Effects of exercise intensity and duration on the excess post-exercise oxygen consumption.

Recovery from a bout of exercise is associated with an elevation in metabolism referred to as the excess post-exercise oxygen consumption (EPOC). A number of investigators in the first half of the last century reported prolonged EPOC durations and that the EPOC was a major component of the thermic effect of activity. It was therefore thought that the EPOC was a major contributor to total daily energy expenditure and hence the maintenance of body mass. Investigations conducted over the last two or three decades have improved the experimental protocols used in the pioneering studies and therefore have more accurately characterized the EPOC. Evidence has accumulated to suggest an exponential relationship between exercise intensity and the magnitude of the EPOC for specific exercise durations. Furthermore, work at exercise intensities >or=50-60% VO2max stimulate a linear increase in EPOC as exercise duration increases. The existence of these relationships with resistance exercise at this stage remains unclear because of the limited number of studies and problems with quantification of work intensity for this type of exercise. Although the more recent studies do not support the extended EPOC durations reported by some of the pioneering investigators, it is now apparent that a prolonged EPOC (3-24 h) may result from an appropriate exercise stimulus (submaximal: >or=50 min at >or=70% VO2max; supramaximal: >or=6 min at >or=105% VO2max). However, even those studies incorporating exercise stimuli resulting in prolonged EPOC durations have identified that the EPOC comprises only 6-15% of the net total oxygen cost of the exercise. But this figure may need to be increased when studies utilizing intermittent work bouts are designed to allow the determination of rest interval EPOCs, which should logically contribute to the EPOC determined following the cessation of the last work bout. Notwithstanding the aforementioned, the earlier research optimism regarding an important role for the EPOC in weight loss is generally unfounded. This is further reinforced by acknowledging that the exercise stimuli required to promote a prolonged EPOC are unlikely to be tolerated by non-athletic individuals. The role of exercise in the maintenance of body mass is therefore predominantly mediated via the cumulative effect of the energy expenditure during the actual exercise.

Impact of indexing resting metabolic rate against fat-free mass determined by different body composition models.

OBJECTIVE: To examine the differences arising from indexing resting metabolic rate (RMR) against fat-free mass (FFM) determined using two-, three- and four-compartment body composition models. DESIGN: All RMR and body composition measurements were conducted on the same day for each subject following compliance with premeasurement protocols. SUBJECTS: Data were generated from measurements on 104 males (age 32.1+/-12.1 y (mean+/-s.d.); body mass 81.15+/-12.85 kg; height 179.5+/-6.5 cm; body fat 20.6+/-7.6%). INTERVENTIONS: Body density (BD), total body water (TBW) and bone mineral mass (BMM) were measured by hydrodensitometry, deuterium dilution and dual energy X-ray absorptiometry (DXA), respectively. These measures were used to determine two (hydrodensitometry: BD; hydrometry: TBW)-, three (BD and TBW)- and four- compartment (BD, TBW and BMM) FFM values. DXA also provided three compartment derived FFM values. RMR was measured using open circuit indirect calorimetry. RESULTS: Three (body fat group: lean, moderate, high) x five (body composition determination: hydrodensitometry, hydrometry, three-compartment, DXA, four-compartment) ANOVAs were conducted on FFM and RMR kJ.kg FFM(-1).d(-1). Within-group comparisons revealed that hydrodensitometry and DXA were associated with significant (P<0.001) overestimations and underestimations of FFM and RMR kJ.kg FFM(-1).d(-1), respectively, compared with four-compartment-derived criterion values. A significant interaction (P<0.001) resulted from DXA's greater deviations from criterion values in lean subjects. While hydrometric means were not significantly (P> or =0.68) different from criterion values intraindividual differences were large (FFM: -1.5 to 2.9 kg; RMR: -6.0 to 3.2 kJ.kg FFM(-1).d(-1)). CONCLUSION: The relationship between RMR kJ.kg FFM(-1).d(-1) and exercise status would best be investigated using three (BD, TBW)- or four (BD, TBW, BMM)-compartment body composition models to determine FFM. Other models either significantly underestimate indexed RMR (hydrodensitometry, DXA) or display large intraindividual differences (hydrometry) compared with four-compartment derived criterion values. SPONSORSHIP: Australian Research Council (small grants scheme).

Use of anthropometric variables to predict relative body fat determined by a four-compartment body composition model.

