Changes in muscular efficiency as it relates to age were examined during inclined submaximal treadmill walking in 298 boys ages 7–15 years. Furthermore, the changes in efficiency with increased work intensity (67–90% V̇O2max) were studied. Efficiency was expressed as submaximal oxygen consumption (V̇O2) and was calculated mathematically as energy out/energy in = (vertical distance) (wt of subject)/(V̇O2 L • min−1) (kcal equivalent). Efficiency, calculated mathematically, was found to significantly increase (p<.01) with age, with the younger children (<9 yrs) being less efficient than the older children (13–15 yrs). These values ranged from 12.8% for the youngest boys (<9 yrs) to 16.4% for the oldest boys (13–15 yrs). In addition, efficiency significantly increased in a linear fashion (p<.01) during submaximal workloads within each age group. No significant interactions (p>.05) between age and workload were found. These values are lower than gross efficiency values during cycling previously reported in the literature for adults; however, they support earlier findings that children increase in efficiency with age and work intensity, regardless if expressed as efficiency or V̇O2 (ml • kg−1 •min−1). These findings suggest that parameters associated with growth and development may influence muscular efficiency with age.
Jill A. Kanaley, Richard A. Boileau, Benjamin H. Massey and James E. Misner
Mary H. Slaughter, Constance B. Christ, Rachel J. Stillman and Richard A. Boileau
This study was designed to determine whether there were differences in the relationships between fat-free body (FFB) to height and the subcomponents of the FFB—bone mineral content, bone width, bone mineral index, and total body water (TBW)—to height relationships among male and female age-group swimmers and nonswimmers. The 178 subjects (ages 8-16 yrs) were grouped by gender and activity level. Least-squares regression analysis was used to test the above relationships. Although there were no statistically significant differences in the FFB to height or the subcomponents of the FFB to height relationships between swimmers and nonswimmers in the male sample, the swimmer lines depicting the relationships typically fell above those of their nonswimmer counterparts. In the female sample, the FFB and TBW to height2.4 relationships differed significantly between the two groups, with the swimmers having greater values per unit of height than the non-swimmers.
Mary H. Slaughter, Constance B. Christ, Rachel J. Stillman, Timothy G. Lohman and Richard A. Boileau
This study was designed to determine the association of selected circumferences with height among black and white, male and female, prepubescent and postpubescent children. Volunteers (N = 232) were grouped according to gender, race, and maturation level. Regression of the logs of the circumferences on the log of height revealed regression coefficients ranging from .74 to 1.3, except for the upper arm circumference (1.7), thus confirming the theoretical expectation of a linear relationship between circumference and height. Within-gender relationships of each circumference with height were determined using regression analysis. In general the prepubescent circumferences deviated below the within-gender line while the postpubescent circumferences typically deviated above it; however, there were exceptions in both sexes. Moreover, the racial differences in the circumference deviation scores were not consistent within either the male or female samples. The consideration of gender, race, and maturation is important in determining the association of circumference with height. The use of circumferences adjusted for height can be useful in studying muscle development in children.
Stephen F. Figoni, Richard A. Boileau, Benjamin H. Massey and Joseph R. Larsen
The purpose of this study was to compare quadriplegic and able-bodied men on selected cardiovascular and metabolic responses to arm-crank ergometry at the same rate of oxygen consumption (V̇O2). Subjects included 11 untrained, spinal cord-injured, C5–C7 complete quadriplegic men and 11 untrained, able-bodied men of similar age (27 years), height (177 cm), and mass (65 kg). Measurement techniques included open-circuit spirometry, impedance cardiography, and electrocardiography. Compared with the able-bodied group, at the V̇O2 of 0.5 L/min, the quadriplegics displayed a significantly higher mean heart rate and arteriovenous O2 difference, lower stroke volume and cardiac output, and similar myocardial contractility. These results suggest that quadriplegic men achieve an exercise-induced V̇O2 of 0.5 L/min through different central cardiovascular adjustments than do able-bodied men. Quadriplegics deliver less O2 from the heart toward the tissues but extract more O2 from the blood. Tachycardia may contribute to low cardiac preload and low stroke volume, while paradoxically tending to compensate for low stroke volume by minimizing reduction of cardiac output.
Constance B. Christ, Mary H. Slaughter, Rachel J. Stillman, Timothy G. Lohman and Richard A. Boileau
Variability associated with the effects of gender, race, maturation (ML), and age on the potassium content of the fat-free body (K/FFB) was investigated in 163 males and 112 females ages 8 to 30 years. Measures of body density (hydrostatic weighing), bone mineral content (single photon absorptiometry), total body water (modified deuterium dilution), and whole body potassium (40K spectroscopy) were obtained. FFB was calculated using a multicomponent equation which accounted for the variability in FFB mineral and water content. Subjects were classified by maturation as prepubescent, pubescent, postpubescent, and adult (Tanner stages). Least-squares multiple regression analysis revealed significant (p<.05) effects of gender and maturation as well as an interaction between whites and blacks with maturation. The significant increase in K/FFB across maturation and age was most evident in the male sample for both racial groups, with K/FFB increasing from 2.37 in prepubescents to 2.54 in adults. The magnitude of increase in K/FFB across maturation was smaller and not statistically significant within the female sample. Hence, consideration of gender, maturation, and age is important in estimating FFB from total body potassium.
Richard A. Boileau, Edward McAuley, Demetra Demetriou, Naveen K. Devabhaktuni, Gregory L. Dykstra, Jeffery Katula, Jane Nelson, Angelo Pascale, Melissa Pena and Heidi-Mai Talbot
A trial was conducted to examine the effect of moderate aerobic exercise training (AET) on cardiorespiratory (CR) fitness. Previously sedentary participants, age 60-75 years, were randomly assigned to either AET treatment or a control group for 6 months. The AET consisted of walking for 40 min three times/week at an intensity that elevated heart rate to 65% of maximum heart rate reserve. The control group performed a supervised stretching program for 40 min three times/week. CR fitness was assessed before and after the treatments during a grade-incremented treadmill walking test. Both absolute and relative peak V̇O2 significantly increased (p < .01) in the AET group, whereas they decreased modestly in the control group. Maximum treadmill time increased significantly (p < .01) in the AET group relative to the control group. These results indicate that CR fitness as measured by peak V̇O2 modestly improves in the elderly with a moderate-intensity, relatively long-term aerobic exercise program.