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Biomedical subjects

A K McConnell

Publications and source records attributed to A K McConnell.

At least 19 recordsLinked to original sources
PubMed2006

Screening elite winter athletes for exercise induced asthma: a comparison of three challenge methods.

BACKGROUND: The reported prevalence of exercise induced asthma (EIA) in elite winter athletes ranges from 9% to 50%. Many elite winter athletes do not report symptoms of EIA. At present there is no gold standard test for EIA. OBJECTIVE: To establish the efficacy of screening for EIA and examine the role of the eucapnic voluntary hyperventilation (EVH) challenge and laboratory based and sport specific exercise challenges in the evaluation of elite winter athletes. METHODS: 14 athletes (mean (SD) age 22.6 (5.7) years, height 177.2 (7.0) cm, body mass 68.9 (16.9) kg) from the Great Britain short-track speed skating (n = 10) and biathlon teams (n = 4) were studied. Each athlete completed a laboratory based and sport specific exercise challenge as well as an EVH challenge, in randomised order. RESULTS: All 14 athletes completed each challenge. Two had a previous history of asthma. Ten (including the two with a previous history) had a positive test to at least one of the challenges. Ten athletes had a positive response to EVH; of these, only three also had a positive response to the sport specific challenge. No athletes had a positive response to the laboratory based challenge. CONCLUSIONS: Elite athletes should be screened for EIA. EVH is a more sensitive challenge in asymptomatic athletes than sport specific and laboratory based challenges. If sporting governing bodies were to implement screening programmes to test athletes for EIA, EVH is the challenge of choice.

Adolescent↗
PubMed2005

Mid-expiratory flow versus FEV1 measurements in the diagnosis of exercise induced asthma in elite athletes.

BACKGROUND: A fall in FEV(1) of > or =10% following bronchoprovocation (eucapnic voluntary hyperventilation (EVH) or exercise) is regarded as the gold standard criterion for diagnosing exercise induced asthma (EIA) in athletes. Previous studies have suggested that mid-expiratory flow (FEF(50)) might be used to supplement FEV(1) to improve the sensitivity and specificity of the diagnosis. A study was undertaken to investigate the response of FEF(50) following EVH or exercise challenges in elite athletes as an adjunct to FEV(1). METHODS: Sixty six male (36 asthmatic, 30 non-asthmatic) and 50 female (24 asthmatic, 26 non-asthmatic) elite athletes volunteered for the study. Maximal voluntary flow-volume loops were measured before and 3, 5, 10, and 15 minutes after stopping EVH or exercise. A fall in FEV(1) of > or =10% and a fall in FEF(50) of > or =26% were used as the cut off criteria for identification of EIA. RESULTS: There was a strong correlation between DeltaFEV(1) and DeltaFEF(50) following bronchoprovocation (r = 0.94, p = 0.000). Sixty athletes had a fall in FEV(1) of > or =10% leading to the diagnosis of EIA. Using the FEF(50) criterion alone led to 21 (35%) of these asthmatic athletes receiving a false negative diagnosis. The lowest fall in FEF(50) in an athlete with a > or =10% fall in FEV(1) was 14.3%. Reducing the FEF(50) criteria to > or =14% led to 13 athletes receiving a false positive diagnosis. Only one athlete had a fall in FEF(50) of > or =26% in the absence of a fall in FEV(1) of > or =10% (DeltaFEV(1) = 8.9%). CONCLUSION: The inclusion of FEF(50) in the diagnosis of EIA in elite athletes reduces the sensitivity and does not enhance the sensitivity or specificity of the diagnosis. The use of FEF(50) alone is insufficiently sensitive to diagnose EIA reliably in elite athletes.

Adult↗
PubMed2005

Impact of changes in the IOC-MC asthma criteria: a British perspective.