OBJECTIVE: To generate equations for the prediction of percent body fat (% BF) via a four-compartment criterion body composition model from anthropometric variables and age. DESIGN: Multiple regression analyses were used to predict % BF from the best-weighted combinations of independent variables. SUBJECTS: In all 79 healthy males (X+/-s.d.: 35.0+/-12.2 y; 84.24+/-12.53 kg; 179.8+/-6.8 cm) aged 19-59 y were recruited from advertisements placed in a university newsletter and on community centres' noticeboards. INTERVENTIONS: The following measurements were conducted: % BF using a four-compartment (water, bone mineral mass, fat and residual) model and a restricted anthropometric profile (nine skinfolds, five girths and two bone breadths). RESULTS: Stepwise multiple regression selected six (subscapular, biceps, abdominal, thigh, calf and mid-axilla) of the nine skinfold measurements to predict % BF and using the sum of these six produced a quadratic equation with a standard error of estimate (SEE) and R(2) of 2.5% BF and 0.89, respectively. The inclusion of age as a predictor further improved the equation (% BF=-0.00057 x ( summation operator 6SF)(2)+0.298 x summation operator 6SF+0.078 x age - 1.13; SEE=2.2% BF, R(2)=0.91). However, the best equation used only the sum of three skinfold thicknesses (mid-axilla, calf and thigh) and age but also included waist girth and biepicondylar femur breadth as predictors (% BF=-0.00258 x ( summation operator 3SF)(2)+0.558 x summation operator 3SF+0.118 x age+0.282 x waist girth - 2.100 x femur breadth - 2.34; SEE=1.8% BF, R(2)=0.94). Analyses of two age groups, <30 and >/=30 y, demonstrated that for the same % BF, the former exhibited a higher sum of skinfold thicknesses. CONCLUSIONS: Equations were generated for the prediction of % BF via the four-compartment criterion body composition model from anthropometric variables and age. Agewise differences for the sum of skinfold thicknesses may be related to an increase in internal fat for the older subjects.

Improved rig for dynamically calibrating skinfold calipers: comparison between Harpenden and Slim Guide instruments.

This article describes an improved rig for the dynamic calibration of skinfold calipers. The new unit is 5% lighter and almost 60% smaller than its predecessor (Carlyon et al., 1996, 1998) with a 9.5 mm solid aluminium base and a quick release caliper mount providing stability to both the rig and caliper. Automation of the gap controller with an electric motor standardizes the jaw opening and closing velocity, thereby enabling hands-free operation. Frictional losses in the moving components of the rig have been reduced by replacing the main bush of the swing arm with a bearing, reducing the mass of the swing arm, adding a support wheel to the end of the swing arm, and replacing fishing swivels with a universal joint to allow for changes in the opening screw angle as the caliper's arm moves through its arc. This rig can also be adapted to different types of calipers by changing the position of the load cell, microswitches, and the caliper mount. A universal mounting bracket that can be secured to almost any table supports the rig in a vertical plane when calibrating the load cell. To demonstrate the versatility of the calibration rig, preliminary data are presented for the upscale and downscale jaw pressures of seven Harpenden and seven Slim Guide calipers.

Measurement of total body water using 2H dilution: impact of different calculations for determining body fat.

This study estimated total body water (TBW) in four groups (twelve per group; sedentary and highly trained men and women) at the time of 2H dosing (T0) and after a 3.5 h equilibration period (Teq). Standard TBW calculations were employed at T0 (no correction for disproportionate urinary tracer loss) and Teq (correction for urinary tracer loss only), plus those calculations that corrected for a disproportionate urinary tracer loss and insensible tracer loss respectively. The measurement of body density enabled the four TBW estimates to be compared for the determination of three-compartment % body fat (BF). The very small difference between the standard and corrected T0 TBW data was not significant (P=0.914) and no GroupxTBW interaction was identified (P=0.125). These results reflect the closeness of the 2H concentration in the urine produced during the equilibration period and the Teq saliva samples. The associated mean % BF values were essentially identical. Although correcting for insensible 2H losses in addition to urinary losses at Teq produced a statistically significant (P<0.001) lower mean TBW (about 200 g) than the standard calculation, this translated to a small difference in % BF (0.3). The larger difference (about 500 g, P<0.001) between the two (T0, Teq) corrected TBW calculations was also associated with a small body composition difference (0.1 % BF), which was less than the propagated error (0.3 % BF) for the three-compartment body composition model. Corrections to the standard calculations of TBW at T0 and Teq for a protocol employing a brief equilibration period (3.5 h) were therefore of marginal use for improving the accuracy of % BF estimates. The TBW difference over time (T0 v. Teq) also had little impact on % BF values.

