BMI is dead; long live waist-circumference indices: But which index should we choose to predict cardio-metabolic risk?

BACKGROUND AND AIMS

There is growing evidence that Body Mass Index (BMI) is unfit for purpose. Waist circumference (WC) indices appear to be the preferred alternative, although it is not clear which WC index is optimal at predicting cardio-metabolic risk (CMR) and associated health outcomes.

METHODS AND RESULTS

We obtained a stratified random probability sample of 53,390 participants from the Health Survey for England (HSE), 2008-2018. The four available CMR factors were; high-density lipoproteins (HDL) cholesterol, glycated haemoglobin (HbA1c), systolic (SBP) and diastolic blood pressure (DBP). Strength of association between the four cardio-metabolic risk factors and competing anthropometric indicators of weight status [BMI, Waist-to-height ratio (WHTR), unadjusted WC, and a new WC index independent of height, WHT·5R = WC/height^0.5] was assessed separately, using simple correlations and ANCOVAs, and together (combined) using MANCOVA, controlling for age, sex and ethnicity. Centile curves for the new index WHT·5R = WC/height^0.5were also provided.

CONCLUSIONS

Waist-circumference indices were superior to BMI when explaining/predicting our CMR factors, before and after controlling for age, sex and ethnicity. No single WC index was consistently superior. Results suggest that WHTR is the strongest predictor of HbA1c, confirming that shorter individuals are at great risk of diabetes. The most appropriate WC index associated with blood pressure was WHT·5R for DBP, or unadjusted WC for SBP. Given HDL cholesterol is independent of height, the best predictor of HDL was WHT.5R. Clearly, "no one size fits all!". MANCOVA identified WHT·5R to be the best single WC index associated with a composite of all four CMR factors.

Common mental disorders among Irish jockeys: prevalence and risk factors

OBJECTIVE

Jockeys compete in a sport, horseracing, renowned for its physical and psychological demands. Previous research has identified that common mental disorders (CMDs) may be prevalent among this unique population of athletes. The aim of the present study was to further explore the prevalence of CMDs among jockeys and to test for associations with potential risk factors.

METHODS

An anonymous survey was distributed to professional jockey online. Self-report screening tools for four CMDs (psychological distress, depression, generalized anxiety, and adverse alcohol use) were included alongside predictor variables from questionnaires assessing for burnout, career satisfaction, social support, and the contemplation of retirement. Binary logistic regression was used to explore associations between CMDs (present versus not present) and risk factors. Eighty-four professional jockeys completed the questionnaire (response rate = 52%).

RESULTS

In total, 79% of jockeys met the threshold for at least one CMD. Prevalence (%) of CMD varied as follows: adverse alcohol (61%), depression (35%), generalized anxiety (27%), and psychological distress (19%). Burnout, career (dis)satisfaction, lower levels of social support, and the contemplation of retirement increased the odds of meeting the criteria for CMDs.

CONCLUSION

The findings indicate that jockeys report CMD symptoms at comparable rates to athletes in other sports. The study was the first to highlight potential risk factors as predictors of CMDs among jockeys, including burnout, career satisfaction, and the current contemplation of retirement. Screening tools for the risk factors demonstrated may, therefore, provide useful in the early identification of CMDs among jockeys. The development of jockey-specific assessment tools, education programmes, and interventions may help better understand and support the mental health of jockeys.

Modeling children's development in gross motor coordination reveals key modifiable determinants. An allometric approach

Children change their body size, shape, and gross motor coordination (GMC) as they grow. Further, GMC is expected to link to changes in children's body size, physical activity (PA), and physical fitness (PF). The objective was to model GMC changes in children followed longitudinally and to investigate associations between these changes and PA and PF levels. A total of 245 children (122 girls) were observed at 6 years of age and followed annually until 9 years. A sequence of allometric models was fitted, that is, 1. body mass, stature, and PA; 2. addition of four PF tests; 3. addition of four more PF tests. In Model 1, changes in GMC are nonlinear, and body mass (-0.60 ± 0.07, P < .001) and stature (2.91 ± 0.35, P < .001) parameter estimates were significant suggesting children with a more linear body size/shape showed higher GMC performances. Girls tend to outperform boys across time, and PA was not associated with GMC changes. Model 2 fitted the data better, and the PF tests (handgrip, standing long jump, 50-yard dash, and shuttle run) were significantly linked to GMC change. In Model 3, adding the remaining PF tests did not change the order of any factors importance. The greatest GMC changes were achieved by children whose body size/shape has an ectomorphic dominance across the years. Considering that leaner and physically fitter children tended to be more coordinated, physical education should also focus on PF development in components related to muscular strength, speed, agility, and aerobic capacity, along with nutritional education to reduce fat mass.

The need to redefine age- and gender-specific overweight and obese body mass index cutoff points

For convenience, health practitioners and clinicians are inclined to classify people/patients as overweight or obese based on body mass index (BMI) cutoff points of 25 and 30 kg m⁻² respectively, irrespective of age and gender. The purpose of the current study was to identity whether, for the same levels of adiposity, BMI is the same across different age groups and gender. A two-way ANCOVA revealed significant differences in BMI between different age groups and gender (plus an interaction), using body fat (%) as the covariate, data taken from a random sample of the English population (n=2993). Younger people had greater BMI than older people for the same levels of adiposity (differences ranged by 4 BMI units for males, and 3 BMI units for females). In conclusion, if BMI thresholds for overweight (BMI=25 kg m⁻²) and obese (BMI=30 kg m⁻²) are to reflect the same levels of adiposity across all gender and age groups within a population, then age- and gender-specific BMI adjustments outlined here are necessary to more accurately/fairly reflect the same critical levels of adiposity.

Longitudinal development of match-running performance in elite male youth soccer players

This study longitudinally examined age-related changes in the match-running performance of retained and released elite youth soccer players aged 8-18 years. The effect of playing position on age-related changes was also considered. Across three seasons, 263 elite youth soccer players were assessed in 1-29 competitive matches (988 player-matches). For each player-match, total distance and distances covered at age group-specific speed zones (low-speed, high-speed, sprinting) were calculated using 1 Hz or 5 Hz GPS. Mixed modeling predicted that match-running performance developed nonlinearly, with age-related changes best described with quadratic age terms. Modeling predicted that playing position significantly modified age-related changes (P < 0.05) and retained players covered significantly more low-speed distance compared with released players (P < 0.05), by 75 ± 71 m/h (mean ± 95% CI; effect size ± 95% CI: 0.35 ± 0.34). Model intercepts randomly varied, indicating differences between players in match-running performance unexplained by age, playing position or status. These findings may assist experts in developing training programs specific to the match play demands of players of different ages and playing positions. Although retained players covered more low-speed distance than released players, further study of the actions comprising low-speed distance during match play is warranted to better understand factors differentiating retained and released players.

