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PubMed2004

[Evaluation of quantitative fit-testing of N95 filtering facepiece respirators using Mask-Fitting Tester and improvement of mask fitting by instruction].

OBJECTIVE: To evaluate quantitative fitness of N95 filtering facepiece respirators (N95 Mask) using Mask Fitting Tester and improvement of fitness by instruction. MATERIALS AND METHODS: One hundred and thirty-three health care workers working at our hospital were tested as to quantitative fitness of N95 Mask using Mask Fitting Tester Model MT-02, Roken type that counts particles more than 0.7 microm in diameter. Based on counting the number of particles more than 0.7 microm in diameter of the air inside and outside the mask, leakage rate is calculated. Permissible range of leakage rate is 10% or below. In case of leakage rate more than 10%, we instructed way of wearing N95 Mask or change a type of N95 Mask. We usually provide three types of N95 Mask. RESULTS: Eighty-seven (65.4%) out of 133 health care workers achieved leakage rate 10% or below at the first test. Forty-six (34.6%) who did not achieve leakage rate 10% or below at the first test received instruction or changed a mask type. Twenty-one (15.8%) achieved desired value by instruction and 19 (14.3%) by changing a mask type. But 6 (4.5 %) could not achieve desired value in spite of instruction or changing to another type of masks available to us. Leakage rate changed from 20.5 +/- 10.9% (10.1-58.6) to 6.3 +/- 4.9% (0-29.5) by instruction or changing a type of mask (p < 0.001). At the first test, mask fitness is better in male than female, and worse in workers who always use N95 Mask at isolation ward or laboratory room than workers who usually do not use N95 Mask. Main problems were choice of mask, fitness to nose, incorrect use of headband. CONCLUSION: It is useful to evaluate N95 Mask quantitative fitness using Mask Fitting Tester Model MT-02, Roken type. At the first test, 34.6% of health care workers have large amount of leakage more than 10%, and by instruction or changing a mask type, most of them could achieve 10% or below. But 4.5% could not achieve desired value. On Infection control, it is important to test quantitative fitness of N95 Mask and to provide more than three types of N95 Mask.

Equipment Design↗

PubMed2006

Increasing the physical fitness of low-fit recruits before basic combat training: an evaluation of fitness, injuries, and training outcomes.

Recruits arriving for basic combat training (BCT) between October 1999 and May 2004 were administered an entry-level physical fitness test at the reception station. If they failed the test, then they entered the Fitness Assessment Program (FAP), where they physically trained until they passed the test and subsequently entered BCT. The effectiveness of the FAP was evaluated by examining fitness, injury, and training outcomes. Recruits who failed the test, trained in the FAP, and entered BCT after passing the test were designated the preconditioning (PC) group (64 men and 94 women). Recruits who failed the test but were allowed to enter BCT without going into the FAP were called the no preconditioning (NPC) group (32 men and 73 women). Recruits who passed the test and directly entered BCT were designated the no need of preconditioning (NNPC) group (1,078 men and 731 women). Army Physical Fitness Test (APFT) scores and training outcomes were obtained from a company-level database, and injured recruits were identified from cases documented in medical records. The proportions of NPC, PC, and NNPC recruits who completed the 9-week BCT cycle were 59%, 83%, and 87% for men (p < 0.01) and 52%, 69%, and 78% for women (p < 0.01), respectively. Because of attrition, only 63% of the NPC group took the week 7 APFT, compared with 84% and 86% of the PC and NNPC groups, respectively. The proportions of NPC, PC, and NNPC recruits who passed the final APFT after all retakes were 88%, 92%, and 98% for men (p < 0.01) and 89%, 92%, and 97% for women (p < 0.01), respectively. Compared with NNPC men, injury risk was 1.5 (95% confidence interval, 1.0-2.2) and 1.7 (95% confidence interval, 1.0-3.1) times higher for PC and NPC men, respectively. Compared with NNPC women, injury risk was 1.2 (95% confidence interval, 0.9-1.6) and 1.5 (95% confidence interval, 1.1-2.1) times higher for PC and NPC women, respectively. This program evaluation showed that low-fit recruits who preconditioned before BCT had reduced attrition and tended to have lower injury risk, compared with recruits of similar low fitness who did not precondition.