Predicting the resting metabolic rate of 30-60-year-old Australian males.

OBJECTIVES: This study: (a) generated regression equations for predicting the resting metabolic rate (RMR) of 30-60-y-old Australian males from age, height, mass and fat-free mass (FFM); and (b) cross-validated RMR prediction equations which are currently used in Australia against our measured and predicted values. DESIGN: A power analysis demonstrated that 41 subjects would enable the detection of (alpha=0.05, power=0.80) statistically and physiologically significant differences of 8% between predicted/measured RMRs in this study and those predicted from the equations of other investigators. SUBJECTS: Forty-one males ([X]+/-s.d.:, 44.8+/-8.6 y; 83.50+/-11.32 kg; 179.1+/-5.0 cm) were recruited for this study. INTERVENTIONS: The following variables were measured: skinfold thicknesses; RMR using open circuit indirect calorimetry; and FFM via a four-compartment (fat mass, total body water, bone mineral mass and residual) body composition model. RESULTS: A multiple regression equation using mass, height and age as predictors correlated 0.745 with RMR and the s.e.e. was 509 kJ/day. Inclusion of FFM as a predictor increased both the correlation and the precision of prediction, but there was no difference between FFM via the four-compartment model (r=0.816, s.e.e.=429 kJ/day) and that predicted from skinfold thicknesses (r=0.805, s.e.e.=441 kJ/day). CONCLUSIONS: Cross-validation analyses emphasised that equations need to be generated from a large database for the prediction of the RMR of 30-60-y-old Australian males.

Muscularity in adult humans: proportion of adipose tissue-free body mass as skeletal muscle.

Muscularity, or the proportion of adipose tissue-free body mass (ATFM) as skeletal muscle (SM), provides valuable body composition information, especially for age-related SM loss (i.e., sarcopenia). Limited data from elderly cadavers suggest a relatively constant SM/ATFM ratio, 0.540 +/- 0.046 for men (mean +/- SD, n = 6) and 0.489 +/- 0.049 for women (n = 7). The aim of the present study was to examine the magnitude and constancy of the SM/ATFM ratio in healthy adults. Whole-body SM and ATFM were measured using multi-scan magnetic resonance imaging. The SM/ATFM ratio was 0.528 +/- 0.036 for men (n = 139) and 0.473 +/- 0.037 for women (n = 165). Multiple regression analysis indicated that the SM/ATFM ratio was significantly influenced by sex, age, body weight, and race. The four factors explained 50% of the observed between individual variation in the SM/ATFM ratio. After adjusting for age, body weight, and race, men had a larger SM/ATFM ratio than women. Both older men and women had a lower SM/ATFM ratio than younger subjects, although the relative reduction was greater in men. After adjustment for sex, age, and body weight, there were no significant differences in the SM/ATFM ratios between Asian, Caucasian, and Hispanic subjects. In contrast, African-American subjects had a significantly greater SM/ATFM ratio than subjects in the other three groups. In addition, the SM/ATFM ratio was significantly lower in AIDS patients than corresponding values in healthy subjects.

Body composition changes in female bodybuilders during preparation for competition.

OBJECTIVE: To determine anthropometric and body composition changes in female bodybuilders during preparation for competition. DESIGN: There was an attempt to match subjects in the control and experimental groups for height and percentage body fat (%BF) for the initial test of this longitudinal study. SUBJECTS: Five competitive bodybuilders (-X +/- s.d.: 35.3 +/- 5.7 y; 167.3 +/- 3.7 cm; 66.38 +/- 6.30 kg; 18.3 +/- 3.5 %BF) and five athletic females (-X +/- s.d.: 30.9 +/- 13.0 y; 166.9 +/- 3.9 cm; 55.94 +/- 3.59 kg; 19.1 +/- 3.3 %BF) were recruited from advertisements in a bodybuilding newsletter and placed on sports centre noticeboards. INTERVENTIONS: The following measurements were conducted 12 weeks, 6 weeks and 3-5 d before the bodybuilders' competitions: anthropometric profile, body density by underwater weighing, total body water via deuterium dilution and bone mineral mass from a dual-energy X-ray absorptiometry scan. A combination of the last three measurements enabled the %BF to the determined by a four compartment model. RESULTS: A significant (P < or = 0.001) 5.80 kg body mass loss by the bodybuilders as they prepared for competition was primarily due to a reduction in fat mass (FM; -4.42 kg; 76.2%) as opposed to fat-free mass (FFM; -1.38 kg; 23.8%). The decreases in body mass and FM over the final 6 weeks were greater than those over the first 6 weeks. Their %BF decreased (P < 0.001) from 18.3 to 12.7, whereas the values for the control group remained essentially unchanged at 19.1-19.6 %BF. These body composition changes by the bodybuilders were accompanied by a significant decline (P < 0.001) of 25.5 mm (76.3-50.8 mm) in the sum of eight skinfold thicknesses (triceps + subscapular + biceps + iliac crest + supraspinale + abdominal + front thigh + medial calf). CONCLUSIONS: Although the bodybuilders presented with low %BFs at the start of the experiment, they still significantly decreased their body mass during the 12 week preparation for competition and most of this loss was due to a reduction in FM as opposed to FFM.

