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PubMed2003

Practical applications of viral fitness in clinical practice.

PURPOSE OF REVIEW: To review recent clinical data regarding viral fitness and its potential utility in clinical practice. Therapeutic failure of antiretroviral regimens is often due to the development of drug resistance. The viral loads achieved by these drug-resistant variants frequently remain suppressed below pretreatment levels. Furthermore, many patients with virologic failure continue to maintain stable CD4 counts and remain clinically well. One possible explanation for these observations is that the resistant virus that emerges during failure of highly active antiretroviral therapy is less fit than its wild-type counterpart as a result of the requirement to maintain resistance mutations that allow it to replicate in the presence of antiretroviral drugs. Since there are many patients with limited treatment options due to extensive resistance or drug toxicities, or both, there is intense interest in exploring the possibility that viral fitness can be exploited for clinical benefit. This review describes the assays that are used to measure fitness and replication capacity, and investigations of their utility in clinical practice. RECENT FINDINGS: A number of methods have been developed to measure viral fitness. Replication kinetic and competitive culture assays are accurate, but labour and time intensive. The availability of a rapid, single-cycle recombinant assay that measures viral replication capacity presents the possibility that assessments of viral fitness could be incorporated into clinical management. The replication capacity assay appears to correlate with more standard measures of viral fitness, and recently accumulated data in both wild-type and drug resistant viral populations suggest that replication capacity describes an intrinsic characteristic of HIV-1. A number of investigations of the clinical utility of fitness and replication capacity assays have established correlations between these measurements and virologic and immunologic outcomes. SUMMARY: Much progress has been made in the past year in our understanding of viral fitness and replication capacity. Assays that measure these viral characteristics have the potential to expand the range of clinical strategies employed against HIV-1. Further investigations are needed to firmly establish the clinical utility of these assays.

Carbamates↗
PubMed1990

Evaluation of an in-situ output probe-microphone method for hearing aid fitting verification.

Several hearing aid prescription procedures specify frequency gain functions in terms of the desired levels of amplified speech. The most direct method for verifying hearing aid fittings based on these procedures requires a measurement of amplified speech in the ear canal. This paper describes the evaluation of a probe microphone measurement procedure designed to measure amplified speech to verify hearing aid fittings using the MSUv3 prescription procedure. With minor modifications, the same protocol could be used with other prescriptive procedures. Hearing aids were fitted to a group of subjects with sensorineural hearing impairment. Data derived from the fittings were analyzed to assess several issues relating to the procedure itself and to prescriptive fittings in general. The main results were: (1) with over the ear hearing aids, most prescriptions can be matched with an RMS error of 5 dB or less through the frequency range from 500 to 2500 Hz; (2) even though actual fittings usually do not perfectly correspond with their prescriptions, differences among frequency gain prescriptions are preserved in hearing aid fittings if the RMS error of the fitting is 5 dB or less; (3) if sound field stimuli presented to the hearing aid are precisely controlled, an in situ output verification method produces valid results; (4) when hearing aids are fitted with gain similar to that prescribed by the MSUv3 procedure, the maximum comfortable speech input level is typically about 72 dB; (5) the SSPL90 prescription generated by the MSUv3 procedure overestimates desired SSPL90 by 7 dB on average.

Audiometry↗
PubMed2003

Hamilton goes empirical: estimation of inclusive fitness from life-history data.

Hamilton's theory of kin selection is one of the most important advances in evolutionary biology since Darwin. Central to the kin-selection theory is the concept of inclusive fitness. However, despite the importance of inclusive fitness in evolutionary theory, empirical estimation of inclusive fitness has remained an elusive task. Using the concept of individual fitness, I present a method for estimating inclusive fitness and its components for diploid organisms with age-structured life histories. The method presented here: (i) allows empirical estimation of inclusive fitness from life-history data; (ii) simultaneously considers all components of fitness, including timing and magnitude of reproduction; (iii) is consistent with Hamilton's definition of inclusive fitness; and (iv) adequately addresses shortcomings of existing methods of estimating inclusive fitness. I also demonstrate the application of this new method for testing Hamilton's rule.

Altruism↗
PubMed1994

Subclonal components of consensus fitness in an RNA virus clone.

