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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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Bente R. Jensen, Line Hovgaard-Hansen and Katrine L. Cappelen

Running on a lower-body positive-pressure (LBPP) treadmill allows effects of weight support on leg muscle activation to be assessed systematically, and has the potential to facilitate rehabilitation and prevent overloading. The aim was to study the effect of running with weight support on leg muscle activation and to estimate relative knee and ankle joint forces. Runners performed 6-min running sessions at 2.22 m/s and 3.33 m/s, at 100%, 80%, 60%, 40%, and 20% body weight (BW). Surface electromyography, ground reaction force, and running characteristics were measured. Relative knee and ankle joint forces were estimated. Leg muscles responded differently to unweighting during running, reflecting different relative contribution to propulsion and antigravity forces. At 20% BW, knee extensor EMGpeak decreased to 22% at 2.22 m/s and 28% at 3.33 m/s of 100% BW values. Plantar flexors decreased to 52% and 58% at 20% BW, while activity of biceps femoris muscle remained unchanged. Unweighting with LBPP reduced estimated joint force significantly although less than proportional to the degree of weight support (ankle).It was concluded that leg muscle activation adapted to the new biomechanical environment, and the effect of unweighting on estimated knee force was more pronounced than on ankle force.

Open access

Mhairi K. MacLean and Daniel P. Ferris

and complexity in the ambulatory tasks. Walking at a single speed on a treadmill is a good way of collecting data for a steady-state condition, but there are very few steady-state conditions in real-world ambulation. Walking in the real world is often over uneven and varied terrain, interspersed with

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Jo Welsman and Neil Armstrong

-related physiological function. Sources of Data for This Paper Over the 20-year period between the first laboratory measurements of children’s peak V ˙ O 2 within the Children’s Health and Exercise Research Centre and 2006, over 1700 treadmill (TM) peak V ˙ O 2 determinations were made with 9- to 18-year-old males

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Jocelyn F. Hafer and Katherine A. Boyer

testing before and after a 30-minute bout of walking on a treadmill. The 30-minute treadmill walk simulated a bout of exercise individuals may complete in a given day. During this bout, participants walked at their normal walking speed (as determined from a 400-m overground walk during the first visit

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Baruch Vainshelboim, Zhongming Chen, Ricardo M. Lima and Jonathan Myers

, USA. All participants who underwent a treadmill exercise test at the Veterans Affairs Palo Alto Health Care System between 1987 and 2014 were considered for inclusion. Clinical information on diagnoses, risk factors, and health behaviors (smoking, alcohol, and drug abuse) was collected at the time of

Open access

Maximilian Pelka, Alexander Ferrauti, Tim Meyer, Mark Pfeiffer and Michael Kellmann

A recovery process with optimal prerequisites that is interrupted is termed disrupted recovery. Whether this process has an influence on performance-related factors needs to be investigated. Therefore, the aim of this study was to examine how a short disturbance of a recovery phase is assessed and whether subsequent repeated-sprint performance is affected by it. A quasi-experimental 2 × 2-factor crossover design with 34 sport-science undergraduate students (age 20.3 ± 2.1 y) was applied. Factors were the type of intervention (power nap vs systematic breathing; between-subjects) and the experimental condition (disturbed vs nondisturbed break; within-subject). Repeated-sprint performance was measured through 6 × 4-s sprint protocols (with 20-s breaks) before and after a 25-min recovery break on 2 test days. Subjective evaluation of the interventions was measured through the Short Recovery and Stress Scale and a manipulation check assessing whether participants experienced the recovery phase as efficacious and pleasant. Regarding the objective data, no significant difference between sprint performances in terms of average peak velocity (m/s) on the treadmill was found. The manipulation check revealed that disturbed conditions were rated significantly lower than regular conditions in terms of appreciation, t 31 = 3.09, P = .01. Short disturbances of recovery do not seem to affect subsequent performance; nevertheless, participants assessed disturbed conditions more negatively than regular conditions. In essence, the findings indicate a negligible role of short interruptions on an objective level. Subjectively, they affected the performance-related assessment of the participants and should be treated with caution.

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Amelia J. Carr, Philo U. Saunders, Laura A. Garvican-Lewis and Brent S. Vallance

Physiological data and training summary for the 20 months from January 2007 to August 2008. (A) Hb mass (g), (B) body mass (kg), (C) treadmill speed (km·h −1 ) at 4 mmol·L −1 blood [La − ], (D) VO 2 max (mL·kg −1 ·min −1 ), (E) 20-km performance time (min), and (F) mean weekly training volume (km). Gray bars

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-individual variability in the peak of oxygen uptake (VO2peak) among girls during circumpubertal years. Methods : The final sample included 51 girls (10.7–13.5 years). VO2peak was derived from an incremental progressive maximal protocol using a motorized treadmill. Anthropometry included body mass, stature and skinfolds

Open access

. Methods.— Twenty five trail runners (mean age 31.2 ±5.1 years) completed a standard graded exercise test on the treadmill for determination of maximal oxygen uptake (VO 2 max 59.5±5.2 ml·kg -1. min -1 ) and LT. Values and velocities for aerobic LT (AET), individual anaerobic LT (IAT according to Dickhuth