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Jianhua Wu, Toyin Ajisafe and Matthew Beerse

This study used both time and frequency domain analyses to investigate walking patterns with ankle load in children and adults. Twenty-two children aged 7–10 years and 20 young adults participated in this study. Three levels of ankle load were manipulated: no load, low load (2% of body mass on each side), and high load (4% of body mass on each side). An instrumented treadmill was used to register vertical ground reaction force (GRF) and spatiotemporal parameters, and peak vertical GRFs were determined. A frequency domain analysis was conducted on the vertical GRF data. Results demonstrate that, in the time domain, children showed adult-like spatiotemporal parameters and adult-like timing and magnitude of the 2 peak vertical GRFs under each load. In the frequency domain, children produced a lower power from the second harmonic than young adults, although both groups showed the highest power from this harmonic and increased this power with ankle load. It was concluded that children aged 7–10 years may start showing adult-like neuromuscular adaptations to increasing ankle load and display similar spatiotemporal control of foot falls and foot–floor kinetic interaction; however, a frequency domain analysis is effective in revealing different kinetic and neuromuscular characteristics between children and adults.

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Matt Greig

extension–flexion repetitions, 3 repeated countermovement jumps, 4 and treadmill running 5 fail to adequately reflect the activity profile of soccer match-play, and therefore, interpretation in relation to injury epidemiology and etiology is limited. In developing an experimental approach to the problem

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Christopher K. Rhea and Matthew W. Wittstein

Much has been learned about the characteristics of gait in overground and treadmill walking. However, there are many contexts in which overground or treadmill walking might not be possible, such as in home-based physical therapy. In those cases, a surrogate task to index gait behavior would be a valuable tool. Thus, the purpose of this study was to evaluate the stride behavior characteristics of stationary stepping compared with treadmill walking. Healthy young adults (N = 10) preformed two 15-minute tasks: (1) treadmill walking and (2) stationary stepping. Several stride behavior characteristics were recorded, including the number of strides taken, minimum and maximum knee angle, stride interval mean, stride interval standard deviation, and detrended fluctuation analysis (DFA) alpha of the stride interval time series. The results showed that stride behavior was similar between tasks when examined at the group level. However, when individual level analyses were used to examine the reliability of each metric between tasks, poor reliability was observed in most metrics, indicating that stationary stepping may not be an appropriate surrogate task for overground or treadmill walking. These results are discussed in the context of a gait dynamics framework, with attention to task constraints that may have influenced the findings.

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Erin M.R. Bigelow, Niell G. Elvin, Alex A. Elvin and Steven P. Arnoczky

To determine whether peak vertical and horizontal impact accelerations were different while running on a track or on a treadmill, 12 healthy subjects (average age 32.8 ± 9.8 y), were fitted with a novel, wireless accelerometer capable of recording triaxial acceleration over time. The accelerometer was attached to a custom-made acrylic plate and secured at the level of the L5 vertebra via a tight fitting triathlon belt. Each subject ran 4 miles on a synthetic, indoor track at a self-selected pace and accelerations were recorded on three perpendicular axes. Seven days later, the subjects ran 4 miles on a treadmill set at the individual runner’s average pace on the track and the peak vertical and horizontal impact magnitudes between the track and treadmill were compared. There was no difference (P = .52) in the average peak vertical impact accelerations between the track and treadmill over the 4 mile run. However, peak horizontal impact accelerations were greater (P = .0012) on the track when compared with the treadmill. This study demonstrated the feasibility for long-term impact accelerations monitoring using a novel wireless accelerometer.

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Eadric Bressel, Gerald Smith, Andrew Miller and Dennis Dolny

Context: Quantification of the magnitudes of fluid resistance provided by water jets (currents) and their effect on energy expenditure during aquatic-treadmill walking is lacking in the scientific literature. Objective: To quantify the effect of water-jet intensity on jet velocity, drag force, and oxygen uptake (VO2) during aquatic-treadmill walking. Design: Descriptive and repeated measures. Setting: Athletic training facility. Participants, Interventions, and Measures: Water-jet velocities were measured using an electromagnetic flow meter at 9 different jet intensities (0-80% maximum). Drag forces on 3 healthy subjects with a range of frontal areas (600, 880, and 1250 cm2) were measured at each jet intensity with a force transducer and line attached to the subject, who was suspended in water. Five healthy participants (age 37.2 ± 11.3 y, weight 611 ± 96 N) subsequently walked (~1.03 m/s or 2.3 miles/h) on an aquatic treadmill at the 9 different jet intensities while expired gases were collected to estimate VO2. Results: For the range of jet intensities, water-jet velocities and drag forces were 0-1.2 m/s and 0-47 N, respectively. VO2 increased nonlinearly, with values ranging from 11.4 ± 1.0 to 22.2 ± 3.8 mL × kg-1 × min-1 for 0-80% of jet maximum, respectively. Conclusions: This study presented methodology for quantifying water-jet flow velocities and drag forces in an aquatic-treadmill environment and examined how different jet intensities influenced VO2 during walking. Quantification of these variables provides a fundamental understanding of aquatic-jet use and its effect on VO2. In practice, these results indicate that VO2 may be substantially increased on an aquatic treadmill while maintaining a relatively slow walking speed.