Adolescent↗

PubMed2004

Generations Exercising Together to Improve Fitness (GET FIT): a pilot study designed to increase physical activity and improve health-related fitness in three generations of women.

A 6-month home-based (HB) physical activity program was compared to a control (CTL) condition in terms of effect on physical activity and health-related fitness in three generations of women (daughter/ mother/maternal grandmother). Volunteers were randomly assigned to a HB or CTL condition. HB participants (n = 28) were asked to participate in lifestyle, aerobic, muscular strength, and flexibility activities at least 3 times per week and they completed 73% of the recommended PA bouts. CTL condition participants (n = 9) were asked to continue their usual pattern of physical activity. Changes in physical activity were measured pre-and post-intervention using the Physical Best questionnaire and pedometer step counts (3-day average). Changes in health-related fitness were assessed using Fitnessgram tests. Group x Time interactions were significant for changes in participation in flexibility activity (d/wk) and steps/day, indicating that the HB group experienced significant positive changes in the expected direction (+305% and +37%, respectively), while the CTL group regressed (-15% and -13%, respectively). The G x T interaction for mile time was significant, although not in the expected direction (CTL group < by 14% and HB group < by 5%). Findings should be interpreted with caution due to several limitations of the study, but several suggestions are made for more effectively studying this topic in the future.

Adolescent↗

PubMed1994

Variation in quantitative respirator fit factors due to fluctuations in leak size during fit testing.

Variation in fit factors during quantitative respirator fit testing was studied for a high degree of fit (aerosol fit factors > 1000) and a low degree of fit (aerosol fit factors < 1000). In a controlled human study, fit factors were determined sequentially for three different exercises by (1) an aerosol fit test (using a portable condensation nuclei counter and room aerosol as the test agent) and (2) the newly developed dichotomous-flow fit test (Dichot). For the higher level of respirator fit, the aerosol fit factors were 30 to 60 times the corresponding flow fit factors, and for the lower level of respirator fit they were 2 to 4 times the flow fit factors. A coefficient of variation (CV) of 84% (GSD 1.6) for the higher respirator fit and 178% (GSD 2.2) for the lower respirator fit data was observed in the human study when aerosol fit factors for the three exercises were pooled. In a similar mannequin study, the center sampling probe gave aerosol fit factors with a CV of 5.4% (GSD 1.05). The flow fit factors for all three exercises pooled had a CV of 36% (GSD 1.3) for the higher respirator fit and 40% (GSD 1.5) for the lower respirator fit data, while the mannequin study gave flow fit factors with a CV of 2.2% (GSD 1.02). Thus, the variation in fit factors obtained in the human study was much higher than that obtained in a mannequin study. However, the variation in the aerosol method relative to the flow method, in the human study, os of the same order of magnitude as in the mannequin study.(ABSTRACT TRUNCATED AT 250 WORDS)

Air↗

PubMed2006

Cardiorespiratory responses of Hi Fit and Low Fit subjects to mental challenge during exercise.