A field-test battery for elite, young soccer players

The validity and reliability of a battery of field-based performance tests was examined. The opinions of coaches, fitness professionals and players (n=170, 172 and 101 respectively) on the importance of performance testing were established using a questionnaire. On 2 occasions, separated by 7 days, 80 elite, young soccer players (mean±SD [and range]: age 13.2±2.6 [8.9-19.1] years; stature 1.59±0.18 m [1.32-1.91]; body mass 50.6±17.1 [26.5-88.7] kg) completed a battery of field-based tests comprised of heart rate response to a submaximal Multi-stage fitness test, 3 types of vertical jump, sprints over 10 and 20 m, and an agility test. Physical performance testing was considered important by coaches (97%), fitness professionals (94%) and players (83%). The systematic bias ratio and the random error components of the 95% ratio limits of agreement for the first and second tests, for the U9-U11 vs. U12-U14 vs. U15-U18 age groups, were [Systematic bias (*/÷ ratio limits)]: Heart rate (Level 5): 0.983 (*/÷ 1.044) vs. 0.969 (*/÷ 1.056) vs. 0.983 (*/÷ 1.055); Rocket jump: 0998 (*/÷ 1.112) vs. 0.999 (*/÷ 1.106) vs. 0.996 (*/÷ 1.093); 10 m sprint: 0.997 (*/÷ 1.038) vs. 0.994 (*/÷ 1.033) vs. 0.994 (*/÷ 1.038); Agility test: 1.010 (*/÷1.050) vs. 1.014 (*/÷1.050) vs. 1.002 (*/÷1.053). All tests, except heart rate recovery from the Multi-stage fitness test, were able to distinguish between different ability and age groups of players (p<0.05). Thus, the field-test battery demonstrated logical and construct validity, and was shown to be a reliable and objective tool for assessing elite, young soccer players.

Colorectal cancer incidence and trend in UK South Asians: a 20-year study

AIMS

South Asians comprise 13.6% of the Wolverhampton population. We aimed to compare the incidence and trend of colorectal cancer in this subgroup with the non South Asian population over a 20-year period.

METHOD

Patients of South Asian origin diagnosed with colorectal cancer from 1989 to 2008 were identified from the hospital histopathology database and compared with those of non South Asian origin. 1991 and 2001 census data were used to standardize for differing age and sex distributions in the two study populations.

RESULTS

The median unadjusted incidence of colorectal cancer from 1989 to 2008 was 6.17 per 100,000 per year in South Asians compared with 71.70 per 100,000 per year in non South Asians (77.79% white British). The age and sex adjusted odds ratio for colorectal cancer in South Asians was 0.2 (P < 0.001). There was an equal increased trend in the incidence in both the South Asians and non South Asians over the study period (0.8% per year). In patients < 50 years, the gender difference in the incidence of cancer was not significant, but as age increased this rose significantly (males > females).

CONCLUSION

There was a markedly lower incidence of colorectal cancer in South Asians compared with non South Asians, maintained over 20 years. Colorectal cancer incidence increased by a small and similar amount over the period in both groups. There was a male preponderance of colorectal cancer in both populations over 50 years.

Modelling the determinants of 2000 m rowing ergometer performance: a proportional, curvilinear allometric approach

Previous studies have investigated the determinants of indoor rowing using correlations and linear regression. However, the power demands of ergometer rowing are proportional to the cube of the flywheel's (and boat's) speed. A rower's speed, therefore, should be proportional to the cube root (0.33) of power expended. Hence, the purpose of the present study was to explore the relationship between 2000 m indoor rowing speed and various measures of power of 76 elite rowers using proportional, curvilinear allometric models. The best single predictor of 2000 m rowing ergometer performance was power at VO(2max)(WVO(2max))(0.28), that explained R(2)=95.3% in rowing speed. The model realistically describes the greater increment in power required to improve a rower's performance by the same amount at higher speeds compared with that at slower speeds. Furthermore, the fitted exponent, 0.28 (95% confidence interval 0.226-0.334) encompasses 0.33, supporting the assumption that rowing speed is proportional to the cube root of power expended. Despite an R(2)=95.3%, the initial model was unable to explain "sex" and "weight-class" differences in rowing performances. By incorporating anaerobic as well as aerobic determinants, the resulting curvilinear allometric model was common to all rowers, irrespective of sex and weight class.

Vibration training improves balance in unstable ankles

Functional ankle instability (FAI) is a common condition following ankle injury characterised by increased risk of injury. Ankle sprains are a common acute form of injury suffered in dancing and loss of balance can affect not only risk of injury risk but also performance aesthetics. Whole body vibration training (WBVT) is a new rehabilitation method that has been linked with improving balance and muscle function. 38 female dancers with self reported unilateral FAI were randomly assigned in 2 groups: WBVT and control. Absolute centre of mass (COM) distribution during single leg stance, SEBT normalised research distances and Peroneus longus mean power frequency (f(med)) where measured pre and post 6-week intervention. There was a significant improvement in COM distribution over the 6 weeks from 1.05 ± 0.57 to 0.33 ± 0.42 cm² (P<0.05), and 4 of the 8 planes of direction in the SEBT Ant, Antlat, Med and Antmed from 77.5 ± 7.1 to 84.1 ± 5.8% (P<0.05) compared to control groups during the course of the 6 week training intervention. There was no evidence of improvement in peroneus longus (f(med)) over time (P=0.915) in either group. WBVT improved static balance and SEBT scores amongst dancers exhibiting ankle instability but did not affect peroneus longus muscle fatigue.