Predicting the resting metabolic rate of young Australian males.

OBJECTIVES: The aims of this study were: (a) to generate regression equations for predicting the resting metabolic rate (RMR) of 18 to 30-y-old Australian males from age, height, mass and fat-free mass (FFM); and (b) cross-validate RMR prediction equations, which are frequently used in Australia, against our measured and predicted values. DESIGN: A power analysis demonstrated that 38 subjects would enable us to detect (alpha = 0.05, power = 0.80) statistically and physiologically significant differences of 8% between our predicted/measured RMRs and those predicted from the equations of other investigators. SUBJECTS: Thirty-eight males (chi +/- s.d.: 24.3+/-3.3y; 85.04+/-13.82 kg; 180.6+/-8.3 cm) were recruited from advertisements placed in a university newsletter and on community centre noticeboards. INTERVENTIONS: The following measurements were conducted: skinfold thicknesses, RMR using open circuit indirect calorimetry and FFM via a four-compartment (fat mass, total body water, bone mineral mass and residual) body composition model. RESULTS: A multiple regression equation using the easily measured predictors of mass, height and age correlated 0.841 with RMR and the SEE was 521 kJ/day. Inclusion of FFM as a predictor increased both the R and the precision of prediction, but there was virtually no difference between FFM via the four-compartment model (R = 0.893, SEE = 433 kJ/day) and that predicted from skinfold thicknesses (R = 0.886, SEE = 440 kJ/day). The regression equations of Harris & Benedict (1919) and Schofield (1985) all overestimated the mean RMR of our subjects by 518 - 600 kJ/day (P < 0.001) and these errors were relatively constant across the range of measured RMR. The equations of Hayter & Henry (1994) and Piers et al (1997) only produced physiologically significant errors at the lower end of our range of measurement. CONCLUSIONS: Equations need to be generated from a large database for the prediction of the RMR of 18 to 30-y-old Australian males and FFM estimated from the regression of the sum of skinfold thicknesses on FFM via the four compartment body composition model needs to be further explored as an expedient RMR predictor.

Effect of creatine supplementation on metabolism and performance in humans during intermittent sprint cycling.

This double blind study investigated the effect of oral creatine supplementation (CrS) on 4 x 20 s of maximal sprinting on an air-braked cycle ergometer. Each sprint was separated by 20 s of recovery. A group of 16 triathletes [mean age 26.6 (SD 5.1) years. mean body mass 77.0 (SD 5.8) kg, mean body fat 12.9 (SD 4.6)%, maximal oxygen uptake 4.86 (SD 0.7) l.min-1] performed an initial 4 x 20 s trial after a muscle biopsy sample had been taken at rest. The subjects were then matched on their total intramuscular creatine content (TCr) before being randomly assigned to groups to take by mouth either a creatine supplement (CRE) or a placebo (CON) before a second 4 x 20 s trial. A muscle biopsy sample was also taken immediately before this second trial. The CrS of 100 g comprised 4 x 5 g for 5 days. The initial mean TCr were 112.5 (SD 8.7) and 112.5 (SD 10.7) mmol.kg-1 dry mass for CRE and CON, respectively. After creatine loading and placebo ingestion respectively, CRE [128.7 (SD 11.8) mmol.kg-1 dry mass] had a greater (P = 0.01) TCr than CON [112.0 (SD 10.0) mmol.kg-1 dry mass]. While the increase in free creatine for CRE was statistically significant (P = 0.034), this was not so for the changes in phosphocreatine content [trial 1: 75.7 (SD 6.9), trial 2: 84.7 (SD 11.0) mmol.kg-1 dry mass, P = 0.091]. There were no significant differences between CRE and CON for citrate synthase activity (P = 0.163). There was a tendency towards improved performance in terms of 1 s peak power (in watts P = 0.07; in watts per kilogram P = 0.05), 5 s peak power (in watts P = 0.08) and fatigue index (P = 0.08) after CrS for sprint 1 of the second trial. However, there was no improvement for mean power (in watts P = 0.15; in watts per kilogram P = 0.1) in sprint 1 or for any performance values in subsequent sprints. Our results suggest that, while CrS elevates the intramuscular stores of free creatine, this does not have an ergogenic effect on 4 x 20 s all-out cycle sprints with intervening 20-s rest periods.

