British Journal of Sports Medicine recent issues

Intense exercise and airway hyper-responsiveness/asthma--importance of environmental factors

Fitch, K., Anderson, S. — 2012-04-05T00:30:04-07:00

Exercise has a paradoxical relationship to asthma. It has been known for nearly 2000 years that exercise can provoke bronchoconstriction,1 termed exercise-induced bronchoconstriction or exercise-induced asthma. Yet exercise has also been prescribed to assist in the management of asthma as long ago as the middle of the 16th century.2 Over the last two decades, evidence has been accumulating that intense repeated exercise can injure airways and promote the development of airway hyperresponsiveness (AHR) and/or asthma in athletes with no past or family history of asthma.3 This issue of BJSM will focus on the third aspect of this triad.

Concerned that Olympic athletes may have been misusing inhaled β₂ agonists (IBA), in 2002 the International Olympic Committee (IOC) introduced the requirement that athletes had to demonstrate current asthma/AHR to use IBA before an event at the Olympic Games.4 It is stressed that...

Respiratory physiology: adaptations to high-level exercise

McKenzie, D. C. — 2012-04-05T00:30:04-07:00

Most exercise scientists would agree that the physiological determinants of peak endurance performance include the capacity to transport oxygen to the working muscle, diffusion from the muscle to the mitochondria, energy production and force generation, all influenced by signals from the central nervous system. In general, the capacity of the pulmonary system far exceeds the demands required for ventilation and gas exchange during exercise. Endurance training induces large and significant adaptations within the cardiovascular, musculoskeletal and haematological systems. However, the structural and functional properties of the lung and airways do not change in response to repetitive physical activity and, in elite athletes, the pulmonary system may become a limiting factor to exercise at sea level and altitude. As a consequence to this respiratory paradox, highly trained athletes may develop intrathoracic and extrathoracic obstruction, expiratory flow limitation, respiratory muscle fatigue and exercise-induced hypoxaemia. All of these maladaptations may influence performance.

Airway injury during high-level exercise

Kippelen, P., Anderson, S. D. — 2012-04-05T00:30:04-07:00

Airway epithelial cells act as a physical barrier against environmental toxins and injury, and modulate inflammation and the immune response. As such, maintenance of their integrity is critical. Evidence is accumulating to suggest that exercise can cause injury to the airway epithelium. This seems the case particularly for competitive athletes performing high-level exercise, or when exercise takes place in extreme environmental conditions such as in cold dry air or in polluted air. Dehydration of the small airways and increased forces exerted on to the airway surface during severe hyperpnoea are thought to be key factors in determining the occurrence of injury of the airway epithelium. The injury-repair process of the airway epithelium may contribute to the development of the bronchial hyper-responsiveness that is documented in many elite athletes.

Assessment and prevention of exercise-induced bronchoconstriction

Anderson, S. D., Kippelen, P. — 2012-04-05T00:30:04-07:00

The assessment of exercise-induced bronchoconstriction (EIB) in athletes requires the measurement of forced expiratory volume in 1 s (FEV₁) before and after vigorous exercise or a surrogate of exercise such as eucapnic voluntary hyperpnoea (EVH) of dry air or mannitol dry powder. Exercise testing in a laboratory has a low sensitivity to identify EIB, and exercise testing in the field can be a challenge in itself particularly in cold weather athletes. The EVH test requires the subject to ventilate dry air containing ~5% CO₂ for 6 min through a low-resistance circuit at a rate higher than that usually achieved on maximum exercise. A ≥10% reduction in FEV₁ is a positive response to exercise and EVH and, when sustained, is usually associated with release of inflammatory mediators of broncho constriction. Another surrogate, mannitol dry powder, given by inhalation in progressively increasing doses, is used to mimic the dehydrating stimulus of exercise hyperpnoea. A positive mannitol test is a 15% fall in FEV₁ at ≤635 mg and reveals potential for EIB. Mannitol has a high specificity for identifying a clinical diagnosis of asthma. Once a diagnosis of EIB is established, the athlete needs to know how to avoid EIB. Being treated daily with an inhaled corticosteroid to reduce airway inflammation, inhaling a β₂ agonist or a cromone immediately before exercise, or taking a leukotriene antagonist several hours before exercise, all inhibit or prevent EIB. Other strategies include warming up prior to exercise and reducing respiratory water and heat loss by using face masks or nasal breathing.