Bone status in professional cyclists

Professional cycling combines extensive endurance training with non weight-bearing exercise, two factors often associated with lower bone mineral density (BMD). Therefore BMD was measured with dual-energy x-ray absorptiometry in 30 professional road cyclists (mean (SD) age: 29.1 (3.4) years; height: 178.5 (6.7) cm; weight: 71.3 (6.1) kg; %fat mass: 9.7 (3.2)%; VO (2)max: 70.5 (5.5) ml.kg (-1).min (-1)) and in 30 young healthy males used as reference (28.6 (4.5) years; 176.5 (6.3) cm; 73.4 (7.3) kg; 20.7 (5.8)%). Adjusting for differences in age, height, fat mass, lean body mass, and calcium intake by ANCOVA, professional cyclists had similar head BMD (p=0.383) but lower total body (1.135 (0.071) vs. 1.248 (0.104) g.cm (-2); p<0.001), arms (0.903 (0.075) vs. 0.950 (0.085), p=0.028), legs (1.290 (0.112) vs. 1.479 (0.138); p<0.001), spine (0.948 (0.100) vs. 1.117 (0.147) g.cm (-2); p<0.001), pelvis (1.054 (0.084) vs. 1.244 (0.142), p<0.001), lumbar spine (1.046 (0.103) vs. 1.244 (0.167), P<0.001), and femoral neck BMD (0.900 (0.115) vs. 1.093 (0.137), p<0.001) compared to reference subjects. Professional cycling appears to negatively affect BMD in young healthy and highly active males, the femoral neck being the most affected site (-18%) in spite of the elevated muscle contractions inherent to the activity.

Individualised assessment of response to clopidogrel in patients presenting with acute coronary syndromes: a role for short thrombelastography?

INTRODUCTION

There is considerable interindividual variation in response to the antiplatelet agent clopidogrel. Hyporesponse predicts negative outcomes in patients presenting with a variety of ischemic cardiac conditions and following intracoronary stent placement. Many tests of clopidogrel activity are time consuming and complex. Short thromboelastography (s-TEG) allows rapid measurement of platelet clopidogrel response.

AIMS

We initiated this study to investigate the utility of s-TEG in assessing the response to clopidogrel in patients presenting with acute coronary syndromes (ACS) and to compare these results with established clopidogrel monitoring techniques.

METHODS

Patients admitted with unstable angina (UA) or Non ST elevation myocardial infarction (NSTEMI) undergoing coronary angiography were recruited. After routine loading with clopidogrel, all patients were tested with s-TEG and Accumetrics Verify-Now rapid platelet function analyzer (VN-RPFA). We used the modified TEG technique of measuring area under the curve at 15 min (AUC15), which allows a rapid estimation of antiplatelet response. Vasodilator-stimulated phosphoprotein phosphorylation (VASP) was also tested in a subgroup of patients. Clinical follow-up was obtained at 1 year. s-TEG results were correlated with VN-RPFA and VASP findings.

RESULTS

A total of 49 patients (33 male, mean age 63) were recruited and tested with s-TEG and VN-RPFA and a total of 39 patients were also assessed with VASP. s-TEG readings correlated well with VN-RPFA (r(2)= 0.54, P < 0.0001) and VASP (r(2)= 0.26, P= 0.001).

CONCLUSION

s-TEG provides timely results which compare to current tests of clopidogrel activity. This technique can also be used to measure a variety of other clotting parameters and as such could develop into a valuable near patient test for the interventional cardiologist.

Rheumatoid cachexia and cardiovascular disease

OBJECTIVE

It has been frequently stated that rheumatoid cachexia (RC) associates with increased cardiovascular risk; however, no studies to date have investigated this. The aim of this study was to investigate the association of RC with multiple novel and classical cardiovascular disease (CVD) risk factors and the presence of established CVD in rheumatoid arthritis (RA).

METHODS

A total of 34 RA patients with RC (RA+RC) were identified from a database of 400 RA patients using published RC criteria and compared to the remaining patients (RA-RC) who did not fulfil RC criteria. All patients were assessed for fat and fat-free mass, albumin (indicator of catabolism), disease activity/severity, novel and classical risk CVD factors and established CVD.

RESULTS

Fat-free mass (kg) and albumin (g/L) were significantly decreased in RA+RC vs. RA-RC patients: 37.3(33.9-41.6) vs. 45.9(41.2-55.5), p<0.001 and 39.6 + or - 6.7 vs. 42.4 + or - 4.9, p=0.001). Percent body fat was not significantly different. No significant differences were detected in either the classical or novel CVD risk factors, 10-year CVD risk or the prevalence of established CVD.

CONCLUSIONS

RC does not appear to be associated with worse CVD profile in RA patients, but this needs to be confirmed in prospective studies.

Can greater muscularity in larger individuals resolve the 3/4 power-law controversy when modelling maximum oxygen uptake?

BACKGROUND

The power function relationship, MR = a.m(b), between metabolic rate (MR) and body mass m has been the source of much controversy amongst biologists for many years. Various studies have reported mass exponents (b) greater than the anticipated 'surface-area' exponent 0.67, often closer to 0.75 originally identified by Kleiber.

AIM

The study aimed to provide a biological explanation for these 'inflated' exponents when modelling maximum oxygen uptake (max), based on the observations from this and previous studies that larger individuals develop disproportionately more muscle mass in the arms and legs.

RESEARCH DESIGN AND SUBJECTS

A cross-sectional study of 119 professional soccer players from Croatia aged 18-34 was carried out.

RESULTS

Here we confirm that the power function relationship between max and body mass of the professional soccer players results in an 'inflated' mass exponent of 0.75 (95% confidence interval from 0.56 to 0.93), but also the larger soccer players have disproportionately greater leg muscle girths. When the analysis was repeated incorporating the calf and thigh muscle girths rather than body mass as predictor variables, the analysis not only explained significantly more of the variance in max, but the sum of the exponents confirmed a surface-area law.

CONCLUSIONS

These findings confirm the pitfalls of fitting body-mass power laws and suggest using muscle-girth methodology as a more appropriate way to scale or normalize metabolic variables such as max for individuals of different body sizes.

Influence of body position when considering the ecological validity of laboratory time-trial cycling performance

The aims of this study were to compare the physiological demands of laboratory- and road-based time-trial cycling and to examine the importance of body position during laboratory cycling. Nine male competitive but non-elite cyclists completed two 40.23-km time-trials on an air-braked ergometer (Kingcycle) in the laboratory and one 40.23-km time-trial (RD) on a local road course. One laboratory time-trial was conducted in an aerodynamic position (AP), while the second was conducted in an upright position (UP). Mean performance speed was significantly higher during laboratory trials (UP and AP) compared with the RD trial (P < 0.001). Although there was no difference in power output between the RD and UP trials (P > 0.05), power output was significantly lower during the AP trial than during both the RD (P = 0.013) and UP trials (P = 0.003). Similar correlations were found between AP power output and RD power output (r = 0.85, P = 0.003) and between UP power output and RD power output (r = 0.87, P = 0.003). Despite a significantly lower power output in the laboratory AP condition, these results suggest that body position does not affect the ecological validity of laboratory-based time-trial cycling.