Air-braked cycle ergometers: validity of the correction factor for barometric pressure.

Barometric pressure exerts by far the greatest influence of the three environmental factors (barometric pressure, temperature and humidity) on power outputs from air-braked ergometers. The barometric pressure correction factor for power outputs from air-braked ergometers is in widespread use but apparently has never been empirically validated. Our experiment validated this correction factor by calibrating two air-braked cycle ergometers in a hypobaric chamber using a dynamic calibration rig. The results showed that if the power output correction for changes in air resistance at barometric pressures corresponding to altitudes of 38, 600, 1,200 and 1,800 m above mean sea level were applied, then the coefficients of variation were 0.8-1.9% over the range of 160-1,597 W. The overall mean error was 3.0 % but this included up to 0.73 % for the propagated error that was associated with errors in the measurement of: a) temperature b) relative humidity c) barometric pressure d) force, distance and angular velocity by the dynamic calibration rig. The overall mean error therefore approximated the +/- 2.0% of true load that was specified by the Laboratory Standards Assistance Scheme of the Australian Sports Commission. The validity of the correction factor for barometric pressure on power output was therefore demonstrated over the altitude range of 38-1,800 m.

Physical activity and cardiovascular risk factors: effect of advice from an exercise specialist in Australian general practice.

OBJECTIVE: To determine whether provision of individualised physical activity advice by an exercise specialist in general practice is effective in modifying physical activity and cardiovascular risk factors in older adults. DESIGN: Randomised controlled trial of individualised physical activity advice, reinforced at three and six months (intervention) versus no advice (control). SETTING: Two general practices in Adelaide, South Australia, 1996. PARTICIPANTS: 299 adults aged 60 years or more who were healthy, sedentary and living in the community. MAIN OUTCOME MEASURES: Changes to physical activity (frequency and duration of walking and vigorous exercise), selected cardiovascular risk factors (blood pressure, body weight, serum lipid levels) and quality of life over 12 months. RESULTS: Self-reported physical activity increased over the 12 months in both groups (P < 0.001). The increase was greater for the intervention than the control group for all measures except time spent walking (P < 0.05). More intervention than control participants increased their intention to exercise (P < 0.001). Serum levels of total and low-density lipoprotein cholesterol and triglycerides fell significantly over the 12 months to a similar extent in the two groups. No other significant changes in cardiovascular risk factors were seen. Quality-of-life scores decreased over the 12 months. The decrease was significantly greater among intervention than control women, but not men, for emotional well-being (P = 0.02), physical well-being (P = 0.04) and social functioning (P = 0.04). DISCUSSION: Provision of general practice-based physical activity advice reinforced three-monthly produced a sustained increase in self-reported physical activity. However, there were no associated changes in clinical measures of cardiovascular risk factors and minimal changes in quality-of-life measures.

Comparison of two hydrodensitometric methods for estimating percent body fat.

This study compared the two following hydrodensitometric methods for estimating percent body fat (%BF): 1) estimation of residual volume (RV) by helium dilution before and after measurement of immersed mass at RV, and 2) determination of immersed mass at a comfortable level of expiration (approximately functional residual capacity) with measurement of the associated gas volume by oxygen dilution. Twelve men [27.9 +/- 7.5 (SD) yr; 79.32 +/- 12.79 kg; 180.5 +/- 9.9 cm] were tested for %BF via both methods on each of two separate visits within 3 days by using a counterbalanced design. The two helium dilution measurements yielded a technical error of measurement of 0.2% BF and an intraclass correlation coefficient of 0.999. Corresponding values for the oxygen dilution method were 0.4% BF and 0.999, respectively. There was no difference (P = 0.80) between the helium dilution (16.9 +/- 9.3% BF) and oxygen dilution (16.9 +/- 9.4% BF) methods, and the individual differences ranged from -0.7 to 0.6% BF. The interclass correlation coefficient between the two methods was 0.999 with a SE of estimate of 0.4% BF. Whereas both methods were precise and reliable and yielded similar results, the oxygen dilution technique was more expedient and was preferred by the subjects because they were not required to exhale to RV.

