Blood lactate and ventilatory thresholds in wheelchair athletes with tetraplegia and paraplegia.

PURPOSE: The purpose of this study was to analyse the influence of spinal cord injury level on blood lactate (BLa) and ventilatory thresholds. METHODS: Ten athletes with tetraplegia (TETRA) and nine athletes with paraplegia (PARA) performed a graded wheelchair propulsion treadmill exercise step test to exhaustion. The aerobic and anaerobic BLa thresholds, the ventilatory threshold and the respiratory compensation point (RCP) were determined. RESULTS: The BLa thresholds were determined in 34 of 38 cases, ventilatory thresholds and RCPs in 31 of 38 cases. The anaerobic BLa threshold (76 ± 7 % [Formula: see text]) and the RCP (77 ± 8 % [Formula: see text]) did not differ significantly from each other (P = 0.92), with a coefficient of variation of 4.8 ± 3.4 % between thresholds. All other thresholds differed significantly from each other (P < 0.05). Thresholds expressed as the percentage of peak oxygen uptake did not differ between TETRA and PARA (P > 0.05) despite altered breathing in TETRA, which included a higher ventilatory equivalent for oxygen and a lower tidal volume. CONCLUSION: Measuring BLa leads to a higher threshold determination rate compared with ventilatory data and the anaerobic BLa threshold can be used to predict the RCP. The altered breathing in TETRA does not seem to have a pronounced effect on the ventilatory threshold or the RCP.

Hand-rim forces and gross mechanical efficiency in asynchronous and synchronous wheelchair propulsion: a comparison.

To compare the force application characteristics at various push frequencies of asynchronous (ASY) and synchronous (SYN) hand-rim propulsion, 8 able-bodied participants performed a separate sub-maximal exercise test on a wheelchair roller ergometer for each propulsion mode. Each test consisted of a series of 5, 4-min exercise blocks at 1.8 m · s-1 - initially at their freely chosen frequency (FCF), followed by four counter-balanced trials at 60, 80, 120 and 140% FCF. Kinetic data was obtained using a SMARTWheel, measuring forces and moments. The gross efficiency (GE) was determined as the ratio of external work done and the total energy expended. The ASY propulsion produced higher force measures for FRES, FTAN, rate of force development & FEF (P<0.05), while there was no difference in GE values (P=0.518). In pair-matched push frequencies (ASY80:SYN60, ASY100:SYN80, ASY120:SYN100 and ASY140:SYN120), ASY propulsion forces remained significantly higher (FRES, FTAN, rate of force development & FEF P<0.05), and there was no significant effect on GE (P=0.456). Both ASY and SYN propulsion demonstrate similar trends: changes in push frequency are accompanied by changes in absolute force even without changes in the gross pattern/trend of force application, FEF or GE. Matched push frequencies continue to produce significant differences in force measures but not GE. This suggests ASY propulsion is the predominant factor in force application differences. The ASY would appear to offer a kinetic disadvantage to SYN propulsion and no physiological advantage under current testing conditions.

Effect of low-compression balls on wheelchair tennis match-play.

The purpose of this study was to compare court-movement variables and physiological responses to wheelchair tennis match-play when using low vs. standard compression tennis balls. Eleven wheelchair basketball players were monitored during repeated bouts of tennis (20 min) using both ball types. Graded and peak exercise tests were completed. For match-play, a data logger was used to record distance and speed. Individual linear heart rate oxygen consumption relationships were used to estimate match-play oxygen uptake. Significant main effects for ball type revealed that total distance (P<0.05), forward distance (P<0.05), and average speed (P<0.05) were higher for play using a low-compression ball. A lower percentage of total time was spent stationary (P<0.001), with significantly more time spent at speeds of 1-1.49 (P<0.05), 1.5-1.99 (P<0.05) and 2.0-2.49 (P<0.05) m ∙ sec(-1) when using the low-compression ball. Main effects for physiological variables were not significant. Greater total and forward distance, and higher average speeds are achieved using a low-compression ball. The absence of any difference in measured HR and estimated physiological responses would indicate that players move further and faster at no additional mean physiological cost. This type of ball will be useful for novice players in the early phases of skill development.

The variability of high intensity exercise tests in -pre-pubertal boys.