Scaling concept II rowing ergometer performance for differences in body mass to better reflect rowing in water

We investigated whether the concept II indoor rowing ergometer accurately reflects rowing on water. Forty-nine junior elite male rowers from a Great Britain training camp completed a 2000 m concept II model C indoor rowing ergometer test and a water-based 2000 m single-scull rowing test. Rowing speed in water (3.66 m/s) was significantly slower than laboratory-based rowing performance (4.96 m/s). The relationship between the two rowing performances was found to be R2=28.9% (r=0.538). We identified that body mass (m) made a positive contribution to concept II rowing ergometer performance (r=0.68, P<0.001) but only a small, non-significant contribution to single-scull water rowing performance (r=0.039, P=0.79). The contribution that m made to single-scull rowing in addition to ergometer rowing speed (using allometric modeling) was found to be negative (P<0.001), confirming that m has a significant drag effect on water rowing speed. The optimal allometric model to predict single-scull rowing speed was the ratio (ergometer speed xm(-0.23))1.87 that increased R2 from 28.2% to 59.2%. Simply by dividing the concept II rowing ergometer speed by body mass (m0.23), the resulting "power-to-weight" ratio (ergometer speed xm(-0.23)) improves the ability of the concept II rowing performance to reflect rowing on water.

Can we use the Jackson and Pollock equations to predict body density/fat of obese individuals in the 21st century?

OBJECTIVE: Jackson and Pollock's (JP) ground-breaking research reporting generalized body density equations to estimate body fat was carried out in the late 1970s. Since then we have experienced an 'obesity epidemic'. Our aim was to examine whether the original quadratic equations established by Jackson and co-workers are valid in the 21st century. METHODS: Reanalyzing the original JP data, an alternative, more biologically sound exponential power-function model for body density is proposed that declines monotonically, and hence predicts body fat to rise monotonically, with increasing skin-fold thicknesses. The model also remains positive irrespective of the subjects' sum-of-skinfold thicknesses or age. RESULTS: Compared to the original quadratic model proposed by JP, our alternative exponential power-function model is theoretically and empirically more accurate when predicting body fat of obese subjects (sums of skinfolds >120mm). A cross-validation study on 14 obese subjects confirmed these observations, when the JP quadratic equations under estimated body fat predicted using dual energy x-ray absorptiometry (DXA) by 2.1% whereas our exponential power-function model was found to underestimate body fat by less than 1.0%. Otherwise, the agreement between the DXA fat (%) and the two models were found to be almost identical, with both coefficients of variation being 10.2%. CONCLUSIONS: Caution should be exercised when predicting body fat using the JP quadratic equations for subjects with sums of skinfolds>120 mm. For these subjects, we recommend estimating body fat using the tables reported in the present manuscript, based on the more biologically sound and empirically valid exponential power-function model.

Associations of obesity with modifiable risk factors for the development of cardiovascular disease in patients with rheumatoid arthritis

OBJECTIVES

To assess the association of body mass index (BMI) with modifiable cardiovascular disease (CVD) risk factors in patients with rheumatoid arthritis (RA).

METHODS

BMI, disease activity, selected CVD risk factors and CVD medication were assessed in 378 (276 women) patients with RA. Patients exceeding accepted thresholds in >or=3 CVD risk factors were classified as having the metabolic syndrome (MetS).

RESULTS

BMI independently associated with hypertension (OR = 1.28 (95% CI = 1.22 to 1.34); p = 0.001), high-density lipoprotein (OR = 1.10 (95% CI = 1.06 to 1.15); p = 0.025), insulin resistance (OR = 1.13 (95% CI = 1.08 to 1.18); p = 0.000) and MetS (OR = 1.15 (95% CI = 1.08 to 1.21); p = 0.000). In multivariable analyses, BMI had the strongest associations with CVD risk factors (F(1-354) = 8.663, p = 0.000), and this was followed by lipid-lowering treatment (F(1-354) = 7.651, p = 0.000), age (F(1-354) = 7.541, p = 0.000), antihypertensive treatment (F(1-354) = 4.997, p = 0.000) and gender (F(1-354) = 4.707, p = 0.000). Prevalence of hypertension (p = 0.004), insulin resistance (p = 0.005) and MetS (p = 0.000) was significantly different between patients with RA who were normal, overweight and obese, and BMI differed significantly according to the number of risk factors present (p = 0.000).

CONCLUSIONS

Increasing BMI associates with increased CVD risk independently of many confounders. RA-specific BMI cut-off points better identify patients with RA at increased CVD risk. Weight-loss regimens should be developed and applied in order to reduce CVD in patients with RA.

The relative contributions of anaerobic and aerobic energy supply during track 100-, 400- and 800-m performance

AIM

The present study set out to identify the relative contribution of the laboratory determined physiological measures, (maximal) accumulated oxygen deficit (AOD) and maximal oxygen uptake (VO(2max)), when predicting track performance.

METHODS

Fourteen volunteers (men: n=10; women: n=4); mean (+/- standard deviation [SD]) height 1.76+/-0.1 (men) vs 1.62+/-0.08 m (women); body mass: 67.9+/-7.1 (men) vs 50.6+/-8.2 kg (women), ran track races at distances of 100, 400 and 800 m. The individually determined (maximal) AOD and VO(2max) were measured under controlled laboratory conditions (68.3+/-10.2 vs 60.7+/-16.1; men vs women, mL x (2) x Eq x kg(-1)) and (68.7+/-7.3 vs 55.6+/-4.3; men vs women, mL x kg(-1) x min(-1)), respectively.

RESULTS

Track performance could be predicted using both laboratory measures, AOD and , with a high degree of accuracy: R2=76.9%, 84.8% and 89.1% for 100, 400 and 800 m, respectively. Data analysis confirmed the dominant energy supply during 100-m sprinting was the anaerobic energy supply processes, reflected as AOD. In contrast, oxidative metabolism (reflected as VO(2max)) was the dominant source of energy supply during 800-m performance.

CONCLUSION

The results support earlier research, rather than present textbook dogma, namely that aerobic and anaerobic processes contribute equally to maximal exercise lasting approximately 60 s.

New resting energy expenditure prediction equations for patients with rheumatoid arthritis

OBJECTIVES

Resting energy expenditure (REE), one of the main components of total energy expenditure, can be measured via indirect calorimetry and/or predicted from equations. The latter may be misleading in RA, as they do not take into account the metabolic alterations occurring in RA. The objectives of this study are to evaluate the accuracy of widely used REE-predictive equations in RA patients against measured REE and to develop RA-specific equations.