BACKGROUND: Since 2001 the International Olympic Committee-Medical Commission (IOC-MC) has required athletes using inhaled beta2 agonists to provide clinical evidence of their asthmatic condition. The aim of this study was to compare the reported prevalence of asthma at the 2000 and 2004 Olympic Games in the Great British Olympic team (Team GB). METHODS: Following local ethics committee approval, 271 athletes (165 men) from the 2004 Team GB volunteered and provided written informed consent. An athlete was confirmed asthmatic if he or she had a positive bronchoprovocation or bronchodilator test as defined by the IOC-MC. Pre-Olympic medical forms from the 2000 Team GB were also examined to establish the prevalence of asthma among the members of Team GB at the 2000 Olympic Games. RESULTS: The prevalence of asthma in the two teams at the 2000 and 2004 Olympic Games was similar (21.2% and 20.7%, respectively). In the 2004 Olympic Games 13 of 62 athletes (21.0%) with a previous diagnosis of asthma tested negative. A further seven with no previous diagnosis of asthma tested positive. CONCLUSIONS: The prevalence of asthma within Team GB remained unchanged between 2000 and 2004. The IOC-MC requirement that asthmatic athletes must submit documented evidence of asthma has highlighted that 13 (21.0%) previously diagnosed as asthmatic failed to demonstrate evidence of asthma while seven athletes with no previous history or diagnosis of asthma tested positive. Screening for asthma within elite athletic populations using bronchoprovocation challenges appears warranted to assist athletes in preparing more effectively for major sporting events.

Asthma↗
PubMed2004

Respiratory muscle training in healthy humans: resolving the controversy.

Specific respiratory muscle training offers the promise of improved exercise tolerance and athletic performance for a wide range of users. However, the literature addressing respiratory muscle training in healthy people remains controversial. Studies into the effect of respiratory muscle training upon whole body exercise performance have used at least one of the following modes of training: voluntary isocapnic hyperpnea, flow resistive loading, and pressure threshold loading. Each of these training modes has the potential to improve specific aspects of respiratory muscle function. Some studies have demonstrated significant improvements in either time to exhaustion or time trial performance, whilst others have demonstrated no effect. We present an overview of the literature that rationalizes its contradictory findings. Retrospective analysis of the literature suggests that methodological factors have played a crucial role in the outcome of respiratory muscle training studies. We conclude that in most well controlled and rigorously designed studies, utilizing appropriate outcome measures, respiratory muscle training has a positive influence upon exercise performance. The mechanisms by which respiratory muscle training improves exercise performance are unclear. Putative mechanisms include a delay of respiratory muscle fatigue, a redistribution of blood flow from respiratory to locomotor muscles, and a decrease in the perceptions of respiratory and limb discomfort.

Adaptation, Physiological↗
PubMed2002

Effects of inspiratory muscle training upon recovery time during high intensity, repetitive sprint activity.

The present study examined the influence of specific inspiratory muscle training (IMT) upon recovery time during repetitive sprint activity, as well as the physiological and perceptual responses to fixed intensity shuttle running. Using a double-blind placebo-controlled design, 24 male repetitive sprint athletes were assigned randomly to either an IMT (n = 12) or placebo (n = 12) group. The self-selected recovery time during a repetitive sprint test and the physiological response to submaximal endurance exercise were determined. Following completion of baseline and pre-intervention measures, the IMT group performed 30 inspiratory efforts twice daily against a resistance equivalent to 50 % maximum inspiratory mouth pressure (MIP) for 6 wk. The placebo group performed 60 breaths once daily, for 6 wk, at a resistance equivalent to 15 % MIP, a load known to elicit negligible changes in respiratory muscle function. The IMT group improved total recovery time during the repetitive sprint test by 6.2 +/- 1.1 % (mean +/- SEM) above the changes noted for the placebo group (p = 0.006). Blood lactate and perceptual responses to submaximal exercise were also significantly attenuated following IMT (p </= 0.01). These data support existing evidence that specific IMT attenuates the blood lactate and perceptual responses to submaximal endurance exercise. In addition, the present study provides new evidence that IMT improves recovery time during high intensity, intermittent exercise in repetitive sprint athletes.

Adult↗
PubMed2001

Inspiratory muscle training improves rowing performance.

