health status, risk preferences, and prevention effort do not appear to be important channels for genetic effects. That genes have meaningful effects on the insurance status suggests an important source of heterogeneity in insurance take up.

Genomewide Association Study of Leisure-Time Exercise Behavior in Japanese Adults

Supplemental digital content is available in the text.

Purpose

Although several genetic factors may play a role in leisure-time exercise behavior, there is currently no evidence of a significant genomewide association, and candidate gene replication studies have produced inconsistent results.

Methods

We conducted a two-stage genomewide association study and candidate single-nucleotide polymorphisms (SNP) association study on leisure-time exercise behavior using 13,980 discovery samples from the Japan Multi-Institutional Collaborative Cohort (J-MICC) study, and 2036 replication samples from the Hospital-based Epidemiologic Research Program at Aichi Cancer Center-2 study. Leisure-time physical activity was measured using a self-administered questionnaire that inquired about the type, frequency and duration of exercise. Participants with ≥4 MET·h·wk⁻¹ of leisure-time physical activity were defined as exhibiting leisure-time exercise behavior. Association testing using mixed linear regression models was performed on the discovery and replication samples, after which the results were combined in a meta-analysis. In addition, we tested six candidate genetic variants derived from previous genomewide association study.

Results

We found that one novel SNP (rs10252228) located in the intergenic region between NPSR1 and DPY19L1 was significantly associated with leisure-time exercise behavior in discovery samples. This association was also significant in replication samples (combined P value by meta-analysis = 2.2 × 10⁻⁹). Several SNP linked with rs10252228 were significantly associated with gene expression of DPY19L1 and DP19L2P1 in skeletal muscle, heart, whole blood, and the nervous system. Among the candidate SNP, rs12612420 in DNAPTP6 demonstrated nominal significance in discovery samples but not in replication samples.

Conclusions

We identified a novel genetic variant associated with regular leisure-time exercise behavior. Further functional studies are required to validate the role of these variants in exercise behavior.

Genetic Factors Associated With Human Physical Activity: Are Your Genes Too Tight To Prevent You Exercising?

The benefits of physical activity (PA) on health and fitness are well known. It has become apparent from studies of heritability that there is a considerable genetic component to PA. However, PA is such a complex phenotype that the measurement and quantification of it provide a challenge to a clearer understanding of its genetic basis. In this review, we assessed available evidence from family and twin studies that have estimated the heritability of PA. Heritability is greater when evaluated by accelerometry compared with questionnaires, and for questionnaires higher in twin than family studies. Accelerometry studies suggest heritability of PA is 51% to 56%. There have been many genome-wide linkage studies, candidate gene studies, and four genome-wide association studies that have highlighted specific genetic factors linked to different PA levels. These studies have generally failed to replicate identified loci, with the exception of the melanocortin 4 receptor, and this may be because of the variability in the measurement techniques used to characterize the behavior. Future work should aim to standardize the procedures used to measure PA in the context of trying to identify genetic causes. The link of genetics to physical exercise is not so tight that it prevents voluntary interventions.

Association of parental body mass index (BMI) with child's health behaviors and child's BMI depend on child's age

Background

Parent’s and child’s body mass index (BMI) are strongly associated, but their relationship varies by child’s sex and age. Parental BMI reflects, among other factors, parents’ behaviors and home environment, which influence their child’s behaviors and weight. This study examined the indirect effect of parent’s BMI on child’s BMI via child health behaviors, conditional on child’s sex and age.

Methods

Data from 2039 children and 1737 parents from eight cities of the U.S. involved in the Childhood Obesity Research Demonstration project tested the association between parental BMI and child’s percentage of 95th BMI percentile (%BMIp95). A generalized structural equation modeling approach to path analysis was used to estimate and test simultaneously the associations among parental BMI and child’s health behaviors and BMI across three age groups (preschool 2-4 yr., elementary 5-10 yr., and middle school 11-12 yr). Child’s health behaviors were examined as mediators.