Most RNA virus populations exhibit extremely high mutation frequencies which generate complex, genetically heterogeneous populations referred to as quasi-species. Previous work has shown that when a large spectrum of the quasi-species is transferred, natural selection operates, leading to elimination of noncompetitive (inferior) genomes and rapid gains in fitness. However, whenever the population is repeatedly reduced to a single virion, variable declines in fitness occur as predicted by the Muller's ratchet hypothesis. Here, we quantitated the fitness of 98 subclones isolated from an RNA virus clonal population. We found a normal distribution around a lower fitness, with the average subclone being less fit than the parental clonal population. This finding demonstrates the phenotypic diversity in RNA virus populations and shows that, as expected, a large fraction of mutations generated during virus replication is deleterious. This clarifies the operation of Muller's ratchet and illustrates why a large number of virions must be transferred for rapid fitness gains to occur. We also found that repeated genetic bottleneck passages can cause irregular stochastic declines in fitness, emphasizing again the phenotypic heterogeneity present in RNA virus populations. Finally, we found that following only 60 h of selection (15 passages in which virus yields were harvested after 4 h), RNA virus populations can undergo a 250% average increase in fitness, even on a host cell type to which they were already well adapted. This is a remarkable ability; in population biology, even a much lower fitness gain (e.g., 1 to 2%) can represent a highly significant reproductive advantage. We discuss the biological implications of these findings for the natural transmission and pathogenesis of RNA viruses.

Animals↗
PubMed2006

Criteria and methods used for the assessment of fitness for work: a systematic review.

The main findings from reports published in scientific journals on the criteria and methods used to assess fitness for work were reviewed. Systematic searches were made using internet engine searches (1966-2005) with related keywords. 39 reports were identified, mostly from the US and western Europe. Assessment of fitness for work is defined by most as the evaluation of a worker's capacity to work without risk to their own or others' health and safety. It is mainly assessed at recruitment (pre-offer or post-offer), and when changes of work or health conditions occur. Five main criteria used by occupational doctors to evaluate fitness for work were identified: the determination of worker's capacity and worker's risk in relation to his or her workplace, as well as ethical, economic and legal criteria. Most authors agreed that assessment tools used need to be specific and cost-effective, and probably none gives unequivocal answers. Outcomes from fitness for work assessments range from "fit" to "unfit", with other possible intermediate categories such as "fit subject to work modifications", "fit with restrictions" or "conditionally fit (temporarily, permanently)". Workplace modifications to improve or adjust working conditions must always be considered. There is confusion about the decision-making process to be used to judge about fitness for work. There is very scarce scientific evidence based on empirical data, probably because there are no standard or valid methodologies for all professions and circumstances.

Health Status↗
PubMedDate not supplied

Facial dimensions and predictors of fit for half-mask respirators in Koreans.

This study investigated the relationship between facial dimensions and the fit of half-mask respirators using fit factors and selected good facial dimension predictor(s) of fit for designing respirators for Korean workers. Three different brands of half-mask respirators-YS, SG, and 3M-were fit-tested on 112 men and 38 women using TSI Portacount 8020, and fit factors were determined. Before fit-testing, 10 facial dimensions were measured. Data were analyzed by descriptive statistics, Pearson's correlation analysis, and quadratic polynomial regression analysis with log-transformed fit factors (LNFF). However, some of the relationships between LNFF and facial dimensions in brand/gender subgroups were found to be curvilinear rather than linear. Because this result indicated that a multiple polynomial regression model including quadratic terms might be more appropriate than a multiple linear regression, data were also analyzed with a quadratic term by examination of the coefficient of partial correlation. No common facial dimension variables were found to be significant for all nine brand/gender subgroups, but the coefficient of regression for the linear term of the bitragion-menton arc was significant in five of nine brand/gender subgroups including male subjects of all three respirator brands. The 3M mask had the highest coefficient of determination values compared with other brands. Using the quadratic term for the 3M mask, face width (bizygomatic breadth) and nose protrusion were good predictors of half-mask fit. In four of nine brand/gender subgroups, nose protrusion was a good predictor of fit through analysis using a quadratic term. Results indicate that face width, bitragion-menton arc, and nose protrusion should be preferentially considered when designing a half-mask respirator for Korean workers.