PURPOSE: To investigate the effects of a period of resistive inspiratory muscle training (IMT) upon rowing performance. METHODS: Performance was appraised in 14 female competitive rowers at the commencement and after 11 wk of inspiratory muscle training on a rowing ergometer by using a 6-min all-out effort and a 5000-m trial. IMT consisted of 30 inspiratory efforts twice daily. Each effort required the subject to inspire against a resistance equivalent to 50% peak inspiratory mouth pressure (PImax) by using an inspiratory muscle training device. Seven of the rowers, who formed the placebo group, used the same device but performed 60 breaths once daily with an inspiratory resistance equivalent to 15% PImax. RESULTS: The inspiratory muscle strength of the training group increased by 44 +/- 25 cm H2O (45.3 +/- 29.7%) compared with only 6 +/- 11 cm H2O (5.3 +/- 9.8%) of the placebo group (P < 0.05 within and between groups). The distance covered in the 6-min all-out effort increased by 3.5 +/- 1.2% in the training group compared with 1.6 +/- 1.0% in the placebo group (P < 0.05). The time in the 5000-m trial decreased by 36 +/- 9 s (3.1 +/- 0.8%) in the training group compared with only 11 +/- 8 s (0.9 +/- 0.6%) in the placebo group (P < 0.05). Furthermore, the resistance of the training group to inspiratory muscle fatigue after the 6-min all-out effort was improved from an 11.2 +/- 4.3% deficit in PImax to only 3.0 +/- 1.6% (P < 0.05) pre- and post-intervention, respectively. CONCLUSIONS: IMT improves rowing performance on the 6-min all-out effort and the 5000-m trial.

Adult↗
PubMed2001

Specific respiratory warm-up improves rowing performance and exertional dyspnea.

PURPOSE: The purpose of this study was a) to compare the effect of three different warm-up protocols upon rowing performance and perception of dyspnea, and b) to identify the functional significance of a respiratory warm-up. METHODS: A group of well-trained club rowers (N = 14) performed a 6-min all-out rowing simulation (Concept II). We examined differences in mean power output and dyspnea measures (modified CR-Borg scale) under three different conditions: after a submaximal rowing warm-up (SWU), a specific rowing warm-up (RWU), and a specific rowing warm-up with the addition of a respiratory warm-up (RWUplus) protocol. RESULTS: Mean power output during the 6-min all-out rowing effort increased by 1.2% after the RWUplus compared with that obtained after the RWU (P < 0.05) which, in turn, was by 3.2% higher than the performance after the SWU (P < 0.01). Similarly, after the RWUplus, dyspnea was 0.6 +/- 0.1 (P < 0.05) units of the Borg scale lower compared with the dyspnea after the RWU and 0.8 +/- 0.2 (P < 0.05) units lower than the dyspnea after the SWU. CONCLUSION: These data suggest that a combination of a respiratory warm-up protocol together with a specific rowing warm-up is more effective than a specific rowing warm-up or a submaximal warm-up alone as a preparation for rowing performance.

Adult↗
PubMed2001

Assessment of maximum inspiratory pressure. Prior submaximal respiratory muscle activity ('warm-up') enhances maximum inspiratory activity and attenuates the learning effect of repeated measurement.

BACKGROUND: The variability of maximal inspiratory pressure (PImax) in response to repeated measurement affects its reliability; published studies have used between three and twenty PImax measurements on a single occasion. OBJECTIVE: This study investigated the influence of a specific respiratory 'warm-up' upon the repeated measurement of inspiratory muscle strength and attempts to establish a procedure by which PImax can be assessed with maximum reliability using the smallest number of manoeuvres. METHODS: Fourteen healthy subjects, familiar with the Mueller manoeuvre, were studied. The influence of repeated testing on a single occasion was assessed using an 18-measurement protocol. Using a randomised cross-over design, subjects performed the protocol, preceded by a specific respiratory warm-up (RWU) and on another occasion, without any preliminary activity (control). Comparisons were made amongst 'baseline' (best of the first 3 measurements), 'short' series (best of 7th to 9th measurement) and 'long' series (best of the last 3 measurements). RESULTS: Under control conditions, the mean increase ('baseline' vs. 'long' series) was 11.4 (5.8)%; following the RWU, the increase (post RWU 'baseline' vs. 'long' series) was 3.2 (10.0)%. There were statistically significant differences between measurements made at all 3 protocol stages ('baseline', 'short' and 'long' series) under control conditions, but none following the RWU. CONCLUSIONS: The present data suggest that a specific RWU may attenuate the 'learning effect' during repeated PImax measurements, which is one of the main contributors of the test variability. The use of a RWU may provide a means of obtaining reliable values of PImax following just 3 measurements.

Adult↗
PubMed1999

Do fire-fighters develop specific ventilatory responses in order to cope with exercise whilst wearing self-contained breathing apparatus?