Results

Parental BMI was related to %BMIp95 across all age groups, and was strongest in 11-12 yr. children. Parental BMI was positively associated with boys’ fruit and vegetable (FV) intake and girls’ sugar-sweetened beverage (SSB) intake. Compared to 2-4 yr., older children had less FVs and physical activity, more screen time and SSB, and higher %BMIp95. Mediation effects were not significant.

Conclusions

Parental BMI was associated with child’s %BMIp95 and some child behaviors, and this association was stronger in older children; older children also exhibited less healthy behaviors. Age- and sex-specific interventions that focus on age-related decreases in healthy behaviors and parental strategies for promoting healthy behaviors among at-risk children are needed to address this epidemic of childhood obesity.

Tracking of voluntary exercise behaviour over the lifespan

Background

The aim of many physical activity interventions is to develop life-long habits of regular exercise and sports activities in leisure time. Previous studies that assessed tracking (i.e. the stability of a trait over the lifespan) of leisure time exercise behaviour across various parts of the life span have treated it as a uniform construct by summing all types of leisure time exercise activities into a single summary score for the total volume of exercise. This study provides new insight by additionally determining tracking across leisure time exercise activities in six different domains: (1) team-based versus solitary activities, (2) competitive versus non-competitive activities, and (3) externally paced versus internally paced activities. We also assessed which of the domains of exercise activities best predicted total volume of exercise at follow-up.

Methods

A large dataset (N = 43,889) from the Netherlands Twin Register (NTR) was used to analyse the tracking of exercise behaviour over time. Using this dataset, we were able to examine tracking as a function of baseline age (8 to 80 years) and tracking duration (2 to 22-year follow-up), taking into account sex differences, using generalized estimating equations.

Results

Two-year tracking coefficients are moderate to high for total volume of exercise across ages at baseline, ranging from .38 to .77 with a median of .57. Tracking coefficients tend to decrease as the distance to follow-up increases, down to a median of .38 for the 22-year tracking coefficients. The patterns of tracking were largely domain-independent and were largely similar for solitary, competitive, non-competitive, externally and internally paced activities. With the exception of team-based activities, tracking was seen to increase as a function of baseline age. Cross-domain tracking did not favour any specific domain of exercise activity as the best predictor for total volume of exercise behaviour and this was true at all baseline ages.

Conclusion

We conclude that exercise behaviour is moderately to highly stable across the life span. In particular in adulthood, where the tracking of exercise mimics that of a classical behavioural trait like personality. This stability reinforces existing evidence that exercise habits are hard to change, but at the same time suggests that successful intervention leading to the adoption of exercise habits will tend to last.

Electronic supplementary material

The online version of this article (10.1186/s12966-019-0779-4) contains supplementary material, which is available to authorized users.

Chronic diseases and objectively monitored physical activity profile among aged individuals - a cross-sectional twin cohort study

INTRODUCTION

High physical activity (PA) at old age indicates good functional capacity enabling independent living. We investigated how different disease conditions are associated with measured PA indicators in old women and men, and whether they recognize this association.

MATERIALS AND METHODS

This cross-sectional twin cohort study in Finland comprised 779 individuals (276 complete twin pairs, including 117 monozygotic pairs), who participated in hip-worn accelerometer monitoring of PA and responded to questions on diseases and mobility limitations at mean age of 73 (range 71-75).

RESULTS

Of the participants, 23.2% reported having a disease restricting mobility. With sex and age in the regression model, the reported disease restricting mobility explained 11.8% of the variation in moderate-to-vigorous PA (MVPA) and 10.4% of the variation in daily steps. Adding stepwise other self-reported diseases and body mass index to the model increased the explanatory power for MVPA up to 18.5% and 25.5%, and for daily steps up to 16.0% and 20.7%, respectively. In the co-twin control analysis the PA differences were smaller in disease-discordant monozygotic than dizygotic pairs.

CONCLUSIONS

Chronic disease conditions are associated with low PA, which individuals may not always recognize. Shared genetic factors may explain part of the associations. Key messages Among community-dwelling older men and women one-fourth of the variation in objectively measured moderate-to-vigorous physical activity is accounted for by age, sex, body mass index and self-reported diseases. Occurrence of chronic diseases is associated with low physical activity and individuals do not always recognize this. Healthcare professionals should pay attention to the low physical activity and mobility of individuals with chronic disease conditions before these result in limitations in independent living.