Effect of pedal cadence on the accumulated oxygen deficit, maximal aerobic power and blood lactate transition thresholds of high-performance junior endurance cyclists.

In this study we investigated the effect of pedal cadence on the cycling economy, accumulated oxygen deficit (AOD), maximal oxygen consumption (VO2max) and blood lactate transition thresholds of ten high-performance junior endurance cyclists [mean (SD): 17.4 (0.4) years; 183.8 (3.5) cm, 71.56 (3.75) kg]. Cycling economy was measured on three ergometers with the specific cadence requirements of: 90-100 rpm for the road dual chain ring (RDCR90-100 rpm) ergometer, 120-130 rpm for the track dual chain ring (TDCR120-130 rpm) ergometer, and 90-130 rpm for the track single chain ring (TSCR90-130 rpm) ergometer. AODs were then estimated using the regression of oxygen consumption (VO2) on power output for each of these ergometers, in conjunction with the data from a 2-min supramaximal paced effort on the TSCR90-130 rpm ergometer. A regression of VO2 on power output for each ergometer resulted in significant differences (P<0.001) between the slopes and intercepts that produced a lower AOD for the RDCR90-100 rpm [2.79 (0.43) l] compared with those for the TDCR120-130 rpm [4.11 (0.78) l] and TSCR90-130 rpm [4.06 (0.84) l]. While there were no statistically significant VO2max differences (P = 0.153) between the three treatments [RDCR90-100 rpm: 5.31 (0.24) l x min(-1); TDCR120-130 rpm; 5.33 (0.25) 1 x min(-1); TSCR90-130 rpm: 5.44 (0.27) l x min(-1)], all pairwise comparisons of the power output at which VO2max occurred were significantly different (P<0.001). Statistically significant differences were identified between the RDCR90-100 rpm and TDCR120-130 rpm tests for power output (P = 0.003) and blood lactate (P = 0.003) at the lactate threshold (Thla-), and for power output (P = 0.005) at the individual anaerobic threshold (Thiat). Our findings emphasise that pedal cadence specificity is essential when assessing the cycling economy, AOD and blood lactate transition thresholds of high-performance junior endurance cyclists.

Exercise training and blood lipids in hyperlipidemic and normolipidemic adults: a meta-analysis of randomized, controlled trials.

OBJECTIVE: To determine the effectiveness of exercise training (aerobic and resistance) in modifying blood lipids, and to determine the most effective training programme with regard to duration, intensity and frequency for optimizing the blood lipid profile. DESIGN: Trials were identified by a systematic search of Medline, Embase, Science Citation Index (SCI), published reviews and the references of relevant trials. The inclusion criteria were limited to randomized, controlled trials of aerobic and resistance exercise training which were conducted over a minimum of four weeks and involved measurement of one or more of the following: total cholesterol (TC), high density lipoprotein (HIDL-C), low density lipoprotein (LDL-C) and triglycerides (TG). SUBJECTS: A total of 31 trials ( 1833 hyperlipidemic and normolipidemic participants) were included. RESULTS: Aerobic exercise training resulted in small but statistically significant decreases of 0.10 mmol/L (95% CI: 0.02, 0.18). 0.10 (95% CI: 0.02, 0.19), 0.08 mmol/L (95% CI: 0.02, 0.14), for TC, LDL-C, and TG, respectively, with an increase in HDL-C of 0.05 mmol/L (95% CI: 0.02, 0.08). Comparisons between the intensities of the aerobic exercise programmes produced inconsistent results; but more frequent exercise did not appear to result in greater improvements to the lipid profile than exercise three times per week. The evidence for the effect of resistance exercise training was inconclusive. CONCLUSIONS: Caution is required when drawing firm conclusions from this study given the significant heterogeneity with comparisons. However, the results appear to indicate that aerobic exercise training produced small but favourable modifications to blood lipids in previously sedentary adults.