In the present study we compared the ventilatory performance whilst wearing self-contained breathing apparatus (SCBA) during exercise, of a group of male fire-fighters (FF, n = 8), with a matched group of male civilians (CV, n = 7). The mean (SEM) physiological characteristics of the subjects (FF vs CV) were: age 31 (2) years vs 32 (4) years; height 179 (2) cm vs 183 (3) cm, P < 0.05; mass 80 (2) kg vs 84 (3) kg; maximum oxygen uptake 4.52 (0.14) 1 x min(-1) vs 4.39 (0.27) 1 x min(-1). Volunteers performed a 23-minute fire-fighting simulation (Firetest), without and with SCBA (Fire-fighter II, Siebe-Gorman/North Safety, Cheshire, UK). During SCBA wear, the FF group used significantly less air and rated their breathlessness significantly lower than the CV group. The mean tidal volume (V(T)) of the FF group remained constant between non-SCBA and SCBA wear conditions, but the CV group increased their mean V(T) by 18%, (P < 0.01). There were no significant between-group differences during the Firetest in total breath duration, inspiratory or expiratory duration, breathing frequency (fb), or heart rate. These data suggest that the respiratory responses of firefighters while wearing SCBA, which are characterised by increases in (fb) but not V(T), may help to reduce their breathlessness during exercise while wearing SCBA.

Adult↗
PubMed1999

The influence of prior activity upon inspiratory muscle strength in rowers and non-rowers.

The aim of this study was to investigate whether a 'warm-up' phenomenon in the strength of the inspiratory muscles exists, and, under this assumption, whether whole body warm-up protocols or a specific respiratory warm-up is more effective in this respect. Eleven club level rowers performed a rowing warm-up, and twelve university students performed a general cycling warm-up. Both groups also performed a specific respiratory warm-up. Inspiratory muscle strength (Mueller manoeuvre) and lung function (flow-volume loops) were measured before and after the three conditions. Isokinetic strength during knee extension was measured before and after the rowing warm-up. The two whole body warm-up protocols had no effect on inspiratory muscle strength or any lung function parameter despite the significant (3.8+/-SD 1.4%; p<0.05) increase in peak torque that the rowing warm-up elicited. The respiratory warm-up induced a significant increase in inspiratory mouth pressure (8.5+/-1.8%; p<0.0001) but not in any other lung function parameter. Following the rowing incremental test to exhaustion, maximum inspiratory pressure decreased by 7.0+/-2.0%, which is an indication of respiratory muscle fatigue. These data suggest that the inspiratory muscle strength can be enhanced with preliminary activity, a phenomenon similar to the one known to exist for other skeletal muscles. In addition, a specific respiratory warm-up is more effective in this respect than whole body protocols.

Adult↗
PubMed1999

Maximum static respiratory pressures in healthy elderly men and women: issues of reproducibility and interpretation.

BACKGROUND: Respiratory muscle strength is assessed using the static pressure generated at the mouth during a maximal inspiratory or expiratory effort [PImax and PEmax, respectively (MSRPs)]. Interpretation of MSRPs relies upon comparison with 'normal' values, but MSRPs show very weak associations with predictors such as physical characteristics. The influence of habitual physical activity upon MSRPs remains undefined. OBJECTIVES: We examined measurement reproducibility, as well as the influence of physical characteristics and habitual physical activity upon MSRPs in healthy elderly people. METHODS: MSRPs were assessed in 41 healthy subjects using a portable mouth pressure meter on two occasions, 1 week apart. Physical activity was assessed in 10 subjects by diary record. Pearson product-moment correlation coefficients were used to assess the association of MSRPs with other measured variables. RESULTS: There was good measurement reproducibility of MSRPs, with coefficients of reproducibility of 10.2 and 12.8% for PImax and PEmax, respectively. MSRPs showed statistically significant negative correlations with age, but correlations with physical characteristics were poor. In contrast, MSRPs were highly correlated with physical activity. CONCLUSIONS: We conclude that MSRPs can be measured reproducibly and that they decline with advancing age. Physical characteristics are not good predictors of MSRPs; this may be due to a strong confounding influence of physical activity making interpretation of measurements problematic. We suggest that the poor predictive power of physical characteristics indicate that reference to 'normal' values be made with caution and that it may be more appropriate to consider functional interpretations of MSRPs based upon factors such as lung and chest wall elastance.

Aged↗
PubMed1997

Inspiratory muscle fatigue following running to volitional fatigue: the influence of baseline strength.