Adult↗
PubMed2004

Frequency-dependent selection with dominance: a window onto the behavior of the mean fitness.

Selection in which fitnesses vary with the changing genetic composition of the population may facilitate the maintenance of genetic diversity in a wide range of organisms. Here, a detailed theoretical investigation is made of a frequency-dependent selection model, in which fitnesses are based on pairwise interactions between the two phenotypes at a diploid, diallelic, autosomal locus with complete dominance. The allele frequency dynamics are fully delimited analytically, along with all possible shapes of the mean fitness function in terms of where it increases or decreases as a function of the current allele frequency in the population. These results in turn allow possibly the first complete characterization of the dynamical behavior by the mean fitness through time under frequency-dependent selection. Here the mean fitness (i) monotonically increases, (ii) monotonically decreases, (iii) initially increases and then decreases, or (iv) initially decreases and then increases as equilibrium is approached. We analytically derive the exact initial and fitness conditions that produce each dynamic and how often each arises. Computer simulations with random initial conditions and fitnesses reveal that the potential decline in mean fitness is not negligible; on average a net decrease occurs 20% of the time and reduces the mean fitness by >17%.

Alleles↗
PubMed2006

The fitness effects of outcrossing in Calylophus serrulatus, a permanent translocation heterozygote.

Small and relatively isolated populations that occupy fragmented habitat are at risk of local extinction. However, fitness consequences of fragmentation related to mating distance, such as inbreeding depression following increased self- and near-neighbor mating, may not follow standard expectations in species with specialized genetic systems. We investigated the effect of mating distance on progeny fitness in Calylophus serrulatus, a primarily autogamous, permanent translocation heterozygote that is restricted to prairie fragments in the North American tallgrass prairie region. We pollinated flowers by hand in the field with pollen sampled at various distances from the maternal parent within and between three populations in southeastern Minnesota. We raised the progeny in a greenhouse and measured fitness-related characters. Because their genetic system prevents loss of heterozygosity throughout much of the genome, regardless of inbreeding, permanent translocation heterozygotes are not expected to exhibit inbreeding depression. Consistent with this expectation, in no case did progeny of self matings suffer significantly reduced mean fitness compared to progeny from crosses between plants. Crosses between plants in the two closely situated (2 km) populations yielded progeny with fitness intermediate to their parents, but crosses between each of those populations and the more distant (20 km) population yielded progeny with reduced fitness, suggesting outbreeding depression at this largest spatial scale. Similarly, fitness of self-pollinated progeny and progeny from "near" crosses (<2 m) within populations tended to be higher than "mid" (10-25 m) and "far" (>35 m) cross-progeny fitness. Under the current conditions of fragmentation, it seems likely that the distant matings that produce outbreeding depression are rare. It appears that mean fitness in this species is maintained in the context of severe fragmentation of its populations, largely because of its genetic system.

Crosses, Genetic↗
PubMedDate not supplied

Fluoroperm extended wear RGP contact lenses: II. Front toric fitting.

Seventeen eyes (10 patients) were fit with front toric rigid gas permeable (RGP) Fluoroperm lenses as part of an extended wear study. These 17 eyes required 40 fittings (an average of 2.35 fittings per eye); only six eyes were fit successfully the first time. What occasioned the large number of fittings was unacceptable visual acuity due to incorrect lens axis. Most fittings had been done with a polymethylmethacrylate (PMMA) fitting set; and it became obvious that the final Fluoroperm lenses rotated differently from the PMMA diagnostic lenses. Ultimately, the use of a Fluoroperm prism-ballasted fitting set resulted in 16 of 17 eyes (94%) seeing well with a front toric lens. We advise that, for front toric fittings, the diagnostic lens be of the same material as the final lens.

Acrylic Resins↗
PubMed1978

Proper fitting of the cervical orthosis.