The aim of the study was to determine the variability of different performance tests during high intensity exercise in active, untrained pre- and early pubertal boys. Participants were habituated to the Wingate anaerobic test (WAnT), force-velocity test (FVt), standing broad jump (SBJ), vertical jump test (VJT) and 40 m sprint test and repeated these procedures once a week for a period of 6 weeks. 54 active, but untrained, prepubertal boys (mean±SD) (age 12.1±0.3 years, stature 1.55±0.06 m, and body mass 47.9±10.2 kg) were recruited. After Wk2, the variability of short-term power output was low in prepubertal boys, for example, for WAnT-determined peak power (CV%=3.4%; ICC=0.982; mean bias±random error=10±50 W) and this trend was also evident for tests of athletic performance (for example, the 40 m sprint test, CV%=1.3%; ICC=0.990; mean bias±random error=0.01±0.59 s). Variability was reduced further at Wk6 for all high intensity exercise tests. The findings of the current study indicate that tests of short-term power output and athletic performance are reliable from a single measurement given an appropriate period of habituation and strict standardisation of test procedures in pre- and early pubertal boys.

Hand-rim forces and gross mechanical efficiency at various frequencies of wheelchair propulsion.

To determine the effects of push frequency changes on force application, fraction of effective force (FEF) and gross efficiency (GE) during hand-rim propulsion. 8 male able-bodied participants performed five 4-min sub-maximal exercise bouts at 1.8 ms(-1); the freely chosen frequency (FCF), followed by 4 counter-balanced trials at 60, 80, 120 and 140% FCF. Kinetic data was obtained using a SMART(Wheel), measuring forces and moments. The GE was determined as the ratio of external work done and the total energy expended. Increased push frequency led to reductions in peak resultant force (P<0.05), ranging from 167 to 117 N and peak tangential force (P<0.05), ranging from 117 to 77 N. However, FEF only demonstrated a significant difference between 60% and 140% FCF (69 ± 9% and 63 ± 7, respectively; P<0.05). Work per cycle decreased significantly (P<0.05) and rate of force development increased significantly (P<0.05) with increased push frequency. GE values were significantly lower at 60%, 120% and 140% FCF than 80% and 100% FCF (P<0.05). No meaningful associations were present between FEF and GE. Under the current testing conditions, changes in push frequency are accompanied with changes in the absolute force values, albeit without changes in either the gross pattern/trend of force application or FEF. Changes in GE are not explained by different levels of force effectiveness.

The effects of rear-wheel camber on maximal effort mobility performance in wheelchair athletes.

This study examined the effect of rear-wheel camber on maximal effort wheelchair mobility performance. 14 highly trained wheelchair court sport athletes performed a battery of field tests in 4 standardised camber settings (15°, 18°, 20°, 24°) with performance analysed using a velocometer. 20 m sprint times reduced in 18° (5.89±0.47 s, P=0.011) and 20° camber (5.93±0.47 s, P=0.030) compared with 24° (6.05±0.45 s). Large effect sizes revealed that 18° camber enabled greater acceleration over the first 2 (r=0.53, 95% CI=0.004 to 0.239) and 3 (r=0.59, 95% CI=0.017 to 0.170) pushes compared with 24°. Linear mobility times significantly improved (P≤0.05) in 15° (16.08±0.84 s), 18° (16.06±0.97 s) and 20° (16.22±0.84 s) camber compared with 24° (16.62±1.10 s). Although no statistically significant main effect of camber was revealed, large effect sizes (r=0.72, 95% CI=0.066 to 0.250) demonstrated that 18° camber reduced times taken to perform the manoeuvrability drill compared with 15°. It was concluded that 18° camber was the best performing setting investigated given its superior performance for both linear and non-linear aspects of mobility, whereas 24° camber impaired linear performance. This was likely to be due to the greater drag forces experienced. Subsequently, athletes would be recommended to avoid 24° camber and young or inexperienced athletes in particular may benefit from selecting 18° as a starting point due to its favourable performance for all aspects of mobility performance in the current study.

Influence of varied tempo music on wheelchair mechanical efficiency following 3-week practice.

