Dale D. Brown

Physiological and biomechanical differences between wheelchair-dependent and able-bodied subjects during wheelchair ergometry

SummaryThe purpose of this study was to compare the physiological and biomechanical responses of wheelchair-dependent persons (WCD) to able-bodied persons (AB) during manual wheelchair ergometry. Five WCD and five AB performed a discontinuous wheelchair ergometer test starting at 12.8 W at 30 rev·min−1 (57 m·min−1) with increments of 7.0 W at 6-min intervals. Biomechanical data were collected 3.5 min into each stage followed by the collection of physiological data. After the fifth stage, peak oxygen consumption was determined by having the subject work against a resistance of 14.7–19.6 N at 30 rev · min−1. The WCD had significantly higher net mechanical efficiency at 26.7, 33.6 and 40.6 W in comparison to the AB. The WCD had significantly greater shoulder extension at the point of initial wheel contact as measured by the shoulder angle, while the AB had significantly greater shoulder range of motion at all work rates in comparison to the WCD. The results demonstrate that a significant physiological difference exists in the manner by which WCD and AB accomplish wheelchair ergometry. The biomechanical differences between AB and WCD were found to be a prominent factor contributing to the higher mechanical efficiency of WCD over AB. It was concluded that basic physiological and biomechanical differences exist between WCD and AB in manual wheelchair locomotion and that these differences are important considerations to the interpretation of data in wheelchair ergometry studies.

Concurrent validation of the Actigraph gt3x+, Polar Active accelerometer, Omron HJ-720 and Yamax Digiwalker SW-701 pedometer step counts in lab-based and free-living settings

Abstract Activity monitors are frequently used to assess activity in many settings. But as technology advances, so do the mechanisms used to estimate activity causing a continuous need to validate newly developed monitors. The purpose of this study was to examine the step count validity of the Yamax Digiwalker SW-701 pedometer (YX), Omron HJ-720 T pedometer (OP), Polar Active accelerometer (PAC) and Actigraph gt3x+ accelerometer (AG) under controlled and free-living conditions. Participants completed five stages of treadmill walking (n = 43) and a subset of these completed a 3-day free-living wear period (n = 37). Manually counted (MC) steps provided a criterion measure for treadmill walking, whereas the comparative measure during free-living was the YX. During treadmill walking, the OP was the most accurate monitor across all speeds (±1.1% of MC steps), while the PAC underestimated steps by 6.7–16.0% per stage. During free-living, the OP and AG counted 97.5% and 98.5% of YX steps, respectively. The PAC overestimated steps by 44.0%, or 5,265 steps per day. The Omron pedometer seems to provide the most reliable and valid estimate of steps taken, as it was the best performer under lab-based conditions and provided comparable results to the YX in free-living. Future studies should consider these monitors in additional populations and settings.

Physical fitness and academic performance in middle school students.

The purpose of this study was to determine whether physical fitness is linked to academic success in middle school students.

Field Evaluation of the New FITNESSGRAM® Criterion-Referenced Standards

BACKGROUND The Cooper Institute established new criterion-referenced standards for the body composition and cardiovascular fitness standards for the FITNESSGRAM(®) program. PURPOSE The purpose of this study was to evaluate differences in the achievement of standards and classification agreement between the old and new standards. METHODS Fitness data were collected during the 2009-2010 school year from 1686 youth (grades 3-12) from six schools (two districts) in a small Midwestern town. Data analyses were completed during the 2010 and 2011 school year. Descriptive statistics were computed to determine the percentage of students classified into the various fitness classifications using both the old and new standards. Classification agreement was examined for alternative tests of cardiovascular fitness (Progressive Aerobic Cardiovascular Endurance Run [PACER] and 1-mile run) and body composition (skinfold determination of body fat and BMI) using both the old and new standards. RESULTS The descriptive results reveal important age and gender differences in reported levels of fitness levels in school-aged youth. For body composition, the percentage of youth achieving the healthy fitness zone (HFZ) was about 10% lower with the new standards than the old ones. For aerobic capacity, a larger percentage of young boys and a smaller percentage of older boys achieved the new HFZ for aerobic capacity. However, a smaller percentage of girls achieved the new HFZ at all ages. The use of test-equating in the revised standards led to significant improvements in the classification agreement between 1-mile run and the PACER. CONCLUSIONS The large data set provided a useful sample to examine the impact of the new fitness standards on the documentation of youth fitness levels in schools. The new standards address a number of measurement issues with the old standards and provide a more appropriate way to evaluate levels of health-related fitness in youth.

Physiologic and metabolic responses to a continuous functional resistance exercise workout.

Lagally, KM, Cordero, J, Good, J, Brown, DD, and McCaw, ST. Physiologic and metabolic responses to a continuous functional resistance exercise workout. J Strength Cond Res 23(2): 373-379, 2009-The purpose of this study was to evaluate the physiologic and perceptual responses to a continuous functional exercise workout. Ten men and 10 women (21.2 ± 2.4 and 21.0 ± 1.5 years) completed a maximal oxygen uptake test, strength test, and body composition analysis. Subjects then participated in 3 familiarization sessions, during which they followed a videotaped routine that consisted of a series of functional resistance exercises performed in a continuous manner. Subjects performed the same routine in a final session, during which &OV0312;O2, &OV0312;co2, respiratory exchange ratio (RER), RPE, and heart rate were measured and blood samples were taken and analyzed for blood lactic acid concentration. Descriptive statistics were calculated for RPE, RER, blood lactic acid concentration, energy expenditure, and absolute and relative oxygen uptake and heart rate. Energy expenditure was calculated using &OV0312;O2 and RER. Independent t-tests were used to examine differences between men and women for oxygen consumption, weight lifted, and energy expenditure during the workout. Subjects had a mean &OV0312;o2 of 27.8 ml·kg−1·min−1 (51% of &OV0312;o2 peak and 47.8% of &OV0312;o2 reserve), a mean heart rate of 156 bpm (83% of maximum heart rate), and a mean RER of 0.91. The mean RPE was 5.9, and the mean difference between pre and post lactic acid concentration was 2.5 mmol·L−1. The mean total caloric expenditure was 289 kcal. Men lifted significantly heavier weights and expended more total calories than women. Caloric expenditure (kcal·kg−1·min−1), &OV0312;o2, and weight lifted were similar between men and women when expressed relatively. Performing dynamic functional exercises in a continuous manner resulted in energy expenditure values, but not relative &OV0312;o2 values, that meet the American College of Sports Medicine recommendations.

