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PubMed2007

Direct fitness or inclusive fitness: how shall we model kin selection?

Two standard mathematical formulations of kin-selection models can be found. Inclusive fitness is an actor-centred approach, which calculates the fitness effect on a number of recipients of the behaviour of a single actor. Direct fitness is a recipient-centred approach, which calculates the fitness effect on the recipient of the behaviour of a number of actors. Inclusive fitness offers us a powerful heuristic, of choosing behaviour to maximize fitness, but direct fitness can be mathematically easier to work with and has recently emerged as the preferred approach of theoreticians. In this paper, we explore the fundamental connection between these two approaches in both homogeneous and class-structured populations, and we show that under simple assumptions (mainly fair meiosis and weak selection) they provide equivalent formulations, which correspond to the predictions of Price's equation for allele frequency change. We use a couple of examples to highlight differences in their conception and formulation, and we briefly discuss a two-species example in which we have a class of 'actor' that is never a 'recipient', which the standard direct fitness method can handle but the usual inclusive fitness cannot.

Biological Evolution↗
PubMed1988

Improving the fit of press-fit hip stems.

The implant-bone fit is critical to the longevity of press-fit total hips. Maximum contact on the internal cortical bone surface, especially proximally, produces more normal strain values and reduces micromotion and sinkage. Stem design computer software was developed to design both individualized hip stems that maximize implant-bone contact for a unique anatomy, and average anatomic hip stems in which the mean error of fit is minimized for many patients. Cadaver femurs were used to test the following two hypotheses: (1) Average anatomic stems, designed using the optimal-fit software for an average femoral geometry, improve implant-bone fit when compared with standard stems; and (2) Individualized optimal-fit stems provide an even better fit than average anatomic stems. Results showed that the average anatomical stems fit better than the standard stems. However, the individualized hip stems, designed from individual three-dimensional geometry data, fit the best.

Aged↗
PubMed2026

Impact of Annual School Fitness Reports on Students' Cardiorespiratory Fitness: A Cluster-Randomized Controlled Trial of Parental Reporting.

BACKGROUND: School-based physical fitness testing is an important population health monitoring tool and has the potential to improve student fitness performance. However, few studies exist on the impact of reporting student fitness to parents. METHODS: Using data from the Fit Study (2014-2017) from 12 California public schools, we used mixed-effects models to compare changes in cardiorespiratory fitness (estimated peak oxygen consumption, calculated from the 1-mile run) and strength (curl-ups and push-ups) over 1 and 2 years between students randomized to having their parents receive an annual fitness report (intervention, n = 1638 students) and control (n = 2070) in grades 5 to 8 (ages 10-15 y). The student sample was 47.9% female, 55.9% Hispanic, and 24.1% Asian. RESULTS: After 1 year, intervention students did not demonstrate differential change compared with control students in estimated peak oxygen consumption (between-group change: -0.03 mL/kg/min; 95% CI, -.367 to 0.302), curl-ups (between-group change: 1.2 curl-ups; 95% CI, -0.306 to 2.660), or push-ups (between-group change: 0.1 push-ups; 95% CI, -0.672 to 0.787). Similarly, no differences were seen after 2 years. CONCLUSION: Sending a 2-page, once-a-year school-based fitness report home to parents-in the absence of environmental changes and/or behavioral coaching and support-does not impact student fitness performance after either 1 or 2 years of reporting.

fitness reporting↗
PubMed2005

Associations of leisure time physical activity, self-rated physical fitness, and estimated aerobic fitness with serum C-reactive protein among 3,803 adults.

OBJECTIVE: Serum C-reactive protein (CRP), a marker of systemic inflammation, is a risk factor for cardiovascular disease. Obesity and physical activity are associated with CRP, though population studies are sparse. METHODS AND RESULTS: We assessed the cross-sectional relationship of physical activity, self-rated fitness and estimated aerobic fitness with serum CRP among a population-based random sample of 3,803 Finnish adults aged 25-74 years. Conditioning, commuting and non-conditioning physical activity was measured by a recall and self-rated physical fitness by a questionnaire. A non-exercise test was used to estimate aerobic fitness. The combined association of aerobic fitness and waist-to-hip ratio (WHR) on CRP was also assessed. Self-rated fitness and aerobic fitness had inverse associations with CRP (adjusted for age, WHR, smoking, anti-hypertensive drugs, aspirin, diabetes, hypercholesterolemia, hormone replacement therapy and menopausal status) in both sexes (p < 0.001). An inverse age-adjusted association of conditioning and non-conditioning physical activity with CRP was found in both sexes. After further adjustments, associations remained significant in women for conditioning and non-conditioning activity (p < 0.001 and p = 0.010, respectively) and borderline significant in men (p = 0.074 and p = 0.070, respectively). Commuting physical activity was inversely associated with CRP among women only (p = 0.012). CONCLUSIONS: Physical activity and fitness may have an anti-inflammatory effect, which is independent of obesity.

