The effect of weight-lifting exercise related to muscle fiber composition and muscle cross-sectional area in humans

Summary Isometric and dynamic strength and endurance of knee extensors were tested in 18 young males. The relative composition of slow (ST) and fast twitch (FT) fibers in the vastus lateralis muscle was registered from needle biopsies. Thigh muscle volume was evaluated from ultrasonic measurements. Six subjects served as controls, six trained with 50%, and six with 80% dynamic strength three times per week for 7 weeks with 20 and 12 repetitions per session, respectively. The training load was adjusted to the increases in strength observed during training. Dynamic strength increased by 42.3% in the 80% group (p< 0.01). In the control group and 50% group no significant increases were observed. Dynamic endurance: Controls showed no change. There was an over-all increase in the 50% group, while the 80% group only increased dynamic endurance for heavier loads. Isometric strength and endurance and fiber composition did not change in any group. In the 50% group the area of FT-realtive to ST-fibers increased 12.4% (p>0.05). Dynamic strength relative to muscle cross section increased by 30% in the 80% group (p<0.01) positively correlated to relative content of FT fibers.The present results confirm the specificity of training and indicate that a high content of FT fibers is a prerequisite for a successful strength training.     

Factors related to allergic sensitization to aeroallergens in a cross-sectional study in adults: The Copenhagen Allergy Study

BACKGROUND: The factors underlying recent increases in the prevalence of respiratory allergy are largely unknown. OBJECTIVE: To assess the association between allergic sensitization and several lifestyle/environmental factors. METHODS: A cross-sectional population-based study of 15-69-year-olds in Copenhagen was carried out in 1990. The participation rate was 77.5% (1112/1435). Different lifestyle/environmental factors (explanatory variables) were defined based on questionnaire data. Dependent (outcome) variables were skin prick test (SPT) positivity or specific IgE positivity to common aeroallergens. Explanatory variables associated with outcome in univariate analysis (P < 0.25) were selected for multivariate analysis. Subsequently, a final model for each dependent variable was obtained by stepwise regression analysis (cut-off for entry/removal of variables: P < 0.1). RESULTS: Male sex, young age, low number of siblings, a positive family history of hay fever and never smoking, were independently associated with both SPT positivity and specific IgE positivity. Furthermore, SPT positivity was positively associated with alcohol consumption (dose-response relationship only), and negatively associated with previous keeping of a dog in the household. The association between alcohol consumption and SPT positivity was mainly due to the consumption of wine and remained after adjustment for educational level. Specific IgE positivity was furthermore associated with body mass index with no apparent dose-response relationship. CONCLUSION: Being male, young age, a positive family history of hayfever, low number of siblings and never smoking, were independently associated with allergic sensitization. In addition, the results indicated a possible relationship of alcohol consumption, body mass index and previous keeping of a dog in the household to allergic sensitization. There is a need for prospective studies of risk factors for respiratory allergy.     

Generality versus specificity: a comparison of dynamic and isometric measures of strength and speed-strength

Considerable debate exists as to whether the qualities of muscle function exist as general or specific physiological capacities. If there is a generality of muscle function then strong relationships would exist between various measures of function for the same muscle(s), independent of the test contraction, mode or velocity. The purpose of this study was to examine the relationship between isometric and dynamic measures of muscle function to determine the existence of generality or specificity. A group of 22 men, experienced in weight training, were tested for lower and upper body dynamic and isometric measures of strength and speed-strength. The changes in these measures consequent to a resistance training programme were also investigated. The results of this study indicated that whilst isometric and dynamic measures of strength did significantly correlate (r=0.57-0.61), the relationship was below that required to denote statistical generality. More important, the changes in isometric and dynamic strength consequent to a dynamic heavy resistance training programme were unrelated (r=0.12-0.15). Thus the mechanisms that contribute to enhanced dynamic strength appearred unrelated to the mechanisms that contribute to enhanced isometric strength. Measures of dynamic and isometric speed-strength were unrelated, as were the changes in these measures resulting from training. The results of this study demonstrated that a generality of muscle function did not exist and that modality specific results were observed. Consequently this study calls into question the validity of isometric tests to monitor dynamically induced training adaptations.     