This study evaluated the effect of fitting of the sternal occipital mandibular immobilization (SOMI) orthosis in restricting sagittal cervical spine motion. Cervical orthotic devices are usually fitted according to the subjective tolerance of the patient. Pressures were recorded after fitting in the usual manner by a certified orthotis and when fitted more loosely. Eight able-bodied adults were fitted in this manner and were then immobilized in a straight-backed chair while lateral cervical spine films were taken in neutral, flexion, and extension. Previously standardized methods were used to measure flexion-extension of the cervical spine. The resting pressures, when fitted in the usual manner, were approximately 105 mmHg at the chin and occiput. When pressure sensors were used to fit the brace loosely, the average pressure was approximately 25 mmHg. The data indicate that regardless of fit, there was no significant difference in the mobility of the entire cervical spine or at any intervertebral level. Recommendations for fitting of the SOMI are discussed.

Cervical Vertebrae↗
PubMed1989

Physical fitness and all-cause mortality. A prospective study of healthy men and women.

We studied physical fitness and risk of all-cause and cause-specific mortality in 10,224 men and 3120 women who were given a preventive medical examination. Physical fitness was measured by a maximal treadmill exercise test. Average follow-up was slightly more than 8 years, for a total of 110,482 person-years of observation. There were 240 deaths in men and 43 deaths in women. Age-adjusted all-cause mortality rates declined across physical fitness quintiles from 64.0 per 10,000 person-years in the least-fit men to 18.6 per 10,000 person-years in the most-fit men (slope, -4.5). Corresponding values for women were 39.5 per 10,000 person-years to 8.5 per 10,000 person-years (slope, -5.5). These trends remained after statistical adjustment for age, smoking habit, cholesterol level, systolic blood pressure, fasting blood glucose level, parental history of coronary heart disease, and follow-up interval. Lower mortality rates in higher fitness categories also were seen for cardiovascular disease and cancer of combined sites. Attributable risk estimates for all-cause mortality indicated that low physical fitness was an important risk factor in both men and women. Higher levels of physical fitness appear to delay all-cause mortality primarily due to lowered rates of cardiovascular disease and cancer.

Adult↗
PubMed2006

Ten-year comparison of BMI, body fat, and fitness in the workplace.

BACKGROUND: Overweight, obestity, and lack of fitness in America is reported to be increasing at an accelerated pace. This national trend has serious health and economic ramifications not only for the general population but also directly for industry. Obesity in the workplace has resulted in increased expenses to industry: directly through increased medical costs and indirectly through decreased productivity. The intent of this study is to define changes in fitness and body fat percentage in a working population in an isogeographical area over the past decade. METHODS: Data accumulated during a routine post-offer testing program were divided into two groups composed of new industry hires tested from 1990 to 1992 and from 2000 to 2002. Body fat was measured with a standard skinfold. The body fat percentage and body mass index (BMI) from year 1990 were compared to those from year 2000. Fitness was assessed through an individual's ability to perform a timed maximum number of sit-ups and squats. RESULTS: There was no significant difference in the BMI between the year 1990 group and the year 2000 group (P = 0.132 for females and P = 0.110 for males). There was a significant increase in body fat percentage from the 1990 group to the 2000 group (P = 0.000 for females and P = 0.000 for males). A significant decrease in fitness was observed for both males and females during the 10-year interval of the study. CONCLUSIONS: Percent body fat appears to be a better indicator than BMI for utilization in industry for evaluation of obesity in the workplace. The differences in significance levels between BMI and percent body fat suggest that a decrease in leisure-time fitness activities could potentially contribute to the trend toward obesity. This study demonstrates that strength and/or fitness are important indicators that industry should monitor in order to improve the health and fitness of the workforce. Direct measurement of percent body fat and fitness indices are a more precise means than BMI for monitoring the workforce especially if employers are going to reward healthy behavior.

Adult↗
PubMed1994

Dietary factors related to fitness in young men and women.

BACKGROUND: In a previous paper we reported an inverse relationship between fitness and serum lipids in this group of young subjects. The present study investigates whether a higher fitness level was associated with a more prudent diet and whether this contributed to the observed relationship between fitness and serum lipids. METHODS: The study sample, comprising 70 women and 49 men ages 23-27 years, was a subgroup of a large random sample. Aerobic fitness was measured directly as maximal oxygen uptake (ml O2 min-1 kg-1) and dietary intake as 7-day food records. RESULTS: The highest fitness tertile had an intake of dietary fiber higher than that of the lowest tertile (25.2 g/10 MJ vs 21.9 g/10 MJ, P < 0.05) and a lower intake of sucrose (7.2 E% vs 9.8 E%, P < 0.01), whereas total fat intake and the ratio between polyunsaturated and saturated fatty acids were similar (35.4 E% vs 36.5 E%, P > 0.05, 0.39 vs 0.34, P > 0.05, respectively). No differences were observed in intake of alcohol, protein, and total carbohydrate. Multiple regression analyses showed no impact of dietary variables upon the relationship between serum lipids and fitness. CONCLUSIONS: Better fitness was associated with a better dietary composition with respect to dietary fiber and sucrose, but not to fat. The observed inverse relationship between fitness and serum lipids was not related to diet.