Adult↗
PubMed2003

Use of self-reports of physical fitness as substitutes for performance-based measures of physical fitness in older adults.

The purpose of the present study was to evaluate the association between self-reported physical fitness and performance-based measures of physical fitness in older adults. The specific components of physical fitness evaluated included aerobic endurance, muscular strength, and flexibility. Adults (25 men and 47 women) ranging in age from 56 to 92 years (M age=75 yr.) were recruited from the local community. Generally, the associations between self-reported and performance-based measures of physical fitness were low to moderate (r = 30-.01). Based on these findings, self-reports of physical fitness should not be used as substitutes for performance-based measures of physical fitness in older adults. Furthermore, present findings suggest that older adults, when asked to rate subcomponents of physical fitness, may not do so but rather evaluate a more general concept of physical fitness with aerobic endurance as the dominant factor.

Aged↗
PubMed1996

Fitness spectrum among random mutants on Mt. Fuji-type fitness landscape.

Statistical properties of a Mt. Fuji-type fitness landscape on a multi-valued sequence space were analysed. We constructed the model landscape based on additivity of the free energy contributed by each residue on a biopolymer, introducing "tolerance functions" that describe tolerance to residue substitution at each site. The fitness spectrum among a random mutant population around a wild-type sequence was theoretically obtained as the probability density distribution function of fitness. As the Hamming distance from the wild-type to the mutants increases, the mean fitness of the mutant population gradually decreases, and the variance of the fitness increases. These features are originated from the anisotropy of the landscape. On the assumption that the free energy is statistically additive around a wild-type in a sequence space of a real biopolymer, one can estimate the Hamming distance from the wild-type to the optimal biopolymer and the fitness of the optimum. Two sets of experimental data were analysed: (1) a promoter strength spectrum of a mutant population produced by the random mutagenesis of a wild-type lac promoter; (2) four stepwise optimization processes of different peptide mixtures evaluated with ligand binding affinity. Analysis of both experiments showed the compatibility with the hypothesis that local fitness landscapes around contemporary biopolymers are near Mt. Fuji-type. The mean slope of each of the four affinity landscapes for (2) was estimated as delta In K(d)/delta d = 1.3 approximately 2.3, where d denotes the Hamming distance from the optimum and K(d) represents the mean dissociation constant of sequences located at the Hamming distance of d. Mt. Fuji-type landscape can be regarded as a zero-th order approximation to the real local landscape just like an "ideal gas". We showed a method to gauge statistically the shape of a near Mt. Fuji-type landscape by measuring mutant fitness spectra.

Animals↗
PubMed2006

The phenomenology of fit: linking the person and environment to the subjective experience of person-environment fit.

The authors distinguished 3 approaches to the study of perceived person-environment fit (P-E fit): (a) atomistic, which examines perceptions of the person and environment as separate entities; (b) molecular, which concerns the perceived comparison between the person and environment; and (c) molar, which focuses on the perceived similarity, match, or fit between the person and environment. Distinctions among these approaches have fundamental implications for theory, measurement, and the subjective experience of P-E fit, yet research has treated these approaches as interchangeable. This study investigated the meaning and relationships among the atomistic, molecular, and molar approaches to fit and examined factors that influence the strength of these relationships. Results showed that the relationships among the approaches deviate markedly from the theoretical logic that links them together. Supplemental analyses indicated that molar fit overlaps with affect and molecular fit gives different weight to atomistic person and environment information depending on how the comparison is framed. These findings challenge fundamental assumptions underlying P-E fit theories and have important implications for future research.

Adult↗
PubMed2004

Curve-fitting overlapped bands: quantification and improvement of curve-fitting robustness in the presence of errors in the model and in the data.