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Kenneth H. Pitetti, Bart Jongmans and Bo Fernhall

The purpose of this study was to examine the validity and reliability of a treadmill (TM) test for adolescents with multiple disabilities, as defined by PL 105-17. Participants were 16 males and 2 females, ages 11 to 21 (M 14.9 ± 3.2), identified by teachers as potentially able to perform a TM test. Data were collected two times, separated by 2 to 3 weeks. Of the 18 adolescents, 5 could not perform the protocol, and 4 could not complete the test. Intraclass (test–retest) reliability coefficients for HRpeak, V̇Epeak, RERpeak, and V̇O2peak were .90, .90, .88, and .77, respectively, for the remaining 9 participants. Although none of these participants were able to meet the criteria commonly associated for a valid TM maximaltest (V̇O2max), they did meet the criteria for a valid TM maximum test (V̇O2peak) (Wasserman, Hansen, Sue, Whipp, & Casaburi, 1994). Further study of the feasibility of treadmill testing for this population is recommended.

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Olivier Girard, Franck Brocherie, Jean-Benoit Morin and Grégoire P. Millet

Purpose:

To determine the intrasession and intersession (ie, within- and between-days) reliability in treadmill sprinting-performance outcomes and associated running mechanics.

Methods:

After familiarization, 13 male recreational sportsmen (team- and racket-sport background) performed three 5-s sprints on an instrumented treadmill with 2 min recovery on 3 different days, 5–7 d apart. Intrasession (comparison of the 3 sprints of the first session) and intersession (comparison of the average of the 3 sprints across days) reliability of performance, kinetics, kinematics, and spring-mass variables were assessed by intraclass correlation coefficient (ICC) and coefficients of variation (CV%).

Results:

Intrasession reliability was high (ICC > .94 and CV < 8%). Intersession reliability was good for performance indices (.83 < ICC < .89 and CV < 10%, yet with larger variability for mean velocity than for distance covered or propulsive power) and kinetic parameters (ICC > .94 and CV < 5%, yet with larger variability for mean horizontal forces than for mean vertical forces) and ranged from good to high for all kinematic (.88 < ICC < .95 and CV ≤ 3.5%) and spring-mass variables (.86 < ICC < .99 and CV ≤ 6.5%). Compared with intrasession, minimal detectable differences were on average twice larger for intersession designs, except for sprint kinetics.

Conclusion:

Instrumented treadmill sprint offers a reliable method of assessing running mechanics during single sprints either within the same session or between days.

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Cal Stone and Maury L. Hull

This paper provides measurements of rider-induced loads during standing cycling. Two strain gauge dynamometers were used to measure these loads while three subjects rode bicycles on a large motorized treadmill; the cycling situation simulated hill climbing while standing. Comparing the results to those previously published for seated cycling revealed that the loading for standing cycling differed fundamentally from that for seated cycling in certain key respects. One respect was that the maximum magnitude normal pedal force reached substantially higher values, exceeding the weight of the subject, and the phase occurred later in the crank cycle. Another respect was that the direction of the handlebar forces alternated indicating that the arms pulled up and back during the power stroke of the corresponding leg and pushed down and forward during the upstroke. Inasmuch as these forces were coordinated (i.e., in phase) with the leaning of the bicycle, the arms developed positive power.

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Martine Hoofwijk, Viswanath Unnithan and Oded Bar-Or

Nine children with spastic cerebral palsy (CP) and 9 controls (mean age 13.5 and 14.0, respectively) completed a maximal walking test on the treadmill. Initial gradient was set at 0% with a speed increase every 2 minutes until the “fastest walking speed” was achieved in the third stage. The gradient was then increased by 2.5–5% every 2 minutes. V̇O2max of the CP children was significantly lower (p = .001) than that of the controls (32.7 vs. 45.2 ml · kg1 · min−1). There was no significant difference in maximal heart rate between the two groups (189 vs. 197). However, the CP subjects had significantly higher (p = .007) ventilatory equivalent for O2 compared to the controls (41.4 vs. 33.6). The lower V̇O2max values of the CP children might reflect inefficient ventilation, compromised circulation, and local fatigue in the spastic limb muscles.

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Costas I. Karageorghis, Denis A. Mouzourides, David-Lee Priest, Tariq A. Sasso, Daley J. Morrish and Carolyn L. Walley

The present study examined the impact of motivational music and oudeterous (neutral in terms of motivational qualities) music on endurance and a range of psychophysical indices during a treadmill walking task. Experimental participants (N = 30; mean age = 20.5 years, SD = 1.0 years) selected a program of either pop or rock tracks from artists identified in an earlier survey. They walked to exhaustion, starting at 75% maximal heart rate reserve, under conditions of motivational synchronous music, oudeterous synchronous music, and a no-music control. Dependent measures included time to exhaustion, ratings of perceived exertion (RPE), and in-task affect (both recorded at 2-min intervals), and exercise-induced feeling states. A one-way repeated measures ANOVA was used to analyze time to exhaustion data. Two-way repeated measures (Music Condition × Trial Point) ANOVAs were used to analyze in-task measures, whereas a one-way repeated measures MANOVA was used to analyze the exercise-induced feeling states data. Results indicated that endurance was increased in both music conditions and that motivational music had a greater ergogenic effect than did oudeterous music (p < .01). In addition, in-task affect was enhanced by motivational synchronous music when compared with control throughout the trial (p < .01). The experimental conditions did not impact significantly (p > .05) upon RPE or exercise-induced feeling states, although a moderate effect size was recorded for the latter (ηp 2 = .09). The present results indicate that motivational synchronous music can elicit an ergogenic effect and enhance in-task affect during an exhaustive endurance task.