The purpose of this study was to analyse adaptations in propulsion technique and gross efficiency in novice able-bodied subjects during the initial phase of learning hand-rim wheelchair propulsion to music. 22 able bodied participants performed wheelchair propulsion (1.1 m·s(-1)) followed by a VO(2) peak test on a wheelchair ergometer. Push frequency, gross efficiency (GE), heart rate, rating of perceived exertion and propulsion technique variables (force application and temporal characteristics) were recorded. Participants were then assigned to a 3-wk practice period listening to i) 125 beats·min(-1) tempo music (LOW); ii) 170 beats·min(-1) tempo music (HIGH); or iii) a control group (CON). Following practice, all participants repeated the pre-testing protocol whilst force application data was collected in practice trials 1 and 9. After accounting for the pre-practice differences in GE (using ANCOVA), GE was higher in LOW compared with CON (P=0.038; 6.6 vs. 6.1% respectively). The differences between CON vs. HIGH and LOW vs. HIGH (P=0.830; P=0.188) were trivial suggesting that only LOW experienced an increase in GE. Practice had a favourable effect on the perceptions of effort, work per cycle, push and cycle time in contrast to the CON group. The use of music in a rehabilitation setting warrants further investigation.

Nevill's explanation of Kleiber's 0.75 mass exponent: an artifact of collinearity problems in least squares models?

Intraspecific allometric modeling (Y = a.mass(b), where Y is the physiological dependent variable and a is the proportionality coefficient) of peak oxygen uptake (VO2peak) has frequently revealed a mass exponent (b) greater than that predicted from dimensionality theory, approximating Kleiber's 3/4 exponent for basal metabolic rate. Nevill (J. Appl. Physiol. 77: 2,870-2,873, 1994) proposed an explanation and a method that restores the inflated exponent to the anticipated 2/3. In human subjects, the method involves the addition of "stature" as a continuous predictor variable in a multiple log-linear aggression model: ln Y = a + c. ln stature + b. ln mass + ln epsilon, where c is the general body size exponent and epsilon is the error term. It is likely that serious collinearity confounds may adversely affect the reliability and validity of the model. The aim of this study was to critically examine Nevill's method in modeling VO2peak in prepubertal, teenage, and adult men. A mean exponent of 0.81 (95% confidence interval, 0.65-0.97) was found when scaling by mass alone. Nevill's method reduced the mean mass exponent to 0.67 (95% confidence interval, 0.44-0.9). However, variance inflation factors and tolerance for the log-transformed stature and mass variables exceeded published criteria for severe collinearity. Principal components analysis also diagnosed severe collinearity in two principal components, with condition indexes > 30 and variance decomposition proportions exceeding 50% for two regression coefficients. The derived exponents may thus be numerically inaccurate and unstable. In conclusion, the restoration of the mean mass exponent to the anticipated 2/3 may be a fortuitous statistical artifact.

The effect of aerobic exercise training on the lipid-lipoprotein profile of children and adolescents.

Longitudinal paediatric population studies have provided evidence that the risk factor theory may be extended to children and adolescents. These studies could assist in identifying individuals at increased coronary risk. Numerous studies have focused on the effects of regular exercise on the paediatric lipoprotein profile, a recognised primary risk factor, with equivocal results. Cross-sectional comparisons of dichotomised groups provide the strongest evidence of an exercise effect. 'Trained' or 'active' children and adolescents demonstrate 'favourable' levels of high density lipoprotein-cholesterol (HDL-C), triacylglycerol, total cholesterol (TC)/HDL-C and low density lipoprotein-cholesterol (LDL-C)/HDL-C, whilst TC is generally unaffected. The evidence regarding LDL-C in these studies is equivocal. A possible self-selection bias means that a cause-effect relationship between exercise and the lipoprotein profile cannot be readily established from this design. Correlational studies are difficult to interpret because of differences in participant characteristics, methods employed to assess peak oxygen uptake and habitual physical activity (HPA), and the statistical techniques used to analyse multivariate data. Directly measured cardiorespiratory fitness does not appear to be related to lipoprotein profiles in the children and adolescents studied to date, although there are data to the contrary. The relationship with HPA is more difficult to decipher. The evidence suggests that a 'favourable' lipoprotein profile may be related to higher levels of HPA, although differences in assessment methods preclude a definitive answer. While few prospective studies exist, the majority of these longitudinal investigations suggest that imposed regular exercise has little, if any, influence on the lipoprotein levels of children and adolescents. However, most prospective studies have several serious methodological design weaknesses, including low sample size, inadequate exercise training volume and a lack of control individuals. Recent studies have suggested that increases in HDL-C and reductions in LDL-C may be possible with regular exercise. The identification of a dose-response relationship between exercise training and the lipoprotein profile during the paediatric years remains elusive.

Do 9- to 12 yr-old children meet existing physical activity recommendations for health?