Elevated Familial Cardiovascular Burden Among Adolescents With Familial Bipolar Disorder

Background: Bipolar disorder (BD) is one of the most heritable medical conditions, and certain phenotypic characteristics are especially familial in BD. BD is also strongly associated with elevated and premature cardiovascular disease (CVD) morbidity and mortality. Thus, far, little is known regarding the familiality of cardiovascular risk in BD. We therefore examined the extent of CVD-related conditions among relatives of: adolescents with BD with a family history of BD (familial BD), adolescents with BD without a family history of BD (non-familial BD) and healthy controls (HC). Materials and Methods: The sample included 372 adolescents; 75 with familial BD, 96 with non-familial BD, and 201 HC. Parents of the adolescents completed the CARDIA Family Medical History interview regarding the adolescents' first- and second- degree adult relatives. We computed a "cardiovascular risk score" (CRS) for each relative, based on the sum of the presence of diabetes, hypertension, obesity, dyslipidemia, stroke, angina, and myocardial infarction (range 0-7). Primary analyses examined for group differences in mean overall CRS scores among first and second- degree relatives combined, controlling for age, sex, and race. Secondary analyses examined first- and second-degree relatives separately, controlling for age, sex, and race. Results: There were significant between-group differences in CRS in first- and second- degree relatives combined, following the hypothesized ordering: CRS was highest among adolescents with familial BD (1.14 ± 0.78), intermediate among adolescents with non-familial BD (0.92 ± 0.79) and lowest in HC (0.76 ± 0.79; F = 6.23, df = 2, p = 0.002, ηp 2 = 0.03). There was a significant pairwise difference between adolescents with familial BD and HC (p = 0.002, Cohen's d = 0.49). A similar pattern of between-group differences was identified when first-degree and second-degree relatives were examined separately. Limitations: familial cardiovascular burden was determined based on parent interview, not evaluated directly. Conclusions: Adolescents with BD with a family history of BD have elevated rates of CVD-related conditions among their relatives. This may be related to genetic overlap between BD and CVD-related conditions, shared environmental factors that contribute to both BD and CVD-related conditions, or a combination of these factors. More research is warranted to better understand the interaction between familial risk for BD and CVD, and to address this risk using family-wide preventive approaches.

Biological/Genetic Regulation of Physical Activity Level: Consensus from GenBioPAC

PURPOSE

Physical activity unquestionably maintains and improves health; however, physical activity levels globally are low and not rising despite all the resources devoted to this goal. Attention in both the research literature and the public policy domain has focused on social-behavioral factors; however, a growing body of literature suggests that biological determinants play a significant role in regulating physical activity levels. For instance, physical activity level, measured in various manners, has a genetic component in both humans and nonhuman animal models. This consensus article, developed as a result of an American College of Sports Medicine-sponsored round table, provides a brief review of the theoretical concepts and existing literature that supports a significant role of genetic and other biological factors in the regulation of physical activity.

CONCLUSIONS

Future research on physical activity regulation should incorporate genetics and other biological determinants of physical activity instead of a sole reliance on social and other environmental determinants.

Self-reported Fitness and Objectively Measured Physical Activity Profile Among Older Adults: A Twin Study

Background

Maintaining good fitness and good level of physical activity are important factors for maintaining physical independence later in life. The aim was to investigate the relationship between self-reported fitness and objectively measured physical activity and sedentary behavior in the elderly.

Methods

Same-sex twin pairs born 1940–1944 in Finland were invited to the study. Altogether 787 individuals (mean age 72.9 years), of whom 404 were female, used a hip-worn triaxial accelerometer for at least 4 days and answered a question on perceived fitness. First, individual differences were studied between four fitness categories. Second, pairwise differences were examined among twin pairs discordant for fitness.