UNC13A influences survival in Italian amyotrophic lateral sclerosis patients: a population-based study

The common variant rs12608932, located within an intron of UNC13A gene on chromosome 19p13.3, has been suggested to influence susceptibility to amyotrophic lateral sclerosis (ALS), as well as survival, in patients of north European descent. To examine this possibility further, we evaluated the association of rs12608932 with susceptibility and survival in a population-based cohort of 500 Italian ALS patients and 1457 Italian control samples. Although rs12608932 was not associated with ALS susceptibility in our series (p = 0.124), it was significantly associated with survival under the recessive model (median survival for AA/AC genotypes = 3.5 years [interquartile range, 2.2–6.4]; CC = 2.5 years [interquartile range, 1.6–4.2]; p = 0.017). Furthermore, rs12608932 genotype remained an independent prognostic factor in Cox multivariable analysis adjusting for other factors known to influence survival (p = 0.023). Overall, minor allele carrier status of rs12608932 was strongly associated with an approximate 1-year reduction of survival in ALS patients, making it a significant determinant of phenotype variation. The identification of UNC13A as a modifier of prognosis among sporadic ALS patients potentially provides a new therapeutic target aimed at slowing disease progression.     

Factors associated with enablement in general practice: cross-sectional study using routinely-collected data.

BACKGROUND: Quality-improvement activities are most often focused on clinical quality indicators. However, patient evaluations are important additional indicators of the quality of general practice consultations, including measures of satisfaction or enablement (that is, the extent to which the consultation enhances the patient's feelings of confidence and ability to cope). There is limited evidence concerning factors associated with enablement in UK general practice. AIM: To identify patient and practice characteristics associated with enablement scores following general practice consultations. DESIGN OF STUDY: Cross-sectional survey using a large routinely-collected dataset of patient evaluations of general practice (190,038 individual patient responses). SETTING: A total of 1031 UK general practices. METHOD: Relationships between health, demographic factors, evaluations of general practice care, and patient self-reported enablement were estimated using multiple regression. RESULTS: The primary predictor of enablement was positive patient evaluation of the GPs' communication. Reported continuity of care accounted for a lower proportion of the variance. Of the included patient demographic variables, ethnicity was a key predictor, with patients from minority ethnic groups reporting greater enablement once other factors were controlled. CONCLUSION: The current results provide support for the construct validity of the enablement measure. However, if enablement is to become a valid and useful measure of quality, it is necessary to understand the mechanisms by which enablement is increased in certain patients and practices. Detailed qualitative research may also be required to explain the relatively high scores of ethnic minority responders, despite lower overall satisfaction scores, and to understand why some items included in the enablement measure are regarded as 'not applicable' by a substantial minority of patients.     

Diffusive sensitivity to muscle architecture: a magnetic resonance diffusion tensor imaging study of the human calf

The aim of this study was to examine the diffusive properties of adjacent muscles at rest, and to determine the relationship between diffusive and architectural properties, which are task-specific to muscles. The principle, second, and third eigenvalues, trace of the diffusion tensor, and two anisotropic parameters, ellipsoid eccentricity (e) and fractional anisotropy (FA), of various muscles in the human calf were calculated by diffusion tensor imaging (DTI). Linear correlations of the calculated parameters to the muscle physiological cross-sectional area (PCSA), which is proportional to maximum muscle force, were performed to ascertain any linear relation between muscle architecture and diffusivity. Images of the left calf were acquired from six healthy male volunteers. Seven muscles were investigated in this study. These comprised the soleus, lateral gastrocnemius, medial gastrocnemius, posterior tibialis, anterior tibialis, extensor digitorum longus, and peroneus longus. All data were presented as the mean and standard error of the mean (SEM). In general, differences in diffusive parameter values occurred primarily between functionally different muscles. A strong correlation was also found between PCSA and the third eigenvalue, e, and FA. A mathematical derivation revealed a linear relationship between PCSA and the third eigenvalue as a result of their dependence on the average radius of all fibers within a single muscle. These findings demonstrated the ability of DTI to differentiate between functionally different muscles in the same region of the body on the basis of their diffusive properties.     

