Matthew T. Mahar

Prediction of functional aerobic capacity without exercise testing

The purpose of this study was to develop functional aerobic capacity prediction models without using exercise tests (N-Ex) and to compare the accuracy with Astrand single-stage submaximal prediction methods. The data of 2,009 subjects (9.7% female) were randomly divided into validation (N = 1,543) and cross-validation (N = 466) samples. The validation sample was used to develop two N-Ex models to estimate VO2peak. Gender, age, body composition, and self-report activity were used to develop two N-Ex prediction models. One model estimated percent fat from skinfolds (N-Ex %fat) and the other used body mass index (N-Ex BMI) to represent body composition. The multiple correlations for the developed models were R = 0.81 (SE = 5.3 ml.kg-1.min-1) and R = 0.78 (SE = 5.6 ml.kg-1.min-1). This accuracy was confirmed when applied to the cross-validation sample. The N-Ex models were more accurate than what was obtained from VO2peak estimated from the Astrand prediction models. The SEs of the Astrand models ranged from 5.5-9.7 ml.kg-1.min-1. The N-Ex models were cross-validated on 59 men on hypertensive medication and 71 men who were found to have a positive exercise ECG. The SEs of the N-Ex models ranged from 4.6-5.4 ml.kg-1.min-1 with these subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Gait adaptations before and after anterior cruciate ligament reconstruction surgery

Gait analyses of rehabilitated individuals with anterior cruciate ligament (ACL) deficiency and reconstruction have identified the final adaptations of increased hip extensor torque and hamstring electromyography (EMG) and decreased knee extensor torque and quadriceps EMG during stance. The initial adaptations to injury and surgery are, however, unknown as are the factors that influence the development of the adaptations. Identification of the initial response to injury would provide a basis for determining whether the final adaptations are learned automatically or if they are the result of a lengthy training period in which various factors may affect their development. The purpose of the study was to evaluate the initial effects of ACL injury and reconstruction surgery on joint kinematics, kinetics, and energetics, during walking. Injured limbs from nine subjects with ACL injury were tested 2 wk after injury, and 3 and 5 wk after surgery. Ten healthy subjects were tested. Kinematic and ground reaction data were collected and combined with inverse dynamics to calculate the joint torques and powers. A knee extensor torque throughout most of stance was observed in the injured limbs at all test sessions. This result was in conflict with previous observations of reduced extensor torque or a flexor torque in rehabilitated patients with ACL reconstruction and patients with ACL deficiency. This result also differed from the typical midstance extensor then flexor torque in healthy control subjects. Trend analysis showed a significant (P < 0.001) change in average position at the hip and knee, extensor angular impulse at the hip, and positive work done at the hip 3 wk after surgery followed by a partial rehabilitation at 5 wk after surgery. Power and work produced at the knee were reduced fivefold (P < 0.001) after 5 wk of rehabilitation and did not recover to pre-surgical levels. The existence of a long-lasting knee extensor torque 2 wk after injury indicated that the adaptation process to ACL deficiency is lengthy, requiring many gait cycles, and that numerous factors could be involved in learning the adaptations.

Impact of short bouts of physical activity on attention-to-task in elementary school children

OBJECTIVE The studys objective was to describe the measurement of on-task behavior and review the research on the effects of short physical activity breaks on attention-to-task in elementary school students, with a particular focus on a promising approach to improving on-task behavior with short bouts of physical activity in the classroom setting. METHODS Procedures to directly observe attention-to-task were detailed. Published studies that measured attention-to-task in elementary school students following physical activity breaks were reviewed. RESULTS Direct measurement of attention-to-task is intensive and demanding on observers. Previous research on attention-to-task following physical activity breaks is sparse. The limited evidence suggests a small to moderate improvement on attention-to-task following physical activity breaks (Effect Sizes typically ranged from 0.13 to 0.60). Teachers can be trained in a relatively short time to effectively lead classroom-based physical activities. Students who participated in classroom-based physical activities that incorporate academic concepts demonstrated significantly better improvements (+8.3%) in attention-to-task than control group participants (-3.1%). CONCLUSIONS Attention-to-task is a variable that directly relates to concerns of classroom teachers. The limited available research has demonstrated moderate to good evidence that physical activity during the school day improves attention-to-task in elementary school students. Because of the positive effects of physical activity on attention-to-task, it is recommended that elementary school teachers consider implementing physical activity sessions throughout the school day in the form of recess and classroom-based physical activities.

