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Biomedical subjects

John A Daniel

Publications and source records attributed to John A Daniel.

2 recordsLinked to original sources
PubMed2004

The effects of graded forward and backward walking on heart rate and oxygen consumption.

STUDY DESIGN: Single-group repeated-measures design. OBJECTIVES: To compare the effects of forward walking (FW) and backward walking (BW) on heart rate (HR) and oxygen consumption (VO2) at treadmill grades of 5%, 7.5%, and 10%. BACKGROUND: Previous studies of locomotion by humans on a treadmill have reported larger cardiovascular exertion and potential biomechanical benefits of BW as compared to FW for treadmill grades ranging from 0% to 5%. The present study extends these findings by examining the cardiovascular effects of BW and FW at treadmill grades greater than 5%. METHODS AND MEASURES: Twenty-nine volunteers participated in this study. Two subjects were excluded, leaving 27 study subjects (15 females, 12 males; mean age +/- SD, 24.0 +/- 3.4 years). VO2 and HR were measured using open-circuit calorimetry and electrocardiogram, respectively. For both forward and backward walking, subjects performed each of the 3 grades for 6 minutes, during which HR and VO2 were measured. Two-way repeated-measures ANOVAs were employed for inferential statistical analysis. RESULTS: Percent maximum heart rate (HR(max)) and percent maximum oxygen consumption (VO2(max)) increased incrementally for treadmill grades of 5% to 7.5% to 10% for both FW and BW (P < .00001). For each of the 3 treadmill grades, percent HR(max) and percent VO2(max) was 17% to 20% higher for BW than for FW (P < .00001). No statistically significant interactions were detected between direction of walking and treadmill grade. CONCLUSIONS: Backward walking on a treadmill at 67.0 m/min (2.5 mph) and grades of 5%, 7.5%, and 10% elicits a greater percent HR(max) and percent VO2(max) than does forward walking under the same conditions and, if incorporated into sustained training regimens, would be expected to improve aerobic endurance.

Adult↗
PubMedDate not supplied

Evaluation of body composition methods for accuracy.

The objective of this study was to evaluate the accuracy of a variety of portable methods and instruments used to estimate body composition or percentage body fat (%BF) in a systematic, comprehensive manner on a wide range of subjects. The %BF was estimated using four skinfold protocols, three girth measurement protocols, two bioelectric impedance analysis (BIA) instruments, and one near-infrared instrument on 121 subjects. The subjects ranged in age from 21 to 51 years; weight ranged from 105 to 226 pounds and %BF from 8.3% to 38.3%; and the group was 29% male. The %BF estimates were compared to the values obtained from the generally accepted reference standard, underwater weighing (UWW). The correlation coefficients (r) between the test methods and UWW ranged from 0.48 to 0.72. Regression analysis resulted in a range of slopes from 0.48 to 0.93, y-intercept range from 3.8 to 13.1, and standard error of the estimate range from 3.8 to 7.5. All of the methods tended to overestimate lower and underestimate higher %BF. With two exceptions, all methods appeared more accurate for males than females. In general, the near-infrared appeared least and BLA appeared most accurate. In conclusion, in our opinion, most of the methods were not sufficiently accurate to use on a wide range of individuals. Although they may be sufficiently accurate on the narrow sample of subjects on which they were developed, they may not be as accurate for the general population.

Adult↗