PURPOSE: The purpose of this study was to investigate whether a sample of 9- to 12-yr-old children fulfilled existing U.S. and UK physical activity recommendations for health. METHODS: Habitual physical activity levels of 79 pre- and early pubertal children were assessed using continuous heart rate monitoring over a period of 4 d. Mean, daily, cumulative physical activity levels spent above heart rate thresholds were compared with U.S. and UK recommended values. RESULTS: In this study, when cumulative amounts of physical activity were considered, at intensities greater than 120 beats x min(-1) and 75% above resting heart rate, pre- and early pubertal British children appear to engage in sufficient physical activity to meet U.S. and UK minimum daily recommendations. CONCLUSIONS: Interpretations of children's physical activity levels depend on thresholds set for intensity of physical activity and whether cumulative or continuous bouts of activity are included in the analysis.

Exercise training induced alterations in prepubertal children's lipid-lipoprotein profile.

PURPOSE: This study examined the effect of exercise training on prepubertal children's (ET, N = 28) lipid-lipoprotein profile, relative to a maturity matched control group (CON, N = 20). METHODS: Training for ET involved stationary cycling for 30 min, 3 times.wk-1 for 12 wk, at 79.3 +/- 1.2% (mean +/- SD) peak heart rate (HR). Controls maintained their usual lifestyle pattern. Plasma concentrations of total triacylglycerol (TG), total cholesterol (TC), and high-density lipoprotein (HDL)-cholesterol (HDL-C) were determined pre- and postintervention. Low-density lipoprotein (LDL)- cholesterol (LDL-C) was subsequently estimated from these concentrations, and the ratios TC/HDL-C and LDL-C/HDL-C were also calculated. There were no pretest differences (P > 0.05) for any of these blood analytes between groups. The following, potentially, confounding variables were also measured: peak VO2, percent body fat (%BF), dietary composition, and habitual physical activity. These variables, with pretest HDL-C, were included as covariates in two-way split plot ANCOVA analyses. Dietary variables were not included as covariates as they were not related to any of the blood analytes. RESULTS: There were no differences over time or between groups for TG and TC (P > 0.05). LDL-C decreased in ET (-10.2%) but remained unchanged in CON (0.3%) over the intervention period (P < 0.05). HDL-C increased in ET (9.3%) but decreased in CON (-8.9%) (P < 0.01). A similar, but inverted, pattern of change (P < 0.01) was revealed for both ratios, TC/HDL-C (-11.6% vs 6.3%, ET and CON, respectively), and LDL-C/HDL-C (-17.2% vs 8.0%, ET and CON, respectively). The favorable alterations in the lipid-lipoprotein profile for ET were independent of alterations in peak VO2 (group x time interaction, P < 0.05), %BF (main effect time, P < 0.01), and habitual physical activity (group x time interaction, P < 0.01). CONCLUSIONS: In conclusion, the favorable alterations in the lipoprotein profile seen in this study would suggest that it is possible to influence the prepubertal lipoprotein profile independent of alterations in confounding variables such as body composition, cardiorespiratory fitness, and habitual physical activity.

Selected predictor variables and the lipid-lipoprotein profile of prepubertal girls and boys.

PURPOSE: It is still unclear how habitual physical activity (HPA), peak VO2, percent body fat (%BF), and dietary composition are related to the lipid-lipoprotein profile in children. The purpose of this study was to identify independent contributions from these selected predictor variables to prepubertal children's lipid-lipoprotein profile. METHODS: Peak VO2, HPA from continuous heart rate monitoring, %BF, 7-d dietary analysis, total cholesterol (TC), total triacylglycerol (TG), high density lipoprotein (HDL) cholesterol (HDL-C), low density lipoprotein (LDL) cholesterol (LDL-C), TC/HDL-C, and LDL-C/HDL-C were determined in 33 prepubertal girls and 38 prepubertal boys (mean +/- SD age, 10.6 +/- 0.7 yr). RESULTS: Bivariate correlation analyses revealed that peak VO2, %BF, and HPA were related to the lipid-lipoprotein profile in girls (P < 0.05). For the boys, HPA was only related to TC/HDL-C (P < 0.05) and LDL-C/HDL-C (P < 0.05), whereas daily energy intake (kJ x d(-1)) was associated with TC and LDL-C (P < 0.05). Multiple linear regression analyses indicated that peak VO2, %BF and HPA were the main predictor variables for the girls. Peak VO2 accounted for 22.7%, 24.8%, 22.5%, and 24.2% of the unique variance (sr(i)2) in TG, HDL-C, LDL-C/HDL-C, and TC/HDL-C, respectively. For TC and LDL-C in girls, sr(i)2 were 18.0% and 22.6%, respectively, from HPA. In contrast, only daily energy intake had a significant unique contribution to the variance of TC (15.4%) and LDL-C (22.0%) for the boys. SUMMARY: The main findings from this study were that the predictor variables are lipid-lipoprotein specific and depend on gender. These results would support the growing evidence that it is important to nurture an active lifestyle in children from an early age and that an awareness of fitness and body fatness is required.