Hereditary haemorrhagic telangiectasia and pulmonary arteriovenous malformations in brain abscess patients: a nationwide,population-based matched cohort study

ObjectivesThe extent of hereditary haemorrhagic telangiectasia (HHT) and pulmonary arteriovenous malformations (PAVMs) as a risk factor for brain abscess is unknown.MethodsNationwide and population-based registries were used to identify persons with first-time hospitalization for brain abscess (index date) and population controls matched by age, sex and residence (1:10). Accounting for competing risks, cumulative incidence curves of new diagnosis of HHT/PAVM after brain abscess were constructed. Next, Cox regression was used for computation of cause-specific hazard rate ratios (HRRs) adjusted for severe liver disease and congenital heart disease as potential confounders.ResultsHHT/PAVM was prevalent before the index date in 2/1384 (0.1%; 95% CI 0.02–0.52) brain abscess patients and 6/13 838 (0.04%; 95% CI 0.02–0.09) matched population controls. After the index date, a new diagnosis of hereditary haemorrhagic telangiectasia or pulmonary arteriovenous malformations was made in 15/1384 brain abscess patients (range 0 days to 17 years) compared with 7/13 812 population controls yielding an adjusted hazard rate ratio of 31.4 (95% CI 9.95–98.9). Cumulative incidence was 1.5% for brain abscess patients and 0.1% for population controls.DiscussionHHT/PAVM should be considered in patients with cryptogenic brain abscess, although absolute risk is low.     

Lack of gender differences in the ability to relax between repetitive maximum isokinetic shoulder forward flexions: a population-based study among northern Swedes

The aim of the present study was to analyse the effects of gender and age in a population-based sample of clinically healthy subjects on: (1) strength, endurance and perception of fatigue, (2) mean frequency (MNF) of the electromyogram (EMG), and (3) the ability to relax between active contractions (signal amplitude ratio; SAR) of the surface EMG of an isokinetic shoulder forward flexion test. With this aim we have analysed aspects of the validity of MNF as an indicator of fatigue, using peak torque as a criterion variable. The subjects were 27 men and 28 women (age range: 20–60 years), who were obtained by random sample from the official census lists (participation rate: 66%). The peak torque and surface EMG of two portions of the trapezius, deltoid and infraspinatus muscles were recorded throughout 100 repetitive maximal isokinetic shoulder forward flexions. No significant differences in the perception of fatigue and relative endurance levels of peak torque and work were found between males and females. Males were significantly stronger than females and, on average, females produced approximately 60% of the output of the males; 76% after normalisation for body mass. The men had significantly lower MNF endurance levels for three of the investigated muscles. When controlled for age and body mass, the men had a significantly higher MNF of the deltoid muscle than did the females. These differences were only found for the deltoid muscle. Significant correlations existed between the MNF of the four muscles and biomechanical output, indicating criterion validity for the MNF variable with respect to fatigue. There were no significant effects of gender or age on the ability to relax between repetitive contractions (SAR). The higher prevalence of musculoskeletal complaints of the neck-shoulder region in females cannot be explained by a higher intrinsic muscle tension. Age, gender, body mass index and biomechanical output can have significant effects upon MNF. These effects are important considerations in the interpretation of MNF, for instance in ergonomic situations. Accepted: 17 July 2000     

Cross-sectional study of muscle strength and bone mineral density in a population of 106 women between the ages of 44 and 87 years: relationship with age and menopause

