The cardiopulmonary exercise test grey zone; optimising fitness stratification by application of critical difference

BACKGROUND

Cardiorespiratory fitness can inform patient care, although to what extent natural variation in CRF influences clinical practice remains to be established. We calculated natural variation for cardiopulmonary exercise test (CPET) metrics, which may have implications for fitness stratification.

METHODS

In a two-armed experiment, critical difference comprising analytical imprecision and biological variation was calculated for cardiorespiratory fitness and thus defined the magnitude of change required to claim a clinically meaningful change. This metric was retrospectively applied to 213 patients scheduled for colorectal surgery. These patients underwent CPET and the potential for misclassification of fitness was calculated. We created a model with boundaries inclusive of natural variation [critical difference applied to oxygen uptake at anaerobic threshold (V˙O2-AT): 11 ml O2 kg-1 min-1, peak oxygen uptake (V˙O2 peak): 16 ml O2 kg-1 min-1, and ventilatory equivalent for carbon dioxide at AT (V̇E/V̇CO2-AT): 36].

RESULTS

The critical difference for V˙O2-AT, V˙O2 peak, and V˙E/V˙CO2-AT was 19%, 13%, and 10%, respectively, resulting in false negative and false positive rates of up to 28% and 32% for unfit patients. Our model identified boundaries for unfit and fit patients: AT <9.2 and ≥13.6 ml O2 kg-1 min-1, V˙O2 peak <14.2 and ≥18.3 ml kg-1 min-1, V˙E/V˙CO2-AT ≥40.1 and <32.7, between which an area of indeterminate-fitness was established. With natural variation considered, up to 60% of patients presented with indeterminate-fitness.

CONCLUSIONS

These findings support a reappraisal of current clinical interpretation of cardiorespiratory fitness highlighting the potential for incorrect fitness stratification when natural variation is not accounted for.

Spontaneous Dissection of the External Iliac Artery Secondary to Golf Club Manufacturing

Spontaneous dissection of the external iliac artery in the absence of aortic disease is extremely uncommon. We report the conservative treatment of a 46-year-old male patient who presented with acute left lower limb ischemia due to an isolated dissection of the external iliac artery secondary to repetitive swinging movements during golf club manufacturing. Although syndromes of nonatherosclerotic vascular disease secondary to repetitive movements in high-level athletic activity have been previously described in cyclists, long distance runners, and rugby players, we believe this to be the first occupational case associated with golf.

The biochemical, physiological and psychological consequences of a "1,000 miles in 1,000 hours" walking challenge

The combined effects of 42 days of chronic sleep disruption and repeated hourly bouts of physical exertion have not been described. This case study reports the physiological and psychological demands placed on one individual who walked 1 mile in each consecutive hour for a period of 1,000 h (42 days), covering a total distance of 1,000 miles. The participant walked at a mean speed of 1.75 m/s completing each mile in approximately 15 min. Over the course of the challenge, the individual lost 1.6 kg in body weight. Markers of skeletal muscle damage, increased gradually whilst free testosterone levels decreased over the course of the challenge. Stress hormones increased whilst inflammatory markers (CRP) initially rose but then returned towards baseline over the course of the study. Cognitive motor performance measured via reaction time was maintained throughout the 42 days. The participant also displayed mood states typical of an elite athlete at baseline and throughout the challenge. Participation in this novel '1,000 mile 1,000 h' walking challenge evoked considerable physiological stress in a fit, healthy middle-aged participant but did not markedly alter cognitive performance or mood over the 42-day period.

The effect of sporting events on emergency department attendance rates in a district general hospital in Northern Ireland

BACKGROUND

Previous studies have reported a conflicting relationship between the effect of live and televised sporting events on attendance rates to emergency departments (ED). The objectives of this study were to investigate the relationship of major sporting events on emergency department attendance rates and to determine the potential effects of such events on service provision.

METHODS

A retrospective analysis of ED attendances to a district general hospital (DGH) and subsequent admissions over a 24-h period following live and televised sporting activities was performed over a 5-year period. Data were compiled from the hospital's emergency record books including the number of attendances, patient demographics, clinical complaint and outcome. Review patients were excluded. Analysis of sporting events was compiled for live local, regional and national events as well as world-wide televised sporting broadcasts.

RESULTS

A total of 137,668 (80,445 men) patients attended from April 2002 to July 2007. Mean attendance rate per day was 80 patients (men = 47). Mean admission rate was 13.6 patients per day. Major sporting events during the study period included; Soccer: 4 FA Cup and 1 World Cup (WC) finals; Rugby: 47 Six Nations, 25 Six nations games involving Ireland, 1 WC final, 2 WC semi-finals, 2 WC quarter-finals and 4 WC games involving Ireland; and Gaelic Football [Gaelic Athletic Association (GAA)]: 5 All-Ireland finals, 11 semi-finals, 11 quarter-finals and 5 provincial finals. There was a significantly higher patient admission rate during the soccer FA Cup final, Rugby Six Nations and games involving Ireland and for GAA semi- and quarter-final games (p = 0.001-0.01). There was no difference identified in total attendance or non-admission rates for sporting events throughout the study period. Although there was no correlation identified between any of these sporting events and total emergency department attendances (r < 0.15, p > 0.07), multinomial logistic regression demonstrated that FA Cup final (p = 0.001), Rugby Six Nations (p = 0.019), Rugby WC games involving Ireland (p = 0.003), GAA All-Ireland semi- and quarter-finals (p = 0.016; p = 0.016) were predictors of patient admission rates.

CONCLUSION

This study suggests that live or televised sporting events do not significantly affect ED attendances to a DGH. However, some events appeared to be predictors of patient admission rates. Although it may be beneficial to consider the effect of sporting events on service stratification during these periods, the overall effect is probably minimal and should not create a major concern for future service provision despite the implementation of the European Working Time Directive.