Winter sports athletes: long-term effects of cold air exposure

Sue-Chu, M. — 2012-04-05T00:30:04-07:00

Athletes such as skaters and skiers inhale large volumes of cold air during exercise and shift from nasal to mouth breathing. Endurance athletes, like cross-country skiers, perform at 80% or more of their maximal oxygen consumption and have minute ventilations in excess of 100 l/min. Cold air is always dry, and endurance exercise results in loss of water and heat from the lower respiratory tract. In addition, athletes can be exposed to indoor and outdoor pollutants during the competitive season and during all-year training. Hyperpnoea with cold dry air represents a significant environmental stress to the airways. Winter athletes have a high prevalence of respiratory symptoms and airway hyper-responsiveness to methacholine and hyperpnoea. The acute effects of exercise in cold air are neutrophil influx as demonstrated in lavage fluid and airway epithelial damage as demonstrated by bronchoscopy. Upregulation of pro-inflammatory cytokines has been observed in horses. Chronic endurance training damages the epithelium of the small airways in mice. Airway inflammation has been observed on bronchoscopy of cross-country skiers and in dogs after a 1100-mile endurance race in Alaska. Neutrophilic and lymphocytic inflammation with remodelling is present in bronchial biopsies from skiers. Repeated peripheral airway hyperpnoea with dry air causes inflammation and remodelling in dogs. As it is currently unknown if these airway changes are reversible upon cessation of exposure, preventive measures to diminish exposure of the lower airways to cold air should be instituted by all winter sports athletes.

Airway dysfunction in swimmers

Bougault, V., Boulet, L.-P. — 2012-04-05T00:30:04-07:00

Elite competitive swimmers are particularly affected by airway disorders that are probably related to regular and intense training sessions in a chlorinated environment. Upper and lower airway respiratory symptoms, rhinitis, airway hyper-responsiveness, and exercise-induced bronchoconstriction are highly prevalent in these athletes, but their influence on athletic performance is still unclear. The authors reviewed the main upper and lower respiratory ailments observed in competitive swimmers who train in indoor swimming pools, their pathophysiology, clinical significance and possible effects on performance. Issues regarding the screening of these disorders, their management and preventive measures are addressed.

Effect of air pollution on athlete health and performance

Rundell, K. W. — 2012-04-05T00:30:04-07:00

Unfavourable effects on the respiratory and the cardiovascular systems from short-term and long-term inhalation of air pollution are well documented. Exposure to freshly generated mixed combustion emissions such as those observed in proximity to roadways with high volumes of traffic and those from ice-resurfacing equipment are of particular concern. This is because there is a greater toxicity from freshly generated whole exhaust than from its component parts. The particles released from emissions are considered to cause oxidative damage and inflammation in the airways and the vascular system, and may be related to decreased exercise performance. However, few studies have examined this aspect. Several papers describe deleterious effects on health from chronic and acute air pollution exposure. However, there has been no research into the effects of long-term exposure to air pollution on athletic performance and a paucity of studies that describe the effects of acute exposure on exercise performance. The current knowledge of exercising in the high-pollution environment and the consequences that it may have on athlete performance are reviewed.

An overview of asthma and airway hyper-responsiveness in Olympic athletes

Fitch, K. D. — 2012-04-05T00:30:04-07:00

Data from the past five Olympic Games obtained from athletes seeking to inhale β2 adrenoceptor agonists (IBA) have identified those athletes with documented asthma and airway hyper-responsiveness (AHR). With a prevalence of about 8%, asthma/AHR is the commonest chronic medical condition experienced by Olympic athletes. In Summer and Winter athletes, there is a marked preponderance of asthma/AHR in endurance-trained athletes. The relatively late onset of asthma/AHR in many older athletes is suggestive that years of endurance training may be a contributory cause. Inspiring polluted or cold air is considered a significant aetiological factor in some but not all sports. During the last five Olympic Games, there has been improved management of athletes with asthma/AHR with a much higher proportion of athletes combining inhaled corticosteroids (ICS) with IBA and few using long-acting IBA as monotherapy. Athletes with asthma/AHR have consistently outperformed their peers, which research suggests is not due to their treatment enhancing sports performance. Research is necessary to determine how many athletes will continue to experience asthma/AHR in the years after they cease intensive endurance training.

Cough and upper airway disorders in elite athletes: a critical review

Boulet, L.-P. — 2012-04-05T00:30:04-07:00

Respiratory diseases such as asthma, chronic cough, recurrent respiratory infections and various upper airways conditions are common in elite athletes, but these conditions are often underdiagnosed and undertreated. Recurrent cough, often observed after exercise, is the most commonly reported symptom in athletes, particularly winter athletes, but it does not predict airway function; its intensity correlates with the dryness of inspired air but may not be associated with airway hyper-responsiveness. Rhinitis, either allergic or not, is highly prevalent in athletes, particularly non-allergic rhinitis in swimmers. Finally, dysfunctional breathing, including vocal cord dysfunction, may mimic or accompany asthma in a significant number of athletes. These conditions should be recognised and treated properly according to current guidelines, although how these last apply in the athlete is uncertain. Furthermore, regulatory agencies' restrictions on the type of drugs allowed for therapeutic use of these conditions in competitive athletes should be checked.