Heart Rates of High School Physical Education Students during Team Sports, Individual Sports, and Fitness Activities.

This study examined how activity type influenced heart rates and time spent in target heart rate zones of high school students participating in physical education classes. Significantly higher average heart rates existed for fitness (142 ± 24 beats per minute [bpm]) compared to team (118 ± 24 bpm) or individual (114 ± 18) activities. Similar results occurred for the percentage of activity time spent within a target heart rate zone (fitness 81.7 ± 15.9%, individual 68.4 ± 30.5%, and team 60.6 ± 30.5%). Boys attained higher heart rates during team activities, while female students had higher rates during individual activities indicating male and female adolescents respond differently to activity types. The highest mean heart rates were observed during fitness activities.

Relationship Between Socioeconomic Status and Physical Fitness in Junior High School Students

BACKGROUND Research on physical fitness often regards socioeconomic status (SES) as a confounding factor. However, few studies investigate the impact of SES on fitness. This study investigated the impact of SES on physical fitness in both males and females, with an economic-based construct of SES. METHODS The sample consisted of 954 6th, 7th, and 8th graders from a public, urban, Illinois middle school. The students participated in the FITNESSGRAM battery of fitness assessments as part of physical education. Descriptive statistics were calculated for height, weight, age, and sex. Students were grouped as high or low SES depending on whether they qualified for the federal free lunch program. A multivariate analysis of variance controlled for age and stratified by sex compared the raw scores from the fitness test for low and high SES students. Odds ratios stratified by sex were calculated for the likelihood of not achieving the FITNESSGRAM Healthy Fitness Zone standards among SES groups. RESULTS Girls of the low SES group had significantly lower scores on the FITNESSGRAM assessments and were significantly less likely to achieve Healthy Fitness Zone status than the girls from the high SES groups. For boys, SES was a significant main effect for body composition but not for the other fitness tests conducted. CONCLUSION SES is related to physical fitness in girls but not in boys. A potential explanation for this is that boys are more likely to engage in vigorous leisure time activity regardless of SES than girls.

Measurement Agreement between Estimates of Aerobic Fitness in Youth: The Impact of Body Mass Index.

Purpose The purpose of this study was to examine the impact of body mass index (BMI) on the agreement between aerobic capacity estimates from different Progressive Aerobic Cardiorespiratory Endurance Run (PACER) equations and the Mile Run Test. Method The agreement between 2 different tests of aerobic capacity was examined on a large data set from 2 suburban school districts (n = 1,686 youth in Grades 3–10). Difference estimates between the Mile Run Test and several PACER equations were computed, and residuals were examined using cluster analysis. The implication of the discrepancy between these tests was also examined using FITNESSGRAM® health-related standards for BMI. Comparisons were made against corresponding estimates of peak oxygen consumption from the Mile run because this equation is more established. Results Results supported a 2-cluster solution. The discrepancy between tests was higher in participants with higher BMI scores (Z scores for residuals in this group ranged from − 0.07 to 1.57). BMI was able to explain 30% to 34% of the disagreement between the Mile and different PACER equations of aerobic fitness. Classification analyses revealed that kappa scores were lower among PACER equations that do not include a BMI term (kappa = .12–.34 vs. .59–.81). Overall, the test-equating approach used in the Fitnessgram program to process PACER data had better agreement than alternative PACER equations that included BMI. Conclusion The results support the inclusion of BMI in prediction equations used to estimate aerobic capacity from the PACER.

Caffeine Affects Heart Rate and Blood Pressure Response to Prolonged Walking

This study investigated the cardiovascular response to walking after caffeine ingestion. Subjects were ten fit, normotensive men (age range, 22 to 30 years of age) who were either high caffeine users (HCU) (more than 300 mg/day) (five subjects) or low caffeine users (LCU) (less than 50 mg/day) (five

Venous and fingertip blood to calculate plasma volume shift following exercise.

This study determined whether fingertip blood samples used to calculate percentage change in calculated plasma volume following exercise were in agreement with values obtained from venous blood samples. Twenty-five subjects engaged in two cycle ergometer exercises at 100 and 200 W, with percentage plasma volume shift (% PVS) determined after each from venous (VB) and fingertip (FT) blood. Values for % PVS were FT -6.25% compared with VB -8.04% (P less than 0.05), with the correlation between the two methods at r = 0.88. The following equation was established: corrected FT % PVS = (0.8662 * FT) - 2.625; SEE = 2.60%. In order to cross-validate this equation, fifteen additional subjects submitted to VB and FT. Corrected FT % PVS using the established equation resulted in a mean value of 9.53 compared with 10.53% for actual VB % PVS. Although these means were not significantly different, there was approximately a 25% chance that the corrected FT % PVS would be more than one standard error of estimate from the regression line. It was concluded that FT underestimates VB % PVS. However, when limited to group data, FT can be corrected to favorably represent VB % PVS following moderate to heavy cycle ergometer exercise.