The effects of ingesting a carbohydrate-electrolyte beverage 15 minutes prior to high-intensity exercise performance

The aim of this study was to examine the effect of ingesting a commercially available carbohydrate-electrolyte (CHO-E) solution on strenuous exercise performance. Ten apparently healthy male volunteers (Mean +/- SD; age 20 +/- 2 yrs; height 178 +/- 7 cm; body mass 77 +/- 10 kg; estimated VO(2 max) 56 +/- 3 ml x kg(-1) x min(-1) completed three experimental trials in random order separated by a minimum of 7 days. For each trial, subjects consumed (8 ml x kg(-1) body mass) either a CHO-E solution (6% carbohydrate, 50 mg Na/500 ml), a non-CHO-E placebo, or no fluid, 15 minutes prior to exercise. The exercise involved intermittent shuttle (20 m apart) running for 1 hr followed by an incremental shuttle running test to exhaustion. Subjects displayed longer exercise times when the CHO-E solution was ingested compared with placebo or no fluid groups (exercise time to exhaustion - CHO-E 649 +/- 95 s, vs. placebo 601 +/- 83 s, vs. no fluid 593 +/- 107 s, P < 0.05). There was a main effect for time for specific gravity of urine (P < 0.05 vs. postexercise, pooled data) and body mass (P < 0.05 vs. postexercise, pooled data). The main finding from this investigation indicates that drinking a CHO-E solution 15 minutes prior to exercise improves performance. This study has practical implications for those sports where drinking during activity is restricted.

Molecular detection of exercise-induced free radicals following ascorbate prophylaxis in type 1 diabetes mellitus: a randomised controlled trial

AIMS/HYPOTHESIS

Patients with type 1 diabetes mellitus are more susceptible than healthy individuals to exercise-induced oxidative stress and vascular endothelial dysfunction, which has important implications for the progression of disease. Thus, in the present study, we designed a randomised double-blind, placebo-controlled trial to test the original hypothesis that oral prophylaxis with vitamin C attenuates rest and exercise-induced free radical-mediated lipid peroxidation in type 1 diabetes mellitus.

METHODS

All data were collected from hospitalised diabetic patients. The electron paramagnetic resonance spectroscopic detection of spin-trapped alpha-phenyl-tert-butylnitrone (PBN) adducts was combined with the use of supporting markers of lipid peroxidation and non-enzymatic antioxidants to assess exercise-induced oxidative stress in male patients with type 1 diabetes (HbA(1c) 7.9 +/- 1%, n = 12) and healthy controls (HbA(1c) 4.6 +/- 0.5%, n = 14). Following participant randomisation using numbers in a sealed envelope, venous blood samples were obtained at rest, after a maximal exercise challenge and before and 2 h after oral ingestion of 1 g ascorbate or placebo. Participants and lead investigators were blinded to the administration of either placebo or ascorbate treatments. Primary outcome was the difference in changes in free radicals following ascorbate ingestion.

RESULTS

Six diabetic patients and seven healthy control participants were randomised to each of the placebo and ascorbate groups. Diabetic patients (n = 12) exhibited an elevated concentration of PBN adducts (p < 0.05 vs healthy, n = 14), which were confirmed as secondary, lipid-derived oxygen-centred alkoxyl (RO.) radicals (a(nitrogen) = 1.37 mT and abeta(hydrogen) = 0.18 mT). Lipid hydroperoxides were also selectively elevated and associated with a depression of retinol and lycopene (p < 0.05 vs healthy). Vitamin C supplementation increased plasma vitamin C concentration to a similar degree in both groups (p < 0.05 vs pre-supplementation) and attenuated the exercise-induced oxidative stress response (p < 0.05 vs healthy). There were no selective treatment differences between groups in the primary outcome variable.

CONCLUSIONS/INTERPRETATION

These findings are the first to suggest that oral vitamin C supplementation provides an effective prophylaxis against exercise-induced free radical-mediated lipid peroxidation in human diabetic blood.

CLINICAL TRIALS REGISTRATION NUMBER

ISRCTN96164937.

Exercise and Mononuclear Cell DNA Damage: The Effects of Antioxidant Supplementation

The purpose of this investigation was to determine the effects of antioxidant supplementation on DNA damage following exercise. Fourteen subjects were randomly assigned to one of two groups and required to ingest either antioxidants (400 mg α-lipoic acid, 200 mg co-enzyme Q10, 12 mg manganese, 600 mg vitamin C, 800 mg N-acetyl cysteine, 400 μg selenium, and 400 IU α-tocopherol per day) or placebos for 7 d. Exercise increased DNA damage, PS, FRAP, and LDH (P < 0.05), but not selectively between groups. LDH and PS concentration decreased 1 h post-exercise (P < 0.05), while LH concentration decreased 1 h post-exercise in the antioxidant group only (P < 0.05). The antioxidant group had a higher concentration of LH (P < 0.05), perhaps due to a selective difference between groups post-exercise (P < 0.05). The main findings of this investigation demonstrate that exhaustive aerobic exercise induces DNA damage, while anti-oxidant supplementation does not protect against damage.

Convergence with terrestrial cercopithecines by the monkey Rhinopithecus roxellanae

Results are presented from a brief study of the behaviour of captive snubnosed monkeys, Rhinopithecus roxellanae. Chief points are that facial colouring and nasal development mimic the colour and form of the genitalia, and that limb proportions, sexual dimorphism, perineal colouring, and behaviour reflect a tendency towards terrestrialism convergent with cercopithecines such as baboons and macaques. Limb proportions, pelage length and tactile behaviour represent cold-weather adaptations.