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Thomas W. Kaminski and Geoff C. Dover

Objective:

To determine the reliability of inversion and eversion concentric isokinetic-strength measurements from the Biodex System 3 isokinetic dynamometer.

Setting:

University biomechanics research laboratory.

Subjects:

Thirty-five volunteers free from any lower leg and ankle injuries within the preceding year.

Measurements:

Peak (PT) and average (AT) isokinetic torque at 30°/s and 120°/s for subtalar-joint inversion and eversion.

Results:

PT intraclass correlation coefficients (ICC2,1) ranged from .54 to .92. AT ICC2,1 ranged from .55 to .91. These ICCs were good to excellent for both PT and AT at each speed and motion tested, except for fair ICCs produced from right-foot-eversion measurements at 30°/s.

Conclusions:

Inversion and eversion subtalar-joint strength measurements from the Biodex System 3 isokinetic dynamometer are reliable.

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Mark Loftin, Patricia Strikmiller, Barbara Warren, Leann Myers, Leslie Schroth, James Pittman, David Harsha and Melinda Sothern

Peak cardiorespiratory responses, physical activity patterns, and the association of VO2peak and physical activity were examined in 16 elementary (ES) and 16 high school (HS) females. Peak responses were assessed during treadmill running, and physical activity patterns were examined over two 12-hour weekdays. Results indicated similar relative VO2peak responses between groups (ES: M = 46.8 ml · kg−1 · min−1;HS:M = 46.6 ml · kg−1 · min−1). No statistical differences (p ≤ .05) were noted when moderate to vigorous physical activity (MVPA) and vigorous physical activity (VPA) were compared. Also, a three-way (Group × HR level × Sustained minutes) ANOVA revealed no statistical differences. A median correlation (r = .27) was found from 8 independent correlations of habitual physical activity and VO2peak. ES and HS appeared similar in regard to VO2peak, accumulative and sustained MVPA and VPA. Low levels of sustained MVPA and VPA (≥ 10 min) were evident in both groups.

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Hans Luttikholt, Lars R. McNaughton, Adrian W. Midgley and David J. Bentley

Context:

There is currently no model that predicts peak power output (PPO) thereby allowing comparison between different incremental exercise test (EXT) protocols. In this study we have used the critical power profile to develop a mathematical model for predicting PPO from the results of different EXTs.

Purpose:

The purpose of this study was to examine the level of agreement between actual PPO values and those predicted from the new model.

Methods:

Eleven male athletes (age 25 ± 5 years, VO2max 62 ± 8 mL · kg–1 · min–1) completed 3 laboratory tests on a cycle ergometer. Each test comprised an EXT consisting of 1-minute workload increments of 30 W (EXT30/1) and 3-minute (EXT25/3) and 5-minute workload increments (EXT25/5) of 25 W. The PPO determined from each test was used to predict the PPO from the remaining 2 EXTs.

Results:

The differences between actual and predicted PPO values were statistically insignificant (P > .05). The random error components of the limits of agreement of ≤30 W also indicated acceptable levels of agreement between actual and predicted PPO values.

Conclusions:

Further data collection is necessary to confirm whether the model is able to predict PPO over a wide range of EXT protocols in athletes of different aerobic and anaerobic capacities.

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Amândio M.C. Santos, Neil Armstrong, Mark B. A. De Ste Croix, Peter Sharpe and Joanne R. Welsman

These studies used multilevel modelling to examine optimised peak power (PPopt) from a force velocity test over the age range 12–14 years. In the first study, body mass, stature, triceps and subscapular skinfold thicknesses of boys and girls, aged 12.3 ± 0.3 y at the onset of the study, were measured on four occasions at 6 monthly intervals. The analysis was founded on 146 PPopt determinations (79 from boys and 67 from girls). Body mass and stature were significant explanatory variables with sum of two skinfolds exerting an additional effect. No gender differences were evident but PPopt increased with age. In the second study, thigh muscle volume (TMV) was estimated using magnetic resonance imaging at test occasions two and four. The analysis, founded on a subsample of 67 PPopt determinations (39 from boys and 28 from girls), demonstrated TMV to be a significant additional explanatory variable alongside body mass and stature with neither age nor gender making a significant contribution to PPopt. Together the studies demonstrate the influence of body size and TMV on young people’s PPopt.

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Jorge Zuniga, Terry J. Housh, Michelle Mielke, Clayton L. Camic, C. Russell Hendrix, Glen O. Johnson, Dona J. Housh and Richard J. Schmidt

The purpose of this study was to cross-validate the fat-free weight (FFW) equations derived on nonathletic children and adolescents for estimating mean power (MP) and peak power (PP) in high school wrestlers. One hundred and three male high school wrestlers performed the Wingate Anaerobic Test to estimate MP and PP, as well as underwater weighing to determine FFW. The follow equations were used to estimate the MP and PP of the wrestlers in the current study.

MP (W) = 9.3 (FFW) − 109.8 EQ.1

PP (W) = 14.1 (FFW) − 162.1 EQ.2

The results in the current study indicated that as percent of the mean values, the equation that predicted MP resulted in a substantially greater total error (TE; 19.9% of the mean) than the equation that predicted PP (8.3% of the mean). These findings indicated that the equation that was derived on nonathletes did not accurately estimate MP in the high school wrestlers. The equation for estimating PP, however, was valid when applied to the current sample of high school wrestlers. These findings supported previous studies that have shown that in adolescent males, exercise training improves the metabolic capabilities of the anaerobic glycolytic system, but not the phosphagen system.

