The Bruce treadmill protocol: does walking or running during the fourth stage alter oxygen consumption values?

OBJECTIVE: To investigate heart rate (HR) and relative oxygen consumption (VO2) measures during two modes (walking or running stages four) of the Bruce treadmill protocol. PARTICIPANTS: Male volunteers (n = 27), ranging in age from 25 to 56 years (M = 39.1 +/- 10.7 yrs). EXPERIMENTAL DESIGN: S's performed to volitional fatigue on the two randomly assigned treadmill tests. MEASURES: HR and VO2 were taken each minute and at point of exhaustion. RESULTS: Dependent "t"-tests revealed a significantly (p < or = 0.05) difference between the protocols at 11 minutes (running = 46.7 +/- 3.9 > walking = 44.6 +/- 3.7 ml[kg.min-1]) and at 12 minutes (running = 49.3 +/- 4.1 > walking = 47.6 +/- 3.5 ml[kg.min-1]) on the VO2 values. A significant differences was noted on HR at 11 minutes (running = 158.1 +/- 13.5 > walking = 156.0 +/- 13.0 bpm) and at 12 minutes (running = 160.4 +/- 11.0 > walking = 157.8 +/- 11.4 bpm) between the protocols. The two-way ANOVA technique revealed no significant differences or interactions on VO2 or HR between younger (< 45 yrs) and older (> or = 45 yrs) subjects during either protocol. A one-way ANCOVA indicated no significant differences between taller and shorter subjects on VO2 during the fourth stage of the Bruce protocol. The correlations, between the two protocols, for HR were strong but were weaker and inconsistent for VO2. The repeated measures ANOVA indicated significant within subject variability between test administrations. CONCLUSIONS: When testing endurance trained males, modality, age and height are not factors in differences of VO2 values during the 4th stage of the Bruce treadmill test but learning effect could be.

PRESS-related statistics: regression tools for cross-validation and case diagnostics.

In the health science literature, a common approach of validating a regression equation is data-splitting, where a portion of the data fits the model (fitting sample) and the remainder (validation sample) estimates future performance. The R2 and SEE obtained by predicting the validation sample with the fitting sample equation is a proper estimate of future performance, tending to correct for the natural upward bias of the R2 and SEE obtained from fitting sample alone. Data-splitting has several disadvantages, however. These include: 1) difficulty, arbitrariness, and inconvenience of matching samples; 2) the need to report two sets of statistics to determine homogeneity; and 3) the lack of equation stability due to diluted sample size. The PRESS statistic and associated residuals do not require the data to be split, yield alternative unbiased estimates of R2 and SEE, and provide useful case diagnostics. This procedure is easy to use, is widely available in modern statistical packages, but is rarely utilized. The two methods are contrasted here using a simulation from original data for predicting body density from anthropometric measurements of a group of 117 women. The PRESS approach is particularly appropriate for smaller datasets; methods of reporting these statistics are recommended.

The relative contribution of strength and physique to running and jumping performance of boys 7-11.

The purpose of this study was to determine the association of static strength with motor performance of 7 through 11 year old boys (N = 60) after accounting for differences in physique, i.e., body size, shape, and composition. Static strength measures included thigh extension, leg extension and plantar flexion measured by electronic transducer and back lift, leg lift, and right and left grips measured by spring dynamometer. Measures of body composition consisted of fat estimated from triceps, subscapsular and calf skinfolds, and fat-free body weight estimated from potassium-40 measurements. Body structure consisted of skeletal widths, and segment girths, lengths and volumes. The dependent variables were vertical jump, standing broad jump, 50-yard dash, 600-yard run and mile run. The measures of strength increased the variance accounted for from 10 to 23% over that when body size, composition and structure were used without strength. An exception was vertical jump where no increase in the variance accounted for was found with the addition of strength variables. The regression equations determined for the sample of 60 boys rendered multiple R's ranging from 0.64 (mile run) to 0.75 (50-yard dash). It was concluded that strength has a significant relation to motor performance and that its contribution can be better assessed after accounting for differences in body size, shape, and composition.

Body composition alterations consequent to an exercise program for pre and postmenopausal women.

The purposes of this study were: (a) to evaluate the effects of an exercise program upon the body composition of premenopausal (no. 43) and postmenopausal (no. 66) women, aged 35-70 years, and (b) to compare exercise Ss with age matched control Ss. Body composition was assessed by skinfold measurement and hydrostatic weighing. Exercise Ss walked or jogged and performed light resistive exercise for 60 minutes per day three times per week for 24 weeks. Control Ss remained sedentary. ANOVAs revealed: (a) no significant (p greater than or equal to .05) differences in exercise training effects between premenopausal and postmenopausal Ss, and (b) exercise Ss exhibited less body fatness while control Ss possessed more body fat as represented by significant changes (p less than or equal to .05) for the exercise and control Ss, respectively in: body density (+.002 g/cc, -.001 g/cc); % fat (-1.2%, +.6%); fat weight (-.4 kg, +1.1 kg); suprailiac skinfold (-.3 mm, +7 mm); and abdominal skinfold (-.3 mm, +1.5 mm). It was concluded that: (a) menopausal status did not alter the effects of exercise in this study, and (b) exercise training produced a positive effect in the exercise Ss by reversing body composition trends associated with a sedentary lifestyle.

The effect of high level physical activity (8.5 METs or greater) and estrogen replacement therapy upon bone mass in postmenopausal females, aged 50-68 years.

The purpose of this study was to assess the effect of physical activity (PA) and estrogen therapy (ET) upon bone mass at the 1/3 and 4 mm distal radial sites in 50 postmenopausal females. The Ss (means age = 57.4 +/- 5.4 yrs) completed: 1) activity and gynecological surveys, 2) Balke treadmill tests (85% of age determined HR), and 3) single photon absorptiometry measurements of the radius. The activity surveys and treadmill tests were used to categorize Ss into high (8.5 METs or greater, n = 27) and low (6.0 METs or less, n = 23) physical activity groups (HPA/LPA), and the gynecological surveys were used to distinguish Ss who were on estrogen therapy (n = 17) and those who had never been on estrogen therapy (n = 33). Data revealed the HPA group had significantly higher BMC (g/cm) and BMC/BW (g/cm2) at the 1/3 distal radial site than the LPA group (.834 g/cm to .721 g/cm, p less than .01; and .698 g/cm2 to .653 g/cm2, p less than .06, respectively) but were not significantly different at the 4 mm distal site. The ET group had a significantly higher bone mass than the never on ET group for BMC/BW at the 4 mm site (.907 g/cm to .809 g/cm p less than .027). It was concluded that high level physical activity (8.5 METs or greater) or estrogen therapy was helpful in reducing the risk of bone loss in postmenopausal women.