The effects of experience on the energy cost of wheelchair propulsion.

BACKGROUND: Gross mechanical efficiency (GE) of experienced wheelchair users is significantly higher than novice able-bodied individuals suggesting energy expenditure (EE) may be reduced in experienced individuals. With knowledge of the energy expended during wheelchair propulsion, nutritional recommendations can be provided for individuals in their early stages of rehabilitation and for habituated wheelchair users. AIM: To investigate the effects of experience on EE during wheelchair propulsion at fixed power outputs (PO's). DESIGN: This was an experimental study. SETTING: The experiment was conducted in a controlled University laboratory. POPULATION: Thirty-one individuals took part in this study. METHODS: Participants were assigned to a group in accordance to their wheelchair propulsion experience: 1) novice able-bodied individuals (NOV; N.=11), 2) able-bodied individuals habituated to three weeks practice (PRAC; N.=11) and 3) experienced paraplegic daily-wheelchair users (EXP; N.=9). Oxygen uptake, EE, GE% and HR were measured during wheelchair propulsion on a motorised treadmill at 10, 18 and 26 W. RESULTS: Energy expenditure analysis revealed a significant main effect of PO and group (P<0.01) and a significant group by PO interaction (P<0.01). Follow-up pair-wise comparisons revealed significantly lower EE in EXP compared to both other groups (P<0.01), but no difference was shown between NOV and PRAC (P=0.15). A lower relative EE of 20, 22 and 32% was reported in the EXP group compared to the NOV group at 10, 18 and 26 W respectively. In comparison to the PRAC group, the EE of the EXP group was 10, 16 and 26% lower in relative terms at the same PO's respectively. CONCLUSION: The EXP expended less EE compared to both NOV and PRAC. CLINICAL REHABILITATION IMPACT: This finding has great implications for nutritionists and health care professionals working in the field of physical activity and weight management since the EE is influenced by experience.

Effect of breakfast glycemic index on metabolic responses during rest and exercise in overweight and non-overweight adolescent girls.

BACKGROUND/OBJECTIVES: The metabolic responses to mixed breakfast meals with different glycemic indexes (GI) and their effects on substrate metabolism during exercise in adolescent girls have not been examined. The interaction with weight status also warrants investigation. This study investigated the effect of mixed breakfast meals containing high GI (HGI) or low GI (LGI) carbohydrates on metabolic responses and fat oxidation during rest and exercise in overweight (OW) and non-overweight (NO) adolescent girls. SUBJECTS/METHODS: A total of 8 OW and 12 NO adolescent girls consumed an isoenergetic HGI (GI=73) or LGI (GI=44) breakfast 120 min before completing a 30-min treadmill walk at 50% \[Vdot]O(2peak). RESULTS: Peak blood glucose concentration was higher for HGI compared with LGI in OW (P=0.023), but not NO (P>0.05) girls. Blood glucose total area under the curve (TAUC) was 13% higher in HGI compared with LGI in OW (P=0.006), but only 4% higher in NO (P=0.072) girls. Plasma insulin data were log(e) transformed (lninsulin). Plasma lninsulin concentrations were not different between HGI and LGI (P>0.05). Peak plasma lninsulin concentration (P=0.016) and TAUC (P=0.001) were greater in OW than NO girls. Fat oxidation during postprandial rest and exercise was not different between breakfasts (P>0.05). CONCLUSIONS: The elevated glycemic response in HGI compared with LGI was more pronounced in OW girls, suggesting a reduced ability to cope with the metabolic demands of the HGI, but not LGI, breakfast. Manipulation of breakfast GI did not alter fat oxidation during rest or subsequent moderate intensity exercise in OW and NO adolescent girls.