Economic analysis of physical activity interventions

Williams, C. M., Lin, C.-W. C., Jan, S. — 2012-04-05T00:30:04-07:00

Wu S, Cohen D, Shi Y, et al. Economic analysis of physical activity interventions. <I>Am J Prev Med</I> 2011;40:149–58.

Background

Physical activity (PA) is beneficial for general health and the prevention and treatment of chronic diseases. Interventions to increase PA range from community-wide interventions such as mass media campaigns to individual interventions such as behaviour change programmes. Previous systematic reviews have investigated the effectiveness of these interventions,1–4 but information on the relative cost effectiveness (ie, the costs per unit of benefit gained) of the interventions is limited.

Aim

To provide a systematic review of interventions to increase PA and to calculate their cost effectiveness.

Searches and inclusion criteria

Seven databases were searched for relevant studies published between 2000 and June 2008. Studies included in two systematic reviews1 4 were also...

The influence of game scheduling on medical encounters at the USA Cup soccer tournament

Waibel, N. G., Roberts, W. O., Lunos, S. — 2012-04-05T00:30:04-07:00

Objective

To investigate the influence of playing multiple games on multiple days on youth soccer medical encounter rates.

Design

Prospective cohort survey study.

Setting

Medical facility at the 2008 Schwan's USA Cup soccer tournament.

Participants

Players presenting to the medical facility for game-related medical evaluation.

Assessment of risk factors

Date, game and half of game for each medical encounter.

Main outcome measures

Game play-related medical encounters per 1000 match hours (MH).

Results

211 players surveyed with 195 eligible and completed questionnaires. There were 4.06, 5.14 and 3.92 medical encounters/1000 MH on 11, 12 and 13 July, respectively, with no significant difference in injury incidence. There was no difference in medical encounter rates of second games compared with first games of the day (p=0.126). Daily medical encounter rates were 5.65, 8.95, 7.83, 6.94 and 4.62/1000 MH on 15, 16, 17, 18 and 19 July, respectively, with statistically significant differences on 16 July (p<0.001) and 17 July (p=0.022) compared with 15 July. Encounter rates of second games compared with first games of the day showed no difference (p=0.385). A linear test for trend from 15 to 19 July was not significant (p=0.092).

Conclusions

The USA Cup format did not show either increased medical encounter rates from the cumulative total of games played or a consistently increased rate in the second game of the day compared with the first. Players, coaches, parents and administrators can feel confident that this tournament format does not pose an additional risk of injury.

Feasibility of a portable pedal exercise machine for reducing sedentary time in the workplace

Carr, L. J., Walaska, K. A., Marcus, B. H. — 2012-04-05T00:30:04-07:00

Background

Sedentary time is independently associated with an increased risk of metabolic disease. Worksite interventions designed to decrease sedentary time may serve to improve employee health.

Objective

The purpose of this study is to test the feasibility and use of a pedal exercise machine for reducing workplace sedentary time.

Methods

Eighteen full-time employees (mean age+SD 40.2+10.7 years; 88% female) working in sedentary occupations were recruited for participation. Demographic and anthropometric data were collected at baseline and 4 weeks. Participants were provided access to a pedal exercise machine for 4 weeks at work. Use of the device was measured objectively by exercise tracking software, which monitors pedal activity and provides the user real-time feedback (eg, speed, time, distance, calories). At 4 weeks, participants completed a feasibility questionnaire.

Results

Participants reported sitting 83% of their working days. Participants used the pedal machines an average of 12.2+6.6 out of a possible 20 working days and pedalled an average of 23.4+20.4 min each day used. Feasibility data indicate that participants found the machines feasible for use at work. Participants also reported sedentary time at work decreased due to the machine.

Discussion

Findings from this study suggest that this pedal machine may be a feasible tool for reducing sedentary time while at work. These findings hold public health significance due to the growing number of sedentary jobs in the USA and the potential of the device for use in large-scale worksite health programmes.

Identifying sedentary time using automated estimates of accelerometer wear time

2012-04-05T00:30:04-07:00

Purpose

The authors evaluated the accuracy of three automated accelerometer wear-time estimation algorithms against self-report. Direct effects on sedentary time (<100 cpm) and indirect effects on moderate-to-vigorous physical activity (MVPA, ≥1952 cpm) time were examined.

Methods

A subsample from the 2004/2005 Australian Diabetes, Obesity and Lifestyle Study (n=148) completed activity logs and wore accelerometers for a total of 987 days. A published algorithm that allows movement within non-wear periods (Algorithm 1) was compared with one that allows less movement (Algorithm 2) or no movement (Algorithm 3). Implications for population estimates were examined using 2003/2004 US National Health and Nutrition Examination Survey data.