METHODS

We assessed REE (via indirect calorimetry and several predictive equations), fat-free mass (FFM; via bioelectrical impedance) and disease activity (CRP) in RA patients and healthy controls. Data from 60 RA patients (experimental group) were used to assess the accuracy of existing REE equations and to develop new equations. The new equations were validated in an independent cross-validation group of 22 RA patients. These two groups were merged and two final equations were developed.

RESULTS

All equations significantly under-predicted measured REE (from 15% to 18.2%, all at P < 0.001) in the RA experimental group, but not in the control group. After both equations demonstrated a high validity in the cross-validation group, the new final REE prediction equations developed from the total RA sample (n = 82) were: Model 1: REE (kcal/day) = 126.1 x FFM(0.638) x CRP(0.045) (R(2) = 0.70) and Model 2: REE (kcal/day) = 598.8 x weight(0.47) x age(-0.29) x CRP(0.066) (R(2) = 0.62).

CONCLUSION

The new equations provide an accurate prediction of REE in RA patients and could be used for clinical monitoring of resting metabolism of these patients without the requirement for specialized personnel.

Blockade of tumour necrosis factor-alpha in rheumatoid arthritis: effects on components of rheumatoid cachexia

OBJECTIVES

Rheumatoid arthritis (RA) is accompanied by increased resting energy expenditure (REE) and decreased fat-free mass (FFM). This is referred to as rheumatoid cachexia and is attributed to high levels of tumour necrosis factor-alpha (TNF-alpha). This study aimed to investigate the effects of anti-TNF-alpha therapy on REE, body composition, physical activity and protein intake in RA patients.

METHODS

Twenty RA patients [50% female; age: (mean +/- s.d.) 61.1 +/- 6.8 yrs; body mass index (BMI): 28.3 +/- 3.7 kg/m2] and 12 age-sex-BMI-matched healthy controls were assessed. REE (indirect calorimetry), body composition (bioelectrical impedance), the International Physical Activity Questionnaire (IPAQ), diet, Health Assessment Questionnaire (HAQ), disease activity [disease activity score 28 (DAS28), erythrocyte sedimentation rate (ESR), C-reactive protein] and serum TNF-alpha were measured before (Baseline) as well as 2 weeks (Time-1) and 12 weeks (Time-2) after initiation of anti-TNF-alpha treatment. Controls were only assessed at Baseline.

RESULTS

RA patients had significantly higher REE than controls at Baseline (1799.4 +/- 292.0 vs 1502.9 +/- 114.5 kcal/day, P = 0.002). Within the RA group, REE increased significantly between Time-1 and Time-2 (P = 0.001) but not between Baseline and Time-2. Sustained significant increases were observed in IPAQ (P = 0.001) and protein intake (P = 0.001). There were no significant changes in FFM or body fat. ESR (P = 0.002), DAS28 (P < 0.001), HAQ (P < 0.001) and TNF-alpha (P = 0.024) improved significantly. Physical activity (P = 0.001) and protein intake (P = 0.024) were significant between-subject factors for the elevation of REE.

CONCLUSIONS

After 12 weeks of anti-TNF-alpha therapy, there were significant improvements in disease activity and physical function, as well as physical activity and protein intake, but no significant changes in REE or FFM. There is a need for longer-term studies in this field.

Cigarette smoking significantly increases basal metabolic rate in patients with rheumatoid arthritis

OBJECTIVE

Basal metabolic rate (BMR) is the most important indicator of human metabolism and its abnormalities have been linked to undesirable health outcomes. Cigarette smoking associates with increased BMR in healthy individuals; it is also related with worse disease outcomes in patients with rheumatoid arthritis(RA), in whom BMR is high due to hypercatabolism caused by systemic inflammation. We aimed to investigate whether smokers with RA demonstrated higher BMR levels than their non-smoking counterparts.

METHODS

A total of 53 patients with RA (36 female, 17 male, 20 current smokers) were assessed for: BMR(indirect calorimetry), anthropometrical data, fat-free mass (bioelectrical impedance), physical function (health assessment questionnaire; HAQ) and disease activity(disease activity score DAS28 and C reactive protein).

RESULTS

RA smokers and non-smokers were not significantly different for age, height, weight, body mass index and fat-free mass. Compared to non-smokers,smokers with RA demonstrated significantly higher BMR (mean (SD) 1513.9 (263.3) vs 1718.1 (209.2) kcal/day; p,0.001) and worse HAQ (1.0 (0.8) vs 1.7 (0.8); p=0.01). The BMR difference was significantly predicted by the interaction smoking/gender (p=0.04). BMR was incrementally higher in light, moderate and heavy smokers (p=0.018), and correlated with the daily number of cigarettes smoked (r=0.68, p=0.04).

CONCLUSION

Current cigarette smoking further increases BMR in patients with RA and has a negative impact on patients self-reported functional status. Education regarding smoking cessation is needed for the RA population.

Are There Limits to Swimming World Records?

The purpose of this article was to investigate whether swimming world records are beginning to plateau and whether the inequality between men and women's swimming performances is narrowing, similar to that observed in running world records. A flattened "S-shaped curve" logistic curve is fitted to 100-m, 200-m, and 400-m front-crawl world-record swimming speeds for men and women from 1 May 1957 to the present time, using the non-linear least-squares regression. The inequality between men and women's world records is also assessed using the ratio, Women's/Men's world record speeds. The results confirm that men and women's front-crawl swimming world-record speeds are plateauing and the ratio between women's and men's world records has remained stable at approximately 0.9. In conclusion, the logistic curves provide evidence that swimming world-record speeds experienced a period of "accelerated" growth/improvements during the 1960 - 1970s, but are now beginning to plateau. The period of acceleration corresponded with numerous advances in science and technology but also coincided with the anecdotal evidence for institutionalised doping. Also noteworthy, however, is the remarkably consistency in the women's/men's world record ratio, circa 0.9, similar to those observed in middle and long distance running performances. These finding supports the notion that a 10 % gender inequality exists for both swimming and running.

The effect of simulated gastric environments on the anti-Helicobacter activity of garlic oil

AIMS

To investigate the effects of simulated gastric conditions upon the anti-Helicobacter pylori effects of garlic oil (GO).

METHODS AND RESULTS

Time course viability experiments assessed the anti-H. pylori activity of GO (16 and 32 microg ml(-1)) in simulated gastric environments. Rapid anti-H. pylori action of GO was observed in artificial gastric juice. Mucus (1-5%) was strongly protective of H. pylori both alone and in the presence of GO, but its protective effect was antagonized by GO. Peptone (5-15 g l(-1)) caused a dose-dependent reduction in the anti-H. pylori activity of GO. Rapeseed oil (5.7-17 g l(-1)) greatly diminished the anti-H. pylori activity of GO. Dextrin (44 and 133 g l(-1)) exhibited direct anti-H. pylori effects and added to those of GO. Simulated meal mixtures decreased but did not eliminate the anti-H. pylori activity of 32 mug ml(-1) GO.