The influence of psychological states on physiological responses during exercise is of considerable importance to individuals for which the efficiency of energy production is critical to occupational performance. Numerous studies have shown that aerobic fitness is associated with enhanced cardiovascular efficiency at rest and that responses to mental stress demonstrate evidence of increased sensitivity (relative increase in HR response) and enhanced efficiency (a decrease in absolute HR). However, the effect of aerobic fitness and its impact on cardiorespiratory (CR) responses to psychological stress during exercise has not been investigated. Therefore, the purpose of this study was three-fold; (1) to examine during exercise, anxiety, effort sense, and CR responses to a mental challenge, (2) to examine anxiety and heart rate (HR) responses from rest to exercise with mental challenge between below average fitness (Low Fit) and well-above average fitness (Hi Fit) individuals (exercising at similar relative intensities), and (3) to examine anxiety, effort sense, and CR responses of Low Fit and Hi Fit individuals to a mental challenge during exercise at a similar relative intensity. Twelve Low Fit and eleven Hi Fit subjects participated in two, 32-minute cycle ergometer rides at 65 % of VO2max. In the mental challenge condition (MCC), subjects rode while participating in mentally challenging tasks (Stroop Color-Word task and mental arithmetic) from min 6 to min 14 of the protocol. In the no mental challenge condition (NMCC), subjects exercised at the same intensity and duration without a stressor. Subjects were counter-balanced between fitness levels and condition. HR, VE, VE/VO2, RR, VO2, RER, effort sense (RPE), and state anxiety (SAI) were assessed at 5, 14, 24, and 30 min. SAI was also assessed at - 5 min before exercise and after 15 min of recovery. In addition, the NASA task load index (NTLX) was used to assess perceived overall workload. SAI increased significantly at 14 min in the MCC. NTLX scores indicated that the MCC was perceived as a greater overall workload. Furthermore, HR, VE, VE/VO2, and RR were significantly elevated during the mental challenge condition at 14 min. The Hi Fit subjects tended to respond to the dual stress of exercise and mental challenge with a relative increase in HR, while absolute HR was similar in both groups. An examination of fitness group differences revealed that SAI and NTLX were similar for Low Fit and Hi Fit subjects when exercising in the MCC, although, Hi Fit subjects demonstrated lower HR responses from 6 min to 14 min. VE, VE/VO2, and RR were similar for Low Fit and Hi Fit subjects. These results suggest that psychological stress during physical activity can exacerbate cardiorespiratory responses and suggests that factors that impact CR adjustment to mental challenge from resting baseline may differ from the factors that impact CR adjustment to mental challenge during exercise. Finally, fitness level attenuates HR and may attenuate additional cardiorespiratory responses while participating in a dual stress condition, of exercise and mental challenge.

Adult↗

PubMedDate not supplied

Respiratory protection as a function of respirator fitting characteristics and fit-test accuracy.

The fitting characteristics of particulate respirators are no longer assessed in the National Institute for Occupational Safety and Health respirator certification program. It is important for respirator program administrators to understand the implications of that change and the additional burden it may impose. To address that issue, a typical respirator fit-testing program is analyzed using a mathematical model that describes the effectiveness of a fit-testing program as a function of the fitting characteristics of the respirator and the accuracy of the fittesting method. The model is used to estimate (1) the respirator assignment error, the percentage of respirator wearers mistakenly assigned an ill-fitting respirator; (2) the number of fit-test trials necessary to qualify a group of workers for respirator use; and (3) the number of workers who will fail the fit-test with any candidate respirator model and thereby fail to qualify for respirator use. Using data from previous studies, the model predicts respirator assignment errors ranging from 0 to 20%, depending on the fitting characteristics of the respirator models selected and the fit-testing method used. This analysis indicates that when respirators do not necessarily have good fitting characteristics, respirator program administrators should exercise increased care in the selection of respirator models and increased care in fit-testing. Also presented are ways to assess the fitting characteristics of candidate respirator models by monitoring the first-time fit-testing results. The model demonstrates that significant public health and economic benefits can result when only respirators having good fitting characteristics are purchased and respirators are assigned to workers using highly accurate fit-testing methods.

Dust↗

PubMed2005

Variable pleiotropic effects from mutations at the same locus hamper prediction of fitness from a fitness component.