Results

Mean difference per day between the criterion and estimated wear time was negligible for all three algorithms (≤11 min), but 95% limits of agreement (LOA) were wide (±≥2 h). Respectively, the algorithms (1, 2 and 3) misclassified sedentary time as non-wear on 31.9%, 19.4% and 18% of days and misclassified non-wear time as sedentary on 42.8%, 43.7% and 51.3% of days. Use of Algorithm 2 (compared with Algorithm 1) affected population estimates of sedentary time (higher by 20 min/day) but not MVPA time. Agreement between Algorithms 1 and 2 was good for MVPA time (mean difference –0.08, LOA: –2.08, 1.91 min), but not for wear time or sedentary time.

Conclusion

Accelerometer wear time can be estimated accurately on average; however, misclassification can be substantial for individuals. Algorithm choice affects estimates of sedentary time. Allowing very limited movement within non-wear periods can improve accuracy.

Physical activity during leisure time and quality of life in a Spanish cohort: SUN (Seguimiento Universidad de Navarra) Project

2012-04-05T00:30:04-07:00

Background

Leisure-time physical activity (LTPA) has been associated with better mental and physical health particularly in cross-sectional studies.

Purpose

To longitudinally assess the association between LTPA, changes in LTPA and health-related quality of life (HRQL).

Methods

Cross-sectional and prospective analysis of the Seguimiento Universidad de Navarra Project, a dynamic cohort study. Information is gathered through mailed questionnaires biannually since 1999. A validated LTPA questionnaire was used to assess LTPA level at baseline. Changes in LTPA were ascertained at 2 and 4 years of follow-up. HRQL was assessed at 4 and 8 years of follow-up with a validated Spanish version of the SF-36 Health Survey. Multivariate regression coefficients, means and their 95% CIs for each of the eight domains of the SF-36 according to quintiles of baseline LTPA and changes in LTPA over time were calculated using generalised linear models.

Results

At 4 years of follow-up, mean scores for upper quintiles of LTPA (second to highest quintile) of physical functioning, general health, vitality, social functioning and mental health were significantly higher than the mean score obtained for participants with the lowest level of LTPA (first quintile). In general, and independent of previous scores in SF-36 survey, the maintenance or the increase in LTPA levels during follow-up was associated with better scores in HRQL after 8 years of follow-up, especially for mental domains.

Conclusion

These findings provide support for an association between LTPA, long-term changes in LTPA and several aspects of HRQL (especially in relation to mental domains) extending previous cross-sectional findings.

Elbow flexor and extensor muscle weakness in lateral epicondylalgia

Coombes, B. K., Bisset, L., Vicenzino, B. — 2012-04-05T00:30:04-07:00

Objective

To evaluate whether deficits of elbow flexor and extensor muscle strength exist in lateral epicondylalgia (LE) in comparison with a healthy control population.

Design

Cross-sectional study.

Participants

150 participants with unilateral LE were compared with 54 healthy control participants.

Main outcome measures

Maximal isometric elbow flexion and extension strength were measured bilaterally using a purpose-built standing frame such that gripping was avoided.

Results

The authors found significant side differences in elbow extensor (–6.54 N, 95% CI –11.43 to –1.65, p=0.008, standardised mean difference (SMD) –0.45) and flexor muscle strength (–11.26 N, 95% CI –19.59 to –2.94, p=0.009, SMD –0.46) between LE and control groups. Within the LE group, only elbow extensor muscle strength deficits between sides was significant (affected–unaffected: –2.94 N, 95% CI –5.44 to –0.44).

Conclusion

Small significant deficits of elbow extensor and flexor muscle strength exist in the affected arm of unilateral LE in comparison with healthy controls. Notably, comparing elbow strength between the affected and unaffected sides in unilateral epicondylalgia is likely to underestimate these deficits.

Trial Registration

Australian New Zealand Clinical Trials Register ACTRN12609000051246.

A to Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance--Part 32

2012-04-05T00:30:04-07:00

Introductory remarks

The letter P brings together two of the most talked about supplement families: proteins, which have been perennially popular since the time of the ancient Olympians and prohormones, which will be dealt with in a later issue. Both supplement families include products which range from simple and relatively inexpensive, to exotic, expensive and emotively marketed. Part 32 also includes information on proline, a non-essential amino acid which is marketed for growth and repair of soft tissue based on its importance in the make-up of collagen.

ProteinS M Phillips L Breen

Skeletal muscle protein turnover rates are ~1%–2%/d and exist in dynamic, usually balanced, equilibrium between muscle protein breakdown (MPB) and muscle protein synthesis (MPS). For example, in the fasted state, MPB>MPS, whereas in response to ingestion of protein-containing meals, MPS>MPB.1 Thus, in healthy adults, muscle mass remains relatively stable due to...