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M. Kathleen Ellis and Lynn A. Darby

This study compared balance and peak oxygen consumption (peak VO2) among hearing, congenital nonhearing, and acquired nonhearing female intercollegiate athletes. Twenty-seven subjects completed two measures of peak VO2 and two measures of balance (static and dynamic). Two pieces of exercise equipment requiring different levels of balance were used: the bicycle ergometer (minimal balance) and the bench-step (maximal balance). Significant differences were found for dynamic balance and for peak VO2 for all subject groups. The significant difference remained among the groups for peak VO2 using the bicycle ergometer when dynamic balance was used as a covariate. There was no significant difference for peak VO2 dependent on type of test when dynamic balance was controlled. The results indicated that dynamic balance affected peak VO2 performance on the bench-step, but not on the bicycle ergometer. These findings suggest that if dynamic balance is required for an assessment of peak VO2, balance should be tested in nonhearing populations.

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Sock Miang Teo-Koh and Jeffrey A. McCubbin

The purpose of this study was to determine the relationship between peak VO2 and the 1-mile walk test (WALK) performance of forty 12–17-year-old males (mean age = 14.13 years) with mental retardation (mean IQ = 50). Test-retest reliability of the WALK was high for WALK times (R = .97), WALK End-HR (R = .88), and WALK HRpeak (R = .92). Test-retest reliability of relative peak VO2 was .90. Partial correlation analysis indicated that when weight and various combinations of variables with weight were held constant, the relationship between WALK time and peak VO2 was strengthened. Multiple regression analysis of WALK performance variables and peak VO2 measures indicated the best model for estimating relative peak VO2: VO2peak = 95.56 − 3.345 (walk time) − 0.174 (WT) and the best model for estimating absolute peak VO2: VO2peak = 2.90 − .176 (walk rime) + .031 (WT). Results indicated the WALK as a reliable field test for the sample tested.

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Joshua M. Thomas and Timothy R. Derrick

The purpose of this research was to determine the effects of step uncertainty on shock attenuation and knee/subtalar synchrony. Uncertainty was manipulated by decreasing the intensity of light and introducing bumps to the running surface. Twelve experienced distance runners ran at their chosen pace on a treadmill with two surfaces (smooth and irregular) and three light intensities (light, medium, dark). Knee angle, subtalar angle, leg impacts, and head impacts were recorded at 1,000 Hz. Heart rate was also monitored. Injury potential was assessed by evaluating the impacts and asynchronous activity between the knee and subtalar joint. Stride length was not influenced by either source of uncertainty. Heart rate increased with the intensity of light on the smooth running surface but decreased with the intensity of light on the irregular surface. The knee was more flexed at heel contact during the irregular surface conditions but was not affected by the intensity of light. This decreased the effective mass of the impact and allowed greater peak leg accelerations and greater impact attenuation during irregular surface running. There was a decrease in the rearfoot angle at contact on the irregular surface that approached significance (p = 0.056). Knee/subtalar asynchrony increased with the intensity of light on the smooth surface but decreased on the irregular surface. It appears that participants used the knee joint to adapt to the irregular surface and thus accommodate changes in the terrain. The subtalar joint may have become more stable during irregular surface running to minimize the chance of inversion sprains. The effects of intensity of light were small and generally mediated the irregular surface effects. Overall, these adaptations likely reduced the potential for injury during irregular surface running but may have been detrimental to performance.

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Sigurbjörn Árni Arngrímsson, Torarinn Sveinsson and Erlingur Jóhannsson

The purpose of this study was to validate an equation that has been used to predict peak oxygen uptake (VO2peak) and, if invalid, to develop a new equation predicting VO2peak from performance on a cycle ergometer test. Forty-five 9- and 15-year-old children underwent a VO2peak test and were randomized into developmental (DEV) and cross-validation (C-V) groups. The equation under validation, which requires knowledge of resting energy expenditure (REE), underestimated VO2peak (p < .05), but once adjusted with a new parameter calculated in DEV, it cross-validated well (r YY′ = .98, SE = .18 L · min−1). The accuracy of a new prediction equation built in DEV, not using REE, was confirmed in C-V (r YY′ = .98, SE = .17 L · min−1) and the slope and intercept were not different from the line of identity (p < .05). VO2peak in schoolchildren can be predicted with good accuracy from an equation based on the whole sample [VO2peak′ = −1.5986 + 0.0115 · (maximal power output) + 0.0109 · (mass) + 0.1313 · (gender) + 0.0085 · (maximal heart rate)].

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Matthew T. Mahar, Gregory J. Welk, David A. Rowe, Dana J. Crotts and Kerry L. McIver

Background:

The purpose of this study was to develop and cross-validate a regression model to estimate VO2peak from PACER performance in 12- to 14-year-old males and females.

Methods:

A sample of 135 participants had VO2peak measured during a maximal treadmill test and completed the PACER 20-m shuttle run. The sample was randomly split into validation (n = 90) and cross-validation (n = 45) samples. The validation sample was used to develop the regression equation to estimate VO2peak from PACER laps, gender, and body mass.

Results:

The multiple correlation (R) was .66 and standard error of estimate (SEE) was 6.38 ml·kg−1·min−1. Accuracy of the model was confirmed on the cross-validation sample. The regression equation developed on the total sample was: VO2peak = 47.438 + (PACER*0.142) + (Gender[m=1, f=0]*5.134) − (body mass [kg]*0.197), R = .65, SEE = 6.38 ml·kg–1·min–1.

Conclusions:

The model developed in this study was more accurate than the Leger et al. model and allows easy conversion of PACER laps to VO2peak.