Respiratory muscle fatigue has been demonstrated following short-term exercise to volitional fatigue, as well as following prolonged submaximal exercise. There is some suggestion that the respiratory muscles of 'athletic' individuals have superior strength and greater fatigue resistance but it is not known whether inspiratory muscle strength influences fatigueability of the inspiratory muscles. The present study examined this question in 24 moderately trained young men. Inspiratory muscle strength was measured at residual volume using a hand held Mouth Pressure Meter before and after an incremental, multistage shuttle run to volitional fatigue. Following the run, there was a significant fall in inspiratory mouth pressures (-10.5 +/- SD 8.2%; p < 0.001 Pre- vs Post Pipeak). The subjects with the weakest inspiratory muscles exhibited significantly greater fatigue than those with the strongest (-17.0 +/- SD 7.8% c.f. 6.8 +/- SD 4.4% for the 25th and 75th percentiles respectively p < 0.01). These data support existing evidence that the respiratory muscles fatigue following high intensity exercise. In addition, they provide new evidence that this phenomenon occurs in moderately trained young men and that the severity of the fatigue is related to the baseline strength of the inspiratory muscles.

Adult↗
PubMed1996

Ventilatory sensitivity to carbon dioxide: the influence of exercise and athleticism.

Endurance training reduces the ventilatory response to a given level of work, and there is evidence that endurance athletes possess attenuated chemosensitivity at rest; but it is unclear whether attenuation persists during exercise. We compared the carbon dioxide sensitivity (S) of endurance-trained (ETG), sprint-trained (STG), and control subjects (CG), at rest and during cycle ergometry. Steady-state carbon dioxide (CO2) inhalation was employed; ventilatory parameters were measured using an ultrasonic flowmeter linked to a computer. CO2 concentrations were measured at the mouth using an infrared CO2 analyzer or mass spectrometer. Mean resting CO2 sensitivity of the ETG was significantly lower than that of the STG (P < 0.05), but not the CG (P < 0.058). S increased from rest to exercise in all endurance-trained subjects, but the responses of the STG and CG were varied. Compared to rest, mean S was significantly higher during exercise for the ETG, but not for the STG or CG. S was the same in all groups during exercise. During air breathing exercise all subjects were mildly hypercapnic. The ETG showed the greatest rise in mean alveolar PCO2, but this could not be attributed to attenuated chemosensitivity since responsiveness during exercise was identical in all three groups.

Adult↗
PubMed1995

Estimation of arterial PCO2 in the elderly.

Arterial PCO2 (PaCO2), determined directly in the radial artery, was compared with indirect estimates of PCO2 in six elderly men (mean age 73.8 yr). Estimates of PaCO2 included arterialized venous PCO2 (PavCO2); end-tidal PCO2; mean alveolar PCO2, calculated by using a reconstruction of the alveolar oscillation in PCO2 and accounting for the presence of dead space (time-weighted mean for PCO2 throughout the respiratory cycle); and values calculated by using the empirical formula developed by Jones et al. (N. L. Jones, D. G. Robertson, and J. W. Kane. J. Appl. Physiol. 47: 954-960, 1979), which incorporates end-tidal PCO2 and tidal volume (PaCO2 derived from end-tidal PCO2 and VT). Measurements were made at rest and during cycle ergometry at 25 and 50 W while the subjects breathed various gas mixtures (euoxic-eucapnic, hypoxic-eucapnic, hyperoxic-eucapnic, and hyperoxic-hypercapnic). The mean differences between the estimates and the actual PaCO2 at rest and in 25- and 50-W exercise were as follows: PavCO2, 0.3 +/- 0.7 (SD), -0.1 +/- 0.7, and 1.8 +/- 1.2 Torr; end-tidal PCO2, 2.9 +/- 1.7, 4.0 +/- 3.1, and 3.7 +/- 3.2 Torr; time-weighted mean of alveolar PCO2, 2.6 +/- 1.9, 3.3 +/- 3.1, and 3.6 +/- 3.8 Torr; and PaCO2 derived from end-tidal PCO2 and VT, 2.4 +/- 1.3, 1.3 +/- 3.0, and 0.6 +/- 2.9 Torr. It is concluded that mean PavCO2 agreed most closely with mean PaCO2 both at rest and in exercise. All methods of deriving PaCO2 using measurements from the respired gases overestimated arterial values at rest. Of the noninvasive techniques, mean estimates calculated using the regression equation developed by Jones et al. corresponded most closely with PaCO2 in exercise.

Adult↗