Resting metabolic rate, body composition and aerobic fitness comparisons between active and sedentary 54-71 year old males.

OBJECTIVE: To test the hypothesis that 55-70 y old male longterm exercisers (LE) have higher resting metabolic rates (RMR) than longterm nonexercisers (LNE). DESIGN: A power analysis demonstrated that this cross-sectional study required 12 subjects per group to detect a 10% RMR difference (kJ x kg FFM(-1) x d(-1)) between the LE and LNE (power = 0.8;alpha = 0.05). SUBJECTS: Twelve LE (X +/- s.d.; 63.5+/-3.4 y; 1.75+/-0.06 m; 69.01+/-8.24 kg; 20.4+/-4.9 %BF) and 12 LNE (63.6+/-5.6 y; 1.72+/-0.07 m; 79.44 12.4 kg; 29.6 4.4 %BF) were recruited from advertisements placed in a newspaper and on university and community noticeboards. INTERVENTIONS: Measurements were conducted for: RMR using the Douglas bag technique; body composition via a four compartment model which is based on determination of body density, total body water and bone mineral mass; and aerobic fitness using a submaximal work test on a cycle ergometer. RESULTS: The LE (93.00+/-7.16 kJ x kg(-1) x d(-1)) registered a significantly greater (P = 0.04) RMR than the LNE (84.70+/-11.23 kJ x kg(-1) x d(-1)) when energy expenditure was expressed relative to body mass, but this difference disappeared (P = 0.55) when the data were corrected for the non-zero intercept of the graph of RMR (MJ/d) against body mass. ANCOVA with FFM as the covariate also indicated that the RMR (MJ/d) difference between the groups was not statistically significant (P = 0.28). The adjusted means for the LE and LNE were 6.39 and 6.62 MJ/d, respectively. CONCLUSIONS: There are no RMR (MJ/d) differences between LE and LNE 54-71 y old males when statistical control is exerted for the effect of FFM and the higher value of the former group for RMR normalised to body mass disappears when this ratio is corrected for statistical bias.

Recruitment of older adults for a randomized, controlled trial of exercise advice in a general practice setting.

OBJECTIVES: The success of any clinical trial depends strongly on recruiting enough participants in a reasonable time period. This paper aims to identify the obstacles, as well as the successful aspects, of recruiting of older participants into an exercise study. DESIGN: This describes the recruitment of 299 older adults into a randomized, controlled trial of exercise advice in a general practice setting. Letters of invitation were sent from two general practices inviting the patients to attend a 15-minute screening appointment. Patients considered eligible for enrollment were then scheduled for a baseline appointment and randomized into the trial. SETTING: Two general practices in Adelaide, South Australia. PARTICIPANTS: Healthy, sedentary, community-dwelling patients aged 60 years or older. RESULTS: A total of 2878 letters of invitation were sent, and 913 patients attended a screening appointment. Of these, 351 (38.4%) were initially eligible, with one-third excluded because they were already too physically active. Two hundred ninety-nine participants, approximately 1 of every 10 patients sent letters, were enrolled in the project at the end of a 15-week period. DISCUSSION: A general practice approach was effective in recruiting 299 older adults to an exercise project within an acceptable time frame. Factors promoting the success of recruitment through general practice included choosing large, well established practices, computerized age-sex registers, and placing minimal demands on the general practitioners and practice staff. A continuing problem with recruiting participants for a project involving exercise is that the volunteer population tends to be healthy and interested in physical activity.

Effect of 3 weeks of detraining on the resting metabolic rate and body composition of trained males.

OBJECTIVE: To examine the hypothesis that detraining decreases the resting metabolic rate (RMR) of long-term exercisers. DESIGN: Eight pairs of subjects were matched for age, mass and training volume. They were then randomly allocated to either a control group (continue normal training) or detraining group (stop normal training but continue activities of daily living). SETTING: Exercise Physiology Laboratory, The Flinders University of South Australia. SUBJECTS: Sixteen male subjects (age 23.1 +/- 4.7 y (s.d.); mass 73.73 +/- 8.9 kg; VO2max 60.2 +/- 6.3 ml. kg-1.min-1; height 180.3 +/- 5.0 cm; body fat 14.6 +/- 5.4%) were selected from a pool of respondents to our advertisements. INTERVENTIONS: Each pair of subjects was measured before and after a 3-week experimental period. RESULTS: Two (groups) x 3 (2-, 3-and 4-compartment body composition models) ANOVAs were conducted on the difference between the pre- and post-treatment scores for percentage body fat, fat-free mass (FFM) and relative RMR (kJ.kg FFM-1.h-1). No significant between-group differences were identified except for the detraining group's small decrease in FFM (0.7 kg, P = 0.05). The main effects for body composition model were all significant; but the overall differences between the multicompartment models and the 2-compartment one were less than their technical errors of measurement. No significant interaction (P = 0.51) resulted from a 2 x 2 ANOVA on the pre- and post-treatment absolute RMR data for the control (315.2 and 311.9 kJ/h) and detraining groups (325.4 and 325.5 kJ/h). CONCLUSIONS: 3-weeks detraining is not associated with a decrease in RMR (kJ/h, kJ.kg FFM-1.h-1) in trained males; hence, our data do not support a potentiation of the RMR via exercise training. The greater sensitivity of the multicompartment models to detect changes in body composition was of marginal value.