This study examined the correlations between isokinetic muscle strength of knee and elbow flexors and extensors with vertebral and femoral bone mineral density in a population of 106 women between the ages of 44 and 87 years. The absolute value of muscle strength correlated significantly with bone mineral density; muscle strength of the upper limb appeared to be more closely correlated with bone mass, while muscle strength in the lower limb was more specific for femoral mineral bone density. The most important finding that these results demonstrated was a concomitant decline in muscle strength of the upper limb and bone mineral density between the 5th and 6th decades. In contrast, they also showed a decline in muscle strength of the lower limbs after the 6th decade, occurring before the decline in bone mineral density observed between the 7th and 8th decades. From these results it would appear that other studies are required to examine the relationship between the essentially hormonal role in postmenopausal decline in muscle strength and the decline in physical activity during the senile period. These elements are important because they must be taken into account in physical exercise programmes designed to prevent osteoporosis.     

Cigarette smoking and age of menopause: a large prospective study

Objectives

One of the possible consequences of tobacco consumption is that it contributes to an earlier age of menopause, though the causal relationship is yet to be confirmed. This study aimed to examine the prospective association between smoking and earlier age of menopause in a cohort of middle age Australian women after adjustment for a number of potential confounders.

Study design

21-Year follow-up of a cohort prospective study, Brisbane, Australia.

Main outcome measures

Age of menopause measured at the 21-year follow-up. Smoking and menopausal status were assessed by self-report. Other covariates were measured prospectively in the previous follow-ups.

Results

This study is based on 3545 women who provided data on their menopausal status at the 21-year follow-up of the study, and prospective as well as concurrent data on smoking. In univariate analysis tobacco smoking during the reproductive life course, socio-economic status and gravidity were significantly associated with earlier age of menopause. In multivariate analyses women who smoked cigarettes were more likely to experience earlier menopause than non-smokers. Compared to current smokers, risk of early menopause was significantly lower in those women who quit smoking in the past.

Conclusions

The data suggest that the impact of smoking is independent of other covariates associated with both smoking and age of menopause. The findings raise the possibility that effective quit smoking interventions may lead to a later age of menopause, and reduce the risk of adverse health consequences of early menopause.     

Factors related to genetic testing in adults at risk for Huntington disease: the prospective Huntington at‐risk observational study (PHAROS)

Huntington disease (HD) is a late onset ultimately fatal neurodegenerative disorder caused by a cytosine–adenine–guanine ( CAG) triplet repeat expansion in the Huntingtin gene which was discovered in 1993. The PHAROS study is a unique observational study of 1001 individuals at risk for HD who had not been previously tested for HD and who had no plans to do so. In this cohort, 104 (10%) individuals changed their minds and chose to be tested during the course of the study but outside of the study protocol. Baseline behavioral scores, especially apathy, were more strongly associated with later genetic testing than motor and chorea scores, particularly among subjects with expanded CAG repeat length. In the CAG expanded group, those choosing to be tested were older and had more chorea and higher scores on the behavioral section of the unified Huntington's disease rating scale at baseline than those not choosing to be tested. Following genetic testing, 56% of subjects with CAG < 37 had less depression when compared to prior to testing, but depression generally stayed the same or increased for 64% of subjects in the expanded group. This finding suggests that approaches to testing must continue to be cautious, with appropriate medical, psychological and social support.     

Using Internet search engines to obtain medical information: a comparative study

Background

The Internet has become one of the most important means to obtain health and medical information. It is often the first step in checking for basic information about a disease and its treatment. The search results are often useful to general users. Various search engines such as Google, Yahoo!, Bing, and Ask.com can play an important role in obtaining medical information for both medical professionals and lay people. However, the usability and effectiveness of various search engines for medical information have not been comprehensively compared and evaluated.

Objective

To compare major Internet search engines in their usability of obtaining medical and health information.