Estimation of the band parameters of overlapped bands often relies on curve-fitting. It has been demonstrated that curve-fitting provides the maximum likelihood estimation of band parameters under a series of assumptions. One of these assumptions is that the curve-fitting model is correct and any error in the data is random. Under real conditions, we have to acknowledge the unavoidable presence of errors in the model and systematic errors in the data. Here, we derive an expression for the estimation of how these errors affect the quality of the parameters obtained from curve-fitting. In addition, we derive theoretical expressions to quantify the extent to which different methods can improve the curve-fitting robustness to these errors. The methods considered are: (i) deterministic and (ii) probabilistic constraints in the band parameters, (iii) curve-fitting band-narrowed data, and (iv) building a more accurate model. The theoretical expressions obtained are tested in the curve-fitting of a synthetic noisy spectrum with either baseline or band shape errors, and in the curve-fitting of the experimental infrared amide I band of the membrane protein bacteriorhodopsin.

Animals↗
PubMed1995

Size of genetic bottlenecks leading to virus fitness loss is determined by mean initial population fitness.

Genetic bottlenecks are important events in the genetic diversification of organisms and colonization of new ecological niches. Repeated bottlenecking of RNA viruses often leads to fitness losses due to the operation of Muller's ratchet. Herein we use vesicular stomatitis virus to determine the transmission population size which leads to fitness decreases of virus populations. Remarkably, the effective size of a genetic bottleneck associated with fitness loss is greater when the fitness of the parental population increases. For example, for starting virus populations with low fitness, population transfers of five-clone-to-five-clone passages resulted in a fitness increase. However, when a parental population with high fitness was transferred, 30-clone-to-30-clone passages were required simply to maintain fitness values.

Animals↗
PubMed1991

Staying fit and staying well: physical fitness as a moderator of life stress.

Previous research suggests that physical fitness moderates the adverse effects of stressful life events. However, a reliance on self-reports of fitness and health may limit the validity of prior investigations. The present research tested the stress-buffering effect of fitness with subjective and objective indicators of exercise, fitness, and physical well-being. For self-reports of health, both self-reports of exercise and objective measures of fitness showed the buffering effect; however, only objective fitness levels buffered stress when visits to a health facility were considered. Additional evidence indicated that this effect was largely independent of measures of psychological distress. Implications for understanding the link between fitness, stress, and health status are discussed.

Affect↗
PubMed2001

Age-related physical fitness and the predictive values of fitness tests for work ability in home care work.

Despite the widespread assessment of physical fitness in occupational medicine and health services, only a few validity studies have been made of the fitness tests used in relation to job demands. The purpose of this study was to assess the physical fitness of female home care workers (n = 132) in relation to age and to evaluate whether the fitness tests used predict work ability over a 5-year period of follow-up. Muscle endurance declined by 18% to 37%, and isometric muscle strength by 10% to 18%, from the youngest (21 to 35 years) to the oldest (45 to 59 years) age group. The proportion of those subjects who could be classified below the average age-related fitness categories according to the maximal oxygen consumption was highest (50%) for the 21-to-35 age group. The logistic regression model showed that obesity (odds ratio [OR] = 7.51) and poor results on the sit-up (OR, 8.9), balance (OR, 6.5), and weight-lifting (OR, 4.6) tests predicted the highest risk for reduced work ability, according to the work ability index used in the 5-year follow-up. Moreover, average results for the trunk side-bending test (OR, 4.6), poor results for the squatting test (OR, 3.8), poor knee extension strength (OR, 4.2), and the average maximal oxygen consumption (l.min-1) (OR, 3.1) indicated a high risk for reduction in work ability. The physical fitness tests were strongly associated with the physical demands of home care work and were relevant for the evaluation of work-related fitness among home care workers.

Adult↗
PubMed1994

The Australian Schools Health and Fitness Survey. Physical fitness related to blood pressure but not lipoproteins.

BACKGROUND: Recent research indicates that levels of conventional coronary heart disease risk factors in children are related to the premature development of atheroma. It is therefore important to determine how risk factors might be modified on a population scale in children. METHODS AND RESULTS: In 1985, the Australian Schools Health and Fitness Survey was conducted on a representative sample of Australian schoolchildren aged 7 to 15 years. In children aged 9, 12, and 15, data on plasma cholesterol, triglycerides, and high-density lipoprotein cholesterol were obtained along with measurements of blood pressure, fitness, and body fatness. From an original sample of 2400 in these three age categories 1919 underwent the full set of measurements. Univariate analysis of these data revealed a strong association between body fatness and plasma lipids. There was no significant association between fitness (measured as physical work capacity at a heart rate of 170 beats per minute per kilogram of lean body mass) and plasma lipids, but a significant negative association was found for fitness and systolic blood pressure (r = -.12, P < .001). Multiple regression analysis revealed that the association of fitness with systolic blood pressure was only partly accounted for by the confounding effect of lower body fatness in fitter children. CONCLUSIONS: These data collected on a representative sample of children under standardized conditions confirm a previous finding of a link between fitness and blood pressure in schoolchildren and also support a growing consensus that fitness is only weakly linked to plasma lipids and lipoproteins in children and adolescents.