Critical appraisal of the estimation of body composition via two-, three-, and four-compartment models.

This review explores the robustness of the assumptions underpinning the two- (fat mass [FM], fat-free mass [FFM]), three- (FM; total body water [TBW], fat free dry solid), and four- (FM; TBW; bone mineral [BM], residual) compartment models of body composition. The measurement of body density (BD) via underwater weighing (UWW) and TBW via isotopic dilution are the two most frequently used two-compartment techniques. The former assumes that the FM and FFM have densities of 0.9007 g/cm(3) and 1.1000 g/cm(3), respectively, while the latter uses a FFM hydration constant. Although both techniques can estimate body composition precisely (technical error of measurement [TEM]: UWW = 0.4 %BF; TBW = 0.6 %BF), the validity of these estimates is adversely affected by biological variability in the assumed percentages for the FFM components (TBW = 73.72%; protein = 19.41%; BM = 5.63%; non-BM = 1.24%). The three-compartment model, which incorporates measures of BD and TBW, greatly increases validity by removing errors relating to variability in TBW, which comprises the largest percentage of the FFM and is furthermore acutely variable. The four-compartment model marginally improves on the three-compartment model by additionally controlling for BM, which displays less variability than the TBW component of the FFM. The three- and four-compartment models therefore provide more valid estimates of body composition than the two-compartment model, and this increased accuracy is not offset by propagation of errors (TEM = 0.7 %BF for both models) from the combinations of multiple measurements (BD, TBW, BM). Am. J. Hum. Biol. 11:175-185, 1999. Copyright 1999 Wiley-Liss, Inc.

Dynamic calibration of mechanically, air- and electromagnetically braked cycle ergometers.

In this study we measured the accuracy of the following types of cycle ergometer against the criterion of a dynamic calibration rig (DCR): 35 friction-braked (Monark), 5 research-grade air-braked (Repco) and 5 electromagnetically braked (2 Siemens, 1 Elema-Schonander, 1 Ergoline, 1 Warren E. Collins). Monark ergometer power outputs over the range 58.9-353.2 W significantly (P < 0.001) underestimated those registered by the DCR with mean accuracies of 91.7-97.8%. The least accurate individual reading for each of the six up-scale (0-353.2 W) power outputs ranged from 81.6 to 91.6%; corresponding down-scale (353.2-0 W) accuracies were 85.1-92.5%. A hysteresis effect was furthermore evident for this ergometer in that up-scale measurements were significantly (P < 0.05) greater than down-scale ones. In addition, when the oldest [mean (SD): 11.3 (2.3) years old] and newest [1.4 (0.8) years old] eight ergometers were compared, the latter were significantly (P < 0.05) more accurate over the range 117.7-294.3 W. Apart from the two lowest power outputs of 47 W (62.2-96.0% accuracy) and 127 W (88.0-97.7% accuracy), the individual up-scale and down-scale accuracies of the Repco ergometers ranged from 98.0 to 104.2% for power outputs of 272.7-1137.8 W and the means were not significantly different from those of the DCR. There was also no evidence of hysteresis. Except for the initial power output of 50 W (40 rev/min: 83.8-99.2% accuracy; 60 rev/min: 93.2-122.6% accuracy), the individual accuracies of the electromagnetically braked ergometers ranged from 89.3 to 101.4% over the up-scale range of 100-400 W, and none of the means were significantly different from those of the DCR. The variability of individual errors for the preceding data emphasises that all cycle ergometers should be validated against the criterion of a DCR if accurate power outputs are required.