The reproducibility and validity of a past year physical activity questionnaire was determined in a sample of 100 adolescents aged 15-18 years, randomly selected from a population-based cohort. Subjects completed four 7-day recalls of activity approximately 3 months apart. The average of the four 7-day recalls of activity was utilized as the "gold standard" against which the past year questionnaire was compared to evaluate validity. The questionnaire was also validated against objective measures, such as physical fitness and body mass index. Interscholastic team rosters were utilized to directly validate the reporting of specific activities. One-month and one-year test-retest reproducibility of the questionnaire were determined. For different measures of activity, the Spearman correlations between the questionnaire and the average of the 7-day recalls ranged from 0.55 to 0.67 in males and 0.73 to 0.83 in females, all significant at p < 0.01. In general, although there was no association between the past year activity questionnaire results and objective measures, there was a significant, albeit weak association between the physical activity questionnaire and time to complete a 1-mile (1.61-km) run (r = -0.47) in females. Subjects reported participating in specific interscholastic sports with an accuracy of 100%, 86%, and 95% for the fall, winter, and spring sports, respectively. Test-retest reproducibility was higher over one month (r = 0.79) than over one year (r = 0.66). These data provide evidence that the questionnaire yields a reasonable estimate of past year or "habitual" physical activity in adolescents.

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This study was conducted to compare gross efficiency (GE), net efficiency (NE), work efficiency (WE), and delta efficiency (DE) between arm crank and cycle exercise at the same relative intensities. Eight college-aged males underwent two experimental trials presented in a randomized counterbalanced order. During each trial subjects performed three intermittent 7-min exercise bouts separated by 10-min rest intervals on an arm or semirecumbent leg ergometer. The power outputs for the three bouts of arm crank or cycle exercise corresponded to 50, 60, and 70% of the mode-specific VO2peak. GE, NE, and WE were determined as the ratio of Kcal.min-1 equivalent of power output to Kcal.min-1 of total energy expended, energy expended above rest and energy expended above unloaded exercise, respectively. DE was determined as the ratio of the increment of Kcal.min-1 of power output above the previous lower intensity to the increment of kcal.min-1 of total energy expended above the previous lower intensity. GE and NE did not differ between arm crank and cycle exercises. However, WE was lower (P < 0.05) during arm crank than cycle exercise at 50, 60, and 70% VO2peak. DE was also lower (P < 0.05) during arm crank than cycle exercise at delta 50-60 and at delta 60-70% VO2peak. It is concluded metabolic efficiency as determined by work and delta efficiency indices was lower during arm crank compared with cycle exercise at the same relative intensities. These findings add to the understanding of the difference in metabolic efficiency between upper and lower body exercise.