The relationship of genotype, fitness components, and fitness can be complicated by genetic effects such as pleiotropy and epistasis and by heterogeneous environments. However, because it is often difficult to measure genotype and fitness directly, fitness components are commonly used to estimate fitness without regard to genetic architecture. The small bacteriophage X174 enables direct evaluation of genetic and environmental effects on fitness components and fitness. We used 15 mutants to study mutation effects on attachment rate and fitness in six hosts. The mutants differed from our lab strain of X174 by only one or two amino acids in the major capsid protein (gpF, sites 101 and 102). The sites are variable in natural and experimentally evolved X174 populations and affect phage attachment rate. Within the limits of detection of our assays, all mutations were neutral or deleterious relative to the wild type; 11 mutants had decreased host range. While fitness was predictable from attachment rate in most cases, 3 mutants had rapid attachment but low fitness on most hosts. Thus, some mutations had a pleiotropic effect on a fitness component other than attachment rate. In addition, on one host most mutants had high attachment rate but decreased fitness, suggesting that pleiotropic effects also depended on host. The data highlight that even in this simple, well-characterized system, prediction of fitness from a fitness component depends on genetic architecture and environment.

Bacteriophage phi X 174↗

PubMed2006

Fitting strategies and candidature criteria for unilateral and bilateral hearing aid fittings.

In this paper, hearing aid fitting strategies are reviewed and candidature criteria for unilateral and bilateral fittings are discussed. Fitting strategies are primarily governed by the objectives of hearing aid fitting that can be set in different ways. Based on common goals, fitting strategies can be broken down into three stages: (1) basic fitting, (2) fine-tuning and (3) verification and validation. A fine-tuning concept basing on so-called meta-controllers is described and the issue of bilateral fitting strategies is discussed. In a first order approach, bilateral hearing aids can be fitted in parallel as unilateral aids, followed by bilateral fine-tuning, making sure that loudness is balanced and overall loudness is accepted. Parallel fitting of bilateral aids is more favourable than sequential fitting to avoid rejection because of a negative experience with unilateral amplification due to difficulties in disadvantageous listening situations. Candidature criteria are presented by means of a flow chart structuring the decision making process and arriving at the conclusion that bilateral fitting should be considered the normal case. If there is any doubt about the benefit of bilateral fitting, a trial with bilateral aids should be performed.

Hearing Aids↗

PubMedDate not supplied

Anatomic fitting studies of a total artificial heart in heart transplant recipients. Critical dimensions and prediction of fit.

Anatomic fitting studies of the Cleveland Clinic-Nimbus total artificial heart were performed in 33 patients undergoing heart transplantation. The pump fit in the pericardial space in 20 men (80%) and 4 women (50%). There was no significant difference between the Fit and Non-Fit groups in external chest dimensions. Among 42 intrathoracic dimensions, the distance from the center of the mitral valve to the diaphragm (Fit: 5.6 +/- 2.2 cm, Non-Fit: 3.6 +/- 0.4 cm, p < 0.00001) and the distance from the caudal end of the pulmonary valve to the diaphragm (Fit: 9.4 +/- 1.6 cm, Non-Fit: 6.3 +/- 0.8 cm, p < 0.0001) were the most critical. To predict anatomic fit, an index (A x B x C) was obtained from chest X-ray measurements (A, the craniocaudal distance from the dorsal region of the 8th left rib to the left diaphragm; B, the maximum left chest width; and C, the maximum anteroposterior sternum-vertebrae dimension). The pump fit in 88.5% of the patients with an index above 1200 cm3, whereas it fit in only 14.3% of the patients with an index below 1200 cm3 (p < 0.001). This index was an easily obtainable, good predictor of anatomic fit.

Diaphragm↗

PubMed2001

Assessing fitness to stand trial: the utility of the Fitness Interview Test (revised edition).

OBJECTIVE: In Canada most evaluations of fitness to stand trial are conducted on an inpatient basis. This costs time and money, and deprives those defendants remanded for evaluation of liberty. This research assessed the predictive efficiency of the Fitness Interview Test, revised edition (FIT) as a screening instrument for fitness to stand trial. METHOD: We compared decisions about fitness to stand trial, based on the FIT, with the results of institution-based evaluations for 2 samples of men remanded for inpatient fitness assessments. RESULTS: The FIT demonstrates excellent utility as a screening instrument. The FIT shows good sensitivity and negative predictive power, which suggests that it can reliably screen those individuals who are clearly fit to stand trial, before they are remanded to an inpatient facility for a fitness assessment. CONCLUSION: We discuss the implications for evaluating fitness to stand trial, particularly in terms of the need for community-based alternatives to traditional forensic assessments.