CONCLUSIONS

The anti-H. pylori activity of GO was noticeably affected by food materials and mucin. However, substantial activity remained under simulated gastric conditions. Further investigation of the therapeutic potential of GO against H. pylori is therefore warranted.

SIGNIFICANCE AND IMPACT OF THE STUDY

Garlic oil may be useful as an alternative treatment against H. pylori, a major cause of gastrointestinal infections in humans.

LDL Particle Size in Habitual Exercisers, Lean Sedentary Men and Abdominally Obese Sedentary Men

Habitual exercisers enjoy considerable protection from coronary heart disease (CHD). Often, however, only modest differences in traditional CHD risk factors are apparent between habitual exercisers and their sedentary counterparts. For this reason, there is increasing interest in novel predictors of CHD, such as a preponderance of small, dense low-density lipoprotein (LDL) particles. Polyacrylamide gel electrophoresis was used to separate lipoprotein subfractions in 32 lean exercisers, 36 lean sedentary men and 21 obese sedentary men aged 30 - 45 years. Well-validated equations were used to determine LDL concentration and peak particle diameter. Waist girth was used to identify lean (< 100 cm) and obese (>or= 100 cm) individuals. LDL concentration was lower in lean exercisers than in lean sedentary men (2.64 +/- 0.44 vs. 3.76 +/- 0.79 mmol . l (-1), p < 0.001), suggesting that habitual exercise influences this risk factor. In contrast, there were no significant differences in LDL peak particle diameter between lean exercisers, lean sedentary men and obese sedentary men (27.92 +/- 0.67, 28.09 +/- 0.62 and 27.77 +/- 0.77 nm, respectively). In multiple linear regression analysis, triglyceride concentration was the only significant predictor of LDL PPD. These data suggest that habitual exercise influences LDL concentration but does not influence LDL particle size in men aged 30 - 45 years.

The ecological validity of laboratory cycling: Does body size explain the difference between laboratory- and field-based cycling performance?

Previous researchers have identified significant differences between laboratory and road cycling performances. To establish the ecological validity of laboratory time-trial cycling performances, the causes of such differences should be understood. Hence, the purpose of the present study was to quantify differences between laboratory- and road-based time-trial cycling and to establish to what extent body size [mass (m) and height (h)] may help to explain such differences. Twenty-three male competitive, but non-elite, cyclists completed two 25 mile time-trials, one in the laboratory using an air-braked ergometer (Kingcycle) and the other outdoors on a local road course over relatively flat terrain. Although laboratory speed was a reasonably strong predictor of road speed (R2 = 69.3%), a significant 4% difference (P < 0.001) in cycling speed was identified (laboratory vs. road speed: 40.4 +/- 3.02 vs. 38.7 +/- 3.55 km x h(-1); mean +/- s). When linear regression was used to predict these differences (Diff) in cycling speeds, the following equation was obtained: Diff (km x h(-1)) = 24.9 - 0.0969 x m - 10.7 x h, R2 = 52.1% and the standard deviation of residuals about the fitted regression line = 1.428 (km . h-1). The difference between road and laboratory cycling speeds (km x h(-1)) was found to be minimal for small individuals (mass = 65 kg and height = 1.738 m) but larger riders would appear to benefit from the fixed resistance in the laboratory compared with the progressively increasing drag due to increased body size that would be experienced in the field. This difference was found to be proportional to the cyclists' body surface area that we speculate might be associated with the cyclists' frontal surface area.

Optimal power-to-mass ratios when predicting flat and hill-climbing time-trial cycling

The purpose of this article was to establish whether previously reported oxygen-to-mass ratios, used to predict flat and hill-climbing cycling performance, extend to similar power-to-mass ratios incorporating other, often quick and convenient measures of power output recorded in the laboratory [maximum aerobic power (W(MAP)), power output at ventilatory threshold (W(VT)) and average power output (W(AVG)) maintained during a 1 h performance test]. A proportional allometric model was used to predict the optimal power-to-mass ratios associated with cycling speeds during flat and hill-climbing cycling. The optimal models predicting flat time-trial cycling speeds were found to be (W(MAP)m(-0.48))(0.54), (W(VT)m(-0.48))(0.46) and (W(AVG)m(-0.34))(0.58) that explained 69.3, 59.1 and 96.3% of the variance in cycling speeds, respectively. Cross-validation results suggest that, in conjunction with body mass, W(MAP) can provide an accurate and independent prediction of time-trial cycling, explaining 94.6% of the variance in cycling speeds with the standard deviation about the regression line, s=0.686 km h(-1). Based on these models, there is evidence to support that previously reported VO2-to-mass ratios associated with flat cycling speed extend to other laboratory-recorded measures of power output (i.e. Wm(-0.32)). However, the power-function exponents (0.54, 0.46 and 0.58) would appear to conflict with the assumption that the cyclists' speeds should be proportional to the cube root (0.33) of power demand/expended, a finding that could be explained by other confounding variables such as bicycle geometry, tractional resistance and/or the presence of a tailwind. The models predicting 6 and 12% hill-climbing cycling speeds were found to be proportional to (W(MAP)m(-0.91))(0.66), revealing a mass exponent, 0.91, that also supports previous research.

Cardiovascular disease risk factors in habitual exercisers, lean sedentary men and abdominally obese sedentary men

OBJECTIVE

To investigate whether the favourable cardiovascular disease (CVD) risk factor profile of habitual exercisers is attributable to exercise or leanness.

DESIGN

Cross-sectional study of 113 nonsmoking men aged 30-45 y. CVD risk factors were compared in exercisers (n=39) and sedentary men (n=74), and in subgroups of lean exercisers (n=37), lean sedentary men (n=46) and obese sedentary men (n=28). Waist girth was used to identify lean (<100 cm) and abdominally obese (> or =100 cm) subgroups.

MEASUREMENTS

Blood pressure, physical activity (7-day recall), physical fitness (maximum oxygen consumption) and fasted lipoproteins, apolipoprotein (apo) B, triglycerides, glucose and fibrinogen.