Estimation of Aerobic Fitness from 20-m Multistage Shuttle Run Test Performance

BACKGROUND Aerobic fitness (VO(2)max) is a key component of youth fitness testing. Criterion-referenced (CR) assessments are used in FITNESSGRAM(®) to assess health risk. PURPOSE The purpose of this study was to develop and cross-validate regression models to estimate VO(2)max from Progressive Aerobic Cardiovascular Endurance Run (PACER) 20-m shuttle run performance in boys and girls aged 10-16 years. Several previously published PACER models were also cross-validated. A secondary purpose was to examine the CR validity of the models. METHODS PACER performance and VO(2)max were assessed in a sample of 244 participants. The sample was randomly split into validation (n=174) and cross-validation (n=70) samples. The validation sample was used to develop the regression models to estimate VO(2)max from PACER, BMI, gender, and age. CR validity was evaluated by comparing classification of the prediction models with classification by the criterion of measured VO(2)max. RESULTS For the Quadratic Model, the multiple correlation between measured and estimated VO(2)max was 0.75, and the SE of estimate (SEE) was 6.17 mL/kg/min. Similar accuracy was found for Linear Model 2 (R=0.74; SEE=6.29 mL/kg/min). Accuracy of these models was confirmed on the cross-validation and total samples. Cross-validation demonstrated that the Quadratic Model and Linear Model 2 were slightly more accurate than previous PACER models. Evidence of CR validity for the newly developed models was of moderate levels. CONCLUSIONS The Quadratic Model and Linear Model 2 provide valid estimates of VO(2)max and compare favorably to previous models. The CR validity evidence for the Quadratic Model and Linear Models developed in this study was slightly better than for the other models examined.

Stride rate recommendations for moderate-intensity walking.

UNLABELLED Current physical activity guidelines recommend physical activity of at least moderate intensity to gain health benefits. Previous studies have recommended a moderate-intensity walking cadence of 100 steps per minute for adults, but the influence of height or stride length has not been investigated. PURPOSE the purpose of the current study was to determine the role of height and stride length in moderate-intensity walking cadence in adults. METHODS seventy-five adults completed three treadmill walking trials and three overground walking trials at slow, medium, and fast walking speeds while V˙O2 was measured using indirect calorimetry. Five stride length-related variables were also measured. RESULTS mixed model regression analysis demonstrated that height explained as much variability in walking intensity at a given cadence as did two different measures of leg length and two different stride length tests. CONCLUSIONS the previous general recommendations of 100 steps per minute were supported for use where a simple public health message is needed. Depending on height, moderate-intensity walking cadence can vary by more than 20 steps per minute, from 90 to 113 steps per minute for adults 198 to 152 cm tall, respectively. Height should therefore be taken into consideration for more precise evaluation or prescription of walking cadence in adults to provide health benefits.

Lower and upper body anaerobic performance in male and female adolescent athletes

Little data exist for upper and lower body mechanical power capability of adolescent athletes. This study compared arm (A) and leg (L) anaerobic peak and mean power (PP and MP) of 20 male and 20 female adolescent athletes after normalization for body mass (BM), fat-free mass (FFM), and lean A and L cross-sectional area (CSA). Power outputs were assessed by the Wingate anaerobic test. FFM and CSA were estimated via anthropometry. No significant (P > 0.05) differences existed between the sexes in Tanner sexual maturity, chronological age, or overall training activity. Males had higher (P < 0.001) absolute PP (W) (L 694 vs 442; A 494 vs 309) and MP (L 548 vs 307; A 337 vs 214). Ratio normalization and ANCOVA were used to remove the influence of body size differences. Ratio normalization showed that males had greater leg PP/BM, MP/BM, MP/FFM, MP/CSA, as well as arm PP/BM and MP/BM, whereas all leg and arm PP and MP ANCOVA adjusted means for BM, FFM, and CSA, except arm MP adjusted for FFM, were significantly (P < 0.01) higher for males than females. We conclude that factors other than muscle mass, possibly qualitative in nature, are responsible for the sex difference in anaerobic performance of adolescent athletes.

Approaches for Development of Criterion-Referenced Standards in Health-Related Youth Fitness Tests

Youth fitness testing in theU.S. has a rich history of over 50 years. Key developments and changes include the development of the American Alliance for Health, Physical Education and Recreation (AAHPER) Youth Fitness Test, the birth of the healthrelated fitness construct, and changes in evaluation and awards. The transitions from performance-related fitness to health-related fitness and from norm-referenced standards to criterion-referenced (CR) standards are noteworthy since they influenced how fitness is assessed and interpreted. The current paper reviews historical trends in fitness testing and explains the advantages of a CR framework. Methods used for establishing CR standards are described, providing a background for the subsequent articles in this supplement to the American Journal of Preventive Medicine.

