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Catrine Tudor-Locke, William D. Johnson and Peter T. Katzmarzyk

Background:

The purpose of this study was to examine the relationship between 2005−2006 National Health and Nutrition Examination Survey (NHANES) accelerometer-determined steps/day and activity counts/day, and between steps/day and estimates of nonwear time (as an indicator of the unmonitored day) and time spent in sedentary behaviors as well as a range of physical activity intensities.

Methods:

Linear regression models were used to characterize the relationship between steps/day, activity counts/day, estimates of wear time, and intensity categories.

Results:

1781 males (mean age = 46.5 years) and 1963 females (mean age = 47.7 years) wore accelerometers 14.0 ± SEM0.06 hours/day. The relationship between steps/day and activity counts/day was positive and strong (R 2 = .87). The relationship between steps/day and time spent in sedentary behaviors was inverse and moderate (R 2 = .25). Stronger and positive relationships were apparent between steps/day and time in light (R 2 = .69) and moderate (R 2 = .63) intensity activities. There was no discernable relationship between steps/day and time spent in low or vigorous intensity activities or with wear time.

Conclusions:

Assessed by accelerometer, steps/day explains 87% of the variation in activity counts/day, 25% of the variation in time in sedentary behaviors, 69% of time in light intensity, and 63% of time in moderate intensity.

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Catrine Tudor-Locke, William D. Johnson and Peter T. Katzmarzyk

Background:

We examined the effects of wear time on a population profile of time-stamped accelerometer outputs using the 2005−2006 National Health and Nutrition Examination Survey (NHANES) data representing 3744 adults ≥ 20 years of age.

Methods:

Outputs included activity counts, steps, and time variables: nonwear (macro-determined), sedentary behavior (<100 activity counts/minute), and time in low (100−499 activity counts/minute), light (500−2019 activity counts/minute), and moderate-to-vigorous physical activity (MVPA; ≥2020 activity counts/minute) intensities. We describe mean values according to a 24-hour clock. Analysis was repeated in a reduced data set with only those who wore the accelerometer for 60 minutes within each considered hour of the day.

Results:

Between 12:00 and 17:00, U.S. adults spend approximately 31 minutes each hour in sedentary behaviors, and approximately 14 minutes, 10 minutes, and 2 minutes in low, light, and MVPA intensity activity, respectively. Removing the effect of nonwear time, sedentary behaviors are reduced in the morning hours and increase in the evening hours.

Conclusion:

At either end of the day, nonwear time appears to distort population estimates of all accelerometer time and physical activity volume indicators, but its effects are particularly clear on population estimates of time spent in sedentary behavior.

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William G. Thorland, Glen O. Johnson, Craig J. Cisar, Terry J. Housh and Gerald D. Tharp

This study assessed strength and muscular power of elite young male runners in order to determine the relationship of these characteristics to age and specialization in either sprint or middle distance events. Forty-eight national junior-level sprint and middle distance runners were evaluated for isokinetic peak torque for leg extension as well as muscular power and fatiguability. Peak torque values were greater for the older runners and for the sprinters when measured at higher velocities. However, when adjusted for body weight, the peak torque values of the sprinters became significantly greater at all testing velocities. Muscular power values were also greater for the older runners, but event-related differences only appeared for peak power and mean power measures (being greater in the sprinters).

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John L. Walker, Tinker D. Murray, Charles M. Johnson, Don L. Rainey and William G. Squires Jr.

This study evaluated the aerobic demands of the 20-minute steady-state jogging speeds for 15 high school students. All subjects performed a discontinuous treadmill test that included submaximal speeds, the Fit Youth Today criterion referenced speeds, and finally a run to voluntary fatigue. Stages lasted 5 minutes. Preliminary data indicated that both groups averaged between 87% (the 9 boys) and 93 % (the 6 girls) of their respective peak oxygen consumption at the criterion referenced speeds during treadmill testing. According to the American College of Sports Medicine guidelines for healthy adults, these intensities represent the upper threshold for aerobic conditioning, and high exercise intensities can increase the risk of injury. Although the results of this study are preliminary in nature and based on a small sample size, we suggest that the criterion referenced distances (speeds) for the FYT 20-minute steady-state jog may need modification.

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Sarah M. Camhi, Susan B. Sisson, William D. Johnson, Peter T. Katzmarzyk and Catrine Tudor-Locke

Background:

Objective physical activity data analyses focus on moderate-to-vigorous physical activity (MVPA) without considering lower intensity lifestyle-type activities (LA). We describe 1) quantity of LA (minutes and steps per day) across demographic groups, 2) proportion of LA to total physical activity, and 3) relationships between LA and MVPA using NHANES 2005−2006 accelerometer adult data (n = 3744).

Methods:

LA was defined as 760 to 2019 counts per minute (cpm) and MVPA as ≥2020 cpm. LA was compared within gender, ethnicity, age, and BMI groups. Regression analyses examined independent effects. Correlations were evaluated between LA and MVPA. All analyses incorporated sampling weights to represent national estimates.

Results:

Adults spent 110.4 ± 1.6 minutes and took 3476 ± 54 steps per day in LA. Similar to MVPA, LA was highest in men, Mexican Americans, and lowest in adults ≥60 years or obese. When LA was held constant, ethnic differences no longer predicted MVPA minutes, and age no longer predicted MVPA steps. LA and MVPA minutes (r = .84) and steps per day (r = .72) were significantly correlated, but attenuated with MVPA modified bouts (≥10 minutes sustained activity).