Adult↗

PubMed2004

Comparison of three procedures for initial fitting of compression hearing aids. II. Experienced users, fitted unilaterally.

This paper is the second in a series comparing three procedures for the initial fitting of multichannel compression hearing aids. The first paper reported the results for a group of 10 experienced hearing aid users fitted bilaterally. This paper reports the results for a different group of 10 experienced hearing aid users fitted unilaterally. The three procedures were: (1) CAMEQ, which aims to amplify speech so as to give equal loudness per critical band over the frequency range 500-5000 Hz, and to give similar overall loudness to normal over a wide range of speech levels; (2) CAMREST, which aims to amplify speech so as to restore normal specific loudness patterns, over a wide range of speech levels; and (3) DSL [i/o], which aims to map the dynamic range of normal-hearing people into the reduced dynamic range of hearing-impaired people, with full restoration of audibility. Each subject was fitted with one Danalogic 163D digital hearing aid, using each of the three fitting procedures in turn; the order was counter-balanced across subjects. Prescribed insertion gains for 55 and 80 dB SPL input levels were verified using real-ear measurements. Immediately after fitting with a given procedure, and 1 week after fitting. the gains were adjusted, when required, by the minimum amount necessary to achieve acceptable fittings. On average, the adjustments were smallest for the CAMREST procedure, slightly larger for the CAMEQ procedure, and largest of all for DSL [i/o]. For the DSL [i/o] the gain changes were mostly negative, especially for high frequencies and the higher input level. After these gain adjustments, users wore the aids for at least 3 weeks before speech reception thresholds (SRTs) for sentences in quiet and in steady and fluctuating background noise were measured. The APHAB questionnaire was also administered. The hearing aids were then refitted with the next procedure. SRTs and APHAB scores did not differ significantly between the three procedures. We conclude that the CAMEQ and CAMREST procedures provide a more appropriate initial fitting than DSL [i/o] for unilaterally experienced hearing aid wearers. Comparison with our earlier study based on bilateral fittings suggests that the preferred gains are similar for unilateral and bilateral fittings.

Acoustic Stimulation↗

PubMed1985

The Dorset Get-Fit Campaign--community fitness testing programme.

A pilot programme promoting fitness and exercise was launched through the local media in the Bournemouth area. The aim was to study the feasibility and effectiveness of a fitness testing programme as a trigger to increase exercise participation. Three hundred and eighty adult volunteers (male and female, all ages) undertook a sub-maximal fitness test and were given advice on exercise and diet by trained counsellors. Two hundred and eighty-five (75%) completed a second, follow-up fitness test, four months later. The results were very encouraging. Almost all of those classified as being unfit at the first test had exercised more frequently and made great improvements in physical fitness by the second test (p less than 0.01). Similarly, most of those who were overweight made substantial weight reductions during the course of the campaign (p less than 0.01). The majority of the group also made important changes in their diet. There appears to be sufficient interest in the general population to recruit people of all ages and fitness levels to join in fitness promotion programmes, but drop-out rates may be appreciative. On the basis of these findings it is proposed that fitness testing is an acceptable and helpful trigger to increased physical activity for both males and females of all ages. Such an increase in exercise appears to result in important improvements in fitness and, in combination with dietary modification, favourable reductions in weight. Further work should now be conducted in the form of controlled trials to compare the costs and effectiveness of fitness testing programmes with other methods of raising exercise levels in the community.

Adolescent↗

PubMed1985

Changes in cardiovascular fitness following physical fitness classes.