Adolescent↗
PubMed1984

The Fitness to stand trial Interview Test: how four professions rate videotaped fitness interviews.

The results of this study provide some preliminary support for the use of the FIT as a method for providing structure to interviewers. The FIT may be particularly useful as a guide for making initial decisions about fitness. It was suggested that a screening evaluation based on the FIT could be completed by any properly trained individual with some professional background. The more difficult cases can be referred for lengthier evaluations. Of course, further research on the use of the FIT with actual defendants in real assessments will need to occur before such a procedure can be used as a matter of routine. Finally, the FIT promises to be an effective research tool for isolating professional group differences in definitions of fitness and the importance of different aspects of it, from both a legal and a mental health perspective.

Expert Testimony↗
PubMedDate not supplied

Comparison of N95 disposable filtering facepiece fits using bitrex qualitative and TSI Portacount quantitative fit testing.

As a means of evaluating the use of denatonium benzoate (bitrex) as a qualitative fit test agent with filtering facepiece respirators, the bitrex qualitative and TSI Protacount(R) quantitative fit-test methods were compared using N95 filtering facepieces. Seventy-nine paired tests (trial) were performed. Detection of bitrex during a qualitative fit test or measurement of a fit factor of <100 during a quantitative fit test constituted a failure. Qualitative and quantitative methods were performed using identical test protocols. Data were analyzed using pass/fail criteria, and matched-pair analysis methods were applied. The results of this study indicate that the use of bitrex during qualitative fit testing of N95 disposable filtering facepieces results in an increase in failure and/or rejection in cases where a TSI Portacount (plus N95 companion accessory) quantitatively establishes an acceptable fit.

Adolescent↗
PubMed2004

Understanding HIV resistance, fitness, replication capacity and compensation: targeting viral fitness as a therapeutic strategy.

The increasingly prevalent emergence of drug-resistant virus strains in patients being treated with highly active antiretroviral regimens and the increasing rates of transmission of drug-resistant virus strains have focused attention on the critical need for additional antiretroviral agents with novel mechanisms of action and enhanced potency. Furthermore, novel means of employing highly active antiretroviral therapy are needed to reduce or eliminate the virological treatment failures that currently occur. Over the past several years, evidence has mounted supporting the fact that the emergence of resistant strains is associated with reductions in viral fitness, yielding decreases in plasma virus load in treated patients harbouring resistant populations of the virus. Additional mutations that serve to modify fitness (compensatory mutations) and mutations that impact the viral replication capacity also emerge under the selective pressure of drug treatment, and have both negative and positive effects on virus growth. Fitness is generally accepted to refer to the ability of HIV to replicate in a defined environment and thus is used to describe the viral replication potential in the absence of the drug. Although viral fitness and replication capacity are related in some ways, it is important to recognise that viral fitness is not the same as viral replication capacity. This review will assess the recent literature on antiviral drug resistance, viral fitness and viral replication capacity, and discuss means by which the adaptability of HIV to respond rapidly to antiviral treatment through mutation may be used against it. This would be done by treating patients with an aim to lock the deleterious mutations into the resistant virus genome, resulting in a positive therapeutic outcome despite the presence of resistance to the selecting agents. The review will specifically discuss the literature on nucleoside and non-nucleoside reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors, fusion inhibitors, as well as other biological factors involved in viral fitness.

Anti-Retroviral Agents↗
PubMed1990

Hydroxyapatite coating enhances fixation of porous coated implants. A comparison in dogs between press fit and noninterference fit.

Intimate contact at the bone-porous surface interface is not always achievable in noncemented prosthetic implantation. We investigated the effect of hydroxyapatite (HA) coating on skeletal attachment in noninterference fit 4 weeks after implantation in 6 mature dogs. The push-out test of HA-coated implants surrounded by a 1-mm gap showed a twofold increased shear strength and fivefold increased shear stiffness compared with titanium alloy (Ti) coated implants. The fixation of Ti implants was reduced by two thirds when inserted in a gap as compared with press fit, whereas HA-coated implants in gap showed anchorage close to implants in press fit. Only minor differences were found between HA and Ti implants in press fit. Histomorphometric analysis showed a significant increase in bone in direct contact to HA-coated implant as compared with Ti implants inserted both in gap and press fit. The study indicates that tightness of surgical fit is an important factor for sufficient fixation of the implant. However, our results demonstrate that hydroxyapatite coating almost eliminates the negative influence of noninterference fit between bone and unloaded implant.