Results

Self-reported fitness explained moderately the variation in objectively measured physical activity parameters: R2 for daily steps 26%, for daily mean metabolic equivalent 31%, for daily moderate-to-vigorous activity time 31%, and lower for sedentary behavior time 14% (all p < .001). Better self-reported fitness was associated with more steps taken on average (8,558 daily steps [very good fitness] vs 2,797 steps [poor fitness], p < .001) and with a higher amount of moderate-to-vigorous activity (61 min vs 12 min p < .001, respectively) in the adjusted multivariable model. Among 156 twin pairs discordant for self-reported fitness, co-twins with better fitness took more steps, did more moderate-to-vigorous activity, and had less sedentary behavior (all, p < .05) compared to their less fit co-twins; however, difference was smaller among monozygotic than dizygotic pairs.

Conclusion

One simple question on self-reported fitness is associated with daily activity profile among community-dwelling older people. However, genetic factors modulate this association to some extent.

Androgen and estrogen actions on male physical activity: a story beyond muscle

Physical inactivity is a pandemic that contributes to several chronic diseases and poses a significant burden on health care systems worldwide. The search for effective strategies to combat sedentary behavior has led to an intensification of the research efforts to unravel the biological substrate controlling activity. A wide body of preclinical evidence makes a strong case for sex steroids regulating physical activity in both genders, albeit the mechanisms implicated remain unclear. The beneficial effects of androgens on muscle as well as on other peripheral functions might play a role in favoring adaptation to exercise. Alternatively or in addition, sex steroids could act on specific brain circuitries to boost physical activity. This review critically discusses the evidence supporting a role for androgens and estrogens stimulating male physical activity, with special emphasis on the possible role of peripheral and/or central mechanisms. Finally, the potential translation of these findings to humans is briefly discussed.

Genome-wide association study of habitual physical activity in over 377,000 UK Biobank participants identifies multiple variants including CADM2 and APOE

BACKGROUND/OBJECTIVES

Physical activity (PA) protects against a wide range of diseases. Habitual PA appears to be heritable, motivating the search for specific genetic variants that may inform efforts to promote PA and target the best type of PA for each individual.

SUBJECTS/METHODS

We used data from the UK Biobank to perform the largest genome-wide association study of PA to date, using three measures based on self-report (nmax = 377,234) and two measures based on wrist-worn accelerometry data (nmax = 91,084). We examined genetic correlations of PA with other traits and diseases, as well as tissue-specific gene expression patterns. With data from the Atherosclerosis Risk in Communities (ARIC; n = 8,556) study, we performed a meta-analysis of our top hits for moderate-to-vigorous PA (MVPA).

RESULTS

We identified ten loci across all PA measures that were significant in both a basic and a fully adjusted model (p < 5 × 10-9). Upon meta-analysis of the nine top hits for MVPA with results from ARIC, eight were genome-wide significant. Interestingly, among these, the rs429358 variant in the APOE gene was the most strongly associated with MVPA, whereby the allele associated with higher Alzheimer's risk was associated with greater MVPA. However, we were not able to rule out possible selection bias underlying this result. Variants in CADM2, a gene previously implicated in obesity, risk-taking behavior and other traits, were found to be associated with habitual PA. We also identified three loci consistently associated (p < 5 × 10-5) with PA across both self-report and accelerometry, including CADM2. We found genetic correlations of PA with educational attainment, chronotype, psychiatric traits, and obesity-related traits. Tissue enrichment analyses implicate the brain and pituitary gland as locations where PA-associated loci may exert their actions.

CONCLUSIONS

These results provide new insight into the genetic basis of habitual PA, and the genetic links connecting PA with other traits and diseases.

Twin studies for the prognosis, prevention and treatment of musculoskeletal conditions

BACKGROUND

Musculoskeletal conditions are highly prevalent in our ageing society and are therefore incurring substantial increases in population levels of years lived with disability (YLD). An evidence-based approach to the prognosis, prevention, and treatment of those disorders can allow an overall improvement in the quality of life of patients, while also softening the burden on national health care systems.

METHODS

In this Masterclass article, we provide an overview of the most relevant twin study designs, their advantages, limitations and major contributions to the investigation of traits related to the domain of musculoskeletal physical therapy.