Conclusions:

LA accumulation differs between demographic subgroups and is related to MVPA: adults who spend more minutes and steps in MVPA also spend them in LA.

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John M. Schuna Jr., Tiago V. Barreira, Daniel S. Hsia, William D. Johnson and Catrine Tudor-Locke

Background:

Energy expenditure (EE) estimates for a broad age range of youth performing a variety of activities are needed.

Methods:

106 participants (6–18 years) completed 6 free-living activities (seated rest, movie watching, coloring, stair climbing, basketball dribbling, jumping jacks) and up to 9 treadmill walking bouts (13.4 to 120.7 m/min; 13.4 m/min increments). Breath-by-breath oxygen uptake (VO2) was measured using the COSMED K4b2 and EE was quantified as youth metabolic equivalents (METy1:VO2/measured resting VO2, METy2:VO2/estimated resting VO2). Age trends were evaluated with ANOVA.

Results:

Seated movie watching produced the lowest mean METy1 (6- to 9-year-olds: 0.94 ± 0.13) and METy2 values (13- to 15-year-olds: 1.10 ± 0.19), and jumping jacks produced the highest mean METy1 (13- to 15-year-olds: 6.89 ± 1.47) and METy2 values (16- to 18-year-olds: 8.61 ± 2.03). Significant age-related variability in METy1 and METy2 were noted for 8 and 2 of the 15 evaluated activities, respectively.

Conclusions:

Descriptive EE data presented herein will augment the Youth Compendium of Physical Activities.

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Catrine Tudor-Locke, Meghan M. Brashear, Peter T. Katzmarzyk and William D. Johnson

Background:

Analysis of the 2005–2006 National Health and Nutrition Examination Survey (NHANES) accelerometer data provides the descriptive epidemiology of peak 30-minute cadence (defined as the average steps/min recorded for the 30 highest, but not necessarily consecutive, minutes in a day) and peak 1-minute cadence (defined as the steps/min recorded for the highest single minute in a day) by sex, age, and body mass index (BMI).

Methods:

Minute-by-minute step data were rank ordered each day to identify the peak 30-minute and 1-minute cadences for 3522 adults (20+ years of age) with complete sex, age, and BMI data and at least 1 valid day (ie, 10/24 hours of accelerometer wear) of accelerometer data. Peak values were averaged across days within participants by sex, age, and BMI-defined categories.

Results:

U.S. adults average a peak 30-minute cadence of 71.1 (men: 73.7, women: 69.6, P < .0001) steps/min and a peak 1-minute cadence of 100.7 (men: 100.9, women: 100.5, P = .54) steps/min. Both peak cadence indicators displayed significant and consistent declines with age and increasing levels of obesity.

Conclusions:

Peak cadence indicators capture the highest intensity execution of naturally occurring ambulatory activity. Future examination of their relationship with health parameters using cross-sectional, longitudinal, and intervention designs is warranted.

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Tiago V. Barreira, Catrine Tudor-Locke, Catherine M. Champagne, Stephanie T. Broyles, William D. Johnson and Peter T. Katzmarzyk

Background:

The purpose of this study was to compare steps/day detected by the YAMAX SW-200 pedometer versus the Actigraph GT3X accelerometer in free-living adults.

Methods:

Daily YAMAX and GT3X steps were collected from a sample of 23 overweight and obese participants (78% female; age = 52.6 ± 8.4 yr.; BMI = 31.0 ± 3.7 m·kg-2). Because a pedometer is more likely to be used in a community-based intervention program, it was used as the standard for comparison. Percent difference (PD) and absolute percent difference (APD) were calculated to examine between-instrument agreement. In addition, days were categorized based on PD: a) under-counting (> −10 PD), b) acceptable counting (−10 to 10 PD), and c) over-counting (> 10 PD).

Results:

The YAMAX and GT3X detected 8,025 ± 3,967 and 7131 ± 3066 steps/day, respectively, and the outputs were highly correlated (r = .87). Average PD was −3.1% ± 30.7% and average APD was 23.9% ± 19.4%. Relative to the YAMAX, 53% of the days detected by the GT3X were classified as under-counting, 25% acceptable counting, and 23% over-counting.

Conclusion:

Although the output of these 2 instruments is highly correlated, caution is advised when directly comparing or using their output interchangeably.

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Elroy J. Aguiar, John M. Schuna Jr., Tiago V. Barreira, Emily F. Mire, Stephanie T. Broyles, Peter T. Katzmarzyk, William D. Johnson and Catrine Tudor-Locke

Walking cadence (steps per minute) is associated with the intensity of ambulatory behavior. This analysis provides normative values for peak 30-min cadence, an indicator of “natural best effort” during free-living behavior. A sample of 1,196 older adults (aged from 60 to 85+) with accelerometer data from the National Health and Nutrition Examination Survey 2005–2006 was used. Peak 30-min cadence was calculated for each individual. Quintile-defined values were computed, stratified by sex and age groups. Smoothed sex-specific centile curves across the age span were fitted using the LMS method. Peak 30-min cadence generally trended lower as age increased. The uppermost quintile value was >85 steps/min (men: 60–64 years), and the lowermost quintile value was <22 steps/min (women: 85+). The highest 95th centile value was 103 steps/min (men: 64–70 years), and the lowest 5th centile value was 15 steps/min (women: 85+). These normative values may be useful for evaluating older adults’ “natural best effort” during free-living ambulatory behavior.