RESULTS

Exercisers were fitter and leaner than sedentary men and had a better CVD risk factor profile. Total cholesterol, LDL-cholesterol and apo B concentrations were lower in lean exercisers than in lean sedentary men, suggesting that exercise influences these risk factors. Indeed, time spent in vigorous activity was the only significant predictor of total cholesterol and LDL-cholesterol in multiple linear regression models. Exercise status had little influence on triglycerides and HDL-cholesterol (HDL-C), and unfavourable levels were only evident among obese sedentary men. Waist girth was the sole predictor of triglycerides and HDL-C, explaining 44 and 31% of the variance, respectively.

CONCLUSIONS

These findings suggest that the CVD risk factor profile of habitual exercisers is attributable to leanness and exercise. Leanness is associated with favourable levels of HDL-C and triglycerides, while exercise is associated with lower levels of total cholesterol, LDL-cholesterol and apo B.

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.

Scaling maximal oxygen uptake to predict cycling time-trial performance in the field: a non-linear approach

The purpose of the present article is to identify the most appropriate method of scaling VO2max for differences in body mass when assessing the energy cost of time-trial cycling. The data from three time-trial cycling studies were analysed (N = 79) using a proportional power-function ANCOVA model. The maximum oxygen uptake-to-mass ratio found to predict cycling speed was VO2max(m)(-0.32) precisely the same as that derived by Swain for sub-maximal cycling speeds (10, 15 and 20 mph). The analysis was also able to confirm a proportional curvilinear association between cycling speed and energy cost, given by (VO2max(m)(-0.32))0.41. The model predicts, for example, that for a male cyclist (72 kg) to increase his average speed from 30 km h(-1) to 35 km h(-1), he would require an increase in VO2max from 2.36 l min(-1) to 3.44 l min(-1), an increase of 1.08 l min(-1). In contrast, for the cyclist to increase his mean speed from 40 km h(-1) to 45 km h(-1), he would require a greater increase in VO2max from 4.77 l min(-1) to 6.36 l min(-1), i.e. an increase of 1.59 l min(-1). The model is also able to accommodate other determinants of time-trial cycling, e.g. the benefit of cycling with a side wind (5% faster) compared with facing a predominately head/tail wind (P<0.05). Future research could explore whether the same scaling approach could be applied to, for example, alternative measures of recording power output to improve the prediction of time-trial cycling performance.

Do judges enhance home advantage in European championship boxing?

There have been many examples of contentious points decisions in boxing. Professional boxing is scored subjectively by judges and referees scoring each round of the contest. We assessed whether the probability of a home win (and therefore home advantage) increased when bouts were decided by points decisions rather than knockouts. Overall, we found that bouts ending in points decisions had a significantly higher proportion of home wins than those decided by a knockout, though this effect varied across time, and controlling for relative quality of boxers was only effective when using more recent data. Focusing on these data, again the probability of a home win was higher with a points decision and this effect was consistent as "relative quality" varied. For equally matched boxers ("relative quality" = 0), expected probability of a home win was 0.57 for knockouts, 0.66 for technical knockouts and 0.74 for points decisions. The results of the present study lend general support to the notion that home advantage is more prevalent in sports that involve subjective decision-making. We suggest that interventions should be designed to inform judges to counter home advantage effects.

Performance Characteristics of Gas Analysis Systems: What We Know and What We Need to Know

It is important that sources of variation in gas analysis measurements are identified and described in an accurate and informative manner. In this paper, we discussed the potential sources of error, which should be considered in any measurement study on gas analysis systems. We then covered how errors in various terms associated with gas laws propagate to outcome measurements of gas exchange to help quantify the relative importance of sources of error. Finally, we performed a literature survey to explore the statistical methods researchers have employed to arrive at conclusions on the performance characteristics of gas analysis methods. We found examples of excellent practice in the literature, but there were also gaps in the knowledge of error in gas analysis systems. Consequently, we supplied guidelines for future method comparison studies. These guidelines included (i) a sample size of at least 40 participants and the citation of confidence intervals, (ii) a description of the relationships between systematic and random errors and the size of measured value, (iii) the parallel examination of test-retest error within a method comparison study, and (iv) an a priori-made judgement on how much systematic and random error between methods is acceptable for practical applications. We stressed that this judgement should be based on expert-agreed position statements about acceptable error, which unfortunately have yet to be formulated for gas analysis systems.

Modelling home advantage in the Summer Olympic Games

Home advantage in team games is well proven and the influence of the crowd upon officials' decisions has been identified as a plausible cause. The aim of this study was to assess the significance of home advantage for five event groups selected from the Summer Olympic Games between 1896 and 1996, and put home advantage in team games in context with other sports. The five event groups were athletics and weightlifting (predominantly objectively judged), boxing and gymnastics (predominantly subjectively judged) and team games (involving subjective decisions). The proportion of points won was analysed as a binomial response variable using generalized linear interactive modelling. Preliminary exploration of the data highlighted the need to control for the proportion of competitors entered and to split the analysis pre- and post-war. Highly significant home advantage was found in event groups that were either subjectively judged or rely on subjective decisions. In contrast, little or no home advantage (and even away advantage) was observed for the two objectively judged groups. Officiating system was vital to both the existence and extent of home advantage. Our findings suggest that crowd noise has a greater influence upon officials' decisions than players' performances, as events with greater officiating input enjoyed significantly greater home advantage.

Physiological factors associated with low bone mineral density in female endurance runners

OBJECTIVE

To explore potential factors that could be associated with low bone mineral density (BMD) in female endurance runners.

METHODS

Fifty two female endurance runners (1,500 m to marathon), aged 18-44 years, took part. Body fat percentage, lumbar spine BMD, and femoral neck BMD were measured using the Hologic QDR 4,500w bone densitometer. Data on training, menstrual cycle status, osteoporosis, and health related factors were obtained by questionnaire. Dietary variables were assessed from a prospective seven day dietary record of macronutrients and micronutrients.

RESULTS

The mean (SD) lumbar spine and femoral neck BMD were 1.11 (0.11) and 0.89 (0.12) g/cm(2) respectively. A backward elimination regression analysis showed that age, body mass, body fat, distance run, magnesium, and zinc intake were the variables significantly associated with BMD. Lumbar spine BMD (g/cm(2)) = -1.90 + (0.0486 x age (years)) + (0.342 x log mass (kg)) - (0.000861 x age(2) (years)) - (0.00128 x distance (km/week)), with an R(2) = 30.1% (SEE = 0.089 (95% confidence interval (CI) 0.05 to 0.23); p<0.001). Femoral neck BMD (g/cm(2)) = -2.51 - (0.00989 x age (years)) + (0.720 x log mass (kg)) + (0.000951 x magnesium (mg/day)) -(0.0289 x zinc (mg/day)) - (0.00821 x body fat (%)) - (0.00226 x distance (km/week)), with an R(2) = 50.2% (SEE = 0.100 (95% CI 0.06 to 0.22); p<0.001). The negative association between skeletal BMD and distance run suggested that participants who ran longer distances had a lower BMD of the lumbar spine and femoral neck. Further, the results indicated a positive association between body mass and BMD, and a negative association between body fat and BMD.