Methods

We applied usability testing as a software engineering technique and a standard industry practice to compare the four major search engines (Google, Yahoo!, Bing, and Ask.com) in obtaining health and medical information. For this purpose, we searched the keyword breast cancer in Google, Yahoo!, Bing, and Ask.com and saved the results of the top 200 links from each search engine. We combined nonredundant links from the four search engines and gave them to volunteer users in an alphabetical order. The volunteer users evaluated the websites and scored each website from 0 to 10 (lowest to highest) based on the usefulness of the content relevant to breast cancer. A medical expert identified six well-known websites related to breast cancer in advance as standards. We also used five keywords associated with breast cancer defined in the latest release of Systematized Nomenclature of Medicine-Clinical Terms (SNOMED CT) and analyzed their occurrence in the websites.

Results

Each search engine provided rich information related to breast cancer in the search results. All six standard websites were among the top 30 in search results of all four search engines. Google had the best search validity (in terms of whether a website could be opened), followed by Bing, Ask.com, and Yahoo!. The search results highly overlapped between the search engines, and the overlap between any two search engines was about half or more. On the other hand, each search engine emphasized various types of content differently. In terms of user satisfaction analysis, volunteer users scored Bing the highest for its usefulness, followed by Yahoo!, Google, and Ask.com.

Conclusions

Google, Yahoo!, Bing, and Ask.com are by and large effective search engines for helping lay users get health and medical information. Nevertheless, the current ranking methods have some pitfalls and there is room for improvement to help users get more accurate and useful information. We suggest that search engine users explore multiple search engines to search different types of health information and medical knowledge for their own needs and get a professional consultation if necessary.     

Testing whether barriers to a hypothetical screening test affect unrelated perceived benefits and vice versa: A randomised,experimental study

ObjectiveDetermine whether (fictitious) health screening test benefits affect perceptions of (unrelated) barriers, and barriers affect perceptions of benefits.MethodsUK adults were recruited via an online survey panel and randomised to receive a vignette describing a hypothetical screening test with either high or low benefits (higher vs. lower mortality reduction) and high or low barriers (severe vs. mild side-effects; a 2 × 2 factorial design). ANOVAs compared mean perceived benefits and barriers scores. Screening ‘intentions’ were compared using Pearson’s χ² test.ResultsBenefits were rated less favourably when barriers were high (mean: 27.4, standard deviation: 5.3) than when they were low (M: 28.5, SD: 4.8; p = 0.010, partial η² = 0.031). Barriers were rated more negatively when benefits were low (M: 17.1, SD: 7.6) than when they were high (M: 15.7, SD: 7.3; p = 0.023, partial η² = 0.024). Most intended to have the test in all conditions (73–81%); except for the low benefit-high barrier condition (37%; p < 0.0005; N = 218).ConclusionsPerceptions of test attributes may be influenced by unrelated characteristics.Practice implicationsReducing screening test barriers alone may have suboptimal effects on perceptions of barriers if benefits remain low; increasing screening benefits may not improve perceptions of benefits if barriers remain high.     

Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study

Summary To investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake ( O ₂) and blood lactate concentrations were measured during submaximal and maximal treadmill running. The data were aligned with each individual's age of peak height velocity. The maximal oxygen uptake ( O _2max; ml · kg^–1 · min^–1) decreased with growth in the untrained group but remained almost constant in the training group. The oxygen cost of running at 15 km · h^–1 ( O ₂₁₅, ml · kg^–1 · min^–1) was persistently lower in the trained group but decreased similarly with age in both groups. The development of O _2max and O ₂₁₅ (1 · min^–1) was related to each individual's increase in body mass so that power functions were obtained. The mean body mass scaling factor was 0.78 (SEM 0.07) and 1.01 (SEM 0.04) for O _2max and 0.75 (SEM 0.09) and 0.75 (SEM 0.02) for O ₂₁₅ in the untrained and trained groups, respectively. Therefore, expressed as ml · kg^–0.75 · min^–1, O ₂₁₅ was unchanged in both groups and O _2max increased only in the trained group. The running velocity corresponding to 4 mmol · 1^–1 of blood lactate ( _la4) increased only in the trained group. Blood lactate concentration at exhaustion remained constant in both groups over the years studied. In conclusion, recent and the present findings would suggest that changes in the oxygen cost of running and O _2max (ml · kg^–1 · min^–1) during growth may mainly be due to an overestimation of the body mass dependency of O ₀₂ during running. The O ₂ determined during treadmill running may be better related to kg^0.75 than to kg¹.     