Pulmonary O2 uptake on-kinetics in endurance- and sprint-trained master athletes.

The purpose of this study was to characterise the VO2 kinetic response to moderate intensity cycle exercise in endurance-trained (END) and sprint or power-trained (SPR) track and field master athletes ranging in age from 45 to 85 years. We hypothesised that the time constant (tau) describing the Phase II VO2 on-response would be smaller in the END compared to the SPR athletes, and that the tau would become greater with increasing age in both groups. Eighty-four master athletes who were competing at either the British or European Veteran Athletics Championships acted as subjects, and were classified as either END (800 m - marathon; n = 41), or SPR (100 - 400 m and field events; n = 43) specialists. Subjects completed two 6 minute "step" transitions to a work rate of moderate intensity on a cycle ergometer and pulmonary gas exchange was measured breath-by-breath. Analysis of variance revealed that SPR athletes had slower VO2 on-kinetics (i.e., greater tau) compared to END athletes at each of the age groups studied: 46 - 55 yrs (END: 25 +/- 6 vs. SPR: 36 +/- 9 s; p < 0.10), 56 - 65 yrs (END: 25 +/- 5 vs. SPR: 35 +/- 10 s; p < 0.05), 66 - 75 yrs (END: 29 +/- 10 vs. SPR: 40 +/- 13 s; p < 0.05), and 76 - 85 yrs (END: 31 +/- 10 vs. SPR: 51 +/- 18 s; p < 0.05). The VO2 on-kinetics became slower with advancing age in the SPR athletes (p < 0.05 between 56 - 65 and 76 - 85 yrs) but were not significantly changed in the END athletes. The slower VO2 on-kinetics in SPR compared to END master athletes is consistent both with differences in physiology (e.g., muscle fibre type, oxidative/glycolytic capacity) and training between these specialist athletes. Master END athletes have similar tau values to their younger counterparts (approximately 25 s) suggesting that participation in endurance exercise training limits the slowing of VO2 on-kinetics with age in this population.

Child-adult differences in whole blood lactate responses to incremental treadmill exercise.

The aim of this study was to evaluate whether fixed blood lactate reference values of 2.5 and 4.0 mmol.1(-1) corresponded to the equivalent intensity of exercise in prepubertal and teenage boys, and men. Twenty six prepubertal boys (mean(sd) age) 11.1(0.4) years), 26 teenage boys (mean(sd) age 14.1(0.3) years), and 23 men (mean(sd) age 22.4(2.7) years) gave informed consent to participate in the study. Oxygen consumption (VO2) and heart rates (HR) corresponding to the 2.5 and 4.0 mmol.1(-1) fixed blood lactate reference values were used as the criterion measures during incremental treadmill exercise. At the 2.5 mmol.1(-1) level there were no significant differences (P > 0.05) in % peak VO2 between groups. For both prepubertal and teenage boys the 4.0 mmol.1(-1) lactate level represented a higher mean % peak. VO2 than for the mean (P < 0.05). The prepubertal and teenage values were again not significantly different (P > 0.05). Factors other than maturation during puberty influence blood lactate responses to exercise.

Intra-individual variation of plasma lipids and lipoproteins in prepubescent children.

Estimates of the average intra-individual biological variability for plasma lipids and lipoproteins differs substantially among published studies. Moreover, this topic does not appear to have received consideration in exercise and health literature with normal, healthy children as subjects. The purpose of this study was, therefore, to determine the short-term, day-to-day variability of the lipid-lipoprotein profile from 19 children [mean (SD), 11.5 (0.8) years] from 3 separate venous blood samples. Intra-individual standard deviations, variances and coefficients of variance were determined for total cholesterol (TC), triacylglycerol (TG), high-density lipoprotein-cholesterol (HDL-C), HDL-C sub-fractions HDL2 and HDL3, and low-density lipoprotein-cholesterol (LDL-C). The intra-individual variation for TC and LDL-C was used to calculate the 95% confidence intervals (CIs) around the National Cholesterol Education Programme (NCEP 1991) cut-off points. The main finding was that all of the measured blood analytes including TC, TG, HDL-C, HDL2, HDL3, and LDL-C varied considerably from day-to-day. Coefficients of total variation ranged from 3.5% for HDL3 to 25.4% for TG. Classification of individuals using NCEP guidelines was difficult based on only one or two blood samples. The magnitude of variation for LDL-C meant that a 95% CI could not be constructed around the NCEP borderline-high classification from either one or two samples. However, averaging three TC and LDL-C measurements increased the likelihood of classification within the 95% CI. The results indicate that when using the NCEP guidelines for children and adolescents, true concentrations for TC and LDL-C should be based on the mean of multiple samples.