CONCLUSIONS

Twin studies can be an important scientific tool to address issues related to musculoskeletal conditions. They allow researchers to understand how genes and environment combine to influence human health and disease. Twin registries and international collaboration through existing networks can provide resources for achieving large sample sizes and access to expertise in study design and analysis of twin data.

A genetic variant in IL-15Rα correlates with physical activity among European-American adults

BACKGROUND

Interleukin-15 (IL-15) is a myokine associated with muscle strength, possibly by attenuating protein breakdown. A variant in the alpha-receptor (IL-15Rα 1775 A>C, rs2228059) partially modulates the muscle strength and size response to resistance training. We examined if this polymorphism associated with habitual physical activity among European-American adults.

METHODS

Men (n = 240, 23.7 ± 0.3 year, body mass index [BMI] 25.3 ± 0.3 kg/m2 ) and women (n = 292, 23.2 ± 0.3 year, 24.0 ± 0.3 kg/m2 ) were genotyped. Physical activity phenotypes were derived from the Paffenbarger Physical Activity Questionnaire. Analysis of covariance (ancova) tested log-transformed differences between the IL-15Rα genotype and physical activity phenotypes by gender with age and BMI as covariates.

RESULTS

Men with the IL-15Rα 1775AA genotype spent more time in light intensity physical activity (39.4 ± 2.4 hr/week) than men with the CC genotype (28.6 ± 2.3 hr/week, (p = .009).

CONCLUSION

Further research is needed to confirm our finding and determine the possible mechanisms by which the IL-15Rα variant modulates light intensity physical activity.

Is physical activity a cause of longevity? It is not as straightforward as some would believe. A critical analysis

There are discrepant findings between (A) observational follow-ups and (B) interventional studies that investigate possible causal association between high physical activity and low mortality. Participation in vigorous physical activity at a specific time-point is an indicator of good fitness and health, and is associated with a reduced risk of death. However, neither randomised controlled trials nor experimental animal studies have provided conclusive evidence to show that physical activity started during adulthood extends lifespan. Consequently, the undisputed health-related benefits of exercise have yet to translate into any proven causal relationship with longevity. Physical activity improves fitness and physical function, and confers other health-related effects. These outcomes have a greater basis in evidence-based data than any claims of a reduced risk of death, especially when recommending physical activity for previously physically inactive middle-aged and elderly adults.

The Interplay between Genes and Psychosocial Home Environment on Physical Activity

INTRODUCTION

Genetic factors contribute to individual differences in physical activity, but it remains uncertain whether the magnitude of the genetic effects is modified by variations in home environments. We aimed to examine to what extent the psychosocial home environment in childhood and adolescence modifies the genetic influences on leisure time physical activity in young adulthood.

METHODS

Participants were Finnish twins (N = 3305) who reported their leisure time physical activity at age 24 yr. The psychosocial home environment was assessed by twins at ages 12, 14, and 17 yr, as well as by their parents when the twins were age 12 yr. Gene-environment interaction modeling was performed with OpenMx software.

RESULTS

Parental ratings of positive home atmosphere as well as the twins' ratings of both positive home atmosphere at age 14 yr and lower relational tensions at ages 12 and 14 yr predicted higher leisure time physical activity levels in young adulthood (regression coefficients = 0.33-0.64). Parental perceptions as well as the twins' perceptions of positive home atmosphere at ages 14 and 17 yr increased the additive genetic variation (moderation effects: 0.55, 95% confidence interval [CI] = 0.29-0.80; 0.60, 95% CI = 0.26-1.05; and 0.52, 95% CI = 0.19-0.87, respectively). The twins' ratings of positive home atmosphere at age 12 yr and lower relational tensions at ages 12 and 14 yr increased the unique environmental variation of their subsequent physical activity (moderation effects: 0.46, 95% CI = 0.19-0.60; 0.48, 95% CI = 0.29-0.64; and 0.85, 95% CI = 0.12-0.95, respectively).

CONCLUSIONS

A psychosocial home environment that is warm and supportive in childhood and adolescence not only increases the mean level of subsequent leisure time physical activity in young adulthood but also modifies the genetic and environmental variances in leisure time physical activity.