Adult↗
PubMed1989

Ratings of perceived exertion in individuals with varying fitness levels during walking and running.

It was the purpose of this investigation to: 1) compare the ratings of perceived exertion (RPEs) in high and low fit individuals when walking and running at comparable exercise intensities and 2) to determine if ventilation (VE) provides a central signal for RPEs. Nine high fit and nine low fit male subjects completed two exercise bouts on a treadmill, one uphill walking and the other level running. Workloads for each bout were set at 90% of each subject's ventilatory threshold (VT) as determined from a graded exercise test. Oxygen consumption (Vo2), heart rate (HR), and VE were all similar between the walk and run trials for the low fit subjects (P greater than 0.05). HR were found to be significantly greater during the walk trial vs. the run trial (P less than 0.05) for the high fit subjects, whereas, VE was significantly greater during the run trial. Oxygen consumption was similar for the high fit subjects during both trials (P greater than 0.05). During the walk and run trials, central (12.1 +/- 1.6 vs. 11.4 +/- 1.5), local (14.0 +/- 1.3 vs. 13.9 +/- 1.1) and overall (12.8 +/- 1.2 vs. 12.4 +/- 1.4) RPEs were not found to be significantly different for the low fit group (P greater than 0.05). In contrast, during the walk vs. the run trial there was a significant increase in central (10.7 +/- 2.0 vs. 9.2 +/- 1.9), local (11.5 +/- 2.0 vs. 9.8 +/- 1.8) and overall (11.2 +/- 2.4 vs. 9.6 +/- 2.3) RPEs for the high fit group (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

Sweat lactate response between males with high and low aerobic fitness.

Sweat lactate indirectly reflects eccrine gland metabolism. However the potential influence of aerobic fitness on sweat lactate is not well-understood. Six males with high aerobic fitness [peak oxygen consumption ( VO(2)peak): 61.6 (2.5) ml.kg(-1).min(-1)] and seven males with low aerobic fitness [ VO(2)peak: 41.8 (6.4) ml.kg(-1).min(-1)] completed a maximal exertion cycling trial followed on a different day by 60 min of cycling (60 rev.min(-1)) in a 30 degrees C wet bulb globe temperature environment. Intensity was individualized at 90% of the ventilatory threshold ( V(E)/ VO(2) increase with no concurrent V(E)/ VCO(2) increase). Sweat samples were collected from the lumbar region every 10 min and analyzed for lactate concentration. Sweat rate (SR) was significantly greater ( p<0.05) for subjects with a high [1445 (254) ml.h(-1)] versus a low [1056 (261) ml.h(-1)] fitness level. Also, estimated total lactate excretion (SRxmean sweat lactate concentration) was marginally greater ( p=0.2) in highly fit males. However, repeated measures ANOVA showed no significant differences ( p>0.05) between groups for sweat lactate concentration at any time point. Current results show highly fit (vs. low fitness level) males have a greater sweat rate which is consistent with previous literature. However aerobic fitness and subsequent variations in SR do not appear to influence sweat lactate concentrations in males.

Adult↗
PubMedDate not supplied

Effect of physical fitness and training on physiological responses to hypogravity.