An exploration of factors related to dissemination of and exposure to internet-delivered behavior change interventions aimed at adults: a Delphi study approach

Background

The Internet is an attractive medium for delivering individualized, computer-tailored behavior change interventions to large numbers of people. However, the actual numbers of people reached seem to fall behind the high expectations. Insight into factors that determine use of and exposure to these Internet interventions is important to be able to increase the reach and improve exposure.

Objective

The aim was to identify potentially important factors that determine whether adults visit an Internet-delivered behavior change intervention, extend their visit, and revisit the intervention.

Methods

A systematic, three-round Delphi study was conducted among national and international experts from Internet intervention research and practice, e-marketing/e-commerce, Web design, and technical website development. In the first round, 30 experts completed a structured, open-ended online questionnaire assessing factors that were, in their opinion, important for a first visit, an extended visit, a revisit and for effective promotion strategies. Based on the responses in this first questionnaire, a closed-ended online questionnaire was developed for use in the second round. A total of 233 experts were invited to complete this questionnaire. Median and interquartile deviation (IQD) scores were computed to calculate agreement and consensus on the importance of the factors. The factors for which no consensus was obtained (IQD > 1) were included in the third-round questionnaire. Factors with a median score of six or higher and with an IQD ≤ 1 were considered to be important.

Results

Of the 62 experts invited for the first round, 30 completed the questionnaire (48% response rate); 93/233 experts completed the second-round questionnaire (40% response rate), and 59/88 completed the third round (67% response rate). Being motivated to visit an Internet intervention and perceiving the intervention as personally relevant appeared to be important factors related to a first visit. The provision of tailored feedback, relevant and reliable information, and an easy navigation structure were related to an extended visit. Provision of regular new content and the possibility to monitor personal progress toward behavior change were identified as important factors to encourage a revisit. Primarily traditional promotion strategies, like word-of-mouth by family and friends, a publicity campaign with simultaneous use of various mass media, and recommendation by health professionals, were indicated as effective ways to encourage adults to visit an Internet intervention.

Conclusions

This systematic study identified important factors related to the dissemination of and exposure to Internet interventions aimed at adults. In order to improve optimal use of and exposure to Internet interventions, potential users may need to be motivated to visit such an intervention and the information provided needs to be personally relevant. Furthermore, several (technical) aspects of the intervention itself need to be taken into account when developing Internet interventions.     

Analyzing the influence of institutions on health policy development in Uganda: a case study of the decision to abolish user fees

Background

During the 2001 election campaign, President Yoweri Museveni announced he was abolishing user fees for health services in Uganda. No analysis has been carried out to explain how he was able to initiate such an important policy decision without encountering any immediate barriers.

Objective

To explain this outcome through in-depth policy analysis driven by the application of key analytical frameworks.

Methods

An explanatory case study informed by analytical frameworks from the institutionalism literature was undertaken. Multiple data sources were used including: academic literature, key government documents, grey literature, and a variety of print media.

Results

According to the analytical frameworks employed, several formal institutional constraints existed that would have reduced the prospects for the abolition of user fees. However, prevalent informal institutions such as “Big Man” presidentialism and clientelism that were both ‘competing’ and ‘complementary’ can be used to explain the policy outcome. The analysis suggests that these factors trumped the impact of more formal institutional structures in the Ugandan context.

Conclusion

Consideration should be given to the interactions between formal and informal institutions in the analysis of health policy processes in Uganda, as they provide a more nuanced understanding of how each set of factors influence policy outcomes.