A program aimed at improving cardiovascular fitness was evaluated. This program involved 298 volunteer middle-aged participants who initially had a bicycle ergometry test to calculate fitness. Other measurements included body fat (estimated by skin fold measurements) and a rating of coronary-prone personality. The participants were given their results and then offered a six-week fitness class consisting of both didactic and exercise segments. After six months, bicycle ergometry was repeated. During this period, mean calculated maximum oxygen uptake (a measure of fitness with a "normal" range of 20 mL/kg/min to 60 mL/kg/min) improved from 38.0 to 39.6 mL/kg/min (t test, P = .0001). Classifying this according to a cardiovascular fitness rating based on age and sex, with 5 being excellent fitness to 1 being very poor fitness, the mean fitness rating went from 3.08 to 3.31 (t test, P = .0001). There was no change in weight or percentage of body fat. Both those who attended the fitness classes and those who did not attend improved equally. Those who did not attend classes had higher ratings on a coronary-prone personality scale compared with those attending classes. In some groups, it appears that significant improvement in cardiovascular fitness may be initiated with a five-minute, office-based bicycle test.

Adult↗

PubMed2002

Modeling viral genome fitness evolution associated with serial bottleneck events: evidence of stationary states of fitness.

Evolution of fitness values upon replication of viral populations is strongly influenced by the size of the virus population that participates in the infections. While large population passages often result in fitness gains, repeated plaque-to-plaque transfers result in average fitness losses. Here we develop a numerical model that describes fitness evolution of viral clones subjected to serial bottleneck events. The model predicts a biphasic evolution of fitness values in that a period of exponential decrease is followed by a stationary state in which fitness values display large fluctuations around an average constant value. This biphasic evolution is in agreement with experimental results of serial plaque-to-plaque transfers carried out with foot-and-mouth disease virus (FMDV) in cell culture. The existence of a stationary phase of fitness values has been further documented by serial plaque-to-plaque transfers of FMDV clones that had reached very low relative fitness values. The statistical properties of the stationary state depend on several parameters of the model, such as the probability of advantageous versus deleterious mutations, initial fitness, and the number of replication rounds. In particular, the size of the bottleneck is critical for determining the trend of fitness evolution.

Animals↗

PubMed2001

Comparison of three procedures for initial fitting of compression hearing aids. I. Experienced users, fitted bilaterally.

We compared the effectiveness of three procedures for the initial fitting of hearing aids with multi-band compression: (1) CAMEQ, which aims to amplify speech so as to give equal loudness per critical band over the frequency range important for speech intelligibility, and to give similar overall loudness to 'normal': (2) CAMREST, which aims to amplify speech so as to restore 'normal' specific loudness patterns, over a wide range of speech levels; (3) DSL I/O, which aims to map the dynamic range of normally hearing people into the reduced dynamic range of hearing-impaired people, with 'full' restoration of audibility. Ten experienced hearing aid users with moderate sensorineural loss were fitted bilaterally with Danalogic 163D digital hearing aids, using each procedure in turn; the order was counterbalanced across subjects. The fitting required specification of gains for input levels of 55 and 80 dB SPL at six centre frequencies. Real-ear measurements were made to ensure that target gains were reached (+/-3 dB). Immediately after fitting with a given procedure, and one week after fitting, the gains were adjusted when required by the minimum amount necessary to achieve acceptable fittings. The amount of adjustment required provides one measure of the adequacy of the initial fitting. On average, the adjustments were smallest for the CAMEQ procedure. The gain changes were slightly larger for the CAMREST procedure and were largest of all for DSL I/O. For the latter, the gain changes were mostly negative, especially for high frequencies and the higher input level. This indicates that the DSL I/O procedure prescribes more high-frequency gain than is preferred by adult users. After these gain adjustments, users wore the aids for at least three weeks before filling out the APHAB questionnaire and taking part in laboratory measurements of the speech reception threshold (SRT) for sentences in quiet and in steady and fluctuating background noise at levels of 60 and 75 dB SPL. Following these tests, the hearing aids were re-fitted with the next procedure. The scores on the APHAB test and the SRTs did not differ significantly for the three procedures. We conclude that the CAMEQ and CAMREST procedures provide more appropriate initial fittings than DSL I/O.