Animals↗
PubMed1997

Development and tracking in fitness components: Leuven longtudinal study on lifestyle, fitness and health.

In the Leuven Growth Study of Belgian Boys the growth and physical performance of Belgian boys followed longitudinally between 12 and 19 years were studied. Subsequently, a subsample (n = 240) of Flemish-speaking males were reexamined at 30 and 35 years. A first question relates to the individual growth patterns in a variety of physical fitness characteristics. The three strength tests (static, functional, explosive) show curves that are qualitatively similar to those for height and weight. Their adolescent spurts occur after the height spurt. Flexibility and the two speed tests appear to reach maximum velocities prior to the height and weight spurts. Longitudinal principal component analysis was applied to the study of growth patterns of several somatic and motor characteristics. The results for height show three components sufficient to provide an adequate representation of the original information. The first component characterizes the general position of an individual growth curve. Components 2 and 3 reflect fluctuation in percentile level during the age period studied and can be conceived as indices of stability and are related to age at peak height velocity (APHV) and peak height velocity (PHV), respectively. Relationships between somatic characteristics, physical performance, and APHV have been studied in a sample of 173 Flemish boys, measured yearly between +/- 13 and +/- 18 years and again as adults at 30 years of age. The sample was divided into three contrasting maturity categories based on the APHV. There are consistent differences among boys of contrasting maturity status during adolescence in body weight, skeletal lengths and breadths, circumferences, and skinfolds on the trunk. There are no differences in skinfolds on the extremities. None of the differences in somatic dimensions and ratios among the three contrasting maturity groups are significant at 30 years of age except those for subscapular skinfold and the trunk/extremity skinfold ratio. During adolescence, speed of limb movement, explosive strength and static strength are negatively related to APHV; thus, early maturers performed better than late maturers. However, between late adolescence and adulthood (30 years), the late maturers not only caught up to the early maturers, but there were significant differences for explosive strength and functional strength in favor of late maturers. Finally, age-specific tracking, using inter-age correlations, of adult health- and performance-related fitness scores were investigated. In addition, the independent contribution of adolescent physical characteristics to the explanation of adult fitness scores was also studied. Tracking between age 13 and age 30 years was moderately high (46% of variance explained) for flexibility, low to moderate (between 19% and 27% of variance explained) for the other fitness parameters and low for pulse recovery and static strength (7% to 11% of variance explained). Between age 18 and age 30 years the tracking was high for flexibility, moderately high for explosive and static strength, and moderate for the other fitness parameters except for pulse recovery. The amount of variance of adult fitness levels explained increased significantly when other characteristics observed during adolescence entered the regressions or discriminant functions.

Adolescent↗
PubMed2006

Do patients with chronic low back pain have a lower level of aerobic fitness than healthy controls?: are pain, disability, fear of injury, working status, or level of leisure time activity associated with the difference in aerobic fitness level?

STUDY DESIGN: Prospective case series with historical controls (normative data). OBJECTIVES: To compare the aerobic fitness level of patients with chronic low back pain (CLBP) with healthy controls matched for gender, age, and level of sport activity and to evaluate the association of the difference in aerobic fitness level with pain intensity, duration and degree of disability, fear of injury, and level of activity during work, including household and leisure time. SUMMARY AND BACKGROUND DATA: Controversy exists whether patients with CLBP have a lower level of aerobic fitness and whether this level may partly depend on the patients' activity level. METHODS: A total of 108 CLBP patients completed questionnaires regarding pain, disability, fear of injury, and activity level and performed a modified Astrand submaximal cycling test. The maximum oxygen consumption (VO2max) was calculated and compared with normative data. Multiple linear regression analysis was performed with the difference of the level of aerobic fitness as dependent variable. RESULTS: VO2max could be calculated in 78% of the patients. Both men and women with CLBP had significant lower VO2max than the healthy referents (10 mL/kg LBM x min(-1) and 5.6 mL/kg LBM x min(-1) respectively, P < 0.001), and this difference was significantly greater in men (P = 0.03). Multiple regression analysis showed that the level of aerobic fitness was not associated with the presumed variables. The patients who stopped the test prematurely were older (P = 0.02) and more disabled (P = 0.01). CONCLUSION: CLBP patients, especially men, seem to have a reduced aerobic fitness level compared with the normative population. No explanatory factor for that loss could be identified.

Adult↗