Effects of short-term isokinetic training on standing long-jump performance in untrained men.

The purpose of this study was to examine the effects of a 6-week isokinetic training program on quadriceps and hamstrings peak torque (PT) and standing long-jump (SLJ) performance. Twelve untrained men (age 31.4 +/- 4.2 years, mean +/- SD) were tested at a velocity of 1.75 rad.s(-1) (100 degrees.s(-1)), before and after a 6-week control period and on completion of a 6-week training program. Training consisted of 3 sets of 10 repetitions, 3 days per week, for 6 weeks. Repeated-measures analysis-of-variance analyses revealed that quadriceps PT increased, on average, by 10.5% as a result of training (p < 0.01). No significant changes in hamstrings PT (p = 0.062) and SLJ performance occurred as a result of training (p > 0.05). The major finding of this study was that PT gains subsequent to isokinetic resistance training did not influence functional performance. That open-chain training did not affect the performance of a closed-chain activity is unsurprising, but on these grounds of nonfunctionality, the use of moderate velocity isokinetic dynamometry in rehabilitation and performance assessment for closed-chain sports needs addressing in future research.

Oxygen uptake-heart rate relationship in élite wheelchair racers.

The American College of Sports Medicine (ACSM) recommends that, as a general rule for health purposes, individuals should exercise at 40%-85% of their maximal oxygen uptakes. Moreover, it has been suggested that 55%-90% of the maximal heart rate may be used as an alternative estimate of these percentage maximal oxygen uptake values. The present study examined the relationship between percentage peak heart rate (% HRpeak) and percentage peak oxygen uptake (% VO2peak) during steady-state incremental intensity wheelchair propulsion of 16 élite, male wheelchair racers (WR). Oxygen uptake was determined during each submaximal exercise stage and heart rate (HR) was continuously monitored. The VO2peak was subsequently determined using a separate protocol. Linear regression equations of % HRpeak versus % VO2peak for each participant included % HRpeak values corresponding to 40%, 60%, 80% and 85% VO2peak. The linear regression equation, derived as the group mean of the slope and intercept terms determined for each individual, was: % peak HR = 0.681 x % peak VO2 + 33.2. The group mean of the individual correlation coefficients for the VO2-HR relationship was 0.99. The values of % HRpeak for each of the % VO2peak values below 85% were significantly greater (P<0.01) than those suggested by the ACSM. This suggests that the ACSM guidelines below 85% VO2peak, based on % HRpeak, may underestimate the relative exercise intensity (i.e. % VO2peak) in the WR population. However, in élite level WR, % HRpeak can be recommended as an alternative estimate of % VO2peak at wheelchair propulsion intensities of 85% VO2peak or more.

Activity analysis of English Premiership rugby football union refereeing.

Little is known about the physiological demands placed on officials during sporting activities. The purpose of this study was to ascertain the movement activities of referees during English Premiership rugby football union matches, and to determine the frequency and duration of these activities. Nine referees who were ranked in the top 20 referees in England were videotaped during a total of 19 matches. During playback of the videotapes, a single observer coded the referees' activities into one of six distinct categories (standing, walking forwards, walking backwards, jogging, running and sprinting) using a computerized video editing system (Observer Video-Pro). The referees were timed over a 20 m distance for the modes of locomotory activity, and the average velocity of the referee for each activity was used to calculate the total distance covered in each mode of activity during matches. The total distance covered during a match was (chi +/- SD) 8581 +/- 668 m. The mean percentage of total playing time spent in each activity was: standing still, 37.0 +/- 11.0%; walking forward, 29.5 +/- 7.2%; walking backward, 9.9 +/- 3.2%; jogging, 12.8 +/- 3.2%; running, 9.8 +/- 2.3%; and sprinting, 1.0 +/- 0.4%. There were a total of 672 transitions between modes of activity during a match. The results of this study suggest that refereeing top English rugby football union matches is physically demanding. Although the major physiological load is placed on the oxygen transport system, frequent sprint bouts and the associated requirements for acceleration and deceleration impose additional metabolic demands on referees. This information may be used in the design of physical training programmes to optimize performance in referees.