Norm-Referenced and Criterion-Referenced Reliability of the Push-Up and Modified Pull-Up

This study determines the test-retest reliability and equivalence reliability (i.e., defined as consistency of 2 tests designed to measure the same construct) of the push-up and the modified pull-up tests from both norm-referenced and criterion-referenced frameworks. Sixty-two (30 boys and 32 girls) 5th- and 6th-grade students (mean age = 11.4 0.9 years) were administered 2 test trials for both the push-up and modified pull-up tests following a 4-week fitness unit. The norm-referenced test-retest reliability estimates, using intraclass correlations from a one-way analysis of variance (ANOVA), were consistently high for 2 trials of both the push-up and modified pull-up (R = .99) and also high for 1 trial (R = .98 for push-up, R = .97 for modified pull-up). Moderately high correlations between the push-up and modified pull-up were obtained (r ≧ .74). Criterion-referenced reliability was estimated with proportion of agreement (Pa), modified kappa (Kq), and Phi coefficient using the FITNESSGRAM(r) standards (Cooper Institute for Aerobics Research, 1999). Criterion-referenced test-retest reliability estimates were high for the push-up (Pa = .97, Kq = .94) and the modified pull-up (Pa = .95, Kq = .90). Equivalence reliability estimates were considerably lower between push-up and modified pull-up test Trial 1 (Pa = .69, Kq = .38, and Phi = .50) and test Trial 2 (Pa = .71, Kq = .42, and Phi = .52). Norm-referenced and criterion-referenced test-retest reliability estimates in this study were acceptable. However, criterion-referenced equivalence reliability findings were not acceptable. Equating of standards between fitness tests designed to measure the same component of fitness should be examined.

Cross-validation of an equating method linking aerobic FITNESSGRAM ® field tests

BACKGROUND Field tests measuring the same construct, in this case, aerobic capacity, use different scales, which makes fitness assessment of children and youth potentially confusing. The Primary Field Test Centered Equating Method has been developed to set tests on the same scale, as illustrated by the conversion of Progressive Aerobic Capacity Endurance Run (PACER) scores to 1-mile run/walk times to estimate VO(2)max. PURPOSE The purpose of this study was to cross-validate the Primary Field Test Centered Equating Method by using a data set of middle school students to assess its effectiveness. METHODS PACER scores of 135 middle school students were converted to 1-mile run/walk times (Mile PEQ) using the proposed method. Several estimates of VO(2)max using PACER scores were then compared to estimated VO(2)max using Mile PEQ and measured VO(2)max. The obtained measures were classified according to the healthy fitness zone (HFZ; FITNESSGRAM(®), version 9) and compared to measured VO(2)max. BMI estimates based on the sample data and the national average also were considered to assess the methods flexibility. RESULTS Agreement levels with actual values were similar for VO(2)max predicted using Mile PEQ and predictions using PACER laps and speed (73%-75%). The t-tests showed no significant difference between actual VO(2)max (M=44.43, SD= 8.36) and VO(2)max predicted using Mile PEQ (M=44.33, SD=5.88). Using BMI averages from sample data and the national data to estimate VO(2)max using Mile PEQ also yields high agreement levels, 70% and 73%, respectively. CONCLUSIONS The Primary Field Test Centered Equating Method performs as well or better in estimating VO(2)max as several other models using PACER scores, especially for boys, and thus may be successfully used in practice. More research is needed to understand the relatively low prediction and classification accuracy in girls.

Practical Guidelines for Valid and Reliable Youth Fitness Testing

Accurate measures of youth fitness are needed by researchers and practitioners. Evidence of validity and reliability are essential before results of youth fitness tests can be used to make sound decisions. This article describes a three-stage paradigm for validation research and provides guidance for conducting and understanding norm-referenced and criterion-referenced validity and reliability research. Advice is provided on how to administer fitness tests and how to use fitness test results in ways that promote reliability and validity in practice. Users of fitness tests are cautioned that interpretation and use of fitness tests involve important educational, pedagogical, and psychological consequences. Confidence in youth fitness test results and the decisions that are made based on these scores depend upon careful test design and administration that incorporate a sound understanding of the principles of validity and reliability.