The studies on the orthostatic tolerance during the hypodynamics exposure seem to be significant in connection with the selection, training and health maintenance of astronauts. Using male human subjects of various physical fitness levels, fluctuations of their physical fitness through 2 weeks of vigorous athletic training were measured in many parameters. For some of the subjects, the effects of 6 hr thermal neutral water immersion exposure in head out supine position on the physical fitness parameters and orthostatic tolerability were compared before training with after training. The results obtained were as follows: (1) Before training, orthostatic tolerability before hypodynamics exposure increased, following the physical fitness levels; the value after the hypodynamics exposure decreased in all the cases, but no differences were observed between the physical fitness levels. (2) As a result of training an increase of the physical fitness capacity was observed. The increase of orthostatic tolerability before hypodynamics exposure was noticed except for athletes. (3) Before hypodynamics exposure the urinary excretion of noradrenaline on non-athlete subjects increased as the physicsl fitness level increased. The values were decreased by physical training, the more so the better the physical fitness. After hypodynamics exposure the same relation was observed. But for athletes the values remain more stable and the decrease by hypodynamics exposure was not so distinctive. Such decreased reaction to hypodynamic conditions seems to reveal the neuro hormonal mechanism for the detrimental adaptation of athletes to hypodynamics. These results suggest that stable athletes do not always have low orthostatic tolerability, but do not respond well to hypodynamic conditions, at least from the orthostatic point of view. The mechanism seems related to sympathetic nerve activity.

Adolescent↗
PubMed1994

Nutrition, dieting, and fitness messages in a magazine for adolescent women, 1970-1990.

PURPOSE: This study was designed to characterize nutrition and fitness messages presented between 1970-1990 in a magazine for adolescent women; to evaluate whether these messages changed over time; and to assess the body shape portrayed as desirable, and whether this changed over time. METHODS: A data collection form was developed to code nutrition and fitness-related written items, advertisements and recipes, and the page coverage allocated to these items. Body shape was assessed by measuring bust:waist and hip:waist ratios of photographs of models wearing bathing suits or underwear. Magazines from even years between 1970-1990 (n = 132) were coded. RESULTS: Both nutrition-related and fitness-related coverage emphasized weight loss and physical appearance. Half the major nutrition-related articles presented a weight-loss plan, and weight loss was frequently addressed in other nutrition articles. The primary reasons presented for following a nutrition of fitness plan were to lose weight and become more attractive. Statements that the product or service would promote weight loss were found in 47% of nutrition-related advertisements. Nutrition coverage did not exhibit a net change over time, whereas fitness coverage increased (F = 6.6, p < .005), and the ratio of nutrition: fitness coverage changed from 10:1 in 1970 to 0.75:1 in 1990. Models' body shapes were less curvaceous than those in magazines for adult women, and the hip:waist ratio decreased over time (F = 7.3, p < .01). CONCLUSIONS: The nutrition and fitness messages in this magazine for adolescent women emphasize body shape and appearance, similar to findings from adult women's magazines, and contribute to the cultural milieu in which thinness is an expectation for women. Between 1970-1990, the emphasis on fitness increased, and the body shape of models tended to become more linear.

Adolescent↗
PubMed2006

Cardiorespiratory fitness: A predictor of cortical plasticity in multiple sclerosis.

Deficits in cognitive abilities are commonly observed among individuals with multiple sclerosis (MS). Recent neuroimaging studies have provided evidence for the existence of cortical plasticity in MS, with cognitively impaired participants recruiting additional brain areas to perform challenging tasks. The existence of altered cerebral activations in MS provides hope for the utilization of neural resources to reduce cognitive deficits that challenge everyday living in MS by employing alternative interventions such as cognitive and fitness training. In this study, we examined whether higher physical fitness levels enhance cognitive and neural plasticity in MS patients. The present study is the first to investigate the impact of cardiorespiratory fitness on cerebrovascular functioning of MS patients. 24 participants with relapsing-remitting MS were recruited for the study. All participants went through a fitness assessment and were scanned in a 3 T MRI system during the Paced Visual Serial Addition Test (PVSAT). Higher fitness levels were associated with faster behavioral performance and greater recruitment of right IFG/MFG, a region of the cerebral cortex recruited by MS patients during performance of PVSAT to purportedly compensate for the cognitive deterioration attributable to MS. In contrast, lower levels of fitness were associated with enhanced ACC activity, suggestive of the presence of greater interference and the potential for error in lower fit MS participants. These results are promising, suggesting the need for further investigation of the utility of aerobic fitness training as a possible method to support the development of additional cortical resources in an attempt to counter the cognitive decline resulting from MS.

Adult↗