Acoustic Stimulation↗

PubMed2005

Use of self-assessed fitness and exercise parameters to predict objective fitness.

PURPOSE: The purpose of this prospective study was to examine the effectiveness of self-assessed fitness and exercise in predicting objectively measured physical fitness. METHODS: Study subjects included 1583 men who entered Marine Corps training in San Diego, CA, between September and November 2002 and completed a questionnaire and an objective fitness test. The questionnaire included demographic and self-assessed fitness/exercise items, and was administered immediately upon entry into the training program. The objective fitness measure was obtained using a standardized test after approximately 1 month of training. RESULTS: Multivariate modeling found that several measures of self-assessed fitness and exercise (estimated number of pull-ups; good, very good, or excellent self-assessed fitness; sweating quite a lot or most or all of the time during physical activity; and competitive experience) were all associated with the objective fitness score. These results remained statistically significant after controlling for age, race, and body mass index (model adjusted R2 = 0.469, P < 0.01). CONCLUSION: In this analysis, self-assessed fitness and exercise parameters that can be easily ascertained with a short questionnaire predicted objective fitness scores approximately 1 month later. This information could be used by recruiters to make recommendations for pre-enlistment conditioning.

Adolescent↗

PubMed2003

Relations among physical activity, physical fitness, and self-perceived fitness in Hong Kong adolescents.

The relationships between physical fitness, activity, and self-perceived fitness in adolescents in Hong Kong were investigated. Regular physical activity patterns, self-perceptions of fitness, and health-related physical fitness were measured in 201 secondary school students (M age = 13.8 yr.). The battery of fitness tests measured cardiovascular capacity, flexibility, muscular strength, muscular endurance, and body fat composition. The boys had a higher self-perception of their own fitness and exercised more outside school than the girls. Participation in physical activity was related to cardiovascular capacity, muscular strength, and body composition. Linear regression analysis indicated that exercise activity and body composition explained a portion of variance in the subjects' self-perceived fitness. These findings highlight the connections between physical activity, fitness, and self-perception of fitness and consequently the need for understanding the concept for better health-promotion strategies.

Adolescent↗

PubMed2006

Relative replication fitness of efavirenz-resistant mutants of HIV-1: correlation with frequency during clinical therapy and evidence of compensation for the reduced fitness of K103N + L100I by the nucleoside resistance mutation L74V.

Efavirenz resistance during HIV-1 treatment failure is usually associated with the reverse transcriptase mutation K103N. L100I, V108I, or P225H can emerge after K103N and increase its level of efavirenz resistance. K103N + L100I is the most drug-resistant of the double mutants but is the least common clinically. We hypothesized that differences in replication efficiency, or fitness, influence the relative frequencies of these secondary efavirenz resistance mutations in clinical isolates. We measured fitness of each secondary mutant introduced into HIV(NL4-3), alone and in combination with K103N, using growth competition assays in H9 cells. In the absence of efavirenz, the fitness of V108I was indistinguishable from wild type. K103N, L100I, and P225H were minimally, but consistently, less fit than wild type. K103N + L100I had a greater reduction in fitness and was less fit than K103N + V108I and K103N + P225H. The fitness defect of K103N + L100I relative to K103N was completely compensated for by the addition of the nucleoside resistance mutation L74V. In the presence of efavirenz, L100I was less fit than K103N, and K103N + L100I was more fit than K103N + V108I. Our studies suggest the primary driving force behind the selection of secondary efavirenz resistance mutations is the acquisition of higher levels of drug resistance, but the specific secondary mutations to emerge are those with the least cost in terms of replication efficiency. In addition, nucleoside and NNRTI resistance mutations can interact to affect HIV replication efficiency; these interactions may influence which mutations emerge during treatment failure. These studies have important implications for the design of more durable NNRTI-nucleoside combination regimens.

Alkynes↗