CONCLUSIONS

The results suggest a negative association between endurance running distance and lumbar spine and femoral neck BMD, with a positive association between body mass and femoral neck and lumbar spine BMD. However, longitudinal studies are required to assess directly the effect of endurance running and body mass on BMD, and to see if the addition of alternative exercise that would increase lean body mass would have a positive effect on BMD and therefore help to prevent osteoporosis.

Modeling elite male athletes' peripheral bone mass, assessed using regional dual x-ray absorptiometry

There is still considerable debate as to whether bone mineral content (BMC) increases in proportion to the projected bone area, A(p), or an estimate of the skeletal bone volume, (A(p))(3/2), being assessed. The results from this study suggest that the bone mass acquisition of elite athletes' arms and legs increases in proportion to the projected bone area, A(p), having simultaneously controlled/removed the effect of the confounding variables of body mass and body fat. Although this supports the use of the traditional bone mineral density ratio (BMD=BMC/A(p)), it also highlights the dangers of overlooking the effect of known confounding variables. Ignoring the effect of such confounding variables, athletic groups whose activities involve upper body strength (rugby, rock climbing, kayaking, weight lifting) had the highest arm BMD, while runners were observed to have the lowest arm BMD (lower than that of the controls). Similarly, leg BMD was highest in rugby players, whose activities included both running and strength training. However, the rugby players were also observed to have the greatest body mass. When the important determinants of body mass, body fat, as well as projected bone area, A(p), were incorporated as covariates into a proportional allometric ANCOVA model for BMC, different conclusions were obtained. The introduction of these covariates had the effect of reducing the sporting differences on adjusted arm BMC, although the "sport" by "side" interaction still identified racket players as the only group with a greater dominant arm BMC (P < 0.05). In contrast, sporting differences in adjusted leg BMC remained highly significant, but with a rearranged hierarchy. The runners replaced the rugby players as having the greatest adjusted leg BMC. The results confirm the benefits of activity on peripheral bone mass as being site-specific but reinforce the dangers of making generalizations about the relative benefits of different exercises ignoring the effects of known confounding variables, such as body size, body composition, and age.

Determinants of 2,000 m rowing ergometer performance in elite rowers

This study examined the physiological determinants of performance during rowing over 2,000 m on an ergometer in finalists from World Championship rowing or sculling competitions from all categories of competion rowing (19 male and 13 female heavyweight, 4 male and 5 female lightweight). Discontinuous incremental rowing to exhaustion established the blood lactate threshold, maximum oxygen consumption (VO(2max)) and power at VO(2max); five maximal strokes assessed maximal force, maximal power and stroke length. These results were compared to maximal speed during a 2,000 m ergometer time trial. The strongest correlations were for power at VO(2max), maximal power and maximal force (r=0.95; P<0.001). Correlations were also observed for VO(2max) (r=0.88, P<0.001) and oxygen consumption (VO(2)) at the blood lactate threshold (r=0.87, P=0.001). The physiological variables were included in a stepwise regression analysis to predict performance speed (metres per second). The resultant model included power at VO(2max), VO(2) at the blood lactate threshold, power at the 4 mmol x l(-1) concentration of blood lactate and maximal power which together explained 98% of the variance in the rowing performance over 2,000 m on an ergometer. The model was validated in 18 elite rowers, producing limits of agreement from -0.006 to 0.098 m x s(-1) for speed of rowing over 2,000 m on the ergometer, equivalent to times of -1.5 to 6.9 s (-0.41% to 1.85%). Together, power at VO(2max), VO(2) at the blood lactate threshold, power at 4 mmol x l(-1) blood lactate concentration and maximal power could be used to predict rowing performance.

Selected issues in the design and analysis of sport performance research

The aim of this review is to discuss some issues in the design and statistical analysis of sport performance research, rather than to supply an authoritative 'cookbook' of methods. In general, we try to communicate some possible solutions to the conundrum of how to maintain both internal and external validity, as well as optimize statistical power, in applied sport performance research. We start by arguing that some sport performance research has been overly concerned with physiological predictors of performance, at the expense of not providing a valid and reliable description of the exact nature of the task in question. We show how the influence of certain factors on competitive performances can be described using linear or logistic regression. We discuss the choice of analysis for factorial repeated-measures designs, which is complicated by the assumption of 'sphericity' in a univariate general linear model, and the relatively low statistical power of the multivariate approach when used with small samples. We consider a little-used and simpler technique known as 'analysis of summary statistics'. In multi-group pre- and post-test designs, a useful technique can be to pair-match individuals on their performance scores in a counterbalanced fashion before the intervention or control has been introduced. Finally, we outline how confidence intervals can help in making statements about the probability of the population difference in performance exceeding the value designated as being worthwhile or not.

Effect of training on accumulated oxygen deficit and shuttle run performance

BACKGROUND

The purpose of the present study was to investigate changes in physiological, metabolic and performance parameters resulting from an intense 6 week training programme.

METHODS

Sixteen volunteers were divided into a control (CN; 4 men and 2 women) and training group (TR; 6 men and 4 women). Laboratory measures included maximal aerobic power (VO2max), submaximal oxygen uptake (10.5 percent or 6 degrees treadmill inclination) and accumulated oxygen deficit (AOD). Performance was assessed during 20 metre shuttle run tests (PST, progressive shuttle run test; HIST, high intensity shuttle run test).

RESULTS

TR improved their HIST performance (m) significantly compared with CN, identified by a significant "group-by-training" interaction (p<0.01). Similarly, AOD values improved more in TR compared with CN (p<0.01). There was a trend for TR to further reduce blood pH values after training compared with CN, although this decrease (approximately 0.05 units) did not attain statistical significance. The change in AOD was strongly correlated with the change in run time to exhaustion (r=0.76, p<0.01) and the change in estimated total work output (r=0.69, p<0.01) during 10.5 percent gradient running and modestly correlated with the change in HIST performance (r=0.49, p<0.05, assuming a directional test).

CONCLUSIONS

The results of the present study suggest changes in the anaerobic capacity, determined as AOD, due to training may be reflected in corresponding changes in laboratory and field performance.